Development of the rete testis in the prenatal ontogeny of rodents and effect of prolactin and thyrotropin on its cellular differentiation

The development of rete testis in the rat, rabbit and guinea pig foetuses has been studied, as well as the influence of prolactin and thyrotropin on differentiation of its cells. It was shown that the rete testis tubules, as well as the seminiferous tubules develop from sex cords, which were derived from coelomic epithelium cells and gonocytes. The development of seminiferous tubules and rete testis was described at various stages of prenatal ontogenesis. Thyrotropin and prolactin exert different effects on differentiation of the rete testis cells: the former increases the mitotic activity of gonocytes and the latter increases that of epithelial cells and enhances degenerative processes in primary germ cells.     

Characteristics of ceruloplasmin synthesis in mammalian embryogenesis. 2. The yolk sac as the site of the primary expression of the ceruloplasmin gene in rats

It was shown that the omphaloid placenta and, first of all, visceral wall of yolk sac is the site of primary synthesis of ceruloplasmin (CP), whereas the activation of CP synthesis in the liver cells is secondary and is revealed from the 12th day of embryo-genesis. The CP synthesis in the yolk sac cells proved by selective CP localization in the cells of the yolk sac visceral wall and, first of all, in the cells of visceral endoderm on sections stained by the method of indirect immunofluorescence and using the reaction of soluble peroxidase-antiperoxidase complex. A specific CP-mRNA has been revealed in the yolk sac cells which is actively translated in the polyribosomes isolated from the yolk sac and in the cell-free translation system from the rabbit reticulocytes. on the 14th day of embryogenesis CP amounts to ca. 4% of all polypeptides secreted by the yolk sac cells. As the embryogenesis proceeds, the relative rate of CP synthesis progressively decreases in the yolk sac and increases in the liver cells. CP synthesized by the yolk sac cells has a molecular mass of ca. 122 kD. Possible causes of differences between the "embryonic" and "adult" rat CPs are discussed. A suggestion has been put forward that the time of activation of CP synthesis coincides with the yolk sac formation (8-9th days of embryogenesis) and the cells of visceral endoderm are the site of primary expression of the CP gene.     

Hexavalent chromium effects on motor activity and some metabolic aspects of Wistar albino rats

The effects of hexavalent chromium on the motor activity and some metabolic aspects of albino rats were studied. 0.07 g Cr(VI)/l administered in drinking water produced no effects on the motor activity of rats, at least over 28 days of treatment. 0.7 g Cr(VI)/l in drinking water and 2 mg Cr(VI)/kg body wt injected i.p. significantly decreased the motor activity of rats after 7 days and 1 day, respectively. The treated rats showed a metabolic disadvantage in relation to the controls. The effects caused by Cr(VI) on the motor activity in rats could be an indication of the neurotoxicity of this metal.     

Autoaggregating Yersinia enterocolitica express surface fimbriae with high surface hydrophobicity

For 13 strains of Yersinia enterocolitica, there was a good correlation between the production of the broad-spectrum, mannose-resistant Yersinia haemagglutinin (MR/Y HA), the presence of fimbriae and high surface hydrophobicity. Each of these characters was expressed in cultures grown at low (less than 32 degrees C) but not at high (Greater than 35 degrees C) temperatures.     

Lipopolysaccharide core mutants of Salmonella typhimurium containing D-glycero-D-manno-heptose

Mutants resistant to several hydrophobic membrane antagonists were isolated from a "deep rough" (rfaC) mutant of Salmonella typhimurium. The resistance was due to an alteration in the core region lipopolysaccharide composition as evidenced by altered bacteriophage and complement sensitivity and by compositional analysis. The principal change in carbohydrate composition was the predominance of the unusual heptose isomer D-glycero-D-manno-heptose. The unusually wide pleiotropic phenotype of this organism is suggested to be due to a fundamental change in the properties of the bacterial outer membrane.     

Effect of interferon treatment on blockade of protein synthesis induced by poliovirus infection

Treatment of HeLa cells with lymphoblastoid interferon leads to a drastic inhibition of infective poliovirus. Even relatively high concentrations of human lymphoblastoid interferon HuIFN-alpha (Ly) (400 IU/ml) do not prevent destruction of the cell monolayer after most of the cells have been infected with poliovirus. Analysis of macromolecular synthesis in a single step growth cycle of poliovirus in interferon-treated cells detected no viral protein synthesis. In spite of this inhibition of viral translation, the shut-off of host protein synthesis in interferon-treated cells is apparent when they are infected both at low and high multiplicities. Although viral RNA synthesis is inhibited considerably in cells treated with interferon, a certain amount is detected, suggesting that some viral replication takes place. Analysis of membrane permeability after poliovirus infection shows a leakage to 86Rb+ ions and modification of membrane permeability to the translation inhibitor hygromycin B at the moment when the bulk of virus protein synthesis occurs. These changes are delayed and even prevented if cells are pretreated with interferon. A situation is described in which host protein synthesis is shut-down with no major changes in membrane permeability, as studied by the two tests mentioned above. Prevention of viral gene expression by inactivation with ultraviolet light of the input virus or by treatment with cycloheximide blocks the shut-off of protein synthesis. This does not occur in the presence of 3 mM guanidine. These observations are in agreement with the idea that some poliovirus protein synthesis takes place in interferon-treated cells and this early gene expression is necessary to block cellular protein synthesis.     

Reactions in vitro of the DNA polymerase-primase from Xenopus laevis eggs. A role for ATP in chain elongation

A form of DNA polymerase alpha was purified several thousandfold from a protein extract of Xenopus laevis eggs. The enzyme effectively converts, in the presence of ribonucleoside triphosphates, a circular single-stranded phage fd DNA template into a double-stranded DNA form and, therefore, must be associated with a DNA primase. We first show by gel electrophoresis in the presence of sodium dodecyl sulfate that both enzymatic activities, DNA polymerase and primase, most probably reside on a greater than 100 000-Da subunit of the DNA polymerase holoenzyme. We then assayed the polymerase-primase at various template/enzyme ratios and found that the DNA complementary strand sections synthesized in vitro belong to defined size classes in the range of 600-2000 nucleotides, suggesting preferred start and/or stop sites on the fd DNA template strand. We show that the stop sites coincide with stable hairpin structures in fd DNA. We have used a fd DNA template, primed by a restriction fragment of known size, to show that the polymerase-primase stops at the first stable hairpin structure upstream from the 3'-OH primer site when the reaction was carried out at 0.1 mM ATP. However, at 2 mM ATP the enzyme was able to travers this and other stop sites on the fd DNA template strand leading to the synthesis of 2-4 times longer DNA strands. Our results suggest a role for ATP in the polymerase-primase-catalyzed chain-elongation reaction.     

Synthesis and application of two reagents for the introduction of sulfhydryl groups into proteins

Two reagents are described which can be used for the introduction of sulfhydryl groups into proteins. Mercaptopropionylhydrazide modifies specifically periodate-oxidized N termini of proteins, provided that the N-terminal residue is serine or threonine. 3-(Phenyldithio)propionimidate introduces a disulfide bond at lysine residues of proteins. Reduction converts the disulfide into a sulfhydryl group. The imidate compound was found to react with a high specificity with only one lysine residue of ribosomal protein L7/L12.     

UDPglucosyltransferase and its kinetic fluorimetric assay

A rapid, kinetic assay for UDPglucosyltransferase has been developed using 1-naphthol as substrate. It is based on the continuous fluorimetric monitoring of 1-naphthyl glucoside formation during the reaction at physiological pH. The conjugate is easily distinguished from aglycone, since their fluorimetric properties differ. Glucoside biosynthesis in vitro by microsomal preparations isolated from the gut and fat body of cockroaches Periplaneta americana and Leucophaea maderae, and from the green gland and hepatopancreas of the crayfish Astacus astacus, has been demonstrated. The effects of buffer, pH, MgCl2, UDP-glucuronic acid, UDP-N-acetylglucosamine, sodium cholate and sonication on the enzyme activity have been assessed. The kinetic parameters of 1-naphthol and UDP-glucose have also been determined.