Glossary of Bio-Medical Terms



X Chromosome

MS = The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species.

AN = abnom: coord M with SEX CHROMOSOME ABBERATIONS (IM) or specific dis (IM) + SEX CHROMOSOME ABERRATIONS (NIM); X-linked disease = GENETIC DISEASES, X-LINKED or specifics; X-CHROMOSOME, HUMAN is also available

UI = D014960


X-Ray Diffraction

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)

AN = an anal chem technique; application to study of crystal structure = CRYSTALLOGRAPHY, X-RAY; NIM

UI = D014961


X-Ray Film

MS = A film base coated with an emulsion designed for use with x-rays.

AN = the film itself: do not confuse with x-ray technique ( = /radiogr or RADIOGRAPHY); /hist: index under RADIOGRAPHY /hist or TECHNOLOGY, RADIOLOGIC /hist

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



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.

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

UI = D014965



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



AN = do not confuse with XANTHINES; includes xanthones

UI = D014966



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)

AN = a specific chem: do not confuse with XANTHINES or XANTHENES

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

UI = D014968


Xanthine Oxidase

MS = An iron-molybdenum flavoprotein containing FLAVIN-ADENINE DINUCLEOTIDE that oxidizes hypoxanthine, some other purines and pterins, and aldehydes. Deficiency of the enzyme, an autosomal recessive trait, causes xanthinuria. EC


UI = D014969



MS = Purine bases found in body tissues and fluids and in some plants.

AN = do not confuse with XANTHENES; XANTHINE is also available

UI = D014970


Xanthinol Niacinate

MS = A vasodilator used in peripheral vascular disorders and insufficiency. It may cause gastric discomfort and hypotension.

UI = D014971



MS = A plant genus of the family ASTERACEAE. The name "prickly burweed" is sometimes used but causes confusion with AMSINCKIA.

AN = coord with specific PLANT COMPONENTS term if pertinent; for use in therapy coord IM with PHYTOTHERAPY (IM) + disease/drug ther (IM) + PLANT PREPARATIONS or its indentations/ther use (IM or NIM) + specific plant chemical /ther use (IM) if pertinent; Manual 26.29

UI = D031210



MS = A genus of gram-negative, aerobic, rod-shaped bacteria found in wet soil containing decaying organic material and in water. Cells tend to be pleomorphic if grown on media containing succinate or coccoid if grown in the presence of an alcohol as the sole carbon source. (From Bergey's Manual of Determinative Bacteriology, 9th ed)

UI = D020584


Xanthogranuloma, Juvenile

MS = Benign disorder of infants and children characterized by multiple nodules with lipid-laden, non-Langerhans-cell histiocytes.

AN = non-neoplastic; a non-Langerhans cell histiocytosis

UI = D014972



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.

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

UI = D014973


Xanthomatosis, Cerebrotendinous

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)

AN = a lipid storage dis

UI = D019294



MS = A genus of PSEUDOMONADACEAE whose cells produce a yellow pigment (Gr. xanthos - yellow). It is pathogenic to plants.

UI = D014974


Xanthomonas campestris

MS = A species of gram-negative, aerobic bacteria that is pathogenic for plants.

UI = D016959



MS = Oxygenated forms of carotenoids. They are usually derived from alpha and beta carotene.

UI = D024341



MS = 2-Amino-1,5-dihydro-4,6-pteridinedione. Pigment first discovered in butterfly wings and widely distributed in plants and animals.

AN = a pigment

UI = D014976



MS = A plant genus of the family RANUNCULACEAE. Members contain isoquinoline alkaloids.

AN = coord with specific PLANT COMPONENTS term if pertinent; for use in therapy coord IM with PHYTOTHERAPY (IM) + disease/drug ther (IM) + PLANT PREPARATIONS or its indentations/ther use (IM or NIM) + specific plant chemical /ther use (IM) if pertinent; Manual 26.29

UI = D031950



MS = A plant genus of the family ARACEAE. The common names of 'Coco Yam' (Cocoyam) or 'Elephant's Ear' may be confused with COLOCASIA and other ARACEAE or with common yam (DIOSCOREA). It contains LECTINS.

AN = coord with specific PLANT COMPONENTS term if pertinent; for use in therapy coord IM with PHYTOTHERAPY (IM) + disease/drug ther (IM) + PLANT PREPARATIONS or its indentations/ther use (IM or NIM) + specific plant chemical /ther use (IM) if pertinent; Manual 26.29

UI = D031063



UI = D014977



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)

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

UI = D004490



MS = Chemical substances that are foreign to the biological system. They include naturally occurring compounds, drugs, environmental agents, carcinogens, insecticides, etc.

AN = GEN only; do not interpret: use the term if used by the author

UI = D015262



MS = A method for diagnosing a disease in one organism by inoculating the putative causative organism in a second animal of a different species. It has been used for the detection of parasites (Trypanosoma cruzi and Trichinella spiralis) when peripheral blood smears are negative. (Segen, Current Med Talk, 1995)

AN = permitted with parasitic diseases as well as microbial infections

UI = D020525


Xenograft Model Antitumor Assays

MS = In vivo methods of screening investigative anticancer drugs, biologic response modifiers or radiotherapies. Human tumor tissue or cells are transplanted into mice or rats followed by tumor treatment regimens. A variety of outcomes are monitored to assess antitumor effectivness.

UI = D023041



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.

AN = a rare gas; Xe-132; sometimes used as an inhalation anesthetic

UI = D014978


Xenon Isotopes

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.

AN = Xe-124,126,128-131,134,136; NIM

UI = D014979


Xenon Radioisotopes

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.

AN = Xe-118-123, 125, 127, 133, 135, 137-142; NIM; /blood-csf-urine /metab permitted but not for tracer studies ( = /diag use)

UI = D014980



MS = An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.

AN = NIM when exper animal: no qualif; when IM, qualif permitted

UI = D014981


Xenopus laevis

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.

AN = NIM when exper animal: no qualif; when IM, qualif permitted

UI = D014982


Xenopus Proteins

MS = Proteins obtained from various species of Xenopus. Included here are proteins from the African clawed frog (XENOPUS LAEVIS). Many of these proteins have been the subject of scientific investigations in the area of MORPHOGENESIS and development.

AN = coord IM with specific protein

UI = D029867



MS = A genus of gram-negative, facultatively anaerobic rod-shaped cells which are motile by peritrichous flagella. Late in the growth cycle, spheroplasts or coccoid bodies occur, resulting from disintegration of the cell wall. The natural habitat is the intestinal lumen of certain nematodes. (From Bergey's Manual of Determinative Bacteriology, 9th ed)


UI = D020593


Xeroderma Pigmentosum

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.

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)

UI = D014983



MS = Xeroradiography of the breast.

AN = do not use /util except by MeSH definition; DF: XEROMAMMOGR

UI = D014984



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.

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

UI = D014985



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.

AN = do not use /util except by MeSH definition; DF: XERORADIOGR

UI = D014986



MS = Decreased salivary flow.

AN = decreased saliva flow

UI = D014987



MS = 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



MS = Polysaccharides consisting of xylose units.

UI = D014990



MS = An adrenergic alpha-agonist used as a sedative, analgesic, and muscle relaxant in veterinary medicine.

UI = D014991



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



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



UI = D014994



MS = A group of enzymes that catalyze the hydrolysis of alpha- or beta-xylosidic linkages. EC catalyzes the endo-hydrolysis of 1,4-beta-D-xylosidic linkages; EC catalyzes the endo-hydrolysis of 1,3-beta-D-xylosidic linkages; EC catalyzes the exo-hydrolysis of 1,4-beta-D-linkages from the non-reducing termini of xylans; and EC 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



MS = A 5-carbon keto sugar.

UI = D014996


XYY Karyotype

MS = Abnormal genetic constitution in males characterized by an extra Y chromosome.

AN = do not use /congen & do not coord with INFANT, NEWBORN, DISEASES; check the tags HUMAN & MALE

UI = D014997