Comparative evaluation of biological properties of Salmonella typhimurium strains of different origin and genetic nature of resistance to antibiotics

The results obtained in the comparative study of the biological characteristics of Salmonella typhimurium strains of different origin are presented. The circulation of two biovariants differing in a number of biological characteristics, mainly in their susceptibility to antibiotics, has been shown. R-plasmids, mostly with the markers of resistance to tetracycline and with a molecular weight of 64 Md, have been isolated from "hospital" and "sporadic" strains possessing multiple antibiotic resistance.     

Membrane resistance change of the frog taste cells in response to water and Nacl

The electrical properties of the frog taste cells during gustatory stimulations with distilled water and varying concentrations of NaCl were studied with intracellular microelectrodes. Under the Ringer adaptation of the tongue, two types of taste cells were distinguished by the gustatory stimuli. One type, termed NaCl-sensitive (NS) cells, responded to water with hyperpolarizations and responded to concentrated NaCl with depolarizations. In contrast, the other type of cells, termed water-sensitive (WS) cells, responded to water depolarizations and responded to concentrated NaCl with hyperpolarizations. The membrane resistance of both taste cell types increased during the hyperpolarizing receptor potentials and decreased during the depolarizing receptor potentials, Reversal potentials for the depolarizing and hyperpolarizing responses in each cell type were a few millivolts positive above the zero membrane potential. When the tongue was adapted with Na-free Ringer solution for 30 min, the amplitude of the depolarizing responses in the NS cells reduced to 50% of the control value under normal Ringer adaptation. On the basis of the present results, it is concluded (a) that the depolarizing responses of the NS and WS cells under the Ringer adaptation are produced by the permeability increase in some ions, mainly Na+ ions across the taste cell membranes, and (b) that the hyperpolarizing responses of both types of taste cells are produced by a decrease in the cell membrane permeability to some ions, probably Na+ ions, which is slightly enhanced during the Ringer adaptation.     

Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two- dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.      

Immobilization stress-induced lesions of structures of the midbrain reticular formation

Emotional stress in rats resulted in blood-brain barrier increased permeability and brain parenchymal vessel disruptions. Stress induced microvascular damages were mainly observed in midbrain reticular formation. In this article the components of midbrain reticular formation were studied 1, 2, 4 and 6 weeks after immobilization stress. The destructive changes in some neurons, glia cells and myelin fibers were shown up to 6 weeks after immobilization. The signs of the recovery were also observed. It was supposed that the brain parenchymal vessel damages under emotional stress were due to the stress induced locus coeruleus dysfunctions.     

Effect of calcium and magnesium ions on different stages of genetic transformation in Bacillus subtilis]

Optimal concentrations of magnesium and calcium ions under their combined effect on genetic transformation in Bacillus suttilis are 2 - 10(-2) M and 4 - 10(-2) M respectively. The same concentrations are optimal under the effect of each cation clone. Magnesium ions are efficient during irreversible DNA binding. In the presence of magnesium ions calcium ions stimulate more late stages of transformation. The greatest efficiency of transformation is shown in consecutive effect of magnesium ions at early stages of transformation and of calcium ions at late transformation stages. This suggests that magnesium and calcium ions stimulate the activity of nuclease, taking part at early and late transformation stages.     

Morphophysiological patterns of life history strategy adoption in Dolly Varden <Emphasis Type="Italic">Salvelinus malma</Emphasis> in Kamchatka

Growth, age composition, gonad maturity and patterns of life history strategy adoption in the population of Dolly Varden from the Kol River (West Kamchatka) are studied. Major factors controlling differentiation of juveniles and trajectories of ontogenetic developments, growth rate and gametogenesis in generations in particular years. The differentiation in a generation into anadromous and resident groupings is completed mainly at the age of 4 years. The process of formation of resident and migratory life history strategy in Dolly Varden is epigenetic. Bifurcation in the life of one specimen is observed once in life, and that in a generation is observed four times: at the first, the second, the third, or the fourth year. The life cycle of females from the Kol River is invariant until they reach the age of 1 year, and that in males is during the 4 years of the freshwater phase. In Kamchatka, all spawners, including precocious males, may reproduce several times during life.