Hormonal effects on the development changes of mouse small intestinal glycolipids

The composition of intestinal glycosphingolipids during normal and hormone-perturbed development was investigated. The concentrations of glycosphingolipids of mouse small intestine were affected by the injection of thyroxine or cortisone during suckling and weaning periods. GDla was reduced by the hormonal treatment among major gangliosides, GM3, GM1 and GD1a, of mouse small intestine during the suckling period. In contrast, asialo GM1 was precociously produced by the treatment, which scarcely found in control suckling mouse small intestine. The results showed that these hormones were related to developmental alteration of small-intestinal glycolipids.     

Antizyme to ornithine decarboxylase is present in the liver of starved rats.

Antizyme to ornithine decarboxylase (ODC) and ODC-antizyme complex were both present in liver cytosols of starved rats. The antizyme was identified by its molecular weight, kinetic properties, formation of a complex with ODC, and reversal of its inhibition by antizyme inhibitor. The average amount of antizyme in liver cytosols of starved rats was 0.1 unit/mg of protein, roughly corresponding to basal hepatic ODC activity in rats fed ad libitum. The presence of ODC-antizyme complex was detected by using antizyme inhibitor. These results indicate that antizyme participates in the regulation of ODC activity in vivo under physiological conditions.     

Stimulation of prostaglandin E2 synthesis by exogenous phospholipase A2 and C in rabbit kidney medulla slices.

We have investigated the effects of phospholipase A2 and C on the synthesis of prostaglandin E2 in rabbit kidney medulla and the release of fatty acids from the medulla slices. Exogenous phospholipase A2 [from Naja naja (Indian cobra) venom] and phospholipase C (from Clostridium welchii) stimulated prostaglandin E2 production in a dose-dependent manner. At the maximal effective concentrations (0.5 unit of phospholipase A2/ml, 2 units of phospholipase C/ml), phospholipase C increased prostaglandin E2 formation to the level observed with phospholipase A2. Phospholipase A2 enhanced the release only of unsaturated fatty acids, whereas phospholipase C stimulated the release of individual free fatty acids (C 16:0, C 18:0, C 18:1, C 18:2 and C 20:4). Moreover, p-bromophenacyl bromide inhibited phospholipase A2-stimulated prostaglandin E2 production and the release of fatty acids, but it had no influence on prostaglandin E2 formation and the release of fatty acids increased by phospholipase C, indicating that the stimulatory effect of phospholipase C is not mediated through the activation of endogenous phospholipase A2. These results suggest the presence of diacylglycerol lipase and monoacylglycerol lipase in the kidney and the importance of this pathway in prostaglandin synthesis by the kidney.     

Cytochemical studies on the localization and functional properties of calcium in anterior pituitary cells

Summary The localization of calcium and its functional properties in anterior pituitary cells were studied using a potassium pyroantimonate technique. In all kinds of secretory cells, the precipitates of the calcium-pyroantimonate complex were distributed on the limiting membrane of the secretory granule. They were present also in the cytoplasmic matrix, the mitochondrial matrix, small smooth vesicles, coated vesicles, and in the nuclear euchromatin area. The precipitates were usually seen at the contact region between the limiting membranes of two adjacent secretory granules, or between the granule limiting membrane and the plasma membrane. When the tissues were incubated in the medium containing A23187 (10 M) for 5 min, the deposits on the granule limiting membrane were increased in number and those on the mitochondrial matrix were decreased; the reaction products almost disappeared on the limiting membranes of the secretory granules after membrane fusion following single or multigranular exocytosis induced by A23187-treatment. In addition, small vesicles in the capillary endothelium contained reaction precipitates. Based on these results we propose a hypothetical model for the relationship between the localization of calcium and secretory activity.This study was supported by grants from the Japan Ministry of Education     

Purification of DNA complementary to the env gene of avian sarcoma virus and analysis of relationships among the env genes of avian leukosis-sarcoma viruses.

The env gene of avian leukosis-sarcoma viruses encodes a glycoprotein that determines the host range and surface antigenicitiy of virions. We have purified radioactive DNA (cDNAgp) complementary to at least a portion of the env gene for viral subgroups A and C; complementary DNA was synthesized with purified virions of wild-type avian sarcoma virus, and RNA from a mutant with a deletion in env was used to select DNA specific to env by molecular hybridization. The genetic complexity of cDNAgp for subgroup A (ca. 2,000 nucleotides) was sufficient to represent the entire deletion and most or all of the env cistron. The deletions in env in two independently isolated strains of virus (Bryan and rdNY8SR) overlap, and cDNAgp represents nucleotide sequences common to both deletions. By contrast, we could detect no overlap between deletions in env and deletions in the adjacent viral gene src. Laboratory stocks of viral subgroups A, B, C, D and E do not contain detectable amounts of env deletions when tested by molecular hybridization; hence, segregation of deletions in env is a less frequent event that the segregation of deletions in the viral transforming gene src (Vogt, 1971). We found extensive homology among the nucleotide sequences encoding the env genes of virus strains indigenous to chickens (subgroups A, B, C, D, and E) although subgorups B, D and E appear to differ slightly from subgroups A and C at the env locus. By contrast, viruses obtained from pheasant cells (subgroups F and G) have env genes with little or no relationship to env genes of chikcen viruses. According to available data, viruses of subgroup F arose by recombination between an avarian sarcoma virus and viral genes in the genome of ring-necked pheasants, whereas subgroup G viruses may be entirely endogenous to golden pheasants.     

Guest-induced conformational change of β-cyclodextrin capped with an environmentally sensitive chromophore

A capped cyclodextrin, 6-deoxy-6-(p-hydroxy-m-nitrophenacylthio)-β-cyclodextrin, was prepared in order to detect any conformational change of the host upon the guest binding. The association constant between the cyclodextrin and 1-adamantanecarboxylate, cyclohexanecarboxylate, p-methylbenzoate, 3,3-dimethylbutyrate, or 2,2-dimethylpropionate was enhanced 20, 5.3, 3.7, 2.3, or 2.0 times, respectively, by chromophore capping. The changes in the electronic, NMR, and circular dichroism spectra as well as pK_a of this cyclodextrin upon binding of the guest strongly indicate a conformational change around the chromophoric moiety of the cyclodextrin.     

The role of cyclic AMP in aldosterone production by isolated zona glomerulosa cells.

The role of cyclic AMP in the regulation of aldosterone production by adrenocorticotropic hormone (ACTH), angiotensin II (A II), potassium, and serotonin was examined in collagenase-dispersed adrenal glomerulosa cells. The ability of 8-bromo cyclic AMP and choleragen to stimulate maximum aldosterone production indicated that cyclic AMP could act as second messenger for certain of the aldosterone-stimulating factors. The actions of ACTH and choleragen on aldosterone and cyclic AMP production were correlated in dog and rat cells, and a similar relation was seen during stimulation of rat cells by serotonin. In contrast, A II and potassium did not cause changes in cyclic AMP formation while stimulating aldosterone production. Intracellular and receptor-bound cyclic AMP were increased 3-fold by 10(-7) M ACTH but not by A II. Addition of a phosphodiesterase inhibitor increased the magnitude of the cyclic AMP response to ACTH but did not change the lack of stimulation by A II or potassium. In dog cells, the effects of A II and potassium on aldosterone production were partially additive to those of ACTH, choleragen, and 8-bromo cyclic AMP. In contrast, no additivity was observed between A II and potassium, or between combinations of the cyclic AMP-dependent stimuli. These results indicate that the actions of ACTH on aldosterone secretion are mediated by cyclic AMP formation, whereas A II and potassium stimulate aldosterone production through an independent mechanism. The lack of additivity between steroid responses to A II and potassium suggests that these factors could share a common mode of action on steroidogenesis in zona glomerulosa cells.