| alpha error | The statistical error (said to be of the first kind or type I) made in testing an hypothesis when it is concluded that a result is positive when it really is not. Alpha error is often referred to as a false positive. (12 Dec 1998) |
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| alpha-farnesene | 3,7,11-Trimethyl-1,3,6,10-dodecatetraene;a straight open-chain hydrocarbon built up of three isoprene units; one of the four isomeric forms occurs in the natural coating of apples. (05 Mar 2000) |
| alpha-fetoprotein | <protein, tumour marker> A protein substance that is normally produced by the liver cells. It is one of the first alpha-globulins to appear in mammalian sera during development of the embryo and the dominant serum proteins in early embryonic life. They reappear in the adult serum during certain pathologic states. Measurement of the alpha-fetoprotein level in the bloodstream has been used as a early detection test for some forms of cancer (hepatocellular carcinoma). Alpha-fetoprotein can also be an important marker in the fluid obtained by amniocentesis for the prenatal diagnosis of anencephaly and other open neural tube defects such as spina bifida. Elevated in: wrong dates for a pregnancy, multiple gestation, midline closure (neural-tube) defects, encephalocele, anencephaly, liver tumours, hepatoblastoma, haemangioendothelioma (occasionally, mild), hepatocellular carcinoma (HCC, hepatoma). The level produced by liver tumours (hepatomas), germ cell tumours (teratocarcinoma and embryonal cell carcinomas) permits the monitoring of response to treatment of these tumours. Decreased in: wrong dates for a pregnancy, chromosome abnormality (including Down syndrome) Acronym: AFP (27 Jun 1999) |
| alpha-fetoproteins | Increases in maternal blood during pregnancy and, when detected by amniocentesis, is an important indicator of open neural tube defects and is also used as a tumour marker in adults with hepatocellular carcinoma, beta-fetoproteins, although a foetal liver protein, has been detected in adult patients with liver disease, gamma-fetoproteins occurs in various neoplasms. See: fetoglobulins. (05 Mar 2000) |
| alpha fibres | Large somatic motor or proprioceptive nerve fibre's conducting impulses at rates near 100 m/sec. (05 Mar 2000) |
| alpha-fucosidase | <enzyme> An enzyme that catalyses the hydrolysis of an an alpha-l-fucoside, producing an alcohol and l-fucose; a deficiency of the lysosomal enzyme will result in fucosidosis. (05 Mar 2000) |
| alpha-galactosidase | <enzyme> An enzyme that catalyses the hydrolysis of terminal, non-reducing alpha-d-galactose residues in alpha-galactosides including galactose oligosaccharides, galactomannans, and galactolipids. Chemical name: alpha-D-Galactoside galactohydrolase Registry number: EC 3.2.1.22 (12 Dec 1998) |
| alpha-globulin | <protein> The serum globulins with the most rapid electrophoretic migration, further subdivided into faster alpha(1)- and slower alpha(2)-globulins. (12 Dec 1998) |
| alpha-glucan branching glycosyltransferase | 1,4-alpha-d-glucan branching enzyme |
| alpha-glucan phosphorylase | <enzyme> Enzyme that catalyses the sequential removal of glycosyl residues from glycogen to yield one glucose-1-phosphate per reaction. Its activity is controlled by phosphorylation (by phosphorylase kinase). (21 Jun 2000) |
| alpha glucosidase | <enzyme> An enzyme which removes the last 1,4-linked alpha-D-glucose residue from the nonreducing end of a long chain (or polymer) of such residues, making an alpha-D-glucose molecule out of it in the process. (09 Oct 1997) |
| alpha-glucosidases | <enzyme> Enzymes that catalyze the exohydrolysis of 1,4-alpha-glucosidic linkages with release of alpha-glucose. Chemical name: alpha-D-Glucoside glucohydrolases Registry number: EC 3.2.1.20 (12 Dec 1998) |
| alpha granule | A granule of an alpha cell that was named as the first of several kinds or because it was acidophilic. (05 Mar 2000) |
| alpha helix | <molecular biology> A particular helical folding of the polypeptide backbone in protein molecules (both fibrous and globular), in which the carbonyl oxygens are all hydrogen bonded to amide nitrogen atoms three residues along the chain. The translation of amino acid residues along the long axis is 0.15 nm and the rotation per residue, 100 |
| alpha-hydroxyethylthiamin pyrophosphate | The activated form of acetaldehyde that is formed during the decarboxylation of active pyruvate. Formed in alcohol fermentation and in carbohydrate metabolism. Synonym: a-hydroxyethylthiamin pyrophosphate. (05 Mar 2000) |