[The bilateral asymmetry of the number of bristles in Drosophila occurring under the influence of methotrexate]. / Bilateral'naia asimmetriia chisla shchetinok u drozofily, voznikaiushchaia pod vliianiem metotreksata.

The data are analyzed on the bilateral asymmetry of the number of dorsal and scutellar chaeta observed under the action of methotrexate in Drosophila of wild strain. It was shown that the incidence of asymmetric specimens induced by methotrexate was abruptly increased as compared to the control. The asymmetry was found to have a statistically significant trend to left side both of the control and the variants of treatment. There was no sex difference revealed between targets of the asymmetry.

Antimutagenic effect of p-aminobenzoic acid on the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine in Salmonella typhimurium.

p-Aminobenzoic acid (PABA) exhibited antimutagenic activity toward N-methyl-N'-nitro-N-nitrosoguanidine(MNNG)-induced mutagenicity in the Ames assay in Salmonella typhimurium. The antimutagenic effects were associated with an increased rate of decomposition of MNNG in the presence of PABA. The participation of other mechanisms, such as the alteration of cellular processes by PABA, however, cannot be excluded.

[Vitamin para-aminobenzoic acid inhibits development of SOS function in tif-1 mutants of Escherichia coli at nonpermissive temperatures]. / Vitamin para-aminobenzoinaia kislota prepiatstvuet razvitiiu "SOS"-funktsii v tif-1-mutantakh Escherichia coli pri nepermessivnoi temperature.

The development of "SOS" inducible functions in lysogenic and non-lysogenic strains of Escherichia coli tif-1 sfiA11 (lambda) at nonpermissive temperature of 42 degrees C was strongly suppressed by para-aminobenzoic acid (PABA). The rate of prophage lambda induction decreased 400 times, as compared to the control level; the efficiency of W-reactivation of UV-irradiated phage lambda decreased 37.5 to 16%. PABA also inhibited to some extent (1.5 times) the process of inducible recombination on the RecF pathway. The processes of spontaneous lambda induction and W-reactivation, as well as spontaneous recombination on RecBC and RecF pathways, were not influenced by PABA. The above data are in accordance with previous studies of PABA action when the manifestation of "SOS" functions was induced by chemical mutagens. The action of PABA has been tentatively interpreted on the basis of negative control of "SOS" repair pathway.

[Genetic activity of para-aminobenzoic acid. The intensification of DNA polymerase I-dependent repair induced by chemical mutagens in toluene-treated Escherichia coli cells]. / Geneticheskaia aktivnost' para-aminobenzoinoi kisloty. Usilenie DNK-polimeraza-I-zavisimoi reparatsii, indutsirovannoi khimicheskimi mutagenami v toluolizirovannykh kletkakh Escherichia coli.

Alkylatio of Escherichia coli DNA that have been made permeable to nucleotides by toluene treatment results in the expression of DNA polymerase I-directed repair synthesis. The system only permits measurement of DNA polymerase I-directed repair synthesis. The latter is not observed in mutant cells deficient in this polymerase. DNA ligation is intentionally prevented by the addition of the inhibitor, nicotinamide mononucleotide. MNU, ENU and MMS elicit DNA polymerase I-directed repair synthesis. MNU and MMS are especially potent in this regard, while EMS is a poor inducer of DNA polymerase I activity in permeabilized cells. The natural compound para-aminobenzoic acid itself (0,0002 mM - 20 mM) doesn't induce DNA polymerase I-directed repair synthesis. However, when PABA is used in complex with alkylating agents as the inducers, the repair synthesis increased 2,0, 1,2 and 2,8 times for MNU, ENU and EMS, respectively, as compared to that elicited by "pure" mutagens. The increasing of DNA repair synthesis in permeabilized bacteria in the experiments with PABA may serve as the foundation for its reparagenic activity. The latter was discovered previously by the authors in experiments on mutagenesis of bacterial cells.

[Para-aminobenzoic acid intensification of DNA repair processes in Escherichia coli K-12]. / Usilenie para-aminobenzoinoi kislotoi protsessov reparatsii DNK v Escherichia coli K-12.

Studies of the role of physiologically active natural compound, para-aminobenzoic acid (PABA) in genetic processes showed that PABA interacts with bacterial DNA and strongly increases the effectiveness of repair processes under the mutagenic action of NMU, NEU, MMS and EMS. These properties of PABA differentially depended on the activity of enzymatic systems fo DNA repair and were most pronounced in repair-proficient strains of Escherichia coli. For example, the cooperative action of E. coli (wild type) of both NMU and PABA led to enhanced viability (13-100 times higher) and decreased the rate of induced reversions (5-60 times lower), in comparison with mutagenic action of "pure" NMU. Therefore, the specific function of PABA was called "reparagenic" and PABA itself "reparagen". UV-spectroscopy and nuclear-magnetic resonance were used to have revealed that PABA does not interact with MMS and NMU in vitro and does not change the rate of the mutagen's hydrolysis. Used in a wide range of concentrations, PABA induces no mutations in bacterial cells and does not increase the rate of genetic recombination. The discovery of the role of PABA in repair process opens up the possibility of examining the interaction between the DNA in a complex with reparagen as well as the dominant and recessive genes of the repair process.