|Medical Dictionary - Dictionary of Medicine and Human Biology|
Crossing of an unknown genotype to a recessive homozygote so that the phenotype of the progeny corresponds directly to the chromosomes carried by the parents of unknown genotype. SYN: backcross (2) .
SYN: orchiectomy. [testis + G. G. ektome, excision]
Plural of testis. [L.]
SYN: testis. [L. testiculus, dim. of testis]
Relating to the testes.
SYN: testis. [L.]
See test. bench t. t. of a device against specifications in a simulated (nonliving) environment. contrast sensitivity t. examination of the visual recognition of the variation in brightness of an object. genetic t. laboratory studies of human blood or other tissue for the purpose of identifying genetic disorders. Relatively large chromosomal abnormalities such as deletion or transposition are identified by microscopic examination of chromosomes from a cell undergoing mitosis (karyotyping). More subtle aberrations can be detected by DNA probes (fabricated lengths of single-stranded DNA that match parts of the known gene). Genetic t. in the broadest sense includes biochemical t. for abnormal substances, or abnormally high or low concentrations of normal substances, that serve as markers of genetic deficiency or abnormality. SYN: DNA diagnostics.Genetic t. has become a standard procedure in a number of settings: screening for genetic diseases such as hemochromatosis, screening of couples planning to have children for the cystic fibrosis carrier state, and screening for genetic mutations known to increase the risk of certain cancers such as retinoblastoma and early-onset breast cancer. In addition, genetic profiling (“genetic fingerprinting”) can establish or rule out identity of source for 2 specimens of human material, or parent-child relationship between 2 persons, with a probability of 99.9%. The availability of tests to diagnose or predict untreatable disorders such as Huntington chorea and to identify persons at increased risk of malignant disease has raised many social, psychological, therapeutic, and legal questions. Authorities recommend that people about to undergo genetic t. receive advance counseling about the implications of positive or negative test results. Lay persons often misunderstand the concept of predisposition or risk, particularly with respect to oncogenes. The majority of people who develop cancer do so because of spontaneous genetic mutation, not because of inherited risk; and of those who inherit the risk, not all develop cancer. The discovery that certain populations, such as Ashkenazic Jews, Mormons, and Amish, have a much higher incidence of certain genetic disorders has threatened to reactivate or reinforce ethnic, racial, and religious prejudices. Social groups most likely to harbor easily identified genetic mutations are by definition those whose gene pools are most distinct, because they have tended to intermarry rather than to mix with outside populations. The 1.3% of Ashkenazic Jews who share a mutation on the BRCA2 tumor suppressor gene may all be descendants of a single person (founder effect). The possibility of identifying a person's genetic predisposition to severe, chronic, or disabling diseases raises the possibility of discrimination by employers and by health, life, and disability insurers. State governments and the federal government have established rules that limit the access of employers and insurers, actual and potential, to a person's genetic profile, and that forbid stigmatization, job discrimination, and refusal to issue insurance or to insure at standard rates, because of genetic profile. histocompatibility t. a t. system for HLA antigens, of major importance in transplantation. proficiency t. a program in which specimens of quality control material are periodically sent to members of a group of laboratories for analysis, with each laboratory's results compared with those of its peers. SEE ALSO: proficiency samples, under sample. reality t. in psychiatry and psychology, the ego function by which the objective or real world and one's subjectively sensed relationship to it are evaluated and appreciated; the ability to distinguish internal from external events. susceptibility t. the determination of the ability of an antibiotic to kill or inhibit the growth of bacteria.
testis, pl .testes (tes′tis, -tez) [TA]
One of the two male reproductive glands, located in the cavity of the scrotum. SEE ALSO: appendix t.. SYN: didymus, genital gland (1) , male gonad, orchis, testicle, testiculus. [L.] abdominal t. an undescended t. that has never descended from the retroperineal/abdominal origin through the internal inguinal ring. cryptorchid t. SYN: undescended t.. ectopic t. a variant of undescended t. wherein testicular position is outside the usual pathway of descent. SEE ALSO: t. ectopia. movable t. SYN: retractile t.. peeping t. an undescended t. that migrates back and forth at the internal inguinal ring. retractile t. a condition in which there is a tendency of the t. to ascend to the upper part of the scrotum or into the inguinal canal, as contrasted with an undescended t.. SYN: movable t., pseudocryptorchism. undescended t. a t. that has failed to descend into the scrotum; there are palpable and nonpalpable (impalpable) variants. SYN: cryptorchid t..
See test types.
1. SYN: androgenic. 2. SYN: androgen. [testis + G. eidos, resemblance]
An androgenic agent used as an antineoplastic agent for treatment of mammary carcinoma.
The most potent naturally occurring androgen, formed in greatest quantities by the interstitial cells of the testes, and possibly secreted also by the ovary and adrenal cortex; may be produced in nonglandular tissues from precursors such as androstenedione; used in the treatment of hypogonadism, cryptorchism, certain carcinomas, and menorrhagia. t. cypionate a preparation with the same actions and uses as t. propionate, but with a prolonged duration of action. t. enanthate a preparation with the same actions and uses as t., but with a prolonged duration of action, being administered in oil. t. phenylpropionate an alternate preparation for the propionate. t. propionate a preparation that has an action similar to but more pronounced and prolonged than that of t.; used in the treatment of undescended testes and in menorrhagia.
A G protein mutation disease resulting in autonomous testosterone overproduction, with precocious puberty.
See test types.
Letters of various sizes used to test visual acuity. Jaeger t. type of different sizes used for testing the acuity of near vision. point system t. a near-vision test chart in which the various t. are multiples of a point (172 inch), lower-case letters being one-half the designated point size; reading 4-point at 16 inches is normal, and is designated N-4. Snellen t. square black symbols employed in testing the acuity of distant vision; the letters vary in size in such a way that each one subtends a visual angle of 5′ at a particular distance.
Relating to or marked by a sustained muscular contraction, as in tetanus. [G. tetanikos]
SYN: tetanoid (1) .
Causing tetanus or tetaniform spasms. [tetanus + G. -gen, producing]
SYN: neonatal tetany.
1. The act of tetanizing the muscles. 2. A condition of tetaniform spasm.
To stimulate a muscle by a rapid series of stimuli so that the individual muscular responses (contractions) are fused into a sustained contraction; to cause tetanus (2) in a muscle.
Combining forms denoting tetanus, tetany. [G. tetanos, convulsive tension]
1. Resembling or of the nature of tetanus. SYN: tetaniform. 2. Resembling tetany. [tetano- + G. eidos, resemblance]
A hemolytic principle, elaborated by Clostridium tetani, which seems to have no role in the etiology of tetanus.
An instrument for measuring the force of tonic muscular spasms. [tetano- + G. metron, measure]
An instrument by means of which tonic spasms are produced by the mechanical irritation of a hammer striking the motor nerve of the muscle affected. [tetano- + L. motor, a mover]
The neurotoxin of Clostridium tetani, which causes the characteristic signs and symptoms of tetanus; chief action is on the anterior horn cells, and the spasms seem to be due to action at inhibitory synapses.
SYN: tetanus toxin. [tetano- + G. toxikon, poison]
1. A disease marked by painful tonic muscular contractions, caused by the neurotropic toxin (tetanospasmin) of Clostridium tetani acting upon the central nervous system. Cf.:lockjaw, trismus. 2. A sustained muscular contraction caused by a series of nerve stimuli repeated so rapidly that the individual muscular responses are fused, producing a sustained tetanic contraction. See emprosthotonos, opisthotonos. [L. fr. G. tetanos, convulsive tension] acoustic t. experimental t. induced by a faradic current, the speed of which is estimated by the pitch of the vibrations. cephalic t. a type of local t. that follows wounds to the face and head; after a brief incubation (1–2 days) the facial and ocular muscles become paretic yet undergo repeated tetanic spasms. The throat and tongue muscles may also be affected. SYN: cerebral t.. cerebral t. SYN: cephalic t.. complete t. t. in which stimuli to a particular muscle are repeated so rapidly that decrease of tension between stimuli cannot be detected. drug t. tonic spasms caused by strychnine or other tetanic. SYN: toxic t.. generalized t. the most common type of t., often with trismus as its initial manifestation; the muscles of the head, neck, trunk and limbs become persistently contracted, and then painful paroxysmal tonic contractions (tetanic seizures) are superimposed; the high mortality rate (50%) is due to asphyxia or cardiac failure. incomplete t. t. (2) in which each stimulus causes a contraction to be initiated when the muscle has only partly relaxed from the previous contraction. local t. the most benign type of t.; the muscles in close proximity to an infected wound develop persistent involuntary contractions, often with transient, intense superimposed spasms triggered by various stimuli. The more distal upper extremity muscles are most often affected; gradual but complete recovery is typical. neonatal t. SYN: t. neonatorum. t. neonatorum t. occurring in newborn infants, usually due to infection of umbilical area with Clostridium tetani, often a result of ritualistic practices; has high fatality rate (about 60%). SYN: neonatal t.. postpartum t. SYN: puerperal t.. puerperal t. t. occurring during the puerperium from infection of the obstetric wound. SYN: postpartum t., uterine t.. Ritter opening t. the tetanic contraction that occasionally occurs when a strong current, passing through a long stretch of nerve, is suddenly interrupted. toxic t. SYN: drug t.. traumatic t. t. following infection of a wound. uterine t. SYN: puerperal t..
A clinical neurologic syndrome characterized by muscle twitches, cramps, and carpopedal spasm, and when severe, laryngospasm and seizures; these findings reflect irritability of the central and peripheral nervous systems, usually resulting from low serum levels of ionized calcium or, less commonly, magnesium. Causes include hyperventilation, hypoparathyroidism, rickets, and uremia. SYN: intermittent cramp. [G. tetanos, tetanus] t. of alkalosis t. due to a loss of acid from the body or an increase in alkali, resulting in a reduction of ionized calcium in plasma and body fluids, e.g., hyperventilation t. (loss of CO2), gastric t. (loss of HCl by vomiting), or injection or ingestion of excessive amounts of sodium bicarbonate. gastric t. t. associated with a gastric disorder, especially with loss of HCl by vomiting. hyperventilation t. t. caused by forced overbreathing, due to a reduction in CO2 in the blood. hypoparathyroid t. SYN: parathyroid t.. infantile t. t. of infants occurring usually in association with rickets, due to dietary deficiency of vitamin D. manifest t. t. from any cause in which neuromuscular hyperexcitability is clearly evident, as opposed to latent t.. SYN: symptomatic t.. neonatal t. hypocalcemic t. occurring in neonates or young infants, due to transient functional hypoparathyroidism in consumption of cow's milk (high phosphorus content). SYN: myotonia neonatorum, tetanism. parathyroid t. t. due to lack of parathyroid function, spontaneous or following excision of the parathyroid glands. SYN: hypoparathyroid t., parathyroprival t.. parathyroprival t. SYN: parathyroid t.. phosphate t. t. due to the ingestion of an excess of alkaline phosphates (Na2HPO4 or K2HPO4); most commonly produced experimentally in animals by the injection of alkaline phosphate, which reduces the ionized calcium of the blood. postoperative t. parathyroid t. caused by injury to or excision of the parathyroids during procedures in the neck. symptomatic t. SYN: manifest t..
Four. [G. tetra-, four]
Absence of upper and lower limbs. [tetra- + G. a- priv. + melos, limb]
Denoting an acid having four acid groups and thereby being able to neutralize 4 Eq of base.
Formerly used as a tranquilizer; resembles reserpine in its actions but duration of effect is shorter.
tetraboric acid (tet′ra-bor′ik)
Perboric or pyroboric acid. SYN: pyroboric acid.
An individual with four arms. [tetra- + G. brachion, arm]
tetrabromophenolphthalein sodium (tet′ra-bro′mo-fe′nol-thal′en, -e-in)
The sodium salt of a brominated dye; it was used early in the development of cholecystography.
tetracaine hydrochloride (tet′ra-kan)
A highly potent local anesthetic used for spinal, nerve block, and topical anesthesia.
An individual with four hands. [tetra- + G. cheir, hand]
An anthelmintic against hookworm and other nematodes. SYN: carbon dichloride, ethylene tetrachloride, tetrachloroethylene.
A diuretic of the thiazide type. SYN: teclothiazide.
Acetylene tetrachloride; a nonflammable solvent for fats, oils, waxes, resins, etc.; used in the manufacture of paint and varnish removers, photographic films, lacquers, and insecticides. Its toxicity exceeds that of chloroform and carbon tetrachloride, and produces narcosis, liver damage, kidney damage, and gastroenteritis. SYN: cellon.
SYN: carbon tetrachloride.
tetracoccus, pl .tetracocci (tet′ra-kok′us, -kok′si)
An old term describing a spherical bacterium that divides in two planes and characteristically forms groups of four cells. [tetra- + G. kokkos, berry]
tetracosactide, tetracosactin (tet′ra-ko-sak′tid, -tin)
Denoting a pulse curve with four upstrokes in the cycle. [tetra- + G. krotos, a striking]
Having four cusps. SYN: quadricuspid.
tetracycline (tet-ra-si′klen, -klin)
A broad spectrum antibiotic (a naphthacene derivative), the parent of oxytetracycline, prepared from chlortetracycline and also obtained from the culture filtrate of several species of Streptomyces; also available as t. hydrochloride and t. phosphate complex. T. fluorescence has been used in studies of growing tumors and calcium deposition in developing bone and teeth.
1. A collection of four things having something in common such as a deformity with four features, e.g., Fallot tetralogy. SYN: tetralogy. 2. In chemistry, a quadrivalent element. 3. In heredity, a bivalent chromosome that divides into four chromatids during meiosis. [G. tetras (t.-), the number four] Fallot t. SYN: tetralogy of Fallot. narcoleptic t. the clinical syndrome of narcolepsy, cataplexy, sleep paralysis, and hypnagogic hallucinations.
Having only four fingers or toes on a hand or foot. SYN: quadridigitate. [tetra- + G. daktylos, finger or toe]
tetradecanoic acid (tet′ra-dek-a-no′ik)
SYN: myristic acid.
Relating to a tetrad.
tetraethylammonium chloride (tet-ra-eth′il-a-mo′ne-um)
A quaternary ammonium compound that partially blocks transmission of impulses through parasympathetic and sympathetic ganglia and is used in pharmacologic studies to block ganglionic transmission; its clinical usefulness is limited; formerly used as an antihypertensive drug.
An anti-knock compound added to motor fuel; has a toxic action causing anorexia, nausea, vomiting, diarrhea, tremors, muscular weakness, insomnia, irritability, nervousness, and anxiety; death may occur. SYN: lead tetraethyl.
An anticholinesterase agent used in the treatment of glaucoma by local instillation in the eye.
tetraethyl pyrophosphate (TEPP) (tet′ra-eth′il)
An organic phosphoric compound used as an insecticide; a potent irreversible cholinesterase inhibitor.
tetraethylthiuram disulfide (tet′ra-eth-il-thi′u-ram)
1. A tetrapeptide (Trp–Met–Asp–Phe–NH2) used to test the secretion of digestive juice. 2. A pterin derivative that is a required cofactor for a number of enzymes; E.G., in the conversion of l-phenylalanine to l-tyrosine; the inability to synthesize tetrahydrobiopterin is associated with forms of malignant hyperphenylalaninemia.
tetraglycine hydroperiodide (tet-ra-gli′sen)
Dissolves in water to the extent of 380 g/L; used for the emergency disinfection of drinking water in amounts to yield 8 ppm of active iodine.
tetragon, tetragonum (tet′ra-gon, tet′ra-go′num)
Quadrangle; a figure having four sides. [tetra- + G. gonia, angle] t. lumbale a quadrangular space bounded laterally by the obliquus externus abdominis muscle, medially by the erector spinae, above by the serratus posterior inferior, and below by the internal abdominal oblique muscle.
Obsolete term for platysma (muscle).
Denoting a compound containing four ionizable hydrogen atoms (four acid groups).
Prefix denoting attachment of four hydrogen atoms; e.g., tetrahydrofolate (H4folate).
tetrahydrocannabinol (THC) (tet′ra-hi′dro-ka-nab′i-nol)
The Δ1-3,4-trans isomer and the Δ6-3,4-trans isomer are believed to be the active isomers present in Cannabis, having been isolated from marijuana. SEE ALSO: cannabis, dronabinol.
5,6,7,8-tetrahydrofolate dehydrogenase (tet′ra-hi-dro-fo′lat)
SYN: dihydrofolate reductase.
tetrahydrofolate methyltransferase (tet′ra-hi-dro-fol′at)
SYN: methionine synthase.
tetrahydrofolic acid (FH4) (tet′ra-hi-dro-fol′ik)
The active coenzyme form of folic acid; participates in one-carbon metabolism. SYN: coenzyme F.
tetrahydrozoline hydrochloride (tet-ra-hi-droz′o-len)
A sympathomimetic agent related to ephedrine, used as a topical nasal and conjunctival decongestant; chronic excessive use may convert an acute congestion into a chronic reactive hyperemia.
Tetrahymena pyriformis (tet-ra-hi′me-na pir-i-for′mis)
A ciliate belonging to a large group characterized by three membranes on one side of the buccal cavity and one on the other; it somewhat resembles the paramecium and, like it, is readily cultured and used extensively for experimental studies. [tetra- + G. hymen, membrane]
tetraiodophenolphthalein sodium (tet′ra-i-o′do-fe′nol-thal′en, -thal′e-in)
SYN: tetrad (1) . [G. tetralogia] Eisenmenger t. SYN: Eisenmenger complex. t. of Fallot a set of congenital cardiac defects including ventricular septal defect, pulmonic valve stenosis or infundibular stenosis, and dextroposition of the aorta so that it overrides the ventricular septum and receives venous as well as arterial blood. Right ventricular hypertrophy is considered part of the t. although it is reactive to the other defects. SYN: Fallot tetrad.
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