|Medical Dictionary - Dictionary of Medicine and Human Biology|
ρ, upper case P
Symbol for recipe in a prescription. See prescription (2) .
Symbol denoting movement of a substance in paper chromatography relative to the solvent front ( i.e., retardation factor); equal to the migration distance of a substance divided by the migration distance of the solvent front.
Symbol for radium.
Obsolete term for making congruous stepwise cuts on apposing bone surfaces for stability after impaction. [Fr. raboter, to plane]
Relating to or suffering from rabies. [L. rabidus, raving, mad]
Highly fatal infectious disease that may affect all species of warm-blooded animals, including humans; transmitted by the bite of infected animals including dogs, cats, skunks, wolves, foxes, raccoons, and bats, and caused by a neurotropic species of Lyssavirus, a member of the family Rhabdoviridae, in the central nervous system and the salivary glands. The symptoms are characteristic of a profound disturbance of the nervous system, e.g., excitement, aggressiveness, and madness, followed by paralysis and death. Characteristic cytoplasmic inclusion bodies (Negri bodies) found in many of the neurons are an aid to rapid laboratory diagnosis. SYN: hydrophobia. [L. rage, fury, fr. rabio, to rave, to be mad] dumb r. SYN: paralytic r.. furious r. the form or stage of r. in which the animal is markedly hyperactive, characterized by periods of agitation, thrashing, running, snapping, or biting. paralytic r. a form or stage of r. marked by paralytic symptoms. SYN: dumb r..
Prefix for racemic.
Used as a uterine relaxant for relief of postpartum pain.
An enzyme capable of catalyzing racemization, i.e., inversions of asymmetric groups; when more than one center of asymmetry is present, “epimerase” is used ( e.g., hydroxyproline, ribulose phosphate).
A racemic compound, or the salt or ester of such a compound. SEE ALSO: racemic.
An optically inactive chemical compound. SEE ALSO: racemic.
racemic (r) (ra-se′mik, -sem′ik)
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.”
racemization (ra′se-mi-za′shun, ras-mi-)
Partial conversion of one enantiomorph into another (as an l-amino acid to the corresponding d-amino acid) so that the specific optical rotation is decreased, or even reduced to zero, in the resulting mixture.
Branching, with nodular terminations; resembling a bunch of grapes. [L. racemosus, full of clusters]
racephedrine hydrochloride (ras-e-fed′rin)
A sympathomimetic drug with peripheral effects similar to those of epinephrine and with the same actions and uses as ephedrine.
The spine. [G. rhachis, spine, backbone]
SYN: lumbar puncture. [rachi- + G. kentesis, puncture]
Forcible correction of lateral curvature of the spine by lateral pressure against the convexity of the curve. [rachi- + G. lysis, a loosening]
SYN: lumbar puncture. [rachio- + G. kentesis, puncture]
A subarachnoid effusion of fluid in the spinal canal. [rachio- + G. chysis, a pouring out]
Conjoined twins united back to back with union of their spinal columns. See conjoined twins, under twin. SYN: rachipagus. [rachio- + G. pagos, something fixed]
SYN: spinal paralysis. [rachio- + G. plege, stroke]
A specially devised instrument for dividing the laminae of the vertebrae. SYN: rachitome. [rachio- + G. tome, incision]
SYN: laminotomy. [rachio- + G. tome, incision]
rachis, pl .rachidesrachises (ra′kis, ra′ki-dez, rak-)
SYN: vertebral column. [G. spine, backbone]
1. Embryologic failure of fusion of vertebral arches and neural tube with consequent exposure of neural tissue at the surface; spina bifida cystica with myelocele or myeloschisis. 2. Spinal dysraphism. [G. rhachis, spine, + schisis, division] r. partialis SYN: merorachischisis. r. totalis SYN: holorachischisis.
Relating to or suffering from rickets (rachitis). SYN: rickety.
SYN: rickets. [G. rhachitis] r. fetalis congenital rickets. SYN: r. intrauterina, r. uterina. r. fetalis annularis congenital enlargement of the epiphyses of the long bones. r. fetalis micromelica a congenital condition in which development of the long bones is deficient. r. intrauterina, r. uterina SYN: r. fetalis. r. tarda SYN: osteomalacia.
A rachitic state or tendency.
Producing or causing rickets. [rachitis + G. genesis, production]
1. The unit for the dose absorbed from ionizing radiation, equivalent to 100 ergs per gram of tissue; 100 r. = 1 Gy. 2. Symbol for radian.
An obsolete procedure involving the video tracking of heart motion by means of image intensification and closed circuit television during fluoroscopy; enabled cardiac motion to be measured by reproducible linear graphic tracing.
SYN: root amputation. [L. radix, root, + G. ektome, excision]
Edward P., Jr., U.S. physiologist, *1922. See R. nomogram.
The property of being radiable.
Capable of being penetrated or examined by rays, especially by x-rays.
In a direction toward the radial side.
1. Relating to the radius (bone of the forearm), to any structures named from it, or to the r. or lateral aspect of the upper limb as compared to the ulnar or medial aspect. SYN: radialis [TA] . 2. Relating to any radius. 3. Radiating; diverging in all directions from any given center. [L. radialis, fr. radius, ray, lateral bone of the forearm]
radialis (ra-de-a′lis) [TA]
SYN: radial (1) . [Mod. L.]
radian (rad) (ra′de-an)
A supplementary SI unit of plane angle. [L. radius, ray]
1. Giving out rays. 2. A point from which light radiates to the eye.
1. To spread out in all directions from a center. 2. To emit radiation. [L. radio, pp. -atus, to shine]
radiatio, pl .radiationes (ra-de-a′she-o, -she-o′nez)
In neuroanatomy, a term applied to any one of the thalamocortical fiber systems that together compose the corona radiata of the cerebral hemisphere's white matter ( e.g., optic radiation, acoustic radiation, etc.). SYN: radiation (3) . [L.] r. acustica [TA] SYN: acoustic radiation. r. corporis callosi [TA] SYN: radiation of corpus callosum. r. inferior thalami [TA] SYN: inferior thalamic peduncle. r. optica [TA] SYN: optic radiation. r. pyramidalis SYN: pyramidal radiation. r. thalami anterior [TA] SYN: anterior thalamic radiation. r. thalami centralis [TA] SYN: central thalamic radiation. r. thalamica posterior [TA] SYN: posterior thalamic radiation.
1. In chemistry, a group of elements or atoms usually passing intact from one compound to another, but usually incapable of prolonged existence in a free state ( e.g., methyl, CH3); in chemical formulas, a r. is often distinguished by being enclosed in parentheses or brackets. 2. Thorough or extensive; relating or directed to the extirpation of the root or cause of a morbid process; e.g., a r. operation. 3. Denoting treatment by extreme, drastic, or innovative, as opposed to conservative, measures. 4. SYN: free r.. [L. radix (radic-), root] acid r. a r. formed from an acid by loss of one or more hydrogen ions; e.g., SO4−, NO3−. color r. SYN: chromophore. free r. a r. in its (usually transient) uncombined state; an atom or atom group carrying an unpaired electron and no charge; e.g., hydroxyl and methyl Free radicals may be involved as short-lived, highly active intermediates in various reactions in living tissue, notably in photosynthesis. The free r. nitric oxide, NO, plays an important role in vasodilation. SYN: r. (4) .Free radicals occur naturally within the body as a result of metabolic processes and can also be introduced from without (through smoking, inhaling environmental pollutants, or exposure to UV radiation). They interact readily with nearby molecules and may cause cellular damage, including genetic alterations. It has been theorized that they are involved in plaque formation in atherosclerosis, in cancer, and in degenerative disorders such as Alzheimer dementia and parkinsonism. Natural enzymes such as superoxide dismutase and peroxidase are thought to counteract free radicals, and there is evidence that many nutrients, including vitamins C and E and β-carotene, also exert an antioxidant effect. see also antioxidant. oxygen-derived free radicals an atom or atom group having an unpaired electron on an oxygen atom, typically derived from molecular oxygen. For example, one-electron reduction of O2 produces the superoxide r., O2·; other examples include the hydroperoxyl r. (HOO·), the hydroxyl r. (HO·), and nitric oxide (NO·). These apparently have a role in reprofusion injury.
Plural of radix.
A rootlet or structure resembling one, as the r. of a vein, a minute veinlet joining with others to form a vein, or the r. of a nerve, a nerve fiber that joins others to form a nerve. [L. radicula, dim. of radix, root]
SYN: rhizotomy. [L. radix (radic-), root, + G. tome, incision]
A spinal nerve root. [L. dim of radix, root]
Neuralgia due to irritation of the sensory root of a spinal nerve. [radicul- + G. algos, pain]
1. Relating to a radicle. 2. Pertaining to the root of a tooth.
SYN: rhizotomy. [radicul- + G. ektome, excision]
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