Medical Dictionary

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isoprecipitin (i′so-pre-sip′i-tin)
An antibody that combines with and precipitates soluble antigenic material in the plasma or serum, or in an extract of the cells, from another member, but not all members, of the same species. [iso- + precipitin]

isoprenaline hydrochloride (i-so-pren′a-len)
SYN: isoproterenol hydrochloride.

isoprenaline sulfate
SYN: isoproterenol sulfate.

isoprene (i′so-pren)
2-Methyl-1,3-butadiene;an unsaturated five-carbon hydrocarbon with a branched chain, which in the plant and animal kingdom is used as the basis for the formation of isoprenoids; e.g., terpenes, carotenoids and related pigments, rubber. Fat-soluble vitamins either are isoprenoid or have isoprenoid side chains; steroids are synthesized via isoprenoid intermediates as are ubiquinone, dolichol, and prenylated proteins.

isoprenoids (i-so-pren′oydz)
Polymers whose carbon skeletons consist in whole or in large part of isoprene units joined end to end; e.g., carotene, lycopene, vitamin A. Vitamins K and E and the coenzymes Q have isoprenoid side chains.

isoprenylation (i-so-pren′il-a′shun)
See prenylation.

isopropanol (i-so-pro′pa-nol)
SYN: isopropyl alcohol.

isoprophenamine hydrochloride (i′so-pro-fen′a-men)
SYN: clorprenaline hydrochloride.

isopropyl alcohol (i-so-pro′pil)
An isomer of propyl alcohol and a homologue of ethyl alcohol, similar in its properties, when used externally, to the latter, but more toxic when taken internally; used as an ingredient of various cosmetics and of medicinal preparations for external use; also available as isopropyl rubbing alcohol, which contains 68 to 72% of i. (by volume) in water; used as a rubefacient. SYN: dimethylcarbinol, isopropanol.

isopropylarterenol hydrochloride (i-so-pro′pil-ar-ter′e-nol)
SYN: isoproterenol hydrochloride.

isopropylcarbinol (i′so-pro-pil-kar′bin-ol)
See butyl alcohol.

isopropyl myristate (i-so-pro′pil)
A pharmaceutic aid used in topical medicinal preparations to promote absorption through the skin.

isopropylthiogalactoside (iPrSGal, IPTG) (i-so-pro′pil-thi′o-ga-lak′to-sid)
An artificial galactoside capable of inducing β-galactosidase in Escherichia coli without being split, as are the natural substrates such as lactose.

isoproterenol hydrochloride (i′so-pro-ter′e-nol)
A sympathomimetic β-receptor stimulant possessing the cardiac excitatory, but not the vasoconstrictor, actions of epinephrine. Chemically it differs from epinephrine in having an isopropyl group replacing the methyl group attached to the nitrogen atom; used in the treatment of bronchial asthma and heart block, including Adams-Stokes attacks. SYN: isoprenaline hydrochloride, isopropylarterenol hydrochloride.

isoproterenol sulfate
Used for inhalation as an aerosol in the treatment of acute asthmatic attacks and chronic pulmonary emphysema; now rarely used because less toxic, more specific agents are preferred. SYN: isoprenaline sulfate.

isopter (i-sop′ter)
A line of equal retinal sensitivity in the visual field. [iso- + G. opter, observer]

isopyknic (i-so-pik′nik)
Having the same density. [iso- + G. phknos, thick, dense, + -ic]

isopyrocalciferol (i-so-pi′ro-cal-sif′er-ol)
9β-Ergosterol;a thermal decomposition product of calciferol; a stereoisomer of pyrocalciferol and ergosterol.

isoquinoline (i-so-kwin′o-len)
1. Ring structure characteristic of the group of opium alkaloids represented by papaverine. 2. A class of alkaloids containing the i. (1) ring structure.

isoriboflavin (i′so-ri′bo-fla-vin)
8-Demethyl-6-methylriboflavin;a riboflavin antimetabolite, differing from riboflavin in that the methyl groups on the isoalloxazine nucleus are in the 6,7 positions rather than the 7,8.

isorrhea (i-so-re′a)
Equality of intake and output of water; maintenance of water equilibrium. [iso- + G. rhoia, a flow]

isosbestic (i-sos-bes′tik)
Denoting the wavelength of light at which two related compounds have identical extinction coefficients; e.g., the wavelength at which the absorption spectra of hemoglobin and oxyhemoglobin cross is their i. point. Spectrophotometry at that wavelength measures total concentration of hemoglobin, regardless of the extent to which it might be oxygenated. [Ger. isosbestisch, fr. G. isos, equal, + sbestos, extinguished]

isoschizomer (i-so-skiz′o-mer)
A restriction endonuclease from different organisms that recognizes and hydrolyzes at the same DNA sequence. [jiso- + G. schizo to split, + -mer]

isosensitize (i-so-sen′si-tiz)
SYN: autosensitize.

isosexual (i-so-sek′shoo-al)
Descriptive of an individual's somatic characteristics, or of processes occurring within, that are consonant with the sex of that individual.

isosmotic (i′sos-mot′ik)
Having the same total osmotic pressure or osmolality as another fluid (ordinarily intracellular fluid); such a fluid is not isotonic if it includes solutes that freely permeate cell membranes. SYN: iso-osmotic.

isosorbide
A compound with diuretic properties prepared by acid dehydration of d-glucitol.

isosorbide dinitrate (i-so-sor′bid di-ni′trat)
A coronary vasodilator that acts via the formation of nitric oxide.

Isospora (i-sos′po-ra)
A genus of coccidia (family Eimeriidae, class Sporozoea), with species chiefly in mammals; the ripe oocysts contain two sporocysts, each of which contains four sporozoites. This genus is now known to be closely related to Toxoplasma and Sarcocystis, with a similar sexual phase in the life cycle and a similar apical complex. [iso- + G. sporos, seed] I. belli a relatively rare species occurring in the small intestine of man, most common in the tropics but probably of worldwide distribution; most infections are subclinical, but sometimes they may cause mucous diarrhea. I. bigemina a species that occurs in the small intestine of the dog, cat, fox, mink, and possibly other carnivores; the most pathogenic coccidium in dogs and cats, causing enteritis and diarrhea; the oocysts are usually sporulated when passed in the feces, but are indistinguishable from those of Toxoplasma gondii, so considerable question remains as to the status of these parasites. I. canis a species of worldwide distribution that is mildly pathogenic in dogs and is not infective in cats. I. felis a species found in the small intestine and sometimes the cecum and colon of cats, lions, and other felids; it is only slightly, if at all, pathogenic in cats and is not infective in dogs. I. rivolta a species that occurs in the small intestine of dogs, cats, dingos, and probably other wild carnivores; pathogenic capabilities are similar to those of I. bigemina. I. suis a species that affects the small intestine of the pig, producing mild diarrhea.

isosporiasis (i-sos-po-ri′a-sis)
Disease caused by infection with a species of Isospora, such as I. belli of humans; human disease usually is mild except in cases of immunodeficiency, as in AIDS, where it may cause an intractable diarrhea.

isostere (i′so-ster)
One of two or more atoms or molecules having the same electron arrangement; e.g., N2 and CO. [iso- + G. stereos, solid]

isostery (i-so-ster′e)
Physiological enzyme or metabolic regulation via competitive inhibition by structural analogs of natural substrates.

isosthenuria (i-sos′the-noo′re-a, i′so-sthe-)
A state in chronic renal disease in which the kidney cannot form urine with a higher or a lower specific gravity than that of protein-free plasma; specific gravity of the urine becomes fixed around 1.010, irrespective of the fluid intake. [iso- + G. sthenos, strength, + ouron, urine]

isosuccinic acid (i′so-suk-sin′ik)
SYN: methylmalonic acid.

isosulfan blue (i-so-sul′fan)
A dye used as a radiographic adjunct to mark lymphatic vessels during lymphography.

isothermal (i-so-ther′mal)
Having the same temperature. [iso- + G. therme, heat]

isothiocyanate (i′so-thi-o-si′a-nat)
The radical of isothiocyanic acid, –N&dbond;C&dbond;S.

isothipendyl (i′so-thi-pen′dil)
An H1 antihistaminic.

isotone (i′so-ton)
One of several nuclides having the same number of neutrons in their nuclei; e.g., K and Ca with 20 each, Fe and Ni with 30 each. [iso- + G. tonos, stretching, tension]

isotonia (i-so-to′ne-a)
A condition of tonic equality in which tension or osmotic pressure in two substances or solutions is the same. [iso- + G. tonos, tension]

isotonic (i-so-ton′ik)
1. Relating to isotonicity or isotonia. 2. Having equal tension; denoting solutions possessing the same osmotic pressure; more specifically, limited to solutions in which cells neither swell nor shrink. Thus, a solution that is isosmotic with intracellular fluid will not be i. if it includes solute, such as urea, that freely permeates cell membranes. 3. In physiology, denoting the condition when a contracting muscle shortens against a constant load, as when lifting a weight. Cf.:auxotonic, isometric (2) .

isotonicity (i-so-to-nis′i-te)
1. The quality of possessing and maintaining a uniform tone or tension. 2. The property of a solution in being isotonic.

isotope (i′so-top)
One of two or more nuclides that are chemically identical, having the same number of protons, yet differ in mass number, since their nuclei contain different numbers of neutrons; individual isotopes are named with the inclusion of their mass number in the superior position (12C) and the atomic number (nuclear protons) in the inferior position (6C). In former usage, the mass numbers follow the chemical symbol (C-12). [iso- + G. topos, part, place] daughter i. an element produced by radioactive decay of another. See radionuclide generator, cow. radioactive i. an i. with an unstable nuclear composition; such nuclei decompose spontaneously by emission of a nuclear electron (β particle) or helium nucleus (α particle) and radiation (γ rays), thus achieving a stable nuclear composition; used as tracers and as radiation and energy sources. See half-life. stable i. a nonradioactive nuclide; an i. that shows no tendency to undergo radioactive decomposition.

isotopic (i-so-top′ik)
Of identical chemical composition but differing in some physical property, such as atomic weight.

isotransplantation (i′so-tranz-plan-ta′shun)
Transfer of an isograft (syngraft).

isotretinoin (i-so-tret′i-noyn)
A retinoid used for treatment of severe recalcitrant cystic acne; a known human teratogen.

isotropic, isotropous (i-so-trop′ik, i-sot′ro-pus)
Having properties that are the same in all directions. [iso- + G. trope, a turn]

isotype (i′so-tip)
An antigenic determinant (marker) that occurs in all members of a class or subclass in the heavy chains of an immunoglobulin or in the type and subtype of light chains of an immunoglobulin molecule. Whereas a given allotypic marker or determinant is thought to occur in only one subclass, an antigenic marker that is isotypic in one subclass may also occur as an allotypic marker in another subclass. [iso- + G. typos, model]

isotypic (i-so-tip′ik)
Pertaining to an isotype.

isovaleric acid (i′so-va-lar′ik, -ler′ik)
3-Methylbutyric acid;a metabolic intermediate in oxidative processes; elevated in cases of isovaleric acidemia.

isovaleric acidemia [MIM*243500]
An inborn error of leucine metabolism characterized by psychomotor retardation, a specific odor reminiscent of sweaty feet, vomiting, acidosis, and coma; associated with excessive production of isovaleric acid upon protein ingestion or during infectious episodes and is due to a deficiency of isovaleryl-CoA dehydrogenase; severe metabolic acidosis results from the large quantities of acid formed. Autosomal recessive inheritance; two forms are known: 1) the acute neonatal form with fulminant metabolic acidosis and rapid death, and 2) the chronic form characterized by intermittent episodes of severe ketoacidosis. SYN: sweaty feet syndrome.

isovaleryl-CoA (i-so-val′er-il)
The condensation product of isovaleric acid and coenzyme A; an intermediate in the catabolism of l-leucine. SYN: isovalerylcoenzyme A. isovaleryl-CoA dehydrogenase an enzyme that participates in the catabolism of l-leucine; it converts isovaleryl-CoA to 3-methylcrotonyl-CoA using FAD; a deficiency in this enzyme will result in isovaleric acidemia.

isovalerylcoenzyme A
SYN: isovaleryl-CoA.

isovalthine (i-so-val′then)
A sulfur-containing compound found in urine.

isovolume (i-so-vol′um)
At the same or equal volume. SEE ALSO: isovolumic.

isovolumetric (i′so-vol-u-met′rik)
SYN: isovolumic.

isovolumic (i′so-vol-u′mik)
Occurring without an associated alteration in volume, as when, in early ventricular systole, the muscle fibers initially increase their tension without shortening so that ventricular volume remains unaltered. SEE ALSO: isometric. SYN: isochoric, isovolumetric.

isoxsuprine hydrochloride (i-soks′soo-pren)
Sympathomimetic amine with potent inhibitory effects on vascular, uterine, and other smooth muscles; used as a vasodilator in various vascular diseases and as a uterine relaxant.

isozyme (i′so-zim)
SYN: isoenzyme.

issue (ish′u)
Archaic term for a discharge of pus, blood, or other matter. [Fr. a going out] nature-nurture i. a controversy concerning the relative importance of heredity (nature) and environment (nurture) in various aspects of individual development, such as intelligence, personality, or mental illness.

isthmectomy (is-mek′to-me)
Excision of the midportion of the thyroid. [G. isthmos, isthmus, + ektome, excision]

isthmic, isthmian (is′mik, is′me-an)
Denoting an anatomical isthmus.

isthmoparalysis (is′mo-pa-ral′i-sis)
Paralysis of the velum pendulum palati and the muscles forming the anterior pillars of the fauces. SYN: faucial paralysis, isthmoplegia. [G. isthmos, isthmus, + paralysis]

isthmoplegia (is′mo-ple′je-a)
SYN: isthmoparalysis. [G. isthmos, isthmus, + plege, stroke]

isthmus, pl .isthmiisthmuses (is′mus, -mi, -mus-ez) [TA]
1. A constriction in the embryonic neural tube delineating the anterior portion of the rhombencephalon, the future metencephalon, form the more rostrally located mesenephalon. 2. SYN: rhombencephalic i.. [G. isthmos] i. of aorta SYN: aortic i.. i. aortae [TA] SYN: aortic i.. aortic i. [TA] a slight constriction of the aorta immediately distal to the left subclavian artery at the point of attachment of the ductus arteriosus. SYN: i. aortae [TA] , i. of aorta. i. of auditory tube SYN: i. of pharyngotympanic tube. i. of cartilage of ear SYN: i. of cartilaginous auricle. i. of cartilaginous auricle [TA] a narrow bridge connecting the cartilage of the external acoustic meatus and the lamina of the tragus with the main portion of the cartilage of the auricle. SYN: i. cartilaginis auris, i. of cartilage of ear. i. cartilaginis auricularis [TA] i. cartilaginis auris SYN: i. of cartilaginous auricle. i. of cingulate gyrus [TA] the narrowing of the cingulate gyrus, at its transition with the hippocampal gyrus behind and below the splenium of the corpus callosum, caused by the anterior extension of the conjoined parieto-occipital and calcarine sulci. SYN: i. gyri cinguli [TA] , i. of gyrus fornicatus, i. of limbic lobe. i. of eustachian tube SYN: i. of pharyngotympanic tube. i. of external acoustic meatus the narrowest portion of this canal in the bony part near its deep termination. SYN: i. meatus acustici externi. i. of fauces [TA] the constricted and short space which establishes the connection between the cavity of the mouth and the oro-pharynx, bounded anteriorly by the palatoglossal folds and posteriorly by the palatopharyngeal folds; the lateral well is the tonsillar fossa. SYN: i. faucium [TA] , oropharyngeal i.. i. faucium [TA] SYN: i. of fauces. i. glandulae thyroideae [TA] SYN: i. of thyroid gland. Guyon i. SYN: i. of uterus. i. gyri cinguli [TA] SYN: i. of cingulate gyrus. i. of gyrus fornicatus SYN: i. of cingulate gyrus. i. of His SYN: rhombencephalic i.. Krönig i. the narrow straplike portion of the resonant field that extends over the shoulder, connecting the larger areas of resonance over the pulmonary apex in front and behind. i. of limbic lobe SYN: i. of cingulate gyrus. i. meatus acustici externi SYN: i. of external acoustic meatus. oropharyngeal i. SYN: i. of fauces. pharyngeal i. SYN: i. of pharynx. i. pharyngis SYN: i. of pharynx. i. pharyngonasalis SYN: choanae. i. of pharyngotympanic tube [TA] the narrowest portion of the auditory tube at the junction of the cartilaginous and bony portions. SYN: i. tubae auditivae [TA] , i. tubae auditoriae&star, i. of auditory tube, i. of eustachian tube. i. of pharynx [TA] passage posterior to the soft palate by which the nasopharynx and oropharynx communicate (i.e., the junction of naso- and oropharynx), closed during swallowing by elevation of the soft palate and contraction of the posterior fascicle of palatopharyngeus (muscle), forming a Passavant cushion. SYN: i. pharyngis, pharyngeal i.. pleural i. SYN: mesopneumonium. i. prostatae [TA] SYN: i. of prostate. i. of prostate [TA] the narrow middle part of the prostate anterior to the urethra. SYN: i. prostatae [TA] . i. rhombencephali SYN: rhombencephalic i.. rhombencephalic i. 1. a constriction in the embryonic neural tube delineating the mesencephalon from the rhombencephalon; 2. the anterior portion of the rhombencephalon connecting with the mesencephalon. SYN: i. (2) [TA] , i. of His, i. rhombencephali. i. of thyroid gland [TA] the central part of the thyroid gland joining the two lateral lobes. SYN: i. glandulae thyroideae [TA] . i. tubae auditivae [TA] SYN: i. of pharyngotympanic tube. i. tubae auditoriae i. of pharyngotympanic tube. i. tubae uterinae [TA] SYN: i. of uterine tube. i. uteri [TA] SYN: i. of uterus. i. of uterine tube [TA] the narrow portion of the uterine tube adjoining the uterus. SYN: i. tubae uterinae [TA] . i. of uterus [TA] an elongated constriction at the junction of the body and cervix of the uterus. SYN: i. uteri [TA] , Guyon i., orificium internum uteri, os uteri internum, ostium uteri internum. Vieussens i. SYN: limbus fossae ovalis.

itaconic acid (it′a-kon′ik)
The decarboxylation product of cis-aconitic acid. SYN: methylenesuccinic acid.

itch
1. An irritating sensation in the skin that arouses the desire to scratch. SYN: pruritus (2) . 2. Common name for scabies. [A.S. gikkan] azo i. itching that occurs among workers in azo dyes. baker i. an eruption on the hands and arms of bakers due to an allergic reaction to flour or other substances handled, or to the grain i. mite. barber i. SYN: tinea barbae. bath i. SYN: bath pruritus. copra i. a dermatitis occurring in workers in copra mills, caused by the presence of a mite, Tyrophagus putrescentiae. Cuban i. SYN: alastrim. frost i. SYN: winter i.. grain i. a wheal-like cutaneous eruption occasionally noted in farmers and grain handlers, caused by the action of the mite Pyemotes ventricosus. grocer i. a vesicular dermatitis seen in grocers and bakers who handle sugar or flour; caused by a mite of the genus Glycophagus. ground i. SYN: cutaneous larva migrans. kabure i. SYN: schistosomiasis japonica. Norway i. SYN: Norwegian scabies. poultryman's i. eruption due to infestation with the mite, Dermanyssus gallinae. rice i. SYN: schistosomiasis japonica. Saint Ignatius i. SYN: pellagra. straw i., straw-bed i. an urticarial eruption caused by the mite, Pyemotes ventricosus, which can infest straw used in mattresses. SYN: dermatitis pediculoides ventricosus. summer i. SYN: pruritus aestivalis. swimmer's i. SYN: schistosomal dermatitis. water i. 1. SYN: cutaneous larva migrans. 2. SYN: schistosomal dermatitis. winter i. a recurrent eczema appearing with the advent of cold weather. SYN: dermatitis hiemalis, frost i., pruritus hiemalis.

itching
An uncomfortable sensation of irritation of the skin or mucous membranes that causes scratching or rubbing of the affected parts. SYN: pruritus (1) .

-ite
1. Of the nature of, resembling. 2. A salt of an acid that has the termination -ous. 3. In comparative anatomy, a suffix denoting an essential portion of the part to the name of which it is attached. SEE ALSO: -ites. [G. -ites, fem. -itis]

iter (i′ter)
A passage leading from one anatomic part to another. SEE ALSO: canaliculus. [L. i. (itiner-), a way, journey] i. chordae anterius SYN: anterior canaliculus of chorda tympani. i. chordae posterius SYN: posterior canaliculus of chorda tympani. i. dentis the route or routes by which one or more teeth erupt. SYN: i. dentium. i. dentium SYN: i. dentis. i. a tertio ad quartum ventriculum SYN: cerebral aqueduct. [L. path from the third to the fourth ventricle]

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