Medications

Melan- (prefix): Prefix meaning dark or black. It comes from the Greek "melas", black. Examples of terms containing melan- include melancholia, melanin, melanocytes, melanoma and melena.Last Editorial Review: 3/26/1998 2:27:00 PM Me...

Meiotic nondisjunction - Medical

Meiotic nondisjunction: Failure of two members of a chromosome pair to separate (disjoin) during meiosis so that both go to one daughter cell and none to the other. This mechanism is responsible for the extra chromosome 21 in trisomy 21 (Down synd...

Meiotic drive - Medical

Meiotic drive: Preferential selection during meiosis (germ cell production). In meiotic drive there is preferential production of certain gametes. This alters the segregation of genes from the Mendelian expectations. Meiotic drive is a mechanism for ...

Meiotic - Medical

Meiotic: Pertaining to meiosis (the process of germ cell formation). Last Editorial Review: 4/27/2011 5:27:15 PM Meiosis: The process of germ cell formation. During meiosis, each chromosome pairs with the other chromosome in the pair and they...

Meiosis - Medical

Meiosis: The process of germ cell formation. During meiosis, each chromosome pairs with the other chromosome in the pair and they exchange segments of genetic material. In both women and men, the autosomes (non-sex chromosomes) pair. In women, the X ...

Meibomitis - Medical

Meibomitis: See: Meibomianitis.Last Editorial Review: 4/27/2011 5:27:15 PM Meibomianitis: Inflammation of the little glands called Meibomian glands located in the eyelids that make a lubricant which they discharge through their tiny openings in th...

Meibomianitis - Medical

Meibomianitis: Inflammation of the little glands called Meibomian glands located in the eyelids that make a lubricant which they discharge through their tiny openings in the edges of the lids. The lubricant is a fatty substance called sebum characte...

Meibomian gland - Medical

Meibomian gland: One of the little glands in the eyelids that make a lubricant called sebum which they discharge through their tiny openings in the edges of the lids. The meibomian glands can become inflamed, a condition termed meibomianitis or mei...

Meibomian cyst - Medical

Meibomian cyst: A cyst of the little glands called Meibomian glands that are located in the eyelids and make a lubricant they discharge through their tiny openings in the edges of the lids. The lubricant is a fatty substance called sebum characteris...

Megrim - Medical

Megrim: Migraine. Usually periodic attacks of headaches on one or both sides of the head. Megrim (migraine) may be accompanied by nausea, vomiting, increased sensitivity of the eyes to light (photophobia), increased sensitivity to sound (phonophobia)...

Megalencephaly - Medical

Megalencephaly: Also called macrencephaly, a condition in which there is an abnormally large, heavy, and usually malfunctioning brain. By definition, the brain weight is greater than average for the age and gender of the child. Head enlargement may b...

Megakaryocyte - Medical

Megakaryocyte: A giant cell in the bone marrow that is the ancestor of blood platelets. Last Editorial Review: 4/27/2011 5:27:15 PM...

Megacolon - Medical

Megacolon: An abnormally enlarged colon. Last Editorial Review: 4/27/2011 5:27:15 PM...

Megabase - Medical

Megabase: Unit of length for DNA fragments that is equal to 1 million nucleotides. A megabase (Mb) is roughly equal to 1 centiMorgan (cM). Last Editorial Review: 11/29/2003 DNA: Deoxyribonucleic acid. One of two types of molecules that encode g...

Mega- (prefix) - Medical

Mega- (prefix): The combining form "mega-" comes from the Greek "megas", great or big and means abnormally large. Megalocephaly is too large a head. Megacardia is too large a heart. Megacolon is too large a colon. Last Editorial Review: 3/26/...

MEF2A - Medical

MEF2A: A transcription factor that participates in vascular development. MEF2A is a member of the myocyte enhancer factor-2 (MEF2) family of transcription factors. Messenger RNA ( mRNA) from MEF2A has been detected in blood vessels during early embry...

MEDVAC - Medical

MEDVAC: Acronym for medical evacuation. MEDVAC typically refers to a team that is organized with the skills for the purpose of proper medical evacuation in situations of emergency. Last Editorial Review: 4/27/2011 5:27:15 PM...

Medulloblastoma - Medical

Medulloblastoma: A type of brain tumor that tends to occur in children, arise in the cerebellum (in the lower part of the brain), and spread along the spine. Medulloblastoma is the most common type of primary brain tumor in childhood. It is a t...

Medulla, adrenal - Medical

Medulla, adrenal: The inner portion of adrenal gland. (The outer portion is the adrenal cortex). The adrenal medulla makes epinephrine (adrenaline) and norepinephrine (noradrenaline). Epinephrine is secreted in response to low blood levels of gluc...

Medulla oblongata - Medical

Medulla oblongata: The base of the brain, which is formed by the enlarged top of the spinal cord. This part of the brain directly controls breathing, blood flow, and other essential functions.Last Editorial Review: 4/27/2011 5:27:15 PM...

Medulla - Medical

Medulla: The innermost part. The adrenal medulla is the innermost part of that gland. The renal medulla is the inner part of the kidney. The spinal medulla is the part of the spinal cord that is lodged within the vertebral canal.Last Editorial Review...

MEDLINE - Medical

MEDLINE: MEDLINE® is the best known database of the U.S. National Library of Medicine (NLM). MEDLINE enables anyone to query the NLM computer's store of journal article references on specific topics. It currently contains 9 million reference...

MEDLARS - Medical

MEDLARS: MEDLARS® is an acronym that stands for Medical Literature Analysis and Retrieval System. It is a computer-based system of the U.S. National Library of Medicine (NLM) that allows rapid access to NLM's store of biomedical information. ...

Medium-chain acyl-CoA dehydrogenase deficiency - Medical

Medium-chain acyl-CoA dehydrogenase deficiency: See: MCAD deficiency. Last Editorial Review: 11/19/2003 MCAD deficiency: Deficiency of an enzyme that makes it impossible to digest certain kinds of fat. MCAD stands for medium-chain acyl-CoA dehy...

Medium-chain acyl-CoA dehydrogenase - Medical

Medium-chain acyl-CoA dehydrogenase: An enzyme abbreviated as MCAD. See: MCAD deficiency. Last Editorial Review: 11/19/2003 MCAD deficiency: Deficiency of an enzyme that makes it impossible to digest certain kinds of fat. MCAD stands for medium...

Mediterranean-style diet - Medical

Mediterranean-style diet: See: Mediterranean diet. Last Editorial Review: 9/22/2004 Mediterranean diet: A diet traditionally followed in Greece, Crete, southern France, and parts of Italy that emphasizes fruits and vegetables, nuts, gra...

Mediterranean Fever - Medical

Mediterranean Fever: A inherited disorder of unknown cause featuring short recurring bouts of fever together with pain in the joints, chest or abdomen. Also called Familial Mediterranean Fever (FMF). Between attacks, the patient seems healthy (...

Mediterranean diet - Medical

Mediterranean diet: A diet traditionally followed in Greece, Crete, southern France, and parts of Italy that emphasizes fruits and vegetables, nuts, grains, olive oil (as opposed to butter) and grilled or steamed chicken and seafood (as opposed to re...

Mediterranean anemia - Medical

Mediterranean anemia: Better known today as thalassemia (or as beta thalassemia or thalassemia major). The clinical picture of this important type of anemia was first described in 1925 by the pediatrician Thomas Benton Cooley. The name thalasse...

Medifast diet - Medical

Medifast diet: The Medifast diet is a low-fat, low-calorie weight loss plan based upon the consumption of specific foods and beverages developed and sold by the Medifast company. The diet plan includes shakes, bars, puddings, soups, oatmeal, hot coco...