Molecular analysis of 5-azacytidine-induced variants in mammalian cells.

5-azacytidine induces 6-thioguanine resistance in AS52 cells. To characterize these resistant clones, we isolated 148 of them from 50 independently treated flasks. Less than nine (6%) of the 148 variants were spontaneous. PCR amplification of the DNA primers flanking the gpt gene produced no product in 15 clones (10%). Of the 133 remaining clones, 52 showed sequence alterations in the gpt structural gene. Of these 52, 34 (65%) were GC-->CG transversions. Only seven were located in CpG sequences. Thus, methyltransferase complexes are not major contributors to 5-azacytidine-induced point mutations in AS52 cells. The remaining 81 clones had no sequence alterations within the coding region of the gpt gene. Southern blot analysis of a sample of these variants (37/81) indicated that the 6-thioguanine-resistant phenotype was not due to local rearrangements or deletions (resolution 50 bp). Sequence analysis of the early promoter region of another sample of these variants (24/81) indicated that lesions in the promoter could not be responsible for the 6-thioguanine resistance observed. Thus, a majority of these variants were formed via a mechanism other than small genomic rearrangements, point mutations or deletions of the gpt structural gene or its promoter. Neither the mechanisms leading to these variants nor the biological and morphological consequences of these variants are known.

Cytogenetic effect of the thiocarbamate herbicides butylate, molinate and vernolate in the mouse bone marrow micronucleus test.

Three thiocarbamate herbicides, butylate (S-ethyl-diisobutylthiocarbamate), vernolate (S-propyl dipropylthiocarbamate) and molinate (S-ethyl-N,N-hexamethylenethiocarbamate) were assayed for cytogenetic effect in the mouse bone marrow micronucleus test. Butylate was inactive in bone marrow, vernolate caused a marginal increase in the incidence of micronucleated polychromatic erythrocytes only at a high toxic dose level. Molinate, the N,N-hexamethylene derivative was, however, strongly active in the bone marrow, causing a high frequency of micronucleated erythrocytes, even at subtoxic concentrations.

Long-term carcinogenicity bioassay of the herbicide atrazine in F344 rats.

In Fischer F344/LATI rats of both sexes the herbicide atrazine was given in the diet at concentrations of 0, 375 and 750 ppm for 126 weeks. Food and water consumption was similar in the treated and control groups. Feeding of atrazine resulted in dose-dependent depression of body weight gain in both sexes. There was no difference in the survival among the females. The males in the treated groups lived significantly longer than the controls. Exposure to atrazine resulted in significantly increased incidence of mammary tumors in the high dose male group. Uterine carcinomas were observed at a dose-related, significantly increased incidence. The number of combined leukemias/lymphomas increased in the treated males and females, but it was statistically significant only for females. The total number of malignant tumors showed a dose-related increase in both sexes. Other tumors and nontumorous lesions occurred at background level and were not influenced by treatment.

Mutagenicity of emission and immission samples around industrial areas.

Urban air particulates (suspended particles and settling dusts), as well as dusts emitted by a Söderberg aluminium production plant and a coal-burning power plant, in the industrial town of Ajka were analysed for polycyclic aromatic hydrocarbon (PAH) content (liquid chromatography) and mutagenicity (Salmonella microsome test). The same parameters for air particulates from Pápa (a town of similar size without much heavy industry) were analysed and compared to those from Ajka. The dust content, PAH concentration and the mutagenic potency of the air in Ajka were higher than in Pápa. Mutagenicity of airborne particulates showed a clear seasonality with a winter maximum and a summer minimum in both towns. The mutagenic potency of air correlated well with the benzo[a]pyrene (BP) and PAH content in Ajka but not in Pápa. The amounts of extractable organic material and mutagenic potency, as calculated for unit quantity of airborne particulate matter, were higher in the Pápa samples. Similar differences between the two towns were observed in the case of deposited dust. As regards the emission dusts, the aluminium plant emissions are responsible for much more of the mutagenicity of the urban air than the power plant emission, which is the main component of air dust pollution in Ajka.

Genotoxicity of selected herbicides.

Twenty-two herbicides were studied in 67 tests for induction of DNA damage, gene mutation and chromosomal changes in vitro and in vivo. Triazine and urea-type herbicides were found to be inactive in all but one test. Of 4 thiocarbamates, molinate and vernolate caused chromosomal changes, namely increased incidence of sister chromatid exchanges and chromosomal aberrations in vitro and increased frequency of micronucleated polychromatic erythrocytes in mouse bone marrow. These compounds, however, did not cause gene mutation and only molinate gave equivocal positive result in bacterial repair test. Out of 11 miscellaneous herbicides, ethofumesate, alachlor, dichlorprop and fluorodifen proved to be positive only in one or two tests. In the light of clastogenicity of some thiocarbamates, serious consideration should be given to start animal carcinogenicity studies with these chemicals.

Mutagenicity and PAH content of airborn particulates and of fallen dusts from two Hungarian towns and emission samples from aluminum reduction and power plants.

Urban air particulates (suspended particles and settling dust), furthermore dust emitted by a Soderberg aluminum reduction plant and a coal burning power plant from an industrial town, Ajka (30,000 inhabitants) were analysed for PAH content (liquid chromatography) and mutagenicity (Salmonella microsome test). Air particulates from Papa--a town of similar size without considerable heavy industry--and corresponding plant emission from Inota, a third town in the study, served as controls. The dust content and the PAH concentration, as well as the mutagenic potency of the air in Ajka were higher than in Papa. Mutagenicity of the airborne particulates showed a clear seasonality with a winter maximum and a summer minimum in both towns. The mutagenic potency of air correlated well with the air BaP and total PAH content in Ajka, but not in Papa. The amounts of extractable organic material and mutagenic potency as calculated for unit quantity of airborne particulate matter was higher in the Papa samples. Similar differences between the two towns were observed in the case of fallen dust, too. On the basis of examination of emitted dust, it can be stated, that in the mutagenicity of urban air, the aluminum plant emission plays a considerably higher role than the power plant emission, which is the main component of air dust pollution in Ajka.

Mutagenicity studies on terbacil, an uracil-analogue pesticide.

The possible mutagenic effect of the uracil analogue pesticide Terbacil was examined on Drosophila melanogaster and in mammalian cell culture. Terbacil did not prove to be mutagenic in the sex-linked recessive lethal mutation test, and it did not cause an increase in sister chromatid exchange in CHO cells. It cannot be considered a chromosome-mutagenic compound. Considering the procaryote studies known from the literature, it is assumed that Terbacil does not represent a genotoxic hazard for the persons involved either in its production or its use.