Experimental Simulation of the Liver Drug Injury for Investigation of New Hepatoprotectors.

Efficient chemotherapy of tuberculosis patients could-be complicated by hepatoprotective responses to antituberculosis drugs. The frequency and nature of the response depend on the drug and the genotypical and phenotypical characteristics of its metabolism in the patients, that should be considered while choosing the hepatoprotector. The liver injury was induced by the reserve antituberculosis drugs in experiments on rats with various acetylation phenotypes. Analysis of the clinicobiochemical and morphological indices revealed differences in the liver injury simulation: prevalence of the cytolytic mechanism in slow acetylators 'vs. the rapid ones.

The B-type lamin is required for somatic repression of testis-specific gene clusters.

Large clusters of coexpressed tissue-specific genes are abundant on chromosomes of diverse species. The genes coordinately misexpressed in diverse diseases are also found in similar clusters, suggesting that evolutionarily conserved mechanisms regulate expression of large multigenic regions both in normal development and in its pathological disruptions. Studies on individual loci suggest that silent clusters of coregulated genes are embedded in repressed chromatin domains, often localized to the nuclear periphery. To test this model at the genome-wide scale, we studied transcriptional regulation of large testis-specific gene clusters in somatic tissues of Drosophila. These gene clusters showed a drastic paucity of known expressed transgene insertions, indicating that they indeed are embedded in repressed chromatin. Bioinformatics analysis suggested the major role for the B-type lamin, LamDm(o), in repression of large testis-specific gene clusters, showing that in somatic cells as many as three-quarters of these clusters interact with LamDm(o). Ablation of LamDm(o) by using mutants and RNAi led to detachment of testis-specific clusters from nuclear envelope and to their selective transcriptional up-regulation in somatic cells, thus providing the first direct evidence for involvement of the B-type lamin in tissue-specific gene repression. Finally, we found that transcriptional activation of the lamina-bound testis-specific gene cluster in male germ line is coupled with its translocation away from the nuclear envelope. Our studies, which directly link nuclear architecture with coordinated regulation of tissue-specific genes, advance understanding of the mechanisms underlying both normal cell differentiation and developmental disorders caused by lesions in the B-type lamins and interacting proteins.

Functional role of cysteine residues in the (Na,K)-ATPase alpha subunit.

The structural-functional roles of 23 cysteines present in the sheep (Na,K)-ATPase alpha1 subunit were studied using site directed mutagenesis, expression, and kinetics analysis. Twenty of these cysteines were individually substituted by alanine or serine. Cys452, Cys455 and Cys456 were simultaneously replaced by serine. These substitutions were introduced into an ouabain resistant alpha1 sheep isoform and expressed in HeLa cells under ouabain selective pressure. HeLa cells transfected with a cDNA encoding for replacements of Cys242 did not survive ouabain selective pressure. Single substitutions of the remaining cysteines yielded functional enzymes, although some had reduced turnover rates. Only minor variations were observed in the enzyme Na(+) and K(+) dependence as a result of these replacements. Some substitutions apparently affect the E1<-->E2 equilibrium as suggested by changes in the K(m) of ATP acting at its low affinity binding site. These results indicate that individual cysteines, with the exception of Cys242, are not essential for enzyme function. Furthermore, this suggests that the presence of putative disulfide bridges is not required for alpha1 subunit folding and subsequent activity. A (Na,K)-ATPase lacking cysteine residues in the transmembrane region was constructed (Cys104, 138, 336, 802, 911, 930, 964, 983Xxx). No alteration in the K(1/2) of Na(+) or K(+) for (Na,K)-ATPase activation was observed in the resulting enzyme, although it showed a 50% reduction in turnover rate. ATP binding at the high affinity site was not affected. However, a displacement in the E1<-->E2 equilibrium toward the E1 form was indicated by a small decrease in the K(m) of ATP at the low affinity site accompanied by an increase in IC(50) for vanadate inhibition. Thus, the transmembrane cysteine-deficient (Na,K)-ATPase appears functional with no critical alteration in its interactions with physiological ligands.

[Medical service marketing at the time of medical insurance]. / Marketing meditsinskoy uslugi v usloviyakh meditsinskogo strakhovaniya.

Presents the approaches to applying the fundamentals of marketing to public health. Medical insurance organization may effectively work as arbitrators and marketing agents; the basic assumption in the theory of marketing underlies their activity. The concept of marketing implies investigation of the requirements of the users of medical services and the development of measures aimed at meeting the requirements of man in terms of health service and health maintenance.

Ca(2+)-loading modulates potencies of cyclosporin A, Mg2+ and ADP to recouple permeabilized rat liver mitochondria.

We studied the relative potencies of cyclosporin A and endogenous effectors (Mg2+ and ADP) to recouple rat liver mitochondria permeabilized by different Ca(2+)-loading in a P(i)-containing medium. Recoupling efficiency of cyclosporin A dramatically decreased at high Ca(2+)-loading (approx. 100 nM of Ca2+/mg protein and more). Mitochondria permeabilized by high Ca2+ were recoupled with approximately equal efficiency by higher cyclosporin A concentrations or by adding 1-5 mM Mg2+ together with low concentrations of cyclosporin A while potentiating effect of ADP on the cyclosporin A recoupling potency was insignificant. Mg2+ ions at concentrations of 3 mM and higher also prevented the carboxyatractylate-induced reversion of cyclosporin A recoupling effect. The data point to competitive relationships between cyclosporin A and/or Mg2+ ions and Ca2+ ions for the site(s) regulating permeability state of the pore.