Prooxidant and cytotoxic action of N-acetylcysteine and glutathione in combinations with vitamin B12b

Prooxidant and cytotoxic effects of thiols N-acetylcysteine (NAC) and glutathione (GSH) were studied in combinations with vitamin B_12b. Both GSH and NAC at physiological doses when combined with B_12b were shown to cause initiation of apoptosis. It was established that the prooxidant action of NAC (or GSH) combined with B_12b, i.e., generation and accumulation of hydrogen peroxide in culture medium, led to intractellular oxidative stress and cell redox imbalance. These effects are completely prevented by nonthiol antioxidants catalase and pyruvate. The chelators of iron phenanthroline and deferoxamine do not suppress the H₂O₂ accumulation in culture medium, but inhibit cell death induced by NAC combined with B_12b or by GSH combined with B_12b. Therefore, the thiols GSH or NAC in combination with vitamin B_12b reveal prooxidant properties and induce, with participation of intracellular iron, apoptotic HEp-2 cell death.     

Sulfate reduction,methanogenesis, and methane oxidation in the Holocene sediments of the Vyborg Bay,Baltic Sea

Methane content and the rates of microbial processes of the carbon and sulfur cycles were determined for the sediments of the Vyborg Bay, Baltic Sea. Formation of the gas-bearing surface sediments in the Vyborg Bay was found to depend on the activity of the modern microbial processes of the transformation of organic matter, resulting in production of significant amounts of reduced gases (methane and hydrogen sulfide). Rapid consumption of sulfate in the course of sulfate reduction coupled to organic matter decomposition both suppressed anaerobic oxidation of methane and promoted microbial methanogenesis. The gasbearing sediments of this area therefore become a source of methane, and methane concentration in the near-bottom water increases significantly.     

Simulation of mechanoelectrical coupling in cardiomyocytes under normal and abnormal conditions

Mathematical models of the electromechanical function of cardiomyocytes and muscle duplexes, the simplest mechanically inhomogeneous myocardial systems, are developed. Using these models, the contribution of mechanoelectrical feedbacks to the contractive activity of the myocardium in normal and abnormal conditions is studied. In particular, the influence of the mechanical conditions of contraction on the shape and duration of the action potentials is reproduced and interpreted. In this context, different types of mechanical heterogeneity of the myocardium are analyzed. It is established that this heterogeneity can play a positive or negative role depending on the distribution of heterogeneous properties and on the order the elements of the system are activated. Using the same models, the contribution of mechanical factors to arrhythmogenesis under calcium overload of cardiomyocytes due to the weakening of the sodium-potassium pump is studied. Methods for correction of the contractive activity of cardiomyocytes in the case of such abnormalities are outlined.     

Flow cytometry-based assay for the activity of NAD(P)H oxidoreductases of the outer mitochondrial membrane

NAD(P)H oxidoreductases of the outer mitochondrial membrane (OMM) are able to activate various xenobiotics and stimulate the production of reactive oxygen species and the opening of the mitochondrial permeability transition pore. However, the role of these systems in the cell damage by xenobiotics and chemotherapeutic drugs is poorly understood because the methods for the selective assessment of their activity have not been elaborated and specific inhibitors are unknown. Here we propose a method for the semiquantitative assessment of the activity of NAD(P)H oxidoreductases of the OMM in intact and permeabilized cells that is based on the flow cytometry detection of dimethylbiacridene, a fluorescent product of two-electron reduction of lucigenin. The method uses the structural feature of mitochondrial organization: the proximity of the sites of one-electron reduction of lucigenin to cation radical (NAD(P)H oxidoreductases of the OMM) to the sites of its subsequent oxidation (cytochrome c oxidase). The inhibition of cytochrome c oxidase by cyanide selectively activates the dimethylbiacridene formation by oxidoreductases of the OMM but not by other cellular oxidoreductases. The proposed protocol allows one to assess the lucigenin reductase (two-electron) activity of NAD(P)H oxidoreductases of the OMM and to compare it with the activity of other cellular systems that can be used for the analysis of the role of these systems in the cell damage by xenobiotics and antitumor drugs.     

A comparative study of the pumping activity of some fouling animals from the White Sea

The pumping activity of the bivalve Mytulus edulus, Hiatella arctica, and solitary ascidian Styela rustica from the White Sea has been studied. The dependence of the pumping activity on the mass and size of animals has been analyzed. It was shown that the mussel is the most active filter-feeder, that the least value of the pumping activity has been registered for H. arctica, and that S. rustica occupies an intermediate position according this index. The results obtained are examined in connection with the competitive relationship of the animals in the fouling community.     

Recombinant phospholipase A<Subscript>1</Subscript> of the outer membrane of psychrotrophic <Emphasis Type="Italic">Yersinia pseudotuberculosis</Emphasis>: Expression,purification, and characterization

The pldA gene encoding membrane-bound phospholipase A₁ of Yersinia pseudotuberculosis was cloned and expressed in Escherichia coli cells. Recombinant phospholipase A₁ (rPldA) was isolated from inclusion bodies dissolved in 8 M urea by two-stage chromatography (ion-exchange and gel-filtration chromatography) as an inactive monomer. The molecular mass of the rPldA determined by MALDI-TOF MS was 31.7 ± 0.4 kDa. The highly purified rPldA was refolded by 10-fold dilution with buffer containing 10 mM Triton X-100 and subsequent incubation at room temperature for 16 h. The refolded rPldA hydrolyzed 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine in the presence of calcium ions. The enzyme exhibited maximal activity at 37°C and nearly 40% of maximal activity at 15°C. The phospholipase A₁ was active over a wide range of pH from 4 to 11, exhibiting maximal activity at pH 10. Spatial structure models of the monomer and the dimer of Y. pseudotuberculosis phospholipase A₁ were constructed, and functionally important amino acid residues of the enzyme were determined. Structural differences between phospholipases A₁ from Y. pseudotuberculosis and E. coli, which can affect the functional activity of the enzyme, were revealed.     

Dynamics of Diversity of Spined Loaches of Genus Cobitis,Inhabiting Caucasus,during the Anthropogenic Period According to the Data of Museum Collections. I. Morphological Variability and Diagnostic Characters of Cobitis saniae (Cobitidae)

Journal of Ichthyology - The variability of morphological characters and coloration features used for identification of the species Cobitis saniae has been studied using the materials from the...