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81.
Soybean callus metabolised applied 6-furfurylamino (8-14C) purine very rapidly to polar compounds, some of which were retained on a Dowex 50 cation exchange resin, and were unaffected by alkaline phosphatase; while others were apparently phosphorylated and were detected in the aqueous fraction. Adenine was detected as an intermediate and it can be concluded that it was formed as a result of the rapid and efficient removal of the furfuryl side chain. The formed adenine was rapidly incorporated into the polar metabolites. Exactly how the presence of this cytokinin stimulates cell division is not apparent from the results.The financial support of the C.S.I.R., Pretoria, and The Natal University Development Fund is gratefully acknowledged. 相似文献
82.
M. Rajalakshmi 《Journal of biosciences》1985,7(2):191-195
The epididymis is an ideal extragonadal target site to inhibit fertility in the male. Synthesis and secretion of constituents
like sialic acids, protein and glycerylphosphoryl choline by the epididymal epithelium under androgen control provide an ideal
fluid environment for sperm maturation. An optimal level of sialic acid secretion by the epididymal epithelium is needed to
maintain functional integrity of sperm. The existence of specific androgen receptors in the epididymis and spermatozoa are
related to their ability to metabolise androgens. 相似文献
83.
Anaerobic, Gram-positive cocci were obtained from chicken feces by direct isolation, which grew on the purines uric acid, xanthine, 6,8-dihydroxypurine, guanine, and hypoxanthine. Adenine and glycine were fermented, but not as readily. Acetate, formate, ammonia, and CO2 were products. The isolated strains were nutritionally non-fastidious, however, they required selenite, molybdate, and tungstate as micronutrients. The cells were spherical and 0.5–0.9 m in diameter. The addition of bile salts enhanced the growth rate in most cases. The organisms proved to be quite resistant to lysis. The guanosine-plus-cytosine (G+C) content of their deoxyribonucleic acid was 33.6 to 34.8 mol%. The peptidoglycan was of the same structure (Gly-Lys-d-Asp) as reported for the anaerobic cocci of Hare group IX. However, the latter strains could only utilize glycine, not purines. Therefore, it is proposed to form a new species, Peptostreptococcus barnesae sp. nov.This paper is dedicated to Prof. Dr. Norbert Pfennig on the occasion of his 60th birthday 相似文献
84.
Thiols and pancreatic beta-cell function: a review 总被引:2,自引:0,他引:2
In pancreatic islets insulin secretion in response to a variety of stimulators is sensitive to the redox state of extracellular and intracellular thiols. In this connection variations of plasma glutathione (GSH) may also be of importance. In the process of stimulus-secretion coupling, membrane thiols play an important role. One major localization of critical thiols appears to be related to the influx of calcium through the voltage-dependent channel. Other transmembranal ion movements and the cAMP system seem to be less sensitive to thiol oxidation than calcium influx via voltage-dependent Ca channels. 相似文献
85.
86.
赵毓橘 《植物生理与分子生物学学报》1985,(4)
在水分供应正常的情况下,切除1/4~1/2的绿豆子叶对上胚轴生长没有明显的抑制作用,但是经0.2M甘露醇处理的幼苗却随着切除的子叶量的增加,上胚轴的生长呈直线剧减,全部切除子叶的幼苗生长几乎完全停止。子叶在水分胁迫状况下对生长的这种作用与它在上胚轴生长区渗透调节中的作用密切相关。幼苗上胚轴的生长与细胞的有效渗透势之间的相关系数为-0.76,有较高的相关性,但是生长与细胞的总渗透势无相关性(相关系数为-0.29)。细胞的渗透势与细胞液中的糖、游离氨基酸和钾离子浓度之间有很高的相关性。表明水分胁迫下生长所需的低渗透势的维持依赖于来自子叶的渗透物质。 相似文献
87.
The phylogenetically related phototrophic bacteria Rhodospirillum tenue and Rhodocyclus purpureus modulate activity of their glutamine synthetases by adenylylation/deadenylylation. Evidence for covalent modification includes the inhibitory effect of Mg2+ on the activity of glutamine synthetase extracted from cells of either species grown on excess ammonia, and the lack of Mg2+ inhibition of activity of the enzyme isolated from N2-(R. tenue) or glutamine (R. purpureus)-grown cells. In addition, snake venom phosphodiesterase treatment of glutamine synthetase from either species grown on excess ammonia relieved Mg2+ inhibition of the enzyme (as measured via the -glutamyl transferase assay), and changed the cation specificity from Mn2+ to Mg2+ (in the biosynthetic assay). 相似文献
88.
Potato tuber ( Solanum tuberosum L. cv. Bintje) callus shows a decrease in fresh weight and an increase in dry weight upon transfer to nutrient medium supplemented with 0.3 or 0.5 M mannitol. The osmolarity of the intracellular fluid increases simultaneously. Probably mannitol is taken up from the medium till the osmolarity of the tissue is in equilibrium with that of the medium. After osmotic adaptation, on a medium with 0.5 M mannitol, growth is negligible, although the tissue retains its viability.
Respiration increases upon transfer to medium with extra mannitol, especially when expressed on a fresh weight basis. On this basis cytochrome and alternative pathway capacities do not change appreciably. The respiratory increase is exclusively caused by an increased engagement of the alternative pathway. The participation of this pathway in uninhibited respiration increases from about 10 to 90% upon transfer to medium with extra mannitol. The increase in respiration is partly correlated with the decrease in fresh weight upon transfer. Per disc, the capacities of the cytochrome and alternative pathway decline. Yet, total respiration per disc significantly increases due to the increased participation of the alternative pathway. This results in an almost equal ATP-production per disc before and after transfer. We suggest, that the alternative pathway functions as a reserve capacity in potato callus, which is switched on when ATP-production coupled to the cytochrome pathway is impaired. 相似文献
Respiration increases upon transfer to medium with extra mannitol, especially when expressed on a fresh weight basis. On this basis cytochrome and alternative pathway capacities do not change appreciably. The respiratory increase is exclusively caused by an increased engagement of the alternative pathway. The participation of this pathway in uninhibited respiration increases from about 10 to 90% upon transfer to medium with extra mannitol. The increase in respiration is partly correlated with the decrease in fresh weight upon transfer. Per disc, the capacities of the cytochrome and alternative pathway decline. Yet, total respiration per disc significantly increases due to the increased participation of the alternative pathway. This results in an almost equal ATP-production per disc before and after transfer. We suggest, that the alternative pathway functions as a reserve capacity in potato callus, which is switched on when ATP-production coupled to the cytochrome pathway is impaired. 相似文献
89.
Pamela J. Weathers James F. Danielli Peter M. Bradley Diane M. Hebb Judith E. Miller Rick L. Pesano 《Physiologia plantarum》1984,61(3):441-448
We report the isolation of a cukaryotic green alga ( Chlorella , strain WPI-2) which accumulates large stores of nitrogen (N) during growth in N-free medium and seems to incorporate14 N2 , yet does not reduce acetylene to ethylene. Total N accumulation during growth on N-free medium and in gases free of combined N was measured by three methods: Kjeldahl, oxidative pyrolysis via chemiluminescence (Antek N analyzer), and Dumas (Coleman N analyzer). Increases in N ranging from 22–64%± 1% were observed. Isotope dilution studies using cells labelled with 15 NO 3 - and then shifted to 14 N2 in N-free medium showed dilution of the 15 N isotope by 14 N from 5.67 to 5.32%± 0.05%. Using a variety of conditions, we were unable to demonstrate the reduction of acctylene to ethylene by WPI-2, although diazotrophic cyanobacteria gave positive results. Although the data on WPI-2 are not conclusive in establishing this alga as a diazotroph, the data do suggest that within the Chlorophyceae there may exist a novel form of nitrogen gas metabolism. 相似文献
90.
Dr. Paul A. Lespinat Yves M. Berlier Guy D. Fauque Rene Toci Gerard Denariaz Jean LeGall 《Journal of industrial microbiology & biotechnology》1987,1(6):383-388
Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D2–H+ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism. 相似文献