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51.
Diazepam in vitro produced a concentration-dependent increase of membrane fluidity in crude synaptic membranes from rat hippocampus, but not cerebellum. Similar effects were obtained with higher concentrations of Ro 15-1788 and PK 11195, while zopiclone was completely inactive. In vivo acute treatment with diazepam and Ro 15-1788 gave results similar to those in vitro. The specific benzodiazepine antagonist also significantly increased membrane fluidity and was not able to reverse diazepam's effect. The data are discussed in terms of a possible role of protein kinase inhibition by the drugs not mediated by the 'central' or 'peripheral' type of benzodiazepine receptors. 相似文献
52.
Dynamics of soil microbial biomass N under zero and shallow tillage for spring wheat,using15N urea 总被引:2,自引:0,他引:2
Summary Field studies to determine the effect of zero and shallow (10 cm) cultivation on microbial biomass were conducted on several Chernozemic soils in western Canada. Using the CHCl3 fumigation method, the distribution of microbial biomass N and the immobilization and subsequent release of added15N (15N-urea) from the microbial biomass were determined in the A horizon, at the 0 to 5 and 5 to 10 cm depth, during the growing season for spring wheat.Temporal variation in microbial biomass N, associated with the development of the rhizosphere, was characterized by an increase between Feekes stage 1 and 5 or 10 and decrease at Feekes stage 11.4. Over the long term, the variation in biomass N between tillage systems corresponded with crop residue distribution. Immobilization of fertilizer N was related to the increase in biomass N from Feekes stage 1, which in turn, was associated with the incorporation of recent crop residues or levels of labile organic matter in the surface soil. The study demonstrated the relatively rapid remineralization of immobilized fertilizer N under field conditions and emphasized the role of the microbial biomass N as both a sink and source of mineral N. 相似文献
53.
Summary Small differences in N2 fixation by nodulated soybeans (Glycine max. (L.) Merr.), inoculated with various strains ofRhizobium japonicum, were assessed in field experiments using15N methodology, and compared with yields of plant dry matter and total N. Percentage of plant-N derived from atmospheric N2 and from fertilizer, and values of %15N atom excess had lower coefficients of variation than did total N and dry matter yield. Nevertheless the precision of estimates of kg N/ha fixed were sufficient to differentiate only the extremes of the range of strains tested, and there were discrepancies between ranking of strains based on % N derived from fertilizer and on total N yield. 相似文献
54.
Isolation and complete nucleotide sequence of the gene for bovine parathyroid hormone 总被引:7,自引:0,他引:7
The structure of the bovine parathyroid hormone (PTH) gene has been analyzed by Southern blot hybridization of genomic DNA and by nucleotide sequence analysis of a cloned PTH gene. In the Southern analysis, several restriction enzymes produced single fragments that hybridized to PTH cDNA suggesting that there is a single bovine PTH gene. The restriction map of the cloned gene is the same as that determined by Southern blot analysis of bovine DNA. The sequence of 3154 bp of the cloned gene has been determined including 510 bp and 139 bp in the 5' and 3' flanking regions, respectively. The gene contains two introns which separate three exons that code primarily for: (i) the 5' untranslated region, (ii) the pre-sequence of preProPTH, and (iii) PTH and the 3' untranslated region. The gene contains 68% A + T and unusually long stretches of 100- to 150-bp sequences containing alternating A and T nucleotides in the 5' flanking region and intron A. The 5' flanking region contains two TATA sequences, both of which appear to be functional as determined by S1 nuclease mapping. Compared to the rat and human genes, the locations of the introns are identical but the sizes differ. Comparable human and bovine sequences in the flanking regions and introns are about 80% homologous. 相似文献
55.
Angie Rizzino Alan B. Blumenthal 《In vitro cellular & developmental biology. Plant》1978,14(5):437-442
Summary We synchronized Drosophila cell lines (Schneider's line 2 and Kc) by allowing the cells to enter the stationary phase of growth and then diluting them into fresh culture medium. The cells
of both cell lines entered S phase, after an 8- to 14-hr delay, in a state of partial synchrony; 60 to 80% of the cell population
accumulated in S phase. Measurements of the cell cycle phases of Schneider's line 2 cells (S=14 to 16 hr; G2=6 to 8 hr; M=0.4 hr) were similar to those of Kc cells.
This work was performed under the auspices of the U.S. Energy Research and Development Administration. A.R. was supported
by an NIH post-doctoral fellowship, No. CA01060. 相似文献
56.
57.
A Levitzki 《Biochemical and biophysical research communications》1977,74(3):1154-1159
An attempt is made to integrate the knowledge on the role of hormones and guanyl nucleotides in regulating adenylate cyclase into a single molecular model. It is suggested that the hormone catalyzes the activation of the enzyme adenylate cyclase by facilitating the conversion of the enzyme from its inactive state to its active form. The hormone is also responsible for the termination of the signal namely the deactivation of the enzyme by inducing the hydrolysis of GTP at its regulatory site. The relative rates of these two processes determine the steady state concentration of the active form of the enzyme. The model also explains the difference in behaviour between GTP and its non-hydrolyzable analogs GppNHp and GTPγS. 相似文献
58.
S Gutteridge D B Winter W J Bruyninckx H S Mason 《Biochemical and biophysical research communications》1977,78(3):945-951
After mild dissociation of cytochrome oxidase protomers, and polyacrylamide gel electrophoresis, copper was found predominantly in polypeptides of Bands V (m.w. 12,100) and VII (m.w. 3,400), and heme a predominantly in polypeptides of Bands I (m.w. 35,300) and II (m.w. 21,000). Some copper was found in Band II – III, and heme a in Band V. 相似文献
59.
M Sugano T Ide H Okamatsu H Takahara 《Biochemical and biophysical research communications》1977,79(4):1092-1097
A method was developed for the determination of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in the microsomal fraction of crypt cells and villi of rat intestinal mucosa. Addition of trypsin inhibitor to homogenizing and incubation media at a proper concentration appeared inevitable for measurement of the activity of the villi fraction. The reductase in crypt cells was also slightly enhanced by the addition of the inhibitor. Using this technique, the enzyme activity in villi was found to be as active as the crypt cell fraction. Since other types of protease inhibitors were not necessarily effective, it was suggested that specific enzyme(s) inactivates the mucosal reductase in the course of measurement. 相似文献
60.
Studies on purine transport and on purine content in vacuoles isolated from Saccharomyces cerevisiae
Maria Nagy 《生物化学与生物物理学报:生物膜》1979,558(2):221-232
The transport of purine derivatives into vacuoles isolated from Saccharomyces cerevisiae was studied. Vacuoles which conserved their ability to take up purine compounds were prepared by a modification of the method of polybase-induced lysis of spheroplasts.Guanosine > inosine = hypoxanthine > adenosine were taken up with decreasing initial velocities, respectively; adenine was not transported.Guanosine and adenosine transporting systems were saturable, with apparent Km values 0.63 mM and 0.15 mM respectively, while uptake rates of inosine and of hypoxanthine were linear functions of their concentrations.Adenosine transport in vacuoles appeared strongly dependent on the growth phase of the cell culture.The system transporting adenosine was further characterized by its pH dependency optimum of 7.1 and its sensitivity to inhibition by .In the absence of adenosine in the external medium, [14C]adenosine did not flow out from preloaded vacuoles. However, in the presence of external adenosine, a very rapid efflux of radioactivity was observed, indicating an exchange mechanism for the observed adenosine transport in the vacuoles.In isolated vacuoles the only purine derivative accumulated was found to be . 相似文献