| xanthelasma palpebrarum | Soft yellow-orange plaques on the eyelids or medial canthus, the most common form of xanthoma; may be associated with low-density lipoproteins, especially in younger adults Synonym: xanthelasma, xanthoma palpebrarum. (05 Mar 2000) |
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| xanthematin | A yellow substance derived from haematin by treating with nitric acid. (05 Mar 2000) |
| xanthemia | Synonym: carotenaemia. Origin: xanth-+ G. Haima, blood (05 Mar 2000) |
| xanthene | <chemical> A yellowish, alcohol and ether soluble compound that serves as the chemical core for the dyes fluoroscein, eosin and rhodamine, by itself, xanthene is used as a fungicide and in organic synthesis. (11 May 1997) |
| xanthene dyes | Derivatives of the compound xanthene; include the pyronins, rhodamines, and fluoresceins. (05 Mar 2000) |
| xanthic | 1. Tending toward a yellow colour, or to one of those colours, green being excepted, in which yellow is a constituent, as scarlet, orange, etc. <botany> Xanthic colours, those colours (of flowers) having some tinge of yellow; opposed to cyanic colours. See Cyanic. 2. <chemistry> Possessing, imparting, or producing a yellow colour; as, xanthic acid. Of or pertaining to xanthic acid, or its compounds; xanthogenic. Of or pertaining to xanthin. <chemistry> Xanthic acid, a heavy, astringent, colourless oil, C2H5O.CS.SH, having a pungent odour. It is produced by leading carbon disulphide into a hot alcoholic solution of potassium hydroxide. So called from the yellow colour of many of its salts. Called also xanthogenic acid. Origin: Gr. Xanqos = yellow: cf. F. Xanthique. Source: Websters Dictionary (01 Mar 1998) |
| xanthide | <chemistry> A compound or derivative of xanthogen. See: Xantho-. Source: Websters Dictionary (01 Mar 1998) |
| xanthidium | <botany> A genus of minute unicellular algae of the desmids. These algae have a rounded shape and are armed with glochidiate or branched aculei. Several species occur in ditches, and others are found fossil in flint or hornstone. Origin: NL, fr. Gr. Xanqos = yellow. Source: Websters Dictionary (01 Mar 1998) |
| xanthidylic acid | The monophosphoric ester of xanthosine. An intermediate in GMP biosynthesis. Synonym: xanthidylic acid, xanthine nucleotide, xanthylic acid. (05 Mar 2000) |
| xanthin | 1. <physiology> A crystalline nitrogenous body closely related to both uric acid and hypoxanthin, present in muscle tissue, and occasionally found in the urine and in some urinary calculi. It is also present in guano. So called from the yellow colour of certain of its salts (nitrates). 2. <chemistry> A yellow insoluble colouring matter extracted from yellow flowers; specifically, the colouring matter of madder. [Formerly written also xanthein. 3. <chemistry> One of the gaseous or volatile decomposition products of the xanthates, and probably identical with carbon disulphide. Origin: Gr. Xanqos = yellow. Source: Websters Dictionary (01 Mar 1998) |
| xanthine | <biochemistry> A purine, the starting point for purine degradation. Its methylated derivatives (theophylline, theobromine, caffeine) are potent cAMP phosphodiesterase inhibitors. (18 Nov 1997) |
| 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) |