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Medical Dictionary


melanopathy (mel′a-nop′a-the)
Any disease marked by abnormal pigmentation of the skin. [melano- + G. pathos, suffering]

melanophage (mel′a-no-faj, me-lan′o-faj)
A histiocyte that has phagocytized melanin. [melano- + G. phagein, to eat]

melanophore (mel′a-no-for, me-lan′o-for)
A dermal pigment cell that does not secrete its pigment granules but participates in rapid color changes by intracellular aggregation and dispersal of melanosomes; it is well developed in fish, amphibians, and reptiles, but absent in humans. [melano- + G. phoros, bearing]

melanoplakia (mel′a-no-pla′ke-a)
The occurrence of pigmented patches on the tongue and buccal mucous membrane. [melano- + G. plax, plate, plaque]

melanoprotein (mel′a-no-pro′ten)
A protein complex containing melanin.

melanorrhagia (mel′a-no-ra′je-a)
SYN: melena. [melano- + G. rhegnymi, to burst forth]

melanorrhea (mel′a-no-re′a)
SYN: melena. [melano- + G. rhoia, a flow]

melanosis (mel-a-no′sis)
Abnormal dark brown or brown-black pigmentation of various tissues or organs, as the result of melanin or, in some situations, other substances that resemble melanin to varying degrees; e.g., m. of the skin may occur in widespread metastatic melanoma, sunburn, during pregnancy, and as a result of chronic infections. [melano- + G. -osis, condition] m. coli m. of the large intestinal mucosa due to accumulation of pigment of uncertain composition within macrophages in the lamina propria. neurocutaneous m. cutaneous giant pigmented nevi associated with m. of the leptomeninges; malignant melanomas may develop in the skin or meninges. oculodermal m. pigmentation of the sclera and skin around the eye, usually unilateral; seen especially in women of Asian descent. SYN: Ota nevus. pustular m. a transient, benign, pustular rash of unknown etiology seen in neonates; leaves a hyperpigmented base when the pustule resolves. Riehl m. a brown pigmentary condition of the exposed portions of the skin of the neck and face with melanin pigment in dermal macrophages, thought to result from photodermatitis due to materials, such as cosmetic ingredients, or oils encountered in various occupations.

melanosome (mel′a-no-som)
The generally oval pigment granule (0.2 by 0.6 μm) produced by melanocytes. SYN: eumelanosome. [melano- + G. soma, body] giant m. a large spherical m. (1 to 6 μ in diameter) formed in the cytoplasm of melanocytes in café-au-lait spots and other melanocytic disorders. SYN: macromelanosome.

Inhibits synthesis and release of melanotropin; neuropeptide Y. SYN: melanotropin release-inhibiting hormone. [melanotropin + G. states, stationary, + -in]

melanotic (mel′a-not′ik)
1. Pertaining to the presence, normal or pathologic, of melanin. 2. Relating to or characterized by melanosis.

melanotonin (mel′a-no-to-nin)
See melatonin.

melanotrichous (mel-a-not′ri-kus)
Having black hair. [melano- + G. thrix (trich-), hair]

melanotroph (mel′a-no-trof)
A cell of the intermediate lobe of the hypophysis that produces melanotropin. [melano- + G. trophe, nourishment]

melanotrophin (mel′a-no-tro′fin)
SYN: melanotropin. [melano- + G. trophe, nourishment, + -in]

melanotropin (mel′a-no-tro′pin)
A polypeptide hormone secreted by the intermediate lobe of the hypophysis in humans (in neurohypophysis in certain other species) which causes dispersion of melanin by melanophores, resulting in darkening of the skin, presumably by promoting melanin synthesis; this effect is readily demonstated in some lower vertebrates, such as frogs and fish; α-m. is an N-acetylated peptide with 13 amino acids; β-m. has 22 amino acids. SYN: intermedin, melanocyte-stimulating hormone, melanophore-expanding principle, melanotrophin.

melanuria (mel-a-noo′re-a)
The excretion of urine of a dark color, resulting from the presence of melanin or other pigments or from the action of phenol, creosote, resorcin, and other coal tar derivatives. [melano- + G. ouron, urine]

melanuric (mel-a-noo′rik)
Pertaining to or characterized by melanuria.

melarsoprol (me-lar′so-prol)
Used in the treatment of the meningoencephalitic stages of trypanosomiasis; may produce a fatal reactive encephalopathy.

Acronym for mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes. One of the mitochondrial disorders, this condition is usually hereditary, with a mutation at the mitochondrial genome at locus 3243.

An acronym for mitochondrial myopathy, encephalopathy, lactacidosis, and stroke; an inherited disorder of the respiratory chain, either a deficiency of NADH:ubiquinone oxidoreductase (complex I of the chain) or of cytochrome c oxidase.

melasma (me-laz′ma)
A patchy pigmentation of sun-exposed skin, seen most commonly in pregnancy. SEE ALSO: chloasma. [G. a black color, a black spot] m. gravidarum chloasma occurring in pregnancy. m. universale SYN: senile melanoderma.

melatonin (mel-a-ton′in)
N -Acetyl-5-methoxytryptamine;a substance formed by the mammalian pineal gland, which appears to depress gonadal function in mammals and causes contraction of amphibian melanophores; a precursor is serotonin; m. is rapidly metabolized and is taken up by all tissues; it is involved in circadian rhythms. [melanophore + G. tonos, contraction, + -in] M. secretion is linked to both the sleep-wakefulness and light-dark cycles. Ocular perception that ambient light is dimming has been shown to trigger, via neural pathways involving the hypothalamus, increased secretion of m. by the pineal gland. Serum levels increase 10-fold just before sleep and peak around midnight. Twenty-four-hour secretion is higher in winter than in summer. The decline of m. secretion with age has been blamed for the tendency to insomnia in the elderly. Because m. acts as an antioxidant in counteracting free radicals, it has been promoted as a means of delaying aging and preventing cancer, heart disease, and Alzheimer dementia. It has also been proposed as an antidepressant because serotonin (5-hydroxytryptamine), whose metabolism is known to be disordered in clinical depression, is a chemical precursor of m.. Adequately controlled, large-scale studies of the efficacy, safety, and optimum dosage of m. are lacking. There is experimental evidence that long-term administration can reset the circadian pacemaker. Anecdotal reports suggest that shorter courses can hasten recovery from jet lag and facilitate adaptation to night-shift work. In one controlled study of 15 emergency physicians, m. did not improve sleep when subjects returned to a normal sleep pattern after working night shifts. The direct soporific effect of m. varies widely from person to person. Limited studies suggest that it may increase the duration of restful nighttime sleep in the elderly. High doses of m. result in prolonged elevation of serum m. level and increased production of prolactin by the pituitary gland. Unlike most hormones, m. is readily absorbed from the digestive tract and is a component of some foods. Hence therapeutic formulations are not subject to federal drug regulations or purity standards. Testing of commercially available preparations of m. has indicated both variation in potency and the presence of possibly harmful contaminants.

J.C., Danish physician. See Dyggve-M.-Clausen syndrome.

melena (me-le′na)
Passage of dark-colored, tarry stools, due to the presence of blood altered by the intestinal juices. Cf.:hematochezia. SYN: melanorrhagia, melanorrhea. [G. melaina, fem. of melas, black] m. neonatorum m. of the newborn; melana occurring in young infants. m. spuria passage in the stool of blood that has been swallowed, especially that swallowed by nurslings from a fissured nipple. m. vera true m. as distinguished from m. spuria.

melenemesis (mel-e-nem′e-sis)
Vomiting of dark-colored or blackish material. SEE ALSO: black vomit. [G. melas, black, + emesis, vomiting]

Frank L., U.S. surgeon, 1889–1963. See M. gangrene, M. ulcer.

melengestrol acetate (mel-en-jes′trol)
A progestational agent.

meletin (mel′e-tin)
SYN: quercetin.

Honey, sugar. SEE ALSO: mel- (3) . [G. meli]

melibiase (mel-i-bi′as)
SYN: α-d-galactosidase.

melibiose (mel-i-bi′os)
A disaccharide formed by the hydrolysis of raffinose by β-fructofuranosidase; also present in plant juices.

melicera, meliceris (mel-i-se′ra, mel-i-se′ris)
A hygroma or other type of cyst that contains a relatively thick, tenacious, semifluid material. [G. meli- keris, a tumor, fr. melikeron, honeycomb, fr. meli, honey, + keros, wax]

melioidosis (mel′e-oy-do′sis)
An infectious disease of rodents in India and Southeast Asia that is caused by Pseudomonas pseudomallei and is communicable to humans. The characteristic lesion is a small caseous nodule, found generally throughout the body, which breaks down into an abscess; symptoms vary according to the tracts or organs involved. SYN: pseudoglanders, Whitmore disease. [G. melis, a distemper of asses, + eidos, resemblance, + -osis, condition]

melissa (me-lis′a)
The leaves from the tops of M. officinalis (family Labiatae), a plant of southern Europe; a diaphoretic. SYN: sweet balm. [G. a bee]

melissic acid (me-lis′ik)
A long-chain saturated fatty acid found in waxes. [G. melissa, bee + -ic]

melissophobia (me-lis′o-fo′be-a)
SYN: apiphobia. [G. melissa, bee, + phobos, fear]

melitis (me-li′tis)
Inflammation of the cheek. [G. melon, cheek, + -itis, inflammation]

melitose (mel′i-tos)
SYN: raffinose.

melitracen hydrochloride (mel-i-tra′sen)
An antidepressant.

melitriose (mel-i-tri′os)
SYN: raffinose.

melittin (mel′i-tin)
The principal component in bee venom; m. is a peptide amide containing 26 amino acids and is a hemolysin. [G. melitta, bee, + -in]

Ernst G., Swedish physician, 1898–1932. See M.-Rosenthal syndrome.

mellitum, gen. melliti, pl .mellita (me-li′tum, -ti, ta)
A pharmaceutical preparation with honey as an excipient. [L. neut. of mellitus, honeyed]

John C., U.S. radiologist, *1928. See M.-Needles osteodysplasty, M.-Needles syndrome.

See mel-.

melodidymus (mel′o-did′i-mus)
A fetus with a supernumerary limb. [melo- + G. didymos, twin]

melomania (mel-o-ma′ne-a)
An abnormal fascination with or devotion to music. [L. melos, song + mania, frenzy]

melomelia (mel-o-me′le-a)
A malformation in which the fetus has one or more rudimentary limbs in addition to the normal limbs. Cf.:micromelia. [G. melos, limb]

meloplasty (mel′o-plas-te)
Old term for plastic surgery of the cheek; also for &dquor;facelift&dquor;. [melo- + G. plastos, formed]

melorheostosis (mel′o-re-os-to′sis)
Rheostosis confined to the long bones. [G. melos, limb, + rheos, stream, + osteon, bone, + -osis]

meloschisis (me-los′ki-sis)
Congenital cleft in the face. [G. melon, cheek, + schisis, a cleaving]

melotia (me-lo′she-a)
Congenital displacement of the auricle onto the cheek. [G. melon, cheek, + ous, ear]

melphalan (mel′fa-lan)
l-Phenylalanine mustard; l-sarcolysine; l-3-[p-[bis(2-chloroethyl)amino]phenyl]alanine;a phenylalanine derivative of nitrogen mustard; an alkalylating antineoplastic agent.

Denature, used to describe RNA polymerase action in decoupling DNA base pairs.

Samuel J., U.S. physiologist, 1851–1920. See M. law, M.-Lyon test.

Abbreviation for Eagle minimum essential medium.

SYN: limb (1) . [L. membrum] inferior m. [TA] SYN: lower limb. superior m. [TA] SYN: upper limb. virile m. obsolete term for penis.

membra (mem′bra)
Plural of membrum. [L.]

membrana, gen. and pl. membranae (mem-bra′na, -bra′ne) [TA]
SYN: membrane (1) . [L.] m. abdominis SYN: peritoneum. m. adamantina SYN: enamel cuticle. m. adventitia 1. SYN: adventitia. 2. SYN: decidua capsularis. m. atlanto-occipitalis anterior [TA] SYN: anterior atlanto-occipital membrane. m. atlanto-occipitalis posterior [TA] SYN: posterior atlanto-occipital membrane. m. basalis ductus semicircularis SYN: basal membrane of semicircular duct. m. basilaris SYN: basal lamina of cochlear duct. m. capsularis the hyaloid vascular network around the posterior pole of the lens in the embryo. m. capsulopupillaris the lateral portion of the vascular tunic of the lens of the eye in the embryo. m. carnosa SYN: dartos fascia. m. cerebri any one of the cerebral meninges. m. choriocapillaris SYN: capillary lamina of choroid. m. cordis SYN: pericardium. m. cricothyroidea SYN: cricothyroid membrane. m. decidua SYN: deciduous membrane. m. eboris the lining membrane of the pulp cavity of a tooth, consisting of the odontoblastic layer. SYN: ivory membrane. m. fibroelastica laryngis [TA] SYN: fibroelastic membrane of larynx. m. fibrosa capsulae articularis [TA] SYN: fibrous layer of joint capsule. m. flaccida SYN: flaccid part of tympanic membrane. m. fusca SYN: suprachoroid lamina of sclera. m. germinativa SYN: blastoderm. m. granulosa SYN: stratum granulosum folliculi ovarici vesiculosi. m. hyaloidea SYN: posterior limiting lamina of cornea. m. hyothyroidea SYN: thyrohyoid membrane. membranae intercostales [TA] SYN: intercostal membranes, under membrane. m. intercostalis externa [TA] SYN: external intercostal membrane. m. intercostalis interna [TA] SYN: internal intercostal membrane. m. interossea antebrachii [TA] SYN: interosseous membrane of forearm. m. interossea cruris [TA] SYN: interosseous membrane of leg. m. limitans 1. SYN: limiting membrane of retina. 2. limiting membrane separating the neural parenchyma from the pia and blood vessels. m. limitans gliae SYN: glial limiting membrane. m. mucosa SYN: mucosa. m. nictitans SYN: plica semilunaris of conjunctiva (2) . m. obturatoria [TA] SYN: obturator membrane. m. perinei [TA] SYN: perineal membrane. m. pituitosa SYN: mucosa of nose. m. preformativa the thickened m. formed by fusion of Korff fibers and the basement membrane of the ameloblasts in a developing tooth. m. propria ductus semicircularis SYN: proper membrane of semicircular duct. m. propria of semicircular duct SYN: proper membrane of semicircular duct. m. pupillaris SYN: pupillary membrane. m. quadrangularis [TA] SYN: quadrangular membrane. m. reticularis organi spiralis [TA] SYN: reticular membrane of spinal organ. m. serosa 1. SYN: serosa, chorion. 2. SYN: serosa (2) . m. serotina obsolete synonym of decidua basalis. m. spiralis tympanic surface of cochlear duct. m. stapedis [TA] SYN: stapedial membrane. m. statoconiorum [TA] SYN: otolithic membrane. m. sterni [TA] SYN: sternal membrane. m. striata SYN: zona striata. m. succingens SYN: pleura. [L. succingere, to surround] m. suprapleuralis [TA] SYN: suprapleural membrane. m. synovialis [TA] SYN: synovial membrane. m. tectoria (articulationis atlantoaxialis medianae) [TA] SYN: tectorial membrane (of median atlantoaxial joint). m. tectoria ductus cochlearis [TA] SYN: tectorial membrane of cochlear duct. m. tensa SYN: tense part of the tympanic membrane. m. thyrohyoidea [TA] SYN: thyrohyoid membrane. m. tympani [TA] SYN: tympanic membrane. m. tympani secundaria [TA] SYN: secondary tympanic membrane. m. versicolor SYN: tapetum (2) . m. vestibularis ductus cochlearis vestibular surface of cochlear duct. m. vibrans SYN: tense part of the tympanic membrane. m. vitellina 1. the membrane enveloping the yolk; specifically, the thickened cell membrane of large-yolked ova; SYN: ovular membrane, vitelline membrane. 2. sometimes used to designate the zona pellucida of a mammalian ovum. SYN: yolk membrane. m. vitrea SYN: posterior limiting lamina of cornea.

membranaceous (mem-bra-na′shus)
SYN: membranous.

membranate (mem′bra-nat)
Of the nature of a membrane.


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