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I A Rapoport

Publications and source records attributed to I A Rapoport.

At least 19 recordsLinked to original sources
PubMed1987

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.

4-Aminobenzoic Acid↗
PubMed1983

[Vitamin para-aminobenzoic acid inhibits development of SOS function in tif-1 mutants of Escherichia coli at nonpermissive temperatures].

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.

4-Aminobenzoic Acid↗
PubMed1982

[Para-aminobenzoic acid intensification of DNA repair processes in 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.

4-Aminobenzoic Acid↗
PubMed1982

[Genetic activity of para-aminobenzoic acid. The intensification of DNA polymerase I-dependent repair induced by chemical mutagens in toluene-treated Escherichia coli cells].

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.

4-Aminobenzoic Acid↗
PubMed1977

[Specific mutagenic effectiveness of 1,4-bis-diazoacetylbutane in relation to individual genes].

A selective effect of 1,4-bis-diazoacetylbutane (DAB) with respect to individual genes is observed when studying its mutagenic action on bacterial strains. Escherichia coli and Salmonella typhimurium. The frequency of mutations to thr+ exceeded in three orders the background of spontaneous variability for this marker. No induced mutations to trp+ and his+ leu+, which might be the result of transition, transversions, suppressor mutations and frame shift mutations, were detected. Mutagenic effect of DAB is due to the functioning of the gene uvr+. Several hypotheses are proposed on possible mechanism of the specific effect of DAB with respect to individual genes.

Adipates↗
PubMed1977

[Triphenylstilbene as a polymodifying agent].

The metalorganic product, triphenylstibine, added to the nutrition medium for Drosophila melanogaster larvae induces multiple modification effects, such as rough eye, wing incision, small bristles and others. Cytological analysis has shown that triphenylstibine induces new puffs and also causes the activation and depression of control puffs in giant chromosomes. A new effect of triphenylstibine is observed: it inhibits the evolution of puffs in giant chromosomes during metamorphosis. The average frequency of "inhibited" puffs is about 15%.

Animals↗
PubMed1976

[Effect of nitrosomethylurea and 1,4-bis-diazoacetylbutane on alkaline ribonuclease activity].

It was shown that at 37 degrees C nitrosomethylurea causes an 8-fold increase (as compared to the normal) of the activity of alkaline ribonuclease. 1,4-Bis-diazoacetylbutane also activated alkaline ribonuclease at 37 degrees C. A dependence of the effect of chemical mutagens studied on the activity of alkaline ribonuclease on their concentration was observed. The activation of ribonuclease by NMU and DAB affords a possibility to understand the molecular mechanisms of the action of chemical mutagens on the metabolism.

Azo Compounds↗
PubMed1976

[Dependence of the mutagenic effect of N-nitroso-N-methylbiuret on the pH index].

The mutagenic effect of nitrosocompounds is known to be dependent on pH. The effect of N-nitrozo-N-methylbiuret on the conidia of Penicillium chrysogenum was studied within the ranges of pH from 5.0 to 7.0, the role of the buffer and distilled water being also considered. It was found that survival, morphological variation and induction of biochemical mutants depended on the value of pH. The optimal conditions for the culture treatment at the exposures tested were provided at pH 6.0 with the use of a phosphate buffer mixture as a substrate.

Biuret↗
PubMed1976

[Stimulation of ribonuclease activity under the influence of nitrosoethylurea].

Nutrosoethyl urea-induced activation of alkaline ribonuclease was accelerated with the increase of the temperature from 22 to 32 degrees C. The reaction rate at 32 degrees C was more than 8 fold increased as compared with the control. Further increase of temperature to 42 degrees C decreased the stimulating effect of nitrosoethyl urea. The effect observed may be taken into consideration when studying a molecular mechanism of the effect of chemical mutagens on cell metabolism.

Enzyme Activation↗