Molecular genetic variety of rickettsiae

In this review modern data on the study of the genome of the representatives of the family Rickettsiaceae and, as follows from the accumulated information, on changes in the nomination and hierarchical place of its pathogenic and avirulent representatives are presented.     

The impact of fishery on the state of populations of the European whitefish Coregonus lavaretus in Lake Imandra

The impact of fishery on the state of populations of the European whitefish Coregonus lavaretus in Lake Imandra, the largest water body of the Kola Peninsula, is considered. The retrospective analysis of catches in the period of 1930 to 1998 indicated that the consequences of an uncontrolled fishery are comparable with the effects of intensive technogenic pollution. As a result of the intensive commercial load on the water body over many decades, the number of age groups decreases, the size-weight indices in fish change, an early maturation at sizes small for the species is observed, and the population structure becomes more simple. Against the background of the improving environmental quality, the numbers of fish under the effects of the uncontrolled amateur and poaching fisheries continue to decrease, which leads to the change of the nucleus of the fish proportion of the community and the change of dominant species.     

Solution structure of duplex DNA containing the mutagenic lesion 1,N(2)-etheno-2'-deoxyguanine

We have used high-resolution NMR spectroscopy and molecular dynamics simulations to determine the solution structure of DNA containing the genotoxic lesion 1, N (2)-etheno-2'-deoxyguanosine (epsilonG), paired to dC. The NMR data suggest the presence of a major, minimally perturbed structure at neutral pH. NOESY spectra indicate the presence of a right-handed helix with all nucleotides in anti, 2'-deoxyribose conformations within the C2'-endo/C1'-exo range and proper Watson-Crick base pair alignments outside the lesion site. The epsilonG residue remains deeply embedded inside the helix and stacks between the flanking base pairs. The lesion partner dC is extrahelical and is located in the minor groove of the duplex, where it is highly exposed to solvent. Upon acidification of the sample, a second conformation at the lesion site of the duplex emerges, with protonation of the lesion partner dC and possible formation of a Hoogsteen base pair. Restrained molecular dynamics simulations of the neutral-pH structure generated a set of three-dimensional models that show epsilonG inside the helix, where the lesion is stabilized by stacking interactions with flanking bases but without participating in hydrogen bonding. The lesion counterbase dC is displaced in the minor groove of the duplex where it can form a hydrogen bond with the sugar O4' atom of a residue 2 bp away.     

Experimental study of the properties of sublines of Rickettsia prowazekii vaccinal strain E

The instability of R. prowazekii strain E cultivated in chick embryos has been demonstrated. The complex of tests permitting determination of differences between various sublines of this strain in their immunogenic potency and residual virulence has been proposed.     

The Intracellular Calcium Kinetics and Action Potential in the Ventricular Myocardium of Spontaneously Hypertensive ISIAH Rats

Biophysics - Here, we show the dependence of intracellular calcium kinetics and the duration of the action potential of cardiomyocytes on an animal’s age in multicellular preparations of the...     

The Effect of Tillage and Mesorelief on the Structure of Soil Microbial Cenoses

The investigation of soil microbial cenoses in cultivated catenas and in virgin soils at the foot of catenas showed that the structure of these microbiocenoses depends on the type of the vegetation cover, the characteristics of mesorelief, and the degree of soil tillage. The microbiocenoses were found to be dominated by the fungal mycelium. The proportion of bacteria and fungal spores was higher and the seasonal variations in the soil microbial communities were more distinct in the cultivated than in the virgin swamp and forest soils. The type of mesorelief was found to appreciably influence microbial populations in the top humus-rich horizons of the cultivated soils and not in the mineral soil horizons.     

Adiabatic Heating of Electrons in the Magnetospheric Current Sheet

Electron dynamics and acceleration in an electromagnetic field configuration modeling the current sheet configuration of the Earth’s magnetotail region is investigated. A focus is made on the role of the dawn?dusk magnetic field component B_y in the convection electron heating by an electric field E_y. For numerical integration of a large number of test particle trajectories over long time intervals, the equations of motion written in the guiding center approximation are used. It is shown that the presence of a B_y ≠ 0 magnetic field significantly changes the electron heating and allows electrons with small pitch angles to gain energy much more efficiently than the equatorial electrons. As a result, the convection heating in the current sheet with B_y ≠ 0 leads to the formation of an accelerated anisotropic population of particles with energies higher than a few hundred electronvolts. The obtained results and spacecraft observations in the Earth’s magnetotail are compared, and possible limitations in the proposed model approaches are discussed.