Regulation by glucocorticoids of rat-liver phenylalanine hydroxylase in vivo

Phenylalanine hydroxylase, a liver-associated enzyme, is induced markedly by glucocorticoids in two permanent rat-hepatoma cell lines. In order to gain evidence that this phenomenon also occurs in vivo, we examined the effect of adrenalectomy and/or hormone supplementation on the levels of phenylalanine hydroxylase in the livers of adult rats: glucocorticoid administration increases, and adrenal ablation reduces, the activity of the hepatic enzyme, and the diminution occurring in the latter instance is entirely prevented by concurrent hormone replacement. These results thus corroborate earlier findings from a single experiment and are consistent with the hypothesis that adrenal corticosteroid hormones participate in modulating phenylalanine-hydroxylase levels within the diploid hepatocyte.     

Maintenance of ovulatory menstrual cycles in chronically cannulated monkeys: a vest and mobile tether assembly

We report maintenance of apparently normal ovulatory menstrual cycles in cynomolgus monkeys up to 3 months after their placement in a vest and mobile tether assembly, with or without chronic cannulation via a femoral to vena caval catheter. Since menstrual cyclicity and characteristic hormonal profiles of the principal ovarian steroids remained normal in these monkeys, use of the vest and mobile tether apparatus described here permits long-term study of the hypothalamic-pituitary-ovarian axis during chronic cannulation without introducing overt aberrancies as a part of the experimental model.     

Catalase and superoxide dismutase in Escherichia coli

We assessed the roles of intrabacterial catalase and superoxide dismutase in the resistance of Escherichia coli to killing by neutrophils. E. coli in which the synthesis of superoxide dismutase and catalase were induced by paraquat 10-fold and 5-fold, respectively, did not resist killing by neutrophils. When bacteria were allowed to recover from the toxicity of paraquat for 1 h on ice and for 30 min at 37 degrees C, they still failed to resist killing by neutrophils. Induction of the synthesis of catalase 9-fold by growth in the presence of phenazine methosulfate did not render E. coli resistant to killing by either neutrophils or by H2O2 itself. The lack of protection by intrabacterial catalase from killing by neutrophils could not be attributed to an impermeable bacterial membrane; the evolution of O2 from H2O2 was no less rapid in suspensions of E. coli than in lysates. The failure of intrabacterial catalase or superoxide dismutase to protect bacteria from killing by neutrophils might indicate either that the flux of O-2 and H2O2 in the phagosome is too great for the intrabacterial enzymes to alter or that the site of injury is at the bacterial surface.     

Purification from Synaptosomal Plasma Membranes of Calpain I, a Thiol Protease Activated by Micromolar Calcium Concentrations

Synaptosomal plasma membranes (SPMs) were prepared from whole rat brain and assayed for calcium-stimulated proteolytic activity. Addition of calcium to SPMs caused a dose-dependent increase in trichloroacetic acid-soluble protein. Two peaks of protease activity directed against a casein substrate were detectable when SPMs were incubated with low-ionic-strength buffer and the extract was fractionated on DEAE-cellulose. The enzyme in peak 1 required less than 1/10 the calcium concentration for activation as the peak 2 protease (Kact1 = 35 microM; Kact2 = 500 microM). The specific thiol-protease inhibitors leupeptin and antipain and the alkylator iodoacetate blocked enzyme activity. The low-sensitivity protease was converted to a high-sensitivity enzyme (Kact = 20 microM) by substrate affinity chromatography in the presence of calcium. This protease was purified 550-fold from SPMs. The high- and low-sensitivity membrane-associated calcium-dependent proteases are part of a family of enzymes, the calpains, previously reported in cytosolic fractions of several tissues.     

The effect of diet on ouabain binding to erythrocytes from obese subjects

Ouabain binding to erythrocyte membranes is increased in obese subjects. Three study groups are compared: 14 reference subjects, 102 +/- 16% of ideal weight; 9 obese on unrestricted diets, 207 +/- 16% of ideal weight; 11 obese on restricted diets, 202 +/- 35% of ideal weight. A reproducible (CV = 11.3%) ouabain-binding assay is used to measure Na+-K+ ATPase sites in erythrocyte membranes. The number of binding sites per red blood cell for obese subjects on unrestricted diets, 431 +/- 30, is greater than for the reference group, 346 +/- 66 (p less than 0.01), or for obese subjects on restricted diets, 371 +/- 68 (p less than 0.05). These data suggest that caloric intake influences the number of Na+-K+ ATPase sites. Scatchard plots indicate only one type of binding site for ouabain with an affinity constant of about 3 X 10(8) M-1.     

Effect of experimentally induced calcium deficiency on the developmental expression of collagen types in chick embryonic skeleton

In order to investigate the effect of embryonic calcium deficiency on the cellular differentiation processes in embryonic skeletogenesis, chick embryos were maintained in long-term shell-less cultures in vitro. The absence of the eggshell, which normally provides over 120 mg of calcium to the embryo during the course of development, resulted in severely retarded and anomalous skeletal formation. The pattern of cytodifferentiation in the skeletal elements during development was assessed by examining collagen type synthesis in both endochondral and intramembranous bones of normal and shell-less embryos as a function of developmental age. Skeletal tissues obtained from these embryos at various developmental stages were maintained in short-term organ culture in medium containing [³H]Pro. The metabolically labeled collagen was isolated from these tissues and typed biochemically based on electrophoresis, ion-exchange chromatography, differential salt fractionation, zone precipitation chromatography, and CNBr peptide mapping. The results indicate that, compared to chronologically equivalent normal controls, calcium-deficient skeletal elements from shell-less embryos appeared to fail to mature into complete bony tissues and instead exhibited partial cartilage phenotype with the expression of cartilage-specific type II collagen.     

Reoccurrence of the microsporidan Perezia pyraustae in the European corn borer, Ostrinia nubilalis, reared on diet containing fumidil B

Fumidil B suppressed the level of Perezia pyraustae infection in the larvae of the European corn borer, Ostrinia nubilalis, while they were feeding on diet containing the drug. After feeding ceased and the gut was emptied of diet containing Fumidil B, the level of infection again increased. Drug levels of 1000 and 1500 ppm in the meridic diet significantly reduced the mean level of P. pyraustae in the adult stage as compared with lower drug levels of 200 and 500 ppm. The level of infection increased throughout the pupal and adult stages, but during the pupal stage it increased much faster in the female than in the male. The rapid increase in the level of infection in the female is discussed in relation to transovariole transmission to the next generation.     

Climatic adaptation in recently shorn merino sheep

Heart rates, respiratory rates, body temperatures, ad libitum ‘day’ and ‘night’ food consumption and body weight changes have been examined in 15 mature Merino wethers shorn in moderate environmental conditions. All sheep showed a depression in food consumption for two days after shearing. Sheep that gained weight during the next three weeks then increased their food consumption at night by approximately 30% although the average daily consumption was only increased by 5%. Sheep that lost weight showed a depressed food consumption throughout the three week period after shearing. Marked increases in the temperature difference between ear skin and air as well as thermal tachypnoea during the warmest period of the day were recorded in all sheep 14–16 days after shearing. This indicated that the critical temperature for all sheep had decreased by about 10°C. These signs of acclimatisation appeared at similar times in all sheep, suggesting that increased resistance to body cooling developed at similar rates in weight gain and weight loss sheep and independent of the origin of body heat production. The results of the investigations are discussed in relation to the concept that the initial response to cold stress includes a depression in food intake and that the duration of this depression is a function of the cold stimulus and the strain it induces in the sheep.