Showing papers in "Mutation Research\/genetic Toxicology in 1987"

Cytogenetic studies on rural populations exposed to pesticides

Abstract: The authors have carried out cytological analysis of 72 h lymphocyte cultures from peripheral blood and internal examinations of 80 workers professionally exposed to a complex of pesticides and that of 24 control persons. There was a significant increase of chromosome aberrations in relation to the duration of exposure. The additive role of alcohol consumption and smoking in evoking aberrations was also studied with inconclusive results because of the limited number of cases. Internal examinations revealed a more frequent occurrence of acute as well as chronic diseases among the workers aged 21-40 years.

Modifying role of dietary factors on the mutagenicity of aflatoxin B1: in vitro effect of vitamins.

Abstract: 19 vitamins including some derivatives have been tested for their ability to suppress mutagenic activity of aflatoxin B1 (AFB1) towards Salmonella typhimurium strain TA100 activated with a rat-liver metabolic activation system. Several vitamins have shown an ability to inhibit the mutagenic potency of AFB1. The values of ID50, i.e. the dose required to inhibit mutagenic activity by 50% calculated from dose-response curves for each vitamin show retinoids, riboflavin, folic acid, menadione, cyanocobalamin, ascorbic acid and pyridoxine to be significantly antimutagenic. Although inhibition by vitamins is apparent over a range of AFB1 concentrations, their effect is more pronounced at lower concentrations of AFB1. When combined data are expressed in terms of specific mutagenicity, riboflavin, retinol and menadione have been found to possess exceptional inhibitory ability in as much as, on a molar basis, only 15–40-fold excess vitamins can inhibit the mutagenic potency of AFB1 by 50%. Their action is possibly mediated through interaction with microsomal activating enzymes. Previous evidence from this laboratory about their inhibitory action on DNA-adduct formation and metabolic activation together with the present results suggest that certain vitamins notably retinoids and riboflavin may have potential anticarcinogenic activity against AFB1.

Pesticide clastogenicity in Chinese hamster ovary cells

Abstract: Paraquat, alachlor, butachlor, phorate and monocrotophos, several of the most extensively used pesticides in Taiwan, were investigated for their clastogenicity using chromosome aberration (CAb) induction in Chinese hamster ovary (CHO) cells. Significance levels of the binomial trend analysis and binomial mutagenicity data test were two criteria for the summary judgement of the pesticide clastogenicity. Except for phorate, all pesticides tested were clastogenic to CHO cells in the absence of in vitro metabolic activation by S9. 5 μl/ml rat-liver extract, S9, were used as the source of in vitro metabolic activation. 3 different outcomes were found after the addition of S9. (1) Paraquat: significant decrease in induced CAbs. (2) Monocrotophos: concomitant occurrence of decreased cytotoxicity and increased clastogenicity. (3) Alachlor, butachlor and phorate: increased cytotoxicities with no sign of enhancement in clastogenicity.

Effects of antimutagenic flavourings on SCEs induced by chemical mutagens in cultured Chinese hamster cells

Abstract: Effects of antimutagenic flavourings such as vanillin, ethylvanillin, anisaldehyde, cinnamaldehyde, coumarin and umbelliferone on the induction of SCEs by MMC were investigated in cultured Chinese hamster ovary cells. None of these 6 flavourings showed any SCE-inducing activity by themselves. However, an obvious increase in the frequencies of SCEs was observed when MMC-pretreated cells were cultured in the presence of each flavouring. All these compounds have either an α, β-unsaturated carbonyl group or a carbonyl functionality neighbouring the phenyl group which may react with an enzyme SH-group and cause higher-order structure changes. SCE-enhancing effects of vanillin were further investigated on 6 other kinds of mutagens. Vanillin was also effective on SCEs induced by EMS, ENNG, ENU or MNU. On the other hand, MMS- or MNNG-induced SCEs were not influenced at all by vanillin. SCE-enhancing effects of vanillin seemed to be dependent on the quality of lesions in DNA.

Mutagenic activity of chloramines.

Abstract: Mutagenesis by chloramines and hypochlorous acid (HOCl) was studied to determine whether these agents could contribute to the mutagenic and potentially carcinogenic activity of stimulated leukocytes and whether environmental exposure to these agents is a cause for concern. Mutagenic activity was measured using the S. typhimurium TA97a, TA100 and TA102 tester strains. Because chloramines and HOCl are bactericidal, react rapidly with cell components, and can destroy the histidine and biotin required for the mutagenesis assay, activity can't be compared directly with that of less toxic or reactive agents. Nevertheless, chloramines were mutagenic when tested under appropriate conditions. TA100 was the most sensitive strain, and the most active mutagens were lipophilic dichloramines (RNCl2) including derivatives of histamine, ethanolamine and putrescine. Lipophilic monochloramines (RNHCl) such as histamine-monochloramine and NH2Cl were less active. Hydrophilic chloramines such as taurine-chloramines had low activity, and HOCl was inactive. The metabolic state of the bacteria was critical. Chloramines were mutagenic when added to bacteria with glucose at 37 degrees C, but killing predominated when chloramines were added at 4 degrees C or 25 degrees C, or at 37 degrees C without glucose. Production of chloramines and HOCl by leukocytes in vivo could contribute to the association of chronic inflammation and cancer as a result of: (1) the entry of membrane-permeable chloramines into normal cells followed by attack on intracellular components including DNA, and (2) the production of secondary mutagens such as compounds with carbonyl groups or carbon-chlorine bonds. On the other hand, chlorination of water supplies is perhaps more likely to destroy than create mutagens, and chloramines from the environment are unlikely to penetrate the skin and mucous membranes.

Implications of treatment-condition-induced genotoxicity for chemical screening and data interpretation.

Abstract: Ionic and pH alterations appear to be directly responsible for the induction of genotoxic effects in cultured mammalian cells. In vivo studies also associate high ion concentrations and pH changes with tumor enhancement of the glandular stomach and urinary bladder of rats. The implications of these findings are directly relevant to the design of in vitro and in vivo tests and to the interpretation of results from tests using materials likely to produce alterations in ionic and/or pH levels.

Mutagenic Activity of 27 Dyes and Related Chemicals in the Salmonella/ microsome and Mouse Lymphoma TK+/-Assays

Abstract: A total of 27 dyes and related chemicals were tested for mutagenicity in both the Salmonella typhimurium plate-incorporation and FMN-modified assays as well as the mouse lymphoma TK+/− assay. Half of the compounds tested were monoazo dyes (14); the remainder consisted of disazo (3), aminotriphenylmethane derivatives (4), and other miscellaneous (6) color compounds. The results obtained in this study are compared with data from dyes of the same batch tested in other laboratories in the Salmonella plate-incorporation assay and in both in vitro and in vivo/in vitro UDS assays. Agreement of results from the various assays that could be compared (excluding results that were equivocal or indeterminate) ranged from 80 to 91%. Sufficient data were available to provide an overall index of in vitro activity for 15 chemicals; of these, 14 compounds could be compared to and agreed with reports of their carcinogenic potential in the literature.

Photochemical instability of 1-nitropyrene, 3-nitrofluoranthene, 1,8-dinitropyrene and their parent polycyclic aromatic hydrocarbons.

Abstract: The environmental contaminants pyrene, 1-nitropyrene, 1,8-dinitropyrene, fluoranthene, and 3-nitrofluoranthene were exposed to light (⩾ 310 nm) either in DMSO, or following coating onto silica. Under all conditions tested the pyrenyl were less stable than the fluoranthenyl compounds. During irradiation in DMSO or on silica, 1-nitropyrene had half-lives of 1.2 and 6 days, while those of 3-nitrofluoranthene were 12.5 and > 20 days, respectively. The photodecomposition of 1,8-dinitropyrene resembled that of 1-nitropyrene with half-lives of 0.7 and 5.7 days. A principle photodecomposition product of 1,8-dinitropyrene was identified as 1-nitropyren-8-ol. It was also found that when the nitroarenes were exposed to light, the loss of compound was associated with a concomitant loss of mutagenicity in Salmonella typhimurium strain TA98. The mechanism of nitrated polycyclic aromatic hydrocarbon decomposition and 1-nitropyren-8-ol formation, and the relevance to the atmospheric disposition of these compounds are discussed.

Correlation of the carcinogenic potential of di(2-ethylhexyl)phthalate (DEHP) with induced hyperplasia rather than with genotoxic activity.

Abstract: It has been reported that in a long-term feeding study 12 000 ppm of di(2-ethylhexyl)phthalate (DEHP) in the diet produced hepatocellular carcinomas in male and female F-344 rats while 6000 ppm DEHP produced the same tumor type in male and female B6C3F1 mice. In terms of the actual numbers of animals with tumors DEHP produced a greater reponse in mice than rats. DEHP and its principal hydrolysis product, mono(2-ethylhexyl)phtalate (MEHP) produce multiple effects in the animal such as liver peroxisomal proliferation and hyperplasia. Accordingly, genotoxicity as DNA repair or unscheduled DNA synthesis (UDS) and cell replication as the percentage of cells undergoing scheduled DNA synthesis (SDS or S phase) were determined in mouse hepatocytes in vitro and in vivo in response to DEHP and MEHP. UDS and SDS were determined by autoradiographic quantitation of [3H]-thymidine incorporation in primary hepatocyte cultures treated directly or isolated from B6C3F1 male mice treated in vivo. No DNA repair was observed in mouse hepatocyte cultures treated with up to 1.0 mM DEHP or 0.5 mM MEHP. No DNA repair was observed in cultures from mice treated with up to 500 mg/kg DEHP 12,24 or 48 h previously or from animals treated up to 28 days with 6000 ppm DEHP in the diet. At 24 h following treatment with 500 mg/kg DEHP, 3.1% of the hepatocytes were in S phase compared to control values of 0.2%. Administration of DEHP in the diet at 6000 ppm produced 9.2% of the cells in S phase at day 7 with the value returning to control levels by day 14. On day 28 of the feeding study the liver to body weight ratios had almost doubled in the group treated with DEHP compared to controls. No increase in the liver-specific enzyme alanine aminotransferase was seen in the serum following treatment with 500 mg/kg DEHP, indicating that the hyperplasia was due to mitogenic stimulation rather than regenerative hyperplasia in response to cytotoxicity. Increases in the endpoints relating to hyperplasia in response to DEHP were greater in the mouse than those that have been reported in the rat. Thus, the carcinogenic response of DEHP correlates better with induced hyperplasia rather than with genotoxicity.

Mutagenic activity of fluorides in mouse lymphoma cells.

Abstract: The L5178Y mouse lymphoma cell forward-mutation assay was used to test for the mutagenic activity of sodium and potassium fluoride at the thymidine kinase locus. Mutants were detected by colony formation in soft agar in the presence of trifluorothymidine. Mutagenic and toxic responses were observed in the concentration range of 300-600 micrograms/ml with both sodium and potassium fluoride. Approximately 3-fold increases in mutant frequency were observed for concentrations in the 500-700 micrograms/ml range that reduced the relative total growth to approximately 10% in the absence or presence of a rat-liver S9 activation system. A sample of 30% sodium fluoride-70% sodium bifluoride (NaHF2) induced a similar mutagenic response but was more toxic with respect to the fluoride concentration. A specificity for fluoride ions in causing mutagenesis was indicated by the fast that much higher concentrations of sodium or potassium chloride were necessary to cause toxicity and increases in the mutant frequency. The possible involvement of chromosomal changes was signaled by the predominant increase in the small colony class of mutants.

Relative genotoxicity of trichloroacetic acid (TCA) as revealed by different cytogenetic assays: bone marrow chromosome aberration, micronucleus and sperm-head abnormality in the mouse

Abstract: Trichloroacetic acid (TCA) has been tested for mutagenicity in a mouse in vivo system. Three different cytogenetic assays — bone marrow chromosomal aberrations, micronucleus and sperm-head abnormalities — have been carried out. Swiss mice have been treated with the chemical, administered via different routes (i.p. and p.o.), and in three acute and/or fractionated doses (5 consecutive daily) equivalent to the highest acute dose, and their cells sampled at different intervals. A variety of anomalies, occurring in higher percentages compared to controls, was observed in all cases. Comparison between single and fractionated dosing revealed the single dosing to be more effective cytogenetically. The results were route and time-dependent but not dose-responsive (exclusive of gaps). The relative sensitivity of the assays has been found to be: chromosome aberration > sperm-head abnormality > micronucleus. The results revealed the genotoxic property of TCA in the present test system.

Mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solutions.

Abstract: The mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solution was assayed with Salmonella typhimurium strains TA97, TA98, TA100, TA102 and TA104 in the presence and absence of S9 mix from phenobarbital- and 5,6-benzoflavone-induced rat liver Ozonated naphthoresorcinol was mutagenic in TA97, TA98, TA100 and TA104 without S9 mix By the addition of S9 mix, the mutagenic activity of ozonated naphthoresorcinol was markedly suppressed in TA98 and TA100, but became positive in TA102 High-performance liquid chromatography (HPLC) after derivatization to 2,4-dinitrophenylhydrazones demonstrated the formation of glyoxal as an ozonation product of naphthoresorcinol Ion chromatographic technique also demonstrated the formation of o-phthalic acid, muconic acid, maleic acid, mesoxalic acid, glyoxylic acid and oxalic acid as ozonation products The mutagenicity assays of these identified products with five Salmonella strains showed that glyoxal and glyoxylic acid were directly mutagenic; the former in TA100, TA102 and TA104, the latter in TA97, TA100 and TA104 In the presence of S9 mix, glyoxylic acid gave a positive response of mutagenicity for TA102 The experimental evidence supported that glyoxal and glyoxylic acid may contribute to the mutagenicity of ozonated naphthoresorcinol

Comparative genotoxic effects of IQ and MeIQ in Salmonella typhimurium and cultured mammalian cells

Abstract: The food mutagens 2-amino-3-methylimidazo[4,5-ƒ]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-ƒ]quinoline (MeIQ) were studied for their genotoxic potential using hepatocytes isolated from untreated and Aroclor 1254 (PCB) pretreated rats as an activation system. Monolayers of hepatocytes co-incubated with Salmonella typhimurium TA98 activated IQ and MeIQ to bacterial mutagens, with MeIQ being about twice as potent as IQ. The mutagenic activities of IQ and MeIQ were increased by using hepatocytes from PCB-pretreated rats. IQ and MeIQ also caused primary DNA damage in the hepatocytes as determined by increases in the rate of alkaline elution of DNA, as well as increases in DNA-repair synthesis. Furthermore, exposure of V79 cells co-cultured with PCB-pretreated hepatocytes to IQ and MeIQ showed evidence of increased sister-chromatid exchanges and a low and variable increase in the number of 6-thioguanine-resistant mutants. The genotoxic potency of IQ and MeIQ in mammalian cells was low or virtually absent compared to their extreme potency in bacteria. This could be due to a lower capacity of mammalian cells to further metabolize the so-called directly acting bacterial mutagens, formed by a cytochrome P-450 dependent N -hydroxylation, to their ultimate reactive forms.

Implication of active oxygen species in the direct-acting mutagenicity of tea.

Abstract: The present study shows that the l -arabinose resistance test with Salmonella typhimurium detects that freshly infused tea is highly mutagenic in the absence of mammalian microsomal activation. Both the mutagenesis protocol (preincubation test) and the additional genetic characteristics of the bacterial tester strain (excision repair deficiency, normal lipopolysaccharide barrier and the presence of plasmid pKM101) were critical factors in the optimal induction by tea of forward mutations to l -arabinose resistance. The TA104 strain — a histidine auxotroph specific to oxidative mutagens — was the most sensitive tester strain of the Ames test to the direct-acting mutagenicity of tea. In comparison with strain TA104, the sensitivity of the Ara forward mutation test was 18 times higher, one cup of tea (200 ml) inducing 3 × 10 6 Ara R mutants. More than 90% of the mutagenicity of 150μl of a fresh tea infusion, or that of the equivalent amount (1.32 mg) of the corresponding lyophilized residue, was suppressed by 10 units of catalase. In contrast to catalase, superoxide dismutase was rather ineffective. These results indicate that hydrogen peroxide is produced in tea solutions, playing an essential role in its mutagenicity. In comparison, the role of superoxide anion seems negligible. Like catalase, the chelating agent DETAPAC showed a protective effect with respect to the mutagenicity of tea, suggesting the additional implication of hydroxyl radicals.

A guide for mutagenicity testing using the dominant lethal assay.

Abstract: The dominant lethal assay has been used and continues to be used to provide information about the effects of chemicals on the gonadal cells of male animals. Guidelines for conducting this test are useful but as with any guideline scientists should avoid interpreting them as protocols. Thus this document is a general approach to dominant lethal testing and should be used in conjunction with other available protocols and procedures.

Extrapolation from in vitro tests to human risk: experience with sodium fluoride clastogenicity.

Abstract: Genotoxic effects observed in vitro, only at high doses or high levels of cytotoxicity, will be false positives if such conditions are not achieved or cannot be tolerated in vivo. However, for such effects to be disregarded there must be a threshold dose or level of cytotoxicity below which genotoxicity is absent. Sodium fluoride (NaF) has previously been shown to be clastogenic in vitro in Syrian hamster cells and human fibroblasts. We have extended these studies in human fibroblasts and included a positive control (mitomycin C, MMC) which is clastogenic in vivo and carcinogenic, and a chemically related control (NaCl). Cytotoxicity was measured as mitotic inhibition and cell death (loss of clonogenicity). The results are used to illustrate the problems associated with quantitative extrapolation from in vitro tests to human risk, as follows. (1) There appears to be a threshold response (clastogenicity vs. dose) with NaF at around 10 micrograms/ml (48 h exposure) but a more definitive conclusion must await elucidation of the mechanisms of clastogenicity. (2) NaCl is weakly clastogenic at 1000 times the threshold dose for NaF. The mechanisms are unlikely to be similar. (3) No clastogenicity was detected with NaF below about 30% mitotic inhibition but the relationship between clastogenicity and mitotic inhibition was similar for NaF and MMC. (4) There was no obvious threshold in the relationship between clastogenicity and cell killing with NaF. MMC was less clastogenic than NaF at equitotoxic doses. Observations 3 and 4 preclude the possibility of regarding the clastogenicity of NaF as a false positive by virtue of associated cytotoxicity.

Effects of the antimutagen cinnamaldehyde on reversion and survival of selected Salmonella tester strains

Abstract: The antimutagenic activity of trans-cinnamaldehyde (C6H5CHCHCHO) on chemically induced mutagenesis has been shown in E. coli. Using the Ames Salmonella typhimurium tester strains TA1535 (hisG46 uvrB rfa) and TA100 (TA1535/pKM101), the effects of cinnamaldehyde on spontaneous reversions and reversions induced by 4-nitroquinoline-N-oxide(4NQO) and ethyl methanesulfonate (EMS) have been examined. To observe the effect of cinnamaldehyde in the absence of functional muc genes, a third strain, TA1535/pGW201 (pKM101 muc140::Tn5) was included in the testing. Modifications of the standard Ames test procedures and direct-plating techniques were employed to study the “antimutagenic” response exerted by cinnamaldehyde. In all strains tested, concentrations of cinnamaldehyde up to 25 μg/ml slightly decreased the number of spontaneous reversions and induced reversions were more markedly reduced. The decreases in the numbers of 4NQO-induced revertants were greater than those decreases which occurred for EMS-induced reversions. There was no effect on viability in 1% (v/v) nutrient broth supplemented minimal medium containing 5–25 μg/ml of cinnamaldehyde. Cinnamaldehyde did not display any mucAB dependent or independent specificity against the mutagens used. On minimal medium supplemented with histidine and biotin, concentrations of cinnamaldehyde above 10 μg/ml were lethal for the strains tested. When the test medium was supplemented with 1–5% (v/v) liquid nutrient broth, viability was not affected at concentrations up to 25 μg/ml. For both TA100 and TA1535 the presence of 20 μg/ml of cinnamaldehyde in 1% (v/v) liquid nutrient broth-supplemented minimal glucose broth extended the lag phase for 2–4 h with no effect on survival. Depending on the test procedure employed, decreases in numbers of revertants may reflect lethality rather than antimutagenesis. When used to test for antimutagenesis rather than mutagenesis, modifications of the standard Ames test procedure may mimic an antimutagenic response due to a decrease in the total number of revertants seen even though enough cells survive to produce a background lawn.

Mutagenicity of selected aniline derivatives to Salmonella following plant activation and mammalian hepatic activation.

Abstract: We compared several phenylenediamines (4-nitro-o-phenylenediamine, NOP; 2-nitro-p-phenylenediamine, NPD; o-phenylenediamine, OPD; p-phenylenediamine, PPD; m-phenylenediamine, MPD) and aniline (ANL) for mutagenicity to Salmonella directly and following activation by plant and mammalian hepatic S9 using plate incorporation and preincubation protocols. In addition, we assayed each chemical for activation by intact plant cells using the plant cell/microbe coincubation protocol. At the concentrations tested, NOP, NPD, OPD, MPD and ANL were active in one or more assays. NPD, OPD and MPD were activated by mammalian hepatic S9 in one or more assay and each was activated by plant S9 or intact plant cells. ANL was mutagenic only in the presence of plant S9. PPD was not active under any of the test conditions.

The effectiveness of S9 and microsomal mix on activation of cyclophosphamide to induce genotoxicity in human lymphocytes.

Abstract: Comparative results are presented on the effectiveness of rat-liver S9 or microsomal mix (M mix) in activating cyclophosphamide (CP) and its ability to induce a clastogenic effect in human lymphocytes in vitro. Structural chromosome changes were analysed exclusively in 1st division (M1) metaphases post-exposure. A high genotoxic response was observed for both metabolizing systems used. With an exposure of 2 h to different concentrations of S9 or M mix, the highest aberration yields were always found for the highest protein content. For CP treatment times of 1, 2 or 4 h together with S9 mix (protein content 10 mg/ml) or M mix (4 mg/ml), the latter was more efficient. With both systems, a lower clastogenic effect of CP was found at 4 h exposure than at 1 h or 2 h. Only a weak cytotoxic effect, reflected mainly by the reduction in the percentage of 3rd cycle cells (M3), and measured in terms of the proportion of M1, M2 and M3 cells, was induced by both systems.

Tests for urethane induction of germ-cell mutations and germ-cell killing in the mouse.

Abstract: Urethane, a chemical that has given varied results in mutagenesis assays, was tested in the mouse specific-locus test, and its effect on germ-cell survival was explored. Altogether 32 828 offspring were observed from successive weekly matings of males exposed to the maximum tolerated i.p. dose of 1750 mg urethane/kg. The combined data rule out (at the 5% significance level) an induced mutation rate greater than 1.7 times the historical control rate. For spermatogonial stem cells alone, the multiple ruled out is 3.2, and for poststem-cell stages, 3.5. Litter sizes from successive conceptions made in any of the first 7 weeks give no indication of induced dominant lethality, confirming results of past dominant-lethal assays. That urethane (or an active metabolite) reaches germ cells is indicated by SCE induction in spermatogonia demonstrated by other investigators. Cytotoxic effects in spermatogonia are suggested by our finding of a slight reduction in numbers of certain types of spermatogonia in seminiferous tubule cross-sections and of a borderline decrease in the number of litters conceived during the 8th and 9th posttreatment weeks. The negative results for induction of gene mutations as well as clastogenic damage are at variance with Nomura's reports of dominant effects (F1 cancers and malformations) produced by urethane.

Mutagenicity in salmonella of hazardous wastes and urine from rats fed these wastes.

Abstract: 15 hazardous industrial waste samples were evaluated for mutagenicity in the Salmonella plate-incorporation assay using strains TA98 and TA100 in the presence and absence of Aroclor 1254-induced rat liver S9. Dichloromethane/methanol extracts of the crude wastes were also evaluated. 7 of the crude wastes were mutagenic, but only 2 of the extracts of these 7 wastes were mutagenic; extracts of 2 additional wastes also were mutagenic. In addition, 10 of the crude wastes were administered by gavage to F-344 rats, and 24-h urine samples were collected. Of the 10 raw urines evaluated, 3 were mutagenic in strain TA98 in the presence of S9 and β-glucuronidase. The 3 crude wastes that produced these 3 mutagenic urines were, themselves, mutagenic. Adequate volumes of 6 of the 10 raw urines were available for extraction/concentration. These 6 urines were incubated with β-glucuronidase and eluted through Sep-Pak® C18 columns; the methanol eluates of 3 of the urines were mutagenic, and these were the same 3 whose raw urines also were mutagenic. In general, the C18/methanol extraction procedure reduced the cytotoxicity and increased the mutagenic potency of the urines. To our knowledge, this is the first report of the mutagenicity of urine from rodents exposed to hazardous wastes. Based on the present results, the use of only strain TA98 in the presence of S9 might be adequate for general screening of hazardous wastes or waste extracts for genotoxicity. The urinary mutagenesis assay does not appear to be a useful adjunct to the Salmonella assay for screening hazardous wastes. The problems associated with chemically fractionating diverse types of hazardous wastes for bioassay are also discussed.

Mutagen levels in urine from snuff users, cigarette smokers and non tobacco users — A comparison

Abstract: The mutagenic activity of concentrates of urine from snuff users, cigarette smokers and non tobacco users has been investigated. A concentration procedure involving use of Sep-Pak C 18 columns and elution with methylene chloride was used. The concentrates were assayed for mutagenicity towards strain TA98 of Salmonella typhimurium , both in the presence and absence of a metabolic activation system, the postmitochondrial liver fraction (S9) from Aroclor 1254 induced rats. The mean mutagenic activity of smokers' urine concentrates was 8.6 × 10 3 revertants per 24 h and significantly higher than the corresponding values for snuff users, abstinent snuff users and non tobacco users, which were (1.3, 1.3 and 0.9) × 10 3 , respectively. No significant difference in mutagenic activity was found between urine from snuff users, whether using or abstaining from snuff, and urine from non tobacco users. It could thus be concluded that the level of urinary mutagens, isolated by adsorption on Sep-Pak C 18 columns, is not elevated by habitual usage of Swedish wet snuff.

Morphological transforming activity and metabolism of cyclopenta-fused isomers of benz[a]anthracene in mammalian cells

Abstract: 4 isomeric cyclopenta-derivatives of benz[e]anthracene (benz[a]aceanthrylene, benz[j]aceanthrylene, benz[l]aceanthrylene, and benz[k]acephenanthrylene) were examined for their ability to morphologically transform C3H10T1/2CL8 mouse-embryo fibroblasts. All of these polycyclic aromatic hydrocarbons studied except benz[k]acephenanthrylene transformed C3H10T1/2CL8 cells to both type II and type III foci in a concentration-dependent fashion. Benz[j]aceanthrylene was the most active, equivalent in activity to benzo[a]pyrene on a molar basis, in producing dishes of cells with transformed foci (94% at 1.0 μg/ml). Benz[e]aceanthrylene, and benz[l]aceanthrylene produced 58% and 85% of the dishes with foci respectively at 10 μg/ml. Metabolism studies with [3H]benz[j]aceanthrylene in C3H10T1/2CL8 cells in which unconjugated, glucuronic acid conjugated, and sulfate conjugated metabolites were measured indicated that the dihydrodiol precursor to the bay-region diol-epoxide, 9,10-dihydroxy-9,10-dihydrobenz[j]aceanthrylene, was the major dihydrodiol formed (55%). Smaller quantities of the cyclopenta-ring dihydrodiol, 1,2-dihydroxy-1,2-dihydrobenz[j]aceanthrylene (14%), and the k-region dihydrodiol, 11,12-dihydroxy-11,12-dihydrobenz[j]aceanthrylene (5%) were also formed. Similar studies with [14C]benz[l]aceanthrylene indicated that the k-region dihydrodiol, 7,8-dihydroxy-7,8-dihydrobenz[l]aceanthrylene was the major metabolite formed (45%). The cyclopenta-ring dihydrodiol, 1,2-dihydroxy-1,2-dihydrobenz[l]aceanthrylene and 4,5-dihydroxy-4,5-dihydrobenz[l]aceanthrylene were formed in minor amounts (< 6%). Therefore, metabolism at the cyclopenta-ring of B(j)A and B(l)A is a minor pathway in C3H10T1/2CL8 cells in contrast to previously reported studies with cyclopenta[cd]pyrene in which the cyclopenta-ring dihydrodiol was the major metabolite. These results suggest that routes of metabolic activation other than oxidation at the cyclopenta-ring such as bay region or k-region activation may play an important role with these unique polycyclic aromatic hydrocarbons in C3H10T1/2CL8 cells.

Base-substitution and frameshift mutagenesis by sodium chloride and potassium chloride in Saccharomyces cerevisiae.

Abstract: Sodium chloride (NaCl) and potassium chloride (KCl) are both capable of inducing lethality and mutations when each is administered at a molarity of two for different lengths of time to logarithmic phase cells of the yeast Saccharomyces cerevisiae. Analysis of the revertants indicates that the reversions can be base substitutions, of both the transition and the transversion type, as well as frameshift mutations. At equal molarity, with the frequency of mutations as the criterion, KCl and NaCl are equally efficient in inducing all types of mutations.

Benomyl-induced mitotic disturbances in Hordeum vulgare

Abstract: Benomyl [methyl-1-(butylcarbamoyl)-2-benzimidazole carbamate], a benzimidazole derivative systemic fungicide was tested with regard to its ability to induce mitotic disturbances such as the inhibition of spindle formation, chromosome disorientation, abnormal chromosome condensation and chromosome malsegregation and also chromatid aberrations in root-meristem cells at the reconstructed karyotype MK 14/2034 of Hordeum vulgare. Benomyl at the concentrations of 10−5 M and 3 × 10−5 M induced mitotic abnormalities which ranged from partial disturbance of centromeric activity of one or several chromatids followed by missegregation, as well as chromosome lagging and micronuclei formation, to complete inhibition of spindle formation. No statistically significant increase of chromatid aberrations was, however, observed.

Induction of chromosome aberrations in lymphocytes of mice after subchronic exposure to benzene.

Abstract: The induction of chromosome aberrations in lymphocytes of mice after subchronic exposure to benzene was investigated. 4 groups of 5 Swiss (ICR) male mice were given orally a solution of benzene every day for 14 days except days 5 and 10. The daily doses were 0, 36.6, 73.2 and 146.4 mg/kg. Mice were sacrificed on day 15, lymphocytes were obtained by perfusion of the spleen and the cells were cultured in RPMI 1640 medium. After 48 h of culture, cells were harvested for cytogenetic analysis. A significant dose-dependent increase in the frequency of cells with chromatid aberrations were found (p

Dominant lethal study of ribavirin in male rats

Abstract: Ribavirin, a new synthetic antiviral agent, was studied for dominant lethal effects in male CD rats. The drug was administered intraperitoneally at doses of 50, 100 and 200 mg/kg/day for 5 days. Males were mated weekly with 8 consecutive batches of female rats. Marginal increase in early foetal death detected in Assessment Weeks 3 and 8 in females mated with the low-dose and high-dose males were not dose-related and were most probably chance events caused by the particularly low vehicle control frequencies for these 2 weeks. Also, the slightly reduced pregnancy proportion among females mated with the high-dose treated males was to a substantial extent the effect of a single male rate which failed to fertilize any females. Ribavirin was, therefore, regarded as being devoid of any mutagenic potential demonstrable by a rat dominant lethal assay.