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Biomedical subjects

A Sreenivasan

Publications and source records attributed to A Sreenivasan.

At least 91 records · Page 5Linked to original sources
PubMed1966

Characterization of ribonucleases and ribonuclease inhibitor in subcellular fractions from rat adrenals.

1. The presence of two RNA-degrading enzymes, one with optimum activity at pH5.6 (acid ribonuclease) and the other with optimum activity at pH7.8 (alkaline ribonuclease), in rat adrenals has been demonstrated. The acid ribonuclease was localized in the mitochondrial fraction whereas the alkaline ribonuclease was present in mitochondria as well as in the supernatant fraction. Freezing and thawing of mitochondria and treatment with Triton X-100 gave a three- to four-fold increase in acid-ribonuclease activity, whereas the mitochondrial alkaline-ribonuclease activity was practically unaffected. 2. The amount of free ribonuclease in the adrenal supernatant was small. Treatment of the supernatant fraction with N-ethylmaleimide resulted in release of large amounts of ribonuclease activity, indicating the presence of a ribonuclease inhibitor having reactive thiol groups. 3. Considerable amounts of free ribonuclease inhibitor in excess over the bound alkaline ribonuclease are present in the rat-adrenal supernatant fraction. The inhibitor is heat-labile and non-diffusible. A 400-500-fold purification of the ribonuclease inhibitor was achieved by ammonium sulphate fractionation, treatment with calcium phosphate gel and DEAE-cellulose chromatography. It is concluded that the adrenal inhibitor is protein in nature, similar to the inhibitor present in rat liver.

Adrenal Glands↗
PubMed1966

The effect of carbon tetrachloride on the lipoproteins of rat-liver cell sap and serum.

1. The lipoproteins of the liver cell sap can be resolved by paper electrophoresis into five components. Almost two-thirds of the total lipid, cholesterol and phospholipid are present in the slowest- and the fastest-moving components. 2. There is a two- to three-fold increase in the lipid content of the liver cell sap after the administration of carbon tetrachloride. 3. The cholesterol and phospholipid contents of the serum alpha- and beta-lipoproteins separated by paper electrophoresis fall after treatment with carbon tetrachloride, whereas the total lipid content of that fraction that remains at the origin rises.

Animals↗
PubMed1965

The role of vitamin B12 in the metabolism of Euglena gracilis var. bacillaris.

1. The concentrations of RNA, DNA and protein are decreased in cells of Euglena gracilis var. bacillaris grown on suboptimum concentrations of vitamin B(12). 2. The addition of vitamin B(12) to deficient cells stimulates the incorporation of [(14)C]formate into the above cell components as well as into thymine of DNA and serine and methionine of protein. 3. In a cell-free system from vitamin B(12)-deficient cells, the incorporation of labelled formate into thymidylate is decreased to a greater extent with uridine than with deoxyuridine as the substrate. 4. The addition of unlabelled glutamate dilutes the radioactivity incorporated into thymine from labelled formate. 5. These results are interpreted to mean that, in DNA synthesis, vitamin B(12) has a greater role in the reduction of ribotides to deoxyribotides than in the reduction of formate to thymine methyl and that the vitamin B(12)-dependent conversion of glutamate into beta-methylaspartate also contributes to thymine synthesis.

Aspartic Acid↗