Biological diversity and the community structure of organisms

Biological diversity and the complexity of the community structure of benthic animals in different bodies of water are evaluated using the Shannon index. The literature data on the communities in Lake Krasnoye (Karelian Isthmus, Leningrad Oblast), Shchuchy Bay of Lake Ladoga, Neva Bay, and the eastern part of the Gulf of Finland have been analyzed. The extrema (maxima and minima) and the inflection point of the curve of functions are determined with the help of derivatives. The rate of the secondary succession is evaluated for the first time by the example of benthic communities. It is shown that the community structure of bottom animals in the Shchuchy Bay ecosystem formed in the process of succession proves to be more complex than in Lake Krasnoye and the Neva Bay communities that have been formed for a long time. Communities of bottom animals are less complex in polluted waters of the top of the eastern part of the Gulf of Finland. It has taken 12 years to reach the maximum diversity of the bottom animal communities in Shchuchy Bay, 16 years in Lake Krasnoye, and 7–10 years in Neva Bay. It is supposed that, under favorable conditions in the waterbodies of a moderate climate and in the absence of heavy pollution or eutrophication, it takes 12–14 years on average to form the most complex community structure of bottom animals (3–4 bit/spec.). The structure of communities in polluted waters remains simple.     

The reconstitution of microsomal redox chains. A comparative analysis of the effectiveness of membrane self-assembly and template binding of electron carriers

The osmotic pressure of solutions of sulphated proteoglycans isolated from the intervertebral discs of animals of various ages was determined. The behaviour of the solutions in salt-added systems was investigated in terms of the Donnan distribution of the mobile ions. It is evident that this effect is the dominating factor in explaining the observed nonidealities. Although marked variations in the compositions of the proteoglycan, with regard to their chondroitin sulphate and keratan sulphate content and hence charge content, occur with increasing age of parent tissue, the osmotic activities of the various preparations are very similar. This is explained by the ;fixation' of the counterions in such a way as to counteract any change in the charge content of the polyion; an ;osmotic buffering' effect. The swelling behaviour of gelatin gels containing the proteoglycan preparations has been measured. In all cases pressures in excess of the sum of the osmotic pressures of the individual components are observed. However, the magnitude of the excess decreases with increasing age of the parent tissue. It is suggested that the age changes, as reflected by a decrease in water content of the gel system, are not the result of changes in the osmotic properties of the individual components but rather reflect changes in the entropic interaction of the proteoglycan with the gelatin matrix. The relevance of this observation to the situation in vivo is discussed.     

Immunohistochemical study of cell phenotypes in organ culture of the rat embryo liver

The organ culture of the liver of a 14 day old rat embryo was used for immunohistochemical recognition of the available cell types. This culture contains the tissue explant, confluent monolayer cells and a zone of single cells (ZSC). At the start of cultivation a monolayer is formed at the expense of cells slipping down together from the explant, and later these cells were seen to migrate actively from the explant and to proliferate. ZSC is formed by cells migrating from the monolayer. Desmin-containing cells (hepatoblasts, Ito cells and myofibroblasts) migrate from the explant to the monolayer and ZSC. In the monolayer hepatoblasts lose gradually desmin and are converted into cytokeratin 18 (CK-18) expressing hepatocytes. In ZSC, hepatoblasts lose desmin, but no CK-18 synthesis occurs in them. The Ito cells (hypothetical progenitor cells) are spreading over the whole culture, and desmin expression in them does not change. The embryonal Ito cells may transform presumably into myofibrils. Myofibroblasts lie flat on the periphery of ZSC. Besides, desmin myofibroblasts express alpha-actin from smooth muscles. Expression of CK-18 in cells depends on the pattern of intercellular interactions. In the monolayer, CK-18 expression extends successively via the adjacent cells towards the explant. In hepatocytes, migrating into ZSC, CK-18 expression stops. In ZSC, CK-18 expression reappears in compact clusters of stopped cells. It supposed that during formation of close contacts in the monolayer the cells-predecessors may be differentiated into hepatocytes, whereas in the case of disturbance of intercellular connections in ZSC the cells-progenitors may be converted into myofibroblasts. However, on the reconstruction of cell contacts in motionless dense clusters the cells in ZSC are differentiated into hepatocytes.     

High velocity mechanical injection of foreign DNA into fish oocytes

High-velocity tungsten microprojectiles were used to introduce into fertilized eggs of loach (Misgurnus fossilis), Rainbow trout (Salmo gairdneri Rich.) and Zebra fish (Brachydanio rerio) DNA sequences of beta-galactosidase and neomycin phosphotransferase genes. No more than 30% of fish oocytes died as a result of bombardment. Experiments revealed marked activity of both enzymes in developing fishes. Neo gene DNA sequences were found in total danio DNA using PCR technique.