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Medical Dictionary


toxanemia (tok-sa-ne′me-a)
Anemia resulting from the effects of a hemolytic poison. [G. toxikon, poison, + anemia]

toxaphene (tok′sa-fen)
A chlorinated hydrocarbon insecticide.

Toxascaris leonina (tok-sas′ka-ris le-o-ni′na)
An ascarid nematode of the dog that differs from Toxocara in that the larvae do not migrate through the lungs; the entire developmental cycle occurs in the gut. This parasite has been found in humans in a few instances and is a cause of visceral larva migrans in children, though less frequently implicated than is Toxocara canis. [G. toxon, bow, + Ascaris]

toxemia (tok-se′me-a)
1. Clinical manifestations observed during certain infectious diseases, assumed to be caused by toxins and other noxious substances elaborated by the infectious agent; in certain infections by Gram-negative bacteria, endotoxins probably play a role when the bacterial cell wall breaks down, releasing a complex lipopolysaccharide; however, the role of other bacterial substances is unclear, except in the case of the specific exotoxins such as those of diphtheria and tetanus. 2. The clinical syndrome caused by toxic substances in the blood. 3. A lay term referring to the hypertensive disorders of pregnancy. SYN: toxicemia. [G. toxikon, poison, + haima, blood]

toxemic (tok-se′mik)
Pertaining to, affected by, or manifesting the features of toxemia.

See toxico-.

toxic (tok′sik)
1. SYN: poisonous. 2. Pertaining to a toxin. [G. toxikon, an arrow-poison]

toxicant (tok′si-kant)
1. SYN: poisonous. 2. Any poisonous agent, specifically an alcoholic or other poison, causing symptoms of what is popularly called intoxication.

toxicemia (tok-si-se′me-a)
SYN: toxemia.

toxicity (tok-sis′i-te)
The state of being poisonous. oxygen t. 1. a body disturbance resulting from breathing high partial pressures of oxygen; characterized by visual and hearing abnormalities, unusual fatigue while breathing, muscular twitching, anxiety, confusion, incoordination, and convulsions; can occur when excessive quantities of oxygen are administered in patients (such as adult respiratory distress syndrome), resulting in worsening of pulmonary infiltrates and clinical deterioration; although the mechanism for development of the condition is obscure, a disruption of enzymatic activity is likely, perhaps as a result of free radical formation. Cf.:retrolental fibroplasia. 2. exposure of the lungs to greater than 60% oxygen for periods exceeding 24–48 hours can lead to severe, irreversible pulmonary fibrosis. SYN: oxygen poisoning.

toxico-, tox-, toxi-, toxo-
Poison, toxin. [G. toxikon, bow, hence (arrow) poison]

Toxicodendron (tok′si-ko-den′dron)
A genus of poisonous plants (family Anacardiaceae), also known as Rhus, with smooth fruits and foliage that contain urushiol, which produces a contact dermatitis (rhus dermatitis); species include poison ivy (T. radicans), poison oak (T. diversilobum), and poison sumac (T. vernix) [toxico- + G. dendron, tree]

toxicogenic (tok′si-ko-jen′ik)
1. Producing a poison. 2. Caused by a poison. [toxico- + G. -gen, producing]

toxicoid (tok′si-koyd)
Having an action like that of a poison; temporarily poisonous. [toxico- + G. eidos, resemblance]

toxicologic (tok′si-ko-loj′ik)
Relating to toxicology.

toxicologist (tok-si-kol′o-jist)
A specialist or expert in toxicology.

toxicology (tok-si-kol′o-je)
The science of poisons, including their source, chemical composition, action, tests, and antidotes. [toxico- + G. logos, study]

toxicopathic (tok′si-ko-path′ik)
Denoting any morbid state caused by the action of a poison.

toxicophobia (tok′si-ko-fo′be-a)
Morbid fear of being poisoned. SYN: toxiphobia. [toxico- + G. phobos, fear]

toxicosis (tok-si-ko′sis)
Any disease of toxic origin. SYN: systemic poisoning. [toxico- + G. -osis, condition] endogenic t. SYN: autointoxication. exogenic t. any disease caused by a poison introduced from without and not generated within the body. thyroid t. SYN: triiodothyronine t.. triiodothyronine t., T3 t. hyperthyroidism resulting from excessive circulating 3,5,3′-triiodothyronine. SYN: thyroid t..

toxiferines (tok-sif′er-enz)
The most potent group of the curare alkaloids; the principal source is Strychnos toxifera.

toxiferous (tok-sif′er-us)
SYN: poisonous. [toxi- + L. fero, to bear]

toxigenic (tok-si-jen′ik)
SYN: toxinogenic.

toxigenicity (tok′si-je-nis′i-te)
SYN: toxinogenicity.

toxilic acid (tok-sil′ik)
SYN: maleic acid.

toxin (tok′sin)
A noxious or poisonous substance that is formed or elaborated either as an integral part of the cell or tissue, as an extracellular product (exotoxin), or as a combination of the two, during the metabolism and growth of certain microorganisms and some higher plant and animal species. [G. toxikon, poison] animal t. SYN: zootoxin. anthrax t. a culture filtrate of Bacillus anthracis containing an exotoxin with at least three different antigenically distinct components: edema factor, lethal factor, and protective antigen. SYN: Bacillus anthracis t.. Bacillus anthracis t. SYN: anthrax t.. bacterial t. any intracellular or extracellular t. formed in or elaborated by bacterial cells. bee t. the t. delivered by a bee sting; contains three active principles: biogenic amines, active peptides, and certain hydrolytic enzymes. botulinus t. a potent exotoxin that is highly neurotoxic from Clostridium botulinum. SYN: botulin, botulismotoxin. cholera t. Vibrio cholerae. Clostridium perfringens alpha t. a phospholipase produced by Clostridium perfringens that increases vascular permeability and produces necrosis. Clostridium perfringens beta t. a substance produced by Clostridium perfringens that causes necrosis and induces hypertension by causing release of catecholamine. Clostridium perfringens epsilon t. a t. produced by Clostridium perfringens that increases the permeability of the gastrointestinal wall. Clostridium perfringens iota t. a binary t. produced by Clostridium perfringens responsible for necrosis and increased vascular permeability. cobra t. SYN: cobrotoxin. Crotalus t. the t. of rattlesnake. diagnostic diphtheria t. SYN: Schick test t.. Dick test t. SYN: streptococcus erythrogenic t.. dinoflagellate t. a potent neurotoxin that is thought to act similarly to botulinus t. by impairing the synthesis or the release of acetylcholine. Responsible for “red tide” loss of shellfish. diphtheria t. Corynebacterium diphtheriae. erythrogenic t. SYN: streptococcus erythrogenic t.. extracellular t. SYN: exotoxin. intracellular t. SYN: endotoxin. normal t. a t. solution holding exactly 100 lethal doses in 1 mL. plant t. SYN: phytotoxin. scarlet fever erythrogenic t. SYN: streptococcus erythrogenic t.. Schick test t. Corynebacterium diphtheriae t. diluted so that the inoculated dose (0.1 or 0.2 mL) will contain 150th of a guinea pig minimal lethal dose. SEE ALSO: Schick test. SYN: diagnostic diphtheria t.. Shiga t. the endotoxin formed by Shigella dysenteriae type 1. Shigalike t. SYN: vero cytotoxin. streptococcus erythrogenic t. a culture filtrate of lysogenized group A strains of β-hemolytic streptococci, erythrogenic when inoculated into the skin of susceptible persons, and neutralized by antibodies that appear during scarlet fever convalescence; three immunologic types (A, B, and C) are recognized. SYN: Dick test t., erythrogenic t., scarlet fever erythrogenic t.. tetanus t. the neurotropic, heat-labile exotoxin of Clostridium tetani and the cause of tetanus; it has been isolated as a crystalline protein (molecular weight 67,000), is one of the most poisonous substances known, and seems to function by blocking inhibitory synaptic impulses. SYN: tetanotoxin.

toxinic (tok-sin′ik)
Relating to a toxin.

toxinogenic (tok′si-no-jen′ik)
Producing a toxin, said of an organism. SYN: toxigenic. [toxin + G. -gen, producing]

toxinogenicity (tok′si-no-je-nis′i-te)
The capacity to produce toxin. SYN: toxigenicity.

toxinology (tok′si-nol′o-je)
The study of toxins, in a restricted sense, with reference to the relatively unstable proteinaceous substances of microbial, plant, or animal origins. [toxin + G. logos, study]

toxinosis (tok-si-no′sis)
Any disease or lesion caused by the action of a toxin. SYN: toxonosis. [toxin + G. -osis, condition]

toxiphobia (tok-si-fo′be-a)
SYN: toxicophobia.

toxisterol (tok-sis′ter-ol)
A toxic substance formed by excessive irradiation of ergosterol or calciferol.

See toxico-.

Toxocara (tok′so-kar′a)
A genus of ascarid nematodes, chiefly found in carnivores, that cause toxocariasis. [G. toxon, bow, + kara, head] T. canis the common ascarid species in the small intestine of the dog, where prenatal infection is a common mode of infection of pups; it is also reported in cats, wolves, foxes, coyotes, and badgers; the second-stage larva is the most frequent cause of visceral larva migrans in the liver of children. T. mystax a common ascarid species of cats, but not reported from dogs; prenatal infection of kittens does not occur, infection being by infective eggs, which hatch in the intestine, releasing second-stage larvae, which then undergo migration through the heart, lung, trachea, mouth, and gut, as with Ascaris lumbricoides in man; mice and other vertebrates, and also some invertebrates ( e.g., earthworms, cockroaches) may serve as transport hosts, in which the migrating larvae encyst in the tissues.

toxocariasis (tok′so-ka-ri′a-sis)
Infection with nematodes of the genus Toxocara; parenterally migrating larvae, chiefly of Toxocara canis, may cause visceral larva migrans; ocular involvement results in either a solitary granuloma in the retina, peripheral inflammatory masses, or chronic endophthalmitis.

toxoid (tok′soyd)
A toxin that has been treated (commonly with formaldehyde) so as to destroy its toxic property but retain its antigenicity, i.e., its capability of stimulating the production of antitoxin antibodies and thus of producing an active immunity.For specific toxoids, see entries under vaccine. SYN: anatoxin. [toxin + G. eidos, resemblance]

toxon, toxone (tok′son, tok′son)
A hypothetical bacterial product, of feeble toxicity and weak affinity for antitoxin.

toxoneme (tok′so-nem)
SYN: rhoptry. [G. toxon, bow, + nema, thread]

toxonosis (tok-so-no′sis)
SYN: toxinosis. [toxo- + G. nosos, disease]

toxophil, toxophile (tok′so-fil, -fil)
Susceptible to the action of a poison; having an affinity for toxins. [toxo- + G. philos, fond]

toxophore (tok′so-for)
Denoting the atomic group of the toxin molecule which carries the poisonous principle. [toxo- + G. phoros, bearing]

toxophorous (tok-sof′ar-us)
Relating to the toxophore group of the toxin molecule.

Toxoplasma gondii (tok-so-plaz′ma gon′de-i)
An abundant, widespread sporozoan species (family Toxoplasmatidae) that is an intracellular, non–host-specific parasite in a great variety of vertebrates. It develops its sexual cycle, leading to oocyst production, exclusively in cats and other felids; proliferative stages (tachyzoites) and tissue cysts (containing bradyzoites) develop in a wide variety of animal species that acquire the infection from ingestion of oocysts, tissue cysts from infected meat, organ transplantation or by transplacental migration, leading to infection in utero. [G. toxon, bow or arc, + plasma, anything formed]

Toxoplasmatidae (tok′so-plaz-mat′i-de)
A family of coccidian sporozoa including the genera Toxoplasma and Frankelia, characterized by endodyogeny and by the presence of cysts (sometimes termed pseudocysts) containing bradyzoites in parenteral cells of the host; schizonts and gamonts are produced in intestinal cells, and gamonts give rise to oocysts. Final hosts of Toxoplasma are cats and other felids; final hosts of Frankelia are unknown.

toxoplasmosis (tok′so-plaz-mo′sis)
Disease caused by the protozoan parasite Toxoplasma gondii, which can produce abortion in sheep, encephalitis in mink, and a variety of syndromes in humans. Prenatally acquired human infection can result in the presence of abnormalities such as microcephalus or hydrocephalus at birth, the development of jaundice with hepatosplenomegaly or meningoencephalitis in early childhood, or the delayed appearance of ocular lesions such as chorioretinitis in later childhood. Postnatally acquired human infections typically remain subclinical; if clinical disease does occur, symptoms include fever, lymphadenopathy, headache, myalgia, and fatigue, with eventual recovery, except in the immunocompromised patient where fatal encephalitis often develops. acquired t. in adults a form of t. that may result in fever, encephalomyelitis, chorioretinopathy, maculopapular rash, arthralgia, myalgia, myocarditis, and pneumonitis; a lymphadenopathic form seems to be more prevalent in adults, and such persons may manifest fever, lymphadenopathy, malaise, and headache, a form frequently found in patients with AIDS. congenital t. t. apparently resulting from parasites in an infected mother being transmitted in utero to the fetus, observed as three syndromes: 1) acute: most of the organs contain foci of necrosis in association with fever, jaundice, hydrocephaly, encephalomyelitis, pneumonitis, cutaneous rash, ophthalmic lesions, hepatomegaly, and splenomegaly; 2) subacute: most of the lesions are partly healed or calcified, but those in the brain and eye seem to remain active, inasmuch as chorioretinitis is observed in more than 80% of diseased infants; 3) chronic: usually not recognized during the newborn period, but chorioretinitis and cerebral lesions may be detected weeks to years later.

toxopyrimidine (toks′o-pi-rim′i-den)
One of the products resulting from the hydrolysis of thiamin by thiaminase and appearing in the urine; a competitive inhibitor of pyridoxal. SYN: pyramin, pyramine.

Joseph, English otologist, 1815–1866. See T. corpuscles, under corpuscle, T. muscle, T. tube.

Abbreviation for tissue plasminogen activator.

Abbreviation for total parenteral nutrition.

Abbreviation for thiamin pyrophosphate.

Abbreviation for total peripheral resistance.

Abbreviation for tocopherolquinone.

Abbreviation for repetition time in magnetic resonance imaging.

Abbreviation for L. tinctura, or tincture.

trabecula, gen. and pl. trabeculae (tra-bek′u-la, -le) [TA]
1. A meshwork; one of the supporting bundles of fibers traversing the substance of a structure, usually derived from the capsule or one of the fibrous septa. 2. A small piece of the spongy substance of bone usually interconnected with other similar pieces. 3. In histopathology, a band of neoplastic tissue two or more cells wide. [L. dim. of trabs, a beam] anterior chamber t. tissue at the angle of the anterior chamber through which aqueous humor exits from the eye. arachnoid t. [TA] fine, delicate strands composed of fibroblast and extracellular collagen that traverse the subarachnoid space between the arachnoid mater, which is attached to the dura, and the pia mater, which is adherent to the surface of the brain. SYN: trabeculae arachnoideae [TA] . trabeculae arachnoideae [TA] SYN: arachnoid t.. trabeculae carneae (of right and left ventricles) [TA] muscular bundles on the lining walls of the ventricles of the heart. SYN: columnae carneae, Rathke bundles, trabeculae carneae ventriculorum dextri et sinistri. trabeculae carneae ventriculorum dextri et sinistri SYN: trabeculae carneae (of right and left ventricles). trabeculae of corpora cavernosa [TA] fibromuscular bands and cords given off from the fibrous envelopes and septum of the corpora cavernosa penis and that separate the cavernous veins. SYN: trabeculae corporum cavernosorum [TA] . trabeculae corporis spongiosi penis [TA] SYN: trabeculae of corpus spongiosum. trabeculae corporum cavernosorum [TA] SYN: trabeculae of corpora cavernosa. trabeculae of corpus spongiosum [TA] the fibrous bands interlacing between the vascular spaces of the corpus spongiosum and glans penis. SYN: trabeculae corporis spongiosi penis [TA] . trabeculae cranii a pair of chondrification centers in the base of the embryonic cartilaginous neurocranium, lying in front of the developing hypophysis; they become the sella turcica. trabeculae lienis splenic trabeculae. trabeculae of lymph node [TA] supporting bundles of connective tissue traversing the substance of the spleen, derived from the capsule of the spleen. SYN: trabeculae nodi lymphoidei [TA] . trabeculae nodi lymphoidei [TA] SYN: trabeculae of lymph node. septomarginal t. [TA] one of the trabeculae carneae in the right ventricle of the heart; it carries part of the right branch of the AV bundle from the septum to the anterior papillary muscle on the opposite wall of the ventricle. SYN: t. septomarginalis [TA] , moderator band, Reil band (1) . t. septomarginalis [TA] SYN: septomarginal t.. trabeculae of spleen SYN: splenic trabeculae. splenic trabeculae [TA] small fibrous bands given off from the capsule of the spleen and constituting the framework of that organ. SYN: trabeculae splenicae [TA] , trabeculae lienis&star, trabeculae of spleen. trabeculae splenicae [TA] SYN: splenic trabeculae. t. testis SYN: septula of testis, under septulum.

trabecular (tra-bek′u-lar)
Relating to or containing trabeculae. SYN: trabeculate.

trabeculate (tra-bek′u-lat)
SYN: trabecular.

trabeculation (tra-bek′u-la′shun)
1. The occurrence of trabeculae in the walls of an organ or part. 2. The process of forming trabeculae, as in spongy bone.

trabeculectomy (tra-bek′u-lek′to-me)
A filtering operation for glaucoma by creation of a fistula between the anterior chamber of the eye and the subconjunctival space, through a subscleral excision of a portion of the trabecular meshwork. [trabecula + G. ektome, excision]

trabeculoplasty (tra-bek′u-lo-plas-te)
Photocoagulation of the trabecular meshwork of the eye using the laser in the treatment of glaucoma. laser t. (LTP) an operation for glaucoma in which laser energy is applied to the trabecular meshwork.Investigations into laser treatments of open-angle glaucoma began in the early 1970s, but not until the late 1980s was LTP adopted as a standard treatment for the condition. In this procedure, a laser (usually argon) is used to create small openings in the trabecular meshwork at the ocular drainage angle, so as to improve the drainage of aqueous humor and relieve intraocular pressure. Laser iridotomy is sometimes performed at the same time. LTP lessens chances of postoperative infection and hemorrhage, and can be performed on an outpatient basis. This technique has achieved a 2-year success rate of over 70% (dropping to 59% after 5 years), but has been effective only in certain types of glaucoma (especially capsular and pigmentary glaucomas).

trabeculotomy (tra-bek-u-lot′o-me)
Surgical opening of the sinus venosus sclerae (canal of Schlemm) to treat glaucoma. [trabekula + G. tome, incision]

trace (tras)
1. Evidence of the former existence, influence, or action of an object, phenomenon, or event. 2. An extremely small amount or barely discernible indication of something.

tracer (tra′ser)
1. An element or compound containing atoms that can be distinguished from their normal counterparts by physical means ( e.g., radioactivity assay or mass spectrography) and can thus be used to follow (trace) the metabolism of the normal substances. 2. A colored or radioactive substance that can be injected in the region of a tumor (melanoma, breast, etc.) to map the flow of lymph from the tumor to its nearest nodal basin; used in sentinel node detection. 3. A colored substance ( e.g., a dye) used as a t. to follow the flow of water. 4. An instrument used in dissecting out nerves and blood vessels. 5. A mechanical device with a marking point attached to one jaw and a graph plate or tracing plate attached to the other jaw; used to record the direction and extent of movements of the mandible. SEE ALSO: tracing (2) . [M.E. track, fr. O. Fr. tracier, to make one's way, fr. L. traho, pp. tractum, to draw, + -er, agent suffix]

See tracheo-.

trachea, pl .tracheae (tra′ke-a, -ke-e) [TA]
The air tube extending from the larynx into the thorax (level of the fifth or sixth thoracic vertebra) where it bifurcates into the right and left main bronchi. The t. is composed of 16–20 rings of hyaline cartilage connected by a membrane (annular ligament); posteriorly, the rings are deficient for one-fifth to one-third of their circumference, the interval forming the membranous wall being closed by a fibrous membrane containing smooth muscular fibers. Internally, the mucosa is composed of a pseudostratified ciliated columnar epithelium with mucous goblet cells; numerous small mixed mucous and serous glands occur, the ducts of which open to the surface of the epithelium. SYN: windpipe. [G. tracheia arteria, rough artery] saber-sheath t. a type of tracheal collapse seen in chronic obstructive pulmonary disease in which there is an increase in the outer posterior tracheal dimension with side-to-side narrowing involving the lower two-thirds of the t.. scabbard t. a deformity of the t. caused by flattening and approximation of the lateral walls, producing more or less pronounced stenosis.


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