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681.
Myocardial infarction in diabetics is often accompanied by poor diabetic control. An assessment of a low-dose insulin infusion regimen in 26 diabetic patients after myocardial infarction found this system to be simple, effective, and safe. 相似文献
682.
J. C. O’Hanlon 《Journal of Ethology》2011,29(1):47-54
Tree trunks are spatially separated habitat patches for the tree-running mantid Ciulfina biseriata (Mantodea: Liturgusidae). This paper investigates how intraspecific interactions may affect spacing patterns in C. biseriata. Many mantid species inhabit tree trunk surfaces, but little is known about how they interact with this type of habitat.
Behavioural observations and choice tests investigated the effect of a conspecific on habitat utilisation. Field surveys were
used to investigate patterns of movement in the field. The decision to inhabit a tree trunk may be affected by the presence
of a conspecific. Whereas adult males seek out females when selecting habitat, females will actively avoid males. Habitat
choice decisions are primarily based on aspects of their mating system rather than on competition for space or food resources.
The behavioural interactions of C. biseriata are described, including novel observations of same-sex mating behaviour in adult males. 相似文献
683.
Six acapsular strains ofCryptococcus neoformans obtained by chemical mutagenesis failed to produce a capsulein vivo and were avirulent in mice following high dose intramuscular, intraperitoneal or intravenous inoculation. Peritoneal granulomas were observed in all animals inoculated with the acapsular mutants. These granulomas were characterized by a large central mass consisting of intact, degenerating and necrotic yeast cells. This was surrounded by concentric layers of a broad band of histiocytes, a narrow band of fibroblasts, and around the periphery, a mass of lymphocytes and plasma cells. These isolates did not revert to an encapsulated or virulent state after more than a year of subculturing or 18 passages through mice. 相似文献
684.
685.
In Escherichia coli, two enzymes catalyze the synthesis of methionine from homocysteine using methyltetrahydrofolate as the donor of the required methyl group: cobalamin-dependent and cobalamin-independent methionine synthases. Comparison of the mechanisms of these two enzymes offers the opportunity to examine two different solutions to the same chemical problem. We initiated the research described here to determine whether the two enzymes were evolutionarily related by comparing the deduced amino acid sequences of the two proteins. We have determined the nucleotide sequence for the metE gene, encoding the cobalamin-independent methionine synthase. Our results reveal an absence of similarity between the deduced amino acid sequences of the cobalamin-dependent and cobalamin-independent proteins and suggest that the two have arisen by convergent evolution. We have developed a rapid one-step purification of the recombinant cobalamin-independent methionine synthase (MetE) that yields homogeneous protein in high yield for mechanistic and structural studies. In the course of these studies, we identified a highly reactive thiol in MetE that is alkylated by chloromethyl ketones and by iodoacetamide. We demonstrated that alkylation of this residue, shown to be cysteine 726, results in complete loss of activity. While we are unable to deduce the role of cysteine 726 in catalysis at this time, the identification of this reactive residue suggests the possibility that this thiol functions as an intermediate methyl acceptor in catalysis, analogous to the role of cobalamin in the reaction catalyzed by the cobalamin-dependent enzyme. 相似文献
686.
Indomethacin inhibition of ovulation in the cow 总被引:1,自引:0,他引:1
Indomethacin or saline was administered via intramuscular, intrauterine or intraovarian routes to dairy cows, within 24 h after standing oestrus was first observed. The incidence of ovulation was determined at slaughter. All of the saline-treated cows (18/18) ovulated. Ovulation was not blocked after intramuscular injection (0/6) or intrauterine infusion (0/6) of indomethacin. In all cows, ovulation was blocked after intraovarian injection (6/6) of indomethacin. These findings add support to the hypothesis that prostaglandins play an essential role in ovulation in the cow as in many other mammalian species. 相似文献
687.
Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells 总被引:10,自引:0,他引:10
The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M. 相似文献
688.
Structural difference of the insulin receptors from circulating monocytes and erythrocytes 总被引:1,自引:0,他引:1
A McElduff R J Comi G Grunberger 《Biochemical and biophysical research communications》1985,133(3):1175-1180
We compared insulin receptors obtained from cells widely used in human studies, the circulating monocytes and erythrocytes. Biochemically, these receptors possess both binding (alpha-subunit) and tyrosine kinase (beta-subunit) activities similar to insulin receptors from other sources. Subtle differences in molecular weight, however, were detected between the alpha-subunits of these two cell types when analyzed by NaDodSO4-PAGE. Crosslinked [125I]insulin-labeled alpha-subunit of the monocyte insulin receptor was of higher apparent molecular weight than the alpha-subunit derived from red cells. Neuraminidase treatment of the alpha-subunits from each cell type indicated more sialic acid residues were present on the monocyte than the red cell alpha-subunit. The structural properties of the insulin receptors of human circulating cells are similar but not identical to insulin receptors of other characterized systems. 相似文献
689.
J. T. BONNER T. A. DAVIDOWSKI W.-L. HSU D. A. LAPEYROLERIE H. L. B. SUTHERS 《Differentiation; research in biological diversity》1982,21(1-3):123-126
A key environmental factor in inducing final fruiting body differentiation in the migrating slugs of cellular slime molds is loss of contact with a surface film of water. If the slug tip reaches above the water film, fruiting tends to occur, but if it stays in contact with the surface water, continued migration is favored. Light is effective in promoting fruiting only if the phototactic slugs orient away from surface (as with overhead light) and therefore, only indirectly affects differentiation. 相似文献
690.
The rat and rabbit transport IgA from blood to bile by a highly efficient transcellular pathway mediated by secretory component (SC). Other mammals do not express SC on liver hepatocytes, but they do transport a small amount of IgA to bile. In the first part of this study, human polymeric IgA was radiolabeled and depleted of SC binding activity by successive affinity adsorption. Transport of this preparation intact to rat bile was 4%, but was reduced to 2% when 50 mg unlabeled asialoglycoprotein was preadministered. The 2% decline corresponds to the percent of asialo-orosomucoid diverted to bile from the lysosomal pathway. In guinea-pigs, missorting of asialo-orosomucoid intact to bile was 10% of the injected dose. Transport of normal human IgA to bile was 1-2%, even though guinea-pigs do not express SC in the liver. Excess unlabeled asialofetuin reduced the transport of asialo-orosomucoid by 10-fold and IgA by 6-fold. This demonstrates that the asialoglycoprotein receptor can mediate transport of IgA to bile in small amounts, but that this transport may be only a biological artifact resulting from limited fidelity of intracellular protein sorting. 相似文献