Assessment of micronuclei induction in peripheral erythrocytes of fish exposed to xenobiotics under controlled conditions

Genotoxicity and oxidative stress biomarkers in Carassius gibelio as endpoints for toxicity testing of Ukrainian polluted river waters

This study aimed to assess oxidative stress and genotoxicity biomarkers in Prussian carp Carassius gibelio laboratory-exposed to water from polluted Ukrainian rivers in order to evaluate their usefulness as endpoints in a short-term bioassay for toxicity testing of freshwaters. The micronucleus (MN) test and the frequency of cells with double nuclei (DN) in erythrocytes and gill cells were used as indicators of chromosome aberrations and abnormalities in cell divisions, respectively. Cellular antioxidant defenses i.e. antioxidant enzyme activities (catalase, Se-dependent glutathione peroxidase, total glutathione peroxidase and glutathione-S-transferase) and oxidative damage, i.e. lipid peroxidation (measured as thiobarbituric acid reactive substances) in the fish liver were used as biomarkers of oxidative stress. Exposure to the polluted river water samples for 96 h resulted in significantly increased MN and DN frequencies, limited increases in antioxidant enzyme activities and no changes in lipid peroxidation. Results suggest that MN and DN frequencies in C gibelio are useful endpoints in a short-term bioassay for genotoxicity testing of environmental water samples in contrast to the oxidative stress biomarkers applied that showed low potential for assessing sublethal effects after a 96 h exposure.

Oxidative stress and genotoxicity biomarker responses in grey mullet (Mugil cephalus) from a polluted environment in Saronikos Gulf, Greece

This study aimed to assess oxidative stress and genotoxicity biomarkers in grey mullet Mugil cephalus from a site receiving discharges from industrial and harbor activities and a reference site in Saronikos Gulf, Greece. Cellular antioxidant defenses, i.e., antioxidant enzyme activities (catalase, selenium [Se]-dependent glutathione peroxidase, glutathione-S-transferase) and oxidative damage, i.e., lipid peroxidation (measured as thiobarbituric acid reactive substances) were used as biomarkers of oxidative stress. The micronucleus test was used for evaluation of chromosome damage, and the frequency of cells with double nuclei was used as an indication of damage to cell divisions. Antioxidant enzyme activities were lower in fish from the polluted site compared with fish from the reference site, suggesting deficiency of the antioxidant system to compensate for oxidative stress. This is further supported by the higher lipid peroxidation levels in fish from the polluted site, which represent oxidative damage. Micronuclei and double-nuclei frequencies were higher in fish from the polluted site compared with fish from the reference site, indicating genotoxic effects. Correlations between biomarkers suggest that observed effects were due to contaminants exhibiting oxidative stress potential that can also induce genotoxicity. Results suggest that the selected biomarkers in M. cephalus are useful for the assessment of pollution impacts in coastal environments influenced by multiple pollution sources.

Studies of micronuclei and other nuclear abnormalities in red blood cells of Colossoma macropomum exposed to methylmercury

The frequencies of micronuclei (MN) and morphological nuclear abnormalities (NA) in erythrocytes in the peripheral blood of tambaqui (Colossoma macropomum), treated with 2 mg.L(-1) methylmercury (MeHg), were analyzed. Two groups (nine specimens in each) were exposed to MeHg for different periods (group A - 24 h; group B - 120 h). A third group served as negative control (group C, untreated; n = 9). Although, when compared to the control group there were no significant differences in MN frequency in the treated groups, for NA, the differences between the frequencies of group B (treated for 120 h) and the control group were extremely significant (p < 0.02), thus demonstrating the potentially adverse effects of MeHg on C. macropomum erythrocytes after prolonged exposure.

Effect of mercury ions on cysteine metabolism in Xenopus laevis tissues

The effect of mercury ions on the level of cysteine, glutathione, sulfane sulfur, and on the activity of rhodanese, 3-mercaptopyruvate sulfurtransferase (MPST) and γ-cystathionase in brain, heart muscle, liver, kidneys, testes and skeletal muscle of adult Xenopus laevis was investigated. Frogs of both sexes were exposed for 7 or 14 days to 1.353mgL(-1) (ppm) of mercury chloride (HgCl(2)) dissolved in water. The activity of the investigated enzymes participating in cysteine metabolism depends on cysteine in their active sites. Mercury ions can bind to -SH groups and, therefore, lower the activity of enzymes and change the level of sulfane sulfur, a product of l-cysteine desulfuration. The effect of mercury was found to depend on the time of exposure and the kind of tissue. In the liver, the main site of glutathione biosynthesis, the ratio of GSH to GSSG was essentially unchanged. The total glutathione level was decreased after 7 days of exposure to mercury, similarly as the activity of rhodanese. Sulfane sulfur levels were significantly increased after a shorter duration, while they decreased after a longer time of exposure. The kidney, brain and testes were able to enhance the level of GSH, probably thanks to high γ-glutamyltranspeptidase activity. These tissues showed an increased value of GSH/GSSG ratio during the shorter exposure to mercury. The activity of sulfurtransferases was decreased, especially after the longer exposure to mercury. In the heart and skeletal muscle, the level of GSH, sulfane sulfur, and the activity of the investigated sulfurtransferases was diminished after 14 days of exposure to Hg. It can be concluded that the main mechanism of toxic Hg activity is generation of reactive oxygen species in cells due to depleted GSH level, and a decreased sulfurtransferases activity either by blocking or oxidation of their -SH groups, what in consequence results in a diminished sulfane sulfur levels in tissues, especially the heart and testes.

Genotoxicity of crude extracts of cyanobacteria from Taihu Lake on carp (Cyprinus carpio)

Genotoxicity of crude cyanobacteria extracts (CBE) from blooms in Taihu Lake, China toward common carp (Cyprinus carpio) was measured. The primary extracellular product was determined by HPLC to be Microcystin-LR (MC-LR, L for leucine and R for arginine) with an average concentration of 2.4 × 10(2) μg MC g(-1) dry weight of cyanobacteria. Acute toxicity to carp, expressed as the 72-h LC(50,) was 53 mg, dw cyanobacteria L(-1). Genotoxicity, as determined by the micronucleus (MN) and comet assays were both dose- and time-depended. Deformities of cellular organelles in liver and gill were observed by use of transmission electron microscopy (TEM). The results showed that MC-LR from cyanobacteria from Taihu Lake could induce genotoxic response and tissue-level morphological changes in common carp.

Genotoxicity of 4-nonylphenol and nonylphenol ethoxylate mixtures by the use of Saccharomyces cerevisiae D7 mutation assay and use of this text to evaluate the efficiency of biodegradation treatments

Nonylphenol ethoxylates (NPnEOs, where n is the number of ethoxylic units in the molecule) are non-ionic surfactants widely used for domestic and industrial purposes. 4-Nonylphenol (4-NP), the main product of NPnEO biodegradation, is a toxic xenobiotic compound classified as endocrine disrupter. While numerous studies reported the toxicity and oestrogenic activity of nonylphenols, little is known about the mutagenicity of these compounds. In this paper, the genotoxicity of 4-NP and NPnEO mixtures was evaluated by using the D7 strain of Saccharomyces cerevisiae as experimental model. The same genotoxicity tests were applied to effluents deriving from experimental packed-bed bioreactors, developed for the treatment of NPnEO contaminated wastewater, in order to evaluate the residual genotoxic potential with respect to the influent waste. The target compounds fed to the bioreactors were 4-NP and NPnEO mixtures possessing an average of 5 or 1.5 ethoxylic units (Igepal CO-520 and Igepal CO-210, respectively). The results showed that 4-NP induced significant cytotoxic effect on S. cerevisiae cells at 50 mg/L, as well as mutagenic effects at the lowest tested concentrations (12 and 25 mg/L). 4-NP was the most genotoxic compound among those assayed, followed by Igepal CO-210, whereas Igepal CO-520 did not induce genotoxicity at any of the assayed concentrations. The genotoxic effects of 4-NP on yeast cells disappeared after the treatment of 4-NP artificially contaminated water in the bioreactor. This indicates that the biological treatment is capable of removing not only the pollutant, but also the toxicity associated to the compound and its degradation metabolites. This study represents, to the best of our knowledge, the first report that evaluates the genotoxicity of both 4-NP, NPnEOs and their potential aerobic degradation products on an eukaryotic organism. The obtained results suggest that the S. cerevisiae D7 strain is a very effective model microorganism to study the induction of genotoxic damage by the compounds under study. Moreover, this yeast assay has been proved effective to evaluate the detoxification effect deriving from biotreatment processes.

Giemsa versus acridine orange staining in the fish micronucleus assay and validation for use in water quality monitoring

This study concerns a comparative analysis of the acridine orange and Giemsa staining procedures for the fish erythrocyte micronucleus assay. The goal was to optimize the assay in the context of field water monitoring. Fish (Carassius carassius) were exposed to a reference genotoxic agent, cyclophosphamide monohydrate 5 mg l(-1) for 2, 4, and 6 days before testing. Slides from each individual were scored using the two procedures. The results show that the assay was more sensitive when acridine orange was used. When slides were Giemsa stained, the presence of ambiguous artefacts, leading to false positives and increasing random variance, reduced the contrast between exposed and control samples. Acridine Orange staining was then applied in the context of water quality monitoring. Fish were exposed for 4 days to water sampled in two hydrological contexts: basal flow and spring flood. The results show that exposure to spring flood water in an agricultural stream can induce mutagenicity.

In vivo cytogenetic and oxidative stress-inducing effects of cypermethrin in freshwater fish, Channa punctata Bloch

Synthetic pyrethroids are considered to be safe over other insecticides. Many of the newest pyrethroids lack ecotoxicity data. However, animal data indicate that their use may pose risk to environmental biota. The cytogenetic effects of cypermethrin, an α-class type II pyrethroid were evaluated using robust genotoxicity assay of chromosomal aberration (CA) and micronucleus (MN) tests in highly mitotic kidney cells and in erythrocytes of a freshwater fish, Channa punctata Bloch. In order to understand biochemical mechanism of genotoxic effects, oxidative stress parameters were also studied in fish erythrocytes. Fish exposed to cypermethrin (0.4, 0.8 and 1.2 μg/l for 48 and 72 h) showed increased frequencies of CA and MN in a concentration-dependent manner. Fish exposed to positive genotoxin, ethyl methane sulfonate (EMS) also showed significant increase in frequencies of CA and MN. The genotoxic effects were invariably accompanied and correlated with increased oxidative stress and disturbance of antioxidant enzymes.

Repeated sampling of Atlantic cod (Gadus morhua) for monitoring of nondestructive parameters during exposure to a synthetic produced water

The past decades of monitoring discharges from oil and gas industry have revealed that although there are indications of adverse effects in tissues of aquatic organisms, little is known about their temporal development. Furthermore, observations in wild-caught individuals have not been clearly reproduced in laboratory studies or caging studies, and vice versa, and the results are therefore not easily interpretable. There is clearly a need for exposure studies designed for monitoring the development of effect markers in individual fish over chronic periods to low contaminant levels. Through repetitive nondestructive sampling, the progression of effects may be monitored in individuals, significantly reducing the number of fish needed in exposure studies. A laboratory exposure study was designed to be able to monitor selected parameters in individual Atlantic cod (Gadus morhua). Passive integrated transponders in combination with visible implant elastomers were used to study individual fish during the exposure period (44 wk). Fish were measured (weight and length) and a blood sample was taken for analysis of hematocrit, DNA damage (micronucleus), and oxidative stress (total oxyradical scavenging capacity) at up to seven time points. There were no apparent adverse effects of treatments on the health of experimental fish, frequency of micronucleated erythrocytes, or oxidative stress in whole blood. It is possible that the time scale was not sufficient for development and detection of parameters included here or that red blood cells may not be a suitable matrix for the selected analyses. Future studies need to include other parameters in blood to investigate their sensitivity to low-concentration exposures.

Cytogenotoxicity induced by PBDE-47 combined with PCB153 treatment in SH-SY5Y cells

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are important recalcitrant halogenated compounds that have been regarded as major environmental pollutants. Recently, their concurrent appearance in the environment and humans and their structural and toxicological profile similarities have sparked interest in the potential toxicologic consequences of their coexposure. The aim of the current study was to evaluate the cytogenotoxic effects induced by 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) combined with 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) treatment in human neuroblastoma cells (SH-SY5Y) in vitro. SH-SY5Y cells were exposed to different concentrations of PBDE-47 (0, 2, 4, 8 μM) with or without PCB153 (5 μM) for 24 h. Thereafter, the cell viability, DNA damage, chromosomal abnormalities, and DNA-protein crosslinks (DPC) were determined. The results show that PBDE-47 and PCB153 alone and in combination induce DNA damage, with an increase in the frequency of micronuclei (MN) and DPC formation with increasing PBDE-47 concentration. In cells coexposed to PBDE-47 and PCB153, the cell viability significantly decreased while the MN frequency, DNA damage and DPC formation were all obviously increased compared to those of cells treated with the corresponding concentrations of PBDE-47 or PCB153 alone. Factorial analysis suggests that there were interactions between PBDE-47 and PCB153. The results imply that PBDE-47 interacts with PCB153 to inhibit cell viability and induce DNA damage, DPC formation, and chromosome abnormalities.

Golden grey mullet and sea bass oxidative DNA damage and clastogenic/aneugenic responses in a contaminated coastal lagoon

Several xenobiotics or their metabolites have redox-cycling properties and potential to induce oxidative stress and DNA damage. The current work aimed to study, under environmental conditions, oxidative DNA damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)) and its association with chromosomal damage measured as erythrocytic nuclear abnormalities (ENAs), in Liza aurata and Dicentrarchus labrax, caught at a costal lagoon (Ria de Aveiro, Portugal) having sites with different contamination profiles. The quantified parameters were also used to assess the lagoon's environmental status. Five critical sites were assessed comparing to a reference site. L. aurata displayed higher 8-OHdG levels and ENAs frequency, respectively, at Laranjo and Vagos. D. labrax 8-OHdG levels were higher at the sites where quantification was possible whereas no differences were found in terms of ENAs. No correlation was found in both species between 8-OHdG and ENAs. Despite no direct linkage between the two biomarkers was found, this study demonstrates species and site dependent genotoxic responses.

Evaluation of micronucleus and erythrocytic nuclear abnormalities in Balkan whip snake Hierophis gemonensis

Over recent years, changes of erythrocytic nuclei have been increasingly used to evaluate genotoxic effects of different compounds such as polycyclic aromatic hydrocarbons (benzo-a-pyrene, naphthalene, β-naphthoflavone), heavy metals (cadmium, mercury), textile mill effluent especially in aquatic ecosystem. However, in fish, both micronuclei and erythrocytic nuclear abnormalities also appear spontaneously and their frequency can be seasonally dependent. The aim of the study was to evaluate the frequency of micronuclei (MN), nuclear abnormalities (NA) including vacuolated nuclei (VN) and cytoplasmic vacuoles (CV) in erythrocytes of Balkan whip snake Hierophis gemonensis and establish the level of spontaneous appearance during the annual cycle. Average frequency of NA was 10.89 ± 4.72% while the MN (0.03 ± 0.03%) and VN (0.04 ± 0.08%) were seldom detected. NA significantly positively correlated with MN (r = 0.319; P < 0.05) and VN (r = 0.363; P < 0.05). Appearance of CV did not correlate with other measured parameters and average frequency was 11.06 ± 8.33%. Significant seasonal variation was found in NA appearance with the lowest value in spring and the highest in winter. VN increase was observed in autumn. MN and CV levels varied between seasons but not significantly. Considering the biological cycle, frequency of NA, VN, MN and CV recorded in pre-hibernation/hibernation increased compared to the active phase, but only NA elevation was significant. Although the obtained results showed differences according to sex, statistical analysis of measured parameters showed the same pattern of seasonal variation in both sexes.

Integrated biological and chemical analysis of organochlorine compound pollution and of its biological effects in a riverine system downstream the discharge point

Pollution in riverine systems, along with its biological effects, may propagate downstream even at considerable distances. We analyzed the organochlorine compound (OC) pollution in a section of the low Ebro River (Northeast Spain) downstream a long-operating chlor-alkali plant. Maximal levels of OCs and of their associated dioxin-like biological activity occurred in residue samples from the plant, and persisted in river sediments some 40km downstream (Xerta site). Biological analysis at multiple organization levels in local carp (Cyprinus carpio, EROD, Cyp1A mRNA expression in the liver, hepatosomatic index, condition factor, and micronuclei index in peripheral blood) showed a similar pattern, with a maximal impact in Ascó, few kilometers downstream the plant, and a clear reduction at Xerta. This combination of chemical, molecular, cellular and physiological data allowed the precise assessment of the negative impact of the chlor-alkali plant on the quality of river sediments and on fish, and suggests that sediments may be a reservoir for toxic substances even in dynamic environments like rivers.

Effects of individual polybrominated diphenyl ether (PBDE) congeners on harbour seal immune cells in vitro

Effects of polybrominated diphenyl ethers (PBDEs) on the immune system of marine mammals are poorly understood. One important innate immune function of granulocytes is the respiratory burst which generates reactive oxygen species (ROS) used to kill engulfed microorganisms. The present study investigates in vitro the effects of BDE-47, -99 and -153, on the formation of ROS, on intracellular level of thiols, on activity and efficiency of phagocytosis and on apoptosis in granulocytes of harbour seals. Compounds were tested at four different concentrations ranging from 1.5 to 12 microM. Results showed that ROS levels, thiol levels and phagocytosis were all affected when harbour seal cells were exposed to the highest concentration (12 microM) of PBDE congeners. Apoptosis was not affected by PBDEs. The observed effects were similar in adults, pups and in the 11B7501 cell line of harbour seals.

Investigation of the genotoxicity of malathion to freshwater teleost fish Channa punctatus (Bloch) using the micronucleus test and comet assay

Malathion [S-(1,2-dicarboethoxyethyl) O, O-dimethyl phosphorodithioate] is a widely used organophosphorus insecticide throughout the world. However, limited efforts have made to study its genotoxic effect in different fish tissues. The present investigation was aimed to assess the genotoxic potential of the pesticide to the freshwater teleost fish Channa punctatus at sublethal concentrations using the micronucleus test and comet assay. Initially, the 96-h LC50 value of commercial-grade malathion (50% EC) was determined as 5.93 ppm in a semistatic system. Based on LC50, three test concentrations (viz. sublethal I, sublethal II, and sublethal III) were determined to be 1.48, 0.74, and 0.59 ppm, respectively, and the fish specimens were exposed to these concentrations. Tissue samplings were done on days 0, 1, 3, 7, 15, 22 and 29 of malathion exposure for assessment of the induction of micronuclei (MN) frequency and DNA damage. The MN formation in the peripheral blood cells was found to be significantly higher (p < 0.05) in the treated specimens at all sampling intervals compared to the control. The MN frequency reached maximum on days 3 and 7 at sublethal I and II concentrations, respectively, followed by a nonlinear decline with the progression of the experiment. Similarly, significant effects (p < 0.05) of both concentration and time of exposure were observed on DNA damage in the gill, kidney, and lymphocytes. All of the tissues exhibited a concentration-dependent increase in DNA damage up to day 3, followed by a nonlinear decrease with the duration of exposure. A comparison of the extent of DNA damage among the tissues showed the sensitivity of gill tissue to malathion.

Genotoxicity of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus

In the present work we have described the genotoxic potential of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus for the first time by three complementary tests: micronucleus test (MN), nuclear lesions (NL) and comet assay (CA). The groups exposed to the zoosporic fungi subjected to the MN and NL test showed statistically significant differences in MN and NL frequencies with respect to the control one. Also, a significant increase (p<0.001) in micronuclei and nuclear lesions frequencies were recorded with the increase in exposure time. A correlation was observed between the frequencies of MN and NL, suggesting the importance for recording this anomaly in order to improve the information obtained with the MN test. Therefore, our results suggest that the nuclear lesions found here should be considered indicators of genotoxicity, in addition to the typical micronuclei forms. The result of the comet assay showed a significant difference in the percentages of the damaged DNA in the comet tail (%TDNA) of the treated groups comparing to the control. A significant (p<0.001) increase in the DNA damage of the treated groups with the increase in exposure time was recorded, confirming the results of the MN and the NL tests. The results of the current study will be useful for future work involving the biomonitoring of regions where Nile tilapia survive. These data allow us to consider O. niloticus niloticus as a good bioindicator of the effects of genotoxic agents that might be present in the aquatic habitat.

Environmental genotoxicity and cytotoxicity in the offshore zones of the Baltic and the North Seas

Micronuclei (MN), nuclear buds (NB) and fragmented-apoptotic cells (FA) were analyzed in mature peripheral blood and immature cephalic kidney erythrocytes of flounder (Platichthys flesus), dab (Limanda limanda) and cod (Gadus morhua) from 12 offshore sites in the Baltic Sea (479 specimens) and 11 sites in the North Sea (291 specimens), which were collected during three research vessel cruises in December 2002, 2003 and in September 2004. The highest levels of environmental genotoxicity (frequencies of MN up to 0.5 per thousand, NB - up to 0.75 per thousand) and cytotoxicity (FA - up to 0.53 per thousand) were observed in flatfishes from areas close to oil and gas platforms in the North Sea and in zones related to the extensive shipping and potentially influenced by contamination from large European Rivers (Elbe, Vistula, Oder). In dab from the offshore zones of the North Sea, the levels of nuclear abnormalities were higher as compared to those in dab from the Baltic Sea. Responses in immature kidney erythrocytes were higher than in mature erythrocytes from peripheral blood. MN frequency lower than 0.05 per thousand (the Baltic Sea) and lower than 0.1 per thousand (the North Sea) could be suspected as a reference level in the peripheral blood erythrocytes of flatfish.

Variation in genotoxic stress tolerance among frog populations exposed to UV and pollutant gradients

Populations of widely distributed species can be subjected to unequal selection pressures, producing differences in rates of local adaptation. We report a laboratory experiment testing tolerance variation to UV-B and polycyclic aromatic hydrocarbons (PAHs) among common frog (Rana temporaria) populations according to their natural exposure level in the field. Studied populations were naturally distributed along two gradients, i.e. UV-B radiation with altitude and level of contamination by PAHs with the distance to emitting sources (road traffic). Tadpoles from eight populations were subjected to (1) no or high level of artificial UV-B; (2) four concentrations of benzo[a]pyrene (BaP) (0, 50, 250, 500microgL(-1)); (3) simultaneously to UV-B and BaP. Since both stressors are genotoxic, the number of micronucleated erythrocytes (MNE) in circulating red blood cells was used as a bioindicator of tadpole sensitivity. High-altitude populations appear to be locally adapted to better resist UV-B genotoxicity, as they showed the lowest MNE numbers. Conversely, no correlation was observed between levels of PAH contamination in the field and tadpole tolerance to BaP in the laboratory, indicating the absence of local adaptation for BaP tolerance in these populations. Nevertheless, the decrease of MNE formation due to BaP exposure with altitude suggests that high-altitude populations were intrinsically more resistant to BaP genotoxicity. We propose the hypothesis of a co-tolerance between UV-B and BaP in high-altitude common frog populations: local adaptation to prevent and/or repair DNA damage induced by UV-B could also protect these highland populations against DNA damage induced by BaP. The results of this study highlight the role of local adaptation along pollutant gradients leading to tolerance variation, which implies that is it necessary to take into account the history of exposure of each population and the existence of co-tolerance that can hide toxic effects of a new pollutant.

Genotoxic and oxidative stress-inducing effects of deltamethrin in the erythrocytes of a freshwater biomarker fish species, Channa punctata Bloch

Deltamethrin, an alpha-cyano class of pyrethroid insecticide is used in insect pest control and antimalaria programs in several countries including India. Although various toxic manifestations of deltamethrin are reported in mammals, its ecotoxicologic dimensions are not adequately researched in ecologically and commercially important fishes. In this study, we report genotoxic effect of deltamethrin in a biomarker fish Channa punctata (Bloch). Adult fish were exposed to three concentrations of technical grade deltamethrin (0.4, 0.8, and 1.2 microg/L) for 48 and 72 h. Ethyl methane sulfonate was used as a positive control. Fish were analyzed for induction of micronucleus (MN), nuclear abnormalities (NAs), and oxidative stress biomarkers in erythrocytes. Deltamethrin significantly induced MN and NAs accompanied by increased lipid peroxidation. Activity of antioxidant enzyme superoxide dismutase was significantly decreased but an increase was observed in reduced glutathione level after 72 h of exposure. The NAs in exposed fish included blebbed, lobed and notched nuclei, and binucleated erythrocytes. Our findings suggest that oxidative stress may, in part, be contributing to deltamethrin-induced genotoxic damage to erythrocytes. Although MN induction is a nonspecific biomarker, it may provide an indication of pollution load of deltamethrin in the affected fish population when used as part of suite of other biomarkers.

A critical analysis of the biological impacts of plasticizers on wildlife

This review provides a critical analysis of the biological effects of the most widely used plasticizers, including dibutyl phthalate, diethylhexyl phthalate, dimethyl phthalate, butyl benzyl phthalate and bisphenol A (BPA), on wildlife, with a focus on annelids (both aquatic and terrestrial), molluscs, crustaceans, insects, fish and amphibians. Moreover, the paper provides novel data on the biological effects of some of these plasticizers in invertebrates, fish and amphibians. Phthalates and BPA have been shown to affect reproduction in all studied animal groups, to impair development in crustaceans and amphibians and to induce genetic aberrations. Molluscs, crustaceans and amphibians appear to be especially sensitive to these compounds, and biological effects are observed at environmentally relevant exposures in the low ng l(-1) to microg l(-1) range. In contrast, most effects in fish (except for disturbance in spermatogenesis) occur at higher concentrations. Most plasticizers appear to act by interfering with the functioning of various hormone systems, but some phthalates have wider pathways of disruption. Effect concentrations of plasticizers in laboratory experiments coincide with measured environmental concentrations, and thus there is a very real potential for effects of these chemicals on some wildlife populations. The most striking gaps in our current knowledge on the impacts of plasticizers on wildlife are the lack of data for long-term exposures to environmentally relevant concentrations and their ecotoxicity when part of complex mixtures. Furthermore, the hazard of plasticizers has been investigated in annelids, molluscs and arthropods only, and given the sensitivity of some invertebrates, effects assessments are warranted in other invertebrate phyla.

Seasonality of nuclear abnormalities in gilthead sea bream Sparus aurata (L.) erythrocytes

The frequencies of erythrocyte nuclear abnormalities, such as irregularly shaped (ISN), vacuolated nuclei (VN), binucleated cells (BN), including micronuclei (MN), were monitored in the peripheral blood of cultured gilthead sea bream (Sparus aurata L.) from the southern Adriatic Sea (Croatia) and assessed for a relation to seasonality. Fish were sampled in February, April, June, and September. The lowest frequencies of ISN and MN were measured in April, and the lowest frequencies of VN and BN were found in February. The highest values of ISN and BN were detected in September. The highest values of MN and the most frequent occurrence of VN occurred in June and April, respectively. The Spearman rank order correlation test revealed a significant positive correlation between the frequencies of ISN, BN and MN; VN did not correlate with any of the measured parameters. The ISN had significantly higher nuclear surface area values than normal nuclei (P < 0.001). Our results demonstrate that the measured parameters displayed a distinct seasonality. Consequently, we conclude that seasonal variations should be taken into account when nuclear abnormalities are used as biomarkers. This variation should be well understood in order to successfully separate true contamination effects from seasonal factors that have the potential to affect the frequency and occurrence of nuclear abnormalities.

Evaluation of genotoxicity using the micronucleus assay and nuclear abnormalities in the tropical sea fish Bathygobius soporator (Valenciennes, 1837) (Teleostei, Gobiidae)

The micronucleus and nuclear abnormalities assays have been used increasingly to evaluate genotoxicity of many compounds in polluted aquatic ecossystems. The aim of this study is to verify the efficiency of the micronucleus assay and nuclear abnormality assay in field and laboratory work, when using erythrocytes of the tropical marine fish Bathygobius soporator as genotoxicity biomarkers. Gill peripheral blood samples were obtained from specimens of Bathygobius soporator. In order to investigate the frequencies of micronuclei and to assess the sensitivity of species, the results were compared with samples taken at the reference site and maintained in the laboratory, and fish treated with cyclophosphamide. The micronucleus assay was efficient in demonstrating field pollution and reproducing results in the labotatory. There were significant higher frequencies of micronuclei in two sites subject to discharge of urban and industrial effluents. The nuclear abnormality assay did not appear to be an efficient tool for genotoxicity evaluation when compared with field samples taken at a reference site in laboratory, with a positive control.

Transcriptional effects of nonylphenol, bisphenol A and PBDE-47 in liver of juvenile Atlantic cod (Gadus morhua)

The transcriptional levels of 10 genes were quantified in liver of Atlantic cod exposed to environmental relevant concentrations of three model toxicants; two alkylphenols (30 microg/L nonylphenol (NP) and 50 microg/L bisphenol A (BPA)) and one brominated flame-retardant congener (5 microg/L PBDE-47). The fish were exposed to the toxicants for 3 weeks, with n=6 in each group (a total of 24 fish were used). NP exposure produced a significant reduction of five CYPs genes (CYP1A (P<0.01), CYP2C33-like (P<0.001), CYP2Y3 (P<0.001), CYP2P1-like (P<0.01) and CYP3C1-like (P<0.01)). A significant reduction was also seen for three CYPs after BPA exposure (CYP2C33-like, CYP2Y3 and CYP3C1-like (P<0.01 for all)). PBDE-47 exposure produced a significant reduction of CYP1A, CYP2C33-like and CYP3C1-like (P<0.05 for all). The genes encoding Phase II enzymes responded in a different manner; NP exposure resulted in a 4.6-fold increase of GST pi (P<0.001), whereas BPA exposure gave no effects on these enzyme genes. PBDE-47 exposure resulted in a 3.3-fold reduction of UGT (P<0.05). No effects were seen on the antioxidant genes GSH-Px and GR for any of the three toxicants. Thus, all three toxicants seem to down regulate several CYPs, giving rise to distinct mRNA expression patterns suggesting that these toxicants act on the same receptors or via the same pathways.

Biomonitoring of genotoxicity using micronuclei assay in native population of Astyanax jacuhiensis (Characiformes: Characidae) at sites under petrochemical influence

Bom Jardim brook is a small stream that flows through an area under the influence of a Petrochemical Complex, demanding control over its quality, so a genotoxic evaluation was performed. This study was conducted in situ, based on previous analysis on the same subject. These were performed both in vitro, with Salmonella typhimurium and human lymphocytes, and in vivo, using bioassays with fish exposed to water from the study area. The purpose of this research was to assess the quality of the aquatic environment and possible effects from petrochemical pollution to surrounding native populations. Micronuclei (MNE) and nuclear abnormalities (NA) frequencies in peripheral blood of Astyanax jacuhiensis, a native fish species collected from the study area, were used as biomarkers. Study period was from summer/99 to spring/2001, using samples obtained seasonally at two ponds upstream from the industrial area (BJN and BJPa) and two sites in Bom Jardim brook (BJ002 and BJ000), which are subject to Complex influence. MNE and NA frequencies found in individuals from BJ002 and BJ000 were similar, showing positive genotoxic responses related to control sites BJN and BJPa. No differential sensitivity could be verified for micronuclei induction between genders of A. jacuhiensis in the studied population. This study showed that sites subject to petrochemical influence were under higher genotoxic impact. Biomarkers adequacy to the case and the sensitivity of A. jacuhiensis for water monitoring could be also inferred.

Organochlorine bioaccumulation and biomarkers levels in culture and wild white seabream (Diplodus sargus)

Persistent organic pollutants (POPs), which can accumulate in the adipose fish tissues, can enter the human food chain through the consumption of fish, and cause risk to health. The use of chemical analysis, and biochemical and cellular responses is a way to detect the impact of pollutants in aquatic systems. The purpose of this study was to investigate the levels of organochlorine compounds (polychlorinated biphenyls - PCB and p,p'-dichlorodiphenyltrichloroethane and its metabolites - tDDT) in, wild and cultivated, white seabream (Diplodus sargus), and also its biological effects that were evaluated by assessing the activity of biotransformation enzymes and genotoxic effects. To achieve that we have sampled five different size classes (I - 13 g, II - 64 g, III - 143 g, IV - 315 g and V - 441 g) of white seabream from a local aquaculture, and also a group of wild fish (375g) in order to compare accumulation and responses between cultured and wild fish. White seabream, cultured and wild, presented low levels of organochlorine content, both in liver and in muscle. Wild white seabream, in comparison to cultured ones at the marketable size, showed lower organochlorine accumulation. Biotransformation enzymes showed negative correlations with organochlorine levels in liver. Micronucleous numbers revealed that wild white seabream are not so exposed to genotoxic compounds as cultured ones.

Bisphenol A in the Aquatic Environment and Its Endocrine-Disruptive Effects on Aquatic Organisms

Bisphenol A [BPA; 2,2-bis(4-hydroxyphenyl)propane], which is mainly used in the production of epoxy resins and polycarbonate plastics, is a known endocrine disruptor and is acutely toxic to aquatic organisms. Due to intensified usage of these products, exposure of organisms to BPA via several routes, such as the environment and food, has increased. The aquatic environment is an important area for the study of BPA. This report reviews the literature concerning contamination routes and degradation of BPA in the aquatic environment and its endocrine-disruptive effects on aquatic organisms.

Analysis of micronucleated erythrocytes in heron nestlings from reference and impacted sites in the Ebro basin (N.E. Spain)

The frequency of micronuclei (MN) in peripheral erythrocytes was tested for 59 heron nestlings (Ardea purpurea, Egretta garzetta and Bubulcus ibis) sampled at two areas (polluted and reference) on the River Ebro (NE Spain) and at its Delta during Spring 2006. Flow-cytometry analysis revealed higher (three- to six-fold) MN counts in samples from the most polluted site relative to samples from the reference area. Samples from the Delta showed intermediate values. Age, morphometric parameters (weight, tarsus size and bill-head length) and maturation status showed no significant differences among the different populations for each species; nor were they correlated with MN levels. The data suggest that elevated levels of MN in chicks in impacted areas reflected the chemical pollution of their nesting sites. The use of nestlings for this assay appears to be a convenient, non-destructive method to assess the impact of pollution in natural bird populations.

Planarian neoblast micronucleus assay for evaluating genotoxicity

Planarian neoblasts are somatic stem cells that have the potential to be used in genotoxicity assays due to their proliferative nature, sensitivity to genotoxic agents, and experimental accessibility. Two freshwater planarian species, Girardia tigrina and Girardia schubarti, were used to develop a neoblast-based micronucleus (MN) assay to assess genotoxicity. Intact or regenerating planarians were exposed to gamma-rays, methyl methanesulphonate (MMS), or cyclophosphamide (CP), and neoblast MN frequency was measured. Exposure to the clastogens had no detectable effect on the MN frequency of intact planarian neoblasts. However, for regenerating individuals, active neoblast proliferation was induced by decapitation, and gamma-ray doses as low as 0.5 Gy, and MMS and CP concentrations as low as 0.8 microM and 100 mM, respectively, induced a significant increase in MN frequency. Exposure to higher doses of gamma-rays consistently resulted in detectable increases in MN frequency. For MMS and CP, concentrations of up to 1.6 microM and 200 mM, respectively, resulted in significant increases in MN frequency, but exposures to higher concentrations led to a decrease to non-significant levels, possibly due to cytotoxic effects of MMS and CP. After completion of regeneration, the MN frequencies returned to those of non-exposed controls, indicating that the neoblast MN assay for regenerating G. tigrina or G. schubarti reflects chromosomal damage caused by acute exposure to clastogenic agents. Upon standardization, this assay may represent an interesting alternative that allows damage caused to freshwater organisms by potentially genotoxic environmental pollutants to be monitored.

Nuclear changes in blood, early liver anomalies and hepatocellular cancers in flounder (Platichthys flesus L.) as prognostic indicator for a higher cancer risk?

Nuclear changes (micronuclei) in blood are a well-established biomarker of toxic injury and related genotoxicity in mussel, fish and humans, as well. Yet, the relationship between the frequencies of micronuclei in blood and nuclear changes in liver cells itself and the higher potential risk to develop liver cancer is not yet fully implemented. We analysed and diagnosed macroscopic liver changes and H&E and Feulgen stained histological liver sections (2 microm of thickness) together with blood smears (stained with Sytox Green) from same individuals in flounder caught along a well-known contaminant gradient in the North Sea. Results showed an increase in micronuclei frequencies in blood at the more contaminated sites and higher frequencies of macroscopically visible neoplastic liver changes. In livers of the same individuals, nuclear changes were diagnosed in early to degenerative liver lesion, extra-focal tissue surrounding neoplastic lesion and various stages during cancer progression from early neoplastic foci, benign adenomas and malignant carcinomas. The aim of this approach is to expand diagnostic criteria, well-established in the frame of BEQUALM to nuclear changes which might help diagnosis of malignancies in doubtful cases.

Erythrocytic nuclear abnormalities in wild and caged fish (Liza aurata) along an environmental mercury contamination gradient

Laranjo basin (Aveiro, Portugal) has been subjected to mercury contamination from a chlor-alkali plant, presenting a well-described mercury gradient. This study aims the assessment of mercury genotoxicity in this area by measuring erythrocytic nuclear abnormalities (ENA) frequency in the mullet Liza aurata, and its relation with total mercury concentration (Hg(t)) in blood. Wild fish were seasonally analysed, and, complementarily, fish were caged for 3 days at three locations differing on their distances to the mercury source. The results from Laranjo were compared with those from a reference area (S. Jacinto). Wild fish from Laranjo showed elevated ENA frequency in summer and autumn in concomitance with increased blood Hg(t). Surprisingly, no ENA induction was found in winter, despite the highest blood Hg(t), which may be explained by haematological dynamics alterations, as supported by a decreased immature erythrocytes frequency. Caged fish displayed ENA induction only at the closest site to the contamination source, also showing a correlation with blood Hg(t).

Effects of PBDE-47 on cytotoxicity and genotoxicity in human neuroblastoma cells in vitro

Polybrominated diphenyl ethers (PBDEs) are an important class of flame retardants. Because of their detection in human breast milk and structural similarity to polychlorinated biphenyls (PCBs), concern has been raised about their potential toxicity, particularly neurotoxic effects in newborns and children. The aim of the current study was to evaluate the cytotoxic and genotoxic effects of 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) in human neuroblastoma (SH-SY5Y) cells in vitro. SH-SY5Y cells were incubated with different concentrations of PBDE-47 (1, 2, 4, 8 microg/ml) for 24 h, and a set of bioassays were conducted to measure: cell viability, cell proliferation (nuclear division index, NDI), lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) formation, cell apoptosis, and DNA breakage and cytogenetic damage. The data showed that PBDE-47 inhibited cell viability, increased LDH leakage, and induced cell apoptosis. All significant effects were observed at concentrations of 4 microg/ml and above (P<0.05). After 24 h exposure, a concentration-dependent increase in ROS formation was observed, and there were obviously increase in comparison to the control at concentrations as low as 2 microg/ml PBDE-47. Log-transformed Olive Tail Moment (OTM) were significantly increased compared with the control at various PBDE-47 concentrations (P<0.05), while a significant increase in the percentage of DNA in the tail was only observed at 8 microg/ml PBDE-47 (P<0.05). PBDE-47 caused a concentration-dependent decrease in NDI, and concentration-dependent increases in chromosome abnormalities as measured by total Micronuclei (MNi)/1000 binucleate cells (BNCs), micronucleated binucleate cells (MNBNCs)/1000 BNCs, and nucleoplasmic bridges (NPBs)/1000 BNCs. The results indicate that PBDE-47 is cytotoxic and genotoxic in SH-SY5Y cells in vitro.

Genotoxic effects of binary mixtures of xenoandrogens (tributyltin, triphenyltin) and a xenoestrogen (ethinylestradiol) in a partial life-cycle test with Zebrafish (Danio rerio)

A partial life-cycle test with the model fish Danio rerio was performed in order to evaluate the genotoxic potential of binary mixtures of xenoandrogenic (tributyltin--TBT; triphenyltin--TPT) and an estrogenic compound (ethinylestradiol--EE2). Five days post-fertilisation larvae were diet-exposed to environmental relevant concentrations of TBT and TPT (25 ng/g-100 ng/g), and water-exposed to ethinylestradiol (3.5 ng/L) for a four-month period; binary mixtures of TBT plus EE2 and TPT plus EE2 were run in parallel. The erythrocytic nuclear abnormalities (ENA) assay in circulating erythrocytes was used to evaluate genotoxicity in the end of the four-month exposure period. A significant increase (p<0.05, Kruskall-Wallis non-parametric ANOVA) in ENA frequency, in comparison with control animals, was observed in those animals exposed to TBT and TPT (the highest doses only), and to EE2 and the binary mixtures, although neither synergistic nor additive effects of the tested compounds were evident. Overall, the results clearly indicate that chronic exposure to low levels of TBT, TPT, EE2 and binary mixtures of TBT plus EE2 and TPT plus EE2 are genotoxic to zebrafish, which may suggest that wild fish populations may be under increased DNA damage in areas contaminated by these endocrine disrupting chemicals.

The use of biomarkers in biomonitoring: a 2-tier approach assessing the level of pollutant-induced stress syndrome in sentinel organisms

The paper outlines a 2-tier approach for wide-scale biomonitoring programmes. To obtain a high level of standardization, we suggest the use of caged organisms (mussels or fish). An "early warning", highly sensitive, low-cost biomarker is employed in tier 1 (i.e. lysosomal membrane stability (LMS) and survival rate, a marker for highly polluted sites). Tier 2 is used only for animals sampled at sites in which LMS changes are evident and there is no mortality, with a complete battery of biomarkers assessing the levels of pollutant-induced stress syndrome. Possible approaches for integrating biomarker data in a synthetic index are discussed, along with our proposal to use a recently developed Expert System. The latter system allows a correct selection of biomarkers at different levels of biological organisation (molecular/cellular/tissue/organism) taking into account trends in pollutant-induced biomarker changes (increasing, decreasing, bell-shape). A selection of biomarkers of stress, genotoxicity and exposure usually employed in biomonitoring programmes is presented, together with a brief overview of new biomolecular approaches.

In vivo genotoxicity of mercury chloride and lead acetate: Micronucleus test on acridine orange stained fish cells

The genotoxic effects of mercury chloride and lead acetate were evaluated in vivo using the micronucleus (MN) assay on acridine-orange (AO) stained peripheral blood erythrocytes, gill and fin epithelial cells of Carassius auratus auratus. Fish were exposed to three different concentrations of mercury chloride (MC) (1 microg/, 5 microg/L and 10 microg/L) and lead acetate (LA) (10 microg/L, 50 microg/L and 100 microg/L) for 2, 4 and 6 days. A single dose of 5 mg/L cyclophosphamide was used as a positive control. In addition to micronuclei, nuclear buds (NBs) were assessed in the erythrocytes. The ratio of polychromatic and normochromatic erythrocytes (PCE/NCE) in peripheral blood was also evaluated to assess cytotoxicity. MN frequencies in all three tissues were elevated in fish exposed to both LA and MC. However, NBs showed different sensitivity to metal treatments. MN frequencies in both control and treated fish were highest in gill cells and generally lower in erythrocytes and fin cells. PCE/NCE rations decreased in relation to MC and LA treatments. The results of this study indicate that LA and MC have genotoxic and cytotoxic damage in fish and confirmed that AO staining is a suitable technique for in vivo MN test in fish.

Formation of micronuclei in erythrocytes of the fathead minnow (Pimephales promelas) after acute treatment with mitomycin C or cyclophosphamide

Despite the widespread use of the fathead minnow in ecotoxicology, there have been relatively few studies on genotoxicity biomarkers in this small, warm-water fish species. Consequently, we investigated the effect of two known genotoxins, mitomycin C and cyclophosphamide, on micronucleus induction in spleen and peripheral blood erythrocytes of this species. Initially, 96-h experiments after intra-peritoneal (i.p.) injections of mitomycin C and cyclophosphamide were undertaken to determine the maximum tolerated dose (MTD). From these studies, MTDs of 10 and 400 mg/kg, respectively, were obtained: doses that were higher than those reported for other fish species. Next, an assessment of micronucleus induction at 1, 2, 4, 8 and 14 days after injection was undertaken for each compound at the MTD. Mitomycin C at 10 mg/kg significantly induced micronuclei in erythrocytes from the spleen, but not from the peripheral blood, at 8 and 14 days. In addition, the overall levels of micronuclei observed were lower than most previously published data from other fish species. In contrast to mitomycin C, treatment with 400 mg/kg cyclophosphamide failed to significantly induce micronuclei in erythrocytes from any of the tissues employed, in contrast to previous reports of significant induction in other species. The reasons for the apparent relative insensitivity of the fathead minnow to these clastogens, with respect to both MTDs and micronucleus induction, are not clear. The fathead minnow, however, has previously been described as relatively insensitive compared to other fish species with respect to selected carcinogens and cytochrome P450 inducers; the latter suggesting that the lack of a significant induction following cyclophosphamide exposure may be due to low metabolic activation in vivo. Consequently, further clarifying work is required to delineate the response shown, considering the extensive use of this species in ecotoxicology research and regulatory testing.

Assessment of the genotoxicity in toad Bufo raddei exposed to petrochemical contaminants in Lanzhou Region, China

Single cell gel electrophoresis or comet assay, micronucleus (MN) test and global DNA methylation detection were used to assess the genotoxicity in toad Bufo raddei exposed to the petrochemical (mainly oil and phenol) polluted area in Lanzhou Region (LZR) comparing with a relatively unpolluted area in Liujiaxia Region (LJXR). The results from the present study indicated that DNA damage and MN frequency in toad from LZR were significantly higher than those from LJXR at the same sampling month, whereas the degree of global DNA methylation was lower, which implies that the petrochemical contaminants at environmental level in LZR were genotoxic to B. raddei. The degree of genotoxic damage was obviously related with the extent of pollution among the three sampling months in LZR. The significantly positive correlations between DNA damage and concentrations of oil and/or phenol existed in liver cells but erythrocytes, implying that liver is more suitable as a sentinel tissue for the assessment of genotoxic impact of low-level contamination. The results from both comet assay and global DNA methylation detection on liver cells showed that the genotoxicity varied significantly with oil and/or phenol concentrations, suggesting that these two methods are relatively sensitive and suitable for monitoring the genotoxicity of petrochemical pollutants on amphibians.