Mapping of the genetic determinant controlling Salmonella K-antigen synthesis. I. Localization of the determinant in conjugation experiments

The preliminary data on the localization of the gene responsible for the synthesis of K-antigen in salmonellae were obtained. Using Salmonella Hfr donors with different onset of the transfer of chromosomal markers and with phenotype K+, the authors selected different classes of recombinants in the process of their crossing with K- recipients. The positive result of the agglutination test with specific K-antiserum indicated that the transconjugate thus obtained possessed phenotype K+. The gene responsible for the synthesis of K-antigen was shown to be localized between minutes 46 and 41 of the genetic map of S. typhimurium. This gene was not cotransduced with the histidine marker localized on minute 44 of the map.     

Immunoelectrophoretic analysis of the antigenic composition of Salmonella typhi in the process of L transformation and reversion

In the study of the antigenic composition of S. typhi L-forms and their revertants were determined. The stable L-forms were characterized by profound disturbances in the synthesis of Vi- and H-antigens. After reversion to bacterial forms all the revertants under study showed the complete restoration of their bacterial antigenic structure.     

Mitochondria-targeted antioxidant provides for enhanced morphogenetic potential in plant tissue cultures

An ability to regenerate plants from tissue cultures is important for biotechnology; however, many species and cultivars a have low morphogenetic potential. Since oxidative stress is one of the factors affecting morphogenesis, we assessed an ability of a membrane-penetrating mitochondria-targeted antioxidant SkQ1 to improve plant regeneration from cultured tissues of Zea mays L., Triticum aestivum L., Saccharum officinarum L., Medicago falcate L., and M. glutinosa M.Bieb. SkQ1 at nanomolar concentrations was found to stimulate both the set of morphogenenic structures and their subsequent development with the formation of plantlets of all plant species tested. SkQ1 constituents, dodecylplastoquinone and dodecyltriphenylphosphonium, could also exert stimulatory effects on plant regeneration from morphogenic callus, although these effects were less prominent than that of SkQ1. SkQ1-mediated stimulation was most pronounced (up to sevenfold) for cultured tissues with a low morphogenetic potential. The observed properties of SkQ1 suggest its possible application in promoting morphogenesis in a wide range of genotypes.     

Behavior of subadult mountain voles of two species (<Emphasis Type="Italic">Alticola strelzowi</Emphasis> and <Emphasis Type="Italic">A. tuvinicus</Emphasis>) in the open field test

A comparative study of mobility and anxiety of subadult flat-headed and Tuva silver voles in an open field test has been performed using arenas 50 and 63 cm in diameter. It is found that individuals of both species demonstrate higher movement speed and cover longer distances, both on the periphery and in general, on the larger arena. Interspecies behavioral differences have been identified only in the arena 63 cm in diameter. Subadult flat-headed voles demonstrate higher mobility and lower anxiety in the test compared to Tuva silver voles. Hypotheses pertaining to specific features of the ecology of the two species reflected in their behavior are proposed.     

Histone synthesis at S- and G2-phases of the mitotic cycle of human diploid fibroblasts

The phase-specific synthesis of the total protein, histones, RNA and DNA in human embryonic fibroblasts synchronized by double thymidine blockade was investigated. It was shown that activation of histone synthesis occurs in three steps, i.e. i) immediately before replication, ii) after DNA synthesis maximum, and, iii) at the G2-phase of the mitotic cycle. During maximal replication of DNA histone synthesis is suppressed. It was assumed that at the pre-replication phase histone synthesis controls decondensation, while and the G2-phase--condensation of chromatin.     

Recombinant fragment 44–77 of the pigment epithelium-derived factor prevents the development of the pathological cornea neovascularization

The pigment epithelium-derived factor (PEDF), a secreted 50 kDa glycoprotein, is one of the most potent endogenous inhibitors of angiogenesis. The fragment 44–77 of PEDF possesses the antiangiogenic properties of the full-sized protein and is a potential drug candidate for the treatment of diseases of visual organs accompanied by pathological neovascularization. An effective biotechnological method for the large-scale production of the PEDF (44–77) fragment as part of the fusion protein with the SspDnaB intein has been developed. The hybrid protein was produced in Escherichia coli bacterial cells in the form of inclusion bodies, solubilized, and subjected to autocatalytic cleavage with the release of the PEDF (44–77) fragment (reaction yield 77%). The target peptide was separated from the intein by tangential ultrafiltration. The final purification of PEDF (44–77) was performed by reversed-phase HPLC. The yield of the target peptide (purity 99%) was 65 mg per 1 l of culture. The antiangiogenic activity of the peptide was confirmed in vitro using mouse endothelial cells SVEC-4-10. It was found that the preparation at a concentration of 1 nM suppresses the proliferation of endothelial cells by 53% and inhibits the formation of tube-like structures by endothelial cells. The ability of the recombinant PEDF (44–77) to block the initial stages of angiogenesis was shown using an experimental model of rabbit corneal neovascularization.