Killer systems of Saccharomyces cerevisiae yeasts

The killer systems of Saccharomyces cerevisiae are a peculiar group of cytoplasmic symbionts of primitive eukaryotes. The genetic material of these symbionts is double-stranded RNA. Their basic properties are linearity of genome, its fragmentation, resulting in two separately replicating major and minor segments, and the ability to control the synthesis of secretory proteins--mycocins which can kill the taxonomically related strains. Secretion of mycocins also confers immunity to their action. The strains containing killer symbionts are toxigenic and resistant to their own toxins, while those with no killer double-stranded RNA are sensitive to mycocins. The killer systems of Saccharomyces cerevisiae possess some properties relevant to viruses and evidently are evolved during the evolution of infectious viruses. Occurrence of such systems in monocellular eucaryotic organisms is an example of genome complication in the course of putting together the virus-like components. The peculiarities of replication and expression of killer systems and their utilization for the construction of vector molecules are discussed.     

Genetic control of the number of copies of type K2 killer plasmids in Saccharomyces cerevisiae

13 non-linked chromosomal mutations derepress the negative genetic control of copy number of K2 yeast killer plasmids and lead to 1.5-2-fold elevating of copy number of that type plasmids -L2A and M2 virus-like dsRNA. The content of both plasmids is increased 3-5-fold in cells with chromosomal ski5 mutation, as compared to the strains of wild type. Expression of ski5 allele is recessive. The dose effect of this allele is observed on haploid and diploid levels. Dominant ochre nonsense suppressors suppress the action of ski5 and the ski6 allele epistates that of ski5.     

Fibrinolytic activity of natural variants of Bacillus mesentericus

The natural variability of the ability to synthesize proteinases by Bacillus mesentericus 64 was studied. The population of this strain was shown to be heterogeneous. Three types of variants (S, M and P) differed in the morphology of their colonies and in the culture characteristics from the typical colonies of the parent strain. The caseinolytic activity of the M variant was three times as high as that of the parent strain, and it also had an elevated fibrinolytic activity and a high rate of blood thrombolysis in experiments in vitro. The rate of proteinase synthesis correlated with the morphological types of sporogenic bacteria.     

Introduction of regulatory subunits of cAMP-dependent protein kinase type II in ZTZ cells with the use of erythrocyte ghosts

The dynamics of distribution of the regulatory subunit of cAMP-dependent protein kinase II following protein injection into 3T3 cells was studied. The cAMP-binding component of protein kinase was injected into the cells, using erythrocyte ghosts. The conditions for protein encapsulation into erythrocyte ghosts were elaborated. The optimal detergent concentrations, incubation time and conditions of vesicular closure following protein injection were selected. The above method provides for a high (50-55%) yield of the erythrocyte ghost-encapsulated protein with a minimum loss of enzymatic activity. Fusion of erythrocyte ghosts containing the labeled protein with 3T3 cells was carried out. Using the cytoradiography technique, the dynamics of distribution of the radiolabeled regulatory subunit within the cell was analyzed. It was demonstrated that after the regulatory subunit has reached the cytoplasm, the protein is translocated into the nucleus and is pooled there is the vicinity of the nucleoli.     

Assignment of the gene for adenine phosphoribosyltransferase on the genetic map of mouse chromosome 8

Two electrophoretic variants of adenine phosphoribosyltransferase (APRT) were identified in a population of wild mice (Mus musculus bactrianus). Breeding tests demonstrated that the APRT variants are under the control of two alleles at an autosomal locus designatedAprt. We have examined the linkage relationships betweenAprt and the markers of chromosome 8 including esterase-1 and the centromere. The recombination distance between the centromere andAprt is 44 ± 7 cM, and that betweenEs-1 andAprt is 25 ± 2 cM, i.e., the probable order of the markers examined is cen-Es-1-Aprt on chromosome 8.     

Phytopathogenicity of avian mycoplasma Mycoplasma gallisepticum S6: Morphologic and ultracytostructural changes in plants infected with the vegetative forms and the viable but nonculturable forms of the bacterium

The data obtained in this study proved that Mycoplasma gallisepticum S6 known as avian pathogen had a phytopathogenic potential. The vegetative forms and the viable but nonculturable (VBNC) forms of this mycoplasma could infect the plants via an assemblage of rootlets, invade different tissues, persist there and cause destructive events characteristic to phytomycoplasmoses. In comparison with the vegetative forms, the VBNC forms induced more prominent destructive changes. This phenomenon might be connected to increasing expression of proteins responsible for virulence in the bacterial cells. The fact that M. gallisepticum S6 could demonstrate virulent features (infectivity, invasiveness, persistence and toxigenicity) in regard to plants seems to require a development of new ways for controlling phytomycoplasmoses taking into account the probable presence of asymptomatic carriers of this bacterium.     

Immunological approach to structural-functional mapping of the membrane receptors

In order to study the structural and functional specificity of different fragments of extracellular domains of the membrane receptors, their immunological blockade and analysis of changes in brain function in health and disease were carried out. Effects of the immunization against unstructured fragments of the neurotrophin receptor (p75 NTR) containing binding sites for a nerve growth factor, amyloid-beta, and proneurotrophin were studied. It was shown that immunization of NMRI mice with synthetic peptides with amino-acid residue sequences corresponding to the p75 NTR fragments 86–93 and 146–153 exerted an adverse effect both on the morpho-functional state of the cortical and hippocampal neurons and on the spatial memory of animals. In contrast, the immunization by the p75 NTR synthetic fragment 167–176 was accompanied by an improvement of these characteristics. The results of the structural-functional mapping of the extracellular domain in neuronal membrane receptors in vivo were in line with the published data of the X-ray analysis. The immunological approach developed in this work provides insight into the peculiarities of the receptor functioning in the course of the Alzheimer’s type neurodegeneration process and favors the development of effective immunological ways for selective therapy of the Alzheimer’s disease.     

Bioavailability of tetracycline hydrochloride capsules (an in vivo study)]

Blood absorption of tetracycline hydrochloride of various dispersity levels from capsules containing tetracycline alone or in combination with additives, such as magnesium carbonate and calcium salts was studied on humans. It was found that higher dispersity levels of tetracycline hydrochloride powder in capsules was not accompanied by increased blood absorption of the antibiotic. Addition of magnesium carbonate and calcium salts to the antibiotic in the process of capsulation markedly retarded the blood absorption. Clear correlation between the antibiotic dissolution rate in vitro and intensity of its blood absorption in volunteers was shown.     

Compensation in behavioral disorders in rats receiving 5,7-DHT neonatally and by transplantation of embryonic raphe nucleus tissue

In 62 male Wistar rats the influence was studied of the transplanted embryonal tissue of raphe nuclei (NR) on the mechanisms of compensation of disturbances of exploratory activity, sensory attention, learning and emotional reactivity induced by neonatal injection of 5,7-DHT. In histochemical studies by Falk-Hillarp method the presence of yellow fluorescence confirmed the specificity of transplanted 5-HT neurones. It is found that NR transplantation causes in animals after 3 months recovery of orienting reaction to sensory stimuli, reduces rats reactivity in the open field, restores the ability to discrimination of emotionally positive influence, disturbed by neonatal injection of 5,7-DHT. The obtained data show the possibility of compensation of behaviour disturbances caused by chronic deprivation of 5-HT system activity by transplantation in the neocortex parenchyma of the embryonal tissue, containing serotoninergic neurones.