Number Of Micronucleated Cells Research Articles

Cytogenetic biomonitoring in mucopolyssacharosis I, II and IV patients treated with enzyme replacement therapy

Background and objectives: The aim of this study was to evaluate genotoxicity and mutagenicity in peripheral blood and buccal mucosal cells in mucopolysaccharidosis (MPS) I, II or VI patients.Methods: A total of 12 patients with MPS type I, II and VI attended at the Institute of Genetics and Inborn Errors of Metabolism treated with enzyme replacement therapy (ERT) and 10 healthy control volunteers were included in this study. Mechanically exfoliated cells from cheek mucosa (left and right side) were used to micronucleus test and single cell gel (comet) assay in peripheral blood cells.Results: The results of this study detected the presence of genetic damage in peripheral blood for all individuals with MPS treated with ERT, regardless of type of MPS as depicted by tail moment results. In addition, an increased number of micronucleated cells were found in buccal cells of MPS type II patients. It was also observed an increase of other nuclear alterations closely related to cytotoxicity as depicted by the frequency of pyknosis, karyolysis and karyorrhexis in buccal mucosa cells of MPS VI patients (p < 0.05).Conclusion: Taken together, such results demonstrate that metabolic alterations induced by the enzymatic deficiency characteristic of MPS associated with ERT therapy can induce genotoxicity and mutagenicity in peripheral blood and buccal mucosa cells, respectively. This effect appears to be more pronounced to MPS II.

Effect of hexavalent chromium on proliferation and differentiation to adipocytes of 3T3-L1 fibroblasts

Heavy metals contamination has become an important risk factor for public health and the environment. Chromium is a frequent industrial contaminant and is also used in orthopaedic joint replacements made from cobalt–chromium-alloy. Since hexavalent chromium (Cr(VI)) was reported as genotoxic and carcinogenic in different mammals, to further evaluate its cytotoxicity, we investigated the effect of this heavy metal in the proliferation and differentiation to adipocytes of 3T3-L1 fibroblasts. These cells, after the addition of a mixture containing insulin, dexamethasone and methylisobutylxanthine, first proliferate, a process known as mitotic clonal expansion (MCE), and then differentiate to adipocytes. In this differentiation process a key transcription factor is induced: peroxisome proliferator-activated receptor gamma (PPAR gamma). We found that treatment of 3T3-L1 fibroblasts with potassium chromate inhibited proliferation in exponentially growing cells and MCE as well as differentiation. A decrease in PPAR gamma content, evaluated by western blot and immunofluorescence, was found in cells differentiated in the presence of chromium. On the other hand, after inhibition of differentiation with chromium, when the metal was removed, differentiation was recovered, which indicates that this may be a reversible effect. We also found an increase in the number of micronucleated cells after treatment with Cr(VI) which is associated with genotoxic effects. According to our results, Cr(VI) is able to inhibit proliferation and differentiation to adipocytes of 3T3-L1 fibroblasts and to increase micronucleated cells, which are all indicative of alterations in cellular physiology and therefore, contributes to further elucidate the cytotoxic effects of this heavy metal.

MRC5 and QU-DB bystander cells can produce bystander factors and induce radiation bystander effect.

Radiation damages initiated by radiation-induced bystander effect (RIBE) are not limited to the first or immediate neighbors of the irradiated cells, but the effects have been observed in the cells far from the irradiation site. It has been postulated that bystander cells, by producing bystander factors, are actively involved in the propagation of bystander effect in the regions beyond the initial irradiated site. Current study was planned to test the hypothesis. MRC5 and QU-DB cell lines were irradiated, and successive medium transfer technique was performed to induce bystander effects in two bystander cell groups. Conditioned medium extracted from the target cells was transferred to the bystander cells (first bystander cells). After one hour, conditioned medium was substituted by fresh medium. Two hours later, the fresh medium was transferred to a second group of non-irradiated cells (second bystander cells). Micronucleated cells (MC) were counted to quantify damages induced in the first and second bystander cell groups. Radiation effect was observed in the second bystander cells as well as in the first ones. Statistical analyses revealed that the number of MC in second bystander subgroups was significantly more than the corresponding value observed in control groups, but in most cases it was equal to the number of MC observed in the first bystander cells. MRC5 and QU-DB bystander cells can produce and release bystander signals in the culture medium and affect non-irradiated cells. Therefore, they may contribute to the RIBE propagation.

Habitat monitoring and genotoxicity in Ucides cordatus (Crustacea: Ucididae), as tools to manage a mangrove reserve in southeastern Brazil

In Brazil, the state of São Paulo contains both preserved areas (Juréia-Itatins Ecological Station) and extremely impacted ones (Cubatão Municipality). This study evaluated the concentrations of five metals (Cu, Cd, Cr, Pb, and Hg) in two mangroves with different levels of anthropogenic impact and the apparent genotoxicity to Ucides cordatus. Water and sediment samples were obtained, and metal concentrations were determined with an atomic absorption spectrophotometer. The genotoxic impact was quantified based on the number of micronucleated cells per 1,000 analyzed (MN‰), using hemolymph slides stained with Giemsa. Metal concentrations in water were below the detection limit, except for lead, although no significant difference was observed between the areas (P > 0.05). Sediment from Cubatão had higher concentrations of Cd, Pb, Cr, and Cu than sediment from Juréia-Itatins (P < 0.05), but no significant differences in metal concentrations were detected among depth strata of the sediment (P > 0.05). Crabs from Cubatão had a 2.6 times higher mean frequency of micronucleated cells (5.2 ± 1.8 MN‰) than those from Juréia-Itatins (2.0 ± 1.0 MN‰; P < 0.0001). The more-polluted conditions found in the mangrove sediments of Cubatão were reflected in the micronucleus assay, demonstrating their genotoxic effect; however, genetic damage should be attributed to a synergistic effect with other kinds of pollutants previously recorded in different environments of Cubatão. U. cordatus proved to be an excellent bioindicator of mangrove pollution. This study established, for the first time, the normal frequency of MN‰ in a population of this species within an ecological station.

Predictive value of micronucleus count in cervical intraepithelial neoplasia and carcinoma

A micronucleus is a small additional nucleus formed due to chromosomal loss or fragmentation. The aim of this study was to assess the utility of micronucleus count as a screening tool in cervical cancer. A total of 132 cases consisting of 42 pre-neoplastic and neoplastic cases and 90 non-neoplastic cases were studied. Only routine Papanicolaou-stained cervical smears were used. In each smear, the number of micronucleated cells and binucleated cells were counted under oil immersion and expressed as a count per 1,000 cells. The micronucleated and binucleated cell counts in pre-neoplastic, neoplastic and non-neoplastic categories were compared for statistical significance. The counts were also correlated with age, duration of marital life, number of pregnancies and abortions. The micronucleus count and the binucleated cell count were significantly higher in the high -grade squamous intraepithelial lesion (HSIL) and invasive carcinoma categories compared to low -grade squamous intraepithelial lesion (LSIL) and non-neoplastic cases. Receiver operating characteristic (ROC) curve analysis revealed that micronucleus count and binucleated cell count possess a high degree of sensitivity and specificity for identifying HSIL and invasive carcinoma. Our results reveal that micronucleus evaluation in routine Pap smears is a very useful biomarker in cervical cancer screening. The binucleated cell count increases the predictive value of this simple test.

Evaluation of micronucleus frequency by acridine orange fluorescent staining in bucccal epithelial cells of oral submucosus fibrosis (OSMF) patients

Oral submucosus fibrosis (OSMF) is a collagen-related disorder seen in habitual betel quids and smokers. This is a high risk precancerous condition in which the connective tissue fibers of the lamina propria and deeper parts of the mucosa becomes stiff with restricted mouth opening. Patients with severe cases have symptoms like difficulties in chewing, swallowing and speaking. In the present study 25 individuals were gutkha chewers and 25 were OSMF patients (chewing gutkha along with smoking) and 25 individuals were taken as controls. A significant increase in the frequency of micronuclei was observed in OSMF patients (34.4±1.79) as compared to gutkha chewers (14.4±0.73) and controls (4.36±0.27). The number of micronucleated cells in OSMF, gutkha chewers and control groups were 19.84±0.69, 12.6±0.51 and 4.20±0.27, respectively and are significantly different at p<0.05. Acridine orange is used due its fluorescence nature and easier visibility of the micronucleus present in the buccal epithelial cells. It is concluded that chewing gutkha along with smoking is more dangerous for human health as it hastens the incidence of OSMF.

Micronucleus assay as a triage tool for borderline cases of cervical dysplasia

Objective: In cases of cervical carcinogenesis the gradient from low to high-grade lesions is characterized by increasing nuclear atypia and the failure of cellular differentiation. These phenotypic changes are presumed to be accompanied by increased genetic instability that can be documented using the micronucleus (MN) assay in exfoliated cervical cells. Material and methods: This blinded prospective study included 169 samples for final analysis; 119 normal cervical cytology, 18 preinvasive lesions and 33 frank carcinoma. A thin smear was prepared from each sample on a glass slide, which was then stained with acridine orange (a DNA specific dye). Around thousand cells per slide were counted under fluorescent microscope, 20-40 X magnification. Number of micro-nucleated cells and total number of micronuclei were recorded to calculate MN cell ratio and total MN ratio. Results: Micro-nucleated cells as well as the total number of micronuclei show increasing trend towards malignization. By ROC curve analysis, for MN cell ratio of 0.1999, the sensitivity is found to be as high as 91.4% with a specificity of 82.8%. Similar results were obtained when total MN ratios were analyzed. Advantage of combining both the ratios together does not confer any additional benefit in terms of sensitivity and specificity. Key words: micro-nucleus (MN); cervical cancer; lowgrade squamous intraepithelial lesion (LSIL); highgrade squamous intraepithelial lesion (HSIL). DOI: http://dx.doi.org/10.4038/sljog.v33i3.4018 Sri Lanka Journal of Obstetrics and Gynaecology 2011; 33 : 104-111

Comparing the level of bystander effect in a couple of tumor and normal cell lines

Radiation-induced bystander effect refers to radiation responses which occur in non-irradiated cells. The purpose of this study was to compare the level of bystander effect in a couple of tumor and normal cell lines (QU-DB and MRC5). To induce bystander effect, cells were irradiated with 0.5, 2, and 4 Gy of 60Co gamma rays and their media were transferred to non-irradiated (bystander) cells of the same type. Cells containing micronuclei were counted in bystander subgroups, non-irradiated, and 0.5 Gy irradiated cells. Frequencies of cells containing micronuclei in QU-DB bystander subgroups were higher than in bystander subgroups of MRC5 cells (P < 0.001). The number of micronucleated cells counted in non-irradiated and 0.5 Gy irradiated QU-DB cells was also higher than the corresponding values for MRC5 cells (P < 0.001). Another difference between the two cell lines was that in QU-DB bystander cells, a dose-dependent increase in the number of micronucleated cells was observed as the dose increased, but at all doses the number of micronucleated cells in MRC5 bystander cells was constant. It is concluded that QU-DB cells are more susceptible than MRC5 cells to be affected by bystander effect, and in the two cell lines there is a positive correlation between DNA damages induced directly and those induced due to bystander effect.

Modulation of cellular defense processes in human lymphocytes in vitro by a 1,4-dihydropyridine derivative

The aim of this pilot study was to assess whether a compound of the β-carbonyl-1,4-dihydropyridine series (AV-153 or sodium 3,5-bis-ethoxycarbonyl-2,6-dimethyl-1,4-dihydropyridine-4-carboxylate), which has high efficiency in stimulating DNA repair, can simultaneously modulate apoptosis in human cells. Peripheral blood lymphocytes of healthy donors were used in this study. DNA strand-break rejoining was assessed with the alkaline comet assay after a 3-h incubation of lymphocytes in the presence of a wide range of concentrations of AV-153 (10 −10–10 −5 M). Apoptotic and micronucleated (MN) cells were scored in phytohaemagglutinin-stimulated lymphocytes after a 72-h incubation with AV-153, using the standard cytokinesis -blocked micronucleus test. The study revealed dual effects of AV-153 on cellular defense systems against endogenously generated DNA damage: the compound per se simultaneously reduces DNA strand breaks and stimulates apoptosis, with a maximal efficiency of 76% and 42%, respectively; in contrast, after genotoxic stress (2 Gy of gamma-radiation) AV-153 reduces DNA strand breaks, the number of MN cells and apoptotic cells in a similar dose-dependent manner. A maximal efficiency of 67% was found for reduction of DNA strand breaks, while for MN cells and apoptotic cells the efficiencies were, respectively, 47% and 44%. While limited in number, these preliminary studies show the direct correlation between the efficiency of AV-153 in reduction of radiation-induced DNA breaks and MN cells on one side, and in reduction of apoptosis on the other. It suggests that the major target of the compound's action on genotoxic stress is DNA repair, followed by reduction of the number of damaged cells entering apoptosis.

No evidence of chromosome damage in children and adolescents with differentiated thyroid carcinoma after receiving 131I radiometabolic therapy, as evaluated by micronucleus assay and microarray analysis

As (131)I therapy, used to achieve ablation of thyroid gland remnant, can cause chromosome damage in cultured peripheral lymphocytes especially, we investigated whether administration of radioiodine may induce early genome damage in peripheral T lymphocytes of adolescents with differentiated thyroid carcinoma (DTC). We studied 11 patients, aged 14.8 +/- 3.1 years, who assumed (131)I (range: 1.11-4.44 GBq) to ablate thyroid remnant. A blood sample for micronucleus assay and for evaluating expression of some genes involved in the DNA repair or the apoptosis pathways was obtained from each patient 1 h before (T(0)) and 24 (T(1)) and 48 h (T(2)) post-radioiodine administration. Compared to T(0), we did not find any difference in the number of micronucleated cells at both T(1) and T(2) in any subject. Nine out of 11 patients had altered expression levels in a majority of the DNA repair and apoptosis genes at T(1), which decreased at T(2). We demonstrated for the first time that peripheral cells of DTC children and adolescents who received (131)I at a mean dosage of 3.50 +/- 0.37 GBq did not show chromosome damage within 48 h from the end of radiometabolic therapy. This may be due to a prompt activation of the cell machinery that maintains the integrity of the genome to prevent harmful double-strand breaks from progressing to chromosome mutations, either by repairing the lesions or by eliminating the most seriously damaged cells via apoptosis.

Comparative Susceptibility of Kidney and Gill Cells of Medaka Fish (Oryzias latipes) to Spontaneous and X-ray-induced Micronucleus Formation

The frequency of micronucleated cells (MNCs) was measured in acridine orange (AO) stained kidney cells obtained from male and female medaka fish (Oryzias latipes) of known body weight before and after X-irradiation at a dose of 4 Gy. The MNC frequency in the kidney cells obtained from untreated and X-ray treated fish did not vary in correlation with the body weight in either gender, and neither did it show a significant gender-related difference. In both the untreated and treated groups, the number of MNCs in kidney cells per fish appeared to follow a Poisson distribution. These results are in agreement with those previously reported for the MNC frequency in gill cells of medaka fish. The average MNC frequency in kidney cells for the untreated fish was 0.4‰ (12/30000), which was significantly lower than 0.8‰ (24/30000) reported for gill cells. Similarly, a relatively lower frequency of X-ray-induced MNCs was evident for kidney cells (2.2‰; 69/30000) vs. gill cells (6.3‰; 191/30000). These results combined with previous reports support the use of AO to detect micronucleus formation in kidney cells, and further indicate that the kidney cell micronucleus assay can be used as a reliable and coincidently applied adjunct to the gill cell assay for medaka fish.

Synthesis and Characterization of a New Macrocyclic Ligand and Its Copper (II), Cadmium (II), and Lead (II) Complexes: Genotoxic Activity of These Complexes in Cultured Human Lymphocytes

A new macrocyclic ligand 1,1′-bis(bis-(6,6′-oxymethylenyl-2,2′-bipyridine) binaphthyl, (L), and its complexes CuL(ClO4)2, CuL(NO3)2·3H2O, CdL(ClO4)2, and PbL(ClO4)2 have been synthesized and characterized on the basis of IR, 1H NMR, 13C NMR, FAB mass, and elemental analyses. Genotoxicity of these metal complexes has also been investigated by cytokinesis-blocked micronucleus assay in cultured human lymphocytes. Blood cultures were set up from two healthy donors, and treatment was done with different test concentrations for 24 and 48 h. The current results indicate that all compounds caused cytotoxicity by decreasing the cell number at the 150 μg/mL doses for 48-h treatments. On the other hand, CuL(ClO4)2, CuL(NO3)2·3H2O and PbL(ClO4)2 exhibited genotoxicity by inducing the number of micronucleated cells at doses of 150 μg/mL for 24-h treatments, but CdL(ClO4)2 did not significantly alter micronucleus induction. Hence, some test compounds may act as mutagens or produce clastogenic effects depending upon their chemical structures.

SFTG international collaborative study on in vitro micronucleus test: IV. Using CHL cells

In this report, are presented the results of an international collaborative study on the in vitro micronucleus assay, using CHL cells. Fourteen laboratories participated in this study which was coordinated by an organizing committee supported by the SFTG (the French branch of the European Environmental Mutagen Society). Nine coded substances, having different modes of action and at different levels were assessed in the in vitro micronucleus test, using a common protocol. Mitomycin C was used as a positive control. In order to help to define a standard protocol on CHL cells, short and long treatment periods followed by various recovery times, with or without cytochalasin B, were compared. After an evaluation of the acceptability of the assays, the tested chemicals were classified as negative, positive or equivocal. Mannitol and clofibrate were judged as negative in all treatment schedules. Bleomycin was positive in all the treatment schedules, with an increase in the number of micronucleated cells in both mononucleate and binucleate cells when using cytochalasin B. This was also shown for the aneugens colchicine, diethylstilboestrol and griseofulvin, as expected. Urethane was judged as equivocal only after long treatment with cytochalasin B, and negative in all other treatment schedules. In any case, no genotoxic compound would have been missed with schedules including a short and a long treatment time, whether the treatment was followed by a recovery period or not and whether cytochalasin B was used or not. Thus, these results show that CHL cells were suitable for accurately detecting clastogenic and aneugenic compounds of various types in the in vitro micronucleus test.

The optimized conditions for the in vitro micronucleus (MN) test procedures using chamber slides

Optimized conditions for an in vitro micronucleus (MN) test procedure were defined using a chamber slide that enabled the preparation of fine specimens without undergoing complicating procedures using culture dishes. The issues investigated are 1) the effect of slide materials on the adhesion of cells, 2) the number of seeding cells necessary to obtain an adequate number of cells for observation and 3) effects of hypotonic treatment and fixation on the cytoplasmic: nuclear area ratio. In addition, we determined cell viability in each chamber using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The results of the investigation were as follows: 1) cell adhesion was best using plastic slides, 2) the optimum number of cells for seeding was 6.6×103 cells/cm2, 3) the best condition for hypotonic treatment was incubation in 75 mM KCl at 37°C for 5 min, and 4) the best condition for fixation was treatment of cells twice for about 2 min in icecold methanol containing 6% acetic acid. Finally, the result of the MTT assay correlated with the number of viable cells in chamber as determined by the trypan blue dye exclusion assay.An in vitro MN test was conducted under these conditions using the known clastogens, Mitomycin C and dimethylnitrosamine. These clastogens dose-dependently induced a significant increase in the number of micronucleated cells with positive responses at concentrations approximately 10 times lower than those of the chromosomal aberration test. On the other hand, the frequency of micronucleated cells in the solvent control was stable and low (0.4-1.7%). These results indicated that the in vitro MN test has a high level of sensitivity to clastogens.It was concluded that the in vitro MN test using chamber slides is a rapid, simple and sensitive method to detect clastogens.

Induction of micronucleated cells in the shed skin of salamanders (Ambystoma sp.) treated with colchicine or cyclophosphamide

The micronucleus (MN) assay can be used to detect the genotoxic effects of chemical agents in virtually any cell that divides frequently. Salamanders (Ambystoma sp.) are amphibians that can be easily maintained and bred in the laboratory and spontaneously shed their skin every 2.5-4 days. In this present study, we have evaluated the usefulness of this shed skin for the MN assay. We exposed salamanders to different concentrations of both the aneugen colchicine (COL) and the clastogen cyclophosphamide (CP) and we determined the frequency of micronucleated cells (MNCs) in their sheds. Fragments of shed skin were placed on clean slides, fixed, stained, observed with a light microscope, and the number of MNCs was counted. The MNC frequency was increased significantly by all doses of COL and CP tested, administered either as single or repeated exposures. The presence of MNCs in the shed skin and the speed of sloughing lead us to propose that the sheds of Ambystoma sp., or other amphibians that slough their skin, are suitable alternative models for detecting genotoxic exposures relevant to aquatic environments.

Effects of a Diet High in Fish Oil (MaxEPA) on the Formation of Micronucleated Erythrocytes in Blood and on the Numberof Atypical Acinar Cell Foci Induced in Rat Pancreas by Azaserine

The present study was performed to investigate the influence of fish oil on the genotoxic effects of azaserine, using the formation of micronucleated erythrocytes as a measure for the degree of initiating potency and the number and size of putative preneoplastic pancreatic atypical acinar cell foci (AACF) as a measure for the actual number of initiated cells. Male Wistar rats were treated twice i.p. with 30 mg azaserine per kg body weight to induce AACF. During the initiation/early promotion phase the rats were maintained on diets containing 5 wt% vegetable oil (safflower and high-oleic sunflower oil), 25 wt% vegetable oil, 25 wt% fat (15% vegetable oil + 10 wt% fish oil), or 25 wt% fat (5% vegetable oil + 20 wt% fish oil), respectively. One day after carcinogen treatment, the numbers of micronucleated polychromatic erythrocytes were determined in blood smears obtained from 10 animals per group. Each high-fat diet resulted in higher percentages of micronucleated polychromatic erythrocytes than the low-fat diet. Dietary fish oil did not significantly influence the number of micronucleated cells. Two weeks after carcinogen treatment, the diets containing fish oil were replaced by the diet containing 25% vegetable oil, and the animals were further maintained for about 14 wk. Pancreatic tissue slides were microscopically evaluated for the number and size of AACF. Dietary fish oil caused an increase in the number and size of AACF, although a clear dose-effect relationship was absent. It was concluded that a high level of dietary fish oil, when given during the induction/early promotion phase, enhances azaserine-induced pancreatic carcinogenesis in rats.

Serial cytological assay of micronucleus induction: a new tool to predict human cancer radiosensitivity

Background and purpose: The micronucleus test, generally done in cultured tumour cells irradiated in vitro, has not gained wide acceptance in predicting human cancer radiosensitivity. The purpose of this study was to see if micronucleus assay by serial scrape smear cytology can predict oral cancer radiosensitivity. Materials and methods: Forty nine oral cancer patients given radiotherapy (60 Gy/25 fractions/5 weeks) form the study population. Serial scrape smears were taken from their tumours before treatment and after delivery of 2, 5, 8 and 12 fractions, stained by Giemsa and the number of micronucleated cells (MNC) noted. The patients were grouped to those who developed tumour recurrence (‘Resistant’) and those who did not (‘Sensitive’), and the pattern of micronucleus induction compared. Results: Both groups of tumours had MNC even before treatment, with statistically significant dose-related increase with radiotherapy. The sensitive group had a higher mean increase in MNC count than the resistant group (6.1 times and 3.6 times the pre-treatment value, respectively) and better correlation with dose ( r = 0.54 vs. 0.43). The increase in MNC count occurred earlier in the resistant group than in the sensitive, the T MNC (time for the pre-treatment value to double) being 3.3 days and 7.6 days, respectively. Also, the resistant group showed a plateauing of the MNC count which the sensitive group lacked. Conclusion: The higher MNC induction in the sensitive tumours suggests the usefulness of the assay as a test of radiosensitivity. The differing patterns of MNC increase suggest that differences in proliferation rate is an important cause of tumour failure. Serial cytological assay of micronucleus induction can identify both radiosensitivity and proliferation characteristics of tumours, and thus may turn out to be a useful test of radiocurability.

Genotoxicity of the herbicide fluchloralin on human lymphocytes in vitro: chromosomal aberration and micronucleus tests

Cultured human lymphocytes were exposed to three different concentrations (2.5, 5.0 and 10.0 μg/ml) of fluchloralin for 24 and 48 h to assess chromosomal aberrations. A significant dose-dependent increase of chromatid type aberration was observed in these cells. Multiple aberrations (MA) were scored at all concentrations after 48 h treatment. To support these results we did micronucleus (MN) test using cytochalasin B to block cytokinesis. At lower concentrations (2.5 to 10.0 μg/ml) the frequency of MN induction was not significantly different. Higher concentrations of fluchloralin (20, 40 and 50 μg/ml) resulted in a significant dependent increase in number of micronucleated cells. This is the first report on genotoxic effects of fluchloralin in human cells.

Genotoxic effects of subacute treatments with wood dust extracts on the nasal epithelium of rats: assessment by the micronucleus and 32P-postlabelling.

Human exposure to wood dust has been epidemiologically linked to a number of enhanced incidences of various neoplasias, including those of the nose. Among different suspected woods, long-term exposure to the dust of beech (Fagus silvatica) is strongly associated with development of these tumors. Experimentally, it has been shown that a simple alcoholic extract of beech wood dust is mutagenic toward some bacteria and tumorigenic on mouse skin. For the present study, different groups of male Wistar rats were treated with aqueous, ethanol, or methanol extract of untreated beech wood dust via nasal drip at three concentrations for 48 h. Animals were killed 24 h after the last treatment and the nasal tissues were isolated to be examined for possible induction of micronuclei and DNA adducts. A clear dose-dependent increase in the number of micronuclei (P < 0.01) was observed after treatment of rats with each alcoholic extract of wood dust. In contrast, no DNA adducts could be detected with these extracts using the 32P-postlabelling technique. No increased number of micronucleated cells was found with solvents alone or with aqueous extract of dust. These data might support the early hypothesis that wood dust per se contains some in vivo genotoxic and thus possibly carcinogenic components extractable by an alcohol.

Lack of evidence of omeprazole genotoxicity in Sprague-Dawley rats.

Omeprazole is a proton pump inhibitor of increasingly wide use in the treatment of peptic ulcers. Although omeprazole has been subjected to an extensive range of genotoxicity tests, which have all been concluded as negative, the ability of this compound to interact with DNA and elicit unscheduled DNA synthesis in the rat gastric mucosa has been the subject of debate. Therefore, we have examined omeprazole using other genotoxicity end-points. In female Sprague-Dawley rats, the administration by the oral route of 100 mg/kg, either as neutral (pH 7.0) suspension or as suspension acidified to pH 1.5, which favours its transformation into the active form of sulphenamide, did not induce DNA fragmentation in gastric mucosa and liver, as detected by the alkaline elution technique. In the same experimental conditions, a frequency of total nuclear anomalies (micronuclei, pyknosis and karyorrhexis) that was significantly higher than in controls was detected with both types of suspension in forestomach and descending colon mucosa. However, in both tissues this higher frequency of nuclear anomalies was mostly due to pyknosis and karyorrhexis, which may be the outcome of a non-genotoxic effect, whereas there was no significant increase in the number of micronucleated cells, and this suggests the absence of clastogenic activity. Finally, in rats initiated with N-nitrosodiethylamine, the oral administration of 100 mg/kg omeprazole for 14 successive days produced a modest but statistically significant increase of liver gamma-glutamyltranspeptidase positive foci, which is consistent with a potential promoting activity.(ABSTRACT TRUNCATED AT 250 WORDS)