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Biomedical subjects

H Rubin

Publications and source records attributed to H Rubin.

At least 253 records · Page 14Linked to original sources
PubMed1971

Temperature-dependent alterations in sugar transport in cells infected by a temperature-sensitive mutant of Rous sarcoma virus.

Cells transformed by Rous sarcoma virus take up 2-deoxyglucose at a faster rate than uninfected cells, under conditions where transformed and nontransformed cells grow at the same rate. In cells infected by a temperature-sensitive mutant, the stimulation of 2-deoxyglucose uptake is temperature dependent: the increase is observed at the permissive (36 degrees C), but not at the nonpermissive (41.5 degrees ) temperature. When infected cells are shifted from the nonpermissive temperature to the premissive temperature, the uptake of 2-deoxyglucose increases from a rate equal to that of uninfected cells to a rate equal to that of cells infected by the wild-type Schmidt-Ruppin Rous sarcoma virus. The reverse change occurs when the infected cells are shifted from the permissive to the nonpermissive temperature. By the use of cytosine arabinoside, an inhibitor of DNA synthesis, it was possible to show that DNA synthesis is neither required for the transformation, which occurs when the infected cells are shifted from the nonpermissive to the permissive temperature, nor for the phenotypic reversion, which occurs in the reverse shift.

Animals↗
PubMed1971

Stimulation of glucose transport in cultures of density-inhibited chick embryo cells.

The rate of glucose transport in sparse, rapidly growing chick-embryo fibroblasts is much greater than that in density-inhibited cells. The addition of fresh chicken serum or trypsin to the medium of density-inhibited cells causes a large increase in the rate of glucose transport that is detectable 15 min after addition. The increase in glucose transport precedes the increase in DNA synthesis by 5-6 hr. Only small changes in rates of transport are seen with nucleosides or a nonmetabolizable amino acid. The increase in glucose transport requires protein synthesis but not RNA or DNA synthesis.

Aminoisobutyric Acids↗
PubMed1971

pH and population density in the regulation of animal cell multiplication.

Sparse and dense cultures of chick embryo cells were affected differently by pH. The rates of cell multiplication and of thymidine-(3)H incorporation into DNA of dense cultures were increased as the pH was increased from 6.6 to 7.6. At pH higher than 7.6 the rate of multiplication decreased slightly in the dense cultures, but the rate of thymidine-(3)H incorporation continued to increase. The discrepancy was due in part to cell death and detachment at very high pH, and in part to a more rapid uptake of thymidine-(3)H at very high pH. Sparse cultures were much less sensitive to pH reduction and, when a suitably conditioned medium was used to minimize cell damage, very sparse cultures grew almost as well at pH 6.7 as at higher pH. The rates of cell multiplication and thymidine-(3)H incorporation at low pH decreased in the initially sparse cultures before they reached confluent cell densities. There was no microscope evidence of direct contact between plasma membranes of cells at these densities although the parallel orientation indicated that the cells were influencing locally each other's behavior. Even at much higher cell densities, electron microscopy revealed large intercellular gaps partly filled with a fragmentary electron-opaque material suspected to be glycoprotein. Wounding experiments showed that pH affected cell migration in a manner similar to its effects on cell multiplication. Low pH inhibited cell migration, but those cells which migrated into the denuded region multiplied as rapidly at low pH as at high pH. The effects of pH on growth were correlated with effects on the uptake of 2-deoxyglucose-(3)H. Dense populations of cells inhibited by low pH were stimulated to incorporate thymidine-(3)H by the addition of small amounts of diethylaminoethyl-dextran. Rous sarcoma cells at high cell density were less sensitive to pH than were normal cells at the same density, but were more sensitive than sparse normal cultures. The results suggest that cell growth is inhibited through the combined effects of both lowered pH and high cell density on cell surface permeability.

Animals↗
PubMed1970

Overgrowth stimulating factor released from Rous sarcoma cells.

An assay is described for a nonzviral factor from the medium of Rous sarcoma cells which stimulates rapid and sustained cellular overgrawth in crowded chick embryo cultures. The factor is nondialyzable and thermnolabile and is released in large amounts several days after the first visible transformation of newly infected chick embryo cells.

Animals↗
PubMed1970

Overgrowth-stimulating activity of disrupted chick embryo cells and cells infected with Rous sarcoma virus.

Sonically disrupted chick embryo cells markedly stimulate DNA synthesis and cell multiplication when added to the medium of population density-inhibited cultures of such cells, but have little effect on the growth rate of sparse cultures. Sonicates from density-inhibited chick embryo cultures have as much overgrowth-stimulating activity as do sonicates from actively growing cells. Sonicates from cells infected with Rous sarcoma virus show markedly increased overgrowth-stimulating activity 4 days after infection. The activity in Rous-cell sonicates falls back to near normal amounts at 6 days concurrently with the appearance of a high content of overgrowth-stimulating activity in the medium. The active material is nondialyzable. It seems that growth-inhibited cells contain material in a sequestered location which, when released, can stimulate rapid growth in similarly inhibited cells.

Animals↗