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Medical Dictionary


mode (mod)
In a set of measurements, that value which appears most frequently. [L. modus, a measure, quantity]

model (mod′el)
1. A representation of something, often idealized or modified to make it conceptually easier to understand. 2. Something to be imitated. 3. In dentistry, a cast. 4. A mathematical representation of a particular phenomenon. 5. An animal that is used to mimic a pathologic condition. [It. midello, fr. L. modus, measure, standard] Adair-Koshland-Némethy-Filmer m. (AKNF) SYN: Koshland-Némethy-Filmer m.. additive m. a m. in which the combined effect of several factors is the sum of the effects that would be produced by each of the factors in the absence of the others. animal m. study in a population of laboratory animals that uses conditions of animals analogous to conditions of humans to simulate processes comparable to those that occur in human populations. Armitage-Doll m. a m. of carcinogenesis with the premise that the main variable determining change in risk is not age but time. Bingham m. a m. representing the flow behavior of a Bingham plastic, in the idealized case. biomedical m. a conceptual m. of illness that excludes psychological and social factors and includes only biological factors in an attempt to understand a person's medical illness or disorder. biopsychosocial m. a conceptual m. that assumes that psychological and social factors must also be included along with the biological in understanding a person's medical illness or disorder. cloverleaf m. a m. for the structure of tRNA; so named because the structure roughly resembles a cloverleaf. computer m. a mathematical representation of the functioning of a system, presented in the form of a computer program. SYN: computer simulation. concerted m. SYN: Monod-Wyman-Changeux m.. cooperativity m. a m. used to explain the property of cooperativity observed in certain enzymes; E.G., allosterism or hysteresis. fluid mosaic m. a m. for the structure of a biomembrane, with lateral diffusibility of constituents and little, if any, flip-flop motion. genetic m. a formalized conjecture about the behavior of a heritable structure in which the component terms are intended to have literal interpretation as standard structures of empirical genetics. induced fit m. 1. a m. to suggest a mode of action of enzymes in which the substrate binds to the active site of the protein, causing a conformational change in the protein; 2. SYN: Koshland-Némethy-Filmer m.. Koshland-Némethy-Filmer m. (KNF m.) a m. to explain the allosteric form of cooperativity; in this m., in the absence of ligands, the protein exists in only one conformation; upon binding, the ligand induces a conformational change that may be transmitted to other subunits. SYN: Adair-Koshland-Némethy-Filmer m., induced fit m. (2) . lock-and-key m. a m. used to suggest the mode of operation of an enzyme in which the substrate fits into the active site of the protein like a key into a lock. logistic m. a statistical m.; in epidemiology, a m. of risk as a function of exposure to a risk factor. mathematical m. representation of a system, process, or relationship in mathematical form, using equations to simulate the behavior of the system or process under study. medical m. a set of assumptions that views behavioral abnormalities in the same framework as physical disease or abnormalities. Monod-Wyman-Changeux m. (MWC m.) a m. used to explain the allosteric form of cooperativity; in this m., an oligomeric protein can exist in two conformational states in the absence of the ligand; these states are in equilibrium and the one that is predominant has a lower affinity for the ligand (which binds to the protein in a rapid equilibrium fashion). SYN: concerted m.. multiplicative m. a m. in which the joint effect of two or more causes is the product of their effects if they were acting alone. multistage m. a mathematical m., mainly for carcinogenesis, based on the theory that a specific carcinogen may affect one among a number of stages in the development of cancer. MWC m. abbreviation for Monod-Wyman-Changeux m.. pathologic m. an animal or animal stock that by inheritance or by artificial manipulation develops a disorder similar to some disease of interest and hence directly or by analogy furnishes evidence of its pathogenesis and may be used as a m. for the study of preventive or therapeutic measures. Reed-Frost m. mathematical m. of infectious disease transmission and herd immunity. The m. gives the number of new cases of an infection that can be expected in a specified time in a closed, freely mixing population of immune and susceptible individuals, with varying assumptions about frequency of contact. Sartwell incubation m. mathematical m. based on empirical observations, showing that incubation periods for communicable diseases have a log-normal distribution; m. holds true for certain kinds of cancers that have well-defined external causes. statistical m. a formal representation for a class of processes that allows a means of analyzing results from experimental studies, such as the Poisson m. or the general linear m.; it need not propose a process literally interpretable in the context of the individual case.

modeling (mod′el-ing)
1. In learning theory, the acquiring and learning of a new skill by observing and imitating that behavior being performed by another individual. 2. In behavior modification, a treatment procedure whereby the therapist or another significant person presents (models) the target behavior that the learner is to imitate and make part of repertoire. 3. A continuous process by which a bone is altered in size and shape during its growth by resorption and formation of bone at different sites and rates. 4. A process by which a representation of an entity is formed.

modification (mod′i-fi-ka′shun)
1. A nonhereditary change in an organism; e.g., one that is acquired from its own activity or environment. 2. A chemical or structural alteration in a molecule. behavior m. the systematic use of principles of conditioning and learning, especially operant or instrumental conditioning, to teach certain skills or to extinguish undesirable behaviors, attitudes, or phobias. chemical m. alteration in the structure of a molecule, typically a macromolecule such as a protein, by chemical means; often, the covalent addition by some reagent. covalent m. alteration in the structure of a macromolecule by enzymatic means, resulting in a change in the properties of that macromolecule; frequently, this type of m. is physiologically relevant.

modifier (mod′˘1 fi′er)
That which alters or limits. biologic response m. agent that modifies host responses to neoplasms by enhancing immune systems or reconstituting impaired immune mechanisms.

modiolus, pl .modioli (mo-di′o-lus, -o-li)
1. [tA] The central cone-shaped core of spongy bone about which turns the spiral canal of the m.. 2. SYN: m. of angle of mouth. [L., the nave of a wheel] m. of angle of mouth [TA] a point near the corner of the mouth where several muscles of facial expression converge. SYN: m. anguli oris [TA] , columella cochleae, m. labii, m. (2) . m. anguli oris [TA] SYN: m. of angle of mouth. m. labii SYN: m. of angle of mouth.

modulation (mod-u-la′shun)
1. The functional and morphologic fluctuation of cells in response to changing environmental conditions. 2. Systematic variation in a characteristic ( e.g., frequency, amplitude) of a sustained oscillation to code additional information. 3. A change in the kinetics of an enzyme or metabolic pathway. 4. The regulation of the rate of translation of mRNA by a modulating codon. [L. modulor, to measure off properly] biochemical m. term describing the m. (either enhancement of activity or reduction of toxicity) of a chemotherapeutic agent by another agent, which may or may not have antineoplastic activity of its own.

That which regulates or adjusts. selective estrogen receptor m. (SERM) pharmaceutical agent with selective estrogen receptor affinity; current preparations have a primary effect on bone and cardiovascular tissues and less effect on endometrial, genital, and breast tissues.

modulus (moj′u-lus, mod′u-)
A coefficient expressing the magnitude of a physical property by a numerical value. [L. dim. of modus, a measure, quantity] bulk m. SYN: m. of volume elasticity. m. of elasticity a coefficient expressing the ratio between stress per unit area acting to deform a body and the amount of deformation that results from it. m. of volume elasticity a coefficient expressing the ratio between pressure acting to change the volume of a substance and the amount of change that results from it. SYN: bulk m.. Young m. a type of m. of elasticity which specifies the force applied to a body in one direction, per unit cross-sectional area of the body perpendicular to that direction, divided by the fractional change in length of the body in that direction.

Julius O.L., German surgeon, 1819–1887. See M. glossitis.

Alfred, German bacteriologist, *1868. See M. grass bacillus.

mofebutazone (mof-e-bu′ta-zon)
An anti-inflammatory agent used for the treatment of arthritis.

mogiarthria (moj-i-ar′thre-a)
Speech defect due to muscular incoordination. [G. mogis, with difficulty, + arthroo, to articulate]

mogilalia (moj-i-la′le-a)
Stuttering, stammering, or any speech defect. SYN: molilalia. [G. mogis, with difficulty, + lalia, speech]

mogiphonia (moj-i-fo′ne-a)
Laryngeal spasm occurring in public speakers as a result of overuse of the voice. [G. mogis, with difficulty, + phone, voice]

Joseph J. Freiherr von, Austrian-Russian surgeon, 1755–1799. See M. fossa, M. space.

Frederic E., U.S. surgeon, *1910, who as a medical student devised a system of microscopicaly controlled removal of skin tumors. See M. fresh tissue chemosurgery technique, M. chemosurgery.

Friedrich, German mineralogist, 1773–1839. See M. scale.

moiety (moy′i-te)
1. Originally, a half; now, loosely, a portion of something. 2. Functional group. [M.E. moite, a half]

Abbreviation for mole (4) .

molal (mo′lal)
Denoting 1 mol of solute dissolved in 1000 g of solvent; such solutions provide a definite ratio of solute to solvent molecules. Cf.:molar (4) .

molality (m) (mo-lal′i-te)
Moles of solute per kilogram of solvent; the molarity is equal to mρ/(1 + mM), where m is the m., ρ is the density of the solution, and M is the molar mass of the solute. Cf.:molarity.

molar (mo′lar)
1. Denoting a grinding, abrading, or wearing away. [L. molaris, relating to a mill, millstone] 2. SYN: m. tooth. 3. Massive; relating to a mass; not molecular. [L. moles, mass] 4. Denoting a concentration of 1 gram-molecular weight (1 mol) of solute per liter of solution, the common unit of concentration in chemistry. Cf.:molal. 5. Denoting specific quantity, e.g., m. volume (volume of 1 mol). first m., first permanent m. sixth permanent tooth or fourth deciduous tooth in the maxilla and mandible on either side of the midsagittal plane of the head following the arch form. Moon molars small dome-shaped first m. teeth occurring in congenital syphilis. mulberry m. a m. tooth with alternating nonanatomical depressions and rounded enamel nodules on its crown surface, usually associated with congenital syphilis. second m. seventh permanent or fifth deciduous tooth in the maxilla and mandible on either side of the midsagittal plane of the head following the arch form. sixth-year m. the first permanent m. tooth. third m. SYN: third-year m. tooth. twelfth-year m. the second permanent m. tooth.

molariform (mo-lar′i-form)
Having the form of a molar tooth. [molar (tooth) + L. forma, form]

molarity (M, m) (mo-lar′i-te)
Moles per liter of solution (mol/L). Cf.:molality.

mold (mold)
1. A filamentous fungus, generally a circular colony that may be cottony, wooly, etc., or glabrous, but with filaments not organized into large fruiting bodies, such as mushrooms. 2. A shaped receptacle into which wax is pressed or fluid plaster is poured in making a cast. 3. To shape a mass of plastic material according to a definite pattern. 4. To change in shape; denoting especially the adaptation of the fetal head to the pelvic canal. 5. The term used to specify the shape of an artificial tooth (or teeth). SYN: mould. pink bread m. SYN: Neurospora.

molding (mold′ing)
Shaping by means of a mold. border m. the shaping of an impression material by the manipulation or action of the tissues adjacent to the borders of an impression. SYN: muscle-trimming, tissue m., tissue-trimming. compression m. 1. the act of pressing or squeezing together to form a shape in a mold; 2. the adaptation of a plastic material to the negative form of a split mold by pressure. SEE ALSO: injection m.. injection m. the adaptation of a plastic material to the negative form of a closed mold by forcing the material into the mold through appropriate gateways. SEE ALSO: compression m. (2) . tissue m. SYN: border m..

mole (mol)
1. SYN: nevus (2) . 2. SYN: nevus pigmentosus. [A.S. mael (L. macula), a spot] 3. An intrauterine mass formed by the degeneration of the partly developed products of conception. [L. moles, mass] 4. (mol) In the SI system, the unit of amount of substance, defined as that amount of a substance containing as many “elementary entities” as there are atoms in 0.0120 kg of carbon-12; “elementary entities” may be atoms, molecules, ions, or any describable entity or defined mixture of entities and must be specified when this term is used; in practical terms, the m. is 6.0221367 × 1023 “elementary entities.” SEE ALSO: Avogadro number. carneous m. SYN: fleshy m.. cystic m. SYN: hydatidiform m.. fleshy m. a uterine mass occurring after fetal death and consisting of blood clots, fetal membranes, and placenta. SYN: carneous m.. hairy m. SYN: nevus pilosus. hydatidiform m., hydatid m. [MIM*231090] a vesicular or polycystic mass resulting from the proliferation of the trophoblast, with hydropic degeneration and avascularity of the chorionic villi; the abnormal tissue typically results from expression of paternally derived chromosomes and a loss of maternal chromosomes. SYN: cystic m., gestational trophoblastic disease. invasive m. SYN: chorioadenoma destruens.

molecular (mo-lek′u-lar)
Relating to molecules.

molecularity (mo-lek′u-lar′i-te)
The number of reactants in an elementary reaction. For example, a reaction involving one reactant is unimolecular; reactions involving two compounds are bimolecular. M. and order are not synonymous. Cf.:order (2) .

molecule (mol′e-kul)
The smallest possible quantity of a di-, tri-, or polyatomic substance that retains the chemical properties of the substance. [Mod. L. molecula, dim. of L. moles, mass] accessory molecules cell surface adhesion molecules on T cells that are involved in binding of one cell to another cell activation, and in signal transduction, e.g., CD4. adhesion molecules molecules that are involved in T helper-accessory cell, T helper-B cell, and T cytotoxic-target cell interactions; extracellular matrix proteins that attract leukocytes from the circulation. cell adhesion m. (CAM) proteins that hold cells together, e.g., uvomorulin, and hold them to their substrates, e.g., laminin. chimeric m. a m. (usually a biopolymer) containing sequences derived from two different genes; specifically, from two different species. Cf.:chimera. class I m. a major histocompatibility complex antigen made up of two noncovalently bonded polypeptide chains, one glycosylated, heavy, and variable with antigen specificity; the other chain is β2-microglobulin. class II m. a major histocompatibility complex membrane-piercing antigen made up of two noncovalently bonded polypeptide chains designated α and β. costimulatory m. membrane-bound or secreted product of accessory cells that is required for signal transduction. endothelial-leukocyte adhesion m. (E-LAM) a glycoprotein on the surface of endothelial cells that is involved in blood leukocyte attachment to vessel walls as well as emigration from the vessels into the tissues. gram-m. the amount of a substance with a mass in grams equal to its molecular weight; e.g., a gram-m. of hydrogen weighs 2.016 g, that of water 18.015 g. intercellular adhesion m.-1 (ICAM-1) a glycoprotein that is expressed on a variety of cells. It is the ligand for LFA-1 as well as the receptor for the rhinoviruses. lectin pathway m. the binding of mannose-binding protein to bacterial carbohydrates resulting in activation of the complement pathway.

molilalia (mol′i-la′le-a)
SYN: mogilalia. [G. molis, with difficulty (a later form of mogis), + lalia, talking]

molimina (-lim′i-na)

molindone hydrochloride (mo-lin′don)
An antipsychotic.

Hans, Austrian chemist, 1856–1937. See M. test.

Jacob A., Dutch oculist, 1832–1914. See M. glands, under gland.

mollities (mo-lish′i-ez)
1. Characterized by a soft consistency. 2. SYN: malacia. [L. mollis, soft]

mollusc (mol′usk)
SYN: mollusk.

Mollusca (mo-lus′ka)
A phylum of the subkingdom Metazoa with soft, unsegmented bodies, consisting of an anterior head, a dorsal visceral mass and a ventral foot. Most forms are enclosed in a protective calcareous shell. M. includes the classes Gastropoda (snails, whelks, slugs), Pelecypoda (oysters, clams, mussels), Cephalopoda (squids, octopuses), Amphineura (chitons), Scaphopoda (tooth shells), and the class of primitive metameric mollusks, Monoplacophora. [L. m., a nut with a thin shell, fr. mollis, soft]

Molluscipoxvirus (mol′lusk-′e-poks-vi-rus)
A genus in the family Poxviridae; causes localized wartlike skin lesions. SYN: molluscum contagiosum.

molluscum (mo-lus′kum)
A disease marked by the occurrence of soft rounded tumors of the skin. [L. molluscus, soft] m. contagiosum SYN: Molluscipoxvirus.

mollusk (mol′usk)
Common name for members of the phylum Mollusca, although usually restricted to the gastropods and bivalves. SYN: mollusc.

John B., 20th century U.S. oncologist. See M. virus.

Paul J., Canadian physician, 1870–1939. See M. test.

Howard C., U.S. obstetrician, 1903–1953. See Caldwell-M. classification.

molt (molt)
To cast off feathers, hair, or cuticle; to undergo ecdysis. SEE ALSO: desquamate. SYN: moult. [L. muto, to change]

mol wt
Abbreviation for molecular weight.

molybdate (mo-lib′dat)
A salt of molybdic acid.

molybdenic, molybdenous (mo-lib′den-ik, -den-us)
Relating to molybdenum.

molybdenum (Mo) (mo-lib′de-num)
A silvery white metallic element, atomic no. 42, atomic wt. 95.94; a bioelement found in a number of proteins ( e.g., xanthine oxidase). See m. target tube. [G. molybdaina, a piece of lead; a metal, prob. galena, fr. molybdos, lead]

molybdenum-99 (99Mo)
A reactor-produced radioisotope of molybdenum with a half-life of 2.7476 days, used in radionuclide generators for the production of technetium-99m.

molybdic (mo-lib′dik)
Denoting molybdenum in the 6+ state, as in MoO3.

molybdic acid
MoO3&chmpnt;H2O;a yellowish crystalline acid, forming molybdates; used in the determination of phosphorus or phosphate.

molybdoenzymes (mo-lib′do-en′zimz)
Enzymes that require a molybdenum ion as a component ( E.G., xanthine oxidase).

molybdoflavoproteins (mo-lib′do-fla′vo-pro′tenz)
Proteins that require a molybdenum ion and a flavin nucleotide as a part of its naturally occurring structure ( e.g., aldehyde dehydrogenase).

molybdopterin (mo-lib-op′ter-in)
A pterin derivative that complexes with molybdenum to form the molybdenum cofactor required by several enzymes.

molybdous (mo-lib′dus)
Denoting molybdenum in the 4+ state, as in MoO2.

molysmophobia (mo-liz-mo-fo′be-a)
Morbid fear of infection. [G. molysma, filth, infection, + phobos, fear]

moment (mo′ment)
The product of a quantity times a distance. [L. momentum (for movimentum), motion, m., fr. moveo, to move] dipole m. the product of one of the two charges of a dipole and the distance that separates them; an important measure of the degree of polarity of many biomolecules.

momism (mom′izm)
A term relating to excessive or overbearing mothering, especially as attributed to American cultural stereotypes.

See mono-.

monad (mo′nad, mon′ad)
1. A univalent element or radical. 2. A unicellular organism. 3. In meiosis, the single chromosome derived from a tetrad after the first and second maturation divisions. [G. monas, the number one, unity]

Constantin von, Swiss histologist, 1853–1930. See M. bundle, M. nucleus, M. syndrome, M. tract.

monamide (mon-am′id)
SYN: monoamide.


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