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991.
Identification of Campylobacter coli isolates from animals and humans by bacterial restriction endonuclease DNA analysis. 总被引:7,自引:0,他引:7 下载免费PDF全文
Ninety-nine Campylobacter coli isolates were examined by bacterial restriction endonuclease DNA analysis (BRENDA) with HindIII. Isolates from poultry from the same environment had identical patterns, patterns of isolates carried by suckling piglets were generally the same as those of isolates recovered from their dams, and one human patient yielded the same BRENDA type when sampled 6 weeks later. The 14 human isolates examined produced 11 distinct BRENDA types. Forty-three C. coli isolates from pigs were represented by 20 BRENDA types. Ten C. coli isolates from the feces of gulls yielded five different BRENDA types. Thirty-two C. coli isolates from live chickens and processed chicken yielded five different BRENDA types. Three human isolates had identical DNA patterns; two were from brothers living in the same house, and the third was from a human with no apparent relationship to the brothers. Another human isolate was identical to a poultry isolate. None of the pig strains had DNA patterns resembling those of human strains, nor were the DNA patterns like those of any strains recovered from poultry or gulls. Four C. coli isolates were subcultured onto agar 23 times over a period of 45 days, and their BRENDA patterns were preserved. BRENDA shows great promise for use in epidemiological studies of C. coli. 相似文献
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Water velocities were measured around water plants in a chalk stream. Low velocities (<100 mm.s?1) were associated with stands of plants while faster flowing water (>500 mm.s?1) was found in open water and above weed beds. An indirect method of estimating mean water velocity through weed beds, using discharge measurements, revealed velocities between 40 and 140 mm.s?1, while open water velocities ranged between 200 and 370 mm.s?1. The significance of the velocities is discussed. 相似文献
995.
Glycerol:NADP+ 2-oxidoreductase (EC 1.1.1.156) was isolated from Schizosaccharomyces pombe, purified and characterized. It had an Mr of 57,000, and SDS-PAGE revealed two polypeptides, of Mr 25,000 and 30,000. Its coenzyme requirement was satisfied exclusively by NADP. The pH optimum for glycerol oxidation was 9.5, for dihydroxyacetone reduction 6.0. Rates of oxidation with some structurally related diols were three- to six-fold lower than for glycerol, while glyceraldehyde and other carbonyl compounds showed negligible rates of reduction. Neither monovalent nor divalent cations activated the enzyme. Apparent Km and Vmax values were determined. The enzyme is similar to glycerol dehydrogenases isolated from Mucor javanicus and from Dunaliella parva but differs considerably from the glycerol:NAD+ 2-oxidoreductase of S. pombe. 相似文献
996.
Three different activated ras genes in mouse tumours; evidence for oncogene activation during progression of a mouse lymphoma. 总被引:13,自引:3,他引:10 下载免费PDF全文
Five unrelated mouse tumours have been shown to carry activated transforming genes using the NIH/3T3 transfection assay. Three of these tumours, a T-cell lymphoma, a fibrosarcoma and a macrophage tumour, were found to carry an activated c-Ki-ras gene. A c-Ha-ras gene was shown to be activated in a myeloid leukaemia and a recently identified member of the 'ras' gene family, N-ras, was found to be activated in a lung carcinoma. The T-cell lymphoma, L5178Y-ES, is a more aggressively growing metastatic variant which arose spontaneously from the parental tumour, L5178Y-E. Although DNA from both parental and variant tumours was shown to transfer a genetic marker to recipient cells equally well, only the metastatic variant carried an activated c-Ki-ras gene detectable by transfection. The altered growth behaviour of the L5178Y-ES cells may therefore be the result of the spontaneous activation of the c-Ki-ras gene after the lymphoma cells had already become tumorigenic. 相似文献
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Eitaro Aihara Courtney L. Hentz Abraham M. Korman Nicholas P. J. Perry Vikram Prasad Gary E. Shull Marshall H. Montrose 《The Journal of biological chemistry》2013,288(47):33585-33597
We report that a localized intracellular and extracellular Ca2+ mobilization occurs at the site of microscopic epithelial damage in vivo and is required to mediate tissue repair. Intravital confocal/two-photon microscopy continuously imaged the surgically exposed stomach mucosa of anesthetized mice while photodamage of gastric epithelial surface cells created a microscopic lesion that healed within 15 min. Transgenic mice with an intracellular Ca2+-sensitive protein (yellow cameleon 3.0) report that intracellular Ca2+ selectively increases in restituting gastric epithelial cells adjacent to the damaged cells. Pretreatment with U-73122, indomethacin, 2-aminoethoxydiphenylborane, or verapamil inhibits repair of the damage and also inhibits the intracellular Ca2+ increase. Confocal imaging of Fura-Red dye in luminal superfusate shows a localized extracellular Ca2+ increase at the gastric surface adjacent to the damage that temporally follows intracellular Ca2+ mobilization. Indomethacin and verapamil also inhibit the luminal Ca2+ increase. Intracellular Ca2+ chelation (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid/acetoxymethyl ester, BAPTA/AM) fully inhibits intracellular and luminal Ca2+ increases, whereas luminal calcium chelation (N-(2-hydroxyetheyl)-ethylendiamin-N,N,N′-triacetic acid trisodium, HEDTA) blocks the increase of luminal Ca2+ and unevenly inhibits late-phase intracellular Ca2+ mobilization. Both modes of Ca2+ chelation slow gastric repair. In plasma membrane Ca-ATPase 1+/− mice, but not plasma membrane Ca-ATPase 4−/− mice, there is slowed epithelial repair and a diminished gastric surface Ca2+ increase. We conclude that endogenous Ca2+, mobilized by signaling pathways and transmembrane Ca2+ transport, causes increased Ca2+ levels at the epithelial damage site that are essential to gastric epithelial cell restitution in vivo. 相似文献
1000.
Sex in many organisms is a dichotomous phenotype--individuals are either male or female. The molecular pathways underlying sex determination are governed by the genetic contribution of parents to the zygote, the environment in which the zygote develops or interaction of the two, depending on the species. Systems in which multiple interacting influences or a continuously varying influence (such as temperature) determines a dichotomous outcome have at least one threshold. We show that when sex is viewed as a threshold trait, evolution in that threshold can permit novel transitions between genotypic and temperature-dependent sex determination (TSD) and remarkably, between male (XX/XY) and female (ZZ/ZW) heterogamety. Transitions are possible without substantive genotypic innovation of novel sex-determining mutations or transpositions, so that the master sex gene and sex chromosome pair can be retained in ZW-XY transitions. We also show that evolution in the threshold can explain all observed patterns in vertebrate TSD, when coupled with evolution in embryonic survivorship limits. 相似文献