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A transfer of contaminants from the land through the rivers forms a significant part of the Arctic seas' pollution. A whole ecosystem is the target of this harmful action. The response of the ecosystem can be considered as the measure of the impact. To assess this impact we designed a mathematical approach based on the Liebig-Shelford law of tolerance, the "narrow path" principle and the Shannon index of diversity to evaluate a prosperity function and a comprehensive risk index for a river or estuary ecosystem. To illustrate this general approach we consider the propagation of the pollutant along the river bed after (1) continuous and (2) pulsed release of a pollutant. The results of calculations show good correspondence with the actual behaviour of natural ecosystems. Further studies are necessary to find out the actual values of the parameters for different pollutants.

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The cellular (viability) and molecular (kinetics of changes in nucleoid viscosity) mechanisms of damage to various strains of microorganisms after single and combined action of SHF electromagnetic radiation and hydrogen peroxide are compared. The conditions are found in which marked synergetic interactions of the agents are realized. The role of repair systems in formation of final products of the interactions is discussed.

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In experiments with models of isogenic Escherichia coli strains, a comparative study was made of the effect of SHF of electromagnetic field and hyperthermia. The survival rate of bacteria was determined and, simultaneously, injuries to genetic supramolecular structures were registered through measuring the anomalous time dependence of cell lysate viscosity. The combined effects of the mixture of these factors with H2O2 microconcentrations were studied. The differences observed in their realization were attributed to the different mechanisms of action of these factors on the repair enzyme systems of the studied cells. It has been found that the effect of microwaves on microorganisms causes much severer damages to DNA that hyperthermia does.

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The effect of low intensity microwaves on the conformational state of the genome of X-irradiated E. coli cells was studied by the method of viscosity anomalous time dependencies. It has been established that within the ranges of 51.62-51.84 GHz and 41.25-41.50 GHz the frequency dependence of the observed effect has a resonance nature with a resonance half-width of the order of 100 MHz. The power dependence of the microwave effect within the range of 0.1-200 microW/cm2 has shown that a power density of 1 microW/cm2 is sufficient to suppress radiation-induced repair of the genome conformational state. The effect of microwave suppression of repair is well reproduced and does not depend on the sequence of cell exposure to X-rays and microwave radiation in the millimeter band. The results obtained indicate the role of the cell genome in the resonant interaction of cells with low intensity millimeter waves.

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It was found that the dependence of the viscosity of calf thymus chromatin dispersions and human leukocytes on ethidium bromide concentration had two peaks indicative of domains with circular supercoiled DNA and varying resistance to ultrasound in the cells and isolated chromatin. The hypothesis of V. D. Paponov and P. S. Gromov (Bull. Exp. Biol. Med., N5, 590, 1985) on the transformation of static relations of nucleosome DNA-containing nuclei into dynamic, after chromatin exposure to ultrasound due to DNA linearization in chromatin domains possessing circular supercoiled DNA, has been confirmed.

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The basic approaches to the assessment of the biological effects of combinations of different agents are briefly discussed. The situations of additivity, synergism and antagonism are defined with hetero- and isoaddition being taken into consideration. The practical application of the methods is illustrated by the analysis of the experimental data on the staphylococcus survival after the combined effect of gamma-irradiation and hydrogen peroxide or incubation at elevated temperature.

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We prove that the sequence of purine and pyrimidine blocks can be restored for circular nucleic acids if molecular weight distributions of fragments of various stages of hydrolysis are known. Hydrolysis of nucleic acid is considered as a progressive fragmentation of a "ciphering", an arbitrary circular polymer, monomers of which have weights from 1 to 6 (corresponding to the real number of purines or pyrimidines in the block), while the site of fragmentation is selected at random. The hydrolysis of circular RNA under the action of pancreatic RNase proceeds in accordance with the model of ciphering. Heuristic method for restoration of the monomer sequence in the ciphering based upon some characteristics of molecular weight distributions (such as Sj(m)-number of the fragments with the weight m containing j unbroken bonds) is considered. Uniqueness of restoration of the monomers sequence of the ciphering based upon known set [Sj(m)] is proved.

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