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21.
Summary The addition of serum to quiescent NIH 3T3 mouse cell cultures resulted in a 10- to 20-fold increase of Rb influx which was resistant to ouabain, and only a three- to fourfold activation of ouabain-sensitive Rb influx. Stimulation of the ouabain-resistant Rb influx following serum addition reached its maximum within 2 min. The stimulation of ouabain-resistant Rb influx was a result ofV
m increase while theK
m for Rb was unchanged. Ouabain-resistant Rb influx, after serum addition, was resistant to amiloride and sensitive to ethacrinic acid. Replacing chloride in the medium by NO3
–, CO3
– and CH3COO– resulted in a drastic decrease in the ouabain-resistant Rb influx. It appeared, therefore, that the ouabain-resistant Rb influx in NIH 3T3 cells was Cl–-dependent. 相似文献
22.
Michael W. Fountain Robert Chiovetti Henri Kercret David O. Parrish Jere P. Segrest 《生物化学与生物物理学报:生物膜》1980,596(3):420-425
A method has been developed for the rapid separation of cells in suspension from non-cell associated lipid vesicles in various assays for vesicle-cell interaction. Separation is achieved on a discontinuous Ficoll-Paque gradient. Cells and free vesicles are totally separated, as evidenced by both radiolabelled vesicles, and vesicles containing the fluorescent dye 6-carboxyfluorescein. The main advantages of this method are the rapidity, efficacy, and gentleness of the separation. Viability of the cells remains consistently high (greater than 96%) throughout the separation. Since this method involves a one-step centrifugation, it precludes the necessity for repeated washings of cells which have been incubated with lipid vesicles. 相似文献
23.
van Onckelen Henri A.; Caubergs Roland; de Greef Jan A. 《Plant & cell physiology》1977,18(5):1029-1040
The influence of light and endogenous plant-growth regulatorson the evolution of - and ß-amylases in cotyledonsof Phaseolus vulgaris L. was investigated. Both enzymes, whichare not present in ungerminated seeds, appear during germinationof intact seedlings or incubation of excised cotyledons. -Amylaseactivity decreases upon exposure to light. This inhibition iscorrelated with a drastic increase in chlorophyll content anda change in the endogenous gibberellin-inhibitor balance. ß-Amylaseactivity was not affected by light treatment but was by thepresence of endogenous cytokinins. (Received February 3, 1977; ) 相似文献
24.
Bacteriophage MS2 RNA: A correlation between the stability of the codon: Anticodon interaction and the choice of code words 总被引:9,自引:0,他引:9
Henri Grosjean David Sankoff Willy Min Jou Walter Fiers R. J. Cedergren 《Journal of molecular evolution》1978,12(2):113-119
Summary The non-random distribution of degenerate code words in Bacteriophage MS2 RNA can be explained partially by considerations of the stability of the codon-anticodon complex in prokaryotic systems. Supporting this hypothesis we note that wobble codons are positively selected in codons having G and/or C in the first two positions. In contrast, wobble codons are statitically less likely in codons composed of A and U in the first two positions. Analyses of nucleotides adjacent to 5 and 3 ends of codons indicate a nonrandom distribution as well. It is thus likely that some elements of RNA evolution are independent of the structural needs of the RNA itself and of the translated protein product.This work was supported by grants from the Belgian Government Actions concertées - Gekon-certéerde Acties, N.F.W.O. and F.K.F.O. as well as from le Ministère de l'éducation du Québec. A preliminary report of this work was given at the EMBO ribosome workshop, Brussels 1976 相似文献
25.
Cyst hatching in Anostraca accelerated by retinoic acid,amplified by Calcium Ionophore A23187, and inhibited by Calcium-channel blockers 总被引:1,自引:1,他引:0
Cyst hatching, under standardized conditions, of the Anostracan species Thamnocephalus platyurus and Streptocephalus dichotomus was significantly accelerated but not increased by applying the morphogen retinoic acid (RA). Cyst hatching was enhanced but not accelerated by artificially increasing the inflow of Ca2+ to the embryonic cells, using Calcium Ionophore A 23 187. Cyst hatching was accelerated and amplified, to a level in excess of the summed effects of each treatment, by a combined application of RA and ionophore. It was inhibited almost quantitatively by the Calcium-channel blockers Nifedipin and Verapamil. The significance of these findings is discussed. 相似文献
26.
A gas chromatographic method has been satisfactorily developed for the determination of gallic acid after enzymatic hydrolysis of methyl gallate by fungal tannase. The technique described herein permits a specific, quantitative analysis of the enzyme. The separate determination of both soluble and fixed tannase is described. 相似文献
27.
28.
Alice Y. Romans Theresa M. Allen William Meckes Robert Chiovetti Lulu Sheng Henri Kercret Jere P. Segrest 《生物化学与生物物理学报:生物膜》1981,642(1):135-148
Human erythrocyte glycophorin is one of the best characterized integral membrane proteins. Reconstitution of the membrane-spanning hydrophobic segment of glycophorin (the tryptic insoluble peptide released when glycophorin is treated with trypsin) with liposomes results in the production of freeze-fracture intrabilayer particles of 80 Å diameter (Segrest, J.P., Gulik-Krzywicki, T. and Sardet, C. (1974) Proc. Natl. Acad. Sci. U.S.A. 71, 3294–3298), with particles appearing at or above a tryptic insoluble peptide concentration of 4 mmol per mol phosphatidylcholine. In the present study, increasing concentrations of tryptic insoluble peptide were added to sonicated small unilamellar egg phosphatidylcholine vesicles and the rate of efflux of 22Na+ was examined by rapid (30 s) gel filtration on Sephadex G-50. Below a concentation of 3–5 mmol tryptic insoluble peptide/mol phosphatidylcholine, 22Na+ efflux occurs at a constant slow rate at given tryptic insoluble peptide concentrations. Above a concentration of 3–5 mM, the rate of efflux is biphasic at given tryptic insoluble peptide concentrations, exhibiting both an initial fast and a subsequent slow component. On the basis of graphic and computer curve-fitting analysis, with increasing tryptic insoluble peptide concentration, the rate of the slow component reaches a plateau at a tryptic insoluble peptide concentration of 3–5 mM and remains essentially constant until much higher concentrations are reached; the fast component increases linearly with increasing tryptic insoluble peptide concentration well beyond 5 mM. The most consistent interpretation of this data is as follows. The slow 22Na+ efflux component is due to perturbations of small unilamellar vesicle integrity by tryptic insoluble peptide monomers. At a tryptic insoluble peptide concentration of 3–5 mmol/mol, a critical concentration is reached following which there is intrabilayer tryptic insoluble peptide self-association. The fast 22Na+ efflux component is due to the increasing presence of tryptic insoluble peptide self-associated multimers the 80-Å particles seen by freeze-fracture electron microscopy) which results in a significantly larger bilayer defect than do tryptic insoluble peptide monomers. The failure of complete saturation of efflux by the fast component is ascribed to the presence of two populations of small unilamellar vesicles, some of which contain tryptic insoluble peptide multimers and some of which do not.Addition of cholesterol to the tryptic insoluble peptide/phosphatidylcholine vesicles decreases the rate of 22Na+ efflux by inhibiting primarily the fast component. Freeze-fracture electron microscopy indicates that the presence of cholesterol has no effect on the size, number or distribution of 80-Å intra-bilayer particles in the tryptic insoluble peptide/phosphatidylcholine vesicles. These results are consistent with a mechanism to explain the fast Na+ efflux component involving protein-lipid boundary perturbations.Efflux of 45Ca2+ from phosphatidylcholine vesicles is also enhanced by incorporation of tryptic insoluble peptide, but only if divalent cations (Ca2+ or Mg2+) are present in the external bathing media as well as inside the sonicated vesicles. If monovalent Na+ only is present in the bathing media no 45Ca2+ efflux is seen. Under conditions where 45Ca2+ efflux is seen, both a fast and a slow component are present, although both appear lower than corresponding rate constants for 22Na+ efflux. These results suggest a coordinated mechanism for ion efflux induced by tryptic insoluble peptide and, together with the 22Na+ efflux studies, may have mechanistic implications for the transbilayer phospholipid exchange (flip-flop) suggesed to be induced at glycophorin/phospholipid interfaces (de Kruiff, B., van Zoelen, E.J.J. and van Deenen, L.L.M. (1978) Biochim. Biophys. Acta 509, 537–542). 相似文献
29.
Henri Cappetta 《Geobios》1981,14(5):563-575
Recent researches in the phosphat-bearing basins ofMorocco have allowed to collect new selachian forms. In this paper, three Ypresian genera from Ouled Abdoun basin, new for Morocco, are described: Heptranchias howellii (Reed, 1946), Alopias denticulatus nov. sp. and Odontorhytis pappenheimiBöhm, 1926. The re-discovery of the genus Odontorhytis allows to state precisely its morphological dental features and to affirm that it is well a selachian and not a teleostean, as it was thought. The stratigraphic distribution of some species is stated precisely. 相似文献
30.
Cladocera and free-living Copepoda from the Fouta Djalon and adjacent mountain areas in West Africa 总被引:4,自引:4,他引:0
Henri J. Dumont 《Hydrobiologia》1981,85(2):97-115
Thirty-two species of Cladocera and 27 species of free-living copepods were identified in a series of samples collected in
25 localities in and around the Fouta Djalon mountains, West Africa. Beside great richness in numbers of species, the nature
of the fauna is noteworthy: at least 20% of the Cladocera and 50% of the copepods are endemic to West Africa. Possible palaeoclimatological
reasons for this are discussed. The cladoceran genus Streblocerus is recorded from Africa for the first time. It is an element of northern origin in the fauna of West Africa. More examples
of this kind are documented among the Copepoda Cyclopoida and Harpacticoida, but the bulk of the fauna is evidently of tropical
origin. In particular, great adaptive radiation is occurring in the local representatives of the genus Tropocyclops. Three new species of Parastenocaris are described; they are the first representatives of this genus found in West Africa. 相似文献