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Biomedical subjects

W B Anderson

Publications and source records attributed to W B Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1982

Plasma membrane-associated component(s) that confer(s) cholera toxin sensitivity to adenylate cyclase.

Incubation of crude normal rat kidney membranes with activated cholera toxin in the presence of DTP, ATP and NAD results in a 10--20 fold stimulation of adenylate cyclase activity. Optimal choleragen activation f the cyclase is shown to be dependent upon the presence of a plasma membrane-associated reconstituting activity, which can be dissociated from the membranes by washing with 10 mM potassium phosphate buffer, pH 7.5, containing 5 mM EDTA and 0.1 mM dithiothreitol. choleragen-catalyzed ADP ribosylation of plasma membrane substrate proteins also requires the presence of reconstituting activity factor. Sephadex G-150 filtration of solubilized reconstituting activity shows a peak activity eluting in the region corresponding to a protein with a molecular weight of approx. 13,000. Reconstituting activity is eluted from DEAE-cellulose at a salt concentration of 40--100 mM KCl. This active factor is not destroyed by trypsin treatment or by boiling for 30 min. These observations indicate that an endogenous membrane-associated factor, along with GTP, may be involved in modulating the ability of choleragen to activate adenylate cyclase.

Adenosine Diphosphate Ribose↗
PubMed1982

The amount of a specific cellular protein (p53) is a correlate of differentiation in embryonal carcinoma cells.

A specific cellular protein of molecular weight of 53-55,000 (p53) has been shown to be induced in all SV40 transformed cells. A similar protein has also been shown to be present in embryonal carcinoma cells and in midgestation murine embryo primary cells, which are not infected by SV40. In embryo cell primaries the amount of the protein was shown to decrease with the increase in the stage of embryo development. As differentiation or decrease in cell growth rate can account for this, and since the growth rate of embryo primary cells cannot be measured, we chose to investigate various embryonal carcinoma cells. We report that the p53 is present in a pluripotent embryonal carcinoma cell OTT6050, and in its differentiated parietal endoderm derivative, PYS-2 cells. The amount of p53 is higher in the undifferentiated EC stem cells than in the differentiated PYS-2 (parietal endoderm) cells. The amount of the protein decreases in F9 embryonal carcinoma cells induced to differentiate to a parietal endoderm cell type by treatment with retinoic acid, as it does following spontaneous differentiation of OTT6050 EC cells. To determine if a change in growth rate, rather than differentiation, might account for the diminished levels of this protein, the amount of p53 was measured in growing and in growth arrested cell populations. When the growth rate of F9 cells was reduced by treatment with 8-bromocyclic AMP there was no change in the amount of p53. The half life of the p53 was compared in the undifferentiated and the differentiated cell types to determine if a change in stability might account, in part, for the altered levels of this protein. The p53 is found to be most stable in the SV40 transformed established clonal cells. It is less stable in the fibroblast clonal cells which were not transformed by SV40. The results of these experiments indicate that a decrease in the amount of p53 primarily correlates with differentiation in the embryonal carcinoma cell lines studied and not with cell growth rate. Furthermore, the decrease appears to be related (in part) to the decreased stability of the p53.

Animals↗
PubMed1982

Multiplication-stimulating activity stimulates the multiplication of F9 embryonal carcinoma cells.

The present study was designed to assess the effectiveness of multiplication-stimulating activity (MSA), an insulin-like growth factor, in supporting the growth of F9 cells (an embryonal carcinoma line with properties similar to embryonic stem cells). Under serum-free growth conditions in a medium supplemented with transferrin and fibronectin, MSA is an effective mitogen. At 100 ng/ml, MSA completely replaces the growth requirement for fetal calf serum. Biologically active MSA polypeptides II and III act as potent growth promoters of F9 cells, whereas MSA I appears to be somewhat less effective. Binding studies carried out with [125I]iodo-MSA indicate that F9 cells possess specific receptors for MSA. Scatchard analysis indicates a single class of MSA receptors with a Ka of 8.2 x 10(9) M-1; about 55,000 MSA molecules can bind per F9 cell. Insulin-like growth factor I and II both complete for MSA binding, whereas insulin does not compete. Since insulin is an effective promoter of F9 cell growth, these results indicate that the mitogenic action of insulin toward F9 cells is not mediated through MSA receptors. It is apparent from these results that MSA is capable of serving as an early embryonic growth factor.

Animals↗
PubMed1981

Gonadotropin stimulation of pregnenolone metabolism in Chinese hamster ovary cells in culture.

To determine if Chinese Hamster Ovary (CHO) cells in culture are able to metabolize steroids, CHO cells were incubated in defined medium with [14C]pregnenolone. As shown, [14C]pregnenolone is metabolized to progesterone and other delta 53 beta steroids; this steroidogenic response is appreciably enhanced upon exposure of the cells to 50 nM gonadotropins (human chorionic gonadotropin and follicle-stimulation hormone). The primary metabolites that accumulate in the medium upon treatment with gonadotropins are 16 alpha-hydroxy-pregnenolone and 16 alpha-17 beta-dihydroxydehydroepiandrosterone. Exposure of the CHO cells to gonadotropins induces significant increases in the activities of 16 alpha-hydroxylase, 17 alpha-hydroxylase, and 17-20 lyase. Similar results are obtained when the CHO cells are treated with 0.1 mM 8-bromocyclic AMP, indicating that the gonadotropin enhancement of steroid metabolism is a cyclic AMP-mediated process. CHO cells apparently lack the cholesterol desmolase complex since 14C-cholesterol is not utilized by these cells to produce other steroid metabolites. These results indicate that CHO cells offer an in vitro system for the study of certain aspects of gonadotropin stimulation of steroidogenesis.

3-Hydroxysteroid Dehydrogenases↗
PubMed1979

Enhancement of hormonal stimulation in intact cells. Potentiation of GTP-dependent activation of adenylate cyclase.

The ability of prostaglandin E1 (PGE1) and cholera toxin to increase cyclic AMP levels is potentiated 6-fold when normal rat kidney (NRK) cells are treated with picolinic acid or histidinol, or grown in isoleucine-deficient medium. The response to (-)-isoproterenol is increased 2-fold in NRK cells treated with picolinic acid but not in cells subjected to isoleucine deprivation. The increase in agonist responsiveness is time-dependent, reaches its maximum at 40 h, and is quickly reversed following removal of picolinic acid or addition of medium with normal amounts of isoleucine. The cholera toxin response is also increased about 7-fold in simian virus 40-transformed NRK cells and Moloney sarcoma virus-transformed NRK cells treated with picolinic acid. GTP-stimulated, but not fluoride-stimulated, adenylate cyclase activities are increased in membranes from NRK cells treated with picolinic acid or starved for isoleucine, indicating that the increased response is due, at least in part, to a specific potentiation of GTP-dependent functions of the adenylate cyclase system. The results demonstrate that GTP-dependent events in hormonal stimulation of adenylate cyclase can be altered in intact cells to modulate hormonal enhancement of cyclic AMP production.

Adenylyl Cyclases↗