Insulin secretion from a continuously subcultivable isolate derived from foetal bovine pancreata beta cells. I. Monolayer cultures.

Monolayer cultures have been derived from bovine embryonic pancreatic cells grown in medium CMRL-1969 supplemented with foetal calf serum. The isolate has been subcultivated up to 10 population doublings. Insulin secretion from the cells into the culture medium declined with increasing passages. Of several insulin secretagogues, glucagon was found to be effective in potentiating insulin release from the cultivated cells into the medium. Insulin secretion rose to approximately 600 μU/culture/day in the presence of glucagon as compared to an average of 10 μU/culture/day in the control. This may be the first demonstration of a beta cell line developed from bovine embryonic pancreas.     

Studies of adult amphibian heart cells in Vitro: DNA synthesis and mitosis

The ventricle of the adult newt heart was excised and cut into several pieces of approximately 0.5 – 1.0 mm. These heart pieces were then cultured for 60 days at 25 °C in a modified Leibovitz medium (L-15). Approximately 37% of the explants were attached to the substrate and more than 33% of the attached explants and approximately 15% of the unattached explants established pulsation rates which ranged 3–67 beats/min. The explants were labeled with 1 μCi/ml of ³H-thymidine for 24 hr at 7, 15, 21, 30, 45 and 60 days of culture initiation, and processed for electron microscopic autoradiography. The examination of the autoradiograms revealed that as the culture continued, the cardiac muscle cells altered their morphology, resembling embryonic cardiac muscle cells. These altered muscle cells were termed dedifferentiated cardiac muscle cells. The number of these dedifferentiated cells increased over the period of culture, showing 10.3–94% dedifferentiated cells after 7–60 days of culture respectively. DNA synthesis and mitosis were observed in the dedifferentiated cardiac muscle cells, apart from the non-muscle cells. The quantitation of the autoradiograms revealed that the number of labeled nuclei in the cardiac muscle cells gradually increased over the period of culture, and a maximum number of labeled cardiac muscle cells (30%) was observed in the third week. The peak was followed by a decline in the eighth week which exhibited 1.5 % labeled cardiac muscle cells. The trend of mitosis was similar to that of DNA synthesis. The maximum number of mitotic figures (9%) was observed in the third week of culture, which was followed by a decline and finally absent in the eighth week. The cardiac non-muscle cells, mostly fibroblasts and endothelial cells, also showed incorporation of ³H-thymidine in their nuclei. The number of labeled non-muscle cells nuclei and the mitotic index were highest (61 and 15% respectively) in the first week of culture, but then they decreased gradually over the eight-week period in culture. This study provides evidence for the first time that the adult amphibian cardiac myocytes can undergo DNA synthesis and mitosis when explanted and cultured. The significance of this cell replication is discussed.     

Catechol and phenol degradation by a methanogenic population of bacteria

An anaerobic population of bacteria became acclimated to catechol and phenol in 32 and 18 days, respectively. Evidence from carbon balance measurements indicates that the aromatic ring is cleaved and that the products are stoichiometrically fermentable to methane and carbon dioxide.     

Effects of sodium tungstate on the nuclear uptake of glucocorticoid-receptor complex from rat liver

Effects of sodium tungstate on the nuclear uptake of rat liver cytosolic glucocorticoidreceptor complex were examined at pH 7. The nuclear uptake of heat-activated [³H]triamcinolone acetonide-receptor complex was blocked completely in the presence of 1 mm tungstate. A preincubation of nuclear preparation with tungstate (>0.1 mm) blocked the subsequent uptake of [³H]triamcinolone acetonide-receptor complex. When the tungstate-treated nuclear preparation was washed with 0.3 M KCl, its [³H]triamcinolone acetonide-receptor complex binding capacity recovered to 50% of that of control samples with no tungstate treatment. A preincubation of chromatin with tungstate yielded similar results. The nuclear-bound [³H]triamcinolone acetonide-receptor complex, formed either by an in vivo administration of [³H]triamcinolone acetonide or by an in vitro incubation of glucocorticoid-receptor complex with isolated nuclei, was extracted by tungstate in a concentration-dependent manner. The majority of nuclear-bound [³H]triamcinolone acetonide could be extracted with 0.1 and 1 mm tungstate from in vitro- and in vivo-labeled nuclei, respectively. The tungstate-extracted steroid-receptor complexes sedimented in 4–5 S and 3.3–3.5 S region in 10 mm KCl- and 0.3 mm KCl-containing sucrose gradients, respectively. Tungstate treatment caused an irreversible loss of the nuclear binding capacity of [³H]triamcinolone acetonide-receptor complex which could not be recovered after dialysis. These studies indicate that tungstate affects both glucocorticoidreceptor complex and certain nuclear or chromatin proteins.     

Immunosuppressive properties of leukotriene D4 and E4 in vitro

Leukotrienes D₄ and E₄ whose physiological function has been associated with smooth muscle contraction, are demonstrated to be potent suppressors of immunocompetent cell function. In concentrations as low as 10^?12 M both leukotriene D₄ and E₄ can inhibit mitogen-induced lymphocyte transformation. Higher concentrations of leukotrienes E₄ and D₄ will inhibit appearance of antibody-forming cells in tissue culture. These data suggest another role for the leukotrienes in addition to their function as slow-reacting substances.     

Enzymes involved in protein transmission by the intestine of the newborn lamb

Summary The intestine of lambs killed immediately after birth and at intervals after the first feed was studied by electron microscope cytochemistry. Ferritin, incorporated into this feed, was found within 2 h of feeding within vesicles throughout the cytoplasm of enterocytes lining the proximal and mid-intestine. Some of these vesicles had fused with the lateral and basal membranes of the enterocytes. Histochemical reaction products for alkaline phosphatase and a series of lysosomal enzymes were localized within the vesicles; the distribution of acid hydrolases, however, was not uniform within each cell. Biochemical estimations of the activity of these enzymes showed greatest activity in the distal intestine of the newborn lamb. The activity of only one of these enzymes,N-acetyl--glucosaminidase, was maximal in the mid-intestine.These observations indicate that cytoplasmic vesicles, translocating proteins across the enterocyte, probably carry intestinal alkaline phosphatase activity in their limiting membrane. Lysosomal enzymes, particularly glucosaminidase, are introduced into these vesicles as they traverse the enterocytes of the mid-intestine. A less specialized complement of lysosomal enzymes is probably introduced into vesicles in the distal intestine where ingested protein may be digested, rather than transported across the cell.