Sister chromatid exchanges, proliferating rate index, and micronuclei in biomonitoring of internal exposure to vinyl chloride monomer in plastic industry workers

The frequency of micronuclei (MN), sister chromatid exchange (SCEs), and the proliferating rate index in peripheral blood lymphocytes from 93 individuals were measured. Fifty-two of the individuals were workers in the plastics industry where they were exposed to vinyl chloride monomer while the remaining 41 individuals served as a control group. In our results, an increase of SCEs and MN, as well as inhibited cell kinetics, was observed in the group of exposed workers. Of the tests used, SCE was found to be the most sensitive endpoint for indicating a biological response. However, since methods for restricting the MN analysis to only cells at risk (i.e., second generation interphase cells) were not used, this statement requires verification.     

Sister chromatid exchanges in lymphocytes of nurses handling antineoplastic drugs

The effects of handling antineoplastic drugs were examined in a group of 23 nurses working in the hematology and oncology departments of different university hospitals in Ankara and in a group of 50 unexposed controls. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges (SCEs) in circulating lymphocytes which result from the breakage and rejoining of DNA at apparently homologous sites on the 2 chromatids of a single chromosome. A significant increased frequency of SCE is observed in nurses in daily contact with antineoplastics (n = 23, mean SCEs/cell +/- SE 6.5 +/- 0.2) as compared to a group of controls (n = 50, mean SCEs/cell 5.2 +/- 0.2). The nurses who smoked also had a higher SCE frequency (n = 15, mean SCEs/cell 7.0 +/- 0.3) than non-smokers, (n = 8, mean SCEs/cell 5.5 +/- 0.3). A significant increase (P less than 0.001) in the mean number of SCE was found for non-smoking nurses as compared to non-smoking controls (n = 27, mean SCEs/cell 4.1 +/- 0.2).     

Sister-chromatid exchanges in lymphocytes from 12 chromium platers: a 5-year follow-up study

To detect the mutagenic effects of hexavalent chromium (Cr) in humans, sister-chromatid exchange (SCE) frequency in lymphocytes and urinary Cr was determined in 66 blood-urine paired samples from 12 male Cr-platers during 5 years (1984-1989). Multiple regression of SCE frequency on age, urinary Cr and smoking habits was analyzed in all 66 samples. Neither age (P = 0.204) nor urinary Cr (P = 0.056) was a significant predictor for SCE frequency. Although urinalysis revealed obvious exposure to Cr in the platers, exposure was unable to influence SCE frequency. Smoking habits were a highly significant (P less than 0.001) positive predictor for SCE frequency, and smoking of one cigarette per day was associated with an increase of 0.054 SCEs/cell in SCE frequency. SCE frequency significantly fluctuated from year to year in 3 subjects. The smoking habits of these 3 subjects did not change during the follow-up period. The results suggest that there are other unknown factors influencing SCE frequency in addition to smoking habits.     

Effects of smoking on spontaneous and induced sister chromatid exchanges in lymphocytes

Spontaneous and mitomycin C-induced sister chromatid exchanges (SCEs) in lymphocytes were analyzed in 24 non-smokers and 24 sex- and age-matched smokers. Mean spontaneous SCE frequency for non-smokers was 9.8 SCEs/cell, and that for smokers was 11.5 SCEs/cell. The difference was statistically significant (P less than 0.001 by t-test). These results suggest that spontaneous SCE frequency in lymphocytes is useful for evaluation of biological effects of environmental mutagens. However, we could not find any effects of smoking on the sensitivities of lymphocytes to mitomycin C in vitro. The effects of mutagens on humans may be independent of one another.     

Analysis of cytogenetic damage in rat lymphocytes following in vivo exposure to nitrobenzene

Male F-344 rats were exposed to target concentrations of 0, 5, 16, or 50 ppm nitrobenzene for 6 h/day, 5 days a week, for 21 days during a 29-day period. Isolated spleen (ISLs) and peripheral blood lymphocytes (PBLs) were cultured in the presence of 2 microM 5-bromodeoxyuridine and scored for sister-chromatid exchange (SCE) and PBLs were also scored for chromosome aberrations. No significant increase in SCE frequency or chromosome aberrations was found in the PBLs, and no significant increase in SCEs was observed in the ISLs at any of the concentrations. Thus, cytogenetic analysis of ISLs and PBLs provide no evidence of a genotoxic potential for nitrobenzene.     

Genotoxicity study in lymphocytes of offset printing workers

The potential cytogenetic damage in offset printing workers was evaluated using sister chromatid exchanges (SCEs), chromosome aberrations (CAs) and micronuclei (MN) as biomarkers in peripheral lymphocytes of 26 volunteers (14 workers, 12 controls). The CA, SCE and MN frequency of offset printing workers was significantly higher than in their controls. The replication index (RI) was not affected while the mitotic index (MI) was affected most in the workers. It can be concluded from this study that chronic occupational exposure to printing dyes and thinner may lead to a slightly increased risk of genetic damage among offset printing workers.     

Increased frequency of chromosomal aberrations and sister chromatid exchanges in peripheral lymphocytes of radiology technicians chronically exposed to low levels of ionizing radiations

Chromosome aberrations (CAs) and sister chromatid exchanges (SCEs) frequencies were estimated in peripheral lymphocytes from 21 radiology technicians, and from 21 non-exposed control subjects. We exclusively considered individuals who neither smoke nor consume drugs or alcohol for a period of at least two years prior to the analysis. Significant differences were found between exposed and controls in terms of SCEs and CAs frequencies.Technicians showed a significant higher number of high-frequency individuals (HFIs) with respect to the control group. Nevertheless, the mean frequency of SCEs observed among technician HFIs did not significantly differ with respect to that observed among control HFIs. Vice versa, the non-HFIs belonging to technicians group showed a statistically higher difference in the SCEs/NSM value with respect to the non-HFIs belonging to control group. Since the differences in the SCEs frequencies between the two groups are due to non-HFIs, our results seem to indicate a general genotoxic effect of the IR, not affected by HFIs.Among technicians, the level of chromosome damage correlated neither with years of radiation exposure nor with the age of the subjects. Vice versa, in the control group, a positive correlation was found between the number of SCEs and age. In both samples the gender status did not influence the frequencies of CAs and SCEs.Our results suggest that chronic long-term exposure to low doses of ionizing radiation could increase the CAs and SCEs frequencies. This study reinforces the relevance of the biomonitoring of hospital workers chronically exposed to ionizing radiation.     

Sister chromatid exchange frequency in cultured isolated porcine urinary bladder epithelial cells (PUBEC) treated with ochratoxin A and alpha

The mycotoxin ochratoxin A (OTA) and its metabolite ochratoxin alpha (OT-alpha) were investigated, to examine their potency to induce sister chromatid exchages (SCE) in cultured poricine urinary baldder epithedial cells (PUBEC) (primary cluture). Serum-free cultured PUBEC were incubated for 5 h with either OTA or OT-alpha, respectively, and subsequently cutured in the presence of 5-bromo-2-deoxyuridine (BrdU). After two cell cycles, mitosis was inhibited by the colchicine derivative Colcemid, cells were fixed and chromosomes were prepared for SCE analysis. For OTA, a dose-dependent increase in SCE frequency was measured in concentrations between 100 pM and 100 nM OTA. At 100nM OTA, SCE frequency increased by about 41%, compared to the base SCE level (7.27 SCEs per chromosome set, solvent control). Higher concentrations of OTA were cytotoxic. The metabolite OT-alpha also increased SCE frequency, but at higher concentrations. At a concentration of 10μM OT-alpha, an increase of about 55% was detected. OT-alpha showed no cytotoxic effect. There results indicate that OTA is genotoxic in this in vitro system, which represents the urinary bladder epithelium, a target organ of OTA in vivo. It could also be shown that OT-alpha, which is said to be non-toxic, is genotoxic in this assay at higher concentrations.     

An updated evaluation of reported no-observed adverse effect levels for chrysotile asbestos for lung cancer and mesothelioma

Although consumption of chrysotile asbestos has decreased since the 1970s, the latency period of asbestos-related cancers is thought to be at least 20–30 years, and therefore the potential health risks associated with historical exposures is still actively researched. This analysis represents an update to a previous paper in which we evaluated the exposure–response relationships for lung cancer and mesothelioma in chrysotile-exposed cohorts. Here, we review several recently published studies as well as updated information from previous studies. For each of the 14 studies considered, we identified the “no-observed adverse effect level” (NOAEL) for lung cancer and/or mesothelioma. NOAEL values for lung cancer ranged from 1.1 to <20 f/cc-years to 1600–3200 f/cc-years, and for mesothelioma ranged from 100–400 f/cc-years to 800–1599 f/cc-years. The range of “best estimate” NOAELs was estimated to be 89–168 f/cc-years for lung cancer and 208–415 f/cc-years for mesothelioma. None of the six cohorts of cement or friction product manufacturing workers exhibited an increased lung cancer risk at any exposure level, while all of the five studies of textile workers reported an increased risk at one or more exposure levels. This is likely because friction and cement workers were exposed to much shorter chrysotile fibers. Of the seven cases of peritoneal mesothelioma reported in the included studies, none were observed in the analyses of cement or friction product manufacturing workers in the absence of crocidolite exposure. These findings will help characterize potential worker and consumer health risks associated with historical and current chrysotile exposures.     

Genotoxicity of gardenia yellow and its components.

Gardenia fruit (Gardenia jasminoides ELLIS) is widely used as a natural food colorant and as a traditional Chinese medicine for treatment of hepatic and inflammatory diseases. "Gardenia yellow" is a natural food colorant which is extracted by ethanol from gardenia fruit. The purpose of this study was to evaluate the genotoxicity of gardenia yellow. Genotoxicity of gardenia yellow and its components, crocetin, gentiobiose (a component of crocin), geniposide and genipin (formed by hydrolysis of geniposide), was studied by Ames test, rec-assay, and sister chromatid exchange (SCE) using V79 cells. Gardenia yellow and its components were found not to be mutagenic in the Salmonella reverse mutation assay. Gardenia yellow and genipin caused damage of DNA in rec-assay. Gardenia yellow induced a significant dose-dependent increase of SCE frequency (8.6 times at 1000 microg/ml as the value for the solvent control). Only genipin induced SCEs significantly among the components of gardenia yellow. Moreover, genipin induced a significant increase of tetraploids at all doses tested (95% at 8 microg/ml). Gardenia yellow preparation was analyzed by capillary electrophoresis (CE), and geniposide was detected. However, genipin was not observed. In conclusion, we have shown that genipin possesses genotoxicity. Furthermore, there were unidentified genotoxicants in gardenia yellow.     

Mutagenicity studies on herring gulls from different locations on the Great Lakes. I. Sister chromatid exchange rates in herring-gull embryos

Unincubated herring-gull (Larus argentatus) eggs were collected from five colonies on the Great Lakes Basin and from one relatively pollutant-clean colony on the Atlantic coast. Eggs were incubated at 38 degrees C with 55% relative humidity, and sister chromatid exchange (SCE) levels were measured in 7-d embryos. For all of the colonies, the average SCE/chromosome frequency ranged from 0.069 to 0.101; however, no significant differences were found. Organochlorine analysis was carried out on egg homogenates for each colony, to determine the levels of several contaminants. There were no relationships found between any of the contaminant levels and the SCE frequencies. The study indicates that either the contaminants present in the herring-gull eggs are not having any genetic effects on the embryos or, alternatively, that there may be genetic damage that measurement of SCEs in the 7-d embryo is unable to detect.     

N-acetyl L-cysteine attenuates oxidant-mediated toxicity induced by chrysotile fibers

Chrysotile, an important commercial variety of asbestos, is known to cause oxidative stress by enhancing production of hydrogen peroxide (H(2)O(2)) and thiobarbituric acid reactive substances (TBARS), depleting glutathione (GSH) and altering levels of GSH redox system enzymes. N-acetyl L-cysteine (NAC), a compound that increases GSH levels, protects cells against chrysotile toxicity. In the present study, rats were exposed intratracheally to a single dose (5 mg/rat) of chrysotile. This was followed by a daily dose of NAC 50 mg/kg. b. wt., i.p. At 1, 4, 8 and 16 days post chrysotile exposure lung lavage fluid was collected to determine H(2)O(2) generation, TBARS production, GSH level and its redox system enzymes activities. A significant decrease in H(2)O(2) and TBARS, an increase in GSH content and its redox system enzymes was observed in chrysotile+NAC animals in comparison to chrysotile-exposed animals. In this preliminary study it appears that NAC may be protecting cells against oxidative damage. This protection may be due to its ability to maintain intracellular GSH/oxidative scavenging capability.     

Chromosome damage in workers in cigarette manufacturing industry

To investigate whether occupational exposure to tobacco dust is genotoxic, a group of employees in a tobacco factory was tested for structural chromosome aberrations (CA), cytokinesis-block micronucleus assay (CBMN) and sister chromatid exchanges (SCE) that are well established as indicators of early biological effects. The study group consisted of 40 tobacco workers and an equal number of matched controls. The results obtained in the exposed group showed a significant increase in chromosome aberrations (R=0.26), micronucleus frequency (R=0.56) and in sister chromatid exchanges (R=0.75), which was additionally influenced by smoking. A significant increase in high frequency cells (HFC) in the exposed group was also observed. Like the SCE frequency, the HFC frequency increased significantly in smokers of the control and exposed smokers. The study indicates that occupational exposure to tobacco dust induces genome damage. A higher risk was observed in women. The micronucleus frequency and sister chromatid exchange tests seem to be more reliable indicators of genome damage than chromosome aberrations in monitoring chronically exposed subjects.     

Nitroimidazole derivatives: non-randomness sister chromatid exchanges in human peripheral blood lymphocytes

Nitroimidazole derivatives exhibited genotoxic effect in different experimental conditions. This study focuses on an evaluation of possible genomic targets, at a chromosomal level, of two 5-nitroimidazoles (ornidazole and metronidazole) using the in vitro human peripheral blood culture as experimental system. We observed that both derivatives showed a decrease in mitotic index (MI) (P < 0.001), an increase in sister chromatid exchanges (SCE) frequency (P < 0.001) and no modifications in cellular proliferation kinetics (CPK). As a null hypothesis we considered the assumption that larger chromosomes should harbor more SCE, which was viewed using a novel sequential G-band (400 band resolution)/SCE technique. The analysis showed highly significant chi square values (P < 0.001), indicating that SCE frequency per chromosome is not proportional to chromosome length. SCE could be considered an instability indicator due to the high correlation between SCEs in certain chromosomal bands and the exposure to nitroimidazole derivatives. Copyright © 2008 John Wiley & Sons, Ltd.     

Elevated frequency of sister chromatid exchanges of lymphocytes in sarin-exposed victims of the Tokyo sarin disaster 3 years after the event

We previously reported that the frequency of sister chromatid exchanges (SCEs) among victims of the Tokyo subway sarin disaster was significantly higher than that of controls 2-3 months after the disaster. It has been reported that the victims were also exposed to the by-products generated during sarin synthesis, i.e., diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP) and N,N-diethylaniline (DEA) during the disaster and we previously found that DIMP, DEMP and DEA induced a significant SCE increase in human lymphocytes in vitro. To monitor the genetic aftereffects of the sarin exposure, SCEs of peripheral blood lymphocytes were measured in fire fighters and police officers involved in the disaster 3 years after the event. We found that the frequency of SCEs was still significantly higher in the exposed subjects than the controls, suggesting a risk of the genetic aftereffects of the sarin exposure. We further found a significant positive correlation between the frequency of SCEs and the inhibition of serum cholinesterase activity in the exposed subjects, suggesting that the elevated frequency of SCEs is related to the sarin exposure. On the other hand, there was no significant difference in natural killer activity between the exposed and the controls.     

The association between frequencies of mitomycin C-induced sister chromatid exchange and cancer risk in arseniasis

In order to examine whether biomarkers of cytogenetic damage and susceptibility, such as spontaneous and mitomycin C-induced sister chromatid exchange (SCE) can predict cancer development, a nested case-control study was performed in a blackfoot endemic area with known high cancer risk. A cohort of 686 residents was recruited from three villages in the arseniasis area. Personal characteristics were collected and venous blood was drawn for lymphocyte culture and stored in a refrigerator. The vital status and cancer development was followed using the National Death Registry, Cancer Registry, and Blackfoot Disease Registry. The follow up period was from August 1991 to July 1997. During this 6-year-period, 55 residents developed various types of cancer. Blood culture samples from 23 of these subjects were unsuitable for spontaneous SCE experiments and 45 of these subjects were unsuitable for mitomycin C-induced SCE experiments due to improper storage. Finally, a total of 32 cancer cases had cytogenetic samples that could be analyzed. About 32 control subjects were selected from those who did not develop cancer in the study period and these subjects were matched to cases by sex, age, smoking habits, and residential area. The results showed that there was no significant difference in the frequencies of spontaneous and mitomycin C-induced SCE between the case and control groups. There was also no significant difference in the net difference of spontaneous and mitomycin C-induced SCE between the case and control groups. These results suggest that SCEs, either spontaneous or mitomycin C-induced, might not be good markers to predict cancer risk.     

In vivo and in vitro studies on the genotoxicity of cadmium chloride in mice

The genotoxic effect of cadmium chloride was evaluated in chromosomes of experimental mice using in vivo and in vitro studies. In vivo the induction of micronuclei, sister chromatid exchange in mouse bone marrow and chromosomal aberrations in both somatic and germ cells was investigated. Doses 1.9, 5.7 and 7.6 mg kg(-1) body wt. (single i.p. treatment) induced a significant and dose-dependent increase in the percentage of polychromatic erythrocytes with micronuclei. Such a percentage reached 2.1% with the highest tested dose, compared with 0.57% for the control (non-treated) and 2.2% for mitomycin c as the positive control. The dose of 1.9 mg kg(-1) body wt. had no significant effect with respect to sister chromatid exchange (SCE) but the doses of 5.7 and 7.6 mg kg(-1)body wt. increased the frequency of SCEs significantly. The frequency of SCE reached 7.35 +/- 0.26 per cell after treatment with the highest tested dose, which is a less than twofold increase compared with the control frequency of 4.6 +/- 0.42 per cell. However mitomycin c induced a much higher effect (12.1 +/- 0.73). Cadmium chloride also induced a significant increase in the percentage of chromosomal aberrations in mouse bone marrow at the doses of 5.7 and 9.5 mg kg(-1) body wt. (single i.p. treatment). The effect is a function of cadmium chloride concentration. Moreover, cadmium chloride induced its maximum effect concerning the induction of chromosomal aberrations in mouse bone marrow cells 24 h after treatment, compared with 12 and 48 h. In germ cells, chromosomal aberrations were observed in mouse spermatocytes 12 days post-treatment with the dose of 5.7 mg kg(-1) body wt. Moreover, a pronounced reduction in the number of spermatocytes was observed after administration of cadmium chloride (0.9, 1.9 and 5.7 mg kg(-1) body wt.) In in vitro studies, the three tested concentrations of 10, 15 and 20 microgram ml(-1) cadmium chloride induced a statistically significant increase in the frequency of SCEs in cultured mouse spleen cells. The concentrations of 15 and 20 microgram ml(-1) also induced chromosomal aberrations in mouse spleen culture. The ability of vitamin C (l-ascorbic acid) to minimize the incidence of chromosomal aberrations induced by cadmium chloride in cultured mouse spleen cells was investigated. Vitamin C at the concentrations of 3 and 6 microgram ml(-1) significantly minimized the percentage of aberrant cells induced by cadmium chloride.     

Genotoxic and aneugenic properties of an imidazole derivative

To contribute to a more accurate characterization of the mutagenic and aneugenic effects of thiabendazole (TBZ), a widely used antiparasitic and food preservative drug, the induction of sister chromatid exchanges (SCEs) and mitotic spindle anomalies as cytogenetic end-points were investigated. Studies were carried out in Chinese hamster ovary (CHO) cells and human peripheral blood lymphocytes. A significant dose-dependent increase in SCE frequency was observed in CHO cells with S9-Mix (P < 0.01) in the 50-100 microg ml(-1) dose-range, while in the absence of S9-Mix, an enhancement of the SCE frequency was exhibited at the highest dose (P < 0.01). In CHO-K1 cells a significant increase in mitotic spindle anomalies (P < 0.01) was observed with the highest concentration assayed reflecting the specific effect of TBZ formulation at the microtubule level. Cell proliferation kinetics (CPK) were not modified by the addition of this pharmaceutical product. In human lymphocyte cultures, exposure to 100 microg ml(-1) TBZ formulation resulted in a significant decrease of the mitotic index (MI) (P < 0.003) and changes in the replication index (RI) (P < 0.05).     

An Evaluation of Reported No-Effect Chrysotile Asbestos Exposures for Lung Cancer and Mesothelioma

Numerous investigators have suggested that there is likely to be a cumulative chrysotile exposure below which there is negligible risk of asbestos-related diseases. However, to date, little research has been conducted to identify an actual “no-effect” exposure level for chrysotile-related lung cancer and mesothelioma. The purpose of this analysis is to summarize and present all of the cumulative exposure-response data reported for predominantly chrysotile-exposed cohorts in the published literature. Criteria for consideration in this analysis included stratification of relative risk or mortality ratio estimates by cumulative chrysotile exposure. Over 350 studies were initially evaluated and subsequently excluded from the analysis due primarily to lack of cumulative exposure information, lack of information on fiber type, and/or evidence of significant exposures to amphiboles. Fourteen studies meeting the inclusion criteria were found where lung cancer risk was stratified by cumulative chrysotile exposure; four such studies were found for mesothelioma. All of the studies involved cohorts exposed to high levels of chrysotile in mining or manufacturing settings. The preponderance of the cumulative “no-effects” exposure levels for lung cancer and mesothelioma fall in a range of approximately 25–1000 fibers per cubic centimeter per year (f/cc-yr) and 15–500 f/cc-yr, respectively, and a majority of the studies did not report an increased risk at the highest estimated exposure. Sources of uncertainty in these values include errors in the cumulative exposure estimates, conversion of dust counts to fiber data, and use of national age-adjusted mortality rates. Numerous potential biases also exist. For example, smoking was rarely controlled for and amphibole exposure did in fact occur in a majority of the studies, which would bias many of the reported “no-effect” exposure levels towards lower values. However, many of the studies likely lack sufficient power (e.g., due to small cohort size) to assess whether there could have been a significant increase in risk at the reported no-observed-adverse-effects level (NOAEL); additional statistical analyses are required to address this source of bias and the attendant influence on these values. The chrysotile NOAELs appear to be consistent with exposure-response information for certain cohorts with well-established industrial hygiene and epidemiology data. Specifically, the range of chrysotile NOAELs were found to be consistently higher than upper-bound cumulative chrysotile exposure estimates that have been published for pre-1980s automobile mechanics (e.g., 95th percentile of 2.0 f/ cc-yr), an occupation that historically worked with chrysotile-containing friction products yet has been shown to have no increased risk of asbestos-related diseases. While the debate regarding chrysotile as a risk factor for mesothelioma will likely continue for some time, future research into nonlinear, threshold cancer risk models for chrysotile-related respiratory diseases appears to be warranted.     

The genotoxic effects of anti-cancer drug gossypol on human lymphocytes and its mitigation by melatonin

Purpose of study: To determine melatonin as a potential natural antioxidant to mitigate the genotoxic effects of promising anti-cancer drug gossypol in human lymphocytes. Introduction: Gossypol, is a polyphenolic compound naturally occurring in cotton seed, was originally identified as a male contraceptive but it has several proposed clinical applications. Gossypol has anti-proliferative effects on cancer cell lines. However, its genotoxic effects on normal cells are not much studied. Hence, there is a paucity of data available. Hence, the study was conducted to investigate gossypol-induced genotoxic effects on lymphocytes. Methods: Peripheral blood lymphocyte cultures (PBLC) were done and exposed by two different doses of an anti-cancer drug, gossypol (0.274?mM, 1.645?mM) to check genotoxic effects. Melatonin (0.2?mM) is used as an antioxidant. Genotoxic indices such as sister chromatid exchanges (SCEs), cell cycle proliferative index (CCPI), average generation time (AGT), population doubling time (PDT) were assayed in the cultures. Result: Gossypol-treated groups indicated significant increases in frequency of SCEs calculated for SCE/plate and SCE/chromosome. Furthermore, CCPI showed a remarkable reduction and increased AGT and PDT levels were found in exposed cultures. When the higher dose of gossypol cultures was treated along with melatonin, these indices were found to be declined and comparable to control. Conclusion: Gossypol, an anti-cancer drug, induces genotoxicity on lymphocyte cells and co-supplementation of melatonin antioxidant ameliorates these toxic effects of gossypol.