Svetlana Podstavková

Effects of supercypermethrin, a synthetic developmental pyrethroid, on four biological test systems

The genotoxic potential of the insecticide supercypermethrin, a second-generation pyrethroid, was studied on four different test systems. It was non-mutagenic to Salmonella typhimurium strains TA1535, TA100, TA1538, TA98 and TA97 in the presence and absence of S9 mixture. It induced gene conversion at the tryptophan locus and induced point mutations at the isoleucine locus in Saccharomyces cerevisiae cells. A slight increase in the frequency of aberrant anaphases and telophases in root tips of Hordeum vulgare and Vicia faba was observed, but no genotoxic effects were detected in Drosophila melanogaster.

General characteristics, molecular and genetic analysis of two new UV-sensitive mutants of Chlamydomonas reinhardtii

Two new UV-sensitive mutants of Chlamydomonas, UVS10 and UVS11, were isolated. Both behave as single nuclear mutations. UVS10 was mapped to linkage group I. UVS11 is a separate, unlinked mutation but has not yet been located to a specific linkage group. Both mutants are proficient in the excision of pyrimidine dimers from nuclear DNA. The survival of UV-irradiated UVS11 is increased when plated in the presence of 1.5 mM caffeine, similar to wild-type. Caffeine has no effect on the survival of UV-irradiated UVS10. UV-irradiated UVS11 frequently divides at least once before dying, in contrast to UVS10 or wild-type. UVS11 also exhibits a much increased frequency of mutation to streptomycin resistance after UV irradiation.

New DNA repair-deficient mutants of Chlamydomonas reinhardtii

Two new UV-sensitive mutants of Chlamydomonas reinhardtii, uvs12 and uvs13, were characterized. Genetic analysis proved that they were non-allelic. They complemented the other repair-deficient mutants uvs8, uvs9, uvs10 and uvs11. While uvs12 may have an impaired excision-repair pathway, uvs13 is, by its UV sensitivity under non-photoreactivating conditions, very similar to uvsE1 and uvs10, but differs in the effect of caffeine on its survival. After UV, survival of some repair-deficient mutants was, under photoreactivating conditions, much lower than that of phr1, while survival of other repair-deficient mutants did not differ from that of a wild-type strain. A lower UV survival of some dark-repair-defective mutants of Chlamydomonas reinhardtii, under photoreactivating conditions, can perhaps be used as an additional criterion for mutants defective in the excision-repair pathway.

Interactions between photolyase and dark repair processes in Chlamydomonas reinhardtii

The participation of DNA photolyase in dark repair processes has been reported in some heterotrophic organisms. To assess the role of photolyase in dark repair in photoautotrophs, double mutants of Chlamydomonas reinhardtii deficient in dark repair and photoreactivation were constructed and assayed for UV sensitivity in different posttreatment light conditions (with or without subsequent photoreactivation). We found that a functional PHR1 gene enhanced dark survival in the excision deficient (uvs9, uvs12) and in the recombination deficient (uvs10) genetic backgrounds but failed to do so in the strain deficient in a repair pathway other than excision and recombination (uvs13). Therefore we can conclude that photolyase may stimulate dark repair processes in C. reinhardtii also via pathway(s) other than nucleotide excision repair. The fact that some of the double mutants deficient in dark repair and photoreactivation survived better in the light than in the dark supports the idea that additional photorepair might be active and may enhance survival in a specific genetic background.

Mutagenic activity of phosmet, the active component of the organophosphorus insecticide Decemtione EK 20 in Salmonella and Saccharomyces assays

Phosmet, the active component of the organophosphorus insecticide Decemtione EK 20, was shown to be mutagenic in the standard Ames Salmonella/mammalian microsome assay in the absence and presence of metabolic activation. It appears to be a direct mutagen inducing base substitution mutations (TA100) as well as a weak frameshift mutagen (TA97). This compound was genotoxic in the Saccharomyces cerevisiae D7 strain. It significantly increased reverse mutation, mitotic crossing-over and slightly, but not significantly, increased gene conversion at the highest concentration used.

A Chlamydomonas reinhardtii UV-sensitive mutant uvs15 is impaired in a gene involved in several repair pathways

In this report, three DNA repair-deficient mutants of Chlamydomonas reinhardtii (uvs13, uvs14, uvs15) were characterized by using genetic, mutational and biochemical analyses. The mutant strain uvs15 belongs to the most sensitive repair-deficient mutants following exposure to all agents used. It is deficient in the nuclear excision-repair pathway, whereas uvs13 and uvs14 are not blocked in removal of pyrimidine dimers. Mutation study also revealed differences among strains. The mutant uvs15 does not mutate after UV and X-ray irradiation, and there is very low mutation rate after MNNG. These findings might indicate the involvement of UVS15 gene product in regulation of several repair pathways. Contrary to this, uvs14 showed higher mutation frequency, both spontaneous and induced after UV and MNNG treatments. Tetrad dissection proved that the uvs13 and uvs14 genes are located on the right arm of the linkage group I in the vicinity of the previously mapped uvs10 gene. Both mutants belong to the same repair pathway, which is different from that of uvs10 and uvs15.

induction of new uv-sensitive mutants of chlamydomonas reinhardtii

Summary In this work the induction of new UV-sensitive mutants of green single-celled algae Chlamydomonas reinhardtii after MNNG-treatment is described. Seven new isolated mutants were characterized by their inactivation curves, and reaction on a caffeine after UV-irradiation. Genetic analysis showed the monogenic determination of five mutants and two mutants were probably double ones.

Genotoxicity evaluation of Rastim 30 DKV, the plant growth regulator, on five test systems

The possible mutagenic activity of Rastim 30 DKV, a new plant growth regulator, was studied on five model test systems. It did not increase the frequency of His+ revertants in Salmonella typhimurium strains TA97, TA98, TA100, TA1535, TA1538 in the absence and the presence of S9 mix. It slightly increased rates of genetic changes in Saccharomyces cerevisiae, mainly convertants at the tryptophan locus. No clastogenic effect was observed after Vicia faba root-tip meristem treatment, and at the lowest concentration used its mitotic activity was significantly increased. No chlorophyll mutants after the treatment of two cultivars of barley were observed. Though no sex-linked recessive lethals were scored in Drosophila melanogaster males, the rates of aneuploids induced in their germ cells were significantly increased.

The mutagenic effect of the new insecticide and acaricide pyridathion

The potential mutagenic effect of the new organophosphate insecticide and acaricide, pyridathion, was tested on Escherichia coli, strains WP2, WP2 uvrA, and on Salmonella typhimurium, strains TA100 and TA98, both with and without metabolic activation. The compound was tested at 1, 10 and 100 micrograms/ml. The analysis of chromosomal aberrations in mouse bone marrow was performed after a single peroral application of pyridathion at doses of 0.6, 1.11, 6.0, 12.0 and 24.0 mg . kg-1 b.w., i.p. application at 6.0 mg . kg-1 b.w., and repeated application (5 times) p.o. at 1.0, 2.5 and 5.0 mg . kg-1 b.w. Analysis of rat bone marrow was performed after a 3-month peroral application of pyridathion at 0.07, 0.175 and 0.35 mg . kg-1 b.w. An analysis of chromosomal aberrations in human peripheral lymphocytes in vitro was performed 24 h after the application of pyridathion into the culture in concentrations of 9.2 X 10(-3), 9.2 X 10(-4) and 9.2 X 10(-5) moles. The insecticide did not exert any mutagenic effect on the bacteria. There was no significant increase in the frequency of chromosomal abnormalities in bone marrow of mice of rats, or in human peripheral lymphocytes in vitro, compared with controls.

Evaluation of the mutagenic effect of the new fungicide trimorphamide

The new Czechoslovak fungicide trimorphamide was tested for its mutagenic activity. To evaluate the potential mutagenic effects on Drosophila, trimorphamide at 0.5, 1.0, 5.0, 10.0% was administered into the cultivation medium, and the sex-linked recessive lethal mutation detection test and the chromosome nondisjunction test were used. After administration of trimorphamide to mice at 60, 150 and 300 mg . kg-1 b.w. perorally, and 30, 70 and 150 mg . kg-1 b.w. intraperitoneally in single and repeated (5X) doses, a cytogenetic analysis of chromosomal aberrations in bone-marrow cells was performed. The cytogenetic analysis of human peripheral lymphocytes for chromosomal aberrations in vitro was performed 24 h after trimorphamide had been applied into the culture in concentrations 19.1 X 10(-3), 19.1 X 10(-4) and 19.1 X 10(-5) M. Under our testing conditions the trimorphamide concentrations used did not show any mutagenic effect upon Drosophila, compared with the controls. Also, under the conditions of the cytogenetic analysis, no significant increase in the frequency of chromosomal abnormalities in mouse bone marrow or in human peripheral lymphocyte was observed compared with the group of controls.