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Biomedical subjects

D S Pradhan

Publications and source records attributed to D S Pradhan.

At least 55 records · Page 3Linked to original sources
PubMed1976

RNA synthesis in Yoshida ascites tumor cells after ultraviolet and gamma irradiation.

The residual RNA synthesis in Yoshida ascites tumor cells following exposure to ultraviolet radiation was insensitive to rifampicin AF/013, an inhibitor of initiation of RNA synthesis in eukaryotic cells. On the other hand, residual RNA synthesis in the ascites tumor cells after gamma-irradiation was inhibited by rifampicin AF/013. In vitro synthesis of RNA on ultraviolet-irradiated ascites chromatin likewise was resistant to rifampicin AF/013. Ultraviolet irradiation was found to decrease the number of RNA chain initiation sites on ascites chromatin considerably whereas the number of initiation sites on ascites chromatin increased considerably after gamma irradiation. These results indicate that ultraviolet irradiation may preferentially affect the DNA segments participating in initiation of RNA synthesis.

Animals↗
PubMed1976

Action of hydrocortisone at a translational level in the rat liver.

Administration of hydrocortisone to adrenalectomised rats elevated levels of both free and membrane-bound polysomes in liver and led to marked shifts in their sedimentation profiles in favour of heavier polysomes. The rate of nascent polypeptide formation was also found to be enhanced in response to the hormone but this effect was mainly confined to the site of free polysomes. These results suggest that besides its well-known potentiating action at the transcription level, the hormone elicits selective stimulatory response at the translation level.

Adrenalectomy↗
PubMed1976

Production and rejoining of single-strand breaks in DNA of Escherichia coli cells after exposure to gamma-rays in the presence of iodoacetic acid under oxic and anoxic conditions.

The presence of iodoacetic acid (IAA, 10(4) M) during exposure of Escherichia coli cells to 25 krad gamma-radiation under anoxia resulted in a greater number of radiation-induced single-strand scissions in DNA. The single-strand breaks produced under oxic conditions of irradiation, however, were only marginally increased when IAA was present during irradiation. Although cells irradiated under anoxic or oxic condition and those irradiated under anoxic condition in the presence of IAA were capable of rejoining single-strand breaks produced in DNA, those irradiated under oxic condition in the presence of IAA had lost this capacity.

DNA Repair↗
PubMed1976

Mechanisms underlying decreased protein and RNA synthesis in the rat spleen following whole-body X-irradiation.

Whole-body exposure of rats to 1000 R X-rays resulted in decreased rates in protein and RNA syntheses in the spleen from the fourth post-irradiation hour. These changes correspond well with impaired ability of nuclei to polymerise RNA, reduction in template efficiency of chromatin, decrease in the activity of RNA polymerase and inhibition in histone phosphorylation. Protection of the spleen by lead shielding during whole-body exposure to X-rays largely eliminated the observed alterations in protein and nucleic acid synthetic machineries. This suggests that the radiation-induced inhibition in protein and RNA syntheses is mainly due to the direct action of radiation on the spleen itself.

Animals↗
PubMed1975

Ineffectiveness of rifampicin in inhibiting RNA synthesis in Escherichia coli and T(4)-infected Escherichia coli cells after exposure to ultraviolet radiation.

Resdiual RNA synthesis in Escherichia coli cells and T(4)-infected E. coli cells exposed to ultraviolet radiation is insensitive to rifampicin. On the other hand, residual RNA synthesis in these cells after gamma irradiation is further inhibited by rifampicin. The specific effect exerted by ultraviolet irradiation on transcription seems to arise from alterations in the DNA structure rather than in bacterial RNA polymerase since RNA synthesis in ultraviolet-irradiated E. coli cells infected with unirradiated T(4) is sensitive to rifampicin.

Coliphages↗
PubMed1975

Effect of procaine hydrochloride on DNA repair in Escherichia coli.

Liquid-holding recovery and rejoining of gamma-radiation-induced DNA single-strand scissions in Escherichia coli could be effectively inhibited by procaine hydrochloride at the concentration of 20 mM. At this concentration, the drug also reversibly altered cellular permeability barrier as evidenced from the uptake of acriflavin by bacterial cells.

Acriflavine↗
PubMed1975

Effect of whole-body irradiation on transcription in the rat thymus.

Studies were carried out to elucidate the mechanism underlying the impairment in RNA synthesis in the rat thymus after whole-body exposure to X-rays (1000 rad). The ability of thymus nuclei to catalyse RNA polymerization in vitro was adversely affected in irradiated rats. Further experiments showed that whole-body irradiation caused a considerable decrease in both the activity of RNA polymerase and the template efficiency of chromatin but not in that of DNA isolated from chromatin. These radiation-induced changes in transcription seem to arise partly from the direct effect of radiation on the thymus itself and partly from the abscopal mechanism(s).

Animals↗