Three twinning types in mink (<Emphasis Type="Italic">Mustela vison</Emphasis>) embryogenesis

The frequency of occurrence of monochorionic twins in the postimplantational embryogenesis of the American mink and their karyotypes were studied. Monochorionic twin pairs were found in which embryos had different chromosome sets: 2n, XX and 2n, XY or 2n and 3n. This fact contradicts the idea that monochorionic twins should be monozygotic and genetically identical but confirms our earlier hypothesis that a third twinning type exists in mink: monozygotic but genetically different. The mechanism of the emergence of this twinning type in mammals is discussed. It is suggested that the high (up to 4.5%) frequency of its emergence in the American mink is related to obligate embryonic diapause, causing abnormal fertilization.     

The comparative roles of acetylcholine and noradrenaline in regulation of spontaneous spike activity of cortical neurons

The effects of acetylcholine and noradrenaline applications on neuronal sponta-neous activity were investigated in slices of guinea-pig parietal cortex. Iontophoretic ejections of both neurotransmitters to the cortical neurons evoked the same-type slowly-developing and long-lasting increase in the rate of spike activity. The different temperature sensitivity of cholinergic and noradrenergic reactions were revealed. During the temperature shift from 32-34 degrees C to 35-36 degrees C the cholinergic effect on neuronal spike activity became extremely strong, that is why even silent at t = 32-32 degrees C neurons became to acetylcholine responsive. Temperature-dependent changes in spike reaction to acetylcholine were accompanied by stable increase in spontaneous spike activity. The noradrenergic reactions did not change with temperature in limits from 32-34 to 35-36 degrees C. In this temperature range spike reactions to glutamate, the main excitation transmitter in the cortex, remained constant. The results obtained suggest that acetylcholine is the main neurotransmitter regulating spontaneous spike activity in cortical neurons.     

Combined effect of heavy metals and shungite on the indicator plankton species

The combined effect of salts of heavy metals and shungite on the test organisms of phyto- and zooplankton has been studied. The toxic effect of both cadmium sulfate and potassium dichromate on the culture of Scenedesmus guadricauda was inactivated in the presence of shungite (100 g/L). The efficiency of photosynthesis, the number of cells, the proportion of living cells, and the lifetime of the microalgae cell population increased after adding shungite to the medium (without toxicants). In addition, in acute experiments that lasted up to 96 h, the toxicity of potassium dichromate, copper sulfate, and cadmium sulfate on crustaceans (Daphnia magna and Ceriodaphnia affinis) was studied in the presence of shungite (0.01 g/L) and without it. This study of the effect of shungite’s presence on crustaceans showed that it protected both Daphnia magna and Ceriodaphnia affinis from the action of toxicants at the minimum concentration (0.01 g/L) of the five tested. Daphnia magna died at higher concentrations of shungite. It was shown that the acute toxicity of heavy metals for the two crustacean species decreased in the series Cu–Cd–Cr. The analysis of the obtained data showed that the shungite concentrations necessary for the inactivation of heavy metals were thousands of times higher for algae than for crustaceans. Therefore, when using the shungite as a protector against the toxic effects of various substances, a preliminary laboratory analysis of the survival of different species of hydrobionts in a specific aquatic environment is necessary.     

Mitochondrial cytopathies: Their causes and correction pathways

Mitochondrial cytopathies are a heterogeneous group of systemic disorders caused by mutations in mitochondrial or nuclear genome. The review presents some data on pathogenic mutations in mitochondrial DNA leading to the imbalance in the oxidation phosphorylation processes and energy metabolism in the cells and eventually to the development of mitochondrial cytopathy. The pathways of medicated correction are examined, which are aimed at obtaining optimal energy efficiency of mitochondria with impaired functions, increase of the efficiency of energy metabolism in the tissues, as well as prevention of mitochondrial membrane damage by free radicals using antioxidants and membrane protectors. A conclusion is drawn on the inefficiency of currently used therapeutic strategies and the necessity of new approaches, which can be gene therapy of mitochondrial diseases. Some modern methods for gene defects correction, capable of restoring or removing the damaged gene, expressing full gene product, or blocking the mutant or strange genes work are analyzed. It is shown that the described approaches to the gene therapy of human mitochondrial diseases demand the introduction of foreign sequences into nuclear or mitochondrial genome of a living person, which completely excludes their practical application because of the uncertainty of the outcome. A perspective approach in solving this problem may be a creation of a system allowing the correction of defect genes without introducing synthetic nucleotides into the human genome. Phenotypic selection combined with a capacity of homologous recombination, artificially imparted to mitochondria of yeast Yarrowia lipolytica, allows for replication of intact human mitochondrial DNA in yeast mitochondria, supporting a full-size native human mitochondrial DNA in the yeast cells and eliminating pathogenic mutations by means of standard sitedirected PCR mutagenesis. After the correction in the Y. lipolytica cells, copies of mitochondrial DNA of an individual patient may be returned to him using the transfection of mesenchymal stromal cells followed by selection of transfectants grown in minimal culture media, in which the cells with higher respiratory mitochondrial activity will gain the advantage.     

Activity of Embryonic Mink Genome during Diapause (Cytogenetic Analysis): Nucleolar and Extranucleolar RNA Synthesis

The nucleolar and extranucleolar RNA synthesis was studied in the mink blastocysts at different stages of embryonic diapause and during the periimplantation period using cytoradioautography. The data obtained suggest a differential and stage specific activity of the embryonic mRNA and rRNA synthesis during the period of delayed implantation.     

Pattern of growth and metabolism of thermotolerant microorganisms on media containing carbohydrates and hydrocarbons

Experiments were carried out to examine the growth and metabolism of thermotolerant yeast Candida tropicalis K-41 and bacteria Micrococcus freudenreichii that do not have a single temperature point but instead have an optimal temperature plateau at which the growth rate and biosynthetic activity remain unaltered or change insignificantly. Upon transition from the carbohydrate to the hydrocarbon pattern of nutrition these microorganisms show significant changes in metabolic processes: optimal concentration of biotin in the medium decreases significantly; the synthesis of riboflavin, nicotinic and pantothenic acids increases in yeast; the synthesis of nicotinic acid, biotin and vitamin B12 increases in bacteria. During microbial cultivation on hydrocarbons the content of cell lipids grows; yeast accumulate actively phospholipids and free fatty acids; bacteria build up intensively waxes and phospholipids. With the near-maximal growth rate the total synthesis of lipids decreases on carbohydrates and increases drastically on hydrocarbons, primarily at the expense of the above fractions.     

Calcium-Dependent Nonspecific Permeability of the Inner Mitochondrial Membrane Is Not Induced in Mitochondria of the Yeast Endomyces magnusii

Mitochondria of the yeast Endomyces magnusii were examined for the presence of a Ca2+- and phosphate-induced permeability of the inner mitochondrial membrane (pore). For this purpose, coupled mitochondria were incubated under conditions known to induce the permeability transition pore in animal mitochondria, i.e., in the presence of high concentrations of Ca2+ and P(i), prooxidants (t-butylhydroperoxide), oxaloacetate, atractyloside (an inhibitor of ADP/ATP translocator), SH-reagents, by depletion of adenine nucleotide pools, and deenergization of the mitochondria. Large amplitude swelling, collapse of the membrane potential, and efflux of the accumulated Ca2+ were used as parameters for demonstrating pore induction. E. magnusii mitochondria were highly resistant to the above-mentioned substances. Deenergization of mitochondria or depletion of adenine nucleotide pools have no effect on low-amplitude swelling or the other parameters. Cyclosporin A, a specific inhibitor of the nonspecific permeability transition in animal mitochondria, did not affect the parameters measured. It is thus evident that E. magnusii mitochondria lack a functional Ca2+-dependent pore, or possess a pore differently regulated as compared to that of mammalian mitochondria.