Evaluation of genotoxicity of combined soil pollution by cadmium and imidacloprid

Cadmium (Cd) is one of the important pollutants of soil and the genotoxicity of Cd-contaminated soil was studied in combination with imidacloprid. The single cell gel electrophoresis or comet assay was used to quantify DNA strand breaks as a measure of DNA damage induced by Cd and imidacloprid contamination in soil. The soil was artificially contaminated by Cd 2 h at 25℃ and were used in the comet assay. DNA damage was measured as the values of percentage of nuclei with tails, tail length, tail DNA, tail moment (TM), and Olive tail moment (OTM). DNA damages of root tips of Vicia faba increased after Cd treatment and there were dose-related increases in DNA damage measured as these parameters. However, the addition of imidacloprid further increased the DNA damage. These data confirmed the genotoxic effect of Cd to plants, and that the combined pollution with imidacloprid can enhance the genotoxicity of Cd.     

溴氰菊酯致大鼠DNA损伤及对肝功能的影响

目的：研究溴氰菊酯（DM）对大鼠外周血淋巴细胞DNA的损伤作用及对肝脏功能的影响。方法：32只雌性Wistar大鼠随机分成4组,染毒剂量分别为0,3．125,6．250,12．500mg／kg,连续灌胃染毒10天。DNA损伤采用单细胞凝胶电泳（彗星实验）进行评价,并测定丙氨酸氨基转移酶（ALT）以反映肝功能变化。结果：染毒组大鼠外周淋巴细胞的尾DNA％（Tail DNA％）、尾矩（Tail Moment）和Olive尾矩（Olive Tail Moment）均高于对照组（P〈0．05）,差别有统计学意义。各染毒组与对照组的肝功能差异均无统计学意义。结论：DM可导致外周血淋巴细胞DNA损伤。     

Cypermethrin-induced DNA damage in organs and tissues of the mouse: evidence from the comet assay

Cypermethrin is the most widely used Type II pyrethroid pesticide because of its high effectiveness against target species and its low mammalian toxicity reported so far. It is a fast-acting neurotoxin and is known to cause free radical-mediated tissue damage. The present study investigates the genotoxic effects of cypermethrin in multiple organs (brain, kidney, liver, spleen) and tissues (bone marrow, lymphocytes) of the mouse, using the alkaline comet assay. Male Swiss albino mice were given 12.5, 25, 50, 100, 200 mg/kg BW of cypermethrin intraperitoneally, daily for 5 consecutive days. A statistically significant (p<0.05) dose-dependent increase in DNA damage was observed in all the organs assessed, as evident from the comet-assay parameters, viz., Olive tail moment (OTM; arbitrary unit), tail DNA (%) and tail length (microm). Brain showed maximum DNA damage followed by spleen>kidney>bone marrow>liver>lymphocytes, as evident by the OTM. Our data demonstrate that cypermethrin induces systemic genotoxicity in mammals as it causes DNA damage in vital organs like brain, liver, kidney, apart from that in the hematopoietic system.     

Environmental and occupational biomonitoring using the Comet assay

Biomonitoring of human populations exposed to potential mutagens or carcinogens can provide an early detection system for the initiation of cell disregulation in the development of cancer. In recent years, the Comet assay, also known as a “single cell gel” (SCG) electrophoresis assay, has become an important tool for assessing DNA damage in exposed populations. This is the method of choice for population-based studies of environmental and occupational exposure to air pollutants, metals, pesticides, radiation, and other xenobiotics as we show in this review. To appreciate the role of the Comet assay in the field of biomonitoring, we review data from 122 studies that employed the assay. These studies evaluated environmental versus occupational exposures and the levels of DNA damage in cells of individuals exposed in each case. Our review of the literature reveals the importance of the need to establish standard methodological conditions that affect unwinding and electrophoresis times and tail values (tail length, tail DNA, tail moment), with the goal of being able to compare data collected in different laboratories throughout the world. The Comet assay is susceptible to subtle artifacts of manipulation depending on the type and timing of sampling performed. Therefore, in the reporting of DNA damage detected by the Comet assay, the context of how the DNA damage was created also needs to be reported and considered in the interpretation of Comet assay results. The success of the Comet assay is reflected by its use over the past 20 years in the field of biomonitoring, and by the increasing number of studies that continue to report its use. As the shortcomings of the assay are identified and considered in the interpretation of DNA damage detection, the Comet assay will continue to provide improved reliability as a biomarker in human biomonitoring studies.     

Genotoxic potential of Cotinus coggygria Scop. (Anacardiaceae) stem extract in vivo

The intention was to evaluate the possible in vivo genotoxic potential in different cell-types, of a methanol extract obtained from the plant stem of Cotinus coggygria Scop., using the sex-linked recessive lethal (or SLRL) test and alkaline comet assay. The SLRL test, revealed the genotoxic effect of this extract in postmeiotic and premeiotic germ-cell lines. The comet assay was carried out on rat liver and bone marrow at 24 and 72 h after intraperitoneal administration. For genotoxic evaluation, three concentrations of the extract were tested, viz., 500, 1000 and 2000 mg/kg body weight (bw), based on the solubility limit of the extract in saline. Comet tail moment and total scores in the group treated with 500 mg/kg bw, 24 and 72 h after treatment, were not significantly different from the control group, whereas in the groups of animals, under the same conditions, but with 1000 and 2000 mg/kg bw of the extract, scores were statistically so. A slight decrease in the comet score and tail moment observed in all the doses in the 72 h treatment, gave to understand that DNA damage induced by Cotinus coggygria extract decreased with time. The results of both tests revealed the genotoxic effect of Cotinus coggygria under our experimental conditions.     

Evaluation of genotoxicity of combined soil pollution by cadmium and imidacloprid

Cadmium (Cd) is one of the important pollutants of soil and the genotoxicity of Cd-contaminated soil was studied in combination with imidacloprid. The single cell gel electrophoresis or comet assay was used to quantify DNA strand breaks as a measure of DNA damage induced by Cd and imidacloprid contamination in soil. The soil was artificially contaminated by Cd (0.0, 0.2, 0.5, 1.0, 2.0 mg· kg^?1 dry soil) or Cd (0.0, 0.2, 0.5, 1.0, 2.0 mg · kg^?1 dry soil) and imidacloprid (0.5 mg · kg^?1 dry soil). Roots ofVicia faba were exposed to the contaminated soil for 2 h at 25°C and were used in the comet assay. DNA damage was measured as the values of percentage of nuclei with tails, tail length, tail DNA, tail moment (TM), and Olive tail moment (OTM). DNA damages of root tips ofVicia faba increased after Cd treatment and there were dose-related increases in DNA damage measured as these parameters. However, the addition of imidacloprid further increased the DNA damage. These data confirmed the genotoxic effect of Cd to plants, and that the combined pollution with imidacloprid can enhance the genotoxicity of Cd.     

Effects of Embryonic Neural Stem Cell Transplantation on DNA Damage in the Brain and Spinal Cord Following Spinal Cord Injury

Embryonic neural stem cell (ENSC) transplantation is used experimentally for the improvement of spinal cord repair following spinal cord injury (SCI). However, the effects of such intervention on oxidative stress and cell death remain unknown. We used in vivo Comet assay in the acute and chronic SCI groups compared with the SCI+ENSC transplantation groups of experimental rats in order to evaluate DNA damage in the spinal cord. Chronic SCI resulted in the generation of oxidative DNA damage in the spinal cord brain and kidneys, as indicated by high Comet assay parameters, including the percentage of DNA in the tail (T%, or TD), tail moment (TM), and tail length (TL). The DNA damage levels significantly decreased after ENSC transplantation in the spinal cords of acute and chronic SCI groups within the lesion site and rostrally and caudally to the injury, and in the brains and kidneys of the chronic SCI group. Thus, ENSC transplantation is found to be an effective tool for limitation of DNA damage following spinal cord injury.     

DNA damage and repair in human peripheral blood lymphocytes following treatment with microcystin-LR

The purpose of this study was to find a possible explanation of the inconsistency of data regarding the genotoxicity of microcystin-LR (MC-LR). We compared the results of the comet assay with the results of the analysis of chromosome aberrations and apoptosis. In order to investigate the influence of MC-LR on DNA damage in human lymphocytes, cells were treated with MC-LR at different concentrations (1, 10 and 25 microg/ml) for 6, 12, 18 and 24 h. Analyses of Olive Tail Moment (OTM) as an indicator of DNA damage showed that MC-LR treatment induced DNA damage in a time-dependent manner, reaching its maximum after 18 h. The lowest values of OTM were observed after 24 h. MC-LR had no effect on the frequency of chromosome aberrations in lymphocytes. Since some data available in the literature indicate that apoptosis may lead to overestimated or false positive results regarding the genotoxicity of mutagens in the comet assay, we measured the frequency of late apoptotic cells by use of the comet assay and the frequency of early apoptotic cells with the TUNEL method. The comet assay results revealed that the highest level of apoptosis was observed after 24 h and the lowest after 18 h. The comparison of the frequency of apoptotic cells determined by the comet assay with DNA damage (OTM) examined by the comet assay revealed a statistically significant, negative correlation. The TUNEL results showed that the frequency of apoptotic cells progressively increased in a dose- and time-dependent manner. The comparison of the frequency of apoptotic cells determined by TUNEL method with DNA damage (OTM) examined by the comet assay showed a significant positive correlation for lymphocytes treated with MC-LR for 6, 12 and 18 h. Therefore, our findings indicate that microcystin-LR-induced DNA damage observed in the comet assay may be related to the early stages of apoptosis due to cytotoxicity but not genotoxicity. In addition, we examined the DNA repair kinetics in lymphocytes following treatment with microcystin-LR and ionizing radiation. Our results indicate that MC-LR has an inhibiting effect on the repair of radiation-induced damage.     

In vivo Comet assay on isolated kidney cells to distinguish genotoxic carcinogens from epigenetic carcinogens or cytotoxic compounds

The objective of this study was to determine the ability of the alkaline in vivo Comet assay (pH>13) to distinguish genotoxic carcinogens from epigenetic carcinogens when performed on freshly isolated kidney cells and to determine the possible interference of cytotoxicity by assessing DNA damage induced by renal genotoxic, epigenetic or toxic compounds after enzymatic isolation of kidney cells from OFA Sprague-Dawley male rats. The ability of the Comet assay to distinguish (1) genotoxicity versus cytotoxicity and (2) genotoxic versus non-genotoxic (epigenetic) carcinogens, was thus investigated by studying five known genotoxic renal carcinogens acting through diverse mechanisms of action, i.e. streptozotocin, aristolochic acids, 2-nitroanisole, potassium bromate and cisplatin, two rodent renal epigenetic carcinogens: d-limonene and ciclosporine and two nephrotoxic compounds: streptomycin and indomethacin. Animals were treated once with the test compound by the appropriate route of administration and genotoxic effects were measured at the two sampling times of 3-6 and 22-26h after treatment. Regarding the tissue processing, the limited background level of DNA migration observed in the negative control groups throughout all experiments demonstrated that the enzymatic isolation method implemented in the current study is appropriate. On the other hand, streptozotocin, 20mg/kg, used as positive reference control concurrently to each assay, caused a clear increase in the mean Olive Tail Moment median value, which allows validating the current methodology. Under these experimental conditions, the in vivo rodent Comet assay demonstrated good sensitivity and good specificity: all the five renal genotoxic carcinogens were clearly detected in at least one expression period either directly or indirectly, as in the case of cisplatin: for this cross-linking agent, the significant decrease in DNA migration observed under standard electrophoresis conditions was clearly amplified when the duration of electrophoresis was increased up to 40min. In contrast, epigenetic and nephrotoxic compounds failed to induce any signifcant increase in DNA migration. In conclusion, the in vivo rodent Comet assay performed on isolated kidney cells could be used as a tool to investigate the genotoxic potential of a test compound if neoplasic/preneoplasic changes occur after subchronic or chronic treatments, in order to determine the role of genotoxicity in tumor induction. Moreover, the epigenetic carcinogens and cytotoxic compounds displayed clearly negative responses in this study. These results allow excluding a DNA direct-acting mechanism of action and can thus suggest that a threshold exists. Therefore, the current in vivo rodent Comet assay could contribute to elucidate an epigenetic mechanism and thus, to undertake a risk assessment associated with human use, depending on the exposure level.     

DNA damage among thyroid cancer and multiple cancer cases, controls, and long-lived individuals

Variation in the detection, signaling, and repair of DNA damage contributes to human cancer risk. To assess capacity to modulate endogenous DNA damage among radiologic technologists who had been diagnosed with breast cancer and another malignancy (breast-other, n=42), early-onset breast cancer (early-onset, age or=75% versus below the median, age-adjusted) was most consistently associated with the highest odds ratios in the breast-other, early-onset, and thyroid cancer groups (with risk increased 10-, 5- or 19-fold, respectively, with wide confidence intervals) and decreased risk among the hyper-normal group. For the other three comet measures, risk of breast-other was elevated approximately three-fold. Risk of early-onset breast cancer was mixed and risk of thyroid cancer ranged from null to a two-fold increase. The hyper-normal group showed decreased odds ratios for tail DNA and OTM, but not CDM. DNA damage, as estimated by all comet measures, was relatively unaffected by survival time, reproductive factors, and prior radiation treatment. We detected a continuum of endogenous DNA damage that was highest among cancer cases, less in controls, and suggestively lowest in hyper-normal individuals. Measuring this DNA damage phenotype may contribute to the identification of susceptible sub-groups. Our observations require replication in a prospective study with a large number of pre-diagnostic samples.     

Comet assay responses in human lymphocytes are not influenced by the menstrual cycle: a study in healthy Indian females

The single-cell gel electrophoresis or Comet assay measures qualitative and quantitative DNA damage in single cells. Its simplicity and non-invasive nature has made it widely accepted for the monitoring of human genotoxicity, employing peripheral blood lymphocytes. Factors, such as gender, age, and dietary and smoking habits are known to affect the Comet assay responses in lymphocytes. However, there is no information regarding the influence of the menstrual cycle on the results of the assay in lymphocytes of females. A study was therefore undertaken among 18 healthy Indian female volunteers to assess the effect of the menstrual cycle on Comet assay responses. During a complete menstrual cycle, only minor changes were observed in the basal levels of DNA damage in the lymphocytes as evident by Comet parameters, such as tail length (microm), tail DNA (%) and Olive tail moment (arbitrary units). To assess the effect of the estrogen 17beta-estradiol (at physiological concentrations of 0.5, 1.0 and 2.0 nM) on the Comet assay responses, an in vitro study was conducted in the human lymphocyte cell line JM-1 and the breast cancer cell line MCF-7. As was evident from the Comet parameters, a significant (p < 0.01) concentration-dependent increase in the level of DNA damage was observed in the MCF-7 cells while no significant change was found in the JM-1 cells. The results indicate that the menstrual cycle does not influence the Comet assay responses in lymphocytes; hence, these can serve as a model for monitoring genotoxicity in females.     

Comet assay responses in human lymphocytes are not influenced by the menstrual cycle: a study in healthy Indian females

The single-cell gel electrophoresis or Comet assay measures qualitative and quantitative DNA damage in single cells. Its simplicity and non-invasive nature has made it widely accepted for the monitoring of human genotoxicity, employing peripheral blood lymphocytes. Factors, such as gender, age, and dietary and smoking habits are known to affect the Comet assay responses in lymphocytes. However, there is no information regarding the influence of the menstrual cycle on the results of the assay in lymphocytes of females.A study was therefore undertaken among 18 healthy Indian female volunteers to assess the effect of the menstrual cycle on Comet assay responses. During a complete menstrual cycle, only minor changes were observed in the basal levels of DNA damage in the lymphocytes as evident by Comet parameters, such as tail length (μm), tail DNA (%) and Olive tail moment (arbitrary units).To assess the effect of the estrogen 17β-estradiol (at physiological concentrations of 0.5, 1.0 and 2.0 nM) on the Comet assay responses, an in vitro study was conducted in the human lymphocyte cell line JM-1 and the breast cancer cell line MCF-7. As was evident from the Comet parameters, a significant (p < 0.01) concentration-dependent increase in the level of DNA damage was observed in the MCF-7 cells while no significant change was found in the JM-1 cells.The results indicate that the menstrual cycle does not influence the Comet assay responses in lymphocytes; hence, these can serve as a model for monitoring genotoxicity in females.     

A comparative evaluation of aflatoxin B1 genotoxicity in fish models using the Comet assay

Aflatoxin B₁ (AFB₁) is classified as a Group I hepatocarcinogen in humans by the International Agency for Research on Cancer (IARC). The alkaline Comet assay is a simple and rapid method by which DNA damage can be demonstrated as a function of tail moment. The present work is the first to evaluate the genotoxicity of AFB₁ in fish using the Comet assay. Two different species of fish were selected as models due to previously established sensitivity to AFB₁: rainbow trout (sensitive) and channel catfish (resistant). Fish were i.p. injected with 0.5 mg AFB₁/1 ml DMSO/1 kg body weight. The Comet assay was performed after 4 and 24 h on whole blood, liver, and kidney cells of both species. Trout blood and kidney tissue tested displayed significant (p<0.05) and extensive DNA damage (shown by increased tail moment) after 4 h which then decreased by 24 h. In liver cells, damage progressively increased over time. Conversely, similarly treated catfish showed no elevation in DNA damage over controls at the same doses. These results suggest that the Comet assay is a useful tool for monitoring the genotoxicity of mycotoxins such as AFB₁ and for evaluating organ specific effects of these agents in different species.     

Alkaline, Endo III and FPG modified comet assay as biomarkers for the detection of oxidative DNA damage in rats with experimentally induced diabetes

Increased production of reactive oxygen species under diabetic condition underlines the higher oxidatively damaged DNA in different tissues. However, it is practically difficult to assess the oxidatively damaged DNA in different internal organs. Therefore, the present study was aimed to evaluate the extent of oxidative stress-induced DNA damage in different organs with the progression of diabetes. Diabetic and control Sprague Dawley rats were sacrificed in time-dependent manner and the lung, liver, heart, aorta, kidney, pancreas and peripheral blood lymphocytes (PBL) were analyzed for both alkaline and modified comet assay with endonuclease-III (Endo III) and formamidopyrimidine-DNA glycosylase (FPG) (hereafter called modified comet assay) for the detection of oxidative DNA damage. The statistically significant increase in olive tail moment (OTM) was found in all the tested tissues. The extent of DNA damage was increased with the progression of diabetes as revealed by the parameter of OTM in alkaline and modified comet assay. Further, the positive correlations were observed between OTM of the lung, liver, heart, aorta, kidney and pancreas with PBL of diabetic rat in the alkaline and modified comet assay. Moreover, significant increase in the 8-oxodG positive nuclei in the lung, liver, heart, aorta, kidney and pancreas was observed in 4th and 8th week diabetic rat as compared to control. Results of the present study clearly indicated the suitability of alkaline and modified comet assay for the detection of multi-organ oxidative DNA damage in streptozotocin (STZ)-induced diabetic rat and showed that damaged DNA of PBL can be used as a suitable biomarker to assess the internal organs response to DNA damage in diabetes.     

Spontaneous and induced genetic damage in T lymphocyte subsets evaluated by the Comet assay

High inter- and intra-individual variability was reported in the level of DNA damage, both spontaneous and induced, when peripheral blood mononuclear leukocytes were used to perform the Comet assay. In order to find out the underlying causes for such variability, different subsets of T lymphocytes were isolated by immunomagnetic cell sorting. The level of DNA damage was evaluated with the alkaline version of the Comet assay by using three different parameters: tail moment, tail length and amount of DNA in the tail (%). Helper T cells (CD4+), cytotoxic T cells (CD8+), their negative fraction and the mixed cell population were evaluated both in untreated cells and after 10 and 20 microM H(2)O(2) treatments. Differences between cell subsets were only observed after H(2)O(2) treatment. The results indicate that, although CD4+ is the fraction with the highest induced level of genetic damage, this value is not high enough to explain the large inter- and intra-individual variability found.     

In vivo Comet assay on isolated kidney cells to distinguish genotoxic carcinogens from epigenetic carcinogens or cytotoxic compounds

The objective of this study was to determine the ability of the alkaline in vivo Comet assay (pH > 13) to distinguish genotoxic carcinogens from epigenetic carcinogens when performed on freshly isolated kidney cells and to determine the possible interference of cytotoxicity by assessing DNA damage induced by renal genotoxic, epigenetic or toxic compounds after enzymatic isolation of kidney cells from OFA Sprague–Dawley male rats. The ability of the Comet assay to distinguish (1) genotoxicity versus cytotoxicity and (2) genotoxic versus non-genotoxic (epigenetic) carcinogens, was thus investigated by studying five known genotoxic renal carcinogens acting through diverse mechanisms of action, i.e. streptozotocin, aristolochic acids, 2-nitroanisole, potassium bromate and cisplatin, two rodent renal epigenetic carcinogens: d-limonene and ciclosporine and two nephrotoxic compounds: streptomycin and indomethacin. Animals were treated once with the test compound by the appropriate route of administration and genotoxic effects were measured at the two sampling times of 3–6 and 22–26 h after treatment. Regarding the tissue processing, the limited background level of DNA migration observed in the negative control groups throughout all experiments demonstrated that the enzymatic isolation method implemented in the current study is appropriate. On the other hand, streptozotocin, 20 mg/kg, used as positive reference control concurrently to each assay, caused a clear increase in the mean Olive Tail Moment median value, which allows validating the current methodology.Under these experimental conditions, the in vivo rodent Comet assay demonstrated good sensitivity and good specificity: all the five renal genotoxic carcinogens were clearly detected in at least one expression period either directly or indirectly, as in the case of cisplatin: for this cross-linking agent, the significant decrease in DNA migration observed under standard electrophoresis conditions was clearly amplified when the duration of electrophoresis was increased up to 40 min. In contrast, epigenetic and nephrotoxic compounds failed to induce any signifcant increase in DNA migration. In conclusion, the in vivo rodent Comet assay performed on isolated kidney cells could be used as a tool to investigate the genotoxic potential of a test compound if neoplasic/preneoplasic changes occur after subchronic or chronic treatments, in order to determine the role of genotoxicity in tumor induction. Moreover, the epigenetic carcinogens and cytotoxic compounds displayed clearly negative responses in this study. These results allow excluding a DNA direct-acting mechanism of action and can thus suggest that a threshold exists. Therefore, the current in vivo rodent Comet assay could contribute to elucidate an epigenetic mechanism and thus, to undertake a risk assessment associated with human use, depending on the exposure level.     

紫外辐射诱导烟草原生质体中DNA损伤的彗星电泳检测

以烟草原生质体为材料,采用彗星电泳检测用0.5W·m^-2紫外线以不同时间（0、5、10、30、60和120s）诱导的烟草原生质体中DNA的损伤。结果表明,在0～10s的时间内代表DNA损伤程度的尾矩、Olive尾矩等参数与紫外线照射时间具有良好的时间依赖关系。本文建立的烟草原生质体体系采用彗星电泳技术,可以快速而灵敏地检测紫外线对植物细胞的损伤程度。     

Application of Euglena gracilis cells to comet assay: evaluation of DNA damage and repair

Alkaline single-cell gel electrophoresis (comet assay) enables sensitive detection of DNA damage in eukaryotic cells induced by genotoxic agents. We performed a comet assay of unicellular green alga Euglena gracilis that was exposed to genotoxic chemicals, 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), benzo[a]pyrene (BAP), mitomycin C (MMC) and actinomycin D (AMD). Tail length and tail moment in migrated DNA were measured as indications of DNA damage. MNNG and BAP were found to cause concentration-dependent increases in DNA damage. The responses were more sensitive than those of human lymphocytes under the same treatment conditions. MMC and AMD showed no positive response, as reported elsewhere. The comet assays performed at specified times after treatment revealed that the DNA damaged by MNNG and gamma-ray irradiation was repaired during the initial 1h. The results clearly show that the comet assay is useful for evaluating chemically-induced DNA damage and repair in E. gracilis. Given the ease of culturing and handling E. gracilis as well as its sensitivity, the comet assay of this alga would undoubtedly prove to be a useful tool for testing the genotoxicity of chemicals and monitoring of environmental pollution.     

Induction and repair of DNA damage as measured by the Comet assay and the yield of somatic mutations in gamma-irradiated tobacco seedlings

The advantage of using the tobacco (Nicotiana tabacum var. xanthi) mutagenicity assay is the ability to analyze and compare on the same plants under identical treatment conditions both the induced acute DNA damage in somatic cells as measured by the Comet assay and the yield of induced leaf somatic mutations. Gamma-irradiation of tobacco seedlings induced a dose-dependent increase in somatic mutations from 0.5 (control) to 240 per leaf (10Gy). The increased yield of somatic mutations was highly correlated (r = 0.996) with the increased DNA damage measured by the Comet assay immediately after irradiation. With increased dose of gamma-irradiation, the averaged median tail moment values ( +/- S.E.) significantly increased from 1.08 +/- 0.10 (control) to 20.26 +/- 1.61 microm (10Gy). Nuclei isolated from leaves 24h after irradiation expressed tail moment values that were not significantly different from the control (2.08 +/- 0.11). Thus a complete repair of DNA damage induced by gamma-irradiation and measurable by the Comet assay was observed, whereas the yield of somatic mutations increased in relation to the radiation dose. Data on the kinetics of DNA repair and of DNA damage induced by gamma-radiation on isolated tobacco nuclei, and on nuclei isolated from irradiated leaves and roots are presented.     

Lymphocyte DNA damage in cigarette factory workers measured by the Comet assay.

To investigate whether there were separate and combined effects of occupational exposure to tobacco dust and smoking on lymphocyte DNA damage, 148 workers from a cigarette manufacturing factory (107 occupationally exposed to tobacco dust from the production department and 41 unexposed controls who were managerial workers) were included in the study. The Tail Moment (TM) of Comet assay was used to measure DNA damage. The two groups had similar mean age, mean duration of work and smoking prevalence. The exposed workers had a larger TM than that of the controls (mean+/-S.D.: 43.43+/-13. 77 vs. 38.89+/-8.98, p<0.05). Smokers had significantly larger TM than non-smokers (47.25+/-14.02 vs. 38.90+/-10.75, p<0.001). Analysis of variance after adjustment for age and gender showed that occupational exposure and smoking had a significant and independent effect on Tail Moment (p=0.025 and p=0.002, respectively) and there was a significant positive two way interaction between the two factors (p=0.019). Age and gender had no significant effect on TM. The present study suggests that smoking and tobacco dust exposure can induce lymphocyte DNA damage and there is a synergistic effect of tobacco dust exposure and smoking on DNA damage.