Influence of carbohydrate side chains on activity of tissue-type plasminogen activator

When messenger RNA (mRNA) from both untreated and phorbol ester-treated melanoma cells is translated in simple reticulocyte lysates, tissue-type plasminogen activator can be immunoprecipitated by an affinity-purified antibody as a approximately 52,000 mol wt protein, with no detectable biological (plasminogen activating) activity. When the reticulocyte lysate system is supplemented with a preparation of microsomal membranes, biological activity becomes detectable and a 63,000 mol wt protein can be immunoprecipitated with the same antibody. Furthermore, when natural tissue-type plasminogen activator (mol wt approximately equal to 70,000) is incubated with different glycosidases, distinct alterations in the electrophoretic mobility of the molecules are observed, together with alterations in the level of biological activity. While treatment with neuraminidase and beta-galactosidase caused decreases in activity, alpha-mannosidase caused an increase. These results suggest that the carbohydrate part of the molecule can influence its biological behavior.     

Cosinor analysis of diurnal changes of the reduced glutathione level in the blood, brain, liver and kidneys of mice, induced by ACTH administration

The influence of a single dose of ACTH(100 I.U. /kg body weight) on the diurnal rhythm of reduced glutathione (GSH) was studied in the blood and brain, liver and kidney homogenates of male mice. Cosinor analysis revealed that ACTH induces changes in the mean diurnal amount of GSH in the blood, brain, liver and kidneys. At the same time, GSH amplitudes in the blood and kidneys increased significantly, whereas in the case of brain and liver they decreased markedly. Moreover, it was found that ACTH induces a shift in GSH acrophases in the blood, brain, liver and kidneys as compared with the control values.     

Injury and recovery in freeze- or heat-damaged Campylobacter jejuni

When exposed to freezing or heat, cells of Campylobacter jejuni were initially sensitized to rifampicin and, with longer exposures, subsequently unable to grow on nutrient or blood agar. Repair of all lesions occurred within 2 h at 37°C while at 43°C organisms were only able to repair the presumably less severe injury caused by short exposures to high or low temperature.     

Promotion of hyphal growth in Ustilago violacea by host factors from Silene alba

Ustilago violacea specifically parasitizes susceptible members of the Caryophyllaceae. We isolated water-soluble compounds from leaves of Silene alba which promoted hyphal development in the dimorphic pathogen. We also isolated hyphal growth promoting -tocopherol from S. alba. The water-soluble activity, which we term hyphal growth factor, or HGF, separated into four bands with gel filtration chromatography and represented over 40% of the total hyphal growth promoting activity isolated from S. alba. The water-soluble HGF activity may be host-specific and may function as a determinant of the host-parasite specificity between U. violacea and caryophyllaceous host plants.Abbreviations HGF Hyphal growth factor - BHT butylated hydroxytoluene     

Cell envelope phospholipid changes in a moderate halophile during phenotypic adaptation to altered salinity and osmotic stress

Abstract The increased content of negatively-charged phospholipids in membranes of Vibrio costicola grown at high salinities is mediated by increased phospholipid synthesis of phosphatidylglycerol relative to phosphatidylethanolamine. This phenomenon provides a system for investigating the factors involved in triggering and controlling haloadaptation in this moderately halophilic bacterium. We review recent experiments, which show that when subjected to sudden increases in external salinity, V. costicola senses both the absolute NaCl concentration and the magnitude of the salt shift. We show that the latter is sensed at least in part via osmotic pressure effects, since shift-up into sucrose-containing media triggers comparable changes in growth and in phospholipid composition and synthesis.     

Different acute effects of the tyrosine hydroxylase inhibitors alpha-methyl-p-tyrosine and 3-iodo-L-tyrosine on hypothalamic noradrenaline activity and adrenocorticotrophin release in the rat

Computerized gas chromatography-mass spectrometry techniques using selected ion monitoring and deuterated internal standards were used to assay simultaneously the medial basal hypothalamic concentrations of dopamine (DA) and noradrenaline (NA) and their major metabolites in individual rats 30 min after the administration of two different inhibitors of tyrosine hydroxylase, alpha-methyl-p-tyrosine (alpha-MT) and 3-iodo-L-tyrosine (MIT). Consistent with inhibition of DA synthesis, administration of both alpha-MT and MIT resulted in marked reductions (P less than 0.005) in the hypothalamic concentrations of DA and its metabolite homovanillic acid as well as in highly significant increases in prolactin secretion. alpha-MT administration, but not MIT, resulted in a highly significant decrease in NA concentration and a highly significant increase in the concentration of the NA metabolite 3,4-dihydroxyphenylethyleneglycol (DHPG). The hypothalamic ratio DHPG/NA was thus markedly increased (P less than 0.005) by alpha-MT indicating increased NA neuronal activity. alpha-MT administration also resulted in increased ACTH secretion (P less than 0.0005), an effect not observed following MIT. It is proposed that the effects on hypothalamic NA activity and ACTH secretion caused by alpha-MT are stress-mediated and unrelated to tyrosine hydroxylase inhibition. MIT is devoid of these effects but exhibits blockade activity, thus indicating it to be a preferable drug for the acute inhibition of tyrosine hydroxylase in neuroendocrine investigations.     

The zinc-containing high Km cyclic nucleotide phosphodiesterase of bakers' yeast

The high Km cyclic nucleotide phosphodiesterase of Saccharomyces cerevisiae was purified by an improved procedure. Its amino acid composition is reported. Its pI is 5.85 +/- 0.1. Sedimentation equilibrium analysis of the native enzyme gave Mr = 88,000 +/- 6,000, whilst gel electrophoresis in the presence of dodecyl sulfate gave a molecular weight of 43,000, indicating that the enzyme is a dimer. Preparations of 94 +/- 4% purity contained about 2.4 atoms of zinc/43,000 daltons. Inactivation of the enzyme by 8-hydroxyquinoline was accompanied by removal of about 2 zinc atoms per monomer. Partially inactivated enzyme regained activity during dialysis against zinc, or, with less effect, cobalt salts. 8-Hydroxyquinoline (Ki = 1.1 mM) and 1,10-phenanthroline (Ki = 0.6 mM) were competitive inhibitors. The enzyme was also inhibited by the nonchelating 1,7-and 4,7-phenanthrolines and by thiols and KCN, but not by NaN3. These inhibitors probably act by binding to, but not chelating, enzyme-bound zinc.     

Low doses of X-rays decrease the risk of diploidy in mouse oocytes

Females from the NMRI/Han mouse strain ovulate a high number of diploid oocytes (about 12%) after gonadotrophin-stimulated ovulation. These oocytes can be fertilized and develop into triploid embryos subsequently. The exposure of such gonadotrophin-primed females to X-ray doses of 0.05, 0.10, 0.20 or 0.40 Gy during the preovulatory period (2 h after the HCG dose) significantly decreased the percentage of diploid oocytes. After the highest dose used, i.e. 0.80 Gy, however, the incidence was on the level from unirradiated females, again. We suggest that the observed negative hump-shaped dose response of diploidy is not caused by secondary modifications induced by irradiation, such as a selective killing of diploid oocytes before ovulation, or a (compensatory) super-ovulation of only normal oocytes, but rather is caused by a direct radiobiological interference of low doses in protecting from gonadotrophin-induced aneuploidy.