Protein kinase(s) in bovine brain coated vesicles

Purified bovine brain coated vesicles contain protein kinase activity which phosphorylates 165, 54 and 50 kDa protein substrates. These phosphorylations do not seem to be induced by a unique protein kinase: indeed, the three substrates present different localizations in coated vesicles, the phosphorylation sites are either serine or threonine residues and vanadate and ATP[gamma S] have different effects on 32P incorporation in the substrates. Comparison of the coated vesicle protein and phosphorylation patterns from different tissues and animal origins shows that only the 50 kDa protein phosphorylation is always observed, compared to the great diversity in other minor phosphorylations which are observed or not in the various coated vesicles. The possible presence of a 50 kDa phosphoprotein phosphatase is also discussed. It is suggested that the 50 kDa protein with its connected specific kinase and phosphatase seems to constitute a regulatory system present in coated vesicles.     

The use of low doses of dopamine in intensive care medicine

The dopamine alpha- and beta-adrenoceptor dose-response curves are investigated in four patients who are exempt from cardiovascular disease. A dose-related increase in CO, HR and SV is observed with infusion rates of up to 3 micrograms kg-1 min-1. With concentrations greater than 10 micrograms kg-1 min-1, both BP and SVR increase. Low-dose dopamine infusion less than 3 micrograms kg-1 min-1 is investigated in ten other patients. With this infusion rate, a selective renal vasodilation is induced without peripheral or cardiac beta-adrenoceptor activation. Dopamine is responsible for an increase in diuresis FENa, GFR and RBF. These properties are indicated in renal failure, and when haemodynamic support is required in cardiac failure, if an infusion rate of up to 10 micrograms kg-1 min-1 is able to reverse cardiac insufficiency.     

Presence of pH2-sensitive circulating interferon among Callithrix jacchus marmosets

Significant and relatively stable levels of serum-interferon were demonstrated in a Callithrix jacchus population. This circulating interferon was acid-sensitive in all cases, classifying it as immune or "gamma-type" interferon. Our results in these hematopoietic chimeras suggest that the presence of immune-type or at least pH 2-sensitive interferon could be related to the presence of two allogenic lymphocyte populations in each marmoset.     

What's new in lysozyme research?

The present review is focused on the main achievements realized in the lysozyme research field since the meeting held in 1972 to commemorate the fiftieth anniversary of the discovery of this enzyme. Despite of extensive structural, physico-chemical, crystallographic, genetic, immunological and evolutionary studies devoted to lysozymes, their biological role is still not exactly known.     

Effect of Escherichia coli lipopolysaccharide on the glucagon and insulin binding to isolated rat hepatocytes

Summary Number and affinity constant of low affinity binding sites of insulin and glucagon to isolated hepatocytes decreased when the cells were incubated with Escherichia coli 0111:B4 lipopolysaccharide. This effect agrees with a non-specific binding of lipopolysaccharide to hepatocytes, similar to the well-recognized non-specific binding of albumin. Also, binding of different lectins to their glycoprotein receptors did not affect the [¹⁴C]lipopolysaccharide interaction with the cell membrane surface. Endotoxin depresses gluconeogenesis from lactate when the precursor was incubated with the cells for short time intervals. The longer the preincubation interval with lipopolysaccharide, the higher the inhibition of gluconeogenesis in the absence and in the presence of glucagon.The effect of endotoxin was also studied on the glucagon-induced synthesis of cyclic AMP and the glucagon binding. Levels of cyclic AMP and hormone binding decreased with increasing both endotoxin concentrations and preincubation intervals at which cells were in contact with endotoxin.     

The sensitivity of halobacteria to antibiotics

Abstract Eleven species of the genera Halobacterium, Halococcus and the recently proposed Haloarcula were tested by the macro-broth dilution method for their sensitivity to 20 antibiotics with different modes of action. The most active were bacitracin, erythromycin, haloquinone, rifampicin and novobiocin. Resistant mutants of H. mediterranei to bacitracin, chloramphenicol and josamycin were obtained with frequencies of spontaneous mutation between 10⁻⁴ and 10⁻⁷.     

Characterization of the amino acids of bovine fibrinogen involved in the fibrinogen-thrombin interaction of the blood clotting process. Comparison with the milk clotting process

Summary Bovine fibrinogen and the A and B chains of bovine fibrinogen have been subjected to chemical modification by a number of reagents and the effects of these procedures on the susceptibility of the proteins to thrombin hydrolysis is described. The reagents used were rose bengal (for photo-oxidation), 2-hydroxy-5-nitrobenzyl bromide, N-acetylimidazole, iodoacetic acid and diethyl pyrocarbonate. Evidence is presented which indicates that the tryptophan and tyrosine residues of fibrinogen are not involved to any great extent in the interaction of this protein with thrombin. Modification with iodoacetic acid suggests that methionine residues play a major role in such interactions, but the fibrinogen chains on which the important residues reside remain uncertain. The use of diethyl pyrocarbonate indicates the participation also of histidine in fibrinogen-thrombin interactions and that, whereas the histidine residues of the B chain are involved to a great extent, it appears that those of the Aa chain are not. The similarities which exist between the fibrinogen-thrombin and the -casein-chymosin systems are discussed.Abbreviations used DEP diethyl pyrocarbonate (ethoxyformic anhydride) - HNBB 2-hydroxy-5-nitrobenzyl bromide - N-Acl N-acetylimidazole - PTC phenylthiocarbamyl - PTH 3-phenyl-2-thiohydantoin.     

ON THE MECHANISM OF ELECTROSHOCK-INDUCED INHIBITION OF PROTEIN SYNTHESIS IN RABBIT CEREBRAL CORTEX

Abstract— The mechanism of electroshock (ES)-induced inhibition of protein synthesis in rabbit cerebral cortex has been investigated by using a cell-free system. The protein biosynthetic activity of the post-mitochondrial supernatant (PMS) obtained from the cerebral cortex of ES-treated animals was found to be markedly lower than in controls (C). This inhibition was accompanied by a decrease of polysomes and an increase of monomers. In addition, a relative increase in light polysomes was evident at short intervals after ES treatment. No difference was found in the total soluble activity and in the activity of the elongation factors and ribonuclease present in the cell sap of C and ES animals. The biosynthetic activity of ES-total. free and membrane-bound ribosomes was approx 45% lower than that of the corresponding C fractions: polysome/monomer ratios were similarly reduced. The total content of cortical ribosomes was not affected by ES. Following ES treatment there was no change in the ribo-somal ability to elongate, terminate and release polypeptide chains, nor a decrease in the polysomal content of poly(A)-containing mRNA. These data strongly suggest that the ES-induced inhibition of protein synthesis results from a defect in the initiation process. The possible mechanisms mediating this defect have been discussed.     

Effect of rye embryo ribosome nuclease on double-stranded RNA

In extracts obtained by treating rye embryo ribosomes with 0.5 M NH₄Cl, nuclease activity was noted towards double-stranded RNA from virus of Penicillium chrysogenum and towards synthetic poly (A)-poly (U) and poly (I)-poly (C) complexes.