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Medical Dictionary


traction (trak′shun)
1. The act of drawing or pulling, as by an elastic or spring force. 2. A pulling or dragging force exerted on a limb in a distal direction. [L. tractio, fr. traho, pp. tractus, to draw] axis t. rarely used procedure to apply t. upon the fetal head in the line of the birth canal by means of axis t. forceps. Bryant t. t. upon the lower limb placed vertically, employed especially in fractures of the femur in children. Buck t. apparatus for applying longitudinal skin t. on the leg through contact between the skin and adhesive tape; friction between the tape and skin permits application of force, which is applied through a cord over a pulley, suspending a weight; elevation of the foot of the bed allows the body to act as a counterweight. SYN: Buck extension. external t. a pulling force created by using fixed anchorage ( e.g., a headcap or bed frame) outside the oral cavity; principally used in the management of midfacial fractures. halo t. application of skeletal t. to the head by means of a halo device. intermaxillary t. SYN: maxillomandibular t.. internal t. a pulling force created by using one of the cranial bones, above the point of fracture, for anchorage. isometric t. t. in which the length of the limb does not change. isotonic t. t. in which the amount of force does not change. maxillomandibular t. a pulling force developed by using elastic or wire ligatures and interdental wiring or splints, or both. SYN: intermaxillary t.. Russell t. an improvement of Buck extension that permits the resultant vector of the applied t. force to be changed; for fractures of the femur. skeletal t. t. pull on a bone structure mediated through a pin or wire inserted into the bone to reduce a fracture of long bones. SYN: skeletal extension. skin t. t. on an extremity by means of adhesive tape or other types of strapping applied to the limb.

tractor (trak′ter, tor)
An instrument for exerting traction upon an organ or structure. [Mod. L. a drawer, see traction] Lowsley t. a slender curved instrument with flexible blades at its tip, which can be opened or closed by rotation at the proximal end of the t.; it is passed through the urethra into the bladder and used to retract the prostate gland downward into the operative field in the initial stages of perineal prostatectomy. Syms t. a collapsible rubber bag attached to the extremity of a tube; the tube is introduced into the bladder through the perineal wound and the bag is inflated; traction produced draws the enlarged prostate into the wound where it is more accessible. Young prostatic t. a short, straight tubular instrument with blades at its tip, which can be rotated open and closed; it is passed into the prostatic urethra, through a prostatotomy incision made during the later stages of open perineal prostatectomy, with its tip into the bladder; direct traction on the instrument brings the prostate gland down into the operative field where enucleation can be more easily performed.

tractotomy (trak-tot′o-me)
Interruption of a nerve tract in the brainstem or spinal cord. [L. tractus, tract, + G. tome, incision] anterolateral t. SYN: anterolateral cordotomy. intramedullary t. SYN: trigeminal t.. pyramidal t. may be mesencephalic (pedunculotomy or crusotomy), medullary (medullary pyramidotomy), or spinal (spinal pyramidotomy). Schwartz t. a medullary spinothalamic t.. Sjöqvist t. SYN: trigeminal t.. spinal t. SYN: anterolateral cordotomy. spinothalamic t. may be spinal (cordotomy), medullary (Schwartz t.), or mesencephalic (Walker t.). trigeminal t. division of the descending fibers of the trigeminal tract in the medulla. SYN: intramedullary t., Sjöqvist t.. Walker t. a mesencephalic spinothalamic t..

tractus (trak′tus)
SYN: tract. [L. a drawing, drawing out, extent, tract, fr. traho, pp. t., to draw] t. anterolaterales SYN: anterolateral system. t. bulboreticulospinalis [TA] SYN: bulboreticulospinal tract. t. caeruleospinalis [TA] SYN: caerulospinal tract. t. cerebellorubralis SYN: cerebellorubral tract. t. cerebellothalamicus SYN: cerebellothalamic tract. t. corticobulbaris SYN: corticobulbar tract. t. corticopontinus [TA] SYN: corticopontine tract. t. corticospinalis SYN: corticospinal tract. t. corticospinalis anterior [TA] SYN: anterior corticospinal tract. t. corticospinalis lateralis [TA] SYN: lateral corticospinal tract. t. descendens nervi trigemini SYN: spinal tract of trigeminal nerve. t. dorsolateralis [TA] SYN: dorsolateral fasciculus. t. fastigiobulbaris SYN: fastigiobulbar tract. t. fastigiospinalis [TA] SYN: fastigiospinal tract. See fastigiospinal fibers, under fiber. t. frontopontinus SYN: frontopontine tract. t. habenulointerpeduncularis [TA] SYN: retroflex fasciculus. t. iliopubicus [TA] SYN: iliopubic tract. t. iliotibialis [TA] SYN: iliotibial tract. t. interpositospinalis [TA] SYN: interpositospinal tract. t. interstitiospinalis [TA] SYN: interstitiospinal tract. t. mesencephalicus nervi trigemini [TA] SYN: mesencephalic tract of trigeminal nerve. t. occipitopontinus SYN: occipitopontine tract. t. olfactorius [TA] SYN: olfactory tract. t. olivocerebellaris [TA] SYN: olivocerebellar tract. t. olivocochlearis [TA] SYN: olivocochlear tract. See olivocochlear bundle. t. opticus SYN: optic tract. t. parietopontinus SYN: parietopontine tract. t. pontoreticulospinalis [TA] SYN: pontoreticulospinal tract. t. posterolateralis [TA] SYN: dorsolateral fasciculus. t. pyramidalis [TA] SYN: corticospinal tract. t. pyramidalis anterior SYN: anterior corticospinal tract. t. pyramidalis lateralis SYN: lateral corticospinal tract. t. raphespinalis anterior [TA] SYN: anterior raphespinal tract. t. raphespinalis lateralis [TA] SYN: lateral raphespinal tract. t. reticulospinalis SYN: reticulospinal tract. t. rubrobulbaris SYN: rubrobulbar tract. t. rubrobulbaris [TA] SYN: rubrobulbar tract. t. rubropontinus [TA] SYN: rubropontine tract. t. rubrospinalis [TA] SYN: rubrospinal tract. t. solitariospinalis [TA] SYN: solitariospinal tract. t. solitarius [TA] SYN: solitary tract. t. spinalis nervi trigemini [TA] SYN: spinal tract of trigeminal nerve. t. spinocerebellaris anterior [TA] SYN: anterior spinocerebellar tract. t. spinocerebellaris posterior [TA] SYN: posterior spinocerebellar tract. t. spinocervicalis [TA] SYN: spinocervical tract. t. spinocervicalis SYN: spinocervical tract. t. spinoolivaris [NA] SYN: spinoolivary tract. t. spinoolivaris [TA] SYN: spinoolivary tract. t. spinotectalis [TA] SYN: spinotectal tract. t. spinothalamicus SYN: spinothalamic tract. t. spinothalamicus anterior [TA] SYN: anterior spinothalamic tract. t. spinothalamicus lateralis [TA] SYN: lateral spinothalamic tract. t. spinovestibularis [TA] SYN: spinovestibular tract. t. spiralis foraminosus [TA] openings in the cochlear area of the bottom of the internal acoustic meatus through which the fibers of the cochlear nerve leave the bony labyrinth to enter the cranial cavity. SYN: spiral foraminous tract. t. supraopticohypophysialis [TA] SYN: supraopticohypophysial tract. t. tectobulbaris [TA] SYN: tectobulbar tract. t. tectopontinus [TA] SYN: tectopontine tract. t. tectospinalis [TA] SYN: tectospinal tract. t. tegmentalis centralis [TA] SYN: central tegmental tract. t. temporopontinus SYN: temporopontine tract. t. trigeminospinalis [TA] SYN: trigeminospinal tract. t. trigeminothalamicus anterior [TA] SYN: anterior trigeminothalamic tract. t. trigeminothalamicus posterior [TA] SYN: posterior trigeminothalamic tract. t. tuberoinfundibularis SYN: tuberoinfundibular tract. t. vestibulospinalis SYN: lateral vestibulospinal tract. t. vestibulospinalis lateralis [TA] SYN: lateral vestibulospinal tract. t. vestibulospinalis medialis [TA] SYN: medial vestibulospinal tract. t. vestibulospinalis medialis [TA] SYN: medial vestibulospinal tract.

trafficking (traf′ik-ing)
SYN: processing (1) . See targeting.

tragacanth, tragacantha (trag′a-kanth, -kan′tha; -santh)
A gummy exudation from Astragalus species, including A. gummifer, shrubs of the eastern end of the Mediterranean; it occurs as bands or strings of a tough gummy substance, forming a jelly-like mucilage with 50 parts of water; used as a demulcent and excipient in emulsions and suspensions. [G. tragakantha, a gum-producing shrub, fr. tragos, goat, + akanthos, thorn]

tragal (tra′gal)
Relating to the tragus.

tragi (tra′ji)
1. Plural of tragus. 2. [NA] The hairs growing at the entrance to the external acoustic meatus.

See t. (muscle).

tragion (tra′je-on)
A cephalometric point in the notch just above the tragus of the ear; it lies 1–2 mm below the spine of the helix, which can be palpated.

tragomaschalia (trag-o-mas-kal′e-a)
Bromidrosis of the axillae. [G. tragomaschalos, with smelling armpits, fr. tragos, goat, + maschale, the axilla]

tragophonia, tragophony (trag′o-fo′ne-a, tra-gof′o-ne)
SYN: egophony. [G. tragos, goat, + phone, voice]

tragus, pl .tragi (tra′gus, -ji)
1. [NA] A tonguelike projection of the cartilage of the auricle in front of the opening of the external acoustic meatus and continuous with the cartilage of this canal. SYN: antilobium, hircus (3) . 2. See tragi (2) . [G. tragos, goat, in allusion to the hairs growing on the part, like a goatee] accessory t. small nodules present at birth, anterior to the t., derived from first branchial arch remnants and often containing central cartilage.

A member of the tumor necrosis factor ligand family that rapidly induces apoptosis in a variety of transformed cell lines. SYN: apo-2L.

training (tran′ing)
An organized system of education, instruction, or discipline. assertive t. a form of behavior modification or therapy in which a client is taught to feel free to make legitimate demands and refusals in situations which previously elicited diffident responses. SYN: assertive conditioning. aversive t. a form of behavior t. or modification in which a noxious event is used to punish or extinguish undesirable behavior. SEE ALSO: aversion therapy. SYN: aversive conditioning. avoidance t. SYN: avoidance conditioning. escape t. SYN: escape conditioning. toilet t. t. directed at teaching a child proper control of bladder and bowel functions; psychoanalytic personality theory believes that the attitudes of both parent and child concerning this t. may have important psychologic implications for the child's later development.

trait (trat)
A qualitative characteristic; a discrete attribute as contrasted with metric character. A t. is amenable to segregation rather than quantitative analysis; it is an attribute of phenotype, not of genotype. [Fr. from L. tractus, a drawing out, extension] Bombay t. Bombay phenomenon. categorical t. in genetics, a feature that can conveniently and effectively be analyzed by sorting into classes either because there is no satisfactory way of measuring it (as with blood groups) or because it falls into natural classes so that the variation among classes far exceeds that within classes ( e.g., the phenotypic effects of many enzyme polymorphisms); existence of categories suggests but does not prove the operation of a major, simple, underlying cause. SYN: qualitative t.. chromosomal t. a t. dependent on a recurrent chromosomal aberration. codominant t. codominant. dominant t. an outstanding mental or physical characteristic. See dominance of traits. dominant lethal t. t., expressed in the phenotype if present in the genotype, that precludes having descendants. All such cases are necessarily sporadic and must represent new mutations as the usual methods of classical genetics provide no means of demonstrating any genetic component whatsoever, except for tenuous arguments such as advanced paternal age. Molecular biology may help although the methods may be tedious; if there is an epistatic gene that may mask the t., the logic is more tractable, though complex. galtonian t. a quantitative genetic t. due to contributions from many more of less equally important loci that resembles a continuous t.. intermediate t. a measurable t. in which there is some evidence of the operation of a simple major cause, but in which the variation within the putative categories is such as to cause overlap and hence ambiguity in classification of any particular reading. liminal t. SYN: threshold t.. marker t. a t. that may be of little importance in itself but which by association, linkage, or other means facilitates the detection, anticipation, or understanding of a disease or (for genetic diseases) the localization of the causative gene on the karyotype. mendelian t. a categorical t. that segregates in accordance with a single-locus genetic system. nonpenetrant t. a genetic t. that is not phenotypically manifest because of nongenetic factors; it therefore does not include recessivity, epistasis, hypostasis, or parastasis but does include environmental factors and pure random effects such as lyonization. penetrant t. a t. that in the appropriate genotypes is phenotypically manifest; strictly, it is the t. that is penetrant, not the gene. See penetrance. qualitative t. SYN: categorical t.. recessive t. dominance of traits. sickle cell t. the heterozygous state of the gene for hemoglobin S in sickle cell anemia. threshold t. a t. that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. SYN: liminal t..

trajector (tra-jek′ter, -tor)
An infrequently used instrument for locating the course of a bullet in a wound. [L. fr. tra-jicio, pp. -jectus, to throw over or across]

tramadol (tra′ma-dol)
An analgesic drug whose mechanism of action is unusual in that one optical isomer exerts typical opioid-type effects and the other isomer interacts with the reuptake and/or release of norepinephrine and serotonin in nerve terminals.

tramazoline hydrochloride (tra-maz′o-len)
An adrenergic and sympathomimetic agent used for nasal decongestion.

trance (trans)
An altered state of consciousness as in hypnosis, catalepsy, or ecstasy. [L. transeo, to go across] death t. a condition of suspended animation, marked by unconsciousness and barely perceptible respiration and heart action. induced t. the artificially induced state of hypnosis or of somnambulistic t.. somnambulistic t. a state of somnambulism, paralysis, anesthesia, or catalepsy induced by suggestion in major hypnosis.

tranexamic acid (tran-eks-am′ik)
A competitive inhibitor of plasminogen activation and of plasmin; used in hemophilia to reduce or prevent hemorrhage.

tranquilizer (trang′kwi-li-zer)
A drug that promotes tranquility by calming, soothing, quieting, or pacifying with minimal sedating or depressant effects. major t. SYN: antipsychotic agent. minor t. SYN: antianxiety agent.

1. Prefix (in italics) denoting across, through, beyond; opposite of cis-. 2. In genetics, a prefix denoting the location of two genes on opposite chromosomes of a homologous pair. 3. In organic chemistry (in italics), a form of geometric isomerism in which the atoms attached to two carbon atoms, joined by double bonds, are located on opposite sides of the molecule. 4. In biochemistry, a prefix to a group name in an enzyme name or a reaction denoting transfer of that group from one compound to another; e.g., transformylase (transfers a formyl group), transpeptidation. [L. trans, through, across]

transacetylase (trans-a-set′i-las)
SYN: acetyltransferase.

transacetylation (trans′a-set-i-la′shun)
Transfer of an acetyl group (CH3CO–) from one compound to another; such reactions, usually involving formation of acetyl-CoA, occur notably in the initiation of the tricarboxylic acid cycle by the transfer of an acetyl group to oxaloacetate to form citrate.

transaction (tranz-ak′shun)
1. Interaction arising from the encounter of two or more persons. 2. In transactional analysis, the unit of analysis involving a social stimulus and a response.

transacylases (trans-as′i-la-sez)
SYN: acyltransferases.

transacylation (trans-as′il-a′shun)
The reversible transfer of acyl groups.

transaldolase (trans-al′do-las)
Transferase interconverting sedoheptulose 7-phosphate and d-glyceraldehyde 3-phosphate to d-erythrose 4-phosphate and d-fructose 6-phosphate; part of the pentose phosphate pathway. SEE ALSO: transketolase.

transaldolation (trans′al-do-la′shun)
A reaction involving the transfer of an aldol group (CH2OH–CO–CHOH–) from one compound to another; such reactions generally involve the sugar phosphates and occur in the phosphogluconate oxidation pathway of carbohydrate catabolism.

transamidation (trans-am′i-da-shun)
The transfer of NH2 from an amide moiety ( E.G., from glutamine) to another molecule.

transamidinases (trans-am′i-di-nas-ez)
SYN: amidinotransferases.

transamidination (trans-am′i-di-na′shun)
A reaction involving the transfer of an amidine group (NH2C&dbond;NH) from one compound to another; the amidine donor is generally l-arginine and the reaction is of significance in the biosynthesis of creatine.

transaminases (trans-am′i-nas-ez)
SYN: aminotransferases.

transamination (trans-am′i-na′shun)
The reaction between an amino acid and an α-keto acid through which the amino group is transferred from the former to the latter; in certain cases the reaction may be between an amino acid and an aldehyde ( e.g., glutamate with glutamate semialdehyde via ornithine transaminase).

transaudient (trans-aw′de-ent)
Permeable to sound waves. [trans- + L. audio, pres. p. audiens, to hear]

transcalent (trans-ka′lent)
SYN: diathermanous. [trans- + L. caleo, to be warm]

transcapsidation (trans-kap-si-da′shun)
The phenomenon whereby the adenovirus capsid of the SV40 adenovirus “hybrid” is replaced by the capsid of another type of adenovirus; extended to include a similar phenomenon in other viruses.

transcarbamoylases (trans-kar-bam′o-i-la-sez)
SYN: carbamoyltransferases.

transcarbamoylation (trans-kar-bam′o-il-a′shun)
The transfer of a carbamoyl moiety from one molecule to another; e.g., the reaction catalyzed by ornithine transcarbamoylase in the urea cycle.

transcarboxylases (trans-kar-boks′i-las-ez)
SYN: carboxyltransferases.

transcendental meditation (TM) (tranz′en-den-tal med′i-ta-shun)
A form of meditation practiced over 2500 years ago in Eastern cultures and which was recently made popular in the West by Maharishi Mahesh Yogi as a means to help increase energy, reduce stress, and have a positive effect on mental and physical health; it involves the person sitting upright for 20 min, with eyes closed, and silently speaking a mantra (a key stimulus word used uniquely by each individual to return to the proper meditative state) whenever thought occurs.

transcobalamins (trans-ko-bal′a-minz)
Substances included in “R binder,” the name given a family of cobalamin-binding proteins; deficiencies have been associated with low serum cobalamin levels, and can lead to megaloblastic anemia.

transcondylar (trans-kon′di-lar)
Across or through the condyles; denoting the line of bone incision in Carden amputation.

transcortical (tranz-kor′ti-kal)
1. Across or through the cortex of the brain, ovary, kidney, or other organ. 2. From one part of the cerebral cortex to another; denoting the various association tracts.

transcortin (trans-kor′tin)
An α2-globulin in blood that binds cortisol and corticosterone; the principal corticosteroid-binding protein in the plasma. SYN: corticosteroid-binding globulin, corticosteroid-binding protein.

transcriptase (tran-skrip′tas)
A polymerase associated with the process of transcription; may be RNA-dependent or DNA-dependent. [L. transcribo, pp. transcriptum, to copy, + -ase] reverse t. rNA-dependent DNA polymerase, present in virions of RNA tumor viruses (retroviruses).

transcription (tran-skrip′shun)
Transfer of genetic code information from one kind of nucleic acid to another, especially with reference to the process by which a base sequence of messenger RNA is synthesized (by an RNA polymerase) on a template of complementary DNA. reverse t. reversal of the normal pattern of t. (from DNA to RNA); the effective means is the viral enzyme reverse transcriptase.

transcutaneous (trans-ku-ta′ne-us)
SYN: percutaneous.

transcytosis (trans-si-to′sis)
A mechanism for transcellular transport in which a cell encloses extracellular material in an invagination of the cell membrane to form a vesicle (endocytosis), then moves the vesicle across the cell to eject the material through the opposite cell membrane by the reverse process (exocytosis). The transport mechanism by which most proteins reach the Golgi apparatus or the plasma membrane; the vesicles targeted toward lysosomes and secretory storage granules appear to be coated with clathrin. SYN: cytopempsis, vesicular transport.

transdermic (trans-der′mik)
SYN: percutaneous.

transduce (trans-doos′)
To effect transduction.

transducer (trans-doo′ser)
A device designed to convert energy from one form to another. SEE ALSO: transduction. piezoelectric t. a t. that converts electric into mechanical energy and vice versa, used in ultrasound diagnosis or therapy. ultrasound t. a piezoelectric t. used in diagnostic ultrasound.

transducin (trans-doo′sin)
A protein that binds guanine nucleotides ( I.E., a G protein), found in retinal rods and cones, that plays a major role in signal transduction; in vertebrate rod cells it acts as a link of the photolysis of rhodopsin to the activation of cGMP phosphodiesterase.

transductant (trans-duk′tant)
A cell that has acquired a new character by means of transduction; may be complete, with integration of the transferred genetic fragment into its genome, or abortive, in which case the genetic fragment is not integrated and passes to only one of the two daughter cells on division.


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