Collaborative study of mutagenicity with Salmonella typhimurium TA102

In vitro genotoxicity evaluation and metabolic study of residual glutaraldehyde in animal-derived biomaterials

Glutaraldehyde (GA) is an important additive that is mainly used in animal-derived biomaterials to improve their mechanical and antimicrobial capacities. However, GA chemical toxicity and the metabolic mechanism remain relatively unknown. Therefore, residual GA has always been a major health risk consideration for animal-derived medical devices. In this study, extracts of three bio-patches were tested via the GA determination test and mouse lymphoma assay (MLA). The results showed that dissolved GA was a potential mutagen, which could induce significant cytotoxic and mutagenic effects in mouse lymphoma cells. These toxic reactions were relieved by the S9 metabolic activation (MA) system. Furthermore, we confirmed that GA concentration decreased and glutaric acid was generated during the catalytic process. We revealed GA could be oxidized via cytochrome P450 which was the main metabolic factor of S9. We found that even though GA was possibly responsible for positive reactions of animal-derived biomaterials' biocompatibility evaluation, it may not represent the real situation occurring in human bodies, owing to the presence of various detoxification mechanisms including the S9 system. Overall, in order to achieve a general balance between risk management and practical application, rational decisions based on comprehensive analyses must be considered.

Utility of a next generation framework for assessment of genomic damage: A case study using the industrial chemical benzene

We recently published a next generation framework for assessing the risk of genomic damage via exposure to chemical substances. The framework entails a systematic approach with the aim to quantify risk levels for substances that induce genomic damage contributing to human adverse health outcomes. Here, we evaluated the utility of the framework for assessing the risk for industrial chemicals, using the case of benzene. Benzene is a well-studied substance that is generally considered a genotoxic carcinogen and is known to cause leukemia. The case study limits its focus on occupational and general population health as it relates to benzene exposure. Using the framework as guidance, available data on benzene considered relevant for assessment of genetic damage were collected. Based on these data, we were able to conduct quantitative analyses for relevant data sets to estimate acceptable exposure levels and to characterize the risk of genetic damage. Key observations include the need for robust exposure assessments, the importance of information on toxicokinetic properties, and the benefits of cheminformatics. The framework points to the need for further improvement on understanding of the mechanism(s) of action involved, which would also provide support for the use of targeted tests rather than a prescribed set of assays. Overall, this case study demonstrates the utility of the next generation framework to quantitatively model human risk on the basis of genetic damage, thereby enabling a new, innovative risk assessment concept. Environ. Mol. Mutagen. 61:94-113, 2020. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Estudos sobre a toxicologia da ε-caprolactama

A ε-caprolactama (CAP) é um monômero precursor de polímeros denominados nylon 6. Esses polímeros destinam-se à produção de tapetes, vestuário e materiais plásticos tais como equipamentos, sistemas e componentes automotivos, conectores, além de embalagens plásticas. Resíduos de CAP podem migrar de embalagens plásticas de nylon 6 para os alimentos. Diante disso, foi de interesse realizar uma revisão dos efeitos relativos à exposição à CAP e o seu impacto sobre a saúde humana. Estudos epidemiológicos indicam a possibilidade da CAP causar inflamações oculares e cutâneas, além de irritações no sistema respiratório. Pode ocorrer ainda hipotensão, taquicardia, palpitações, rinorréia, ressecamento nasal, efeitos geniturinários e sobre a reprodução como distúrbios nas funções menstrual e ovariana, e complicações no parto; além de problemas neurológicos e hematológicos. Estudos com animais são consistentes com tais relatos. Os estudos de genotoxicidade in vitro e in vivo por via oral e intraperitoneal mostram em sua grande maioria, resultados negativos, bem como ausência de efeitos carcinogênicos em ratos e camundongos e sobre o desenvolvimento e reprodução em ratos e coelhos.

Genotoxic Activities of Aniline and its Metabolites and Their Relationship to the Carcinogenicity of Aniline in the Spleen of Rats

Aniline (in the form of its hydrochloride) has been shown to induce a rather rare spectrum of tumors in the spleen of Fischer 344 rats. The dose levels necessary for this carcinogenic activity were in a range where also massive effects on the blood and non-neoplastic splenotoxicity as a consequence of methemoglobinemia were to be observed. This review aimed at clarifying if aniline itself or one of its metabolites has a genotoxic potential which would explain the occurrence of the spleen tumors in rats as a result of a primary genetic activity. The database for aniline and its metabolites is extremely heterogeneous. With validated assays it ranges from a few limited Ames tests (o- and m-hydroxyacetanilide, phenylhydroxylamine, nitrosobenzene) to a broad range of studies covering all genetic endpoints partly with several studies of the same or different test systems (aniline, p-aminophenol, p-hydroxyacetanilide). This makes a direct comparison rather difficult. In addition, a varying number of results with as yet not validated systems are available for aniline and its metabolites. Most results, especially those with validated and well performed/documented studies, did not indicate a potential of aniline to induce gene mutations. In five different mouse lymphoma tests, where colony sizing was performed only in one test, aniline was positive. If this indicates a peculiar feature of a point mutagenic potential or does represent a part of the clastogenic activity for which there is evidence in vitro as well as in vivo remains to be investigated. There is little evidence for a DNA damaging potential of aniline. The clastogenic activity in vivo is confined to dose levels, which are close to lethality essentially due to hematotoxic effects. The quantitatively most important metabolites for experimental animals as well as for humans (p-aminophenol, p-hydroxyacetanilide) seem to have a potential for inducing chromosomal damage in vitro and, at relatively high dose levels, also in vivo. This could be the explanation for the clastogenic effects that have been observed after high doses/concentrations with aniline. They do not induce gene mutations and there is little evidence for a DNA damaging potential. None of these metabolites revealed a splenotoxic potential comparable to that of aniline in studies with repeated or long-term administration to rats. The genotoxicity database on those metabolites with a demonstrated and marked splenotoxic potential, i.e. phenylhydroxylamine, nitrosobenzene, is unfortunately very limited and does not allow to exclude with certainty primary genotoxic events in the development of spleen tumors. But quite a number of considerations by analogy from other investigations support the conclusion that the effects in the spleen do not develop on a primary genotoxic basis. The weight of evidences suggests that the carcinogenic effects in the spleen of rats are the endstage of a chronic high-dose damage of the blood leading to a massive overload of the spleen with iron, which causes chronic oxidative stress. This conclusion, based essentially on pathomorphological observations, and analogy considerations thereof by previous authors, is herewith reconfirmed under consideration of the more recently reported studies on the genotoxicity of aniline and its metabolites, on biochemical measurements indicating oxidative stress, and on the metabolism of aniline. It is concluded that there is no relationship between the damage to the chromosomes at high, toxic doses of aniline and its major metabolites p-aminophenol/p-hydroxyacetanilide and the aniline-induced spleen tumors in the rat.

Acrylamide: review of toxicity data and dose-response analyses for cancer and noncancer effects

Acrylamide (ACR) is used in the manufacture of polyacrylamides and has recently been shown to form when foods, typically containing certain nutrients, are cooked at normal cooking temperatures (e.g., frying, grilling or baking). The toxicity of ACR has been extensively investigated. The major findings of these studies indicate that ACR is neurotoxic in animals and humans, and it has been shown to be a reproductive toxicant in animal models and a rodent carcinogen. Several reviews of ACR toxicity have been conducted and ACR has been categorized as to its potential to be a human carcinogen in these reviews. Allowable levels based on the toxicity data concurrently available had been developed by the U.S. EPA. New data have been published since the U.S. EPA review in 1991. The purpose of this investigation was to review the toxicity data, identify any new relevant data, and select those data to be used in dose-response modeling. Proposed revised cancer and noncancer toxicity values were estimated using the newest U.S. EPA guidelines for cancer risk assessment and noncancer hazard assessment. Assessment of noncancer endpoints using benchmark models resulted in a reference dose (RfD) of 0.83 microg/kg/day based on reproductive effects, and 1.2 microg/kg/day based on neurotoxicity. Thyroid tumors in male and female rats were the only endpoint relevant to human health and were selected to estimate the point of departure (POD) using the multistage model. Because the mode of action of acrylamide in thyroid tumor formation is not known with certainty, both linear and nonlinear low-dose extrapolations were conducted under the assumption that glycidamide or ACR, respectively, were the active agent. Under the U.S. EPA guidelines (2005), when a chemical produces rodent tumors by a nonlinear or threshold mode of action, an RfD is calculated using the most relevant POD and application of uncertainty factors. The RfD was estimated to be 1.5 microg/kg/day based on the use of the area under the curve (AUC) for ACR hemoglobin adducts under the assumption that the parent, ACR, is the proximate carcinogen in rodents by a nonlinear mode of action. When the mode of action in assumed to be linear in the low-dose region, a risk-specific dose corresponding to a specified level of risk (e.g., 1 x 10-5) is estimated, and, in the case of ACR, was 9.5 x 10-2 microg ACR/kg/day based on the use of the AUC for glycidamide adduct data. However, it should be noted that although this review was intended to be comprehensive, it is not exhaustive, as new data are being published continuously.

Effects of glutaraldehyde exposure on human health

Glutaraldehyde (GA) is widely used in the industrial, scientific and biomedical fields. Many adverse health effects on humans have been reported in association with biomedical uses of GA, with 2-3.5% aqueous GA solution generally used for cold sterilization and GA exposure ranges of 0.001 to 2.6 ppm for this type of use. GA is metabolized extensively to CO(2), but urinary excretion of it is low. Sensory irritant effects, sensitization of skin and respiratory organs and other symptoms have been reported among endoscopy nurses and medical radiation technologists. The prevalence of chronic bronchitis and nasal symptoms in humans is significantly correlated with peak concentrations of GA exposure. The extent of primary skin irritation depends on the duration and site of contact, and the severity of symptoms is dose-related. Chronic inhalation affects the nose and respiratory tract, and lesions become severe with prolonged duration of exposure. Increases in neither mortality nor tumor incidence have been found in workers with less than 0.2 ppm GA exposure, no evidence of carcinogenic activity has been obtained in experimental animal studies. There has been no clear evidence of genetic toxicity of GA in either in vitro or in vivo studies, and neither developmental nor reproductive toxicity has been found in humans or animals. To prevent hazards from GA exposure, use of closed-system, fully automated washing machines is recommended, since numerous symptoms have been found in individuals with less than 0.05 ppm GA exposure, the recommended peak exposure limit in many countries.

Ability of antioxidants to prevent oxidative mutations in Salmonella typhimurium TA102

An assay for the ability of antioxidants to prevent mutations induced by various oxidants in Salmonella typhimurium TA102 cells was developed. Protection against hydrogen-peroxide-induced mutagenicity was observed for quercetin, caffeic acid, ascorbic acid and dimethyl sulfoxide (used as a solvent for water-insoluble antioxidants). No protective effect was observed for green tea extract (weakly pro-oxidative), catechin, rutin, sinigrin, ferulic acid and alpha-tocopherol. Mutagenicity caused by tert-butyl hydroperoxide (tBOOH) was prevented most effectively by quercetin and ascorbic acid, whereas weaker effects were observed for green tea extract and for rutin, and no effect being observed for the other antioxidants tested. The results for hydrogen peroxide indicate iron chelation to be the most important protective mechanism. Radical scavenging appeared to be effective only with dimethyl sulfoxide and ascorbic acid, which are effective scavengers of hydroxyl radicals and were used here in high concentrations. It is proposed that the hydrogen-peroxide-induced mutations in the Salmonella cells are caused by hydroxyl radicals generated by iron ions closely associated with DNA. Protection against mutagenicity caused by tert-butyl hydroperoxide appears to occur mainly through the scavenging of alkoxyl and possibly of alkyl radicals.

Genotoxicity of maleic hydrazide, acridine and DEHP in Allium cepa root cells performed by two different laboratories

The purpose of this paper was to compare the results of the Allium cepa chromosome aberration assay between two laboratories under the same test protocol and at the same time, use chemicals and onions obtained in their own homeland. For this study three chemicals were selected: di(2-ethylhexyl)phthalate (DEHP), maleic hydrazide, and acridine. Both laboratories found genotoxicity with a positive dose-response relationship for maleic hydrazide and acridine. However, for DEHP the results were quite different--one of the laboratories found this compound not genotoxic but the other found a positive response. Although the comparative study was inconclusive for DEHP, it was successful for the maleic hydrazide, acridine and also for the positive control (methyl methanesulfonate). Further studies need to be performed in the case of DEPH.

Subsequent products after antioxidant actions of beta-carotene and alpha-tocopherol have no Salmonella mutagenicity

Beta-carotene and alpha-tocopherol are important antioxidants biologically, but whether their oxidized products are toxic or not remains to be discovered. Here, we chromatographically separated 5 pure products or isomeric mixtures from reaction mixtures of beta-carotene and reactive oxygens, and 17 lipid-radical scavenging products of alpha-tocopherol. The products were tested for mutagenicity using Salmonella typhimurium TA98, TA100, TA102, and TA104, in the presence and absence of S9. None showed mutagenicity against any of the four strains, or cytotoxicity that influenced the survival of the bacteria. Lipid-peroxides have been known to increase the formation of mutagens from dietary procarcinogens such as heterocyclic amines. So, we also measured the activity to increase 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) mutagenicity. The products from beta-carotene and alpha-tocopherol did not increase, but rather several of them suppressed, the mutagenicity of Trp-P-2. Thus, the products of beta-carotene and alpha-tocopherol formed after the antioxidant actions were not genotoxic.

Genetic toxicology studies with glutaraldehyde

Glutaraldehyde (GA; CAS no. 111-30-8) has a wide spectrum of industrial, scientific and biomedical applications, with a potential for human exposure particularly in its biocidal applications. The likelihood for genotoxic effects was investigated in vitro and in vivo. A Salmonella typhimurium reverse mutation assay showed no evidence for mutagenic activity with strains TA98, TA1535, TA1537 and TA1538, with or without metabolic activation. However, there was a weak mutagenic response (1.9-2.3-fold at the highest non-toxic concentration) with TA100 in the presence of metabolic activation. In a Chinese hamster ovary (CHO) forward gene mutation assay (HGPRT locus) there were no consistent, statistically significant, reproducible or dosage-related increases in the frequency of 6-thioguanine resistant cells. There were no reproducible or dosage-related increases in sister chromatid exchanges in an in vitro test in CHO cells. An in vitro cytogenetics study in CHO cells showed no evidence for an increase in chromosomal aberrations on treatment with GA, either in the presence or absence of metabolic activation. In vivo, a mouse peripheral blood micronucleus test showed no increase in micronucleated polychromatophils at sampling times of 30, 48 and 72 h after acute gavage dosing with GA at 40, 80 and 125 mg kg(-1) (corresponding to 25, 50 and 85% of the LD(50)). The absence of an in vivo clastogenic potential was confirmed by no increase in chromosomal aberrations in a rat bone marrow cytogenetics study with sampling at 12, 24 and 48 h after acute gavage dosing with GA (12.5, 30 or 60 mg kg(-1) with males, and 7.5, 20 or 40 mg kg(-1) with females). Thus, in this series of tests, GA produced genotoxic effects in vitro only in a bacterial reverse mutation assay with no evidence for in vivo genotoxicity.

Toxicological, medical and industrial hygiene aspects of glutaraldehyde with particular reference to its biocidal use in cold sterilization procedures

Aqueous solutions of > or =5% glutaraldehyde (GA) are of moderate acute peroral toxicity and those of < or =2% are of slight toxicity. By single sustained skin contact, aqueous GA solutions of > or =45% are of moderate acute percutaneous toxicity, those of 25% are of slight toxicity and those of </=15% do not present an acute percutaneous hazard. Vapor generated at ambient temperature may cause sensory irritant effects to the eye and respiratory tract, but not acute respiratory tract injury. The 50% decrease in respiratory rate (rd(50)) is 13.86 ppm. A 0.1% solution of GA is not irritating to the eye; the threshold for conjunctival irritation is 0.2% and for corneal injury it is 1.0%. Eye injury is moderate at 2% and severe at > or =5%. Primary skin irritation depends on the duration and contact site, occlusion and solvent. By sustained contact, the threshold for skin irritation is 1%, above which erythema and edema are dose related. With 45% and higher, skin corrosion may occur. There is a low incidence of skin sensitizing reactions, with an eliciting threshold of 0.5% aqueous GA. However, GA is neither phototoxic nor photosensitizing. Subchronic repeated exposure studies by the peroral route show only renal physiological compensatory effects, secondary to reduced water consumption. Repeated skin contact shows only minor skin irritant effects without systemic toxicity. By subchronic vapor exposure, effects are limited to the nasal mucosa at 1.0 ppm, with a no-effect concentration generally at 0.1 ppm. There is no evidence for systemic target organ or tissue toxicity by subchronic repeated exposure by any route. A chronic drinking water study showed an apparent increase, in females only, of large granular cell lymphocytic leukemia but this was not dosage related. This is most likely the result of a modifying effect on the factor(s) responsible for the expression of this commonly occurring rat neoplasm. A chronic (2-year) inhalation toxicity/oncogenicity study showed inflammatory changes in the anterior nasal cavity but no neoplasms or systemic toxicity. In vitro genotoxicity studies--bacterial mutagenicity, forward gene mutation (HGPRT and TK loci), sister chromatid exchange, chromosome aberration, UDS and DNA repair tests--have given variable results, ranging from no effect through to weak positive. In vivo genotoxicity studies--micronucleus, chromosome aberration, dominant lethal and Drosophila tests--generally have shown no activity but one mouse intraperitoneal study showed bone marrow cell chromosome aberrations. Developmental toxicity studies show GA not to be teratogenic, and a two-generation study showed no adverse reproductive effects. Percutaneous pharmacokinetic studies showed low skin penetration, with lowest values measured in vitro in rats and human skin. Overexposure of humans produces typical sensory irritant effects on the eye, skin and respiratory tract. Some reports have described an asthmatic-like reaction by overexposure to GA vapor. In most cases this resembles reactive airways dysfunction syndrome, and the role of immune mechanisms is uncertain. Local mucosal effects may occur if medical instruments or endoscopes are not adequately decontaminated. Protection of individuals from the potential adverse effects of GA exposure requires that there be adequate protection of the skin, eyes and respiratory tract. The airborne concentration of GA vapor should be kept below the recommended safe exposure level (e.g. the threshold limit value) by the use of engineering controls. Those who work with GA should, through a training program, be aware of the properties of GA, its potential adverse effects, how to handle the material safely and how to deal with accidental situations involving GA. If effects develop in exposed workers, the reasons should be determined immediately and corrective methods initiated. (c) 2001 John Wiley & Sons, Ltd.

Morphological transformation and effect on gap junction intercellular communication in Syrian hamster embryo cells as screening tests for carcinogens devoid of mutagenic activity

A large fraction of chemicals observed to cause cancer in experimental animals is devoid of mutagenic activity. It is therefore of importance to develop methods that can be used to detect and study environmental carcinogenic agents that do not interact directly with DNA. Previous studies have indicated that induction of in vitro cell transformation and inhibition of gap junction intercellular communication are endpoints that could be useful for the detection of non-genotoxic carcinogens. In the present work, 13 compounds [chlordane, Arochlor 1260, di(2-ethylhexyl)phthalate, 1,1,1-trichloro-2, 2-bis(4-chlorophenyl)ethane, limonene, sodium fluoride, ethionine, o-anisidine, benzoyl peroxide, o-vanadate, phenobarbital, 12-O-tetradecanoylphorbol 13-acetate and clofibrate] have been tested for their ability to induce morphological transformation and affect intercellular communication in Syrian hamster embryo cells. The substances were selected on the basis of being proven or suspected non-genotoxic carcinogens, and thus difficult to detect in short-term tests. The data show that nine of the 13 compounds induced morphological transformation, and seven of the 13 inhibited intercellular communication in hamster embryo cells. Taken together, 12 of the 13 substances either induced transformation or caused inhibition of communication. The data suggest that the combined use of morphological transformation and gap junction intercellular communication in Syrian hamster embryo cells may be beneficial when screening for non-genotoxic carcinogens.

Detection of oxidative mutagenesis by isoniazid and other hydrazine derivatives in Escherichia coli WP2 tester strain IC203, deficient in OxyR: strong protective effects of rat liver S9

Strain IC203, deficient in the OxyR function, was sensitive to both cytotoxic and mutagenic effects of isoniazid (INH) whereas its parent, WP2 uvrA/pKM101, was resistant to these effects. Four other hydrazine compounds, hydrazine hydrate (HZH), phenylhydrazine (PHZ), hydralazine (HLZ) and nialamide (NLD), were mutagenic in WP2 uvrA/pKM101. Increases in mutagenicity were observed in IC203 for HZH and PHZ but not for HLZ and NLD. Growth inhibition zones by HZH, PHZ and NLD were larger in IC203 than in WP2 uvrA/pKM101. The enhancements in the effects of INH, HZH and PHZ in IC203 with respect to its oxyR+ parent are considered to be caused by the production of reactive oxygen species. This is consistent with its inhibition in IC203 by S9 from liver of uninduced rats, probably through the action of catalase. Mutagenicities of INH, PHZ and HLZ were low in strains IC204, a derivative of WP2 uvrA carrying a deletion of the umuDC genes, and IC206, a derivative of IC204 deficient in the MutY glycosylase. In these strains, HZH and NLD induced a high level of revertants which carry suppressor mutations resulting exclusively from G:C-A:T transitions, thus suggesting a direct reaction of the two hydrazines with cytosine.

Comparisons on chemically-induced mutagenicity among four bacterial strains, Salmonella typhimurium TA102 and TA2638, and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101: collaborative study I

A collaborative study of chemically-induced mutagenicity was performed using the four bacterial strains Salmonella typhimurium TA102 and TA2638 and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101 in order to compare the specific spectrum of response to chemicals among the four strains and to determine the usefulness (sensitivity) of each strain. Twenty laboratories participated in this study. As the first step, 29 compounds were tested for mutagenicity using the plate incorporation method with or without metabolic activation. The compounds consisted of 12 chemicals judged previously positive only in E. coli WP2 uvrA/pKM101, 15 of their derivatives, and the 2 well-known mutagens hydrazine and formaldehyde. The strains and the chemicals were sent from a central source to each laboratory. The tests were performed in two laboratories per chemical. Concerning the result with each strain, the number of chemicals which showed mutagenic activity were 10, 7, 9 and 17 in TA102, TA2638, WP2/pKM101 and WP2 uvrA/pKM101, respectively. Among these 29 compounds tested, no qualitative difference in the response to chemicals among the four strains was observed with 17 compounds, being 12 negative chemicals and 5 positive chemicals. The remaining 12 compounds showed varying results among the four strains. On the comparison of TA102 and WP2 uvrA/pKM101, the same qualitative response to chemicals was observed with 22 compounds. Thus, although compounds tested in this study were selected, partly based on a previously-judged positive response only in E. coli WP2 uvrA/pKM101, 76% of test chemicals showed the same sensitivity in TA102, 7 chemicals (24%) were only positive in the E. coli strains. Of these 7 chemicals, 5 were the acrylic acid ester derivatives and the chloroacetic acid ester derivatives possessing a common structure of a functional group esterized between acid and alcohol with two or more carbon radicals.

New applications of bacterial systems to problems in toxicology

Bacterial systems have long been of use in toxicology. In addition to providing general models of enzymes and paradigms for biochemistry and molecular biology, they have been adapted to practical genotoxicity assays. More recently, bacteria also have been used in the production of mammalian enzymes of relevance to toxicology. Escherichia coli has been used to express cytochrome P450, NADPH-cytochrome P450 reductase, flavin-containing monooxygenase, glutathione S-transferase, quinone reductase, sulfotransferase, N-acetyltransferase, UDP-glucuronosyl transferase, and epoxide hydrolase enzymes from humans and experimental animals. The expressed enzymes have been utilized in a variety of settings, including coupling with bacterial genotoxicity assays. Another approach has involved expression of mammalian enzymes directly in bacteria for use in genotoxicity systems. Particularly with Salmonella typhimurium. Applications include both the reversion mutagenesis assay and a system using a chimera with an SOS-response indicator and a reporter.

Comparison of three short-term assays: results on seven chemicals. Potential contribution to the control of water genotoxicity

Three short-term assays (the SOS chromotest, the Ames fluctuation test and the newt micronucleus test) were used to evaluate the genotoxicity of seven chemicals (4-nitroquinoline 1-oxide, potassium dichromate, formaldehyde, sodium hypochlorite, benzo[a]pyrene, cyclophosphamide and 2-naphthylamine). In the SOS chromotest, all seven compounds except sodium hypochlorite and cyclophosphamide were found to induce primary DNA damage in E. coli. With the Ames fluctuation test, all seven chemicals except sodium hypochlorite showed mutagenic activity on Salmonella typhimurium TA100, TA102 or TA98. The newt micronucleus assay detected a clastogenic effect of all seven compounds except formaldehyde on the peripheral blood erythrocytes of Pleurodeles waltl larvae. For each compound, the sensitivity of the tests was compared; (1) the SOS chromotest is the least sensitive assay in every case, (2) the Ames fluctuation test is the most sensitive assay for studied chemicals with direct genotoxic effect and (3) the newt micronucleus assay is the most sensitive test for tested compounds with indirect genotoxic activity. The potential contribution of these three tests in the monitoring of water genotoxicity is discussed.