Biology bulletin of the Academy of Sciences of the USSR最新文献

A general analysis of data on survival of patients with inoperable lung cancer obtained from 59 publications was undertaken by the linear regression method. It is suggested that the parameters reflecting the kinetics of survival of these patients be used as a "historical control" for assessment of the efficacy of new methods and treatment of lung cancer. It was shown with the aid of this control that antitumor chemotherapy increases the 6-month survival rate of patients with an immediate positive effect after chemotherapy.

The reaction of plankton to the toxic effect of pesticides is considered at four levels: the cell, the organism, the population, and the biocenosis. The basis for the methodological approach to evaluation of response at the cell level was the principle of phase reactions. Depending on concentration, the pesticides may either suppress or stimulate the plankton organisms. Temperature may be decisive intoxic effects (pesticides are effective in a range of 15 to 25 degrees C). Most pesticides having algacidal activity are effective in a range of concentrations of 1-10 mg/liter. Phytoplankton as a whole has a high buffer capacity with respect to pesticides. Changes in ratios of basic components of phytoplankton effected by pesticides most often lead to a change of the dominant. Analogical changes are characteristic also for zooplankton; pesticides lead to the elimination of water fleas from its composition. The stimulating effect of a low concentration of pesticides, changes in the functional activity of the components of bacterial plankton, and changes coupled with this in biogeochemical cycles of nitrogen and phosphorous as well as elimination of water fleas from the plankton promotes the development of "secondary" eutrophication, that is, an increase in the biomass of the phytoplankton.

A series of experiments showed the quantity and composition of nitrogen lost in gaseous form from fertilizers in soil is largely determined by the conditions of denitrification. Loss of nitrogen from ammonium sulfate or calcium nitrate was mainly through the release of nitrous oxide and molecular nitrogen, while nitrogen was released from sodium nitrite in the form of nitric oxide. Under anaerobic conditions and at neutral soil pH in the presence of glucose, the more reduced gaseous forms of nitrogen were released. However, the oxides of nitrogen predominated under conditions unfavorable for denitrification. The nitrogen oxides were not the terminal products of nitrogen conversion (nitrates and nitrites). By a process of dissimilation, the nitrogen oxides acted as electron acceptors for microorganisms, being converted to N2O and N2. The reduction of NO generally led to the formation of N2O as an intermediate, and depended on pH, aeration, and the presence of an energy source for the denitrifying organisms.

A comparative analysis is given of various types of systems of selecting biologically active substances. A theoretical probability model of tests on chemical compounds for biological activity (screening) has been constructed which permits an evaluation of the efficacy of screening on the basis of fairly reasonable assumptions. It has been shown that this efficacy decreases in time with a fixed number of types of activity taken into consideration and rises sharply with an increase in the number of types of activity of chemical compounds taken into account in the tests.

On the basis of analysis of the literature and personal data, principles of dosimetry were determined and an analysis was given of biological effects of radionuclides on plants when administered aerially and by root. A comparison was made of radiosensitivity of barley and dependence of sensitivity on the growth phase of the plant at the time of irradiation with a standard LD50 and UD50. The possibility of using correlated paramaters of bioinformation, such as the sensitivity indicator of evaluation of biological effects caused by small radiation doses, is considered. On the basis of correlations of the data obtained a prognosis is made of the probability of losses in harvest of grains subjected to radionuclides at various periods of development.

Factors have been studied which are responsible for the resistance of cells of several strains of Chlorella to physical and chemical stresses; measurements have been made of the effects of UV and x irradiation, heat treatment, detergents, cadmium salts, and insecticides. Cells which were resistant to the effects of physical factors were also resistant to chemical intoxication. A positive correlation was found between the resistance of cells to the described factors and the level of endogenous thiols in the cells, as well as the free radical content. This in turn is due to an increased number of reaction centers in the electron-transport chain.

A culture of Pseudomonas aeruginosa 2x was observed for its spontaneous variability for growth on p-xylene and the intermediate products of its metabolism. The highest variability was found for ability to grow on p-xylene and pyrocatechol, and a variability an order of magnitude lower was found for ability to grow on protocatechuate and p-toluate. No variability was found for the character "ability to grow on p-hydroxybenzoate." The activity of the key enzymes for the oxidation of p-xylene was studied in p-xylene-negative strains. The difference between the p-xylene-positive wild type strain and the spontaneous p-xylene-negative strains was found to be linked to changes in the regulatory mechanisms for several enzymes: p-xylene methylhydroxylase and the enzymes involved in the breakdown of the aromatic ring. In addition, the appearance of p-xylene-negative strains was linked with a significant fall in the specific activity of all enzymes, except pyrocatechuase, which was replaced by metapyrocatechuase on a number of substrates.