(n.) An area in the pigmented layer of the choroid coat of the eye in many animals, which has an iridescent or metallic luster and helps to make the eye visible in the dark. Sometimes applied to the whole layer of pigmented epithelium of the choroid.
Example Sentences:
(1) A tapetum or basal retinula cells are not developed.
(2) Ophthalmoscopic examinations performed during recovery revealed changes of slight increase in tapetal islets, suggestive of a slight progression and organization within the tapetum followed by an arrest of the toxic insult within the tapetal tissue.
(3) In conditions that simulate the tapetum they continue normal gametophytic development to produce functional pollen.
(4) It was concluded that the morphology and structural architecture of choroidal melanocytes of dogs or cats are different from those of human eyes and closely correspond to the tapetum.
(5) These observations led to this comparative study on several morphological, histochemical and biochemical parameters on mature ferrets, dogs and cats including: (1) the number of center tapetum cell layers, (2) thickness of center tapetum, (3) presence of a microtubule-like structure in each tapetal rod, (4) presence of electron-dense cores in tapetal rods after prolonged fixation in glutaraldehyde, (5) retention of reflection or color of tapetum after prolonged glutaraldehyde fixation, (6) zygomatic bones of eye orbits, (7) zinc content in tapetum, (8) cysteine in the tapetum, (9) cysteine sulfinic acid decarboxylase in liver, (10) thickness of retina from center tapetum, (11) anterior view of skull configuration, and (12) lateral view of skull configuration (jaw and teeth).
(6) Blebs made with Hanks' solution over the pigmented RPE resorbed 22% faster than those over the tapetum.
(7) The receptory area of the ocellus terminates in a tapetum which contains granules, soluble in alcohol.
(8) The retina and tapetum of kittens born to taurine-deficient and taurine-supplemented mothers were compared.
(9) This species possesses a choroidally located tapetum lucidum in the superior fundus and over this tapetal area, melanosomes are absent from the RPE cells.
(10) A semicircular area of the retinal epithelium in the superior fundus is further specialized as a tapetum lucidum.
(11) In contrast, the tapetum lowers luminance threshold by at most 0.16 log unit.
(12) It is speculated that the hereditary defect may be defective synthesis of the tapetal rodlet matrix or of the zinc-complexing substance of the tapetum.
(13) As the entire fundus is overlain with a choroidally located tapetum cellulosum, only at the extreme periphery is an occasional melanosome present in these epithelial cells.
(14) These rodlets are the reflective material of the tapetum and are arranged with their long axes perpendicular to the incoming light.
(15) The reflecting material of the tapetum lucidum of the sea catfish (Arius felis) was chromatographed on Sephadex LH-20 in methanol-dimethyl sulphoxide-formic acid.
(16) Over the tapetum however it is reduced to a trilaminate structure and when associated with the indented capillary profiles is further reduced to a single thickened basal lamina.
(17) As for a receptor mechanism, the tapetum, or reflective layer of the retina, present in most land mammals, but absent in humans, enhances dim illumination.
(18) This pathophysiological correlation indicates that the occiptiomesencephalic projections of the internal sagittal stratum and the peristriate interhemispheric connections of the tapetum are not necessary for smooth pursuit system function.
(19) Plants expressing the modified glucanase from tapetum-specific promoters exhibited reduced male fertility, ranging from complete to partial male sterility.
(20) Its principal features include (1) the presence of a dense matrix, possibly a new type of tapetum lucidum, in the pigment epithelium, (2) a well developed photoreceptor layer containing large rods, single, double and triple cones, and (3) well developped inner nuclear and plexiform layers, with the exception of horizontal cells which are few and relatively small.
Tetrad
Definition:
(n.) The number four; a collection of four things; a quaternion.
(n.) A tetravalent or quadrivalent atom or radical; as, carbon is a tetrad.
Example Sentences:
(1) A constellation of histologic lesions was identified in brain (diffuse meningoencephalitis with bilaterally symmetrical thalamic necrosis), liver (pericholangiohepatitis), lung (pneumonitis), and spleen (lymphoid hyperplasia); this tetrad is apparently unique to this model system.
(2) Optimal formation of complete tetrads occurred at a narrow range of pH values around 6.0.
(3) Tetrad dissection of sporulated diploids heterozygous for the wild-type and mutant allele resulted in a 2:2 segregation of mutant and wild-type phenotype indicating a single gene mutation.
(4) Increased nondisjunction is reflected by a marked increase in tetrads with two and zero viable spores.
(5) At each of these synaptic sites, L1 and L2 are invariable contributors to two of the four elements of a postsynaptic tetrad.
(6) Each glandular unit originates from an isogenic group of cells of which the four elements (tetrade) are disposed on two levels.
(7) A possibility to construct a genetic map of the yeast Pichia pinus MH4 is demonstrated on the basis of tetrad analysis.
(8) 74 of the patients showed acne conglobata, 12 acne tetrade, 11 acne fulminans, and 69 acne papulopustulosa.
(9) The mutations were assigned to specific chromosomes by chromosome loss procedures, and linkage relationships were determined subsequently by standard tetrad analysis.
(10) We used the telomeric repeat of Chlamydomonas reinhardtii, TTTTAGGG, which contains 3 guanines and has a long interguanine A + T tract, to determine whether these sequences can form intrastrand and interstrand guanine tetrads.
(11) The possibility that extragenic suppressors account for growth of clathrin-deficient cells was examined by deletion of CHC1 from haploid cell genomes by single-step gene transplacement and independently by introduction of a centromere plasmid carrying the complete CHC1 gene into diploid cells before eviction of a chromosomal CHC1 locus and subsequent tetrad analysis.
(12) The article generalizes the experience in surgical treatment of Fallot's tetrad in 20 infants.
(13) With respect to behavior, the resulting compounds appeared, presumably as a consequence of their singular generation, to contain an interstitial heterochromatic region that caused the distribution of exchanges between the elements of the compound to be abnormal (many zero and two-exchange tetrads with few, if any, single-exchange tetrads).
(14) Tetrad analysis showed the two suppressors were located about 10 map units apart, the missense suppressor being the more distal to the centromere.
(15) Defective proteinase B activity segregates 2:2 in meiotic tetrads.
(16) Fine genetic mapping was carried out by conventional tetrad analysis using the integrated LEU2 gene as a marker.
(17) Evidence for a centromeric effect on NRD was obtained, suggested by a negative correlation between the degree of NRD, c, and the distance between the region of exchange and the centromere as inferred from SET's (single exchange tetrads).
(18) Allelism tests and tetrad analysis clearly proved that the cat4 complementation group is a new class of mutant alleles affecting carbon source-dependent gene expression.
(19) In isosequential crosses, 90-95% of tetrads are 8:0.
(20) The distinguishing criteria are: lack of pigment in infected red blood cells; no circulating schizonts or gametocytes; "atypical" malarialike organisms; tetrad groups, rods, or exclamation-mark forms; and persisting parasitemia after treatment for malaria.