Activity of growth hormone peptides bGH 96-133 and hGH 95-133 in 3T3-F442A cells.

Chemically synthesized bovine growth hormone (bGH) bGH 96-133 and its human homologue, hGH 95-133, have similar in vitro biological activities. Unlike native GH, bGH 96-133 and hGH 95-133 were completely without adipogenic or anti-insulin activity at doses up to 10 microM. bGH 96-133 had insulin-like activity, with a 100% increase in glucose uptake at 10 microM.

Cytotoxicity of crotoxin on murine erythroleukemia cells in vitro.

The cytotoxic effect of crotoxin, a heterodimeric phospholipase A2 from the venom of Crotalus durissus terrificus, was examined on murine erythroleukemia cells in vitro. Crotoxin cytocidal effect on cell growth had an EC50 of approximately 0.1-0.

Growth hormone and fibronectin expression in 3T3 preadipose cells.

In the present study we focused on the relationship between GH action and the extracellular matrix in 3T3-F442A preadipose cells. Results from Northern blotting indicated that in serum-free medium, the presence of 2 nM met-human GH down-regulated levels of fibronectin messenger RNA by approximately 40, 60, and 70% as compared with control levels on days 1, 2, and 4, respectively. GH-dependent reduction of levels of collagen alpha 1(I) mRNA expression occurred later and was less pronounced than effects on levels of fibronectin mRNA, suggesting a specificity in the matrix-altering function of GH.

Up-regulation of vinculin expression in 3T3 preadipose cells by growth hormone.

In an effort to define biochemical events relevant to the adipogenic action of GH, the effect of GH on expression of the cytoskeletal element vinculin was studied in 3T3-F442A preadipose cells. Results from Western blotting indicated that in serum-free medium 2 nM met-hGH induced an approximately 100% increase in vinculin expression relative to that in cells maintained in serum-free medium alone. GH-elicited alterations in vinculin expression were dose dependent.

Growth hormone and adipose differentiation: growth hormone-induced antimitogenic state in 3T3-F442A preadipose cells.

An additional activity for pituitary growth hormone is described--i.e., the in vitro induction of an antimitogenic state in murine 3T3-F442A preadipocyte fibroblasts.

Antagonism by growth hormone of insulin-sensitive hexose transport in 3T3-F442A adipocytes.

We have studied the effects of GH on basal and insulin-stimulated hexose transport by 3T3-F442A adipocytes in a hormonally defined serum-free medium. Adipocytes preincubated in defined medium exhibit a low level of hexose transport which is acutely (15 min) stimulated (greater than 5-fold) by insulin (EC50, 0.1-0.

Growth hormone-dependent events in the adipose differentiation of 3T3-F442A fibroblasts: modulation of macromolecular synthesis.

GH is necessary but not sufficient to induce adipose differentiation of 3T3-F442A fibroblasts in serum-free medium. Human (h) GH (2 nM) treatment of 3T3-F442A cells in serum-free medium caused a time-dependent (maximal at 48-72 h) and dose-dependent (EC50, approximately 0.2 nM) decrease (40-60%) in de nova protein synthesis.

Growth hormone-induced alteration of morphology and tubulin expression in 3T3 preadipose cells.

Effects of growth hormone on morphology and cytoskeletal protein expression were examined in 3T3-F442A preadipocytes in serum-free medium. Between 2 and 5 days of culture 2 nM methionyl human growth hormone converted 3T3-F442A cells from a flat fibroblastic morphology to a rounded form with numerous membrane convolutions. Growth hormone treated cultures manifested a 30-40% reduction in cell volume.

Expression of growth hormone-independent adipogenesis by a 3T3 cell variant.

We have examined the regulation of adipogenesis of a 3T3-F442A cell variant. The variant, designated 3T3-GH-independent clone 16 (GI-16), was isolated after serum-induced adipogenic commitment. 3T3-GI-16 fibroblasts displayed a lower serum requirement for adipogenesis than the 3T3-F442A parent cell.

Role of insulin in growth hormone-stimulated 3T3 cell adipogenesis.

The role of insulin during GH-stimulated adipogenesis of 3T3-F442A fibroblasts was investigated. Adipogenesis in defined medium (DM), as quantified by the level of glycerol-3-phosphate dehydrogenase activity, revealed that there existed a strict requirement for both insulin and GH during adipogenesis. The concentration of insulin required to elicit half-maximal adipogenesis was approximately 20 nM.

Anti-fertility and other actions of gossypol analogues.

From a series of gossypol derivatives studied, we conclude that the carbonyl groups of gossypol are needed for inhibition of erythrocyte anion transport and the hydroxy groups affect but are not essential to that inhibition. In an in vitro mouse erythroleukemia cytocidal assay, the most active compounds were gossypol and apogossypol. The latter was not active in the inhibition of erythrocyte anion transport or in a spermicidal assay.

Murine erythroleukemia cell variants: isolation of cells that have amplified the dihydrofolate reductase gene and retained the ability to be induced to differentiate.

A series of murine erythroleukemia cell (MELC) variants was generated by selection for the ability to grow in increasing concentrations of the folate antagonist methotrexate (MTX). Growth of the parental MELC strain DS-19 was completely inhibited by 0.1 microM MTX.

Antagonistic effect of butyrate on hexamethylene bisacetamide induced differentiation of murine erythroleukemia cells.

Butyrate, at concentrations greater than 0.75 mM, induces hemoglobin accumulation in murine erythroleukemia cells (MELC). At concentrations below 0.

Effect of gossypol on erythrocyte membrane function: specific inhibition of inorganic anion exchange and interaction with band 3.

The effects of gossypol on membrane functions of the human erythrocyte were studied. Gossypol (10 microM) had no effect on spontaneous hemolysis, osmotic fragility, cell volume, cholinesterase activity, hexose transport, ouabain-sensitive inorganic cation transport, ouabain-insensitive inorganic cation transport and nucleoside transport. Conversely, 10 microM gossypol inhibited inorganic anion transport by approximately 90% for three different substrates, i.

Cytocidal effect of gossypol on cultured murine erythroleukemia cells is prevented by serum protein.

The interaction of gossypol (G) with cultured murine erythroleukemia cells (MELC) was studied in vitro. G was cytocidal (inhibited growth greater than 90%) to MELC at greater than 10 microM, but not at less than 5 microM in medium supplemented with 10 and 15% fetal calf serum (FCS). Five micromolar of G was cytocidal in 2 and 5% FCS.

Transport of the folate compound methotrexate decreases during differentiation of murine erythroleukemia cells.

The relationship of folate transport and chemically induced differentiation of murine erythroleukemia cells (MELC) was examined. MELC were found to have a carrier-mediated transport system for reduced folates. Chemically induced differentiation of MELC caused a 10-fold decrease in the rate of influx of the folate analog methotrexate.

Binding and degradation of 125I-labeled insulin by a clonal line of rat pituitary tumor cells.

Receptor sites for insulin on GH3 cells were characterized. Uptake of 125I-labeled insulin by the cells was dependent upon time and temperature, with apparent steady-states reached by 120, 20 and 10 min at 4, 23 and 37 degrees C, respectively. The binding sites were sensitive to trypsin, suggesting that the receptors contain protein.

Insulin binding to liver plasma membranes from rats rendered diabetic by alloxan. A kinetic demonstration of two classes of binding sites in equilibrium with each other.

The association of 125I-labelled insulin with liver plasma membranes from diabetic rats was consistent with more than one compartment of binding. After a short association period, insulin dissociation comprised rapid and slow phases. After a long association period, dissociation was only at a slow rate.

Insulin receptors convert to a higher affinity state subsequent to hormone binding. A two-state model for the insulin receptor.

Kinetic experiments were performed to determine the effects of insulin receptor occupancy on insulin binding. The following results were obtained: (a) the rate constant (k1) for uptake of 125I-insulin by liver plasma membranes was 2 X 10(6) M-1 s-1 and invariant at applied hormone concentrations of 7.5 to 100 X 10(-11) M.

Up-regulation of insulin receptors in rat liver plasma membranes.

Kinetic experiments (uptake versus time) were utilized to examine the effects of occupancy on insulin receptor availability in rat liver plasma membranes in vitro. The following observations were made: 1) at 4 degrees C, a 3-h exposure of membranes to 100 nM native insulin, followed by removal of unbound hormone, resulted in a subsequent decrease of 125I-insulin binding at 4 degrees C. In a similar experiment at 23 degrees C, no decrease of 125I-insulin binding was observed.

Distribution of superoxide dismutase, catalase, and peroxidase activities among Treponema pallidum and other spirochetes.

Representative members of Spirochaetales were surveyed for their content of superoxide dismutase (SOD), catalase, and peroxidase activities. Only Leptospira exhibited peroxidase activity. Obligately anaerobic cultivable Treponema and Spirochaeta possessed no SOD or peroxidative capabilities.

Formation of a receptor state from which insulin dissociates slowly in hepatic cells and plasma membranes.

125I-insulin dissociated from rat hepatocytes and liver plasma membranes with a time course suggestive of more than a single kinetic process. Dissociation curves were resolved into rapidly and slowly dissociating components. Increasing times of hormone-cell or hormone-membrane incubation prior to the initiation of dissociation increased the proportion of slowly dissociable 125I-insulin and decreased the proportion of rapidly dissociating hormone.