Limitation of ischemic necrosis by the use of antioxidant ionol

Inhibitory effect of Ionol on lipid peroxidation (LPO) in the infarction zone and out of it after experimental myocardial infarction in the experiments on rats was investigated. The results of measurements, performed by two independent methods: point counting and the computer image analysis were compared. It was shown that LPO activation out of the ischaemic zone was prevented and dimensions of the ischaemic necrosis were limited by Ionol, which did not influence LPO activation in the ischaemic zone. Data obtained by both methods coincide qualitatively, the computer image analysis being more sensitive and effective.     

Squares of different sizes: effect of geographical projection on model parameter estimates in species distribution modeling

In species distribution analyses, environmental predictors and distribution data for large spatial extents are often available in long‐lat format, such as degree raster grids. Long‐lat projections suffer from unequal cell sizes, as a degree of longitude decreases in length from approximately 110 km at the equator to 0 km at the poles. Here we investigate whether long‐lat and equal‐area projections yield similar model parameter estimates, or result in a consistent bias. We analyzed the environmental effects on the distribution of 12 ungulate species with a northern distribution, as models for these species should display the strongest effect of projectional distortion. Additionally we choose four species with entirely continental distributions to investigate the effect of incomplete cell coverage at the coast. We expected that including model weights proportional to the actual cell area should compensate for the observed bias in model coefficients, and similarly that using land coverage of a cell should decrease bias in species with coastal distribution. As anticipated, model coefficients were different between long‐lat and equal‐area projections. Having progressively smaller and a higher number of cells with increasing latitude influenced the importance of parameters in models, increased the sample size for the northernmost parts of species ranges, and reduced the subcell variability of those areas. However, this bias could be largely removed by weighting long‐lat cells by the area they cover, and marginally by correcting for land coverage. Overall we found little effect of using long‐lat rather than equal‐area projections in our analysis. The fitted relationship between environmental parameters and occurrence probability differed only very little between the two projection types. We still recommend using equal‐area projections to avoid possible bias. More importantly, our results suggest that the cell area and the proportion of a cell covered by land should be used as a weight when analyzing distribution of terrestrial species.     

Position of eukaryotic initiation factor eIF5B on the 80S ribosome mapped by directed hydroxyl radical probing

Eukaryotic translation initiation factor eIF5B is a ribosome-dependent GTPase that mediates displacement of initiation factors from the 40S ribosomal subunit in 48S initiation complexes and joining of 40S and 60S subunits. Here, we determined eIF5B's position on 80S ribosomes by directed hydroxyl radical cleavage. In the resulting model, eIF5B is located in the intersubunit cleft of the 80S ribosome: domain 1 is positioned near the GTPase activating center of the 60S subunit, domain 2 interacts with the 40S subunit (helices 3, 5 and the base of helix 15 of 18S rRNA and ribosomal protein (rp) rpS23), domain 3 is sandwiched between subunits and directly contacts several ribosomal elements including Helix 95 of 28S rRNA and helix 44 of 18S rRNA, domain 4 is near the peptidyl-transferase center and its helical subdomain contacts rpL10E. The cleavage data also indicate that binding of eIF5B might induce conformational changes in both subunits, with ribosomal segments wrapping around the factor. Some of these changes could also occur upon binding of other translational GTPases, and may contribute to factor recognition.     

Long-term survival and resistance of submerged pseudomonad cultures in the exopolymer mass

An issue on the cellular forms that ensure survival of pseudomonads is important due to wide occurrence of these bacteria in the environment and their role for clinical microbiology. The present work demonstrates the high survival potential of Pseudomonas aurantiaca and P. аeruginosa in the mass of exopolymers produced by cells. Exopolymer formation occurred only during incubation of the post-stationary phase cultures of P. aurantiaca (at 4°C) and P. aeruginosa (at 4 and 20°C). After storage for 1.5–12 months, the number of colony-forming units in the exopolymer was 30 to 68% of the viable cell titer in stationary-phase cultures. Antibiotic-tolerant persister cells that were revealed in the exopolymer cultures after treatment with ciprofloxacin (2.5–100 μg/mL) were more resistant to the antibiotic than persisters in suspension cultures, with the threshold doses of 25 and 2.5 μg/mL, respectively. The cells embedded in the exopolymer were found to be more resistant to 5-min heating at 60–70°C than the vegetative cells of suspension cultures, which did not survive such heat treatment conditions. Electron microscopic investigation revealed morphological heterogeneity of exopolymer-embedded pseudomonads, including the presence of the cells similar to cystlike dormant forms. The populations developing on solid media inoculated with the exopolymer mass with cells were found to contain 1.5 to 2 orders of magnitude more persisters tolerant to high ciprofloxacin doses (25 μg/mL for P. aurantiaca and 100 μg/mL for P. aeruginosa) than the populations developing after inoculation with second-transfer vegetative cells of the cells of planktonic cultures. The results obtained improve our understanding of pseudomonad survival in the environment.     

Critical scaffolding regions of the tumor suppressor Axin1 are natively unfolded

The Wnt pathway tumor-suppressor protein Axin coordinates the formation of a critical multiprotein destruction complex that serves to downregulate β-catenin protein levels, thereby preventing target gene activation. Given the lack of structural information on some of the major functional parts of Axin, it remains unresolved how the recruitment and positioning of Wnt pathway kinases, such as glycogen synthase kinase 3β, are coordinated to bring about β-catenin phosphorylation. Using various biochemical and biophysical methods, we demonstrate here that the central region of Axin that is implicated in binding glycogen synthase kinase 3β and β-catenin is natively unfolded. Our results support a model in which the unfolded nature of these critical scaffolding regions in Axin facilitates dynamic interactions with a kinase and its substrate, which in turn act upon each other.     

Possible role of lipid peroxidation in the pathogenesis of arrhythmias in myocardial infarct

The effect of myocardial infarction sustained by rats on the resistance of their isolated auricles to H2O2, an inductor of lipid peroxidation (LP), was studied. Atrial resistance to the LP inductor depends on the level of developed tension (DT) and the decrease of DT leads to augmentation of atrial resistance to the arrhythmogenic effect of LP. The experimental myocardial infarction causes appreciable disturbances in the function of automatism of the auricles, 60% of which lose their capability of spontaneous contractile activity. When compared with the control under equal DT, the auricles of the "infarction" series are less resistant to H2O2: the time of arrhythmias and arrests in them are 2.3 times as much as in the control. In infarction, the pretreatment with ionol reduces both the quantity of the auricles which stopped before H2O2 administration and the quantity of the auricles responding by arrhythmia to LP induction. The data point to the possibility of the use of antioxidants for preventing arrhythmias in experimental myocardial infarction.     

Ultrastructure of Yersinia pseudotuberculosis in the process of their reversible transition into the dormant (non-culturable) state in association with blue-green algae

The ultrastructural organization of Y. pseudotuberculosis in the process of the transition of vegetative cells into the dormant (noncultivable) state in interaction with blue-green algae of the species Anabaena variabilis was studied by the method of transmission electron microscopy. The use of type specific Y. pseudotuberculosis serum made it possible to identify Y. pseudotuberculosis cells in the bacterial association and to find out whether their antigenic properties remained intact in time. The dormant forms of Y. pseudotuberculosis, recultivated by passage through the axenic culture of unfusoria (Tetrahymena pyryformis), were also studied with the use of electron microscopy. The revertants were found to be at different stages of restoration of their typical morphological characteristics and antigenic properties were partially retained. The fine structure of Y. pseudotuberculosis cells in the initial culture was shown to be similar to that of the revertants of dormant forms, morphological criteria of the dormant cell ultrastructure were established. The cyclic processes of reversible transition from vegetative forms to dormant ones in bacterial populations under the influence of hydrobios is regarded as an adaptive mechanism of their existence in the environment.