Medical Dictionary banner
Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


musicotherapy (mu′sik-o-thar′a-pe)
An adjunctive treatment of mental disorders by means of music.

L.C. Alfred de, French poet, 1810–1857; person in whom M. sign was studied. See M. sign.

mussitation (mus-i-ta′shun)
Movements of the lips as if speaking, but without sound; observed in delirium, semicoma, and severe Parkinson disease. [L. mussito, to murmur constantly, fr. musso, pp. -atus, to mutter]

See Guéneau de M..

must (must)
Unfermented juice of the grape or other fruits. [L. mustum, new wine, ntr. of mustus, fresh]

William T., Canadian thoracic surgeon, 1914–1987. See M. operation, M. procedure.

mustard (mus′tard)
1. The dried ripe seeds of Brassica alba (white m.) and B. nigra (black m.) (family Cruciferae). 2. SYN: m. gas. [O.Fr. moustarde, fr. L. mustum, must] black m. the dried ripe seed of Brassica nigra or of B. juncea; it is the source of allyl isothiocyanate; it contains sinigrin (potassium myronate); myrosin; sinapine sulfocyanate; erucic, behenic, and synapolic acids; and fixed oil; a prompt emetic, a rubefacient, and a condiment. m. chlorohydrin SYN: hemisulfur m.. hemisulfur m. an antineoplastic agent. SYN: m. chlorohydrin, semisulfur m.. nitrogen mustards (HN2) compounds of the general formula R— N(CH2CH2C1) the prototype is HN-2 nitrogen m., mechlorethamine, in which R is CH3. Some have been used therapeutically for their destructive action upon lymphoid tissue in lymphosarcoma, leukemia, Hodgkin disease, and certain other cancers; most are blister agents. SEE ALSO: mechlorethamine hydrochloride. semisulfur m. SYN: hemisulfur m.. sulfur m. SYN: m. gas. uracil m. uracil m.. white m. the ripe seeds of Brassica (Sinapis) alba; less pungent than black m., but with the same constituents and uses.

mustard oil
Term applied to any of the organic isothiocyanates in general, but more specifically to allyl isothiocyanate; such oils are metabolically convertible to thiocyanates and may thus lead to goiter. expressed m. the fixed oil expressed from the seeds of Brassica alba and B. nigra; it contains the glycerides of oleic, arachidic, and other fatty acids; used as salad oil and in the manufacture of oleomargarine. volatile m. SYN: allyl isothiocyanate.

mustine hydrochloride (mus′ten)
SYN: mechlorethamine hydrochloride.

mutacism (mu′ta-sizm)
SYN: mytacism.

mutagen (mu′ta-jen)
Any agent that promotes a mutation or causes an increase in the rate of mutational events, e.g., radioactive substances, x-rays, or certain chemicals. [L. muto, to change, + G. -gen, producing] frame-shift m. a m., such as an acridine derivative, that causes a reading-frame-shift mutation; codons (base triplets) are read out of phase and different amino acids are utilized.

mutagenesis (mu-ta-jen′e-sis)
1. Production of a mutation. 2. Production of genetic alteration through use of chemicals or radiation. cassette m. the production of mutants within a region (often bounded by unique restriction sites) by the use of synthetic oligonucleotides that fill the gap with mutants designed into the synthetic genetic material. insertional m. mutation caused by insertion of new genetic material into a normal gene, particularly of retroviruses into chromosomal DNA. site-directed m. the controlled alterations of selected regions of a DNA molecule.

mutagenic (mu-ta-jen′ik)
Promoting mutation.

mutant (myu′tant)
1. A phenotype in which a mutation is manifested. 2. A gene that is rare and usually harmful, in contrast to a wild-type gene, not necessarily generated recently. active m. a m. with overt phenotypic expression. amber m. a m. with a mutation resulting in a UAG codon. auxotrophic m. m. with a nutritional requirement not present in the wild-type organism. SYN: defective organism, deficiency m.. cold-sensitive m. a m. that is defective at low temperature but functional at normal temperature. Cf.:temperature-sensitive m.. conditional-lethal m. SYN: conditionally lethal m.. conditionally lethal m. a viral m. that can replicate under some (permissive) conditions but not under other (restrictive or nonpermissive) conditions, the parent (wild-type) strain being able to replicate under both conditions. See suppressor-sensitive m., temperature-sensitive m.. SYN: conditional-lethal m.. deficiency m. SYN: auxotrophic m.. inactive m. a m. that is not phenotypically manifest. SYN: silent m.. petite m. a m. with a mutation that caused the microorganism to grow very slowly or to form small colonies. [Fr. small] quick-stop m. a bacterial m. that ceases replication immediately when the temperature reaches a certain level. Cf.:temperature-sensitive m.. silent m. SYN: inactive m.. suppressor-sensitive m. a conditionally lethal, host range, bacteriophage m. that produces nonsense codons and can replicate only in a host bacterium able to translate the nonsense codon; the mutation's effects are lethal ( i.e., prevent replication of the virus) in a bacterium without such a suppressor mechanism. temperature-sensitive m. a viral m. that is able to replicate at one portion of a temperature range but not at another, the parent (wild-type) strain being able to replicate over the whole temperature range; usually a product is not made at the elevated temperature. Cf.:cold-sensitive m., quick-stop m.. uninducible m. a m. that cannot be induced. virulent phage m. a m. of a phage that is unable to establish lysogeny.

mutarotase (mu′ta-ro-tas)
SYN: aldose 1-epimerase.

mutarotation (mu′ta-ro-ta′shun)
The process of changing specific rotation at a given wavelength; e.g., a solution of α-d-glucose recrystallized from its solution in acetic acid and freshly dissolved in water gives a rotation of [α] = +112.2°, but when recrystallized from a boiling aqueous solution (as the β-form) it shows an initial rotation of [α] = +18.7°; either solution upon standing slowly changes its specific rotation to a value of [α] = +52.7°, indicating a mixture of the two forms of d-glucose. SYN: birotation, multirotation.

mutase (mu′tas)
Any enzyme that catalyzes the apparent migration of groups within one molecule, e.g., phosphoglycerate phosphomutase; sometimes the transfer is from one molecule to another, e.g., phosphoglucomutase, phosphoglyceromutase (both phosphotransferases).

mutation (mu-ta′shun)
1. A change in the chemistry of a gene that is perpetuated in subsequent divisions of the cell in which it occurs; a change in the sequence of base pairs in the chromosomal molecule. 2. De Vries term for the sudden production of a species, as distinguished from variation. [L. muto, pp. -atus, to change] addition m. SYN: reading-frame-shift m.. addition-deletion m. SYN: reading-frame-shift m.. amber m. a m. that results in the formation of the codon UAG, which results in the premature termination of a polypeptide chain. Cf.:suppressor m.. back m. reversion of a gene to an ancestral form due to further m. to the original codon or one coding for the same amino acid. SYN: reverse m.. deletion m. SYN: reading-frame-shift m.. frame-shift m. SYN: reading-frame-shift m.. induced m. a m. caused by exposure to a mutagen. lethal m. a mutant trait that leads to a phenotype incompatible with effective reproduction. missense m. a m. in which a base change or substitution results in a codon that causes insertion of a different amino acid into the growing polypeptide chain, giving rise to an altered protein. [mis-sense by analogy with non-sense] natural m. SYN: spontaneous m.. neutral m. a m. with a negligible impact on genetic fitness. new m. redundant term for a heritable trait present in the offspring but in neither parent, i.e., not a pre-existing mutant form inherited. nonsense m. SYN: suppressor m.. ochre m. a m. yielding the termination codon UAA, resulting in premature termination of a polypeptide chain. Cf.:suppressor m.. opal m. SYN: umber m.. point m. a m. that involves a single nucleotide; it may consist of loss of a nucleotide, substitution of one nucleotide for another, or the insertion of an additional nucleotide. reading-frame-shift m. a m. that results from insertion or deletion of a single nucleotide into, or from, the normal DNA sequence; since the genetic code is read three nucleotides at a time, all nucleotide triplets distal to the m. will be one step out of phase and misread, and hence translated as different amino acids. SYN: addition m., addition-deletion m., deletion m., frame-shift m.. reverse m. SYN: back m.. silent m. the form of a genetic trait distinguishable at the genotypic level but not at the level of arbitrary phenotype ( e.g., clinical, immunological, or electrophoretic). site specific m. an alteration of the structure of a gene at a specific sequence, usually referring to experimentally produced changes in gene sequence. somatic m. a m. occurring in the general body cells (as opposed to the germ cells) and hence not transmitted to progeny. spontaneous m. a m. that arises naturally and not as a result of exposure to mutagens. SYN: natural m.. suppressor m. 1. a second m. that alters the anticodon in a tRNA so that it can recognize a nonsense (stop) codon, thus suppressing termination of the amino acid chain. Cf.:amber m., ochre m., umber m.. 2. genetic changes such that the effect of a m. in one place can be masked by a second m. in another location. There are two types: intergenic suppression (occurring in a different gene) and intragenic suppression (occurring in the same gene but at a different site). SYN: nonsense m.. transition m. a point m. involving substitution of one base-pair for another, i.e., replacement of one purine for another and of one pyrimidine for another pyrimidine without change in the purine-pyrimidine orientation. transversion m. a point m. involving base substitution in which the orientation of purine and pyrimidine is reversed, in contradistinction to transition m.. umber m. a m. yielding the termination codon UGA, resulting in premature termination of a polypeptide chain. Cf.:suppressor m.. SYN: opal m.. up promoter m. a m. that increases the frequency of initiation of transcription.

mute (mut)
1. Unable or unwilling to speak. 2. A person who has not the faculty of speech. [L. mutus]

mutein (mu′ten)
A term used for a protein arising as a result of a mutation. [mutation + protein]

mutilation (mu-ti-la′shun)
Disfigurement or injury by removal or destruction of any conspicuous or essential part of the body. [L. mutilatio, fr. mutilo, pp. -atus, to maim]

mutism (mu′tizm)
1. The state of being silent. 2. Organic or functional absence of the faculty of speech. [L. mutus, mute] akinetic m. subacute or chronic state of altered consciousness, in which the patient appears alert intermittently, but is not responsive, although his/her descending motor pathways appear intact; due to lesions of various cerebral structures. SYN: coma vigil. elective m. m. due to psychogenic causes. SYN: voluntary m.. voluntary m. SYN: elective m..

muton (mu′ton)
In genetics, the smallest unit of a chromosome in which alteration can be effective in causing a mutation (a single nucleotide change). [mutation + -on]

mutualism (mu′tu-al-izm)
Symbiotic relationship in which both species derive benefit. Cf.:commensalism, metabiosis, parasitism.

mutualist (mu′tu-al-ist)
SYN: symbion. [L. mutuus, in return, mutual]

Obsolete abbreviation for mendelevium.

Abbreviation for millivolt.

Abbreviation for maximum voluntary ventilation.

Abbreviation for molecular weight.

myalgia (mi-al′je-a)
Muscular pain. SYN: myodynia. [G. mys, muscle, + algos, pain] epidemic m. SYN: epidemic pleurodynia. m. thermica SYN: heat cramps, under cramp.

myasthenia (mi-as-the′ne-a)
Muscular weakness. [G. mys, muscle, + astheneia, weakness] m. angiosclerotica SYN: intermittent claudication. m. gravis a disorder of neuromuscular transmission marked by fluctuating weakness and fatigue of certain voluntary muscles, including those innervated by brainstem motor nuclei; caused by a marked reduction in the number of acetylcholine receptors in the postsynaptic membrane of the neuromuscular junction, resulting from an autoimmune mechanism. SYN: Goldflam disease.

myasthenic (mi′as-then′ik)
Relating to myasthenia.

myatonia, myatony (mi-a-to′ne-a, mi-at′o-ne)
Abnormal extensibility of a muscle. [G. mys, muscle, + a priv. + tonos, tone] m. congenita SYN: amyotonia congenita.

myatrophy (mi-at′ro-fe)
SYN: muscular atrophy.

mycelia (mi-se′le-a)
Plural of mycelium.

mycelian (mi-se′le-an)
Pertaining to a mycelium.

mycelioid (mi-se′le-oyd)
Resembling a mycelium. [mycelium + G. eidos, resemblance]

mycelium, pl .mycelia (mi-se′le-um, -a)
The mass of hyphae making up a colony of fungi. [G. mykes, fungus, + helos, nail, wart, excrescence on animal or plant] aerial m. the portion of m. that grows upward or outward from the surface of the substrate, and from which propagative spores develop in or on characteristic structures that are distinctive for various generic groups. nonseptate m. one in which there are no septa, or “cross-walls,” in the hyphae; inasmuch as the latter are not divided into numerous individual cells, the multinucleated protoplasm may flow throughout the tubelike structures. septate m. one in which septa, or “cross-walls,” divide the hyphae into numerous uninucleated or multinucleated cells.

mycet-, myceto-
Fungus. SEE ALSO: myco-. [G. mykes, fungus]

mycete (mi′set)
A fungus. [G. mykes, fungus]

mycetism, mycetismus (mi′se-tizm, -tiz′mus)
Poisoning by certain species of mushrooms. SYN: muscarinism. [G. mykes, fungus] m. cerebralis a condition characterized by transient hallucinogenic symptoms following ingestion of mushrooms such as Psilocybe and Panaeolus. m. choliformis a severe and occasionally fatal illness due to the consumption of Amanita phalloides and other poisonous mushroom species. m. gastrointestinalis a relatively mild type of mushroom poisoning characterized by nausea, vomiting, and diarrhea and caused by eating certain species of Boletus, Lactarius, Entoloma, and Lepiota. m. nervosa mushroom poisoning that involves the parasympathetic nervous system and causes gastrointestinal distress, after consumption of species such as Amanita, Inocybe, and Clitocybe. m. sanguinareus a transient hemoglobinuria and jaundice caused by eating the mushroom Helvella esculenta, either raw or cooked.

mycetogenetic, mycetogenic (mi-se′to-je-net′ik, mi′se-to-; -jen′ik)
Caused by fungi. SYN: mycetogenous. [G. mykes, fungus, + gennetos, begotten]

mycetogenous (mi-se-toj′e-nus)
SYN: mycetogenetic.

mycetoma (mi-se-to′ma)
A chronic infection involving the subcutaneous tissue, skin, and contiguous bone; characterized by the formation of localized lesions with tumefactions and multiple draining sinuses. The exudate contains granules that may be yellow, white, red, brown, or black, depending upon the causative agent. M. is caused by two principal groups of microorganisms: 1) actinomycetoma is caused by actinomycetes, including species of Streptomyces, Actinomadurae, and Nocardia, 2) eumycetoma is caused by true fungi, including species of Madurella, Exophiala, Pseudallescheria, Curvularia, Neotestudina, Pyrenochaeta, Aspergillus, Leptosphaeria, Plemodomus, Polycytella, Fusarium, Phialophora, Corynespora, Cylindrocarpon, Pseudo-chaetosphaeronema, Bipolaris, and Acremonium. SYN: Madura boil, Madura foot, maduromycosis.

Fungus. SEE ALSO: mycet-. [G. mykes, fungus]

mycobacteria (mi′ko-bak-te′re-a)
Organisms belonging to the genus Mycobacterium. atypical m. species of m. other than M. tuberculosis or M. bovis that can cause disease in immunocompromised humans; being replaced by the designation of MOTT (M. Other Than Tuberculosis). Runyon group I m. m. that produce a bright yellow color when grown in the presence of light. Organisms placed in this group include Mycobacterium kansasii. SYN: photochromogens. Runyon group II m. m. that produce a yellow pigment even when grown in the dark; when grown in the light, the pigment is orange. These organisms behave as saprophytes do in humans and are usually nonpathogenic to laboratory animals. SYN: scotochromogens. Runyon group III m. m. that are either colorless or that slowly produce a light yellow pigment when grown in the presence of light. Organisms placed in this group include Mycobacterium avium and M. intracellulare. SYN: nonchromogens. Runyon group IV m. m. that grow rapidly and that do not produce pigment. Organisms placed in this group belong to such species as Mycobacterium ulcerans and M. marinum.

Mycobacteriaceae (mi′ko-bak-ter-e-a′se-e)
A family of aerobic bacteria (order Actinomycetales) containing Gram-positive, spherical to rod-shaped cells. Branching does not occur under ordinary cultural conditions. They are usually acid-fast. They occur in soil and dairy products and as parasites on humans and other animals. The type genus is Mycobacterium.

mycobacteriosis (mi′ko-bak-ter′e-o′sis)
Infection with mycobacteria.

Mycobacterium (mi′ko-bak-ter′e-um)
A genus of aerobic, nonmotile bacteria (family Mycobacteriaceae) containing Gram-positive, acid-fast, slender, straight or slightly curved rods; slender filaments occasionally occur, but branched forms rarely are produced. Parasitic and saprophytic species occur. A number of species are associated with infections in immunocompromised people, especially those with AIDS. The type species is M. tuberculosis. It is the type genus of the family Mycobacteriaceae. [myco- + bacterium] M. abscessus SYN: M. chelonae abscessus. M. avium a bacterial species causing tuberculosis in fowl and other birds. Causes opportunistic infections in humans. M. avium-intracellulare complex an opportunistic agent of infection, particularly in people with AIDS. Difficult to treat because M. avium-intracellulare is resistant to many antibiotics. The organism may also cause chronic lower respiratory tract infections in patients who are not severely immunocompromised, especially those with underlying abnormal lung parenchyma. M. bovis a bacterial species that is the primary cause of tuberculosis in cattle; transmissible to humans and other animals, causing tuberculosis. SYN: tubercle bacillus (2) . M. chelonae rapid-growing m. (Runyon group IV) that cause sporadic infection in any tissue or organ system in humans following cardiothoracic surgery, peritoneal- and hemodialysis, augmentation mammaplasty, arthroplasty, and immunocompromised patients. M. chelonae abscessus a bacterial species originally found in a traumatic infection of the knee. SYN: M. abscessus. M. fortuitum a saprophytic bacterial species found in soil and in infections of humans, cattle, and cold-blooded animals. Causes skin abscesses. M. intracellulare a bacterial species found in lung lesions and sputum of humans; may cause bone and tendon-sheath lesions in rabbits; some strains are pathogenic for mice. Recently linked to opportunistic infections in humans. SYN: Battey bacillus. M. kansasii a bacterial species causing a tuberculosislike pulmonary disease; found to cause rare infections (and usually lesions) in spinal fluid, spleen, liver, pancreas, testes, hip joint, knee joint, finger, wrist, and lymph nodes. M. leprae a bacterial species that causes Hansen disease (leprosy); an obligatory intracellular m. that has not been propagated in the laboratory, but that will survive in the 9-banded armadillo (Dasypus novemcinctus). SYN: Hansen bacillus, leprosy bacillus. M. marianum former name for M. scrofulaceum. M. marinum a bacterial species causing spontaneous tuberculosis in salt water fish; it also occurs in other cold-blooded animals, in some aquaria and swimming pools in which it may cause human cutaneous infection (see swimming pool granuloma), irrigation canals and ditches, and ocean beaches. M. microti a bacterial species causing generalized tuberculosis in voles; transmissible to guinea pigs, rabbits, and calves, causing localized infections. M. paratuberculosis a bacterial species causing Johne disease, a chronic enteritis in cattle. M. phlei a bacterial species found in soil and dust and on plants. SYN: Moeller grass bacillus. M. scrofulaceum a bacterial species frequently associated with cervical adenitis in children. M. smegmatis a saprophytic bacterial species of bacteria found in smegma from the genitalia of humans and many of the lower animals; it is also found in soil, dust, and water. M. tuberculosis a bacterial species that causes tuberculosis in humans; it is the type species of the genus M.. SYN: Koch bacillus, tubercle bacillus (1) . M. ulcerans a bacterial species causing Buruli ulcers in humans; transmissible from soil, usually after an injury, and possibly by an insect vector. M. vaccae a rapidly growing scotochromogenic, nonpathogenic species that is distributed widely in nature. M. xenopi a bacterial species found in a skin lesion of a cold-blooded animal, Xenopus laevis; a rare cause of nosocomial human pulmonary tuberculosis.

mycobactin (mi′ko-bak′tin)
A complex lipid factor reported to be required for the growth of Mycobacterium tuberculosis in human plasma; appears to be identical with the lipid factor extracted from M. phlei and essential for the growth of M. johnei.

mycocide (mi′ko-sid)
SYN: fungicide. [myco- + L. caedo, to kill]

mycodermatitis (mi′ko-der-ma-ti′tis)
An obsolete term to designate an eruption of mycotic (fungus, yeast, mold) origin.

mycogastritis (mi′ko-gas-tri′tis)
Inflammation of the stomach due to the presence of a fungus. [myco- + G. gaster, stomach, + -itis, inflammation]

mycolic acids (mi-kol′ik)
Long-chain cyclopropanecarboxylic acids (C19–C21), further substituted by long-chain (C24–C30) alkanes containing free hydroxyl groups, found in certain bacteria; these waxy substances appear to be responsible for the acid-fastness of the bacteria that contain them. SYN: mykol.

mycologist (mi-kol′o-jist)
A person specializing in mycology.

mycology (mi-kol′o-je)
The study of fungi: their classification, edibility, cultivation, and biology. [myco- + G. logos, study] medical m. the study of fungi that produce disease in humans and other animals, and of the diseases they produce, their ecology, and their epidemiology.

mycophage (mi′ko-faj)
A virus, the host of which is a fungus, in contradistinction to a bacteriophage, the host of which is a bacterium. SEE ALSO: mycovirus. [myco- + G. phago, to eat]

Mycoplasma (mi′ko-plaz′ma)
A genus of aerobic to facultatively anaerobic bacteria (family Mycoplasmataceae) containing Gram-negative cells that do not possess a true cell wall but are bounded by a three-layered membrane; they do not revert to bacteria containing cell walls or cell wall fragments. The minimal reproductive units of these organisms are 0.2–0.3 μm in diameter. The cells are pleomorphic, and in liquid media appear as coccoid bodies, rings, or filaments. Colonies of most species consist of a central core, growing down into the medium, surrounded by superficial peripheral growth. They require sterol for growth. They also require enrichment with serum or ascitic fluid. These organisms are found in humans and other animals and can be pathogenic. The type species is M. mycoides. SYN: Asterococcus. [myco- + G. plasma, something formed (plasm)] M. buccale a species which is an infrequent parasitic inhabitant of the human oropharynx; it is the predominant m. in the oropharynx of nonhuman primates. M. faucium a bacterial species that is a rare member of the normal flora of the human oropharynx; it is occasionally found in the oropharynx of nonhuman primates. M. fermentans a bacterial species found in ulcerative genital lesions associated with fusiform bacteria and spirilla and also on the apparently normal genital mucosa of humans. M. genitalium a bacterial species that may be a causative agent of urethritis; cross-reacts immunologically with M. pneumoniae; can cause serious infections involving the respiratory tract, heart, bloodstream, central nervous system, and prosthetic valves and joints. M. hominis a bacterial species that is the causative agent of pelvic inflammatory disease and other genitourinary tract infections; can also cause chorioamnionitis and postpartum fever; can be an oropharyngeal commensal and has caused nosocomial wound infections. M. laidlawii SYN: Acholeplasma laidlawii. M. orale a bacterial species of M. associated with the buccal and pharyngeal cavities of humans and animals. M. pharyngis a bacterial species occurring as a commensal in the human oropharynx. M. pneumoniae a bacterial species causing otitis and upper and lower respiratory tract disease including primary atypical pneumonia in human beings. SYN: Eaton agent. M. salivarium a bacterial species found in the human pharynx.

mycoplasma, pl .mycoplasmata (mi′ko-plaz′ma, -plaz′mah-ta)
A vernacular term used only to refer to any member of the genus M..

Mycoplasmatales (mi′ko-plaz′ma-ta′lez)
An order of Gram-negative bacteria containing cells which are bounded by a three-layered membrane but which do not possess a true cell wall. The minimal reproductive units are 0.2 to 0.3 μm in diameter. Pathogenic and saprophytic species occur. These organisms reproduce through the breaking up of branched filaments into coccoid, filterable elementary bodies. The order includes the so-called pleuropneumonia-like organisms, under organism (PPLO).

mycopus (mi′ko-pus)
SYN: mucopus.


. . . Feedback