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Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


methylchloroform (meth-il-chlor′o-form)
SYN: trichloroethane.

3-methylcholanthrene, 20-methylcholanthrene (meth′il-kol-an′thren)
A highly carcinogenic hydrocarbon that can be formed chemically from deoxycholic or cholic acids, or from cholesterol; it induces the synthesis of cytochrome P-450 mRNA; the choice between 3- or 20- for the methyl group depends upon whether hydrocarbon (inner) or steroid (outer) numbering is chosen; in the latter case, the formal relationship to the cholic acids and cholesterol is clear.

methylcitrate (meth-il-sit′trat)
A minor metabolite that accumulates in individuals with propionic acidemia.

methylcobalamin (meth-il-ko-bal′a-men)
SYN: vitamin B12.

3-methylcrotonyl-CoA (meth-il-kro′ton-il)
An intermediate in the degradation of l-leucine; accumulates in a deficiency of M. carboxylase. 3-methylcrotonyl-CoA carboxylase a biotin-dependent enzyme in the pathway of l-leucine degradation that catalyzes the reaction of M. with CO2, ATP, and water to form ADP, orthophosphate, and 3-methylglutaconyl-CoA; a deficiency of this enzyme causes episodes of severe metabolic acidosis.

5-methylcytosine (meth′il-si′to-sen)
A minor base that is present in both bacterial and human DNA.

methyldichloroarsine (MD) (meth′il-di-klor-o-ar′sen)
A vesicant; irritating to the respiratory tract and will produce lung injury and eye injury; has been used in certain military operations.

methyldopa (meth-il-do′pa)
An antihypertensive agent, also used as the ethyl ester hydrochloride, with the same action and uses. SYN: alpha methyl dopa.

methylene (meth′i-len)
The moiety, &cbond;CH2&cbond;.

methylene azure
SYN: azure I.

methylene blue [C.I. 52015]
A basic dye easily oxidized to azure, with dye mixtures; used in histology and microbiology, to stain intestinal protozoa in wet mount preparations, to track RNA and RNase in electrophoresis, and as an antidote for methemoglobinemia; its redox indicator properties are useful in milk bacteriology. Kühne m. m. in absolute alcohol and phenol solution. Loeffler m. a stain for diphtheria organisms that contains m. in dilute ethanol plus a slight amount of potassium hydroxide; dye solution gives best results when aged to a polychrome state. new m. [C.I. 52030] a basic thiazin dye used for supravital staining of reticulocytes in blood smears. polychrome m. an alkaline solution of m. that undergoes progressive oxidative demethylation with aging (ripening) to produce a mixture of m., azures, and methylene violet; boiling with sodium carbonate or other oxidizing agents accomplishes this result quickly, although it is not as highly regarded.

methylene chloride
Mobile liquid with a pungent odor; harmful vapor. Organic solvent used for cellulose acetate plastic; degreasing and cleaning fluids; and in food processing. Pharmaceutical aid (solvent).


methylenesuccinic acid (meth′il-en-suk′sin-ik)
SYN: itaconic acid.

methylene white
SYN: leucomethylene blue.

methylenophil, methylenophile (meth-i-len′o-fil, -fil)
Staining readily with methylene blue; denoting certain cells and histologic structures. SYN: methylenophilic, methylenophilous. [methylene + G. philos, fond]

methylenophilic, methylenophilous (meth′i-le-no-fil′ik, meth′il-e-nof′i-lus)
SYN: methylenophil.

methylergometrine maleate (meth′il-er-go-met′ren)
SYN: methylergonovine maleate.

methylergonovine maleate (meth′il-er-go-no′ven)
A partially synthesized derivative of lysergic acid with oxytocic action, used to prevent or treat postpartum uterine atony and hemorrhage. SYN: methylergometrine maleate.

methylglucamine (meth-il-gloo′ka-men)
Cation commonly used in water-soluble iodinated radiographic contrast media. SYN: N-m.. m. diatrizoate SYN: meglumine diatrizoate.

3-methylglutaconic aciduria (meth-il-gloo-ta-kon′ik)
Elevated levels of 3-methylglutaconic acid in the urine. An inherited disorder whose mild form is a result of a deficiency of 3-methylglutaconyl-CoA hydratase, leading to delayed speech development.

3-methylglutaconyl-CoA hydratase
An enzyme that catalyzes the reaction of trans-3-methylglutaconyl-CoA and water to form 3-hydroxy-3-methylglutaconyl-CoA; this enzyme participates in the pathway for l-leucine degradation; a deficiency of this enzyme will result in 3-methylglutaconic aciduria.

methylglyoxal (meth′il-gli-ok′sal)
Pyruvaldehyde;the aldehyde of pyruvic acid; an intermediate of carbohydrate metabolism in certain organisms. SYN: pyruvic aldehyde. m. bis(guanylhydrazone) an antineoplastic agent.

methylglyoxalase (meth′il-gli-oks′a-las)
SYN: lactoylglutathione lyase.

methyl green [C.I. 42585]
A basic triphenylmethane dye used as a chromatin stain and, in combination with pyronin, for differential staining of RNA (red) and DNA (green); also used as a tracking dye for DNA in electrophoresis.

methylhexaneamine (meth′il-hek-san′a-men, -min)
A volatile sympathetic amine base, used as an inhalant nasal decongestant.

methylkinase (meth′il-ki′nas)
SYN: methyltransferase.

methylmalonate semialdehyde (meth′il-ma-lon-at)
An intermediate in l-valine catabolism; elevated in certain inborn disorders.

methylmalonic acid (meth′il-ma-lon′ik)
2-Methylpropanedioic acid, an important intermediate in fatty acid metabolism; seen in elevated levels in cases of vitamin B12 deficiency. Note that methylmalonate is not methyl malonate, which is the dimethyl ester of malonate. SYN: isosuccinic acid.

methylmalonic acidemia
SYN: ketotic hyperglycinemia.

methylmalonic aciduria
Excretion of excessive amounts of methylmalonic acid in urine owing to deficient activity of methylmalonyl-CoA mutase or deficient cobalamin reductase. Two types occur: 1) an inborn error of metabolism resulting in severe ketoacidosis shortly after birth, with long-chain urinary ketones; autosomal recessive inheritance, caused by mutations in the methylmalonyl-CoA mutase gene (MCM) on chromosome 6p [MIM*251000]; 2) acquired, a type due to vitamin B12 deficiency [MIM*251110] due to defective synthesis of adenosylcobalamin.

An intermediate in the degradation of several metabolites ( e.g., valine, methionine, odd-chain fatty acids, theronine); elevated in cases of pernicious anemia. methylmalonyl-CoA epimerase an enzyme that catalyzes the interconversion of d-methylmalonyl-CoA and l-methylmalonyl-CoA. methylmalonyl-CoA mutase an enzyme that catalyzes a reversible interconversion of l-methylmalonyl-CoA and succinyl-CoA; a cobalamin-dependent enzyme; deficiency of this enzyme will result in methylmalonic acidemia.

SYN: dimethylmercury.

methylmorphine (meth-il-mor′fen)
SYN: codeine.

methylol (meth′i-lol)
Hydroxymethyl; the moiety, &cbond;CH2OH.

methyl orange
A weakly acid dye used as a pH indicator (red at 3.2, yellow at 4.4). SYN: helianthine.

methylose (meth′i-los)
A sugar in which the carbon atom farthest from the carbonyl group is a methyl (CH3).

methylparaben (meth-il-par′a-ben)
An antifungal preservative. SYN: methyl hydroxybenzoate.

methylpentose (meth-il-pen′tos)
A hexose (a 6-deoxyhexose) in which carbon-6 is part of a methyl group; e.g., rhamnose, fucose.

methylphenidate hydrochloride (meth-il-fen′i-dat)
A central nervous system stimulant used to produce mild cortical stimulation in various types of depressions; commonly used in the treatment of hyperkinetic or hyperactive (attention deficit disorder) children.

methylprednisolone (meth′il-pred-nis′o-lon)
An anti-inflammatory glucocorticoid. m. acetate has the same actions and uses as m.; aqueous suspensions are suitable for intrasynovial and soft tissue injection. sodium m. succinate it has the same metabolic and anti-inflammatory actions as the parent compound, m.; because of its solubility it can be administered in small volumes.

methyl red
A weakly acid dye used as a pH indicator (red at 4.8, yellow at 6.0); easily reduced with loss of color, and pH readings must be made rapidly.

5-methylresorcinol (meth′il-re-sor′sin-ol)
SYN: orcinol.

methylrosaniline chloride (meth′il-ro-zan′i-len, -lin)
SYN: crystal violet.

methyl salicylate
The methyl ester of salicylic acid, produced synthetically or distilled from Gaultheria procumbens (family Ericaceae) or from Betula lenta (family Betulaceae); used externally and internally for the treatment of various forms of rheumatism. SYN: checkerberry oil, gaultheria oil, sweet birch oil, wintergreen oil.

methyl-tert-butyl ether (MTBE)
Used to dissolve gallbladder stones.

methyltestosterone (meth′il-tes-tos′ter-on)
A methyl derivative of testosterone, with the same actions and uses, except that it is active when given orally or sublingually. Used in the treatment of hypogenitalism. SYN: 17α-m..

methylthioadenosine (meth′il-thi′o-a-den′o-sen)
Adenosine carrying an –SCH3 group in place of OH at position 5′; the –SCH3 group is transferred to α-aminobutyric acid to form l-methionine in some bacteria. M. is formed from S-adenosyl-l-methionine in the course of spermidine synthesis by loss of the alanine moiety. SYN: thiomethyladenosine.

methylthiouracil (meth′il-thi-o-u′ra-sil)
An antithyroid compound with the same action as propylthiouracil, but with a smaller dose required.

methyltocol (meth-il-to′kol)
A methylated tocol; e.g., tocotrienol, the tocopherols.

methyltransferase (meth-il-trans′fer-as)
Any enzyme transferring methyl groups from one compound to another. SYN: demethylase, methylkinase, transmethylase.

methyl violet [C.I. 42535]
Mixtures of tetra-, penta-, or pararosanilin which vary in shade of violet depending on the extent of methylation (designated R for reddish shades, B for bluish shades); the hexamethyl compound is known as crystal violet, the pentamenthyl compound as m. 6B. As stains, m. has many bacteriological, histological, and cytological applications.

methylxanthines (meth′il-zan′thinz)
A chemical group of drugs derived from xanthine (a purine derivative); members of the group include theophylline, caffeine, and theobromine.

methyl yellow
SYN: butter yellow.

methyprylon, methyprylone (meth-i-pri′lon, -lon)
A sedative and hypnotic.

methysergide maleate (meth-i-ser′jid)
A serotonin antagonist, weakly adrenolytic, chemically related to methylergonovine; used in the prophylactic treatment of vascular headache (migraine); untoward effects are common.

methysticum (me-this′ti-kum)
The root of Piper m. (family Piperaceae), a plant of the Pacific islands, used by the natives as an intoxicant. It has been used in diarrhea and in inflammatory affection of the urogenital tract. SYN: kava (1) .

Abbreviation for metmyoglobin.

metmyoglobin (metMb) (met′mi-o-glo′bin)
Myoglobin in which the ferrous ion of the heme prosthetic group is oxidized to ferric ion; ferrimyoglobin.

metoclopramide hydrochloride (met′o-klo-pram′id)
An antiemetic agent.

metocurine iodide (met-o-kur′en)
A nondepolarizing neuromuscular blocking agent used to provide relaxation during surgical operations. SYN: dimethyl d-tubocurarine, dimethyl tubocurarine iodide.

metolazone (me-tol′a-zon)
A diuretic with antihypertensive activity.

metopagus (me-top′a-gus)
Conjoined twins united at the forehead. See conjoined twins, under twin. [G. metopon, forehead, + pagos, something fixed]

metopic (me-to′pik, me-top′ik)
Relating to the forehead or anterior portion of the cranium. [G. metopon, forehead]

metopion (me-to′pe-on)
A craniometric point midway between the frontal eminences. SYN: metopic point. [G. metopon, forehead]

metopism (met′o-pizm)
Persistence of the frontal suture in the adult. [G. metopon, forehead]

metopoplasty (met′o-po-plas-te, me-top′o-plas-te)
Plastic surgery of the skin or bone of the forehead. [G. metopon, forehead, + plastos, formed]

metoposcopy (met′o-pos′ko-pe)
The study of physiognomy. [G. metopon, forehead, + skopeo, to view]

metoprolol tartrate (me-to′pro-lol)
A β-adrenergic blocking agent used in the treatment of hypertension; exhibits some cardioselectivity.

Metorchis (met-or′kis)
A genus of opisthorchid fish-borne flukes parasitic in the gallbladder of fish-eating mammals and birds, common in north temperate regions. M. conjunctus is a species that occurs in dogs and cats, and occasionally in humans, in North America. [G. meta, behind, + orchis, testicle]

metoxenous (me-tok′se-nus)
SYN: heterecious. [G. meta, beyond, + xenos, host]


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