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191.
192.
Découverte de microfaunes de l'Albienmoyen et supérieur dans la vallée de Joux (Jura Vaudois,Suisse)
The discovery of Foraminifera and Ostracodesin the dark green, sandy-glauconitic marl clay in the Joux Valley (in the Vaudois Jura) suggests to date these sediments Middle and Upper Albian. The Ostracode associations are similar to those found in the Paris Basin, but different from those which characterize the subalpine region. 相似文献
193.
Two specific genera of Bohemian Llanvirn(Sarka Formation), Reticulocarpos and Lagynocystis have been recognized in Traveusot, le Pissot and Pierre Melière Formations (Llanvirn and Llandeilo of the Armorican Massif). Though three species are new (R. pissotensis, R. sp., Lagynocystis sp.) this discovery once more underlines the relationships between Bohemia and Armorican Massif during this period. 相似文献
194.
Summary Uracil transport inSaccharomyces cerevisiae is mediated by a specific permease which does not recognize other pyrimidines such as uridine, cytosine, thymine, 2-hydroxypyrimidine or 5-amino-uracil; hypoxanthine and 6-amino-uracil slightly inhibit the uptake of uracil in a strain lacking cytosine permease activity. Wild type cells concentrate extracellular uracil before its transformation into UMP and subsequent incorporation into nucleic acids. A strain lacking UMP pyrophosphorylase and uridine ribohydrolase (strainfur 1–8 rh, in which the endogenous production as well as the utilization of uracil are lacking) is able to concentrate14C-2 uracil from the medium. At the same time no other14C-2 labelled compound could be detected in this strain, thus suggesting that the uptake of uracil in yeast occurs by active transport which is not coupled to the UMP pyrophosphorylase. The optimal pH of uracil uptake in standard growth conditions was 4.3. It was deduced from experiments performed on strainfur 1–8 rh with3H-5 and14C-2 uracil that the intracellular pool of uracil is recycled once the steady-state has been reached. First order kinetics with similar rate constants were observed for uracil efflux in strainfur 1–8 rh (k min–1=0.75±0.08) as well as in the strain lacking uracil permease,fur 1–8 rh fur 4–6 (k min–1=0.60±0.08). The intracellular pool of14C-2 uracil can be chased in strainfur 1–8 rh by addition of3H uracil without inducing a large initial acceleration of the exit rate (the rate constant remained at 0.60). 2-4-dinitrophenol inhibits the uptake of uracil but also reduces the efflux of uracil in strainfur 1–8 rh fur 4–6. These data and the comparison with cytosine transport in the same organism support the hypothesis that, whereas uracil uptake is a permease mediated active transport, the efflux of uracil does not involve the uracil uptake permease. A coefficient of permeability of 7.4×10–7 cm sec–1 was calculated for uracil. 相似文献
195.
A procedure is described which is capable of detecting the changes in size and/or density of small membrane vesicles resulting from solute uptake. Vesicles which have taken up solute sediment more slowly in a density gradient, the ratio of glycine uptake/vesicle-trapped space is not uniform in the vesicle population, and vesicles with higher uptake/space ratios are preferentially retarded upon centrifugation.Alanine transport activity is associated with glycine transport activity in that retardation of vesicles due to glycine uptake equally retards vesicles possessing alanine uptake activity. 相似文献
196.
Jean W. MacCluer 《American journal of human genetics》1977,29(2):216-217
197.
C-Glycosylflavones have been identified in Ephedra antisyphilitica, Gnetum gnemon and Welwitschia mirabilis. The C-glycosidic moieties of apigenin and luteolin derivatives have been identified as glucose and/or xylose for these species. 相似文献
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200.
Chi's are genetic elements that stimulate generalized recombination in their locale in phage λ. All Chi's, wherever located on λ's chromosome, act asymmetrically in crosses blocked in DNA replication: (1) They stimulate exchange primarily to their left on the conventional λ map, and (2) the stimulated exchange is frequently nonreciprocal, the recombinant carrying the Chi element being produced less often than the complementary product. 相似文献