Medical Dictionary

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infraorbital (in′fra-or′bi-tal)
Below or beneath the orbit. SYN: suborbital.

infrapatellar (in-fra-pa-tel′ar)
Inferior to the patella; denoting especially a bursa, a pad of fat, or a synovial fold. SYN: subpatellar (2) .

infrapsychic (in-fra-si′kik)
Denoting ideas or actions originating below the level of consciousness.

infrared (IR, ir) (in′fra-red)
That portion of the electromagnetic spectrum with wavelengths between 730 and 1000 nm.

infrascapular (in-fra-skap′u-lar)
Inferior to the scapula. SYN: subscapular (2) .

infrasonic (in′fra-son′ik)
Denoting those frequencies that lie below the range of human hearing. [infra- + L. sonus, sound]

infraspinatus (in-fra-spi-na′tus)
See i. (muscle).

infraspinous (in-fra-spi′nus)
Below a spine or spinous process; specifically, the fossa infraspinata. SYN: subspinous (1) .

infrasplenic (in′fra-splen′ik, -sple′nik)
Beneath or below the spleen.

infrasternal (in-fra-ster′nal)
Inferior to the sternum. SYN: substernal (2) .

infrasubspecific (in′fra-sub-spe-si′fik)
Denoting a category of organisms of rank lower than subspecies.

infratemporal (in-fra-tem′po-ral)
Below the temporal fossa.

infrathoracic (in′fra-tho-ras′ik)
Below or at the lower portion of the thorax.

infratonsillar (in-fra-ton′si-lar)
Below the palatine tonsil or cerebellar tonsil.

infratrochlear (in′fra-trok′le-ar)
Inferior to the trochlea or pulley of the superior oblique muscle of the eye.

infraumbilical (in′fra-um-bil′i-kal)
Inferior to the umbilicus. SYN: subumbilical.

infraversion (in′fra-ver′shun)
1. A turning (version) downward. 2. In physiologic optics, rotation of both eyes downward. 3. SYN: infraclusion.

infriction (in-frik′shun)
The application of liniments or ointments combined with friction. [L. in, on, + frictio, a rubbing]

infundibula (in-fun-dib′u-la)
Plural of infundibulum.

infundibular (in-fun-dib′u-lar)
Relating to an infundibulum.

infundibulectomy (in′fun-dib′u-lek′to-me)
Excision of the infundibulum, especially of hypertrophied ventricular septal myocardium encroaching on the ventricular outflow tract in the tetralogy of Fallot. [infundibulum + G. ektome, excision]

infundibuliform (in-fun-dib′u-li-form)
SYN: choanoid. [L. infundibulum, funnel, + forma, form]

infundibulin (in-fun-dib′u-lin)
A 20% solution of an extract of the posterior lobe of the hypophysis cerebri.

infundibuloma (in-fun-dib′u-lo′ma)
A pilocytic astrocytoma arising in the neurohypophysis of the pituitary. [infundibulum + G. -oma, tumor]

infundibulo-ovarian (in-fun-dib′u-lo-o-va′re-an)
Relating to the fimbriated extremity of a uterine tube and the ovary.

infundibulopelvic (in-fun-dib′u-lo-pel′vik)
Relating to any two structures called infundibulum and pelvis, such as the expanded portion of a calyx and the pelvis of the kidney, or the fimbriated extremity of the uterine tube and the pelvis.

infundibulum, pl .infundibula (in-fun-dib′u-lum, -u-la)
1. [TA] A funnel or funnel-shaped structure or passage. 2. SYN: i. of uterine tube. 3. The expanding portion of a calyx as it opens into the renal pelvis. 4. [TA] SYN: conus arteriosus. 5. Termination of a bronchiole in the alveolus. 6. Termination of the cochlear canal beneath the cupola. 7. [TA] The funnel-shaped, unpaired prominence of the base of the hypothalamus behind the optic chiasm, enclosing the infundibular recess of the third ventricle and continuous below with the stalk of the hypophysis. [L. a funnel] ethmoid i. SYN: ethmoidal i.. ethmoidal i. [TA] a passage from the middle meatus of the nose communicating with the anterior ethmoidal cells and frontal sinus. SYN: i. ethmoidale [TA] , ethmoid i.. i. ethmoidale [TA] SYN: ethmoidal i.. i. of gallbladder [TA] tapering portion of gallbladder, opposite the fundus, as the body of the gallbladder narrows to the neck (from which the cystic duct proceeds). SYN: i. vesicae biliaris [TA] , i. vesicae felleae&star. i. hypophysis [TA] i. hypothalami [TA] SYN: i. of pituitary gland. hypothalamic i. SYN: i. of pituitary gland. i. of lungs in the embryo, one of the expanded extremities of the subdivisions of the lung buds; in later development minute pouches (the air sacs) appear in its wall. i. of pituitary gland [TA] the apical portion of the tuber cinereum extending into the stalk of the hypophysis. SYN: i. hypothalami [TA] , hypothalamic i.. i. of right ventricle [TA] i. tubae uterinae [TA] SYN: i. of uterine tube. i. of uterine tube [TA] the funnel-like expansion of the abdominal extremity of the uterine (fallopian) tube. SYN: i. tubae uterinae [TA] , i. (2) . i. vesicae biliaris [TA] SYN: i. of gallbladder. i. vesicae felleae i. of gallbladder.

infusible (in-foo′zi-bl)
1. Incapable of being melted or fused. 2. Capable of being made into an infusion.

infusion (in-fu′zhun)
1. The process of steeping a substance in water, either cold or hot (below the boiling point), in order to extract its soluble principles. 2. A medicinal preparation obtained by steeping the crude drug in water. 3. The introduction of fluid other than blood, e.g., saline solution, into a vein. [L. infusio, fr. in-fundo, pp. -fusus, to pour in]

Infusoria (in-foo-so′re-a)
Archaic term for Ciliophora. [Mod. L. pertaining to or found in an infusion, fr. in-fundo, pp. in-fusus, to pour in]

infusorian (in-fu-so′re-an)
Archaic term for a member of the class Infusoria, now the phylum Ciliophora.

Ingelfinger
Franz, U.S. nephrologist and editor, 1910–1980. See I. rule.

ingesta (in-jes′ta)
Solid or liquid nutrients taken into the body. [pl. of L. ingestum, ntr. pp. of in-gero, -gestus, to carry in]

ingestion (in-jes′chun)
1. Introduction of food and drink into the stomach. 2. Incorporation of particles into the cytoplasm of a phagocytic cell by invagination of a portion of the cell membrane as a vacuole. [L. in-gero, to carry in]

ingestive (in-jes′tiv)
Relating to ingestion.

Ingrassia
Giovanni F., Italian anatomist, 1510–1580. See I. process.

ingravescent (in-gra-ves′ent)
Increasing in severity. [L. ingravesco, to grow heavier, fr. gravis, heavy]

inguen (ing′gwen) [TA]
SYN: groin (1) . [L.]

inguinal (ing′gwi-nal)
Relating to the groin.

inguinocrural (ing′gwi-no-kroo′ral)
Relating to the groin and the thigh.

inguinodynia (ing′gwi-no-din′e-a)
Rarely used term for pain in the groin. [L. inguen (inguin-), groin, + G. odyne, pain]

inguinolabial (ing′gwi-no-la′be-al)
Relating to the groin and the labium.

inguinoperitoneal (ing′gwi-no-per′i-to-ne′al)
Relating to the groin and the peritoneum.

inguinoscrotal (ing′gwi-no-skro′tal)
Relating to the groin and the scrotum.

INH
Abbreviation for isonicotinic acid hydrazide.

inhalant (in-ha′lant)
1. That which is inhaled; a remedy given by inhalation. 2. A drug (or combination of drugs) with high vapor pressure, carried by an air current into the nasal passage, where it produces its effect. 3. Group of products consisting of finely powdered or liquid drugs that are carried to the respiratory passages by the use of special devices such as low pressure aerosol containers. SYN: insufflation (2) . SEE ALSO: inhalation, aerosol. [see inhalation]

inhalation (in-ha-la′shun)
1. The act of drawing in the breath. SYN: inspiration. 2. Drawing a medicated vapor in with the breath. 3. A solution of a drug or combination of drugs for administration as a nebulized mist intended to reach the respiratory tree. [L. in-halo, pp. -halatus, to breathe at or in] solvent i. i. of volatile organic solvents used in glue, nail polish remover, lacquer thinners, cleaning fluid, lighter fluid, and gasoline, for the purpose of self-intoxication. SEE ALSO: glue-sniffing.

inhale (in-hal′)
To draw in the breath. SYN: inspire.

inhaler (in-hal′er)
1. SYN: respirator (2) . 2. An apparatus for administering pharmacologically active agents by inhalation. metered-dose i. a device used to administer a defined dose of medication for inhalation; used frequently in the treatment of asthma and other respiratory conditions.

inherent (in-her′ent)
Occurring as a natural part or consequence; latent imminent; intrinsic. [L. inhaerens, sticking to, adhering]

inheritance (in-her′i-tans)
1. Characters or qualities that are transmitted from parent to offspring by coded cytologic data; that which is inherited. 2. Cultural or legal endowment. 3. The act of inheriting. [L. heredito, inherit, fr. heres (hered-), an heir] alternative i. 1. SYN: mendelian i.. 2. galton term for an assumed form in which all the characters are derived from one parent. blending i. galton term for i. in which no component is conspicuous or obtrusive. codominant i. i. in which two alleles are individually expressed in the presence of each other; there may be other alleles available at the locus that may or may not exhibit codominance. collateral i. the appearance of characters in collateral members of a family group, as when an uncle and a niece show the same character inherited from a common ancestor; in recessive characters it may appear irregularly, in contrast to dominant characters transmitted directly from one generation to the next. cytoplasmic i. transmission of characters dependent on self-perpetuating elements not nuclear in origin ( e.g., mitochondrial DNA). SYN: extranuclear i.. dominant i. dominance of traits. extrachromosomal i. transmission of characters dependent on some factor not connected with the chromosomes. extranuclear i. SYN: cytoplasmic i.. galtonian i. i. in which a measurable phenotype is generated by many loci, the contributions of which are statistically independent, additive, and of about equal value. (The latter are in accordance with the classical central limit therein and justify the use of the multivariate normal distribution in galtonian genetics). SYN: polygenic i.. holandric i. SYN: Y-linked i.. hologynic i. transmission of a trait from mother to her daughters but to no sons, attributed to attached (partially fused) X chromosomes, to cytoplasmic i., or to sex limitation with abnormal segregation, e.g., hematocolpos. maternal i. transmission of characters that are dependent on properties of the egg cytoplasm produced by nuclear genes or by mitochondrial genes or both. mendelian i. i. in which stable and undecomposable characters controlled entirely or overwhelmingly by a single genetic locus are transmitted over many generations. See Mendel first law, law of segregation, law of independent assortment. SYN: alternative i. (1) . mosaic i. i. in which the paternal influence is dominant in one group of cells and the maternal in another. Cf.:lyonization. multifactorial i. i. involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors. Cf.:galtonian i.. polygenic i. SYN: galtonian i.. recessive i. dominance of traits. sex-influenced i. i. that is autosomal but has a different intensity of expression in the two sexes, e.g., male pattern baldness. sex-limited i. i. of a trait that can be expressed in one sex only, e.g., testicular feminization. sex-linked i. the pattern of i. that may result from a mutant gene located on either the X or Y chromosome. X-linked i. the pattern of i. that may result from a mutant gene on an X chromosome. Y-linked i. the pattern of i. that may result from a mutant gene located on a Y chromosome. SYN: holandric i..

inherited (in-her′it-ed)
Derived from a preformed genetic code present in the parents. Contrast with acquired.

inhibin (in-hib′in)
One of several proteins that participate in differentiation and growth. Two glycoproteins, i. A and i. B, are secreted by Sertoli cells in the testis and granulosa cells in the ovary, inhibiting FSH secretion by direct action on the pituitary. [inhibit + -in]

inhibit (in-hib′it)
To curb or restrain.

inhibitine (in-hib′i-ten)
SYN: carnosine.

inhibition (in-hi-bish′un)
1. Depression or arrest of a function. SEE ALSO: inhibitor. 2. In psychoanalysis, the restraining of instinctual or unconscious drives or tendencies, especially if they conflict with one's conscience or with societal demands. 3. In psychology, a generic term for a variety of processes associated with the gradual attenuation, masking, and extinction of a previously conditioned response. 4. The reduction of the rate of a reaction or process. [L. inhibeo, pp. -hibitus, to keep back, fr. habeo, to have] allogeneic i. i. or injury to allogeneic cells that occurs when lymphocytes are mixed and cultured with other cells of different genotypes in vitro. central i. suppression or diminution of outgoing impulses from a reflex center. competitive i. blocking of the action of an enzyme by a compound that binds to the free enzyme, preventing the substrate from binding and thus preventing the enzyme from acting on that substrate. The competitive inhibitor is often a substrate analog and binds at the active site; however, this is not an absolute requirement for competitive i.. Saturating concentrations of substrate can remove the i.. Cf.:isostery. SYN: selective i.. contact i. cessation of replication of dividing cells that come into contact, as in the center of a healing wound. end product i. SYN: feedback i.. feedback i. i. of activity by an end product of the pathway of which that activity is a part; e.g., thyroliberin stimulates thyroglobulin production, and thyroglobulin decreases thyrotropin formation. SYN: end product i., retroinhibition. hapten i. of precipitation i. of precipitation that occurs when the antibody has combined with hapten of the same specificity as the subsequently added antigen. hemagglutination i. i. of nonimmune hemagglutination by antibody specific for the hemagglutinin; e.g., viral hemagglutination will not occur if antibody specific for the virus is added before addition of red blood cells. The i. is specific and is widely used for virus identification and for antibody determination. noncompetitive i. a type of enzyme i. in which the inhibiting compound does not compete with the natural substrate for the active site on the enzyme, but inhibits the reaction by combining with the enzyme-substrate complex or with the free enzyme. potassium i. arrest of the heart in the fully relaxed state as a result of potassium intoxication. proactive i. a type of interference or negative transfer, observed in memory experiments and other learning situations, when something learned previously interferes with present learning or recall. Cf.:retroactive i.. product i. i. of an enzyme activity by a product of the reaction catalyzed by that enzyme. reciprocal i. 1. SYN: reciprocal innervation. 2. SYN: systematic desensitization. reflex i. a situation in which sensory stimuli decrease reflex activity. residual i. the i. or suppression of tinnitus by use of a sound-generating device (residual inhibitor) that masks the sounds of tinnitus and produces a residual sound-inhibiting effect when the device is turned off. retroactive i. the partial or complete obliteration of memory by a more recent event, particularly new learning. Cf.:proactive i.. selective i. SYN: competitive i.. substrate i. i. of an enzyme activity by a substrate of the reaction catalyzed by that enzyme; often, this type of i. occurs at elevated substrate concentrations in which the substrate is binding to a second, non-active site on the enzyme. uncompetitive i. an inhibitory effect on a metabolic function, such as an enzyme, not based on competition for the binding site of the naturally occurring substrate, but on a different effect on the molecule whose function is being inhibited. Wedensky i. i. of muscle response resulting from application of a series of rapidly repeated stimuli to the motor nerve where slower frequency of stimulation results in muscle response.

inhibitor (in-hib′i-ter, -tor)
1. An agent that restrains or retards physiologic, chemical, or enzymatic action. 2. A nerve, stimulation of which represses activity. SEE ALSO: inhibition. α-glucosidase i. an oral agent that aids in the control of diabetes mellitus by delaying the absorption of glucose from the digestive system.α-Glucosidase inhibitors such as acarbose block the function of enzymes produced by mucosal cells of the proximal small bowel that normally break down complex dietary carbohydrates into simple sugars, including glucose. As a consequence, postprandial rises in blood glucose occur much more gradually. Administered before meals, acarbose can reduce peak postprandial glucose levels by as much as 75 mg/dL. Hence it permits reduction in the dose of oral antihyperglycemic agents or insulin. The drug is not absorbed into the circulation and acts only topically on intestinal lining cells. By itself it cannot induce hypoglycemia, but by reducing the need for insulin, it can increase the risk of hypoglycemia for a given dose of a sulfonylurea or insulin. It may cause flatulence, bloating, and diarrhea as complex carbohydrates reach the colon instead of being digested and absorbed. angiotensin-converting enzyme inhibitors (ACEI) a class of drugs used in the treatment of hypertension and congestive heart failure; they produce a reduction of peripheral arterial resistance, although the exact mechanism of action has not been fully determined; they block the conversion of angiotensin I to angiotensin II, a powerful vasoconstrictor. aromatase inhibitors drugs, such as aminoglutethimide, that inhibit aromatase, an enzyme used in the synthesis of estrogens. Bowman-Birk i. a polypeptide that will inhibit both trypsin and chymotrypsin. carbonate dehydratase i. an agent, usually chemically related to the sulfonamides, that inhibits the activity of carbonate dehydratase, producing a general decrease in the formation of H2CO3 in the tissues. SEE ALSO: acetazolamide, dichlorphenamide. SYN: carbonic anhydrase i.. carbonic anhydrase i. SYN: carbonate dehydratase i.. C1 esterase i. an α2-neuraminoglycoprotein that inhibits the enzymatic activity of C1 esterase, the activated first component of complement. A deficiency of this i. results in a lack of inhibition of C1r and C1s leading to uncontrolled activation of the complement cascade and edema. cholinesterase i. a drug, such as neostigmine, which, by inhibiting biodegradation of acetylcholine, restores myoneural function in myasthenia gravis or after nondepolarizing neuromuscular relaxants have been administered. familial lipoprotein lipase i. an i. found in certain individuals that inhibits lipoprotein lipase resulting in accumulation of chylomicrons, VLDL, and triacylglycerols; similar in symptoms to familial lipoprotein lipase deficiency. glucosidase inhibitors agents such as acarbose that reduce gastrointestinal absorption of carbohydrates. This group of drugs has been known popularly as “starch blockers.” They lower plasma glucose levels and tend to cause weight loss. A limiting side effect is flatulence. HMG CoA-reductase inhibitors drugs that interfere with the biosynthesis of cholesterol; used to treat hyperlipidemia.HMG-CoA reductase inhibitors, generically called statins, lower total cholesterol and LDL cholesterol in people with hyperlipidemia, delay progression of atherosclerosis, and decrease the risk of cardiovascular morbidity and mortality. In the synthesis of cholesterol in the liver, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) is converted to mevalonic acid by the enzyme HMG-CoA reductase. Normally this enzyme is inhibited by a high dietary intake of cholesterol, and conversely a reduction of dietary cholesterol may increase HMG-CoA reductase activity. Drugs that block the action of HMG-CoA reductase are structural analogs of HMG-CoA and competitively inhibit the enzyme, preventing cholesterol synthesis. A decline in intracellular cholesterol levels promotes increased expression of cell surface LDL receptors and uptake of circulating LDL. Controlled studies have shown that in people with a history of angina pectoris or heart attack, lovastatin, pravastatin, and simvastatin substantially reduce cardiovascular mortality, conferring protection against unstable angina and lowering the risk of fatal and nonfatal myocardial infarction, the number and duration of hospitalizations, the need for revascularization procedures, and the incidence of transient ischemic attacks and strokes. Prospective studies on the use of these agents by people with normal cholesterol levels have shown substantial reduction in the risk of a major coronary event in postmenopausal women and in people of both sexes over 65. In contrast, studies in which cholesterol was lowered by diet alone or by other drugs ( e.g., cholestyramine, gemfibrozil) have shown no consistent effect on the rate of either heart attacks or strokes. The beneficial effects of cholesterol lowering with statins are independent of concomitant medicines such as aspirin, beta-blockers, and calcium-channel blockers. Hence physical regression of atheroma may not be the principal mechanism by which cholesterol lowering alters cardiac risk. There is experimental evidence that statins affect immune function and the proliferation and metabolism of macrophages and endothelial cells independently of changes in plasma LDL concentrations. Animal studies suggest that statins may reduce the risk of thrombosis after plaque disruption by inhibiting platelet aggregation and maintaining a favorable balance between prothrombotic and fibrinolytic mechanisms. Not all statins have shown equal protective effect. Benefits have been clearly demonstrated only with “natural” statins produced by fermentation (lovastatin, pravastatin, and simvastatin). Synthetic statins have different chemical structures and are metabolized differently; although they lower LDL cholesterol, there are no data to show that they prolong life or reduce the risk of heart attack. human α1-protease i. (α1PI) SYN: α1-antitrypsin. β-lactamase inhibitors drugs such as clavulanic acid, which are used to inhibit bacterial β-lactamases; often used with a penicillin or cephalosporin to overcome drug resistance. lipoprotein-associated coagulation i. (LACI) formerly known as anticonvertin; a protein that inhibits the extrinsic pathway of coagulation by binding to the tissue factor III-factor VII-Ca2+-factor Xa complex. mechanism-based i. SYN: suicide substrate. monoamine oxidase i. (MAOI) a class of chemical compounds that exert antidepressant effect by the reversible or irreversible inhibition of monoamine oxidase A. ovulation i. a compound that inhibits ovulation; often found in oral contraceptives. protease i. a newly developed class of synthetic drug used in the treatment of HIV infection, with a mode of action different from those of previously used antiretroviral agents including nucleoside analogs.HIV-1 protease activity is critical for the terminal maturation of infectious virions. Protease inhibitors specific for HIV-1 competitively inhibit this enzyme, thereby preventing the maturation of virions capable of infecting other cells. These agents can reduce the viral load (level of HIV RNA in the serum) below the measurable level in a patient with AIDS. Their use has been shown to reduce the risk of disease progression and mortality in patients with HIV infection. They have also been found to improve CD4 counts and reverse AIDS dementia in some patients. Protease inhibitors are administered in combination with nucleoside analogs (nucleoside reverse transcriptase inhibitors) in order to exploit the different modes of action of these 2 classes of antiviral drug. Because emergence of resistance to protease inhibitors has already been a problem, combination regimens including 3 agents are standard. A few strains of HIV have shown resistance to all available protease inhibitors. Significant side effects of protease inhibitors include elevation of cholesterol and triglyceride levels, insulin resistance and emergence of frank diabetes mellitus, and cosmetically objectionable lipodystrophy (excessive accumulation of fat in the abdomen and breasts accompanied by fat wasting in the face, extremities, and buttocks). Protease inhibitors currently in use include indinavir, nelfinavir, ritonavir, and saquinavir. Several others are in various stages of development and testing. proton pump i. agents that block the transport of hydrogen ions into the stomach and hence are useful in the treatment of gastric hyperacidity, as observed in ulcer disease. 5α-reductase inhibitors Drugs that inhibit the action of 5α-reductase, resulting in lower levels of prostatic dihydrotestosterone, produced by the enzyme from testosterone as the primary androgen in the prostate. residual i. a sound-generating device, worn in the ear, that inhibits or suppresses the sounds of tinnitus by masking, with a residual inhibitory effect when the device is turned off. respiratory i. a compound that inhibits the respiratory chain. SYN: respiratory poison. selective norepinephrine reuptake i. a class of chemical compounds that selectively, to varying degrees, inhibit the reuptake of norepinephrine by the presynaptic neurons and are posited to exert their antidepressant effect by this mechanism. selective serotonin reuptake i. a class of chemical compounds that selectively, to varying degrees, inhibit the reuptake of serotonin by presynaptic neurons and are posited to exert their antidepressant effect by this mechanism. serine protease inhibitors a class of highly polymorphic inhibitors of trypsin, elastase, and certain other proteases synthesized by hepatocytes and macrophages SEE ALSO: α1-antitrypsin. SYN: serpins. serotonin norepinephrine reuptake i. a class of antidepressant drugs whose action is thought to result from inhibition of presynaptic reuptake of serotonin and norepinephrine. suicide i. SYN: suicide substrate. trypsin i. 1. a peptide formed from trypsinogen via hydrolysis under the catalytic influence of enteropeptidase, with trypsin also produced as a result; so called because the peptide masks or inhibits the active site of the trypsin molecule; 2. one of the polypeptides, from various sources ( e.g., human and bovine colostrum, soybeans, egg white), that inhibit the action of trypsin. Cf.:Bowman-Birk i.. α1-trypsin i. SYN: α1-antitrypsin. uncompetitive i. a type of enzyme i. in which the inhibiting compound only binds to the enzyme-substrate complex.

inhibitory (in-hib′i-tor-e)
Restraining; tending to inhibit.

iniac (in′e-ak)
Relating to the inion. SYN: inial.

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