Mobile phone specific radiation disturbs cytokinesis and causes cell death but not acute chromosomal damage in buccal cells: Results of a controlled human intervention study

Several human studies indicate that mobile phone specific electromagnetic fields may cause cancer in humans but the underlying molecular mechanisms are currently not known. Studies concerning chromosomal damage (which is causally related to cancer induction) are controversial and are based on the use of questionnaires to assess the exposure. We realized the first human intervention trial in which chromosomal damage and acute toxic effects were studied under controlled conditions. The participants were exposed via headsets at one randomly assigned side of the head to low and high doses of a UMTS signal (n = 20, to 0.1 W/kg and n = 21 to 1.6 W/kg Specific Absorption Rate) for 2h on 5 consecutive days. Before and three weeks after the exposure buccal cells were collected from both cheeks and micronuclei (MN, which are formed as a consequence of structural and numerical chromosomal aberrations) and other nuclear anomalies reflecting mitotic disturbance and acute cytotoxic effects were scored. We found no evidence for induction of MN and of nuclear buds which are caused by gene amplifications, but a significant increase of binucleated cells which are formed as a consequence of disturbed cell divisions, and of karyolitic cells, which are indicative for cell death. No such effects were seen in cells from the less exposed side. Our findings indicate that mobile phone specific high frequency electromagnetic fields do not cause acute chromosomal damage in oral mucosa cells under the present experimental conditions. However, we found clear evidence for disturbance of the cell cycle and cytotoxicity. These effects may play a causal role in the induction of adverse long term health effects in humans.

DNA Purification from Bloodstains and Buccal Cells/Saliva on FTA® Cards

FTA® cards enable efficient, long-term storage of blood and buccal cells/saliva samples for future forensic DNA analysis; these are typically collected as known reference samples, as opposed to evidentiary, crime scene samples. Upon contact with the FTA® card, cells are lysed and the DNA is immobilized. Different FTA® cards are available and have been specially formulated based on sample type: bloodstains are added to the traditional FTA® Card, while colorless sources (e.g., buccal cells/saliva) are added to the FTA® Indicating Card. The main difference between these cards is the presence of a pink dye embedded in the indicating cards that becomes white when exposed to colorless fluids, like saliva; this aids in location confirmation of the stain for future sampling. Although DNA can be eluted/extracted from FTA® punches using various methods or, alternatively, direct STR amplification from unpurified punches can be performed, the protocol herein describes a simple purification method for bloodstained punches from FTA® Cards as well as buccal/saliva-stained punches from FTA® Indicating Cards. Following this purification, STR amplification can be performed via the "punch-in" method.

Association of buccal micronucleus cytome assay (BMNCyt) biomarkers with inorganic element concentration and genetic polymorphisms in welders

Welding fumes are classified as carcinogenic to humans. The aim of the present study was to measure buccal micronucleus cytome assay biomarkers and to evaluate their association with inorganic elements and genetic polymorphisms (XRCC1, OGG1, XRCC3, GSTM1, and GSTT1) in welders (n = 98) and control individuals (n = 100). Higher levels of DNA damage and cell death were observed in the exposed group. Also, a significant correlation between the frequency of micronuclei and Na, Si, Cl, Ti, Cr, Zn and Mg concentrations. The formation of micronuclei, binucleated cells, cell death was associated with polymorphisms in repair pathways. The OGG1Ser326Cys and XRCC3 241Thr/Met genotypes were associated with cell death. Individuals with GSTM1 null genotype had a higher frequency of micronuclei. These results demonstrate that the deleterious effects of exposure to welding fumes are exacerbated by lifestyle habits, and genetic polymorphisms can influence DNA damage and cell death.

Rapid and inexpensive method of PCR ready DNA isolation from human peripheral blood and saliva

BACKGROUND

The isolation of nucleic acids is a frequently performed procedure in the molecular biology area. Although several rapid DNA isolation techniques from human peripheral blood and saliva have been developed, there are still some disadvantages - volume, time, cost, and yield are a few notable ones.

OBJECTIVE

We aim to develop a rapid and inexpensive method to isolate high-molecular-weight genomic DNA from human peripheral blood and saliva that can be used for molecular biology experiments.

METHODS

Five DNA isolation methods with slightly varying protocols were used. High-quality DNA obtained from one specific method was further amplified by PCR and the template with good amplification was further used for performing RFLP and sequencing.

RESULTS

Out of 5 different isolation methods (R1 to R5), DNA obtained from the R4 was of good quality (molecular weight is > 10 kb and 260/280 ratio is 1.89 ± 0.2), which allows successful PCR amplification and good separation in Restriction Fragment Length Polymorphism analysis. Sequencing by the Sanger Sequencing produced a good readable sequence of an amplified fragment from Method R4 DNA.

CONCLUSION

In the present study we have developed a simple, rapid, and cost-effective DNA isolation method, which uses low sample volume and yields good quantity and high-quality product. The DNA obtained is highly fit for molecular genetics research applications.

Genomic instability in Buccal mucosal cells of children living in abnormal conditions from Santos-Sao Vicente Estuary

The aim of this study was to evaluate genomic instability and cytotoxicity in buccal mucosa cells of children living in abnormal conditions from Santos Sao Vicente estuary. The study area is located between coordinates 23°58'11.8"S and 46°24'26.3"W, in the southwestern zone of the Sao Paulo State, Brazil. A total of 40 children was distributed into two groups: exposed and non-exposed groups. The frequency of micronuclei increased to buccal mucosa cells of children living in Santos Sao Vicente estuary when compared to the non-exposed group (p < 0.05). No remarkable differences on buccal cells were found inpyknosis, karyorrhexis and karyolysi between groups. Taken together, our results suggest that children living in contaminated areas comprise a high group for genomic instability on buccal mucosa cells. Given that the current investigation is a preliminary study, further analysis with a larger sample of children is interesting as a future perspective.

The Genotoxic and Cytotoxic Effects of CT Scan on Buccal Epithelial Cells

Background:

Diagnostic radiation is reported to cause significant damage in buccal cells, while the same effects after natural cell turn over cycle were not checked for in previous studies. The buccal cells were studied in patients exposed to computed tomography (CT) scans for evaluating the cells with micronuclei and cytotoxic changes, namely, pyknotic cells, karyorrhectic cells and karyolytic cells. The pre-exposure counts were compared with postexposure counts on 10 and 20 days corresponding to first and second cell turnover cycles.

Aim:

The aim of this study is to estimate the counts of micronucleus and cytotoxic changes in buccal cells post-exposure to CT scans and report on variance of the same with first and second buccal cell turnover cycles.

Materials and Methods:

This is an observational study, wherein the buccal smears of patients undergoing CT scans were made before and after CT scan exposures as needed. Papanicolaou (PAP) staining and analysis were performed as per standard criteria for micronuclear and cytotoxic changes, respectively. Statistical test used was paired t-tests.

Results:

The micronuclear counts revealed 0.4% positive cells before exposure and 1.4% positive cells post 10 days and 20 days of exposure were significant (P < 0.005). The cytotoxic changes showed around 2.5% positive cells before and 5.7% positive cells 10 days after CT exposure (P < 0.005). The cytotoxic cell values from baseline to 20^th day were not significant (P < 0.25).

Conclusion:

CT scans have caused genotoxic effects notable after two cell turnover cycles but the cytotoxic changes have significantly decreased naturally after 2^nd cell turnover as per our study.

Age related micronuclei frequency ranges in buccal and nasal cells in a healthy population

BACKGROUND

Micronuclei (MNs) are extranuclear DNA-containing bodies and determining MN frequencies is a measure of genomic instability. An age-related increase in MN frequencies in lymphocytes has been quantified, but this effect has not yet been measured in nasal and buccal cells.

METHODS

We determined the effect of age on the MN frequency distributions in buccal and nasal cells among a sample of a general adult population in Switzerland. To maximize the power to detect an effect of age in our population study, we recruited preferentially younger and older working age adults. We harvested buccal and nasal cells from 32 young (19-36 year) and 33 working age (47-71 years) participants. The collected cells were washed, centrifuged, and stained (Feulgen) before microscopic manual counting in 2000 cells. Based on these results, we developed an age-dependent background MN frequency chart to help interpret an individual's MN frequency score as an early signal for the effect of genotoxic exposure.

RESULTS

MN frequencies were respectively 0.53‰ and 0.47‰ for buccal and nasal among the younger and 0.87‰ and 1.03‰ in the older working age group. This corresponded to a multiplicative slope of 14% and 20% per 10 years of age for buccal and nasal cells, respectively.

CONCLUSION

Based on our study results, we are able to propose an approach for interpreting an individual's MN screening results.

Chromosome fragility in the buccal epithelium in patients with Fanconi anemia

Fanconi anemia (FA) is a rare genome instability syndrome characterized by progressive bone marrow failure and predisposition to cancer, especially head and neck squamous cell carcinoma. Surgical resection is the standard of care for solid tumors, as patients with FA do not tolerate genotoxic chemotherapies or radiation, leading to poor prognosis. It is therefore imperative to develop chemoprevention strategies such as the identification of novel biomarkers to detect the formation of the tumor before its emergence and to use them in clinical trials aimed to counteract genome instability of patients with FA in tissues at risk. Micronuclei (MN) are chromosome fragments that are left behind in anaphase and appear in daughter cells as small additional nuclei. In this work, we analyzed MN frequencies in exfoliated buccal cells from 40 patients with FA and 24 controls. We found that MN frequency was significantly increased in the FA cohort indicating that we can detect chromosome fragility in patients with FA in basal conditions and in a tissue that is divided in vivo. Consequently, the MN assay in exfoliated buccal cells of patients with FA could be used in cancer risk studies and clinical trials aimed to identify cancer chemopreventive drugs.

Nucleic Acid Extraction from Human Biological Samples

Nucleic acid isolation is often the starting point for all downstream experiments in biomedical research. It is therefore the most crucial step in any molecular technique. DNA and RNA extraction follow protocols with standardized reagents, many of which are available in quality-controlled commercial kits. Irrespective of the protocol, successful extraction of high-quality nucleic acid from biological tissues requires sufficient disruption of the tissue and cellular structures, denaturation of nucleoprotein complexes, inactivation of nucleases, and nucleic acid purification. These steps can be modified based on nucleic acid of interest and biological sample source. This chapter addresses DNA and RNA extraction from a variety of sample and tissue types, including saliva, and formalin-fixed, paraffin-embedded tissues, which are often archived in clinical pathology laboratories. Special considerations and common pitfalls of each protocol will also be discussed, as will nucleic acid quantitation techniques.

Physical activity, black carbon exposure, and DNA methylation in the FOXP3 promoter

Background

Physical activity is associated with improvement in lung function; however, pollution exposure during physical activity can lead to a transient reduction in lung function. This paradoxical relationship may be linked to altered T regulatory (Treg) cell activity, which increases with exercise and suppresses airway inflammation, but decreases in association with exposure to air pollution. To clarify these relationships, we investigated buccal cell DNA methylation of the forkhead box p3 (FOXP3) gene promoter, a proposed biomarker of Treg activity. We hypothesized that active urban children would have lower FOXP3 promoter methylation, associated with better lung function compared to non-active children. We also hypothesized that this relationship would be attenuated by high exposure to the air pollutant black carbon (BC).

Methods

We performed a cross-sectional study of 135 children ages 9–14 who live in New York City. Activity was measured across 6 days. BC exposure was assessed by personal monitors worn for two 24-h periods, followed by lung function assessment. Buccal swabs were collected for DNA methylation analysis of three regions (six CpG sites) in the FOXP3 promoter.

Results

In multivariable regression models, overall, there was no significant relationship between physical activity and FOXP3 promoter methylation (p > 0.05). However, in stratified analyses, among children with higher BC exposure (≥1200 ng/m³), physical activity was associated with 2.37% lower methylation in promoter 2 (CpGs −77, −65, and −58) (β_estimate = −2.37%, p < 0.01) but not among those with lower BC exposure (β_estimate = 0.54%, p > 0.05). Differences across strata were statistically significant (p_interaction = 0.04). Among all children, after controlling for BC concentration, promoter 2 methylation was associated with reduced FEV₁/FVC (β_estimate = −0.40%, p < 0.01) and reduced FEF_25–75% (β_estimate = −1.46%, p < 0.01).

Conclusions

Physical activity in urban children appeared associated with lower FOXP3 promoter methylation, a possible indicator of greater Treg function, under conditions of high BC exposure. Reduced FOXP3 promoter methylation was associated with higher lung function. These findings suggest that physical activity may induce immunologic benefits, particularly for urban children with greater risk of impaired lung function due to exposure to higher air pollution. FOXP3 promoter buccal cell methylation may function as a useful biomarker of that benefit.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0364-0) contains supplementary material, which is available to authorized users.

Genotoxic risk assessment in professionals working hairdressers area using buccal micronucleus assay, in Aydın City, Turkey

The aim of this study was to determine the genotoxic risk of professional hairdressers in Aydın City, Turkey, through investigating the micronucleus frequencies in buccal mucosa epithelial cells. All the hairdresser working hairdresser area were included in the genotoxic risk group (GRG = 20) in Aydın City, Turkey. The control group (CG = 20) comprised healthy individuals matching the gender and age of the GRG. Buccal mucosal scraping from all the 40 subjects of GRG (10 women and 10 men) and CG (10 women and 10 men) was stained with Giemsa stain and observed under light microscope (×40) for the presence of micronuclei (M 10 N) and karyolysis, pyknosis, condensed chromatin, karyorrhexis, nuclear bud, and binucleates in the exfoliated epithelial cells. There are significance between the incidence of MN in GRG and CG (P = <0.005) using one-way ANOVA, Kolmogorov-Smirnov Z test, and Spearman Rank Correlation Tests.

Association of CXCL12 gene promoter methylation with periodontitis in patients with diabetes mellitus type 2

OBJECTIVES

CXCL12 is widely expressed, constitutive chemokine involved in tissue repair and regeneration, while the extent of its expression is important in various chronic inflammatory conditions. Involvement of DNA methylation in CXCL12 gene suppression (CXCL12) has been shown in malignancy and some autoimmune diseases. The aim of this study was to investigate whether the alterations in DNA methylation of CXCL12 are also involved in progression of periodontitis in combination with diabetes, as these chronic inflammatory conditions are strongly interrelated.

DESIGN

Study included 72 subjects divided in three groups: healthy control (C, n=21), periodontitis (P, n=29) and diabetes/periodontitis group (D/P, n=22). DNA extracted from epithelial cells obtained by sterile cotton swabs from buccal mucosa was subjected to methylation specific polymerase chain reaction (MSP) to obtain DNA methylation pattern of CXCL12 promoter.

RESULTS

CXCL12 promoter was predominantly unmethylated in all groups. However, increase in the frequency of the methylated form and increase in percent of methylation of CXCL12 promoter in periodontitis and diabetes/periodontitis group compared to control group were found, although without statistical significance. However, statistically significant increase in Tm of MSP products in diabetes/periodontitis group was observed. Correlation analysis revealed statistically significant relationship between the extent of DNA methylation of the CXCL12 promoter and periodontal parameters, as well as between DNA methylation of CXCL12 and glycosylated hemoglobin.

CONCLUSION

Presented results suggest that chronic inflammation contributes to the change of CXCL12 DNA methylation in buccal cells and that DNA methylation profile of CXCL12 promoter plays important role in development and progression of periodontal disease.

Predictors of biospecimen donation in the Black Women's Health Study

PURPOSE

Although African-Americans experience higher cancer morbidity and mortality rates compared to their White counterparts, their participation in biospecimen research is lower than that of their white peers. This study investigated the prevalence and predictors of biospecimen donation in a large, cohort study of Black women.

METHODS

The BWHS is a follow-up study of U.S. Black women aged 21-69 years enrolled through postal health questionnaires. Between January 2004 and December 2007, participants were sent a consent form with a postage-paid return envelope, and a mouthwash collection kit. Univariate and age- and educational status-adjusted logistic regression models were used to estimate the association of socio-demographic, lifestyle and medical factors with donation of biospecimens.

RESULTS

Buccal cells with consent forms were obtained from 26,790 women, for a response rate of 51 %. The strongest predictors of biospecimen donation were age: response increased from 48.6 % among those aged <40 to 63.1 % among those aged 60 and older [RR 1.30 (95 % CI 1.27, 1.34)]; multivitamin use [RR (95 % CI) 1.32 (1.30, 1.34)]; physician visit in the previous 2 years [RR (95 % CI) 1.61 (1.58, 1.65)], and a history of breast [RR (95 % CI) 1.59 (1.56, 1.63)], colon [RR (95 % CI) 1.18 (1.16, 1.20)], and cervical [RR (95 % CI) 1.63 (1.60, 1.67)] cancer screening.

CONCLUSIONS

We found that 51 % of women in the geographically-dispersed Black Women's Health Study cohort were willing to provide mouthwash samples to be used for genetic analyses. The response in this study is encouraging given published findings of low overall participation rates of African-Americans in genetic studies.

The association of nuclear abnormalities in exfoliated buccal epithelial cells with the health status of different agricultural activities farmers in Peninsular Malaysia

BACKGROUND

Pesticide exposure possesses risk of genotoxicity to humans, particularly farmers. Despite accumulating evidences linking genotoxicity to pesticide exposure, epidemiological studies to address pesticide toxicity in occupationally exposed farmers in Malaysia remain underreported. Thus, this study was aimed to determine the presence of nuclear abnormalities through the assessment of micronucleus (MN) and binucleus (BNu) frequencies in exfoliated buccal epithelial cells from farmers who were exposed to pesticides. A cross-sectional study of farmers among different agricultural activities farmers in Bachok and Pasir Puteh, Kelantan, North East of Peninsular Malaysia was done to evaluate the presence of nuclear abnormalities and its correlation with their health status and farming activities.

RESULTS

Analysis of buccal cells revealed that the frequency of MN was significantly higher (p < 0.05) in farmers as compared to controls. In contrast, no significant difference (p > 0.05) was observed for BNu frequency in between groups. Correlation analysis showed that apart from a significant (p < 0.05) and positive correlation between the duration of fertilizers exposure and frequencies of MN (r = 0.42, P = 0.001) and BNu (r = 0.37, P = 0.02), no other correlation of various confounding factors on the formation of MN and BNu were observed.

CONCLUSION

In conclusion, pesticide and fertilizers exposure may contribute to the promotion of nuclear anomalies among Malaysian farmers who are engaged in mixed plantation activities. Further assessment of larger populations is important to address and overcome the potential risk of pesticide-induced genotoxicity.

Preliminary study of genotoxicity evaluation of orthodontic miniscrews on mucosa oral cells by the alkaline comet assay

Miniscrew implants are widely used nowadays in orthodontic treatments due to their good results in clinical practice. However, data regarding the biocompatibility of commercially available orthodontic miniscrews and temporary devices are very scarce, and their role as genotoxicity inducers has been not previously evaluated with the alkaline comet assay. The aim of this study was to investigate the DNA damage in buccal cells of patients subjected to orthodontic treatments. The alkaline comet assay has been applied in oral mucosa cells from patients treated with conventional orthodontic treatment in comparison to patients treated additionally with miniscrews, non-treated volunteers (control) and smoking volunteers (positive control). The application of orthodontic appliances and miniscrews induced significant and similar (2-fold) increases of %DNA in tail in comparison to control group. Females experienced a significant increase in %DNA in all the treatments in comparison to the control group, whereas males showed significant damage only with the combined orthodontic and miniscrew treatment. In conclusion, conventional orthodontic appliances induced genotoxicity, and the incorporation of miniscrews assayed did not imply any additional increase of DNA damage.

Tobacco smoking-response genes in blood and buccal cells

Tobacco smoking is a well-known cause of various diseases, however, its toxic mechanisms for diseases are not completely understood, yet. Therefore, we performed biological monitoring to find tobacco smoking-responsive mechanisms including oxidative stress in Korean men (N=36). Whole genome microarray analyses were performed with peripheral blood from smokers and age-matched nonsmokers. We also performed qRT-PCR to confirm the microarray results and compared the gene expression of blood to those of buccal cells. To assess the effects of tobacco smoking on oxidative stress, we analyzed urinary levels of malondialdehyde (MDA), a lipid peroxidation marker, and performed PCR-based arrays on reactive oxygen species (ROS)-related genes. As results, 34 genes were differently expressed in blood between smokers and nonsmokers (ps<0.01 and >1.5-fold change). Particularly, the genes involved in immune responsive pathways, e.g., the Fcγ-receptor mediated phagocytosis and the leukocyte transendothelial migration pathways, were differentially expressed between smokers and nonsmokers. Among the above genes, the ACTG1, involved in the maintenance of actin cytoskeleton, cell migration and cancer metastasis, was highly expressed by smoking in both blood and buccal cells. Concerning oxidative stress, smokers showed high levels of urinary MDA and down-regulation of expressions of antioxidant related genes including TPO, MPO, GPX2, PTGR1, and NUDT1 as compared to nonsmokers (ps<0.05). In conclusion, these results suggest that systemically altered immune response and oxidative stress can be tobacco-responsive mechanisms for the related diseases. Based on consistent results in blood and buccal cells, expression of the ACTG1 can be a tobacco smoking-responsive biomarker.

S-glutathionylation of buccal cell proteins as biomarkers of exposure to hydrogen peroxide

Background

Exogenous or endogenous hydrogen peroxide (H₂O₂) is a reactive oxygen species (ROS) that can lead to oxidation of cellular nucleophiles, particularly cysteines in proteins. Commercial mouthwashes containing H₂O₂ provide the opportunity to determine clinically whether changes in S-glutathionylation of susceptible proteins in buccal mucosa cells can be used as biomarkers of ROS exposure.

Methods

Using an exploratory clinical protocol, 18 disease-free volunteers rinsed with a mouthwash containing 1.5% H₂O₂ (442 mM) over four consecutive days. Exfoliated buccal cell samples were collected prior and post-treatment and proteomics were used to identify S-glutathionylated proteins.

Results

Four consecutive daily treatments with the H₂O₂-containing mouthwash induced significant dose and time-dependent increases in S-glutathionylation of buccal cell proteins, stable for at least 30 min following treatments. Elevated levels of S-glutathionylation were maintained with subsequent daily exposure. Increased S-glutathionylation preceded and correlated with transcriptional activation of ROS sensitive genes, such as ATF3, and with the presence of 8-hydroxy deoxyguanosine. Data from a human buccal cell line TR146 were consistent with the trial results. We identified twelve proteins that were S-glutathionylated following H₂O₂ exposure.

Conclusions

Buccal cells can predict exposure to ROS through increased levels of S-glutathionylation of proteins. These post-translationally modified proteins serve as biomarkers for the effects of H₂O₂ in the oral cavity and in the future, may be adaptable as extrapolated pharmacodynamic biomarkers for assessing the impact of other systemic drugs that cause ROS and/or impact redox homeostasis.

General significance

S-glutathionylation of buccal cell proteins can be used as a quantitative measure of exposure to ROS.

•

Hydrogen peroxide is both a toxin and an endogenous signaling molecule.

•

The use of hydrogen peroxide mouthwash causes ROS mediated damage in cheek cells.

•

S-glutathionylated proteins are biomarkers for this damage.

•

S-glutathionylated proteins may be of future value as pharmacodynamic markers.

DNA methylation of the allergy regulatory gene interferon gamma varies by age, sex, and tissue type in asthmatics

Background

Asthma is associated with allergic sensitization in about half of all cases, and asthma phenotypes can vary by age and sex. DNA methylation in the promoter of the allergy regulatory gene interferon gamma (IFNγ) has been linked to the maintenance of allergic immune function in human cell and mouse models. We hypothesized that IFNγ promoter methylation at two well-studied, key cytosine phosphate guanine (CpG) sites (-186 and -54), may differ by age, sex, and airway versus systemic tissue in a cohort of 74 allergic asthmatics.

Results

After sampling buccal cells, a surrogate for airway epithelial cells, and CD4+ lymphocytes, we found that CD4+ lymphocyte methylation was significantly higher in children compared to adults at both CpG sites (P <0.01). Buccal cell methylation was significantly higher in children at CpG -186 (P = 0.03) but not CpG -54 (P = 0.66). Methylation was higher in males compared to females at both CpG sites in CD4+ lymphocytes (-186: P <0.01, -54: P = 0.02) but not buccal cells (-186: P = 0.14, -54: P = 0.60). In addition, methylation was lower in CD4+ lymphocytes compared to buccal cells (P <0.01) and neighboring CpG sites were strongly correlated in CD4+ lymphocytes (r = 0.84, P <0.01) and weakly correlated in buccal cells (r = 0.24, P = 0.04). At CpG -186, there was significant correlation between CD4+ lymphocytes and buccal cells (r = 0.24, P = 0.04) but not at CpG -54 (r = -0.03, P = 0.78).

Conclusions

These findings highlight significant age, sex, and tissue-related differences in IFNγ promoter methylation that further our understanding of methylation in the allergic asthma pathway and in the application of biomarkers in clinical research.

Assessment of genotoxic and molecular mechanisms of cancer risk in smoking and smokeless tobacco users

Inexpensive forms of tobacco are widely used in developing countries such as India. We have evaluated genotoxicity endpoints (chromosome aberrations, micronucleus frequency, comet assay) and polymorphisms of the XRCC1 and p53 genes among smokers and smokeless tobacco (SLT) users in rural Tamilnadu, South India. Cytogenetic, DNA damage and SNP analyses were performed on peripheral blood samples; micronucleus frequency was measured in peripheral blood and buccal mucosa exfoliated cells. Both categories of tobacco users had elevated levels of genotoxic damage. SNP analysis of tobacco users revealed that 17% carry the XRCC1 gln399gln genotype and 19% carry the p53 pro72pro genotype. Both genotypes are associated with increased risk of cancer.

Evaluation of quality of DNA extracted from buccal swabs for microarray based genotyping

Buccal cell usage has been shown by many to be a cost effective and safe method to isolate DNA for various biological experiments especially large epidemiological studies (Garcia-Closas et al. Cancer Epidemiol Biomarkers Prev 10:687-696, 2001). Non-invasive DNA collection methods are preferred over phlebotomy in order to increase study participation and compliance in research centers and for sick patients in hospital settings. There have been conflicting reports about the methodology and results obtained from using buccal DNA. It is not very clear if phlebotomy can be confidently replaced by buccal cell DNA. It is often left for the user to take an intelligent decision. To address this issue, we compared the performance of buccal and blood DNA from same subjects in a genotyping experiment and this paper reports the results. Cotton swab derived buccal cells were scraped from the inner side of cheeks from 16 subjects, and blood was also drawn from the same 16 subjects participating in a genotypic association study of a lipid disease. The DNA quality was assessed by resolving on agarose gels, checking purity (A260/A280) and finally by microarray hybridization. This study showed that DNA degradation affects the total yield and performance of the buccal DNA when compared to the blood DNA in microarray based genotyping. Genotyping results can be seriously compromised if care is not taken to check the quality and yields of such specimens.

Elevated Frequencies of Micronuclei and other Nuclear Abnormalities of Chrome Plating Workers Occupationally Exposed to Hexavalent Chromium

BACKGROUND

Biomonitoring provides a useful tool to estimate the genetic risk from exposure to genotoxic agents. The aim of this study was to assess the potential cytogenetic damage associated with occupational exposure to hexavalent chromium by using micronuclei (MN) as a biomarker.

METHODS

This was a cross-sectional study and all participants were males. Both the exposed and control individuals were selected from Coimbatore, Southern India. Exfoliated buccal cells from 44 chrome plating workers and 40 age and sex matched control subjects were examined for MN frequency and nuclear abnormalities (NA) other than micronuclei, such as binucleates, broken eggs, karyorrhexis, karyolysis and pyknosis.

RESULTS

Results showed statistically significant difference between chrome plating workers and control groups. MN and NA frequencies in chrome plating workers were significantly higher than those in control groups (p < 0.05) and also significantly related to smoking habit (P < 0.05). A significant difference in NA was observed in workers exposed to chromium for longer duration. In addition to this, a higher degree of NA was observed among smokers.

CONCLUSION

MN and other NA reflect genetic changes, events associated with carcinogenesis. Therefore the results of this study indicate that chrome plating workers are under risk of significant cytogenetic damage. Therefore, there is a need to educate those who work with heavy metals about the potential hazard of occupational exposure and the importance of using protective measures.