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21.
Influence of Phosphate on the Growth and Nodulation Characteristics of Rhizobium trifolii 总被引:3,自引:2,他引:1
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The growth and nodulating characteristics of Rhizobium trifolii 6 and 36 differed under different external phosphate conditions. Under growth conditions designed to deplete the internal phosphate content of the rhizobia, strain 6 maintained a generation time of 5 h during the exponential phase over two cycles of growth in phosphate-depleted medium. In contrast, the generation time of strain 36 was extended from 3.5 to 9.8 h over two cycles of phosphate-depleted growth, although the organism eventually achieved the same cell density and cellular phosphate content as that of strain 6 at stationary phase. Phosphate-depleted strain 6 required 0.51 ± 0.08 μM phosphate to commence proliferation, whereas phosphate-depleted strain 36 required 0.89 ± 0.04 μM phosphate under the same conditions. Phosphate-depleted strain 6 maintained viability when exposed to external phosphate concentrations subcritical for growth to occur, whereas phosphate-depleted strain 36 lost viability within 48 h when exposed to medium containing phosphate at concentrations subcritical for growth. Phosphate-depleted strain 36 was inferior to phosphate-depleted strain 6 at nodulating subterranean clover (Trifolium subterraneum L. cv. Mt. Barker) by taking 2 to 4 days longer to develop nodules in phosphatedepleted plant grown medium at pH 5.5. Nodulation by phosphate-depleted strain 36 was accelerated either by including phosphate in the plant growth medium at pH 5.5 or by raising the solution pH of phosphate-depleted plant growth medium to pH 6.5. External phosphate and pH effects were not observed on the nodulating capabilities of phosphate-depleted strain 6 or on luxury phosphate-grown cells of either strain. Phosphatedepleted strains 6 and 36 proliferated to a similar extent on the rhizoplanes even under stringently low external Pi concentrations. The phosphatase activities of both phosphate-depleted strains were significantly (P = 0.05) higher at pH 6.5 than at pH 5.5, and the activity of strain 6 was significantly higher (P = 0.05) than that of strain 36 at pH 5.5 and 5.0. 相似文献
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George B. Stefano Erica Braham Patrick Finn Edward Aiello Michael K. Leung 《Cellular and molecular neurobiology》1987,7(2):209-219
1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress. 相似文献
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Summary The production of 9-cis-1, 18-octadecenedioic acid from different substrates by the mutant S76 of Candida tropicalis was studied. It was found that the mutant could convert oleyl alcohol, oleic acid, and methyl oleate to 9-cis-1, 18-octadecenedioic acid through either the diterminal oxidation of the alcohol or the -oxidation of the terminal methyl group of the mono acid. The geometric configuration of the product was identified by different analytical methods. The results demonstrated that no change in the geometric configuration of molecular structure happened during the bioconversion of such unsaturated substrates to 9-dioic acid. To enhance the production of this dioic acid in the medium, calcium carbonate was added as a trapping agent. The IR spectrum, 1H NMR and 13C-satellite spectra of this compound were presented.Dedicated to Professor Dr. K. Esser on the occasion of his 65th birthday 相似文献
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鼎突多刺蚁群体结构和生活史的研究 总被引:5,自引:0,他引:5
本文报告了鼎突多刺蚁(Polyrhachis vicina Roger)的群体结构和生活史。通过研究表明,鼎突多刺蚁一年发生一代,以蚁后、雄蚁、工蚁、幼虫和卵越冬。卵和幼虫在冬天发育停滞(或极慢)。到了春天,随着气温的上升,卵和幼虫又恢复正常发育。据室内人工饲养观察,卵的发育历期为23.8±2.5天(平均温度26℃)幼虫为20.4±4.4天(26℃),工蚁蛹为19.8±5.5天(27℃)。成长工蚁在5—11月出现;8—11月,雄蚁从蛹中羽化;10月,雌蚁从蛹中羽化。雌蚁分飞交尾后,进入邻近蚁巢或回到原巢,脱翅成为蚁后。蚁巢内存在着多后现象。 相似文献
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Stimulation of progesterone and prostaglandin E2 production by lipoxygenase metabolites of arachidonic acid 总被引:1,自引:0,他引:1
The role of several lipoxygenase metabolites of arachidonic acid in the action of luteinizing hormone-releasing hormone (LHRH) on ovarian hormone production was investigated. Like LHRH, treatment of rat granulosa cells with 5-HETE, 5-HPETE, 12-HETE, 15-HETE or 15-HPETE stimulated progesterone (P) and prostaglandin E2 (PGE2) production. 12-HEPE was most potent and stimulated P and PGE2 equally well. By contrast, 5-HETE stimulated P better than PGE2, while 15-HETE was a potent stimulator of PGE2 but not of P. Stimulation of P and PGE2 by LHRH or 12-O-tetradecanoylphorbol 13-acetate (TPA) was further augmented by several HETEs and HPETEs. Like protein kinase C, arachidonic acid metabolites appear to mediate the multiple actions of LHRH in the ovary. 相似文献
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