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Biomedical subjects

S Bhattacharya

Publications and source records attributed to S Bhattacharya.

At least 541 records · Page 30Linked to original sources
PubMed1982

Influence of gonadotropins and gonadal hormones on climbing perch thyroid nucleic acids.

Climbing perch thyroidal RNA content fluctuated in different phases of the reproductive cycle, highest at spawning (36.08 +/- 3.69 micrograms/mg tissue) and lowest at postspawning (6.88 +/- 0.76 microgram/mg tissue) whereas DNA remained unaltered. Treatment of intact perch with salmon gonadotropin (SG-G100) or ovine LH for 15 days significantly stimulated thyroidal RNA content. Stimulatory effect of SG-G100 was greater (p less than 0.001) than LH (p less than 0.005). FSH had no such effect. Gonadotropin (GtH) treatment could not alter thyroidal DNA. Ovarian steroids, 17 beta-estradiol (E2) and estrone (E1) remarkably elicited RNA content. Ovariectomy of perch caused striking depletion of RNA. Administration of GtH to ovariectomized perch had no effect on thyroid RNA but E1 and E2 supplementation resulted in significant stimulation in comparison to ovariectomized control. Findings indicate that GtH mediated its stimulatory effect on perch thyroidal RNA via the release of ovarian steroids.

Animals↗
PubMed1981

ATP requirement for in vitro DNA synthesis in permeable cells of Bacillus brevis.

DNA synthesis in permeable cells of Bacillus brevis is almost completely dependent on the presence of ATP. Nevertheless, DNA synthesis in this system reflects primarily DNA repair rather than replication, as shown by the response to replication inhibitors, density shift experiments, and product size analysis. The apparent dependence of DNA synthesis on ATP was due to the stabilization of the deoxyribonucleoside triphosphate pools against degradation. These observations indicate that dependence of DNA synthesis on ATP is not a sufficient criterion for semiconservative DNA replication.

Adenosine Triphosphate↗
PubMed1981

Inhibition of deoxyribonucleic acid replication in Bacillus brevis by ribonucleic acid polymerase inhibitors.

The incorporation of [3H]thymidine into deoxyribonucleic acid by exponentially growing cells of Bacillus brevis was inhibited by streptolydigin and rifampin in the same concentration range in which these drugs inhibit ribonucleic acid synthesis. Complete inhibition occurred within one-third generation time after drug addition, suggesting an effect on deoxyribonucleic acid chain elongation.

Aminoglycosides↗
PubMed1981

The content of apolipoprotein B in chylomicron particles.

The number of particles and the mass of apoprotein B were measured in samples of rat lymph chylomicrons in order to assign the mass of apoprotein B per particle. Chylomicron numbers were estimated by electron microscopy after negative staining with 2% potassium phosphotungstate at pH 4.8. The distribution of particle numbers was plotted against particle volume. An exponential relationship was found. Integration of the function gave an estimate of the total number of particles for the total chylomicron volume, which was calculated from the chemical composition and the partial specific volumes of the constituents. Apoprotein B was measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two procedures were employed to allow for the influence of artefactual flattening of the chylomicrons on the electron microscope grid. First, it was reasoned that the flattening artefact would be greatest for the largest particles, so measurements of subfractions of smaller chylomicrons would be less affected by flattening. The mass of apoprotein B per particle was 0.48 x 10(6) daltons in the smallest subfraction. Second, a correction was applied such that the apparent volume of the oblate spheroid produced by flattening was converted to the true volume of the native spherical particle. The flattening artefact increased exponentially with particle size and was an inverse power function of the surface tension. At an assumed value of chylomicron surface tension of 2 mN/m, the apoprotein B per particle was 0.47 x 10(6) daltons.

Animals↗
PubMed1980

Noncoordinate control of the synthesis of different species of RNA in Escherichia coli K12 during uridine starvation.

During uridine starvation in Escherichia coli K12, the rate of RNA accumulation comes down to about 7% of the nonstarved rate. This is achieved, in part, by an eight-fold increase in the assembly time of stable RNA molecules. However, the assembly time of mRNA molecules is not enhanced as much, being longer by a factor of 3 in starved cells compared to nonstarved ones. It, therefore, appears that the rate of synthesis of these two RNA species is noncoordinately controlled during uridine starvation. This control does not seem to be mediated by guanosine tetraphosphate.

Escherichia coli↗