Comparative mutagenicity studies of azo dyes and their reduction products in Salmonella typhimurium

The arabinose-resistant and Ames assay systems of Salmonella typhimurium were used to evaluate the mutagenic potential of azo dyes and their aromatic amine reduction products. Azo dyes, namely direct black 38, direct blue 15, and direct red 2, were mutagenic in the arabinose-resistant and Ames assays with both hamster and rat liver S9 activation. Both assays gave relatively higher mutagenic responses with hamster S9. Reduction products of these dyes, namely benzidine, o-dianisidine, and o-tolidine, were mutagenic in the Ames assay. Benzidine was weakly mutagenic and o-dianisidine and o-tolidine were nonmutagenic in the arabinose-resistant assay. These results indicate that both arabinose-resistant tester SV50 and Ames tester TA98 were sensitive in detecting mutagenicity of azo dyes. The use of the standard plate protocol with Ames tester TA98 is more efficient than the modified azo dye protocol in detecting mutagenicity of aromatic amine reduction products. Additional modifications in either the standard plate or modified azo dye protocols may improve detection of mutagenicity of these compounds in the arabinose-resistant assay system.

Arsenic in garden soils and vegetable crops in Cornwall, England: Implications for human health

Total concentrations of arsenic in surface (0-15cm) garden soils in the historical mining area of Hayle-Camborne-Godolphin, Cornwall, England are large and range widely (144-892 μg/g). Amounts of water soluble and acid-fluoride extractable soil arsenic are significantly correlated with total content.Examination of 6 salad and vegetable crops grown in 32 gardens has shown arsenic concentrations in the edible tissues to be only slightly elevated. There were strong correlations between arsenic in beetroot, lettuce, onion and peas and soil arsenic (total, water soluble and acid extractable). Regression equations have been calculated. Ridge regression analysis applied to test the importance of other soil variables has shown both iron and phosphorus to influence the uptake of arsenic.Arsenic in all the vegetables sampled was below the statutory limit in the U.K. of 1 mg/kg fresh weight. Implications for health should be assessed in relation to other exposure routesvia water, air and directly ingested dust and soil.

In vivo cytogenetic studies on mice exposed to ethylene dibromide

The pesticide, ethylene dibromide (EDB), was evaluated with in vivo cytogenetic assays to determine its genotoxicity. CD1 male mice were exposed to EDB through intraperitoneal injections. Bone marrow cells isolated from femora were analyzed for sister-chromatid exchange (SCE), chromosome aberration and micronucleus formation. The results showed that only certain concentrations of EDB tested caused a slight but significant increase in SCEs and chromosome aberrations. However, these increases were not dose-related. No increase in the polychromatic erythrocytes with micronuclei was observed following EDB exposure. Also, EDB did not cause cell-cycle delay in comparison with controls. Thus, it appears that EDB is not an effective genotoxic agent in vivo in mice.

Factors affecting the induction of pollen plants of intergeneric hybrids of Triticum aestivum X Triticum-Agropyron

Experimental results showed that the use of potato extract as a basic component of culture medium had a promoting effect on producing calli in anther culture of the intergeneric hybrids of Triticum aestivum × Triticum-Agropyron (intermediate type). The induction frequencies of pollen callus on the Potato-II medium containing potato extract as the main component was much higher than that found on N6 and W5 media. The induction frequencies of pollen callus and green plantlets in four intergeneric hybrid material inoculated at the late-uninucleate pollen stage were all higher than those inoculated at the mid-uninucleate stage. Appropriate increases in culture temperature significantly increased pollen callus induction frequencies of the intergeneric hybrids. The genotype and physiological state of anther donor plants also influenced pollen callus and green plantlet induction frequencies.

Detection of sister-chromatid exchanges in human peripheral lymphocytes induced by ethylene dibromide vapor

A method using sister-chromatid exchanges (SCEs) for genotoxic testing of gaseous compounds is described. Human peripheral lymphocyte cultures previously stimulated with phytohemagglutinin were placed in sterile dialysis tubing and then put in an enclosed flask containing additional culture media. Air, with or without ethylene dibromide (EDB), was bubbled through the flask for up to 8 h. The cultures were harvested 75 h after culture initiation, and second-division cells were scored for induction of SCEs according to established procedures. The SCE frequency was approximately doubled in cultures treated with EDB. A similar experiment with air alone resulted in only slight increases in SCEs. The results indicate that this system is potentially useful for detecting genotoxicity of gases and vapors and may be useful for the detection of genotoxic agents in occupational settings.

Genotoxic activity of nitrosated coal dust extract in mammalian systems

The genotoxicity of coal dust extract nitrosated by NaNO2 was investigated because of an elevated incidence of gastric cancer in coal miners. Human peripheral lymphocytes were used to determine the frequency of sister chromatic exchanges (SCE) and chromosome aberrations. Chinese Hamster Ovary (CHO) cells were also used to measure SCEs. The mouse lymphoma forward mutation assay comprised the final in vitro system, while the micronucleus test on mouse bone marrow cells was used as an in vivo assay. The SCE frequency in human lymphocytes increased from 9.2 per cell in untreated cultures to 31.6 per cell in cultures treated with 10.0 microliter/ml of nitrosated coal dust extract (NCDE) (P less than .0001). Chromosome aberrations were tested during two phases of the cell cycle; the results indicate that NCDE causes an increase in aberrations in each cell phase tested. The SCE frequency in the CHO system increased from 9.0 per cell in untreated cultures to 18.0 per cell in cultures treated with 3.3 microliter NCDE per ml of medium (P less than .001). In the mouse lymphoma system, the background mutation frequency was tripled at 2.0 microliter NCDE per ml of medium. NCDE was not found to be active in the murine micronucleus assay. No consistent increase in genetic activity was observed with nonnitrosated coal dust extract alone or with NaNO2 alone. Metabolic activation greatly reduced or eliminated genetic activity. These results indicate that nitrosated coal dust extract is genetically active in in vitro mammalian systems without metabolic activation. These findings suggest that the nitrosation of ingested coal dust may be responsible for the elevated incidence of gastric cancer in coal miners.

Validation of the Salmonella (SV50)/arabinose-resistant forward mutation assay system with 26 compounds

Mutagenic sensitivity of the Salmonella/arabinose-resistant (Arar) assay system using the tester strain SV50 was evaluated with 26 compounds both by the preincubation and the standard plate incorporation tests. The mutagenic activity of all 26 compounds was also tested with TA98 and/or TA100 of the Ames Salmonella/microsome assay system. The results indicate that 13 and 10 of 26 compounds were mutagenic and nonmutagenic, respectively, in both assay systems. PR toxin and hydrogen peroxide were mutagenic only in the Arar assay, while 2-nitrofluorene was mutagenic only in the Ames assay. The results also show that the mutagenic response of SV50 to 13 of 15 mutagenic compounds was much higher (2.1-154-fold) if the compounds were tested with the preincubation rather than the plate incorporation test. The mutagenic activity of 4 compounds (diethyl sulfate, niridazole, PR toxin and hydrogen peroxide) in the Arar assay was detected only with the preincubation test. Since the Arar assay using tester strain SV50 has similar mutagenic sensitivity as the Ames assay to chemicals with different modes of action and since it requires only one tester strain, we find this assay system to be useful for screening environmental mutagens. Based on the effectiveness of the preincubation test in this study, it is recommended that the preincubation test instead of the plate incorporation test be used for the Arar assay system with tester strain SV50.

Comparative studies on spontaneous and mitomycin-C-induced sister-chromatid exchanges in smokers and non-smokers

Both spontaneous and mitomycin-C-induced sister-chromatid exchanges were analyzed in 6 smokers and 6 non-smokers. The average number of spontaneous SCE in smokers' cells was 8.33 +/- 1.08. The frequency in the non-smoking controls was 4.41 +/- 0.72. This difference is highly significant (P less than 0.001). Smokers also had more SCE at all levels of mitomycin C testes. Analysis of variance showed these differences to be highly significant (P less than 0.001).

Mitosis of nerve cells in the cerebral cortex of adult rats

Adult rats 4-5 months old and 150-200g in body weight were used in this experiment. Lesions were made with antiseptic precaution by excising portions (0.7 x 0.4 x 0.1cm) of the cerebral cortices under ether anesthesia. The animals were sacrificed by decapitation at the time intervals ranging from 1 to 30 days after the operation. Specimens of the brain were removed from the lesions with their adjacent normal areas, and processed for histological and histochemical studies. Mitotic figures were observed in nerve cells adjacent to the lesions. The mitotic process of these neurons is similar to that of the other tissue cells, as it can also be divided into four stages--prophase, metaphase, anaphase and telophase. However, neurons are entirely different from the neuroglia and other tissue cells in that these have characteristic cell processes, i.e. axon and dendrites, while most of the neurons are pyramidal cells of layers II and V of the cerebral cortex. The other characteristic feature is that the dividing neuron contains Nissl bodies in the cytoplasm.