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81.
tRNA genes and pathogenicity islands: influence on virulence and metabolic properties of uropathogenic Escherichia coli 总被引:13,自引:2,他引:11
82.
Molecular clones of the mouse t complex derived from microdissected metaphase chromosomes 总被引:27,自引:0,他引:27
Dan Röhme Howard Fox Bernhard Herrmann Anna-Maria Frischauf Jan-Erik Edström Paul Mains Lee M. Silver Hans Lehrach 《Cell》1984,36(3):783-788
Fragments of the proximal half of mouse chromosome 17 including the t-complex region were microdissected from metaphase spreads. DNA was isolated from a pool of such fragments, and was cloned on microscale. Individual clones were used to probe genomic digests of DNA from a pair of Chinese hamster cell lines with or without mouse chromosome 17, and livers of congenic inbred lines of mice carrying wild-type and/or t-haplotype forms of chromosome 17. The data obtained indicate that 95% of the low copy number microclone inserts recognize DNA sequences present on mouse chromosome 17. It has been possible to use one-third of these clones to identify restriction-fragment-length polymorphisms between wild-type and t-haplotype DNA on a congenic background. These results demonstrate that these clones have been derived from the t-complex or regions closely linked to it. Clones of this type should provide starting points for a molecular analysis of this region of the mouse genome. 相似文献
83.
Bernhard Schink 《Archives of microbiology》1984,137(3):250-255
A new mesophilic, sporeforming, strictly anaerboic bacterium was isolated form enrichments with 2,3-butanediol as sole substrate and pasteurized freshwater sediment as inoculum. Cells were large, motile rods, and elliptical spores were formed subterminally or centrally. They stained Gram-negative, but no typical outer membrane layer could be observed by electron microscopy of ultrathin sections. 2,3-Butanediol, acetoin, fructose, glucose, sucrose, xylose, malate and citrate served as substrates and were completely converted to acetate with concomitant reduction of carbon dioxide. Growth on glucose (t
dmin=1.4 h) was faster than on butanediol (t
dmin=3.6 h). No growth occurred on hydrogen/carbon dioxide, on formate or on methanol. The guanine plus cytosine content of the DNA was 29.1%. The new isolate is described as a new species, Clostridium magnum sp. nov. 相似文献
84.
J Hüttermann E Haindl G Schmidt W A Bernhard 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1977,32(5):431-438
X-irradiation at 77 K and subsequent warming to 150 K of single crystals of 5-chloro-and 5-bromodeoxyuridine produces a radical located at position C5' of the deoxyribose moiety. The radical exhibits identical spectral properties in both crystal systems. It is characterized by interaction of the unpaired electron with an alpha-proton(-17-0, -8-7, -33-7G), a beta-proton (18-6, 21-3, 17-5 G) as well as an OH-proton (4-8, 7-9, 12-8 G). The principal values of the g-tensor are 2-0034, 2-0049 and 2-0042. The spectral parameters are discussed in relation to those of the same or similar radicals in other nucleosides (-tides). 相似文献
85.
Helmut Klocker Bernhard Auer Helmut J. Burtscher Monica Hirsch-Kauffmann Manfred Schweiger 《Molecular & general genetics : MGG》1982,188(2):309-312
Summary The UV photoproduct, thymine dimer (
), is excorporated with a remarkably low rate from the DNA of human fibroblasts grown in cell culture. An UV dose of 18 J/m2 creates 0.045%
(related to thymine). Within the first two days of repair logarithmically growing and quiescent fibroblasts exhibit the same repair rates; thereafter, the proportion of
is lower in growing cells due to recovery of DNA replication. Only about 50% of the lesions are excised within 24 h. In quiescent cells, 13% of the thymine dimers originally present can be detected as late as a week after UV-irradiation. Two distinct first-order rate constants indicate that approximately half of the dimers are less accessible to repair. Repair measured by the nucleoid decondensation technique corresponds to the faster repair rate, whereas the slow repair rate cannot be detected by this method. Saturation of repair is found beyond 27 J/m2. The remarkably slow rate of excision indicates that thymine dimers are not lethal lesions in human fibroblasts. 相似文献
86.
Summary The generally accepted concept that dorsoventral flatness and/or small size of benthic stream invertebrates staying on the surface of the bottom substratum allows a current-sheltered life in the boundary layer (Ambühl 1959) is checked by means of the new technique of Laser Doppler Anemometry (LDA). With LDA measurement of flow can be done nearly punctually without any mechanical disturbance. Mapping the current velocities around the body of Ecdyonurus cf. venosus (Insecta, Ephemeroptera) and Ancylus fluviatilis (Gastropoda) gives evidence that boundary layer separation occurs above the animals' bodies. Our results indicate that the velocities around the body of benthic stream invertebrates and probably the forces acting on them are much more complicate than is suggested by the currently accepted boundary layer concept. 相似文献
87.
88.
The term monophagy is applied to animal species which are linked to a single plant-reprospecies at least during part of their ontogeny. Aspects of subsequent evolution of monophagous animal species and their plant host species are discussed. 相似文献
89.
The neurogenic locus mastermind (mam) of Drosophila is required for the segregation of epidermal from neural cell lineages. Previous studies have shown that during neurogenesis mam appears to be expressed throughout the ectoderm, mesoderm, and neuroblast layer of the germ band. Here it is demonstrated that during early embryogenesis mam is expressed ubiquitously; however, the predominant domains of accumulation of mam RNA and protein during gastrulation are along the ventral longitudinal surface, including cells of the mesoderm, endoderm, mesectoderm, and neuroectoderm. The regions of elevated mam accumulation coincide with the realm of action of dorsoventral patterning genes. 相似文献
90.
Santhini Ramasamy Gilbert A. Boissonneault Eric A. Decker Bernhard Hennig 《Journal of biochemical and molecular toxicology》1991,6(1):29-35
High plasma levels of linoleic acid (18:2) may injure endothelial cells, resulting in decreased barrier function of the vascular endothelium. The effects of linoleic acid on endothelial barrier function (transendothelial movement of albumin), membrane-bound enzyme activities, and possible autooxidation of linoleic acid under experimental conditions were studied. The exposure of endothelial monolayers to 18:2 for 24 hr at 60, 90, and 120 μM. fatty acid concentrations caused a significant increase in transendothelial movement of albumin, with maximum albumin transfer at 90 μM. Fatty acid treatment resulted in the increased appearance of cytosolic lipid droplets. Activities of the membrane-bound enzymes, angiotensin-converting enzyme (ACE), and Ca2+-ATPase increased steadily with increasing time of cell exposure to 90 μM 18:2, reaching significance at 24 hr. Treatment of endothelial cultures with up to 120 μM 18:2 did not cause cytotoxicity, as evidenced by a nonsignificant change in cellular release of [3H]-adenine. Incubation of 18:2-supplemented serum-containing culture media with 1000 μM 18:2 at 37°C for up to 48 hr did not result in formation of autooxidation products. These results suggest that 18:2 itself, and not its oxidation products, plays a major role in disrupting endothelial barrier function. 相似文献