Cytogenetic and immunological specificity of mammalian hybrid cell lines

Karyotypes of the hybrid cell lines NS-RL-3 (TK- -sheep kidney cells and rabbit lymphocytes) and betaCR-NS (TK- -rabbit beta-cells and TK- -sheep kidney cells) were investigated. It was shown that both hybrid cell lines were characterized by presence of both sheep and rabbit chromosomes, which number and structure varies depending on the cell type and the number of passages. In some cases the aberrant chromosomes were identified. It was observed, that 40-50% of the NS-RL-3 cells survived in culture in the presence of the human blood serum, and also were identified during 7-28 days after their introduction into the organism of the animal. Thus, the partial immunological tolerance of the hybrid cell lines has been suggested.     

Detection of light intensity in the frog retina: evidence from dark and light adaptation

The frog retina was stimulated with light flashes homogeneous in space but not time. The time heterogeneity of stimulation was created by abrupt change of a referent stimulus for a stimulus with different luminance. Such changes form a time pattern, as well as sharp borders of luminance between the neighbor areas of the visual field form a spatial pattern. The electroretinogram recorded in response to presentation of a triad of stimuli: the onset of a short flash of homogeneous light after long dark (or light) adaptation of a retina, brief sequence of the referent and test light flashes varied in luminance, and the offset, with returning to the initial level of adaptation. It was shown that responses of the retina under conditions of time heterogeneity of stimulation could be divided in two types as well as under conditions of spatial heterogeneity. Such a dual change in amplitude confirms our earlier hypothesis on the existence of two mechanisms of luminance coding in the frog retina. The first mechanism encodes power characteristics of light, it forms the information on the absolute level of the environmental luminance. Its activity is connected basically with receptors and cells of the external plexiform layer of the frog's retina. It is responsible for the b-wave of the electroretinogram. The other mechanism associated with RERG is based on a vector code of stimuli. This mechanism forms the information on spatial and time differentiation of the light flow in the visual field and is connected basically with cells of the internal plexiform layer. The results suggest that the frog retina has the individual mechanism for time pattern detection, distinguishing it from the homogeneous light flow in a similar way as in case of spatial light pattern detection. It is possible that the first mechanism is responsible for the detection of any new stimulus in general, irrespective of its specificity, whereas the second mechanism serves for the measurement of suprathreshold differences between stimuli.     

The endosymbiotic bacterium Wolbachia enhances the nonspecific resistance to insect pathogens and alters behavior of Drosophila melanogaster

To determine biologically important effects of the cytoplasmic endosymbiont Wolbachia, two substrains of the same Drosophila melanogaster strain have been studied, one of them infected with Wolbachia and the other treated with tetracycline to eliminate the bacterium. Female D. melanogaster infected with Wolbachia are more resistant to the fungus Bauveria bassiana (an insect pathogen) than uninfected females; infected females also exhibited changes in oviposition substrate preference. Males infected with the bacterium are more competitive than uninfected males. The possible role of Wolbachia in the formation of alternative ecological strategies of D. melanogaster is discussed.     

Resistance of Penicillium piceum F-648 to hydrogen peroxide under short term and prolonged oxidative stress

Resistance of Penicillium piceum F-648 to hydrogen peroxide under short-term and prolonged oxidative stress was studied. An increase in the activity of intracellular catalase in fungal cells after short-term exposure to hydrogen peroxide was shown. Activation of fungal cells induced by H2O2 depends on H2O2 concentration, time of exposure, and the growth phase of the fungus. Variants of P. piceum F-648 that produced two forms of extracellular catalase with different catalytic properties were obtained due to prolonged adaptation to H2O2. Catalase with low affinity for substrate was produced predominantly by the parent culture and variant 3; however, a high substrate affinity of catalase was observed in variant 5. Variant 5 of P. peniceum F-648 displayed a high catalytic activity and operational stability of catalase in the presence of phosphate ions and the concentration of substrate less than 30 mM at pH more than 7.     

Identification of the hereditary variants of skin melanoma

The identification of hereditary variants of cutaneous melanoma and analysis of the role of hereditary factors and syndromes predisposing to cutaneous melanoma were carried out. The involvement of individual nevus phenotypes in the development of this disease was determined. Based on a survey of recent molecular biological data and our studies, the etiological and genetic heterogeneity of cutaneous melanoma is reported. In relatives of patients with cutaneous melanoma and persons with multiple pigmented nevi, the malignant tumors proved to be differentiated in the direction of the neural crist tissues and/or derivatives of cutaneous mesenchyma. Based on the evidence obtained, the approaches have been developed to formation of risk groups for the purpose of early diagnostics of cutaneous melanoma.     

Effect of three types of ecological stress on the variability of morphological traits in Drosophila melanogaster

The effect of temperature, nutrition, and density stresses on phenotypic and genetic variation in morphological traits (thorax length, wing length, number of sternopleural and abdominal bristles, and number of arista branches) was examined in Drosophila melanogaster. In addition, the effect of stress on developmental stability measured as fluctuation asymmetry of bilateral traits was analyzed. All of the stresses were shown to increase phenotypic variation and fluctuating asymmetry of bilateral traits. Genetic variation of morphometric traits estimated using the isofemale line technique was higher under stressful than under normal conditions. Biotic and abiotic stresses were similar in their effect on phenotypic and genetic variation. The effect of stress on variability of morphometric traits was generally higher than on that of meristic traits. Possible causes of the increase of genetic variation under stress are discussed.     

Plant resistance genes: molecular and genetic organization,function and evolution

Remarkable progress is achieved now in comprehension of mechanisms that determine functioning of genes responsible for plants' phytopathogenic resistance (genes R). Cloning of great number of Monocotyledones and Dicotyledones resistance genes show that most of proteins coded by these genes have conserved amino-acid motives, which show high homology to amino-acid motives of proteins with well-designated function. Common structures for most proteins produced by genes R include nucleotide-blinding site (NBS), leucine-rich repeat (LRR), site containing homology with the cytoplasmic domains of the Drosophila Toll protein and the mammalian interleukin-1 receptor (TIR), coiled-coil structure (CC), transmembrane domain (TM), and serine/threonine proteinkinase domain (PK). They are combined within the basic classes of resistance genes proteins as follows: TIR-NBS-LRR, CC-NBS-LLRR, NBS-LRR, PK, TM-CC, LRR-TM, LRR-TM-PK. The domains of proteins produced by plant resistance genes cause specific recognition of avirulence genes products and activate signaling cascade, which gives rise to resistance reaction. Some classes of plant resistance genes probably have the same evolutionary origin as the genes that control the innate immunity of ancient animals. The evolution of plant R genes proceeds primarily by duplication and equal or unequal meiotic recombination. The research on genes R functioning besides its theoretical value is a matter of considerable practical interest for construction of plant genotypes resistant against harmful organisms. The progress in comprehension of mechanisms responsible for specificity of avirulence determinants in phytopathogenic organisms recognition makes possible the creation of artificial resistance genes.     

Protein S3 in the human 80S ribosome adjoins mRNA from 3'-side of the A-site codon

The protein environment of mRNA 3' of the A-site codon (the decoding site) in the human 80S ribosome was studied using a set of oligoribonucleotide derivatives bearing a UUU triplet at the 5'-end and a perfluoroarylazide group at one of the nucleotide residues at the 3'-end of this triplet. Analogues of mRNA were phased into the ribosome using binding at the tRNAPhe P-site, which recognizes the UUU codon. Mild UV irradiation of ribosome complexes with tRNAPhe and mRNA analogues resulted in the predominant crosslinking of the analogues with the 40S subunit components, mainly with proteins and, to a lesser extent, with rRNA. Among the 40S subunit ribosomal proteins, the S3 protein was the main target for modification in all cases. In addition, minor crosslinking with the S2 protein was observed. The crosslinking with the S3 and S2 proteins occurred both in triple complexes and in the absence of tRNA. Within triple complexes, crosslinking with S15 protein was also found, its efficiency considerably falling when the modified nucleotide was moved from positions +5 to +12 relative to the first codon nucleotide in the P-site. In some cases, crosslinking with the S30 protein was observed, it was most efficient for the derivative containing a photoreactive group at the +7 adenosine residue. The results indicate that the S3 protein in the human ribosome plays a key role in the formation of the mRNA binding site 3' of the codon in the decoding site.