| rac | 1. <molecular biology> Small GTP-binding protein involved in regulating actin cytoskeleton the activated form of rac seems to induce membrane ruffling (whereas rho acts on stress fibres). Rac may be activated by specific GAPs such as Bcr and n chimaerin. 2. <prefix> Prefix for racaemic. (21 Jun 2000) |
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| racaemic | <chemistry> Denoting a mixture of optically active compounds that is itself optically inactive, being composed of an equal number of dextro-and levorotatory substances, which are separable. Those compounds internally compensated (i.e., having an internal plane of symmetry), and therefore not separable into d and l (or + and -) forms, are termed meso. (05 Mar 2000) |
| racaemic calcium pantothenate | <chemistry> A mixture of the calcium salts of the dextrorotatory and levorotatory isomers of pantothenic acid; same uses as calcium pantothenate. (05 Mar 2000) |
| racaemic mixture | <chemistry> A 50:50 mixture of two enantiomers (such a mixture does not rotate plane-polarized light). (09 Jan 1998) |
| raccoon | <zoology> A North American nocturnal carnivore of the genus procyon of the family procyonidae (Procyon lotor) which allied to the bears, but much smaller, and having a long, full tail, banded with black and gray. Two subgenera and seven species are currently recognised. Its body is gray, varied with black and white. Called also coon, and mapach. Origin: F. Raton, prop, a little rat, fr. Rat rat, perhaps of German origin. See Rat. Source: Websters Dictionary (01 Mar 1998) |
| raccoon eye | <clinical sign, ophthalmology> The appearance of the eyes produced by subconjunctival haemorrhage and/or periorbital ecchymosis. Synonym: bilateral medial orbital ecchymoses. (21 Jun 2000) |
| race | 1. The descendants of a common ancestor; a family, tribe, people, or nation, believed or presumed to belong to the same stock; a lineage; a breed. "The whole race of mankind." (Shak) "Whence the long race of Alban fathers come." (Dryden) Naturalists and ehnographers divide mankind into several distinct varieties, or races. Cuvier refers them all to three, Pritchard enumerates seven, Agassiz eight, Pickering describes eleven. One of the common classifications is that of Blumenbach, who makes five races: the Caucasian, or white race, to which belong the greater part of the European nations and those of Western Asia; the Mongolian, or yellow race, occupying Tartary, China, Japan, etc.; the Ethiopian, or negro race, occupying most of Africa (except the north), Australia, Papua, and other Pacific Islands; the American, or red race, comprising the Indians of North and South America; and the Malayan, or brown race, which occupies the islands of the Indian Archipelago, etc. Many recent writers classify the Malay and American races as branches of the Mongolian. 2. Company; herd; breed. "For do but note a wild and wanton herd, Or race of youthful and unhandled colts, Fetching mad bounds." (Shak). 3. <botany> A variety of such fixed character that it may be propagated by seed. 4. Peculiar flavor, taste, or strength, as of wine; that quality, or assemblage of qualities, which indicates origin or kind, as in wine; hence, characteristic flavor; smack. "A race of heaven." "Is it [the wine] of the right race ?" (Massinqer) 5. Hence, characteristic quality or disposition. "And now I give my sensual race the rein." (Shak) "Some . . . Great race of fancy or judgment." (Sir W. Temple) Synonym: Lineage, line, family, house, breed, offspring, progeny, issue. Origin: F. Race; cf. Pr. & Sp. Raza, It. Razza; all from OHG. Reiza line, akin to E. Write. See Write. 1. A progress; a course; a movement or progression. 2. Esp, swift progress; rapid course; a running. "The flight of many birds is swifter than the race of any beasts." (Bacon) 3. Hence: The act or process of running in competition; a contest of speed in any way, as in running, riding, driving, skating, rowing, sailing; in the plural, usually, a meeting for contests in the running of horses; as, he attended the races. "The race is not to the swift." (Eccl. Ix. 11) "I wield the gauntlet, and I run the race." (Pope) 4. Competitive action of any kind, especially when prolonged; hence, career; course of life. "My race of glory run, and race of shame." (Milton) 5. A strong or rapid current of water, or the channel or passage for such a current; a powerful current or heavy sea, sometimes produced by the meeting of two tides; as, the Portland Race; the Race of Alderney. 6. The current of water that turns a water wheel, or the channel in which it flows; a mill race. The part of the channel above the wheel is sometimes called the headrace, the part below, the tailrace. Origin: OE. Ras, res, rees, AS. Raes a rush, running; akin to Icel. Ras course, race. Source: Websters Dictionary (01 Mar 1998) |
| race relations | Cultural contacts between people of different races. (12 Dec 1998) |
| racefemine | <drug> Used as a uterine relaxant for relief of postpartum pain. Chemical name: Dl-threo-alpha-Methyl-N-(1-methyl-2-phenoxyethyl)phenethylamine (21 Jun 2000) |
| racemase | <enzyme> Enzymes that catalyze inversion of the configuration around an asymmetric carbon in a substrate having one (racemase) or more (epimerase) centre(s) of asymmetry. For example; hydroxyproline, ribulose phosphate). Registry number: EC 5.1 (21 Jun 2000) |
| racemate | <chemistry> A salt of racemic acid. Source: Websters Dictionary (01 Mar 1998) |
| raceme | <plant biology> An indeterminate inflorescence in which a main main stem produces a series of flowers on lateral stalks, the oldest at the base and the youngest at the top. (09 Oct 1997) |
| racemed | <botany> Arranged in a raceme, or in racemes. Source: Websters Dictionary (01 Mar 1998) |
| racemic | <chemistry> Pertaining to, or designating, an acid found in many kinds of grapes. It is also obtained from tartaric acid, with which it is isomeric, and from sugar, gum, etc, by oxidation. It is a sour white crystalline substance, consisting of a combination of dextrorotatory and levorotatory tartaric acids. Origin: Cf. F. Racemique. See Raceme. Source: Websters Dictionary (01 Mar 1998) |
| racemic mixture | A mixture of equal amounts of the two stereoisomersof an optically active substance. (09 Oct 1997) |