Volume 45, Nº 5 (2018)

In this study, we used the mouse model of chemically induced hepatocarcinogenesis to investigate the chromosomal aberrations in hepatic cells. The model was obtained by combined treatment of mice with Dipin (radiomimetic drug) followed by partial hepatectomy. Cytological analysis of isolated liver cells treated with Dipin has demonstrated a number of hepatocytes with structural nuclear abnormalities and multiple micronuclei. Karyotype analysis of polyploid hepatocytes has shown numerous chromosomal aberrations including alleged morphological manifestations of chromothripsis, a special type of genomic reorganization characterized by the local disintegration of chromosomes. Micronuclei with chromosomal fragments have developed as a result of double-strand DNA breaks and might serve as the initial substrate for chromothripsis. The emergence of micronuclei containing chromosomal fragments is the most important result of the treatment employed. Therefore, the presented model of liver cancer (hepatocarcinogenesis) can be used to study the process of chromothripsis in the future.

Dynamic changes in the enzymatic activity of lactate dehydrogenase, L-lactate-cytochrome-c-coxidoreductase, and alcohol dehydrogenase were analyzed in the seedlings of sorghum, a plant resistant to oxygen deficiency, and peas, a plant vulnerable to oxygen deficiency, cultivated under the conditions of flooding. The subcellular localization and isoform composition of the enzymes were characterized. The mechanism underlying the adaptive reaction of cell metabolism was devised from analysis of the results obtained. The reaction is supposed to involve lactate dehydrogenase and L-lactate-cytochrome-c-oxidoreductase enzymes that suppress cytoplasm acidification in sorghum and pea roots in the case of flooding.

To specificate phylogenetic relationships between sibling-species Sicista of the caucasica group and to determine their position in the genus Sicista, comparative analysis of the nucleotide sequences of a fragment (903 bp) of the first exon of the IRBP (interphotoreceptor retinoid-binding protein) gene of nuclear DNA has been carried out for three Sicista species (S. caucasica, S. kluchorica, and S. kazbegica) of the caucasica group. Some other Sicista species (S. concolor, S. tianschanica, and Sicista species of the groups betulina and subtilis) have been taken for comparison. The results reflect the monophyly of the group and its division into the three clades corresponding to sibling-species of the group. It has been shown that the average genetic distances between S. caucasica and S. kluchorica calculated on the nucleotide sequences of a fragment (903 bp) of the first exon of IRBP gene using three-parametrical Tamura’s model (T92) do not exceed 0.4%. The level of differences of each of these two species from S. kazbegica is 0.7%, which is comparable to the interspecific genetic distances for Sicista sibling-species of the group betulina (intergroup genetic distances exceed 2%).

The seasonal developmental rhythm, floral and fruit morphology, anthesis, and fructification of Asarum sieboldii were studied in a natural plant community in the southern part of the Russian Far East. The flower structure was investigated in ditails. It was found that the flower does not have a gynostemium. The flowers are protogynous. At the first anthesis stage, the anthers are closed and cross-pollination may be realized by ants (Hymenoptera) or flies (Dolichopodidae, Diptera). At the second stage of anthesis, there is direct contact of anthers with the pistil stigma and self-pollination occurs. The perianth is involved in the formation of fruit. The fruit is a six-locular, fleshy, half-inferior capsule. Asarum sieboldii has a high productivity of fruits and seeds. The fruit set is 89% after self-pollination. Viable seeds per fruit is 29 ± 2, the seed set is 69 ± 5%. The agents of seed dissemination are ants: Leptothorax acervorum and Myrmica ruginodis (Formicidae, Hymenoptera).

The influence of increased zinc concentrations on seed germination, growth activity, photosynthetic apparatus, and water metabolism in two perennial grasses (Phleum pratense L. and Elytrigia repens (L.) Nevski) was studied in laboratory and vegetation experiments to assess plant metal tolerance. In laboratory conditions it was established that seeds of both species may germinate in a wide range of zinc concentrations. In vegetation experiments, the possibility of successful growth and accumulation of biomass of both grasses in the presence of high zinc concentration in the root medium was revealed. At the same time, high water contents in root and shoot tissues were maintained, as well as the necessary intensity of photosynthesis (due to maintenance of the efficiency of photosystem II and the amount of carotenoids). It was noted that the established high resistance of both species of grasses to zinc, as well as their ability to accumulate significant amounts of metal ions in the roots, indicates that P. pratense and E. repens may be used for phytoremediation of soils contaminated with zinc.

A study of the brain of 47 species from 15 lepidopteran families has revealed that only one neuroblast corresponds to each calyx cup of the mushroom body and that mushroom body neuroblasts have been found in the imagoes of 13 out of 25 species caught in the field. It is considered that the proliferative centers consisting of several neuroblasts are not characteristic of lepidopteran mushroom bodies, whereras Kenyon cell neurogenesis in the imago appears to be a widespread phenomenon.

We have investigated behavioral responses of Rana arvalis Nilss. tadpoles to water carrying various water-soluble chemical stimuli: natural lake water; dechlorinated tap water; water in which tadpoles were kept; water with chemical characteristics of the jellylike remains of their own or other clutches after tadpole hatching; boiled nettle, which was used as food for laboratory animals; and water containing toxins of the skin glands of the common toad Bufo bufo L. The preference for natural water over the tap water was revealed, as well as the fact that naive tadpoles were attracted by the “smell” of nettles and tried to avoid toxins.

Biofilms are aform of existence of bacteria in the environment, due to which bacteria can expand the boundaries of their habitats during contamination of different surfaces under diverse conditions. The most important environmental factors affecting biofilms are discussed. These factors include temperature, osmolarity, the concentration of ferrous iron ions, the availability of nutrients, the quality of materials on which biofilms are formed, and light and theambient acidity.

The appearance of Daphnia (Ctenodaphnia) magna Straus, 1820 in the pelagial of Sevan Lake caused significant changes in the communities of planktonic algae, bacteria, and heterotrophic nanoflagellates. Phytoplankton and nanoflagellates were the most affected by the direct impact of D. magna, and the number and biomass of bacteria increased due to the reduction in the trophic pressure of the protists. It was also facilitated by the increased supply of phosphorus as a result of the activity of the cladocerans, as well as the decrease in the number and biomass of phytoplankton, which competes with heterotrophic bacteria for the nutrients.