Proteins made in the mammalian cell cycle.
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Biomedical subjects
T O Fox
Publications and source records attributed to T O Fox.
Cyclic membrane changes in animal cells: transformed cells permanently display a surface architecture detected in normal cells only during mitosis.
A membrane site exposed only during mitosis in normal 3T3 cells, but exposed in all polyomavirus transformed 3T3 (Py3T3) cells, has been detected The site was identified by the specific binding of a wheat-germ agglutinin conjugated with fluorescein isothiocyanate. The receptor site has been studied previously. It binds wheat-germ agglutinin, causing the selective agglutination of Py3T3 cells, but not normal 3T3 cells. A short treatment with low concentrations of trypsin exposes cryptic sites in 3T3 cell membranes; this permits agglutination of these cells. The experiments reported here indicate that these sites normally are exposed during a brief period of the cell cycle for 3T3 cells. Specific hapten inhibitors of agglutination also inhibit the binding of the conjugated agglutinin and prevent fluorescence.
Animals↗
Relationship between virus-induced cellular deoxyribonucleic acid synthesis and transformation by simian virus 40.
The fraction of cells in a confluent 3T3 cell monolayer induced by simian virus 40 infection to replicate deoxyribonucleic acid and divide corresponds to those cells which eventually become transformed. Virus-induced cells were partially separated from noninduced cells by sedimentation through Ficoll gradients. Three- to eightfold higher transformation frequencies were obtained with those cells that began to synthesize cellular deoxyribonucleic acid and divide shortly after simian virus 40 infection as compared to noninduced cells.
Cell Division↗
Animal cells: noncorrelation of length of G1 phase with size after mitosis.
The interval between mitosis and initiation of DNA synthesis (G(1)) varied over a fourfold range for Chinese hamster ovary cells, an established line. This was not because of size differences. Synchlronous cells of different sizes began DNA synthesis at similar times after mitosis. A novel technique of centrifugation for separating cells according to size is described.
Animals↗
Studies on the role of catecholamines in the regulation of the developmental pattern of hypothalamic aromatase.
Experiments were conducted to study the regulation of the developmental pattern of aromatase in the forebrain of the perinatal rat. Two experimental designs were used: aromatase measured in primary cultures of fetal hypothalamic cells and in cell-free preparations of forebrain tissue excised at varying ages. In cultured cells, aromatase decreased logarithmically at a slow rate (t1/2 = 7.8 days). Norepinephrine caused a pronounced dose (4 x 10(-6) M) and time-dependent (2-6 days) drop in aromatase without affecting the levels of 5 alpha-reductase or substance P. In isolated tissue, aromatase activity was compared with the concentrations of norepinephrine and dopamine in the forebrain of males vs females at different perinatal ages and in discrete forebrain areas at postnatal day 4. In no case was a sex difference in catecholamines seen. An overall developmental decline in aromatase was associated with developmental increases in catecholamine levels. Acute treatment with the beta-agonist, isoproterenol, had no effect on brain aromatase activity.
Animals↗