显微红外研究巨噬细胞膜电融合后膜蛋白二级结构的变化

首次尝试了将显微傅里叶变换红外光谱术应用于研究电融合后细胞膜蛋白质二级结构的变化,发现脉冲电场作用于细胞具有穿透效应,施加电脉冲后,整个细胞的蛋白质体系能量增加,表明电泳冲对蛋白的二结构影响很大;同时,还发现用唾液酸苷酶和蛋白酶Ｐｒｏｎａｓｅ分析处理巨噬细胞膜表面后,膜上蛋白质二级结构无序化程度增加,用酶适度处理的细胞将更易发生电融合。     

外显子和内含子的序列复杂性

引入了两个新的关于序列复杂性的测度,并以此为指标分析比较了结构基因序列中的外显子和内含子的复杂性差异。     

Oxidation of prostacyclin and its analogs by three 15-hydroxyprostaglandin dehydrogenases

A study of the oxidation of prostacyclin and some of its analogs by three 15-hydroxyprostaglandin dehydrogenases was undertaken to determine the structural features of these compounds which might influence their rate of enzymatic inactivation. The effect of some structural changes seemed to be determined by the substrate specificity of individual enzymes. Other changes influenced the rate of oxidation by all three enzymes similarily. Among this latter group it was noted that a 15S hydroxyl group is necessary for oxidation to occur and that steric changes in the carboxy side chain and structural changes in the epoxy ring have a greater effect on the affinity of the substrate for the enzyme than on its maximum rate of oxidation. Certain analogs of prostacyclin are not substrates for one or more of the enzymes tested. Of these, (5S)-9-deoxy-5,9 alpha-epoxy-PGF1 and its methyl ester are potent inhibitors of only the placental enzyme---an interesting case of apparent selective metabolic regulation.     

Adriamycin effects on transplasma membrane redox functions in porcine neutrophils

Transplasma membrane electron transport, as assayed by external ferricyanide reduction, has been related to control of growth and hormone response of cells. Elicitor-stimulated transmembrane NADPH oxidase is important for bacteriocidal superoxide production by neutrophils. Since adriamycin is myelosuppressive and can stimulate superoxide production, its effects on the two redox systems of porcine neutrophil plasma membranes were compared. Adriamycin inhibits transplasma membrane ferricyanide and stimulates superoxide production activated by phorbol myristate acetate (PMA). Ferricyanide reduction in PMA-treated cells becomes resistant to inhibition by adriamycin. These results provide evidence for an independent effect of adriamycin on transmembrane ferricyanide reduction and on superoxide generation.     

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.     

Fusion of phosphatidylserine and mixed phosphatidylserine-phosphatidylcholine vesicles Dependence on calcium concentration and temperature

Dynamic light scattering has been used to study the temperature dependence of Ca²⁺-induced fusion of phosphatidylserine vesicles and mixed vesicles containing phosphatidylserine and different phosphatidylcholines. The final vesicle size after Ca²⁺ and EDTA incubation serves as a measure of the extent of fusion. With phosphatidylserine vesicles, the extent of fusion shows a sharp maximum at an incubation temperature which depends on the Ca²⁺ concentration between 0.8 and 2 mM. The shift in the fusion peak temperature with Ca²⁺ concentration is similar to the typical shift in the phase transition temperature with divalent cation concentration in acidic phospholipids. The results suggest a direct correlation between the fusion peak temperature and the phase transition temperature in the presence of Ca²⁺ prior to fusion. With mixed vesicles containing up to 33% of a phosphatidylcholine in at least 2 mM Ca²⁺, the extent of fusion as a function of incubation temperature also shows a maximum. The fusion peak temperature is essentially independent of the quantity and type of phosphatidylcholine and the Ca²⁺ concentration, and identical to that with pure phosphatidylserine in excess Ca²⁺. The results imply that Ca²⁺-induced molecular segregation occurs first, and fusion subsequently takes place between pure phosphatidylserine domains.     

Metabolism of prostaglandins in spontaneously hypertensive rats: NAD"-dependent 15-hydroxyprostaglandin dehydrogenase activity is decreased in kidney and increased in lung.

Renal, pulmonary and gastric NAD⁺-dependent 15-hydroxyprostaglandin dehydrogenase activities were determined in both spontaneously hypertensive and normotensive rats at 6 and 12 weeks of age. Renal enzyme activity in hypertensive rats was only 30–40% of that present in normotensive controls at both ages. In contract, pulmonary enzyme activity in hypertensive animals was twice as active as that in normal controls. There was no significant difference in gastric enzyme activity. NAD⁺-dependent 9-hydroxyprostaglandin dehydrogenase activity, the enzyme responsible for the conversion of vasoinactive PGF metabolites to PGE metabolites, also failed to show any difference in two types of rat kidneys. The results indicate that, in hypertension, prostaglandin inactivation is impaired in kidney but is facilitated in lung.     

Protein Synthesis and Accumulation in Bean Cotyledons during Growth

Analysis of total protein, of specific proteins by gel electrophoresis and immunoelectrophoresis, and of protein synthetic activity in vitro confirmed that intense protein synthesis and accumulation occurred as the French bean (Phaseolus vulgaris L). seed grew from 12 to 20 millimeters. These techniques showed that there was no globulin-1 (G1) fraction (requiring high salt for solubility) present in 6-millimeter seeds, and only very small amounts were synthesized in seeds less than 9 millimeters long. The 7- to 9-millimeter stages represent a 2-day transition period over which genetic information for the G1 protein becomes actively expressed, accounting for at least 50% of all protein synthesized in this tissue during the following 14 days. At maturity, the electrophoretic analysis confirmed that G1 globulin was the major storage protein, representing some 50% of the dry seed protein. Cell-free protein synthesis assays, including immunoprecipitation of the in vitro products, clearly showed G1 polypeptides to be among the polysome-directed products.