Evaluation of the mutagenicity of simple substituted quinoxalines in Salmonella typhimurium

Limited information is available on the genotoxicity of simple quinoxalines, distinct from the food related carcinogenic derivatives bearing an aromatic amino group. Isolated positive results, with no apparent structure–activity relationships, were reported in earlier studies on alkyl substituted quinoxalines, raising a safety concern in some regulatory authorities in view of the potential human exposure related to their use as food flavors. In order to elucidate the genotoxic hazard posed by simple quinoxalines, in this work a random set of mono- and bi-substituted methyl, chloro- and hydroxyl- quinoxalines have been tested in an OECD-compliant bacterial reversion test (TG 471). The results obtained do not highlight any genotoxic potential in the set of quinoxalines examined, and suggest that this may be a common trait for other simple substituted quinoxalines. Earlier published positive findings were not confirmed in this work, which call for a cautious approach in the use of literature data for regulatory purpose.     

Ecological risk of heavy metals in sediments of the Luan River source water

Distribution and characteristics of heavy metals enrichment in sediment were surveyed including the bio-available form analyzed for assessment of the Luan River source water quality. The approaches of sediment quality guidelines (SQG), risk assessment code and Hakanson potential ecological risk index were used for the ecological risk assessment. According to SQG, The results show that in animal bodies, Hg at the sampling site of Wuliehexia was 1.39 mg/kg, Cr at Sandaohezi was 152.37 mg/kg and Cu at Hanjiaying was 178.61 mg/kg exceeding the severe effect screening level. There were 90% of sampling sites of Cr and Pb and 50% sites of Cu exceeded the lowest effect screening level. At Boluonuo and Wuliehexia, the exchangeable and carbonate fractions for above 50% of sites were at high risk levels and that for above 30% of sites at Xiahenan and Wulieheshang were also at high risk levels. Other sites were at medium risk level. Compared to soil background values of China, Hg and Cd showed very strong ecological risk, and the seven heavy metals of Hg, Cd, Cu, As, Pb, Cr, Zn at ecological risk levels were in the descending order. The results could give insight into risk assessment of environmental pollution and decision-making for water source security.     

Relationship between chlorofluorocarbon chemical structure and their Salmonella mutagenicity

This paper is a quantitative analysis of the relationship between the chemical structure and the Salmonella mutagenicity of a number of chlorofluorocarbons (CFC). The molecules were characterized by both molecular orbital and physical chemical parameters. The results of the analysis indicated that the CFC mutagenicity is correlated with two parameters: the free energy of binding to biological receptors, and the energy of the highest occupied molecular orbital (HOMO). Since these are the same factors that would favor the cytochrome P-450-catalyzed metabolism, it would appear that the CFC mutagenicity is determined more by the rate of initial activation than by the rate of DNA attack.     

石油污水和石油化工废水的致突变性检测

目的:对石油开采和石油化工废水的制突变性进行检测。方法:采用蚕豆根尖细胞微核实验法。结果:各排口废水的根尖细胞微核率均明显高于对照组(P<0.01)。提示各厂排放的废水可能具有较强的致突变作用。     

Screening of endocrine disruption activity in sediments from the Uruguay River

Sediment constitutes an important sink of endocrine disruptor compounds; however, the potential of sediments to act as a source of endocrine disruptors should be more extensively investigated. The main objective of this study was to determine whether exposure of immature common carp to Uruguay River sediments undergo physiological and endocrine alterations. The lower Uruguay River watershed supports intensive agricultural and forest production, receives municipal sewage discharge and industrial effluent, and a new large pulp mill was constructed in 2006. A 30-day semi-static assay was performed using sediments from four sites along the Uruguay River and compared with an unexposed group in dechlorinated water as a negative control. We focused on two upstream and two downstream sites of a new elemental chlorine free pulp mill. The results showed that plasma vitellogenin levels increased in fish along the river and significant differences were found between the exposed and unexposed groups. Condition factor and gonadosomatic index were not different; however, a significant difference in hepatosomatic index was observed in fish exposed to sediment from an industrial site. A significant reduction in primary spermatocyte accumulation was observed in the exposed group compared with that in the control group, and some individuals exposed to sediments from industrial sites presented with testis–ova. Our results suggest that Uruguay River sediments act as an important source of estrogenic compounds that could be responsible for the alterations observed. Future studies are needed to identify the causal agents and determine exposure routes.     

Evaluation of the mutagenicity of aminoglycoside antibiotics in Salmonella typhimurium and Saccharomyces cerevisiae.

The mutagenicity of aminoglycoside antibiotics (KM, AKM, DKB, RSM, AMK, GM, TOB) has been studied in cells of the bacteria Salmonella typhimurium and in the yeast Saccharomyces cerevisiae. The bacterial strains (Ames') monitor reverse mutation (point mutation) and the yeast strain D5 monitors mitotic crossing-over, mitotic gene conversion and point mutation. None of these antibiotics demonstrated any mutagenic activities in either the bacteria or the yeast.     

Study on the mutagenicity and antimutagenicity of beta-ionone in the Salmonella/microsome assay.

beta-Ionone (BIO) is a degraded (C(13)) sesquiterpenoid compound found in a variety of edible and aromatic plants. BIO and other ionone derivatives have been used in fragrance products and as flavoring food additives. In this study we investigated the mutagenic and antimutagenic activities of BIO using the Salmonella/microsome assay. Mutagenicity was evaluated by two tests with Salmonella typhimurium strains TA100, TA98, TA97a and TA1535, without and with addition of S9 mixture. A first assay was performed by the plate incorporation procedure and a confirmation test by the pre-incubation method. In either test, no increase in the number of his(+) revertant colonies over the negative (solvent) control values was noted with any of the four tester strains thereby indicating that BIO was not genotoxic in the Salmonella assay. Antimutagenic activity was investigated by testing (by the plate incorporation method) different non-toxic doses of BIO against one or more non-toxic doses of direct-acting (sodium azide: SA, 4-nitroquinoline-N-oxide: 4-NQNO, 2-nitrofluorene: 2-NF and nitro-o-phenylenediamine: NPD) as well as indirect-acting (cyclophosphamide: CP, benzo[a]pyrene: B[a]P, aflatoxin B1: AFB1, 2-aminoanthracene: 2-AA, and 2-aminofluorene: 2-AF) mutagens. BIO did not alter the effects of any direct-acting mutagen or B[a]P and 2-AF. Mutagenic effects of AFB1 and CP, however, were markedly and dose-dependently antagonized by BIO. It has been reported that, in the rat liver, activation of B[a]P and 2-AF depend on CYP1A1 activity, and that CYP2B subfamily is involved in the metabolic activation of CP and AFB1. It has also been described that BIO is a potent inhibitor of CYP2B1/2 and a weaker inhibitor of CYP1A1. Therefore, antagonism of CP-and AFB1-induced mutagenic effects by BIO could have been mediated-at least in part-by the inhibition of CYP2B enzymes.     

Salmonella/microsome mutagenicity tests of heat-processed milk samples

Samples of whole milk were heat treated by commercial heat-sterilization, by commercial heat-pasteurization or by a laboratory heat-pasteurization (65 degrees C for 30 min). Each sample was tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100 with and without S-9 mix. Dichloromethane extracts of milk heated at 100, 135 and 150 degrees C for 5 hr were also tested for mutagenicity using the same assay. None of these samples exhibited mutagenicity in the Ames assay used.     

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.     

Detection of genotoxicity in fried bacon by the Salmonella/mammalian microsome mutagenicity assay

The potential for mutagen formation in fried bacon and the possible reduction or elimination of this hazard was examined in the Salmonella/mammalian microsome mutagenicity assay using Salmonella typhimurium strain TA98. Alkaline dichloromethane extracts were prepared from green pork bellies, commercial bacon (nitrite-treated and nitrite-free), and pilot-plant bacon (nitrite-free). When fried, all forms of bacon and the green belly samples gave positive mutagenic responses with the plate-incorporation technique. Unfried samples were not mutagenic. Aroclor-activated rat-liver S-9 fractions plus NADPH were essential to demonstrate a mutagenic response. When the frying temperature was held constant (171°C) maximum mutagen formation was observed in samples fried for 6 min; when samples were fried for 6 min a mutagenic response which increased with temperature, in a linear manner, was observed at temperatures above 125°C. Volatile nitrosamines were not detected in the bacon samples. The data indicate the generation of one or more mutagens in fried bacon and green pork belly, the levels of which can be reduced by decreasing heating temperature and/or time.     

Bioactive actinomycetes from Krishna River sediments of Andhra Pradesh

Sediment samples from Krishna River at Nagayalanka of Andhra Pradesh, India were investigated as a source of actinomycetes to screen for the production of novel bioactive compounds. During our investigation on fresh water actinomycetes from 5 different river sediment samples, a total of 80 actinomycetes were isolated. Out of these 80 isolates, 30 isolates which showed distinct macromorphological characteristics were selected. The antimicrobial and enzymatic activities were studied for all the 30 isolates. The preliminary study for antimicrobial activity by cross streak method indicated that 16 isolates (53.3%) have excellent antagonistic properties. All these 16 isolates were subjected to detailed submerged fermentation studies. It was observed that 12 isolates (40.0%) exhibited antibacterial activity, 9 isolates (30.0%) showed antifungal activity while 5 isolates (16.6%) showed both antibacterial and antifungal activities. All the 30 isolates were also subjected for the determination of enzymatic activities 25 isolates (83.3%) exhibited amylolytic activity while 27 isolates (90.0%) showed proteolytic activity. Among these isolates, six promising isolates were selected for detailed morphological, cultural, physiological and biochemical studies. It was established that these isolates belong to the Streptomyces genus by virtue of their cell wall composition pattern and were identified as strains of different Streptomyces species like S. rochei, S. alanosinicus, S. erumpens, S. griseoplanus, S. gancidicus and S. nigrogriseolus.     

A notable antimutagenicity of two nonmutagenic novel oxadiazoles in Salmonella mutagenicity assay

The mutagenic activity of two newly synthesized oxadiazoles: 1,3-bis(5-benzylthio-1,3,4-oxadiazol-2-yl) benzene (M1) and 1,4-bis(5-benzylthio-1,3,4-oxadiazol-2-yl) benzene (M2) was studied in Salmonella typhimurium strains TA97, TA100, TA102 and TA1537 in the presence and absence of S9mix. The antimutagenicity of M1 and M2 against H2O2, sodium azide (SA) and 4-nitro-o-phenylene diamine (NPD) using the tester strains TA102, TA100 and TA97, respectively, was also investigated. The two compounds were found to be nonmutagenic using the four tester strains. However, they showed high mutagenic repression activity against hydrogen peroxide (95% and 97% for M1 and M2, respectively, at a concentration of 335 micrograms/plate). Moderate mutagenic repression against NPD (58% and 55% for M1 and M2, respectively, at a concentration of 167.5 micrograms/plate) and low mutagenic repression against SA (21% and 33% for M1 and M2 respectively, at a concentration of 335 micrograms/plate) was detected. The obtained results are very encouraging to test the above mentioned compounds as anticarcinogens.     

In vitro activation assays with hepatic S9 preparation from wild and laboratory reared woodchucks in the Salmonella mutagenicity test

The Salmonella mutagenicity assay was utilized to compare hepatic S9 fractions derived from wild and laboratory reared woodchucks (Marmota monax). Two promutagens, 7,12-dimethylbenz[a]anthracence (DMBA) and 2-amino-fluorene (AF) were tested at 5 concentrations with the tester strains TA98 and TA100, against 2 levels of S9 fraction. AF produced similar number of revertants with the S9 fraction from wild and laboratory-reared animals. DMBA produced 2-4 times more revertant colonies at 50 microliter S9/plate with wild woodchuck S9 than with S9 from the laboratory-reared animals with both tester strains. It was concluded that natural inducers in the wild woodchuck diet may have contributed to the increased reversion frequency over laboratory reared woodchucks. Dose-response parameters for the activation of DMBA by S9 fraction from woodchucks and rats were compared with TA100. Woodchuck S9 had 3-40 more revertants/nmol and a 100-fold lower threshold of response than S9 from Aroclor 1254-induced rats.     

Mutagenicity evaluation of tetrahydro-amino acridine by the Salmonella/microsome mutagenicity ames test

1,2,3,4-tetrahydro-5-amino acridine (THA), a cholinesterase inhibitor currently under investigation for use in the treatment of senile dementia, exhibited mutagenic activity with and without metabolic microsomal S-9 activation against tester strain TA97a in the Salmonella typhimurium incorporation assay. The mutagenic response was concentration-dependent within the dose range of 500 to 2,500 μg/plate.     

In vitro mutagenicity of water contaminants in complex mixtures

Trihalomethanes, Carbon tetrachloride and trichloroethylene were tested in single, binary and multi-complex mixtures using standard tester strains TA1535, TA1537, TA98 and TA100 of Salmonella typhimurium with and without addition of an in vitro metabolizing fraction S-9. Chloroform (CHCl3) was found to be mutagenic in all strains without S-9 activation. However, when tested with Bromoform (15%), which was nonmutagenic singly, the combined effect of the mixture was nonmutagenic. CCl4 was a direct mutagen (without S-9) in all strains except TA 1535. When combined with 85% CHCl3, only strains TA1535 and TA1537 were mutagenic. When tested with mammalian activation (S-9), CCl4 was mutagenic in all strains. However, when tested with CHCl3 (CHCl3 and CCl4-85:15), the mutagenic capability was lost. With or without S-9 Activation multi-complex mixture of CHCl3, CCl4 and TCE (85:8:7) was mutagenic for a narrow range of doses in all strains.     

Comparative mutagenicity tests in the Salmonella/microsome assay with rat and woodchuck S9 preparations

The Salmonella mutagenicity assay was utilized to compare the hepatic S9 fractions from untreated and 3-methylcholanthrene (MC) induced woodchucks with Aroclor 1254 induced rats. Three known promutagens, benzo[a]pyrene (BP), 7,12-dimethylbenz[a]anthracene (DMBA), and 2-aminofluorene (AF) were tested at 5 concentrations with the strain TA100 against 3 levels of S9 fraction. Both woodchuck S9 fractions were as effective as the rat S9 in activating BP and both were more effective than the rat S9 in activating DMBA. Untreated woodchuck S9 was also as effective as rat S9 in activating AF. The protein content of the S9 fraction did not differ significantly between rats and woodchucks, but the P-450 content of the rat S9 was approximately 3.5 times that of woodchuck.     

A comparative study of five nitro musk compounds for genotoxicity in the SOS chromotest and Salmonella mutagenicity

Five nitro musk compounds widely used in cosmetics and detergents were examined for DNA-damaging and mutation-inducing properties. For this purpose two short-time assays were used, the SOS chromotest and the Salmonella/mammalian microsome test. Musk ambrette showed mutagenicity in Salmonella typhimurium TA 100 requiring metabolic activation by rat liver postmitochondrial supernatant (S9) but it lacked mutagenicity in the absence of S9 and genotoxicity in the SOS chromotest. Musk xylene, musk ketone, musk moskene and musk tibetene showed neither mutagenicity nor genotoxicity in the presence and absence of S9.