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81.
82.
Laurence S. Kaminsky F.Peter Guengerich Ghazi A. Dannan Steven D. Aust 《Archives of biochemistry and biophysics》1983,225(1):398-404
R- and S-warfarin metabolite profiles (regio- and stereoselectivity) have been determined with hepatic microsomes from untreated rats and rats treated with nine individual polybrominated biphenyl (PBB) congeners, a commercial mixture of PBBs, and, for comparison with phenobarbital and 3-methylcholanthrene. The metabolic rates have been correlated with cytochrome P-450 (P-450) isozyme concentrations in the microsomes determined by immunochemical quantitation techniques (G. A. Dannan, F. P. Guengerich, L. S. Kaminsky, and S. D. Aust, (1983) J. Biol. Chem., 258, 1282–1288). The warfarin hydroxylase activities of the P-450 isozyme components of the various microsomal preparations (F. P. Guengerich, G. A. Dannan, S. T. Wright, M. V. Martin, and L. S. Kaminsky (1982) Biochemistry, 21, 6019–6030) were multiplied by the corresponding isozyme concentrations to obtain an assessment of the potential warfarin hydroxylase capacity of the microsomes, and the results were compared with actual activities. The results of these studies and comparisons indicate that substrate regio- and stereoselectivities of microsomal-bound P-450s are essentially retained on purification of the isozymes to homogeneity and reconstitution, that warfarin metabolism by microsomal preparations can be used to predict microsomal P-450 isozyme compositions, and that microsomal warfarin hydroxylase activity is greater than would be predicted based on the approx 20:1 ratio of P-450 to NADPH-P-450 reductase in the microsomes and on the known activities of constituent isozymes. Two P-450 isozymes which are induced by treatment of rats with phenobarbital appear to be more tightly linked to NADPH-P-450 reductase than does an isozyme induced by β-naphthoflavone. 相似文献
83.
Systemic administration of the enkephalin analog FK 33.824 was previously shown to inhibit ACTH secretion in man. In this study, the direct action of this analog on cortisol release was studied. The enkephalin analog (1 uM and 10 uM) did not influence basal or ACTH-stimulated cortisol production by cultured isolated adrenocortical cells prepared from the hyperplastic adrenal glands from three patients with Cushing's disease. Naloxone (10 uM) had also no direct effect on cortisol release. It is concluded that the met-enkephalin analog used in this study and naloxone do affect the hypothalamo-pituitary-adrenal axis via a central effect. 相似文献
84.
Steven H. Bertz 《Bulletin of mathematical biology》1983,45(5):849-855
A new formula for the complexity of graphs is proposed and applied to the points lines and ‘connections’ of some chemically relevant graphs. 相似文献
85.
Lynn M. Riddiford Craig R. Roseland Steven Thalberg Anna T. Curtis 《Journal of insect physiology》1983,29(3):281-286
The juvenile hormone antagonist ETB (ethyl-4-2(t-butylcarbonyloxy)-butoxybenzoate) caused formation of precocious larval-pupal intermediates after the 4th (penultimate)-larval instar of the tobacco hornworm, Manduca sexta, when 50 μg were applied to any 3rd stage larvae or to 4th stage larvae within 12 hr after ecdysis. This dose was most effective within 12 hr after ecdysis to the 3rd stage. In the black mutant larval assay for juvenile hormone, ETB had activity, 0.75 μg per larva giving half-maximal score. In vitro ETB acted as a juvenile hormone to prevent the ecdysteroid-induced change in commitment at concentrations above 0.1 μg/ml with an ED50 at 2.8 μg/ml and as a partial juvenile hormone antagonist to 0.1 μg/ml juvenile hormone I at concentrations between 10?3 and 10?2 μg/ml. By contrast, EMD (ethyl-E-3-methyl-2-dodecenoate) had little juvenile hormone-like activity in vitro up to its limits of solubility (100 μg/ml) and exhibited sporadic partial juvenile hormone antagonistic activity in vitro at concentrations between 1 and 100 μg/ml. Since these concentrations were 10–1000 times that of juvenile hormone I in the medium, EMD apparently is not an efficient competitor. 相似文献
86.
Maureane Hoffman Steven R. Feldman Salvatore V. Pizzo 《Biochimica et Biophysica Acta (BBA)/General Subjects》1983,760(3):421-423
Mouse peritoneal macrophages activated by bacillus Calmette-Guerin (BCG) were incubated with human α2-macroglobulin converted to its ‘fast’ form with either trypsin or methylamine before being stimulated with phorbol myrystate acetate. Both α2-macroglobulin-trypsin and α2-macroglobulin-methylamine inhibited macrophage production of superoxide anion (O2−) while native α2-macroglobulin had little effect except at high concentration. The α2-macroglobulin ‘fast’ forms, which bind with a Kd of about 8 nM, inhibited 50% generation of O2−(ID50) at a concentration of 7 nM while α2-macroglobulin inhibited O2− production with an ID50 of 141 nM. The ‘fast’ forms of α2-macroglobulin may play a role in the feedback regulation of inflammatory reactions. 相似文献
87.
Methylation of the Flagellin of Salmonella typhimurium 总被引:2,自引:2,他引:0
The methylation of endogenous proteins by Salmonella typhimurium SL 870 was investigated in cell-free extracts by using S-adenosylmethionine as methyl donor. Several lines of evidence are presented which suggest that one of the methylated products is the protein flagellin. Mutant strains of SL 870 (nml−fla+ and nml+fla−) were also found to synthesize epsilon-N-methyl-lysine. It is proposed that S. typhimurium possesses at least two genes specifying different methylating enzymes. One gene product is a flagellin-specific methylating enzyme, whereas the other gene(s) codes for enzymes that methylate one or more other cell proteins. 相似文献
88.
Alkaline Sucrose Gradient Sedimentation of Chromosomal Deoxyribonucleic Acid from Escherichia coli PolA+ and PolA− Strains During Thymine Starvation 下载免费PDF全文
Single-strand breaks were not detected in the deoxyribonucleic acid of Escherichia coli after thymine starvation for up to 180 min, even in a sensitive PolA(-) strain. 相似文献
89.
Chloroplast and Cytoplasmic Ribosomes of Euglena: Selective Binding of Dihydrostreptomycin to Chloroplast Ribosomes 总被引:3,自引:0,他引:3 下载免费PDF全文
Dihydrostreptomycin binds preferentially to chloroplast ribosomes of wild-type Euglena gracilis Klebs var. bacillaris Pringsheim. The K(diss) for the wild-type chloroplast ribosome-dihydrostreptomycin complex is 2 x 10(-7) M, a value comparable with that found for the Escherichia coli ribosome-dihydrostreptomycin complex. Chloroplast ribosomes isolated from the streptomycin-resistant mutant Sm(1) (r)BNgL and cytoplasmic ribosomes from wild-type have a much lower affinity for the antibiotic. The K(diss) for the chloroplast ribosome-dihydrostreptomycin complex of Sm(1) (r) is 387 x 10(-7) M, and the value for the cytoplasmic ribosome-dihydrostreptomycin complex of the wild type is 1,400 x 10(-7) M. Streptomycin competes with dihydrostreptomycin for the chloroplast ribosome binding site, and preincubation of streptomycin with hydroxylamine prevents the binding of streptomycin to the chloroplast ribosome. These results indicate that the inhibition of chloroplast development and replication in Euglena by streptomycin and dihydrostreptomycin is related to the specific inhibition of protein synthesis on the chloroplast ribosomes of Euglena. 相似文献
90.