Allium cepa chromosome aberration and micronucleus tests applied to study genotoxicity of extracts from pesticide-treated vegetables and grapes

The Allium cepa assay is an efficient test for chemical screening and in situ monitoring for genotoxicity of environmental contaminants. The test has been used widely to study genotoxicity of many pesticides revealing that these compounds can induce chromosomal aberrations in root meristems of A. cepa. Pesticide residues can be present in fruit and vegetables and represent a risk for human health. The mutagenic and carcinogenic action of herbicides, insecticides and fungicides on experimental animals is well known. Several studies have shown that chronic exposure to low levels of pesticides can cause birth defects and that prenatal exposure is associated with carcinogenicity. This study evaluated the potential application of plant genotoxicity tests for monitoring mutagens in edible vegetables. The presence of pesticides and genotoxic compounds extracted from 21 treated vegetables and eight types of grapes sampled from several markets in Campania, a region in Southern Italy, was monitored concurrently. The extracts were analysed for pesticides by gas chromatography and high-performance liquid chromatography, and for genotoxicity using two plant tests: the micronucleus test and the chromosomal aberration test in A. cepa roots. Thirty-three pesticides were detected, some of which are not approved. Genotoxicity was found in some of the vegetables and grapes tested. Allium cepa tests proved to be sensitive in monitoring genotoxicity in food extracts. The micronucleus test in interphase cells gave a much higher mutagenicity than the chromosomal aberration test in anaphase-telophase cells.     

Preliminary evaluation of the genotoxic potential of a hydrophilic polymer with three preservation systems

This study compared the genotoxic potential of a polymeric associative thickener used in topically applied emulsions preserved with three different preservative systems. The method used for the assessment of genotoxicity is the in vitro micronucleus test [Organization for Economic Cooperation and Development (OECD) guideline number 487]. When changing an additive such as a preservation system in a raw material, it is crucial to re-evaluate its toxicity potential because this change may significantly alter its properties. This study shows that at the levels tested neither of the systems evaluated demonstrated any cytotoxic or genotoxic effects. Skin exposure must take into consideration factors such as duration, skin condition and metabolism, but most importantly concentration. Although preservatives can be toxic at high concentrations, they are usually safe at the concentrations used in cosmetic raw materials and formulations. If used to preserve raw materials, they undergo further dilution when added to the formulation.     

Mutagenicity assessment of food contact material migrates with the Ames MPF assay

ABSTRACT

A major challenge in the safety assessment of food contact materials (FCM) is the evaluation of unknown non-intentionally added substances (NIAS). Even though consumer exposure levels may be quantitatively low, these substances are considered to be of high toxicological concern if they act as DNA reactive mutagens. From a safety assessment perspective, it is therefore important to detect their presence in FCM migrates. The present study applied the Ames MPF assay to assess the mutagenicity of migrates obtained from 30 food contact material samples out of 3 categories: plastics, composite materials and coatings. As a food simulant, 95% ethanol (EtOH) had a superior performance to less volatile simulants when evaluating recovery rates of representative model substances in different volatility categories. To monitor possible interference of the FCM matrix with Ames MPF results, migrates were spiked with reference substances and recovery rates were established. Out of 30 samples tested, two caused significant inhibition of revertant formation in the presence of the spiking control. Overall detection limits of the applied test method were estimated by determination of the lowest effective concentrations (LEC) for 10 Ames-positive substances. Even though the current limits of detection are not sufficient to entirely fulfil regulatory and safety requirements, three out of 30 FCMs showed evidence of dose-dependent effects in the Ames MPF assay. Overall, the data obtained supported the relevance of testing FCM migrates for DNA reactive contaminants and showed the value of the Ames MPF assay for the safety assessment of FCMs.     

Ultrastructural Interactions and Genotoxicity Assay of Cerium Dioxide Nanoparticles on Mouse Oocytes

Cerium dioxide nanoparticles (C_eO₂ ENPs) are on the priority list of nanomaterials requiring evaluation. We performed in vitro assays on mature mouse oocytes incubated with C_eO₂ ENPs to study (1) physicochemical biotransformation of ENPs in culture medium; (2) ultrastructural interactions with follicular cells and oocytes using Transmission Electron Microscopy (TEM); (3) genotoxicity of C_eO₂ ENPs on follicular cells and oocytes using a comet assay. DNA damage was quantified as Olive Tail Moment. We show that ENPs aggregated, but their crystal structure remained stable in culture medium. TEM showed endocytosis of C_eO₂ ENP aggregates in follicular cells. In oocytes, C_eO₂ ENP aggregates were only observed around the zona pellucida (ZP). The comet assay revealed significant DNA damage in follicular cells. In oocytes, the comet assay showed a dose-related increase in DNA damage and a significant increase only at the highest concentrations. DNA damage decreased significantly both in follicular cells and in oocytes when an anti-oxidant agent was added in the culture medium. We hypothesise that at low concentrations of C_eO₂ ENPs oocytes could be protected against indirect oxidative stress due to a double defence system composed of follicular cells and ZP.     

脱氢乙酸钠遗传毒性研究

目的研究脱氢乙酸钠(Na-DHA)的遗传毒性。方法细菌回复突变试验采用鼠伤寒沙门菌TA97a、TA98、TA100、TA102和TA1535菌株,设1 667、556、185、62和21μg/皿5个剂量组,同时设自发回复突变组、溶剂对照组和阳性对照组,在加和不加代谢活化系统(S9)的情况下计数每皿回复突变菌落数。微核试验采用昆明小鼠,设549.0、275.0和137.0 mg/kg BW 3个剂量组,同时设阴性对照组和阳性对照组,Na-DHA灌胃给予小鼠2次,间隔24 h,末次给予6 h后取股骨做骨髓涂片,观察红细胞(RBC)、嗜多染红细胞(PCE)和出现微核的嗜多染红细胞(MN)数,计算每组PCE/RBC和MN/PCE(微核发生率)。体外哺乳类细胞染色体畸变试验采用中国仓鼠卵巢(CHO)细胞,设2 000、1 000、500μg/ml 3个剂量组,同时设阴性对照组、溶剂对照组和阳性对照组,处理6和24 h,观察300个中期分裂相/组,记录畸变类型和数目,计算畸变率。结果各剂量组TA97a、TA98、TA100、TA102和TA1535的回复突变菌落数与自发回复突变组比较,差异均无统计学意义(P0.05)。各剂量组微核发生率与阴性对照组比较,差异均无统计学意义(P0.05)。各剂量组CHO细胞染色体畸变率与阴性对照组比较,差异均无统计学意义(P0.05)。自发回复突变组和阴性对照组三项试验的回复突变菌落数、微核发生率及染色体畸变率均低于阳性对照组,差异有统计学意义(P0.01)。结论本研究条件下,未发现Na-DHA具有遗传毒性。