|Medical Dictionary - Dictionary of Medicine and Human Biology|
Presence of four breasts on an individual. [tetra- + G. mastos, breast]
A protozoan or other microorganism possessing four flagella. [tetra- + G. mastix, whip]
Having four breasts.
Conjoined twins possessing four arms (tetrabrachius), or four legs (tetrascelus). See conjoined twins, under twin. [tetra- + G. melos, limb]
A genus of stomach-infecting parasitic nematodes (family Spiruridae) of birds. When filled with eggs, the female worm is enormously enlarged and has a globular, blood-red appearance. Species include T. americana, found in the proventriculus of chickens (sometimes severely pathogenic in young chicks), turkeys, grouse, and quail, and transmitted by infected cockroaches and grasshoppers, and T. fissispina, found in the proventriculum of ducks, geese, wild waterfowl, pigeons, and doves but rarely in gallinaceous birds. [see tetrameric]
tetrameric, tetramerous (tet′ra-mer′ik, te-tram′e-rus)
Having four parts, or parts arranged in groups of four, or capable of existing in four forms. [tetra- + G. meros, part]
tetramethylammonium iodide (tet-ra-meth′il-a-mo′ne-um)
Dissolves in water to the extent of 0.25 g/L; used for the emergency disinfection of drinking water.
A derivative of putrescine, C8H20N2, similar in its action to muscarine.
SYN: erythrityl tetranitrate.
A compound of four nucleotides; once thought to represent the actual structure of nucleic acid (t. theory).
Weakness of all four extremities. SYN: quadriparesis.
A compound of four amino acids in peptide linkage.
Peromelia involving all four extremities. [tetra- + G. peros, maimed, + melos, limb]
Phocomelia involving all four limbs.
SYN: quadriplegia. [tetra- + G. plege, stroke]
See polyploidy. [G. tetraploos, fourfold, + eidos, form]
A malformed individual with four feet. [G. tetrapous, fr. tetra- + pous, foot]
A molecule containing four pyrrole nuclei; e.g., porphyrin.
A sugar containing four molecules of a monosaccharide; e.g., stachyose.
A malformed individual with four legs. [tetra- + G. skelos, leg]
Relating to a cell nucleus in which one chromosome is represented four times while all others are present in the normal number. [tetra- + chromosome]
A figure exceptionally and abnormally occurring in mitosis, in which there are four asters. [tetra- +G. aster, star]
Duplication of the growth of the eyelashes (in four rows). [tetra- + G. stichos, row]
Hydrocarbons or their derivatives formed by the condensation of eight isoprene units ( i.e., four terpenes) and therefore containing 40 carbon atoms; e.g., various carotenoids.
Denoting a quadrivalent element or radical. [tetra- + G. atomos, atom]
A genus of parasitic protozoan flagellates, formerly part of the genus Trichomonas but now separated into a distinct genus by the presence of four anterior and one trailing flagella, a pelta, and a disc-shaped parabasal body. See Trichomonas. [tetra- + Trichomonas] T. ovis a species that occurs in the cecum or rumen of domestic sheep.
SYN: quadrivalent. [tetra- + L. valentia, strength]
The compound CN4H2 with the structure of tetrazolium.
Any of a group of organic salts having the general structure that on reduction (cleaving the 2,3 bond) yields a colored insoluble formazan; used as a reagent in oxidative enzyme histochemistry. nitroblue t. (NBT) a pale yellow dye that is converted on reduction to colored formazans in the histochemical demonstration of dehydrogenases; used in hematology for staining of neutrophils to help indicate the presence of bacterial infections.
tetrodotoxin (TTX) (tet′ro-do-tok′sin)
A potent neurotoxin found in the liver and ovaries of the Japanese pufferfish, Sphoeroides rubripes, other species of pufferfish, and certain newts; produces axonal blocks of the preganglionic cholinergic fibers and the somatic motor nerves. T. blocks voltage-gated Na+ channels in excitable tissues.
A monosaccharide containing only four carbon atoms in the main chain; e.g., erythrose, threose, erythrulose.
A malformed individual with four ears, four eyes, two faces, and two almost separate heads. SYN: tetraotus. [tetra- + G. ous (ot-), ear]
An oxide containing four oxygen atoms; e.g., OsO4.
An outmoded colloquial term, popularly applied to ringworm and eczema, and occasionally applied to other eruptions. [A.S. teter]
F.E.K. von, German anatomist, 1842–?. See T. ligament.
Weblike. [L. textum, something woven]
Relating to the texture of the tissues.
The composition or structure of a tissue or organ. [L. textura, fr. texo, pp. textus, to weave]
A tissue. [L.]
Abbreviation for time-varied gain control; time-gain compensation.
Abbreviation for transforming growth factors, under factor.
Abbreviation for transforming growth factor α.
Abbreviation for transforming growth factor β.
1. Abbreviation for T helper cells, under cell. 2. Symbol for thorium.
Alan P., U.S. surgeon, *1925. See T. procedure.
See chemothalamectomy. [thalamus + G. ektome, excision]
Relating to the thalamencephalon.
That part of the diencephalon comprising the thalamus and its associated structures. [thalamus + G. enkephalos, brain]
Relating to the thalamus.
The thalamus. [G. thalamos, bedroom (thalamus)]
Relating to the efferent connections of the thalamus with the cerebral cortex.
Relating to the thalamus, usually the dorsal thalamus, and the lenticular nucleus (putamen and globus pallidus).
Destruction of a selected portion of the thalamus by stereotaxy for the relief of pain, involuntary movements, epilepsy, and, rarely, emotional disturbances; produces few, if any, neurologic deficits or undesirable personality changes. [thalamus + G. tome, incision]
thalamus, pl .thalami (thal′a-mus, -mi) [TA]
The large, ovoid mass of gray matter that forms the larger dorsal subdivision of the diencephalon; it is placed medial to the internal capsule and the body and tail of the caudate nucleus. Its medial aspect forms the dorsal half of the lateral wall of the third ventricle; its dorsal surface can be subdivided into a lateral triangle forming the floor of the body (central part) of the lateral ventricle, and a medial triangle covered by the velum interpositum; its tail-like caudal part curves ventralward around the posterolateral aspect of the cerebral peduncle and ends in the lateral geniculate body. The t. is composed of a large number of anatomically and functionally distinct cell groups or nuclei, usually classified as 1) sensory relay nuclei (ventral posterior nucleus, lateral and medial geniculate body) each receiving a modally specific sensory conduction system and in turn projecting each to the corresponding primary sensory area of the cortex; 2) “secondary” relay nuclei (ventral intermediate nucleus and ventral anterior nucleus) receiving fibers from the medial segment of the globus pallidus, the contralateral deep cerebellar nuclei ( i.e., cerebellothalamic fibers), and the pars reticulata of the substantia nigra which project to various regions of the motor cortex; 3) a nucleus associated with the limbic system: the composite anterior nucleus receiving the mamillothalamic tract and projecting to the fornicate gyrus; 4) association nuclei (medial dorsal nucleus, lateral nucleus including the large pulvinar) each projecting to a particular large expanse of association cortex; 5) the midline and intralaminar nuclei or “nonspecific” nuclei (centromedian nucleus, central lateral nucleus, paracentral nucleus, nucleus reuniens). SEE ALSO: dorsal t.. [G. thalamos, a bed, a bedroom] dorsal t. the large part of the diencephalon located dorsal to the hypothalamus and excluding the subthalamus and the medial and lateral geniculate bodies (sometime the latter two are collectively called the metathalamus); the dorsal t. includes the major motor and somatosensory relay nuclei, nuclei that project to association areas, and the intralaminar nuclei. SEE ALSO: t.. ventral t. SYN: subthalamus.
thalassemia, thalassanemia (thal-a-se′me-a, tha-las-a-ne′me-a)
Any of a group of inherited disorders of hemoglobin metabolism in which there is impaired synthesis of one or more of the polypeptide chains of globin; several genetic types exist, and the corresponding clinical picture may vary from barely detectable hematologic abnormality to severe and fatal anemia. [G. thalassa, the sea, + haima, blood] α t. t. due to one of two or more genes that depress (severely or moderately) synthesis of α-globin chains by the chromosome with the abnormal gene. Heterozygous state: severe type, t. minor with 5–15% of Hb Barts at birth, only traces of Hb Barts in adult; mild type, 1–2% of Hb Barts at birth, not detectable in adult. Homozygous state: severe type, erythroblastosis fetalis and fetal death, only Hb Barts and Hb H present; mild type not clinically defined. SEE ALSO: hemoglobin H. A2 t. β t., heterozygous state. β t. t. due to one of two or more genes that depress (partially or completely) synthesis of β-globin chains by the chromosome bearing the abnormal gene. Heterozygous state (A2 t.): t. minor with Hb A2 increased, Hb F normal or variably increased, Hb A normal or slightly reduced. Homozygous state: t. major with Hb A reduced to very low but variable levels, Hb F very high level. β-δ t. t. due to a gene that depresses synthesis of both β- and δ-globin chains by the chromosome bearing the abnormal gene. Heterozygous state: t. minor with Hb F comprising 5–30% of total hemoglobin but distributed unevenly among cells, Hb A2 reduced or normal. Homozygous state: moderate anemia with only Hb F present, no Hb A or Hb A2. SYN: F t.. F t. SYN: β-δ t.. t. intermedia a clinical variant of t. characterized by an intermediate degree of severity. These patients have severe anemia but usually do not require regular blood transfusions. Intermedia disorders represent a heterogeneous group of genetic disorders and may include cases with homozygous or heterozygous abnormalities in the β-globin chain gene. α t. intermedia hemoglobin H. Lepore t. [MIM*142000.0020 and others] t. syndrome due to production of abnormally structured Lepore hemoglobin. Heterozygous state: t. minor with about 10% of Hb Lepore, Hb F moderately increased, Hb A2 normal. Homozygous state: t. major with only Hb F and Hb Lepore produced, no Hb A or Hb A2. t. major [MIM*141800–142310 passim] the syndrome of severe anemia resulting from the homozygous state of one of the t. genes or one of the hemoglobin Lepore genes with onset, in infancy or childhood, of pallor, icterus, weakness, splenomegaly, cardiac enlargement, thinning of inner and outer tables of skull, microcytic hypochromic anemia with poikilocytosis, anisocytosis, stippled cells, target cells, and nucleated erythrocytes; types of hemoglobin are variable and depend on the gene involved. SYN: Cooley anemia, primary erythroblastic anemia. t. minor [MIM*141800–142310 passim] the heterozygous state of a t. gene or a hemoglobin Lepore gene; usually asymptomatic and quite variable hematologically, with target cells, mild hypochromic microcytosis, and often slightly reduced hemoglobin level with slightly increased erythrocyte count; types of hemoglobin are variable and depend on the gene involved.
thalassophobia (thal′a-so-fo′be-a, tha-las′o-)
Morbid fear of the sea. [G. thalassa, the sea, + phobos, fear]
thalassoposia (thal′a-so-po′ze-a, tha-las′o-)
SYN: mariposia. [G. thalassa, the sea, + posis, drinking]
Treatment of disease by exposure to sea air, by sea bathing, or by a sea voyage. [G. thalassa, the sea]
A hypnotic drug which, if taken in early pregnancy, may cause the birth of infants with phocomelia and other defects; under investigational use for treatment of leprosy and as an immunomodulator in HIV infections and graft vs. host reactions.
Denoting conidia produced with no enlargement or growth after delimitation by septa in the hypha (thallus); the entire parent cell becomes an arthroconidium.
thallium (Tl) (thal′e-um)
A white metallic element, atomic no. 81, atomic wt. 204.3833; 201Tl (half-life equal to 3.038 days) is used to scan the myocardium. [G. thallos, a green shoot (it gives a green line in the spectrum)] t.-201 (201Tl) the radioisotope of t. used widely for myocardial nuclear imaging; it is also taken up by certain tumors.
In older classification systems, a primary division of the plant kingdom whose members, with a few exceptions, were devoid of true roots, stems, and leaves; it included bacteria, fungi, and algae. [G. thallos, a green shoot, + phyton, plant]
A member of the division Thallophyta.
Poisoning by thallium; marked by stomatitis, gastroenteritis, peripheral and retrobulbar neuritis, endocrine disorders, and alopecia. [thallium + G. toxikon, poison, + -osis, condition]
A simple plant or fungus body that is devoid of roots, stems, and leaves. The vegetative growth of a fungus. [G. thallos, a young shoot]
Death. SEE ALSO: necro-. [G. thanatos, death]
Relating to the processes involved in life and death. [thanato- + G. bios, life, + logos, study]
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