Comparisons of warfarin metabolism by liver microsomes of rats treated with a series of polybrominated biphenyl congeners and by the component-purified cytochrome P-450 isozymes

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.     

The met-enkephalin analog FK 33-824 and naloxone do not directly influence cortisol secretion by cultured human adrenocortical cells

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.     

On the complexity of graphs and molecules

A new formula for the complexity of graphs is proposed and applied to the points lines and ‘connections’ of some chemically relevant graphs.     

Action of two juvenile hormone antagonists on lepidopteran epidermis

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.     

Women as hunters among the matses of the Peruvian Amazon

Matses women of the Peruvian Amazon rain forest hunt with men, and couples bring back more meat than men alone. This results from the association of women with capture of collared peccary, a large catch. Typical Amazonian beliefs about women persist, but some new features (like day care) are pertinent to Matses hunting adaptation.     

α2-macroglobulin ‘fast’ forms inhibit superoxide production by activated macrophages

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 K_d 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.     

Methylation of the Flagellin of Salmonella typhimurium

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.     

Alkaline Sucrose Gradient Sedimentation of Chromosomal Deoxyribonucleic Acid from Escherichia coli PolA+ and PolA− Strains During Thymine Starvation

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.     

Chloroplast and Cytoplasmic Ribosomes of Euglena: Selective Binding of Dihydrostreptomycin to Chloroplast Ribosomes

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.