Conceptual Glossary of Medical Terms.

Site presented by Bill Tillier

Use this index to navigate around the glossary:

Introduction      Sources      Other web-based glossaries.

A - C      D - F      G - K      L - O     P - S     T - Z.

Created: July 03, 2001.

To Search for a term on this page:

On most computers, "Ctrl" + F will open a search you can use to look for text on the webpage.

Other web-based glossaries:

Common Terms in Evolutionary Biology and Genetics by M.Tevfik DORAK http://dorakmt.tripod.com/evolution/glossary.html

The Human Genome Program of the U.S. Department of Energy: http://www.ornl.gov/hgmis/publicat/primer2001/dictionary.html

Dr. Koop's Medical Encyclopedia: http://www.drkoop.com/conditions/ency/index.html

A meta list of dictionaries: http://stommel.tamu.edu/~baum/hyperref.html

Hypertexts for Biomedical Sciences. Glossary.

Your Dictionary: http://www.yourdictionary.com/

National Human Genome Research Institute (NHGRI) Glossary: http://www.nhgri.nih.gov/DIR/VIP/Glossary/

The National Women's Health Information Center:  http://www.womenshealth.gov/

1000 Dictionaries.com: http://www.1000dictionaries.com/dindex.html

A Glossary of Basic Medical Terms.


This glossary presents an overview of terms and concepts often encountered in dealing with the medical community. It has a general focus on neuromuscular disorders. There is some redundancy in the entries and I hope that where I repeat a definition, it presents a slightly different and thus helpful addition to understanding the given concept. Many of these terms are very scientific. Medicine is a scientific topic, so much of the terminology seems very complex to begin with. I encourage the reader to get the most they can out of this glossary and not worry if some terms "sound like Latin" (they likely are Latin!). Many of these entries are about genetics because many diseases are genetic in nature. This glossary is not comprehensive, there are many different diseases and I am not trying to be a textbook. Pronunciation guidelines are presented in { }. Selected sources are listed at the end. In many cases, terms are very specific and I have not always provided references; if the reader needs more information on a topic, please submit it to a search engine and go from there. If you see any mistakes, please feel free to let me know at: btillier@shaw.ca THANKS.


A - C      D - F      G - K      L - O     P - S     T - Z.

Abdomen {AB-doe-men}: The part of the body that contains the stomach, small intestine, colon, rectum, liver, spleen, pancreas, kidneys, appendix, gallbladder, and bladder. #

Ablation: Surgical destruction or removal of tissue, an organ, or a precise region of a particular structure. Ablation may involve surgical cutting (excision); chemical destruction, such as injection of phenol; or the use of high frequency electrical current or radio waves. For example, pallidotomy is a procedure used in the treatment of Parkinson's disease or certain other movement disorders. The procedure involves surgical ablation of part of the internal portion of the globus pallidus (GPi)--i.e., a brain region involved in regulating movement--in an attempt to "rebalance" movement and posture control. Once a wire probe is inserted into and precisely positioned within the GPi, it heats and destroys adjacent tissue through the emission of radio waves.

Abscess {AB-cess}: Infection that has formed a pocket of pus. #

Accessory cell: Cell required for, but not actually mediating, a specific immune response. Often used to describe antigen-presenting cells (APC; see below).

Acetaminophen (Tylenol): Acetaminophen, with brand names such as Tylenol, Panadol, Tylenol Arthritis and Excedrin is one of the safest analgesic painkillers used for arthritis pain relief. The medication is often used in combination with other drugs. Acetaminophen is the most commonly used over-the-counter, non-narcotic analgesic.

Acetylcholine (ACh) {ah-SEA-TILL-co-line}: An important neurotransmitter in the body and especially in muscle. ACh is a major transmitter substance at many neural (nerve) synapses and at the neuromuscular junction of vertebrate muscles. When a nerve impulse arrives at the nerve ending, ACh, which is stored there, is often released. ACh released by muscle nerves makes muscles contract. ACh is destroyed by an enzyme, acetylcholinesterase, and thus it is effective only briefly. The brain makes it from the precursor nutrient choline. ACh is also known to play an important role in memory and learning and is in abnormally short supply in the brains of those with Alzheimer's disease. Certain muscular disorders, for example, myasthenia gravis, involve problems with acetylcholine. *

Achondroplasia: The most common and well known form of short limbed dwarfism characterized by a normal trunk size with disproportionately short arms and legs, and a disproportional large head; autosomal dominant condition.

Acoustic {ah-KOOS-tick}: Related to sound or hearing. #

Acquired disease: to come to have as a new or additional characteristic, trait, or ability (as by sustained effort, by mutation, or through environmental forces) For example, in spontaneous (genetic) disease the cells inherited from the parents all start out normal, but during the lifespan, as cells replicate, a defect in the gene code occurs and causes an acquired disease. This is a common way cancer starts, for example, a person exposed to some environmental factor may develop genetic mutations that lead to cancer during the person's lifetime. We can say that this cancer has a genetic aspect but it is not hereditary or inherited - it is not passed onto their children. More on cancer: The transition from a normal cell to a malignant cancer is driven by changes to the cell's DNA. All cells acquire mutations over their lifetime, but most are quickly repaired by the cell's maintenance machinery. This machinery is not foolproof, however, and if mutations are missed in two classes of gene that control growth - proto-oncogenes and tumour suppressor genes - the cancer cycle can begin. Also see: Cancer as an example of; Hereditary diseases, Familial disease and Congenital diseases.

Acquired mutations: see somatic mutations.

Acquired immune deficiency syndrome (AIDS): A viral disease that destroys the body's ability to fight infections, leaving the body susceptible to many other diseases. ##

Actin {Act-tin}: a very important protein abundantly present in many cells, especially in muscle cells, that significantly contributes to the cell's structure and motility (movement). Actin can very quickly assemble into long strands called microfilaments. These microfilaments have a variety of roles - they form part of the cell's cytoskeleton, they interact with myosin to permit movement of the cell, and they pinch the cell into two during cell division. In skeletal muscle, actin fibers are long and thin and are thus called the "thin" filaments of muscle. Actin, works along with another protein called myosin, to produce contractions of muscles. Myosin filaments are thick protein threads (called "thick" filaments) that lie parallel to the thin microfilaments of actin. In muscle contraction, filaments of actin alternately chemically link and unlink with those of myosin in a creeping or sliding action. (Think of the myosin as the oars on a boat and the actin as the water). Based on: http://www.encyclopedia.com/ *

Action tremor: a tremor that occurs during the performance of voluntary movements. Such tremors include postural, isometric, kinetic, and intention tremors. Active immunity: A type of acquired immunity whereby resistance to a disease is built up by either having the disease or receiving a vaccine against it.

Activities of Daily Living (ADLs): The activities of daily living (ADLs) and the instrumental activities of daily living (IADLs) are important measures of a person's ability to function in life. A variety of medical conditions can impair these activities.
ADLs are self-care activities that a person must perform every day (e.g., eating, dressing, bathing, transferring between the bed and a chair, using the toilet, controlling bladder and bowel).
The ADLs are remembered by the pneumonic DEATH which includes:
D- dressing
E - eating (self feeding)
A - ambulating (walking)
T - transferring
H - hygiene
IADLs are activities that enable a person to live independently in a house or apartment (e.g., preparing meals, performing housework, taking drugs, going on errands, managing finances, using a telephone).
The IADLs are activities that require a higher level of function than the ADLs and are therefore more sensitive to loss than the ADLs. Patients with functional decline generally lose the ability to do their IADLs prior to losing ADL function.
The IADLs are remembered by the pneumonic SHAFT
The pneumonic describes activities as outlined below:
S - shopping
H - housekeeping
A - accounting
F - food preparation
T - transportation

Actomyosin: A term sometimes used to refer to the system of actin and myosin that, along with other substances (proteins), constitutes muscle fiber and is responsible for muscular contraction.*

Acute: A sudden, usually more severe presentation of symptoms. *

Adaptive immune response: Immune response mediated by B and T cells after exposure to a specific antigen. Involves memory, self/nonself recognition, and specificity

Adaptive Mutation (also called stationary-phase mutation): Mutation increases in cells under strong environmental stress, at least some mutations allow for growth. It is thus a model of mutational escape of growth control (such as in oncogenesis). Implies that evolution can be hastened when environmental challenges arise.

Addison's disease: Disease resulting from deficiency in the secretion of adrenocortical hormones. ***

Adenocarcinoma {AD-en-o-CAR-sin-o-ma}: Cancer arising in gland forming tissue. An example is breast cancer. #

Adenoma {ADD-in-oma}: A benign tumor made up of glandular tissue. For example, an adenoma of the pituitary gland may cause it to produce abnormal amounts of hormones. ##

Adenosine {ADD-din-NO-sin} triphosphate {tri-FOS-fate} (ATP): energy-carrying molecule found in the cells of all living things. ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. Cells require chemical energy for three general types of tasks: to drive metabolic (chemical) reactions that would not occur automatically; to transport needed substances across membranes; and to do mechanical work, such as moving muscles.
An analogy between ATP and rechargeable batteries is appropriate. The batteries are used, giving up their potential energy until it has all been converted into kinetic energy and heat/unusable energy. Recharged batteries (into which energy has been put) can be used only after the input of additional energy. Thus, ATP is the higher energy form (the recharged battery) while ADP is the lower energy form (the used battery). When the terminal (third) phosphate is cut loose, ATP becomes ADP (Adenosine diphosphate; di= two), and the stored energy is released for some biological process to utilize. The input of additional energy (plus a phosphate group) "recharges" ADP into ATP (as in my analogy the spent batteries are recharged by the input of additional energy).
ATP Formation: Adenosine diphosphate + inorganic Phosphate + energy produces Adenosine Triphosphate
ATP energy: Energy is stored in the covalent bonds between phosphates, with the greatest amount of energy (approximately 7 kcal/mole) in the bond between the and third phosphate groups. This covalent bond is known as a pyrophosphate bond.
ATP Energy release: Adenosine Triphosphate produces Adenosine diphosphate + energy + inorganic Phosphate

Also: organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of proteins. It is broken down by a chemical process called hydrolysis to yield adenosine diphosphate (ADP), inorganic phosphorus, and energy. ADP can be further broken down to yield adenosine monophosphate (AMP), additional phosphorus, and more energy. Outside of the cell, ATP has also been found to act as a neurotransmitter. ATP receptors are widespread through the body. On its own it is known to have effects in the arteries, intestines, lungs, and bladder. It is also often released in tandem with other neurotransmitters, perhaps to add chemical stability. *

Adenovirus {ADD-din-NO-virus}: One of a group of DNA-containing viruses associated with acute upper respiratory tract (URT) infections, i.e. "colds". In addition, they also cause a number of other types of infection. *

Adenylate {ADD-den-oh-late} Deaminase {DEE-em-in-ase} Deficiency: One of a group of metabolic diseases of muscle in which a known biochemical defect (in this case, deficiency of an enzyme known as adenylate deaminase) is associated with symptoms of exercise intolerance. The cardinal symptoms are usually fatigue and muscle pain. **

Adjuvant therapy {ADGE-joo-vant}: Treatment given in addition to the primary treatment. #

Adjuvant chemotherapy: Chemotherapy given to kill any remaining cancer cells, usually after all detectable tumor is removed by surgery or radiotherapy. ##

ADLs: see Activities of Daily Living

Admixture: The mixing of two genetically distinct populations.

Adrenal glands {ah-DREE-nal}: A pair of small glands, one located on top of each kidney. The adrenal glands produce sex hormones and hormones that help control heart rate, blood pressure, the way the body uses food, and other vital functions.

Adult Acid Maltase Deficiency: Also known as Type 2 glycogenesis, adult acid maltase deficiency is associated with an accumulation of glycogen in the tissues of the body resulting in muscle weakness. This deficiency is related to a decrease in production of acid maltase. It is a genetic disorder, transmitted by an autosomal recessive form of inheritance. Muscle weakness is experienced later in life and is proximal, primarily affecting the hips. Unlike infantile acid maltase deficiency, heart and liver are not involved. **

Advanced maternal age: Women over age 34 (age 35 at time of delivery). These women are at increased risk for genetic changes in fetus. %

Affinity: A measure of the binding constant of a single antigen combining site with a monovalent antigenic determinant.

AFP (Alpha fetoprotein): A tumor marker. ##

Agenesis: Absence of an organ, usually due to total failure of its development in the embryo.

Agent: Any particle or material that is able to transmit a disease. *

Agglutination: The aggregation of particulate antigen by antibodies. Agglutination applies to red blood cells as well as to bacteria and inert particles covered with antigen.

Aggresome: The abnormal aggregation (clumping together) of proteins is an important part of many diseases - the clumps form into inclusion bodies that are toxic and disrupt the operation of the cell. In severe cases, plaques (sheets) of abnormal protein matter dominate the cell. Normally, cells have ways to avoid protein aggregation (they take out the garbage of broken proteins). In the normal cell, enzymes called proteases cut up old and abnormal proteins. This is partly based upon the shape of the protein, sometimes a protein will resist being cut up and is called protease resistant. When this happens, inclusion bodies form. Research now shows that various proteins are moved into inclusion bodies by a transport protein called dynein along hollow tubes called microtubules. Inclusion bodies created by microtubule transport are now called aggresomes. The role of these protein aggregrations in disease is unclear (a cause or an effect of something else?) and is being researched.

Agonist muscles: A muscle whose contraction executes an intended movement. Muscles that are attached in such a way that when they contract, they develop forces that reinforce each other. *

AID: Some people use the abbreviation AID for (A)uto (I)mmune (D)isease. This is easily confused with AIDS.

AIDS (acquired immune deficiency syndrome): A variety of opportunistic infections resulting from the disabling of the body's immune system after infection with HIV. AIDS involves a range of otherwise rare conditions including Kaposi's sarcoma, a rare skin cancer, and respiratory infections, especially pneumocystis pneumonia. *

Akinesia: absence of movement or loss of the ability to move such as temporary or prolonged paralysis or "freezing in place."

Akinetic: Referring to absence or poverty of voluntary movement; loss of the ability to move all or part of the body.

Alemtuzumab (uh-lem-TOOZ-uh-mab): is a monoclonal antibody. It is used to treat a certain type of leukemia in patients whose disease has progressed, despite treatment with other chemotherapeutic agents. It is being researched as a treatment for inclusion body myositis.

Alleles {AL-eel-ills}: Chromosomes occur in pairs. Each chromosome has a copy of each gene, one inherited from the mother and one from the father, so, there are two copies of each gene present. However, these two gene copies are not always identical, there can be minor variations in the nucleotide sequences from the gene on one chromosome to the gene on the other. These different forms of the same gene are called alleles. An individual may inherit the same versions of a given gene from his or her parents, or may get two different alleles (one from each parent) for a given gene. A population of individuals may contain many different alleles of a gene.
If you have two copies of the same allele for a given gene, you are said to be homozygous for that gene; if you have two different alleles you are called heterozygous.Homozygotes can pass on only one allele for that gene; heterozygotes can pass on either one of their alleles to each offspring, at random.
In a heterozygous individual: One of the two alleles is usually dominant over the other and determines the trait that will be expressed in the organism (the phenotype) and "overriding" the other, recessive, allele. For some traits, alleles may also be co-dominant-i.e., neither acts as dominant or recessive. An example is the human ABO blood system; persons with type AB blood have one allele for A and one for B. (Persons with neither are type O).
In homozygous individuals, for a given trait, and there will only be one form available for expression (if both code for blue eyes, the eyes have to be blue). In this case it does not matter if an allele (and the trait it carries) is dominant or recessive (because both alleles are the same). In a heterozygous pairing, one allele is usually dominant and the other recessive, and this dominance determines the trait that is expressed. A dominant allele will override the traits of the recessive allele. For example, if blue eye colour is dominant and if there is one blue and one brown gene, then the person will have blue eyes (but their alleles for brown eyes may be passed onto their children).
The overall composition of alleles in an organism is called the genotype. Most traits are determined by more than two alleles and two or more gene sites control some traits. Therefore, multiple alleles may be involved in the determination of a single trait. Also, all genetic traits are the result of the interactions of alleles. Mutation, crossing over, and environmental conditions selectively change the frequency of phenotypes (and thus their alleles) within a population.
In a population of individuals: there may be numerous alleles of a given gene, each with a unique nucleotide sequence. The measure of how common an allele is in a population is called the allele frequency. For example, the gene that codes for the basic information for eye colour is on each of the two chromosomes, but the actual colour may differ on the two genes, say, blue on one and brown on the other. These variations provide the basis for variation between individuals. * Also: Allele If the DNA sequence at a given locus (often a gene or a marker) varies between different chromosomes in the population, each different version is an allele. If there are two alleles at a given locus, the allele that is less common in the population is the minor allele.

Allelic: Relating to one of a series of two or more alternate forms of a gene that occupy the same position or locus on a specific chromosome.

Allelic exclusion: The ability of heterozygous lymphoid cells to produce only one allelic form of antigen-specific receptor when they have the genetic endowment to produce both. Genes other than those for the specific receptors are usually expressed codominantly.

Allergen: An antigen responsible for producing allergic reactions by inducing IgE formation.

Allergy: A term covering immune reactions to non-pathogenic antigens, which lead to inflammation and deleterious effects in the host.

Allogeneic: The allelic variation observed among members of the same species.

Allograft: A tissue transplant (graft) between two genetically nonidentical members of a species.

Allopurinol (al-oh-PURE-i-nole) is used to treat chronic gout (gouty arthritis). This condition is caused by too much uric acid in the blood. This medicine works by causing less uric acid to be produced by the body. Allopurinol will not relieve a gout attack that has already started. Also, it does not cure gout, but it will help prevent gout attacks. However, it works only after you have been taking it regularly for a few months. Allopurinol will help prevent gout attacks only as long as you continue to take it. Allopurinol is also used to prevent or treat other medical problems that may occur if too much uric acid is present in the body. These include certain kinds of kidney stones or other kidney problems. Certain medicines or medical treatments can greatly increase the amount of uric acid in the body. This can cause gout or kidney problems in some people. Allopurinol is also used to prevent these problems, and can be given as either a tablet or an injection if necessary.

Allotypes: Antigenic determinants that are present in allelic (alternate) forms. When used in association with immunoglobulin, allotypes describe allelic variants of immunoglobulins detected by antibodies raised between members of the same species.

Alopecia {al-oh-PEE-she-ah}: Hair loss. #

Alpha-fetoprotein (AFP): A protein excreted by the fetus into the amniotic fluid and from there into the mother's bloodstream through the placenta.

Alpha 2-adrenergic agonist: A drug that reduces the activity of the neurotransmitter norepinephrine by stimulating certain receptors within the central nervous system (central presynaptic alpha 2-adrenergic receptors). The release of norepinephrine triggers action within the sympathetic nervous system. This part of the nervous system regulates certain involuntary activities during stress, such as increasing the heart rate, deepening breathing, and raising blood pressure. Norepinephrine also plays a role in regulating mood and emotion. The administration of alpha 2-adrenergic agonists may result in a reduced heart rate and lowered blood pressure and have depressive or sedative effects.

ALS: see amyotrophic lateral sclerosis

Alternate (Alternative) pathway: The mechanism of complement activation that does not involve activation of the C1, C4, C2 pathway by antigen-antibody complexes, and begins with the activation of C3.

Alternative splicing: RNA instructions contain a number of exons that carry the instructions to make a protein, as well as introns, pieces of RNA that do not contain instructions. The RNA strand is processed to remove the introns and splice the exons together to form a final transcript called messenger RNA, or mRNA, before the ribosomes create the protein. It is this final processing step that largely determines the specific protein created.
If each gene created one mRNA that gave instructions for a single protein, the number of genes in the human genome would be the same as the number of proteins that make up the human body-but that is not the case.
Transcripts are not always processed the same way. Sometimes an exon is left out. Sometimes an extra exon is included. Exons can be extended or truncated. These variations create multiple alternative splice forms of a gene sequence. As a result, one gene can encode multiple versions of mRNA, leading to multiple proteins. Each splice form of an RNA sequence holds instructions for a different protein. And so the biological complexity of human life unfolds.
Also see protein synthesis.

Alzheimer's {ALTZ-high-mers} disease (AD): degenerative brain disorder that develops in mid-to-late adult life and results in a progressive and irreversible decline in memory and various other cognitive functions. The disease is marked by the destruction of nerve cells and neural connections in the cerebral cortex of the brain and by a significant loss of brain mass. Alzheimer's disease is the most common form of dementia. The disease develops differently among individuals, and this suggests that more than one pathologic process may lead to the same outcome. Typically, the first symptom to appear is forgetfulness, as short-term memory and immediate recall become impaired. As the disease progresses, memory loss becomes more severe and the person's language, perceptual, and motor skills deteriorate. Mood becomes unstable, and the person tends to become irritable and more sensitive to stress and may become intermittently angry, anxious, or depressed. At a biochemical level, there are similarities between AD and certain muscular problems (IBM). *

Alu repetitive sequence: The most common dispersed repeated DNA sequence in the human genome accounting for 5% of human DNA. The name is derived from the fact that these sequences are cleaved by the restriction endonuclease Alu.

Ambulant (ambulatory): Able to walk; may be used to describe patients who do not require a wheelchair or are not confined to bed.

Ambulation: another term for walking. *

Amenorrhea {AH-men-or-ree-ah}: Absence or stoppage of the menstrual period. #

Amino acid sequence: The linear order of the amino acids in a peptide or protein. %

Amino acids: The end product of protein digestion and also the building blocks of which proteins are constructed. A natural organic compound characterized by an amino group (NH2). Amino acids are the subunits of proteins. A sequence or chain of amino acids makes up a protein.
Sequences of different amino acids create the various types of proteins. There are twenty different amino acids generally found in proteins, although some are less common than others, and a few specialized proteins contain amino acids different from the twenty. Many other amino acids that are not incorporated into proteins also occur in living organisms.
In the human diet, nine of the twenty different types must be present. These nine are known as 'essential' amino acids. The liver can manufacture the remaining 'nonessential' types. Amino acids cannot be stored in the body for more than four hours, so all of the essential ones must be provided in the diet. In addition to their use in building proteins, amino acids are also used for making certain hormones, vitamins, coenzymes, and neurotransmitters. *

Aminoglutethimide: An anticancer drug that belongs to the family of drugs called nonsteroidal aromatase inhibitors. Aminoglutethimide is used to decrease the production of sex hormones (estrogen or testosterone) and suppress the growth of tumors that need sex hormones to grow. %

Amniocentesis {AM-Knee-OH-cent-tea-sis}: A prenatal diagnosis method using cells removed from the amniotic fluid to determine the number and kind of chromosomes of the fetus and, when indicated, perform biochemical studies. %
Amniocentesis {AM-knee-oh-cent-tee-sis}: Withdrawal of a sample of the fluid (amniotic fluid) surrounding an embryo in the uterus by piercing the amniotic sac through the abdominal wall. As the amniotic fluid contains cells from the embryo (mostly shed from the skin), cell cultures enable chromosome patterns to be studied so that prenatal diagnosis of chromosomal abnormalities (such as Down's syndrome) can be made. Metabolic errors and other diseases, such as spina bifida, can also be diagnosed prenatally from the biochemistry of the cells or that of the fluid.

Ampicillin (beta-lactamase): An antibiotic derived from penicillin that prevents bacterial growth by interfering with cell wall synthesis.

Amplification: Any process by which specific DNA sequences are replicated disproportionately greater than their representation in the parent molecules.

Amplitude: the "size" or "height" of a tremor; the extend or breadth of a tremor's range.

Amyloid {AM-ill-Lloyd}: Amyloid is a heterogenous, meshwork collection of pathologic fibrillar proteins. Normally, these protein fragments are broken down and eliminated, but amyloid resists the action of the normal celluar mechanisms that deal with abnormal proteins, leading to abnormal accumulations. Abnormal accumulations of amyloid (called amyloid referring to their starch like appearance) are found to be insoluble and consist of protein fibrils, composed of many different types of proteins. These deposits are usually detected by staining with the dye Congo red [hence the term congophilic meaning attracted to congo]. A buildup of amyloid in the brain is associated with Alzheimer's disease (AD), Creutzfeldt-Jakob disease, and bovine spongiform encephalopathy, also seen in muscles in inclusion body myositis and also are associated with the aging process. The amyloid cascade hypothesis is a prominent theory for understanding the causes behind AD. This hypothesis states that AB deposits into plaques, and these neurotoxins propagate a neurodegenerative cascade and possibly AD.

Amyloid hypothesis of Alzheimer's disease (AD): Alzheimer's disease (AD) may be caused by deposition of amyloid beta-peptide (Abeta) in plaques in brain tissue. According to the amyloid hypothesis, accumulation of Abeta in the brain is the primary influence driving AD pathogenesis. The rest of the disease process, including formation of neurofibrillary tangles containing tau protein, is proposed to result from an imbalance between Abeta production and Abeta clearance.

Beta-amyloid is a fragment of a protein that is snipped from another protein called amyloid precursor protein (APP). It is a free-floating protein found in the cerebrospinal fluid; in Alzheimer's patients, one form appears to accumulate in the central nervous system and form amyloid plaques.

Amyloidogenesis: The production of amyloid. *

Amyloidosis {AM-ill-Lloyd-doses}: Accumulation in the tissues of various insoluble fibrillar proteins (amyloid) in amounts sufficient to impair normal function. - The build up of amyloid to a degree that it causes damage to the tissues or action of those tissues in the body. Amyloidosis is a disease caused by the abnormal accumulation of protein molecules in body tissues. These proteins are fragments of immunoglobulin (antibody) molecules which are normally present in the blood to give protection against bacteria and other infectious agents. Normally, antibody molecules are constantly being synthesized by cells of the immune system and then, after a finite life span, degraded so that there is a balance between production and degradation. In this way our active immune system protects our bodies from a constantly changing array of infectious bacteria and viruses. In primary amyloidosis a defect occurs in the immune system. Excessive amounts of certain antibody molecules are produced and fragments of these molecules get deposited in tissues. These tissue deposits, as they enlarge, damage normal tissues and cause the disease that we know as primary amyloidosis.

Amyotrophic {A-MY-A-trow-fic} lateral sclerosis {SKLer-row-sis}, ALS: Also known as Lou Gehrig's disease and motor neuron disease. It is a rapidly progressive and fatal disease of the motor neurons in the spinal cord and lower brain that control the voluntary muscles throughout the body. As these motor neurons die, the ability of the brain to control muscle movement is lost. There is a progressive loss of motor function. Speech and swallowing are often affected. Intellect is not affected. It can occur in either sex, usually first detected in mid to late adulthood. In most cases, the cause is unknown and at the present time, there is no treatment or cure. **

Anaesthesia (or Anesthesia) {ann-S-these-e-ah}: a partial or complete loss of sensation or feeling, especially of pain. *
Also: Anesthesia: Loss of feeling resulting from the administration of drugs or gases. #

Anaesthetic (or Anesthetic) {ann-AS-thet-tic}: An anaesthetic is a substance that makes you unable to feel pain. A general anaesthetic is a drug which causes unconsciousness (for example, those used in an operation). A local anaesthetic causes loss of feeling just in one part of the body (as in having a tooth filled). People with neuromuscular disorders pose special risks for having a general anaesthetic, but preparation minimizes the dangers. *

Analgesic {ann-AL-geez-ic}: Simply put, analgesics are a class of drugs used to relieve pain. The pain relief induced by analgesics occurs either by blocking pain signals going to the brain or by interfering with the brain's interpretation of the signals, without producing anesthesia or loss of consciousness. There are basically two kinds of analgesics: non-narcotics and narcotics.
Non-Narcotic Analgesics: Acetaminophen is the most commonly used over-the-counter, non-narcotic analgesic.
Narcotic Analgesics: There are two types of narcotic analgesics: the opiates and the opioids (derivatives of opiates). Opiates are the chemicals (alkaloids) found in opium (a white liquid extract of the unripe seeds of the poppy plant).
Opioids are any medication which bind to opioid receptors in the central nervous system or gastointestinal tract. There are four broad classes of opioids:
-Endogenous opioid peptides (produced in the body - endorphins, dynorphins, enkephalins)
-Opium alkaloids (morphine, codeine, thebaine)
-Semi-synthetic opioids (heroin, oxycodone, hydrocodone, dihydrocodeine, hydromorphone, oxymorphone, nicomorphine)
-Fully synthetic opioids (pethidine or Demerol, methadone, fentanyl, propoxyphene, pentazocine, buprenorphine, butorphanol, tramadol, and more)
Opioids are used in medicine as strong analgesics, for relief of severe or chronic pain. Interestingly, there is no upper limit for the dosage of opioids used to achieve pain relief, but the dose must be increased gradually to allow for the development of tolerance to adverse effects (for example, respiratory depression). According to eMedicine, "Some people with intense pain get such high doses that the same dose would be fatal if taken by someone who was not suffering from pain.
Examples of Analgesics:
Acetaminophen (Tylenol) Acetaminophen, with brand names such as Tylenol, Panadol, Tylenol Arthritis and Excedrin is one of the safest analgesic painkillers used for arthritis pain relief. The medication is often used in combination with other drugs. Acetaminophen is the most commonly used over-the-counter, non-narcotic analgesic.
Codeine (Tylenol #2,3,4)
Darvocet (Propoxyphene/Acetaminophen)
Darvon (Propoxyphene)
Duragesic (Fentanyl Patch)
Hydromorphone (Palladone, Dilaudid)
Morphine (MSContin, Oramorph)
Oxycodone (OxyContin, Roxicodone)
Percocet (Oxycodone/Acetaminophen)
Percodan (Oxycodone/Aspirin)
Talwin NX (Pentazocine/Naloxone)
Ultracet (Tramadol/Acetaminophen)
Ultram (Tramadol)
Vicodin (Hydrocodone/Acetaminophen)

Analog (Analogue): (1) A chemical compound or agent that is similar to another in structure yet differs concerning a particular element; it may have a similar or different mode of action. (2) A tissue, organ, or other bodily structure that has the same function or organization as another yet has a different evolutionary origin.

Anaphylatoxin: Substance capable of releasing histamine from mast cells.

Anaphylaxis: Immediate hypersensitivity response to antigenic challenge, mediated by IgE and mast cells. It is a life-threatening allergic reaction, caused by the release of pharmacologically active agents.

Anaplastic {an-ah-PLAS-tik}: A term used to describe cancer cells that divide rapidly and bear little or no resemblance to normal cells. #

Anastomosis {an-as-to-MO-sis}: A procedure to connect healthy sections of the colon or rectum after the cancerous portion has been surgically removed. #

Androgen {AN-dro-jin}: A hormone that promotes the development and maintenance of male sex characteristics. #

Anecdotal {AN-eck-dote-ill} evidence: This refers to individual patients saying how they feel, saying they feel better or worse after some sort of treatment. Anecdotal evidence is usually not considered "scientific" because it relies on the person's perception and this is often not reliable. When a disease is very common, it is easier to conduct "scientific" research and anecdotal evidence is largely irrelevant to Doctors and researchers. However, a researcher tying to learn about a rare disease affecting only a few people would have to rely more on anecdotal evidence. Also, anecdotal evidence may have to be used more in disorders where they are no clinical tests developed. Often, a clinical measure of some disease symptom is used to help diagnose the disorder. If tests have not been developed, Doctors have to rely more on the individual's own statements. *

Anemia {a-KNEE-me-ah}: A condition caused by a decrease in the number of circulating red blood cells. This decrease can be a side effect of chemotherapy that depresses the bone marrow. May cause symptoms including tiredness, shortness of breath, and weakness.

Aneuploidy {A-NEW-ploy-dee}: Normally humans have 46 chromosomes. In aneuploidy, there are abnormal numbers of chromosomes (too many or too few). (i.e. Down syndrome, Turner syndrome). %

Angiogenesis: The production of blood vessels. Cancer tumors"create" blood vessels to supply themselves with nutrients. Anticancer drugs that stop angiogenesis are under development. *

Angiogram {AN-jee-o-gram}: An X-ray of blood vessels. A dye is injected into an artery to outline the blood vessels on the X-ray picture. Also called an arteriogram {ar-TEER-ee-o-gram}. #

Ankle Foot Orthosis (AFO): A medical device commonly constructed of a plastic-like material used to maintain or stabilize the ankle joint position. *

Annotation (of the genome): Once a gene base sequence has been determined for a chromosome, it is annotated. The information about what specific sequences encode what proteins is linked to the code and gene labels are ascribed to sections of code.

Anorexia {an-o-REX-ee-ah}: A lack of appetite; no desire for food. #

Anoxia {an-OX-ee-ah}: Absence or lack of oxygen. **

Antagonist: (1) A drug that blocks a receptor, preventing stimulation. (2) A muscle whose contraction opposes an intended movement.

Antagonist muscles: Muscles that are attached in such a way that when they contract, they develop forces that oppose each other. *

Anti-inflammatory: a substance that soothes inflammation or reduces the inflammatory response of the tissue directly. Anti-inflammatories work in a number of different ways, but rarely inhibit the natural inflammatory reaction. *

Antiandrogens {an-tee-AN-dro-jens}: Drugs used to block the production or interfere with the action of male sex hormones.

Antibiotic: A biochemical substance, produced particularly by mold fungi, employed in combating infection, especially by bacteria. Penicillin, produced by strains of the mold Penicillium notatum, is the most widely used antibiotic. *

Antibiotic resistance. The ability of a microorganism to produce a protein that disables an antibiotic or prevents transport of the antibiotic into the cell.

Antibody (Ab): a soluble protein molecule produced and secreted by B cells in response to an antigen, which is capable of binding to that specific antigen. The synthesis, or manufacture, of antibodies is initiated when a foreign substance, referred to as an antigen, enters the body. Lymphocyte cells respond to the foreign substance by making an antibody with a molecular arrangement that fits the shape of molecules on the surface of the foreign substance so that the antibody combines with it. Common antigens are the protein components of bacteria and viruses. Antigens may enter the body during infection or may be deliberately introduced by vaccination (Immunization) in order to stimulate the production of antibodies. The binding of antibodies to the surfaces of bacteria, viruses, or toxins can neutralize and eliminate these harmful substances. Animals do not have antibodies to substances to which they have not been previously exposed, but one animal is able to produce enough different kinds of antibodies to fit the molecular arrangement of any foreign substance it is likely to encounter. In diseases such as multiple sclerosis and systemic lupus erythematosus, the body mistakenly makes antibodies against its own normal tissue components (Autoimmune Diseases).
In simple terms:
-the antigen is the virus (invader)
-the antibody is our immune response to the antigen (and our immunity to future exposures to the virus). *

Antibody-dependent, cell-mediated cytotoxicity (ADCC): A phenomenon in which target cells, coated with antibody, are destroyed by specialized killer cells (NK cells and macrophages), which bear receptors for the Fc portion of the coating antibody (Fc receptors). These receptors allow the killer cells to bind to the anti-body-coated target.

Anticholinergics: Drugs that block the action of acetylcholine, a neurotransmitter whose effects oppose dopamine. By blocking acetylcholine's action, these drugs increase dopamine's ability to control movement.

Anticholinesterase Medications: Medications suppressing the function of the enzyme, acetylcholinesterase (AChE), which is essential in controlling normal nerve impulses, hence the name anticholinesterase. Anti-cholinesterase medications are used to provide symptomatic relief (but do not address the causes) of myasthenia gravis. The enzyme, AChE is found in nervous tissue, red blood cells and muscles. The suppression of this enzyme can eventually lead to spasms and convulsions and finally to paralysis and death. Also used as a method of insecticide - the action of anticholinesterase is the same in insects and mammals, but insects are far more sensitive. **

Anticipation: The phenomenon of increased severity and earlier onset of genetic disease when a mutation is transmitted from one generation to the next. ***

Anticoagulant: A substance or drug that causes blood to clot; Heparin is an example. #

Anticodon. A nucleotide base triplet in a transfer RNA molecule that pairs with a complementary base triplet, or codon, in a messenger RNA molecule.

Anticonvulsant {an-ti-kon-VUL-sant}: Medicine to stop, prevent, or control seizures (convulsions). #

Antiemetic {an-tee-eh-MET-ik}: A medicine to prevent or relieve nausea or vomiting. #

Antifungal agent: A drug used to treat fungal infections. ##

Antigen: any substance that evokes the production of an antibody when introduced into the body of an animal. Antigens can enter the body through the respiratory tract, digestive tract, skin, or blood vessels. The most common antigens are proteins such as those found in bacteria and viruses. Also: Antigen: Molecule that can bind specific antibodies or lymphocytes of the immune system. An antigen is immunogenic if it can generate an immune response. An autoantigen is a self-antigen.

Antigen-binding site: The part of an immunoglobulin molecule that binds antigen specifically.

Antigen-presenting cell (APC): A specialized type of cell, bearing cell surface class II MHC (major histocompatibility complex) molecules, involved in processing and presentation of antigen to inducer, or helper , T cells. Examples: macrophage, dendritic cells.

Antigen receptor: The specific antigen-binding receptor on T or B lymphocytes; these receptors are transcribed and translated from rearrangements of V genes.

Antigenic determinant: A single antigenic site or epitope on a complex antigenic molecule or particle.

Antigen processing: Large molecules are broken down (processed) within macrophages into peptides and presented within the groove of MHC molecules.

Antigenic switching. The altering of a microorganism's surface antigens through genetic rearrangement, to elude detection by the host's immune system.

Antineoplastic agent: A drug that prevents, kills, or blocks the growth and spread of cancer cells. ##

Antimicrobial agent. Any chemical or biological agent that harms the growth of microorganisms.

Antioxidants: Agents that inhibit or neutralize potentially harmful compounds known as free radicals. Free radicals are produced during metabolic activity. High levels of free radicals may eventually lead to impaired functioning and destruction of neurons and other bodily cells. Certain antioxidants are thought to neutralize free radicals before cellular damage occurs.

Anti-rheumatic Drugs: The major classes of drugs used to treat rheumatoid arthritis include:
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs). Drugs belonging to this class bring symptomatic relief of both inflammation and pain, but have a limited effect on the progressive bone and cartilage loss associated with rheumatoid arthritis. They act by slowing the body's production of prostaglandins. Common NSAIDs include: aspirin, ibuprofen (Advil, Motrin, Nuprin, Medipren), naproxen (Naprosyn, Aleve) and indomethacin (Indocin). NSAIDs also include a new class of prescriptions medicines known as COX-2 inhibitors like Celebrex®.
Corticosteroids. These drugs are very powerful anti-inflammatory agents. They are the synthetic analogs of cortisone, produced by the body. Corticosteroids are used to reduce inflammation and suppress activity of the immune system. The most commonly prescribed are prednisone and dexamethasone.
Disease Modifying Anti-Rheumatic Drugs (DMARDs). DMARDs influence the disease process itself and do not only treat symptoms, hence their name. DMARDs also have anti-inflammatory effects, and most were borrowed from the treatment of other diseases, such as cancer and malaria. Antimalarials DMARDs include chloroquine (Aralen) and hydroxychloroquine (Plaquenil). Powerful DMARDs include: methotrexate (Rheumatrex), sulfasalazine, cyclosporine, azathioprine (Imuran) and cyclophosphamide (Cytoxan), azathioprine, sulfasalazine, penicillamine, and organic gold compounds such as aurothioglucose (Solganol), gold sodium thiomalate (Aurolate) and auranofin (Ridaura).
Slow-Acting Antirheumatic Drugs (SAARDs). SAARDs are a special class of DMARDs and the effect of these drugs is slow acting and not so quickly apparent as that of the NSAIDs. Examples are hydroxychloroquine and aurothioglucose.
Immunosuppresive cytotoxic drugs. This class of drugs is used if treatment with NSAIDs and SAARDs have no effect. Immunosuppresive drugs have a stabilizing effect on the immune system. Since the inflammation associated with chronic arthritis is due to malfunctions of the immune system, use of this class of drugs has been shown to be beneficial for the treatment of rheumatoid arthritis as well. Examples are: methotrexate, mechlorethamine, cyclophosphamide, chlorambucil, and azathioprine.

Antisense: Antisense is an adjective referring to the DNA strand that is not normally transcribed or to the RNA that is complementary to it. The DNA antisense strand is complementary to the DNA "sense" strand that is normally transcribed. The antisense DNA strand is not transcribed to make mRNA. An antisense RNA is complementary to the mRNA that is transcribed from the DNA "sense" strand.

Antisense mRNA: An approach used to turn selected genes off (gene silencing, Gene knockdown or Gene knockout ). Antisense mRNA is an exogenous (manmade) mRNA transcript that is complementary to endogenous mRNA (the mRNA in the cell). The antisense stand is the noncoding strand complementary to the coding sequence of mRNA. Introducing a transgene coding for antisense mRNA is a strategy used to block expression of a gene of interest. Messenger RNA (mRNA) is normally single-stranded. Its sequence of nucleotides is called "sense" because it results in a gene product (protein). Normally, its unpaired nucleotides are "read" by transfer RNA anticodons as the ribosome proceeds to translate the message into protein. When mRNA forms a double strand (dsRNA) with a complementary antisense RNA sequence, translation is blocked. It is now clear that the dsRNA triggeres the RNAi response. Antisense RNA is being looked at as a possible therapy for diseases, for example, antisense RNA that is complementary to the proto-oncogene BCL-2 is being examined as a possible therapy for certain B-cell lymphomas and leukemias. See RNA interference (RNAi).

Antisense oligodeoxynucleotides (ODNs) are synthetic molecules that, because they are antisense, block mRNA translation. Antisense ODNs are synthesized in the hope that they can be used as therapeutic agents to block disease processes by blocking the synthesis of a particular protein. This would be achieved by the binding of the ODN to the mRNA from which that protein is normally synthesized. One type has been approved for human therapy: The U. S. FDA has approved fomivirsen (Vitravene ) for use against CMV infections of the eye. Fomivirsen is an antisense ODN that degrades the mRNA of two essential viral proteins.

Antiserum Blood serum containing specific antibodies against an antigen. Antisera are used to confer passive immunity to many diseases.

Antispasmodic: antispasmodics are medications that ease cramps in smooth and skeletal muscles. *

Aphagia {a-PHAGE-gee-ah}: Difficulty or inability to swallow. **

Aphasia {a-PHASE-ee-ah}: Total or partial loss of the ability to use or understand words. **

Apheresis: {ah-FAIR-ah-sis} or {AH-fur-RHEE-sis} Any procedure in which blood is drawn from a donor or patient and a component (platelets, plasma, or white blood cells) is separated out, the remaining blood components being returned to the body. *

Apnea {ap-KNEE-ah}: Cessation of breathing. **

ApoE genotype: A susceptibility gene that contributes to the risk of developing Alzheimer's disease. ***

Apolipoprotein E (ApoE) {APP-poe-lip-poe-protein}: a plasma protein involved in the transport of cholesterol and other hydrophobic [don't like water] molecules. Certain forms of apolipoprotein E have been linked to disorders of cholesterol metabolism and coronary heart disease. Interestingly, ApoE-4 is also a major risk factor for Alzheimer's disease. *

Apoptosis {ap-POP-toe-sis}: Cell death due to a programmed pattern of gene expression; a form of cell death in which certain enzymes activate to degrade DNA within the nucleus, resulting in cellular degeneration and loss. Cells may die from various causes. For example, by injury. Science now understands that cells are also programmed for a given life-span and that there are mechanisms within the cell designed to end its life. This process is often called programmed cell death (PCD). Programmed cell death is also called apoptosis. It is now well recognized that apoptosis is essential in many aspects of normal development and is required for maintaining tissue homeostasis (balance). Failure of cells to properly regulate apoptosis can have catastrophic consequences. Cancer and many diseases (AIDS, Alzheimer's disease, Parkinson's disease, heart attack, stroke, etc.) are thought to arise from deregulation of apoptosis (either turned off or turned on too soon). *

Apraxia: Loss of the ability to sequence, coordinate, and execute certain purposeful movements and gestures in the absence of motor weakness, paralysis, or sensory impairments. Apraxia is thought to result from damage to the cerebral cortex, such as due to stroke, brain tumors, head injury, or infection. It may also occur as a result of impaired development of the cortex as in certain neurodevelopmental disorders, including Rett syndrome. Apraxia may affect almost any voluntary movements, including those required for proper eye gaze, walking, speaking, or writing.

Archimedes spirals: a relatively simple test used to evaluate tremor severity. During this test, the patient is asked to draw increasingly wider circles on a piece of paper.

Areflexia: Absence of reflexes. ***

Arrhythmia {a-rith-ME-ah}: An irregular heartbeat. ##

Arterial Blood Gases: A measure of the oxygen and carbon dioxide levels in the bloodstream. **

Arthrogryposis {Arthro-grig-posis} Multiplex Congenita: A syndrome characterized by multiple joint contractures, present at birth. It is a non-progressive syndrome where muscles are poorly developed. Both sides of the body are affected equally. The senses are not involved. The cause is unknown. **

Arthrogyrposis {Arthro-grig-posis}: Fixation of a joint in a flexed or contracted position; may be due to adhesions in or around the joint. ***

Artifact: a peculiar test or experimental result which is due to some unusual detail (often a mistake) in the procedure which invalidates the usual interpretation of the test or experiment. *

Artificial insemination: The placement of sperm into a female reproductive tract or the mixing of male and female gametes by other than natural means.
One common method is IN VITRO FERTILIZATION (IVF), sperm and eggs are joined in a test tube, and the resulting embryo is inserted into the female for implantation.

Ascites {a-SYE-teez}: Abnormal buildup of fluid in the abdomen. #

Ase. As a suffix, words ending in -ase are usually enzymes. *

Aspiration {as-per-AY-shun}: Removal of fluid from a lump, often a cyst, with a needle. #

Aspiration Pneumonia: Inflammation of the lungs as a result of inhaling food particles or other foreign matter. **

Assisted Cough: Application of pressure to the abdomen to strengthen the cough. **

Association Studies: An approach to gene mapping that looks for associations between a particular disease phenotype and allelic variation.

Asterixis: involuntary, jerking or flapping movements, especially of the hands. Extending the patient's arm with the wrist bend in a backward position may induce this form of tremor, which may be associated with advanced liver disease.

Astrocyte {as-tro-sight}: One of the brain cells that supports the nervous tissue. A type of glial cell. Glial cells are the connective tissue cells of the central nervous system (CNS), serving as the supportive structure that holds together and protects neurons. Astrocytes are relatively large glial cells with thread-like projections that connect with neurons and small blood vessels (capillaries). These projections form part of the so-called "blood-brain barrier." This barrier slows or prevents the passage of unwanted substances, such as harmful chemicals, infectious agents, etc., from the bloodstream into the brain. Astrocytes also accumulate in areas where nerves have been damaged (astrocytosis), sealing off these areas. An excess of astrocytes in damaged areas of the CNS is known as gliosis.

Astrocytoma {as-tro-sy-TO-ma}: A type of brain tumor #

Astrocytosis: The spread of astrocytes into damaged tissue. *

Asymmetric {a-sim-met-trick}: Referring to lack of symmetry; usually affecting only one side of the body. ***

Asymmetric division: Generation of distinct fates in progeny from a single mitosis. Oriented division may position daughter cells in different microenvironments or intrinsic determinants may be segregated into only one daughter. Observed in some but not all stem cells and can occur in other types of progenitor cell.

Asymptomatic {eh-sym-TOE-matic}: Without discernible symptoms. **

Ataxia {a-TAX-ee-a}: A condition characterized by an impaired ability to coordinate voluntary movements. Ataxia may result from damage to the cerebellum, cerebellar pathways, or the spinal cord due to various underlying disorders, conditions, or other factors. These may include infection, head injury, stroke, brain tumors, neurodegenerative disorders, alcohol or drug intoxication, or certain hereditary diseases (e.g., Friedreich's ataxia, ataxia-telangiectasia). Associated symptoms may vary, depending upon the site of damage within the central nervous system. However, the condition is often characterized by incoordination, postural imbalance, and a lurching, unsteady manner of walking (gait). Additional findings may include slurred speech (dysarthria); rapid, involuntary, rhythmic eye movements (nystagmus); and/or other abnormalities.
Defective muscular coordination, esp. that manifested when voluntary muscular movements are attempted. *** See: National Ataxia Foundation: http://www.ataxia.org/
Also: Shaky movements and unsteadiness. It results from a failure of the brain to regulate and coordinate posture and muscle movements. **

Ataxia Telangiectasia: A hereditary, progressive disease, transmitted as an autosomal recessive trait. In addition to ataxia, it is associated with vascular lesions of the skin and eye, frequent respiratory infections, abnormal movements of the eyes and immune system disorders. ** A hereditary, progressive disorder that typically becomes apparent in early childhood and is characterized by increasing neurodegenerative changes of the cerebellum, a brain region involved in producing coordinated voluntary movements, sustaining balance, and maintaining proper posture. Associated symptoms typically include delayed motor development; an unsteady, awkward manner of walking; drooling; impaired articulation of speech (dysarthria); dependence on thrusts of the head to achieve proper focusing of the eyes; and involuntary, rapid, jerky eye movements (nystagmus). Affected children may also develop involuntary, "shock-like" muscle spasms (myoclonus); sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); or irregular, jerky, relatively rapid involuntary movements (chorea). AT is also typically associated with permanent widening (dilation) of groups of blood vessels (telangiectasias), particularly in sun-exposed skin regions of the face and the transparent membranes covering the whites of the eyes. In addition, AT is characterized by deficient functioning of the immune system (immunodeficiency), leading to recurrent respiratory and skin infections and an increased risk of certain malignancies (e.g., certain leukemias or lymphomas). The disorder, which is transmitted as an autosomal recessive trait, is thought to result from defective repair of DNA.

Ataxia of Charlevoix-Saguenay: An autosomal recessive disorder with symptoms appearing in the first few months of life. It is slowly progressive, affecting nerve cells. Frequent falls and loss of balance are noted early. A mobility aid is usually required between the ages of 25 and 40. It has no effect on either intelligence or life expectancy. **

Ataxic gait {ah-TAK-sik}: Awkward, uncoordinated walking. #

ATG or AUG: The codon for methionine; the translation initiation codon. Usually, protein translation can only start at a methionine codon (although this codon may be found elsewhere within the protein sequence as well). In eukaryotic DNA, the sequence is ATG; in RNA it is AUG. @@

Athetosis: Involuntary, relatively slow, writhing movements that essentially flow into one another. Athetosis is often associated with chorea, a related condition characterized by involuntary, rapid, irregular, jerky movements. Although athetosis may be most prominent in the face, neck, tongue, and hands, the condition may affect any muscle group. Athetosis may occur in association with certain neurodegenerative diseases, such as Huntington's or Wilson's disease, or cerebral palsy (CP). It may also result from infections affecting the brain or the use of particular medications.

ATP: see adenosine triphosphate.

Atrophy: Atrophy: From the Greek words a, meaning not, and trophe = nourishment. Definition: a decrease in the size of an organ or tissue (wasting). Common causes of diseases involving muscle atrophy are a lack of nutrients or blood supply or loss of signals from nerve cells.
Wasting away or loss of a cell, tissue, or organ due to disease, malnutrition, insufficient blood supply, or other causes, such as loss of skeletal muscle mass due to peripheral nerve damage. The tissue usually shrinks (gets smaller) and its function is usually impaired as the amount of atrophy increases. Various diseases can cause atrophy.

Atopy: A term used by allergists to describe IgE-mediated anaphylactic responses in humans, usually genetically determined.

Attenuated: weakened; no longer infectious (an attenuated virus used as a vaccination).

Atypical: Irregular; not standard or characteristic; not conforming to type.

Atypical cell: Mild to moderately abnormal cell. #

Atypical hyperplasia {hy-per-PLAY-zha}: A benign condition in which tissue has certain abnormal features. This condition increases the risk of cancer. #

Auditory: Pertaining to the sense of hearing or the organs involved in hearing.

Augmentation: A phenomenon that may occur as a result of the use of certain medications (particularly levodopa). Augmentation is characterized by the emergence of worsening symptoms earlier in the day (e.g., early evening, afternoon, or morning). Many people who take levodopa and some who take other dopamingeric agents develop augmentation, especially those who have severe symptoms or are taking high doses of the drug.

Autoantibody: An antibody that attacks molecules or cells or tissues of their own body. *

Autoantigen: An autoantigen is a self-antigen.

Autograft: A tissue transplant from one area to another on a single individual.

Autoimmune Disease: A disease that results when the immune system mistakenly attacks the body's own tissues. Reumathoid arthritis and systemic lupus erythematosus are autoimmune diseases. The body's immune system normally makes proteins called antibodies to protect the body against viruses, bacteria, and other foreign materials. These foreign materials are called antigens. In an autoimmune disorder such as lupus, the immune system loses its ability to tell the difference between foreign substances (antigens) and its own cells and tissues. The immune system then makes antibodies directed against "self." These antibodies, called "auto-antibodies," react with the "self" antigens to form immune complexes. The immune complexes build up in the tissues and can cause inflammation, injury to tissues, and pain. Includes diseases such as: rheumatoid arthritis, multiple sclerosis, lupus, and Graves' disease. *

Autoimmunity: A condition in which the body's immune system mistakenly fights and rejects the body's own tissues. Autoimmunity (autoallergy): An immune response to "self" tissues or components. Such an immune response may have pathological consequences leading to autoimmune diseases.

Autologous {aw-TOL-o-gus}: From the same person. An autologous blood transfusion is blood removed and then transfused back to the same person at a later date. #

Autonomic nervous system: the part of the nervous system that is concerned with the control of involuntary bodily functions. It regulates the function of glands, especially the salivary, gastric, and sweat glands, and the adrenal medulla; smooth muscle tissue, and the heart. The autonomic nervous system may act on these tissues to reduce or slow activity or to initiate their function. *

Autophagy and the ubiquitin/proteasome system comprise the cell's garbage disposal systems. Autophagy or autophagocytosis, is a process of sequestering organelles and long-lived proteins in a double-membrane vesicle inside the cell, where the contents are subsequently delivered to the lysosome for degradation. Autophagy is part of everyday normal cell growth and development. Its main purpose is to maintain a balance between biogenesis (production) of cell structures, and their degradation and turnover (see Bruce Alberts et al.: Molecular biology of the cell, 4th edition, Garland Publishing 2002, NCBI Bookshelf). For example, a liver-cell mitochondrion lasts around ten days before it is degraded and its contents are reused. Autophagy also plays a major role in the destruction of bacteria, viruses, and unnecessary proteins that have begun to aggregate within a cell and may potentially cause problems. It is especially prominent in insects that undergo complete metamorphosis; larval tissue is recycled to become appendages in an adult insect. The rate of autophagy increases when the cell is subjected to nutrient deprivation, and also when it receives stimuli that result in organelle proliferation. When autophagy involves the total destruction of the cell, it is called autophagic cell death (also known as cytoplasmic cell death or type II cell death). This is one of the main types of programmed cell death. As such, it is a regulated process of cell death in a multicellular organism, or in a colony of individual cells such as yeast (see Daniel J. Klionsky and Scott D. Emr: "Autophagy as a Regulated Pathway of Cellular Degradation", Science Vol. 290 p.1717, 1 Dec. 2000). Autophagy can be further separated into two types: macroautophagy and microautophagy. Macroautophagy involves the formation of a membrane containing target materials moving into the lysosome/vacuole while microautophagy is the invagination of the lysosome/vacuole of target materials. Although both micro and macroautophagy serve as fundamental functions in plants and metazoa (multicellular animals), as well as in other eukaryotes such as slime moulds and yeast. Cytoplasmic autophagy is different from other methods of protein degradation, i.e. Polyubiquitination. The the ubiquitin/proteasome system breaks down ubiquitinated proteins, but it may not recognize misfolded proteins and protein aggregates. In contrast to the specificity of the proteasome, the autophagosome engulfs entire cellular pockets, including the cytoplasm and organelles. Then it fuses with a lysosome, and its cellular contents are degraded and recycled. Autophagy has been implicated in a range of disorders and hence is of major interest, for example, data indicate that autophagy is necessary for the disposal of neurotoxic protein aggregates. In later stages of neurodegenerative disorders, including Huntington disease, Alzheimer disease and Parkinson disease, protein aggregates may overwhelm endogenous autophagy, leading to neuronal cell death.

Autopoiesis {Auto-poe-EE-AH-sis}: 'auto' meaning 'self', and 'poiesis' meaning (roughly) 'creation' or 'production'. Self-production. A system is Autopoietic if the bits and pieces of which it is composed interact with each other in such a way as to continually produce and maintain that set of bits and pieces and the relationships between them.

Autosome: Any paired chromosome that is not a sex chromosome (an X or Y). Humans have 22 pairs of autosomes. They are identical in both males and females. Each pair of autosomes (one from the father, one from the mother) carries genes for the same traits. Autosomes plus the sex chromosomes make up the entire genome of humans, for males, 22 pairs of autosomes plus an XY sex pair, for females, the same 22 pairs of autosomes plus an XX sex pair. **

Autosomal dominant trait: Human traits, including an individual's eye color, hair color, or expression of certain diseases, result from the interaction of one gene inherited from the father and one gene from the mother. In autosomal dominant disorders, the presence of a single copy of a mutated gene may result in the disease. In other words, the mutated gene may dominate or "override" the instructions of the normal gene on the other chromosome, potentially leading to disease expression. Individuals with an autosomal dominant disease trait have a 50 percent risk of transmitting the mutated gene to their children.

Autosomal recessive trait: Human traits, including an individual's hair color, specific blood group, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. With autosomal recessive disorders, two copies of the disease gene must be inherited in order for an individual to potentially develop the disease. If both the mother and father carry a copy of the disease gene, each child has a 25 percent risk of inheriting the two genes for the disease. There is a 50 percent risk that their children may inherit one copy of the disease gene and be carriers for the disease trait (heterozygous carriers). In addition, there is a 25 percent chance that the parents' offspring will inherit two normal copies of the gene and will not develop the disorder nor be carriers for this disease trait.

Autoradiograph: A photographic picture showing the position of radioactive substances in tissues.

Avidity: The summation of multiple affinities, for example when a polyvalent antibody binds to a polyvalent antigen.

Axilla {ak-SIL-a}: The underarm. #

Axillary nodes: Lymph nodes - also called lymph glands - found under the armpit (axilla). ##

Axillary lymph node dissection: Surgical removal of lymph nodes found in the armpit region. #

Axons: Nerve fibers. Axons are the relatively slender extensions of neurons that transmit nerve impulses away from nerve cell bodies. The ends of the axons or "terminals" release chemical substances known as neurotransmitters, enabling the transmission of nerve impulses to other neurons or effector organs. The whitish, fatty, protein-containing substance called myelin forms an insulating, protective, cylindrical sheath around some axons, serving to increase the speed and efficiency of nerve impulse transmissions.

Axonal {AXE-on-al}: Referring to an axon, which is the part (called a process) of a neuron that conducts impulses away from the cell body. ***

B lymphocyte (B cell): The precursors of antibody-forming plasma cells; these cells carry immunoglobulin and class II MHC (major histocompatibility complex) antigens on their surfaces.

Basophil: A polymorphonuclear leukocyte., whose basophils granules contain heparin, histamine and other vasoactive amines. Within tissues, these cells are known as mast cells q.v.

Babinski's Reflex: A reflex where the great ("big") toe flexes toward the top of the foot and the other toes fan out when the sole of the foot is firmly stroked; normal in children but abnormal after about 2 years old. In people more than 2 years old, the presence of a Babinski's reflex generally indicates damage to the nerve paths connecting the spinal cord and the brain (the corticospinal tract). *

BAC: An acronym for 'Bacterial Artificial Chromosome'

Bacillus. A rod-shaped bacterium.

Bacillus thuringiensis (Bt). A bacterium that kills insects; a major component of the microbial pesticide industry.

Baclofen: A mainstay of antispastic drug therapy, baclofen is a GABA agonist that stimulates the GABAB autoreceptor. When stimulated, this autoreceptor inhibits muscle activity. In experimental systems, baclofen inhibits the release of noradrenaline, and acetylcholine from peripheral nerve endings, and acetylcholine, noradrenaline, dopamine, serotonin, and glutamate from CNS neurons.

Bacterial Artificial Chromosome (BAC): A vector used to insert DNA fragments (100- to 300-kb insert size; average, 150 kb) in Escherichia coli cells. Based on naturally occurring F-factor plasmid found in the bacterium E. coli. BACs are constructed that carry DNA from humans or mice or wherever, and the BAC is inserted into a host bacterium. As with the plasmid, when that bacterium is grown, the BAC is replicated as well. Huge pieces of DNA can be easily replicated using BACs - usually on the order of 100-400 kilobases (kb). Using BACs, scientists have cloned (replicated) major chunks of human DNA. BACs can hold up to 300,000 base pairs. In the human genome, human DNA was cut into fragments of 100,000 to 200,000 base pairs using restriction enzymes. The fragments were cloned into BACs and inserted into bacteria which stored and replicated the DNA so it could be obtained in large enough quantities to be sequenced. It took about 20,000 BAC clones to hold the human genome. Also see YAC.

Bacteriocide. A class of antibiotics that kills bacterial cells.

Bacteriophage (phage or phage particle). A virus that infects bacteria. Altered forms are used as vectors for cloning DNA.

Bacterium: A microscopic organism composed of a single cell (not always infectious).

Balanced translocation: A balanced translocation is a condition in which the correct number of chromosomes are present, but two pieces of chromosomal material have switched places. A person who has a balanced translocation is often called a "carrier". The individual who has a balanced translocation usually appears completely normal and healthy, but when a carrier attempts to have children, that is when problems are encountered. Those who have a balanced translocation are plagued by infertility, repeated miscarriages, and their offspring are at an increased risk for birth defects and chromosomal abnormalities. The risk of abnormal offspring is approximately 10 to 15 percent, regardless of which parent has the balanced translocation. When a person who carries a balanced translocation has children it is possible that the egg or sperm may have an unbalanced distribution of the genetic material. This is usually in the form of a loss of genetic material, called a monosomy and a gain of genetic material, which is a trisomy. It is also possible that the child would have a normal arrangement of chromosomes or also that they would also have a balanced translocation. However the risks of having a child with a chromosomal disorder are greatly increased.

Ballismus: An abnormal neuromuscular condition that is generally considered a severe form of chorea. Involvement of the upper muscles of the arms and legs results in uncontrolled, violent, flinging or throwing actions. These swinging or jerky movements may be sporadic or continuous and, in some patients, restricted to one side of the body (hemiballismus). Ballismus often occurs in association with other abnormal involuntary movements, including athetosis, chorea, and dystonia.

Barium enema: The use of a milky solution (barium sulfate): given by an enema to allow X-ray examination of the lower intestinal tract. ##

Barium solution {BA-ree-um}: A liquid containing barium sulfate that is used in X-rays to highlight parts of the digestive system. #

Barium swallow: The use of a milky solution (barium sulfate), given orally to allow X-ray examination of the upper intestinal tract. ##

Barr body: The condensed single X chromosome seen in the nuclei of somatic cells of female mammals.

Base pair: a pair of hydrogen-bonded nitrogenous bases (one purine and one pyrimidine) that join the component strands of the DNA double helix.

Basal ganglia (brain): Cells of the basal ganglia, deep within the brain, govern coordination. Specialized nerve cell clusters of gray matter deep within each cerebral hemisphere and the upper brainstem, including the striate body (caudate and lentiform nuclei) and other cells groups such as the subthalamic nucleus and substantia nigra. The basal ganglia assist in initiating and regulating movement.

Basal cell carcinoma: The most common type of skin cancer. ##

Base: see nucleotide bases.

Base sequence: The order of nucleotide bases in a DNA molecule. %

Basophil: A white blood cell that contributes to inflammatory reactions. Along with mast cells, basophils are
responsible for the symptoms of allergy.

B cells: Small white blood cells crucial to the immune defenses. Also known as B lymphocytes, they are derived from the bone marrow and develop into plasma cells that are the main source of antibodies.

Becker Muscular Dystrophy (BMD): A chronic, progressive X-linked recessive disorder with symptoms similar to Duchenne. However, the onset of symptoms is later, progression is slower and losses of physical abilities occur later in life. Symptoms are usually first noted in the early teens, and include clumsiness, difficulty running or walking up stairs and frequent falls. **

Bed sores: see pressure sores.

Benign {be-NINE}: Not cancerous; does not invade nearby tissue or spread to other parts of the body. %

Benign growth: A swelling or growth that is not cancerous and does not spread from one part of the body to another. ##

Benign myoclonus of infancy: A neurologic condition that typically becomes apparent by approximately 4 months of age. Affected infants and children experience relatively short, mild episodes of myoclonus, or sudden, involuntary, "shock-like" spasms of muscles, particularly of the head, neck, trunk, and arms. Development is typically normal, and myoclonus usually ceases by age 2 or 3.

Benzodiazepines: A class of medications that act upon the central nervous system to reduce communication between certain neurons, lowering the level of activity in the brain. Benzodiazepines are effective in reducing anxiety, stress, or agitation; promoting sleep; alleviating restlessness; and relaxing muscles.

Beta-adrenergic receptor: a specialized molecular structure on the surface membrane of a neuron that selectively receives the neurotransmitter norepinephrine. Reception of this neurotransmitter causes changes in the neuron that increase its likelihood of "firing" or sending its own signal to other neurons. The activities of norepinephrine affect that part of the nervous system involved in the control of some involuntary body functions, such as blood pressure regulation, etc. (sympathetic nervous system).

beta-DNA. The normal form of DNA found in biological systems, which exists as a right-handed helix.

Bicalutamide: An anticancer drug that belongs to the family of drugs called antiandrogens. %

Bilateral: Having or affecting two sides.

Bioarchaeology: The study of evolution using information about the genome. Areas of study: Study evolution through germline mutations in lineages. Study migration of different population groups based on maternal genetic inheritance. Study mutations on the Y chromosome to trace lineage and migration of males. Compare breakpoints in the evolution of mutations with ages of populations and historical events.

Bioassay: The inoculation of tissue into another animal in order to see if it is infective (if it is, the animal will develop disease). *

Bioinformatics and Computational Biology: Bioinformatics: The science of managing and analyzing biological data using advanced computing techniques. Especially important in analyzing genomic research data.
The use of computers in solving information problems in the life sciences; mainly, it involves the creation of extensive electronic databases on genomes, protein sequences, etc.

Biological drug, "biologicals" or "biological response modifiers": A biological drug differs from a pharmaceutical drug in its gross structure and in the way it is produced. Biological drugs are manufactured utilizing living organisms (mammalian, bacteria, insect or plant cells) to produce a complex molecule, usually protein, and then this molecule is purified through a complex manufacturing process into a form suitable for use. Compared to pharmaceuticals, the complexity of the process required to develop a biologic is far greater. Additionally, since there are many materials of mammalian derivation used in the production of these types of drugs, a substantial cost is incurred in the assurance that potential pathogens (viruses and bacteria) are prevented from entering the production process. This dramatically increases the production costs for biological drugs. Examples of Biologicals: Vaccines, bacterins, and toxoids: prevention against an infectious agent. Antiserum, antitoxins, antibodies, immunoglobulins, and immunostimulants: treatment after exposure to an infectious agent.(i.e. tetanus antitoxin). One class of antirheumatic drugs are proteins derived by bioengineering that influence the inflammatory process. These agents include those directed against important mediators of inflammation including: tumor necrosis factor a (TNF-a) and interleukin-1. Antibodies that bind TNF-a (infliximab, Remicade® or adalimumab, Humira®) and bioengineered receptor molecules (etanercept, Enbrel®) are two examples of anti-TNF therapy. A recombinant human antagonist of another mediator of inflammation, interleukin 1 (IL-1) is also available (anakinra, Kineret®) for treating rheumatoid arthritis. Also contrast with: Pharmaceutical drugs.

Biological therapy {by-oh-LOGIC-kul}: Treatment to stimulate or restore the ability of the immune system to fight infection and disease. Also called immunotherapy. #

Biopsy {BY-op-see}: The removal of a sample of tissue, which is then examined (often under a microscope) to check for abnormal cells. Many illnesses show characteristic changes in tissue that appear on biopsy. Biopsy is considered a very reliable way to diagnose many illnesses. When only a sample of tissue is removed, the procedure is called incisional biopsy; when the whole tumor is removed, it is an excisional biopsy. Removing tissue or fluid with a needle for biopsy is called needle biopsy or needle aspiration. %

Bioremediation: The use of biological organisms such as plants or microbes to aid in removing hazardous substances from an environmental area.

Biosynthesize: To form or produce (during normal physiologic functions) a chemical compound in the body.

Biotechnology: A set of biological techniques developed through basic research and now applied to research and product development. In particular, biotechnology refers to the use by industry of recombinant DNA, cell fusion, and new bioprocessing techniques.

Biphasic: having two distinct stages or phases.

Birefringence of amyloid: {BY-ra-fringe-gence} Birefringence occurs when tissue stained with Congo red is viewed through a crossed polarizing microscope. Birefringence means the amyloid can polarize (split) transmitted light into two beams. Dichromism occurs when the tissue is viewed with polarized light and a green filter. Dichromism means two colour: the amyloid turns from red to green depending on the orientation of the tissue under polarized light. *

Bladder: The hollow organ that stores urine. #

Blastocyst {BLAST-ta-cyst}: After fertilization in the fallopian tube, the egg passes into the womb in the form of a ball of cells called the blastocyst. The blastocyst's outer cells destroy cells of the uterine wall, forming a cavity into which the blastocyst sinks and implants. Also: An early stage of embryonic development that consists of a hollow ball of cells with a localized thickening (the inner cell mass) that will develop into the actual embryo; the remainder of the blastocyst (the outer layer) is composed of trophoblast - the precursor cells of the human placenta.

Blocking antibody: A functional term for an antibody molecule capable of blocking the interaction of antigen with other antibodies or with cells.

Blood count: The amount of white cells, red cells and platelets in a sample of blood drawn from a patient's body. An elevation or decrease in the blood count may indicate infection, anemia, or danger of excessive bleeding from cuts and injuries. #

Blood cells: Cells produced in the bone marrow; they consist of red blood cells, white blood cells, and platelets. ##

Blotting: A technique for detecting one RNA within a mixture of RNAs (a Northern blot) or one type of DNA within of a mixture of DNAs (a Southern blot). A blot can prove whether a given species of RNA or DNA is present, how much is there, and its approximate size. Basically, blotting involves gel electrophoresis, transfer to a blotting membrane (typically nitrocellulose or activated nylon), and incubating with a radioactive probe. Exposing the membrane to X-ray film produces darkening at a spot correlating with the position of the DNA or RNA of interest. The darker the spot, the more nucleic acid was present there. @@

Bone marrow: The spongy material found inside the bones. Blood cells are made in the bone marrow. ##

Bone marrow suppression: A decrease in the production of blood cells. ##

Bone marrow transplantation: A procedure in which doctors replace diseased marrow destroyed by treatment with high doses of anticancer drugs or radiation. The replacement marrow may be taken from the patient before treatment or may be donated by another person. When the patient's own marrow is used, the procedure is called autologous {aw-TOE-LOW-gus} bone marrow transplantation. Allogenic: The infusion of bone marrow from one individual (donor): to another. Syngeneic: The infusion of bone marrow from one identical twin into another. %

Bone scan: A picture of the bones using a radioactive dye that shows any injury, disease, or healing. This is a valuable test to determine if cancer has spread to the bone, if anticancer therapy has been successful, and if affected bony areas are healing. ##

Bone marrow biopsy and aspiration: The procedure by which a needle is inserted into a bone to withdraw a sample of bone marrow. ##

Botulinum toxin (BTX): Any of a group of toxins, designated as A through G, produced by Clostridium botulinum bacteria. Localized injection of minute amounts of commercially prepared BTX may help to relax an overactive muscle by blocking the release of acetylcholine, a neurotransmitter responsible for the activation of muscle contractions. BTX-A is currently the only form (i.e., serotype) of botulinum toxin approved for clinical use. (BTX-A [BOTOX®] is produced by Allergan, Inc. and used in the United States and many other countries. Outside the U.S., it is available as Dysport® from Ipsen, Ltd.) It was originally introduced in the 1970s for the treatment of misalignment of the eyes (strabismus) and involuntary contraction of eyelid muscles (blepharospasm) associated with dystonia or facial nerve disorders. BTX-A is now increasingly being used as a therapeutic option for selected patients with other disorders characterized by severely increased muscle activity (hyperactivity), such as tremor, other focal dystonias, and spasticity. BTX-B is currently under investigation (by Athena Neurosciences, Inc.) for patients with cervical dystonia.

Bovine Spongiform Encephalopathy (BSE): A neurodegenerative disorder of cattle thought to be caused by an abnormal form of the prion protein. Bovine Amyloid Spongiform Encephalopathy (BASE): A newly discovered form of the abnormal prion protein thought to cause Bovine Spongiform Encephalopathy (BSE).

BP: Abbreviation for base pair(s).

Brachytherapy {BRAK-ee-THERE-ah-pee}: Treatment with radioactive sources placed into or very near the tumor; includes surface application, body cavity application (intracavitary), and placement into the tissue (interstitial). Sometimes called internal radiation therapy. #
Also: A procedure in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor Also called internal radiation, implant radiation, or interstitial radiation therapy. *

Bradykinesia: The gradual loss of spontaneous movement; slowness of voluntary movements.

Brain stem: The region of the brain consisting of the medulla oblongata, pons, and midbrain. The brainstem primarily contains white matter interspersed with some gray matter. This area of the brain serves as a two-way conduction path, conveying nerve impulses between other brain regions and the spinal cord. In addition, most of the 12 pairs of cranial nerves from the brain arise from the brainstem, regulating breathing, digestion, heartbeat, blood pressure, pupil size, swallowing, and other basic functions. The brain stem, which is an extension of the brain into the top of the spinal cord, handles basic survival systems like respiration, digestion and heart control. It also is involved with alertness (being awake and conscious). *

Brancher Enzyme Deficiency: A metabolic muscle disease, associated with failure to thrive, liver and spleen enlargement and liver failure. It is a genetic disorder, transmitted via an autosomal recessive form of inheritance with onset of symptoms noted in early childhood. **

BRCA1: About half of all patients with hereditary breast or ovarian cancer have mutations in a gene called BRCA1. Researchers suspect that it is involved in DNA repair, controlling cell division and regulating gene activity. Understanding BRCA1 should also make it easier to design genetic screening programs to identify individuals at risk and catch cancer early.
BRCA1 is a big protein - three times the size of haemoglobin, for example. Its chain of 1,863 amino acid links folds into a complex three-dimensional structure. Like a molecular Swiss Army knife, different parts are designed for different jobs.
Most of the mutations associated with breast and ovarian cancers beset the two regions at the chain ends. These areas vary least between different species, showing that their function is important enough for natural to stamp out slip-ups that would lead to variation.
One end of BRCA1 - the 'N' terminus - bonds to another protein. The two form a catalyst that joins a small molecule called ubiquitin to other proteins. Ubiquitin tags proteins for destruction - an important stage in the body's defense against cancer. Based on: Nature Science Update, September 26, 2001, John Whitfield, http://www.nature.com/nsu/nsu_pf/010927/010927_9.html.
BRCA1 breast cancer susceptibility gene: A mutated version of BRCA1, which predisposes a person toward developing breast cancer. %
BRCA1: A gene that normally helps to restrain cell growth. %

Breast self-examination (BSE): A manual self-examination of the breasts. ##

Bronchogenic {BRONC-coe-gen-ic} carcinoma: A cancer originating in the lungs or airways. ##

Bronchoscopy {BRONC-cos-co-pee}: The insertion of a flexible, lighted tube through the mouth into the lungs to examine the lungs and airways. ##

Bruxism {BUCK-cism}: grinding or gnashing of the teeth, often done while asleep. Involuntary grinding, clenching, or gnashing of the teeth, particularly during sleep or times of stress. Without appropriate protection, such as the use of night guards that cover the teeth, severe dental problems may result. Bruxism may also be a feature of certain neurologic movement disorders, including dystonia of the jaw, mouth, and lower face (oromandibular dystonia [OMD]), Rett syndrome, or tardive dyskinesia.

BSE: Bovine spongiform encephalopathy ("mad cow disease"). A brain disease of cows caused by prion infection. See related terms. *

Buserelin: An anticancer drug that belongs to the family of drugs called gonadotropin-releasing hormones. In prostate cancer therapy, buserelin blocks the production of testosterone in the testicles. *

Bypass: An operation in which the doctor creates a new pathway for the flow of body fluids. #

Cachexia: Muscle wasting. Physical wasting with loss of weight and muscle mass caused by disease. Patients with advanced cancer, AIDS, and some other major chronic progressive diseases may appear cachectic. Cachexia is a wasting syndrome that causes weakness and a loss of weight, fat, and muscle. Anorexia (lack of apppetite) and cachexia often occur together. Cachexia can occur in people who are eating enough, but who cannot absorb the nutrients.

Caenorhabditis elegans (C. elegans): A small worm (a soil nematode) that is commonly used as a model organism to study genetics and development.

Calcifications: Small calcium deposits, often in the breast tissue that can be seen by mammography or other X-rays. #

Calpain: Cysteine proteinase found in many tissues. Hydrolyzes a variety of endogenous proteins including neuropeptides, cytoskeletal proteins, proteins from smooth muscle, cardiac muscle, liver, platelets and erythrocytes. Two subclasses having high and low calcium sensitivity are known. Removes Z-discs and M-lines from myofibrils. Activates phosphorylase kinase and cyclic nucleotide-independent protein kinase. These molecules have been found in organisms from Drosophila to mammals. Also: Recently, the biological importance of various proteinases in cellular function has been emphasized. The processing rather than digesting activity of these enzymes makes it possible to modulate directly the activities and/or functions of other proteins both precisely and irreversibly. Calpain is one such modulating intracellular proteinase. The precise functions of calpain in vivo, however, have not yet been clearly identified. The ubiquitous and constitutive expression of mammalian calpains strongly suggests that they are involved in basic and essential cellular functions. This may be one of the reasons why we cannot specify precisely the physiological functions of calpain. p94 (also called calpain 3), a mammalian calpain homologue predominantly expressed in skeletal muscle, is genetically proved to be responsible for limb-girdle muscular dystrophy type 2A. See: http://www.biochemj.org/bj/328/0721/bj3280721.htm

Calveolin: A muscle-related protein. Calveolin abnormalities are linked to LGMD type 1C. *

CAM: cell adhesion molecules. Although this could mean any molecule involved in cellular adhesive phenomena, it has acquired a more restricted sense, namely a molecule on the surface of animal tissue cells, antibodies (or Fab fragments) against that specifically inhibit some form of intercellular adhesion.

Cancer: A term for diseases in which abnormal cells divide without control. The transition from a normal cell to a malignant cancer is driven by changes to the cell's DNA. All cells acquire mutations over their lifetime, but most are quickly repaired by the cell's maintenance machinery. This machinery is not foolproof, however, and if mutations are missed in two classes of gene that control growth - proto-oncogenes and tumour suppressor genes - the cancer cycle can begin. Thus, cancer begins in one cell and as the cell replicates, the cancer grows larger. Cancerous cells can invade nearby tissue and can spread through the bloodstream and lymphatic system to other parts of the body. In cancer, the cells inherited from the parents all start out normal, but as described above, during the lifespan, as cells replicate, a defect in the gene code occurs and persists and causes cancer. For example, a person exposed to some environmental factor may develop genetic mutations that lead to cancer during the person's lifetime. We can say that cancer has a genetic aspect but it is not hereditary or inherited - it is not passed onto the children. Also, cancer is not contagious, one person cannot pass it on to another.

Cancer cell of origin: Precancerous cell that gives rise to a cancer stem cell. May be a mutated stem cell, or a committed progenitor that has acquired self-renewal capacity through mutation.

Cancer-initiating cell General term that encompasses both cancer cell of origin and cancer stem cell.

Cancer stem cell Self-renewing cell responsible for sustaining a cancer and for producing differentiated progeny that form the bulk of the cancer. Cancer stem cells identified in leukaemias and certain solid tumours are critical therapeutic targets.

Candidiasis {CAN-did - DIE - ah - sis}: A common fungal infection. ##

Carbonic anhydrase inhibitors: A class of medications that inhibits activity of the enzyme carbonic anhydrase. This zinc-containing enzyme is present in red blood cells and the renal tubules. These tubules form part of the filtering units of the kidneys. Carbonic anhydrase activity serves to accelerate the transfer of carbon dioxide from tissue to the blood and on to the lungs. By restricting carbonic anhydrase activity, these agents decrease hydrogen ion concentrations in the renal tubules, increasing excretion of sodium, potassium, bicarbonate, and water. Certain carbonic anhydrase inhibitors are prescribed to promote urinary production and excretion (i.e., as diuretics) or to lower fluid pressure within the eyes for those with glaucoma. They are also used to treat other conditions including epilepsy or certain neurologic movement disorders.

Carcinoembryonic antigen (CEA) {CAR-SIN-oh-EM-Bree-on-ic}: A blood tumor marker. ## CEA assay: a laboratory test to measure the level of carcinoembryonic antigen (CEA), a substance that is sometimes found in an increased amount in the blood of colorectal cancer patients. #

Carcinogen {kar-SIN-o-jin}: A substance or agent that is known to cause cancer. %

Carcinoma in situ {kar-sin-OE-ma in SY-too}: Cancer that involves only the tissue in which it began; it has not spread to other tissues. #

Carcinoma {kar-sin-OH-ma}: Cancer that begins in the lining or covering of an organ. #

Cardiomegaly {card-dee-oh-MEG-oh-lee}: Enlargement of the heart. ***

Cardiomyopathy: Disease of the myocardium, esp. that caused by primary disease of the heart muscle. ***

Carnitine {CAR-na-teen} (also: L-carnitine; Carnitor; Levocarnitine) a naturally occurring molecule that is present, especially in vertebrate muscle, that transports fatty acids into cellular mitochondria and transports potentially toxic metabolic waste products, out of mitochondria. Carnitine is vital to muscle and heart tissue as part of the normal metabolism of fatty acids. It is a nitrogen-containing, short-chain carboxylic acid technically, it is not an amino acid. It is a water-soluble, vitamin-like compound that is readily synthesized in the body from lysine and methionine. Supplements are available as a prescription (or over the counter in the USA). *

Carnitine {CAR-na-teen} Deficiency: Caused by a deficiency of carnitine. This disorder is one of the metabolic diseases of muscle and is characterized by a number of symptoms including muscle weakness of the proximal muscles of the shoulders and hips, face, palate and neck and difficulty swallowing. Symptoms usually begin in childhood and are slowly progressive. **

Carpal tunnel syndrome: Pain or numbness that affects some part of the median nerve distribution of the hand (the palmar side of the thumb, the index finger, the radial half of the ring finger, and the radial half of the palm) and may radiate into the arm. There may be a history of cumulative trauma to the wrist***

Carrier: A person who has one faulty copy of a particular gene, and one copy that is normal. In autosomal recessive disorders, carriers show no symptoms of the disorder in most cases, because the normal copy provides for healthy function, a person must have two copies of the faulty gene for the disorder to be expressed. In X-linked recessive disorders, females are carriers, because they have normally have one normal X Chromosome to "protect" them from symptoms of the disease. **

Cartilage {CAR-til-lij}: Firm, rubbery tissue that cushions bones at joints. #

Cascade: see pathogenic cascade, also see upstream *

CAT (computed axial tomography {TOM-rog-gra-fee}) scan (computed tomography CT scan): A test using computers and X-rays to create images of various parts of the body. ##

Catheter {KATH-e-ter}: A thin plastic tube. When a catheter is placed in a vein, it provides a pathway for drugs, nutrients, or blood products. Blood samples also can be removed through the catheter. When placed in a body cavity (bladder): it provides a pathway to drain fluid away from the body. #

Caudate nuclei: One of the 3 major substructures that, together with the globus pallidus and putamen, form the basal ganglia. The caudate nuclei and putamen, which are relatively similar structurally and functionally, are collectively known as the striatum. Specialized clusters of nerve cells or nuclei within the caudate receive input from certain regions of the cerebral cortex. This information is processed and then relayed (by way of the thalamus) to areas of the brain responsible for controlling complex motor functions. The caudate nuclei are specifically thought to process and transmit cognitive information that influences the initiation of complex motor activities.

Causality: the cause of a disorder. Also see Multiple and Interactive Causality.

Caveolin: A small molecular weight protein shown to be associated with the caveolar plasma membranes. Caveolin-3, or M-caveolin, was identified as a muscle-specific form of the caveolin family. In skeletal muscle, caveolin-3 is localized to the sarcolemma, coinciding with dystrophin. Some caveolin-3 co-purifies with the dystrophin-associated glycoprotein complex and can be immunoprecipitated with dystrophin antibodies, which suggests the existence of a discrete protein complex containing both proteins. However, it does not appear that CAV3 is an integral member of the DGC, since its association is not as strong as that of other members. The number and size of caveolae are abnormal in DMD-patients.

cDNA / cDNA clone: "complementary DNA"; a piece of DNA copied from an mRNA. The term "clone" indicates that this cDNA has been spliced into a plasmid or other vector in order to propagate it. @@ DNA that is synthesized (man made) to be complementary to a mRNA molecule. By definition a cDNA represents a portion of the DNA that specifies a protein (is translated). If the sequence of the cDNA is known, by complementarity, the sequence of the DNA is known.
mRNA is very unstable outside of a cell, so scientists use special enzymes to convert it to cDNA, or complementary DNA. cDNA is a much more stable compound and, importantly, because it was generated from a mRNA in which the introns had been removed, cDNA represents only expressed DNA sequence. cDNA is a form of DNA prepared in the laboratory using an enzyme called reverse transcriptase. cDNA production is the reverse of the usual process of transcription in cells since the procedure uses mRNA as a template rather than DNA. Unlike genomic DNA, cDNA contains only expressed DNA sequences, or exons.

Cell: the basic unit of structure and function of which all plants and animals are composed. The cell is the smallest unit in the living organism that is capable of integrating the essential life processes. There are many unicellular (one - cell) organisms, e.g., bacteria and protozoans, in which the single cell performs all life functions. In higher organisms, a division of labour has evolved in which groups of cells have differentiated into specialized tissues, which in turn are grouped into organs and organ systems.
Cells can be separated into two major groups - prokaryote cells whose DNA is not segregated within a well-defined nucleus (center) surrounded by a membranous nuclear envelope. Bacteria are prokaryotes. The second, larger group is the eukaryotes, cells with a membrane-enveloped nucleus (center). All organisms other than bacteria consists of one or more eukaryotic cells. Prokaryotes are smaller in size and simpler in internal structure than eukaryotes and are believed to have evolved much earlier.
All cells share a number of common properties; they store information in genes made of DNA, they use proteins as their main structural material; they build proteins in the cell's ribosomes using the information encoded in the DNA and mobilized by means of RNA; they use adenosine triphosphate as the means of transferring energy for the cell's internal processes; and they are enclosed by a cell membrane, composed of proteins and a double layer of lipid (fat) molecules, that controls the flow of materials into and out of the cell.
Cells are like huge cities made up of atoms that form molecules that form chemicals that form structures that work together in the cell to do the many jobs that the cell needs done. One of the basic miracles of life is how these chemicals come together to create living matter.
Many diseases and disorders stem from basic problems in the cell and a good understanding of the cell is necessary in understanding disease.*

CELL FUSION: The melding of two or more cells into one cell. When undifferentiated stem or progenitor cells fuse with mature differentiated cells, the resultant cell can retain the mature cell phenotype.

Cell line: A culture of a particular type of cell that can be reproduced indefinitely, thus making the cell line "immortal".

Cell-mediated cytotoxicity (CMC): Killing (lysis) of a target cell by an effector lymphocyte.

Cell-mediated immunity (CMI): Immune reaction mediated by T cells; in contrast to humoral immunity, which is antibody mediated. Also referred to as delayed-type hypersensitivity.

Cell Membrane: (also known as plasma membrane) is found in all cells. It: 1) separates the inner parts of the cell from the outer environment; and 2) acts as a selectively permeable barrier to allow certain chemicals, (like water), to pass and to prevent others from passing. *

Cell replacement therapy: Reconstitution of tissue by functional incorporation of transplanted stem-cell progeny. Distinct from 'bystander' trophic, anti-inflammatory or immunomodulatory effects of introduced cells.

Cell Theory: one of the foundations of modern biology. Its major tenets are: 1) All living things are composed of one or more cells; 2) Chemical reactions take place within cells; 3) All cells originate from preexisting cells; and 4) Cells contain hereditary information, which is passed from one generation to another. *

Cellular culture: A culture of individual cells in a test-tube. Culture: A batch of cells, which can be microorganisms or of animal or plant origin, that are grown under specific conditions of nutrient levels, temperature, pH, oxygen levels, osmotic factors, light, pressure, and water content. Cultures of cells are prepared in the laboratory for a wide spectrum of scientific research. *

Cellular immunity: Immune protection provided by the direct action of immune cells.

Cellulitis {CELL-U-light-tus}: The inflammation of an area of the skin (epithelial layer). ##

CentiMorgan: The extent of recombination between two genes on the same chromosome can be used as a map distance to measure their relative locations. Map units are defined as 1 unit (or centiMorgan cM)and equal 1% crossover. Also: A centimorgan is the distance between two genes that will recombine with a frequency of exactly one percent. This term is named afer Thomas Hunt Morgan, who first conceptualized linkage while working with Drosophila. 1 centimorgan (cM) corresponds to a region within which a crossover is expected once every 100 meioses. This implies a 1% chance of a single crossover at single meiosis, and because the probability of a double crossover is exceedingly small (about 0·01%), this also corresponds to a chance of roughly 1% of recombination at each meiosis.

Central Core Disease: One of the congenital myopathies. It is transmitted by an autosomal dominant mode of transmission and is evident at birth or shortly after. The infant usually appears floppy and subsequent milestones are delayed. Infants are often born with a congenital dislocated hip as well. Most patients reach adulthood with a mild handicap that requires no treatment. **

Central oscillators: nerve cells that discharge signals that result in alternating fluctuations of electrical impulses along certain tracts of the central nervous system.

Central Nervous System: The brain and spinal cord. Contrast: Peripheral nervous system.

Central venous catheter (central line): A special intravenous tubing that is surgically inserted into a large vein near the heart and exits from the chest or abdomen. The catheter allows medications, fluids, or blood products to be given and blood samples to be taken.

Centromere: The term introduced by Darlington (1936) for the specialized chromosome region which reacts to the spindle at nuclear division and to which spindle fibers attach during cell division. The anchor point for the protein filaments that pull freshly divided chromosomes apart during cell division. Centromeres consist mainly of tandem repeats, 171 bases long, known as alpha-satellite DNA. This DNA tends to remain tightly packed in a structure called heterochromatin, where it is not transcribed into RNA.

Central Dogma of Genetics: The central idea that DNA leads to RNA leads to Protein. This chain depicts the unidirectional flow of genetic information from DNA into protein, the molecule most often associated with a specific phenotype.

Cerebellar ataxia: clumsiness of willed movements. The patient staggers when walking; he cannot pronounce words properly and has nystagmus. *

Cerebellum (brain): The cerebellum is located at the back of the brain beneath the occipital lobes. The cerebellum fine tunes our motor activity or movement, e.g. the fine movements of our fingers as they print a story or colour a picture. It helps us maintain our posture, our sense of balance or equilibrium by controlling the tone of our muscles and senses the position of our limbs. *
Also: Cerebellum {SARAH-bell-um}: The portion of the brain forming the largest segment of the rhombencephalon. It lies dorsal to the pons and medulla oblongata, overhanging the latter. It consists of two lateral cerebellar hemispheres and a narrow medial portion, the vermis. Three pairs of fibre bundles, the inferior, middle, and superior peduncles connect it to the brainstem. The cerebellum is involved in synergic control of skeletal muscles and plays an important role in the coordination of voluntary muscular movements. It receives afferent impulses and discharges efferent impulses, but is not a reflex center in the usual sense; however, it may reinforce some reflexes and inhibit others. ***
Also: the largest part of the hindbrain. The cerebellum is essential for the maintenance of muscle tone, balance, and the synchronization of activity in groups of muscles under voluntary control, converting muscular contractions into smooth coordinated movement. It does not, however, initiate movement and plays no part in the perception of conscious sensations or in intelligence. A two-lobed region of the brain located behind the brainstem. The cerebellum receives messages concerning balance, posture, muscle tone, and muscle contraction or extension. Working in coordination with the basal ganglia and thalamus, the cerebellum integrates, adjusts, and refines messages transmitted to muscle groups from the cerebral cortex (i.e., motor cortex). Thus, the cerebellum plays an essential role in producing smooth, coordinated voluntary movements; maintaining proper posture; and sustaining balance.

Cerebral cortex: The outer region of the brain's cerebral hemispheres. Comprised of gray matter, the cerebral cortex contains several deep folds (gyri) and grooves (sulci or fissures). Two sulci divide the surfaces of both cerebral hemispheres into four distinct lobes that are named for overlying bones of the skull. These include the frontal, temporal, occipital, and parietal lobes. The cerebral hemispheres are joined by a thick band of nerve fibers known as the corpus callosum. The cerebral cortex is responsible for integrating higher mental functioning and conscious thought, sensations, and general movements.

Cerebrospinal fluid {sir-REE-bro-SPY-nal}(CSF): The fluid that flows through and protects the 4 cavities (ventricles) of the brain, the spinal cord's central canal, and the space (known as the subarachnoid space) between the middle and inner layers of the membrane (meninges) enclosing the brain and spinal cord. Laboratory analysis of CSF, usually obtained via lumbar puncture, may help to diagnose central nervous system infections, certain tumors, or particular neurologic disorders. During lumbar puncture, CSF is removed from the spinal canal via a hollow needle inserted between certain bones of the spinal column within the lower back (i.e., usually the third and fourth lumbar vertebrae).

Cervical myelopathy: Any pathological condition of the spinal cord involving the cervical or lumbar vertebrae and related tissues. ***

Cervical carcinoma: A cancer of the cervix (the neck of the uterus). ##

Cervical nodes: Lymph nodes in the neck. ##

Cervical canal {SER-vi-kal}: The passage in the cervix that connects the body of the uterus with the upper vagina. #

Cervix {SIR-viks}: The lower, narrow end of the uterus. #

Channelopathy: A term coined to describe diseases that are caused by defective ion channel proteins.

Chaperone proteins: The ability of a protein to perform its function in the cell depends in part upon its ability to assume and retain its proper functional conformation. The proper conformation is achieved by regulated folding during synthesis, aided by chaperone proteins. Mutations and other changes that divert proteins from their normal folding pathways or that destabilize their native state may underlie several human diseases. Chaperone proteins promote the proper folding and shaping of other proteins during biological processes. Molecular chaperones, such as "heat-shock proteins," are thought to combat stress-related damage to protein function caused by exposure to heat or cold. Also: Stress to the cell also causes protein denaturation: the protein molecule loses its native functional conformation when it unfolds. Chaperones assist the damaged molecule to regain its functional conformation. If cellular stress proceeds unchecked by such antistress mechanisms as the protein-refolding action of chaperones, intracellular proteins become denatured and insoluble. These denatured proteins tend to stick to one another, precipitate, and form inclusion bodies. The development of inclusion bodies is a common pathologic process in Parkinson's, Alzheimer's, and Huntington's diseases, even in the absence of cellular stress. Denatured and aggregated proteins cannot function and must either be rescued or eliminated with the help of chaperones.

Chaperonopathy, Chaperonopathies: Cells maintain a complete set of functionally competent proteins normally and in the face of injury or stress with the use of various mechanisms, including systems of proteins called molecular chaperones. The typical function of a chaperone is to assist a nascent polypeptide chain to attain a functional conformation as a new protein and then to assist the protein's arrival at the site in the cell where the protein carries out its functions. It has become increasingly clear that disruption of chaperoning mechanisms contributes to aging and disease - chaperonopathies. A genetic or acquired defect could affect one or more of the specialized chaperone domains. The manifestations of a chaperonopathy depend on the domain or function that is impaired or abolished. Acquired chaperonopathies are associated with post-translational modifications of the chaperone and usually become clinically evident late in life. See: N Engl J Med 353;14 October 6, 2005

Charcot-Marie-Tooth Disease: Also known as CMT, peroneal muscular atrophy and hereditary motor and sensory neuropathy, Charcot-Marie-Tooth disease is a disorder affecting (chronically demyelinating) the peripheral nerves. Onset of symptoms is typically in the teens to early 20's. Weakness and atrophy of the muscles of the feet, lower legs and hands with foot deformities and some loss of sensation are commonly experienced. The degree of disability varies greatly among individuals, even within the same family. **

Chemical: Most of the Universe consists of matter and energy. Energy is the capacity to do work. Matter has mass and occupies space. Physical matter, be it liquid, gas or a solid, is made up of molecules that are in turn made up of atoms. Atoms are the smallest particle into which an element can be divided. Elements are substances consisting of one type of atom, for example, pure (24K) gold is composed of only one type of atom, gold atoms. Examples of earth elements with their symbols, include; aluminum (Al), argon (Ar), arsenic (As), calcium (Ca), carbon (C), copper (Cu), gold (Au), helium (He), hydrogen (H), iron (Fe), lead (Pb), nitrogen (N), oxygen (O), phosphorus (P), platinum (Pt), Potassium (K), sulfur (S), etc. There are only about 115 naturally occurring elements on earth, because the number of elements is limited, the number of possible types of matter found on the earth is also limited. Different atoms come together and are held together by different types of chemical bonds, very weak electrical attractions between them.
Molecules can be thought of as chains of atoms held together in a particular order by bonds. Different types of atoms will have different types of bonding properties making it more likely for some atoms to lump together with each other and less likely for others to join together. Often two things will join to form a third product, for example two hydrogen atoms (H) combine with one oxygen atom (O) to form one molecule of water (H2O). The atoms in the "new" molecule are held together by bonds. A pail of water is a large collection of water molecules (H2O).
Some molecules also tend to react with each other and these types are usually called "chemicals." These reactions are governed by the properties of each of the different molecules that come together. An example of a chemical reaction is a fire: one molecule of propane (C3H8) combines with 5 Oxygen (O2) to burn and produce 3 carbon dioxide (CO2), 4 water (H2O) and heat and light. The properties of a given chemical are determined by several factors including; the type of atoms the substance is made out of, the electrical properties of the individual atoms, the order of the atoms, the size of the molecules, the shape the molecule may be folded into, etc. Biological chemicals are often referred to as organic or biochemicals. Biological systems are based on the chemical bonding properties of carbon and usually include some ratios of the following elements: C, H, N, O, P, S. Biochemicals work in the body in complex networks and an abnormality in one chemical may upset a complex web of function, often resulting in an illness. *

Chemodenervation: Interruption of a nerve impulse pathway via administration of a chemical substance, such as botulinum toxin (BTX). For example, intramuscular injections of BTX produce local relaxation of treated muscles by inhibiting the release of acetylcholine, a neurotransmitter that is present at the junctions of nerve and muscle cells and that regulates the delivery of messages from neurons to muscle fibers.

Chemotaxis: Migration of cells along a concentration gradient of an attractant.Chemokines: chemokines are signaling molecules that attract immune cells to infected cells. A type of cytokine.

Chemotaxis: Migration of cells along a concentration gradient of an attractant.

Chemotherapy {kee-mo-THERE-a-pee}: Treatment with anticancer drugs. %

Chimera {KI-mir-rah} Chimerical {KI-miracle}: An organism that contains cells or tissues with a different genotype. These can be mutated cells of the host organism or cells from a different organism or species. In some cases, humans share genetic material with relatives, for example, 8% of non-identical twins pairs have chimaeric blood.
Also: 1). In experimental embryology, the individual produced by grafting an embryonic part of one animal on to the embryo of another, either of the same or of another species. 2). An organism that has received a transplant of genetically and immunologically different tissue, such as bone marrow. 3). Dizygotic twins that retain each other as immunologically distinct types of erythrocytes. 4). A protein fusion in which two different proteins are linked via peptide bonds; usually genetically engineered. Chimeric antibodies may have the Fab fragment from one species fused with the Fc fragment from another. 5). Any macromolecule fusion formed by two or more macromolecules from different species or from different genes.
Also: In medicine, a person composed of two genetically distinct types of cells. Human chimeras were first discovered with the advent of blood typing when it was found that some people had more than one blood type. Most of them proved to be "blood chimeras" -- non-identical twins who shared a blood supply in the uterus. Those who were not twins are thought to have blood cells from a twin that died early in gestation. Twin embryos often share a blood supply in the placenta, allowing blood stem cells to pass from one and settle in the bone marrow of the other. About 8% of non-identical twin pairs are chimeras.
Many more people are microchimeras and carry smaller numbers of foreign blood cells that may have passed from mother across the placenta, or persist from a blood transfusion. In vitro fertilization (IVF) is also contributing to the number of human chimeras. To improve success rates, two or more embryos are placed in the uterus so women who have IVF have more twin pregnancies than usual. More twins mean more chimeras.
In Greek mythology, the Chimera was an awesome fire-breathing monster with the head of a lion, the body of a goat, and the tail of a serpent. The Chimera was killed by the hero Bellerophon mounted, in most versions of the tale, on Pegasus, the winged horse.
Also: Chimera (chi·me·ra) [Gr. chimaira a mythological fire-spouting monster with a lion's head, goat's body, and serpent's tail] an individual organism whose body contains cell populations derived from different zygotes, of the same or of different species; it may occur spontaneously, as in twins (blood group chimeras), or be produced artificially, as an organism that develops from combined portions of different embryos, or one in which tissues or cells of another organism have been introduced. Cf. mosaic.
== heterologous chimera, a chimera in which the foreign cells or tissues are derived from an organism of a different species.
== homologous chimera, a chimera in which the foreign cells or tissues are derived from an organism of the same species but of a different genotype.
== isologous chimera, a chimera in which the foreign cells or tissues are derived from a different organism of the same genotype, such as an identical twin.
== radiation chimera, an organism that survives with immunologic characteristics of host and donor after a bone marrow graft from an antigenically different donor, the host having first been subjected to sublethal whole-body irradiation so that there is reduced or no immune response to foreign cells by the donor.

Chondrosarcoma {KON-dro-sar-KO-ma}: Cancer in cartilage. #

Chorea {KOR-ree-ah}: Jerky, irregular, relatively rapid involuntary movement that primarily involves muscles of the face or extremities. Choreic movements are relatively simple and discrete or highly complex in nature. Although involuntary and purposeless, these movements are sometimes incorporated into deliberate movement patterns. When several choreic movements are present, they often appear relatively slow, writhing, or sinuous, resembling athetosis. Chorea may occur in association with certain neurodegenerative diseases, including Wilson's disease and Huntington's disease, or systemic disorders, such as lupus. In addition, chorea is a dominant feature in Sydenham's chorea or may result from the use of certain medications, such as particular anticonvulsant or antipsychotic agents.

Chorionic villus sampling (CVS): {CORE-ree-on-ick Vill-is} a fetal monitoring technique in which a sample of chorionic villus is extracted through the cervix or abdomen under ultrasound visualization. The earliest recommended time for sampling is the ninth week of pregnancy. The cells obtained are subjected to chromosomal and biochemical studies to determine if any abnormalities are present in the fetus. Also: A screening and diagnostic procedure performed during which tissue samples are obtained from a portion of the placenta using a specially guided needle via ultrasound. The placenta is the organ attached to the lining of the uterus that links the blood supplies of the developing fetus and the mother. The tissue sample is obtained from the layer from which the chorionic villi develop. Blood from the fetus flows through the umbilical cord to the placenta and enters minute blood vessels arranged in multiple "thread-like" projections or chorionic villi surrounded by maternal blood. Tissue samples obtained during chorionic villus sampling are analyzed to detect certain genetic or chromosomal abnormalities.

Chromosome jumping: A research technique developed to move rapidly up or down a chromosome in search of a particular gene. It enables researchers to make large jumps over uninformative regions of DNA. ###

Chromosome: Chain-like structures found within the nuclei of cells and containing the genetic material. Each chromosome consists of DNA and proteins and carries part of the genetic code for making a copy of the organism. A normal human cell contains 46 chromosomes, 22 pairs of autosomes and one pair of sex chromosomes, either XX or XY. **

Chromosome banding: A technique for staining chromosomes so that bands appear in a unique pattern particular to the chromosome. %

Chromosome Painting: A more recent method to work out karyotypes is to use 24-colour chromosome painting, in which each chromosome is labeled with a different colour fluorescence. Also see Fluorescence in situ hybridization (FISH).

Chromosome walking: A research technique in which overlapping fragments of a chromosome are checked one at a time in search of a particular gene. It covers smaller regions than chromosome jumping. ###

Chronic Immune Demyelinating Polyneuropathy (CIDP): A disease involving de-myelination of the peripheral nerves (both sensory and motor). Causes weakness in the arms and legs and sometimes sensory problems (tingling in the hands and feet). A more chronic form of Guillain-Barré Syndrome. Also called: chronic idiopathic polyneuritis and chronic relapsing (dysimmune)
polyneuropathy. Also: Chronic Immune Demyelinating Polyneuropathy (CIDP) is a sporadic acquired polyneuropathy that presents with both proximal and distal weakness and impaired tendon reflexes in the extremities. In addition, sensory loss is usually present, most often with deficits to vibration and touch. The pathogenesis of this disease is presumed to be autoimmune, with evidence of both cell-mediated and humoral processes, but the mechanism is unknown. Tends to be seen in conjunction with inclusion body myositis. See: Click

Chronic wasting disease (of deer): A brain disease found only in deer and elk, very similar to BSE and thought caused by a prion. See prion. *

Chronic fatigue syndrome (CFS): A syndrome characterized by debilitating fatigue and a combination of flu-like symptoms such as sore throat, swollen lymph glands, low-grade fever, headaches, and muscle pain or weakness.
Also: a collection of persistent, debilitating symptoms, the most notable of which is severe, lasting fatigue. In other countries it is known variously as myalgic encephalomyelitis, chronic fatigue and immune dysfunction syndrome, and post-viral fatigue syndrome. Dr. George Beard, who called it neurasthenia, first recognized it as a syndrome in the 1860s. He believed it to be a neurosis with a fatigue component. Somewhat controversial: definitions and theories of its cause have changed over the years; many cases have been called imaginary because doctors could find no cause. In the mid-1980s it came to the public's attention, as affluent women in their thirties began to seek treatment. (For unknown reasons, more women than men seek treatment for the disease.)*

Chronic: When an illness or symptom persists for a long period of time. **

CIDP: see Chronic Immune Demyelinating Polyneuropathy.

Circadian: A rhythm of biological functions occurring in a 24-hour periodic cycle (e.g., sleeping, eating, etc.).

Cis: Meaning on the near side of; often used to refer to geometric configurations of atoms or mutations on the same molecule or chromosome.

Cistron: Synonymous with gene. Originally defined as a functional genetic unit within which two mutations cannot complement. Now equated with the term gene, as the region of DNA that encodes a single polypeptide (or functional RNA molecule such as tRNA or rRNA).

Cladogenesis: The evolutionary process whereby one species splits into two or more species.

Class I, II and III MHC molecules: Proteins encoded by genes in the major histocompatibility complex (q.v.). Class I molecules are designated HLA-A, B, or C. Class II molecules are designated DP, DQ or DR.

Class switch: See isotype switch.

Classical pathway: The mechanism of complement activation initiated by antigen-antibody aggregates and proceeding by way of C1, C4 and C2.

Clinical trials: Research studies that involve patients. Clinical trials of new forms of therapy require a series of complex and exhaustive procedures to be carried out, usually on both animals and on humans, before any new form of therapy can be declared safe and effective. The precise regulation of this process is regulated in differing ways in different countries. However, the general principles are the same.
Some terms come up over and over in the discussion of clinical trials. It's useful to learn these basic terms and their meanings. The definitions below will help you begin to understand the basic differences between the main types of clinical trials and how they are used in the development and understanding of new forms of therapy.
COHORT: A group of people in a study who share some common trait, for example one cohort will receive one treatment, one will receive another treatment. Each person is assigned to a cohort.
DOUBLE BLIND:A system of conducting clinical trials that prevents either the patients or the physicians carrying out the actual treatment from knowing which patients are receiving the product being tested as compared to the comparison product or placebo.
MULTICENTER:Implying that more than one health center or research center is enrolling patients into a specific trial according to a commonly agreed protocol.
PHASE I: Phase I trials are preliminary trials (in perhaps 10-20 patients) designed to see if a new drug can be safely given to humans and, if so, what the highest dose is that patients can tolerate; such trials are usually carried out in small numbers of patients and are not normally intended to discover whether a new drug has any clinical activity.
PHASE II:Phase II trials are also relatively small trials (in perhaps 20-50 patients) designed to see if doses of the drug that we know to be tolerable from phase I trials can in fact demonstrate activity in the treatment of a specific disease; such trials may use one or more doses of the new drug.
PHASE III: Phase III trials are usually much larger trials designed to prove that a particular type of therapy is as good or better than some standard form of therapy
PLACEBO: Normally an inert or inactive substitute made to look like the active form of a new drug, so that the patient and the physician-researcher are unable to tell whether the patient is receiving active drug or the inactive comparative product.
PROTOCOL: The predetermined structure of the trial or, in other words, the set pattern by which all the investigators have agreed to diagnose, treat, and evaluate the patients enrolled into the trial.
RANDOMIZED: A way of distributing different therapeutic options between groups of patients such that each new patient entered into a clinical trial has a preset chance of receiving any one of the therapeutic options being tested against each other. *

Clinically significant: Researchers try to measure new treatments by looking at objective measurements of some sort. If a treatment leads to improvement on these measures to a significant degree, it is said to show clinical significance. Researchers are looking for significant improvements on clinical measurements, for example, a treatment lowers a chemical level in the blood and this is linked to an improvement in the condition of people with the disorder. It is also important to consider functional measures. That is, how well a person is able to function - does the treatment improve one's ability to function or not? Some treatments may not show clinically significant improvements, yet the patients may say they can function better or visa versa. *

Clonal analysis: Investigation of properties of single cells. Essential for formal demonstration of self-renewal and potency.

Clonal deletion: The loss of lymphocytes of a particular specificity due to contact with either "self" or artificially introduced antigen.

Clonal selection theory: The prevalent concept that specificity and diversity of an immune response are the result of selection by antigen of specifically reactive clones from a large repertoire of preformed lymphocytes, each with individual specificities.

Clone: A group of identical genes, cells, or organisms derived from a single ancestor. %
Clone (verb): To "clone" something is to produce copies of it. To clone a piece of DNA, one would insert it into some type of vector (say, a plasmid) and put the resultant construct into a host (usually a bacterium) so that the plasmid and insert replicate with the host. An individual bacterium is isolated and grown and the plasmid containing the "cloned" DNA is re-isolated from the bacteria, at which point there will be many millions of copies of the DNA - essentially an unlimited supply. @@

Cloning DNA: The process of making genetically identical copies. Using specialized DNA technology to produce multiple, exact copies of a single gene or other segment of DNA to obtain enough material for further study. This process, used by researchers in the Human Genome Project, is referred to as cloning DNA. The resulting cloned (copied) collections of DNA molecules are called clone libraries.

Cloning: In cloning, a procedure known as somatic-cell transfer is used. This creates an embryo* in a petri dish. From there, several possible alternatives exist, cells can be withdrawn to try to create cell lines or populations of stem cells, or the whole embryo can be implanted in a woman's uterus in an attempt to reproduce a whole individual.
-Therapeutic cloning: also called "nuclear transplantation" (nuclear as in the nucleus of the cell). Designed to create stem cells for medical research or to create other medically useful "parts." A subtype is cloning used to make many copies of an entire cell. The genetic makeup of these cloned cells, called a cell line, is identical to the original cell.
-Reproductive cloning: A type of cloning that produces complete, genetically identical animals such as the famous Scottish sheep, Dolly. In reproductive cloning the objective is to produce a "replica" of the whole individual.
*Some people object to calling this an embryo, saying this term should be used only for implanted embryos. They propose the term "activated egg" or "ovasome" instead.

Cloning vector: DNA molecule originating from a virus, a plasmid, or the cell of a higher organism into which another DNA fragment of appropriate size can be integrated without loss of the vector's capacity for self-replication; vectors introduce foreign DNA into host cells, where the DNA can be reproduced in large quantities. Examples are plasmids, cosmids, and yeast and bacterial artificial chromosomes; vectors are often recombinant molecules containing DNA sequences from several sources.

Clonus: Involuntary movement of rapidly alternating contraction and relaxation of a muscle. Ankle Clonus is the most common form of Clonus. Reflexive Spasms in the Calf Muscles, cause the Foot and Leg to bounce up and down, when the Knee is bent and the toes are on the floor.

Cluster determinant (CD): Cluster of antigens with which antibodies react that characterize a cell surface marker.

CNS: Central nervous system. *

Co-contraction: The simultaneous contraction of agonist and antagonist muscles.

Cogwheel phenomenon: rhythmic brief increase in resistance during passive movement about a joint.

Cobalt 60: Radioactive substance used as a radiation source to treat cancer. #

Coding sequence: The portion of a gene or an mRNA which actually codes for a protein. @@

Codon: In an mRNA, a codon is a sequence of three nucleotides which codes for the incorporation of a specific amino acid into the growing protein. The sequence of codons in the mRNA unambiguously defines the primary structure of the final protein.@@

Co - enzyme Q-10: (ubiquinone) {YOOH-bick-quin-own} Co-Enzyme Q10 is an enzyme that works within the cells in the body. Enzymes are catalysts that cause a chain of reactions to occur. Within the mitochondria of the cell, Co-Q10 is necessary for the metabolism of fats and carbohydrates. This translates into ATP or cellular energy. *

Colectomy {ko-LEK-to-mee}: An operation to remove all or part of the colon. In a partial colectomy, the surgeon removes only the cancerous part of the colon and a small amount of surrounding healthy tissue. #

Colon {KO-lun}: The long, coiled, tube-like organ that removes water from digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus. The colon is sometimes called the large bowel or the large intestine. #

Colonoscope {ko-LON-o-skope}: a flexible, lighted instrument used to view the inside of the colon. #

Colonoscopy {ko-lun-OS-ko-pee}: Examination of the colon through a flexible, lighted instrument called a colonoscope. %

Colony-stimulating factor (CSF): An injectable substance used to stimulate the bone marrow to produce more cells. ##
Also: Colony-stimulating factors: Substances that stimulate the production of blood cells. Treatment with colony-stimulating factors (CSF) can help the blood-forming tissue recover from the effects of chemotherapy and radiation therapy. These include granulocyte colony-stimulating factors (G-CSF) and granulocyte-macrophyage colony-stimulating factors (GM-CSF). #

Colostomy {ko-LOS-to-mee}: An opening created by a surgeon into the colon from the outside of the body. A colostomy provides a new path for waste material to leave the body after part of the colon has been removed. #

Colposcope {KUL-po-skope}: A magnifying instrument used to examine the vagina and cervix. #

Colposcopy: Examination of the vagina and cervix with an instrument called a colposcope. ##

Combinatorial Chemistry: Combinatorial chemistry essentially means reacting a set of starting chemicals in all possible combinations. See: http://www.accessexcellence.org/AB/BA/combiChem/

Combination chemotherapy: The use of more than one drug during cancer treatment. ##

Combinatorial joining: The joining of segments of DNA to generate essentially new genetic information, as occurs with Ig genes during the development of B cells. Combinatorial joining allows multiple opportunities for 2 sets of genes to combine in different ways.

Commitment: Engaging in a programme leading to differentiation. For a stem cell, this means exit from self-renewal.

Common bile duct: Bile ducts are passageways that carry bile. Two major bile ducts join together to form the common bile duct, which empties into the upper part of the small intestine (the part next to the stomach.) #

Common disease: A disease where both genetic and environmental factors contribute. This makes understanding causes and how they interact more complex. Treatments may be similarly complex. *

Complement: A complex series of more than 20 proteins in the blood whose action 'complements' the work of antibodies. The complement proteins spring into action when they "see" a cell marked by antibodies, assembling into a killing machine that punches a hole in the cell's surface. This reaction appears to spin out of control in some autoimmune diseases.
Also: Complement destroys bacteria, produces inflammation and regulates immune reactions. A set of blood proteins that act in a cascade of reactions to attack pathogens that are outside of cells (extracellular). After activation, pathogens are coated with a layer of complement, which can either kill the pathogen or target it for destruction by phagocytes.

Complement receptor: A structure found on erythrocytes, lymphocytes, neutrophils, monocytes and macrophages that binds C3 fragments.

Complement mediated: Immune reactions activating the complement response.

Complement cascade: A precise sequence of events usually triggered by an antigen-antibody complex, in which each component of the complement system is activated in turn.

Complement components: An enzymatic system of serum proteins triggered by the classical and alternative pathways, and resulting in target cell lysis, phagocytosis, opsonization and chemotaxis.

Complementary Base pairs: Due to their chemical properties, certain bases will always pair up together: Adenine (A) pairs with thymine (T); Cytosine ( C) pairs with guanine (G). This feature is called complementary pairing and is an important feature in the DNA and RNA strands. If we know that one strand is ATAGGC, then the other strand must be TATCCG. If the two strands separate, each will serve as a template for the other. This is an important feature because it allows high accuracy in the duplication of the DNA's message.

Complementary DNA (cDNA): A single strand of DNA synthesized in the lab to complement the bases in a given strand of messenger RNA. Complementary DNA represents the parts of a gene that are expressed in a cell to produce a protein. ###

Complexonomics: Proposed name for the emerging field of protein - protein interaction study. Many proteins work together in complicated complexes, or "protein societies."

Concatamer: A DNA molecule consisting of two or more separate molecules linked end-to-end to form a long linear structure.

Concatamer integration: Occurs when the entire genome of the vector including the bacterial plasmid is integrated into the
host genome.

Conformational diseases: Several diverse disorders, including the prevalent dementias and encephalopathies, are now believed to arise from the same general disease mechanism. In each, there is abnormal unfolding and then aggregation of an underlying protein. The gradual accumulation of these aggregates and the acceleration of their formation by stress explain the characteristic late or episodic onset of the clinical disease. The understanding of these processes at the molecular level is opening prospects of more rational approaches to investigation and therapy.

Contigs: contiguous sequences - see sequencing.

Consensus sequence: A 'nominal' sequence inferred from multiple, imperfect examples. @@

Constant region: The part of the antibody's structure that is characteristic for each antibody class. Constant region (C region): The invariant carboxyl-terminal portion of an antibody molecule, as distinct from the variable region which is at the amino-terminal of the chain.

Congenital: Strictly speaking - a condition that is present at birth.

Congenital anomalies: Structural defects present at birth. Congenital anomalies may be inherited or sporadic, isolated or multiple, apparent or hidden, gross or microscopic. They cause nearly half of all deaths in term newborns. A major anomaly is apparent at birth in 3 to 4% of newborns; up to 7.5% of children manifest a congenital defect by age 5 yr. Etiology may involve genetic and/or teratogenic factors. Different factors operating at the same period of organogenesis may produce identical defects. Genetic factors may cause many single anomalies and syndromes. They may operate via simple mendelian or multifactorial inheritance. Some syndromes, such as Down syndrome, result from chromosomal abnormalities. Teratogenic factors include environmental toxins, radiation, diet, drugs, infection, and metabolic disorders. Incidence varies with the type of defect; the geographic area, presumably due to genetic and/or environmental factors (spina bifida occurs in 3 to 4/1000 births in areas of Ireland but in 1/1000 in the USA); and cultural practices (consanguineous marriages increase the risk of genetic abnormalities). Increasing age of the mother (and, to a lesser extent, of the father) may increase the risk of chromosomal defects, especially Down syndrome. Genetic diseases like Duchenne Muscular Dystrophy are not considered congenital as they do not manifest until after birth. Based on: The Merck Manual of Diagnosis and Therapy Section 19. Pediatrics Chapter 261. Congenital Anomalies.

Congenital Myopathies: considered a separate group of muscle disorders due to their characteristic histopathological patterns. Most congenital myopathies have been defined on account of the morphological findings in enzyme histochemical preparations. In effect, the diagnosis of this group of diseases continues to be made on the histological pattern of muscle biopsies. However, progress has been made in elucidating the molecular genetic background of several of the congenital myopathies. Examples: congenital myopathies for which gene defects and mutant proteins have been found (central core disease, nemaline myopathies, desminopathy, actinopathy, certain vacuolar myopathies, and myotubular myopathy) and the other disease with central nuclei (centronuclear myopathy). These are marked by structural abnormalities, among them inclusions of often still obscure connotation and origin. As we now know, for instance, there is not a single disease nemaline myopathy, but rather at least four genetic types. Mutations have been discovered in the tropomyosin-2 and -3 genes, in the nebulin, and in the actin gene ACTA-1, respectively. In this latter group of ACTA-1 gene-related nemaline myopathy, accumulation of filamentous actin, most likely of mutant actin, has also been described giving rise to the term actinopathy. This myopathy and those related to the accumulation of desmin, the intermediate filament of skeletal muscle fibres and, thus, called desmin-related myopathies (DRM) or desminopathies when mutations in the desmin gene are involved, have resulted in the emerging concept of protein surplus/plus myopathies marked by the mutation-related accumulation of muscle fibre-specific proteins, in contrast to the concept of minus protein myopathies, i.e. many muscular dystrophies. Accumulation of desmin or actin within muscle fibres in respective myopathies is a parallel to accumulation of proteins within neurons and glial cells in certain neurodegenerative disorders such as Lewy bodies in Parkinson disease and Rosenthal fibres in Alexander disease. Suggesting that alpha-synuclein as a small neuronal protein accumulates with the aid of chaperone proteins Based on: Introduction: Recent Advances in Hereditary Neuromuscular Diseases of Childhood, by Antje Bornemann and Hans H. Goebel, Brain Pathology 11: 190-192 (2001).*

Congenital Fibre Type disproportion: One of the congenital myopathies, inherited via an autosomal recessive mode of transmission. Babies affected with this disorder are usually floppy at birth with variable degrees of weakness. The weakness is worse in the first two years of life, after which it either improves or stabilizes. **

Congenital Hypotonia: Diagnosed at birth, this disorder is characterized by abnormal muscle tone only. The reflexes are normal and there is no evidence of muscle wasting or weakness. Blood and laboratory tests reveal no abnormal results. Prognosis is good and children can usually be expected to develop normally. **

Congenital hypomyelinating neuropathy (CHN) is an early-onset motor-sensory neuropathy associated with abnormal myelination of peripheral nerves and a variable inheritance pattern. It presents at birth, typically with hypotonia and limb weakness, neuropathy, and arthrogyrposis. *

Congenital: A trait or disorder that is present at and existing from the time of birth. **

Congenital Myasthenic {MY-AS-then-ick} Syndrome: A form of myasthenia gravis that is caused by an inborn error in the neuromuscular junction. Affected children are born with the disorder and usually develop symptoms by their first birthday. **

Congenital Myopathies {MY-op-path-ee}: A group of inherited muscle disorders characterized by a specific structural change within the muscle. They often present in a similar way with either a floppy infant syndrome at birth or in infancy or later with muscle weakness. They may have different modes of inheritance. **

Congenital Muscular Dystrophies: A group of muscle disorders where affected children are born with varying degrees of muscle weakness. **

Congestion: Excessive or abnormal accumulation of secretions, usually in the lungs or airways. **

Congestive heart failure: A buildup of fluid in the lungs or extremities, or both (especially the legs). This occurs if the heart cannot pump the blood adequately. ##

Congo red: A dye that is used to stain tissues to be examined under the microscope. It detects the protein amyloid. *

Congophilic: Material in histological sections (tissue samples seen under the microscope) that becomes stained by Congo red. *

Conization {ko-ni-ZAY-shun}: The surgical removal of a cone-shaped piece of tissue from the cervix and cervical canal. Conization may be used to diagnose or to treat a cervical condition. % Also called cone biopsy. #

Consanguinity {CON-san-guin-ity}: A genetic relationship. Consanguineous individuals have at least one common ancestor in the preceding few generations.

Conservative change: An amino acid change that does not significantly affect the function of the protein. %

Conserved sequence: A base sequence in a DNA molecule (or an amino acid sequence in a protein) that has remained essentially unchanged throughout evolution. Conserved DNA sequences are believed to be involved in important functions that are similar in different species. ###

Contact dermatitis: In general, a skin rash resulting from exposure to either an irritating (e.g., an acid) or allergicsubstance.

Contiguous {CON-tig-you-ous} genes: Genes physically close on a chromosome that when acting together express certain traits.

Contractures: Fixed resistance to passive stretching of certain muscles due to shortening or wasting (atrophy) of muscle fibers or the development of scar tissue (fibrosis) over joints.

Contracture: the shortening of a muscle caused by either disease of the muscle (and/or weakness) or maintaining a joint in a particular position long enough to allow permanent shortening of the muscle and joint capsule. *

Contralateral: the opposite side. For example, during brain surgery for essential tremor, if the surgery is performed on the right side of the brain, the left side of the body will be affected.

Controlled-release formulation: A form of a drug (e.g., L-dopa) that is absorbed slowly by the digestive system, prolonging the duration of effect of each dose.

Coombs' test: A test named for its originator, R.R.A. Coombs, used to detect non-agglutinating antibodies on red blood cells by addition of an anti-immunoglobulin antibody.

Cordocentesis: the removal of a sample of fetal blood by inserting a hollow needle through the abdominal wall of a pregnant woman, under ultrasound guidance, into the umbilical vein. The blood is subjected to chromosome analysis and biochemical and other tests to determine the presence of abnormalities.

Corpus {COR-pus}: A distinct bodily mass or organ having a specific function. #

Corticobasal degeneration (CBD): A slowly progressive disorder characterized by neurodegenerative changes of certain brain regions, including the cerebral cortex (particularly the frontal and parietal lobes) and parts of the basal ganglia. Most patients initially develop symptoms in their 60s or 70s. Primary findings may include stiffness (rigidity); slowness of movement (bradykinesia); loss of the ability to coordinate and execute certain purposeful movements of the arms or legs (limb apraxia); the sensation that a limb is not one's own ("alien limb phenomenon"); and other sensory abnormalities. Affected individuals may also develop slurred, labored speech (dysarthria); dystonia; and irregular, involuntary, "shock-like" contractions of certain muscle groups, particularly of the hands and forearms, that may be provoked or aggravated by voluntary movement and certain external stimuli (action and reflex myoclonus).

Corticospinal: Referring to or connecting the outer region of the brain (cerebral cortex) and the spinal cord.

Corticosteroids (steroids): A type of chemical substance naturally produced in the body. There are various types of steroid. Steroids are responsible for maintaining many of the workings of the body. A steroid is also an artificial form of the natural chemical substance that is used for treating particular medical conditions. There are various types of these steroids. A steroid is also a drug that increases the development of your muscles. These drugs are sometimes taken illegally by people taking part in sports competitions.

Corticosteroid agents: Synthetic medications similar to corticosteroid hormones, which are naturally produced by the outer regions of the adrenal glands (adrenal cortex). Corticosteroid agents may be prescribed to treat inflammatory conditions; as long-term therapy to suppress the immune system (immunosuppressive therapy) in order to prevent rejection of a transplanted organ; as hormone replacement therapy for those with insufficient levels of natural corticosteroid hormones; or as therapy for other conditions. High dose, long-term corticosteroid therapy may result in various adverse effects, including an increased susceptibility to infection; osteoporosis, a bone disorder characterized by a progressive loss of bone mass; high blood pressure (hypertension); tissue swelling (edema); or retarded bone growth in children.

Course: How a disease will present itself over time in a person. *

COX: see cytochrome oxidase *

Cramps: A true cramp is a specific condition in which muscles undergo painful involuntary contractions (muscle shortening). The classic muscle cramp is neural in origin, meaning abnormal nerve activity rather than abnormal muscle activity cause the contractions. This type of contraction problem usually has a sudden onset and may be ended by stretching the muscle passively. True cramps can occur in anyone, particularly after exercise or at night. Neuromuscular diseases in which classic cramps are common are amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). A second kind of cramp, which doesn't involve abnormal nerve activity, occurs when a muscle is temporarily locked in a contracted state. This is technically called a contracture, but isn't to be confused with the more common use of "contracture" to indicate fixed joints. *

Cranial: Of or from the cranium or skull.

Cranial nerve nuclei: Specialized groups of nerve cells (nuclei) that give rise to and convey or receive impulses from sensory and motor constituents of the cranial nerves, which are the 12 pairs of nerves that emerge from the brain. These nerve pairs convey sensory impulses for various functions including taste, smell, hearing, and vision; motor impulses involved in controlling eye movements, chewing, swallowing, facial expressions, etc.; and impulses for transmission to certain organs and glands for regulation of various involuntary or autonomic activities.

Cranial neuropathy: Disease or damage of a cranial nerve or nerves. The cranial nerves are the 12 nerve pairs that arise directly from the brain and are involved in conveying impulses for various functions including smell, hearing, vision, and taste; pupil contraction; eye movements; facial expressions; movements of the tongue, head, and shoulders; etc. Cranial neuropathy may result in associated muscle weakness; abnormal sensations, such as numbness, tingling, or pain; or other findings. Specific symptoms depend upon the specific nerve(s) affected.

Craniopharyngioma {KRAY-nee-oh-fah-rin-jee-O-ma}: Type of brain tumor #

Craniotomy {kray-nee-OTT-toe-me}: An operation in which an opening is made in the skull so the doctor can reach the brain. #

Creatine {CREE-a-teen}: Creatine is an amino acid (amino acids are the building blocks of protein) which is made in the body by the liver and kidneys, and is derived from the diet through meat and animal products. In the body, creatine is changed into a molecule called "phosphocreatine" which serves as a storage reservoir for quick energy. Phosphocreatine is especially important in tissues such as the voluntary muscles and the nervous system which periodically require large amounts of energy. The amount of phosphocreatine in the muscles of people with some neuromuscular disorders, such as mitochondrial myopathies or inflammatory myopathies, is lower than normal. Researchers are currently trying to see if creatine supplementation in these people may improve muscle strength by bolstering the muscle's energy stores.

Creatine kinase (CK) (also known as "phosphocreatine kinase," or CPK): an enzyme (a type of protein), that catalyzes, ("encourages,") a biochemical reaction to occur, adding a phosphate group to creatine, turning it into the high-energy molecule phosphocreatine. Phosphocreatine is burned as a quick source of energy by our cells. During the process of muscle degeneration, muscle cells break open and their contents find their way into the bloodstream. Because most of the CK in the body normally exists in muscle, a rise in the amount of CK in the blood indicates that muscle damage has occurred, or is occurring.
Higher amounts of serum CK can indicate muscle damage due to chronic disease or acute muscle injury. The level of the CK may be a relative measure of the amount of disorder and CK levels may be monitored to see if treatment is having an effect.
Creatine kinase is made up of three important subtypes (isoenzymes):
CK-BB (CK1). Exists primarily in the brain. CK-BB can be an important indicator of tissue damage in the brain from stroke, trauma or other causes.
CK-MB (CK2). The primary indicator used to diagnose a heart attack because it exists in the highest amount in the heart. If CK-MB makes up more than 5 percent of a total CK level, a heart attack is suspected. CK-MB rarely rises following chest pain caused by angina, pulmonary embolism or congestive heart failure, making it a valuable tool for determining whether a heart attack is the cause of chest pain. Furthermore, if one part of CK-MB (CK-MB2) is greater than another part (CK-MB1) by a ratio of 1.5 or more, then this is another indication that a heart attack has occurred.
CK-MM (CK3). Exists primarily in skeletal muscle. Elevated levels may suggest muscle disorders or injury to skeletal muscle. Creatine kinase tests may measure total CK levels or may break down the individual levels of CK-BB, CK-MB and CK-MM.

Creatinine {CREE-at-in-neen}: an inactive breakdown product of creatine. Creatinine has no function in the body and is simply excreted in urine, where it is monitored clinically as a marker of kidney function. Measured in the urine as urinary creatinine levels (CRTU). Often creatinine and creatine are (inappropriately) used interchangeably.

Creutzfeldt-Jakob {KROITS-Felt Ya-Cop} disease (CJD): A rare, degenerative, life-threatening brain disorder characterized by severe, progressive dementia; visual disturbances; muscle weakness; and abnormal involuntary movements, such as sudden, brief, "shock-like" muscle spasms (myoclonus), tremor, and relatively slow writhing motions that appear to flow into one another (athetosis). Most frequently, Creutzfeldt-Jakob disease erupts spontaneously (sporadically), with no detectable cause, although , about 10 percent of cases are familial, potentially suggesting a hereditary predisposition to the disease. Evidence suggests that CJD may be caused by mutations in the human prion protein gene or contamination with abnormal prion protein ("prion" was named for "protein infectious agent"). Changes in the prion protein appear to lead to distinctive neurodegenerative abnormalities, i.e., relatively small, round, "sponge-like" (spongiform) cavities or gaps in certain brain regions. CJD belongs to a group of related neurodegenerative disorders categorized as types of "transmissible spongiform encephalopathy" (TSE) or spongiform encephalopathy (SE). It appears that similar diseases also can occur in other animals, for example, bovine spongiform encephalopathy (BSE) (seen in cattle - the so-called "mad cow disease"); Scrapie (in sheep); Chronic wasting disease (in deer); Feline spongiform encephalopathy (FSE in house cats).
Also see: Human prion Diseases. Also see prion.
TYPES of CJD seen:
Sporadic Creutzfeldt-Jakob Disease (CJD) is the most common of the human prion diseases accounting for approximately 80% of all cases. 5 variants are known (excluding the so-called thalamic variant which actually is the sporadic form of Fatal Familial Insomnia or FFI, see below ). The sCJD variants differ for clinical and histopathological characteristics as well as for the molecular features such as the genotype at codon 129 of the prion protein gene and the type of the scrapie prion protein.
Sporadic Familial Insomnia (sFI): Very rare cases of patients who have clinical and histopathological features indistinguishable from FFI but do not have the mutation on the prion protein gene that characterizes FFI.
Familial CJD, FFI, and Gerstmann-Sträussler-Scheinker Syndrome (GSS): The familial form of prion diseases includes diseases that have the clinical and pathological features of CJD, FFI, or GSS. In a few cases, the pathological features are mixed or undefined. Currently, over 20 mutations of the prion protein gene are known to cause a prion disease in humans.
Acquired CJD: It has been shown that human to human transmission of CJD can occur as the result of tissue implant, use of contaminated neurosurgical instruments, or administration of hormones extracted from contaminated human organs. Approximately 200 such cases, called iatrogenic CJD, are known to have occurred around the world.
Variant CJD (vCJD) or New variant CJD (nvCJD): name given to a newly identified human TSE which is significantly different from other forms of CJD. There is strong evidence that the nvCJD has been acquired by humans from eating material from cattle affected by the bovine spongiform encephalopathy or "mad cow" disease, which occurred with epidemic proportions in the UK since the 1980's. The nvCJD has well defined and consistent clinical and pathological features that make it relatively easy to identify and that distinguish it from sporadic CJD. Variant CJD is the form associated with bovine spongiform encephalitis and appears to occur only in persons with MM homozygosity at the PrP gene at the codon 129 position. Clinical expression usually starts with psychiatric problems, including anxiety and insomnia, sometimes accompanied by painful sensory complaints. The disease is progressive to an akinetic-mute state that results in death within a median of 14 months after onset.

Kuru: is a prion disease that is virtually extinct today. It was originally described in members of a tribe of the New Guinea known to practice endocannibalism. The epidemics probably originated from the consumption of contaminated meat from a member of the tribe affected by sporadic CJD.

Crossreact: Refers to the interaction of an antibody with an antigen that did not specifically or originally trigger its production. For example, in an abnormal autoimmune reaction, an antibody that was initially formed in response to an invading bacterium may inappropriately react against certain of the body's own tissues that contain some of the same amino acid sequences as within the microorganism.

Cross-reactivity: The ability of an antibody, specific for one antigen, to react with a second antigen; a measure of relatedness between two different antigenic substances.

Cryosurgery {kry-o-SIR-ja-ree}: Treatment with an instrument that freezes and destroys abnormal tissues. #

Cryptorchidism {kript-OR-kid-izm}: A condition in which one or both testicles fail to move from the abdomen, where they develop before birth, into the scrotum; also called undescended testicles. #

CSF: Cerebrospinal fluid *

CT or CAT scan: Detailed pictures of areas of the body created by a computer linked to an X-ray machine. Also called computed tomography {TOM-og-raph-ee} scan or computed axial tomography scan.

Culture: A batch of cells, which can be microorganisms or of animal or plant origin, that are grown under specific conditions of nutrient levels, temperature, pH, oxygen levels, osmotic factors, light, pressure, and water content. Cultures of cells are prepared in the laboratory for a wide spectrum of scientific research.

Cyanosis {SIGH-in-oh-sis}: A bluish discoloration of the skin caused by insufficient levels of oxygen in the blood. A person with cyanosis is said to be cyanotic {SIGH-in-ought-tick}. **

Cyst: A closed sac or capsule, usually filled with fluid or semisolid material. #

Cystectomy {sis-TEK-to-mee}: Surgery to remove the bladder. #

Cystic fibrosis (CF): A genetic disease involving a sticky buildup of mucus in the lungs (which makes breathing difficult and leads to infections), as well as pancreatic insufficiency (which leads to digestive problems). It is a recessive disease, occurring only when a child inherits two mutated copies of the CF gene - one from each parent. About one in 28 Caucasians carry the gene defect. ###

Cystitis {SIS-tie-tus}: An inflammation of the bladder. ##

Cytokines: In general, a cytokine is any substance that promotes cell growth and cell division. Powerful chemical substances secreted by cells. They include lymphokines produced by lymphocytes and monokines produced by monocytes and macrophages. Cytokines are a large group of molecules that regulate interactions in the immune system. Cytokines are messengers that carry biochemical signals to regulate local and systemic immune responses, inflammatory reactions, wound healing, formation of blood cells, and many other biologic processes. More than 100 cytokines have been identified, e.g. Interleukin 1 (Il-1).
Also: Proteins (usually GlycoProteins) of relatively low molecular mass and usually consist of a single chain. Cytokines are signaling chemicals secreted by various Leukocytes to activate other cells, coordinate, and regulate all important biological processes: Cell Growth, Immunity, Cell Activation, Inflammation, Tissue Repair, Fibrosis and MorphoGenesis.
Cytokine Mechanisms:
-Autocrine: effects only the producing cell
-Endocrine: travel through the bloodstream, acting on numerous distant cells
-Paracrine: acts locally on target cells, adjacent to the producing cell

Cystoscope {SIS-toe-scope}: An instrument that allows the doctor to see inside the bladder and remove tissue samples or small tumors. #

Cystoscopy (sist-OSS-ko-pee): Examination of the bladder and urethra using a thin, lighted instrument (called a cystoscope) inserted into the urethra. Tissue samples can be removed and examined under a microscope to determine whether disease is present. %

Cyto {SIGHT-toe}: cyto is a prefix that refers to cells. *

Cytochrome oxidase: An enzyme complex of the respiratory chain in the mitochondria [the important energy factory of the cell]. *

Cytochrome oxidase (COX): An enzyme complex comprising the terminal two cytochromes (cytochromes a and a3) of the respiratory chain in the mitochondria. It is responsible for the reduction of oxygen, receiving two electrons from cytochrome c (which precedes it in the chain) and combining them with two hydrogen ions and an oxygen atom to form water. Abnormalities in COX have been implicated the normal aging process and in various diseases, including Alzheimer's disease and various muscle diseases. See also: mitochondrial myopathies. *

Cytogenetics {sight-toe-genetics}: The study of inheritance in relation to the structure and function of cells. The branch of biology that deals with heredity and the cellular components, particularly chromosomes, associated with heredity.

Cytoplasm: Part of the fluid within the cell. Protoplasm not including the nucleus of the cell. A complex, semi-fluid, translucent substance composed of proteins, fats, and other molecules suspended in water. Cytoplasm is basically the substance that fills the cell. It is a jelly-like material that is eighty percent water and usually clear in colour. It is more like a viscous (thick) gel than a watery substance, but it liquefies when shaken or stirred. The cytoplasm, as seen through an electron microscope, appears as a three-dimensional lattice of thin protein-rich strands. These lattices are "struts" known as micro tubular lattice (MTL) that serve to interconnect and support the other "solid" structures in the cytoplasm. In other words, the MTC is like a fence that is made up of laths that are connected together. This fence's main purpose is to hold together the organelles within the cytoplasm.
Cytoplasm is the home of the cytoskeleton, a network of cytoplasmic filaments that are responsible for the movement of the cell and give the cell its shape. The cytoplasm contains dissolved nutrients and helps dissolve waste products. The cytoplasm helps materials move around the cell by moving and churning through a process called cytoplasmic streaming. The nucleus often flows with the cytoplasm changing the shape as it moves. The cytoplasm contains many salts and is an excellent conductor of electricity, which therefore creates a medium for the vesicles, or mechanics of the cell. The function of the cytoplasm and the organelles which sit in it, are critical the cell's survival. *

Cytoskeletal: a network of protein filaments and microtubules within the cytoplasm of a cell that controls the cell's shape, maintains intracellular organization, and is involved in cell movement.

Cytotoxic {sight-toe-TOX-ic}: Causing the death of cells - often refers to drugs used in chemotherapy. #

Cytotoxic T lymphocytes (CTLs): A subset of T lymphocytes that can kill body cells infected by viruses or transformed by cancer. CTLs recognize surface markers on other cells in the body that label those cells for destruction. In this way, CTLs help to keep virus-infected or malignant cells in check. Cytotoxic (Cytolytic) T cell: Cell that kills target cells bearing appropriate antigen within the groove of an MHC class I molecule that is identical to that of the T cell.


A - C      D - F      G - K      L - O     P - S     T - Z.

D gene: A small segment of immunoglobulin heavy-chain and T-cell receptor DNA, coding for the third hypervariable region of most receptors.

Database mining: Database mining is the process of finding and extracting useful information from raw datasets. Data mining is a key element of a larger process called knowledge discovery in databases, or KDD. Data mining is defined as "exploration and analysis by automatic and semiautomatic means, of large quantities of data in order to discover meaningful patterns and rules".
One example of a rapidly growing database is the biomedical literature, which consists of vast numbers of observations. The observations of interest to a single researcher are so numerous and are distributed among so many journals that it is virtually impossible for a researcher to obtain all the information that is important and available for their work. For example, the keyword anthrax is found in only 1172 of the 11 million articles that have been published in biomedical journals over the past 35 years, but those articles are distributed among 364 different journals. This is compounded by the fact that research areas that overlap can belong to different fields, with their respective observations published in unconnected literatures. Text mining (a subset of data mining) methods, such as grammar induction, (grammar induction is a form of natural language processing, or NLP) can be used to uncover these hidden relationships (the undiscovered knowledge ) and can connect observations. These connections take the form of testable hypotheses.
In a genetics context, computational genomics has identified a classification of three successive levels for the management and analysis of genetic data in scientific databases: Genomics; Gene expression; and Proteomics. Genome database mining is the identification of the protein-encoding regions of a genome and the assignment of functions to these genes on the basis of sequence similarity homologies against other genes of known function. Gene expression database mining is the identification of intrinsic patterns and relationships in transcriptional expression data generated by large-scale gene expression experiments. Proteome database mining is the identification of intrinsic patterns and relationships in translational expression data generated by large-scale proteomics experiments.
Improvements in genome, gene expression and proteome database mining algorithms will enable the prediction of protein function in the context of higher order processes such as the regulation of gene expression, metabolic pathways and signaling cascades. Thus, the final objective of such higher-level functional analysis will be the elucidation of high-resolution structural and functional maps of the human genome.
Also see: In Silico Biology.

DC inhibitors: Drugs that block decarboxylase, one type of enzyme that breaks down dopamine. Also called AADC inhibitors, they include carbidopa and benserazide.

Decarboxylase: A category or subclass of enzymes that removes or eliminates a molecule of carbon dioxide from a carboxylic group. Carbidopa is an inhibitor of the decarboxylation of levodopa.

Debrancher Enzyme Deficiency: A metabolic muscle disorder inherited by an autosomal recessive mode of transmission. It is associated with liver enlargement and a failure to thrive in the first year of life. Children born with this disorder are floppy at birth with poor head control. Intellect is not affected and life expectancy is considered normal. **

Deflazacort: A cortisone derivative for use in children with DMD or BMD. It mimics the positive benefits of prednisone without the same degree of side effects. It is thought that Deflazacort will slow down the deterioration caused by these disorders and thus will "buy time" for people with muscular dystrophy as researchers work to find a cure. **

Dehydration: Excessive loss of fluid from the body. #

Degenerative: Marked by or pertaining to deterioration; particularly, deterioration of the function or structure of tissue or changes from a higher to a lower or less functionally active form.

Degenerate codon: A codon that specifies the same amino acid as another codon.

Degron: Amino acid sequence, conformational determinant or chemically modified protein structure that confers metabolic instability to proteins and acts as a degradation signal.

Dejerine-Sottas Disease: One of the diseases of the peripheral nerve, Dejerine-Sottas disease is a disorder affecting infants. It is inherited via an autosomal recessive mode of transmission. Symptoms include slow development of motor skills and muscle weakness affecting hands and legs. Rate of progression and severity of symptoms may vary from child to child, but it is usually severe. **

Delayed type hypersensitivity (DTH): A T cell-mediated reaction to antigen, which takes 24-48 hours to develop fully, and which involves release of lymphokines and recruitment of monocytes and macrophages. Also called c cell-mediated immunity.

Deletion: The loss of a segment of the genetic material from a chromosome. %
Also: A loss of DNA sequence that can range from a single base pair within a gene to a large part of the chromosome. ***

Deletion mapping: The use of overlapping deletions to localize the position of an unknown gene on a chromosome or linkage map.

Dementia: a chronic or persistent disorder of the mental processes due to organic brain disease. It is marked by memory disorders, changes in personality, deterioration in personal care, impaired reasoning ability, and disorientation. Presenile dementia occurs in young or middle-aged people. The term is sometimes reserved for Alzheimer's disease and Pick's disease, but it is important to distinguish these conditions from those brain diseases for which curative treatment may be available. Also: A neurological condition characterized by a progressive decline in intellectual functioning, resulting in impaired judgment, memory, and abstract thinking; disorientation; and personality disintegration. Dementia may result due to various underlying conditions, including certain neurodegenerative diseases, such as Alzheimer's disease or Huntington's disease; brain injury or tumors; inflammation of the brain (encephalitis); successive strokes; or a condition known as normal-pressure hydrocephalus, which is characterized by enlargement of cavities (ventricles) of the brain, with cerebrospinal fluid (CSF) pressure at the upper end of normal. (CSF flows through and protects the ventricles of the brain, the spinal canal, and the space between layers of the membrane [meninges] enclosing the brain and spinal cord.) Normal-pressure hydrocephalus is associated with dementia, gait disturbances, and an inability to control urination (urinary incontinence).

Demyelination {de-MY-lin-ation}: Destruction or removal of the myelin sheath of nerve tissue. ***

Denature. To induce structural alterations that disrupt the biological activity of a molecule. Often refers to breaking hydrogen bonds between base pairs in double-stranded nucleic acid molecules to produce in single-stranded polynucleotides or altering the secondary and tertiary structure of a protein, destroying its activity.

Denaturation: The reversible unfolding of a protein from its native conformation into an unfolded state, either by heat, alteration of pH or ionic strength, or by chemical treatment.

Denaturation (of DNA): The reversible separation of the two strands of DNA as a result of the disruption of the hydrogen bonds following exposure to high temperature or chemical treatment.

Denervation: interruption of the nerve supply to the muscles and skin. The muscle is paralyzed and its normal tone (elasticity) is lost. The muscle fibres shrink and are replaced by fat. A denervated area of skin loses all forms of sensation and its subsequent ability to heal and renew its tissues may be impaired. *

Dendrites: The relatively narrow, branching projections that extend from the cell bodies of neurons. Nerve cells may contain multiple dendrites, which are stimulated by neurotransmitters, receive impulses from the nerve fibers (axons) of other neurons, and convey them toward their nerve cell bodies.

de novo: Latin for anew or afresh.

Deoxyribonucleic acid (DNA) {de-OXY-ribo-new-clay-ic}: the genetic material of nearly all living organisms. Located in the cell nucleus, DNA controls heredity by providing the information necessary for cells to replicate and to produce proteins. Also: The genetic material of living organisms; the substance of heredity. It is a large, double-stranded, helical molecule that contains genetic instructions for growth, development, and replication. The rungs of this double helix are made of base pairs. ###

Dermatomyositis (DM): A disorder of unknown cause, characterized by inflammatory changes in the skin (dermato) and muscle (myositis). It is thought to be an autoimmune disease, but this is not clear as yet. Can be found at any age, with peaks before puberty and around age 40. Rash, often confined to the face, is followed by weakness in muscles that are often tender and achy. Treatment protocols often utilize steroids such as prednisone. **

Determinant: Part of the antigen molecule which binds to an antibody-combining site or to a receptor on T cells (see hapten and epitope).

Development: Traditionally, a process of differentiation, in biology, of an organism. Emerging models of development emphasize a complex interactive process between the organism and its environment.

Developmental anomaly: A defect that is the result of imperfect development of the embryo before birth. #

Diabetes. A disease associated with the absence or reduced levels of insulin, a hormone essential for the transport of glucose to cells.

Diagnosis: The process of formulating a diagnosis, sometimes called clinical decision making. The Doctor uses the information gathered from your history and clinical tests and physical examination to develop a list of possible causes of the symptoms, called the differential diagnosis. For example, these stomach symptoms could be gall bladder or it could be appendicitis. The Doctor then decides what further tests to order to help refine the list or identify the specific disease responsible for the patient's complaints. Examples may be blood tests, specialized tests and scans or a biopsy. During this process, some possible diseases (hypotheses) may be discarded and new ones added as tests either confirm or deny the possibility that a given disease is present. The list is refined until the Doctor feels justified in moving forward to treatment. After treatment is begun, the response to the treatment is monitored and if the expected response is not seen, the list of possible diagnoses may be revised as needed. Diagnosis of muscle disorders is a difficult area and often patients are initially misdiagnosed. *

Diaphragm {DYE-a-fram}: The most important muscle for breathing, located between the chest cavity and the abdominal cavity. **

Diapedesis: Migration of cells through the walls of blood capillaries into the tissue spaces. Diapedesis is an important part of the reaction of tissues to injury (inflammation).

Dietitian (also registered dietitian): A professional who plans diet programs for proper nutrition. #

Dideoxynucleotide (didN). A deoxynucleotide that lacks a 3' hydroxyl group, and is thus unable to form a 3'-5' phosphodiester bond necessary for chain elongation. Dideoxynucleotides are used in DNA sequencing and the treatment of viral diseases.

Differential Diagnosis: a short list of disorders a patient may have based upon the symptoms presented. The Doctor generally prioritizes the disorder he or she thinks is most likely, followed by other possibilities. The differential diagnosis is used when symptoms are ambiguous and could represent one disorder or another. Usually, as symptoms progress and more observations are made (or treatments are tried), some diagnoses will be favored and some discounted. For example, these symptoms could be either a gall bladder attack or appendicitis .

Differentiated: Clearly defined. #

Differentiation: The process by which cells acquire new and unique characteristics and form specialized cells. Once differentiated, cells remain so and do not regress or jump into other types. In embryonic development, a few stem cells differentiate into all of the different specialized cell types in the body (about 200 - 250 types).

Differentiation antigen: A cell surface antigenic determinant found only on cells of a certain lineage and at a particular developmental stage; used as an immunologic marker.

Digestive system: The organs that take in food, turn it into products that the body can use, and get rid of waste. The digestive system includes the salivary glands, mouth, esophagus, stomach, liver, pancreas, gallbladder, intestines, and rectum. #

Digital rectal exam (DRE): An exam to detect rectal or prostate problems. The doctor inserts a lubricated, gloved finger into the rectum and feels for abnormal areas. #

Dilation and curettage {dil-ah-TAY-shun and KYOO-re-tahzh}: A minor operation in which the cervix is expanded enough to permit the cervical canal and uterine lining to be scraped with a spoon-shaped instrument called a curette. Also called a D and C. #

Diploid: Referring to cells that contain two of each type of chromosome. The normal amount of DNA in a somatic cell. A haploid cell only contains one set of chromosomes (as in a gamete cell - eggs or sperm). *
A diploid cell is one that has two copies of its genetic information. Each copy is from a different parent. All of the cells in the human body (except sperm or egg cells) are diploid.

Diplopia {DIP-plo-pee-a}: Double vision, which may also be monocular. ***

Directions in medical terminology:
Anterior - toward the front
Posterior - toward the back
Medial - toward the middle
Lateral - toward the outside
Rostral - toward the mouth (beak)
Caudal - toward the feet
Dorsal - toward the back surface
Ventral - toward the belly or undersurface *

Disease marker: In medicine generally, any sign that can be used diagnostically with respect to a specific disorder. A sign or feature that occurs along with a particular disease and can be reliably used to indicate the presence of the disease. A number of biochemical markers have been discovered, for example, prostatic specific antigen (PSA) is generally elevated in the blood when disease (cancer) of the prostate is present.
A vulnerability marker exists before, during, and after a particular disorder. Vulnerability markers are, generally speaking, 'risk' factors associated with particular disorders and include such things as particular genes that predispose one to a particular syndrome.

Disease-Modifying Anti-Rheumatic Drugs: see DMARDS

-Charcot-Marie-Tooth Disease (CMT)(Also known as Hereditary Motor and Sensory Neuropathy (HMSN) or Peroneal Muscular Atrophy (PMA))
-Friedreich's Ataxia (FA)
-Dejerine-Sottas Disease (DS)(Also known as CMT Type 3 or Progressive Hypertrophic Interstitial Neuropathy)

-Myasthenia Gravis (MG)
-Lambert-Eaton Syndrome (LES)
-Congenital Myasthenic Syndrome (CMS)

Dislocation: one bone end completely coming off the end of the opposing bone end so that their surfaces no longer approximate. *

Disomy {DIS-so-me}: An abnormal chromosome represented twice in a single cell. ***

Distal: away from the center. Hand (fingers) and feet (toes) are distal from the body. *
Also: Farthest from the center, from the medial line, or from the trunk; opposed to proximal. ***

Diploid: Most human cells are diploid, containing all 46 chromosomes: one copy of both members of each homologous pair (eg, two versions of chromosome 14). The full diploid human chromosome complement can be expressed as 46, XX in a woman and 46, XY in a man.

Diuretics: Medications that promote the excretion of urine. Such medications are often prescribed to help reduce excess fluid levels in the body, such as associated with chronic heart failure, high blood pressure (hypertension), or certain kidney (renal) or liver (hepatic) disorders. Diuretics help to remove excess water from the body by increasing the amount that is excreted as urine.

DMARDS: Disease-Modifying Anti-Rheumatic Drugs. DMARDs appear to decrease some inflammation though they are not categorized as antiinflammatory drugs. They are unlike NSAIDs since they do not decrease prostaglandin production, do not directly relieve pain, nor reduce fever. In effect, DMARDs slow the disease process by modifying the immune system in some way. Many misconceptions have become a prelude to the use of DMARDs for arthritis. The effectiveness, safety, side effects, and duration of use all have been questioned by concerned patients. Studies throughout the years have shown DMARDs to be very effective drugs, with uncommonly observed serious side effects. Frequent laboratory monitoring helps control the risk of side effects. Once thought to be a short-term treatment, DMARDs are now regarded as a long-term solution to controlling symptoms. DMARDs include methotrexate, leflunomide (Arava-), etanercept (Enbrel-), infliximab (Remicade-), adalimumab (Humira-), anakinra (Kineret-), antimalarials, gold salts, sulfasalazine, d-penicillamine, cyclosporin A, cyclophosphamide and azathioprine (Imuran).
Methotrexate: Methotrexate (MTX) is used widely for treating the symptoms and stemming the destruction of psoriatic arthritis. It is available by pill or injection. It is well tolerated in low doses, but has a number of side effects, including possible liver damage. It can be used up to six months for maximum effect. Individuals using it should comply with their physicians' instructions carefully.
Sulfasalazine: About one-third of psoriatic arthritis patients respond quickly to sulfasalizine, which was developed to treat inflammatory bowel disease. It also may induce long-term remissions of the disease. This drug has less dangerous side effects than some other systemic psoriasis and psoriatic arthritis treatments, including methotrexate. However, many people cannot tolerate sulfasalazine because of side effects, including nausea, vomiting and loss of appetite.
Cyclosporine: Cyclosporine is a drug that suppresses the immune system and was originally developed for use with organ transplantation. It is approved by the U.S. Food and Drug Administration to treat psoriasis, and is also used to treat psoriatic arthritis. It may be used with methotrexate, but frequent tests are required to check for kidney damage.
Antimalarials: This therapy is often used to treat rheumatoid arthritis, and is sometimes used in psoriatic arthritis. However, it can make skin psoriasis worse in some patients. On the other hand, if a person needs to take an antimalarial in order to travel, it has been reported that the antimalarial hydroxychloroquine (Plaquenil) is less likely to cause a psoriatic flare than quinacrine or chloroquine. A health care provider should be consulted about the available antimalarial treatments and alternatives.
Gold: This therapy, also called chrysotherapy, involves injecting gold salts and ingesting gold capsules. It may treat arthritis in the limbs, and even induce remission. Some people have reported it makes their lesions worse. Blood and urine samples are required to prevent kidney damage. The use of gold has declined somewhat in recent years as new therapies have been developed.
Azathioprine (brand name Imuran): This immunosuppressive drug has potent anti-inflammatory effects, and may improve skin lesions. Blood tests must be performed often because it can damage bone marrow.
Corticosteroids: Steroid medications taken by mouth are generally not recommended for long-term treatment of psoriatic arthritis, but they may relieve acute, severe joint inflammation. Large doses injected into muscles should be avoided, because the lesions can worsen after the therapy is discontinued. Occasionally, systemic steroids can provoke more severe forms of psoriasis, such as pustular psoriasis. However, selective low-dose steroid injections to inflamed joints, tendons and the area around joints can improve range of motion and limit contraction.

DMD: Duchenne muscular dystrophy.

DNA (deoxyribonucleic acid).

DNA chip (also called microarrays): Today, researchers use "DNA chips" to study genes in cells. These chips are small pieces of glass or plastic which contain "dots" of individual nucleotides (deposited with an ink jet printer) from every gene in the organism under study. Groups of dots may represent one gene. The chips are digitalized and exposed to various conditions. Researchers can use chemicals to see which dots become active under which conditions and computers can examine these complex interactions - which genes flash on and off and when. In this way, specific genes can be singled out and linked to specific experimental conditions. This is an important tool in gene research. *

DNA probe: A specific sequence of single-stranded DNA used to seek out a complementary sequence of single-stranded DNA. Probes are usually labeled radioactively or chemically to make them easier to detect, thus revealing the target DNA sequence. ###

DNA sequence: The relative order of base pairs, whether in a fragment of DNA, a gene, a chromosome, or an entire genome. %

DNA Sequencing: see sequencing.

DNA transfection: The introduction of DNA into mammalian cells and its subsequent expression within those cells.

DNA repair genes: Certain genes that are part of a DNA repair pathway; when altered, they permit mutations to pile up throughout the DNA. %

DNase (Deoxyribonuclease): One of a series of enzymes that can digest DNA.

Domain: A compact segment of an immunoglobulin molecule, made up of about 110 amino acids around an S-S bond, and encoded by a unique segment of DNA, surrounded by nontranslated sequences.

Dominant Inheritance (Autosomal): In this type of inheritance pattern, a disorder typically appears in each generation, passed on by one parent of either sex who also has the disease. Each child born to an affected parent has a 50% chance of inheriting the disorder and a 50% chance of being unaffected. There is no carrier status. **
Dominant: a term applied to the trait (allele) that is expressed regardless of the second allele. If one parent has a single defective gene that dominates its normal counterpart, then each child has a 50 percent risk of inheriting the faulty gene and the disorder. *
Dominant: Refers to a characteristic that is apparent even when the relevant gene is present in only one copy. A dominant disorder can be inherited from only one parent. ###

Dopamine: A neurotransmitter that controls movement and balance and is essential to the proper functioning of the central nervous system (CNS). Dopamine assists in the effective transmission of electrochemical signals from one nerve cell (neuron) to another.

Dopamine agonist (DA): A drug that acts like dopamine. DAs combine with dopamine receptors to mimic dopamine actions. Such medications stimulate dopamine receptors and produce dopamine-like effects.

Dopamine autoreceptor: A type of dopamine receptor that acts like a thermostat, preventing excess dopamine release as levels rise.

Dopamine receptor: A molecule on a receiving nerve cell (neuron) that is sensitive (or receptive) to stimulation (arousal) by dopamine or a dopamine agonist. At least five types have been identified including D1, D2, D3 receptors and the dopamine autoreceptor.

Dopamine receptor antagonist: A pharmacologic agent that binds to and blocks the action of dopamine receptors, essentially hindering receptor activity by preventing stimulation by dopamine.

Dopaminergic dysfunction: Malfunction of dopamine receptors.

Dorsiflexion: Movement of a part at a joint to bend the part toward the dorsum, or posterior aspect of the body. ***

Dosage measures: dosage is commonly measured in grams (g) or milligrams (mg) or micrograms (ug). 1000 micrograms = 1 milligram and 1000 milligrams = 1 gram. For most medications, doses in the milligrams are common (grams of a drug would generally be a large dosage).

Dosage (in genetics): the amount of a gene present. In some mutations, genes are lost or added, affecting the proper dosage of the gene.

Dosage compensation: Another term for X chromosome inactivation. To prevent the double dosage of X genes in females.

Dosimetrist {do-SIM-uh-trist}: A person who plans and calculates the proper radiation dose for treatment. #

Double-stranded complementary DNA (dscDNA). A duplex DNA molecule copied from a cDNA template.

Double helix: The shape that two linear strands of DNA assume when bonded together. %

DOUBLE BLIND: see clinical trials

Downstream: an event that happens as the result of some earlier (upstream) event. A car boiling over is the downstream result of a leak in the radiator. Many diseases are the downstream result of some earlier event (a trigger).

Downstream (re: DNA): The direction on a DNA template from the 3' end to the 5' end, or toward the site of the initiation of transcription. Also see upstream *

DR antigens: MHC class II molecules found on B cells and antigen-presenting cells of humans.

Drosophila melanogaster: A type of fruit fly used as a model organism to study genetics and development. ###

Drug resistance: The result of the cell's ability to resist the effects of a specific drug. ##

Duchenne {DO-shen} Muscular Dystrophy (DMD): An X-linked recessive disorder of muscle caused by an absence of a protein known as dystrophin. Symptoms are caused by muscle weakness that results in progressive difficulty with walking, mobility and activities of daily living. There is presently no cure or treatment. **
Also: Duchenne muscular dystrophy: A genetic disease that prevents muscles from developing properly in early childhood and may be crippling. Primarily affecting males, it is caused by a mutant gene on the X chromosome. ###
DMD/BMD in females: In rare instances, females have been found which have a DMD or BMD phenotype. Theoretically, at a molecular level, several potential causes can be envisaged;
= disease-causing mutations present in both DMD genes (i.e. on both X-xhromosomes, one from each parent)
=non-random X-inactivation
=tanslocations disrupting the DMD-gene
The most frequently identified cause detected so far is a (balanced) translocation disrupting the DMD-gene. As a consequence, the DMD-gene is split in two and joined with a segment of another chromosome (autosome) and no functional dystrophin can be produced. In other cases, manifesting carriers (DMD/BMD females) have been identified who have a non-random X-inactivation. Females carrying two mutated dystrophin genes have not been reported so far. (From: Leiden Muscular Dystrophy pages, http://www.dmd.nl/index.html

Duct: A tube through which body fluids pass. #

Duodenum {doo-a-DEE-num}: The first part of the small intestine. #

Duplication: Inclusion of two copies of the same genetic material in a genome. A chromosome aberration resulting from unequal crossing over or exchange of segments between two homologous chromosomes. ***

Dynein (dynactin): Within a cell, there are various things that have to move or be transported. Cytoplasmic dynein and dynactin are proteins involved in the movement of different cell parts within the cell. This movement is often made though microtubules. The dynein binds to its "cargo", and provides the force to move this cargo along a microtubule from one end to the other. *

Dysarthria {DIS-art-three-a}: Difficulty in speaking because of impairment of the organs of speech or their innervation. It can be caused by weakness of the tongue or facial muscles. **
Also: Difficult and defective speech due to impairment of the tongue or other muscles essential to speech. Mental function is intact. ***

Dysesthesias: Unpleasant sensations that are produced in response to normal stimuli.

Dysferlin: A muscle-related protein (discovered in 1998) Dysferlin abnormalities are linked to at least two forms of muscular dystrophy (Miyoshi myopathy and one type of Limb-Girdle muscular dystrophy (LGMD2B)). *

Dyskinesias: Abnormal neuromuscular conditions characterized by disorganized or excessive movement (also known as hyperkinesia). Forms of dyskinesia include sudden, brief, "shock-like" muscle contractions (myoclonus); involuntary, rhythmic, oscillatory movements of a body part (tremor); rapid involuntary jerky movements (chorea); relatively slow writhing motions (athetosis); or abrupt, purposeless, simple or complex muscle movements or vocalizations (motor or vocal tics).

Dyskinesias while awake (DWA): Uncontrolled, sporadic movements of the legs and, in some cases, the arms. These movements may be very rapid (myoclonic) or quite slow and prolonged (dystonic); they usually disappear upon voluntary action. Some researchers suspect that these movements may represent a wakeful form of periodic limb movements in sleep (PLMS).

Dysphagia {DIS-phage-ee-ah}: Difficulty in swallowing. Dysphagia can be caused by weakness in the muscles that affect swallowing. **

Dysplasia {dis-PLAY-zha}: Abnormal cells that are not cancer. #

Dyspnea {DISP-knee-ah}: Labored or difficulty breathing. **
Also: Difficult or painful breathing; shortness of breath. ##

Dyspraxia: Partial loss of the ability to coordinate and perform certain purposeful movements and gestures in the absence of motor or sensory impairments.

Dystonia {DIS-stone-knee-ah}: Prolonged muscle contractions that may cause twisting and repetitive movements or abnormal posture. Dystonia is a neurological movement disorder characterized by involuntary muscle contractions, which force certain parts of the body into abnormal, sometimes painful, movements or postures. Dystonia can affect any part of the body including the arms and legs, trunk, neck, eyelids, face, or vocal cords.
If dystonia causes any type of impairment, it is because muscle contractions interfere with normal function. Features such as cognition, strength, and the senses, including vision and hearing are normal. While dystonia is not fatal, it is a chronic disorder and prognosis is difficult to predict.
It is the third most common movement disorder after Parkinson's Disease and Tremor, affecting more than 300,000 people in North America. Dystonia does not discriminate - affecting all races and ethnic groups.
See: Dystonia Medical Research Foundation http://www.dystonia-foundation.org/

Dystonic: Referring to dystonia; sudden jerky or repetitive movements and muscle spasms due to impaired muscle tone and abnormal muscle rigidity.

Dystrophic {DIS-trough-ick}: Relating to dystrophy, which are progressive changes that may result from defective nutrition of a tissue or organ.

Dystrophin {DIS-trow-fin} Protein: For years researchers looked for abnormalities to explain dystrophy of the muscles. When Louis Kunkel, Harvard Medical School, discovered problems with this protein, in 1987, it was called dystrophin, thinking that the "cause" for muscle dystrophies had been found. It now turns out that there are many important proteins involved in muscular dystrophies.
Dystrophin is a large, rod-like protein that is found at the inner surface of muscle fibres. Dystrophin is missing in Duchenne Muscular Dystrophy (DMD) patients or reduced in amount in Becker Muscular Dystrophy (BMD) patients. The lack of dystrophin protein is accompanied with a condition of muscle hardening known as fibrosis, which restricts blood supply to the muscles that then die. *

Dystrophin gene: a gene controls Dystrophin protein production, mutations of this gene cause dystrophin abnormalities. The gene was isolated in 1986. It's one of the longest genes so far isolated, stretching across 2.3 million base pairs. In fact, its extraordinary length explains its high rate of mutation. The gene has 79 exons (the segments that code for protein) but these make up only 0.6% of total gene due to large introns between them. It lies on the X chromosome, making DMD an X-linked genetic disorder, more specifically, DMD is a recessive X-linked genetic disorder where heterozygotes are not affected, although they might exhibit very mild symptoms (usually called Becker's MD). *

Dystrophin-associated proteins (DAPs): Dystrophin-associated proteins are vital to the maintenance of membrane integrity, cell adhesion and normal cellular function. Mutations in the genes encoding for parts (primarily proteins) in the dystrophin-glycoprotein complex, leads to severe muscle wasting diseases such as Duchenne/Becker muscular dystrophy, congenital muscular dystrophy and certain forms of limb girdle muscular dystrophy. *

Dystrophin-associated glycoproteins (DAGs). *

Dystrophin-Glycoprotein Complex (DGC): The dystrophin-glycoprotein complex spans the plasma membrane of the muscle and links the cortical cytoskeleton with the extracellular matrix.
The DGC is a large oligomeric (a polymer or polymer intermediate containing relatively few structural units) protein complex of the sarcolemma of skeletal muscle. Biochemical and structural characterization of the DGC indicates that it consists of dystrophin, a large, rod-shaped cytoskeletal protein that binds F-actin; alpha- and beta-dystroglycan, which bind the G domain of laminin-2 and the cysteine-rich region of dystrophin, respectively; the syntrophins and dystrobrevin, intracellular proteins that bind the carboxyl terminus of dystrophin; and the sarcoglycan-sarcospan (SG-SSPN) complex. Based on interactions of the DGC with the extracellular matrix and the cytoskeleton, and the consequences of loss of function in genes encoding DGC components, Kevin Campbell proposed that at least one function of the DGC is to provide mechanical reinforcement of the sarcolemma and to maintain membrane integrity during cycles of muscle contraction and relaxation. The absence of dystrophin disrupts these interactions, rendering the sarcolemma susceptible to damage from muscle contraction and thus leading to muscle cell necrosis in patients with DMD.
Based on: http://www.physiology.uiowa.edu/campbell/public/Research.htm
Also: Dystrophin-glycoprotein complex (DGC). The DGC forms a critical link between the cytoskeleton and the extracellular matrix (the area around but outside of the cell). The DGC is characterized by a number of proteins. *

Dystrophinopathy (dystrophinopathies): Disorders related to abnormality of dystrophin, for example, Duchenne muscular dystrophy and Becker's
Duchenne's muscular dystrophy is caused by mutations in the dystrophin gene -- usually deletions or gene inversions -- that produce total or near-total loss of the dystrophin protein from skeletal muscle, resulting in early and progressive loss of muscle function. Mutations in the dystrophin gene that cause less severe deficits in the final protein product result in Becker's muscular dystrophy, a milder disease that was historically considered a separate clinical entity. This disorder differs from Duchenne's muscular dystrophy in its later onset and milder course. When genomic research showed that these two clinically distinct disorders involved the same gene, a family of clinical disorders known as dystrophinopathies was identified. A third dystrophinopathy, X-linked dilated cardiomyopathy, was subsequently discovered. This disorder is caused by specific mutations in the dystrophin gene that lead to the selective loss of dystrophin from cardiac muscle, while dystrophin levels in skeletal muscles remain normal or nearly normal. These mutations appear to affect one of the promoter regions of the gene, resulting in the selective loss of gene transcription in cardiac tissue. Discovery of the gene coding for dystrophin thus provided the means to understand a molecular relation among three seemingly different clinical disorders. As with hemophilia A, the relation between the genotype and the clinical outcome is the result of the functional effect of different mutations on dystrophin. From: ScienceWeek Student's Edition. scienceweek.com October 03, 2003.

Dystrophy {DIS-tra-fee}: From the Greek words dys, meaning abnormal or faulty, and trophe, nourishment. Definition: a disorder caused by defective "nutrition" or metabolism.

Dystrophy proteins (general discussion): There are a number of proteins implicated in muscular dystrophies and more being discovered everyday. Protein manufacture is controlled by instructions on genes. Any problems in these instructions will lead to abnormal protein manufacture. A new term we can use to describe these protein problems is proteinopathy. There are many proteins involved in the muscle. Even a tiny problem in the structure of one of these proteins can cause a muscular dystrophy. Eventually, we will identify these gene problems and use gene therapy to repair them. A number of muscle related proteins have been discovered and named, including; Dystrophin, Merosin, Integrin, Fukutin, beta-Sarcoglycans, alpha-Sarcoglycans, Calveolin, Emerin, Calpain, and Dysferlin. *

Dysuria {DIS-YOUR-ee-ah}: Difficult or painful urination. ##

E. coli: Common bacterium that has been studied intensively by geneticists because of its small genome size, normal lack of pathogenicity, and ease of growth in the laboratory. %
E. coli: A common Gram-negative bacterium useful for cloning experiments. Present in human intestinal tract. Hundreds of strains of E. coli exist.@@

Edema {eh-DEE-ma}: Swelling caused by a collection of fluid in the soft tissues. #

Effector organs: Organs that produce a nerve-stimulated effect, such as a muscle contraction or glandular secretion.

Effusion: A collection of fluid in a body cavity, usually between two adjoining tissues. For example, a pleural effusion is the collection of fluid between two layers of the pleura (the lung's covering). ##

Electrical stimulation (ES): A test in which a small electrical charge is applied to a muscle via a needle to determine the level of muscle responsiveness.

Electrocardiogram (EKG or ECG): An EKG is a graphic tracing of the electrical activity of the heart. **

Electroencephalogram (EEG): A record of the electrical activity of the brain as recorded by a machine called an electroencephalograph. Also called encephalogram . *

Electromyography and Nerve Conduction Velocities: See appendix (Quest).

Electromyography (EMG): Commonly known as an EMG, a test where muscle function is recorded and then studied. The activity of nerves and muscles produces electrical signals called action potentials. The electrical impulses are picked up by electrodes placed on the skin and amplified on a screen in the form of wavelike tracings. Normal muscle is electrically silent when at rest, but when it is active, as during contraction or stimulation, an electrical current is generated. The current will show characteristic patterns in normal muscle and the patterns obtained can be studied to help diagnose muscle disorders. In this test, tiny needles are inserted into the muscle (sort of like acupuncture with wires attached). Usually a person cannot feel this and it is not painful to have done. Usually a computer is used to help record the findings and interpret the results. Usually several muscles are tested. *

Electromyogram: The report produced by an electromyography study. *

Electrophysiologic studies: The study of the electrical activity associated with a specific body function (e.g., EMG, EEG, etc.).

ELSI: Ethical, legal and social implications (a part of the HGP).

Embolus: Plug or clot of cells within a blood vessel. #

Embryo {EM-bree-oh}: An organism at an early stage of development, before birth. In humans the term refers to the products of conception within the uterus up to the eighth week of development, during which time all the main organs are formed (after that it is a fetus). Embryology is the study of the development of embryos. Embryogenesis {EM-bree-oh-genesis}:The development and growth of an embryo.

Embryo provider: An individual or couple having custody of and decision making authority over an embryo.

Embryonic stem (ES) cells: At the time of implantation, the mammalian embryo is a blastocyst. Part of the structure is the inner cell mass (ICM) that will develop into the baby. The cells of the inner cell mass are considered pluripotent; that is, each is capable of producing descendants representing all of the hundreds of differentiated cell types in the newborn baby. If the proper signals can be discovered, it may be possible to cause these cells to differentiate along a particular pathway, e.g., to form insulin-secreting beta cells of the islets of Langerhans.
Embryonic stem cell: Pluripotent stem-cell lines derived from early embryos before formation of the tissue germ layers.

Emerin: A muscle-related protein. Emerin abnormalities are linked to Emery-Dreifuss MD. *

Emery Dreifuss Muscular Dystrophy: Also known as humeroperoneal muscular dystrophy, this is one of the X-linked recessive disorders. It is usually noted within the first decade of life. Symptoms include wasting and weakness of the shoulder and upper arm muscles, and contractures of the neck, elbows and the Achilles tendon. The muscle weakness is slowly progressive, but cardiac abnormalities may be severe and life-threatening. **

Emesis {EM-eh-sis}: vomit. #

EMG: see electromyography.

Endoplasmic reticulum (ER) and endoplasmic reticulum stress: Protein synthesis involves a lot more than stringing amino acids together in the right order. To function correctly, each linear strand of amino acids has to fold into just the right three-dimensional shape and may also have to be modified by addition of sugars or other accessory molecules.
Cells synthesizing proteins have mechanisms to maintain quality. Recently, cell biologists have learned a great deal about how the cell manages this quality control for the protein assembly line located within a convoluted network of membranous tubes known as the endoplasmic reticulum (ER). Roughly one-third of the cell's proteins, mainly those that end up in cellular membranes or are secreted to the outside, are made in the ER.
Researchers have shown that the ER membrane contains three separate sensor molecules that respond when excessive amounts of unfolded proteins build up inside. This can happen with mutant proteins, such as the ones that cause hereditary Alzheimer's and Parkinson's disease. But it can also occur under more normal conditions if for some reason proteins are synthesized faster than they can fold and be modified. To alleviate this "ER stress," the sensors trigger a series of signaling pathways that shut down the synthesis of most proteins while turning up the production of those needed for protein folding and degradation.
This so-called unfolded protein response (UPR) is intended to protect the cell, but it's not foolproof. Sometimes, for example, the UPR can't eliminate the abnormal protein buildup in the ER. In that event, prolonged activity of the UPR may trigger cell death and may thus contribute to the neuronal loss of Alzheimer's, Parkinson's, and other neurodegenerative diseases. And the UPR may even backfire by protecting the cells of cancerous tumors from the lack of oxygen and nutrients they experience as tumors grow.

Encapsulated {en-KAP-soo-lay-ted}: Confined to a specific area; enclosed. #

Encephalitis: {IN - seffa- light - us} Inflammation of the brain. Encephalitis is most commonly caused by certain viral infections or may occur subsequent to prior infection due to immune reactions that indirectly result in inflammation (postinfectious encephalitis). Although associated symptoms and findings may be variable, features may include fever, headache, irritability, listlessness (lethargy), and weakness. Some affected individuals may also develop confusion, disturbances of speech and memory, abnormal involuntary movements, paralysis of one side of the body, seizures, and/or coma. For those with involvement of the protective membranes enclosing the brain and spinal cord (meningitis), characteristic findings may include nausea, vomiting, stiffness of the neck, abnormal sensitivity to light (photophobia), and/or other symptoms.

Encephalomyelitis {IN-seffa- MY-oh-light-tus} Acute inflammation of the brain and spinal cord. ***

Encephalopathies: {IN-seffa-LOP-pa-thees}Any abnormal conditions or diseases of the structure or function of the brain, particularly chronic, degenerative conditions.

Encephalopathy {IN-seffa-LOP-pa-thee}: Any dysfunction of the brain. ***

Enchancing antibodies: Antibodies which enhance the survival of a graft or of a tumour.

Endocrine {END-da-crin} glands (endocrine system): A compact collection of secretory cells that discharges its secretions into the blood, instead of to a free surface through a duct. (In contrast, other glands including sweat glands, salivary glands, and glands of the gastrointestinal system secrete the substances they produce through ducts, and those substances are used in the vicinity of the gland). There are five major ductless glands in mammals, whose only function is the manufacture, storage, and release of one or more specific organic chemical compounds called hormones. The five glands are the pituitary, the gonads, the adrenals, the thyroid, and the parathyroids. Other organs, such as the kidney, the stomach, and the pancreas, contain scattered patches of specialist cells with endocrine functions.
The regulation of body functions by the endocrine system depends on the existence of specific receptor cells in target organs that respond in specialized ways to the tiny quantities of the hormonal messengers. Some endocrine hormones, such as thyroxine from the thyroid gland, affect nearly all body cells; others, such as progesterone from the female ovary, which regulates the uterine lining, affect only a single organ. The amounts of hormones are maintained by feedback mechanisms that depend on interactions between the endocrine glands, the blood levels of the various hormones, and activities of the target organ. Endocrine hormones coordinate the cellular activity required for growth, reproduction, and many other functions. Hormones act by regulating cell metabolism. By accelerating, slowing, or maintaining enzyme activity in receptor cells, hormones control growth and development, metabolic rate, sexual rhythms, and reproduction. The actions of endocrine glands are linked with those of the brain by the hypothalamic control of the pituitary gland. Disorders of the endocrine system develop when there is an overproduction (hyper-) or underproduction (hypo-) of hormones. Some endocrine disorders like thyroid disease, diabetes, or Addison's disease can be manifested by muscle abnormalities.

Endocrinologist {en-do-kri-NOL-o-jist}: A doctor that specializes in diagnosing and treating hormone disorders. #

Endogenous: growing or originating from within the body.

Endogenous opiate system: A morphine-like substance that is produced within the body.

Endometrial carcinoma: A cancer of the lining of the uterus. ##

Endometriosis {en-do-me-tree-OH-sis}: A benign condition in which tissue that looks like endometrial tissue grows in abnormal places in the abdomen. #

Endometrium {en-do-ME-tree-um}: The inner layer of the uterus. #

Endoscopy {en-DOS-ko-pee}: A procedure in which the doctor looks inside the body through a lighted tube called an endoscope. %

Endothelial cells: are the cells that make up the inside of blood vessels.

Endotheliopathy: pathology or disease of the endothelial cells.

Engorgement: Swelling, usually with fluid. #

Enterostomal therapist {en-ter-roe-STO-mul}: A health care specialist trained to help patients care for and adjust to their colostomy. #

Enzyme {IN-zyme}: A protein that speeds up (catalyzes) a specific chemical reaction. *

Enzymes, Elevated: see appendix (Quest).

Enzyme-linked immunosorbent assay (ELISA): An assay in which an enzyme is linked to an antibody and a coloured substrate is used to measure the activity of bound enzyme and, hence, the amount of bound antibody.

Eosinophil: White blood cell that contains granules filled with chemicals damaging to parasites, and enzymes that damp down inflammatory reactions. Eosinophil: A polymorphonuclear leukocyte with large eosinophilic (i.e. red) cytoplasmic granules.

Eosinophil chemotactic factor of anaphylaxis (ECF-A): A substrate released from mast cells during anaphylaxis which attracts eosinophils.

Ependymoma {eh-PEN-di-MO-ma}: A type of brain tumor #

Epidemiological study: examination of the distribution of disease as well as the determining factors related to specific diseases or health-related problems in a specific population.

Epidemiology {EP-PEA-dee-me-ology}: The changes in the numbers of cases of a disease in relation to time and space. How a disease spreads, the pattern of infection of a disease. *

Epigenesis {EP-PAH-gen-ah-sis}: The theory that an individual is developed by successive differentiation of an unstructured egg rather than by a simple enlarging of a preformed entity.
Also: Related to the doctrine that the entity that will develop into a viable system (e.g., the germ cell developing into an organism) is acted upon and depends both on the conditions in its environment as well as its internal coding (i.e., it is both the phenotype and genotype that determines the emergence of the living organism). Epigenetic

Epigenetic: (epi = over/upon) Changes that influence the phenotype without influence on the genotype. Changes in the properties of the cell that do not represent inheritable changes to the genetic material. Epigenetic refers to mitotically or meiotically heritable changes in gene expression that do not involve a change in DNA sequence. Epigenetic changes can be inherited mitotically in somatic cells, providing a potential mechanism by which environmental effects on the epigenome can have long-term effects on gene expression.

Epigenetic change: A stable change in phenotype that arises from processes other than the alteration of bases in genomic DNA.

Epigenetic marks: Molecules attached to DNA that can determine whether genes are active and used by the cell.

Epigenome: The Human Epigenome Project (HEP) aims to identify, catalogue and interpret genome-wide DNA methylation patterns of all human genes in all major tissues. Methylation is the only flexible genomic parameter that can change genome function under exogenous influence. Hence it constitutes the main and so far missing link between genetics, disease and the environment that is widely thought to play a decisive role in the aetiology of virtually all human pathologies. Methylation occurs naturally on cytosine bases at CpG sequences and is involved in controlling the correct expression of genes. Differentially methylated cytosines give rise to distinct patterns specific for tissue type and disease state. Such methylation variable positions (MVPs) are common epigenetic markers. Like single nucleotide polymorphisms (SNPs), they promise to significantly advance our ability to understand and diagnose human disease.

Episome: A part of a gene. *

Epistasis {EH-PIT-tis-sis}: In genetics: An interaction between nonallelic genes, especially an interaction in which one gene suppresses the expression of another. Epistasis is kind of like dominance, but it refers to interactions between genes, not between alleles of a gene. A gene is epistatic to another gene if it suppresses the phenotype of the latter gene. The opposite of epistatic is hypostatic, but the term is rarely used. Frequently only one or a few alleles of a gene are epistatic to the other gene, while one or more are not. Also: 2. A film that forms over the surface of a urine specimen. 3. The suppression of a bodily discharge or secretion.

Epithelial carcinoma {ep-I-THEE-lee-ul kar-si-NO-ma}: Cancer that begins in the cells that line an organ. #

Epitope: A unique shape, or marker, carried on an antigen's surface, which triggers a corresponding antibody response. Also: Epitope: Discrete site on an antigen, such as a particular amino acid sequence of a protein, that is recognized by an antibody or immune-cell receptor.

Epitope spreading: Diversification and spread of the immune response to autoantigens.

Equivalence zone: In a precipitin reaction, the region in which the concentration of antigen and antibody leads to maximal precipitation.

Equivocal {ee-QUIV-al-cal}: open to more than one interpretation, ambiguous. Unequivocal means without any doubt, clear. *

Ergot: A plant alkaloid produced by the fungus Claviceps purpurea.

Ergot-derived medication: A medication that has a chemical structure based on ergot, a plant alkaloid produced by a fungus called Claviceps purpurea. Permax® and Parlodel® are examples of ergot-derived medications that may be used to treat certain neurologic movement disorders.

Erythema {air-ith-theme-ah}: Redness of the skin. ##

Erythrocyte {EAR-rith-throw-sites}: The hemoglobin-containing cell found in the blood of vertebrates, red blood cells. *
Also: The red blood cell that carries oxygen to body cells and carbon dioxide away from body cells. ##

Escherichia coli (E. Coli): A commensal bacterium inhabiting the human colon that is widely used in biology, both as a simple model of cell biochemical function and as a host for molecular cloning experiments.

Esophageal atony: Lack of normal muscle tone within the esophagus, the muscular tube that transports food from the throat to the stomach.

Esophagitis {ES-soph-pah-gi-tus}: inflammation of the esophagus (gullet). Symptoms include heartburn, regurgitation of bitter fluid, and sometimes difficulty in swallowing. Hernia, fungus infection or virus infection may cause it. *

Esophagus {ES-soph-pah-gus} (esophageal): Organ carrying food from the mouth and the stomach. #

Essential tremor (ET): A common, slowly and variably progressive neurologic movement disorder characterized by involuntary, rhythmic, "back and forth" movements (i.e., tremor) of a body part or parts. In ET patients, tremor is primarily a "postural" or "kinetic" tremor or may be a combination of both types: i.e., tremor occurs while voluntarily maintaining a fixed position against gravity (postural tremor) and/or when conducting self-directed, targeted actions (kinetic intention tremor). In many individuals with ET, both hands are affected, although the condition may sometimes initially be noted in the dominant hand. ET also frequently affects the head, with tremor occurring in a "no-no" horizontal pattern in about three quarters of patients and the remainder affected by vertical "yes-yes" tremors. Less commonly, patients have tremor involving the voice, tongue, or roof of the mouth (palate), leading to impaired articulation of speech (dysarthria). Rarely, tremor may affect the trunk or lower limbs, particularly with advanced stages of disease. ET may appear to occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal dominant trait.

Estrogen receptor assay (ER assay): A test that determines if breast cancer is stimulated by the hormone estrogen. ##

Estrogen {ES-troe-jin}: A female hormone produced primarily by the ovaries. #

Ethics: The study of fundamental principles that defines values and determines moral duties and obligation. %
Ethical, Legal, and Social Implications (ELSI): A program set up by the HGP to consider ethical issues of the genome. Rapid advances in the science of genetics and its applications present new and complex ethical and policy issues for individuals and society. ELSI programs that identify and address these implications have been an integral part of the U.S. HGP since its inception. These programs have resulted in a body of work that promotes education and helps guide the conduct of genetic research and the development of related medical and public policies.
Ethical concerns are a major part of genome research:
Privacy and confidentiality of genetic information. Who owns and controls genetic information? Is genetic privacy different from medical privacy?
Fairness in the use of genetic information by insurers, employers, courts, schools, adoption agencies, and the military, among others. Who should have access to personal genetic information, and how will it be used?
Psychological impact, stigmatization, and discrimination due to an individual's genetic differences. How does personal genetic information affect self-identity and society's perceptions?
Reproductive issues including adequate and informed consent and the use of genetic information in reproductive decision making. Do health care personnel properly counsel parents about risks and limitations? What are the larger societal issues raised by new reproductive technologies?
Clinical issues including the education of doctors and other health-service providers, people identified with genetic conditions, and the general public; and the implementation of standards and quality-control measures. How should health professionals be prepared for the new genetics? How can the public be educated to make informed choices? How will genetic tests be evaluated and regulated for accuracy, reliability, and usefulness? (Currently, there is little regulation at the federal level.) How does society balance current scientific limitations and social risk with long-term benefits?
Fairness in access to advanced genomic technologies. Who will benefit? Will there be major worldwide inequities?
Uncertainties associated with gene tests for susceptibilities and complex conditions (e.g., heart disease, diabetes, and Alzheimer's disease). Should testing be performed when no treatment is available or when interpretation is unsure? Should children be tested for susceptibility to adult-onset diseases?
Conceptual and philosophical implications regarding human responsibility, free will versus genetic determinism, and concepts of health and disease. Do our genes influence our behavior, and can we control it? What is considered acceptable diversity? Where is the line drawn between medical treatment and enhancement?
Health and environmental issues concerning genetically modified (GM) foods and microbes. Are GM foods and other products safe for humans and the environment? How will these technologies affect developing nations' dependence on industrialized nations?
Commercialization of products including property rights (patents, copyrights, and trade secrets) and accessibility of data and materials. Will patenting DNA sequences limit their accessibility and development into useful products?

Etiology {EE-tee-ology}: Refers to the search for and study of the cause(s) of a disease or disorder. **

Euchromatin {YOO-chrome-uh-tin}: Euchromatin is "active" chromatin, containing DNA sequences that are being transcribed into RNA. Thought to contain the active genes of an organism.

Eugenics {YOU-genics}: The science that studies the inheritable factors that determine the physical and mental qualities of the human race, with the aim of improving the quality of life for future generations. The term was first coined by Sir Francis Galton in 1883. Eugenics is now concerned primarily with the detection and - where possible - elimination of such genetic diseases as Down's syndrome with the aid of prenatal diagnosis. Also: The study of methods of improving the quality of human populations by the application of genetic principles. Positive eugenics would seek to do this by selective breeding programs. Negative eugenics aims to eliminate harmful genes (e.g. those causing haemophilia and colour blindness) by counseling any prospective parents who are likely to be carriers.

Eukaryote {YOU-care-ee-oat}: Cell or organism with membrane-bound, structurally discrete nucleus and other well-developed subcellular compartments. Eukaryotes include all organisms except viruses, bacteria, and blue-green algae. Compare prokaryote. %

Evidence based medicine: medical practice using the treatments that have been shown to offer the best results in controlled (scientific) clinical studies. Evidence based medicine is a trend in medicine, especially when insurance companies are paying (who want to see evidence supporting the treatments they pay for). *
Also: Evidence-based medicine/health care: a new paradigm, replacing the traditional medical paradigm which is based on authority. It is dependent on the use of randomized controlled trials, as well as systematic reviews (of a series of trials) and meta-analysis, although it is not restricted to these. There is also an emphasis on the dissemination of information, as well as its collection, so that the evidence can reach clinical practice. It therefore has commonality with the idea of research-based practice. It is also closely linked with the Cochrane Collaboration which is a worldwide network of centres, whose aim is to promote and foster this approach. *

Evolution (biological): Refers to the natural (as opposed to supernatural) origin and transformation of the living inhabitants of the planet earth throughout its geological history to the present day. Many have speculated on evolution since the time of the Greeks. The ideas which have come down to us, however, originate in the European Enlightenment. This period saw the beginning of Newtonian mechanics, mathematics and other modern scientific developments, including John Ray's species concept and C. Linnaeus' system for classifying organisms. The power of rational thought in science to explain the material universe presented a deep challenge to received wisdom, especially the biblical account of creation according to the Christian Church. Evolution by natural processes - as opposed to special creation by God - was already on the mind of most educated people. Linnaeus came to accept a limited transformation of species later in his life; other prominent figures who wrote on the possibility of evolution include the naturalist, G.L. Buffon and Charles Darwin's grandfather, Erasmus Darwin.
The first comprehensive theory of evolution is due to Jean Baptiste de Lamarck (1809) who was very much a product of the Enlightenment, both in his determination to offer a naturalistic explanation of evolution and in his systems approach. Thus, he dealt at length with physics, chemistry and geology before embarking on presenting evidence that biological evolution has occurred. He also suggested a mechanism of evolution, whereby new species could arise through changes in the relationship between the organism and its environment in the pursuance of its basic needs, which produce new modifications in its characteristics that become inherited after many successive generations.
Lamarck's theory was widely misrepresented to be merely "the inheritance of acquired characters", or caricatured as changes resulting from the "wish" fulfillment of the organism. Half a century later, Charles Darwin was to include a number of Lamarck's ideas in his own theory of evolution by natural selection. The theories of evolution and heredity are closely intertwined in their historical development. Just as evolutionists needed a theory of heredity, so plant breeders in the eighteenth century who inspired Mendel's discovery of genetics were motivated by the question as to whether new species could evolve from existing ones. In accounting for change or transformation, it is also necessary to locate where constancy or stability resides.
Darwin's (1859) theory of evolution by natural selection states that, given the organisms' capability to reproduce more of their numbers than the environment can support, and there are variations that can be inherited, then, within a population, individuals with the more favorable variations would survive to reproduce their kind at the expense of those with less favorable variations. The ensuing competition and "struggle for life" results in the "survival of the fittest", so that the species will become better adapted to its environment. And if the environment itself changes in time there will be a gradual but definite "transmutation" of species. Thus, nature effectively 'selects' the fittest in the same way that artificial selection practiced by plant and animal breeders ensures that the best, or the most desirable characters are bred or preserved. In both cases, new varieties are created after some generations.
In addition to natural selection, Darwin invoked the effects of use and disuse, and the inheritance of acquired characters in the transmutation of species. It is clear, however, that those Lamarckian ideas do not fit into the theory of natural selection, and Darwin's followers all regard the lack of a theory of heredity and variation as the weakest link in the argument for natural selection. When Mendelian genetics was rediscovered at the turn of the present century and Weismann identified the material basis of heredity as the "germplasm" in germ cells which became separate from the rest of the animal's body in the course of early development, it seemed to offer a perfect explanation of how Mendelian genes could be passed on unchanged from one generation to the next. Darwinism was promptly reinterpreted according to the gene theory in the 'neo-Darwinian synthesis' from the 1930s up to the 1950s and 60s. This coincided with an extremely productive and exciting period in the history of biology as the gene theory itself continued to inspire a series of discoveries that culminated in the DNA double helix and the genetic code.
The neo-Darwinian synthesis began with the mathematical representation of genes in populations and in plant breeding (biometrical genetics), which, together provide a rigorous theory of Darwinian natural selection in terms of genes for both discontinuous and continuously varying characters. Systematics and paleontology for their part, defined phylogenetic relationships and 'adaptive radiations' of the major groups in accordance with Darwin's dictum of 'descent with modification'. At the same time, the detailed study of chromosomes together with mutational and other cytogenetic analyses eventually clarified the molecular basis of Mendelian genes, which are located to linear arrays on chromosomes. Heritable variations are generated by random mutations in these genes, different forms (alleles) of which are subject to natural selection via the different characters they determine, As the genes, according to Weismann, are insulated from environmental influences, they are passed on unchanged to the next generation, except for rare random mutations. From: http://www.i-sis.org.uk/encyclo.php

Ewings sarcoma {YOO-ingz sar-KO-ma}: a bone cancer that forms in the middle (shaft) of large bones. Most often affects the hipbones and the bones of the upper arm and thigh. #

Ex Vivo: Referring to the use or positioning of a tissue or cell after removal from an organism while the tissue or cells remain viable. Example: removal of an organ for reparative surgery, after which it is returned to its original site. adjective: in an artificial environment outside the living organism.

Exacerbation: {X-sass-sir-bay-shon} Aggravation of symptoms or increase in the severity of a disease. **

Exaptation: {X-zap-tation} The utilization of a structure or feature for a function other than that for which it was developed through natural selection.

Excema {EX-eh-ma}: Skin irritation characterized by redness and open weeping. #

Excision: Surgical removal. ##

Exegesis: {X-AH-gee-sis} Critical explanation or analysis, especially of a text.

Exon: "expressed sequences" A segment of a gene that is transcribed by RNA as a first step in making a protein.. In many genes the exons are separated by "intervening" segments of DNA, known as introns, which do not code for proteins; these introns are removed by splicing to produce messenger RNA. A DNA sequence that is ultimately translated into protein.

Exonuclease An enzyme that breaks down nucleic acids only at the ends of polynucleotide chains, thus releasing one nucleotide at a time, in sequential order.

Expressed sequence tags (ESTs): ESTs are short sequences of complementary DNA expressed by a full-length gene. By itself, an EST is not sufficient to identify a gene or its function, but it may be useful for probes, gene mapping, chromosome identification and other purposes. ESTs provide researchers with a quick and inexpensive route for discovering new genes, for obtaining data on gene expression and regulation, and for constructing genome maps. Expressed Sequence Tags are small pieces of DNA sequence (usually 200 to 500 nucleotides long) that are generated by sequencing either one or both ends of an expressed gene. The idea is to sequence bits of DNA that represent genes expressed in certain cells, tissues, or organs from different organisms and use these "tags" to fish a gene out of a portion of chromosomal DNA by matching base pairs. The challenge associated with identifying genes from genomic sequences varies among organisms and is dependent upon genome size as well as the presence or absence of introns - the intervening DNA sequences interrupting the protein coding sequence of a gene. mRNA is very unstable outside of a cell, so scientists use special enzymes to convert it to cDNA, or complementary DNA. cDNA is a much more stable compound and, importantly, because it was generated from a mRNA in which the introns had been removed, cDNA represents only expressed DNA sequence. Once cDNA representing an expressed gene has been isolated, scientists can then sequence a few hundred nucleotides from either end of the molecule to create two different kinds of ESTs. Sequencing only the beginning portion of the cDNA produces what is called a 5' EST. A 5' EST, which is obtained from the portion of a transcript that usually codes for a protein. These regions tend to be conserved across species and do not change much within a gene family. Sequencing the ending portion of the cDNA molecule produces what is called a 3' EST. As these ESTs are generated from the 3' end of a transcript, they are likely to fall within noncoding, or untranslated regions (UTR), and therefore tend to exhibit less cross-species conservation than do coding sequences. Just as a person driving a car may need a map to find a destination, scientists searching for genes also need genome maps to help them to navigate through the billions of nucleotides that make up the human genome. For a map to make navigational sense, it must include reliable landmarks or "markers". Currently, the most powerful mapping technique, and one that has been used to generate many genome maps, relies on STS mapping. A Sequence Tagged Site (STS) is a short DNA sequence that is easily recognizable and occurs only once in a genome (or chromosome). The 3' ESTs serve as a common source of STSs due to their likelihood of being unique to a particular species, and provide the additional feature of pointing directly to an expressed gene. Because ESTs represent a copy of just the interesting part of a genome - that which is expressed, they have proven themselves again and again as powerful tools in the hunt for genes involved in hereditary diseases. ESTs also have a number of practical advantages in that their sequences can be generated rapidly and inexpensively; only one sequencing experiment is needed per each cDNA generated; and they do not have to be checked for sequencing errors as mistakes do not prevent identification of the gene from which the EST was derived. Using ESTs, scientists have rapidly isolated some of the genes involved in Alzheimer's disease and colon cancer.

Expression: To "express" a gene is to cause it to function.

Expressivity: The range of phenotypes resulting from a given genotype (myotonic dystrophy or cystic fibrosis, for example, may have a variable degree of severity). This is different from pleiotropy which refers to a variety of different phenotypes resulting from the same genotype, or from penetrance.

Extrapyramidal system: Refers to central nervous system structures (i.e., outside the cerebrospinal pyramidal tracts) that play a role in controlling motor functions. The extrapyramidal system includes substructures of the basal ganglia and the brainstem and interconnections with certain regions of the cerebellum, cerebrum, and other areas of the central nervous system. Extrapyramidal disturbances may result in postural and muscle tone abnormalities as well as the development of certain involuntary movements.

External radiation {ray-dee-AY-shun}: Radiation therapy that uses a machine to aim high-energy rays at the cancer. Also called external-beam radiation. %

Extravasation (X-trav-ah-sat-shun}: The leaking of intravenous fluids or medications into tissue surrounding the infusion site. Extravasation may cause tissue damage. ##

Fab: Fragment of antibody containing the antigen-binding site, generated by cleavage of the antibody with the enzyme papain, which cuts at the hinge region N-terminally to the inter-H-chain disulphide bond and generates two Fab fragments from one antibody molecule.

F(ab')2: A fragment of an antibody containing two antigen-binding sites generated by cleavage of the antibody molecule with the enzyme pepsin which cuts at the hinge region C-terminally to the inter-H-chain disulphide bond.

Facioscapulohumeral {Phase-see-oh-scap-u-low-humor-ril} Muscular Dystrophy: An autosomal dominant form of muscular dystrophy, usually appearing late in the first decade of life. Symptoms include weakness of the facial and extraocular muscles. Whistling, drinking through a straw and closing the eyelids tightly may be difficult or impossible. Shoulder and upper arm muscles become involved and weakness slowly progresses to include other muscle groups. Progression usually takes place over decades. **

Facultative: {fackle-ta-tive} Capable of occurring or not occurring; contingent.

Failure to Thrive: Failure of growth and development in infants, toddlers, preschoolers, school-age children, or adolescents to meet realistic expectations due to genetic, physical, psychological, or social factors. Failure to thrive in infants and children is usually noticed by failure to gain height and weight. It is important to determine whether the failure to thrive results from problems intrinsic to the patient or from problems within the environment. Problems intrinsic to the patient are usually medical problems. Problems within the environment are usually psychosocial. If the period of failure to thrive has been short, and the cause is determined and can be corrected, normal growth and development will resume. If failure to thrive is prolonged, the effects may be long lasting, and normal growth and development may not be achieved. *

Fallopian tubes {fa-LOPE-ee-en}: The pair of tubes, one on each side of the uterus, through which an egg travels from the ovary to the uterus. #

Familial disease: refers to diseases tending to occur in more members of a family than would be expected by chance alone. Familial often is used interchangeably with hereditary, however, in its strict sense, familial means that more cases of disease occur in family members in the same generation than would be expected by chance. This does not mean that the disease is hereditary (it is not passed on from one generation to the next - from parent to child. See also acquired, congenital and hereditary disease.

Familial Amyloidotic Polyneuropathy (FAP) {FAM-mill-ill AM-ill-lloyd-odd-ic poly-neur-rop-pathy}: a group of autosomal dominant disorders in which the majority are caused by point mutations in the transthyretin (TTR) gene on chromosome 18, resulting in abnormal deposition of amyloid in the peripheral nerves and in other organs, including the heart, kidneys, and eyes. It often presents in adulthood as a generalized sensori-motor and/or autonomic neuropathy, sometimes accompanied by gastrointestinal symptoms. At least 55 disease-causing mutations have been identified in the transthyretin gene. In addition, carpal tunnel syndrome, vitreous opacities, and other systemic abnormalities may be part of the presentation for some of the TTR gene mutations.

Familial {FAM-ill-yill} Myasthenia Gravis: Myasthenia gravis occurring in two or more members of the same family. Symptoms usually become evident in the first decade of a child's life. **

Fasciculation: {fas-ICK-u-lay-shon} Brief spontaneous involuntary contraction of a few muscle fibres, which is seen as a flicker or "twitch" of movement under the skin. It is most often associated with disease of the lower motor neurones (e.g. motor neurone disease). Fasciculation may be seen in the calf muscles of normal individuals. Fasciculation is seen most clearly in muscles close to the surface of the skin. Sometimes called a fibrillation. *

Fatigue: Fatigue can mean a subjective feeling of tiredness or an objective measurement of a decline in muscle force with use, but is always distinguished from weakness. Fatigue is often associated with myasthenia gravis, ALS, SMA, myotonic disorders, metabolic disorders (McArdle's and Tarui's diseases) and mitochondrial disease. It can be a feature of many of the muscular dystrophies as muscles weaken and greater energy is expended to move them.

Fc: Fragment of antibody without antigen-binding sites, generated by cleavage with papain; the Fc fragment contains the C-terminal domains of the heavy immunoglobulin chains.

Fc receptor (FcR): A receptor on a cell surface with specific binding affinity for the Fc portion of an antibody molecule. Fc receptors are found on many types of cells.

Fecal occult blood test {FEE-kul-o-KULT}: A test to check for hidden blood in stool. (Fecal refers to stool. Occult means hidden.) %

Femoral artery: Major artery in the area of the groin and thigh. #

Fetoscopy: the inspection of a fetus before birth by passing a special fibreoptic instrument known as a fetoscope through the abdomen of a pregnant woman into her uterus. Fetoscopy, usually performed in the 18th-20th week of gestation, allows the inspection of the fetus for visible abnormalities and blood sampling by inserting a hollow needle under direct vision into a placental blood vessel. The blood can then be examined for abnormalities and hence the prenatal diagnosis of blood disorders (such as thalassaemia, haemophilia, and sickle-cell disease) and Duchenne muscular dystrophy.

Fetus {feet-tus}: a mammalian embryo during the later stages of development within the uterus. In human reproduction, it is defined as an unborn child from its eighth week of development.

Fetal alcohol syndrome: A link between excessive alcohol consumption during pregnancy and birth defects; characteristics include small head and eyes, folds of the skin that obscure the inner juncture of the eyelids, short, upturned nose, and thin lips.

Fibroid {FY-broid}: A benign uterine tumor. #

Fibromyalgia: FMS {fibromyalgia syndrome) is a widespread musculoskeletal pain and fatigue disorder for which the cause is still unknown. Fibromyalgia means pain in the muscles, ligaments and tendons - the fibrous tissues in the body (but not in the joints). FMS used to be called fibrositis, implying that there was inflammation in the muscles, but research later proved that inflammation did not exist. *

Fibrosarcoma {FY-bro-sar-KO-ma}: A form of bone cancer that occurs mainly in middle-aged and elderly people. #

Fibrosis: {FIB-roe-sis} The formation of excessive fibrous tissue, as in a reparative or reactive process. *

Fibrositis {FIB-ra-sight-tus}: Inflammatory hyperplasia of white fibrous connective tissue, especially surrounding the muscles and causing pain and stiffness. *

Finasteride: A drug used to reduce the amount of male hormone (testosterone) produced by the body. *

Fine Motor Skills: usually referring to the more delicate, controlled activities done with the hands. Often muscles are used individually rather than as a large group. *

Fine-needle aspiration: A procedure in which a needle is inserted, under local anesthesia, to obtain a sample for the evaluation of suspicious tissue. ##

Fingerprint Body Myopathy: One of the congenital myopathies, this is a non-progressive disorder, present from birth, characterized by generalized weakness and hypotonia. It may be associated with delayed motor milestones. **

FISH: Florescent in situ hybridization.

Fistula: An abnormal opening between two areas of the body. ##

Flexion: The act of bending (as opposed to extending) a joint.

Flow cytometry: Test that measures DNA content in tumors. #

Fluorescence in-situ hybridization [FISH]): A technique for uniquely identifying whole chromosomes or parts of chromosomes using florescent tagged DNA. A process which vividly paints chromosomes or portions of chromosomes with fluorescent molecules. This technique is useful for identifying chromosomal abnormalities and gene mapping. In-situ means in its original place. Hybridization {high-bird-die-zation} means the pairing of two complementary strands of single-stranded DNA, giving rise to a hybrid molecule. Hybrid refers to the offspring resulting from the mating of two unrelated individuals.

Fluorescent antibody: An antibody coupled with a fluorescent dye, used with a fluorescence microscope to detect antigen on cells, tissues, or microorganisms.

Fluoroscopy {flor-OS-ko-pee}: Use of an X-ray machine to examine parts of the body directly rather than taking a picture and developing it, as in conventional X-rays. Fluoroscopy uses more radiation than a single X-ray. #

Focal compression: A squeezing together [of a nerve in a localized area]; the condition of being pressed together. ***

Foldosomes: Proteins are assisted in proper folding by other chaperone proteins refered to as foldosomes.

Founder effect: The derivation of a new population (e.g. on an oceanic island) from a single individual or a limited number of immigrants. The founder(s) represent a very small sample of the gene pool to which it or they formerly belonged. Natural selection operating on this more restricted genetic variety yields gene combinations different from those found in the ancestral population.

Founder/ancestor/precursor cell: General terms for cell without selfrenewal ability that contributes to tissue formation. In some cases they generate tissue stem cells.

Founder mutation: A mutation arising in a small founder population, then being passed on to the descendants of that population. Often confined to a given family or to a given geographic location.

Fragile-X syndrome: An X-linked trait. Fragile X syndrome is a hereditary condition which causes a wide range of mental impairment, from mild learning disabilities to severe mental retardation. It is the most common cause of genetically-inherited mental impairment. In addition to mental impairment, fragile X syndrome is associated with a number of physical and behavioral characteristics.

Frameshift: A change in the reading frame of the gene (this occurs if the number of base pairs in the deletion or insertion is not a multiple of three). In most cases, the altered reading frame results in a truncated or elongated protein. ***
Example: THE CAT SAT X... could be frameshifted by a deletion to become THC ATS ATX ... Because frameshift mutations alter the genetic message so much, their effects are usually very severe. Also see protein synthesis. *

Free Radicals (also called "other reactive oxygen species" (ROS)) : Free radicals are extremely reactive chemical compounds - often containing oxygen - that are naturally produced in the body during metabolism of foods. They are also produced in connection with exposure to air pollution, smoke, and sunlight.
Often chemical bonds are formed when two atoms share a pair of electrons. When these bonds split apart, they usually don't leave an electron behind. But when some bonds split (certain weak bonds for example), they can leave a molecule with an odd, unpaired electron, forming a free radical. Free radicals are very unstable and react quickly with other compounds, trying to capture another electron to gain stability (to achieve a paired state again). Generally, free radicals attack the nearest stable molecule, "stealing" an electron. When the "attacked" molecule loses an electron, it is oxidized and becomes a free radical itself, beginning a chain reaction. The oxidized molecules are sometimes damaged by the electron loss and acquire new properties - for example, becoming insoluble. Once the process is started, it can cascade, leading to more and more chemical damage until the whole cell becomes diseased or dies. Based on: http://www.ncrr.nih.gov/newspub/apr99rpt/Radicals.htm (defunct)
Some free radicals arise normally during metabolism. Sometimes the body's immune system's cells create them to neutralize viruses and bacteria. However, environmental factors such as pollution, radiation, cigarette smoke and herbicides can also create free radicals. Healthy cells have multiple protective mechanisms against oxidative stress and succeed in preventing cell damage to the extent that these protective mechanisms are effective. In addition, many dietary constituents are important sources of protective agents that range from antioxidant vitamins and minerals to food additives that might enhance the action of natural antioxidants. Indeed, at least part of the beneficial effects of a high fruit and vegetable diet is thought to derive from the variety of plant antioxidants that might act as beneficial supplements in humans. On the other hand, materials such as pesticides, polyunsaturated lipids, and a variety of plant and microorganism-derived toxins might increase oxidant effects in humans. Based upon: http://www.bb.iastate.edu/~jat/glutchp.html
Antioxidant chemicals (in vitamins, foods etc.) neutralize free radicals by donating one of their own electrons, ending the electron-"stealing" reaction. The antioxidant nutrients don't become free radicals in the chain reaction because they are chemically stable either with or without the extra electron. They act as scavengers, helping to prevent cell and tissue damage that could lead to cellular damage and disease. From: http://www.healthchecksystems.com/antioxid.htm
An accumulation of free radicals in a cell is known as oxidative stress. Oxidative stress is being increasingly implicated in human disease processes, particularly those involving an inflammatory component. Oxidative stress is also associated with aging, older cells display higher levels of oxidative stress, perhaps due to the breakdown of protective cell mechanisms that normally remove damaged radical elements. *

Freund's complete adjuvant: A water-in-oil emulsion that contains an immunogen, an emulsifying agent, and killed mycobacteria which enhance the immune response to the immunogen; termed "incomplete" Freund's adjuvant if mycobacteria are not included.

Friedreich's Ataxia: A progressive, autosomal recessive disorder of the nervous system. Onset of symptoms occurs in childhood. Clinical features include progressive ataxia of gait, dysarthria, clumsiness, muscle weakness, scoliosis and heart problems. Most people lose their ability to walk as the disorder progresses. **

Froment's sign: Increased resistance to passive movements of a limb that may be detected upon voluntary activity of another body part.

Frontal lobe (brain): The brain area in the front of the head (behind the forehead) is called the frontal cortex. The parts that produce movement of the body are found in the frontal lobes. This area plays an important part in our memory, intelligence, concentration, temper and personality. It helps us set goals, make plans and judge our priorities. Another region guides our eye and head movements and sense of orientation. Broca's area, important in language production, is found in the frontal lobe, usually on the left side. The frontal lobes are linked with making decisions and judgments - reasoning and logic (thinking), sensing functions and voluntary movement. When you plan what you want to do tomorrow, you are using the frontal cortex. *

Frozen section: A technique in which tissue is removed and then quick-frozen and examined under a microscope by a pathologist. ##

FSE: Feline (cat) spongiform encephalopathy. See prion. *

Fukutin {FOOK-ka-tin}: A muscle-related muscle protein. Abnormalities are linked to Fukuyama CMD*

Fukuyama {FOOK-ka ya-ma} Congenital Muscular Dystrophy (FCMD): One of the muscular dystrophies, following an autosomal recessive form of transmission. Onset of symptoms always occurs before 9 months of age, and children with this disorder are usually born floppy. Hip and knee contractures are not uncommon by age 3 and few children learn to walk. Sucking reflex may be weak. Children often have severe developmental delays, seizures and difficulty learning to speak. **

Functional gene tests: Biochemical assays for a specific protein, indicating a specific gene is not merely present but active. %

Functional Impairment: Impairment of normal day-to-day functions. No longer being able to drive a car is an example of a functional impairment. *

Functional Magnetic Resonance Imaging (fMRI): A noninvasive, diagnostic scanning procedure that produces detailed, computerized images. The use of a "contrast agent" or dye enhances the detail of the images. Sequencing of these images may help physicians visualize the body's functioning, thus aiding differential diagnosis.

Fungus: Member of a class of relatively primitive vegetable organism. Fungi include mushrooms, yeasts, rusts, molds and smuts.


A - C      D - F      G - K      L - O     P - S     T - Z.

Gait: a description of how one walks. The movement of the body, especially of the legs and feet in walking determine the gait. Various conditions can lead to abnormalities in the gait. *

Gait apraxia: Loss of the ability to consciously sequence and execute the movements required to coordinate walking. Gait apraxia may result in unsteady walking patterns; "toe-walking"; a widely based, jerky gait; and balance difficulties.

Gallbladder: A small organ that stores bile. It is located below the liver. #

Gametes: sex cells, eggs in the female and sperm in the male. Gametes differ from ordinary body cells (somatic cells) because they have only one copy of each of the 23 chromosomes (somatic cells have 22 pairs of autosomes and one pair of sex chromosomes, either an XX or an XY pair to comprise a total of 46 chromosomes). *

Gamete provider: A person who is a biological parent of an embryo, but who does not necessarily have custody of the embryo or decision making authority.

Gamma-aminobutyric acid (GABA): An amino acid neurotransmitter that inhibits or decreases the electrical activities of nerve cells. GABA is the primary inhibitory neurotransmitter in the brain.

Gamma knife radiosurgery: a highly specialized technique using a device that produces ionizing radiation to produce a lesion in the target tissue. This device focuses a beam of high intensity irradiation to a targeted area and is used as localized therapy to treat individuals with certain brain diseases (e.g., brain tumors, certain movement disorders, etc.).

Gamma rays: Like as X-rays but from a different radioactive source. #

Gastroenterologist {GAS-tro-en-ter-OL-oh-jist}: A doctor who specializes in diagnosing and treating diseases of the digestive system. #

Gastrointestinal tract: The digestive tract, where the body processes and uses food. It includes the esophagus, stomach, liver, small and large intestines, and rectum. #

Gastrostomy tube: A plastic tube inserted into the stomach through a surgical incision in the abdomen. A gastrostomy tube is used to deliver liquified food to the digestive system when swallowing becomes dangerous or difficult.

Gel electrophoresis: A method to analyze the size of DNA (or RNA) fragments. In the presence of an electric field, larger fragments of DNA move through a gel slower than smaller ones. If a sample contains fragments at four different discrete sizes, those four size classes will, when subjected to electrophoresis, all migrate in groups, producing four migrating "bands". @@

Gene: As more about genes is discovered, the definition of a gene tends to change. There are now several definitions and more being suggested all the time. Also, gene structure (what it is) and gene function (what it does) is being distinguished more these days (these definitions are not always the same.
The unit of inheritance; a working subunit of DNA. Each of the body's genes contains the code for a specific product, typically, a protein. %
Also: The chemical sequence that provides the instructions for making proteins. Each protein is created by the instructions carried by a gene. The gene is not simply read from one end to another when a protein is formed, instead, genes are composed of information units that can be read, or expressed, in a variety of combinations, thus potentially making any one gene the template to any number of proteins.
Also: Genes are defined as one or more pieces of DNA (code or sequence) that specify a protein. Research is now discovering that DNA segments that constitute a single gene may be spread out in separate pieces on the chromosome. Also, the code sequences may be combined in different ways meaning that one gene can make a whole family of protein products, for example, one gene may make several enzymes. Also, sequences can sometimes be read in either direction, each direction yielding a different protein. There can also be genes within genes and overlapping genes as well. Thus, genes are not discrete physical units with fixed boundaries on the chromosome.
Genes may contain thousands or even millions of base pairs, for example, the longest gene found to date is the dystrophin gene (muscle protein) with about 2.3 million base pairs. Not all genes are so long, the myc gene, which is important in cancer, has about 5000 base pairs. Recent research shows that there are only about 30,000 genes in the human, however, this figure is undergoing revision as further research is done (such a low number is a surprise, it had been widely predicted to be about 100,000). It seems clear that the complexity of humans is not accounted for by the number of genes present, rather in their expression and interactions. *

Gene amplification: Any process by which specific DNA sequences are replicated disproportionately greater than their representation in the parent molecules; during development, some genes become amplified in specific tissues. %

Gene Coding sequence versus promoter: Most of the genes in an average mammal are instructions for making proteins. The gene can be divided into two parts, the coding sequence, which tells the cell how to make the protein (i.e., encodes the protein sequence), and the regulatory sequence, which tells the cell when and where to make the protein. The regulatory sequence may include the promoter, enhancers, and sometimes introns, but these are often collapsed and just called the promoter.

Gene cloning: Isolating a gene and producing many identical copies of it so that it can be studied in detail. ###

Gene defects (example terms for): If a particular allele leads to a completely nonfunctional protein product, either because the protein is mutated or because no protein is produced, the allele is called a nullomorph (Latin, "no form") or a null allele: If the allele confers less function than the wild-type, it is called a hypomorph ("low form"), if it confers more function, it is called a hypermorph ("high form"). If the protein is mutated such that it has a new function, not present in the wild-type (normal type), it is called a neomorph ("new form"). Nullomorphs and hypomorphs are also called "loss-of-function" mutations (often abbreviated LOF); hypermorphs and neomorphs are called "gain-of-function". One rare but very interesting kind of neomorph is an antimorph, or "dominant negative", a mutant protein which is not only nonfunctional, but can prevent the normal protein from doing its job.

Gene Definitions (Examples):
Interested readers should see: Evelyn Fox Keller, The century of the gene, Harvard University Press, 2000.
>Functional definition: MENDEL (1866) Mendel's gene (1866) was the character or constant factor that controls one specific phenotypic trait.
>BEADLE AND EPHRUSSI (1935) Working on genes responsible for eye pigmentation in Drosophila => proposed that genes code for enzymes: One gene - one enzyme
>BEADLE AND TATUM (LATE 1940s) Geneticists found out that some enzymes are made of several subunits, each one encoded by a different gene One Gene - One polypeptide concept.
Gene deletion: The total loss or absence of a gene.

Gene (genetic) drift: Allele frequency changes in populations caused by random events rather than by natural selection, especially the effects of sampling error on the gene pool of small populations.

Gene expression: The process by which the information encoded in a gene is converted into protein or some form of RNA. The DNA sequence is first transcribed into RNA and then usually - but not always - translated into protein. ### Also: Gene expression: The process by which a gene's coded information is translated into the structures present and operating in the cell (either through proteins or RNAs). %

Gene expression profiling: Knowledge of the changes in gene expression typical for certain types and stages of diseases can give insight into the molecular changes involved in disease development and progression and provide molecular markers for diagnosis and prognosis. The cDNA array technology is a high throughput method that allows the simultaneous determination of the expression levels of thousands of genes.

Gene families: Groups of closely related genes that make similar products.
Gene Flow: the transfer of genes (actually, alleles) from one population to another.

Gene linkage map: (also called a linkage map): A map of the relative positions of genetic loci on a chromosome. Genes that are generally inherited together are located close to each other on the chromosome and said to be linked. ###

Gene pool: the totality of genetic information in a given population at a given time.

Gene product: The biochemical material, either RNA or protein, resulting from expression of a gene. The amount of gene product is used to measure how active a gene is; abnormal amounts can be correlated with disease-causing alleles. %

Gene Sequencing: See sequencing.

Gene targeting: A method scientists use to alter or turn off a particular gene in animals - used in research. ###

Gene testing: Examining a sample of blood or other body fluid or tissue for biochemical, chromosomal, or genetic markers that indicate the presence or absence of genetic disease. %

Gene transcription: The process that copies the gene's DNA sequence into messenger RNA; the first step in gene expression.

Gene translation: The process by which transcribed messenger RNA directs the synthesis of proteins from amino acids. ###

Gene Traps: Gene traps are splice acceptor-containing constructs which, if inserted into an exon or intron, can simultaneously inactivate a locus and provide locus-specific reporter expression. Also: gene trap - vectors that carry the reporter gene (with or without the start codon ATG) 3' to a splice acceptor site (a splice acceptor site is used instead of a promoter). Used primarily in ES cells to screen for genes expressed during mouse embryogenesis.

Gene therapy: Treatment that alters genes. Addition of a functional gene or group of genes to a cell by gene insertion to correct an hereditary disease. % Also: Treatment of a disease by introducing a new gene into a cell. The new gene may be used to replace a function that is missing because of a defective gene. ###

Generic: Relating to or descriptive of a general group or class. Not having a brand name - generic "no-name" soap. For example, a drug sold under or identified by its official nonproprietary or chemical name and not its brand name. Example: Acetaminophen is sold as Tylenol (brand name). Generic prescription drugs are usually cheaper that "Name brand" (proprietary) drugs. Generic advice applies to wide groups of people (people should avoid smoking).

Genetic anticipation: A phenomenon in which the onset of symptoms of a hereditary disease appears to occur at a progressively earlier age in successive generations. Genetic anticipation has been demonstrated in a number of hereditary disorders (such as Huntington's disease, dentatorubropallidoluysian atrophy, etc.) in which the gene mutation consists of abnormally long sequences or "repeats" of particular coded instructions (e.g., unstable expansion of CAG repeats). With other disorders in which genetic anticipation has previously been suggested (e.g., essential tremor), studies have indicated that increased awareness of the condition in affected families may be responsible for earlier recognition of symptom onset.

Genetic assimilation. Eventual extinction of a natural species as massive pollen flow occurs from another related species and the older crop becomes more like the new crop.

Genetic code: The sequence of nucleotides, coded in triplets (codons) along the mRNA that determines the sequence of amino acids in protein synthesis. The DNA sequence of a gene can be used to predict the mRNA sequence, and the genetic code can in turn be used to predict the amino acid sequence. The old view was that the code was a blueprint for making a protein or a cell or a person etc. Each gene would give the instructions for a given piece (a protein). This view has now been rejected, it is now seen that genes work together in a more flexible way to create an end product. Richard Dawkins makes the analogy that the genetic code is like a cooking recipe. It gives a list of ingredients and a sequence to follow and at the end we get a cake. But we can not take a cake and look at a piece and say, this crumb was made by the second word in the recipe. All of the genes contribute together to the recipe like all of the ingredients go into the cake.

Genetic counseling: Advice given to those people in whose families there is a history of inherited diseases, such as cystic fibrosis and muscular dystrophy. Families at risk are told of their chances of developing the disease, the likelihood of their children being affected, and what means of prevention and treatment of the disease are available.

Genetic determinism: Genetic Determinism is the idea that our genes determine who we are at every level: physical, emotional, and behavioral. Genetic disease. A disease that has its origin in changes to the genetic material, DNA. Usually refers to diseases that are inherited in a Mendelian fashion, although noninherited forms of cancer also result from DNA mutation.

Genetic Disorders: For a brief review: see appendix. Disorders (or predispositions) that are passed on from parents to children as part of the genetic code.

Genetic disorders website: A comprehensive website presents links to genetic disorders and links to over 50 disorders: http://dir.yahoo.com/Health/Diseases_and_Conditions/Genetic_Disorders/
(partial list of disorders): Achondroplasia, Achromatopsia, Acid Maltase Deficiency, Adrenoleukodystrophy, Aicardi Syndrome, Alpha-1 Antitrypsin Deficiency, Androgen Insensitivity Syndrome, Apert Syndrome, Arrhythmogenic Right Ventricular Dysplasia, Ataxia Telangiectasia, Blue Rubber Bleb Nevus Syndrome, Canavan Disease, Cri Du Chat Syndrome, Cystic Fibrosis, Dercum's Disease, Fanconi Anemia, Fibrodysplasia Ossificans Progressiva, Fragile X Syndrome, Galactosemia, Gaucher Disease, Hemochromatosis, Hemophilia, Huntington's Disease, Hurler Syndrome, Hypophosphatasia, Klinefelter Syndrome, Krabbes Disease, Langer-Giedion Syndrome, Leukodystrophy, Long QT Syndrome, Marfan Syndrome, Moebius Syndrome, Mucopolysaccharidosis (MPS), Nail Patella Syndrome, Nephrogenic Diabetes Insipidus, Neurofibromatosis, Niemann-Pick Disease, Osteogenesis Imperfecta, Porphyria, Prader-Willi Syndrome, Progeria, Proteus Syndrome, Retinoblastoma, Shwachman Syndrome, Sickle Cell Disease, Smith-Magenis Syndrome, Stickler Syndrome, Tay-Sachs, Thrombocytopenia Absent Radius (TAR) Syndrome, Treacher Collins Sydrome, Triose Phosphate Isomerase Deficiency, Trisomy, Tuberous Sclerosis, Turner's Syndrome, Urea Cycle Disorder, Waardenburg Syndrome, Williams Syndrome and Wilson's Disease.
-Another very good site: National Center for Biotechnology Information (NCBI) http://www.ncbi.nlm.nih.gov/disease/
-From: http://members.tripod.com/~dorakmt/genetics/notes05.html
More than 4500 inherited genetic diseases are known but still only 2% of human diseases can be attributed to primarily genetic causes. We each inherit hundreds of genetic mutations from our parents, as they did from their forebears. In addition, the DNA in our own cells undergoes an estimated 30 new mutations during our lifetime, either through mistakes during DNA copying or cell division or, more often, because of damage from the environment. Because most of these are in somatic cells, they are not passed on to the next generation. It is also estimated that each human being is a carrier of around five recessive lethal genes (that are usually not expressed).
=>Single-gene disorders (autosomal or sex-linked):
-Cystic fibrosis,
-hereditary haemochromatosis,
-Huntington's chorea,
-sickle cell disease, thalassemia, haemophilia, phenylketonuria-PKU (point mutations),
-Duchenne muscular dystrophy (DMD),
-adenosine deaminase (ADA) deficiency causing severe combined immune deficiency (SCID),
-Tay-Sachs disease.
=>Multiple-gene disorders (traits):
-Insulin-dependent diabetes mellitus (IDDM),
-multiple sclerosis (MS),
-rheumatoid arthritis (RA),
=>mtDNA disorders:
-Leber's hereditary optic neuropathy (LHON),
-neurologically-associated retinitis pigmentosa (NARP),
-myoclonic epilepsy and ragged red-fiber disease (MERRF),
-maternally inherited myopathy
-cardiomyopathy (MMC).
=>Chromosomal disorders:
-a) numerical (aneuploidy): Trisomy 21 (Down syndrome; 47, +21), Trisomy 13 (Patau syndrome; 47, +13), Trisomy 18 (Edwards syndrome; 47, +18), Monosomy X (Turner syndrome; 45, X), Klinefelter syndrome (47, XXY)
-b) structural: deletion (Di George syndrome: del 22; Cri-du-chat syndrome: 5p-)
-c) others: uniparental disomy (lack of the paternal copy of chromosome 15q: Prader-Willi syndrome, Angelman syndrome); Mosaicism (skewed X chromosome inactivation: colour blindness)
=>Other genetic disorders:
-DNA repair defects (xeroderma pigmentosum, ataxia telangiectasia, Bloom's syndrome, Fanconi's anemia))
Also: Genetic diseases take a particularly heavy toll among the young, resulting in one-fifth of all infant mortalities, half of all miscarriages, and 80 percent of all cases of mental retardation. Genetic disease afflicts perhaps 15 percent of the general population, but if one considers disease which are polygenic or have a strong genetic component (such as cancer, Alzheimer's disease, diabetes, and cardiovascular disease), then they account for fully 75 percent of all deaths in the United States. *

Genetic heterogeneity: Manifestation of similar or the same observable characteristics or traits (i.e., phenotype) resulting from different genetic mechanisms, such as changes (mutations) of different genes or a combination of genes.

Genetic linkage map: A chromosome map showing the relative positions (not the physical locations) of the known genes on the chromosomes of a given species. %

Genetic marker: A gene or DNA sequence having a known location on a chromosome and associated with a particular gene or trait. Genetic markers associated with certain diseases can be detected in the blood and used to determine whether an individual is at risk for developing a disease. * Also: A genetic marker is a variable DNA sequence that has a nonvariable component that is sufficiently specific to localise it to a single genomic locus and a variable component that is sufficiently heterogeneous to identify differences between individuals and between homologous chromosomes in an individual. Genetic markers have a pivotal role in gene mapping. Sequence variations at genetic markers are not usually functional.

Genetic screening: Testing of a population (or individual) to identify those at risk for a specific genetic disease or those at risk for transmitting such a disease to their children. ###

Genetic Syndromes: There are four mechanisms by which the abnormalities seen in genetic syndromes can arise. 1). Malformations. A malformation is due to a primary error of development or morphogenesis of an organ or tissue. Therefore all malformations are congenital, although, occasionally, they cannot be diagnosed until later in life. Malformations can be single or multiple and be minor or major. Approximately 14% of newborn babies have a minor malformation and around 3% have a major malformation. Common examples are spina bifida, cleft lip and/or palate.
2). Disruption. A disruption is a morphological defect due to external factors disturbing the normal developmental process. These factors include ischaemia, infection and trauma. An example of a disruption is seen when a strand or band of amnion (one of the linings of the sac enveloping the baby) becomes entwined around a baby's forearm or digit, which can lead to a congenital amputation of the limb.
3). Deformation. A deformation results from an abnormal mechanical force that distorts an otherwise normal structure. An example is talipes, which can occur secondary to compression as a result of reduced amniotic fluid.
4). Dysplasia. This is due to an abnormal organization of cells of a tissue, usually seen in parts of the body where that tissue is normally present. An example of this is the short limb dwarfism achrondroplasia.

Genetic Testing: see appendix (Quest).

Genetic variation: A phenotypic variance of a trait in a population attributed to genetic heterogeneity.

Geneticist: A scientist who studies genes, the basic units of heredity, and their variations. ###

Genetics: The scientific study of heredity. How particular qualities or traits are transmitted from parents to offspring. Also see human genetics. %

Genome projects: Research and technology development efforts aimed at mapping and sequencing some or all of the genome of human beings and other organisms.

Genome: All the genetic material in the chromosomes of a particular organism; its size is generally given as its total number of base pairs. %

Genomics: the study of the genome. *
Structural genomics: initiatives are being launched worldwide to generate the 3-D structures of one or more proteins from each protein family, thus offering clues to their function and providing biological targets for drug design.
Comparative genomics: analyzing DNA sequence patterns of humans and well-studied model organisms side by side - has become one of the most powerful strategies for identifying human genes and interpreting their function.

Genomic Disorders: Human diseases that result from recurrent DNA rearrangements involving unstable genomic regions. The clinical phenotype is the result of an abnormal dosage of genes (loss or gain of genes) located in the rearranged genomic regions. Genomic disorders are recombination based conditions (as opposed to monogenic disorders that only involve specific mutations within a gene and reflect errors of DNA replication and/or repair). A number of human diseases involve this mechanism, including types of Charcot-Marie-Tooth disease, Facioscapulohumeral Muscular Dystrophy, Emery-Dreifuss Muscular Dystrophy and Spinal Muscular Atrophy.

Genome maps: Charts that indicate the ordered arrangement (physical locations) of the genes or other DNA markers within the chromosomes. %

Genomic imprinting: An occurrence when the expression of a gene is affected by the parental origin for that gene (example, a gene that has a greater effect if inherited from the father). ***
Also: In genomic imprinting, a fully functional gene becomes inactivated when it is transmitted by one parent, but not if transmitted by the other parent. This inactivation can be reset, by some unknown process, each generation by passage through the germline. Genomic imprinting is involved in many human diseases and is probably crucial in the evolution of sexual reproduction. But despite its medical and theoretical importance, virtually nothing is known about the mechanism that results in this form of epigenetic gene silencing.

Genomes to Life (GTL): A new project of the U. S. Department of Energy. Building on the successes of the Human Genome Project, DOE has initiated an ambitious program to achieve the most far-reaching of all biological goals: a fundamental, comprehensive, and systematic understanding of life.
The plan for the 10-year program (from 2002) is to use DNA sequences from microbes and higher organisms, including humans, as starting points for systematically tackling questions about the essential processes of living systems. Advanced technological and computational resources will help to identify and understand the underlying mechanisms that enable organisms to develop, survive, carry out their normal functions, and reproduce under myriad environmental conditions. Website: http://doegenomestolife.org/

Genotoxin: A chemical or other agent that damages cellular DNA, resulting in mutations or cancer. *

Genotype: The gene (genetic) composition of an individual. %
Also: The allelic composition of an organism. *

Germ cells: The reproductive cells of the body, either egg or sperm cells. %

Germ line: Refers to genes in germ cells as opposed to somatic cells, that is, genes in their unrearranged state rather than those rearranged for production of a protein.

Germ Line cell: A cell that divides to produce gametes (egg and sperm cells). The fusion of one sperm cell and one egg cell represents the only genetic link between the bodies of parents and the body of their child. The cells destined to produce sperm and eggs are set aside very early in embryonic life, for example, by the 15th week of gestation, the human female fetus has already set aside each and every cell that may someday develop into a mature egg. *

Germ Line Mosaicism: See appendix (Quest). Germline mosaicism: The presence of a gene mutation for a disease trait in some yet not all of an individual's sexual reproductive cells (germ cells) within the ovaries or testes (gonads). Germline mosaicism is sometimes suspected when parents have more than one child with a genetic disorder transmitted as a dominant trait yet neither parent appears to be affected by the condition.

Germ line mutations: Mutations in egg or sperm genetic code. Germ line mutations will be found in every cell descended from the zygote to which that mutant gamete contributed. If an offspring is successfully produced, every one of its cells will contain the mutation. Included among these will be the next generation of gametes, so if the offspring is also able to become a parent, that mutation will pass down to yet another generation. (contrast with somatic mutations)

Germ Line Mosaicism: See appendix (Quest).

Gland: Organ that manufactures chemical substances. A gland may vary from a single cell to a complex system of tubes that unite and open onto a surface through a duct. The endocrine glands, e.g., the thyroid, adrenals, and pituitary, produce hormones that are secreted directly into the bloodstream. Exocrine glands secrete their substances onto an external or internal body surface. Most exocrine glands, e.g., the salivary and lacrimal glands, release their secretions through ducts. However, some open directly onto a body surface, as in the sebaceous glands of the skin and the digestive glands of the intestinal mucosa. A simple exocrine gland may consist only of a tube lined with secretory cells. In more complex types, clumps of cells produce the secretion and a duct or system of ducts discharges the secreted material. Some glands have dual functions, e.g., the liver, pancreas, ovary, and testis produce both a secretion that is emitted through a duct and a hormone that is taken up by the blood. Such structures are called mixed glands. Among the substances produced by exocrine glands in humans are sweat, lubricants like mucus and tears, and digestive juices. There are specialized exocrine glands in the animal world that produce such substances as the shells of bird eggs, spider webs, and the cocoons of the silkworm larvae. Simple glands are also common in the plant kingdom. The sweet nectar of flowers and the resinous pitch of pine trees are substances produced by plant glands.

Glia cells (or glial): A type of cell found in the nervous system, they outnumber neurons by about five to one. The glia are cells of supporting tissue for the nervous system. They have processes but do not form or conduct action potentials, and they retain the capacity to divide throughout life. There are various types:
'astrocytes (Star-shaped cells that provide physical and nutritional support for neurons: 1) clean up brain "debris"; 2) transport nutrients to neurons; 3) hold neurons in place; 4) digest parts of dead neurons; 5) regulate content of extracellular space)
'oligodendroglial cells (oligocytes) (Provide the insulation (myelin) to neurons in the central nervous system.)
'microglia (Like astrocytes, microglia digest parts of dead neurons.)
'Schwann Cells (Provide the insulation (myelin) to neurons in the peripheral nervous system.)
'satellite cells.(Physical support to neurons in the peripheral nervous system.)

Glioma {glee-O-ma}: A name for brain tumors that begin in the glial cells, or supportive cells, in the brain. "Glia" is the Greek word for glue. #

Gliosis: A proliferation of astrocytes in damaged areas of the central nervous system (CNS). Astrocytes are relatively large glial cells, which are the connective tissue cells of the CNS. Astrocytes have various functions, including accumulating in areas where nerve cells (neurons) have been damaged. Gliosis and neuronal loss in certain brain regions are findings seen in various neurodegenerative disorders.

Globus pallidus: A major substructure of the basal ganglia deep within the brain. Specialized groups of nerve cells in the globus pallidus function as an "intermediate relay system." This system processes and transmits information from the basal ganglia by way of the thalamus to areas of the brain that regulate complex motor functions (e.g., motor cortex, premotor area of frontal lobe).

Glottis: The slit-like opening between the vocal cords; the region of the voice box (larynx) consisting of the vocal cords and the opening between them.

Glutamate: An amino acid that is a primary excitatory neurotransmitter in the central nervous system. This chemical agent plays an essential role in initiating and transmitting nerve impulses, crossing synapses to stimulate postsynaptic neurons.

Glycoform: A type of protein with a specific type of glycoprotein attached. i.e. two proteins would be of the same glycoform if they carried the same glycoprotein. *

Glycoprotein: an organic compound composed of both a protein and a carbohydrate joined together in covalent chemical linkage. These structures occur in many life forms; they are prevalent and important in mammalian tissues. The attached carbohydrate may have several effects: it may help the protein to fold in the proper geometry, stabilize the protein, affect physical properties such as solubility or viscosity, helps it to orient correctly in a membrane, or make it recognizable to another biochemical or cell. Many proteins released by cells to the blood and other fluids are glycoproteins. One set of glycoproteins also carry the blood group determinants. The carbohydrate portion of a glycoprotein is usually a small sugar or no more than 8 to 10 individual monosaccharide units. Combinations of up to seven of the many different sugar molecules known to occur in nature comprise the saccharide portions of mammalian glycoproteins: glucose, glucosamine, galactose, galactosamine, mannose, fucose, and sialic acid (a derivative of glucosamine). The linkage between the oligosaccharide and the protein occurs by formation of a chemical bond to only one of four protein amino acids: asparagine, hydroxylysine, serine, or threonine. Solutions of glycoproteins usually exhibit high viscosity, an observation explaining the highly viscous character of egg white, which is composed largely of the glycoprotein ovalbumin. Salivary mucus contains the glycoprotein called mucin. Among other glycoproteins, one particularly interesting example is isolated from certain antarctic fishes who survive near-freezing water temperatures as a result of freezing-point depression of their blood serum by a globular glycoprotein. This molecule is a remarkably effective freezing point depressant. From: The Columbia Encyclopedia http://www.bartleby.com/65/gl/glycopro.html *
-Oligosaccharides consist of a few monosaccharide units joined together by glycosidic bonds.
They occur in the body attached to lipids and proteins. The resulting glycosylated proteins and lipids are called glycoproteins and glycolipids.
-Glycoproteins - proteins that contain oligosaccharides - comprise proteins which are designed for secretion, incorporation into membranes, or localization inside membranous organelles. The polypeptide chains of glycoproteins are synthesized under genetic control (proteinbiosynthesis). Their oligosaccharide chains are generated by enzymes, covalently linked to the polypeptide, and further processed in the endoplasmic reticulum and/or the Golgi apparatus.
-The oligosaccharide components of glycoproteins serve different functions. They are recognition markers for the sorting and distribution of proteins to the proper destinations within or outside the cells. They mediate molecular and cell-cell recognition. In addition, they anchor proteins to the exterior surface of the plasma membrane. Oligosaccharide markers also participate in protein degradation. The properties of the mucus secreted by mucosa cells are determined largely by their constituent glycoproteins, so-called mucins.
-Cells are covered with complex oligosaccharides that are components of glycosylated membrane proteins and lipids. They mediate the interactions of cells with other cells as well as with molecules such as hormones. For example, the AB0 blood group substances are oligosaccharides attached to membrane sphingoglycolipids.
-Although there is a large number of monosaccharides, only eight of them commonly occur in oligosaccharides: glucose, galactose, mannose, fucose (6-deoxygalactose), N-acetylglucosamine, N-acetylgalactosamine, N-acetylneuraminic acid (sialic acid), and N-acetylmuramic acid. However, there are a large variety of oligosaccharides due to the various possible ways to combine those eight monosaccharides. From: http://www.degussa_health_nutrition.de/degussa/html/e/health/eng/kh/c6.3.htm
Glycoproteins:Various types of compounds consisting of carbohydrates covalently linked with other types of chemical constituents are classified under the general name of glycoconjugates. The major groups of glycoconjugates are the glycoproteins, glycopeptides, peptidoglycans, glycolipids and lipopolysaccharides.
Glycoproteins are widely distributed in all forms of life, with the possible exception of the eubacteria. They occur in cells, both in soluble and membrane-bound forms, as well as in the extracellular matrix and in extracellular fluids. The commonest glycoproteins are those in which the carbohydrate is linked to the protein by glycosyl linkages. Glycosylation represents one of the important co-translational and post-translational modifications of proteins.
A glycoprotein is a compound containing carbohydrate (or glycan) covalently linked to protein. The carbohydrate may be in the form of a monosaccharide, disaccharide(s). oligosaccharide(s), polysaccharide(s), or their derivatives (e.g. sulfo- or phospho-substituted). One, a few, or many carbohydrate units may be present. Proteoglycans are a subclass of glycoproteins in which the carbohydrate units are polysaccharides that contain amino sugars. Such polysaccharides are also known as glycosaminoglycans. http://www.chem.qmw.ac.uk/iupac/misc/glycp.html *

Glycomics (variation: Glyconomics): The study of sugar-modifications to proteins that affect structure and function. Attachment of specific sugar residues can have an important impact on the activities of proteins. Biologists are finding
that minor differences in sugar structures can have a huge impact on biological functions. Also: Glycomics - the systematic identification and characterization of all the carbohydrates (sugar) chains used by organisms - a young and relatively undeveloped field when compared to genomics and proteomics.

GMO: Genetically modified organism. Often refers to plant strains that have been genetically modified to strengthen or reduce certain traits. A very controversial topic due to the danger that such modification may somehow damage Natural gene forms and lead to unanticipated (and uncontrollable?) consequences.

Gower Sign, Gower's sign: used to describe the process of rising from the floor by crawling up the knees using one's hands, locking out the knees with the hands, then arching the back into extension. A sign of marked weakness in the Quadriceps and Gluteal muscles of the lower extremity. *
Also: A characteristic sign seen in Duchenne muscular dystrophy. It refers to the way that young boys stand up from a lying position. They use their arms and hands to "walk up" their legs, and then push their upper bodies to a standing position. **

Grade (Tumor): The grade of a tumor depends on how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread. Grading systems are different for each type of cancer. %

Graft: Healthy skin, bone, or other tissue taken from one part of the body to replace diseased or injured tissue removed from another part of the body. #

Graft versus host reaction (GVH): The pathologic consequences of a response initiated by transplanted immunocompetent T lymphocytes into an allogeneic, immunologically incompetent host. The host is unable to reject the grafted T cells and becomes their target.

Granulocyte {GRAN-new-low-sight}: White blood cells filled with granules containing potent chemicals that allow the cells to digest microorganisms, or to produce inflammatory reactions.

Gray matter: Nerve tissue that primarily consists of nerve cell bodies, dendrites, and unmyelinated axons, thus having a gray appearance. In contrast, white matter predominantly contains myelinated nerve fibers.

Gross Motor Skills: refers to the larger, less refined movements of the legs, arms, and trunk. Muscle groups function in concert to perform the desired activity. *

Guaiac test: A test that checks for blood in the stool. ##

Guillain-Barr Syndrome: One of the diseases of the peripheral nerve, GBS affects the peripheral nervous system, including the spinal nerves and the cranial nerves. The cause is unknown, but it often follows a respiratory or flu-like illness. It is believed to be related to an auto-immune mechanism. Early symptoms include fever, malaise, and nausea. Muscular weakness usually begins in the lower limbs and moves upward. Paralysis without loss of sensation is experienced. The progression of the paralysis may stop at anytime. At its maximum point, the paralysis and other symptoms remain unchanged for days or weeks. Improvement begins spontaneously and continues for weeks or occasionally, for months. A full recovery is likely. **

H-2 complex: The major histocompatibility complex situated on chromosome 17 of the mouse; contains subregions K, I and D.

HAEMOPOIETIC STEM CELL: A cell capable of generating all the cells of the blood and lymph for the life of an animal after transplantation. This is a functional activity that can be isolated from the bone marrow by various methods and phenotypes.

Hallervorden-Spatz disease: A slowly progressive hereditary disorder characterized by abnormal accumulations of iron pigments in certain regions of the basal ganglia (e.g., globus pallidus and substantia nigra). This autosomal recessive disorder typically becomes apparent during late childhood or adolescence. Associated symptoms may include progressive stiffness and resistance to movement (rigidity); increasing difficulties speaking and eating; sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); the presence of multiple, irregular, jerky motions that may combine to appear flowing or writhing in nature (choreoathetosis); and/or other abnormalities.

Hallucinations: Perceptions that occur in the absence of external stimuli and while an individual is awake. Hallucinations may involve any of the senses, including hearing (auditory hallucinations), vision (visual hallucinations), smell (olfactory hallucinations), taste (gustatory hallucinations), and touch (tactile hallucinations). Hallucinations may occur with high-dose administration of certain medications or the abuse of particular drugs (hallucinogens) that cause increased stimulation or excitation of the central nervous system. They may also be caused by chronic alcohol abuse; sensory deprivation; certain types of seizures due to impairment or damage of a limited area of the brain (e.g., temporal lobe epilepsy); psychotic illnesses characterized by disturbances in thought, behavior, and emotional reactions (schizophrenia); or certain organic disorders, such as Huntington's disease.

Haploid: A single set of chromosomes (half [23] of the full set [46] of genetic material), present in the egg and sperm cells of animals and in the egg and pollen cells of plants. That is, not pairs of chromosomes. Human beings have 23 chromosomes in their reproductive cells. % Haploid Gametes (sperm and ova) are haploid. They contain only one member of each homologous chromosomal pair (for example, only one version of chromosome 14). All ova have chromosomal complement 23,X and sperm are either 23,X or 23,Y. When sperm and ova fuse to form a zygote, the diploid chromosomal complement is restored.

Haplotype: A particular combination of closely linked genes on a chromosome inherited from one patient. A series of alleles at linked loci along a single chromosome.

Hapten: A compound, usually of low molecular weight, that is not itself immunogenic but that, after conjugation to a carrier protein or cells, becomes immunogenic and induces antibody, which can bind the hapten alone in the absence of carrier.

Hardy-Weinberg Law: The concept that both gene frequencies and genotype frequencies will remain constant from generation to generation in an infinitely large, interbreeding population in which mating is at random and there is no selection, migration or mutation.

Heat-shock proteins: Any of various proteins that are synthesized by living cells in response to increased temperature. They function mainly as molecular chaperones, protecting the cell's proteins as they become unfolded due to heating and enabling them to refold correctly. Another protein, ubiquitin, is regarded as a heat-shock protein and acts as a marker for proteins destined for degradation. Many of the heat-shock proteins are also induced by other stresses, both natural and unnatural, including reduced oxygen concentration, changes in osmotic potential, ionizing radiation, and toxins. *

Heavy chain (H chain): The larger of the two types of chains that comprise a normal immunoglobulin or antibody molecule.

Helper T cells TH: A subset of T cells that typically carry the CD4 marker and are essential for turning on antibody production, activating cytotoxic T cells and initiating many other immune responses. Helper T cells: A class of T cells which help trigger B cells to make antibody against thymus-dependent antigens. Helper T cells also help generate cytotoxic T cells.

Hemangioma {HIM-mang-gee-oh-ma}: A purple colored birthmark consisting of overgrowth of blood vessels. #

Hematocrit (Hct): The percentage of red blood cells in the blood. A low hematocrit measurement indicates anemia. ##

Hematologist: A doctor who specializes in the problems of blood and bone marrow. ##

Hematology {Heem-ma-tology}: The science that studies the blood. ##

Hematoma {HEEM-ma-tome-ah}: A localized swelling filled with blood resulting from a break in a blood vessel. Often caused by a trauma (a bruise). *

Hematopoiesis {He-ma-toe-poe-ee-sis}: The process of formation of blood cells in bone marrow.

Hematuria {HIM-mat-URE-EE-ah}: Blood in the urine. ##

Hemichorea: Irregular, abrupt, relatively rapid involuntary (i.e., choreic) movements that are unilateral or involve muscle groups on one side of the body.

Hemizygote: Refers to a cell, organism, or individual with only one of a pair of genes for a specific trait. This term is often used to describe males who inherit one copy of an X-linked disease trait. It may also refer to the state in which genetic material is deleted from one member of a chromosomal pair.

Hemoccult (Guaiac): test: A test that checks for hidden blood in the stool. ##

Hemoglobin: A protein contained in the red blood cells; responsible for carrying oxygen. #

Hemorrhage: Loss of blood through heavy, uncontrolled bleeding. #

Heparin: A drug that decreases the clotting tendency of blood. The heparins are polymers of O- and N-linked sulfated glucosamines and hexuronic acids (iduronic and glucouronic) joined by glycoside linkages, and they are the most acidic organic acids in the human body. When administered as pharmacological agents, the heparins have anticoagulant activity, but they are not ordinarily present in blood, and their normal function has been a mystery. Mast cells are one of the two types of cells (the other type being basophils) that synthesize heparin.

Hepatomegaly {HEP-ta meg-a-lee}: An enlargement of the liver. ***

Hereditary: Inherited; inborn; referring to the genetic transmission of a trait, condition, or disorder from parent to offspring.

Hereditary diseases (inherited diseases): are transferred through the genes from a parent to a child. The cells that the child receives already are defective and the disease is predisposed or caused by these inherited defects. Depending upon the type of defect, the child may also subsequently pass on the defect to his or her children. Also see acquired, congenital and familial disease.

Hereditary Motor-Sensory Neuropathy (HMSN): HMSNs are a group of progressive disorders affecting the motor and sensory components of the peripheral nervous system. The molecular basis of inherited neuropathies has allowed identification of these disorders. HMSNs encompass the following disorders:
-HMSN Type I hypertrophic form of Charcot-Marie-Tooth disease (CMT)
-HMSN Type II neuronal form of CMT
-HMSN Type III (Dejerine-Sottas disease) Hereditary neuropathy with liability to pressure palsies (HNPP)
-Congenital hypomyelinating neuropathy (CHN)
-Refsum's disease
-Familial amyloidotic polyneuropathy (FAP)

Hereditary mutation: A gene change in the body's reproductive cells (egg or sperm) that becomes incorporated in the DNA of every cell in the body; also called germline mutation. %

Heredodegenerative: Pertaining to genetically transmitted (hereditary) neurologic disorders characterized by progressive neuronal loss and other neurodegenerative changes (e.g., associated gliosis). For example, the term "heredodegenerative dystonias" is used to refer to several, usually hereditary disorders in which neurodegenerative changes may lead to dystonia as a primary feature and other neurologic symptoms are typically present. However, in some patients with such disorders, dystonia may not always develop and other neurologic features may be primary findings. Disorders that have been categorized as heredodegenerative dystonias include ataxia-telangiectasia, Hallervorden-Spatz disease, Huntington's disease, Parkinson's disease, progressive supranuclear palsy, neuroacanthocytosis, and Wilson's disease.

Heterophile antigen: A cross-reacting antigen that appears in widely ranging species such as humans and bacteria.

Heterozygous carriers: The term "heterozygosity" refers to the state of having different genes that occupy the same position (locus) on one or more paired chromosomes. "Heterozygous carriers" describes individuals who carry a single copy of a mutated gene for a disease trait, such as females who have a copy of a disease gene for an X-linked disorder. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed, typically in a random pattern (known as "random X chromosome inactivation"). Therefore, females who are heterozygous for an X-linked disease trait often have no disease manifestations or less severe symptoms than affected males. However, because males have one X chromosome from the mother and one Y chromosome from the father, males who carry an X-linked disease trait will typically fully express the mutated gene. Rarely, females who are heterozygous for an X-linked disease trait may manifest symptoms with about the same severity as affected males.

Herpes zoster: A virus that settles around certain nerve ends, causing blisters, swelling, and pain. This condition is also called shingles. ##

Herpes {HER-peas}: Herpes is a common viral infection. The most common forms cause oral herpes (cold sores or fever blisters), and genital herpes (genital sores).
There are several types of herpes viruses:
Herpes Simplex Type 1 (HSV-1): most commonly, HSV-1 occurs above the waist (mouth).
Herpes Simplex Type 2 (HSV-2): most commonly, HSV-2 occurs below the waist (genitals). (These viruses look identical under the microscope, and either type can infect the mouth or genitals.)
Human herpes virus 3 (HHV-3): is the official name for herpes zoster virus, also called varicella zoster virus, the cause of chickenpox. Like its close relative, herpes simplex virus, herpes zoster likes to infect skin cells and nerve cells.
Human herpes virus 4 (HHV-4) is the official name of Epstein-Barr virus, the major cause of infectious mononucleosis, or mono.
Human herpes virus 5 (HHV-5): is the official name of cytomegalovirus (CMV). CMV is also a cause of mono. It can be sexually transmitted, can cause problems to newborns, and can cause hepatitis. Occasionally it is transmitted by blood transfusion. It is very common among homosexual men and is often associated with but is not the cause of AIDS. CMV infection is one of the most difficult complications of AIDS, often leading to severe visual problems or even blindness, infection of the gastrointestinal tract, diarrhea, and a variety of other difficult problems-even death.
Human herpes virus 6 and 7: (HHV-6) (HHV-7): these are recently discovered viruses. Like all human herpes viruses, HHV-6 and 7 are ubiquitous. In other words, they are so common that most of humankind has been infected at some point-usually early in life. It is not at all clear what clinical effects these viruses cause. *

HERVs: human endogeneous retroviruses.

Heterochromatin {HETT-err-oh-CHROME-uh-tin}: The chromosomal regions that are condensed during interphase and at the time of nuclear division. They show what is considered an abnormal pattern of staining as opposed to euchromatin. Can be subdivided into constitutive regions (present in all cells) and facultative heterochromatin (present in some cells only). The inactive X chromosome of female mammals is an example of facultative heterochromatin. The heterochromatin common to all active cells is designated constitutive heterochromatin. It is generally thought that it does not contain "genes". Heterochromatin is not transcribed and consists, in part, of satellite DNA. Note: facultative {fackle-ta-tive} (Capable of occurring or not occurring; contingent).
Pericentromeric (material surrounding the centromere) constitutive heterochromatin is a major part of the genome of humans and other eukaryotic organisms. Although it includes the centromere and other genetic elements and has many novel physical and genetic properties, the molecular structure and functional organization of heterochromatin is poorly understood owing to the relatively low density of genes and the abundance of repetitive DNA sequences.
Recent research suggests that pericentromeric heterochromatin and subteleomeres appear to be zones of active genetic recombination and may be important regions for the mixing and matching of duplicated DNA to form new genes. The variability in overall genome size across human populations is due to variation in the sizes of pericentromeres and subtelomeres. In the case of chromosome 21, this variation makes the chromosome 45% larger in some people than in others. The expansion of subtelomeres could be functionally and evolutionarily significant. (Trask, B. J., van den Engh, G.,Mayall, B. & Gray, J.W. Am. J. Hum. Genet. 45, 739-752 (1989).)
"Evolutionary geneticists are now pondering the significance of the processes that have shaped modern genomes. The more they learn, the less those vast stretches of non-coding DNA that litter most genomes seem like just junk. Pericentromeres and subtelomeres may be incubators for new genes. Duplications may help to generate genetic variation. And natural selection may continually force genomes to become leaner and fitter. Undoubtedly these processes have also left behind heaps of rubbish. But just as the surface of the Moon holds a record of its impact history in its craters, those genetic wastelands can serve as records of the dynamic history of individual genomes. Now equipped with the best maps yet, the explorers are setting out." Jonathan Knight, NATURE VOL 417 23 MAY 2002.

Heterogeneity {HETER-roe-gen-ee-at-tee}: Heterogeneity simply means diversity. In the context of genetic analysis, phenotypic heterogeneity simply means that there are diverse forms of a particular trait.

Heterozygote: An individual who received unlike alleles from its parents for a given characteristic. Having two alleles that are different for a given gene. *

Heterozygous: hetero = different. Being composed of different things. For example, when two alleles are different, in such cases the dominant allele is expressed. *

Heterozygosity: The presence of different alleles at one or more loci on homologous chromosomes.

HGP: Human Genome Project.

HHMI: Howard Hughes Medical Institute.

Hierarchical shotgun method: see sequencing.

Hilar: Referring to a depression or recess at the exit or entrance of a duct into a gland or of nerves and vessels into an organ. ***

Hinge region: A flexible, open segment of an antibody molecule that allows bending of the molecule. The hinge region is located between Fab and Fc and is susceptible to enzymatic cleavage.

Histamine: A local hormone that acts as a powerful stimulant of gastric secretion, constriction of bronchial smooth muscle, and dilation of blood vessels.

Histocompatibility: Literally, the ability of tissues to get along; in immunology, it means identity in all transplantation antigens. These antigens, in turn, are collectively referred to as histocompatibility antigens.

HIV (human immunodeficiency virus): A virus that infects T cells of the immune system via the T4 antigen site, rendering the body's ability to ward off infection less effective. Such infection usually leads to the development of AIDS. *

HLA complex: See: Human leukocyte antigens. Also see 'Major histocompatibility complex'.

Hodgkin's Disease: The most common form of lymphoma. It originates in the lymph nodes or the lymph tissues. #

Homeobox genes (HOX genes): Genes that regulate the early stages of embryonic development. These genes tend to be very similar between various diverse species (even from humans to insects).

Homeostasis: Homeostasis is one of the fundamental characteristics of living things. It refers to the maintenance of the internal environment within tolerable limits. All sorts of factors affect the suitability of our body fluids to sustain life; these include properties like temperature, salinity, acidity, and the concentrations of nutrients and wastes. Because these properties affect the chemical reactions that keep us alive, we have built-in physiological mechanisms to maintain them at desirable levels.
When a change occurs in the body, there are two general ways that the body can respond. In negative feedback, the body responds in such a way as to reverse the direction of change. Because this tends to keep things constant, it allows us to maintain homeostasis.
On the other hand, positive feedback is also possible. This means that if a change occurs in some variable, the response is to change that variable even more in the same direction. This has a destabilizing effect, so it does not result in homeostasis. Positive feedback is used in certain situations where rapid change is desirable. An example of positive feedback is the phenomenon of autocatalysis, which occurs in some digestive enzymes such as pepsin. Pepsin is a protein-digesting enzyme that works in the stomach. However, the stomach does not secrete pepsin; it secretes an inactive form, called pepsinogen. When one pepsinogen molecule becomes activated, it helps to activate other pepsinogens nearby, which in turn can activate others. In this way, the number of active pepsin molecules can increase rapidly, by using positive feedback.

Homeotic Mutations.Certain genes that determine how parts of the body are shaped, or patterned, are called homeotic genes. In homeotic mutations, one body structure is replaced by a different structure. For example, an insect leg may be replaced by an insect wing. Since homeotic mutant phenotypes can lead to differences in body shape, but not be lethal to the animal, homeotic mutations should be an effective means for evolutionary change.

Homocystinuria: A metabolic abnormality characterized by excessive amounts of the amino acid homocystine in the urine. Homocystinuria, which may be transmitted as an autosomal recessive trait, may result from deficient activity of certain enzymes involved in the metabolic conversion of the amino acid methionine to cysteine. Associated symptoms and findings often include developmental delay; dislocated lens of the eyes (ectopia lentis); thin, weak muscles; progressive mental retardation; psychiatric abnormalities; skeletal defects; blockage of a blood vessel by a piece of a blood clot (thrombus) carried in the bloodstream (thromboembolism); and/or other abnormalities.

Homology: Two traits are homologous if they are identical by descent. For example, a horse's foreleg, a human's arm, and a whale's flipper are all homologous. If two traits are similar in appearance or function but are not inherited from a common ancestor, they are merely analogous; e.g., a bird's wing and a bat's wing are homologous as limbs but merely analogous as wings, because the two species derived flight independently from separate wingless ancestors. If birds were descended from bats (or vice versa), or if birds and bats had evolved from the same flying reptile, their wings would be both analogous and homologous. In a molecular biology sense, if two genes are homologous they are both derived from the same original gene in some ancestral species; homologous genes do not necessarily have identical functions (just as a whale's flipper and a human hand have evolved in very different ways), but they are likely to be similar both in effect and in regulation.

Homologous: Similar in position, structure and evolutionary origin but not necessarily in function.

Homologous chromosomes: Chromosomes that pair during meiosis; each homologue is a duplicate of one chromosome from each parent.

Homologous recombination: A process by which one DNA segment can replace another DNA segment that has a similar sequence. Homologous recombination is used by researchers to create "knockout" mice in whom the function of a specific gene is disrupted. ###

Homozygote: An individual who received identical alleles from each parents for a given characteristic. When two alleles of a gene are the same. Having identical alleles at one or more loci in homologous chromosome segments. If two pure homozygotes breed, they will produce identical offspring (called a pure strain). *

Hormonal therapy: Treatment (often) of cancer by removing, blocking, or adding hormones. Also called hormone therapy or endocrine therapy. %

Hormone: Chemical substance produced by glands in the body that enters the bloodstream and causes effects in other tissues. # Hormones regulate growth, metabolism, and reproduction. ##

Hospice: A concept of supportive care to meet the special needs of patients and family during the terminal stages of illness. The care may be delivered in the home or hospital by a specially trained team of professionals. ##

Housekeeping genes: Those genes expressed in all cells because they provide functions needed for sustenance of all cell types. %

http://: An Internet prefix - this refers to Hypertext Transfer protocol. It is the major computer language of the Internet. When you see this start a phrase, you know this refers to a webpage address on the Internet.

HUGO: Human Genome Organization. The Human Genome Organization (HUGO) is the international organization of scientists involved in the Human Genome Project (HGP), the global initiative to map and sequence the human genome. HUGO was established in 1989 by a group of the world's leading genome scientists to promote international collaboration within the project.

Human Endogenous Retrovirus (HERV): There are at least several ancient viruses, known as HERVs (human endogenous retroviruses), that took up permanent residence within the genetic code of the ancestors of Human Beings (called the host of the virus). As these host species evolved into Homo sapiens (us), the viruses continued to travel along with the host species genetic code. Endogenous means they are produced within, or grow within or are contained within an organism or tissue. In this case, the genetic code for the viruses is contained within everyone's genetic code. HERV gene sequences occupy about 1% of the human genome. HERV's don't usually make humans sick, because they (virus and host) have evolved together over millions of years and the viral genetic code usually just continues to ride along with us without causing disease.
Today, we are specifying different types of HERVs and implicating several types in human diseases. For example, active HERV-W (type W) is seen in some cases of schizophrenia. What this implies is still unclear. In another example, the Multiple Sclerosis associated Retro Virus (MSRV) has been isolated from plasma of MS patients and was found to be phylogenetically and experimentally related to Human Endogenous RetroViruses (HERVs). This has lead to research on possible retroviral involvement in the pathogenic cascade in multiple sclerosis (MS). *

Human genome: The full collection of genes needed to produce a human being.

Human Genome Project: The Human Genome Project (HGP) traces its roots to an initiative in the U.S. Department of Energy (DOE). Since 1945, DOE and its predecessor agencies have been charged by Congress to develop new energy resources and technologies and to pursue a deeper understanding of potential health and environmental risks posed by their production and use. Such studies have since provided the scientific basis for individual risk assessments of nuclear medicine technologies, for example.
In 1986, DOE took a bold step in announcing its Human Genome Initiative, convinced that DOE's missions would be well served by a reference human genome sequence. Shortly thereafter, DOE and the National Institutes of Health developed a plan for a joint HGP that officially began in 1990.
Although the HGP originally was planned to last 15 years, rapid technological advances and worldwide participation have accelerated the expected completion date to 2003. In June 2000, scientists announced biology's most stunning achievement: the generation of a working draft sequence of the entire human genome. In addition to serving as a scaffold for the finished version, the draft provides a road map to an estimated 90% of genes on every chromosome and already has enabled gene hunters to pinpoint genes associated with more than 30 disorders.
Their website: http://www.ornl.gov/hgmis/

Human leukocyte antigens (HLA): HLA are proteins found in the membranes (outer coating) of nearly every cell in the body (all cells that have a nucleus). These antigens are in especially high concentrations on the surface of white blood cells (leukocytes). HLA antigens are the major determinants used by the body's immune system for recognition and differentiation of self from non-self (foreign substances). There are many different major histocompatibility (HLA) proteins and individuals possess only a small, relatively unique set that is inherited from their parents. It is unlikely that 2 unrelated people will have the same HLA make-up. Children, on average, will have one-half of their HLA antigens that match one-half of their mothers antigens; the other one-half of the child's antigens will match one-half of their father's antigens. This is particularly important in identifying good "matches" for tissue grafts and organ transplants, such as a kidney transplant or bone marrow transplant. Many HLA molecules exist, but some are of special interest because they are more common in certain autoimmune diseases. For example, HLA-B27 antigen is found in 80-90% of people with ankylosing spondylitis and Reiter's syndrome, and this can aid in the diagnosis of these diseases. HLA-B27 is also present in 5-7% of people without autoimmune disease. Thus, the mere presence of this HLA molecule is not indicative of disease. HLA types can also used to determine relationships between children and parents when such relationships are in question. However, newer, more specific genetic testing is now available for this purpose. Each person has unique HLA antigens (although identical twins may match each other). To better understand the role of HLA molecules in autoimmune diseases, transgenic animals expressing human HLA genes associated with disease have been developed. The creation of transgenic mice expressing functional HLA molecules has been an important step toward the creation of an in vivo model for enhancing our understanding of the function of human molecules in disease induction and predisposition.

Human leukocyte antigen test (HLA): A special blood test used to examine the HLAs and match a blood or bone marrow donor to a recipient for transfusion or transplant. ##

Human gene therapy: Insertion of normal DNA directly into cells to correct a genetic defect. %

Human Blood: liquid medium (plasma) containing several types of specialized cells in suspension. The circulatory system provides the mechanism by which the blood transports substances to and from the organs and tissues. The circulating blood continuously supplies oxygen, nutrient substances, and other materials necessary for the viability and activity of all the cells of the body and carries away cell products, including carbon dioxide and other waste materials. If blood flow ceases, death occurs within minutes because of the effects of an unfavorable environment on highly susceptible cells. %
The constancy of the composition of the blood is made possible by the circulation, which conveys blood through the organs that regulate the concentrations of its components. In the lungs blood acquires oxygen and releases carbon dioxide transported from the tissues. The kidneys remove excess water and dissolved waste products. Nutrient substances derived from food reach the bloodstream after absorption by the intestinal tract. Endocrine glands release their secretions into the blood, which transports these hormones to the tissues in which they exert their effects. Many substances are recycled through the blood; for example, iron released during the destruction of old red cells is conveyed by the plasma to sites of new red cell production where it is reused. Each of the numerous components of the blood is kept within appropriate concentration limits by an effective regulatory mechanism. In many instances feedback control systems are operative; thus a declining level of blood sugar leads to accelerated release of sugar into the blood so that a potentially hazardous depletion of blood sugar does not occur.
Blood cells:
There are four major types of blood cells: red blood cells, platelets, lymphocytes, and phagocytic cells. Collectively, the lymphocytes and phagocytic cells constitute the white blood cells. Each type of blood cell has a specialized function: red cells take up oxygen from the lungs and deliver it to the tissues; platelets participate in forming blood clots; lymphocytes are involved with immunity; and phagocytic cells occur in two varieties - granulocytes and monocytes - and ingest and break down microorganisms and foreign particles. The circulating blood functions as a conduit, bringing the various kinds of cells to the regions of the body in which they are needed: red cells to tissues requiring oxygen, platelets to seal over points of injury, lymphocytes to areas of infection, and phagocytic cells to sites of microbial invasion and inflammation. *

Human Genome Initiative: Collective name for several projects begun in 1986 to (1) create an ordered set of DNA segments from known chromosomal locations, (2) develop new computational methods for analyzing genetic map and DNA sequence data, and (3) develop new techniques and instruments for detecting and analyzing DNA. This DOE (Department of Energy) initiative is now known as the Human Genome Program. The national effort, led by DOE and NIH (now including the National Human Genome Research Institute), is known as the Human Genome Project. %

Human papilloma {PA-pill-loam-ma} virus (HPV): There are more than 100 types of HPV. Some produce warts - plantar warts on the feet, common hand warts, juvenile warts, butcher's warts (meat and poultry workers seem to have more warts on their hands than would be expected in the general population), and genital warts. About 30 types of HPV can infect the genital area - the vulva, vagina, cervix, rectum, anus, penis, or scrotum. Some types may cause genital warts. Some types may cause changes in cells. These types increase the risk of cervical and certain other cancers. Most types seem to have no harmful effect at all. *

Human genetics: The study of human heredity occupies a central position in genetics. Much of this interest stems from a basic desire to know who humans are and why they are as they are. At a more practical level, an understanding of human heredity is of critical importance in the prediction, diagnosis, and treatment of diseases that have a genetic component. The quest to determine the genetic basis of human health has given rise to the field of medical genetics. In general, medicine has given focus and purpose to human genetics, so that the terms medical genetics and human genetics are often considered synonymous. *

Human macrophage/monocyte chemotactic and activating factor (MCAF) also called human macrophage chemoattractant
protein-1 (MCP-1) is a protein containing 76 amino acid residues. It plays an important role in the inflammatory
response of blood monocytes and tissue macrophages.

Human Prion Diseases: Diseases of humans that affect primarily the nervous system. They can be sporadic (spontaneous), transmitted by infection or familial (inherited). The hallmark of these diseases is the presence of microscopic vacuolization of the brain tissue, called spongiform degeneration, and of an abnormal form of a protein, called prion protein, which is a normal component in brain and other tissues. The abnormal prion protein is resistant to digestion with enzymes that breakdown normal proteins, and accumulates in the brain. See Creutzfeldt-Jakob disease (CJD). See prion.

Humoral immunity: Immune protection provided by soluble factors such as antibodies, which circulate in the body's fluids or 'humors', primarily serum and lymph. Humoral immunity: Any immune reaction that can be transferred with immune serum is termed humoral immunity (as opposed to cell-mediated immunity). In general, this term refers to resistance that results from the presence of specific antibody.

Huntington's disease: A genetic disease of the central nervous system that produces progressive dementia and involuntary movements. It usually starts between ages 30 and 50 and slowly progresses to death. Since it is a dominant disease, a child of a parent with Huntington's disease has a 50-50 chance of inheriting it. Also: Huntington's disease (HD): A hereditary, progressive, neurodegenerative disorder primarily characterized by the development of emotional, behavioral, and psychiatric abnormalities; gradual deterioration of thought processing and acquired intellectual abilities (dementia); and movement abnormalities, including involuntary, rapid, irregular jerky movements (chorea) of the face, arms, legs, or trunk. HD may be inherited as an autosomal dominant trait or, less commonly, appear to occur randomly for unknown reasons (sporadically). The disorder results from abnormally long sequences or "repeats" of certain coded instructions (i.e., unstable expanded CAG repeats) within a gene (located on chromosome p16.3). Progressive nervous system dysfunction associated with HD results from loss of neurons in certain areas of the brain, including the basal ganglia and cerebral cortex.

Hybrid: A term used to mean any offspring produced by two parents of different varieties of a species.

Hybridization: The reaction by which the pairing of complementary strands of nucleic acid occurs. DNA is usually double-stranded, and when the strands are separated they will re-hybridize under the appropriate conditions. Hybrids can form between DNA-DNA, DNA-RNA or RNA-RNA. @@
Also: DNA Hybridization: A method of determining the similarity of DNA from different sources. Single strands of DNA from two sources, e.g. different bacterial species, are put together and the extent to which double hybrid strands are formed is estimated. The greater the tendency to form these hybrid molecules, the greater the extent of complementary base sequences, i.e. gene similarity. The method is one way of determining the genetic relationships of species.

Hybridoma: A hybrid cell that results from the fusion of an antibody-secreting cell with a malignant cell; the progeny secrete antibody without stimulation and proliferate continuously both in vivo and in vitro.

Hydrocephalus {hy-dro-SEF-al-lus}: The abnormal buildup of cerebrospinal fluid in the ventricles of the brain. #

Hyper: as a prefix, hyper commonly refers to over, as in hyperactive - overly active.

Hyperalimentation: The intravenous administration of a highly nutritious solution. ##

Hyperglycemia: An abnormally high level of the simple sugar glucose in the blood.

Hyperkalemic: Pertaining to hyperkalemia, a condition characterized by unusually high concentrations of potassium in the blood. Potassium, a positively charged ion, helps to regulate water balance, nerve conduction, and muscle contraction. Hyperkalemia may lead to various signs and symptoms, such as diarrhea, nausea, abdominal cramps, weakness, and, with increasing severity, abnormal heart rhythms and muscle paralysis.

Hyperkinetic: Characterized by excessive movement because of abnormally increased motor activity or function. Certain movement disorders are termed "hyperkinetic" such as tics or essential tremor.

Hyperphosphorylation: excessive phosphorylation of a protein, as a result of activation of kinases, deactivation of phosphatases, or both.

Hyperplasia {hy-per-PLAY-zha}: Excessive growth of cells. #

Hypersensitivity: State of reactivity to antigen that is greater than normal for the antigenic challenge; hypersensitivity is the same as allergy and denotes a deleterious outcome rather than a protective one.

Hyperthermia {hy-per-THERM-mee-a}: Treatment that involves heating a tumor. #

Hypertrophy {HIGH-pert-tra-fee}: enlargement of a tissue or organ. Muscle hypertrophy occurs in various muscular disorders. In some cases, specific groups of muscle become enlarged when they try to compensate (overwork) for other muscles that become weakened (atrophied). Also: A non-tumorous enlargement of an organ or a tissue as a result of an increase in the size rather than the number of constituent cells: *

Hypervariable regions: Portions of the light and heavy immunoglobulin chains that are highly variable in amino acid sequence from one immunoglobulin molecule to another, and that, together, constitute the antigen-binding site of an antibody molecule. Also, portions of the T-cell receptor which constitute the antigen-binding site.

Hyperventilation: Abnormally rapid breathing usually accompanied by air swallowing. Hyperventilation results in excessive intake of oxygen and increased elimination of carbon dioxide, which may eventually lead to a disturbance in the body's acid-base balance.Hypo: as a prefix, hypo commonly refers to under, as in hypodermic needle - a needle going under the skin (dermis).

Hypo: as a prefix - under or a lack of something

Hypogonadism: Defective internal secretion of the gonads. ***

Hypokalemic: Referring to hypokalemia, which is characterized by abnormally low potassium levels in the blood. Potassium, the primary positively charged ion (cation) of muscle, plays an important role in regulating muscle contraction, nerve conduction, and other bodily functions. Hypokalemia may result in confusion, fatigue, weakness, and, in severe cases, paralysis and heart rhythm abnormalities.

Hypokinetic: Diminished movement and decreased motor function. Some movement disorders are hypokinetic, such as Parkinson's disease.

Hypoparathyroidism: An endocrine condition characterized by insufficient secretion of parathyroid hormone due to injury, disease, or congenital abnormalities of the parathyroid glands. Parathyroid hormone plays an essential role in regulating calcium balance in the body. Hypoparathyroidism results in low calcium blood levels (hypocalcemia), leading to various symptoms and findings. For example, hypoparathyroidism may cause a condition known as tetany in which increased excitability of nerves and muscles results in uncontrollable, painful muscle spasms and cramping; abnormal involuntary movements resembling chorea; spasmodic closure of the larynx (laryngospasm); and other findings. Hypoparathyroidism may also lead to seizures; abnormal calcium deposits (calcifications) in the basal ganglia; loss of transparency of the lenses of the eyes (cataracts); dry, scaly skin; weakened tooth enamel; and/or other abnormalities.

Hyporeflexia: A diminished function of the reflexes. ***

Hypothalamus: Area at the base of the brain that controls various functions including hormone production in the pituitary. #

Hypothesis {HI-poth-a-sis}: A theory developed to explain something. A hypothesis is either supported or not supported by scientific research. Often several hypotheses are considered and revised as research takes place. If enough support is found and no contradictory findings are present, the hypothesis can be generally accepted as fact.

Hypotonia: Hypotonia means "lack of muscle tone," or absence of the normal degree of tension in the muscle at rest. The condition is seen most often in infants and children with neuromuscular problems, who may appear "floppy" because of the lack of muscle tone. Hypotonia can occur in many muscle disorders, including acid maltase deficiency, mitochondrial disorders, congenital myopathies (central core disease, nemaline myopathy and myotubular myopathy), congenital myotonic dystrophy, congenital muscular dystrophies, neonatal and infantile myasthenia gravis, SMA type 1 and "benign" congenital hypotonia. *

Hysterectomy {hiss-ter-ECK-toe-mee}: An operation that removes the uterus and cervix. Does not necessarily mean the removal of ovaries. #

Ia: "Immune response-associated" proteins, found on B cells and antigen-presenting cells of mice; an old term now replaced with MHC (major histocompatibility complex) class II molecules.

IADLs (Instrumental activities of daily living) see Activities of Daily Living (ADLs).

Iatrogenic {EYE-at-tro-genic}: A condition caused by medical intervention or drug treatment.

ICAM: Glycoproteins that are present on a wide range of human cells, essential to the mechanism by which cells recognise each other, and thus important in inflammatory responses.

Ichthyosis {ICK-thee-oh-sis}: A condition in which the skin is dry and scaly, resembling fish skin. ***

Ideogram: To simplify the information gained from karyotypes, geneticists developed a schematic diagram, called an ideogram, to represent each chromosome. The three characteristics scientists use to identify a chromosome are readily visible in an ideogram: length; the banding pattern of the dye, which reflects the type of nucleotides concentrated in the chromosome; and the location of the centromere, a waist-like constriction required for proper movement during cell division. Idiotypes: The unique and characteristic parts of an antibody's variable region, which can themselves serve as antigens.

Idiopathic {ID-dee-oh-path-ick}: arising spontaneously or from an obscure or unknown cause. A disorder or condition of spontaneous origin; self-originated or of unknown cause. The term is derived from the prefix "idio-" meaning one's own and "pathos" indicating disease.

Idiopathic inflammatory myopathies (IIM): The idiopathic inflammatory myopathies are a heterogeneous (they are all different) group of uncommon diseases. The incidence rate of IIM is approximately 5 cases per million population, but there appears to be an increase in the rate over the last two decades. They are systemic rheumatological diseases of unknown etiology, characterized by a chronic inflammatory myositis resulting in muscular weakness with or without organ system dysfunction. The three disorders that comprise this group of muscle disorders are polymyositis (PM), dermatomyositis (DM), and a more recently defined disorder called inclusion body myositis (IBM). *

Idiotype: The combined antigenic determinants (idiotopes) found on antibodies of an individual that are directed at a particular antigen; such antigenic determinants are found only in the variable region.

Ileostomy {ILL-ee-ost-toe-me}: A surgical opening in the abdomen connected to the small intestine to allow stool to be emptied into a collection bag. ##

Imaging: Procedures that produce pictures of areas inside the body. %

Immediate-type hypersensitivity: Hypersensitivity tissue reaction occurring within minutes after the interaction of antigen and antibody.

Immortal strand: The hypothesis of selective retention of parental DNA strands during asymmetric self-renewal. Potential mechanism to protect stem cells from the mutations associated with replication.

Immune adherence: The adherence of particulate antigen coated with C3b to tissue having cells with C3b receptors.

Immune complex: Antigen bound to antibody.

Immune modulators: Substances that control the expression of the immune response.

Immune response: The reaction of the immune system to foreign substances.

Immune response (Ir) gene: A gene controlling an immune response to a particular antigen; most genes of this type are in the MHC (major histocompatibility complex), and the term is rarely used to describe other types of Ir genes outside the MHC.

Immune system: The complex group of cells and organs that defends the body against infection and disease. %

Immunoblotting: A research method used to study proteins. *

Immunocompetent: capable of mounting an immune response.

Immunocytochemistry: Study of the chemistry of cells using techniques that employ immune mechanisms. #

Immunogen: A substance capable of inducing an immune response (as well as reacting with the products of an immune response). An antigen is immunogenic if it can generate an immune response. Compare with antigen.

Immunogenicity: The ability to or the degree to which a particular substance may provoke an immune response; having the properties of an antigen or any substance that may trigger a particular immune reaction, such as the production of antibodies.

Immunoglobulin (Ig): A general term for all antibody molecules. Each Ig unit is made up of two heavy chains and two light chains and has two antigen- binding sites.

Immunoglobulins: a family of large protein molecules, also known as antibodies.

Immunohistochemistry: The testing of sections of tissue for specific proteins by attaching them with specific antibodies, and then looking for the antibodies through the enzymes to which they were connected. *

Immunolabelling: The testing of sections of tissue (or electron microscopy samples) by attaching antibodies to specific proteins in the tissue. The antibodies may have further labels attached to them and it is these that act as the labels. *

Immunostaining: As in immunohistochemistry but using a dye as the indicator. *

Immunosuppression: Weakening of the immune system that causes a lowered ability to fight infection and disease. ##

Immunotherapy: The artificial stimulation of the body's immune system to treat or fight disease. ##

Implant radiation {ray-dee-AY-shun}: A procedure in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near the tumor. %

Impotent {IM-po-tent}: Unable to have an erection adequate for sexual intercourse. %

Imprinting: A chemical modification of a gene allele which can be used to identify maternal or paternal origin of chromosome.

Incomplete penetrance: The gene for a condition is present, but not obviously expressed in all individuals in a family with the gene.

Inborn errors of metabolism: Inherited diseases resulting from alterations in genes that code for enzymes. %

Incidence: Incidence is a measure of the number of cases of a disease per number of individuals. The incidence of disease X is 1 per 1000 in coal miners per 100 years. This figure also allows us to determine a person's probability of being diagnosed with a disease during a given period of time (if you are a coal miner, your chances are 1 in 1000 of getting this disease every 100 years of life lived). The frequency of occurrence of a condition, symptom, disease, or injury. Used to estimate the likelihood that an individual will be affected by a specific condition.
Incidence is the number of newly diagnosed cases of a disease. An incidence rate is the number of new cases of a disease divided by the number of persons at risk for the disease. If, over the course of one year, five women are diagnosed with breast cancer, out of a total female study population of 200 (who do not have breast cancer at the beginning of the study period), then we would say the incidence of breast cancer in this population was 0.025. (or 2,500 per 100,000 women-years of study). Also: Incidence: a rate measuring the number of new episodes of illness arising in a population over a period of time. It can be expressed in terms of sick persons or episodes per 1000 individuals at risk or in terms of per 100,000. Also called morbidity. Compare also with prevalence, morbidity and mortality.

Incisional biopsy: Taking a piece of tissue out for study. #

Inclusion Body Myositis (IBM): One of the inflammatory myopathies, with onset most frequently after the age of 50. It is more common in males. Slowly progressive muscle weakness occurs in the extremities and hip girdle region. There are several types, the most common, a spontaneous form.

Inclusion body: An abnormal collection or aggregation of protein and/or other material within a cell. The presence of inclusion bodies is linked with several diseases, including inclusion body myositis (muscle), Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, and Alzheimer's diseas.

Incomplete penetrance: The gene for a condition is present, but not obviously expressed in all individuals in a family with the gene. %

Incomplete dominance: The alleles of a gene do not always have a simple dominance relationship, depending on the protein function and the type of mutation. Two alleles may be co-dominant, in which the heterozygote exhibits the full characteristics of both alleles, or incompletely dominant, in which the heterozygote has a phenotype in between the two homozygotes. Codominance or incomplete dominance can frequently be predicted by knowing the function of the gene.

Incontinence {in-KAHN-tin-nens}: Inability to control the flow of urine from the bladder (urinary incontinence) or the escape of stool from the rectum (fecal incontinence). %

Indolent: {IN-doe-lent} Slow to heal, grow, or develop; inactive. A disease or condition causing little or no pain or annoyance. *

Inherited disease: See hereditary. A disease passed from one generation to the next by a defect in the genetic code. Also see acquired, congenital and familail disease.

Infantile Acid Maltase Deficiency: Also known as Pompe's disease and Type I glycogenesis. Infants appear normal for a few weeks after birth but then develop severe hypotonia and enlargement of the heart and liver, as glycogen accumulates in these organs. It follows an autosomal recessive form of transmission. It is rapidly progressive and life expectancy does not usually exceed 1 year of age. **

Infiltrating cancer: Cancer that can grow beyond its site of origin into surrounding tissue. #

Infiltration: The leaking of fluid or medicines into tissues, which can cause swelling. ##

Inflammation: reaction of the body to injury or to infectious, allergic, or chemical irritation. The symptoms are redness, swelling, heat, and pain resulting from dilation of the blood vessels in the affected part with loss of plasma and leucocytes (white blood cells) into the tissues.
Common Causes:
-Microbial infections: One of the commonest causes of inflammation is microbial infection. Viruses lead to death of individual cells by intracellular multiplication . Bacteria release specific exotoxins - chemicals synthesized by them that specifically initiate inflammation or endotoxins, which are associated with their cell walls. Additionally, some organisms cause immunologically-mediated inflammation through hypersensitivity reactions. Parasitic infections and tuberculous inflammation are instances where hypersensitivity is important.
-Hypersensitivity reactions: A hypersensitivity reaction occurs when an altered state of immunological responsiveness causes an inappropriate or excessive immune reaction that damages the tissues.
-Physical agents: Tissue damage leading to inflammation may occur through physical trauma, ultraviolet or other ionizing radiation, burns or excessive cooling ('frostbite').
-Irritant and corrosive chemical: Corrosive chemicals (acids, alkalis, oxidizing agents) provoke inflammation through gross tissue damage. However, infecting agents may release specific chemical irritants that lead directly to inflammation.
-Tissue necrosis: Death of tissues from lack of oxygen or nutrients resulting from inadequate blood flow (infarction) is a potent inflammatory stimulus. The edge of a recent infarct often shows an acute inflammatory response.
The four principal effects of acute inflammation:
-Redness: An acutely inflamed tissue appears red, for example skin affected by sunburn, cellulitis due to bacterial infection or acute conjunctivitis. This is due to dilatation of small blood vessels within the damaged area.
-Heat: Increase in temperature is seen only in peripheral parts of the body, such as the skin. It is due to increased blood flow (hyperaemia) through the region, resulting in vascular dilatation and the delivery of warm blood to the area. Systemic fever, which results from some of the chemical mediators of inflammation, also contributes to the local temperature.
-Swelling (tumor.): Swelling results from edema, the accumulation of fluid in the extra vascular space as part of the fluid exudate, and to a much lesser extent, from the physical mass of the inflammatory cells migrating into the area.
-Pain: For the patient, pain is one of the best known features of acute inflammation. It results partly from the stretching and distortion of tissues due to inflammatory edema and, in particular, from pus under pressure in an abscess cavity. Some of the chemical mediators of acute inflammation, including bradykinin, the prostaglandins and serotonin, are known to induce pain.
-Loss of function: Loss of function, a well-known consequence of inflammation. Movement of an inflamed area is consciously and reflexively inhibited by pain, while severe swelling may physically immobilize the tissues.
Acute versus Chronic:
Acute inflammation is a stereotyped response to recent or ongoing injury. Although the process is complex, the principal features are dilatation and leaking of vessels, and recruitment of circulating neutrophils - an important type of white blood cell (see Human blood cells).
Chronic inflammation ("late-phase inflammation") is a response to prolonged problems, orchestrated by T-helper lymphocytes. It may feature recruitment and activation of T- and B-lymphocytes, macrophages, eosinophils, and/or fibroblasts. The process is complex. Inflammation within the muscle tissue can disrupt its proper function. This is seen in two disorders, polymyositis (PM) and dermatomyositis (DM). In these disorders, treatment is designed to reduce the inflammation. *

Inflammatory response: Redness, warmth, swelling, pain and loss of function produced in response to infection, as the result of increased blood flow and an influx of immune cells and secretions.

Inflammatory muscle disease (IMD) also referred to as inflammatory myopathy or as a group, the inflammatory myopathies: autoimmune disorders of unknown cause (idiopathic) which results in muscle weakness. The muscles involved are the "skeletal" muscles, that is, the muscles of the limbs making movement difficult. Sometimes the muscles of swallowing or phonation, or even breathing may be involved. In inflammatory muscle disease, the cardiac muscle may be involved, resulting in cardiac failure or arrhythmias. The term "myositis" is given to these muscle diseases. Myositis can occur at any age and even occurs in children. Both men and women may develop the disorder. Sometimes , myositis may occur without other manifestations of disease, or myositis may be a part of a more full-blown autoimmune disorder, such as systemic lupus erythematosus. Types of IMD include Polymyositis; Dermatomyositis; and Inclusion body myositis. *

-Dermatomyositis (PM/DM)
-Polymyositis (PM/DM)
-Inclusion Body Myositis (IBM)

Informed consent: Process in which the patient is fully informed of all risks and complications of a planned procedure and agrees to proceed. #

Infusaport: A type of permanent catheter, round in shape, surgically inserted into a neck vein. Allows administration of IV fluids, blood products and medicines. Blood can also be drawn through it. #

Infusion: Delivering fluids or medications into the bloodstream over a period of time. ##

Inhibition: The restraint, suppression, or arrest of a process or the action of a particular cell or organ; the prevention or slowing of the rate of a chemical or an organic reaction. The term "reciprocal inhibition" refers to the restraint or "checking" of one group of muscles upon stimulation (excitation) and contraction of their opposing (antagonist) muscles.

Infusion pump: A device that delivers measured amounts of fluids or medications into the bloodstream over a period of time. ##

Inhibitor: A substance that blocks, restricts, or interferes with a particular chemical reaction or other biologic activity.

Injection: Pushing a medication into the body with the use of a syringe and needle. ##

Innate immune response: Nonspecific immune response to antigens, including anatomic and physiologic barriers, endocytic and phagocytic activity, and inflammatory secretions.

Inner cell mass: In human development, the blastocyst forms a hollow sphere consisting of an layer of outer cells and inside the hollow sphere, a cluster of cells called the inner cell mass. The outer layer of cells will go on to form the placenta and other supporting tissues needed for fetal development in the uterus. The inner cell mass will form all of the tissues of the human body, therefore, these are the cells that develop into the fetus. These inner cell mass cells are pluripotent. This means that they are able to give rise to many, but not all cell types necessary for fetal development (for example, they are able to give rise to fetal tissues, but not placental tissue). The ICM differentiates into three layers, the outer, ectoderm, the middle (mesoderm) and an iner layer, the endoderm. Each of which will have special roles to play in building the complete organism. In this differentiation, the pluri-potent stem cells undergo further specialization into stem cells that give rise to cells that have a particular function. Examples of this include blood stem cells, which give rise to red blood cells, white blood cells and platelets; and skin stem cells that give rise to the various types of skin cells.

Innervate: To stimulate a part, as the nerve supply of an organ. ***
Also: To supply (an organ or a body part) with nerves. To stimulate (a nerve, muscle, or body part) to action.

Insidious {IN-sid-ee-ous}: Coming on very slowly, usually over a long period of time. The person may not notice problems at first. *

in silico: in silicon. Research conducted in a computer, for example, data mining of a genome data base done with computer programs. Also: Building computer models of the intricate processes that take place inside cells, organs, and even people. The ultimate goal: an entire organism modeled in silicon, allowing researchers to test new therapies much as engineers "fly" new airplane designs on supercomputers. Also: using computer based information to study and model biological systems. Data mining is an example.

in situ: Latin. In the site of. Refers to diseases (tumors) that haven't grown beyond their site of origin. #

in situ hybridization: Hybridization of a labeled probe to its complementary sequence within intact, banded chromosomes.

Instrumental activities of daily living (IADLs): see Activities of Daily Living (ADLs).

Insulin: A small protein, a pancreatic hormone, of about 51 amino acids. It is critical in the metabolism of carbohydrates. *

Integrin: A muscle-related protein. Integrins are integral membrane proteins that act as receptors for laminins. Integrin has specificity for skeletal and cardiac muscle. It is concentrated at myotendinous junctions. It is also detected at neuromuscular junctions and along the sarcolemmal membrane. The interactions are independent of the dystrophin-dystroglycan complex. Some patients with congenital muscular dystrophy have integrin-a7 mutations. *

Inter: Between two things. *

Interferon {in-ter-FEAR-on}: A family of glycoproteins derived from human cells which normally has a role in fighting viral infections by preventing virus multiplication in cells. They are secreted by vertebrate cells in response to a wide variety of inducers and confer resistance against many different viruses, inhibit proliferation of normal and malignant cells, impede multiplication of intracellular parasites, enhance macrophage and granulocyte phagocytosis, augment natural killer cell activity, and show several other immunomodulatory functions.

Interleukins: Glycoproteins secreted by a variety of leukocytes which have effects on other leukocytes.

Interleukin {in-ter-LOO-kin}: interleukin-1 A soluble protein (17 kD: 152 amino acids) secreted by monocytes, macrophages or accessory cells involved in the activation of both T-lymphocytes and B lymphocytes and potentiates their response to antigens or mitogens. Its biological effects include the ability to replace macrophage requirements for T-cell activation, as well as affecting a wide range of other cell types. at least two IL-1 genes are active and alpha and beta forms of IL-1 are recognised. It is released early in an immune system response by monocytes and macrophages. It stimulates T-cell proliferation and protein synthesis. Another effect of IL-1 is that it causes fever.

Interleukin-2 {in-ter-LOO-kin}: A type of biological response modifier (a substance that can improve the body's natural response to disease). It stimulates the growth of certain disease-fighting blood cells in the immune system. Also called IL-2. %

Intermolecular help: Mechanism by which T cells specific for an antigen help B cells produce antibodies against a self antigen, provided that complexes are formed between the 2 antigens.

Internal image: A spatial configuration of the combining site of an anti-idiotype antibody which resembles the epitope to which the idiotype is directed.

Internet: see world wide web*

Intra: Within something. *

Intramuscular (IM) injection: Into the muscle. ##

Intrathecal chemotherapy {intra-THEE-kal}: Injection of anticancer drugs into the cerebrospinal fluid. #

Intravenous (IV): Administration of a drug directly into a vein. #

Intravenous immunoglobulin (IVIg): A sterile solution of concentrated antibodies extracted from healthy people. IVIG is used to prevent bacterial infections in people with low or inappropriate antibody production. Injected into a vein or muscle.

Introns: "intervening sequences" Noncoding DNA sequences that interrupt the sequences containing instructions for making a protein (exons). Introns are not represented in messenger RNA; only the exons are translated into protein. The function of introns is still being explored. Also called "Junk DNA". ###
Introns are portions of genomic DNA which ARE transcribed (and thus present in the primary transcript) but which are later spliced out (are NOT translated). They thus are not present in the mature mRNA. Repeats (mutations) in introns can (somehow) lead to genetic diseases. A trinucleotide mutation has been found in Friedreich's Ataxia (FA). The FA trinucleotide expansion is the first disease-causing mutation found to occur in an intron. The FA mutation supports previous evidence that introns influence gene expression.

Invasive cancer: Cancers that are capable of growing beyond their site of origin and invading surrounding tissue. #

Inversely related: One thing affects another so that when one increases the other decreases. *

in vitro: Latin. Outside a living organism. For example, in a test-tube.

in vitro {VEE-tro}Fertilization (IVF): A technique for helping infertile couples to conceive, popularly known as the 'test-tube baby' technique. The woman is induced to produce eggs (ovulate) by hormone treatment. The eggs are then removed and fertilized in the laboratory (in vitro) by her partner's (or a donor's) sperm. The resulting early embryos are checked for normal development before being placed in the woman's uterus to continue growing until birth. Unless the patients are chosen very carefully, the success rate of in vitro fertilization in humans is very low. IVF in animals, however, is widely used with success.

in vivo: Latin. In the living state - inside a living organism. *

In vitro stem cell: Self-renewal ex vivo in cells that do not overtly behave as stem cells in vivo. Occurs due to liberation from inductive commitment signals or by creation of a synthetic stem-cell state.

Ion: An electrically charged atom or group of atoms due to the loss or gain of one or more electrons. Positively charged ions, known as cations, include potassium, calcium, sodium, hydrogen, ammonium, and magnesium. Negatively charged ions, called anions, include chloride, phosphate, and bicarbonate. The transfer of ions across cellular membranes plays an essential role in vital bodily processes, including enzyme activation, protein metabolism, acid-base balance, nerve impulse transmission, and muscle contraction.

Ion channels: All cells acquire the molecules and ions they need from their surrounding extracellular fluid (ECF). Molecules and ions can move spontaneously (passively) down their concentration gradient (i.e., from a region of higher to a region of lower concentration) by diffusion. In this process, called Facilitated diffusion, transmembrane proteins create a water-filled pore through which ions and some small hydrophilic molecules can pass by diffusion. The channels can be opened (or closed) according to the needs of the cell. Molecules and ions can also be moved against their concentration gradient, but this process, called active transport, requires the expenditure of energy (usually from ATP).
Facilitated diffusion of ions takes place through proteins, or assemblies of proteins, embedded in the plasma membrane. These transmembrane proteins form a water-filled channel through which the ion can pass down its concentration gradient. The transmembrane channels that permit facilitated diffusion can be opened or closed. They are said to be "gated".
Some types of gated ion channels:
-ligand-gated: Ion channels open or close in response to binding a small signaling molecule or "ligand". Some ion channels are gated by extracellular ligands; some by intracellular ligands. In both cases, the ligand is not the substance that is transported when the channel opens. Examples: Acetylcholine (ACh), Gamma amino butyric acid (GABA).
-mechanically-gated: Example: Sound waves bending the cilia-like projections on the hair cells of the inner ear open up ion channels leading to the creation of nerve impulses that the brain interprets as sound.
-voltage-gated: In so-called "excitable" cells like neurons and muscle cells, some channels open or close in response to changes in the charge (measured in volts) across the plasma membrane. Example: As an impulse passes down a neuron, the reduction in the voltage opens sodium channels in the adjacent portion of the membrane. This allows the influx of Na+ into the neuron and thus the continuation of the nerve impulse. Some 7000 sodium ions pass through each channel during the brief period (about 1 millisecond) that it remains open.
Active Transport: Active transport is the pumping of molecules or ions through a membrane against their concentration gradient. It requires:
-a transmembrane protein (usually a complex of them) called a transporter and energy. The source of this energy is ATP.
Voltage-gated ion channels play a critical role in coupling excitation at the neuromuscular junction to activation of contractile elements within a muscle fiber. Abnormal channel function can lead to either muscle paralysis or delayed relaxation. For example, the discovery of the origin of the inherited disorder, called Andersen's syndrome, is the first known human ion channel disorder, or channelopathy, that has been linked to muscle abnormalities and developmental defects.
Channelopathy is a term coined to describe diseases that are caused by defective ion channel proteins.

Isaac Syndrome: Also known as neurotonia, it can appear at any age and in either sex. There is no known cause. Individuals experience brief contractions of muscles, known as myokymia that can range in severity from very mild to quite severe. Associated symptoms are insomnia, difficulty walking, and stiffness of the wrists. The body may become stooped. An effective treatment, in the form of diazepam or Clonazepam is used to relieve the continuous contractions. **

Ischemic {is-SCHEME-ick}damage: Injury caused by lack of oxygen.

Isochromosome: A metacentric chromosome produced during mitosis or meiosis when the centromere splits transversely instead of longitudinally; the arms of such chromosome are equal in length and genetically identical, however, the loci are positioned in reverse sequence in the two arms.

Isograft: A tissue transplanted between two genetically identical individuals.

Isohemagglutinins: Antibodies to major red blood cell antigens present normally as a result of inapparent immunization by cross-reactive antigens in bacteria, food, etc.

Isotypes: Classes of antibody that differ in the constant region of their heavy chain (Fc portion); distinguishable also on the basis of reaction with antisera raised in another species. These differences also result in different biological activities of the antibodies.

Isotype switch: The shift of a B cell or its progeny from the secretion of antibody of one isotype or class of antibody with the same V regions but a different heavy- chain constant region and, hence, a different isotype (class switch).

Itis {EYE-tus}: as a suffix, -itis refers to an inflammation or infection. Appendicitis is an inflammation of the appendix. Myositis is an inflammation of muscle. *

J chain (joining chain): A polypeptide involved in the polymerization of immunoglobulin molecules IgM and IgA.

J gene: A gene segment coding for the J or joining segment in immunoglobulin DNA; V genes translocate to J segments in L chains, and to D and J segments in H chains. Also, codes for a portion of the T-cell receptor.

Joint contractures: Permanent flexing or extension of joints in fixed postures due to shortening of muscle fibers. Contractures, abnormal fixation of the limbs, and associated deformity may result from prolonged immobility of developing joints.

Junction: The place of union or coming together of two parts. **

Juvenile myoclonic epilepsy: A form of idiopathic epilepsy or recurrent seizures of unknown origin, with symptom onset typically occurring from approximately 12 to 16 years of age. The condition is characterized by sudden, involuntary, "shock-like" muscle jerks (myoclonus) that primarily occur during the morning or with stress, fatigue, or alcohol consumption. Patients may later develop generalized tonic-clonic seizures associated with loss of consciousness and rhythmic contraction and relaxation of all muscle groups.

K cell: An effector lymphocyte with Fc receptors which allow it to bind to and kill antibody-coated target cells.

Karyotype {carry-a-type}: The chromosomes of an individual, defined by their number, form and size. In practice, in a cell, the nucleus is intact and the chromosomes are a relatively indistinguishable mass of spaghetti-like material. But in a cell preparing to divide (in mitotic division), the nuclear boundary breaks down, and the chromosomes condense into near-rigid rods. Breaking such a cell open onto a glass slide, the researcher releases a jumbled cluster of chromosomes that are then stained with dye so that they can be studied under a microscope. The jumble of stained chromosomes is photographed, and the images are rearranged into ordered pairs to create a karyotype, a picture of the chromosomes, the standard form used to display and study chromosomes. In this configuration, the chromosomes are ordered by length from the largest (chromosome 1) to the smallest (chromosome 22 in humans), followed by the sex chromosomes. Karyotypes are used in clinical tests, such as amniocentesis, to determine if all the chromosomes appear normal and are present in the correct number. *

Killer T cell: A T cell with a particular immune specificity and an endogenously produced receptor for antigen, capable of specifically killing its target cell after attachment to the target cell by this receptor. Also called cytotoxic T cell.

Kinesigenic: Caused by sudden voluntary movement; movement induced. More specifically, this term is often used to describe abrupt episodes of involuntary movement that are provoked by sudden motions or unexpected stimuli.

KB: abbreviation for kilobase, one thousand bases. A 25KB segment of DNA = a segment 25,000 individual DNA neucleotides long.

Knockout studies: An experimental method for understanding the function of DNA sequences and the proteins they encode. Researchers inactivate genes in living organisms and monitor any changes that could reveal the function of specific genes.
Knockout mice: Mice are often used for knockout experiments. It appears that mice are a well suited animal for these studies as many of the basic genes are identical in mice and humans. Discovery of the genes function in mice can thus point the way to our understanding of the gene's function in humans. Experimental mice created by disrupting the function of a specific gene are called knockout mice.

Klinefelter syndrome: An endocrine condition caused by a an extra X chromosome (47,XXY); characterized by the lack of normal sexual development and testosterone, leading to infertility and adjustment problems if not detected and treated early.

Kuru: A disease found in the Fore tribe in New Guinea, and due to the eating of human tissue. *


A - C      D - F      G - K      L - O     P - S     T - Z.

Label-retaining cell: Candidate for adult tissue stem cell because of slow division rate and/or immortal strand retention. Interpret with caution.

Lactic acidosis: An accumulation of lactic acid in the blood, whatever the cause. Any disease that leads to tissue hypoxia, exercise, hyperventilation, or some drugs (e.g. oral hypoglycemic agents) may cause this condition. ***

Lafora's disease: A progressive myoclonic encephalopathy (PME) that is inherited as an autosomal recessive trait. Associated symptoms typically begin in childhood or early adolescence and include frequent seizures characterized by loss of consciousness and rhythmic contraction and relaxation of all muscle groups (generalized tonic-clonic seizures); sudden, involuntary, "shock-like" muscle jerks (myoclonus); and rapidly progressive deterioration of thought processing and acquired intellectual abilities (dementia). Removal and microscopic examination of minute tissue samples (e.g., muscle fibers, liver cells, etc.) reveal abnormal, characteristic deposits of complex proteins and carbohydrates within the fluid portion of cells (intracytoplasmic inclusions known as "Lafora bodies").

Lambert-Eaton Syndrome: Also known as myasthenic syndrome, this disorder and its symptoms are quite different from myasthenia gravis, despite the similarity in name. It is found more frequently in men than in women and usually occurs after the age of 40. Symptoms include weakness and tiredness around the hips and subsequent difficulty rising from a chair. It progresses to involve legs, shoulders and arms. Backache that improves as the day progresses and fatigue are also common symptoms. Exercise works to improve symptoms. **

Lance-Adams syndrome: Also known as "posthypoxic" or "postanoxic action myoclonus," this condition is characterized by the development of chronic action myoclonus due to a temporary lack or inadequate supply of oxygen to the brain (cerebral hypoxia or anoxia). Patients with action myoclonus experience sudden, involuntary, "shock-like" muscle contractions that may be triggered or aggravated by voluntary movement. Lance-Adams syndrome is also often associated with cerebellar ataxia or lack of coordination, postural imbalance, and other associated findings.

Laparoscopy {lap-a-ROS-ko-pee}: A surgical procedure in which a lighted instrument shaped like a thin tube is inserted through a small incision in the abdomen. #

Laparotomy {lap-a-ROT-o-mee}: An operation in which the surgeon opens the abdomen. #

Laryngectomy: The surgical removal of the larynx. ##

Laser: A powerful beam of intensely focused light that can develop intense heat when focused at close range, sometimes used in surgery. #

Lateral (or horizontal) transmission: transmission of a disease from one animal to another except from the parent to the offspring. Generally this is the transmission between two animals alive at the same time and for one to be exposed to the agent from the other. *

Leigh disease: A disorder of mitochondrial function that typically becomes apparent during infancy. Also known as subacute necrotizing encephalomyelopathy, the disorder may be characterized by feeding and swallowing difficulties, vomiting, muscle weakness, low muscle tone (hypotonia), and delayed acquisition of motor and language skills. Affected infants and children may also develop seizures; an impaired ability to coordinate voluntary movements (ataxia); involuntary, rapid, rhythmic eye movements (nystagmus); tremor; dystonia; and/or other abnormalities. The disorder, which has a number of underlying causes, may occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal recessive or X-linked trait. Leigh disease is associated with characteristic changes of the central nervous system (CNS), including symmetric regions of localized tissue loss (necrosis) and neurodegenerative changes of the basal ganglia, thalamus, brainstem, spinal cord, and other regions of the CNS.

Lesion: A lump or abscess that may be caused by injury or disease, such as cancer. ##

Leukemia: Cancer of the blood. White blood cells may be produced in excessive amounts and are unable to work properly. ## Originates in the blood-forming tissues of the bone marrow, lymph nodes and spleen. #

Leukocyte: All white blood cells.

Leukodystrophy: An incurable disease of the central nervous system in which the formation of the myelin is abnormal. This may be due to a specific biochemical defect***

Leukopenia {Luka-PEEN-ee-ah}: A low number of white blood cells. ##

Leukotrienes: In general, a "leukotriene" is a member of a family of pharmacologically active substances that are products of eicosanoid metabolism (usually, arachidonic acid), some of which contain a peptide moiety based on cysteine. The leukotrienes are classified as "local hormones", i.e., hormones that are not stored, but which are synthesized in response to specific stimuli. They are formally derived from icosanoic acid and contain a set of 3 conjugated double bonds (thus the suffix "- triene"). They were originally discovered in association with leukocytes (thus the prefix "leuko-")

Lidocaine {LIE-doe-cane}: Drug most commonly used for local anesthesia. #

Ligand: A ligand is a substance which is capable of binding specifically and reversibly with a binder. A molecule that binds to a specific receptor protein. A ligand is termed an antigen when the binder is an antibody.

Ligase {LIE-gaze}: An enzyme that functions in DNA repair. %
An enzyme, T4 DNA ligase, which can link pieces of DNA together. The pieces must have compatible ends (both of them blunt, or else mutually compatible sticky ends), and the ligation reaction requires ATP. @@

Light chain (L chain): The light chain of immunoglobulin is a structural feature that occurs in two forms: kappa and lambda.

Limb-Girdle Muscular Dystrophy (LGMD): LGMD is now recognized as a group of related but specific disorders affecting mostly the muscles of the shoulder and pelvic girdles, which stabilize the upper arms and legs. Each type is caused by a defect on a gene making a muscle protein, thus the protein is abnormal and doesn't work properly in the muscle. At least a dozen different LGMD genes have been discovered already. An autosomal recessive form of muscular dystrophy that can appear at any age from childhood to the second or third decade of life. Degree of weakness and eventual disability are quite variable. Shoulder and hip girdle muscles are most often affected. In some cases, respiratory muscles can become involved. Progressive nature of the disorder may result in loss of ambulation or respiratory failure. **
Also: The main features of the limb-girdle type are that the muscles of the upper or "proximal" parts of the limbs are mainly involved, the muscles of the face are spared and the symptoms of the weakness are usually first noted in late childhood, adolescence or adult life (thus differing from the Duchenne type). Both males and females might be affected and their brothers or sisters are much more often affected than their parents or children. The term "limb-girdle muscular dystrophy" may be applied loosely to many quite different disorders. People who have been given this diagnosis should receive up to date advice about the particular type that is affecting them or members of their family. There has been considerable progress in establishing the genetic causes for many of the muscular dystrophies. The methods available for the diagnosis of the conditions which are not true muscular dystrophies but which may cause limb-girdle muscle weakness have also improved. Three genes responsible for different forms of LGD have been identified, and work is underway to determine the cause of the remaining cases and establish reliable diagnostic tests. (From: http://www.muscular-dystrophy.org/) *

Limbic encephalitis {IN-cep-ah-light-us}: Inflammation of the limbic system of the brain. ***

Limbic system (brain): This major brain division is a group of structures referred to as the limbic system. This area is deep in the center of the brain and is involved in our emotions. Included in this system are the hypothalamus, part of the thalamus, amygdala (active in producing aggressive behaviour) and hippocampus (plays a role in our ability to remember new information). The hypothalamus regulates temperature, eating, sleeping and the endocrine system. The pituitary gland is linked to the hypothalamus and is the "master gland" of the endocrine system. *

Lineage priming: Promiscuous expression in stem cells of genes associated with differentiation programmes.

Linear accelerator: A machine that creates high-energy radiation to treat cancers, using electricity to form a stream of fast-moving subatomic particles. Also called megavoltage (MeV), linear accelerator or a linac. #

Linkage: The independent segregation of chromosomes during meiosis ensures that alleles at two genes on different chromosomes are distributed randomly to gametes (the genes are 'unlinked'). However, when two genes lie on the same chromosome, their relationship following chromosomal segregation is determined by recombination between homologous chromosomes occurring during meiosis. The closer
the physical location of the two genes, the less likely it is that a recombination event will separate them, and the more likely it is that alleles at those genes will be observed to co-segregate (into gametes, and
thereby into offspring). This genetic 'linkage' provides a powerful tool for disease gene localisation.

Linkage analysis: A gene-hunting technique that traces patterns of heredity in large, high-risk families, in an attempt to locate a disease-causing gene mutation by identifying traits that are co-inherited with it.Linkage analysis represents the computational tool which allows identification of those genomic regions which show statistically significant co-segregation with disease and are therefore likely to be harbouring susceptibility loci. %

Linkage disequilibrium (LD): The frequency, in a population of linked genes, which is governed by factors other than chance. Linkage disequilibrium is the condition in which the haplotype frequencies in a population deviate from the values they would have if the genes at each locus were combined at random. When there is no such deviation, the linkage disequilibrium = 0, then the population is said to be in linkage equilibrium. "Equilibrium is an important concept in population genetics. I think it is easiest to illustrate it by thinking of two genes each with two alleles. If there is nothing particular going on in the population then what we would expect is the association between the two alleles, both within each locus, and between the loci to be random. They will not be any more likely to co occur than you would expect on the basis of their separate frequencies in the population - that is known as linkage equilibrium. The opposite is linkage disequilibrium where there is a non-random association between the two alleles at different loci." Linda Partridge.
Alleles of loci that are close to each other are inherited together and are called linked loci. Cross over is a random process of exchanging loci between chromosomes in the phase of meiosis i.e. between homologous chromosomes producing haploids. Cross over is more likely to take place between loci that are far apart on the chromosomes. That is why linked loci move together. Therefoer the distance between loci determine the likelihood of cross over (the frequency of recombination)- if this frequency is 50% (high) then this implies that the loci are far apart from each other (due to the random process). With all this in mind, when two alleles at a loci are seen together on a chromosome more than expected (i.e. something out of the random chance theory) then these loci are in linkage disequilibrium. That also explains why closely linked loci show disequilibrium - meaning they appear together on the same chromosome more often than expected by chance.
An example is the non-random pairing of alleles in the MHC region on Chromosome 6 and it is influenced by the low recombination rate in the MHC region.

Liver: the liver is one of the most important organs in the body and one fairly vulnerable to disease. The following is from: http://www.hepnet.com/liver/disease.html
The characteristic structure and organization of the liver enables it to perform vital roles in regulating, synthesizing, storing, secreting, transforming, and breaking down many different substances in the body. In addition, the liver's ability to regenerate lost tissue helps maintain these functions, even in the face of moderate damage.
Hepatitis, or inflammation of the liver, has numerous potential causes: infections with viruses, bacteria, fungi, or protozoa; exposure to toxins such as alcohol, drugs, or chemical poisons; and autoimmunity.
The liver can compensate for a significant amount of damage, but eventually liver function will decline markedly (decompensation), as manifested by diminished synthesis, abnormal clearance and excretion, ascites, and portal hypertension.
Acute hepatitis may get better without significant effects, but unresolved inflammation that persists for longer than six months is termed chronic hepatitis. Chronic hepatitis may be caused by ongoing infection and associated inflammation or by repeated exposure to toxins, such as alcohol. Whatever the offending agent, chronic inflammation may lead to irreversible liver scarring and fibrosis, a condition known as cirrhosis of the liver. Occasionally, acute infection results in massive tissue destruction and high risk of death (fulminat hepatitis).
Cirrhosis is defined as irreversible, diffuse fibrosis (or scarring) of the liver that is a common endpoint for many chronic liver diseases; it carries an increased risk of liver decompensation, hepatic failure, and the development of hepatocellular carcinoma.
Major Liver Viruses:
Hepatitis A: is a liver disease caused by the hepatitis A virus (HAV).
Hepatitis B: is a serious disease caused by a virus that attacks the liver. The virus, which is called hepatitis B virus (HBV), can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death
Hepatitis C: is a liver disease caused by the Hepatitis C virus (HCV), which is found in the blood of persons who have the disease. HCV is spread by contact with the blood of an infected person.
Hepatitis D: is a defective virus that needs the hepatitis B virus to exist, therefore, in humans, hepatitis D virus infection only occurs in the presence of hepatitis B infection. Hepatitis D virus (HDV) is found in the blood of persons infected with the virus.
Hepatitis E: is a virus (HEV) transmitted in much the same way as hepatitis A virus. Hepatitis E, however, does not often occur in the United States.

Local treatment: Treatment that affects a specific part of the body and the area close to it. %

Locus: The site on a chromosome where a gene is located. * Locus A locus is a unique chromosomal location defining the position of an individual gene or DNA sequence. In genetic linkage studies, the term can also refer to a region involving one or more genes, perhaps including noncoding parts of the DNA.

Long-term reconstitution: Lifelong renewal of tissue by transplanted cells. The definitive assay for haematopoietic, epidermal and spermatogonial stem cells. Transplantation assay may not be appropriate for all tissues.

Lou Gehrig's disease: see ALS

Lumbar puncture: A procedure during which a sample of fluid (i.e., cerebrospinal fluid [CSF]) is removed from the spinal canal for diagnostic or therapeutic purposes. During the procedure, CSF is obtained via a hollow needle inserted between two bones of the spinal column within the lower back (i.e., usually the third and fourth lumbar vertebrae). Laboratory analysis conducted on CSF may help to diagnose central nervous system infections, certain tumors, or particular neurologic disorders. In some cases, lumbar puncture may also be performed to inject certain medications into the CSF, such as particular anticancer (chemotherapeutic) agents.

Lumpectomy {lum-PEC-to-mee}: Surgery to remove a lump and a small margin of normal tissue surrounding it. #

Lupis: lupus erythematosus: A chronic inflammatory collagen disease affecting connective tissue and or kidneys (skin or joints); LE, systemic lupus erythematosus, SLE, disseminated lupus erythematosus.
Lupus is a chronic inflammatory disease that can affect various parts of the body, especially the skin, joints, blood, and kidneys. The body's immune system normally makes proteins called antibodies to protect the body against viruses, bacteria, and other foreign materials. These foreign materials are called antigens. In an autoimmune disorder such as lupus, the immune system loses its ability to tell the difference between foreign substances (antigens) and its own cells and tissues. The immune system then makes antibodies directed against "self." These antibodies, called "auto-antibodies," react with the "self" antigens to form immune complexes. The immune complexes build up in the tissues and can cause inflammation, injury to tissues, and pain.

Lymph {limf}: Transparent, slightly yellow fluid that carries lymphocytes, bathes the body tissues and drains into the lymphatic vessels. Contains cells that help fight infection.

Lymph nodes: Small, bean-shaped organs located along the channels of the lymphatic system. Bacteria or cancer cells that enter the lymphatic system may be found in the nodes. Also called lymph glands. %
Also: Lymph nodes also called lymph glands: Hundreds of small oval bodies that contain lymph. Lymph nodes act as our first line of defense against infections and cancer. ## Nodes filter bacteria or cancer cells that may ravel through the lymphatic system. #

Lymphangiography {limf-an-jee-OG-ra-fee}: X-ray study of lymph nodes and lymph vessels made visible by the injection of a special dye. #

Lymphatic system {lim-FAT-ik}: The tissues and organs, including the bone marrow, spleen, thymus, and lymph nodes, that produce and store cells that fight infection and disease. This system also has channels that carry lymph. %

Lymphedema {Lim-fa-DEE-ma}: Swelling of the arm that can follow surgery to the lymph nodes under the arm. Also called Milk Arm. # Swelling either from obstructed cancerous lymph nodes or from surgically removed lymph nodes. ##

Lymphocytes: Small white blood cells produced in the lymphoid organs and paramount in the immune defenses. White blood cells kill viruses and defend against the invasion of foreign material.

Lymphokines: Powerful chemical substances secreted by lymphocytes. These soluble molecules help and regulate the immune responses.

Lymphoma: A cancer of the lymphatic system. Doctors differentiate the different lymphomas by the type of cell that is involved in the makeup of the tumor. Treatments depend on the type of cell that is seen. ##
Also: A cancer that originates in the body's lymphatic tissues, primarily the lymph nodes or the lymph tissue of such organs as the stomach, small intestine or bone. #

Lysosomal: Referring to lysosomes, which are membrane-bound bodies (organelles) outside the nuclei of cells that contain various enzymes engaged in intracellular digestion.

Lysosomal storage diseases: Inborn errors of metabolism in which deficiency or impaired functioning of particular lysosomal enzymes leads to an abnormal accumulation of certain substances (e.g., fats, complex carbohydrates) within particular cells, progressively affecting multiple bodily tissues and organs. (Lysosomes are membrane-bound, enzyme-containing bodies within cells that engage in digestive processes; enzymes are proteins that accelerate the rate of certain chemical reactions in the body.) Most lysosomal storage disorders (e.g., mucolipidoses, mucopolysaccharidoses, lipidoses, etc.) are thought to be inherited as autosomal recessive traits.

Macrophage: a large and versatile immune cell that acts as a microbe-devouring phagocyte, an antigen presenting cell and an important source of immune secretions.

Macrophage-activating factor (MAF): Actually several lymphokines, including interferon, released by activated T cells, which together induce activation of macrophages, making them more efficient in phagocytosis and cytotoxicity.

Magic Thinking: Young children often believe that certain events are caused by their thoughts, wishes or hopes. Such belief equates thinking with doing: "If I only can think it strongly enough, it will happen." A variant of such reasoning is what we could call "superstitious prayer" often practiced by children and some adults. The idea is that if I persist with my appeal to God, I will eventually get him to do what I want. People under great stress, or who are seriously ill will sometimes fall into magic thinking. "If only I think (or do) this, this disease will go away." People who are ill are also often vulnerable to others taking advantage of this phenomenon. So, there are many "miracle cures" sold to patients who are "grasping at straws for a cure."
There are several "layers" of medicine, ranging from conservative, proven medicine, to experimental medicine (but still carried out within the medical community). In addition, there are many "alternative medicines", for example, acupuncture. These sorts of practices may well have a sound basis and may somehow help treat illness, but the scientific evidence is not currently available to decide the issue either way. At the other extreme are "charlatan" therapies that have no basis and are simply schemes to take financial advantage of people when they are ill. Unfortunately, there are a great number of these sorts of schemes and many people invest their money and hope into them. Many people strongly believe in these "miracle cures" and so, the charlatan has many people willing to testify as to the benefit of his cure. Sadly, many of these patients are caught in magic thinking, thinking that the "special formula" (usually a herb, mineral, etc.) has cured them. *

Magnetic resonance imaging: (MRI) is a test that uses radio waves to measure magnetic fields within the tissues to produce computerized pictures. These images provide information about both the structure and biochemical function of tissue. Because the process uses radio waves, it is much safer than using X rays or gamma rays, however, this procedure is more expensive. MRI is one way to look for problems in the brain (in nerves) or in the muscle. *

Magnetic resonance imaging (MRI): A sophisticated test using a magnet linked to a computer that provides in-depth images of organs and structures in the body.

Major histocompatibility complex (MHC): A group of genes that controls several aspects of the immune response. MHC genes code for self markers on all body cells. The set of gene loci specifying major histocompatibility antigens, for example HLA in man. Major histocompatibility complex (MHC): A cluster of genes on chromosome 6 in humans, encoding cell surface molecules that are polymorphic and that code for antigens which lead to rapid graft rejection between members of a single species which differ at these loci. Several classes of protein such as MHC class I and II proteins are encoded in this region. These in humans, are known as 'Human leukocyte antigens' (HLA).

Malignant Hyperthermia: A syndrome affecting individuals undergoing general anaesthesia, marked by rapid rise in body temperature, signs of increased muscle metabolism and usually, rigidity. The sensitivity is inherited as an autosomal dominant trait. It is also seen in boys with Duchenne muscular dystrophy. **

Malignant tumor.: A tumor. made up of cancer cells of the type that can spread to other parts of the body. ##

Malignant {ma-LIG-nant}: Cancerous. Also used as a term meaning very serious or deadly: "he has a malignant personality" (he is not a nice person)

Mammogram {MAM-oh-gram} (Mammography): A low-dose X-ray / picture of the breasts to determine whether abnormal growths or cysts are present. ##

Manifesting carrier: In the context of neuromuscular disorders: There are as wide a variety of presentations of manifesting carriers as there are of males with Duchenne muscular dystrophy and Becker muscular dystrophy. Some girls may have a muscular dystrophy that is as severe as boys with Duchenne muscular dystrophy. Other women may only have very mild problems with muscle weakness late in adult life. Some women get aches and pains in their muscles as their first complaint and may notice enlargement of their calves and other muscles.
There are other manifestations of Duchenne muscular dystrophy, for example involvement of intellectual function and of heart muscle. Problems in these areas can be the only signs that someone is a manifesting carrier. These presentations are less common than a woman noticing a mild but progressive weakness involving usually first her legs but later on the arms as well. Most manifesting carriers notice some progression of their muscle problem with time; however it is rare for there to be any sudden deterioration.
Do all manifesting carriers come from families where people are known to have Duchenne or Becker muscular dystrophy?
No. It is very important to note that the diagnosis of a manifesting carrier may be made in someone who has absolutely no family history of Duchenne muscular dystrophy or Becker muscular dystrophy at all. In the days before it was possible to look at the dystrophin gene and protein by special laboratory tests, a female could only be suspected of being a manifesting carrier of Duchenne or Becker muscular dystrophy if she had a definite family history of the condition or had an affected son herself. Now that it is possible to look at muscle biopsy samples directly with dystrophin staining, the diagnosis has been made in women and girls who were previously thought to have a form of limb-girdle muscular dystrophy.
These people usually have no family history of any muscle problems whatsoever. It is an important diagnosis to make in these cases because, unlike most of the forms of limb-girdle muscular dystrophy, the risk of having a child who may be affected with DMD or BMD is relatively high. Like any carrier of Duchenne or Becker muscular dystrophy, a manifesting carrier has a one in four chance of having an affected son in any pregnancy. There is no clear evidence to suggest that being a manifesting carrier tends to run in families. So if one carrier in any family has muscle problems this does not seem to make it any more likely that other members of the family will also manifest any problems relating to being a carrier.
Why do some women run into problems like this?
It is thought that people who are manifesting carriers of any X-linked condition such as Duchenne muscular dystrophy and Becker muscular dystrophy generally have some problem in the mechanism which we know as 'X-inactivation'. Because men only have one X-chromosome and women have two, one copy of the X-chromosome in every cell in a woman's body is 'switched off' very early in development. The process is usually random; on average half the cells have one X-chromosome active and the other half the other. In people who are manifesting carriers of Duchenne and Becker muscular dystrophy most cells have the faulty X-chromosome active. The X-inactivation patterns can be studied in blood and most manifesting carriers show a non-random pattern. Some manifesting carriers may show an apparently random pattern in blood. It is thought that these women may have skewed inactivation only or mainly in their muscle cells.
see Skewed X inactivation.

MAO-B inhibitors: Inhibitors of the enzyme monoamine oxidase B. MAO-B helps break down dopamine; inhibiting it prolongs the action of dopamine in the brain.

Marker: A gene with a known location on a chromosome and a clear-cut phenotype, used as a point of reference when mapping a new mutant.

Mast cell: Mast cells are white blood cells (leukocytes) containing dense granules of various substances, with mast cells often associated with connective tissue. A granule-containing cell found in tissue. The contents of mast cells, along with those of basophils, are responsible for the symptoms of allergy.

Mastectomy {Mas-TEK-toe-mee}:
- Segmental (lumpectomy): Removal of the lump and a small amount of surrounding breast tissue.
- Simple (modified mastectomy): Removal of the entire breast.
- Radical: Removal of the entire breast along with underlying muscle and lymph nodes of the armpit.
- Prophylactic mastectomy: Many women and men at risk of having a BRCA1 or BRCA2 mutation, especially those with children, choose to undergo DNA testing. Many of those positive for a mutation are considering prophylactic mastectomy to prevent breast cancer. Also called preventive mastectomy, it is the surgical removal of one or both breasts to try to prevent or reduce the risk of breast cancer. It involves removal of as much of the at-risk tissue as possible. It is not a guarantee against cancer, however. Some women have developed breast cancer after prophylactic mastectomies.##

Maternal transmission: The transmission of a disease from the mother to the offspring (not necessarily before birth). *

Maternally inherited disorder: A disorder that is inherited from the mother's genome or the maternal side of a family. ***

Mean: An average; intermediate or middle position in value, quantity, or degree. The "arithmetic mean" is a statistical measure derived by adding a set of values and dividing the total by the number of values.

Medially: Toward the middle; closer to or oriented toward the midline or median plane of a body or structure. The "median plane" refers to the imaginary plane that divides a body into symmetrical parts.

Mediastinal: {Media-stein -ill} Mediastinum. The region in mammals between the pleural sacs, containing the heart and all of the thoracic viscera except the lungs.

Medline (also called PubMed): This is a service that indexes research related to medicine. Most reputable research is indexed on medline. There are web sites on the Internet that allow people to search Medline for various topics and look at summaries of the studies that have been done. This information is generally written for other researchers and Doctors. Medline can be a very helpful source of information, especially, when faced with unusual disorders. A web site offering public access is at http://www.ncbi.nlm.nih.gov/PubMed/ This site is run by the National Library of Medicine, National Institutes of Health (USA) *

Meiosis {MY-oh-sis}: process of division in a living cell by which the number of chromosomes is reduced to half the original number. Meiosis occurs only in the process of gametogenesis, i.e., when the gametes, or sex cells (ovum in female and sperm in the male), are being formed. Because fertilization consists of the fusion of two separate nuclei, one from each of the sex cells, meiosis is necessary to prevent the doubling of the chromosome number in each successive generation. An ordinary body cell is diploid; i.e., it contains two of each type of chromosome. The members of each pair are known as homologous chromosomes. An ovum or sperm is haploid; i.e., it contains only a single chromosome of each type and, therefore, half the number of chromosomes of the diploid cell. When the ovum and sperm (haploid cells) fuse, the diploid number is restored, and the plant or animal growing from the fertilized egg (zygote) has the usual diploid number of chromosomes in its cells. *

Melanoma: A cancer of the pigment-forming cells of the skin or the retina of the eye. Usually begins in a mole. ##

Meme: {ME-mmm} A unit of cultural information, such as a cultural practice or idea, that is transmitted verbally or by repeated action from one mind to another.

Memetics: the theoretical and empirical science that studies the replication, spread and evolution of memes.

Memory: In the immune system, memory denotes an active state of immunity to a specific antigen, such that a second encounter with that antigen leads to a larger and more rapid response.

Memory cells (immune system). During a typical immune response to infection, antigen-specific lymphocytes divide extensively, generating a high number of effector cells to combat the infection. Once the infectious agent has been cleared, these effector cells are no longer needed and the vast majority of them die by apoptosis. However, some the activated cells survive long-term and carry an immunological memory to the original priming antigen; memory reflects an increased frequency of antigen-specific T and B cells, an increased sensitivity of these cells to antigenic activation and the persistence of direct effector functions. Means that if that specific antigen is encountered again, the memory cells will quickly reactivate to fight it.

MERFF syndrome (myoclonus epilepsy with ragged-red fibers): A rare hereditary disorder characterized by neurologic and muscle abnormalities due to defects of genetic material (DNA) in mitochondria, the rod-like structures outside the nuclei of cells that serve as a primary source of cellular energy. Removal and microscopic examination of minute samples of muscle fibers reveal structurally abnormal mitochondria (a finding known as "ragged-red fibers"). Associated symptoms include muscle weakness; sudden, involuntary, "shock-like" muscle contractions induced by voluntary movements or in response to external stimuli (action or reflex myoclonus); repeated seizures (epilepsy); progressively impaired coordination of voluntary movements (ataxia); and/or gradual deterioration of intellectual functioning (dementia). Some affected individuals may also have additional abnormalities, such as hearing loss; degeneration of the nerves (i.e., optic nerves) that convey impulses from the retinas to the brain (optic atrophy); short stature; heart muscle disease (cardiomyopathy); or other findings.

Merosin: A muscle-related protein. Genetic defects affecting the structure or expression of merosin are the causes of some types of congenital muscular dystrophy, for example, merosin abnormalities are linked to Merosin-Deficient Congenital Muscular Dystrophy. However, the precise nature of the functions of merosin in muscle remain unknown. *

Mesothelium: A single layer of squamous epithelial cells found in the serous membranes that line the pleura and the pericardial and peritoneal cavities.

Mesothelioma: a form of cancer that is almost always caused by previous exposure to asbestos. In this disease, malignant cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart). Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products. There is no association between mesothelioma and smoking.
"Only a fraction of subjects exposed to asbestos develop malignant mesothelioma (MM), suggesting that additional factors may render some individuals more susceptible. We tested the hypothesis that asbestos and Simian virus (SV40) are cocarcinogens. Asbestos and SV40 in combination had a costimulatory effect in inducing ERK1/2 phosphorylation and activator protein-1 (AP-1) activity in both primary Syrian hamster mesothelial cells (SHM) and primary human mesothelial cells (HM). Ap-1 activity caused the expression and activation of matrix metalloprotease (MMP)-1 and MMP-9, which in turn led to cell invasion. Experiments using siRNA and chemical inhibitors confirmed the specificity of these results. The same effects were observed in HM and SHM. Experiments in hamsters showed strong cocarcinogenesis between asbestos and SV40: SV40 did not cause MM, asbestos caused MM in 20% of hamsters, and asbestos and SV40 together caused MM in 90% of hamsters. Significantly lower amounts of asbestos were sufficient to cause MM in animals infected with SV40. Our results indicate that mineral fibers and viruses can be cocarcinogens and suggest that lower amounts of asbestos may be sufficient to cause MM in individuals infected with SV40." Proc Natl Acad Sci U S A. 2006 Sep 11; Crocidolite asbestos and SV40 are cocarcinogens in human mesothelial cells and in causing mesothelioma in hamsters. Kroczynska B, Cutrone R, Bocchetta M, Yang H, Elmishad AG, Vacek P, Ramos-Nino M, Mossman BT, Pass HI, Carbone M. see simian virus

Messenger RNA (mRNA): RNA transcribed from the DNA making up a gene. It transmits genetic information from the nucleus to the cytoplasm, where it directs the synthesis of proteins. % Also: RNA transcribed from genes undergoes posttranscriptional processing and the resultant mature mRNA is used as the template for the translation process that results in synthesis of a protein.

Metabolic {MET-ah-ball-ick}: the process of metabolism, see metabolism.

-Phosphorylase Deficiency (MPD or PYGM)(Also known as McArdle's Disease)
-Acid Maltase Deficiency (AMD)(Also known as Pompe's Disease)
-Phosphofructokinase Deficiency (PFKM)(Also known as Tarui's Disease)
-Debrancher Enzyme Deficiency (DBD)(Also known as Cori's or Forbes' Disease)
-Mitochondrial Myopathy (MITO)
-Carnitine Deficiency (CD)
-Carnitine Palmityl Transferase Deficiency (CPT)
-Phosphoglycerate Kinase Deficiency (PGK)
-Phosphoglycerate Mutase Deficiency (PGAM or PGAMM)
-Lactate Dehydrogenase Deficiency (LDHA)
-Myoadenylate Deaminase Deficiency (MAD) *

Metabolism: {Met-tab-ball-ism} The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized. Also: Refers to the ongoing chemical processes of cells of the body, including catabolism and anabolism. Catabolism or so-called "destructive metabolism" is the breakdown of complex chemical compounds into simpler substances, typically liberating or releasing energy. In contrast, anabolism or "constructive metabolism" refers to the "building up" or conversion of simple substances into more complex chemical compounds, requiring energy consumption (provided by catabolic processes).

Metabolomics: The study of the thousands of small chemicals, such as sugars and fats that are the products of metabolism in the body. If tests could be made to measure these chemicals, it could provide earlier and more accurate diagnoses of many diseases. The general aim of metabolomics is to identify measure and interpret the complex time-related concentration, activity and flux of endogenous metabolites in cells, tissues, and other biosamples such as blood, urine, and saliva.
Metabolic analysis can be divided into four general areas:
-Target compound analysis
= The quantification of specific metabolites (Substances that are used by or produced by enzyme reactions or other metabolic processes)
-Metabolic profiling
=Quantitative or qualitative determination of a group of related compounds or of specific metabolic pathways
=Qualitative and quantitative analysis of all metabolites (Substances that are used by or produced by enzyme reactions or other metabolic processes)
-Metabolic Fingerprinting
=Sample classification by rapid, global analysis
There are really three major areas of interest going on today:
1). Genomics: the study of the genome and the basic genetic message it carries.
2). Proteomics: The study of the proteins in the body and how they work and interact with each other. The proteome is the full set of proteins produced by the human genome at any one time. Unlike the genome, which is the same in most cells, the proteome is very dynamic. Distinct sets of proteins are produced in different cell types and at developmental stages.
3). Metabolomics - The study of the thousands of small chemicals, such as sugars and fats, that are the products of metabolism in the body.
Combining information from metabolomics, proteomics and genomics will help to obtain an integrated understanding of cell biology.

Metachromatic leukodystrophy: A type of hereditary leukodystrophy caused by a deficiency of the enzyme cerebroside sulfatase, an enzyme that is essential for the degradation of sulfatide. ***

Metaplasia: The transformation of one cell (or a tissue) into a different type. This is an abnormal process; for example, metaplasia of the epithelium of the bronchi may be an early sign of cancer.

Metastasis {met-TAS-ta-sis}: Spread of cancer to another organ, usually through the bloodstream or lymphatic system. # Cells in the metastatic (secondary) tumor. are like those in the original (primary) tumor. The plural is metastases.

Metastasize: To spread from the first cancer site, for example, breast cancer that spreads to the bone. ##

Methylation: Addition of a methyl group (-CH3) to DNA or RNA.

Metric units: commonly used in the scientific community (worldwide) and in the English and European traditions. (Imperial measures are still commonly used in everyday measures in the United States)
kilo = one thousand of the basic unit (kilometre = 1000 metres, kilogram = 1000 grams)
metre = basic unit of length (about 39 inches)
gram = basic unit of weight
litre = basic unit of volume
centi = one hundredth (1/100) of the basic unit (1 metre = 100 centimetres)
milli = one thousandth (1/1000) of the basic unit (1 metre = 1000 millimetres)
micro = one millionth (1/1,000,000) of the basic unit
nano = one billionth (1/1,000,000,000) of the basic unit

MHC class I molecule: A molecule encoded to genes of the MHC which participates in antigen presentation to cytotoxic T (CD8+) cells.

MHC class II molecule: A molecule encoded by genes of the MHC which participates in antigen presentation to helper T (CD4+) cells.

MHC restriction: The ability of T lymphocytes to respond only when they 'see' the appropriate antigen in association with "self" MHC class I or class II proteins on the antigen presenting cells.

microarrays: Microarrays (in which nucleic acids representing genes are spotted onto or synthesized on a substrate and then tested against a sample) gauge mRNA levels - and thus gene expression. With these tools, many different genes can be studied, enabling expression patterns to be discerned in, for example, diseased versus normal tissue or in early- stage disease tissue versus late- stage disease tissue.

Microchimerism: The presence of two genetically distinct and separately derived populations of cells, one population being at a low concentration, in the same individual or an organ such as the bone marrow. Microchimerism may be due to transfer of cells between mother and fetus or between two twins. Other sources of microchimerism include blood transfusions and transplants. See also: Chimera.

Microchips: A microchip (sometimes just called a "chip") is a unit of packaged computer circuitry (usually called an integrated circuit) that is manufactured from a material such as silicon at a very small scale. Microchips are made for program logic (logic or microprocessor chips) and for computer memory (memory or RAM chips).

Microbes: Tiny living organisms, including bacteria, viruses, fungi and protozoa.

Microglia: immune cells from inside the CNS *

Microorganisms: Plants or animals so small they can only be seen under a microscopic .

Microsatellite: Microsatellites consist of multiple repeats of a short sequence (typically 2-8 bp) such as: CACACA . . . . The alleles of a microsatellite are differentiated by the number of repeats they involve (eg, CA12 would denote 12 CA repeats in a row).

Microtubule: These are hollow structures (like drinking straws) made out of protein that are distributed throughout the cytoplasm of eukaryotic cells, providing structural support and assisting in moving the cell and transport of things within the cell. *

Migration inhibition factor (MIF): A lymphokine that inhibits the motility of macrophages in culture.

Mimetic: {me-MET-tick} a drug that mimics the action of a protein in the body. Many proteins can not be given directly as medicines because of problems in delivery - they break down when ingested or injected. Therefore, the development of copycat proteins is an important step in treating certain protein related disorders and in treating protein problems created by certain types of therapies (example, side effects of certain chemotherapies). As more protein structures are elaborated, more and more mimetic drugs will be developed. Mimetics is the area of research involved in this development.

Minicore Myopathy: One of the congenital myopathies, this disorder presents with hypotonia, general muscle wasting, mild facial weakness and delay in motor milestones. It is often associated with scoliosis. **

Minor histocompatibility antigens: These antigens, encoded outside the MHC, are numerous, but do not generate rapid graft rejection or primary responses of T cells in vitro. They do not serve as restricting elements in cell interactions.

Minus Protein Myopathies: a term recently coined to refer to cases of muscular disease linked to protein abnormalities. In many cases, muscular disease is being linked with reduced or absent proteins. This term refers to these protein deficiencies.
Also: Minus protein myopathies: Muscle disorders involving reduced or deficient muscle proteins. A term referring to the discovery that a large number of proteins are reduced or deficient in many muscular disorders, mostly muscular dystrophies. Some of these deficiencies are primary, others can be secondary. *

Missense {MISS-sense} mutation: Of or relating to a mutation that changes a codon for one amino acid into a codon for a different amino acid. %

Mitochondria {MY-toe-con-dree-ah}: BACTERIUM-SIZED organelles residing in most of our cells - convert fuel from food into the body's most biologically useful form of energy, adenosine triphosphate or ATP.
A structure within the cell which contain enzymes responsible for processing oxygen and converting fatty acids from the food we eat into energy. Mitochondria are the principal source of energy within cells. Mitochondria vary greatly in shape, size, and number. They are most numerous in cells with a high level of metabolic activity. Every cell contains hundreds or thousands of mitochondria. The mitochondria are unique because they contain a small amount of their own genetic material (the rest of the of our genetic material is all contained in the cell nucleus). Each mitochondria contains several copies of mitochondrial DNA (mtDNA) (the mitochondrial 'genome'), a situation that has profound effects because mitochondrial genome mutations can produce energy failure in those cells that depend on oxidative phosphorylation to maintain a high metabolic rate, a description that largely pertains to muscle and nerve cells. mtDNA is a circular strand of DNA that encodes 13 of the 70 or so subunits required by the mitochondria to process energy. In mammals mtDNA makes up less than 1% of the total DNA in the cell. Human mtDNA is inherited only via the female line. *

Mitochondrial DNA (mtDNA): Mitochondria are the only non-nuclear (not housed inside the nucleus) constituents of the cell with their own DNA (mtDNA) and machinery for synthesizing RNA and proteins. This remarkable capability reflects their descent from bacteria. Each cell contains hundreds or even thousands of mitochondria and mtDNAs. At fertilization all mitochondria in the zygote come from the oocyte; thus, both mtDNA and most mtDNA-related diseases are maternally inherited. Patients with mitochondrial genome defects usually harbor a mixture of normal and mutant mtDNAs, a condition known as heteroplasmy. A tissue with 20 percent mutant mtDNAs, unsurprisingly, suffers different effects than one with 90 percent. Moreover, the proportion of mutated mtDNAs can vary both in space (among tissues) and in time (over the patient's lifespan); one mutation may cause two diseases, or a patient may have totally different diseases early and later in life.
Besides maternally inherited and sporadic mtDNA mutations, there are also Mendelian-inherited errors in mtDNA. The discovery of two disorders has highlighted this seemingly paradoxical situation. In one, mtDNA deletions arise in muscle because of a defect in a nuclear gene that probably increases mtDNA's proclivity to suffer deletions. The second defect, which our group discovered, is a quantitative error in the mtDNAs present in specific tissues: "mtDNA depletion." Again, the defect is probably in a nuclear gene, most likely controlling mtDNA replication and, ultimately, the number of mitochondrial genomes in different tissues. From: http://www.columbia.edu/cu/21stC/issue-1.3/dna-mitoch.html

Mitochondrial metabolism: Defects of mitochondrial metabolism are associated with a wide spectrum of disease. These diseases range from systemic, lethal pediatric disease to late-onset, tissue-specific neurodegenerative disorders. They have been identified mainly in postmitotic tissues like brain, heart and skeletal muscle of healthy humans of advanced age but not in young people.

Mitochondrial Myopathies: Mitochondrial myopathies are a group of neuromuscular diseases caused by damage to the mitochondria. Nerve cells in the brain and muscles require a great deal of energy, and thus appear to be particularly damaged when mitochondrial dysfunction occurs. Some of the more common mitochondrial myopathies include Kearns-Sayre syndrome, myoclonus epilepsy with ragged-red fibres (MERRF), and mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes (MELAS). The symptoms of mitochondrial myopathies include muscle weakness or exercise intolerance, heart failure or rhythm disturbances, dementia, movement disorders, stroke-like episodes, deafness, blindness, vomiting, and seizures. The disorders range in severity from progressive weakness to death. The age of onset ranges from birth to adulthood, with the majority of cases occurring before the age of 20. Exercise intolerance or muscle weakness usually develops by the age of 20. During physical activity, muscles may become easily fatigued or weak. Muscle cramping may rarely occur. Nausea, headache, and breathlessness are also sometimes associated with mitochondrial myopathies. *

Mitogen: A substance that stimulates the proliferation of many different clones of lymphocytes.

Mitosis {MY-toe-sis}: The process of nuclear division in cells that produces daughter cells that are genetically identical to each other and to the parent cell. %
Also: mitosis: the process of nuclear division in a living cell by which the carriers of hereditary information, or the chromosomes, are exactly replicated and the two copies distributed to identical daughter nuclei. Mitosis is almost always accompanied by cell division (cytokinesis), and the latter is sometimes considered a part of the mitotic process. The pattern of mitosis is fundamentally the same in all cells.

Mixed lymphocyte reaction (MLR): When lymphocytes from two individuals are cultured together, a proliferative response is generally observed, as the result of reactions of T cells of one individual to MHC antigens on the other individual's cells.

Molecule: Molecules are made up of two or more atoms, either of the same element or of two or more different elements, joined by one or more covalent chemical bonds. Smallest particle of a compound that has all the chemical properties of that compound. *

Molecular farming: The development of transgenic animals to produce biomedical proteins (i.e. tissue plasminogen activator, factor IX, and human hemoglobin).

Monoamine: A molecule containing one amine group. An amine is an organic compound containing nitrogen. The so-called "biogenic monoamines" are natural, biologically active compounds that often function as neurotransmitters, including dopamine, serotonin, noradrenaline, and epinephrine.

Monoclonal: Literally, coming from a single clone. A clone is the progeny of a single cell. In immunology, monoclonal generally describes a preparation of antibody that is monogenous, or cells of a single specificity.

Monoclonal antibodies (MAb): Artificially manufactured antibodies that can locate and bind to cancer cells wherever they are in the body (for diagnostic or treatment purposes). Can be used alone or used to deliver drugs, toxins, or radioactive material directly to the tumor. cells. # Antibodies are a part of your immune system. When an antigen (such as a foreign protein in a germ) enters the body, the body makes natural antibodies to fight against it. These antibodies attach to the antigen and mark it for destruction by your immune system. A monoclonal antibody (MAb) is an antibody that has been created in a laboratory - cloned from a single antibody hence monoclonal. It is a kind of treatment that is very different from chemotherapy. Most chemotherapies are chemicals that kill all rapidly dividing cells in your body. An MAb is designed to bind to and help destroy only certain cells. In the lab, MAbs can be designed to attach to specific antigens found on certain cells. Like a natural antibody, an MAb binds to a specific antigen, much like a 'lock and key,' and results in the destruction of the targeted cell. This 'lock and key' or 'antibody to antigen' binding makes MAbs a very targeted and effective new treatment.

Monocyte: A large phagocytic white blood cell which, when enters tissue, develops into a macrophage. Large circulating white cell, 2-10% of total white cells, phagocytic, indented nucleus. Migrates to tissues, where it is known as a macrophage.

Monokines: Powerful chemical substances secreted by monocytes and macrophages that help to direct and regulate the immune response. Monokines: Soluble substances secreted by monocytes, which have a variety of effects on other cells.

Monotherapy: A drug used alone to treat a disease (opposite of combination therapy).

Morbidity: The condition of being diseased or sick; also the incidence of disease or rate of sickness.

Mortality: Mortality is another term for death. A mortality rate is the number of deaths due to a disease divided by the total population. If there are 25 lung cancer deaths in one year in a population of 30,000, then the mortality rate for that population is 83 per 100,000.

Mosaic (mo·sa·ic) 1. a pattern made of numerous small pieces fitted together. 2. in genetics, an individual or cell cultures having two or more cell lines that are karyotypically or genotypically distinct but are derived from a single zygote. Cf. chimera. 3. in embryology, the condition in the fertilized eggs of some species, such as the sea urchin, whereby the cells of early stages have developed cytoplasm which determines the parts that are to develop. 4. in plant pathology, a viral disease characterized by mottling of the foliage.

Mosaicism {MOE-say-a-cisim}: Mosaics are animals that have more than one genetically-distinct population of cells that all arise from a single zygote. The fraction of cells having each specific genotype is quite variable, reflecting how early during embryogenesis the mosaicism originated. In most but not all cases, the mosaicism can be detected in cells from all tissues. If some of the types of cells have abnormalities, and if the proportion of abnormal cells in a mosaic is sufficiently large, that individual will manifest disease. Conversely, if the abnormal cells are proportionally small in comparison to cytogenetically normal cells, the normal cells may be sufficient to prevent disease or reduce its severity. For example, a large majority of humans having Turner's syndrome (X chromosome monosomy) die prior to birth. Many of the Turner's individuals that do survive are found to be mosaics with a substantial fraction of normal cells (e.g. 46 XX/45 XO mosaics).
Also: mosaicism (mo·sa·i·cism) in genetics, the presence in an individual of two or more cell lines that are karyotypically or genotypically distinct and are derived from a single zygote. Cf. chimerism.
== erythrocyte mosaicism, the mixture of two blood types in each of nonidentical twins as a result of anastomosis of placental blood vessels.
== confined placental mosaicism, mosaicism in which a chromosomal abnormality (usually trisomy) is restricted to the placenta; it occurs in about 2 per cent of viable pregnancies and is a possible cause of intrauterine growth restriction.
==gonadal mosaicism, mosaicism that results from mosaicism within the gonad so that some of the germ cells are mutants. More than one offspring of a gonadal mosaic for a dominant trait may show the trait although it is not manifested in the parent.

Motor cortex (brain): The motor cortex is an area in the brain that helps coordinate all voluntary muscle movements. *

-Amyotrophic Lateral Sclerosis (ALS)(Also known as Lou Gehrig's Disease)
-Infantile Progressive Spinal Muscular Atrophy (SMA, SMA1 or WH)(Also known as SMA Type 1, Werdnig-Hoffman)
-Intermediate Spinal Muscular Atrophy (SMA or SMA2)(Also known as SMA Type 2)
-Juvenile Spinal Muscular Atrophy (SMA, SMA3 or KW)(Also known as SMA Type 3, Kugelberg-Welander)
-Spinal Bulbar Muscular Atrophy (SBMA)(Also known as Kennedy's Disease and X-linked SBMA)
-Adult Spinal Muscular Atrophy (SMA)

M-protein (or monoclonal immunoglobulin): A protein associated with peripheral neuropathy or monoclonal gammopathies. Monoclonal proteins have been found in 10% of patients with idiopathic polyneuropathies, a prevalence six to 10 times that in the general population. The prevalence of monoclonal gammopathies increases with age as well. ***

mRNA: See messenger RNA.

mtDNA: Mitochondrial DNA. There are two kinds of DNA that are found in a cell: nuclear and mitochondrial. Nuclear DNA is found within the nucleus of the cell and is composed of two sources of DNA, one source is the egg from the mother and the other is the sperm from the father. MtDNA is inherited only from our mothers and only females can pass it on to their children. (The Y chromosome which is found in the nucleus, is also uniparentally inherited, and is transmitted exclusively from father to son). Human mtDNA is a closed circular molecule of 16,569 nucleotides with some 37 genes and is thus about 200,000 times shorter than nuclear DNA. mtDNA codes for 13 essential genes of oxidative phosphorylation, and for 2 structural rRNAs and 22 tRNAs necessary for their expression. Together, nuclear DNA and mtDNA carry the information needed to synthesise all of the proteins in our bodies. mtDNA and nuclear DNA interact in the cell to create / code for protein products.

Mucosa (Mucous membranes): The lining of the mouth and gastrointestinal tract. ##

Mucositis: Inflammation of the lining of the mouth or gastrointestinal tract. ##

Mucous membranes: Tissues lining such organs as the mouth and intestine. The mucous membranes keep the organs moist by secreting juices. #

MULTICENTER: see clinical trials

Multicore Myopathy: One of the congenital myopathies, this disorder presents with early onset of limb and trunk weakness with delayed or failure to attain motor milestones. **

Multifactorial: A characteristic influenced by many factors, both genetic and environmental. Multifactorial diseases or disorders are thought to be due to an interaction between environmental factors and a number of genes, the latter contribution being referred to as polygenic. A number of congenital malformations (e.g. cleft lip, palate, spina bifida) and common disorders in adults (e.g. diabetes mellitus, cancer, schizophrenia) are thought to be multifactorial in origin. The risk for an individual of developing a multifactorial disorder is determined by the number of affected members in the family and the relationship to the patient. This risk, known as an empiric risk, does not require knowledge of the nature of the genetics nor environmental factors in the pathogenesis. *

Multifocal: A disorder arising from or pertaining to many locations. Each location may differ slightly in terms of specific symptom presentation. *

Multimodality therapy: The combined use of more than one method of treatment, e.g., surgery and chemotherapy. #

Multiple and Interactive Causality: Complex diseases like cancer or some of the neuromuscular disorders, often have complex, interactive causes.
-This means several things:

  1. One (or more) causes can result in the disease.
  2. Several causes may "work together" to lead to abnormalities.
  3. Over time, abnormalities may interact with other factors to alter the course of the illness.
  4. Eventually, the abnormalities lead to one or more symptoms.
  5. Multiple and interactive causes make it more difficult to understand these diseases (and how to treat them).

Multiple sclerosis {SKLer-row-sis}: A chronic autoimmune inflammatory disease of the central nervous system marked by intermittent damage to the myelin sheath that covers the nerve cell axons (sclerosis means a thickening or hardening of a body part, as of an artery, especially from excessive formation of fibrous interstitial tissue). Visual changes and muscle weakness occur often and have no consistent pattern; as the disease progresses, different nerves may be affected at different times, exacerbating the current symptoms or creating new problems. The disease may progress steadily, or acute attacks may be followed by partial or complete temporary remission of symptoms. Most patients live a relatively normal lifespan. Recent research implicates viruses as a possible cause. ***

Murine models: research models of disease, using rats or mice as the animal being infected. *

Muscle Ache: see muslce pain.

Muscle Biopsies: see appendix (Quest).

Muscle: contractile tissue found in animals, the function of which is to produce motion. *

Muscle Pain: There are two basic types of muscle pain. The first is an acute pain (sometimes called a "muscle burn") felt during exertion. It is caused by a buildup of lactic acid, a byproduct of exercise that dissipates from the muscle tissues within an hour. As soon as someone stops exercising, or shortly afterward, the pain goes away. The second type is a longer lasting muscle soreness after exercise. No one knows for sure exactly what causes muscle soreness, but many scientists think that this delayed pain is caused by microscopic tears in the muscles when a certain exercise or activity is new or novel. These tiny tears eventually produce inflammation, and corresponding pain, 24 to 36 hours later. "White blood cells start to repair the damaged muscle after about 12 to 24 hours and they release a number of chemicals which are likely to be involved in the generation of local muscle pain," said Dr. Mark Tarnopolsky, a specialist in neuromuscular disorders at the McMaster University Medical Center in Hamilton, Ontario. "You see damage at the microscopic level immediately after exercise, yet the soreness is usually delayed for about 24 hours and peaks at 48 hours." The good news is that as these little tears repair themselves, they prepare the muscles to handle the same type of exercise better the next time."The muscle gets more resilient, meaning the next time you do that same exercise you won't get damaged as much," said Dr. Priscilla Clarkson, a professor of exercise science at the University of Massachusetts and a leading researcher on muscle soreness. "That doesn't mean you are stronger, or mean you can lift more weight. It just means your muscle fibers are likely stronger so they won't tear as easily. Over time they'll build up and become a stronger fiber to lift more weight." Performing certain exercises can almost guarantee delayed soreness: running, hiking or skiing downhill, for example, and lowering weights - what weight lifters refer to as "negatives." In these downhill or downward motions, called eccentric muscle actions, the muscle fibers have to lengthen and then contract, "like putting on the brakes," Dr. Clarkson explained. "It's that lengthening-contraction that puts the most strain on the fiber and does the most damage." Of the 600 or so muscles in the human body, about 400 of them are skeletal. The largest of these are the muscles most susceptible to delayed soreness, Dr. Wadler said. . . . In most cases, delayed muscle soreness is not serious, and the soreness fades after a day or two of rest. Weight lifters typically work out the lower body one day and the upper body the next to give fatigued muscles a chance to recover. And conditioned athletes, like cyclists and runners, often alternate between easy and hard days of exercise. "Stress-adapt, stress-adapt so you can handle more and more exercise," said Dr. Tarnopolsky. "That's what an athlete strives for." (From NYT, November 16, 2004).

Muscle Structure: A whole skeletal muscle is considered an organ of the muscular system. Each organ or muscle consists of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape and some narrow. In some muscles the fibers are parallel to the long axis of the muscle, in some they converge to a narrow attachment, and in some they are oblique.
Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds, or even thousands, of muscle fibers bundled together and wrapped in a connective tissue covering. Each muscle is surrounded by a connective tissue sheath called the epimysium. Fascia, connective tissue outside the epimysium, surrounds and separates the muscles. Portions of the epimysium project inward to divide the muscle into compartments. Each compartment contains a bundle of muscle fibers. Each bundle of muscle fiber is called a fasciculus and is surrounded by a layer of connective tissue called the perimysium. Within the fasciculus, each individual muscle cell, called a muscle fiber, is surrounded by connective tissue called the endomysium.Skeletal muscle cells (fibers), like other body cells, are soft and fragile. The connective tissue covering furnish support and protection for the delicate cells and allow them to withstand the forces of contraction. The coverings also provide pathways for the passage of blood vessels and nerves.
Commonly, the epimysium, perimysium, and endomysium extend beyond the fleshy part of the muscle, the belly or gaster, to form a thick ropelike tendon or a broad, flat sheet-like aponeurosis. The tendon and aponeurosis form indirect attachments from muscles to the periosteum of bones or to the connective tissue of other muscles. Typically a muscle spans a joint and is attached to bones by tendons at both ends. One of the bones remains relatively fixed or stable while the other end moves as a result of muscle contraction.
Skeletal muscles have an abundant supply of blood vessels and nerves. This is directly related to the primary function of skeletal muscle, contraction. Before a skeletal muscle fiber can contract, it has to receive an impulse from a nerve cell. Generally, an artery and at least one vein accompany each nerve that penetrates the epimysium of a skeletal muscle. Branches of the nerve and blood vessels follow the connective tissue components of the muscle of a nerve cell and with one or more minute blood vessels called capillaries. Diagram: Click here. From: http://training.seer.cancer.gov/module_anatomy/unit4_2_muscle_structure.html (defunct)

Muscle tone: The low level of contraction in a muscle not being intentionally contracted.

Muscular Dystrophy: This term is actually a misnomer based on the wrong assumption made many years ago that muscle was being damaged by a lack of nutrients. In modern usage, it refers to a group of genetic myopathies in which a muscle protein is absent, deficient or abnormal. The disorders classified as "muscular dystrophies" are myopathies in which a genetic defect results in structural damage to the muscle. Other myopathies involve damage to the muscle's contraction apparatus or energy production system.

-Duchenne Muscular Dystrophy (DMD)(Also known as Pseudohypertrophic)
-Becker Muscular Dystrophy (BMD)
-Emery-Dreifuss Muscular Dystrophy (EDMD)
-Limb-Girdle Muscular Dystrophy (LGMD)
-Facioscapulohumeral Muscular Dystrophy (FSH or FSHD)(Also known as Landouzy-Dejerine)
-Myotonic Dystrophy (DM)(Also known as Steinert's Disease)
-Oculopharyngeal Muscular Dystrophy (OPMD)
-Distal Muscular Dystrophy (DD) (Miyoshi myopathy (MM))
-Congenital Muscular Dystrophy (CMD)

MuSK: Muscle-specific receptor tyrosine kinase (MuSK). In mysathenia gravis: Some patients have typical myasthenic symptoms but no detectable anti-acetycholine receptor antibody. Among these patients, a significant proportion have been reported to have antibodies directed towards a muscle specific kinase protein (MuSK). In these patients, the mechanisms of the disease may be different and also the role of the thymus may be different too.

Mutagen: an external agent (for example a toxic chemical or radiation) that causes mutations in DNA. *

Mutation: A mutation is any change in the existing DNA base sequence of an organism. Most mutations are harmful, causing death or disease, a few are neutral, and a very few are beneficial and contribute the organism's reproductive success. Mutations are the wellspring of genetic variation, variation is central to Darwin and Wallace's theory of evolution by natural selection. *

Mutations: Explanation of Point Mutations and Frameshift Mutations:
An "out of frame deletion" is one that changes what is called the "reading frame" of the gene. For a cell to make a protein from a gene, it has to interpret the gene starting at one end and reading straight through to the other end. If the cell gets confused, it will make a garbled protein with the wrong sequence of amino acids. If the deletion is "in frame" then the cell is able to skip over the missing portion and make a normal protein that is missing a little chunk from the middle. The trick to determining if a deletion is in or out of frame is whether or not the missing DNA bases are a multiple of three.
Here is a short primer about DNA, genes and mutations. Basically, a gene is a portion of the DNA that contains the instructions to make a particular protein. Each gene is like a sentence - it has a distinct starting point and a distinct stopping point. The tricky part is that not all of the portions of the gene are used to make a protein. Inside each gene there are alternating strings of DNA called "exons" and "introns" - the exons actually contain the important protein making information, and the introns serve as sort of "spacers" between the exons. The dystrophin gene, which is huge, has approximately 79 exons.
The DNA code is like an alphabet that contains only four letters: A, G, T and C (in RNA the T is replaced by a U). These letters are used to make 61 different three-letter words (like "ACG" or "GCU" etc.), also referred to as "codons." These words are strung together to make up genes. Although these three-letter words don't make a lot of sense to us, our cells understand them perfectly. Each three-letter word represents a particular amino acid. Our cells read the three-letter words of the exons in sequence and string together the correct amino acids to make a protein (like dystrophin). A type of mutation called a "point mutation" occurs when a single letter is accidentally changed. This type of mutation can convert one three-letter word into another and thus change the amino acid specified at that point in the protein. Sometimes point mutations are harmless, but sometimes they spell big trouble. For instance, if a three-letter word that specifies a particular amino acid is accidentally mutated to specify no particular amino acid or to specify a "stop" signal, then the resulting protein will be too short and may not be functional. This type of mutation is called a "nonsense" mutation or a "premature stop codon." Other types of mutations can involve missing letters (deletions) or extra letters (duplications) rather than substitutions.
A frameshift mutation occurs when DNA letters are deleted or duplicated in multiples other than three. This is because the cell recognizes the beginning of a gene by finding the specific three-letter word that tells the cell to start "reading" and progresses through each three-letter word until it reaches the word that says stop (like a period). If only one letter in the middle of a gene is inadvertently lost or added through a mutation, the cell may get confused about which group of three letters represents a particular word.
For example, if the sentence
loses a "T" from the word "CAT, " the sentence would be read as
The same thing happens in the dystrophin gene if it contains too few or extra letters that are not multiples of three. The cell reads the remaining words after the change incorrectly.
Researchers are wondering if gentamicin could be used to sort of trick the cells into ignoring extra or missing letters so that the correct sequence of three-letter words in the remainder of the gene would be restored. In this scenario, there would still be a some missing genetic information, but hopefully this loss would not be as severe as mangling the reading frame of the entire gene (a partial dystrophin protein is almost always better than none).
In general, point mutations tend to cause less ill effects than frameshift mutations because they often only lead to one wrong amino acid in the resulting protein (except for the cases mentioned above where the change introduces a "stop" signal).
Based upon a transcript from the Muscular Dystrophy Association (USA) written by Sharon Hesterlee, Ph.D., Director of Research Development.

Myalgia {MY-al-gee-ah}: Myalgia, or muscle pain, can be caused by mechanical stress without muscle injury (as in classic or non-neural muscle cramps), or by injury. Muscle injury can occur in anyone who "overdoes it" during exercise, including those with types of muscular dystrophy that render muscle cells more fragile. Muscle injury can also occur in response to problems with the immune system, as in polymyositis and dermatomyositis, or in response to a lack of energy and buildup of toxic metabolites, as in carnitine palmityl transferase deficiency. *

Myasthenia: From myo, meaning muscle; a, without; and sthenos, strength. Definition: muscle weakness or lack of strength. Today, "myasthenia" refers specifically to muscle weakness resulting from faulty communication between nerve and muscle at the place where nerve and muscle meet (the neuromuscular junction).

Myasthenia {MY-AS-then-ee-ah} Gravis {Grav-ISS}: chronic disorder that causes varying degrees of muscular weakness, especially after the muscle has been exercised. The muscles initially affected are those concerned with eye movements, facial expressions, chewing, swallowing, and respiration. The heart is not usually involved. The disease spreads to the neck, trunk, and limb muscles; respiratory difficulties or respiratory arrest may occur in severe cases. Muscles first fail to contract after prolonged use; they seem to become weaker with repeated mild activities but then regain their strength after rest. Eventually, muscular paralysis may remain, with degeneration of muscle fibres and infiltration of lymph cells.
Myasthenia gravis can occur at any age, but it rarely begins before the age of 10 or after 70, and it occurs more frequently in females. There is a tendency for the condition to be more prevalent in some families. Some symptoms show sudden onset, while others may be present for 10 to 20 years without becoming any worse; this is especially true of visual problems such as double vision, drooping eyelids, and eye wandering.
The affected person may have difficulty in climbing stairs, in rising from chairs, in lifting objects, or in raising his arms over his head. All of the lower facial muscles may become involved, so that speech takes on a nasal quality, and the affected person may even have to support his chin with one hand in order to talk. Neck weakness may be mild or so severe that the head cannot be held erect. Each affected person seems to manifest his own set of difficulties; he may be perfectly mobile and yet have difficulty in breathing, or he may be bedridden but free of respiratory problems.
The disease is an autoimmune disorder that breaks the linkage between the nervous system's stimulation of a muscle and the muscle's response. Autoantibodies bind to receptors on muscle cells that normally respond to acetylcholine, a neurotransmitter that stimulates muscles to contract. The binding action destroys the receptors or blocks their response to acetylcholine.
Treatment includes anticholinesterase drugs, which stimulate the transmission of nerve impulses, or corticosteroid drugs (such as prednisone). In severe cases removal of the thymus, especially in persons with thyroid tumors, has improved the clinical course of the disease. The disorder also may regress spontaneously for up to several years. Some persons die from sudden respiratory arrest, but in most cases the disease is not fatal. *

Myelin {MY-oh-lin}: Fatty substance that covers and protects nerves. The whitish, fatty substance forming the segmented, multilayered wrappings or "sheaths" around certain long nerve fibers or axons. Myelin sheaths electrically insulate axons, serving to speed the transmission of nerve signals (action potentials).

Myelinated: Referring to long nerve fibers (axons) that have myelin sheaths. Consisting of segmented, multilayered wrappings of myelin, a whitish protein, myelin sheaths wrap around certain nerve fibers, providing electrical insulation and serving to speed the transmission of nerve signals.

Myelin sheath: The insulating envelope of myelin that surrounds the core of a nerve fiber or axon and facilitates the transmission of nerve impulses. In the peripheral nervous system, the sheath is formed from the cell membrane of the Schwann cell and, in the central nervous system, from oligodendrocytes. *

Myelogram {MY-oh-lo-gram}: An X-ray of the spinal cord and bones of the spine. #

Myeloma {MY-oh-loam-ah}: A malignant tumor. of the bone marrow associated with the production of abnormal proteins. ## Myeloma: A tumour of plasma cells, generally secreting a single species of immunoglobulin.

Myelopathy: Any disease or disorder of the spinal cord or bone marrow

Myelosuppression: A decrease in the production of red blood cells, platelets, and some white blood cells by the bone marrow. ##

Myo {MY-oh}: a prefix that refers to muscle. *

Myoclonic: Pertaining to myoclonus or irregular, involuntary, shock-like contractions or spasms of a muscle or muscle group.

Myoclonus {MY-ock-quin-ous}: Twitching or clonic spasm of a muscle or group of muscles. ***
Also: myoclonus: a sudden spasm of the muscles typically lifting and flexing the arms. Myoclonus is a major feature of some progressive neurological illnesses with extensive degeneration of brain cells. myoclonic adj. Also: A neurologic movement disorder characterized by brief, involuntary, twitching or "shock-like" contractions of a muscle or muscle group. These jerk-like movements may be accompanied by periodic, unexpected interruptions in voluntary muscle contraction, leading to lapses of sustained posture (known as "negative myoclonus"). So-called "positive" and "negative" myoclonus are often seen in the same individuals and may affect the same muscle groups. Myoclonus is often a nonspecific finding, meaning that it may occur in the setting of additional neurologic abnormalities and be associated with any number of underlying conditions or disorders. In other patients, myoclonus appears as an isolated or a primary finding. Depending on the underlying cause and other factors, the shock-like muscle jerks may occur repeatedly or infrequently; may tend to appear under specific circumstances (e.g., with voluntary movements or in response to specific external sensory stimuli); and may affect any body region or regions.

Myofascial Pain Syndrome (MPS): myofascia is a thin film that wraps individual muscle fibres and whole muscles. Myofascial pain is thought to be caused by chemical changes in the myofascia that made it prone to calcification causing a tightening and rigidity of the fascia. The film loses its elasticity and becomes painful.

Myoglobinuria: Myoglobin in the urine. It may occur following muscular activity, trauma, or as a result of a deficiency of muscle phosphorylase. ***

Myopathic: Any disease or abnormal condition related to striated muscle. ***

Myopathy{MY-op-path-ee}: From the Greek words myo, meaning muscle, and pathos, disease or suffering. Definition: any disease or abnormal condition of voluntary muscle.
The myopathies are usually subdivided into those that are inherited (see muscular dystrophy) and those that are acquired. The acquired myopathies include polymyositis and muscular diseases complicating endocrine disorders or carcinoma. All are typified by weakness and wasting of the muscles, which may be associated with pain and tenderness. *
-Hyperthyroid Myopathy (HYPTM)
-Hypothyroid Myopathy (HYPOTM)
-Myotonia Congenita (MC)(Two forms: Thomsen's and Becker's Disease)
-Paramyotonia Congenita (PC)
-Central Core Disease (CCD)
-Nemaline Myopathy (NM)
-Myotubular Myopathy (MTM or MM)
-Periodic Paralysis (PP)(Two forms: Hypokalemic and Hyperkalemic)

Myophosphorylase Deficiency: Also known as McArdle's disease, this disorder occurs when there is a deficit in the enzyme myophosphorylase and a person is unable to utilize glycogen as a source of energy. A person with this disorder will experience difficulty and crampy pain with heavy lifting or exercise. It is usually inherited via autosomal recessive inheritance. Onset is usually before age 10 and it is more common in males. **

Myosin {My-oh-sin}: Myosin is one of the major proteins making up the filaments (myofilaments) in muscle. Myosin, working with along with actin, is responsible for the contraction of muscle. In muscle cells, myosin is arranged in long filaments called thick filaments that lie parallel to the microfilaments of actin. In muscle contraction, filaments of actin alternately chemically link and unlink with those of myosin in a creeping or sliding action. (Think of the myosin as the oars on a boat and the actin as the water). Based on: http://www.encyclopedia.com/

Myositides -- See Myositis.

Myositis {MY-o-sight-us}: From the Greek word myo, meaning muscle, and the Greek suffix itis, meaning inflammation of.
An inflammation of the muscle, which can result from infection, injury, or attack by the immune system on muscle tissueany of a group of muscle diseases in which inflammation and degenerative changes occur. Polymyositis is the most commonly occurring example, but myositis may be found in relation to systemic connective-tissue diseases and a minority are caused by bacterial or parasitic infections. *

Myositis Ossificans: A rare disorder characterized by deposition of true bone in subcutaneous tissue and along muscle. It usually appears in the first or second year of life and is progressive. The extent of disability is variable depending on the extent of ossification. It is thought to be genetic in origin. Treatment is symptomatic. **

Myositis-specific antibodies (MSA) About 50% of patients with polymyositis or dermatomyositis have specific MSA or myositis associated antibodies (MAA). MSA are almost never found in patients without myositis, even if they have other muscle diseases of autoimmune diseases.

Myotilin: Myotilin, a muscle protein that allows it to contract and relax. Has been confirmed to play a role in causing limb-girdle muscular dystrophy type 1A. *

Myotonia (adjective myotonic): From myo, meaning muscle, and tonos = tone. Definition: inability to relax muscles after contraction.

Myotonia {MY-ah-toe-knee-ah}: Myotonia occurs when contracted muscles relax too slowly due to electrical problems in the muscle or nerve cells. A person with myotonia may have difficulty releasing his grip after holding an object - the sensation is sometimes described as stiffness. Myotonia can be sensitive to exercise, temperature or diet, and occurs in paramyotonia congenita, myotonia congenita, hyperkalemic periodic paralysis and myotonic dystrophy. *

Myotonia Congenita: Also known as Thomsen's disease, this disorder is an autosomal dominant form of muscle disease. There is no muscle weakness or wasting and no systemic symptoms, distinguishing it from myotonic dystrophy. The major symptom is myotonia that is often quite severe and widespread and can result in a functional disability. An affected person may have difficulty relaxing the grip, opening the eyes, running and swallowing. It is a painless disorder and breathing is not affected. **

Myotonic {MY-oh-ton-ick} Dystrophy: This genetic disorder involves (but isn't limited to) both myotonia and structural damage to muscles (dystrophy). Myotonic dystrophy (DM) is the most common muscular dystrophy in adults, and is the second most common muscular dystrophy after Duchenne muscular dystrophy. It is an autosomal dominant genetic disorder affecting one in 8,000 individuals. Onset is usually in the second or third decade and the life span of affected individuals is typically six decades. A congenital form of DM can occur in second or third generations, however, and can be fatal for affected infants. Characteristics of DM include myotonia, as well as progressive weakening and wasting of the voluntary muscles of the eyes, face, neck, arms and legs. Muscles related to involuntary activities such as swallowing and breathing, as well as those surrounding the internal organs such as the upper and lower digestive tracts, the gall bladder, and the uterus may also be affected as the disease progresses in an individual. Other characteristics include cataracts, cardiac conduction abnormalities, cognitive deficits, and frontal balding.
The genetic causes of three forms of DM have been identified:
>DM1, also known as Steinert's disease
>DM2, also known as proximal myotonic myopathy (PROMM)
>Congenital myotonic dystrophy (CMyD)
DM1 and DM2 have similar clinical presentations, however, DM2 may present with milder symptoms. Both DM1 and DM2 are equally prevalent. CMyD is the most serious form of DM. Affected infants typically have severe muscle weakness, hypotonia and difficulties with breathing, sucking and swallowing. Intensive clinical intervention is necessary to improve the chance of survival of such children. CMyD and early onset DM1 are attributable to the phenomenon of anticipation. The abnormal repeat expansion that has been identified as the cause of DM1 can lengthen in successive generations, which lowers the age of onset and increases symptom severity.
All three forms of DM are caused by an abnormal nucleotide repeat expansion. In DM1 and CMyD, the expansion is in a noncoding region of the DMPK (Dystrophia-myotonica protein kinase) gene on chromosome 19. In DM2, the expansion is in a noncoding region of the ZNF9 (zinc finger protein 9) gene on chromosome 3.2 The fact that both repeat expansions occur in noncoding regions of these genes, yet result in very similar multi-systemic symptoms, has led researchers to hypothesize that mutant RNA is a contributing factor to DM.
For more information (and where this is from) see: http://www.neurocast.com/site/content/sessions_05_2002.asp

Myotubular Myopathy: Also known as centronuclear myopathy, this disorder is characterized by hypotonia, feeding difficulties and delay of motor milestones. Facial weakness, ptosis and opthalmoplegia may be present. Different forms may be autosomal dominant or autosomal recessive. Another form, X-linked myotubular myopathy, is the most severe and is often fatal. Babies have respiratory difficulties and swallowing problems from birth and often require ventilator support. **

Nadir {NAY-der}: Period of time following chemotherapy treatment when blood counts generally are at their lowest levels and patients are at greatest risk of developing infection and other blood-related side effects. #

National Organization for Rare Disorders (NORD): A federation of voluntary health organizations dedicated to helping people with rare diseases and to assisting the organizations that serve them. Headquarters: P.O. Box 8923, New Fairfield, CT 06812. Toll-free phone: (800) 999-6673. Or call (203) 746-6518. Fax: (203) 746-6481. Home page: http://www.rarediseases.org/   ###

Natural Course: The course of an untreated disease. How the disease will affect a person and how it will progress over time. Different diseases have different courses - the way each disease affects a person and the rate of progression. In addition, the course can be somewhat individual, each person may display a slightly different course for some diseases (neuromuscular diseases are like this).

Natural killer cells (NK): Large granule-filled lymphocytes that take on tumor cells and infected body cells. They are known as 'natural' killer because they attack without first having to recognize specific antigens. NK cell: Naturally occurring, large, granular, lymphocyte-like killer cells that kill various tumour cells; they may play a role in resistance to tumours. Also, they participate in ADCC. They do not exhibit antigenic specificity, and their number does not increase by immunization.

Natural selection: The phenomenon whereby selective pressures in the environment make survival and subsequent reproduction more likely for some individuals and less likely for others, based upon their genetic characteristics. Those who are better equipped to the environment and more likely to survive and reproduce will therefore contribute their genetic material to future generations. This is also referred to as "survival of the fittest."

Nausea {NAW-sea-ah}: The feeling that one might vomit. #

Necrosis {nee-CRO-sis}: Dead tissue. Also: Cell death. Loss of cells, tissues, or parts of a structure or organ due to the progressively degrading actions of certain enzymes, such as the degradation of DNA within the nucleus of dying cells. Necrosis may result from a loss of blood supply (ischemia), infection, excessive exposure to ionizing radiation, certain chemicals, or extreme temperatures.

Negative findings: Results of tests are described as negative if nothing abnormal is found. *

Nemaline Myopathy: Also known as rod body myopathy, this disorder is characterized by diffuse myopathy, facial weakness, a high arched palate and weakness of arm, leg and trunk muscles. It is present at birth or appears in infancy. The severity of the symptoms ranges from benign and non-progressive in some cases, to severe, progressive and fatal in others. **

Neodarwinism: (Also called the "new synthesis" or the "modern synthesis"). The merging of Darwin's idea that organisms and populations show gradual change with Mendel's concepts. Suggests that evolutionary change is the result of random mutations that natural selection acts upon. Emphasis on natual selection, gradualism, and populations as the units of evolutionary change.

Neoplasm {KNEE-oh-plasm}: A new and abnormal formation of tissue: a tumor. or growth. Tumors may be benign or malignant. Benign tumors remain localized as a discrete mass. They may differ appreciably from normal tissue in structure and excessive growth of cells, but are rarely fatal. Benign tumors are usually treated by complete surgical removal. Cells of malignant tumors, i.e., cancers, have characteristics that differ from normal cells in other ways beside cell proliferation. For example, they may be deficient in some specialized functions of the tissues where they originate. Malignant cells are invasive, i.e., they infiltrate surrounding normal tissue; later, malignant cells metastasize, i.e., spread via blood and the lymph system to other sites. *
Also: Neoplasm: A new growth of tissue or cells; a tumor. that is generally malignant. ##

Neoplastic: Relating to the formation of a neoplasm (tumor) or a new, abnormal growth characterized by uncontrolled, progressive multiplication of cells. Neoplasms may be benign or malignant.

Nephro-tomography {NEF-ro to-MOG-ra-fee}: Diagnostic procedure using X-rays in which a three-dimensional view of the kidney can be constructed. #

Nerve: A macroscopic structure of the body, comprising a collection of fibres that conveys impulses between a part of the central nervous system and some other body region. Motor nerves transmit impulses from the brain and spinal cord to the muscles. **

Nerve cells, types of: The central nervous system consists of two major types of cells, neurons and glial cells. Neurons constitute about half the volume of the central nervous system (CNS) and glial cells make up the rest. Glial cells provide support and protection for neurons. They are thus known as the "supporting cells" of the nervous system. The four main functions of glial cells are: to surround neurons and hold them in place, to supply nutrients and oxygen to neurons, to insulate one neuron from another, and to destroy and remove the carcasses of dead neurons (clean up). The three types of CNS supporting cells are Astrocytes, Microglia cells and Oligodendrocytes.
The supporting cells of the peripheral nervous system (PNS) are known as Schwann Cells.
-Astrocytes: {astro-sight} star shaped glial cells that perform a variety of functions in the CNS. Astrocytes provide physical support to neurons and clean up debris within the brain. They also provide neurons with some of the chemicals needed for proper functioning and help control the chemical composition of fluid surrounding neurons. Finally, astrocytes play a role in providing nourishment to neurons.
In order to provide physical support for neurons astrocytes form a matrix that keep neurons in place. In addition, this matrix serves to isolate synapses. This limits the dispersion of transmitter substances released by terminal buttons; thus aiding in the smooth transmission of neural messages.
Astrocytes also perform a process known as phagocytosis. Phagocytosis occurs when an astrocyte contacts a piece of neural debris with its processes (arm of the astrocyte) and then pushes itself against the debris eventually engulfing and digesting it. Astrocytes provide nourishment to neurons by 1) receiving glucose from capillaries 2) breaking the glucose down into lactate (the chemical produced during the first step of glucose metabolism) 3) releasing the lactate into the extra cellular fluid surrounding the neurons. The neurons receive the lactate from the extra cellular fluid and transport it to their mitochondria to use it for energy. In this process astrocytes store a small amount of glycogen, which stays on reserve for times when the metabolic rate of neurons in the area is especially high.
-Microglia {micro-gill-ee-ah} are the smallest of the glial cells. Some act as phagocytes cleaning up CNS debris. Most serve as representatives of the immune system in the brain. Microglia protect the brain from invading microorganisms and are thought to be similar in nature to microphages in the blood system
-Oligodendrocytes {All-ee-gah-dendro-sight}: The principle function of oligodendrocytes is to provide support to axons and to produce the Myelin {MY-ah-lynn} sheath, which insulates axons. Myelin is 80% lipid and 20% protein and allows for the efficient conduction of action potentials down the axon. Oligodendrocytes unlike Schwann cells of the PNS, form segments of myelin sheaths of numerous neurons at once. The processes of a given oligodendrocyte wrap themselves around portions of the surrounding axons. As each process wraps itself around, it forms layers of myelin. Each process thus becomes a segment of the axon's myelin sheath.
- Schwann cells: the supporting cells of the PNS. Like oligodendrocytes, Schwann cells wrap themselves around nerve axons, however, a single Schwann cell makes up a single segment of an axon's myelin sheath. Oligodendrocytes on the other hand, wrap themselves around numerous axons at once.
In addition to creating the myelin sheaths of PNS axons, Schwann cells also aid in cleaning up PNS debris and guide the regrowth of PNS axons. To do this Schwann cells arrange themselves in a series of cylinders that serves as a guide for sprouts of regenerating axons. If one of these sprouts encounters a cylinder the sprout will grow through the tube at the rate of 3-4 mm per day. Nonproductive sprouts simply wither away.
Axons that have myelin sheaths are called "myelinated" (or medullated) nerve fibres, while those that lack these sheaths are "unmyelinated" nerve fibres. Myelin serves as an insulator by preventing chemicals from leaking through the membrane. Considering this, it might seem that the myelin sheath would prevent the conduction of a nerve impulse altogether, and this would be true if the sheath were continuous. It is, however, interrupted by some constrictions called "nodes of Ranier," which occur between adjoining Schwann cells. At these nodes, the fibre membrane is especially permeable to sodium and potassium ions. Two major neural disorders, multiple sclerosis and Guillain-Barre syndrome, are associated with abnormalities of myelination. From: http://members.tripod.com/blustein/index.htm *

Nerve Conduction Studies (NCS): In these tests, a tiny electrical current is sent down a nerve, for example, from the wrist to the fingertip. Readings measure the ability of the nerve to carry the signal. One measure looks at the speed of the impulse - nerve conduction velocities (NCV). Conduction speed is influenced by a coating around axons, called myelin. Myelin insulates each axon and normally forces action potentials to "jump" quickly from one end of the axon to the other. If the myelin breaks down (as in Charcot-Marie-Tooth 1), the action potential travels more slowly.
The second measure is of the strength of the action potential in the nerve, which is proportional to the number of axons that contribute to it. If axons degenerate (as in amyotrophic lateral sclerosis) or become clogged with debris (as in Charcot-Marie-Tooth 2), the action potential becomes smaller. The test is painless, the person feels a minor "twitch" in the muscle when the signal is sent. *

Nerve conduction velocity (NCV) test: A diagnostic study during which both sensory and motor nerves are repeatedly stimulated in order to measure the speed at which nerve impulses are conducted. Unusually slow conduction velocities suggest damage to nerve fibers (e.g., loss of the protective covering surrounding certain nerve fibers [demyelination] or other disease process).

Nervous System:
AUTONOMIC NERVOUS SYSTEM (ANS): Division of the body's nervous system that regulates viscera (stomach and intestines) and smooth muscles: heart and circulatory system, kidneys, lungs, bladder, bowel, pupils, etc. The ANS is most important in two situations: those emergency situations that cause stress and require us to "fight" or take "flight" (run away) and those non-emergency situations that allow us to "rest" and "digest". In most situations, we are unaware of the workings of the ANS since it functions in an involuntary, reflexive manner. For example, we do not notice when blood vessels change size. There are two branches of the ANS (see SNS and PNS below) that usually function in balance with each other: when one is activated, the other is suppressed.
SYMPATHETIC NERVOUS SYSTEM (SNS): Division of the ANS, primarily aroused in states of stress, both positive and negative stress. Signs of SNS arousal include increased heart rate and respiration, cold and pale skin, dilated pupils, raised blood pressure.
PARASYMPATHETIC NERVOUS SYSTEM (PNS): Division of the ANS, primarily aroused in states of rest and relaxation. Signs of PNS arousal include decreased heart rate and respiration, warm and flushed skin, normally reactive pupils, lowered blood pressure. *

Neuralgia {NER-ral-gee-ah}: Severe sharp pain occurring along the course of a nerve. ***

Neuritis {NER-ite-tus}: Inflammation of a nerve, usually associated with a degenerative process. ***

Neuroacanthocytosis: Also known as choreoacanthocytosis, this is a genetic disorder that most often becomes apparent between the ages of 25 to 45 years. The disorder is usually transmitted as an autosomal recessive trait. Associated symptoms may include generalized chorea; dystonia affecting muscles of the mouth and tongue; potentially mutilating lip- and tongue-biting; and sudden, involuntary, repetitive muscle movements (motor tics) and vocalizations (vocal tics). Patients may also develop personality changes and cognitive decline, seizures, parkinsonism, atrophy of muscle tissue (amyotrophy), and difficulties speaking and swallowing. Neuroimaging studies may reveal atrophy of certain regions of the basal ganglia (e.g., caudate nuclei and putamen [striatum]). The disorder may be confirmed by blood tests revealing the presence of abnormal circulating red blood cells that have spur-like or thorny projections (acanthocytosis).

Neuroanatomy: The anatomy of the brain, spinal cord and peripheral nervous system. *

Neuroblastoma: A malignant hemorrhagic tumor. composed principally of cells resembling neuroblasts that give rise to cells of the sympathetic system, esp. adrenal medulla. This condition occurs chiefly in infants and children. ***

Neurochemical: Referring to the chemistry or biochemical processes of the nervous system, such as activities involving naturally produced chemicals (i.e., neurotransmitters) that enable nerve cells (neurons) to communicate.

Neurodegenerative: Marked by or pertaining to neurologic degeneration; deterioration of the structure or function of tissue within the nervous system.Neurofibrillary tangles: Intraneuronal structures formed from paired helical filaments, which are composed of abnormally phosphorylated tau proteins, wound together in a double helix. ***

Neurofibromatosis: One of the most common single gene conditions affecting the human nervous system; in most cases, "cafe au lait" spots, are the only symptom; inherited as an autosomal dominant trait, with 50% being new mutations.

Neurogenenic culture: The growth of nervous tissue in the test tube for study. *

Neurogenesis: The production of new nervous tissue. Active production of new neurons, astrocytes, glia, and other neural lineages from undifferentiated neural progenitor or stem cells. A rather inactive process in most areas of the adult brain.

Neuroimaging: The production of detail, contrast, and clearness in images of the brain and spinal cord (central nervous system) through the use of computed tomography (CT) scanning, magnetic resonance imaging (MRI), positron emission tomography (PET) scanning, or other imaging techniques to assist in diagnosis, treatment decisions, or research.

Neurologist {new-ROL-o-jist}: Doctor who specializes in the diagnosis and treatment of disorders of the nervous system. #

Neurology: medical specialty concerned with the diagnosis and treatment of functional or organic disorders of the nervous system (i.e., the brain, spinal cord, and nerves). Neurological disorders have always been among the most subtle and baffling of human illnesses, and despite continuing advances in their field, neurologists remained unable to effectively treat many disorders of the nervous system. For example, Multiple sclerosis (MS) is a progressive disease of the central nervous system in which scattered patches of myelin in the brain and spinal cord are destroyed. *

Neuromuscular junction: The point of contact between nerve and muscle is the neuromuscular junction, where the chemical substance acetylcholine is secreted, initiating the changes that cause the muscle to contract. *

Neuromuscular: Anything that pertains to the nerves and muscles. **

Neuromuscular disorders: Conditions that affect components of a motor unit (motor neuron cells of the spinal cord, nerve, neuromuscular junction, and muscle fibres), sensory and autonomic nerves or their supportive structures are included in the broad category of neuromuscular disorders. Also referred to as neuromuscular diseases (NMDs). %
To function, muscles need proper signals from the brain and if there is a problem either in the brain or in the nerves between the brain and the muscle, then there can be problems. These disorders are also called neuropathic disorders. Amyotrophic lateral sclerosis (ALS) and poliomyelitis are examples. In these cases, the muscle itself is usually not diseased. In some cases, the nerves are OK but there is a problem of some sort right in the muscles. Diseases and disorders that result from direct abnormalities of the muscles are called primary muscle diseases. These problems fall into several categories. To work, muscles need protein. This protein is made in the body according to genetic instructions. To work properly the protein must be the right kind, the right size and the right shape. If the protein is somehow defective (a mistake in the instructions) then the muscles will slowly fail. This is what we see in many of the muscular dystrophies. Note: Sometimes all muscle problems are lumped under the heading Neuromuscular disorders.
There are various types of muscle diseases (From mdausa.org):
-Duchenne Muscular Dystrophy (DMD)(Also known as Pseudohypertrophic)
-Becker Muscular Dystrophy (BMD)
-Emery-Dreifuss Muscular Dystrophy (EDMD)
-Limb-Girdle Muscular Dystrophy (LGMD)
-Facioscapulohumeral Muscular Dystrophy (FSH or FSHD)(Also known as Landouzy-Dejerine)
-Myotonic Dystrophy (DM)(Also known as Steinert's Disease)
-Oculopharyngeal Muscular Dystrophy (OPMD)
-Distal Muscular Dystrophy (DD) (Miyoshi myopathy (MM))
-Congenital Muscular Dystrophy (CMD)
-Amyotrophic Lateral Sclerosis (ALS)(Also known as Lou Gehrig's Disease)
-Infantile Progressive Spinal Muscular Atrophy (SMA, SMA1 or WH)(Also known as SMA Type 1, Werdnig-Hoffman)
-Intermediate Spinal Muscular Atrophy (SMA or SMA2)(Also known as SMA Type 2)
-Juvenile Spinal Muscular Atrophy (SMA, SMA3 or KW)(Also known as SMA Type 3, Kugelberg-Welander)
-Spinal Bulbar Muscular Atrophy (SBMA)(Also known as Kennedy's Disease and X-linked SBMA)
-Adult Spinal Muscular Atrophy (SMA)
-Dermatomyositis (PM/DM)
-Polymyositis (PM/DM)
-Inclusion Body Myositis (IBM)
-Myasthenia Gravis (MG)
-Lambert-Eaton Syndrome (LES)
-Congenital Myasthenic Syndrome (CMS)
-Hyperthyroid Myopathy (HYPTM)
-Hypothyroid Myopathy (HYPOTM)
DISEASES OF PERIPHERAL NERVE: -Charcot-Marie-Tooth Disease (CMT)(Also known as Hereditary Motor and Sensory Neuropathy (HMSN) or Peroneal Muscular Atrophy (PMA))
-Friedreich's Ataxia (FA)
-Dejerine-Sottas Disease (DS)(Also known as CMT Type 3 or Progressive Hypertrophic Interstitial Neuropathy)
-Myotonia Congenita (MC)(Two forms: Thomsen's and Becker's Disease)
-Paramyotonia Congenita (PC)
-Central Core Disease (CCD)
-Nemaline Myopathy (NM)
-Myotubular Myopathy (MTM or MM)
-Periodic Paralysis (PP)(Two forms: Hypokalemic and Hyperkalemic)
-Phosphorylase Deficiency (MPD or PYGM)(Also known as McArdle's Disease)
-Acid Maltase Deficiency (AMD)(Also known as Pompe's Disease)
-Phosphofructokinase Deficiency (PFKM)(Also known as Tarui's Disease)
-Debrancher Enzyme Deficiency (DBD)(Also known as Cori's or Forbes' Disease)
-Mitochondrial Myopathy (MITO)
-Carnitine Deficiency (CD)
-Carnitine Palmityl Transferase Deficiency (CPT)
-Phosphoglycerate Kinase Deficiency (PGK)
-Phosphoglycerate Mutase Deficiency (PGAM or PGAMM)
-Lactate Dehydrogenase Deficiency (LDHA)
-Myoadenylate Deaminase Deficiency (MAD) *

Neuron: A nerve cell. The structural and functional unit of the nervous system. Neuron: An individual nerve cell.

Neuronal: Pertaining to a neuron or neurons.

Neuropathy {neur-ROP-pathy}: From the Greek words neuron, meaning nerve or sinew, and pathos, disease or suffering. Definition: any disease of the nervous system. Amyotrophic lateral sclerosis and spinal muscular atrophy, in which loss of nerve cells prevents muscles from working, are neuropathies, as are diseases in which nerve fibers malfunction, such as Charcot-Marie-Tooth and Dejerine-Sottas disease.

Neuroprotective effect: Having the ability to prevent or slow the death of neurons. The drug selegiline (Eldepryl®) may have a neuroprotective effect, possibly by preventing formation of free radicals.

Neuroreceptor: Specific sites on the surface of a nerve cell to which certain special substances (neurotransmitters) bind, initiating the conduction of impulses (or signals) to other nerve cells.

Neurosurgeon {NER-ro-SER-jun}: Doctor who specializes in surgery on the brain and other parts of the nervous system. #

Neurotransmitter: any of a group of chemical agents released by neurons (nerve cells) to stimulate neighbouring neurons, thus allowing impulses ("signals") to be passed from one cell to the next throughout the nervous system. Although a large number of chemical substances are believed to act as neurotransmitters, only a few have been identified. Among those known are acetylcholine, norepinephrine (noradrenalin), dopamine, and serotonin. Some chemical agents, such as acetylcholine, excite (activate) neurons, while others act as inhibiting substances (GABA, dopamine, serotonin). *

Neutropenia {NEW-tro-peen-ee-ah}: A decreased number of neutrophils, a type of white blood cell. ##
Also: Neutropenia: Less than the normal number of neutrophils, a type of white blood cell, which help to defend against bacterial infections. #

Neutrophil: White blood cell that is abundant and important in phagocytosis. Also called polymorphonuclear leukocytes, contain cytoplasmic granules that contain enzymes used to destroy and degrade bacteria.

Newborn screening (for genetic disorders): Examining blood samples from a newborn infant to detect disease-related abnormalities or deficiencies in gene products. %

Niche: Cellular microenvironment providing support and stimuli necessary to sustain self-renewal.

Night Splints: a static type of splint or orthosis worn at night to help maintain a stretch at a particular joint. *

NIH: National Institutes of Health (United States)

Nitrosoureas {ny-TRO-so-yur-EE-ahz}: Group of anticancer drugs that can cross the blood-brain barrier. Carmustine (BCNU): and lomustine (CCNU): are nitrosoureas. #

NT: Abbreviation for nucleotide.

Nodular {NOD-u-lar}: Forming nodules. #

Nomenclature: System of names used in a particular scientific discipline to consistently and methodically designate certain classifications and avoid confusion or ambiguity.

Noncoding RNA: Molecules of RNA produced from DNA that are not used to produce proteins.

Non-ergotoline medication: A dopamine agonist medication that has action similar to that of pergolide (Permax®) and bromocriptine (Parlodel®) but is not derived from an ergot. Examples of nonergotoline medications that are used to treat some neurologic movement disorders include pramipexole (Mirapex®) and ropinirole (Requip-.)

Non-Hodgkin's lymphoma: A cancer of the lymphatic system. Non-Hodgkin's lymphoma is related to Hodgkin's disease but is made up of different cell types. See Lymphoma. ##

Non-kinesigenic: Not induced by movement; provoked by factors other than sudden motions. This term often refers to abrupt episodes of involuntary movement that occur spontaneously or may be worsened by fatigue, stress, alcohol or caffeine intake, heat or cold, fasting, or other factors.

Non-sarcolemmal Muscular Dystrophies: The muscular dystrophies are characterized by progressive muscle weakness and wasting. Pathologically the hallmarks are muscle fibre degeneration and fibrosis. Several recessive forms of muscular dystrophy are caused by defects in proteins localized to the sarcolemma. However, it is now apparent that others are due to defects in a wide range of proteins including those which are either nuclear-related (Emery-Dreifuss type muscular dystrophies, oculopharyngeal muscular dystrophy), enzymatic (limb-girdle muscular dystrophy 2A, myotonic dystrophy) or sarcomeric (limb-girdle muscular dystrophies 1A and 2G). Although the clinical and molecular basis of these disorders is heterogeneous, all display myopathic morphological features. These include variation in fibre size, an increase in internal nuclei, and some myofibrillar distortion. Degeneration and fibrosis occur, but usually not to the same extent as in muscular dystrophies associated with sarcolemmal protein defects. This review outlines the genetic basis of these non-sarcolemmal forms of dystrophy and discusses current ideas on their pathogenesis. Susan C. Brown, Francesco Muntoni and Caroline A. Sewry, Brain Pathology 11: 193-205 (2001)

Non-synonymous SNPs: An SNP that alters the DNA sequence in a coding region such that the aminoacid coding is changed. The new code specifies an alternative aminoacid or changes the code for an aminoacid to that for a stop translation signal or vice versa. Synonymous SNPs alter the DNA sequence but do not change the protein coding sequence as interpreted at translation, because of redundancy in the genetic code: several different codes can specify the same aminoacid. Nonsynonymous SNPs can also be called coding SNPs.

Nonsense mutation: Of or relating to a mutation in a structural gene that changes a nucleotide triplet into a stop codon, thus prematurely terminating the polypeptide chain during protein synthesis. *

Noradrenaline (norepinephrine): A vasoconstrictor whose release triggers action within the sympathetic nervous system, the part of the nervous system that regulates certain involuntary responses during times of stress. Noradrenaline serves as a neurotransmitter that stimulates receptors (alpha- and beta-adrenergic receptors) at effector organs supplied or innervated by certain sympathetic nerve fibers (postganglionic adrenergic fibers). In addition to its production by neurons, noradrenaline is also secreted by the inner region of the adrenal glands (adrenal medulla). The release of noradrenaline serves to deepen breathing, raise blood pressure, and increase the heart rate. It also plays a role in regulating mood.

Northern analysis: A technique for transferring electrophoretically resolved RNA segments from an agarose gel to a nitrocellulose filter paper sheet via capillary action.

NREM sleep: Non-REM (nonrapid eye movement) sleep, which is the normal period of dreamless, lighter sleep as compared to the deeper REM sleep. NREM sleep accounts for the major portion of sleep.

NSAIDs: non-steroidal anti-inflammatory agents: The major effect of these agents is to reduce acute inflammation thereby decreasing pain and improving function. All of these drugs also have mild to moderate analgesic properties independent of their anti-inflammatory effect. All NSAIDs work by blocking prostaglandins, hormone-like substances that contribute to pain, inflammation, fever and muscle cramps.
Aspirin is the oldest drug of the non-steroidal class, and it remains an economical, effective choice. However, because of its higher rate of GI toxicity, its narrow window between toxic and anti-inflammatory serum levels and the inconvenience of multiple daily doses, aspirins use as the initial choice of drug therapy has largely been replaced by the newer NSAIDs. There are now a large number of NSAIDs from which to choose, and at full dosage all are potentially equally effective. Likewise, the toxicities of the currently available NSAIDs are similar. However, there is a great deal of variation in tolerance and response to a particular NSAID. Long acting NSAIDs that allow daily or twice daily dosing will improve compliance and help with morning stiffness.
Common NSAIDs include: aspirin, ibuprofen (Advil, Motrin, Nuprin, Medipren), naproxen (Naprosyn, Aleve) and indomethacin (Indocin). NSAIDs also include a new class of prescriptions medicines known as COX-2 inhibitors like Celebrex®.
Mechanism: NSAIDs inhibit prostaglandin synthesis by blocking cyclooxygenase enzymes, COX-1 and COX-2.
Cyclooxygenase-1 (COX-1) is an enzyme which is normally present in a variety of areas of the body, including sites of inflammation and the stomach. The COX-1 enzyme of the stomach produces certain chemical messengers (called prostaglandins) that ensure the natural mucus lining which protects the inner stomach. Common anti-inflammatory drugs like aspirin block the function of the COX-1 enzyme along with another enzyme, COX-2 (see below). When the COX-1 enzyme is blocked, inflammation is reduced, but the protective mucus lining of the stomach is also reduced, which can cause stomach upset, ulceration, and bleeding from the stomach and intestines.
Another enzyme, cyclooxygenase-2 (COX-2), also produces these chemical messenger molecules, but the COX-2 enzyme is located specifically in areas of the body that are responsible for inflammation and not in the stomach. When the COX-2 enzyme is blocked, inflammation is reduced. Since the COX-2 enzyme does not play a role in the normal function of the stomach or intestinal tract, medications which selectively block COX-2 do not present the same risk of injuring the stomach or intestines. Newly developed drugs that selectively block the COX-2 enzyme are called COX-2 inhibitors. The COX-2 selective inhibitors selectively block prostaglandins generated via COX-2. Prostaglandins are important mediators of both pain and inflammation. Drugs include: naproxen (Anaprox, Naprelan, Naprosyn, Aleve) ibuprofen (Motrin), indomethacin (Indocin), nabumetone (Relafen), celecoxib (Celebrex), valdexocib (Bextra), rofecoxib (Vioxx), and several others. The COX-2 inhibitors represent a new class of drugs that do not affect COX-1, but selectively block only COX-2. This selective action provides the benefits of reducing inflammation without irritating the stomach. These drugs pose a advantage in comparison to previous anti- inflammatory drugs because their mechanism of action carries nowhere near the risk of stomach ulceration and bleeding. The COX-2 inhibitor is now on the market in the form of celecoxib (Celebrex). It is widely expected that COX-2 inhibitors will be of great value to people with arthritis and variety of pain conditions.
Blocking these enzymes impedes the production of the prostaglandins that cause the pain and swelling of arthritis inflammation. The common anti-inflammatory drugs (like aspirin, ibuprofen, and naproxen) all act by blocking the action of both the COX-1 and COX-2 enzymes.

Nuclear scans: Pictures of the inside of the body taken after slightly radioactive material is swallowed or injected into the bloodstream. #

Nucleic acid {NEW-clay-ick}: Nucleic acids, Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA), serve as storage units for our hereditary information.

Nucleoside {NEW-clee-oh-side}: - sugar - base combination. Any of various compounds consisting of a sugar, usually ribose or deoxyribose, and a purine or pyrimidine base. Ribose is a sugar molecule with 5 oxygen atoms and 5 carbon atoms. Deoxyribose is a sugar with 4 oxygen atoms and 5 carbon atoms (de means less than). *

Nucleotide {NEW-clee-oh-tide}: Phosphate - sugar - base. Each nucleotide consists of three parts - a phosphate group, a sugar (ribose or deoxyribose), and a nitrogen containing base attached to the sugar. The sugar acts like a bridge between the phosphate to the base. A chain can be formed when the phosphate group links one - sugar - base combination to the next one. These chains form either DNA or RNA. *

Nucleotide bases: There are two structures involved, each with two kinds of bases: pyrimidine bases, consisting of cytosine and thymine and a purine structure consisting of adenine and guanine. Another pyrimidine base was later discovered and called uracil. %
The bases were given one letter abbreviations: A is for adenine; G is for guanine; C is for cytosine; T is for thymine; and U is for uracil.
In DNA, the bases are: adenine; guanine; cytosine; and thymine.
In RNA, the bases are: adenine; guanine; cytosine; and uracil.
Due to their chemical properties, certain bases will always pair up together: Adenine (A) pairs with thymine (T); Cytosine pairs with guanine (G). This feature is called complementary pairing and is an important feature in the DNA and RNA strands. If we know that one strand is ATAGGC, then the other strand must be TATCCG. If the two strands separate, each will serve as a template for the other. This is an important feature because it allows high accuracy in the duplication of the DNAs message.

Nucleus {NEW-clee-ous}: At the heart of every cell is its control center, called the nucleus. Inside the nucleus are forty-six threadlike structures known as chromosomes, and each one of these structures contains thousands of genes. Chromosomes and genes are made of deoxyribonucleic acid, or DNA, which transfers the heredity material from generation to generation. The DNA of which each gene is composed contains a genetic instruction for manufacturing one of the many proteins that make up the human body and keep it running. %

Null cells: An early population of lymphocytes bearing neither T-cell nor B-cell differentiation antigens.

Nystagmoid {nah-STAG-moid} jerks: Jerking movements that sometimes occur in normal people when tired and when there is an exaggerated movement of the eyes. They do not imply disease. *

Nystagmus {nah-STAG-mus}: Constant involuntary, cyclical movement of the eyeball in any direction***
Also: rapid involuntary movements of the eyes that may be from side to side, up and down, or rotatory. Nystagmus may be congenital and associated with poor sight; it also occurs in disorders of the part of the brain responsible for eye movements and their coordination and in disorders of the organ of balance in the ear or the associated parts of the brain. *

Obsessive-compulsive behaviors: The performance of certain repetitive actions or rituals in response to persistent thoughts or impulses. For example, obsessions may consist of repeated doubts, such as wondering whether the stove was left on; a need for routine; or impulses to perform certain inappropriate actions. Compulsions frequently include repeated checking and rechecking, such as ensuring that the stove is indeed off; touching particular objects in a specific pattern or sequence; repetitive hand washing; or other repetitious behavior performed in an attempt to prevent or relieve anxiety, distress, or a feeling of dread.

Obstructive sleep apnea: A sleep disorder characterized by episodes of temporary cessation of breathing due to obstruction of the airway.

Occipital Lobes (brain): These lobes contain regions that contribute to our visual field or how our eyes see the world around us. They help us see light and objects and allow us to recognize and identify them. This region is called the visual cortex. The occipital lobes are located near the rear of the brain. *

Occupational therapy: use of self-care and work and play activities to promote and maintain health, prevent disability, increase independent function, and enhance development. This form of therapy evolved from the recognition that work helps to restore the mentally and physically ill, particularly after the acute phase of illness has passed. Because any form of therapy must be consistent with others, any treatment program designed by an occupational therapist is coordinated with the work of doctors, nurses, and other related professional personnel in setting up a specific program for a patient. *
Also: A form of therapy where people with neuromuscular disorders can learn how to compensate for physical limitations and adapt to daily living needs. An occupational therapist will assess a client for such things as mobility aids, seating, a computer or aids to help functioning on a day to day basis. **

OCN (Oncology certified nurse): A registered nurse who has met the requirements and successfully completed a certification examination in oncology. ##

Oculomotor: Relating to or causing movement of the eyes.

Oculopharyngeal Muscular Dystrophy: An autosomal dominant form of muscular dystrophy that is characterized mainly by ptosis and dysphagia. It usually occurs later in life (40 to 70 years). Progression is slow, but weakness of throat muscles may become a serious problem. In addition, most people have some degree of facial weakness and may experience weakness and atrophy in the muscles of the hips and shoulders. In Canada, it is most common in Quebec. **

Oligodendrocyte {ALL-lee-go-den-dro-sight}: One type of glia cell (nervous system), responsible for producing the myelin sheaths of the neurones of the central nervous system and therefore equivalent to the Schwann cells of the peripheral nerves. Myelin forming cells of the CNS that produce, maintain, and repair myelin sheaths surrounding axons. The loss or injury of these cells, produces multiple demyelinated areas on many different axons.

Oligodendroglioma {All-lee-go-den-dro-glee-OH-ma}: A type of brain tumor. #

Oligonucleotide: A short string of nucleotides; a single-stranded segment of DNA, often used in research as a probe to find a matching sequence of DNA or RNA. ###

Oncogenes {on-KO-genes}: Genes that normally play a role in the growth of cells but, when over expressed or mutated, can foster the growth of cancer. %
Also: Oncogene: A gene that is capable of causing the transformation of normal cells into cancer cells. ###

Oncologist {on-KOL-o-jist}: A doctor who specializes in treating cancer. %

Oncology clinical nurse specialist: A registered nurse with a master's degree who specializes in the education and treatment of cancer patients. ##

Oncology {on-KOL-o-gee}: The study and treatment of cancer. ##

Oophorectomy {oo-for-REC-to-mee}: Removal of the ovaries. #

Open Reading frame (ORF): The entire length of a DNA molecule that starts with a start codon and ends with a stop codon. Detection of an open reading frame in DNA implies the presence of a gene that codes for a protein.

Operator: Site of repressor binding on a DNA molecule; part of an operon.

Operon: Definition 1: A controllable unit of transcription consisting of a number of structural genes transcribed together. Contains at least two distinct regions: the operator and the promoter code. The first described example was the lac operon. Definition 2: The transcription of the operon product is a polycistronic mRNA.

Ophthalmoplegic Muscular Dystrophy: One of the muscular dystrophies, usually becoming evident in adulthood. Extraocular muscles are involved first, with muscles involved in swallowing being affected later on. It is typically inherited as an autosomal dominant disorder. **

Ophthalmoscope {off-THAL-mo-skope}: A lighted instrument used to examine the inside of the eye, including the retina and the optic nerve. #

Opiate: Any preparation or derivative of opium.

Opioids: Means "like or similar to opium" and refers to medications with opium-like effects. This term is used to describe any synthetic drug that possesses the characteristic properties of opiate narcotics but is not derived from opium.

Opsonin: A substance, usually antibody or complement component, which coats a particle such as a bacterium and enhances phagocytosis by phagocytic cells.

Opsonization: Literally means "preparation for eating". The coating of a bacterium with antibody and/or complement that leads to enhanced phagocytosis of the bacterium by phagocytic cells.

Optic nerve: The nerve that carries messages from the retina to the brain. #

Orchiectomy {or-key-EK-toe-me}: surgical removal of testicles. #

Organelles: Parts of a cell. Cell organelles are a bit like the organs in a human body. They all have their own role to play and they have a distinctive shape and size. Many organelles are present in all eukaryotic cells, although the number that a specific cell contains depends on the function of that cell. *

Organic: (1) Referring to or arising from an organ or organs. (2) Regarding substances that arise or are derived from living organisms. (3) Pertaining to chemicals that contain carbon.

Orthosis {OR-tho-sis}: a medical device usually constructed of a metal, leather or plastic-like material that is used at a joint or joints for one of the following reasons: support, provide a stretch, prevent injury, or stabilize a proximal joint to allow for distal joint mobility. *

Orthostatic hypotension: A sudden decrease in blood pressure that occurs when the affected individual sits up or stands. In some cases, it may occur as a side effect of certain medications.

Orthotic {OR-thought-tic}: commonly used to refer to a plastic or leather insert used in the shoe. *

Orthotist: the professional who measures for and manufactures orthoses. *

Osteogenesis imperfecta: A condition also known as brittle bone disease; characterized by a triangular shaped face with yellowish brown teeth, short stature and stunted growth, scoliosis, high pitched voice, excessive sweating and loose joints.

Osteosarcoma {OSS-tee-o-sar-KO-ma}: Cancer of the bone that is most common in children. Also called osteogenic sarcoma. #

Ostomy {OS-to-mee}: Operation to create an opening from an area inside the body to the outside. #

Ovaries {O-var-eez}: The pair of female reproductive organs that produces eggs (ova): and hormones. They are located in the lower abdomen, one on each side of the uterus. #

Oxidative Stress: see Appendix (Quest).

Oxidative stress: An accumulation of free radicals in a cell is known as oxidative stress. Oxidative stress is being increasingly implicated in human disease processes, particularly those involving an inflammatory component. Oxidative stress is also associated with aging, older cells display higher levels of oxidative stress, perhaps due to the breakdown of protective cell mechanisms that normally remove damaged radical elements. Also see free radical. *


A - C      D - F      G - K      L - O     P - S     T - Z.

PAGE : polyacrylamide gel electrophoresis, a research technique used to separate molecules. *

Paired helical filaments (PHFs): Paired helical filaments accumulate in the brains of subjects affected with Alzheimer's disease (AD) and certain other neurodegenerative disorders, including corticobasal degeneration (CBD). In AD, neurofibrillary tangles contain paired helical filaments (PHFs), which appear to be formed primarily from abnormal aggregations of tau proteins. Hyperphosphorylated tau, is also a component of muscle cytoplasmic twisted tubulofilaments (TTFs) (which are ultrastructurally similar to PHFs), in spontaneous inclusion body myositis.

Palliative therapy {PAL-ee-eh-tiv}: A treatment that may relieve symptoms without curing the disease. # Treatment aimed at the relief of pain and symptoms of disease but not intended to cure the disease. ##

Palpation {pal-PAY-shun}: A simple technique in which a doctor presses on the surface of the body to feel the organs or tissues underneath. #

Pancreas {pan-kree-us}: A gland located in the abdomen. It makes pancreatic juices and produces several hormones including insulin. #

Pancreatectomy {pan-kree-a-TEK-to-mee}: Surgery to remove the pancreas. In a total pancreatectomy, the duodenum, common bile duct, gallbladder, spleen, and nearby lymph nodes are also removed. #

Pap test, Pap (Papanicolaou) smear: Microscopic examination of cells collected from the cervix. #
Also: Pap test: Microscopic examination of cells collected from the cervix. It is used to detect changes that may be cancer or may lead to cancer, and it can show non-cancerous conditions, such as infection or inflammation. Also called Pap smear. %

Para- : A prefix meaning beside, the parathyroid gland is beside the thyroid gland.

Paracentesis {PARA-cen-tea-sis}: Removing fluid from the abdomen using local anesthesia and needle and syringe. ##

Paramyotonia Congenita: A form of periodic paralysis that is quite distinctive. It is characterized only by myotonia, without any attacks of paralysis. The myotonia is worse after repeated use or exercise and is exacerbated by cold. It follows an autosomal form of inheritance and onset of symptoms usually occurs in adulthood. **

Paraparesis {para-FAR-ee-sis}: Partial paralysis affecting the lower limbs. ***

Paraparetic: Relating to paraparesis. A person with paraparesis. ***

Paraproteinemias: A group of related diseases characterized by an unbalanced or disproportionate proliferation of immunoglobulin-producing cells, usually from a single clone. These cells frequently secrete a structurally homogeneous immunoglobulin (M-component) and/or an abnormal immunoglobulin. Amyloidosis Multiple Myeloma, Cryoglobulinemia, POEMS Syndrome.

Parasite: a plant or animal that lives, grows and feeds on or within another living organism.

Parasympathetic nervous system: Part of the nervous system that, together with the sympathetic nervous system, forms the autonomic nervous system (ANS). The ANS controls the functioning of involuntary structures, including the heart, glands, and smooth muscle. The parasympathetic nervous system regulates nerve transmissions to certain effector organs under normal conditions, as opposed to times of stress. It serves to "steady" involuntary activities and conserve or restore energy. Parasympathetic responses may include slowing of the heart and breathing rates, contraction of the pupils, an increase in glandular activity, and an acceleration in the rate of peristalsis.

Parathyroid glands: Two pairs of endocrine glands located in the neck at the back of the thyroid gland. The parathyroid glands produce parathyroid hormone, which increases blood calcium levels by causing bones to release calcium into the blood, the kidneys to conserve calcium, and the intestines to increase calcium absorption from food. When blood calcium levels are high, the parathyroid glands reduce their production of parathyroid hormone, essentially reversing the process.

Paratope: An antibody combining site that is complementary to an epitope.

Parenteral {Parent-TER-ill}: Inoculation into the body (not taken by mouth) *

Paresthesias: Abnormal sensations occurring spontaneously or in response to stimulation. Paresthesias may include prickling, tingling, burning, or tickling feelings; numbness; "pins and needles"; or cramp-like sensations. Various neurologic movement disorders may be characterized by paresthesias, including restless legs syndrome (RLS), paroxysmal kinesigenic dyskinesia (PKD), and paroxysmal non-kinesigenic dyskinesia (PNKD).

Parietal: Pertaining to the walls of a cavity.

Parietal {PER-rye-a-till} Lobes (brain): The parietal lobes interpret sensory signals received from other areas of the brain such as our vision, hearing, motor, sensory and memory areas. Together, memory and the new information that is received give meaning to objects. A furry object touching your skin, that purrs and appears to be your cat, will have a different meaning than a furry object that barks and you see to be a dog. *

Parkinson's disease (PD): A slowly progressive degenerative disorder of the central nervous system characterized by slowness or poverty of movement (bradykinesia), rigidity, postural instability, and tremor primarily while at rest. Additional characteristic findings include a shuffling, unbalanced manner of walking; forward bending or flexion of the trunk; a fixed or "mask-like" facial expression; weakness of the voice; abnormally small, cramped handwriting (micrographia); depression; or other symptoms and findings. Such abnormalities are thought to result from progressive loss of nerve cells within a certain region of the substantia nigra of the brain and the associated depletion of the neurotransmitter dopamine.

Parkinsonism: A constellation of the following symptoms: tremor, rigidity, bradykinesia (slow movements), and loss of postural reflexes. Although classically seen in Parkinson's disease, parkinsonism may have other causes. In the elderly, parkinsonism may be caused by dopamine-blocking drugs, multiple system atrophy, striatonigral degeneration, Shy-Drager syndrome, cortico basal degeneration, diffuse Lewy body disease, and Alzheimer's disease with parkinsonism. In younger people, parkinsonism may be caused by juvenile-onset dystonia/parkinsonism, Westphal variant of Huntington's disease, Wilson's disease, L-dopa-responsive dystonia, Hallervorden-Spatz disease, and progressive pallidal degeneration.

Paroxysm {PARROT-cism}: A sudden, periodic attack or recurrence of symptoms of a disease. ***

Paroxysmal: {PARROT-cismal}Pertaining to or occurring in paroxysms or sudden, recurrent episodes. The term paroxysms often describes transient episodes of abnormal involuntary movements (e.g., chorea, athetosis, dystonia, and/or ballismus) or ataxia, which is characterized by an impaired ability to coordinate voluntary movements.

Paroxysmal movement disorders: Certain neurologic movement disorders characterized by abrupt, transient episodes of abnormal involuntary movement, such as chorea, athetosis, dystonia, and/or ballismus (i.e., the paroxysmal dyskinesias) or impaired coordination of voluntary actions and other associated findings (i.e., paroxysmal ataxias). Depending upon the specific disorder present, episodes may be precipitated or worsened by different factors. As examples, in those with paroxysmal kinesigenic dyskinesia (PKD), episodes may be triggered by sudden voluntary movements. In non-kinesigenic dyskinesia (PNKD), episodes occur spontaneously and may be worsened by caffeine or alcohol consumption, stress, fatigue, or other factors. In patients with paroxysmal kinesigenic ataxias, episodes may be triggered by sudden voluntary movements or postural changes. These disorders may be familial, appear to occur randomly for unknown reasons (sporadically), or occur secondary to other underlying conditions or disorders (symptomatic).

Parthenogenesis: The development of an individual from an egg without fertilization.

Passive immunization: Immunization by the administration of preformed antibody into a nonimmune individual.

Pathogen: anything (usually an organism) that causes a disease. *

Pathogenesis: The development of a disease.

Pathogenic {PATH-oh-genic}: anything that causes pathology (disease).

Pathogenic cascade: the idea that an initial cause leads to a series of pathological changes that culminate in the end disease or symptoms. There may be several steps between the initial cause and the end point, making it difficult to link the symptoms seen with the initial cause. In some cases, an initial cause may lead to more than one disease end state. The situation is further complicated when two or more causes interact to cause the initial disruption, or when we consider that other mid-level factors often interact to influence the outcome.
Things are set in motion by some factor that causes an initial abnormality, then a series of other abnormalities arise in a chain of events, like dominos falling.
-Biological systems are complex and are made up of intricate interconnected subsystems. Think of the gears and wheels inside an old pocket watch. Each wheel turning another, turning yet another keeps the time. A problem with any one gear will throw off the time. Each subsystem plays a small but critical role, for example, to carry out a certain chemical reaction. Often, one subsystem will depend on the output of another and may in turn, create a certain product that another subsystem uses. When one subsystem is altered and becomes abnormal, often several other subsystems become abnormal in turn. The end result is that the overall smooth biological operation is disrupted, but not by one simple abnormality, rather, by a whole series of abnormalities, each representing a critical sub-component system that has become abnormal.
-Example: Think of the subsystems of a car: there is the electrical system, the steering system, the braking system, the cooling system, the transmission, the engine itself, the suspension, etc. Let's imagine a cascade failure. The fan cooling the radiator on many cars is run by electricity. If the fuse blows on the fan, the radiator may not have enough air passing through it to cool the water going through the engine. The engine will overheat and eventually be damaged and quit. If the engine stops, the power steering pump will stop and power steering will be lost (and power brakes too). Each subsystem problem may provide a symptom. Let's look at the cascade of symptoms seen in our example: the fan stops - we no longer can hear it running, the radiator starts to steam, the red "hot" light on the dashboard comes on, the engine makes a funny noise, the engine stops, steering becomes very hard, the brakes feel very weak.
-In a disease cascade we can often see three basic phases:
>Initial causes that set things in motion (called a trigger or triggering event). These may be external (like radiation's impact in causing cancer, or like the impact of a virus) or they may be internal (like a mutation within cells arising from cell division). Initial abnormalities are called upstream.
>Second, "middle level" effects. These are often invisible and are initially difficult to understand.
>Finally, there are the end stage effects, usually seen as the symptoms of disease that a person has. End stage abnormalities are called downstream.
>In summary, conditions that involve a cascade of abnormalities are much more difficult to understand. Also, treatment is complex as well. It does only limited good to find and treat the end symptoms or "middle problems," we need to go back to the start to discover and fix the first malfunctions (trying to fix the power steering pump won't help fix the initial cause - the overheating problem). *

Pathognomonic {PATH-THOG - no-monic}: Indicative of a disease, esp. its characteristic symptoms. ***

Pathological fracture: A break in a bone usually caused by cancer or some disease condition. ##

Pathologist {path-OL-o-jist}: Doctor who identifies diseases by studying cells and tissues under a microscope. #

Pathology: The study of disease by the examination of tissues and body fluids under the microscope. ##

Pathophysiology: The effects of disease on body functions; the physiology of altered function seen in disease. ("Patho-" is a combining form denoting any disease state, and "physiology" refers to the study of the processes and functioning of the human body.)

pathy: when seen as a suffix, refers to a disease process - as in pathology. Example: Myopathy: Myo = muscle, myopathy is a pathology of muscle. *

PCR see Polymerase chain reaction.

Pedigree: A diagram of the heredity of a particular trait through many generations of a family. %

Predispositions to Illness: Predisposition to certain diseases is a major factor in who develops an illness. If a person has the factors that predispose an illness to develop, then the risk of that person getting that illness increases. Often predisposing factors interact with our behavior to further increase or decrease the risk.
-For example, certain factors predispose people to get lung cancer.
-Here are some alternatives:

  1. person is not predisposed, does not smoke (lowest risk situation) and does not get lung cancer
  2. person is not predisposed, does not smoke (lowest risk situation) and gets lung cancer
  3. person is not predisposed, smokes and does not get lung cancer
  4. person is not predisposed, smokes and gets lung cancer
  5. person is predisposed, does not smoke and does not get lung cancer
  6. person is predisposed, does not smoke and gets lung cancer.
  7. person is predisposed, smokes (highest risk situation) and does not get lung cancer
  8. person is predisposed, smokes (highest risk situation) and gets lung cancer

-Inherent factors: Many predispositions are genetic factors that a person is born with.
-External factors: Many factors that people are exposed to from the environment can predispose later disease. For example, getting some virus infections can predispose a person to other types of illness later on.
-It is not clear what factors (if any) might predispose IBM to develop. This is an important avenue for research. If we know about predispositions ahead of time, we can sometimes alter our lifestyle to try to minimize our risk of developing illness.
-Note: There are also factors that appear to protect people from certain illnesses as well. These factors can again be internal (genetic) or external (for example, in our diet).

Penetrance: The proportion of individuals with a given genotype (heterozygotes for a dominant gene) who express an expected trait, even if mildly. If a disease gene is not causing the disease in all its carriers, its penetrance is low [not to be mixed with variable expression]. BRCA1 mutations show both age-dependent penetrance and overall reduced penetrance, the lifetime risk for a female mutation carrier being estimated at around 70%. Breast cancer is also an example of an autosomal condition where penetrance is sex-dependent. While male mutation carriers can develop breast cancer (particularly with BRCA2 mutations), females are at much greater risk. HFE has a very low penetrance which is age and sex-dependent. Penetrance: The probability that a particular phenotype is expressed in a person with a particular genotype.

Peptide: A group of two or more amino acids strung together. Peptides in turn make up proteins. Proteins break down into different peptides and these break down into various amino acids. A dipeptide contains two amino acids (di means two), polypeptide contains many amino acids. *

Percutaneous umbilical blood sampling (PUBS): the insertion of a needle through the mother's abdomen, like an amniocentesis, for the purpose of drawing a blood sample from the umbilical vein of the umbilical cord. A small sample of fetal blood is withdrawn through a slender needle passed through the woman's abdomen into the baby's umbilical cord. Although the procedure is similar to an amniocentesis for the woman, it requires a high-level of expertise by those performing and assisting in the procedure. It is available in a limited number of high-risk pregnancy centers. PUBS is generally performed after the 18th week in pregnancy. The timing depends on the reason the test is being done.

Peri-: A prefix meaning around. The perinatal period is around the time of birth.

Pericentromeric (also pericentromere): Material surrounding the centromere. See heterochromatin.

Periodic apnea: Episodes of the temporary cessation of spontaneous breathing. Periodic apnea may be characterized by absence of airflow, absence of chest wall movements, or airway obstruction that may result from poor control of tongue movements, impaired coordination of upper airway muscles, or other abnormalities.

Periodic limb movements in sleep (PLMS): Repeated stereotypic movements of the limbs (usually the legs) that occur during sleep. These movements typically consist of upward extension of the great toe and foot as well as flexion of the ankle, knee, or hip; they occur every 15 to 40 seconds and 0.5 to 6.0 seconds, usually during NREM sleep and have a duration of 0.5 to 6.0 seconds.

Periodic Paralysis: Includes the hypokalemic and hyperkalemic types. These rare disorders occur anytime from infancy to the 30's. They are characterized by bouts of limb and neck weakness and paralysis that range from severe episodes weeks or months apart in the hypokalemic variety, to milder episodes hours or days apart in the hyperkalemic type. They are both genetic disorders, transmitted via an autosomal dominant transmission. Males are affected more often than females in hypokalemic periodic paralysis while the incidence is equal between males and females in the hyperkalemic type. **

Peripheral {per-IF-er-ill} Neuropathy (PN): affects two million people in the U.S., typically middle-aged and elderly individuals. It is a neurological disorder that affects the sensory, motor and/or autonomic nerves, and is caused by abnormal function of these nerves due to various etiologies. These disorders can originate from numerous causes, such as diabetes, alcoholism, HIV, toxin exposure, metabolic abnormalities, vitamin deficiency, or adverse effects of certain drugs. However, after evaluations for the etiologies of these PNs are performed, 32-70% of all peripheral neuropathies remain idiopathic. With the development of autoimmune and genetic tests, these idiopathic peripheral neuropathies can often be diagnosed.

Peripheral edema: unusual fluid accumulation, resulting in swelling of the arms or legs.

Peripheral neuropathy: Inflammation, degeneration, or damage of nerves of the peripheral nervous system (PNS). The PNS includes nerves that extend from the brain and spinal cord (central nervous system) to various parts of the body. Peripheral neuropathy may involve motor nerves, causing muscle weakness, and/or sensory nerves, resulting in pain, abnormal sensations, such as numbness or tingling, or other findings.

Peripheral stem cell support: A method for replacing bone marrow destroyed by cancer treatment. Certain cells in the blood that are similar to those in bone marrow are removed from the patient's blood before treatment. The cells are given back after treatment to help the bone marrow recover. #

Peripheral {per-IF-er-ill}: Related to, located in, or constituting an outer boundary or periphery.

Peripheral Nervous system: The part of the vertebrate nervous system constituting the nerves outside the central nervous system and including the cranial nerves, spinal nerves, and sympathetic and parasympathetic nervous systems.

Peristalsis: {Paree-stall-sis} Rhythmic, wave-like contractions of smooth or involuntary muscle fibers that propel food through the digestive tract.Permanent section: Thin slices of biopsy tissue that are mounted on slides and looked at under a microscope. A permanent section takes several days to prepare. It tells doctors if the tissue is diseased, the type of abnormality there is, and other information that helps to plan treatment. #

Peroneal {PARA-knee-al} palsy: Paralysis of the fibula or lateral side of the leg. ***

PET scan: see positron emission tomography

Petechiae {pet-TEEK-kee-eye}: Small hemorrhages of the tiny blood vessels found just below the skin surface. They often result from a low platelet count and disappear when the platelet count rises again. #

Phage: A virus for which the natural host is a bacterial cell. %

Phagocytes: Large white blood cells that contribute to the immune defenses by ingesting and digesting microbes or other cells and foreign particles.

Phagocytosis: The engulfment of a particle or a microorganism by leukocytes.

Pharmaceutical drugs: Pharmaceutical products are drugs obtained by creating, mixing or compounding chemicals. This classification includes drugs for prevention of disease, maintenance of health, and treatment of infections. Examples of pharmaceutical products are: antihistamines, antimicrobials (antibiotics), disinfectants, mastitis preparations, anti-inflammatory agents, steroids, dextrose therapy, dietary products, fluid therapy, gastrointestinal drugs, hormones, insecticides, parasiticides, vitamins and minerals.

Pharmacodynamics: The actions of drugs on the body. The drug's molecular actions.

Pharmacogenetics: Pharmacogenetics is the science of increasing the effectiveness of drugs and minimizing their side effects by studying the genetic causes of the variation in individual patients' response (efficacy, safety, etc.) to drugs. The influence of gene variants on drug actions are evaluated.

Pharmacogenomics {PHARM-ma-co-gen-nom-icks}: Refers to the general study of all of the many different genes that determine drug behavior. A broader term than pharmacogenetics, referring to genome-wide analysis of the determinants of drug response.
Pharmacogenomics is the study of how an individual's genetic inheritance affects the body's response to drugs. The term comes from the words pharmacology and genomics and is thus the intersection of pharmaceuticals and genetics. Pharmacogenomics combines traditional pharmaceutical sciences such as biochemistry with annotated knowledge of genes, proteins, and single nucleotide polymorphisms.
Anticipated Benefits of Pharmacogenomics
More Powerful Medicines: Pharmaceutical companies will be able to create drugs based on the proteins, enzymes, and RNA molecules associated with genes and diseases. This will facilitate drug discovery and allow drug makers to produce a therapy more targeted to specific diseases. This accuracy not only will maximize therapeutic effects but also decrease damage to nearby healthy cells.
Better, Safer Drugs the First Time: Instead of the standard trial-and-error method of matching patients with the right drugs, doctors will be able to analyze a patient's genetic profile and prescribe the best available drug therapy from the beginning. Not only will this take the guesswork out of finding the right drug, it will speed recovery time and increase safety as the likelihood of adverse reactions is eliminated.
More Accurate Methods of Determining Appropriate Drug Dosages: Current methods of basing dosages on weight and age will be replaced with dosages based on a person's genetics - how well the body processes the medicine and the time it takes to metabolize it. This will maximize the therapy's value and decrease the likelihood of overdose.
Advanced Screening for Disease: Knowing one's genetic code will allow a person to make adequate lifestyle and environmental changes at an early age so as to avoid or lessen the severity of a genetic disease. Likewise, advance knowledge of a particular disease susceptibility will allow careful monitoring, and treatments can be introduced at the most appropriate stage to maximize their therapy.
Better Vaccines: Vaccines made of genetic material, either DNA or RNA, promise all the benefits of existing vaccines without all the risks. They will activate the immune system but will be unable to cause infections. They will be inexpensive, stable, easy to store, and capable of being engineered to carry several strains of a pathogen at once.
Improvements in the Drug Discovery and Approval Process: Pharmaceutical companies will be able to discover potential therapies more easily using genome targets. Previously failed drug candidates may be revived as they are matched with the niche population they serve. The drug approval process should be facilitated as trials are targeted for specific genetic population groups - providing greater degrees of success. The cost and risk of clinical trials will be reduced by targeting only those persons capable of responding to a drug.
Decrease in the Overall Cost of Health Care: Decreases in the number of adverse drug reactions, the number of failed drug trials, the time it takes to get a drug approved, the length of time patients are on medication, the number of medications patients must take to find an effective therapy, the effects of a disease on the body (through early detection), and an increase in the range of possible drug targets will promote a net decrease in the cost of health care. See: http://www.ornl.gov/hgmis/medicine/pharma.html
To stratify a population based upon genetic differences to drug (medication) response. Based upon genetic factors, one group in a population may respond well to a medication, another group will respond poorly. Being able to test for these genetic differences would allow the Doctor to avoid using the medication in poor responders. In the future, pharmacogenomics will guide the development of new medicines, each designed a bit differently for each particular group in the population with the goal of getting the maximum response for each group.
Also: Pharmacogenomics: Moving Away from One-Size-Fits-All Therapeutics. Within the next decade, researchers will begin to correlate DNA variants with individual responses to medical treatments, identify particular subgroups of patients, and develop drugs customized for those populations. The discipline that blends pharmacology with genomic capabilities is called pharmacogenomics.
Genomic data and technologies also are expected to make drug development faster, cheaper, and more effective. Most drugs today are based on about 500 molecular targets; genomic knowledge of the genes involved in diseases, disease pathways, and drug-response sites will lead to the discovery of thousands of new targets. New drugs, aimed at specific sites in the body and at particular biochemical events leading to disease, probably will cause fewer side effects than many current medicines. Ideally, the new genomic drugs could be given earlier in the disease process. As knowledge becomes available to select patients most likely to benefit from a potential drug, pharmacogenomics will speed the design of clinical trials to bring the drugs to market sooner. *

Pharmacokinetics: The action of the body on drugs - the processes of drug absorption, distribution and elimination.

Pharmacotherapy: The use of drugs in the clinical treatment of disease.

Phase: Denotes the haplotypic configuration of linked loci. The diplotype U1U3-V1V2 is consistent with two possible phases: (1) U1-V1 on one chromosome and U3-V2 on the other; or (2) U1-V2 on one chromosome and U3-V1 on the other. If a child receives U1-V1 on a paternally derived
chromosome from a father with diplotype U1U3-V1V2 it either implies that the father was in phase (1) and no recombination has occurred, or he was in phase (2) and there has been recombination.

Phenotype: The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences. The expression of a specific trait, such as stature or blood type, based on genetic and environmental influences. *

Phlebitis {fleb-EYE-tis}: A painful inflammation or irritation of a vein. #

Phonation: The production of speech; utterance of sounds through use of the vocal cords.

Phosphofructokinase {Phos-fro-FRUCT-toe-kine-aze} Deficiency: Metabolic disorder of muscle resulting from absence of the enzyme PFK. Symptoms include fatigue and achy pain in the muscles that increases with additional exertion. Attacks may be accompanied by nausea and vomiting. Occurs typically in childhood, with wide variation in severity and progression. **

Phosphorylation. The addition of a phosphate group to a compound.

Photosensitivity: Extreme sensitivity to the sun, leaving the patient prone to sunburns. This can be a side effect of some cancer drugs and radiation. ##

Physical medicine and rehabilitation: also called PHYSIATRY {FIZZ- eye-ah-tree} performed by a physiatrist {FIZZ-eye ah-trist}, PHYSICAL THERAPY, REHABILITATION MEDICINE, PHYSIOTHERAPY: medical specialty concerned with the treatment of chronic disabilities and with the restoration of normal functioning to the disabled through physical modes of treatment, such as exercise. This specialized medical service is generally aimed at rehabilitating persons disabled by pain or ailments affecting the motor functions of the body. Physical medicine is one means employed to assist these patients to return to a comfortable and productive life, often despite the persistence of a medical problem.
Also: The treatment of stiffness, muscle weakness and pain in the body, esp. by rubbing and moving the sore parts

Physical map (genetic): Map which locates features in real space and where the distance between markers is the actual distance, such as the number of base pairs.

Physiologic tremor: A form of rapid tremor that may occasionally occur in any individual. Physiologic tremor is typically the result of fear, anxiety, or excitement. Physiologic tremor may affect the arms, legs, and, in some patients, the face or neck.

Physiotherapy: The physical and therapeutic techniques commonly used to maintain strength and maximize range of motion, posture and comfort in clients. **
Also: The treatment of injuries or disabilities using physical methods, such as massage, manipulation, exercise, and heat. Physiotherapists play an important role in restoring mobility to patients confined for a long period to bed or a wheelchair; they also enable the rehabilitation of those handicapped by strokes, cerebral palsy, polio, etc., or immobilized by fractures. Physiotherapy is also useful in reducing the pain and stiffness of arthritis. *

Phytanic acid: An acid that accumulates in the serum and tissues in Refsum's disease and attributed to the hereditary absence of phytanate alpha-oxidase. ***

Pick's disease: A rare cause of dementia in middle-aged people. The damage is mainly in the frontal and temporal lobes of the brain, in contrast with the diffuse degeneration of Alzheimer's disease. *

Pinocytosis: Ingestion of liquid or very small particles by vesicle formation in a cell.

Pituitary {pi-TOO-I-tare-ee} gland: The main endocrine gland. It produces hormones that control other glands and many body functions. #

PKU: Phenylketonuria, an enzyme deficiency condition characterized by the inability to convert one amino acid, phenylalanine, to another, tyrosine, resulting in mental deficiency. plasmid double-stranded, circular, bacterial DNA into which a fragment of DNA from another organism can be inserted.

Placebo {Pla-SEE-bo}: An inert substance often used in clinical trials for comparison. ## Also see clinical trials.

Plaques: A spherical mass comprised primarily of amyloid fibrils and interwoven neuronal processes, frequently, although not exclusively, observed in Alzheimer's disease. ***
Also: The proteinaceous elements that may build up in brain tissue as a result of certain types of disease or infection. *

Plasma cells: Large antibody-producing cells that develop from B cells. Plasma cell: End-stage differentiation of a B cell to an antibody-producing cell.

Plasmapheresis {plaz-muh-far-REE-sis or plaz-muh-FAIR-ah-sis} Apheresis: Any procedure in which blood is drawn from a donor or patient and a component (platelets, plasma, or white blood cells) is separated out, the remaining blood components being returned to the body. In plasmapheresis the plasma (the liquid portion of the blood) is separated from donated blood, the red blood cells being returned to the donor. In some diseases, such as myasthenia gravis, plasmapheresis is used to attempt to remove the disease-causing substances from the blood. *

Plasmapheresis {PLASMA - fair-ree-sis}: Removal of a portion of blood, separation of the blood cells by centrifugation so as to remove the plasma portion containing antibodies and replacement with plasma or sterilized albumin separated from donor blood. It is often part of the treatment protocol in myasthenia gravis, polymyositis and dermatomyositis. **

Plasmid: A circular piece of DNA present in bacteria or isolated from bacteria. Escherichia coli, the usual bacteria in molecular genetics experiments, has a large circular genome, but it will also replicate smaller circular DNAs as long as they have an "origin of replication". Plasmids may also have other DNA inserted by the investigator. @@

Plasticity: Unproven notion that tissue stem cells may broaden potency in response to physiological demands or insults.

Platelet count: The number of platelets in a blood sample. ##

Platelets: Blood cells that seal off injuries and prevent excessive bleeding without clotting. #

Pleiotropy: A characteristic of genes. Many genes affect more than one trait simultaneously; this is called pleiotropy ("many effects"). Genes that aren't normally pleiotropic may have neomorphic alleles which are.

Pluripotent {Plur-ee-pote-tent}: cells capable of giving rise to most tissues of an organism. *

Point mutation: Substitution of one nucleotide for another within a gene resulting in a missense, nonsense, or splice mutation. ***

Poliomyelitis (Polio)(or infantile paralysis): Acute viral infection, mainly of children but also affecting older persons. There are three immunologic types of poliomyelitis virus; exposure to one type produces immunity only to that type, so infection with the other types is still possible. Poliomyelitis is both endemic and epidemic in all parts of the world. Spread of the infection is primarily through contact with an infected person. Most people who contract polio either exhibit no symptoms or experience only minor illness; however, such individuals can harbor the virus and spread it to others. The virus enters the body by way of the mouth, invades the bloodstream, and may be carried to the central nervous system, where it causes lesions of the gray matter of the spinal cord and brain. The illness begins with fever, headache, stiff neck and back, and muscle pain and tenderness. If there is involvement of the central nervous system, paralysis ensues. Of those patients who develop paralytic poliomyelitis, about 25% sustain severe permanent disability, another 25% have mild disabilities, and 50% recover with no residual paralysis. The disease is usually fatal if the nerve cells in the brain are attacked (bulbar poliomyelitis), causing paralysis of essential muscles, such as those controlling swallowing, heartbeat, and respiration. There is no specific drug for treatment. The incidence of poliomyelitis declined radically in the United States when a mass immunization program with the Salk vaccine was begun in 1955. By 1961 the Sabin vaccine, a preparation made from living organisms and taken orally, was released for use. Since then the disease has been virtually eliminated in the United States and Europe, but vaccination programs continue because of polio's continued existence in other parts of the world and the ease of travel. For reasons not clearly understood, some people who have had severe polio experience postpolio syndrome, a condition in which new weakness and pain occurs years later in previously affected muscles. *

Poly-: A prefix meaning multiple.

Polyclonal activator: A substance that induces activation of many individual clones of either T or B cells. See Mitogen.

Polycystic kidney disease (PKD): A group of conditions characterized by fluid filled sacs that slowly develop in both kidneys, eventually resulting in kidney malfunction.

Polygenic disorders: Genetic disorders resulting from the combined action of alleles of more than one gene (e.g., heart disease, diabetes, and some cancers). Although such disorders are inherited, they depend on the simultaneous presence of several alleles; thus the hereditary patterns are usually more complex than those of single-gene disorders. Compare single-gene disorders. %
Also: Susceptibility to a disease arising from the combined action of several genes, each of which confers a moderate degree of risk. *

Polymerase chain reaction (PCR): A method for amplifying a DNA base sequence in vitro.

Polymerase {POL-er-mer-raise}, DNA or RNA: Enzymes that catalyze the synthesis of nucleic acids on preexisting nucleic acid templates, assembling RNA from ribonucleotides or DNA from deoxyribonucleotides. %
Polymerase: An enzyme which links individual nucleotides together into a long strand, using another strand as a template. There are two general types of polymerase - DNA polymerases (which synthesize DNA) and RNA polymerase (which makes RNA). Within these two classes, there are numerous subtypes of polymerase, depending on what type of nucleic acid can function as template and what type of nucleic acid is formed. A DNA-dependant DNA polymerase will copy one DNA strand starting from a primer, and the product will be the complementary DNA strand. A DNA-dependant RNA polymerase will use DNA as a template to synthesize an RNA strand. @@

Polymerase chain reaction (PCR): A method for making multiple copies of DNA or amplifying a DNA base sequence. PCR also can be used to detect the existence of a defined sequence in a DNA sample. %
Polymerase {pall-ah-mer-ase} chain reaction (PCR): A sensitive technique of molecular genetics in which the DNA of a single cell, treated with polymerase enzymes, is induced to replicate many times. This enables the DNA to be amplified in sufficient quantities to enable genetic analysis. The technique may be utilized in the course of preimplantation diagnosis of genetic disorders.

Polymorphism: Generally, the ability to appear in many forms. A polymorphism is a genetic variant that appears in at least 1% of a population. Examples: the human ABO blood groups; the human Rh factor; the human major histocompatibility complex (MHC). By setting the cutoff at 1%, it excludes spontaneous mutations that may have occurred in - and spread through the descendants of - a single family. Also: In biology, a discontinuous genetic variation resulting in the occurrence of several different forms or types of individuals among the members of a single species. A discontinuous genetic variation divides the individuals of a population into two or more sharply distinct forms. The most obvious example of this is the separation of most higher organisms into male and female sexes. Another example is the different blood types in humans. In continuous variation, by contrast, the individuals do not fall into sharp classes but instead are almost imperceptibly graded between wide extremes. Examples include the smooth graduation of height among individuals of human populations. If the frequency of two or more discontinuous forms within a species is too high to be explained by mutation, the variation-as well as the population displaying it-is said to be polymorphic. A polymorphism that persists over many generations is usually maintained because no one form possesses an overall advantage or disadvantage over the others in terms of natural selection. Some polymorphisms have no visible manifestations and require biochemical techniques to identify the differences that occur between the chromosomes, proteins, or DNA of different forms. *
Also: Polymorphism Implies genetic variation at a designated locus. A locus that is polymorphic has at least two alternative alleles. Unfortunately, polymorphism has alternative, more specific definitions (none universally accepted), an important example being 'the existence of two or more genetic variants (alleles, [other] sequence variants, chromosomal structure variants) at significant frequencies in the population.' In this series, polymorphism is used either as a component of the term single nucleotide polymorphism or it refers simply to a locus at which genetic variation is evident. Unless stated otherwise, its usage implies nothing about the type of variation observed or its frequency.

Polymorphonuclear leukocyte: White cell, granular cytoplasm. Neutral staining (neutrophil) - most frequent, phagocytic. Basophilic staining - basophil q.v. Eosinophilic staining - eosinophil q.v.

Polymyositis (PM): A disorder of skeletal muscle, of unknown cause, characterized by acute or sub-acute onset and frequent improvement of symptoms. It is one of the inflammatory myopathies. Symptoms include difficulty climbing stairs or rising from low seats, lifting packages or working with arms outstretched or over the head. It is treated with steroids and immunosuppressive drugs. **

Polyp {POL-ip}: A mass of tissue that develops on the inside wall of a hollow organ such as the colon. # A growth of tissue protruding into a body cavity, such as a nasal or rectal polyp. Polyps may be benign or malignant. ##

Polypeptide: A chain of amino acids. A chain of polypeptides makes up a protein.

Population Genetics: The study of variation in genes among a group of individuals.

Population genomics: To identify the underlying genes responsible for common chronic disorders in a population. *

Port - Implanted: A catheter connected to a quarter-sized disc that is surgically placed just below the skin in the chest or abdomen. The tube is inserted into a large vein or artery directly into the bloodstream. Fluids, drugs, or blood products can be infused, and blood can be drawn through a needle that is stuck into the disc. Examples: Port-o-cath, Infusaport, Lifeport. ##

Port - Peritoneal: A catheter connected to a quarter-sized disc that is surgically placed in the abdomen. The catheter is inserted to deliver chemotherapy to the peritoneum (abdominal cavity).

Position effect variegation (PEV): Position-effect variegation is a process which causes variable, mosaic inactivation of a gene when that gene is removed from its normal chromosomal environment.

Positional cloning: Locating the gene for a specific trait by comparing the DNA of people who have that trait to the DNA of relatives who don't have the trait. ###

Positive findings: Results of a test are described as positive if the Doctor finds evidence of the abnormality he or she is looking for. *

Positron emission tomography (PET scan): A procedure that provides an analysis of the amount of metabolic activity taking place in various parts of the brain. To do a PET-scan the patient is injected with a radioactive glucose-like substance that is absorbed into cells, particularly those that are metabolically active. The individual's brain is scanned in a manner similar to a CAT scan. Positron emission tomography (PET): An advanced, computerized imaging technique that uses radioactively-labels substances (e.g., glucose) to demonstrate chemical and metabolic activities in the brain as well as track other brain functions. Brain structures are also visualized on PET scans.

Positron emission tomography (PET) scanning: A noninvasive, diagnostic procedure used to record the uptake and distribution of certain substances in the tissues and organs of the body. Thus, PET assists in evaluating various metabolic and physiological activities in the body. During this procedure, three-dimensional, color-coded images are created based upon the detection of positively charged particles (positrons). The positrons are produced by certain biochemicals (e.g., glucose) carrying radioactive substances that have been introduced into the body (via intravenous injection). PET scanning may help to detect abnormal biochemical patterns associated with certain neurologic conditions, such as Parkinson's disease, brain tumors, seizure disorders, and psychiatric abnormalities.

Postpolio Syndrome (PPS), Post Polio Muscular Atrophy (PPMA): A condition that can strike polio survivors anywhere from 10 to 40 years after their recovery from polio. PPS is caused by the death of individual nerve terminals in the motor units that remain after the initial polio attack. Symptoms include fatigue, slowly progressive muscle weakness, muscle and joint pain, and muscular atrophy. The severity of PPS depends upon how seriously the survivors were affected by the first polio attack. Doctors estimate the incidence of PPS at about 25 percent of the survivor population. The only way to be sure a person has PPS is through a neurological examination aided by other laboratory studies (for example, magnetic resonance imaging (MRI), neuroimaging, electrophysiological studies, and muscle biopsies or spinal fluid analysis).
There is some degree of overlap in the symptoms seen in PPS and in other muscular diseases and also some commonality in the treatments used. Management of the late effects of polio attempts to control those factors contributing to loss of functional abilities in three ways. First, pain and inflammation of muscles, joints and supportive tissues must be reduced though traditional therapy techniques. This includes the use of anti-inflammatory medications, heat, stretching, and other methods of physical therapy. Second, any activity that is the source of repeated injury and strain must be changed. Frequently an increased amount of weakness in leg muscles demands a return to the use of canes, crutches, braces, or wheelchairs in order to avoid continued strain. It is understandable that polio survivors often do not wish to return to the use of these assistive devices but they may be necessary to reduce the pain resulting from strain and to stop the vicious cycle. Third, polio survivors should exercise on a regular basis. There are three types of exercises that are normally recommended. Flexibility exercises are most important. They must be done to keep the spine flexible and mobile, as well as to prevent tightness of muscles and joints. Conditioning exercises should be done to promote cardiopulmonary fitness. It can often be challenging to design conditioning exercises for polio survivors because of limited strength in extremities for doing sustained exercise. Swimming is an excellent type of activity for achieving some cardiovascular conditioning without overly straining limb muscles. Carefully designed strengthening exercises can also be utilized. Patients must be careful to not exercise too vigorously and produce new injury and symptoms. Often it is the muscles that were not severely involved with polio that can benefit the most from resuming mild strengthening exercises. If an attempt at strengthening exercises is carried out and new muscle pain and weakness develop, then it is clear that the weakened muscle is susceptible to overuse injury and further exercise of that muscle should be discontinued. *

POST-TRANSCRIPTIONAL CONTROL OF GENE EXPRESSION: Post-transcriptional control (PTC) mechanisms are all the regulatory events that take place after an RNA molecule is made (i.e., after the transcription process). This includes the decoding of the RNA molecule so that a protein is synthesized. For example, how efficiently RNA is utilized to make protein, or how long RNA lives in a cell, have a direct impact on how much protein is produced.
Post-transcriptional control processes regulate the amount of proteins made in all tissues and cell types. Multiple diseases are caused by the altered control of these regulatory events. PTC's approach is to discover and develop small molecule drugs that affect (inhibiting or enhancing) protein production by targeting post-transcriptional control mechanisms.

Post-transcriptional gene silencing (PTGS): At least some organisms have the ability to destroy (or "silence") specific RNAs (after transcription from DNA but before translation). Researchers have shown that PTGS occurs in both plants and animals and plays roles in viral defense and transposon silencing mechanisms. PTGS has been documented in a variety of organisms with a number of diverse situations, and may even play a role in regulation of development. PTGS appears to be a natural and ancient mechanism for defending against RNA based invaders. Small interfering RNAs (siRNAs) play a central role in PTGS.
Related terms: Cosuppression -Silencing of an endogenous gene caused by the introduction of a transgene or infection by a virus. This term, which can refer to silencing at the post-transcriptional (PTGS) or transcriptional (TGS) level, has been primarily adopted by researchers working with plants.
RNA-induced silencing complex (RISC):A nuclease complex, composed of proteins and siRNA that targets and destroys endogenous mRNAs that are homologous to the siRNA within the complex.
Double Stranded RNA (dsRNAs): Protein interactions with double-stranded RNA (dsRNA) are critical for many cell processes; however, in contrast to protein dsDNA interactions, surprisingly little is known about the molecular basis of protein dsRNA interactions. The double-stranded RNA-binding domain (dsRBD) is a 65 70 amino acid sequence/structure motif that mediates dsRNA interactions in a large variety of proteins.
RNA interference (RNAi):Post-transcriptional gene silencing (PTGS) induced by the direct introduction of dsRNA. The term "RNA interference" was first used by researchers studying C. elegans. See RNA interference.
Short interfering RNAs (siRNAs): Current models of PTGS indicate that these 21-23 nucleotide dsRNAs mediate PTGS. siRNAs are apparently produced by cleavage of dsRNA introduced directly or via a transgene or virus. Amplification by an RNA-dependent RNA polymerase (RdRP) may occur. siRNAs are incorporated into the RNA-induced silencing complex (RISC), guiding the complex to the homologous endogenous mRNA where the complex cleaves the transcript. siRNAs have also been referred to as "guide RNAs". In the cytoplasm, the siRNAs serve as guides for endonucleolytic cleavage of homologous mRNA degradation in association with the RNA-induced silencing complex (RISC). In the nucleus, short RNAs possibly guide methylation of homologous DNA , although it cannot be ruled out that dsRNA triggers RdDM directly.
See: http://www.ambion.com/hottopics/rnai/rnai_jun2001.html

Post translational modifications of protein: See protein synthesis.

Potency: The range of commitment options available to a cell.
=Totipotent Sufficient to form entire organism. Totipotency is seen in zygote and plant meristem cells; not demonstrated for any vertebrate stem cell.
=Pluripotent Able to form all the body's cell lineages, including germ cells, and some or even all extraembryonic cell types. Example: embryonic stem cells.
=Multipotent Can form multiple lineages that constitute an entire tissue or tissues. Example: haematopoietic stem cells.
=Oligopotent Able to form two or more lineages within a tissue. Example: a neural stem cell that can create a subset of neurons in the brain.
=Unipotent Forms a single lineage. Example: spermatogonial stem cells.

Postural tremor: Any tremor that is present while an individual voluntarily maintains a position against gravity, such as holding the arms outstretched.

Precursor: Literally a "forerunner," such as a substance that precedes another in a biochemical reaction.

Pre-morbid behaviour: what behaviour was like before the illness or injury occurred. *

Prader-Willi syndrome: A condition characterized by obesity and insatiable appetite, mental deficiency, small genitals, and short stature. May be deletion of #15 chromosome.

Precursor: One chemical element that changes into another or that forms part of another. *

Predictive gene tests: Tests to identify gene abnormalities that may make a person susceptible to certain diseases or disorders. %

Predisposition: To have a tendency or inclination towards something in advance. %

Prefrontal lobe: Portion of the brain largely concerned with behaviour, learning, judgment and personality. Of, relating to, or situated in the anterior (front) part of the frontal lobe. *

Preimplantation screening: The development of In Vitro Fertilization along with the development of micromanipulation techniques and DNA amplification technology (polymerase chain reaction or PCR) has led to the ability to screen for genetic defects in very early human development, after fertilization but prior to implantation in the uterus.
This process is called "Preimplantation Genetic Diagnosis" or "PGD." In this process, a couple in which one or both partners carry a genetic mutation undergoes In Vitro Fertilization to create several early embryos in a glass dish. A single cell is removed from an embryo once it has achieved an 8-cell stage (two days after fertilization in the laboratory). The genetic material from this cell is then put through the DNA amplification process to make millions of copies of the gene that may contain the mutation. The amplified DNA is then tested to determine whether or not the embryo from which the DNA was obtained carries the genetic mutation. In this manner, each embryo can be tested and only unaffected embryos can be selected to be transferred into the uterus of the female partner where hopefully, a normal implantation and pregnancy will occur.
PGD has many technical problems and has not grown to be as widely used as prenatal diagnosis. These issues include: contamination, allele dropout or other allele defects (amplification of one allele), and misdiagnosis due to mosaicism (the cell tested may not represent all of the cells in the embryo). PGD is also limited by the success rate of IVF.

Premorbid: Before the onset of an illness.

Prenatal diagnosis: Examining fetal cells taken from the amniotic fluid, the primitive placenta (chorion), or the umbilical cord for biochemical, chromosomal, or gene alterations. %
Prenatal diagnosis (antenatal {anti-natal} diagnosis): Diagnostic procedures carried out on pregnant women in order to discover genetic or other abnormalities in the developing fetus. These techniques involve tests done to determine the health and condition of an unborn fetus within the mother's womb. There are a variety of noninvasive and invasive techniques available for prenatal diagnosis. Each of them can be applied only during specific time periods during the pregnancy for greatest utility. Ultrasound scanning remains the cornerstone of prenatal diagnosis. Other procedures include estimation of the level of alpha-fetoprotein in the mother's serum and the amniotic fluid; chromosome and enzyme analysis of fetal cells obtained by amniocentesis or, at an earlier stage of pregnancy, by chorionic villus sampling (CVS); and examination of fetal blood obtained by fetoscopy or cordocentesis. If the results indicate that the child is likely or certain to be born with severe malformation or abnormality, the possibility of abortion is discussed by the doctors involved with the parents. Until recently, prenatal genetic diagnosis was dependent on CVS and amniocentesis, but it may now be extended to the earliest stages of embryonic development, before implantation occurs (preimplantation diagnosis). Access to these early embryos requires the removal and in vitro fertilization of egg cells: three days after fertilization one or two cells are aspirated from the six- to eight-cell embryo; alternatively, tissue is removed from an embryo at five or six days, when it has reached the blastocyst stage. Isolated cells can then be genetically analyzed, using the polymerase chain reaction amplification technique to produce enough DNA for genetic diagnosis. Even before pregnancy, this technique can be used to enable a prospective mother to be identified as the carrier of a gene defect, by means of the mouthwash test. When a defect is detected, genetic counseling is offered.

Prenatally: Before birth.

Presenile dementia: Dementia that occurs in young or middle-aged people. The term is sometimes reserved for Alzheimer's disease and Pick's disease. *

Presenilin: Presenilins are a type of protein, they have been discovered only recently, not much is known about them, but genetic findings strongly suggest that the elucidation of the functions of this protein may be crucial for the understanding of the pathogenesis of at least many cases of Alzheimer's disease. *

Presentation: The way a disease expresses itself in a person. What goes wrong in a given person. Usually refers to symptoms and signs that characterize an illness. *

Pressure sores: Pressure sores are areas of injured skin and tissue. They are usually caused by sitting or lying in one position for too long. This puts pressure on certain areas of the body. The pressure can reduce the blood supply to the skin and the tissues under the skin. When a change in position doesn't occur often enough and the blood supply gets too low, a sore may form. Pressure sores are also called bed sores, pressure ulcers and decubitus ulcers.
Also: Initially it is observed as a red mark on the skin that forms due to excessive pressure at that particular point. These can develop into areas of severe tissue injury and eventually cause tissue death if the pressure is not alleviated. *

Presymptomatic diagnosis: Diagnosis of a genetic condition before the appearance of symptoms. In many cases, a genetic illness can be predicted but not yet treated. %

Prevalence: The total number of cases of a disease in a given population at a specific time.
Also: Prevalence: the total number of people alive who have a disease. Can be reported either at a particular time (point prevalence) or over a period of time (period prevalence). It can be expressed either in terms of sick people (persons) or episodes of sickness per 1000 individuals at risk or per 100,000. Often confused with incidence.

Primary lymphoid organs: Organs in which the maturation of T and B lymphocytes take place and antigen-specific receptors are first acquired.

Primary responses: The immune response to a first encounter with antigen. The primary response is generally small, has a long induction phase or lag period, consists primarily of IgM antibodies, and generates immunologic memory.

Primary tumor: The original cancer site. For example, breast cancer that has spread to the bone is still called breast cancer. ##

Primer: Short preexisting polynucleotide chain to which DNA polymerase can add new deoxyribonucleotides.

Prion {PREE-on}: Prion Protein (PrP or PrPc or chromosomal PrP): A normal protein found in cells, function currently unknown.

[Pathological] Prion Protein, abnormal form of the prion protein (PrPsc): The sc stands for scrapie and designates the abnormal form. An abnormal form of the prion protein that is linked to a variety of fatal neurodegenerative diseases of animals and humans called transmissible spongiform encephalopathies (TSE) or spongiform encephalopathy (SE).
=In normal cells, proteins are sensitive to enzymes called proteases. Proteases see old and defective proteins and cut them up into smaller pieces so that the cell can dispoose of them. If a protein resists being cut up by proteases, then it can accumulate within the cell in abnormal protein aggregations and cause damage. The normal prion protein is sensitive to proteases. However, in some cases, the normal prion is connverted into an abnormal form that resists being cut up and disposed of, leading to abnormal protein aggregations. Conversion of the normal protease-sensitive prion protein (PrP) to its abnormal protease-resistant isoform (PrP-res) is a major feature of the pathogenesis associated with transmissible spongiform encephalopathy (TSE) diseases.
=PrP is encoded by the PrP gene located on chromosome 20. The familial form of CJD is determined by mutations in this gene. PrP is a 253 amino acid peptide; Prion disease is caused by this protein, with an identical amino acid sequence but a unique confirmation. The aggregation of these aberrant forms of protein induces neuronal dysfunction.
=Also: All mammals produce PrP in cells of the central nervous system and other tissues (including muscle). Changes in normal PrP are believed to lead to an altered protein referred to by some scientists as a "prion" (proteinacious infectious particle). Scientists believe that when abnormal PrP comes in contact with normal PrP, it distorts the shape of the normal protein structure. Scientists do not know what factors trigger this conversion. Some believe the abnormal PrP itself causes the conversion, while others believe a virus-like entity may be involved. Most scientists agree that the accumulation of abnormal PrP in brain cells results in altered function and eventual death of cells.
=The function of the normal form of the prion protein is unknown. Only when it is in the aberrant configuration (the wrong shape) does the prion protein cause disease. The pathogenic protein can enter the brain through infection, or it can arise from a mutation in the gene that encodes the protein. Once present in the brain it multiplies by inducing healthy proteins to refold into the aberrant shape. The normal protein structure is believed to consist of a number of flexible coils called alpha helices. In the aberrant protein some of these helices are stretched out into flat structures called beta strands. As prion proteins multiply they accumulate within nerve cells, destroying them. Progressive nerve cell destruction eventually causes brain tissue to become riddled with holes in a sponge-like, or spongiform, pattern.
=Diseases caused by prions include: Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal familial insomnia (FFI), and kuru. Other prion diseases, suffered by animals, include scrapie, bovine spongiform encephalopathy (BSE - commonly called mad cow disease), chronic wasting disease (CWD) of mule deer and elk and feline spongiform enceplopathy (FSE - of house cats).
=For decades physicians believed that these diseases resulted from infection with slow-acting viruses, so-called because of the lengthy incubation times required for the illnesses to develop. These diseases were, and sometimes still are, referred to as slow infections. There is a lot of ongoing controversy over this - is the prion the real infectious agent in these diseases? Or, is some undiscovered virus also out there? We do know that prions are resistant to exposure to high heat and ionizing ultraviolet radiation, which normally inactivates viruses by destroying their nucleic acid. Thus, prions are unlike all other known disease-causing organisms in that they appear to lack nucleic acid - i.e., DNA or RNA - which is the genetic material that all other life-forms contain. Another unusual characteristic of prions is that they not only cause disease through infection but can be responsible for hereditary and sporadic forms of disease as well - for example, Creutzfeldt-Jakob disease manifests in all three ways, with sporadic cases being the most common, the prion protein can act as an infectious agent, spreading disease when transmitted to another organism, or it can arise from an inherited mutation. Prion diseases also show a sporadic pattern of incidence, meaning that they seem to appear in the population at random. The underlying molecular process that causes the aberrant protein to form in these cases remains to be found.
=Researchers suspect that other neurodegenerative disorders such as Alzheimer's disease or Parkinson's disease may arise from molecular mechanisms similar to those that cause the prion diseases. Indeed, abnormal protein aggregation characterizes many, if not all, neurodegenerative disorders, the most commonly, Alzheimer Disease and Parkinson's disease, but also Creutzfeldt-Jakob disease, motor neuron diseases, the large group of polyglutamine disorders, including Huntington's disease, as well as diseases of peripheral tissue like familial amyloid polyneuropathy (FAP). * See here for a brief note. Also see entry for Creutzfeldt-Jakob disease.
=Kuru: is a prion disease that is virtually extinct today. It was originally described in members of a tribe of the New Guinea known to practice endocannibalism. The epidemics probably originated from the consumption of contaminated meat from a member of the tribe affected by sporadic CJD. Clinical and pathologically, Kuru is fairly different from nvCJD. (For details, see Progress in Pathology (N. Kirkham and N.R. Lemoine, Eds), Churchill Livingstone, Edinburgh, 1998, Vol. 4, pp. 39-77.

Probability: The long term frequency of an event relative to all alternative events, and usually expressed as decimal fraction. %

Proband: An affected individual, also called an index case. Individual in a family who first brought the family to medical attention. %

Probiotics: Preparations of live micro-organisms added to food (or used as animal feed), claimed to be beneficial to health by restoring microbial balance in the intestine. The organisms commonly involved are lactobacilli, bifidobacteria, streptococci, and some yeasts and moulds, alone or as mixtures.

Progesterone {pro-JES-ter-own}: A female hormone produced by the ovaries. ##

Progenitor cell: Generic term for any dividing cell with the capacity to differentiate. Includes putative stem cells in which self-renewal has not yet been demonstrated.

Progesterone-receptor assay: A test that determines if breast cancer is stimulated by the hormone progesterone. ##

Prognosis: The projected (expected or probable) outcome of a disease; the life expectancy. ##
Also: Prognosis {prog-NO-sis}: The probable outcome or course of a disease; the chance of recovery. %

Progressive disease: a disorder that keeps getting worse and worse over time.

Progressive external ophthalmoplegia: A specific type of slowly worsening weakness of the ocular muscles, usually associated with a pigmentary retinopathy. ***

Progressive muscle relaxation: Progressive muscle relaxation is one example of a deep relaxation technique that can be used to reduce symptoms of stress, anxiety, insomnia, and certain types of chronic pain. Based upon the simple premise of tensing, or tightening, one muscle group at a time followed by a release of the tension. *

Progressive supranuclear palsy (PSP): A progressive neurological disorder characterized by neurodegenerative changes of certain brain regions, including particular areas of the basal ganglia and the brainstem. Symptom onset most often occurs in the sixth decade of life. Associated findings may include balance difficulties, sudden falls, stiffness (rigidity), slowness of movement (bradykinesia), an impaired ability to perform certain voluntary eye movements, and visual disturbances. Affected individuals may also develop slurred speech; swallowing difficulties; personality changes; dystonia; sudden, involuntary, "shock-like" muscle contractions (myoclonus); or other abnormalities. The disorder usually appears to occur randomly for unknown reasons (sporadically); however, there are some reports of families with multiple affected members, suggesting a possible hereditary component to the disease.

Prokaryote {pro-CARE-ee-oat}: Cell or organism lacking a membrane-bound, structurally discrete nucleus and other subcellular compartments. Bacteria are prokaryotes. Compare eukaryote. %

Promoter: A region of DNA to which RNA polymerase binds before initiating the transcription of DNA into RNA.

Promoter: A chemical agent that causes the expression of a gene or changes in the way that a gene acts. *
Also: Promoter: A segment of DNA that acts as a controlling element in the expression of a gene. It marks the site of initiation of gene transcription. ###
Promoter: The first few hundred nucleotides of DNA "upstream" (on the 5' side) of a gene, which control the transcription of that gene. The promoter is part of the 5' flanking DNA, i.e. it is not transcribed into RNA, but without the promoter, the gene is not functional. @@

Prophylactic: Referring to preventive treatment (i.e., prophylaxis); a medication, procedure, or device that serves as a preventive against disease.

Prophylactic {pro-fill-lact-tic} surgery: Surgery to remove tissue that is in danger of becoming cancerous, before cancer has the chance to develop. Surgery to remove the breasts of women at high risk of developing breast cancer is known as prophylactic mastectomy.

Prophylaxis: Protection from or the prevention of disease; preventive (i.e., prophylactic) therapy; often refers to the use of a drug, mechanical agent, or procedure to prevent infection with certain microorganisms (e.g. bacteria).

Prostate specific antigen (PSA): An enzyme produced by the glandular epithelium of the prostate. Increased quantities are secreted when the gland enlarges and levels of PSA in the blood are significantly elevated in cancer of the prostate, although there is no clear `cutoff' level for normality. PSA levels tend to be much higher in advanced prostate cancer and the rate of fall on treatment is a good prognostic indicator of response. May also be found in an increased amount in the blood of men who have benign prostatic hyperplasia, or infection or inflammation of the prostate. *

Prostate gland {PROSS-tate}: A gland in the male reproductive system just below the bladder. It surrounds part of the urethra, the canal that empties the bladder. #

Prostatectomy {pros-ta-TEK-toe-mee}: An operation to remove part or all of the prostate. Radical (or total) prostatectomy is the removal of the entire prostate and some of the tissue around it.

Prostatic Intraepithelial Neoplasia (PIN): An abnormal type of cell found in a prostate biopsy. Believed to be the most likely precursor of prostate cancer. It is a proliferative lesion i.e. it is composed of prostatic epithelial cells that are dividing more rapidly than normal epithelium. However, the cells have not yet become cancerous. *

Prostatic acid phosphatase {FOS-fa-tays} (PAP): An enzyme produced by the prostate. It may be found in increased amounts in men who have prostate cancer. *

Prosthesis {pros-THEE-sis}: An artificial replacement for a missing body part. #

Protease(s): Enzymes that cut proteins into pieces. The destruction of proteins (after they are used or if they are somehow abnormal) is vital to cell health. *

Protease resistant protein: Normally, cells have ways to avoid abnormal protein aggregation (they take out the garbage of broken proteins). In the normal cell, enzymes called proteases cut up old and abnormal proteins. This is partly based upon the shape of the protein, sometimes a protein will resist being cut up and is called protease resistant. When this happens, inclusion bodies form, also called aggresomes. See aggresome.

Proteasomes {pro-tea-ah-soames}: large structures within the cell that contain proteases and are responsible for the destruction of proteins. *

Protein: A large molecule composed of one or more chains of amino acids in a specific order; the order is determined by the base sequence of nucleotides in the gene coding for the protein. Proteins are required for the structure, function, and regulation of the body's cells, tissue, and organs, and each protein has unique functions.
Also: Protein: A large, complex molecule composed of amino acids. Proteins are made based on instructions contained in genes. The sequence of the amino acids, and thus the function of the protein, is determined by the sequence of the base pairs in the gene that encodes it. Proteins are essential to the structure, function, and regulation of the body. Examples are hormones, enzymes, and antibodies.
Also: Protein: A molecule composed of amino acids linked together in a particular order specified by a gene's DNA sequence. Proteins perform a wide variety of functions in the cell; these include serving as enzymes, structural components, or signaling molecules. ###
Also: complex molecule composed of amino acids and necessary for the chemical processes that occur in living organisms. Proteins are basic constituents in all living organisms. Proteins constitute about 80 percent of the dry weight of muscle, 70 percent of that of skin, and 90 percent of that of blood. The importance of proteins is related more to their function than to their amount in an organism or tissue. All known enzymes, for example, are proteins and may occur in very minute amounts; nevertheless, these substances catalyze all metabolic reactions, enabling organisms to build up the chemical substances - other proteins, nucleic acids, carbohydrates, and lipids - that are necessary for life. **
Also: Proteins are classified by their biological function. Proteins include the enzymes, which are responsible for catalyzing the thousands of chemical reactions of the living cell; keratin, elastin, and collagen, which are important types of structural, or support, proteins; hemoglobin and other proteins that transport gases in the body; ovalbumin, casein, and other nutrient molecules; antibodies, which are molecules of the immune system; protein hormones, which regulate metabolism; and proteins that perform mechanical work, such as actin and myosin, the contractile muscle proteins.
Classified by biological function, proteins include
-enzymes, responsible for catalyzing the thousands of chemical reactions of the living cell;
-keratin, elastin, and collagen, which are important types of structural, or support, proteins;
-hemoglobin and other gas transport proteins;
-ovalbumin, casein, and other nutrient molecules;
-antibodies, which are molecules of the immune system (see immunity);
-protein hormones, which regulate metabolism;
-proteins that perform mechanical work, such as actin & myosin, the contractile muscle proteins. *

Protein (multiprotein) complexes: see protein synthesis.

Protein analysis: Researchers use complex machines to sequence and identify protein components. For example, the MALDI TOF/TOF mass spectrometer. This system is intended to enable high speed analysis to yield a better understanding of proteins and their role in the onset and treatment of disease. This is a very complex topic. For an introduction, see: http://masspec.scripps.edu/information/history/perspectives/borman.html
Terms: matrix-assisted laser desorption/ionization (MALDI), time of flight (TOF)

Protein Folding
Nature Editor's Summary
20 July 2006
Atom-by-atom folding
In the past, protein folding has been more approachable via theory than via experiment. But recently, theory has begun to be confirmed experimentally. In contrast to the belief that all proteins fold in one sudden movement, some in fact fold and unfold gradually, in a random series of steps called downhill folding. Sadqi et al. have used a novel NMR approach to monitor unfolding of a protein atom-by-atom from the native state. The results have greater resolution than had been previously achieved, and confirm that folding is a statistical process best understood by a downhill landscape funnel model. In addition, cooperativity can be understood by mapping the atomic interactions within a protein.
News and Views: Structural biology: Proteins downhill all the way
The hundreds of hydrogen atoms in a protein can be used as reporters to describe how the protein folds into and out of shape. The results challenge the dogma that this is always an all-or-nothing process. Jeffery W. Kelly

Protein product: Any given protein molecule assembled under the direction of a gene. Genetic mistakes can create an abnormal protein that will not function properly. Problems can arise in the size, shape or composition of the protein molecule.

Protein structure: The molecular organization of a protein. The properties of a protein ultimately depend on its primary structure, the sequence of amino acids in the protein. Every protein molecule has a characteristic three-dimensional shape, or conformation. Because the physiological activity of most proteins is closely linked to their three-dimensional architecture, specific terms are used to refer to different aspects of protein structure. The term primary structure denotes the precise linear sequence of amino acids that constitutes the polypeptide chain of the protein molecule. The physical interaction of sequential amino-acid subunits results in a so-called secondary structure. Most globular proteins also undergo extensive folding of the chain into a complex three-dimensional geometry designated as tertiary structure. Two or more polypeptide chains that behave in many ways as a single structural and functional entity are said to exhibit quaternary structure. Protein abnormalities are an important aspect of many human diseases. The precise three-dimensional structure of a protein molecule is referred to as its native state and appears, in almost all cases, to be required for proper biological function (especially for the enzymes). If the tertiary or quaternary structure of a protein is altered, e.g., by such physical factors as extremes of temperature, changes in pH, or variations in salt concentration, the protein is said to be denatured; it usually exhibits reduction or loss of biological activity. *
More: There are four levels of structure found in polypeptides and proteins. The primary structure of a polypeptide of protein determines its secondary, tertiary, and quaternary structures.
Primary Structure. The sequence of amino acids that make up a protein. The primary structure of polypeptides and proteins is the sequence of amino acids in the polypeptide chain with reference to the locations of any disulfide bonds. The primary structure may be thought of as a complete description of all of the covalent bonding in a polypeptide chain or protein. The most common way to denote a primary structure is to write the amino acid sequence using the standard three-letter abbreviations for the amino acids. For example: gly-gly-ser-ala
Secondary Structure. Local folding of peptide creates distinctive structures shared by many proteins including alpha-helicies and beta-pleated sheets. Secondary structure is the ordered arrangement or conformation of amino acids in localized regions of a polypeptide or protein molecule. Hydrogen bonding plays an important role in stabilizing these folding patterns. The two main secondary structures are the alpha helix and the anti-parallel beta-pleated sheet. There are other periodic conformations, but the alpha-helix and beta-pleated sheet are the most stable. A single polypeptide or protein may contain multiple secondary structures. An alpha-helix is a right-handed or clockwise spiral in which each peptide bond is in the trans conformation and is planar. The amine group of each peptide bond runs generally upward and parallel to the axis of the helix; the carbonyl group points generally downward. The beta-pleated sheet consists of extended polypeptide chains with neighboring chains extending anti-parallel to each other. As with the a-helix, each peptide bond is trans and planar. The amine and carbonyl groups of peptide bonds point toward each other and in the same plane, so hydrogen bonding can occur between adjacent polypeptide chains.
Tertiary Structure. Further folding of the protein to give a unique three dimensional structure. The tertiary structure of a polypeptide or protein is the three-dimensional arrangement of the atoms within a single polypeptide chain. For a polypeptide consisting of a single conformational folding pattern (e.g., an alpha helix only), the secondary and tertiary structure may be one and the same. Also, for a protein composed of a single polypeptide molecule, tertiary structure is the highest level of structure that is attained. Tertiary structure is largely maintained by disulfide bonds.
Quarternary Structure. The way multiple subunits of a protein interact. Quaternary structure is used to describe proteins composed of multiple subunits (multiple polypeptide molecules, each called a 'monomer'). Most proteins with a molecular weight greater than 50,000 consist of two or more noncovalently-linked monomers. The arrangement of the monomers in the three-dimensional protein is the quaternary structure. The most common example used to illustrate quaternary structure is the hemoglobin protein. Hemoglobin's quaternary structure is the package of its monomeric subunits. Hemoglobin is composed of four monomers. From: http://chemistry.about.com/library/weekly/blprotein.htm

Protein synthesis: Proteins are manufactured by the cell from instructions contained in the base sequence of DNA in the gene. Protein synthesis is the overall process by which the information coded in the DNA base sequence is translated into functional proteins in cells. Proteins are the foundation of all biological functions, which in turn, are the basis of all expressed traits. Thus, the body's proteins are of critical interest to medicine.
At one time it was thought that the genetic (DNA) code would correspond one-for-one with the proteins in the body, thus for each unique protein, there would be one unique gene (DNA) sequence. This would have simplified finding solutions to many protein related diseases. Unfortunately, this is not the case. It turns out that there are several mechanisms that allow one gene sequence to synthesize a number of different protein products. This adds several layers of complexity to protein synthesis. To understand all of the final proteins and how they are made, we will need to understand the initial code plus all of the various ways that the code can be modified to yield multiple protein products.
There are several mechanisms that allow one gene sequence to synthesize a number of different protein products. I will outline several below:
Alternative splicing:Estimates are that at least 30% of human genes undergo alternative splicing. Alternative splicing creates a splitting of the DNA code into fragments that are then recombined during RNA transcription in different ways to create multiple protein products. This reshuffling of the code is done by a special group of proteins called spliceosomes. For example, the code CAT can be rearranged into TAC or ATC or CTA. In this way, three different (new) sequences can be created from the single original code. Knowing the original code is of little help if the protein of interest has been created through alternative splicing.
Protein folding: is a critical aspect to protein function. In some cases, protein folding may be governed by the genetic instructions that control protein synthesis. However, at least in some cases, part of this folding is assisted by a set of proteins called chaperone proteins that help fold the proteins into the correct shape for proper function. Differences in the shape of the same protein can spell the difference between normal function and disease (prion protein is an example).
Protein (multiprotein) complexes: In addition to the shape of each protein, it turns out that proteins also often function in clusters or clumps called protein complexes. In these cases, the overall composition and shape of the complex and the internal interactions among its component proteins are an important part of protein function. To understand how an individual protein in a cluster operates, scientists will have to understand how the overall cluster functions. Protein complexes add another layer of complexity to protein synthesis and function and a great deal of science will have to take place to understand these complicated interactions.
Post translational modifications of protein: A number of different mechanisms can come into play after translation (protein manufacture) that can alter protein function. Currently, little is understood about the significance of these mechanisms. Again, these mechanisms can create unique proteins, not determined by the initial DNA sequence. The most common post translational mechanism is called glycosylation (the addition of glycan chains to proteins).
Frameshifting: frameshifting occurs as a regulatory mechanism for controlling the gene expression of specific proteins. At a particular step in the translation elongation cycle the ribosome shifts from its reading frame at which it initiated translation to a new reading frame. The consequence of this event is that the ribosome will continue to translate the mRNA in the new reading frame until it encounters a termination codon. Hence, the resulting protein product will be encoded partly by the normal frame upstream of the frameshift event and partly in the new reading frame downstream of the frameshift site . Frameshifting can occur spontaneously, in response to environmental stimuli, such as amino acid starvation, or as a consequence of "programmed frameshifting."
Programmed frameshifting occurs as a consequence of local changes in mRNA structure or sequence that stimulate frameshifting. These structural motifs reduce the efficiency of normal decoding or increase the efficiency of frameshift decoding, or both. A variety of structural motifs lead to different mechanisms of programmed ribosome frameshifting. From: www.biology.ucsc.edu/classes/bio112/Lecture%2011,%202000.pdf

Protein denaturing: Proteins denature when exposed to heat and other stress. This is what makes an egg turn white in the frying pan. Denaturing involves a breakdown of the protein's folding and thus its function is lost. *

Protein folding: The shape of a protein is critical to its function. Abnormalities in the shape of proteins are associated with a number of diseases. *

Protein microarray: Small "computer" chips containing protein samples that can analyze samples of other proteins. When a chip is "washed over" with a sample, some of the sample proteins will adhere to the chip and can be identified. Adherence is an important protein property and this information is critical, especially in pharmaceutical research. These arrays will allow rapid research on proteins, and will be important in developing future medications and in the diagnosis of protein based disorders. *

Protein misfolding: -Proteins must be in the proper shape to function properly. A number of disorders involve protein misfolding, including Alzheimer's Disease, Parkinson's, type II diabetes and likely IBM. These diseases all closely resemble each other as they all involve the abnormal deposition of proteins in the form of amyloid fibrils or plaques. This is called amyloidosis: accumulation in the tissues of various insoluble fibrillar proteins (amyloid) in amounts sufficient to impair normal function.
There are about 50,000 proteins in a person, with an average length of about 300 residues. This is a very small subset of the billions of possible proteins that could be formed. Recall proteins are formed from the 20 basic amino acids in different sequences. Protein has two basic shapes, a globular, soluble state and a "hard" fibrous form, often created by extreme heat or by high pH values. The globular forms are the ones that do the biological work in the cells. It is now known that any protein can form amyloid fibrils. It appears that the ability to form these fibrils is generic to most (all?) proteins - different proteins are prone to misfold and when they do, they form these very similar fibrils. Different proteins have different characteristics, mainly their propensity to misfold varies widely.
Normally, the shape and properties of a protein are determined by their amino acid side chains and how they interact with each other as the protein is packed together, as protein complexes interact with each other and as they interact within the cell. In the abnormal fibrils, the structure is taken over and governed by the strong hydrogen bonding of the atoms in the main chain, forming extended beta sheets of protein. This abnormal bonding and structure interferes with the specific interactions of the side chains that usually dictate the structure and function of the protein. Once misfolded, the protein is irreversibly lost to its primordial amyloid structure.
Affected tissues are often found to be riddled with these thread-like fibrils, sometimes assembled into plaques, with a single predominant protein (sometimes this is amyloid protein, sometimes another protein such as Tau protein for example). Affected tissues are often full of abnormal protein, the amount of protein involved ranges from scarcely detectable quantities to kilograms.
Possible causes: A genetic mutation may make a protein more vulnerable to reverting to its abnormal shape or perhaps to increase the propensity of an incompletely folded protein to form into an aggregate. Some can be transmitted from person to person, likely by the ingestion of already aggregated proteins. The formation of amyloid fibrils is seeded by preformed aggregates. So, once the chain reaction starts, it gathers steam and more and more proteins become abnormal. This is the likely mechanism of the spread of mad cow disease (humans can get it from eating "infected" beef). In other cases, the cell environment is out of wack and this creates the problem. To maintain their normal shape, proteins must exist in a very carefully controlled cellular environment. In older cells where the normal cellular maintenance mechanisms have started to wear out, the environment is more vulnerable to creating misfolded protein, thus amyloidosis is more common in older people.
see: Christopher M. Dobson, Protein-misfolding diseases: Getting out of shape, Nature, 418, 729 - 730 (15 Aug 2002).

Proteinopathy {protein-OP-path-ee}: An abnormality in a protein that leads to disease. Many diseases are related to protein abnormalities within the cell. *

Proteome: The full set of proteins encoded by a genome, or, all of the functioning proteins present in a cell. Each species has its own unique genome and proteome.*

Proteomics: The study of protein expression and function. Proteomics: the study of the proteome. *

Proto-oncogene {pro-toe-ON-co-gene}: Normal gene controlling cell growth. #
Also: Proto-oncogene: A normal gene that can be altered (either through mutation or through nearby insertion of viral DNA) to become an active oncogene. ###

Protocol: A treatment plan. ## Also see clinical trials.

Protoplasm: The complex, semi-fluid, translucent substance that constitutes the living matter of plant and animal cells and manifests the essential life functions of a cell. Composed of proteins, fats, and other molecules suspended in water, it includes the nucleus and cytoplasm. *

Proximal: Closer to the body - towards the center of the body. For example, muscles controlling the pelvic or shoulder girdles, which hold large components of the total body mass against the force of gravity*

PSA: see Prostate-specific antigen.

Pseudogenes: Genes that can no longer produce proteins after being disabled by mutations. Some pseudogenes can still produce noncoding RNA.

Pseudohypertrophy: A common characteristic in Duchenne muscular dystrophy where the calf muscles are prominent. This prominence is due to increased fat deposits rather than enlargement of the muscle tissue. **

Psychogenic: Having a psychological cause. Psychogenic: Of mental or emotional origin; referring to a symptom, condition, or disorder that is caused by mental, psychological, or emotional factors rather than physical illness.

Psychosis: Refers to any mental disorder characterized by severe distortion of thinking, comprehension, and judgment (i.e., mental capacity); impaired contact with reality; and abnormal emotional responses and disorganized behaviors. Symptoms may include false beliefs despite evidence to the contrary (delusions), such as fears of persecution; the perception of sounds, sights, or other sensations in the absence of external stimuli (hallucinations); apparent lack of emotion (affect); abnormal thought patterns; disorganized, incoherent speech; and/or agitated, aggressive behaviors. Psychosis may be of physical (i.e., organic) origin, such as due to brain damage, neurological diseases, underlying metabolic disorders, etc., or "functional," meaning that it is produced or caused by factors other than organic disease.

PTC: A test sometimes used to help diagnose cancer of the pancreas. A thin needle is put into the liver. Dye is injected into the bile ducts so blockages can be seen on X-rays. #

Ptosis {TOE-sis}: Dropping or drooping of an organ or part, as the upper eyelid from paralysis. ***

PubMed: see Medline *

PubMed Central: An initiative to provide the full text of Medical Journals on the Internet for free. *

Pulmonary: Referring to the lungs.

Punnett squares: A probability diagram illustrating the possible offspring of a mating. *

Purkinje cell {Per-kin-gee}: A large, drop-shaped, densely branching neuron that is the characteristic cell of the cerebellar cortex. *

Putamen: One of the 3 major brain regions that, together with the caudate nuclei and the globus pallidus, comprise the basal ganglia. Relatively similar in function and structure, the putamen and the caudate nuclei are collectively referred to as the striatum. Specialized groups of nerve cells within the putamen receive input from various regions of the cerebral cortex. The messages are processed and relayed by way of the thalamus to the motor cortex, influencing voluntary movement.

Putative {PUTE-TA-tive}: Generally regarded as such; supposed. A putative cause of an illness is a supposed cause. *

Pyo-: A prefix meaning pus. Pyocephalus is pus in the brain.

Rad: (Radiation-absorbed dose} A measure of the amount of radiation a person receives. One chest X-ray equals 1/10 of a rad. #

Radiation therapy: {ray-dee-AY-shun} Treatment with high-energy rays to kill or damage diseased cells. External radiation therapy is the use of a machine to aim high-energy rays at the cells. Internal radiation is the placement of radioactive material inside the body as close as possible to the disease (usually cancer). %

Radical nephrectomy: Surgical removal of the kidney, large portions of the surrounding tissue and neighbouring lymph nodes. #

Radioallergosorbent test (RAST): A solid-phase radioimmunoassay for detecting IgE antibody specific for a particular allergen.

Radioimmunoassay (RIA): A widely used technique for measurement of primary antigen-antibody interactions, and for the determination of the level of important biological substances in mixed samples. It takes advantage of the specificity of the antigen-antibody interaction and the sensitivity that derives from measurement of radioactively labelled materials.

Radioisotope bone scan: Diagnostic procedure in which a harmless amount of radioactive chemical is injected into the bloodstream and concentrates in cancer cells. A scanning device is passed over the body and senses any radioactivity and makes a picture of its location in the body. #

Radiologist A physician with special training in reading diagnostic X-rays and performing specialized X-ray procedures. #

Radionuclide scanning: An exam that produces pictures (scans) of internal parts of the body. The patient is given an injection or swallows a small amount of radioactive material. A machine called a scanner then measures the radioactivity in certain organs. %

Random Genetic Drift: The random fluctuation in population allele frequencies as genes are transmitted from one generation to the next.

Randomized: Chosen at random. In a research study it means choosing subjects to be given a particular treatment by means of a computer programmed to choose names at random. # see clinical trials.

Range of Motion: Range of motion exercise refers to activity whose goal is improving movement of a specific joint. This motion is influenced by several structures: configuration of bone surfaces within the joint, joint capsule, ligaments, and muscles and tendons acting on the joint. Injury, disease, surgery, or immobilization of a joint may affect the normal joint range of motion. There are two types of range of motion. Active Range of Motion: how far a person can voluntarily move a body part at a joint. Active range of motion is movement of the joint provided entirely by the individual performing the exercise. In this case, there is no outside force aiding in the movement. Passive range of motion: movement applied to the joint solely by another person or persons or a passive motion machine. When passive range of motion is applied, the joint of the individual receiving exercise is completely relaxed while the outside force takes the body part, such as a leg or arm, throughout the available range. *

Reading frame: When mRNA is translated by the cell, the nucleotides are read three at a time. By starting at different positions, the groupings of three that are produced can be entirely different. @@

Reagin: Allergist's term for IgE antibodies.

Recessive allele: A gene that is expressed only when its counterpart allele on the matching chromosome is also recessive (not dominant). Autosomal recessive disorders develop in persons who receive two copies of the mutant gene, one from each parent who is a carrier. %

Receptor: A molecule on a neuron that receives a neurotransmitter. Reception of the neurotransmitter causes changes in the neuron which increase or decrease its likelihood of "firing," or sending its own signal to other neurons. Dopamine receptors are located on corpus striatum neurons, and on nigral cells.

Recessive: Refers to a characteristic that is apparent only when two copies of the gene encoding it are present - one from the mother and one from the father. ###
Also: Recessive: A gene that is phenotypically manifest in the homozygous state but is masked in the presence of a dominant allele. Imagine a situations where both parents carry a single defective gene but are protected by the presence of a normal gene, which is generally sufficient for normal function. Two defective copies of the gene are required to produce a disorder. Each child has a 50 percent chance of being a carrier like each parent and a 25 percent risk of inheriting the disorder and a 25 percent chance of having two normal genes (not having the disorder and not being a carrier). *

Recombinant DNA technologies: Procedures used to join together DNA segments in a cell-free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome. %
Also: Recombinant DNA technology: Techniques for cutting apart, splicing together, and producing pieces of DNA from different sources. ###

Recombinant DNA molecules: A combination of DNA molecules of different origin that are joined using recombinant DNA technologies. %

Recombination: The natural process of breaking and rejoining DNA strands to produce new combinations of genes and, thus, generate genetic variation. Gene crossover during meiosis. %

Rectum: The last 5 to 6 inches of the colon leading to the outside of the body. #

Recurrence: The reappearance of a disease after a period of remission. ##

Red blood cells (Erythrocytes): Cells in the blood that deliver oxygen to tissues and take carbon dioxide from them. ##

Red blood count (RBC): The number of red blood cells seen in a blood sample. ##

Reduced penetrance: Reduced expression of a genetic disorder. The term penetrance refers to the frequency with which a specific genetic mutation produces its typical effect in those with the genetic abnormality. For example, if fewer than 100 percent of individuals who inherit a gene mutation for an autosomal dominant disorder develop the disease, the specific trait is said to have "reduced penetrance."

Reducing Body Myopathy: One of the congenital myopathies, it is a progressive and often fatal disorder. Hypotonia occurs early and motor milestones are either late or not attained. Profound weakness is progressive and involves both distal and proximal muscles. **

Refsum's Disease: A demyelinating, motor-sensory neuropathy with an autosomal recessive inheritance pattern affecting children and adults. Common clinical features include motor and sensory neuropathy, retinitis pigmentosa, night blindness, ataxia, ichthyosis, and sensorineural hearing loss. Refsum's disease is associated with abnormally high levels of phytanic acid in the blood or plasma *

Reflex: Involuntary, predictable response to a particular stimulus.

Refractory: Resistant to or not readily yielding to treatment.

Regenerative medicine: Reconstruction of diseased or injured tissue by activation of endogenous cells or by cell transplantation.

Regression: The shrinkage of an abnormal growth (cancer). ##

Relapse: The reappearance of a disease after its apparent cessation. ##

REM sleep: The period of sleep that is associated with dreaming, rapid eye movements (REM), and certain involuntary muscle movements.

Remission: Complete or partial disappearance of the signs and symptoms of disease. ##
Also: Remission: a partial decrease or complete subsidence of the clinical and subjective characteristics of a chronic or malignant disease; disappearance of symptoms and general improvement of an individual; it may be spontaneous or the result of therapy. "In remission" refers to the period during which such a decrease or subsidence occurs. Spontaneous remission refers to the improvement of an individual without current treatment. The exact mechanisms responsible for spontaneous remissions in various disorders are not well understood at present, but much research is done on the topic.
Several points are important in relation to remission: It is important to understand that many diseases tend to be cyclical. Arthritis, multiple sclerosis, myasthenia gravis, allergies, and gastrointestinal complaints are examples of diseases that normally "have their ups and downs." It is important to recognize life events that may correlate with these ups and downs, for example, changes in stress, in diet, in medications, etc. We need to become aware of these features because in some cases what we do may influence these ups and downs, Second, sometimes people take alternative therapies that may happen to coincide with remissions. In the course of talking to people about your illness, many people will suggest they know of certain vitamins, minerals or other formulas or treatments that "will completely cure" your disorder. These people are usually very sincere (they often site examples; the best friend of their best friend recovered). Sometimes the basis for these beliefs are rare but possible spontaneous remissions. Third: it is vital that the patient who is in remission and feels better continue to work with their Doctor, and to observe their treatment and lifestyle modifications. If one feels "cured" and resumes a high energy lifestyle, they may threaten the remission. Remissions are unpredictable and diseases are prone to reoccur, especially if the person neglects their care. *

Repeat sequences: The length of a nucleotide sequence that is repeated in a tandem cluster.

Repetitive DNA: A surprising portion of any genome consists not of genes or structural elements, but of frequently repeated simple sequences. These may be short repeats just a few nt long, like CACACA etc. They can also range up to a few hundred nt long. Examples of the latter include Alu repeats, LINEs, SINEs. The function of these elements is often unknown. In shorter repeats like di- and tri-nucleotide repeats, the number of repeating units can occasionally change during evolution and descent. They are thus useful markers for familial relationships and have been used in paternity testing, forensic science and in the identification of human remains. @@

Reporter gene - encodes for an easily detectable protein. For example, lacZ, CAT (chloramphenicol acetyltransferase), and the luciferase genes all encode for bacterial enzymes. The presence of bacterial enzymes can be easily monitored by simple and sensitive assays of enzyme activity, without any interference from host cell enzymes. The regulatory sequence for the gene of interest can be identified by attaching the reporter sequence to various fragments of DNA sequence taken from upstream or downstream of the gene.

Reprogramming: Increase in potency. Occurs naturally in regenerative organisms (dedifferentiation). Induced experimentally in mammalian cells by nuclear transfer, cell fusion, genetic manipulation or in vitro culture.

Respiratory burst: Oxygen dependent increase in metabolic activity within phagocytic cells stimulated by bacteria or parasites, to be microbicidal.

Response element: By definition, a "response element" is a portion of a gene which must be present in order for that gene to respond to some hormone or other stimulus. Response elements are binding sites for transcription factors. Certain transcription factors are activated by stimuli such as hormones or heat shock. A gene may respond to the presence of that hormone because the gene has in its promoter region a binding site for hormone-activated transcription factor. @@

Restless legs syndrome (RLS): A neurologic movement disorder characterized by unusual, uncomfortable sensations (paresthesias/dysesthesias) deep within the calves and/or thighs, resulting in an irresistible urge to move the legs, and motor restlessness in response to or in an effort to alleviate discomfort. In some patients, the arms may also be affected. Symptoms become obvious or worse during periods of relaxation or inactivity; occur most frequently during the evening or the early part of the night; and may be temporarily relieved by voluntary movements of the affected area. Most patients experience associated sleep disturbances, including difficulties drifting off to and remaining asleep. RLS is also often associated with periodic limb movements of sleep (PLMS) or repeated, stereotypic, upward extension of the great toe and foot, potentially followed by flexion of the knee, hip, or ankle. Episodes of PLMS typically occur during periods of lighter (i.e., non-REM) sleep.

Restorative sleep: A refreshing sleep, i.e., receiving a sufficient amount of rest to feel refreshed and to engage in the activities of daily living without experiencing excessive daytime sleepiness (EDS).

Reproductive cells: Egg and sperm cells. Each mature reproductive cell carries a single set of 23 chromosomes.

Restriction: To "restrict" DNA means to cut it with a restriction enzyme. @@

Restriction enzyme: A class of enzymes ("restriction endonucleases") generally isolated from bacteria, which are able to recognize and cut specific sequences ("restriction sites") in DNA. @@

Restriction fragment length polymorphism (RFLP): A variation in DNA sequence that is easily recognized because it occurs at a site where a restriction enzyme cuts a specific sequence, producing DNA fragments of varying lengths. RFLP's often serve as genetic markers. ###
The acronym is pronounced "riflip". Although two individuals of the same species have almost identical genomes, they will always differ at a few nucleotides. Some of these differences will produce new restriction sites (or remove them), and thus the banding pattern seen on a genomic Southern will thus be affected. For any given probe (or gene), it is often possible to test different restriction enzymes until you find one which gives a pattern difference between two individuals - a RFLP. The less related the individuals, the more divergent their DNA sequences are and the more likely you are to find a RFLP. @@

Reticuloendothelial system: A network of phagocytic cells.

Retina: The nerve-rich membrane that forms the innermost region of the eye. As light passes through other areas of the eye (including the cornea, pupil, and lens), it is bent or refracted to focus on the retina, which contains nerve cells that respond to light (photoreceptors). Images formed on the retina are converted into nerve impulses that are transmitted to the brain via the optic nerve (second cranial nerve).

Retinal: Referring to the retina, which is the nerve-rich membrane forming the innermost region of the eye. As light passes through the eye, it is bent (refracted) to focus on the retina, which contains photoreceptors or specialized nerve cells that respond to light. Images formed on the retina are converted into nerve impulses, which are then transmitted to the brain by the optic nerve (also known as the second cranial nerve).

Retinitis pigmentosa: A chronic progressive disease that has its onset in early childhood. It is marked by degeneration of the retinal epithelium, esp. the rods, without inflammation; atrophy of the optic nerve; and widespread pigmentary changes in the retina. An early symptom is defective night vision followed by a constricted field of vision. ***

Retrotransposon: A transposable genetic element in which transposition involves a process of reverse transcription with an RNA intermediate similar to that of a retrovirus.

Retrovirus: A type of RNA virus that, unlike other RNA viruses, reproduces by transcribing itself into DNA. An enzyme called reverse transcriptase allows a retrovirus's RNA to act as the template for this RNA-to-DNA transcription. The resultant DNA inserts itself into a cell's DNA and is reproduced along with the cell and its daughters. The life cycle is completed when the viral DNA in selected daughter cells makes an RNA copy of itself that covers itself in a protein coat and leaves the cell. Retroviruses sometimes destroy the cells whose DNA they alter, as with HIV, the virus that causes AIDS, and sometimes cause them to become cancerous, as with the viruses that cause certain leukemias. Lentiviruses are retroviruses that cause slowly progressing diseases, such as AIDS. *

Reverse transcriptase: An enzyme which will make a DNA copy of an RNA template - a DNA - dependent RNA polymerase. RT is used to make cDNA. @@

Reye syndrome: A potentially life-threatening disease characterized by sudden inflammation and swelling of the brain (acute encephalopathy) and rapid fat accumulation within certain internal organs (viscera), particularly the liver, occurring subsequent to certain viral infections, such as chickenpox or upper respiratory tract infections (e.g., influenza B). Reye syndrome primarily occurs in children and adolescents, although it has sometimes been reported during infancy or young adulthood. About a week after the onset of a viral infection, patients may develop uncontrollable vomiting, followed by a rapid onset of listlessness, confusion, and memory loss, a state of unconsciousness (coma), seizures, and/or other findings, potentially leading to life-threatening complications. Evidence suggests that the use of aspirin-containing preparations (salicylates) as a treatment for particular viral infections plays a role in the development of Reye syndrome. Therefore, experts advise that such medications be avoided for the treatment of viral infections during infancy, childhood, adolescence, and young adulthood.

RFLP: Restriction fragment length polymorphism; variations occurring within a species in the length of DNA fragments generated by a species endonuclease.

Rhabdomyolysis: a condition characterized by dissolution of striated muscle fibres, with leakage of muscle enzymes, myoglobin, potassium, calcium, and other intracellular constituents, can occur in anyone under particular circumstances and that the consequences can be severe and sometimes fatal. There are no prospective studies of the incidence of rhabdomyolysis and many mild cases probably go unrecognised. Rhabdomyolysis is defined as an acute increase in serum concentrations of creatine kinase to more than five times the upper normal limit-and when myocardial infarction has been excluded as a cause (CK-MB fraction less than 5%). Visible myoglobinuria (tea or cola coloured urine) occurs when urinary myoglobin exceeds 250 µg/ml (normal < 5 ng/ml). The causes of rhabdomyolysis are legion, but all lead to a critical increase in sarcoplasmic calcium and intracellular damage by activation of calcium dependent proteases and phospholipases. Risk is increased by pre-existing metabolic factors such as hypokalaemia, hypophosphataemia, and hyponatraemia. Single episodes are most commonly caused by infections (viral, bacterial, or other), drugs, or physical factors such as compartment syndromes, ischaemia, reperfusion (including surgical procedures), and pressure from hard surfaces in comatose patients. Severe or unaccustomed exertion, particularly in extremes of heat, is a common precipitant and has been reported in long distance runners, bodybuilders, and military recruits, and may also follow prolonged seizures, certain involuntary movement disorders, and rigors. It is also known to occur in polo ponies and racehorses.

Rheumatoid {ROOM-ah-toid} arthritis: Chronic, progressive disease in which inflammatory changes occur throughout the connective tissues of the body. Most characteristically the process attacks joints of the hands, feet, wrists, knees, hips, or shoulders. Inflammation and thickening of the synovial membranes (the sacs that hold the fluid that lubricates the joints) cause irreversible damage to the joint capsule and the articular (joint) cartilage as these structures are replaced by scar tissue. *

Rheumatoid factor: An autoantibody (usually IgM) which reacts with the individual's own IgG. Present in rheumatoid arthritis.

Rheumatologist: A rheumatologist is an internist or pediatrician who is qualified by additional training and experience in the diagnosis and treatment of arthritis and other diseases of the joints, muscles and bones. Certain muscle disorders appear to be related to problems in immune function, for example, Myasthenia gravis, is a comparatively rare autoimmune disorder, manifesting as a progressive muscular weakness which can occur at any time of life. Other examples include polymyositis and dermatomyositis. *

Rheumatology: The medical science that deals with the study and treatment of rheumatic diseases. Many believe that underlying the rheumatic diseases are endocrine factors and immune responses (and/or auto immune problems). There are many forms of arthritis and other rheumatic diseases, including: Ankylosing Spondylitis, Juvenile Arthritis, Pseudogout, Back Pain, Lyme Disease, Psoriatic Arthritis, Myopathies, Rheumatoid Arthritis, Fibromyalgia, Osteoarthritis, Scleroderma, Giant Cell Arteritis, Osteoporosis, Sjogren's Syndrome, Gout, Polymyalgia Rheumatica, Systemic Lupus Erythematosus, HIV-Associated Rheumatic Disease Syndromes, and Tendinitis / Bursitis. *

Rhythmical myoclonus: Involuntary, shock-like contractions or spasms of a muscle or muscle group that occur in a rhythmical pattern. This usually occurs as a result of a lesion in the central nervous system.

Ribonucleic acid {RYE-bo-new-clay-ic} (RNA): A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose. %

Ribonucleoprotein (RNP): Any complex of protein and RNA that forms during the synthesis of RNA in eukaryotes; the protein is involved in the packaging and condensation of the RNA. Certain RNPs are restricted to the nucleus whereas others are found in both the nucleus and the cytoplasm. The most common RNP occurring in the nucleus is heterogeneous nuclear RNP (hnRNP), which consists of protein bound to the primary transcript of DNA (see transcription). It may be associated with small nuclear RNP (snRNP), which is involved in the removal of intron sequences from the primary transcript to form messenger RNA, which eventually leaves the nucleus (see gene splicing). A third type, small cytoplasmic RNP (scRNP), is found in the cytoplasm; its function is unknown.

Ribosomal RNA (rRNA): A type of RNA found in the ribosomes of cells. %

Ribosome: Small cellular components composed of specialized ribosomal RNA and protein; site of protein synthesis. %
Ribosome: A cellular particle which is involved in the translation of mRNAs to make proteins. Ribosomes are a complex consisting of ribosomal RNAs (rRNA) and several proteins. @@

Rigidity: Stiffness and resistance to movement. May be a symptom of a neurologic movement disorder such as Parkinson's disease.

Risk factor: A habit, trait, condition, or genetic alteration that increases a person's chance of developing a disease. %

RNA: Ribonucleic acid.

RNAi (RNA interference): RNAi appears to be a highly potent and specific process which is actively carried out by special mechanisms in the cell, known as the RNA interference machinery. While the complete details of how it works are still unknown, it appears that the machinery, once it finds a double-stranded RNA molecule, cuts it up, separates the two strands, and then proceeds to destroy other single-stranded RNA molecules that are complementary to one of those segments. dsRNAs direct the creation of small interfering RNAs (siRNAs) which target RNA-degrading enzymes (RNAses) to destroy transcripts complementary to the siRNAs.
The phenomenon of RNAi, first described just over a decade ago, has revolutionized functional genomics. It allows targeted genes to be easily and efficiently switched off using short stretches of double-stranded RNA (dsRNA) that contain the same sequence as mRNA transcribed from the target gene.
RNAi has recently been applied as an experimental technique to "knockout" genes in model organisms for experimental analysis in determining the function of a gene. Repressing a gene from being expressed allows for testing of the protein and its role in the life of a cell or larger organism. Since RNAi may not totally abolish expression of a gene, using it against a gene is sometimes referred as a "knockdown", to distinguish it from procedures in which the DNA sequence encoding a gene is totally removed.
The dsRNAs that trigger RNAi may be usable as drugs. The first application to reach clinical trials is in the treatment of macular degeneration. RNAi has also been shown effective in the complete reversal of induced liver failure in mouse models.
Related term: small temporal RNAs (stRNAs):21-22 nt RNAs that control the timing of development in Caenorhabditis elegans. stRNAs are found in virtually all bilaterally symmetric animals, including flies and humans. Research has shown that the stRNA and RNAi pathways intersect: both require the RNA-processing enzyme Dicer to produce the active small-RNA component that represses gene expression.
Related term: Short or Small Interfering RNAs (siRNAs): siRNAs are able to suppress the expression of the corresponding genes. Suppression takes place at the RNA level. siRNAs may prove to be more effective at gene-specific suppression than antisense RNAs.
Related term: miRNA (microRNA): non-coding RNAs that appear to regulate the production of proteins from other genes.
Also see: Post-transcriptional gene silencing (PTGS).

RNase: Ribonuclease; an enzyme which degrades RNA. It is ubiquitous in living organisms and is exceptionally stable. The prevention of RNase activity is the primary problem in handling RNA. @@

Romberg sign: The inability to maintain body balance when the eyes are shut and the feet are close together. The sign is positive if the patient sways and falls when the eyes are closed. This is seen in sensory ataxia. ***
Also: Romberg's sign: evidence of a sensory disorder affecting those nerves that transmit information to the brain about the position of the limbs and joints and the tension in the muscles. The patient is asked to stand upright. Romberg's sign is positive if he maintains his posture when his eyes are open but sways and falls when his eyes are closed. *

RT-PCR (reverse transcription-polymerase chain reaction) is the most sensitive technique for mRNA detection and quantitation currently available. RT-PCR is a method of RNA quantitation, RT- PCR can also be used for cloning, cDNA library construction, probe synthesis, differential display, and signal amplification in in situ hybridizations. The technique consists of two parts: synthesis of cDNA from RNA by reverse transcription (RT) and amplification of a specific cDNA by polymerase chain reaction (PCR).

S-phase fraction: Measure of number of cells dividing at any one time. #

Salicylates: Medications derived from salicylic acid, including aspirin (acetylsalicylic acid). Such compounds have anti-inflammatory, pain-relieving (analgesic), and fever-reducing (antipyretic) activities. Salicylates act to reduce the production of certain hormone-like chemicals known as prostaglandins that may have varying actions, potentially leading to inflammatory effects, increased pain sensitivity, fever, etc. Prolonged aspirin use may damage the stomach or intestinal lining, causing peptic ulcers and bleeding from the digestive tract. (Peptic ulcers are well-defined, raw areas where the mucous membrane lining the stomach, esophagus, or upper region of the small intestine has been eroded by acidic digestive [i.e., gastric] juices.) In addition, excessive intake of salicylates may lead to salicylate toxicity, characterized by rapid breathing, irritability, vomiting, and other findings.

Salpingo-oophorectomy {sal-PING-o oo-for-EK-to-mee}: Surgical removal of the fallopian tubes and ovaries. #

Sandhoff's disease: A neurodegenerative metabolic disorder that is characterized by symptoms and findings similar to those associated with Tay-Sachs disease as well as possible, moderate enlargement of the liver and spleen (hepatosplenomegaly). Sandhoff's disease is a lysosomal storage disease in which deficiency of the enzymes hexosaminidase A and B results in an abnormal accumulation of certain fats (i.e., gangliosides) in particular tissues of the body. The disorder is transmitted as an autosomal recessive trait and affects only non-Jewish individuals (as opposed to Tay-Sachs disease, which primarily occurs in individuals of Ashkenazi Jewish ancestry).

Sarcoglycanopathies: Mutations in the proteins of the sarcoglycan complex appear to be a significant cause of recessive autosomally inherited muscular dystrophy. The phenotypes range from closely resembling Duchenne (DLMD = Duchenne-like muscular dystrophy / SCARMD = severe childhood autosomal recessive muscular dystrophy) to the late-onset forms of Limb- Girdle muscular dystrophy (LGMD) Together, these diseases are indicated as the "sarcoglycanopathies". The differences in the expression of the sarcolgycans, especially those between SGCA/SGCC versus SGCB/SGCD (where smooth muscle seems unaffected), have been suggested to cause clinical differences. Straub et al. suggest that, based on the differences in sarcoglycan expression, analysis of skin biopsies might be helpful in the diagnosis of LGMD.
LGMD-2D: alpha-sarcoglycan mutations
LGMD-2E: beta-sarcoglycan mutations
LGMD-2C: gamma-sarcoglycan mutations
LGMD-2F: delta-sarcoglycan mutations
unknown: epsilon-sarcoglycan
LGMD-1C: caveolin-3 mutations (autosomal dominant form of Limb-Girdle muscular dystrophy)
Also: Sarcoglycanopathies: Diseases caused by abnormalities of one of the Sarcoglycan muscle proteins see Sarcoglycans. *

Sarcoglycans: Mutations in the proteins of the sarcoglycan complex appear to be a significant cause of recessive autosomally inherited muscular dystrophy. The phenotypes range from closely resembling Duchenne (DLMD = Duchenne-like muscular dystrophy / SCARMD = severe childhood autosomal recessive muscular dystrophy) to the late-onset forms of Limb-Girdle muscular dystrophy (LGMD) Together, these diseases are indicated as the "sarcoglycanopathies". The differences in the expression of the sarcolgycans, especially those between SGCA/SGCC versus SGCB/SGCD (where smooth muscle seems unaffected), have been suggested to cause clinical differences. The smooth muscle DGC (dystroglycan complex) contains dystrophin, alpha- and beta-dystroglycan, beta-, delta- and epsilon-sarcoglycan and sarcospan.
There are several types of Sarcoglycan:
- (alpha)-Sarcoglycan: mutations were found in both alleles of the gene in a family with late-onset severe childhood autosomal recessive muscular dystrophy (SCARMD). Later, mutations were described in other SCARMD families and in families with limb-girdle muscular dystrophy type 2D (LGMD-2D).
-ß (beta)-Sarcoglycan: involved in limb-girdle muscular dystrophy type 2E (LGMD2E).
- (gamma)-Sarcoglycan. Involved in severe childhood autosomal recessive muscular dystrophy (SCARMD) or limb-girdle muscular dystrophy type 2C (LGMD2C).
- (delta)-Sarcoglycan: problems found in patients who have a severe DMD-like course of muscular dystrophy, i.e. limb-girdle muscular dystrophy type 2F (LGMD2F).
-epsilon-Sarcoglycan: still being researched. *

Sarcolemma {Sarc-co-lem-ma}: The cell membrane surrounding the muscle fibres. It provides the infrastructure needed for the muscle to function. There are a group of muscular dystrophies linked to abnormalities in the proteins of the sarcolemma (cell membrane defects). This group of disorders can be called sarcolemmopathy (SLP). SLP includes: merosinopathy, DMD, Becker MD, four kinds of sarcoglycanopathies (SGP), dysferlinopathy and caveolinopathy. From: Eijiro Ozawa, Ichizo Nishino and Ikuya Nonaka, Brain Pathology 11, 218-230 (2001).

Sarcoma {sar-KOM-a}: Cancer arising in the connective tissues, sarcomas are generally divided into bone and soft-tissue tumors
Also: Soft tissue sarcoma is a malignant tumor. of the soft tissues of the body, such as muscle, fat, tendon, and the joint lining. (It is uncommon, with fewer than 6,000 cases a year in the United States.) When the sarcoma starts in bone rather than soft tissue, it is called osteogenic sarcoma (osteosarcoma), the most common of the type. *

Sarcotubular Myopathy: One of the congenital myopathies, this is a non-progressive form of muscle disease. There may be a slight delay of motor milestones. Walking or running may be clumsy. Intellect is not affected. **

Satellite cells: Sparse population of mononucleate cells found in close contact with muscle fibres in vertebrate skeletal muscle. During exercise, some damage is normally done to the muscle. It's repaired when immature muscle cells called satellite cells divide and fuse with the damaged muscle to help it regenerate. In some cases, where protein defects are present in the muscle, satellite cells can move in with the proper protein and, at least temporarily, boost muscle function.
Satellite cells are set aside during embryonic development, when muscle fibers form from the fusion of individual cells called myogenic precursor cells. During adult life, the satellite cells respond to the need for increased muscle mass by dividing. Some of the new cells become new myogenic precursor cells, and other satellite cells arise to replace them. Because satellite cells have this capacity for self-replacement, they're like stem cells with restricted potential. Some researchers have suggested stimulating satellite cells as a way of treating muscular dystrophy.

SCARMD = severe childhood autosomal recessive muscular dystrophy. This condition may be confused with DMD in boys, and in girls may be difficult to distinguish from the manifesting carrier state, though the mode of inheritance is completely different. Either sex may be affected, and creatine kinase levels are very high. The progression of the muscle weakness may be fast but is usually somewhat milder than DMD. Muscle biopsy shows an active muscular dystrophy, but the protein dystrophin that is defective in DMD is normal in the autosomal recessive form. *

Scaropenia: As Humans age, muscle mass is lost. The Greek word "sarco" refers to flesh and "penia" indicates a deficiency. "Sarcopenia" is a general term for the loss of skeletal muscle mass, quality, and strength, usually associated with the aging process, that can lead to frailty in the elderly. Examples of skeletal muscle properties that contribute to its overall quality include, but are not limited to: contractility, fiber size and type, fatiguability, hormone responsiveness, glucose uptake/metabolism and capillary density. Sarcopenia is believed to be due predominantly to disuse atrophy of skeletal muscle fibers. However, age-associated changes in myofibrillar protein metabolism, nutritional status, neuromuscular function and in the production of, or tissue responsiveness to trophic factors, may also represent important underlying causes of sarcopenia. Very little is known about which age-related changes in specific muscle properties (e.g., mass, strength, torque development, fiber type distribution, fatigue characteristics, contractile properties) significantly affect physical function and performance of specific tasks (e.g., walking, maintaining balance, IADLs).
Assumptions have been made that age-related changes in muscle mass are associated with a reduced metabolic rate (leading to obesity and increased risk for chronic diseases) and in the development of non-insulin dependent diabetes mellitus in old age. The extent to which such metabolic changes can be attributed solely to age-related loss of muscle mass or to complex changes in body composition (e.g., increases in body fat) remains to be established. Controversy also exists over other putative morbid consequences of sarcopenia, which include osteoporosis (e.g., potential relationship between muscle weakness and decreased bone quality), increased susceptibility to fracture (independent of risk of falling), and altered thermoregulation (e.g., decreased thermogenic capacity of muscle due to reduced mass). Based on: The National Institute on Aging (NIA) and the National Institute of Arthritis and Musculoskeletal Skin Diseases (NIAMS) http://grants.nih.gov/grants/guide/pa_files/PA_96_038.html
Also: Sarcopenia, the loss of muscle mass and function, is an important consequence of aging. The prevalence of sarcopenia, depending on the definition used, varies from 10% to 30% in men over the age of 60, and women over the age of 30. The principle component of the decrease in fat-free mass is in the loss of muscle mass; there is little change in non-muscle lean mass. Between 20 and 80 years of age, the cumulative decline in skeletal muscle mass amounts to 35%- 40%. The depletion of muscle mass does not result in weight loss because of the corresponding accumulation of body fat.
The loss of muscle mass results from a decrease in the number as well as a cross-sectional area of muscle fibers. There is a preferential atrophy of fast twitch, type II fibers. There is an increase in intramuscular fat and connective tissue. These changes reduce the contractile tissue volume available for locomotion and metabolic functions. Aging is associated with decreased synthesis of skeletal muscle proteins, and attenuated myosin heavy chain and actin synthesis rates, which are important also for adenosine triphosphate (ATP) generation of high-energy phosphate bonds for mechanical energy.
The loss of muscle mass that occurs with aging is associated with a reduction in muscle strength and power between 50 and 70 years of age, due primarily to muscle fiber loss and selective atrophy of type II fibers. Loss of muscle strength is even greater after the age of 70; 28% of men over the age of 74 can not lift objects weighing more than ten pounds over their heads. With increasing age, there is a progressive reduction in muscle power, the speed of strength generation, and fatigability: the ability to persist in a task.
Loss of muscle mass and strength leads to impairment of physical function, as indicated by the impaired ability to arise from a chair, climb stairs, generate gait speed, and maintain balance. The impairment of physical function contributes to loss of independence, depression, dependency, and increased risk of falls and fracture in the elderly. From: http://www.theantiagingdoctor.com/sarcopenia.htm

Scavenger cells: Any of a diverse group of cells that have the capacity to engulf and destroy foreign material, dead tissues or other cells.

Schwartz-Jampel Syndrome: Also known as chondrodystrophic myotonia, this syndrome affects children at birth who present with a variety of signs and symptoms including short stature with a short neck, flexion contractures, kyphosis (convex curve of the spine) and facial characteristics such as low set ears, 2 rows of eye lashes, narrow palpebral fissures, pinched nose and abnormalities of the teeth. Intellect is often impaired. There is no known cause for this disorder and no effective treatment is available. **

Sclerosis: A thickening or hardening of a body part, as of an artery, especially from excessive formation of fibrous interstitial tissue. A disease characterized by this thickening or hardening.

Scoliosis {sko-LEE-oh-sis}: Sideways deviation in the normally straight line of the spine. In the case of neuromuscular disorders, it results from muscular weakness or localized muscle imbalance. The curvature may be flexible at first with little rotation, but as the disorder progresses the curves become more pronounced and fixed. It can be treated with surgery with varying degrees of success. ** Also Scoliosis: Lateral or "sideways" curvature of the normally vertical line of the spine. Progressive spinal deformity may be associated with numerous neuromuscular and neurodevelopmental disorders (neurogenic scoliosis), such as cerebral palsy, spinal muscular atrophy, and Rett syndrome. The severity of the deformity varies, depending upon the degree of weakness, the nature and progression of the underlying disorder, or other factors.

Scrapie: Specifically, a TSE disease of sheep or goats. Scrapie is sometimes loosely used to refer to the abnormal form of the prion protein. *

Screening: Looking for evidence of a particular disease such as cancer in persons with no symptoms of disease. Checking for disease when there are no symptoms. %

Scrotum {SKRO-tum}: The pouch of skin that contains the testicles. #

Search engine: see www *

Second set rejection: Accelerated rejection of an allograft in an already immune recipient.

Secondary lymphoid organs: Organs in which antigen-driven proliferation and differentiation of B and T lymphocytes takes place.

Secretory component: A surface receptor on epithelial cells lining mucosal surfaces which binds dimeric IgA and transports it through the cell into mucosal secretions.

Seizures: Episodes of uncontrolled electrical activity in the brain. These abnormal electrical disturbances may lead to involuntary jerking, spasms, or rhythmic contraction and relaxation of certain muscle groups and impaired control of involuntary functions such as breathing or bladder or bowel control. There may also be loss of consciousness or sensory or behavioral abnormalities.

Selection: There are now several types of selection described and complex genetic research is learning more about how selection operates every day.
Natural Selection:Mutations occur from time to time in the nucleotide sequence of DNA. These changes provide a source of variation (without this, the code would simply be copied identically and no evolution would occur). The basic idea in natural selection is that certain mutations are beneficial for the organism and are thus selected for, becoming more and more widespread in the species.
The genetic code governs the production of proteins. If a change occurs in the genetic code (in the nucleotide sequence), then the new sequence may produce a different protein (this is not automatic, in some cases a change slips in and the old protein is still produced - see substitutions). Usually, the old protein does a specific job in the organism and in some way or another, every protein is vital to long term health. If the new protein does not't work properly, it will usually affect the health of the individual who inherits it. If the protein is so defective that the individual becomes infertile or dies prematurely, then the individual may produce less or no offspring (a measure called reproductive fitness). In this case, the mutation is eventually weeded out of the gene pool of the species (the people with the mutation have fewer children and eventually it dies out). If the mutation gives the individual a reproductive advantage (if it somehow helps them have more children - increases reproductive fitness), then the mutation will become more and more widespread in the population (eventually becoming universal). This is sometimes called positive selection. Over millions of years, a series of beneficial changes slowly accumulates that alters the genome of the species, always increasing reproductive fitness. Thus, while the mutations that occur are random, there is selection of those most likely to lead to more children being born. Hence, the contributions to succeeding generations are not random but are 'selected' by based upon whether they give a reproductive advantage or not. Calculations suggest that in the past 30 million years (since our split with from Old World Monkeys), more than a third of the changes in our amino acids have been the result of natural selection. On average, there is one adaptive change every 80 years.
Directional selection: Natural selection that favours the establishment of one particular advantageous mutation within a population, resulting in a change in phenotype (this is the external presentation of a genotype) in that direction. Directional selection occurs when the environment of a population is changing in some definitive way. This usually means that one extreme for the frequency distribution for some traits gradually becomes less adaptive as the environment changes and is selected against. Provided the population has sufficient variability and the change is not too rapid, the result will normally be to shift the frequency distribution in a direction that is adaptive relative to the changing conditions. The development of insecticide- resistant populations of insects or antibiotic resistance in bacteria are two examples of directional selection. If the change is very rapid, the population has low genetic/phenotypic variability, or another species is available that is already well-adapted to the changing environment, the population is question may well be excluded or restricted as a result of the changing conditions. Directional selection can cause the evolution of a species with time, but does not increase biodiversity
Stabilizing selection:Natural selection that acts to maintain the constancy of a species over successive generations. It involves selection against the extremes of the range of phenotypes for a particular characteristic. For example, babies whose birth weight is substantially below or above the average of 3.6 kg historically have a greater mortality than babies of average birth weight (although medical advances have now greatly reduced this pattern of selection in humans). Stabilizing selection is characteristic of relatively stable environments with high biological diversity. The latter means that most niches are filled. Under such conditions, the overall pattern of selection is against the extremes in the frequency distribution for most traits. The result is that the population tends to maintain the status quo with respect to prevailing adaptations. Another perspective is to assume that most populations are optimally adapted for the niche they occupy and that there is little opportunity to expand into adjacent niches that are already occupied by similarly well-adapted organisms. Stabilizing selection is the one mode that does not result in adaptive change and/or evolution.
Disruptive selection:If a population is exposed to different patterns of selection in different parts of its range, the sub-populations may well diverge with time, each responding to the local selection pattern. Such disruptive selection can also be viewed as different patterns of directional selection occurring within the range of a species. If gene flow is restricted between the sub-populations, they may well evolve into different species, given time for the development of isolating mechanisms that would serve to keep the populations distinct, even if they later come into contact. Disruptive selection can increase biodiversity In the extreme case, where one species evolves into several, the process is known as adaptive radiation. Disruptive selection can also operate within a species to produce distinctive morphotypes. The example of hooknose and jack phenotypes in male coho salmon is one such case. Where such selection generates pronounced differences between the sexes, as in the plumage and singing behavior of birds, the process is known as sexual selection. Sexual selection is probably best viewed as a special case of disruptive selection.
Neutral selection: Scientists now believe that many mutations may occur and have no effect on health. These mutations may become more common in a population solely due to random fluctuations, a process called neutral evolution. Kimura, a Japanese biologist found that most DNA variation is produced by neutral selection.
Purifying selection: It appears that some parts of the organism are super sensitive to mutations and can't tolerate ever minor changes to their structures. Any changes to the genes linked to these areas are ruthlessly weeded out. The genes that control the brain are an example. This constitutes a third type of evolution. It is characterized by silent substitutions far outnumbering replacement substitutions.

Selective renal arteriography {ar-ter-ee-OG-ra-fee}: Diagnostic method using X-rays and a special chemical to obtain a picture of the kidney blood vessels. #

Selenium: An essential trace mineral in the human body. This nutrient is an important part of antioxidant enzymes that protect cells against the effects of free radicals that are produced during normal oxygen metabolism. The body has developed defenses such as antioxidants to control levels of free radicals because they can damage cells and contribute to the development of some chronic diseases. Selenium is also essential for normal functioning of the immune system and thyroid gland. Also strongly implied in cancer prevention (especially of prostate cancer), research on this aspect continues. *

Self-renewal: Cycles of division that repeatedly generate at least one daughter equivalent to the mother cell with latent capacity for differentiation. This is the defining property of stem cells.

Selfish genes: The idea of Richard Dawkins (1976) proposing that organisms are automatons controlled by 'selfish genes' whose only imperative is to replicate at the expense of other 'selfish genes'.

Semen: The fluid that is released through the penis during orgasm. Semen is made up of sperm from the testicles and fluid from the prostate and other sex glands. *

Seminal vesicles {SEM-in-al VESS-I-kulz}: Glands that help produce semen. #

Seminoma {sem-in-O-ma}: A type of testicular cancer that arises from sex cells, or germ cells, at a very early stage in their development. #

Sense 1. In molecular biology, that strand of a DNA molecule whose sequence is represented in mRNA.
2. In molecular biology, an RNA molecule normally processed into mRNA and translated (rather than the
complementary sequence).

Sense strand: A gene has two strands: the sense strand and the antisense strand. The Sense strand is, by definition, the same 'sense' as the mRNA; that is it can be translated exactly as the mRNA sequence can.@@

Sensorimotor: Pertaining to both the sensory and motor aspects of a bodily function.

Sensory cortex (brain): The sensory cortex receives and processes sensory signals from the surface of the body. *

Sequelae: Plural of sequela, which is any abnormal condition that occurs subsequent to and/or is caused by disease, injury, or treatment.

Sequence: As a noun, the sequence of a DNA is a buzz word for the structure of a DNA molecule, in terms of the sequence of bases it contains. As a verb, "to sequence" is to determine the structure of a piece of DNA; i.e. the sequence of nucleotides it contains.@@

Sequencing (verb): Determination of the order of nucleotides (the base sequence) in a DNA or RNA molecule or the order of amino acids in a protein.
     -1953: DNA structure discovered
     -1977: Sanger sequencing technique developed
     -1988: Human Genome project initiated
     -1995: Influenza genome sequenced (5Mb)
     -1998: High throughput sequencing machine developed by PE Biosystems
     -2000: Drosophila genome sequenced (180Mb)
     -2001: Human genome rough draft (2.91Bb)
There are two basic approaches:
1). Sanger Sequencing technique: Limitation: DNA sequences less than 1kb long can only be sequenced. Therefore, the idea is to sequence shorter strands of DNA and computationally assemble these reads.
2). Shotgun sequencing: Obtain many reads of length of about 550 bases from different locations on the target molecule. Determine sequence by computationally assembling these reads.
Some sequencing terms:
     -Contig: The result of joining a collection of overlapping sequences or clones.
     -Scaffold: The result of connecting contigs using linking information from paired end reads from plasmids or BACs.
     -STS: A unique genomic locus (~less than 500bp) for which PCR has been developed.
     -EST: Single Raw sequence read from a cDNA clone.
     -SNP: Single nucleotide position in the genome sequence for which two or more alternative alleles are present.
     -BAC: A vector used to clone DNA fragments.
Overview: DNA sequencing usually involves these basic steps:
1). An organism is selected for study.
2). DNA is isolated from cells and purified.
3). DNA is cut into random, manageable sections that overlap each other.
4). The DNA fragments are inserted into packages for cloning.
5). The order of bases is read for each piece.
6). Use the overlaps to assemble the overall sequence of code.
Step 1: Polymerase Chain Reaction: PCR is used to generate many copies of DNA from an initially small sample. PCR is important when sequencing DNA because it creates millions of copies of a single DNA strand or fragment, which lets scientists perform thousands of reactions on the same string of DNA. For example, when a scientist wants to research the skin cells of an individual, rather than removing ten million or so cells, they instead take a few thousand or even a few hundred cells and isolate the desired DNA, which they then replicate using PCR. The result is several million strings of perfectly alike DNA.
Step 2: A terminator base (tagged ddNTPs (dideoxyribonucleic acid triphosphates)) is inserted that stops the copying process. Where it stops is random. A number of different strings of DNA are created that all start at the same place but that end at different bases (some segments are shorter, some longer).
Step 3: Gel Electrophoresis: Solutions containing the DNA fragments are placed within a thick gel. A mild electric current is applied to the gel, causing one end of the gel to have a positive charge and the other to have a negative charge. The fragments begin to move from the negative end of the gel towards the positive end, the short strings move faster than the larger ones. The DNA becomes spread out over the gel with the smaller strands ending up closer to the positive side of the gel and the longer pieces on the negative side. Each string ends with a terminator (a ddNTP), which researchers detect with X-rays or now, more commonly, with computerized detectors that read fluorescent colored dyes (one color for each of the four bases).
Step 4: Computers detect dye colors of the DNA primer fragments (the known nucleotide starting each fragment) and the letter of the nucleotide following the primer (the first location); the computer continues to move along, detecting the letter at each subsequent location until the termination sequence. The computer reads two pieces of information, the position of the termination base (which indicates the length of the fragment) and the color (that identifies the base that ends the fragment).
The fragments are sorted into a hierarchy based on their length and using the overlapping code:
The code sequence for this overall fragment is ascertained by looking at the terminal bases (from the top down in this example), yielding: T G A T G T C T
Another useful overview.
Step 1: cut the DNA with restriction enzymes
Step 2: clone the DNA into BACs and insert them into Bacteria for storage.
Step 3: BACs are fingerprinted and cut into fragments. Overlaps are used to see the order of the BAC clones. Each BAC is mapped using landmarks to see where its DNA came from within the human genome - this creates a physical map.
Step 4: Each BAC is cut into smaller overlapping fragments to sequence.
Step 5: The sequences from all of these tiny fragments are reassembled into contigs (contiguous sequences).
Step 6: We know the order and the overlap of the BACs (from step 3) so now, longer and longer sequences can be put into the correct order.
Step 7: Once the whole genome sequence is known, it has to be annotated. The information about genes and the proteins they encode has to be ascribed to specific sequences in the code.
Genome maps:depict the order in which genes, genetic markers, and other landmarks are found along the chromosomes.
Genetic linkage maps:also known as linkage maps. The order of specific DNA markers along a chromosome, discovered by examining how they are inherited through generations. Gives a relative position of markers to each other (not a physical location of the markers). Also: Genetic linkage maps assign chromosomal locations to genetic landmarks - either genes or distinct short sequences of DNA - on the basis of how frequently markers are inherited together. Linkage maps exploit a phenomenon called recombination or crossing over. As developing sperm and egg cells divide, pairs of maternal and paternal chromosomes sometimes break and exchange pieces with one another. Genes and markers that are physically close to one another on the chromosome are said to be tightly linked; they are much less likely to be separated by recombination than are gene markers that are located far apart. In 1994, international collaborators published a comprehensive linkage map charting more than 5,000 markers and more than 400 genes. After scientists use genetic linkage maps to assign a gene to a relatively small area on a chromosome, they next examine the region up close to learn the gene's precise location. To do this, scientists turn to physical maps.
Physical maps: Details the exact physical location of landmarks in the genome. Distances between landmarks are measured in base pairs. Also: To construct a physical map, a chromosome (or the whole genome) is first broken into smaller pieces of DNA. Scientists then copy or clone the pieces in the laboratory, obtaining millions of identical copies of specific DNA segments. They next line up the clones to reflect the order that existed on the original chromosome. Information about the location and known genetic content of these unique and ordered DNA fragments (called contigs) is stored in a computer, while clones of the ordered pieces themselves are stored in laboratory freezers. When genetic linkage maps indicate that a gene lies in a particular region, scientists can go to the freezer and retrieve clones of interest; they then use the clones as the raw material for DNA sequencing - actually identifying the order of each and every chemical base in the gene.
Benefiting from the increasingly detailed maps and sophisticated DNA sequencing techniques and tools, scientists are mapping and isolating new disease genes at the rate of several per month.
Landmarks: Unique chemical sites that identify specific coordinates on a chromosome. Examples: RFLPs, VNTRs, STSs.

Sequencing detail:
There are two approaches to sequencing, the hierarchical shotgun method and the whole-genome shotgun method.
The hierarchical shotgun method
This is a map-based, clone by clone method. The genome is broken into small pieces. Pieces are sequenced. Pieces are reassembled. The first set of large segments is used to make a physical map which determines the origin of each segment and the relative position of segments. Each segment is again cut into small overlapping pieces and the sequence of each is determined (called shotgun sequencing). The overlaps are now used to reassemble the overall sequence of the larger segments. Larger segments are added together until the whole genome is complete.
This method is very reliable but has been slow in the past. This is the primary method used by the HGP.
The whole-genome method:
The whole genome is shattered into fragments. The small fragments are sequenced individually. A computer reassembles the overall sequences. No map is used. This method is fast but not as reliable. This is the method primarily used by Venter and the Celera company.
Eventually, both methods were used in combination.
A puzzle analogy:The cut pieces of the puzzle are all turned picture side up (equivalent to sequencing). In the whole-genome method, we take each piece individually and try to fit it into each other piece to see where it fits. In the hierarchical shotgun method, we compare each piece with the picture of the puzzle on the box lid (equivalent to the physical map) and we try to piece together like pieces with like pieces. (so, we start by piecing together blue pieces that make up the sky and white ones that make up the clouds). This method requires the construction of the map to guide out final assembly.
The Sanger approach is also called the chain-termination method (also called the dideoxy chain termination method) and was developed in 1977 by Fred Sanger at the MRC Laboratory of Molecular Biology. It is based on two facts about DNA synthesis:
1. When a single stranded DNA template is placed together with the 4 deoxynucleotide triphosphates (dNTP's) and a short primer that hybridizes to the beginning of the DNA template, DNA polymerase will direct the synthesis of a complementary strand (complementary to the DNA strand that is to be sequenced).
2. If di deoxynucleotide triphosphates (di dNTP's) are included, DNA strand elongation will terminate when a didNTP is incorporated. This is because di deoxynucleotides lack a 3' hydroxyl group which is needed to form a bond to an adjacent nucleotide. In the original Sanger method, four reaction tubes are set up:
The A, T, G, C tubes each contain:
>1. The DNA template to be sequenced.
>2. A primer sequence which is complementary to the beginning of the template to be sequenced. (Therefore some information about the sequence has to be known in order to use this protocol)
>3. DNA polymerase.
>4. All four dNTP's (dATP, dTTP, dGTP, dCTP)
>5. One radioactively labeled dNTP, usually 32P dATP. This is needed to expose X-ray film and results in an autoradiogram of a polyacrylamide gel.
>6. One di-deoxynucleotide triphosphate per tube: A reaction tube: di dATP; T reaction tube: di dTTP; G reaction tube: di dGTP; C reaction tube: di dCTP
The ratio of the di deoxynucleotide to the deoxynucleotide in each tube is one to one hundred. So that once for every 100 nucleotides added to the nucleotide in question in the template, a di deoxy form of the nucleotide is added. For example, in tube A, each time a thymine nucleotide is encountered in the sequencing reaction, a deoxyadenosine is added for 99 out of 100 times. One out of 100 times a di deoxyadenosine is added. At that point, the synthesis of the strand will terminate. The reaction in the tube will result in collections of DNA strands of differing lengths which reflect the position of the thymine nucleotide in the template strand in question. When the reactions are complete, formamide is added to denature the DNA template from the newly synthesized strands. Each reaction is loaded into a separate lane of a polyacrylamide gel. The gel is fine enough to resolve DNA fragments that differ by a single nucleotide. After electrophoresis, the gel is exposed to X-ray film and an autoradiogram is made. The bands correspond to the lengths of fragments in each reaction tube. The sequence is read from the bottom of the gel to the top. The DNA strand that was sequenced is complementary to the sequence read on the gel.
This method was refined by using ddNTPs tagged with four fluorescent dyes of different colors, contained in one test tube. Computers are now used to detect the different colors of the ending pieces of the DNA segments after Gel Electrophoresis to determine the letters and length of the DNA chain.
Summary:The Sanger approach involves copying DNA strands with dNTP (deoxyribonucleic acid triphosphates) and terminating them with tagged ddNTPs (dideoxyribonucleic acid triphosphates), which will show the location of the nucleotides in the strands though the use of X-ray machines. This technique was very slow and tedious, usually taking many years to sequence only a few million letters in a string of DNA that often contain hundreds of millions or even billions of letters. However, because of this process's accepted accuracy and the lack of new techniques, many researchers still use a similar method today. The recent advances in automated DNA sequencing still follow Sanger's basic protocol, however, researchers and companies have modified the original method to make sequencing automated, faster, safer, easier, cheaper and more accurate.

Sequencing-by-hybridization (SBH): Sequencing by hybridization is a novel DNA sequencing technique in which an array (SBH chip) of short sequences of nucleotides (probes) is brought in contact with a solution of (replicas of) the target DNA sequence. A biochemical method determines the subset of probes that bind to the target sequence (the spectrum of the sequence), and a combinatorial method is used to reconstruct the DNA sequence from the spectrum.

Seroma: Collection of tissue fluid. #

Serotonin (3-[2-aminoethyl]-5-indolol): A vasoconstrictor found in many tissues of the body that is present in relatively high concentrations in portions of the central nervous system (e.g., hypothalamus, basal ganglia, etc.). Serotonin functions as a neurotransmitter, regulating the delivery of messages between nerve cells (neurons). This neurotransmitter is thought to play some role in regulating consciousness and mood states. Serotonin is also present in other tissues of the body such as the intestines and blood platelets.

Serum: The clear liquid that separates from the blood when it is allowed to clot. This fluid retains any antibodies that were present in the whole blood.

Serum sickness: A hypersensitivity reaction consisting of fever, rashes, joint pain and glomerulonephritis, resulting from localization of circulating, soluble, antigen-antibody complexes, which induce inflammatory reactions. Serum sickness was originally induced following therapy with large doses of antibody from a foreign source - e.g. horse serum.

Sex Chromosome: The 23rd chromosomal pair, where the sex of the unborn child is determined. Each female carries two X chromosomes and each male carries one X and one Y chromosome. At conception, a child receives an X chromosome from mom and either an X chromosome (resulting in a female child) or a Y chromosome (resulting in a male child) from dad. **

Shingles: See Herpes zoster. ##

Shotgun cloning: see sequencing.

Shotgun sequencing method: see sequencing.

Shunt: A catheter (tube) that carries fluid from one place in the body to another. #

Sialic acid {Sigh-al-ick} scientific name: N-acetylneuraminic acid (NANA)
-Recent findings in the study of hereditary inclusion body myositis imply that a genetic defect causes an enzyme problem that affects the production of sialic acid, in turn affecting muscle cells. In the present theory, as I understand it, if sialic acid is low, there will be abnormal accumulation, or storage, of certain waste protein products in the muscle cells of affected individuals. As these products build up, they form inclusion bodies in the muscle cells, the cells become damaged and gradually lose their ability to function properly, causing disease symptoms. -Sialic acid is a type of glycoprotein.
-A blood test exists for Sialic Acid: Lipid-associated sialic acid (LSA, LASA-P) in plasma.
-Sialic acid is already used in medicine as high levels of sialic acid are associated with malignancies and inflammatory conditions. This nonspecific test may be elevated in a variety of chronic, benign medical conditions. Elevations in blood LASA levels have been reported in patients with mammary (63%), gastroenteric (65%), pulmonary (79%), and ovarian (94%) neoplasms as well as those with leukemia (86%), lymphoma (87%), melanoma (84%), sarcoma (97%), and Hodgkin disease (91%). LASA levels can also be elevated in patients with certain benign diseases, including inflammatory disorders. Thus, like carcinoembryonic antigen (CEA), the assay for LASA does not have the specificity or sensitivity necessary for cancer detection. However, recent studies have suggested that LASA levels may be useful in monitoring the course of therapy and detecting disease recurrence in certain cancer patients. Last section from: http://www.labcorp.com/datasets/labcorp/html/chapter/mono/sc033500.htm *

Sialidosis: A lysosomal storage disease in which deficiency of the enzyme neuraminidase leads to abnormal accumulation of certain complex carbohydrates (sialyloligosaccharides) in particular tissues and organs. There are different variants of the disorder, based upon age of onset, severity, and other factors. Sialidosis type I, also known as "cherry-red-spot myoclonus syndrome," usually becomes apparent during the second decade of life. Associated symptoms include the development of characteristic, cherry-red circular areas within the middle layers of the eyes; gradual loss of visual clarity; and sudden, involuntary, "shock-like" contractions (myoclonus) of muscles of the arms and legs. The myoclonus is progressive in nature and may be triggered by voluntary movements (action myoclonus) or certain external stimuli, such as sound (reflex myoclonus). Sialidosis is inherited as an autosomal recessive trait.

Sialorrhea: Excess production of saliva, or increased retention of saliva in the mouth, due to difficulty swallowing.

Sickle cell anemia: A genetic disease in which the hemoglobin protein is mutated, giving red blood cells a twisted shape that may painfully block circulation. This often leads to medical crises and may cause an early death. The recessive disease occurs in children who have inherited the mutated gene from both their parents, mostly among people of African or Mediterranean origin. ###

Side effects: Secondary effects of drugs used for disease treatment. ##
Side effects: Problems that occur when treatment affects healthy cells. For example, common side effects of cancer treatment are fatigue, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores. % Also: Side effect: An effect of a drug that is not the main or intended effect. Side effects may be of no concern, or they may be bothersome or even dangerous, in which case they may limit the upper dose a patient can tolerate. Side effects are also called adverse effects.

Sigmoidoscope {sig-MOY-do-skope}: A lighted instrument used to view the inside of the lower colon. #

Sigmoidoscopy {sig-moy-DOS-ko-pee}: A procedure in which a doctor looks inside the rectum and the lower part of the colon (sigmoid colon) through a lighted tube. The doctor may collect samples of tissue or cells for closer examination. Also called proctosigmoidoscopy or "procto".

Signal transduction pathway: A cascade of signals involved in the process of gene transcription and cell growth. *

Signs: These are what people can see - a skin rash is a sign of illness that the Doctor can see. *

Simian vacuolating virus 40 or Simian virus 40 (SV40): a polyomavirus that is found in both monkeys and humans. Like other polyomaviruses, SV40 is a DNA virus that has the potential to cause tumors, but most often persists as a latent infection.
The virus was first identified in 1960 in cultures of rhesus monkey kidney cells that were being used to produce polio vaccine. It was named for the effect it produced on infected green monkey cells, which developed an unusual number of vacuoles. The virus is dormant and shows no visible effects in Rhesus monkeys. The virus has been found in many macaque populations in the wild, where it rarely causes disease. However, in monkeys that are immunodeficient;due to, for example, infection with Simian immunodeficiency virus SV40 acts much like the human JC and BK polyomaviruses, producing kidney disease and sometimes a demyelinating disease similar to PML. In other species, particularly hamsters, SV40 causes a variety of tumors, generally sarcomas.
The molecular mechanisms by which the virus reproduces and alters cell function were previously unknown, and research into SV40 vastly increased biologists' understanding of gene expression and the regulation of cell growth.
"SV40 is a DNA tumor virus thrust upon human populations primarily as a contaminant in various vaccine preparations. Some estimates suggest that millions of people are currently infected with the virus. The virus causes primary brain tumors, bone tumors, lymphomas, and mesotheliomas when injected into some rodent models. It has also been detected in a similar spectrum of human tumors. However, epidemiological studies have failed to conclusively demonstrate a higher incidence of disease in affected populations. To date, over 60 reports from 49 different laboratories have shown SV40 sequences in tissues from human cancer patients. Six studies, however, have failed to detect evidence of virus in similar tissues. Some have suggested that SV40 may act as a cocarcinogen with asbestos to cause mesothelioma formation, or that it may be responsible for the 10-20% of mesotheliomas with no reported history of asbestos exposure. This report briefly covers the historical evidence for SV40 carcinogenesis and then covers experiments now underway to better understand the role of SV40 in human mesotheliomas. Inhal Toxicol. 2006 Nov;18(12):995-1000.The role of SV40 in malignant mesothelioma and other human malignancies.Pershouse MA, Heivly S, Girtsman T. also see mesothelioma.

Simulation (relating to radiation): A process involving special X-ray pictures that are used to plan radiation treatment so that the area to be treated is precisely located and marked for treatment. #

Single-nucleotide polymorphisms (SNPs) {Snips}: DNA sequence variations that occur when a single nucleotide (A, T, C, or G) in the genome sequence is altered. Each variation is responsible for a unique gene allele.
Single Nucleotide Polymorphisms (SNPs) represent a natural genetic variability at high density in the human genome. A synonymous expression is biallelic marker corresponding to the two alleles that may differ in a given nucleotide position in a diploid cell. A SNP represents an alternate nucleotide in a given and defined genetic location at a frequency exceeding 1 % in a given population. SNPs may occur in noncoding regions (nonfunctional SNPs) as well as in coding regions (cSNPs or functional SNPs). cSNPs often generate polymorphic variants of expressed proteins that sometimes affect their functional properties. Since SNPs are biallelic they are not as informative as, for example, microsatellites which can have many alleles and may be associated with rare diseases. The allelic frequencies of a given SNP may vary in different populations. On average, an SNP is believed to be present in every 300 to 1000 bases in humans. Thus there may be several million nucleotide positions in the human genome at which there is some degree of natural variation. From: The Chinese National Human Genome Center, Beijing (CHGB)
Scientists believe SNP maps will help them identify the multiple genes associated with such complex diseases as cancer, diabetes, vascular disease, and some forms of mental illness. These associations are difficult to establish with conventional gene-hunting methods because a single altered gene may make only a small contribution to disease risk.
Scientists have identified about 10 million locations where single-base DNA differences occur in humans. This information promises to revolutionize the processes of finding chromosomal locations for disease-associated sequences and tracing human history.
Also: Single nucleotide polymorphism (SNP) A DNA variant that represents variation in a single base. A common SNP can be defined as a locus at which two SNP alleles are present, both at a frequency of 1% or more. Across the human genome there could be 10 million common SNPs.

Single photon emission computed tomography (SPECT): A noninvasive scanning procedure during which a radioactive substance known as a radionuclide is introduced into the body to help evaluate the function and structure of certain organs or tissues. The amount of the substance taken up by particular tissues may depend upon the amount of blood flow within such regions. For example, absence of radionuclide uptake in a targeted region may indicate a lack of blood flow in certain areas. Following intravenous administration of the radioactive compound, a specialized rotating camera detects the radiation emanating from the radionuclides in the form of particles known as protons. The recorded images may produce colorized, horizontal and vertical cross sections and be reconstructed by computer to create three-dimensional images. By evaluating the blood supply to particular tissues, SPECT may be particularly helpful in detecting certain changes within the central nervous system or the heart.

Single-gene disorder: Hereditary disorder caused by a mutant allele of a single gene (e.g., Duchenne muscular dystrophy, retinoblastoma, sickle cell disease). %
Also: Single gene disorders: Diseases caused by a single mutation in a single gene. These are rare diseases, There are about 1000 single gene disorders that affect from 1 to 4 percent of the population. Single gene disorders are relatively easy to research (in contrast to common diseases that involve two or more genes in interaction). One of the early results of research will be reliable predictive screening tests followed by improved and new treatments. *

Single-stranded DNA: DNA normally exists in two complementary strands that form a double helix, but it can be separated into two strands of single-stranded DNA. Separation becomes necessary when genes are being transcribed or when DNA is replicated prior to cell division. ###

Sinus bradycardia: an abnormally slow heart rate (i.e., of less than 60 beats per minute).

Sjogren's syndrome: A chronic, slowly progressive autoimmune disorder characterized by dryness of the eyes and mouth and recurrent salivary gland enlargement. This is called the sicca complex and is diagnostic. ***

Skewed X inactivation (sometimes called nonrandom X inactivation): see X inactivation.

Slow-reacting substance of anaphylaxis (SRS-A): A group of leukotrienes released by mast cells during anaphylaxis which induces a prolonged constriction of smooth muscle. This prolonged constriction is not reversible by treatment with antihistamines.

Small intestine: The part of the digestive tract that extends from the stomach to the large intestine. #

SNP Single Nucleotide Polymorphism {SNIP} A type of polymorphism in which two chromosomes differ in a given segment by the identity of a single base pair.

SNP noise: Inter-patient variability. Small genetic (single base pair) differences between individuals complicate doing research on genetic diseases. To overcome this, researchers are using temporal series - looking at effects and changes in one individual over time.

Sociobology: Controversial field that studies how natural selection, previously used only to explain the evolution of physical characteristics, shapes behavior in animals and humans. The theory has contributed to the understanding of certain evolutionary traits in the animal world, such as how instinctive parental behaviors of animals are determined in part by the need to ensure survival of offspring. A related aspect of sociobiology deals with altruistic behaviors in general. In a theory called kin selection, animals that behave altruistically would have their genes passed on by helping relatives who share their genes survive to reproduce, just as they would by producing offspring of their own. The theory first gained attention when Edward O. Wilson of Harvard published Sociobiology (1975); it became controversial when he proposed extending the theory to explain human social behavior and psychological patterns. Critics charged that this application of sociobiology was a form of genetic determinism and that it failed to take into account the complexity of human behavior and the impact of the environment on human development.

Soft Tissue Sarcoma: Soft-tissue sarcomas are tumors that arise in muscles, tendons, fat, and blood vessels - the soft tissues that connect, support, and surround other parts of the body. About one-half of cases occur in the arms and legs, but soft-tissue sarcomas can develop at any site in the body. #

Somatic mutation: Gene changes that arise within individual somatic cells and accumulate throughout a person's lifetime; also called acquired mutations. It is important to understand that somatic mutations are not passed on to children, they die with the cell they occurred in, or with the individual in which they occur. Somatic mutations can produce several effects to the cell: kill the cell, make the cell cancerous, damage the operation of the cell. *

Somatic cell nuclear transfer (SCNT): The transfer of a cell nucleus from a somatic cell into an egg from which the nucleus has been removed. A cloning method used in research to develop new therapies for disease. Recent research in SCNT has shown that a patient's own genetic material could be used to develop stem cell therapies specifically tailored to that individual's medical condition, thus avoiding an immune rejection response.
SCNT involves the removing the nucleus of an egg cell, replacing it with the material from the nucleus of a "somatic cell" a skin, heart, nerve or any other non-germ cell), and stimulating this cell (through electric shock) to begin dividing. This egg cell is never fertilized by sperm. The genetic material within the cell is nearly identical to the genetic material extracted from the skin or other cell.
Once the cell begins dividing, stem cells can be extracted from it five to six days later, just as they can be extracted from embryos created through in vitro fertilization. By using SCNT, scientists hope to understand how the protein factors in the egg cell cause these already specialized somatic cells to become stem cells. Once researchers learn how this cell "de-differentiation" occurs, they will no longer need to use egg cells. The sole purpose of this technology is to develop treatments for diseases and medical conditions. *

Somatic cells: All body cells except the reproductive cells - any cell of the body other than egg or sperm. *

SOS Response: A set of inducible physiological reactions that help a cell survive after strong environmental stress, such as ultraviolet light. The response includes enhanced DNA repair, transient inhibition of cell division, increased frequency of mutagenesis to name a few. Hypermutation is seen in E. Coli (adaptive mutation), presumably to offer the cell more gene varieties to respond to the stress. Adaptive mutation is controlled (positively and negatively) by the SOS system.

Southern blotting: A technique for transferring electrophoretically resolved DNA segments from an agarose gel to a nitrocellulose filter paper sheet via capillary action; the DNA segment of interest is probed with a radioactive, complementary nucleic acid, and its position is determined by autoradiography.

Spasmodic dysphonia (SD): A manifestation of dystonia. SD involves the muscles of the larynx and surrounding muscles and therefore involves speech. In individuals with SD, speech in blocked by intermittent spasms of the voice box (larynx).Spastic paraparesis: Paralysis usually involving groups of muscles; characterized by excessive tone and spasticity of muscles, exaggeration of tendon reflexes, positive Babinski's reflex, no atrophy or wasting, except from prolonged disuse, and absence of reaction of degeneration. This form of paralysis is due to lesions of the upper motor neurons or the cerebrum. ***

Spasmodic torticollis (ST): A form of dystonia involving the muscles of the neck, and therefore called "cervical dystonia." As a result of the abnormal involuntary contractions of the neck muscles, the head may be rotated, tilted, flexed, extended, or any combination of these postures. The movements may be quick, sustained, or patterned and, therefore, may be associated with tremor.

Spasmolytic: Antispasmodic; referring to agents that may eliminate or relieve spasms, typically of involuntary (i.e., smooth) muscle, such as within the arteries, the intestine, the ring-shaped muscles around certain natural openings or passages (sphincters), the bladder, the muscular tubes that carry urine from the kidneys to the bladder (ureters), etc.

Spasticity: An abnormal increase in muscle tone that may be caused by certain types of damage to the nerve pathways regulating muscles. Spasticity is a common complication of cerebral palsy, brain injuries, spinal cord injuries, multiple sclerosis, and stroke. Spasticity can lead to incoordination, loss of function, pain, and permanent muscle shortening, or contracture.

Species barrier: When a disease infects animals of one species but does not cross over into other species. Crossover is a very serious event as a disease may be much more severe in the second species. *

Speculum {SPEK-yoo-lum}: An instrument used to widen the opening of the vagina so that the cervix is seen more easily. #

Sperm banking: Freezing sperm for use in the future. This procedure can allow men to father children after loss of fertility. *

Spinal cord: The spinal cord transmits messages between the brain and the rest of the neurons in the body. Spinal cord: The cylindrical structure of nerve tissue that, together with the brain, comprises the central nervous system. The spinal cord is an extension of the medulla oblongata--which is part of the lowest region of the brain (brainstem)--and is contained within a central canal in the spinal column. The spinal cord and the brain are surrounded by a protective, 3-layered membrane (meninges). Cerebrospinal fluid (CSF) flows through the cavities (ventricles) of the brain, the spinal cord's central canal, and the space between the middle and inner layers of the meninges (subarachnoid space). The spinal cord consists of an inner core of gray matter and surrounding areas of white matter, composed of bundles of myelinated nerve fibers (axons) known as spinal tracts. These include ascending tracts that carry sensory impulses up the spinal cord to the brain and descending tracts that transmit motor impulses from the brain down the spinal cord. Nerves emerge from both sides of the spinal cord (i.e., spinal nerves) through the narrow gaps (foramina) between bones of the spinal column (vertebrae). The spinal nerves, which are attached to the spinal cord by specialized nerve bundles (spinal nerve roots), contain both motor and sensory neurons.

Spinal Cerebellar Degeneration: An autosomal dominant group of degenerative disorders with symptoms that include gait ataxia, dysarthria, spasticity, dystonia, dementia, loss of vision and hearing and peripheral neuropathy. Onset of symptoms is usually between the ages of 20 and 40 years. Most people will eventually lose their ability to walk. Life expectancy is shortened. **

Spinal Fusion: A surgical procedure done to correct scoliosis. In this procedure, the vertebrae in the spine are surgically joined. **

Spinal Muscular Atrophy: The muscle wasting or atrophy in this genetic disorder results from loss of signals from nerve cells in the spinal cord. An autosomal recessive disorder of muscle weakness and wasting caused when the motor nerves that stimulate and control muscles fail to function. As a result, the muscles atrophy. There are a number of types of SMA, and a variety of presentations of the disorder. Severity of symptoms can range from life threatening in Type I SMA, to mild weakness in the adult form. At present, there is no treatment or cure. **

Spleen: A lymphoid organ in the abdominal cavity that is an important center for immune system activities.

Splice variant: Transcripts are not always processed the same way. Sometimes an exon is left out. Sometimes an extra exon is included. Exons can be extended or truncated. These variations create multiple alternative splice forms of a gene sequence (Splice variants). As a result, one gene can encode multiple versions of mRNA, leading to multiple proteins. Each splice form of an RNA sequence holds instructions for a different protein. And so the biological complexity of human life unfolds. Splice variants are sequences that occur naturally within the cells and tissues of individuals. The physiological activity of splice variant products and the original protein, from which they are varied, may be the same (although perhaps at a different level), opposite, or completely different and unrelated. In addition, variants may have no activity at all. When a variant and the original sequence have the same or opposite activity, they may differ in various properties not directly connected to biological activity, such as stability, clearance rate, tissue and cellular localization, temporal pattern of expression, up or down regulation mechanisms, and responses to agonists or antagonists.
Also see alternative splicing.

Splice mutation: Point mutation that alters the protein product by preventing normal post-transcriptional processing of RNA. *

Spondolytic polyradiculopathy: Inflammation of one or more vertebrae with diffuse root involvement. ***

Spongiform encephalopathy (SES): A disease of the brain, see Prion. *

Spontaneous disease: In medicine, spontaneous refers to disease arising without apparent cause. Not inherited. See acquired disease. See also sporadic.

Spontaneous mutation: A mutation arising from a mistake during DNA replication (not caused by an external mutagen). *

Spontaneous remission: see remission.

Sporadic {SPORE-rad-ic}: Occurring occasionally in a random or isolated manner.

Sporadically: Occurring intermittently, randomly, or in isolation.

Sputum: Secretions produced by the lungs. ##

Squamous cell carcinoma: Cancer arising from the skin or the surfaces of other structures, such as the mouth, cervix, or lungs. ##

SSRIs: Selective serotonin reuptake inhibitors. Drugs belonging to this class are antidepressant agents that selectively inhibit the absorption of serotonin at certain nerve membranes (e.g., presynaptic neuronal membranes). These drugs increase the concentration of serotonin within the central nervous system and enhance serotonin's neurotransmission activities.Stage: The extent of an illness - how far it has progressed. In cancer, especially whether the disease has spread from the original site to other parts of the body. %

Staging: Performing exams and tests to learn the extent a disease has progressed. ##

Stain (Staining): Different stains are used to study tissue samples in biopsies. Different chemicals and abnormalities in the tissue react and "show up" when exposed to different types of stains. These are important tests in diagnosis. *

Stem cell: A cell that can continuously produce unaltered daughters and also has the ability to produce daughter cells that have different, more restricted properties.

Stem-cell homeostasis: Persistence of tissue stem-cell pool throughout life. Requires balancing symmetric self-renewal with differentiative divisions at the population level, or sustained asymmetric self-renewal.

Stem cells: Single cells that have the capacity 1) to self-renew (make more stem cells) as well as 2) to differentiate into and to make specialized cell types (such as nerve cells, muscle, blood, etc.).
' Adult stem cells: Stem cells in the developed organism; these include the various types of multipotent and unipotent stem cells, but to date do not include known pluripotent stem cells.
' Embryonic germline (EG) cells: EG cells are pluripotent stem cell lines derived from the primitive germline cells that exist between the blastocyst stage of development until their conversion within gonads to egg or sperm stem cells. Their properties are similar to those of ES cells.
' Embryonic stem (ES) cells: ES cells are pluripotent cell lines established, usually, from the inner cell mass of the blastocyst stage of development. Within the population of cultured ES cells are cells that can produce more ES cells, or under conditions of differentiation, give rise to collections of cells that include most, if not all cell types that can be found in a postimplantation embryo, fetus, or developed organism, but not trophoblast or placenta. To date no ES cells cultured in vitro can give rise to developed organisms or even developed organs. A test of pluripotency of mouse ES cells is to inject them into blastocysts prior to implantation; the progeny of these cells can participate in all germline and somatic tissues along with host blastocyst-derived cells.
' Multipotent stem cells: Stem cells whose progeny are of multiple differentiated cell types, but all within a particular tissue, organ, or physiological system. For example, blood-forming (hematopoietic) stem cells (HSC) are single multipotent cells that can produce progeny that include HSC, blood cell-restricted oligopotent progenitors, and all cell types and elements (e.g., platelets) that are normal components of the blood.
' Pluripotent stem cells: Stem cells that include in their progeny all cell types that can be found in a postimplantation embryo, fetus, or developed organism, but not embryonic components of the trophoblast and placenta (these are usually called extra-embryonic).
' Totipotent stem cells: Stem cells that include in their progeny all cell types that can be found in an embryo, fetus, or developed organism, as well as the cells that form the embryonic components of the trophoblast and placenta.
' Unipotent stem cells: Stem cells that self-renew as well as give rise to a single mature cell type; e.g., spermatogenic stem cells.

Stemness: Unproven notion that different stem cells are regulated by common genes and mechanisms.

Stereotactic: refers to use of precise coordinates to identify deep structures of the brain. The coordinates may be obtained by fitting a patient's head with a special frame and taking a CT or MRI scan. The position of the brain structures relative to the frame permits fine localization of the deep brain structures. Stereotactic methods are used during brain surgery for tremor, Parkinson's disease, and dystonia. These brain structures are located with precise, three-dimensional coordinates.

Stereotaxis {stair-ee-o-TAK-sis}: Use of a computer and scanning devices to create three-dimensional pictures. This method can be used to direct a biopsy, external radiation, or the insertion of radiation implants. #

Stereotypic: Inappropriate, persistent repetition of particular bodily postures, actions, or speech patterns. These are typically involuntary, rhythmic, coordinated, and purposeless movements, postures, or vocalizations that may appear ritualistic or purposeful in nature. Stereotypies may be associated with a variety of neurologic and behavioral disorders, such as Tourette syndrome, obsessive-compulsive disorders, Rett syndrome, restless legs syndrome, schizophrenia, and autism.

Stereotypical: Conforming to a repetitive pattern as in repetition of particular movements or gestures.

Steroid {Steer-roid}: A term applied to a large group of substances chemically related to sterols. Steroid hormones include those of the adrenal cortex. The cortex or outer portion of gland produces a hormone called cortisone. Prednisone is a cortisone preparation and is an example of a steroid drug. **
Also: A type of hormone drugs that are used to relieve swelling and inflammation. #

Sticky ends: After digestion of a DNA with certain restriction enzymes, the ends left have one strand overhanging the other to form a short (typically 4 nt) single-stranded segment. This overhang will easily reattach to other ends like it, and are thus known as "sticky ends". @@

Stiffness, Cramps and Twitching see appendix - Quest

Stoma: An artificial opening between two cavities or between a cavity and the surface of the body. ## An opening in the abdominal wall; also called an ostomy. #

Stomatitis: {Stoma-Tight-us} Temporary inflammation and soreness of the mouth. ##

Stool: The waste matter discharged in a bowel movement; feces.

Strains (of a Disease): Different forms of a disease, usually with different characteristics from other forms. These are known as separate strains. *

Stretch reflex: Contraction of a muscle stimulated by rapid stretching.

Stretch-loop circuits: Pathways of electrical impulses along specific nerve fibers (alpha motoneurons) that result in a "stretch" reflex in a muscle.

Stress: The research literature does not agree about what phenomena the term stress includes and which it excludes. Stress is equated with 'anxiety', 'conflict', 'frustration' and 'defense'. The dictionary definition uses words such as: strain, pressure and force.
Our stress depends upon how we see life. There is no situation that in itself will cause us distress. It really depends on how the individual perceives and interprets the situation, and the individual's 'coping skills'. Thus some people react to hard work and responsibility with worry and anxiety while the same amount and type of work can be challenging and rewarding for others. Ideally, we will have enough stress but not too much. Manageable levels of stress, for reasonable duration, mobilize your resources and get you going on tackling the tasks and problems in your life. An overload of stress from either too little or too much arousal going on for too long produces first unpleasant feelings, and then physical damage and fatigue and ultimately even death. Stress can be felt or perceived as good or bad but the body reacts the same way in either case. Stress is the body's non specific response to any demand on it whether that demand is pleasant or not. Sitting in a dentist's chair is stressful but so is enjoying a passionate kiss with a lover.
A stress response is made up of several different parts:
1. the event, situation or environment in which the person finds herself.
2. the person's judgment or appraisal of whether it is threatening or potentially harmful
3. the physical and /or emotional reaction to it. This reaction may be either a conscious reaction (such as leaving the stress situation) or a subconsciously controlled reaction (such as irritability)
Stress is commonly viewed as a frustrated 'fight or flight' response - a basic human survival mechanism left over from our primordial 'roots' when we could best respond to perceived dangers by either fighting or fleeing; seen in this way today, stress behavior and emotions are sometimes regarded as problematic and inappropriate responses to unpleasant or threatening situations in modern society (we get caught in traffic and our body kicks in the fight or flight reaction). Stress is a powerful reaction within the body designed to do two major things: to increase awareness, and provide a source of energy. *

Striatum: An area of the brain that controls movement and balance. It is connected to and receives signals from the substantia nigra.

Subcutaneous tissue: The tissue under the skin. #

Subcutaneous injection: Into the fatty tissue under the skin. ##

Subluxation {sub-LAX-ation}: Similar to dislocation but the bone ends are not completely separate. They are no longer in correct, functional alignment. *

Substantia nigra: A dark band of gray matter deep within the brain where cells manufacture the neurotransmitter dopamine for movement control. Degeneration of cells in this region may lead to a neurologic movement disorder such as Parkinson's disease.

Substitutions, of the DNA code: When a base in the nucleotide sequence is altered, a substitution is said to have occurred.
Silent substitutions: in some cases, the triplet code can be mutated in one position and the protein will not be altered. These are called silent substitutions.
Replacement substitutions:mutations in the code sequence (triplet) that lead to an altered protein product being produced. In theory, comparing silent and replacement substitutions will indicate natural selection. If genes mutate randomly, then mutations will occur at sites resulting in silent mutations equally often as at sites resulting in replacement. If evolution is neutral, after 10 million years, the ratio of these mutations will be equal. However, natural selection will favour some of the replacement mutations and make them spread faster. If, for example, 1 percent of silent sites in a gene change in 10 million years, natural selection might change 5 percent of the replacement sites. These comparisons allow scientists to judge rates of random silent mutation versus random replacement mutation and get a sense of the strength of natural selection going on in a given gene in a given population. Some example help understand this idea. Genes for some of the immune system proteins that have to recognize pathogens are rapidly undergoing natural selection, replacement mutations outnumber silent ones 4 to 1. If a pathogen evolves a new structure, the immune molecule involved has to evolve rapidly to keep up. Animals with the revised immune molecule will be selected for a bit more often (they can handle the pathogen better) than animals with the old structure. Another gene showing strong natural selection is called BRCA1. This gene has rapidly evolved since our split with other apes. It is normally involved in the repair of DNA and development in embryos. In humans, this gene is sensitive to mutations that increase the chances of getting cancer. So, while the variations in this gene appear to be involved in our evolution from apes, they also lead to increases in cancer. *

Subtelomeres: Regions of material that sit adjacent to the telomeres that cap the ends of chromosomes. These areas appear to be analogous regions of repetitive DNA (pericentomeres). Subtelomeres seem to be zones of active genetic recombination. Recent research suggests that these zones may be important regions for the mixing and matching of duplicated DNA to form new genes. These areas also display a great deal of variation across human populations. See heterochromatin.

Suppression: A mechanism for producing a specific state of immunologic unresponsiveness by the induction of suppressor T cells. This type of unresponsiveness is passively transferable by suppressor T cells or their soluble products.

Suppressor T cells: A subset of T cells that turn off antibody production and other immune responses.

Sural {SIR-rill}: Relating to the calf of the leg. ***

SV40 see Simian vacuolating virus 40 or Simian virus 40.

Sydenham's chorea: A disease of childhood usually associated with rheumatic fever and marked by involuntary purposeless contractions of the muscles of the trunk and extremities; anxiety; and impairment of memory and sometimes speech. ***

Sympathetic nervous system: Part of the nervous system that along with the parasympathetic nervous system forms the autonomic nervous system (ANS). The ANS regulates the functioning of involuntary structures, such as the glands, smooth muscle, and heart. The sympathetic nervous system regulates certain involuntary responses during times of strong emotion, such as fear or anger; exercise; or other forms of stress. These responses, sometimes referred to as the "fright-or-flight response," include widening of the pupils; increased heart and breathing rates; constriction of most blood vessels, raising blood pressure; widening of those blood vessels that supply skeletal muscles; and reduction in the rate of peristalsis.

Symptomatic treatment: Treatment designed to try to relieve symptoms of a disorder but not primarily focused on treating the underlying causes or disease (which is usually untreatable). *

Symptoms: These are things we feel about our body - I feel a pain in my stomach. We have to report to the Doctor how we feel and these feelings represent our symptoms. Symptoms along with signs are two important parts of making a diagnosis. *

Synapse: The junction between two neurons or between a neuron and an effector organ. As a nerve impulse reaches a synapse, the terminal or end of the "presynaptic" neuron's axon releases neurotransmitters, which diffuse across the gap and bind to receptors of the "postsynaptic" neuron or the effector organ (i.e., muscle or gland). As the electrical impulse is conducted across the gap, electrical changes are triggered that serve to continue or hinder transmission of the impulse.

Syngeneic: Literally, genetically identical.

Syngraft: Same as isograft.

Synthesis: The formation of a complex chemical compound through the union of simpler substances.

Syndrome: A recognizable pattern or group of symptoms or signs that appear together and that tend to indicate, with some consistency, the presence of a certain disease or other condition. The term syndrome is often used when the symptoms of an illness tend to be multiple, diverse and varied. Also, syndrome is sometimes associated with disorders that do not have well understood causes.

[Alpha-] synuclein [a-synuclein] (alpha the letter from the Greek alphabet): a protein that is important in the brain. Abnormal tangles of this protein are associated with Lewy bodies seen in Parkinson's Disease.

Synucleopathies: diseases associated with abnormal deposits of Alpha-synuclein protein. These include: Parkinson disease, Parkinson disease with dementia; dementia with Lewy bodies; multiple system atrophy; Hallenvordern-Spatz disease; found also in Alzheimer's disease and Down syndrome (20 to 60 %). Frequently seen with abnormal tau protein.

Systemic disease: A disease that affects the entire body instead of a specific organ. ##

Systemic: Pertaining to or affecting the body as a whole.

Systemic lupus erythematosus (SLE): see Lupus.

Systemic treatment {sis-TEM-ik}: Treatment that reaches cells all over the body by traveling through the bloodstream. %


A - C      D - F      G - K      L - O     P - S     T - Z.

T cell: A lymphocyte which undergoes a developmental stage in the thymus.

T-dependent antigen: An immunogen that is able to induce antibody synthesis only in the presence of lymphokines released by helper T cells.

T-independent antigen: An immunogen which induces antibody synthesis in the absence of lymphokines released by T cells; the antibodies are generally only of the IgM isotype.

Tardive {TAR-dif} dyskinesia {DIS-KIN-ease-ee-ah} : A condition of slow, rhythmical, automatic stereotyped movements, either generalized or in single muscle groups. These occur as an undesired effect of therapy with certain psychotropic drugs, esp. the phenothiazines. ***

Tardive {TAR-dif}dystonia {DIS-TONE-ee-ah}: A form of tardive dyskinesia characterized by chronic dystonia due to administration of medications that block dopamine D2 receptors (dopamine receptor antagonists), such as certain antipsychotic agents. (Dopamine receptors are molecules on the surfaces of receiving nerve cells that are sensitive to stimulation by dopamine, a neurotransmitter that controls movement and balance. Several types of dopamine receptors have been identified, including D1, D2, and D3.) Dystonia is a neurologic movement disorder characterized by sustained muscle contractions that often result in repetitive twisting motions or unusual postures or positions. Tardive dystonia is the most common form of secondary dystonia--i.e., dystonia that results from certain environmental factors or "insults" that affect the brain. In adults, tardive dystonia often initially affects facial or neck muscles. Dystonia may remain limited to such regions or extend to affect adjacent muscles of the trunk and arms. Children are more likely to be affected by generalized dystonia that involves muscles of the trunk and legs.

Taste alteration: A temporary change in taste perception. ##

Tau protein: Tau protein is widely expressed in the mammalian nervous system, where it plays a role in the assembly and stabilization of microtubules [microtubule: sort of like a skeleton made out of proteins within the cell, helping to give structure to normal cells]. The most common neurodegenerative diseases are characterized by the presence of abnormal filamentous (filaments - like you see in a light bulb) protein inclusions in nerve cells of the brain. In Alzheimer's disease, these inclusions are made of hyperphosphorylated tau protein. Together with the extracellular - beta amyloid deposits, they constitute the defining neuropathological characteristics of Alzheimer's disease. Tau is the predominant protein component of the paired helical filaments (PHFs) and neurofibrillary tangles (NFTs) which are characteristic abnormalities of the Alzheimer's diseased brain and in IBM. *
Also: Tau: A protein that is involved in microtubule formation. Tau is the predominant protein component of the paired helical filaments (PHFs) and neurofibrillary tangles (NFTs) which are characteristic pathological lesions of Alzheimer's disease (AD). In AD, aggregations of altered tau-protein form neurofibrillary tangles inside of cells. The structures produced in this way interfere with the function of, and eventually destroy, nerve cells. Tau protein may also play a role in other diseases (Inclusion body myositis) and may also be a marker for other diseases (for example, Multiple sclerosis patients show increased tau levels in cerebrospinal fluid compared to research controls). *

Tauopathy: disease caused by the abnormal accumulation of tau protein. When this occurs in the brain, after insoluble tau begins to accumulate, substantial neurodegeneration, followed by loss of neurons is seen. The most common example is Alzheimer's Disease. A range of inclusion body disorders appears linked to the accumulation of tau, among other proteins. Frequently seen with abnormal a-synuclein protein.

Tay-Sachs disease: A fatal degenerative disease of the nervous system due to a deficiency of hexosamidase A, causing mental deficiency, paralysis, mental deterioration, and blindness; found primarily but not exclusively among Ashkenazi Jews. Autosomal recessive. Also: A progressive neurodegenerative metabolic disorder that belongs to a group of diseases called lysosomal storage diseases. Also known as GM2 gangliosidosis type I or infantile type, Tay-Sachs disease results from deficiency of the enzyme hexosaminidase A, which leads to an abnormal accumulation of certain fats (i.e., gangliosides) in particular tissues, particularly nerve cells of the brain. An autosomal recessive disorder, Tay-Sachs disease primarily affects individuals of northeastern European Jewish (Ashkenazi Jewish) ancestry. Symptom onset typically begins from about 3 to 6 months of age. Associated symptoms may include an exaggerated startle response, increasing listlessness, loss of previously acquired skills (psychomotor regression), severely diminished muscle tone (hypotonia), and the development of characteristic, cherry-red circular areas within the middle layers of the eyes (Tay's sign). With disease progression, affected infants and children may develop increasing muscle stiffness or rigidity; seizures; sudden, involuntary, "shock-like" contractions of multiple muscle groups in response to certain stimuli (generalized, stimuli-sensitive myoclonus); enlargement of the brain (metabolic megalencephaly); deafness; blindness; and dementia. Life-threatening complications may develop between 2 to 5 years of age.

Tendon: A tough fibrous cord of tissue that attaches muscle to bone (or other structures of the body).

T cells: Small white blood cells that orchestrate and/or directly participate in the immune defenses. Also known as T lymphocytes, they are processed in the thymus and secrete lymphokines.

Teletherapy: Treatment in which a radiation source is at a distance from the body. Linear accelerators and cobalt machines are used in teletherapy. #

Telethonin: A muscle-related protein implicated in LGMD 2G*

Telmisartan {tel-mi-SAR-tan} : Also know as Micardis, is a hypertension medication used in order to aide high blood pressure which directly raises the threat of coronary heart disease.

Telomeres {TEA-low-meres} Genetic material on the the tips of chromosomes. As cells reproduce, a bit of the telomere on each chromosome is cut off. When the telomere is exhausted, the cell can no longer reproduce. The "lifespans" of different cells are thus controlled by their telomere length. Premature shortening of the telomeres is linked to disease and premature death.

Temporal Lobes (brain): The primary auditory cortex helps us hear sounds and gives sounds their meaning, e.g. the bark of a dog. The temporal lobes are the primary region responsible for memory. It also contains Wernicke's area (language and speech functions.) *

Temporal series: A series of measurements taken over time. Used in many types of research. Example, to look at a temporal series of gene activity over time. Another example is taking a biopsy before a treatment (exercise for example) and then doing another biopsy after a period of time.

Teratogenic: Possessing the ability to disrupt normal fetal development and causing fetal abnormalities.

Teratogens {TER-RAT-ta-gen}: Any agent that raises the incidence of congenital malformations. The agent is said to be teratogenic. Teratogenic factors include environmental toxins, radiation, diet, drugs, infection, and metabolic disorders.

Teratoma: Teratoma (literally, "monster tumor"). A type of cyst or tumor that contains tissue or cells normally found in other locations. Tumors usually contain cells of all three embryologic germ cell layers. Teratomas are a germ cell tumor present at birth that may contain hair, teeth, and other tissues. Teratomas account for approximately 15-20% of all ovarian cancers. Most teratomas are benign.

Testicles (TES-tih-kuls): The two egg-shaped glands found inside the scrotum. They produce sperm and male hormones. Also called testes. %

Testicular self-examination (TSE): A simple manual self-examination of the testes. ##

Tetrahymena: A protozoan that has been studied by a University of California, Santa Barbara scientist for the past 46 years has been assigned high priority for genome sequencing by the National Human Genome Research Institute (NHGRI). It is a single-celled organism that split off from an ancestor in common with humans about two billion years ago. Yet it carries many of the same genes as humans, and therefore can be used to understand the function of many human genes.

Thalamus: An area of the brain consisting of 2 relatively large masses of gray matter. The thalamus relays information from most sensory organs to the outer region of the cerebrum or cerebral cortex; receives and processes messages from the body concerning heat, cold, pain, pressure, and touch; and influences motor activity of the cerebral cortex.

Therapeutic: Pertaining to treatment. #

Therapeutic cloning: see cloning.

Thermography {ther-MOG-ra-fee}: Test to measure and display heat patterns of tissues near the surface of the skin. Abnormal tissue generally is warmer than healthy tissue. #

Thoracentesis (Pleural tap): A procedure to remove fluids from the area between the two layers (pleura): covering the lung. ##

Thoracic: {THOR-ras-ic} Concerning the chest. #

Thrombocytopenia: {Throm-boe-sight-ah-PEAN-ee-ah} Decreased number of platelets circulating in the blood. The decrease can be a side effect of chemotherapy. # If the platelet count is too low, bleeding could occur. ##

Thrombophlebitis {throm-boe-fleh-BY-tis}: Inflammation of a vein that occurs when a blood clot forms. #

Throughput: In computer technology, throughput is the amount of work that a computer can do in a given time period.

Thymectomy {Thigh-mect-toe-me}: A treatment in myasthenia gravis where the thymus gland is surgically removed. **

Thymus {THIGH-mus} Gland: Located under the breastbone, this gland is involved in the production of antibodies. It is believed to play a central role in the development of myasthenia gravis. **

Tics: Involuntary, compulsive, stereotypic muscle movements or vocalizations that abruptly interrupt normal motor activities. These repetitive, purposeless motions (motor tics) or utterances (vocal tics) may be simple or complex in nature; may be temporarily suppressed; and are often preceded by a "foreboding" sensation or urge that is temporarily relieved following their execution. Simple tics include abrupt, isolated movements, such as repeated facial twitching, blinking, or shoulder shrugging, and simple sounds, including grunting, throat clearing, or sighing. Complex tics may involve more sustained, complex movements, such as deep knee bending or leg kicking, or complex vocalizations, including repeating another person's words or phrases (echolalia) or, rarely, explosive cursing (coprolalia). Tourette syndrome is defined as the presence of multiple motor and vocal tics for at least one year, changes in the nature of the tics (e.g., complexity, severity, anatomical location) during the course of the disorder, and symptom onset before age 21.

Tinnitus {TIN-ni-tus}: A sound in one ear or both ears, such as buzzing, ringing, or whistling, occurring without an external stimulus and usually caused by a specific condition, such as an ear infection, the use of certain drugs, a blocked auditory tube or canal, exposure to loud noise, or a head injury. Some people experience chronic tinnitus, often of unknown cause. *

Tissue {TISH-oo}: A group or layer of cells that together perform a specific function. %

Tissue stem cell: Derived from, or resident in, a fetal or adult tissue, with potency limited to cells of that tissue. These cells sustain turnover and repair throughout life in some tissues.

Titration {Tie-TRAY-shon} (in chemotherapy): Using the largest amount of drug possible while keeping side effects from becoming intolerable. #

Titre: The reciprocal of the last dilution of a titration giving a measurable effect; e.g. if the last dilution giving significant agglutination is 1:128, the titre is 128.

Tolerance: (in immunology) A state of nonresponsiveness to a particular antigen or group of antigens. Tolerance: Diminished or absent capacity to make a specific response to an antigen, usually produced as a result of contact with that antigen under nonimmunizing conditions.

Tone: Resistance or tension in a muscle when a limb or other body part is moved passively and in a relaxed state about a joint. A state of muscle tension balanced by partial contraction or alternate contraction and relaxation.

Tonsils and adenoids: Prominent oval masses of lymphoid tissues on either side of the throat.

Totipotent: cells having unlimited capability. Totipotent cells have the capacity to specialize into extraembryonic membranes and tissues, the embryo, and all postembryonic tissues and organs. *

Toxic metabolites: Potentially harmful substances formed as the result of normal body functions.Toxins: Agents produced by plants and bacteria, normally very damaging to mammalian cells, that can be delivered directly to target cells by linking them to antibodies or lymphokines.

Toxoid: A nontoxic derivative of a toxin used as an immunogen for the induction of antibodies capable of cross-reacting with the toxin.

Tracheostomy {Trak-KEY-ost-toe-me}: A surgical opening through the trachea in the neck to provide an artificial airway. ##

Tracheotomy {Trak-KEY-ought-toe-me}: A surgical opening in the trachea or windpipe through which a tube is inserted to assist with respiration. **

Trait: Any detectable phenotypic property of an organism. %

Trans: Meaning across (as in transatlantic) often used to refer to the geometric configuration of two mutant alleles (ab) across from each other on a pair of homologous chromosomes (Ab/aB).

Transcript Image: A list of expressed genes and their percent abundance. A snapshot of a genome's activity in a particular tissue at the time the RNA was isolated.

Transcription: The process of copying DNA to produce an RNA transcript. This is the first step in the expression of any gene. The resulting RNA, if it codes for a protein, will be spliced, polyadenylated, transported to the cytoplasm, and by the process of translation will produce the desired protein molecule. @@

Transcription: DNA template directed synthesis of RNA by RNA polymerase.*
Transcription: The process of copying information from DNA into new strands of messenger RNA (mRNA). The mRNA then carries this information to the cytoplasm, where it serves as the template for the manufacture of a specific protein. %

Transcriptomics: The large-scale analysis of messenger RNAs (molecules that are transcribed from active genes) to determine when, where, and under what conditions genes are expressed.

TRANSDIFFERENTIATION: The process of tissue-specific stem or progenitor cells differentiating into atypical cell lineages--ie, haemopoietic stem-cell making neurons. Somatic cell cloning is the ultimate example of transdifferentiation.

Transduction: The movement of genes from a bacterial donor to a bacterial recipient using a phage as the vector. A process whereby a cell can gain access to and incorporate foreign DNA brought in by a viral particle. In neurology: The process whereby stimulus energy is converted to neural activity (action potentials) From "transduco" or "to lead over".

Transfection: A method by which experimental DNA may be put into a cultured mammalian cell. Such experiments are usually performed using cloned DNA containing coding sequences and control regions (promoters, etc.) in order to test whether the DNA will be expressed. Since the cloned DNA may have been extensively modified (for example, protein binding sites on the promoter may have been altered or removed), this procedure is often used to test whether a particular modification affects the function of a gene.@@

Transfer RNA (tRNA): A class of RNA having structures with triplet nucleotide sequences that are complementary to the triplet nucleotide coding sequences of mRNA. The role of tRNAs in protein synthesis is to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA. %

Transgene: the foreign gene that is inserted into a host's genome.

Transgenic organism: One into which a cloned genetic material has been experimentally transferred, a subset of these foreign gene express themselves in their offspring. Turner syndrome a chromosomal condition in females (usually 45,XO) due to monosomy of the X chromosome; characterized by short stature, failure to develop secondary sex characteristics, and infertility.

Transgenic mice: These are mice with a specific gene from another animal inserted into them. Used in research. *
Also: A mouse which carries experimentally introduced DNA. The procedure by which one makes a transgenic mouse involves the injection of DNA into a fertilized embryo at the pro-nuclear stage. The DNA is generally cloned, and may be experimentally altered. It will become incorporated into the genome of the embryo. That embryo is implanted into a foster mother, who gives birth to an animal carrying the new gene. Various experiments are then carried out to test the functionality of the inserted DNA. @@

Transient: Temporary; transitory; not lasting or enduring.

Transit-amplifying cell: Proliferative stem-cell progeny fated for differentiation. Initially may not be committed and may retain self-renewal.

Translation: The process of turning instructions from mRNA, base by base, into chains of amino acids that then fold into proteins. This process takes place in the cytoplasm, in structures called ribosomes.
Also: The process of decoding a strand of mRNA, thereby producing a protein based on the code. This process requires ribosomes (which are composed of rRNA along with various proteins) to perform the synthesis, and tRNA to bring in the amino acids. @@

Translational research: The purpose of translational research is to test, in humans, novel therapeutic strategies developed through experimentation. Translational research should be regarded as a two-way road: Bench to Bedside and Bedside to Bench. However, Bedside to Bench efforts have regrettably been limited because the scientific aspects are poorly understood by full time clinicians and the difficulty of dealing with humans poorly appreciated by basic scientists. Translational research would be most useful to the scientific community at large if journals would foster specific interest for the publication of ex vivo human observation.

Translocation: A translocation is the transfer of genetic material from one chromosome to another. There are two main types. Reciprocal translocations occur when two different chromosomes exchange segments. Reciprocal translocations occur in the general population at a rate of approximately 1 in 500 persons. This type of translocation most often involves a two-way exchange of segments between two different chromosomes. A break occurs in each chromosome, and the segments below that break switch positions. If the reciprocal translocation is balanced, meaning there is no loss or gain of chromosomal material after the exchange, and no genes are disrupted, the individual who carries the translocation is normal. However, carriers of balanced translocations can produce eggs or sperm that are genetically imbalanced, meaning that the eggs or sperm have extra chromosomal material or not enough chromosomal material. Robertsonian translocations occur when two chromosomes fuse together, creating one chromosome that contains most of the original two. A Robertsonian translocation (named for W. R. B. Robertson, the scientist who first described them) occurs when two chromosomes join around their centers. The resulting translocation chromosome consists of most of the two original chromosomes. This type of translocation happens among chromosomes 13, 14, 15, 21, and 22. Robertsonian translocations are found in about one of every 1,000 individuals. The most common combinations are between chromosomes 13 and 14 and between chromosomes 14 and 21. An individual with a balanced Robertsonian translocation will have 45 chromosomes instead of the normal set of 46, since two chromosomes have joined to form one translocation chromosome. As with balanced reciprocal translocation carriers, individuals who carry a balanced Robertsonian translocation, while normal, can produce gametes that are genetically imbalanced. Robertsonian translocations between chromosomes 14 and 21, one of the most common combinations, are of particular clinical relevance. An individual with this translocation could have a child with three copies of chromosome 21, resulting in Down's syndrome (trisomy 21). Women who carry a Robertsonian translocation between chromosomes 14 and 21 have an approximately 10% risk of giving birth to a baby with Down's syndrome, and men who carry this translocation have a 1-3% risk. Down's syndrome due to a translocation shows no relation to maternal age (as does standard trisomy 21), but a parent with a balanced Robertsonian translocation who has already given birth to a child with Down's syndrome has a relatively high risk (10-30%) of having additional affected children.

Transmissible spongiform encephalopathy (TSE): A disease that can be transmitted from one animal to another that will produce changes in the brain that appear similar to a sponge. In transmissible spongiform encephalopathies (TSEs), of which BSE is the most well known type, an insoluble form of a protein called a prion accumulates in the brain - with fatal consequences. In different TSEs, these accumulations look different. See prion. *

Transposons - Transposable Genetic Elements ("Jumping genes"): A mobile genetic element that can replicate itself and insert itself into the genome, including interrupting genes and disrupting their function, an insertional mutagen.
One of a class of genes that are capable of moving spontaneously from one chromosome to another, or from one position to another in the same chromosome; also known as jumping genes or transposable elements.
Transposable genetic elements do not reside at only a single locus, but they can change position on the same chromosome or move to a non-homologous chromosome. Transposable elements were first identified in maize and later in Drosophila. In bacteria, transposable elements are called transposons.
A transposable element is a bit of DNA that can move from place to place in an organism's genome. It is excised from one site and inserted at another site either on the same or on a different one. The movement of a transposable element can generate mutations or chromosomal rearrangements and thus affect the expression of other genes.
=Long Terminal direct Repeats (LTR):A sequence directly repeated at both ends of a defined sequence, of the sort typically found in retroviruses.
=Long Interspersed Nuclear Elements (LINEs) or Long Interspersed Elements: Families of long (average length = 6 500 bp), moderately repetitive (about 10,000 copies). LINEs are cDNA copies of functional genes present in the same genome; also known as processed pseudo- genes. Highly repeated sequences, 6K-8K base pairs in length, which contain RNA polymerase II promoters. They also have an open reading frame that is related to the reverse transcriptase of retroviruses but they do not contain LTRs (long terminal repeats). Copies of the LINE 1 (L1) family form about 15% of the human genome.
=Short Interspersed Nuclear Elements (SINES): Families of short (150 to 300 bp), moderately repetitive elements of eukaryotes, occurring about 100,000 times in a genome. SINES appear to be DNA copies of certain tRNA molecules, created presumably by the unintended action of reverse transcriptase during retroviral infection. Highly repeated sequences, 100-300 bases long, which contain RNA polymerase III promoters. The primate Alu and the rodent B1 SINEs are derived from 7SL RNA, the RNA component of the signal recognition particle. Most other SINEs are derived from tRNAs including the MIRs (mammalian-wide interspersed repeats).

Transurethral resection {TRANZ-yu-REE-thral ree-SEK-shun}: Surgery performed with a special instrument inserted through the urethra. Also called TUR. #

Transvaginal ultrasound: Sound waves sent out by a probe inserted in the vagina. The waves bounce off the ovaries, and a computer uses the echoes to create a picture called a sonogram. Also called TVS#

Trauma: A wound or injury. #

Treatment port: The place on the body at which the radiation beam is aimed. #

Tremor: Rhythmic, involuntary, oscillatory (or to-and-fro) movements of a body part.

Trigger points (TrP): A series of characteristic points in the body where myofascia may become sore and present as lumps under the skin. Associated with stress. These lumps may not be painful unless they are pressed, when pressed, they are very painful. Linked to Myofascial Pain Syndrome. *

Trinucleotide repeat disorders: When the cause of a disease can be traced to having too many copies of a certain nucleotide triplet in the DNA, the disease is said to be a trinucleotide repeat disorder. Today, there are 14 documented trinucleotide repeat disorders that affect human beings. Huntington's Disease is part of this group as is Spinobulbar Muscular Atrophy (SBMA).
Three nucleotides, such as CAG, CTG or GAA, are tandemly repeated an abnormal number of times within a gene. The genetic transmission of trinucleotide repeat expansion disorders within families may show a pattern of increasing severity and earlier age of onset; this phenomenon is called anticipation and is the result of an increase in the expansion size. ***

tRNA: See transfer RNA.

Trophoblast {tro-foe-blast}: the tissue that forms the wall of the blastocyst. At implantation it forms two layers, an inner cellular layer (cytotrophoblast) and an outer syncytial layer (plasmoditrophoblast), which forms the outermost layer of the placenta and attains direct contact with the maternal bloodstream. Trophoblast sampling was the name originally given to the technique now known as chorionic villus sampling.

TSE: see Transmissible spongiform encephalopathy. *

Tumor. debulking: Surgically removing as much of the tumor. as possible. #

Tumor suppressor: Genes that normally restrain cell growth but, when missing or inactivated by mutation, allow cells to grow uncontrolled. %
Also: A gene that helps prevent the transformation of normal cells into cancer cells. When both copies of a tumour-suppressor gene are mutated in a cell, however, the lack of suppression may lead to the development of cancer. ### The best-known examples of tumor suppressors are the proteins p53 and Rb.

Tumor markers: Substances found in abnormal amounts in the blood, in other body fluids, or in tumor. tissue of some patients with certain types of cancer. %

Tumor: A mass of excess, abnormal mass of tissue. Tumors are either benign (non cancerous) or malignant (cancerous). #

Tumor necrosis factor (TNF): Tumor necrosis factor-a (TNF-a) and interleukin-1 (IL-1) are the major macrophage-derived cytokines present in the rheumatoid joint and both induce the synthesis and secretion from synovial fibroblasts of matrix-degrading proteases, prostanoids, interleukin-6 (IL-6), interleukin-8 (IL-8) and granulocyte-macrophage colony stimulating factor (GM-CSF). Consequently, attention has focused on inhibition of TNF-a as a way to treat RA. The best studied of the monoclonal anti-TNF antibodies is infliximab (Remicade®), originally referred to as cA2.

Ubiquinone: see co-enzyme Q 10.

Ubiquitin: A small protein found universally (it is ubiquitous) in eukaryotes (in cells), that tags proteins destined for degradation by proteasomes. Ubiquitin is important in both the normal life of the cell and in a cell's response to stress; it is considered to be a heat-shock protein. Proteins tagged for destruction are broken down and removed because they are damaged or no longer needed by the body. Such "tagged" protein molecules are said to have been ubiquitinated.

Ultrasonography {ul-tra-son-OG-ra-fee}: (Ultrasound) An exam in which sound waves are bounced off tissues and the echoes are converted into a picture (sonogram). %
Ultrasound:Diagnostic procedure that bounces high-frequency sound waves off tissues and changes the echoes into pictures. #
Ultrasonography (sonography): the use of ultrasound, usually in excess of 1 MHz, to produce images of structures of the human body that may be observed on a TV screen and subsequently transferred to photographic film. It is based on the principle of detecting the reflected waves (echoes) occurring at interfaces within human organs, following a short pulse of ultrasound. This is repeated many times to build up a complete picture.

Ultraviolet radiation {ul-tra-VI-o-let ray-dee-AY-shun}: Invisible rays that are part of the energy that comes from the sun. Ultraviolet radiation can burn the skin and cause skin cancer. It is made up of two types of rays, UVA and UVB. Skin specialists recommend that people use sun screens that block both kinds of radiation. %

UNESCO: United National Educational, Scientific, and Cultural Organization.

Unfolded protein response (UPR) see: Endoplasmic reticulum (ER) and endoplasmic reticulum stress.

Unidentified reading frame (URF): An open reading frame encoding a protein of undefined function.

Unilateral: Affecting, pertaining to, or confined to one side only.

Unresponsiveness: Inability to respond to antigenic stimulus. Unresponsiveness may be specific for a particular antigen (see tolerance), or broadly nonspecific as a result of damage to the entire immune system, for example after whole body irradiation.

Untranslated Region (UTR): That part of a gene which is not translated into protein.

Upper GI (gastro-intestinal) series: X-rays of the upper digestive system that are taken after a person drinks a barium solution, which outlines the digestive organs on the X-rays. #

Upper motor neurons: Nerve cells extending from the brain to the spinal cord that control movement.

Up-regulation: Process that increases ligand/receptor interactions due to an increase in the number of available receptors.

Upstream: an event or cause that in turn causes other (downstream) features to develop. Many systems in biology consist of a series of steps and changing one step early in the cycle changes the subsequent events. In medicine, the symptoms we see are often the downstream effects of upstream events or causes. For example, some medications (upstream cause) appear to cause MG (downstream symptom) in some patients. This process is also called a cascade, the first events set off a series of events that occur in a cascade of effects ending in the final downstream events. Often researchers have to trace back from downstream symptoms to upstream causes and this can be very complex, especially if more than one upstream cause can lead to that particular downstream symptom. *
Upstream/Downstream (genetics): In an RNA, anything towards the 5' end of a reference point is "upstream" of that point. This orientation reflects the direction of both the synthesis of mRNA, and its translation - from the 5' end to the 3' end.
In genetics - Toward the 5' end of a nucleotide sequence. In DNA, sequences located to the opposite direction to transcription (which runs from 5' to 3' on the sense strand of the DNA).

Urea {YUR-ee-ah}: Main waste material in urine. #

Ureterostomy: A surgical procedure consisting of cutting the ureters from the bladder and connecting them to an opening (Stoma) on the abdomen, allowing urine to flow into a collection bag. ##

Ureters {YUR-a-terz}: Tubes that carry urine from each kidney to the bladder. #

Urethra {yur-EE-thra}: Tube that empties urine from the bladder. #

URL: see www *

Urologist {yur-OL-o-jist}: Doctor who specializes in diseases of the urinary organs in females and the urinary and sex organs in males. #

Vaccination: Originally referred to immunization against smallpox with the less virulent cowpox (vaccinia) virus; more loosely used for any immunization against a pathogen.

Vaccine: A substance that contains antigenic components from an infectious organism. By stimulating an immune response (but not disease), it protects against subsequent infection by that organism.

Vacuole {VAC-cue-ole}: A small cavity or hole in the cytoplasm of a cell, bound by a single membrane and containing water, food, or metabolic waste. Abnormal vacuolation is a characteristic of various diseases (for example, of Inclusion body myositis). *

Vagina {va-JYE-na}: The muscular canal extending from the cervix to the outside of the body. #

Vagus {Viegh-GUS} nerve: The pneumogastric or 10th cranial nerve. It is a mixed nerve, having motor and sensory functions and a wider distribution than any of the other cranial nerves. ***

Variable expressivity: Varying manifestation of a genetic trait. The term "expressivity" refers to the degree to which a hereditary trait appears in an individual. Thus, in individuals with a gene mutation for an autosomal dominant disorder that has variable expressivity, the specific characteristics that are manifested may vary in range and degree from mild to severe.

Variable region: (V region) That part of an antibody's structure that differs from one antibody to another. The V region and the constant region make up the whole antibody.

Variant form of Creutzfeldt-Jakob disease (vCJD or nvCJD): name given to a newly identified human TSE which is significantly different from other forms of CJD. see Creutzfeldt-Jakob disease.

Vasectomy (vas-EK-toe-mee): An operation to cut or tie off the two tubes that carry sperm out of the testicles. %

Vascular: Pertaining to or containing blood vessels.

Vasoconstrictor: A chemical substance whose actions result in the narrowing of blood vessels.

Vasodilator: A chemical substance whose actions cause an increase in the diameter of blood vessels.

Vasomotor: Pertaining to the muscles and nerves that control blood vessel diameter, thereby regulating or modulating blood pressure.

Vector: A self-replicating DNA molecule that transfers a DNA segment between host cells.
Vector: The DNA "vehicle" used to carry experimental DNA and to clone it. The vector provides all sequences essential for replicating the test DNA. Typical vectors include plasmids, cosmids, phages, BACs and YACs.

Vein: A blood vessel that carries blood from the tissues toward the heart and lungs. #

Venacavography: Diagnostic method using X-rays to obtain a picture of the major vein that collects blood coming out of the kidney. #

Venipuncture: Puncturing a vein in order to obtain blood samples, to start an intravenous drip, or to give medication. ##

Ventral intermediate (VIM) nucleus: A specific region of the thalamus. This area of the brain is involved in the control of movement and is the "target" area for thalamotomy and deep brain stimulation when treating patients with tremor.

Ventricles {VEN-trih-kulz}: Four connected cavities in the brain. #

Vertical transmission: The transmission of an illness from the parent(s) to the offspring. *

Vesicant {VES-ee-cant}: A medication or agent that may cause blistering. ##

Viral vectors: Scientists are trying to find ways to fix defective genes. The most promising strategy to combat genetic diseases is to directly intervene via gene therapy. We need a method to introduce a modified (repaired) gene into the body, this method is called a "vector." The most efficient "vector" for gene insertion is the virus. By first neutralizing a virus (so it cannot make the patient sick), scientists can insert the correct gene into the virus, and then insert the virus into the patient. *

Viroid {VIR-roid}: Small virus-like particle. Under study as the possible cause of disease. *

Virulence: An index of an organism's disease causing ability. *

Virulent: Referring to or characterized by virulence or the degree to which an invading microorganism, such as a bacterium or virus, is able to produce disease. Measures of virulence may be based upon the microorganism's ability to invade bodily tissues and the severity of the disease produced.

Virus: Submicroscopic microbe that causes infectious disease. Viruses can only reproduce in living cells. A non-cellular infective agent consisting of a genome contained within a protein coat and, in some complex forms, a surrounding envelope of a fat and protein. The genome can be either DNA or RNA in single or double-stranded form. Viruses range in size from 20 to 400 nm, and form particles that may crystallize and are resistant to treatment with antibiotics. They are generally considered to be non-living, but are clearly biological in nature. Viruses can replicate only by invading a living cell (the host) and taking over the host cell's metabolic processes in order to synthesize more virus particles. Virus infection leads to severe cellular dysfunction and most viruses therefore produce pathological symptoms. Some cause severe and virulent disease. A retrovirus (HIV) is thought to cause AIDS, several viruses (e.g. Epstein-Barr virus, human papillomavirus) cause particular forms of cancer in humans, and many viruses have been shown to cause tumors in animals. Other viruses that infect humans cause measles, mumps, smallpox, yellow fever, rabies, poliomyelitis, influenza, and the common cold. *

VNTR: Variable number tandem repeats; any gene whose alleles contain different numbers of tandemly repeated oligonucleotide sequences.

Voluntary Muscle: Muscles whose movements are controlled by the individual. **

Watchful waiting: Closely monitoring a patient's condition but withholding treatment until symptoms appear or change. Also called close observation. *

Weakness: Weakness is a failure of a muscle to develop an expected force. Weakness may affect all muscles or only a few, and the pattern of muscle weakness can be an indication of the type of muscle disease. Often associated with muscle weakness is the wasting (atrophy) of affected muscle groups. *

Web page: see world wide web *

Websites: Major NMD-related websites include:
-Muscular Dystrophy Association http://www.mdausa.org/
-ClinicalTrials http://www.clinicaltrials.gov/
-PubMed [primary health and medical-related scientific literature] http://www.ncbi.nlm.nih.gov/
-Online Mendelian Inheritance in Man (OMIM) http://www.ncbi.nlm.nih.gov/Omim/
-Muscular Dystrophy Association of Canada http://www.mdac.ca/
-Myositis Association of America http://www.myositis.org/
-National Institute on Disability & Rehabilitation Research (NIDRR) Rehabilitation Research and Training Center in Neuromuscular Diseases at UC Davis. http://www.rehabinfo.net/ [Formerly Neuromuscular Diseases Clearinghouse (medpmr.ucdavis.edu)]
-NEUROMUSCULAR DISEASE CENTER, Washington University School of Medicine, St. Louis, MO. http://neuromuscular.wustl.edu/
-National Organization on Disability http://www.nod.org/
-National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov/
-Office of Rare Diseases (National Institutes of Health) http://rarediseases.info.nih.gov/ord/
-The Department of Neurology and Neuroscience at Cornell University Medical College [extensive links] http://neuro.med.cornell.edu/VL/
-U.S. National Library of Medicine http://gateway.nlm.nih.gov/gw/Cmd
-Muscular Dystrophy Campaign web site http://www.muscular-dystrophy.org/
-Myositis support group web site: http://www.myositissupportgroup.org/

Western blotting analysis: A technique used to identify a specific protein; the probe is a radioactively labeled antibody raised against the protein in question.

White blood count (WBC): The actual number of white blood cells seen in a blood sample. ##

White blood cells: Cells produced by the bone marrow and lymph nodes. They help the body fight infection. #
Also: White blood cells (WBC): General term for a variety of cells responsible for fighting invading germs, infection, and allergy-causing agents. Specific white blood cells include granulocytes and lymphocytes. ##

White matter: Bundles of myelinated nerve fibers or axons. These nerve fibers have a creamy white appearance due to myelin, a whitish substance that primarily contains fats and proteins. Myelin forms a protective, insulating sheath around certain axons, functioning as an electrical insulator and ensuring efficient nerve conduction. The breakdown, destruction, or loss of myelin from a nerve or nerves (demyelination), such as seen in certain neurodegenerative diseases, results in impaired nerve impulse transmission.

Whole-genome shotgun method: see sequencing.

Wild-type (gene): The allele of a gene that produces the "normal" protein in its normal time and place is called the wild-type allele, because it is the one that will be found in most wild individuals of the species (for most genes, anyway). The mutated gene is the "non-wild" type.

Wilms' tumor.: A kidney cancer (tumor.) that occurs in children, usually before age 5. %

Wilson disease: A rare genetic disorder of copper metabolism, leading to an excessive accumulation of copper in certain tissues and organs, including the liver, brain, kidneys, or corneas of the eyes. Without prompt, appropriate treatment, the disorder may result in progressive liver disease, degenerative changes of the brain, psychiatric abnormalities, and other symptoms. Neurologic findings may include tremor; involuntary, rapid, jerky movements combined with relatively slow, writhing movements (choreoathetosis); impaired muscle tone and sustained muscle contractions, producing repetitive movements and abnormal posturing; increasingly slurred speech; and difficulties swallowing. Some patients may also experience increasing irritability, anxiety, severe depression, unusual behaviors, or other psychiatric problems.

Wilson's disease: A hereditary syndrome transmitted as an autosomal recessive trait in which a decrease of ceruloplasmin permits accumulation of copper in various organs (brain, liver, kidney, and cornea) associated with increased intestinal absorption of copper. ***

Wobble: The ability of certain bases at the third position of an anticodon in tRNA to form hydrogen bonds in various ways, causing alignment with several possible codons. Referring to the reduced constraint of the third base of an anticodon as compared with the other bases thus allowing additional complementary base pairings.

World wide web (www): Often also called the Internet. This is a vast collection of "pages" (over one billion) of information posted by individuals, organizations and other groups. Much of this information is open to anyone, other pages cost money to look at. There is a wide diversity of information posted and one has to be very careful - is the information posted by a credible source? To use the Internet, you need a computer that has a modem hookup (telephone or cable) and you need an interface program on your computer, usually either Microsoft Explorer or Netscape.
Each web page has an address called a URL (Uniform resource locator). Most addresses start with the prefix: http:// and end in a suffix. Common suffixes are .com .ca .edu .org .htm and .net To find information, there are devices called "search engines" that look for key words and phrases. So, if you put "Calgary" into a search engine, you will get a list of all URLs related to, or that mention Calgary. Explorer and Netscape each have their own built in search engines. Other common search engines you can use are Google.com, Excite.com, Lycos.com, etc.

X chromosome: One of the chromosomes involved in sex determination. Normal human females have two X chromosomes in each somatic cell (one is her father's single X chromosome and the other comes from one of her mother's two X chromosomes) while normal males have one X and one Y chromosome in each somatic cell (one from one of his mother's two X chromosomes and the Y from his father). Because males have only a single X chromosome and because almost all the genes on the X have no counterpart on the Y chromosome, any gene on the X (even if it is recessive in females), will be expressed in males.
(Humans usually have 46 chromosomes per diploid cell consisting of 22 pairs of autosomes and one pair of sex chromosomes - either XX or XY. In the usual course of events, individuals with the XX are female and individuals with the XY, are male.)*

X-linked dominant trait: Human traits, such as an individual's specific blood group, eye color, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. In X-linked dominant disorders, the gene mutation for the disease trait is transmitted as a dominant gene on the X chromosome and therefore may "override" the instructions of the normal gene on the other chromosome, resulting in expression of the disease. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed (random X chromosome inactivation). As a result, females often have less severe symptoms than affected males. In contrast, because males have one X chromosome from the mother and one Y chromosome from the father, those who inherit an X-linked dominant disease trait typically fully express the mutated gene on the X chromosome, causing a more severe form of the disorder that may result in lethality before or shortly after birth. Fathers with an X-linked dominant trait transmit the gene to their daughters but not to their sons. Mothers with a single copy of an X-linked dominant gene have a 50 percent risk of transmitting the gene to their daughters as well as to their sons.

X-linked recessive trait: Human traits, such as a person's eye color, specific blood group, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. In X-linked recessive disorders, the gene mutation for the disease trait is located on the X chromosome. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed (random X chromosome inactivation). However, because males have one X chromosome from the mother and one Y chromosome from the father, those who inherit an X-linked recessive disease trait typically fully express the mutated gene on the X chromosome. Some females who carry a single copy of the disease gene (heterozygous carriers) may have certain symptoms associated with the disorder; however, such findings are usually more variable and less severe than those seen in affected males. Fathers with an X-linked recessive trait may transmit the gene to their daughters but not to their sons. Mothers with an X-linked recessive gene have a 50 percent risk of transmitting the gene to their daughters and their sons. also: X-linked Recessive Inheritance of Disorders: A form of inheritance where the faulty gene is carried on the X (sex) chromosome. An X-linked disorder is transmitted to male children by their mothers who carry the faulty gene on their X chromosome. When his mother is a carrier, a male child has a 50% chance of inheriting the faulty gene and having the disorder and a 50% chance of being unaffected. A female child has a 50% chance of being a carrier like her mother and a 50% chance of being unaffected. **

X Chromosome Inactivation (also Lyonization after Mary Lyon - the geneticist who first described it): Human females inherit two copies of every gene on the X chromosome, (one from the mother and one from the father), whereas males inherit only one. If both X chromosomes were active, females would have twice as many X genes as males. To avoid this, in females one X is inactivated and one remains functional (active) in each cell. So, the cells of females have only one functioning copy of each X-linked gene - the same number as males. The inactivated X can be seen as a dense, stainable structure, called a Barr body (after its discoverer) in the interphase nuclei of female mammals.
X inactivation occurs early in embryonic development. In any given cell, the X chromosome (either the one from her mother or the one from her father) that becomes inactivated and converted into a Barr body is a matter of chance. After inactivation has occurred, all the descendants of that cell will have the same X chromosome inactivated. In other cells, the inactivation may effect the other X chromosome. When the X chromosomes of all of the organism's cells are examined, we will see an overall "mosaic effect" or a patchwork of active maternal Xs and paternal Xs. An organism whose cells vary in effective gene content and hence in the expression of a given trait, is called a genetic mosaic. This patchwork pattern can sometimes be seen expressed in an organism, for example, the patchwork coloured coat of a Calico Cat, or a skin condition seen in humans called anhidrotic ectodermal dysplasia. In this condition, the person has patchy areas where they have normal sweat glands and other areas where they have none. The areas with sweat glands and without sweat glands appear in definite patterns, generally they exhibit v-stripes across the back.
X inactivation in the female embryo appears to be entirely random. There is no predicting whether it will be the maternal X or the paternal X that is inactivated in a given cell. This is not the case for the females extraembryonic membranes (that go on to form the amnion, placenta, and umbilical cord). In all the cells of the extraembryonic membranes, it is father's X chromosome that is inactivated. It appears that in many cases with complete (>97%) skewing of X inactivation, the phenotype is also either normal, consistent with a single gene disorder, or consistent with classical Turner syndrome. Based upon: //www.ultranet.com/~jkimball/BiologyPages/S/SexChromosomes.html#x-inactivation
In the context of neuromuscular disorders: because the defect is on the X chromosome, the conventional wisdom was that while females will carry and may pass on the defective X chromosome (they are carriers), they will not manifest the illness (because while one X is defective, the other healthy X will be able to compensate enough to produce normal function). It turns out that in the average case, given random X inactivation, this is more or less the case. There are enough healthy X chromosomes functioning (those escaping inactivation) to allow normal function. However, in some cases, the healthy X is inactivated at a higher than random rate (a nonrandom or skewed rate) and therefore, there are not enough healthy X chromosomes present to maintain healthy function and some degree of symptomatology is expressed (in this case, muscle weakness). This phenomenon is rare but is seen in disorders like Duchenne Muscular Dystrophy and Becker Muscular Dystrophy. Mothers of children with these disorders who show symptoms themselves are referred to as manifesting mothers or manifesting carriers. Symptoms may manifest at any age in the mother.
Also: X Chromosome Inactivation: In humans, as in the majority of animals, the feature that differentiates females from males is that females possess two X chromosomes, whereas males posses one X and one Y chromosome. The number of X chromosome RNA transcripts are kept approximately equal in both sexes, however, due to a phenomenon called X chromosome inactivation by which one of the X chromosomes in every female cell is inactivated. The inactivated X chromosome, usually referred to as a Barr body, is condensed and remains inactivated in all progeny of the initial cell (Griffiths et al., 1996). The precise time in development that inactivation occurs is not known, although it is speculated to occur before the 64 cell stage (Migeon et al., 1996; Gilbert, 1994).
X inactivation is usually a random process, thus females are actually mosaics of cells containing different X genotypes (Griffiths et al., 1996).
Also: Skewed X inactivation (sometimes called nonrandom X inactivation): Genes for several recessive traits are located on the X chromosome, and their expression is therefore usually restricted to hemizygous (having only one copy of a gene) males who have inherited a mutated X from their mothers, who are non-manifesting carriers. On rare occasions women have been found who express these traits, usually due to genetic events such as chromosome loss or translocation that cause the woman to have a homozygous genome. If, however, rather than undergoing the typically random inactivation, the majority of woman's normal X chromosomes became preferentially inactivated, mutant X-linked traits carried on the active chromosome can become expressed (Jorgensen et al., 1992). This phenomenon has been well documented in several studies of female monozygotic twins heterozygous for X-linked disorders. In these pairs one twin has skewed X inactivation toward the normal chromosome, and thus expresses the recessive phenotype, while her twin has skewed inactivation toward the mutant chromosome and thus exhibits no symptoms (allowing enough healthy X chromosomes to support normal function). It is also possible that the tendency to have skewed X inactivation is heritable.

X chromosome autosome translocation syndrome: Movement (translocation) of genetic material from the X chromosome to an autosome. The X/autosome translocation can occur de novo (be new) or be inherited from a parent. Translocation from an X chromosome to an autosome with a variable phenotype or lethality. Most unbalanced X-autosomal translocations result in multiple abnormalities; a smaller proportion cause gonadal dysgenesis without other anomalies or mental retardation. Females with balanced translocation may be fertile, suffer from gonadal dysgenesis, or have multiple congenital/mental retardation syndrome, mostly without gonadal dysfunction. Some are short and may or may not have menstrual disorders, small uterus, and aortic stenosis. X;6 chromosomal translocation was reported in a male in association with delayed development, sensorineural hearing loss, and craniofacial, urogenital, osteoarticular, and other abnormalities. See translocation and balanced translocation.
In the context of neuromuscular disorders
: The most frequently identified cause of females who have a DMD or BMD phenotype is a (balanced) translocation disrupting the DMD-gene on the X chromosome. As a consequence, the DMD-gene is split in two and joined with a segment of another chromosome (autosome) and no functional dystrophin can be produced. Several studies have been published which describe female-DMD translocation cases. Some of these have been characterized in detail, including, mapping, cloning and even sequencing of the translocation breakpoints

Xenobiology: The introduction of material from one species into another.

X-ray: High-energy radiation used in low doses to diagnose diseases and in higher doses to treat cancers. #

Xeroradiograph {ZEE-roe-ray-dee-OG-ra-fee}: Type of mammography in which a picture of the breast is recorded on paper rather than on film. #

XLDC = X-linked dilated cardiomyopathy. X-linked dilated cardiomyopathy (XLDC, sometimes abbreviated as XLDCM) is a clinical phenotype (expression) of dystrophinopathy which is characterized by preferential myocardial involvement without any overt signs of skeletal myopathy. It is a familial myocardial disease that presents with lethal congestive heart failure in young males in their teens or early twenties. A significant portion of XLDC-patients carry mutations in the dystrophin gene.

YAC: Yeast artificial chromosome. This is a method for cloning very large fragments of DNA (up to 1,000,000 base pairs). Not as stable as BACs.

XYY syndrome: Genetic condition in males with extra Y chromosome (in 1 in 1000 male births). Symptoms: tall stature (over 6'), may include sterility, developmental delay, learning problems. %

Y chromosome: One of the chromosomes involved in sex determination. Normal human males carry one X chromosome and one Y chromosome in each somatic cell, while normal females have two X chromosomes in each somatic cell. ###

Zaspopathy: a type of muscular dystrophy.


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Sources of Information:

=Entries with *: Terms Bill has assembled from various sources, the primary sources this material is based on are:
-An excellent basic overview of the body: http://www.innerbody.com/htm/body.html
-Excellent but simple site on muscles: ttp://www.innerbody.com/image/musfov.html
-Medline Plus Health Information: http://www.nlm.nih.gov/medlineplus/
-National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov/
-Encyclopaedia Britannica: http://www.britannica.com/
-American Heritage Collegiate Dictionary (via http://www.bartleby.com
-Columbia Encyclopaedia (via http://www.bartleby.com )
-A Dictionary of Biology (Oxford) (Via http://www.xrefer.com/ )
-Athena Diagnostics (a reference laboratory): http://www.athenadiagnostics.com/
-The UK Creutzfeldt-Jakob Disease Surveillance Unit: http://www.cjd.ed.ac.uk/
-A general information search engine: http://www.factmonster.com/

=Entries with ** are from the Muscular Dystrophy Association of Canada.

=Entries with *** From: http://www.athenadiagnostics.com

=Entries with @@ are taken from: http://seqcore.brcf.med.umich.edu/doc/educ/dnapr/mbglossary/mbgloss.html A Molecular Biology Glossary: A Quick and Dirty Reference to Terms Used in Molecular Biology, Dr. Robert H. Lyons, Director, University of Michigan DNA Sequencing Core.

=Entries with % are taken from the Office of Rare Diseases, National Institutes of Health, http://rarediseases.info.nih.gov/ord/glossary_a-e.html

=Entries with # are from: http://www.cancersurvivors.org/Resources/glossary.htm

=Entries with ## are from: http://www.meds.com/glossary.html

=Entries with ### are from: https://www.hhmi.org/educational-materials


Mail Bill: btillier@shaw.ca