In vivo genotoxic effects of mercuric chloride in rat peripheral blood leucocytes using comet assay

In vivo genotoxic effects of commercial grade cypermethrin on fish peripheral erythrocytes

The study explicates the genotoxic effects of commercial grade cypermethrin on peripheral erythrocytes of Catla catla, chronically exposed to two environmentally relevant concentrations. The fish was treated with sub-lethal concentrations 0.12 μg/L and 0.41 μg/L (1/10th and /1/3rd of 96 h LC₅₀ ) of cypermethrin for 45 days. DNA damage in the exposed fish was assessed using alkaline comet assay, presence of micronuclei (MN), erythrocyte nuclear and cytoplasmic abnormalities. Exposure to cypermethrin induced a dose-dependent increase in percent DNA damage, micronucleus frequency and erythrocyte abnormalities. Nuclear anomalies such as notched nuclei, lobed nuclei, bridged nuclei, and deformed nuclei; and cytoplasmic anomalies like anisochromasia, vacuolated cytoplasm, lobed cells, and echinocytes were observed. The findings revealed the genotoxic potential of commercial formulations pyrethroid cypermethrin at concentrations found in the environment and their potential deleterious effects on nontarget aquatic organisms.

Toxicological effect of sumithion pesticide on the hematological parameters and its recovery pattern using probiotic in Barbonymus gonionotus

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Sumithion induced hematoxicity and their recovery pattern in Barbonymus gonionotus was measured.

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Sumithion induces severe formation and prevalence of micronuclei and significantly (p< 0.05) increased white blood cells.

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Blood glucose, red blood cell, hematocrit, and hemoglobin were found to be decreased after the exposure of sumithion.

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In recovery experiment, the recovery rate was significantly higher in probiotic treated groups than other treatments.

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Fish micronucleus and hematology is an effective biomarker for toxicity test of an organophosphate.

The experiment was conducted to clarify sumithion induced hematoxicity in silver barb (Barbonymus gonionotus) through in vivo exposures (25 % and 50 % of LC₅₀ of sumithion) and subsequent recovery patterns using normal and probiotic treated feed were also assessed. Three treatments each incorporating three replications were used in the experiment for different days (1, 7, 14, 21, and 28). Treatment T₁ was control (0 mg/L), and two concentrations, such as 2.61 mg/L (25 % of 96 h LC₅₀), 5.21 mg/L (50 % of 96 h LC₅₀) were used as Treatment T₂ and T₃, respectively. After 28 days of exposure to pesticide half of the fishes of T₂ and T₃ were reared in sumithion free water with normal (T₂N, T₃N) and probiotic treated feed (T₂P, T₃P). The median lethal concentration (50 %) for 96 h was 10.42 mg/L. In pesticide-treated groups, values of each hematological parameter (blood glucose, red blood cell, hematocrit, and hemoglobin) decreased but prevalence and severity of micronucleus and white blood cells increased significantly (p< 0.05) with concentration and time duration. Other blood indices including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were correspondingly changed in comparison to the control. In the recovery experiment, the silver barb recovered spontaneously, but the recovery rate was significantly higher in probiotic treated groups than normally treated groups in time and duration reliant fashion. In conclusion, persistent sublethal dosages of sumithion caused hematological abnormalities in silver barb. Probiotic supplement can recover the damage but only 28 days of recovery is not enough to recover the total alterations.

Malathion-Induced Hematoxicity and Its Recovery Pattern in Barbonymus gonionotus

An experiment was conducted to assess malathion-induced hematological responses of Barbonymus gonionotus (silver barb) and its recovery patterns in malathion-free water. Fish (45 days old) were exposed to two sublethal concentrations, namely, 25% and 50% (i.e., 3.78 and 7.56 ppm) of LC₅₀ (15.13 ppm) of malathion for 28 days, followed by a postexposure recovery period for the same time. The hematological parameters were examined after 1, 7, 14, 21, and 28 days of exposure as well as after the postexposure recovery time. Except in the case of the control group (0% of malathion), the obtained results revealed that malathion exposure resulted in significantly (p < 0.05) higher prevalence and severity of micronucleus and lower values of Hb, PCV, and RBC and significantly higher values of WBC in a concentration- and time-dependent manner. The values of blood glucose, MCV, MCH, and MCHC showed mixed trends during the experiment. During the recovery period, all blood parameters (micronucleus, glucose, Hb, PCV, RBC, WBC, MCV, MCH, and MCHC) partially recovered, which means that the recovery period was not long enough for the organisms to recover from the previous exposure. The study thus confirms that hematology is a sensitive indicator for fish to detect toxicity caused by different chemicals. Changes in these parameters can provide useful information about environmental conditions and risk assessment of aquatic organisms.

Attenuation of Hg(II)-induced cellular and DNA damage in human blood cells by uric acid

Mercury (Hg) is a widespread environmental pollutant and toxicant which induces multiple organ damage in humans and animals. Hg toxicity is mediated by the induction of oxidative stress in target cells. We have used uric acid (UA), a potent antioxidant found in biological fluids, to protect human red blood cells (RBC) and lymphocytes against Hg-mediated cell, organelle and genotoxicity. RBC were incubated with HgCl2, an Hg(II) compound, either alone or in presence of UA. Incubation of RBC with only HgCl2 increased production of nitrogen and oxygen radical species, enhanced methemoglobin levels, heme degradation, free ferrous iron, oxidation of proteins and membrane lipids and reduced antioxidant capacity of cells. UA enhanced the antioxidant capacity of RBC and restored metabolic, plasma membrane-bound and antioxidant enzyme activities. Scanning electron microscopy showed that UA prevented HgCl2-mediated morphological changes in RBC. HgCl2 dissipated the mitochondrial membrane potential and increased lysosomal membrane damage in lymphocytes, but UA pre-treatment attenuated these effects. Genotoxicity analysis by comet assay showed that UA protected lymphocyte DNA from HgCl2-induced damage. Importantly, UA itself did not exhibit any deleterious effects in either RBC or lymphocytes. Thus, UA protects human blood cells from Hg(II)-mediated oxidative damage reducing the harmful effects of this extremely toxic metal. We suggest that UA performs a similar protective role in the plasma against heavy metal toxicity.

Biological effects of multimetal (Ni, Cd, Pb, Cu, Cr, Zn) mixture in rainbow trout Oncorhynchus mykiss: Laboratory exposure and recovery study

The present study tested the biological consequences of exposure to a multimetal mixture as a multiple chemical stressor on Oncorhynchus mykiss at molecular, cellular, physiological and whole-organism levels and on biomarker responses of this fish during the depuration period. To represent environmentally relevant multiple chemical stressors, in our study, we used the mixture of Zn, Cu, Ni, Cr, Pb and Cd at the concentrations corresponding to Maximum-Permissible-Concentrations (MPCs) acceptable for the EU inland waters. This study was undertaken with a view to elucidate if changes in the MPC of the test mixture components (Ni, Pb, Cd) could cause significantly different biomarker responses in O. mykiss from those previously determined in the carnivorous and omnivorous fishes exposed to the mixture of the same metals but at different MPCs of Ni, Pb and Cd. This study has revealed that exposure to mixtures of metals at MPC produces genotoxic effects in fish blood erythrocytes and a lethargic effect on O. mykiss behaviour, and, also, significantly increases the levels of Cd, Cr and Ni accumulated in the gills tissue. O. mykiss successfully depurated Cr and Ni in less than 28 days, however, the level of Cd decreased by only approximately 40% over the same period. A significant capacity of O. mykiss to restore its DNA integrity (Comet assay) after exposure to metal mixtures was revealed. However, the 28-day recovery period proved to be insufficiently long for erythrocytes with nuclear abnormalities to recover to the unexposed level. In conclusion, changes in the MPCs of Ni, Pb and Cd in the test mixture produce biological effects similar to those previously determined in S. salar, R. rutilus and P. fluviatilis exposed to the mixture of the same metals but at lower MPCs of Ni and Pb and at higher MPC of Cd.

Genetic damage in human populations at mining sites in the upper basin of the San Jorge River, Colombia

Contamination with mining wastes affects the environmental health and public, especially the human populations that live in these environments. The aim of this study was to evaluate the genotoxicity and levels of mercury (Hg) and arsenic (As) in blood samples from human populations exposed to mining activities in the upper basin of the San Jorge River. A total of 100 individuals participated in the study, 50 as an exposed group (Bocas de Ure = 15 individuals, Mina el Alacrán = 19 individuals, Torno Rojo = 16 individuals) and 50 individuals participated as the control group. Hg and As contents in blood samples were analyzed with atomic absorption spectrophotometry. A comet assay in peripheral blood lymphocytes and a micronucleus (MN) cytome assay (BMCyt) in exfoliated buccal cells were used to assess the effects of exposure to heavy metals on human communities located in mining areas. Higher concentrations of Hg and As were observed in human populations located in mining areas. The comet assay and BMCyt data revealed DNA damage and cell death in human communities located in mining areas. A positive association between blood arsenic and genetic damage was found. These data confirm the public health risk of the population near mining sites. Our findings suggest that populations that live at sites close to mining activities have high contents of heavy metals and genotoxic effects, representing a risk to human health.

Aberrations of the peripheral erythrocytes and its recovery patterns in a freshwater teleost, silver barb exposed to profenofos

The present experiment was conducted to explicate the genotoxic effects of profenofos, an organophosphate insecticide, on the erythrocytes of silver barb (Barbonymus gonionotus). Silver barb were exposed to a solution of 10% and 50% of lethal concentrations (LC₅₀) of profenofos as sub-lethal concentrations at different days (1, 7, 15, and 30 d), along with a control (0% profenofos). Subsequent recovery patterns were assessed allowing the fish exposed to profenofos free water for the same period that they were exposed to profenofos. Our results revealed that with the progression of time and concentration, fish exposed to profenofos showed significantly (p < .05) higher level of erythrocytic nuclear abnormalities (ENA) such as micronuclei, bi-nuclei, degenerated nuclei, notched nuclei, nuclear bridge and nuclear buds, as well as erythrocytic cellular abnormalities (ECA) such as echinocytic, elongated, fusion, spindle, tear-drop and twin shaped cells. After exposure, the silver barb recovered spontaneously, and the abnormal erythrocytic parameters were normalized with a concentration- and duration-dependent fashion. Therefore, these abnormalities and their recovery can be used to assess the toxic levels of pesticides on aquatic organisms. There is great potential to use this technique as in vivo to predict susceptibility of aquatic animals to environmental pollution.

Advances in Understanding How Heavy Metal Pollution Triggers Gastric Cancer

With the development of industrialization and urbanization, heavy metals contamination has become a major environmental problem. Numerous investigations have revealed an association between heavy metal exposure and the incidence and mortality of gastric cancer. The mechanisms of heavy metals (lead, cadmium, mercury, chromium, and arsenic) contamination leading to gastric cancer are concluded in this review. There are four main potential mechanisms: (1) Heavy metals disrupt the gastric mucosal barrier by decreasing mucosal thickness, mucus content, and basal acid output, thereby affecting the function of E-cadherin and inducing reactive oxygen species (ROS) damage. (2) Heavy metals directly or indirectly induce ROS generation and cause gastric mucosal and DNA lesions, which subsequently alter gene regulation, signal transduction, and cell growth, ultimately leading to carcinogenesis. Exposure to heavy metals also enhances gastric cancer cell invasion and metastasis. (3) Heavy metals inhibit DNA damage repair or cause inefficient lesion repair. (4) Heavy metals may induce other gene abnormalities. In addition, heavy metals can induce the expression of proinflammatory chemokine interleukin-8 (IL-8) and microRNAs, which promotes tumorigenesis. The present review is an effort to underline the human health problem caused by heavy metal with recent development in order to garner a broader perspective.

Mercury-induced genotoxicity in marine diatom (Chaetoceros tenuissimus)

In this paper, we present an evaluation of genotoxic responses in marine diatom, Chaetoceros tenuissimus, isolated from Kandla Creek (lat 23.03° N, long 70.22° E), Gujarat, India, in terms of impairment of DNA integrity as a function of their exposure to elevated levels of mercury (Hg) under laboratory conditions. DNA integrity in C. tenuissimus was determined by partial alkaline unwinding assay. To our knowledge, this is the first such genotoxicity study to be conducted on marine diatom cultures towards understanding the relationship between Hg toxicity and DNA damage. Furthermore, we studied the impact of Hg on the growth of C. tenuissimus as a function of their exposure to enhanced levels of Hg in terms of decreasing chlorophyll a (chl a) concentrations. The data show the genotoxic effect of Hg on the growth of C. tenuissimus as well as DNA integrity to a great extent. Based on the results of our investigations, it is suggested that C. tenuissimus can be used as sentinel species for bio-monitoring of pollution due to genotoxic contaminants.

DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO₃)₂ exposure and its associated adverse health effects.

In vivo genotoxicity and cytotoxicity assessment of cadmium chloride in peripheral erythrocytes of Labeo rohita (Hamilton)

Cadmium chloride (CdCl2) induced genotoxicity and cytotoxicity has been assessed in the peripheral blood erythrocytes of freshwater fish Labeo rohita exposed to 0.37 and 0.62mg/L of CdCl2 in water for 100 days. The blood samples of the fish were collected at different intervals (days 1, 3, 5, 10, 15, 30, 60 and 100) of exposure period to analyze DNA damage using comet assay and the occurrence of micronuclei and other cellular anomalies. The results of comet assay showed a significant increase in the mean percentage of tail DNA at both the concentrations. Exposure to CdCl2 also induced micronuclei in addition to many nuclear abnormalities such as nuclear bud, binucleates, lobed, notched and vacuolated nuclei. Cytoplasmic abnormalities like echinocytes, acanthocytes, notched, microcytes and cells with vacuolated cytoplasm were also observed. The metal exposed groups showed significant variation in the frequency of cellular abnormalities as well as the extent of DNA damage in comparison to controls. These frequencies increased significantly (p<0.05) in concentration dependent manner, peaking on 10th day while a decreasing trend was observed after 15 days of the exposure period.

Assessment of genotoxicity of inorganic mercury in rats in vivo using both chromosomal aberration and comet assays

The major objective of the present investigation was to assess the genotoxic effects of mercuric chloride (HgCl2), an inorganic mercury (Hg), in rats ( Rattus norvegicus) using two different genetic endpoints, namely, chromosomal aberration (CA) and comet assays following both short-term (acute) and long-term (chronic) exposures. The study showed that the acute exposures to HgCl2 at 2 and 5 mg/kg body weight (b.w.) induced nonsignificant effects. HgCl2 at 10 and 12 mg/kg b.w. was significantly toxic and is exhibited by the induction of different types of CAs like chromatid breaks, chromosomal breaks, clumps and damaged cells and types of comets. HgCl2 at 15 mg/kg b.w. was found to be highly toxic, as mitostatic condition of cells were observed in CA assay. Chronic exposure to the lowest dose (2 mg/kg b.w.) of HgCl2 for 15 consecutive days produced a significant genotoxicity. Although Hg was found to induce both DNA strand breakage and chromosomal breaks in a dose-dependent manner, the results of the present investigation showed that the combination of comet and CA assays provided a better choice for assessing the genotoxicity of inorganicHg.

Genotoxic effects of Tabebuia impetiginosa (Mart. Ex DC.) Standl. (Lamiales, Bignoniaceae) extract in Wistar rats

Tabebuia sp. is native to tropical rain forests throughout Central and South America. Although the biological and pharmacological effects of bark extracts have been intensely studied, little is known on the extract obtained from the flower. Herein, the genotoxic potential of a flower extract from T. impetiginosa ("ipê roxo") on the blood and liver cells of Wistar rats was evaluated. Experimental procedures involved only male animals. Graduated concentrations of the extract, viz., 100, 300 and 500 mg kg(-1) of body weight, were gavage-administered and 24 h latter cells were collected and processed for analysis. With the exception of the 100 mg kg(-1) dose, a significant increase in DNA damage was noted, when compared with a negative control group. Although the genotoxic potential of this extract was higher in liver cells, the response in both tissues was related to dose-dependency. Even though DNA damage can be corrected before conversion into mutations, further study is recommended to arrive at a better understanding of incurred biological effects.

Quercetin protects human-derived liver cells against mercury-induced DNA-damage and alterations of the redox status

Aim of this study was to investigate the cytotoxic and genotoxic properties of inorganic and organic mercury compounds, i.e., HgCl(2) and methylmercury (MeHg). In addition, the DNA-protective and antioxidant effects of the flavonoid quercetin (QC) were studied. All experiments were conducted with human-derived liver cells (HepG2), which possess antioxidant and drug-metabolizing enzymes in an inducible form. 8-Hydroxydeoxyguanosine (8-OHdG) and comet formation were monitored as endpoints of DNA damage. The impact of the metal compounds on the redox status was also investigated, since it is assumed that their toxic effects are due to oxidative damage. A number of biochemical parameters related to oxidative stress, namely glutathione, malondialdehyde, protein carbonyl and formation of reactive oxygen species (ROS) were measured after treatment of the cells with the mercury compounds in the presence and absence of quercetin. To elucidate the mechanisms that underlie the effects of QC, three protocols (pre-, simultaneous and post-treatment) were used. Both mercury compounds (range 0.1-5.0μM) caused induction of DNA migration and formation of 8-OHdG. In combination with the flavonoid (range 0.1-5.0μM), DNA-protective effects of QC were observed after pre- and simultaneous treatment but not when the flavonoid was added after treatment with the metal compounds. Exposure to the metal compounds led also to substantial changes of all parameters of the redox status and co-treatment experiments with QC showed that these alterations are reversed by the flavonoid. Taken together, the results of our experiments indicate that these two mercury compounds cause DNA damage and oxidative stress in human-derived liver cells and that the flavonoid reduces these effects. Since the concentrations of the metals and of the flavonoids used in the present work reflect human exposure, our findings can be taken as an indication that QC may protect humans against the adverse effects caused by the metal.

In vitro mercury exposure on spermatozoa from normospermic individuals

Epidemiological evidence suggests that exposure to industrial metal aerosols is detrimental to the male reproductive system. Oxidative stress has been identified as a crucial factor leading to male factor infertility largely due to peroxidative damage to the sperm cell membrane. The objectives of the present study were to test the effect of mercury in the concentration range from 50 to 800 micromol(-1), in vitro, on the sperm membrane and DNA integrity, motility and acrosomal status of human spermatozoa. We found a significant increase in the Lipo Per Oxidation (LPO) indicating the deleterious effect of mercury on the sperm membrane integrity. This effect was prominent at the concentration of 800 microM mercury. There was also a strong negative correlation between LPO rate and percentage of viable spermatozoa (r = -0.941, p<0.001). Data obtained from SCGE assay technique revealed that mercury is capable of inducing DNA breaks in the sperm nuclei. Almost, 88% of DNA breaks were of double-stranded. The correlation between LPO rate and percentage of DNA breaks was found to be 0.918 (p<0.001). Performing the gelatin digestion test indicates that mercury was able to alter the integrity of acrosomal membranes showing an abnormal acrosome reaction. In this regard, a strong correlation was found between LPO rate and percentage of halos (r = -0.893, p<0.001). Taken together, mercury induced membrane impairments, lowered sperm viability, DNA breaks and a decreased rate in the acrosome reaction of human spermatozoa leading to sperm dysfunction. Entering mercury in the male gonads and seminal plasma may exert deleterious effects on the human spermatozoa. Hence, considering the wide spread use of mercury and its compounds, these metals should regarded with more concern.

Mercuric dichloride induces DNA damage in human salivary gland tissue cells and lymphocytes

Amalgam is still one of the most frequently used dental filling materials. However, the possible adverse effects especially that of the mercuric component have led to continued controversy. Considering that mercury may be released from amalgam fillings into the oral cavity and also reach the circulating blood after absorption and resorption, it eventually may contribute to tumorigenesis in a variety of target cells. The present investigation focuses on genotoxic effects below a cytotoxic dose level of mercuric dichloride (HgCl(2)) in human samples of salivary glands and lymphocytes to elucidate a possible role in tumor initiation. DNA migration due to single strand breaks, alkali labile sites and incomplete excision repair was quantified with the aid of the single cell microgel electrophoresis (Comet) assay. The concepts of Olive Tail Moment, percentage of DNA in the Tail and Tail Length were used as measures of DNA damage. To control for cytotoxic effects, the trypan blue exclusion test was applied. Human samples of the parotid salivary gland and lymphocytes of ten donors were exposed to HgCl(2)concentrations from 1 to 50 microM. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) served as controls. Increasing dose-dependent DNA migration could be demonstrated after exposure to HgCl(2) in cells of the salivary glands and lymphocytes. In both cell types a significant increase in DNA migration could be shown starting from HgCl(2)concentrations of 5 microM in comparison to the negative control. The viability of the cell systems was not affected except at the highest concentration (50 microM) tested. These data indicate genotoxic effects of mercuric dichloride in human salivary glands and lymphocytes at concentrations not leading to cytotoxic effects or cell death. Consequently, a contributory role in oral salivary gland tumor initiation warrants further investigation.

Zinc-induced DNA damage and the distribution of metals in the brain of grasshoppers by the comet assay and micro-PIXE

The distribution and concentration of selected elements by PIXE method and DNA damage using comet assay in brains of 1st instars of grasshoppers Chorthippus brunneus from unpolluted (Pilica) and polluted (Olkusz) site, additionally exposed to various doses of zinc during diapause or after hatching, were measured. We tried to assess the degree of possible pre-adaptation of the insects to heavy metals and evaluate the utility of these parameters in estimation of insect exposure to industrial pollutants. Additionally, the mechanism of zinc toxicity for grasshopper brains was discussed. We observed the correlation between experimental zinc dose, zinc contents in the brain and DNA damage in neuroblasts, but only in groups exposed to lower zinc concentration. For higher zinc concentration the amount of the metal in brain and DNA damage remained at the control level. Some site-related differences in DNA damage between grasshoppers from Pilica and Olkusz were observed during short-term exposure (after hatching). Significant increase in the calcium contents in the brain, proportional to zinc concentration in sand, was also observed, especially in the offsprings from Olkusz. The results may be the basis for further searching for molecular mechanisms of defense against heavy metals in insects living in polluted habitats.

Bull Spermatozoa under Mercury Stress

Defective sperm function is the most prevalent cause of male infertility and is difficult to treat. This study was designed to evaluate the effect of mercuric chloride (HgCl2) at 50-300 micromol/l concentration range, in vitro, on the sperm membrane and DNA integrity, viability, reduced glutathione (GSH) content and acrosomal status of the bull spermatozoa. The samples were processed for sperm analyses using semen-diluting fluid [phosphate-buffered saline (PBS), pH 7.2]. I recorded a meaningful increase in the lipid peroxidation (LPO) rate and a drastic fall in the spermatocrit values under mercury additions, dominantly at 300 microM mercury concentration, indicating a deleterious effect of mercury on the sperm membrane intactness. There was also a strong negative correlation between LPO rate and percentage of viable spermatozoa (r = -0.9, p < 0.001). GSH content was significantly impaired. Data obtained from Comet assay [single-cell gel electrophoresis (SCGE)] technique revealed that mercury is capable of inducing DNA breaks in the sperm nuclei. Interestingly, 90% of DNA breaks were double-stranded. The correlation between LPO rate and percentage of DNA breaks was found to be 0.9 (p < 0.001). Results of the gelatin test indicate that mercury is capable of altering the integrity of acrosomal membranes, showing an abnormal acrosome reaction. In this regard, a strong correlation was found between LPO rate and percentage of halos (r = -0.9, p < 0.001). In conclusion, mercury proved to be a potential oxidant in the category of 'environmental factors' to bull spermatozoa. Hence, considering the widespread use of mercury and its compounds, these metals should be regarded with more concern.

Comparative study of the comet assay and the micronucleus test in amphibian larvae (Xenopus laevis) using benzo(a)pyrene, ethyl methanesulfonate, and methyl methanesulfonate: establishment of a positive control in the amphibian comet assay

The present investigation explored the potential use of the comet assay (CA) as a genotoxicity test in the amphibian Xenopus laevis and compared it with the French standard micronucleus test (MNT). Benzo[a]pyrene (B[a]P), methyl methanesulfonate (MMS), and ethyl methanesulfonate (EMS) were used as model compounds for assessing DNA damage. Damage levels were measured as DNA strand breaks after alkaline electrophoresis of nuclei isolated from larval amphibian erythrocytes using the CA in order to establish a positive control for further ecotoxicological investigations. The results led to the selection of MMS as a positive control on the basis of the higher sensitivity of Xenopus laevis to this compound. The CA and MNT were compared for their ability to detect DNA damage with the doses of chemical agents and exposure times applied. EMS and MMS were shown to increase micronucleus and DNA strand break formation in larval erythrocytes concurrently. However, B[a]P increased micronucleus formation but not that of DNA strand breaks. Time-dose experiments over 12 days of exposure suggest that the CA provides an earlier significant response to genotoxicants than does the MNT. In Xenopus the CA appears to be a sensitive and suitable method for detecting genotoxicity like that caused by EMS and MMS. It can be considered a genotoxicity-screening tool. The results for B[a]P show that both tests should be used in a complementary manner on Xenopus.

Evaluation of inflammatory reactions and genotoxic effects after exposure of nasal respiratory epithelia to benzene

BACKGROUND

The aim of this study was to identify inflammatory changes as well as genotoxic effects in cultivated human respiratory epithelial cells after in vitro exposure to benzene.

METHODS

Primary cell cultures of nasal respiratory mucosa were exposed to synthetic air enriched with 5,000 microg/m(3) of benzene at an air/liquid interface over 8 h and then to synthetic air only over the following 24 h. Controls were continuously exposed to synthetic air over 32 h. To detect inflammatory reactions, release of prostaglandin E(2) was quantified using a competitive enzyme immunoassay. The Comet Assay was used to quantify the ratio of apoptotic cells with benzene-induced DNA fragmentation.

RESULTS

Prostaglandin release as well as DNA fragmentation increased after 8 h of exposure and remained elevated throughout the following 24 h but did not increase in controls.

CONCLUSIONS

High concentrations of benzene induce an inflammatory response and possibly fragmentation of DNA in respiratory epithelial cells. These findings have to be discussed with respect to possible mutagenic or carcinogenic effects of benzene in nasal respiratory cells.

In vivo genotoxic effect of nickel chloride in mice leukocytes using comet assay

DNA damage induced by nickel chloride (NiCl2) in leucocytes of Swiss albino mice has been studied in vivo. The comet assay or the alkaline single cell gel electrophoresis (SCGE) assay was used to measure the DNA damage. The mice were administered orally with acute doses of 3.4, 6.8, 13.6, 27.2, 54.4 and 108.8 mg/kg body weight (b.wt.) NiCl2. Samples of whole blood were collected at 24, 48 and 72 h, first week and second week post-treatment for alkaline SCGE assay to study single/double strand breaks in DNA. A significant increase in mean comet tail length indicating DNA damage was observed with NiCl2 at 24, 48 and 72 h post-treatment (P<0.05). A gradual decrease in the mean tail length was observed at 72 h post-treatment indicating repair of the damaged DNA. The mean tail length showed a dose-related increase and time dependent decrease after treatment with NiCl2 when compared to controls. The study also confirms that the comet assay is a sensitive and rapid method to detect DNA damage caused by heavy metals like nickel (Ni).