[The regression time of heat-shock puffs in the polytene chromosomes of Drosophila melanogaster as a criterion for assessing the effect of different stress exposures]. / Vremia regressii puffov teplovogo shoka v politennykh khromosomakh drozofily Drosophila melanogaster kak kriterii dlia ostenki éffekta razlichnykh stressovykh vozdeistvii.

The time of regression of heat shock puffs was studied in the polytene chromosomes of Drosophila melanogaster larvae of mutant stock (1(1)ts403, defective in heat shock protein (HSP) system, and of the wild type stock Canton S after heat shock (37 degrees C), after placing of larvae to anaerobic conditions (dipping into physiological solution), and after combination of these treatments. It is shown that the time of regression of heat shock puffs depends on the specificity of the treatment (heat shock or anaerobic conditions), its duration (13 or 30 min), or on the peculiarity of functioning of HSP system in the cells of different stock larvae. Our results are in accordance with the idea of the HSP genes expression autoregulation, and allow to use the heat shock puff regression time as a criterion for estimation of damaging effects of stress factors.

[Mechanisms ensuring the resistance of the genetic material of the cell to stress exposures]. / Mekhanizmy, obespechivaiushchie ustoichivost' geneticheskogo materiala kletki k stressovym vozdeistviiam.

A brief review of studies performed in the Department of Genetics of St. Petersburg University by M.E. Lobashev and his disciples is presented. The results of these studies prove that the formation of a mutation is a multistage process involving many cell and organism systems (including repair systems, systems that determine sexual dimorphism, etc.), which are affected by environmental factors (e.g., extreme temperatures). They can hinder or accelerate the mutational process, in this way providing both a superadditive effect and adaptive response. Recent studies deal with a universal system of heat shock proteins, which is involved in the maintenance of resistance of genetic material and genetic processes in the cell.

[Role of heat-shock proteins in recovery of cell proliferation following high temperature treatment of Drosophila melanogaster larvae]. / Rol' belkov teplovogo shoka v vosstanovlenii kletochnoi proliferatsii posle vozdeistviia vysokoi temperaturoi na lichinok Drosophila melanogaster.

The processes of the recovery of proliferation activity of nervous ganglion cells following heat-shock (37 degrees C, 30 min) were compared in two strains of Drosophila melanogaster (Canton S--the wild-type strain and 1(1)ts403--the mutant with the defect in the heat-shock protein system). The ts-mutant is characterized by the delay n reaching the maximum level in the HSP's synthesis and by more prolonged synthesis of these proteins after heat shock as compared with the wild-type strain. The block in cell proliferation after heat-shock is also more prolonged in the ts mutant's nervous ganglion in comparison with the wild-type strain. These results are n accordance with the hypothesis about the role of HSP's in cell proliferation.

[Role of heat-shock proteins in the recovery of mitotic chromosome damage induced by high temperature in Drosophila melanogaster]. / Rol' belkov teplovogo shoka v vosstanovlenii industirovannykh vysokoi temperaturoi povrezhdenii mitoticheskikh khromosom u Drosophila melanogaster.

The synthesis of the heat-shock proteins (HSP) and the frequency of the mitotic chromosome damages (pulverizations, chromosome, chromatid stickiness, etc.) was studied in the cells of larva nervous ganglion in the process of recovery after heat shock (37 degrees C, 30 min). Analysis was performed in two strains of Drosophila melanogaster (Canton S-the wild type and the mutant l(1)ts403 with the defect in the HSP system). Correlation between the dynamics of HSP synthesis and the alteration of the chromosome pulverization and stickiness frequency was shown for both Drosophila strains under study. These results, in accord with the data on HSPs' binding to chromosomes following heat shock and their role as molecular chaperones, allowed to suggest that HSPs took part in chromosome condensation and in the recovery of heat shock induced damages leading to chromosome and chromatid stickiness.

[The dynamics of the induction and regression of puffs 87A, 87C and 93D in the polytene chromosomes of Drosophila melanogaster under the action of anoxia and high temperature]. / Dinamika induktsii i regressii puffov 87A, 87C i 93D v politennykh khromosomakh drozofily Drosophila melanogaster pri deistvii anoksii i vysokoi temperatury.

A study was made of the heat shock puff activity in salivary glands of Drosophila melanogaster larvae after 5 and 20 min treatments with anoxia (dipping into physiological solution), heat shock (37 degrees C), and simultaneously with both the agents. The simultaneous treatment with heat shock and anoxia, as well as treatment with anoxia only blocked the induction of heat shock puffs. They appeared 10-15 min after the treatment during recovery under aerobic conditions. There was a super-additive effect of the simultaneous treatment on the heat shock puffing duration. A specific regulation of the 93D locus was observed. The 93D puff was induced by a 5 min simultaneous treatment with anoxia and heat shock and, as a rule, was not induced by the analogous 20 min treatment. The role of anoxia in blocking heat shock puff induction under simultaneous effects of heat shock and anoxia is discussed.