| xanthine alkaloids | Alkaloids, which contain xanthine as their nitrogenous base. (12 Dec 1998) |
|---|---|
| xanthine bronchodilator | <pharmacology> A group of medications that work by a common mechanism to effect bronchodilation (open up air passages) in the lungs. Used in the treatment of asthma and related conditions. Examples include: theophylline, aminophylline and dyphylline. (27 Sep 1997) |
| xanthine dehydrogenase | <enzyme> An enzyme that catalyses the oxidation of xanthine in the presence of NAD+ to form urate and NADH. It acts also on a variety of other purines and aldehydes. Chemical name: Xanthine:NAD+ oxidoreductase Registry number: EC 1.1.1.204 (12 Dec 1998) |
| xanthine nucleotide | The monophosphoric ester of xanthosine. An intermediate in GMP biosynthesis. Synonym: xanthidylic acid, xanthine nucleotide, xanthylic acid. (05 Mar 2000) |
| xanthine oxidase | <enzyme> Dehydrogenases involved in conversion of hypoxanthine to xanthine and xanthine to uric acid, as the final catabolism of purines. Deficient in the human disease xanthinuria. (18 Nov 1997) |
| xanthine ribonucleoside | 9-beta-d-ribosylxanthine;the deamination product of guanosine (O replacing -NH2). Synonym: xanthine ribonucleoside. Abbreviation: Xao (05 Mar 2000) |
| xanthinine | <chemistry> A complex nitrogenous substance related to urea and uric acid, produced as a white powder; so called because it forms yellow salts, and because its solution forms a blue fluorescence like quinine. Origin: Gr. Xanqos = yellow + quinine. Source: Websters Dictionary (01 Mar 1998) |
| xanthinol niacinate | <chemical> 3-pyridinecarboxylic acid compound with 3,7-dihydro-7- (2-hydroxy-3-((2-hydroxyethyl)methylamino)propyl)-1,3- dimethyl-1h-purine-2,6-dione (1:). A vasodilator used in peripheral vascular disorders and insufficiency. It may cause gastric discomfort and hypotension. Pharmacological action: vasodilator agents. Chemical name: 3-Pyridinecarboxylic acid, compd. With 3,7-dihydro-7-(2-hydroxy-3-((2-hydroxyethyl)methylamino)propyl)-1,3-dimethyl-1H-purine-2,6-dione (1:1) (12 Dec 1998) |
| xanthinuria | 1. Excretion of abnormally large amounts of xanthine in the urine. 2. A disorder resulting from defective synthesis of xanthine oxidase, characterised by urinary excretion of xanthine in place of uric acid, hypouricaemia, and, in some cases, the formation of xanthine stones; autosomal recessive inheritance. Synonym: xanthiuria, xanthuria. Origin: xanthine + G. Ouron, urine (05 Mar 2000) |
| xanthism | A pigmentary anomaly of blacks, characterised by red or yellow-red hair colour, copper-red skin, and often by dilution of iris pigment. Synonym: rufous albinism. Origin: G. Xanthos, yellowish (05 Mar 2000) |
| xanthium | <botany> A genus of composite plants in which the scales of the involucre are united so as to form a kind of bur; cocklebur; clotbur. Origin: NL, fr. Gr. Xanqion a plant used for dyeing the hair yellow, said to be the Xanthium strumarium, from xanqos = yellow. Source: Websters Dictionary (01 Mar 1998) |
| xanthiuria | 1. Excretion of abnormally large amounts of xanthine in the urine. 2. A disorder resulting from defective synthesis of xanthine oxidase, characterised by urinary excretion of xanthine in place of uric acid, hypouricaemia, and, in some cases, the formation of xanthine stones; autosomal recessive inheritance. Synonym: xanthiuria, xanthuria. Origin: xanthine + G. Ouron, urine (05 Mar 2000) |
| xantho- | <prefix> A combining form meaning yellow; as in xanthocobaltic salts. Used also adjectively in chemistry. Origin: Gr. Xanqos = yellow (29 Oct 1998) |
| xanthoastrocytoma | <tumour> Pleomorphic xanthoastrocytoma, a rare variant of astrocytoma usually presenting early in life with seizures. The tumour is superficially located and composed of pleomorphic glial cells, lipidised astrocytes, and perivascular lymphocytes. Synonym: xanthoastrocytoma. (05 Mar 2000) |
| xanthocarpous | <botany> Having yellow fruit. Origin: Gr. Karpos = fruit. (27 Oct 1998) |