PubMed · 5900740
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R J Furie. 1966. Urine specific gravity and renal function.. https://pubmed.ncbi.nlm.nih.gov/5900740/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Vacuolar-type H(+)-ATPases (V-ATPases) are ubiquitous in eukaryote endomembranes, where they are responsible for lumenal acidification. The ratios of H+ translocated per ATP hydrolyzed (which may be important in controlling the activity of these pumps) have previously been found to be variable, noninteger and sensitive to cytosolic as well as lumenal pH. The mechanistic implications of these findings are explored here with reaction kinetics. Experimental data for this analysis comprise supra- and superlinear V-ATPase current-voltage relationships, isolated as bafilomycin-sensitive currents in vacuolar membranes from Beta using the "whole vacuole" patch clamp configuration. Whereas simple models with one reaction cycle fail to provide an adequate description of the data (mainly because of a weak sensitivity of the zero-current voltage to the transmembrane pH gradient), a model with two linked reaction loops allowing partial coupling of H+ translocation to ATP hydrolysis does provide good descriptions. All experimental data obtained with the same vacuolar pH (4.3) could be reduced to a model with eleven independent parameters. Best fits have been obtained on the basis of a binding domain possessing 3 H+ binding sites per ATP hydrolyzed and a net charge of -2 when unoccupied. The enzyme could reorientate its access site between the vacuolar and cytoplasmic side when zero, one or three H+ are bound.
It was recently demonstrated that endo-N-acetyl-beta-D-glucosaminidases (ENGase) acting on N-glycosylproteins are produced by myxobacteria. In this study, it was shown that the secretion of ENGase during vegetative growth of Myxococcus xanthus was cell-density-dependent. The activity produced per cell increased up to 6 x 10(8) cells/ml and stabilized thereafter (maximum level). Two of the developmental mutants used in this study (bsgA and csgA) were locked for ENGase secretion into the maximum level regardless of cell density. To explain the pattern of ENGase secretion, we postulated the presence of a molecule that induces the enzyme until it reaches a proper concentration threshold. Although the chemical structure of this cell density signal was not determined during this study, its occurrence during vegetative growth of M. xanthus was strongly suggested by the results.
Isoprinosine (IPS) is a synthetic drug whose antiviral effect on rotavirus replication in vitro has been characterized in terms of the decrease in metachromasia after acridine orange staining. The present study describes the effect of IPS on the synthesis of viral RNA in vitro. MA-104 cell cultures infected with simian rotavirus strain SA-11 were incubated with zero, 250, 500 and 1,000 micrograms/ml IPS and 22, 24, 48, 52, 72 and 76 h after infection the cultures were submitted to a 1-h starvation period, followed by a 2-h pulse with 10 microCi/ml of [3H]-uridine. The homogenates of virus-infected cultures treated or not with IPS were submitted to phenol/chloroform extraction followed by polyacrylamide gel electrophoresis. The amount of radioactivity in viral RNA eluted from the gel strips was determined. Inhibition of viral RNA synthesis was highest at the IPS concentration of 1,000 micrograms/ml at 72 h after infection, corresponding to 78% inhibition. Although the results obtained in vitro suggest that IPS may be useful for the treatment of rotavirus infection, an in vivo demonstration of its efficacy is needed.