Development of the Biosphere in the Context of Some Fundamental Inventions of Biological Evolution

Traditionally, the evolution of flora and fauna on the Earth as well as the evolution of their physical and chemical environment are considered separately. At the same time, when considering the global evolutionary changes, it becomes clear that the evolution of all these components occurs in close relationship and that they together constitute a unified evolutionary process. Thus, we should talk about their co-evolution and that the whole biosphere is a united functional system. In this chapter, we briefly discuss some of the major “inventions” of ancient life that are responsible for global biosphere transformations and which “worked” in the biosphere until now (photosynthesis, eukaryotic cell, multicellular organism, and the other findings). The evolution of the Precambrian life as well as the Phanerozoic stage of the biosphere evolution are considered in this context

Threshold detachment of negative ions by electron impact

The description of threshold fragmentation under long range repulsive forces is presented. The dominant energy dependence near threshold is isolated by decomposing the cross section into a product of a back ground part and a barrier penetration probability resulting from the repulsive Coulomb interaction. This tunneling probability contains the dominant energy variation and it can be calculated analytically based on the same principles as Wannier's description for threshold ionization under attractive forces. Good agreement is found with the available experimental cross sections on detachment by electron impact from $D^{-}$, $O^{-}$ and $B^{-}$.Comment: 4 pages, 4 figures (EPS), to appear in Phys.Rev.Lett, Feb. 22nd, 199

Restricted MHC–peptide repertoire predisposes to autoimmunity

MHC molecules associated with autoimmunity possess known structural features that limit the repertoire of peptides that they can present. Such limitation gives a selective advantage to TCRs that rely on interaction with the MHC itself, rather than with the peptide residues. At the same time, negative selection is impaired because of the lack of negatively selecting peptide ligands. The combination of these factors may predispose to autoimmunity. We found that mice with an MHC class II–peptide repertoire reduced to a single complex demonstrated various autoimmune reactions. Transgenic mice bearing a TCR (MM14.4) cloned from such a mouse developed severe autoimmune dermatitis. Although MM14.4 originated from a CD4+ T cell, dermatitis was mediated by CD8+ T cells. It was established that MM14.4+ is a highly promiscuous TCR with dual MHC class I/MHC class II restriction. Furthermore, mice with a limited MHC–peptide repertoire selected elevated numbers of TCRs with dual MHC class I/MHC class II restriction, a likely source of autoreactivity. Our findings may help to explain the link between MHC class I responses that are involved in major autoimmune diseases and the well-established genetic linkage of these diseases with MHC class II

Optical limiting behavior of bismuth oxide-based glass in the visible range

The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for β, the two-photon absorption coefficient, and σe, the absorption cross section due to free carriers, were determined. The values for β and σe are dependent on the amount of bismuth oxide in the glass composition

ЦИКЛОФИЛИН А: СТРОЕНИЕ И ФУНКЦИИ

Cyclophilins belong to a large family of ancient conservative proteins with peptidyl-prolyl-cis-trans isomerase activity. The main member of this family – cyclophilin A – was discovered as an intracellular ligand for cyclosporine A. Further investigations revealed a wide range of functions of cyclophilin A. Cyclophilin A is involved in T-cell signaling, it takes part in folding, assembly and intracellular transport of proteins, as well as acts as an antioxidant. Different cell types secrete cyclophilin A under infection or oxidative stress. Cyclophilin A is one of the main factors involved in inflammation and pathogenesis of autoimmune, cardiovascular and other diseases. This protein is thought to take part in tumor progression. In this review we describe the structure of cyclophilin A and its main known functions in health and disease.Циклофилины – большое семейство консервативных, филогенетически очень древних белков, обладающих пептидил-пролил-цистранс-изомеразной активностью. Наиболее распространенным среди них является циклофилин А, который был обнаружен как внутриклеточный лиганд для связывания с циклоспорином А. Изучение механизма супрессии циклоспорина А, в основе которой лежит его взаимодействие с циклофилином А, послужило мощным толчком для исследований последнего. Было установлено, что циклофилин А принимает участие в проведении сигналов в Т-лимфоцитах, участвует в фолдинге, сборке и внутриклеточном транспорте белков, а также играет роль антиоксиданта. При инфекциях и оксидативном стрессе различные типы клеток способны секретировать циклофилин А. Он является одним из центральных факторов, участвующих в воспалении и патогенезе аутоиммунных, сердечно-сосудистых и других заболеваний. Предполагается, что циклофилин А может принимать участие в прогрессии опухолей. Настоящий обзор посвящен описанию строения и известных функций циклофилина А в норме и при различных патологических процессах