Virulence-associated characteristics and phage lysogenicity of two morphologically distinct colonies of Vibrio cholerae O139 serogroup

Abstract The presence of a temperate phage was demonstrated in a strain of Vibrio cholerae O139 isolated from a patient. Spontaneous variants with translucent colonies had lost this phage. The loss of the phage was associated with increased hydrophobicity, indicating the loss of the capsule. These clones were sensitive to serum bactericidal activity, showed decreased expression of such presumed virulence factors as proteases, motility and mannose-sensitive pili. Furthermore, excision of the phage made the strain dependent on purines for growth.     

Influence of opioid peptides on nerve tissue in vitro

The influence of opioid peptides (gamma- and beta-endorphins, leu- and met-enkephalins, as well as certain synthetic analogs of enkephalin) was investigated on organotypic cultures of rat spinal and sympathetic ganglia. The cellular composition and size of the zone of growth were evaluated on the basis of intravital observations and an analysis of the specimen obtained using the method of impregnation, according to Holmes and the detection of catecholamines with glyoxylic acid. It was established that under the action of all the investigated substances that possess high affinity for opiate receptors, growth of the neurites from an explant was enhanced, and the number of glial and fibroblastoid cells in the growth zone was increased. The effect was observed most distinctly on a model of sympathetic ganglia. The tested compounds exhibited a significant growth-stimulating effect in the range of concentrations 10^–8–10^–14 M. The maximum size of the growth zone of the explants of the sympathetic ganglia in the case of a mean effective concentration of the peptides 10^–10 M by the third to fifth day of culturing was approximately 2–2.5 times this value in the control. The reaction was similar to the response of the nerve cells to nerve growth factor, used as a standard. Thus, the opioid peptides exhibit a pronounced growth effect on the structures of the nerve tissue under conditions of culture. It is suggested that this group of compounds, together with its currently well-known functions, may play a definite role in processes of the development and regenera-of nerve tissue.Institute of Experimental Cardiology, All-Union Cardiologic Science Center, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 4, pp. 550–557, July–August, 1985.     

Change inLimnaea stagnalis neuronal response to acetylcholine during intracellular and extracellular perfusion with serotonin

The modifying effect of adding serotonin to the intra- and extracellular environment on the inward currents generated by the cell following intracellular application of acetylcholine was shown during studies on unidentified isolatedLimnaea stagnalis neurons using techniques of intracellular perfusion and voltage clamping. Serotonin inhibited response to achetylcholine in both cases in most of the test neurons. Serotonin intensified this response when applied to the intracellular environment and produced the opposite effect of reducing the amplitude of inward acetylcholine currents when administered extracellularly. Cyproheptadine, the serotonin receptor blocker, inhibited the enhancing effect of serotonin produced by adding this neurotransmitter to the intracellular fluid, but mimicked the inhibitory effects of serotonin on response to acetylcholine, whether added to the intra- or extracellular environment. Findings would suggest the presence of intracellular serotonin receptors in the mollusk neurons; one of their possible functions could be controlling the sensitivity of the cell surface cholinoreceptors.N. K. Koltsov Institute of Developmental Biology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 326–332, May–June, 1986.     

Developmental changes in gene expression during pollen differentiation and maturation inNicotiana tabacum L

Total and polysome-bound ribosomes and the uptake and incorporation of³H-uridine and¹⁴C-leucine were examined in dividing microspores and in pollen grains isolated from anthers of 6 different developmental stages. Direct evidence was obtained that the formation of cytoplasm of the vegetative cell following microspore division is related to a rapid activation of RNA and protein synthesis and of ribosomes in differentiating pollen. Total ribosomes associated with gametophytic programme rose about 10times and the process of differentiation was accompanied by a rapid increase in uptake capacity of pollen grains for both uridine and leucine. Pollen development after cytoplasm synthesis and starch deposition continued by pollen maturation, which was characterized by a decline in RNA synthesis, dissociation of polysomes and by a further rise of transport activity of pollen grain wall for exogenous substrates, indicating probable pollen adaptation for utilization of metabolites from the degenerating tapetal cytoplasm.     

Influence of 2,4-d and lactose on pollen embryogenesis in anther culture of potato

Anthers of diploid genotypes of Solanum tuberosum capable of androgenesis were cultured on different media to examine the effect on induction of pollen embryogenesis of 2,4-d and lactose. Anthers cultured in callogenic medium with 2,4-d and sucrose produced pollen derived embryoids only exceptionally. When sucrose was replaced by lactose the frequency of embryogenesis was as high or higher than in embryogenic auxin-free medium. Substitution of lactose for sucrose in the embryogenic medium had no effect. Supplementing the embryogenic medium with 2,4-d strongly reduced the frequency of pollen embryoids in the presence of sucrose but not with lactose.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid     

Sequence of the gene for a NAD(P)-dependent formaldehyde dehydrogenase (class III alcohol dehydrogenase) from a marine methanotroph Methylobacter marinus A45

Abstract A fragment of Methylobacter marinus A45 DNA has been cloned and sequenced, and an open reading frame has been identified that could code for a 46-kDa polypeptide. Comparison of the deduced amino acid sequence of the polypeptide against the protein data bank has revealed strong similarity with a number of alcohol dehydrogenases, with highest similarity towards class III alcohol dehydrogenases, which recently have been shown to be identical to glutathione-dependent formaldehyde dehydrogenases. We were unable to measure appreciable levels of NAD(P)-dependent formaldehyde dehydrogenases or alcohol dehydrogenase activities using aldehydes or primary or secondary alcohols in cell-free extracts from batch cultures of M. marinus A45. However, formaldehyde dehydrogenases activity was detected on zymograms. Our data suggest that, although NAD(P)-linked formaldehyde dehydrogenase or alcohol dehydrogenase activities are undetectable in cell-free extracts of most methylotrophs employing the ribulose monophosphate pathway for formaldehyde assimilation and dissimilation, the gene encoding formaldehyde dehydrogenase is present in M. marinus A45 and may be present in more of these organisms as well.     

An immunochemical study of antigen expression in potato spindle tuber viroid (PSTV) - infected tomato leaves and calluses

A polyspecific antiserum against protein extracted from PSTV-infected tomato leaves was prepared and the IgGs were separated by affinity chromatography on a beaded cellulose adsorbent with an immobilized “healthy” antigen. The antibody not adsorbed entered into a preferential reaction with the antigen from PSTV-infected leaves as estimated by an enzyme-linked immunosorbent assay. The immunochemical reactions did not significantly exceed the control background, if antigens from tomato leaves infected with potato viruses X, Y and M were analyzed. By immunoblot technique we revealed, however, that several antigens not detected in healthy leaves appeared in the leaves infected either with PSTV or with viruses X and M. An accumulation of a major antigen having a molecular mass of about 70 kDa was observed in viroid-infected leaves only, suggesting the specificity for viroid infection. The antigen was found not to be an alkaline endoproteinase - the pathogenesis-related protein P-69. Some antigens with molecular masses approximately 38.0, 23.7 and 22 kDa, which occurred in PSTV-infected leaves and in healthy calluses, were not detectable in PSTV-infected calluses. No reaction exceeding the control level was observed using enzyme-linked immunosorbent assay for antigens from silver nitrate-treated tomato leaves, although such leaves showed symptoms similar to that caused by viroids.     

The influence of sugars on nitrate reductase induction by exogenous nitrate or nitrite in excised pisum sativum roots

Nitrate reductase (NR) induction is enhanced by exogenously supplied sucrose in excised pea roots exposed to both exogenous nitrate and exogenous nitrite. NR synthesis is preferentially supported by sugars transported to the cells at the moment, however NR induction can take place for some time without exogenous sugar influx if roots are saturated with sugars during precultivation. Steady high NR levels are dependent on steady sugar and nitrate influxes. NR induction is low in roots precultivated for 20 h without sucrose although sugar content is still high in them. This suggests that compartmentation of sugars in the cells is of major importance during NR induction. Total nitrate content in roots exposed to nitrate is not influenced by sucrose supplied together with nitrate. Some nitrite is oxidized to nitrate in roots exposed to exogenous nitrite ; we assume that this nitrate is responsible for NR induction. Our results indicate that sugars, besides many indirect effects on NR induction, may also directly influence NR synthesis either as coinducers or as derepressors of NR synthesis. Our results further show that NR is not a product-inducible enzyme.     

The influence of exogenously supplied sucrose on glutamine synthetase and glutamate dehydrogenase levels in excisedPisum sativum roots

Glutamine synthetase (GS) level is positively influenced by exogenously supplied sucrose in isolated pea roots (similarly as nitrate reductase - NR), glutamate dehydrogenase (GDH) level negatively. Comparison with previous results shows that GS level decreases more slowly than NR level when sucrose is omitted from the medium; the rate of changes in GS level corresponds rather to that in GDH level. The increase in GDH level in the tips of isolated roots cultivated in the medium lacking sucrose stops after approx. 24 h, but continues for at least 72 h in more mature root parts. GS level decreases during the first 24 h in the tips of isolated roots (compared with roots of intact seedlings) cultivated both with sucrose and without it (without sucrose more), however it again rises in the course of further cultivation with sucrose. The differences in GS and GDH levels caused by omission of sucrose are small in isolated roots from which root tips were removed, the difference in NR level in decapitated roots is similar to that found in isolated roots with root tips left. Decapitated isolated roots cultivated without sucrose contain higher amounts of soluble sugars than corresponding roots with root tips left. These facts are dismissed with regard to sugar consumption, transport, and compartmentalisation, and with respect to production in root tips and other plant parts of unknown compounds involved in GS and GDH regulation. The results obtained suggest that GDH functions in pea roots in the deaminating direction.