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At least 163 records · Page 9Linked to original sources

PubMed2002

Genotoxicity of fecal water in a free-living Irish population.

The alkaline single-cell gel electrophoresis (comet) assay was used to investigate the genotoxicity of fecal water (FW) isolated from 47 Irish subjects using Caco-2 colonocytes as target cells. Two methods of comet assay analysis were compared to determine the extent of DNA damage and to categorize the samples as having no, low-to-moderate, or high genotoxicity. FW was isolated from stool samples by centrifugation and tested for its ability to induce DNA damage in Caco-2 cells. DNA damage was assessed using the comet assay by measuring the extent of DNA migration from the nucleus (microns, tail length) or by classifying the nuclei into five different categories depending on their morphology. Data collected from the two methods were used to categorize the FW samples on the basis of their genotoxic activity. Both methods showed good agreement. There was an approximately 50:50 split, with half the samples having some level of genotoxic activity and half having no genotoxicity. About one-third of the samples were considered to be highly genotoxic. There was a trend for low pH of the FW to be associated with increased DNA damage, but this was not significant. The results presented in this report show a relatively high incidence of genotoxic FW in samples derived from a free-living Irish population. Our data demonstrate the suitability of classifying nuclei on the basis of their morphology as a means of determining DNA damage. This procedure is very rapid and, therefore, advantageous in analyzing a large number of slides in the absence of an image analysis system.

Adolescent↗

PubMed2005

Genotoxicity of environmental agents assessed by the alkaline comet assay.

Generation of DNA damage is considered to be an important initial event in carcinogenesis. A considerable battery of assays exists for the detection of different genotoxic effects of compounds in experimental systems, or for investigations of exposure to genotoxic agents in environmental or occupational settings. Some of the tests may have limited use because of complicated technical setup or because they only are applicable to a few cell types. The single cell gel electrophoresis (comet) assay is technically simple, relatively fast, cheap, and DNA damage can be investigated in virtually all mammalian cell types without requirement for cell culture. The aim of this thesis was to evaluate the comet assay as a genotoxicity test in genetic toxicology of environmental agents, encompassing both experimental animal models and biomonitoring. The comet assay detects strand breaks (SB). The cells are embedded in agarose and lysed, generating nucleus-like structures in the gel (referred to as nucleoids). Following alkaline electrophoresis, the DNA strands migrate toward the anode, and the extent of migration depends on the number of SB in the nucleoid. The migration is visualized and scored in a fluorescence microscope after staining. Broad classes of oxidative DNA damage can be detected as additional SB if nucleoids are incubated with bacterial DNA glycosylase/endonuclease enzymes. Oxidized pyrimidines and purines can be detected by incubation with endonuclease III and formamidopyrimidine DNA glycosylase, respectively. The animal experimental studies indicated that the comet assay was able to detect genotoxic effects of diesel exhaust particles in lung tissue, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced DNA damage in colon epithelial cells and liver tissue, and benzene-induced damage in bone marrow and liver cells. The strength of the comet assay was further outlined by application of repair enzymes, indicating no oxidative DNA base damage following IQ treatment. High levels of oxidative DNA lesions were detected after exposure to benzene or X-ray irradiation. The comet assay did not detect DNA damage in colon or liver following ingestion of diets containing of high contents of animal fat or sucrose, although other indices of DNA damage were found. Determined from the results of a large Japanese study, the discrimination between carcinogens and non-carcinogens appears to be similar between the comet assay and alkaline elution, which also detects SB. This suggests that the comet assay is a reliable genotoxicity test in animal experimental systems. In the biomonitoring studies, we investigated the effect of common exposures and lifestyle factors (rather than effects of known carcinogens) on the level of oxidative DNA damage in mononuclear blood cells of humans. In the first study, based on repeated measurements, it was shown that interindividual variation and seasonal variation were major determinants for the basal level of SB, whereas no effect of age, exercise, or antioxidant intake could be detected. The effect of exercise was further investigated under both normoxic and hypoxic circumstances, showing a strong effect of hypoxia, and only effect of exercise in terms of SB in hypoxia. In a placebo-controlled parallel dietary fruit and vegetable (or the corresponding amount of antioxidants) intervention study, no effects of the level of oxidative DNA damage or sensitivity to hydrogen peroxide were observed. Although this may seem in contrast to other antioxidant intervention studies, a critical literature survey of antioxidant intervention studies on oxidative DNA damage suggested that well-controlled studies tended to show no effect of antioxidant supplementation. In summary, the aggregated data from the publications included in this thesis, and other publications encompassing the comet assay, indicate that the comet assay is a reliable method for detection of DNA damage in tissues of experimental animals. Although not all types of genotoxic exposures should be expected to result in DNA damage in mononuclear blood cells, the comet assay seems to be a valuable tool for detection of genotoxic exposure in humans. The comet assay indicates that DNA damage is abundant in mammalian cells and affected by lifestyle and many environmental exposures, including diet, exercise, hypoxia, and sunlight.

Animals↗

PubMedDate not supplied

Genotoxic effects of pentachlorophenol, lindane, transfluthrin, cyfluthrin, and natural pyrethrum on human mucosal cells of the inferior and middle nasal conchae.

BACKGROUND: Animal experiments and epidemiological studies suggest that pentachlorophenol (PCP) and gamma-hexachlorocyclohexane (lindane) should be classified as possible human carcinogens. In the past, both have had a variety of applications in the civilian and military sectors and in forestry. They have, e.g., been used to impregnate and treat uniforms and other fabrics and to control human lice. Animal experiments indicate that PCP in particular causes mutations and chromosome aberrations and thus DNA damage. Studies on whether or not this also applies to newer substances and especially to natural type I and type II pyrethroids still are not available. What is particularly lacking are data on the genotoxic effects of these substances on human target cells. Our study describes the genotoxic effects of PCP, lindane, transfluthrin, cyfluthrin, and natural pyrethrum on human mucosal cells of the inferior and middle nasal conchae. METHODS: Epithelial cells were isolated from nasal mucosa, which was removed in the surgical treatment of chronic sinusitis and nasal concha hyperplasia. After the cells had been tested for vitality using the trypan blue exclusion test, the short-term culture method was used. The material was incubated with PCP (0.3, 0.75, and 1.2 mmol), lindane (0.5, 0.75, and 1.0 mmol), transfluthrin (0.05, 0.1, 0.5, 0.75, and 1.0 mmol), cyfluthrin (0.05, 0.1, 0.5, 0.75, and 1.0 mmol), natural pyrethrum (0.001, 0.005, 0.01, 0.05, and 0.1 mmol), and N-methyl-N'-nitro-N-nitrosoguanidine for 60 minutes. Substance-induced DNA damage (single-strand and double-strand breaks) were determined using single-cell microgel electrophoresis. A fluorescence microscope was used together with an image processing system to analyze the results obtained. RESULTS: After exposure to all tested substances, a high percentage of the cells of the middle nasal concha in particular were found to have severely fragmented DNA as a result of strong genotoxic effects. Although the reaction of the cells of the inferior nasal concha was significantly less strong (p < 0.001), the tested substances were nevertheless found to have a notable genotoxic effect on these cells too. CONCLUSION: Our study strongly suggests that exposure to PCP, lindane, transfluthrin, cyfluthrin, and natural pyrethrum has a genotoxic effect on the epithelial cells of human nasal mucosa. In addition, we have shown that nasal structures differ in susceptibility to the various pesticides used in the tests. Thus, the study provides new evidence supporting the biological plausibility of PCP- and lindane-induced effects, thereby helping evaluate potential PCP- and lindane-induced mucous membrane carcinomas of these parts of the nose. In addition, our study shows that other substances that today are widely used for controlling pests have a considerable genotoxic effect on human target cells. The results obtained indicate the need for additional studies on the genotoxicity of these substances and their adverse effects on human health.

Adolescent↗

PubMed2000

Genotoxicity of instant coffee and of some phenolic compounds present in coffee upon nitrosation.

Instant coffee exhibits genotoxic activity upon nitrosation at acidic pH values in the Ames tester strain TA100. Using adsorption chromatography (Amberlit XAD-2) it was observed that the major fraction of molecules responsible for the genotoxic activity upon nitrosation was not retained on this resin, suggesting that the polar molecules present in instant coffee could be responsible for the genotoxicity observed upon nitrosation. Some phenolic molecules present in instant coffee (catechol, caffeic acid, and chlorogenic acid) were also genotoxic upon nitrosation under the same experimental conditions. The concentrations of nitrosatable phenolic compounds in the studied coffee were determined by HPLC and their contributions to the total genotoxicity observed were studied. The results obtained suggest that besides phenolic compounds other molecules were also involved in the genotoxicity of this beverage upon nitrosation. Teratogenesis Carcinog. Mutagen. 20:241-249, 2000.

Adsorption↗

PubMed2003

cDNA microarray gene expression profiling of hydroxyurea, paclitaxel, and p-anisidine, genotoxic compounds with differing tumorigenicity results.

The potential application of toxicogenomics to predictive toxicology has been discussed widely, but the utility of the approach remains largely unproven. Using cDNA microarrays, we compared the gene expression profiles produced in mouse lymphoma cells by three genotoxic compounds, hydroxyurea (a carcinogen), p-anisidine (a noncarcinogen), and paclitaxel (carcinogenicity unknown). To minimize the effect of biological variability and technological limitations, quadruplicate observations were made for each compound and a subset of genes yielding reproducible induction/repression was selected for comparison. A method was applied to attach normalized expression data to genes with a low false-discovery rate (<0.1) to yield more confidence regarding differential expression. This analysis identified genotoxicity-specific gene expression. Seven genes were consistently upregulated and 12 downregulated more than 2-fold by the three genotoxic compounds. Using additional genes, the expression pattern induced by the genotoxic noncarcinogen, p-anisidine, was readily distinguished from that associated with the genotoxic carcinogen, hydroxyurea. Comparison of paclitaxel-induced expression data to data for p-anisidine and hydroxyurea suggested that paclitaxel's profile is more similar to the genotoxic noncarcinogen. With further supporting evidence it may be possible to perform large-scale monitoring of gene expression during drug and chemical development that can provide an early warning of potential toxicological responses.

Aniline Compounds↗

PubMed2001

Genotoxic effects of carbon black particles, diesel exhaust particles, and urban air particulates and their extracts on a human alveolar epithelial cell line (A549) and a human monocytic cell line (THP-1).

The possible genotoxicity of small particulate matter has been under investigation for the last 10 years. Diesel exhaust particles (DEP) are considered as "probably carcinogenic" (IARC group 2A) and a number of studies show genotoxic effects of urban particulate matter (UPM). Carbon black (CB) is carcinogenic in rats. In this study the cytotoxic and genotoxic potency of these three particle types was investigated by exposing human cells (A549 and THP-1 cell lines) in vitro to CB, DEP (SRM 1650, NIST), and UPM (SRM 1648, NIST) for 48 hr. Cytotoxicity was assessed using the Alamar Blue assay, whereas genotoxicity was assessed using the single-cell gel electrophoresis (comet assay). The particles were characterized with regard to their mean diameter in tissue culture medium (CB 100 nm, DEP 400 nm, UPM 2 microm), their total carbon content (CB 99%, DEP 85%, UPM 15%), and their acid-soluble metal composition (UPM >> CB approximately DEP). The concentrations ranged from 16 ng/ml to 16 microg/ml for cytotoxicity tests and from 16 ng/ml to 1.6 microg/ml for genotoxicity tests. In both assays, paraquat was used as a reference chemical. The CB, DEP, and UPM particles showed no significant cytotoxicity. However, all three particles were able to cause significant DNA damage, although to a different extent in the two cell lines. The genotoxicity of washed particles and dichloromethane extracts was also investigated. In THP-1 cells CB washed particles and DEP extracts caused significant DNA damage. This difference in effect may be related to differences in size, structure, and composition of the particles. These results suggest that CB, DEP, and UPM are able to cause DNA damage and, therefore, may contribute to the causation of lung cancer. More detailed studies on influence of size, structure, and composition of the particles are needed.

Air Pollutants↗

PubMed2004

Bacterial and mammalian-cell genotoxicity of mixtures of chlorohydroxyfuranones, by-products of water chlorination.

The genotoxic responses of mixtures of four chlorohydroxyfuranones (CHFs), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 3,4-dichloro-5-hydroxy-2(5H)-furanone (MCA), 3-chloro- 4-(chloromethyl)-5-hydroxy-2(5H)-furanone (CMCF) and 3-chloro-4-methyl-5-hydroxy-2(5H)-furanone (MCF), were compared with the genotoxicity of the individual compounds. Genotoxicity was evaluated in the Salmonella reversion assay (Ames test), the in vitro Chinese hamster ovary (CHO) cell Hprt mutation assay, and in the CHO chromosome aberration test. When tested individually, the concentrations of the chemicals that were chosen for the mixtures induced no or only a modest increase in the genotoxic effects, and caused little or no cytotoxicity. In the Ames test, the genotoxic responses caused by the mixtures of CHFs did not follow simple additivity. Synergism was observed with strains TA97 and TA98, and antagonism with strain TA100. In the CHO/Hprt mutation assay, the mutagenic response of the mixtures was inconsistent, with near additivity seen with a mixture of CHFs that resulted in 12% cell survival. In contrast, the four CHFs together consistently caused more structural chromosome damage (mainly chromatid-type breaks and exchanges) compared to the sum of net effects of the four CHFs tested alone. Also, a potentiating effect was consistently seen for the cytotoxicity of the CHF mixtures both in the CHO/Hprt mutation assay and the chromosome aberration test. The present results indicate that the genotoxic effects of CHF mixtures can be greater than additive. Such effects may be worth considering in the cancer risk assessment of chlorinated drinking water.

Animals↗

PubMed2005

Modulation of the genotoxicity of pesticides reacted with redox-modified smectite clay.

Pesticides are toxic agents intentionally released into the environment; their use raises public health and environmental concerns. In recent years there has been much attention to the biotic degradation of pesticides. Abiotic mechanisms in the soil can contribute to pesticide degradation yet the toxicological impact of such degradation is unclear. This study combines for the first time an investigation into abiotic mechanisms of degradation coupled with toxicological endpoints in mammalian cells. The genotoxicity of three commonly used agricultural pesticides was assessed before and after exposure to redox-modified clay minerals. The objectives of the study were to determine the genotoxicity of 2,4-dichlorophenoxy acetic acid (2,4-D), dicamba, and oxamyl, using single cell gel electrophoresis with Chinese hamster ovary (CHO) cells, and to determine the effect of the iron oxidation state in clay minerals (ferruginous smectite SWa-1) on the genotoxic potency of the pesticides. 2,4-D alone or following reaction with redox-modified clays did not induce DNA damage in CHO cells. Oxamyl alone induced a concentration-dependent increase in genomic DNA damage; however, its genotoxicity declined after reaction with reduced clay minerals. Dicamba was not genotoxic when directly analyzed. When dicamba was reacted with reduced clay, a concentration-dependent increase in genomic DNA damage was observed. This is the first reported case of a pesticide being converted into a genotoxin after exposure to redox-modified smectites. These data introduce a new paradigm on the interaction between redox-modified clays and pesticide-related environmental genotoxicity.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1992

Rational approach to the quantification of genotoxicity.

The question of how many and which short-term tests (STT) are necessary for a satisfactory characterization of the genotoxic properties of chemicals is still open. The answer is important for both basic mutagenicity research and risk assessment. This paper, aimed at giving a rational answer to the problem, analyzes with multivariate statistical methods the data generated by the International Program for the Evaluation of Short-Term Tests for Carcinogens (IPESTTC). Although it has been found that this data base has a limited reliability for assessing the ability of STTs to predict carcinogenicity, the IPESTTC results are an important source of information on the relationships among different assays, and their ability to identify genotoxic chemicals. A scale of genotoxicity of the chemicals was established by studying with factor analysis their results in 20 IPESTTC tests. The next step of the analysis consisted in the identification of the STT batteries which are the most able to reproduce the genotoxicity scale based on the entire set of STTs. Different batteries were ranked according to their ability to quantify genotoxicity. As a general conclusion, this study indicated that an articulated range of STTs is necessary, and it is not possible to use only one assay (e.g., Salmonella) as an exhaustive indicator of genotoxicity.

Carcinogenicity Tests↗

PubMed1994

Detection of genotoxic effects in human gastric and nasal mucosa cells isolated from biopsy samples.

To assess genotoxic burdens from chemicals, it is necessary to relate observations in experimental animals to humans. The success of this extrapolation would be increased by including data on chemical activities in human tissues. Therefore, we have developed techniques to assess DNA damage in human gastric and nasal mucosa (GM, NM) cells. Biopsy samples were obtained during gastroscopy from macroscopically healthy tissue of the stomach or from healthy nasal epithelia during surgery. The specimens were incubated for 30-45 min at 37 degrees C with a digestive solution. We obtained 1.5-8 x 10(6) GM cells and 5-10 x 10(5) NM cells per donor, both with viabilities of 80-95%. The cells were incubated in vitro for 1 hr at 37 degrees C with the test compounds added in their appropriate solvents. In GM cells, we studied N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), sodium dichromate (Na2Cr2O7), nickel sulphate (NiSO4), cadmium sulphate (CdSO4), and lindane. In NM cells, lindane was investigated. Each compound was assessed for DNA damaging activity in cells of at least three different human donor samples using the microgel single cell assay. Similar studies were performed with GM and NM cells obtained from Sprague-Dawley rats. We have found human GM cells to be more sensitive to the genotoxic activity of MNNG than rat GM cells (low effective concentration [LEC] = 0.16 and 0.625 micrograms/ml for human and rat, respectively). Human cells were also more sensitive to the cytotoxic/genotoxic activity of NiSO4 (LEC = 5 and 19 mumoles/ml for human and rat, respectively). CdSO4 was genotoxic in human GM cells (LEC = 0.03-0.125 mumoles/ml), whereas no dose-related genotoxicity was observed in rat GM at concentrations up to 0.5 mumoles/ml. In contrast, approximately equal responses regarding genotoxicity and cytotoxicity were observed in rat and human GM for Na2Cr2O7 (0.25-1 mumoles/ml). Lindane, however, was genotoxic in three out of four rat GM but not in human GM cells (0.5-1 mumoles/ml), whereas it was active in both rat and human NM cells. Together with other recently published in vivo findings, our results with lindane can be interpreted according to a parallelogram approach. In view of possible human exposure situations and the sensitivities of the two target tissues from both species, the data imply that lindane will pose a health risk to humans by inhalation but not by ingestion.

Adult↗

PubMed1994

Effects of light on the cytotoxicity and genotoxicity of benzo(a)pyrene and an oil refinery effluent in the newt.

The genotoxicity and/or toxicity of benzo(a)pyrene (BaP) were evaluated under different lighting conditions in larvae and embryos of the newt Pleurodeles waltl. Visible light alone (1,220 lx; 2.1 mW/cm2), UVA alone (250 microW/cm2), or BaP alone (500, 50, 25, 12.5 ppb) had no toxic effects on the larvae. Conversely, toxic effects were observed in animals exposed to BaP (500 ppb)+daylight, or BaP (> or = 25 ppb)+UVA. BaP solutions (50 or 12.5 ppb) were irradiated for 24 hr (Irr BaP) prior to being assayed in the dark. The genotoxicity of BaP (50 ppb) as evaluated in the micronucleus test (on day 8) was halved by its previous exposure to UVA, and was abolished at the lowest concentration (12.5 ppb). In other experiments, the larvae were exposed alternatively to BaP or Irr BaP (18 hr in the dark) and UVA (6 hr in water), every day for 8 days. All animals that had accumulated non-irradiated BaP (50 ppb) showed signs of severe toxicity, and 90% died before the end of the test. On the other hand, irradiated BaP (50 ppb) was 4-fold less toxic and half as genotoxic as non-irradiated BaP. In addition, exposure of the animals to UVA alone for 4 days prior to treatment with BaP did not affect the genotoxicity or toxicity of this hydrocarbon. In the dark, the embryotoxicity of BaP was markedly attenuated by the presence of the jelly coats (10% vs. 24%). With dejellied embryos, comparable mortality (24%) was observed after exposure to 25 ppb BaP for 54 or 312 hr. Although UVA alone did not affect growth of the embryos, the toxicity of BaP was enhanced by the combined action of the two agents together or in succession (BaP+UVA or BaP then UVA). Larvae were treated with an oil refinery effluent (EF). At the concentration employed (125 ml/l), EF was not found to be genotoxic in the dark. However, in animals exposed to both EF and UVA, there was a progressive increase in level of micronucleated erythrocytes with increasing duration of daily exposure to UVA (9, 15, 24 hr). Moreover, the genotoxic potential of irradiated EF+UVA was systematically below that of non-irradiated EF+UVA for all durations of exposure to ultraviolet light. Irradiation of this type of effluent might help reduce its harmful effects on aquatic species. Our results also suggest that metabolic activation is not necessary for hydrocarbons to induce toxic effects.

Animals↗

PubMed1989

Volatile nitrosamine levels and genotoxicity of food samples from high-risk areas for nasopharyngeal carcinoma before and after nitrosation.

Traditional life-style, especially food habits, infection by Epstein-Barr virus (EBV) and genetic factors, have been associated with an increased risk of nasopharyngeal carcinoma (NPC). N-Nitroso compounds and other carcinogens either present in food or formed endogenously, as well as food constituents that activate EBV, have been suspected as etiological factors in NPC pathogenesis. For their characterization preserved food items, frequently consumed in NPC endemic areas in Tunisia, South China and Greenland, were sampled and screened for the presence of mutagens and volatile nitrosamines before and after nitrosation. Aqueous extracts as well as 2 organic extracts of the samples were assayed for genotoxicity in 2 Salmonella typhimurium strains and the SOS chromotest. The same extracts had previously been analyzed for volatile nitrosamines and for EBV-activating substances in Raji cells. In our study, 13 out of 16 food samples showed a weak, directly-acting genotoxicity in the SOS chromotest in at least one of the extracts, but only one sample from Greenland was found to be weakly mutagenic in Salmonella TA 98. Chemical nitrosation for 9 out of 15 samples of aqueous food extracts increased the genotoxic effect in the SOS chromotest. Levels of volatile nitrosamines were also elevated for 12 out of 15 samples; highest levels of N-nitrosodimethylamine were found in hard salted and dried fish from China (1,200 micrograms/kg) and highest N-nitrosopyrrolidine levels in a Tunisian spice (3,840 micrograms/kg). In non-nitrosated aqueous food extracts, the level of volatile nitrosamines and genotoxic activities were not correlated with the EBV-inducing activity of the same samples. After chemical nitrosation, EBV-inducing activity was decreased or showed no change and was not correlated with increases in either the genotoxicity or the nitrosamine levels. Our results suggest that EBV-activating compounds belong to a different class of substances. However, there was an association between the changes in genotoxicity and nitrosamine levels due to nitrosation.

Carcinoma↗

PubMedDate not supplied

Monitoring genotoxicity during the photocatalytic degradation of p-nitrophenol.

p-Nitrophenol is a common structural unit of many pesticides and was chosen as a model compound to monitor genotoxicity during photocatalytic degradation. The genotoxicity of p-nitrophenol (PNP) and its breakdown products was measured using a bioluminescent bacterial bioassay, Vitotox. The genotoxic potential decreased with the concomitant photocatalytic degradation of the parent PNP concentration. The rate of genotoxicity reduction was slower than the rate of removal of the parent PNP, due to the formation of genotoxic by-products. After 6 h of photocatalytic treatment the total genotoxicity was removed. These results indicate that bioassays can be used as a simple and highly sensitive method for monitoring the general toxicity of chemical pollutants before, during and after photocatalytic treatment or other destructive processes.

Aliivibrio fischeri↗

PubMed2002

Improved sample preparation of biomaterials for in vitro genotoxicity testing using reference materials.

New biomaterial related reference materials with known genotoxic properties were produced in order to study the sample preparation and in vitro genotoxicity testing of biomaterials. We incorporated genotoxic substances like benzo[a]pyrene into the biomaterial Tecoflex, a polyurethane frequently used for catheters and other applications. We demonstrated that the model compound benzo[a]pyrene is sufficiently extracted by organic solvents, whereas cell culture medium only extracts very limited quantities. By changing the medium several times during extraction the extracted amount was augmented. Using higher amounts of organic solvent in relation to the reference material's surface led to a higher recovery of extracted benzo[a]pyrene. For the in vitro genotoxicity testing using the Mammalian Cell Gene Mutation Test (HPRT test), Mammalian Chromosome Aberration Test, and bacterial umu- and SOS-tests, concentration of extracts is a prerequisite because of the low sensitivity of the test systems. Often cytotoxicity interferes with the evaluation of genotoxic effects. We demonstrated that some recommendations of the ISO 10993-Part 3 and 12,(1),(2) dealing with the biological evaluation of medical devices, seem to be insufficient, and new rules for the in vitro genotoxicity testing of biomaterials have to be established.

Animals↗

PubMed2002

Assessment of the genotoxicity of resin and zinc-oxide eugenol-based root canal sealers using an in vitro mammalian test system.

Endodontic sealers frequently are placed in direct contact with living tissues. Thus root canal sealers should have good biocompatibility. However, the pathobiologic effects, especially genotoxicity, of various root canal sealers widely used in dentistry have not been studied systematically on eukaryotic cells. The aim of this study was to examine the genotoxic potential of resin and zinc oxide-eugenol-based root canal sealers using a mammalian test system. In this study, tetrazolium bromide reduction assay, DNA precipitation assay, and DNA fragmentation analysis were performed to investigate the cytotoxic and genotoxic effects of four different root canal sealers on cultured V79 cells. The results show that all the root canal sealers tested are cytotoxic to V79 cells. The toxicity decreased in the order of N2 > AH26 > AHplus > Canals. In addition, N2, AH26, and AHplus exhibited genotoxicity by causing DNA single-strand breaks and digestion of genomic DNA. However, N2 is the most toxic root canal sealer among those tested. Taken together, these findings suggest that the sealers evaluated in this study show different toxic effects depending on the types and components. Root canal sealers containing formaldehyde and bisphenol A diglyether proved to be not only cytotoxic but also genotoxic. This mammalian test system might be used routinely for evaluation of the genotoxicity of dental materials in future investigations.

Animals↗

PubMed1987

Correlations between embryotoxic and genotoxic effects of phenytoin in mice.

The anticonvulsant drug phenytoin (DPH) has been suspected to produce embryotoxicity through an arene oxide intermediate. This drug was also found to be a genotoxic agent. These hypotheses were tested in pregnant mice modulating the phases I and II metabolizing enzymes. DPH was studied by assessing embryotoxicity, teratogenicity, and genotoxicity, the latter by the micronucleus test on the polychromatic erythrocytes of dams and fetuses. DPH embryotoxicity was potentiated by inhibiting both cytochrome P-450 and epoxide hydrase and decreased by inducing cytochrome P-450. Equivocal results were obtained by modulating cytochrome P-448. The main DPH metabolite, p-hydroxyphenytoin (HPPH), was ineffective both per se and after cytochrome induction or epoxide hydrase inhibition. DPH did not exert genotoxicity on the maternal organism, no matter which modulating agent was used. In the fetus, however, weak genotoxic effects were observed. These effects significantly increased with inhibition of epoxide hydrase; they disappeared with induction of both cytochromes P-448 and P-450 or with inhibition of the latter. No genotoxicity was exerted by HPPH, even when the enzymatic pattern was modulated. It is concluded that the major role in DPH embryotoxicity is played by the unchanged drug, while the presence of the arene oxide is determinant for genotoxic effects.

Abnormalities, Drug-Induced↗

PubMed2002

Genotoxicity of cyanobacterial extracts containing microcystins from Polish water reservoirs as determined by SOS chromotest and comet assay.

Toxicity of cyanobacterial blooms, an increasing problem around the world, is connected to the increase in bloom samples containing microcystins, caused by excessive eutrophication of drinking- and recreational water reservoirs. Microcystins are the most common group of cyanobacterial hepatotoxins. In Poland they are produced mainly by the Microcystis genus. The toxicity of microcystins has been well documented, but investigation into their genotoxicity has been insufficient relative to the study of their overall toxicity. Therefore, the aim of this study was the estimation and comparison of the genotoxicity of cyanobacterial extracts with microcystins (CEMs) using the SOS chromotest (bacterial test) with Escherichia coli PQ37 and the comet assay with human lymphocytes. Cyanobacterial bloom samples were collected in the summer months from two Polish water reservoirs, one at Sulejów and one at Jeziorsko. The SOS chromotest, which used prokaryotic cells (without metabolic activation), and the comet assay, which used eukaryotic cells, both indicated the potential genotoxic effect of CEMs. Cyanobacterial extracts caused DNA damage in human lymphocytes in vitro. The maximum level of DNA damage was observed after 12 h incubation with CEMs. The bacterial test indicated a dependence of the degree of CEM genotoxicity, the composition, and the concentration of microcystins in each bloom sample examined with the time of exposure. Differences between the genotoxicity of cyanobacterial extract and the standard microcystin-LR were noticeable. This was probably caused by the interaction of different microcystin variants. The results showed that CEMs from Polish water reservoirs were genotoxic, which was reflected by the stimulation of the SOS repair system in bacterial cells (SOS chromotest) and by the damage induced in DNA in human lymphocytes (comet assay).

Comet Assay↗

PubMed2006

Comparative evaluation of genotoxicity of captan in amphibian larvae (Xenopus laevis and Pleurodeles waltl) using the comet assay and the micronucleus test.

Captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) is a fungicide used to inhibit the growth of many types of fungi on plants used as foodstuffs. The toxic and genotoxic potentials of captan were evaluated with the micronucleus test (MNT; AFNOR,2000) and the comet assay (CA) using amphibian larvae (Xenopus laevis and Pleurodeles waltl). Acute toxicity results showed that captan was toxic (1) to Xenopus larvae exposed to from 2 mg/L to 125 or 62.5 microg/L, depending on the nature of the water [reconstituted water containing mineral salts or mineral water (MW; Volvic, Danone, France)] and (2) to Pleurodeles exposed to from 2 mg/L to 125 microg/L in both types of water. The MNT results obtained in MW showed that captan (62.5 microg/L) was genotoxic to Xenopus but not genotoxic to Pleurodeles at all concentrations tested. CA established that the genotoxicity of captan to Xenopus and Pleurodeles larvae depended on the concentration, the exposure times, and the comet parameters (tail DNA, TEM, OTM, and TL). The CA and MNT results were compared for their ability to detect DNA damage at the concentrations of captan and the exposure times applied. CA showed captan to be genotoxic from the first day of exposure. In amphibians, CA appears to be a sensitive and suitable method for detecting genotoxicity such as that caused by captan.

Amphibians↗