Glossary of Bio-Medical Terms
X
RETURN TO INDEX X Chromosome
AN = A 11 qualif except /cytol /transpl; /genet permitted; abnorm: coord IM with SEX CHROMOSOME ABNORMALITIES (IM) or specific dis (IM) + SEX CHROMOSOME ABNORMALITIES (NIM); X-linked dis: coord IM or NIM with dis /genet (IM) + LINKAGE (GENETICS) (IM or NIM)
MS = The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in man and other male-heterogametic species.
UI = D014960
X-Ray Diffraction
AN = an anal chem technique; application to study of crystal structure = CRYSTALLOGRAPHY, X-RAY; NIM
MS = The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
UI = D014961
X-Ray Film
AN = the film itself: do not confuse with x-ray technique ( = /radiogr or RADIOGRAPHY); /hist: index under RADIOGRAPHY /hist or TECHNOLOGY, RADIOLOGIC /hist
MS = A film base coated with an emulsion designed for use with x-rays.
UI = D014962
X-Ray Intensifying Screens
MS = Screens which absorb the energy in the x-ray beam that has penetrated the patient and convert this energy into a light pattern which has as nearly as possible the same information as the original x-ray beam. The more light a screen produces for a given input of x-radiation, the less x-ray exposure and thus shorter exposure time are needed to expose the film. In most film-screen systems, the film is sandwiched between two screens in a cassette so that the emulsion on each side is exposed to the light from its contiguous screen.
UI = D014963
X-Ray Therapy
AN = see note on RADIOTHERAPY when tempted to use for IM; do not index as IM or NIM coord when using /radiother: assume all /radiother is X-RAY THERAPY unless otherwise specified (as /radiother + RADIUM /ther use or /radiother + ULTRAVIOLET THERAPY, etc.): Manual 19.8.63; DF: X RAY THER
UI = D014964
X-Rays
AN = almost never IM; /diag use = RADIOGRAPHY (general) or /radiogr with diseases; /ther use = X-RAY THERAPY or /radiother with diseases (see note on X-RAY THERAPY); do not index as IM or NIM coord when using /rad eff: assume all /rad eff is X-RAYS unless otherwise specified (as /rad eff + GAMMA RAYS); TN 158: how to index IM or NIM, also Manual 19.8.60, 19.8.61, 19.8.63, 28.11.2; X-ray or x-ray in translations: follow text
MS = Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release energy - in the same energy range as gamma rays (0.010-10 Mev), but of non-nuclear origin, of shorter wavelength than ultraviolet; soft x-rays or Grenz rays are less penetrating and longer in wavelength than hard x-rays.
UI = D014965
Xamoterol
AN = a cardiotonic
MS = A selective beta-1-adrenergic partial agonist. Because it is a partial agonist it acts like an agonist when sympathetic activity is low and as an antagonist when sympathetic activity is high. It reduces myocardial ischemia and improves ventricular function in patients with mild to moderate heart failure. In patients with severe heart failure it has been shown to produce benefits in systolic and diastolic function.
UI = D017307
Xanthenes
AN = do not confuse with XANTHINES; includes xanthones
UI = D014966
Xanthine
AN = a specific chem: do not confuse with XANTHINES or XANTHENES
MS = A purine base found in most body tissues and fluids, certain plants, and some urinary calculi. It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine. The methylated xanthine compounds caffeine, theobromine, and theophylline and their derivatives are used in medicine for their bronchodilator effects. (Dorland, 28th ed)
UI = D019820
Xanthine Alkaloids
MS = Alkaloids, which contain xanthine as their nitrogenous base.
UI = D014967
Xanthine Dehydrogenase
MS = An enzyme that catalyzes 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. EC 1.1.1.204.
UI = D014968
Xanthine Oxidase
AN = /defic: consider also XANTHINES /urine (IM) + PURINE-PYRIMIDINE METABOLISM, INBORN ERRORS (IM)
MS = An iron-molybdenum flavoprotein containing FAD that oxidizes hypoxanthine, some other purines and pterins, and aldehydes. Deficiency of the enzyme, an autosomal recessive trait, causes xanthinuria. EC 1.1.3.22.
UI = D014969
Xanthines
AN = do not confuse with XANTHENES
UI = D014970
Xanthinol Niacinate
AN = a vasodilator
MS = 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.
UI = D014971
Xanthogranuloma, Juvenile
AN = non-neoplastic; a non-Langerhans cell histiocytosis
MS = Benign disorder of infants and children characterized by multiple nodules with lipid-laden, non-Langerhans-cell histiocytes.
UI = D014972
Xanthomatosis
AN = non-neoplastic; a metab skin dis manifest of lipidosis; coord with organ/disease term (IM); xanthogranuloma goes here (IM) + GRANULOMA (IM) but note XANTHOGRANULOMA, JUVENILE is available
MS = A condition of morphologic change in which there is accumulation of lipids in the large foam cells of tissues. It is the cutaneous manifestation of lipidosis in which plasma fatty acids and lipoproteins are quantitatively changed. The xanthomatous eruptions have several different distinct morphologies dependent upon the specific form taken by the disease.
UI = D014973
Xanthomatosis, Cerebrotendinous
AN = a lipid storage dis
MS = A lipid storage disease, inherited as an autosomal recessive trait, characterized by xanthomas of the tendons, the white matter of the brain, and the lungs, and by spasticity, ataxia, pyramidal paresis, mental retardation, dementia, early cataracts, and atherosclerosis. It is associated with elevated plasma and tissue levels of cholestanol and defective bile synthesis, with the deposition of cholestanol in the central nervous system and myelin of peripheral nerves. The lesions contain cholesterol and dehydrocholesterol. (Dorland, 28th ed)
UI = D019294
Xanthomonas
AN = pathogenic for plants
MS = A genus of PSEUDOMONADACEAE whose cells produce a yellow pigment (Gr. xanthos - yellow). It is pathogenic to plants.
UI = D014974
Xanthomonas campestris
AN = pathogenic for plants
MS = A species of gram-negative, aerobic bacteria that is pathogenic for plants.
UI = D016959
Xanthophyll
AN = a carotenoid pigment
MS = beta,epsilon-Carotene-3,3'-diol. A carotenoid alcohol widespread in nature. It is present in egg yolk, algae, and petals of yellow flowers, among other sources.
UI = D014975
Xanthopterin
AN = a pigment
MS = 2-Amino-1,5-dihydro-4,6-pteridinedione. Pigment first discovered in butterfly wings and widely distributed in plants and animals.
UI = D014976
Xanthurenates
UI = D014977
Xenarthra
AN = SLOTHS, ARMADILLOS & anteaters; do not confuse X ref AARDVARKS with X ref AARDWOLVES see CARNIVORA; do not confuse X ref ANTEATERS with X ref SPINY ANTEATER see ECHIDNA; IM; qualif permitted
MS = An order of New World mammals characterized by the absence of incisors and canines from among their teeth, and comprising the ARMADILLOS, the SLOTHS, and the anteaters. The order is distinguished from all others by what are known as xenarthrous vertebrae (xenos, strange; arthron, joint): there are secondary, and sometimes even more, articulations between the vertebrae of the lumbar series. The order was formerly called Edentata. (From Random House Unabridged Dictionary, 2d ed; Walker's Mammals of the World, 5th ed, vol. I, p515)
UI = D004490
Xenobiotics
AN = GEN only; do not interpret: use the term if used by the author
MS = Chemical substances that are foreign to the biological system. They include naturally occurring compounds, drugs, environmental agents, carcinogens, insecticides, etc.
UI = D015262
Xenon
AN = a rare gas; Xe-132; sometimes used as an inhalation anesthetic
MS = A noble gas with the atomic symbol Xe, atomic number 54, and atomic weight 131.30. It is found in the earth's atmosphere and has been used as an anesthetic.
UI = D014978
Xenon Isotopes
AN = Xe-124,126,128-131,134,136; NIM, no qualif
MS = Stable xenon atoms that have the same atomic number as the element xenon, but differ in atomic weight. Xe-124, 126, 128-131, 134, and 136 are stable xenon isotopes.
UI = D014979
Xenon Radioisotopes
AN = Xe-118-123, 125, 127, 133, 135, 137-142; NIM; /blood-csf-urine /metab permitted but not for tracer studies ( = /diag use)
MS = Unstable isotopes of xenon that decay or disintegrate emitting radiation. Xe atoms with atomic weights 121-123, 125, 127, 133, 135, 137-145 are radioactive xenon isotopes.
UI = D014980
Xenopus
AN = NIM when exper animal: no qualif; when IM, qualif permitted
MS = An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.
UI = D014981
Xenopus laevis
AN = NIM when exper animal: no qualif; when IM, qualif permitted
MS = The commonest and widest ranging species of the clawed "frog" (Xenopus) in Africa. This species is used extensively in research. There is now a significant population in California derived from escaped laboratory animals.
UI = D014982
Xeroderma Pigmentosum
AN = /blood supply /chem /secret /ultrastruct permitted; if non-neopl, coord IM with precoord organ/dis term (IM); if neopl, coord IM with organ/neopl term (IM)
MS = A rare, pigmentary, and atrophic autosomal recessive disease affecting all races. It is manifested as an extreme photosensitivity to ultraviolet light as the result of a deficiency in the enzyme that permits excisional repair of ultraviolet-damaged DNA.
UI = D014983
Xeromammography
AN = do not use /util except by MeSH definition; DF: XEROMAMMOGR
MS = Xeroradiography of the breast.
UI = D014984
Xerophthalmia
AN = dryness of the eyes; do not restrict to the xerosis of vit A defic: use for any cause; do not confuse with DRY EYE SYNDROMES
MS = Dryness of the eye surfaces caused by deficiency of tears or conjunctival secretions. It may be associated with vitamin A deficiency, trauma, or any condition in which the eyelids do not close completely.
UI = D014985
Xeroradiography
AN = do not use /util except by MeSH definition; DF: XERORADIOGR
MS = A photoelectric method of recording an X-ray image on a coated metal plate, using low-energy photon beams, long exposure time and dry chemical developers.
UI = D014986
Xerostomia
AN = decreased saliva flow
MS = Decreased salivary flow.
UI = D014987
Xipamide
AN = a diuretic
MS = 4-Chloro-5-sulfamoyl-2',6'-salicyloxylidide. Sulfamoyl diuretic and saluretic with antihypertensive activity. It is bound to plasma proteins, thus has a delayed onset and prolonged action.
UI = D014988
Xiphoid Bone
UI = D014989
Xylans
AN = polysaccharides
MS = Polysaccharides consisting of xylose units.
UI = D014990
Xylazine
MS = An adrenergic alpha-agonist used as a sedative, analgesic, and muscle relaxant in veterinary medicine.
UI = D014991
Xylenes
MS = A family of isomeric, colorless aromatic hydrocarbon liquids, that contain the general formula C6H4(CH3)2. They are produced by the destructive distillation of coal or by the catalytic reforming of petroleum naphthenic fractions. (From McGraww-Hill Dictionary of Scientific and Technical Terms, 5th ed)
UI = D014992
Xylitol
MS = A five-carbon sugar alcohol derived from xylose by reduction of the carbonyl group. It is as sweet as sucrose. It is used as a noncariogenic sweetner and as a sugar substitute in diabetic diets. (From Dorland, 28th ed)
UI = D014993
Xylose
AN = a pentose
UI = D014994
Xylosidases
MS = A group of enzymes that catalyze the hydrolysis of alpha- or beta-xylosidic linkages. EC 3.2.1.8 catalyzes the endo-hydrolysis of 1,4-beta-D-xylosidic linkages; EC 3.2.1.32 catalyzes the endo-hydrolysis of 1,3-beta-D-xylosidic linkages; EC 3.2.1.37 catalyzes the exo-hydrolysis of 1,4-beta-D-linkages from the non-reducing termini of xylans; and EC 3.2.1.72 catalyzes the exo-hydrolysis of 1,3-beta-D-linkages from the non-reducing termini of xylans. Other xylosidases have been identified that catalyze the hydrolysis of alpha-xylosidic bonds.
UI = D014995
Xylulose
AN = a pentose
MS = threo-2-Pentulose. A 5-carbon keto sugar.
UI = D014996
XYY Karyotype
AN = do not use /congen & do not coord with INFANT, NEWBORN, DISEASES; check the tags HUMAN & MALE CATALOG: do not use /in inf
MS = Abnormal genetic constitution in males characterized by an extra Y chromosome.
UI = D014997