Genotoxicidad de los hidrocarburos aromáticos policíclicos extraídos mediante el sistema diclorometano-etanol-tolueno en muestras del aire de Cúcuta, Norte de Santander, Colombia / Genotoxicity of polycyclic aromatic hydrocarbons extracted by dichloromethane-ethanol-toluene system air samples from Cúcuta, Norte de Santander, Colombia

Los contaminantes del aire han sido y siguen siendo, los principales factores que contribuyen a las enfermedades crónicas como el asma y enfermedades cardiovasculares. La contaminación del aire por material particulado (PM) es un problema mundial y en los últimos años, el PM se ha convertido en un tema importante de investigación ya que tiene un impacto negativo significativo en la salud humana; el PM es generado por las actividades industriales y tubos de escape de vehículos de motor. Sin embargo, diversos componentes nocivos del PM, como los hidrocarburos aromáticos policiclicos (HAP) en general, son sos­pechosos de ser carcinogénicos. Este trabajo tiene como objetivo identificar los HAP presentes en el PM2.5 del aire de Cúcuta, extraídos por primera vez, mediante el sistema diclorometano-etanol-tolueno e investigar la importancia del fraccionamiento de la materia organica del PM2.5 para detectar los HAP presentes en las fracciones del PM2.5. La identificación de los HAP considerados como contaminantes prioritarios y reconocidos por su afectación a la salud de la población se realizó, mediante cromatografía de gases con detector FID. Los efectos genotoxicos de la materia orgánica del PM2.5 extraída con una mezcla de DCM-etanol-tolueno fueron evaluados mediante el ensayo Cometa.

Air pollutants have been and still are the main factors that contribute to chronic diseases such as asthma and cardio­vascular disease. Air pollution by particulate matter (PM) is a global problem and in recent years, the PM has become an important research topic since it has a significant negative impact on human health; the PM is generated by industrial activities and exhaust pipes of motor vehicles. However, various harmful components of PM such as polycyclic aromatic hydrocarbons (PAHs) in gen­eral, are suspected of being carcinogenic. This work aims to identify the PAHs present in the PM 2.5 air Cúcuta, first extracted by the dichloromethane-ethanol-toluene system and investigate the importance of organic matter fractionation of PM 2.5 to detect PAHs present in the fractions of PM 2.5. The identification of PAHs considered as priority pollutants and recognized for their effects on health of the population was performed by gas chromatography with FID detector. The genotoxic effects of PM2.5 organic mat­ter, extracted with a mixture of DCM-ethanol-toluene, was evaluated by the Comet assay.

DNA damage in Wistar Kyoto rats exercised during pregnancy

Abstract Purpose: To evaluate DNA damage levels in pregnant rats undergoing a treadmill exercise program. Methods: Wistar Kyoto rats were allocated into two groups (n= 5 animals/group): non-exercise and exercise. The pregnant rats were underwent an exercise protocol on a treadmill throughout pregnancy. Exercise intensity was set at 50% of maximal capacity during maximal exercise testing performed before mating. Body weight, blood pressure and glucose levels, and triglyceride concentration were measured during pregnancy. At day 10 post-natal, the animals were euthanized and maternal blood samples were collected for DNA damage. Results: Blood pressure and glucose levels and biochemical measurements showed no significant differences. Increased DNA damage levels were found in exercise group compared to those of non-exercise group (p<0.05). Conclusion: The exercise intensity protocol used in the study might have been exhaustive leading to maternal increased DNA damage levels, demonstrating the relevance of an adequate protocol of physical exercise.

Principios y relevancia del ensayo cometa / Principles and relevance of the comet assay

Desde hace varias décadas el ensayo Cometa, o electroforesis alcalina de células individuales, se ha convertido en un método establecido para el estudio del daño de ácido desoxirribonucleico, con múltiples aplicaciones en ensayos de genotoxicidad, estudios de biomonitoreo en humanos, epidemiologia molecular y ecotoxicología; así como una herramienta fundamental para investigaciones sobre daño y reparación del ácido desoxirribonucleico. Este ensayo se distinguió por su simplicidad, sensibilidad, versatilidad, rapidez y economía. Es una poderosa técnica que se basa en la visualización microscópica de las imágenes del ácido desoxirribonucleico después que las células son embebidas en agarosa, lisadas y sometidas a una electroforesis alcalina. Esta metodología básica ha sido ampliada, y permite ahora, detectar con alta sensibilidad una gran variedad de daños del ácido desoxirribonucleico en cualquier tipo de células. La inclusión en este ensayo, de enzimas capaces de producir lesiones específicas en la hebra de ácido desoxirribonucleico, ha incrementado su rango de detección y sensibilidad. Pero es importante tener claro que su especificidad no es absoluta. El propósito es destacar algunos aspectos útiles de este método y sus ventajas; describir la experiencia en algunos aspectos técnicos del proceder, normalizado según las condiciones del laboratorio en el instituto para ampliar su utilización en el país.

For several decades now the comet assay (single cell gel electrophoresis assay) has been the method used for the study of deoxyribonucleic acid damage, with multiple applications in genotoxicity assays, biomonitoring studies in humans, molecular epidemiology and ecotoxicology, and a fundamental tool for research into deoxyribonucleic acid damage and repair. The comet assay has stood out for its simplicity, sensitivity, versatility, rapidity and economy. It is a powerful technique based on microscopic visualization of deoxyribonucleic acid images after the cells have been embedded in agarose, lysed and subjected to alkaline electrophoresis. This basic methodology has been broadened, and may now detect with great sensitivity a large variety of deoxyribonucleic acid damage in any type of cell. Inclusion in the assay of enzymes capable of producing specific lesions on the deoxyribonucleic strand has broadened its detection range and sensitivity. However, it is important to bear in mind that its specificity is not absolute. The purpose of the present study is to point out some useful aspects and advantages of the method, and describe the experience with some technical aspects of the procedure, standardized in keeping with the conditions in the laboratory at the institute to extend its use in the country.

Various methods available for detection of apoptotic cells- A review.

Apoptosis is a process of programmed cell death occurring in multicellular organisms in whom development, maintenance and sculpturing organs and tissues. Taken together, apoptotic processes are of widespread biological significance; being involved in e.g. development, differentiation, proliferation/homoeostasis, regulation and function of the immune system and in the removal of defected harmful cells. Dys regulation of apoptosis can play a primary or secondary role leading to cancer whereas excessive apoptosis contributes to neuro degeneration, autoimmunity, AIDS, and ischemia. Gaining insight into the techniques for detecting apoptotic cells will allow the development of more effective, higher specific and therefore better-tolerable therapeutic approaches. The goal of this review article is to provide a general overview of current knowledge, on the various technical approaches for detecting apoptotic cells.

Niveles de plomo y daño en el ADN en niños con trastornos del espectro autista / Lead levels and DNA damage in children with autistic spectrum disorders

Introducción: los trastornos del espectro autista se consideran una familia de alteraciones del neurodesarrollo, caracterizada por dificultades en la comunicación y la interacción social, así como la existencia de un comportamiento estereotipado y repetitivo. Aunque existen varias hipótesis que involucran a factores genéticos y ambientales en su etiopatogenia, la verdadera contribución de estos aún se desconoce. En este estudio se explora la relación entre los niveles séricos de plomo, el daño del ADN y la severidad del autismo. Métodos: se estudiaron 15 niños con el diagnóstico de trastornos del espectro autista entre 4 y 11 años de edad y un grupo control del mismo rango de edad. El coeficiente de inteligencia fue evaluado mediante la prueba de Terman-Merrill y los niños fueron clasificados en dos grados de retardo mental (ligero y moderado/severo). Los niveles de plomo en sangre fueron medidos por espectrometría de masa, mientras que el daño del ADN fue determinado en linfocitos de sangre periférica con el empleo de un ensayo de electroforesis alcalina (ensayo del cometa). Resultados: no se mostró diferencia significativa en los niveles de plomo entre los grupos. El daño del ADN fue mayor en los pacientes autistas en relación con el grupo control, cuya diferencia fue significativa (p< 0,05), cuando comparamos los grupos teniendo en cuenta la severidad del retardo mental. Los pacientes con trastorno moderado/severo mostraron un daño del ADN significativamente superior a los que presentaron trastornos ligeros y al grupo control. Conclusiones: los resultados confirman la presencia de daño del ADN en pacientes con trastornos del espectro autista, lo cual sugiere que este pudiera ser un factor que se relaciona con la severidad del retardo mental en estos enfermos

Introduction:autistic spectrum disorders are considered to be a family of neurodevelopmental alterations characterized by difficulty to communicate and interact socially, as well as stereotyped, repetitive behavior. Though several hypotheses involve genetic and environmental factors in the etiopathogeny of this condition, their actual participation is still unknown. The present study explores the relationship between serum lead levels, DNA damage and the severity of autism. Methods: a study was conducted with 15 children 4-11 years old diagnosed with autistic spectrum disorders and a control group from the same age range. The intelligence quotient was measured by the Terman-Merrill test, and children were classified into two degrees of mental retardation (mild and moderate/severe). Blood lead levels were measured by mass spectrometry, whereas DNA damage was determined in peripheral blood lymphocytes using the alkaline electrophoresis assay (the comet assay). Results: this study did not show any significant difference in lead levels between the groups. DNA damage was greater in autistic patients than in the control group, and the difference was significant (p<0.05) when mental retardation severity was considered. Patients with a moderate/severe disorder showed significantly greater DNA damage than those with mild disorders and the control group. Conclusions: results confirm the presence of DNA damage in patients with autistic spectrum disorders, suggesting that this factor could be related to mental retardation severity

Cell cycle inhibitory effects of leaf extract from Curcuma vamana M. Sabu & Mangaly on mitotically synchronous cultures of Physarum polycephalum Schw.

Leaf extracts of C. vamana, endemic to Kerala state in India, were found to inhibit cell cycle progression in synchronous cultures of P. polycephalum in a concentration and phase-specific manner. Crude alkaloid extract (CAE) elicited maximum cell cycle delays in comparison to soxhletted chloroform, acetone and aqueous extracts. Total alkaloid content of CAE was found to be 64.9 mg/g. CAE showed lowest DPPH radical scavenging activity. Other extracts with higher free radical scavenging activity exhibited lesser cell cycle inhibiting potential. Upto 21% decrease in nuclear DNA was observed in CAE treated samples. However, genotoxicity as evidenced by comet assay was not observed. The extracts were also found to be non-toxic to human RBCs at the highest concentration tested (750 µg/mL). CAE treatment completely suppressed a 63 kDa polypeptide with a concomitant, but weak induction of a 60 kDa polypeptide suggesting that these may be cell cycle related. CAE was found to possess potent antiproliferative activity against PBLs. The study clearly demonstrates the cell cycle inhibitory activity of C. vamana leaf extracts, with CAE being the most potent of them.

Application of Comet assay to assess the effects of white bean meal on DNA of human lymphocytes

This study was conducted to evaluate the potential induction of genotoxic effects of white bean flour using the Comet assay. The test was conducted with human lymphocytes present in whole blood immediately after collection, by incubation with white bean flour in three concentrations (3.92, 9.52 and 18.18 mg/mL) at 37 ºC for 4 h followed by preparation of slides. Samples were considered positive (above 20% damage) when the damage observed to cellular DNA was higher than the negative control. No genotoxic potential was found at the doses tested. However, it would be premature to suggest absence of risk to human health of DNA damage since the exposure of cells to the extract was restricted to four hours rather than a whole cell cycle. Additionally, further information on toxicology should be obtained in future studies.

Este estudo foi realizado para avaliar o potencial de indução de efeitos genotóxicos da farinha de feijão branco utilizando o teste do Cometa. O ensaio foi realizado com linfócitos humanos presentes no sangue imediatamente após a coleta, por incubação com farinha de feijão branco em três concentrações (3,92, 9,52 e 18,18 mg/mL) a 37 ºC por 4 h, seguida de preparação das lâminas. As amostras foram consideradas positivas (acima de 20% de dano), quando os danos observados no DNA celular foram maiores do que o controle negativo. Verificou-se que as doses testadas não mostraram potencial genotóxico. No entanto, seria prematuro fazer recomendações sobre o padrão de riscos para a saúde humana resultantes de danos ao DNA já que exposição das células ao extrato foi restrito ao período de quatro horas e não durante um ciclo celular completo. Além disso, outras informações sobre a toxicologia devem ser obtidas no futuro.

Genotoxicity of cadmium in rat lung cells assessed by an alkaline comet assay and the possible protective role of selenium

Cadmium is a highly toxic heavy metal with many hazardous effects. Selenium is an essential trace element with antioxidant properties. To evaluate the cadmium-induced DNA damage in rat lung cells and the possible protective role of selenium. Thirty-six adult male albino rats were used in this experiment. They were divided into four equal groups. Group I was the control group. Group II included rates that were injected intraperitoneally with cadmium chloride [CdCl[2]] [1.0 mg/kg/day] for 8 weeks. Group III included rates injected intraperitoneally with sodium selenite [Na[2]SeO[3]] [0.25 mg/kg/day] for 8 weeks. Group IV included rats injected intraperitoneally with both CdCl[2] [1.0 mg/kg/day] and Na[2]SeO[3] [0.25 mg/kg/day] for 8 weeks. At the end of the experiment, the lungs of rats were taken and processed for single-cell gel electrophoresis [comet assay]. In the control group, comets appeared with large bright heads and small tails. The injection of CdCl[2] in group II induced DNA damage in rat lung cells, indicated by increased migration in the comet assay. Comet cells appeared with small heads and long tails. Statistically, there was a significant increase in tail length, tail moment, and tail% DNA compared with the control. Injection of selenium alone did not show any difference from the control. Concomitant administration of both cadmium and selenium resulted in a partial decrease in the DNA damage in rat lung cells indicated by decrease in DNA migration in the comet assay. Comet cells appeared with large heads and relatively small tails compared with those of group II. A significant decrease was also observed in tail length, tail moment, and tail% DNA compared with group II. CdCl[2] could significantly induce DNA damage in rat lung cells. It was suggested that selenium could partially ameliorate DNA damage induced by cadmium

Evaluation of DNA damage in oral precancerous and squamous cell carcinoma patients by single cell gel electrophoresis.

Context: Single cell gel electrophoresis (SCGE) or "comet assay" is a rapid and very sensitive fluorescent microscopic method for detecting various forms of DNA damage at individual cell level. Aims: The aim of the present study was to detect the extent of DNA damage in oral cancer, oral submucous fibrosis (OSMF) and leukoplakia in comparison to normal individual. Settings and Design: A total of 44 consecutive patients with oral cancer (n=26), leukoplakia (n=12) and OSMF (n=6) and 10 healthy normal volunteers with normal oral epithelia (controls) were recruited from Dr. R. Ahmed Dental College and Hospital and were assessed for the extent of DNA damage using SCGE following clinical diagnosis. Materials and Methods: Peripheral blood was collected by venepuncture and comet assay was performed using SCGE. Mean tail length was compared between diagnostic groups and between different oral habit groups using t-tests and analysis of variance (ANOVA). Pearson's product moment correlation was used to examine the linear association between the extent of DNA damage and oral habit pack-years. Scheffe's pair-wise test was employed to adjust for multiple comparisons. Results: None of the controls were associated with any oral habits. Mean (±SD) tail lengths (in mm) for cancer (24.95 ± 5.09) and leukoplakia (12.96 ± 2.68) were significantly greater than in controls (8.54 ± 2.55, P<0.05). After adjustment, well-, moderately, and poorly differentiated carcinomas had significantly greater tail length than controls. Whereas the extent of DNA damage in cancer cases was significantly greater in leukoplakia than in compared to OSMF (11.03 ± 5.92), the DNA damage in latter was not different from controls. DNA damage for people with any oral habit (19.78 ± 7.77) was significantly greater than those with no habits (8.54 ± 2.55; P<0.0001). Conclusions: DNA damage measured by SCGE is greater in leukoplakia and squamous cell carcinoma, but not in OSMF. Deleterious oral habits are also associated with greater DNA damage.

Evaluation of DNA damage in agricultural workers exposed to pesticides using single cell gel electrophoresis (comet) assay.

BACKGROUND: Pesticides are used in agriculture to protect crops, but they pose a potential risk to farmers and environment. The aim of the present study is to investigate the relation between the occupational exposure to various pesticides and the presence of DNA damage. MATERIALS AND METHODS: Blood samples of 210 exposed workers (after a day of intense spraying) and 50 control subjects belonging to various districts of Punjab (India) were evaluated using Comet assay. Sixty workers who showed DNA damage were selected for follow up at 5-6 months after the first sampling during a low or null spraying period. RESULTS: Significant differences were found in DNA damage between freshly exposed workers and controls and freshly exposed and followed up cases. There was significant increase in the comet parameters viz. mean comet tail length and frequency of cells showing migration in exposed workers as compared to controls (72.22 ± 20.76 vs. 46.92 ± 8.17, P<0.001; 31.79 vs. 5.77, P<0.001). In the second samples, followed up cases showed significant decrease in frequency of damaged cells as compared to freshly exposed workers of first sampling (P<0.05). The confounding factors such as variable duration of pesticide exposure, age, smoking, drinking and dietary habits etc which were expected to modulate the damage, were instead found to have no significant effect on DNA fragmentation. CONCLUSION: The evidence of a genetic hazard related to exposure resulting from the intensive use of pesticides stresses the need for educational programs for agricultural workers to reduce the use of chemicals in agriculture.

Cadmium chloride toxicity suppresses osteogenic potential of rat bone marrow mesenchymal stem cells through reducing cell viability and bone matrix mineralization.

Background and Objectives: Cadmium an environmental pollutant, exert several risks to human health. In this study we investigated the effect of cadmium chloride (CdCl 2 ) on Viability, morphology and bone Matrix Miniralization of Rat Bone Marrow Mesenchymal Stem Cells (rMSCs). Materials and Methods: rMSCs were cultured in DMEM containing 15% FBS and pen-strep. After 21 days of treatment with the selected doses of 750 and 2000 nM of CdCl 2 viability, colony forming unit, population doubling number, DAN breakage and the morphology of the cells were studied. Also to study the effects of CdCl2 on differentiation property, the morphology and bone matrix mineralization via estimation of intracellular calcium concentration and quantitative alizarin red were also evaluated in the cells using Hoechst, Acridine orange and Alizarin red staining. Data was analyzed using one-way ANOVA and Tukey ' s test and the means difference was considered significant at P<0.05. Results: The mean viability, colony forming unit, population doubling number and also the mean bone matrix mineralization of the rMSCs treated with CdCl 2 significantly reduced in a dose dependent manner. Nuclear fragmentation and cytoplasm shrinkage was also seen in the treated cells. Conclusion: CdCl 2 can reduce the viability and bone matrix mineralization of rMSCs even at low doses.

Progress on DNA quantification in estimation of postmortem interval / 法医学杂志

Estimation of postmortem interval (PMI) is one of the difficult problems in forensic medicine. With the development of molecular biological techniques, DNA quantification methods were widely applied in estimating PMI. The postmortem degradation of DNA in different tissues and organs was discussed in this article and the recent DNA quantitative techniques being used for estimating PMI were reviewed. These techniques included single cell gel electrophoresis, Feulgen staining image analysis, flow cytometry.

Evaluación bioquímica de trabajadores rurales expuestos a pesticidas / Biochemical evaluation on rural workers exposed to pesticides

Los pesticidas utilizados en agricultura pueden representar un riesgo potencial para la salud de los agricultores expuestos y para el medio ambiente. El objetivo de este trabajo fue evaluar trabajadores frutihortícolas expuestos a plaguicidas, categorizados por: exposición directa (n = 45), exposición indirecta (n = 50) y controles (n = 50) mediante biomarcadores de exposición y efecto: colinesterasa (ChE), acetilcolinesterasa (AChE), catalasa (CAT), peroxidación de lípidos (TBARS), Indice de Daño Ensayo Cometa (IDEC) e Indice de Daño Ensayo Reparación (IDER). Los resultados indican: a) inhibición significativa de AChE (p < 0.001) en expuestos directos e indirectos; b) aumento en los niveles de TBARS (p < 0.001) en los directos; c) reducción de CAT significativa (p < 0.01) y d) aumento de IDEC e IDER (p < 0.001) en ambos grupos. Los resultados obtenidos reflejan modificaciones en el balance oxidativo junto con daño al ADN en los trabajadores estudiados. Estos hallazgos representan una contribución en la evaluación subclínica de exposición a agroquímicos en nuestro país.

Pesticides are used in agriculture to protect crops but may represent a potential risk to farmers and the environment. The aim of this work was to evaluate horticultural workers exposed to pesticide, categorized by: direct exposure (n = 45), indirect exposure (n = 50) and controls (n = 50) using exposure and effect biomarkers: cholinesterase (ChE), acetylcholinesterase (AChE), catalase (CAT), lipid peroxidation (TBARS), Damage Index Comet Assay (IDEC) and Damage Index Repair Assay (IDER). Our results show: a) an AChE inhibition in directly and indirectly exposed population (p < 0.001), b) significant increase in the levels of TBARS in direct exposure (p < 0.001), c) the CAT reduction was significant (p < 0.01), d) a significant increase in IDEC and IDER in both exposed groups (p < 0.001). Our results evidence variations in oxidative balance and DNA damage in exposed workers. These findings represent a contribution to the sub-clinical evaluation of subjects exposed to agrochemicals in our country.

DNA degradation of porcine retinal cells for estimation of postmortem interval / 法医学杂志

OBJECTIVE@#To investigate DNA degradation of porcine retinal cells by single cell gel electrophoresis (SCGE) for estimation of postmortem interval (PMI).@*METHODS@#Degradation of retinal cells was observed by SCGE at 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24h after death respectively, under the environmental conditions of being kept in dark place as well as a controlled temperature of (15 +/- 2) degrees C and humidity of (50 +/- 5)%. The comet pictures were captured by fluorescence microscope and analyzed by single cell gel electrophoresis (IMI 1.0).@*RESULTS@#From 2h to 24h postmortem, the degree of degradation of retinal DNA increased with the prolongation of PMI. The postmortem regression functions of head DNA%, L(T)/L(H), I(T)/I(H) were y = 92.227-5.188 x + 0.019 x2 + 0.001 x3 (R2 = 0.971), y = 0.035e(0.191x) (R2 = 0.947), y = 0.099e(0.264x) (R2 = 0.955), respectively.@*CONCLUSION@#The examination of retinal cell DNA degradation by SCGE is useful for estimating PMI.

DNA degradation in nucleolus of skeletal muscle, heart, liver, kidney and brain in mice after death / 法医学杂志

OBJECTIVE@#To study the change of DNA degradation in nucleolus of mice organs and its relationship with the postmortem interval, and to investigate a new accurate method to estimate the postmortem interval.@*METHODS@#Eight parameters of cell nuclei were chosen, including the head DNA level, the tail DNA level, the head radius, the tail length, the tail moment, the Olive moment, the head area and the tail area. The changes of DNA degradation were analyzed in skeletal muscle, myocardium, liver, kidney and brain in mice at different intervals (0-72 h postmortem) by using single-cell gel electrophoresis and fluorescent microscope connected with auto-analysis-image system.@*RESULTS@#The tail DNA level, the tail length, the tail moment, the Olive moment and the tail area showed an increasing tendency. The head DNA level, the head radius and the head area showed a decreasing tendency within 72h postmortem in mice. A quadratic regression equation (P < 0.001) and multiple regression equation of DNA degradation tendency were established (P < 0.000 1).@*CONCLUSION@#The regression equations established can be used as a new method for estimating postmortem interval in forensic practice.

Desenvolvimento e validação de técnica quantitativa de análise de imagem para avaliação do teste do cometa corado pela prata / Development and validation of a quantitative image analysis method to evaluate comet assay (silver staining)

INTRODUÇÃO: O ensaio do cometa ou técnica da eletroforese de células isoladas é largamente empregado para avaliação de danos e reparo do DNA em células individuais. O material pode ser corado por técnicas de fluorescência ou por sal de prata. Este último apresenta vantagens técnicas, como o tipo de microscópio utilizado e a possibilidade de armazenamento das lâminas. A análise dos cometas pode ser feita de modo visual, porém há a desvantagem da subjetividade dos resultados, que pode ser minimizada por análise digital automatizada. OBJETIVOS: Desenvolvimento e validação de método de análise digital de cometas corados por sal de prata. MÉTODOS: Cinquenta cometas foram fotografados de maneira padronizada e impressos em papel. Além de medidas manualmente, essas imagens foram classificadas em cinco categorias por três avaliadores, antes e depois de pré-processadas automaticamente pelo software ImageJ 1.38x. As estimativas geradas pelos avaliadores foram comparadas quanto sua correlação e reprodutibilidade. Em seguida, foram desenvolvidos algoritmos de análise digital das medidas, com base em filtros estatísticos de mediana e de mínimo. Os valores obtidos foram comparados com os estimados manual e visualmente após o pré-processamento. RESULTADOS: As medidas manuais das imagens pré-processadas apresentaram maior correlação intraclasse do que as imagens preliminares. Os parâmetros automatizados apresentaram alta correlação com as medidas manuais pré-processadas, sugerindo que este sistema aumenta a objetividade da análise, podendo ser utilizado na estimativa dos parâmetros dos cometas. CONCLUSÃO: A presente análise digital proposta para o teste do cometa corado pela prata mostrou-se factível e de melhor reprodutibilidade que a análise visual.

BACKGROUND: Comet assay or single cell gel electrophoresis is a useful and widely applied technique for the assessment of DNA damage and repair in individual cells. Nuclei can be stained with fluorescence methods or silver salts. The latter has technical advantages such as the type of microscope used and the possibility of slide storage. Comet analysis may be performed visually, however, there is the disadvantage of subjective results, which can be minimized by automated digital analysis. OBJECTIVES: Development and validation of digital analysis method for silver stained comet assays. METHODS: Fifty comets were photographed in a standardized way and printed on paper. Before and after being automatically preprocessed by ImageJ 1.38x software, the images were manually measured and classified into five categories by three evaluators. Their estimates were compared as to their correlation and reproducibility. Afterwards, an algorithm for automated digital analysis of the comet measurements was developed based on statistical filters of median and minimum. These results were compared with those manually and visually estimated after preprocessing. RESULTS: Manual measurements of preprocessed images showed higher intraclass correlation than the original ones. Automated results had high correlation with the pre-processed manual measurements, suggesting that this system increases objectivity and can be used in the estimation of comet parameters. CONCLUSIONS: Digital analysis of silver stained comet assay proved to be feasible and better reproducible than the visual analysis.

Induction of DNA double-strand breaks at various stages of the cell cycle using the comet assay

The present study reports improvements in the current protocols of the neutral comet assay to measure radiation induced DNA damage. Different biochemical steps, including mierogel preparation, lysis and enzymatic/chemical treatments have been modified and optimized to estimate the fraction of cells and DNA damage, at different stages of the cell cycle, in a higher dose range of X-rays. Among all tail parameters that were used to measure the DNA damage induced by ionizing radiation, the tail intensity was found to be the most sensitive. In this study DNA damage induced by X-ray doses as low as 5 Gy was detected. A developed analytical method has been used for the simultaneous estimation of the fraction of cells and DNA damage, at different stages of the cell cycle. The results of bivariate analysis of tail intensity versus DNA content showed a remarkable decrease in tail intensity with transition of cells from G1 to S-phase and increase slightly with transition to G2/M phase. This effect is observed at all doses including unirradiated cells, indicating that the effect is not caused by X-rays and the comet assay based on the current tail parameters may not be relevant to measure DNA damage in cells at different stages of the cell cycle. The results revealed a highly significant decrease in comet area, at all stages of the cell cycle, after irradiation with all doses, indicating the high sensitivity of this parameter to X-rays. The results of dose response curves showed a linear decrease in the comet fluorescence with the X-ray dose, at all stages of the cell cycle. This reduction in comet fluorescence was attributed to partial unwinding of DNA at the strand break sites during the alkaline treatment after electrophoresis, with the consequent reduction in ethiduim bromide stainibitliy and fluorescence of DNA. This observation provides a basis for estimating the fraction of damaged DNA, based on the fluorescence decrement induced by ionizing radiation. The results of this method showed a linear increase in DNA damage with dose, at various stages of the cell cycle, with rates which vary in the following order G0> G2/M> S > G 1. These results suggest that G0 and G2IM cells are the most sensitive to X-rays among all phases of the cell cycle and synchronization of tumor cells in these phases during radiotherapy may be more efficient in treatment of cancers

Relationship between the postmortem interval and nuclear DNA changes of heart muscular cells in mice / 法医学杂志

OBJECTIVE@#To study the changes of DNA degradation in cells of rats and its relationship with the postmortem interval.@*METHOD@#8 parameters of cell nuclear (including the tail length, the head radius, the percentage of head DNA, the percentage of tail DNA, the tail moment, the olive moment, the head area and the tail area) were chosen to study their changes in the procedure of DNA degradation in myocardium cells in 111 rats at different postmortem interval from 0 to 72 h by using single-cell gel electrophoresis (SCGE) technology and fluorescent microscope combined with auto-analysis-image system method.@*RESULTS@#An evident comet tailing was observed in DNA of myocardium cells after electrophoresis, and their changes in all these 8 parameters of cell nuclear were greatly associated with the extension of postmortem interval, which indicate the degradation rate and degree of DNA in the nuclear has a close relationship with postmortem interval in the periods from 0 to 72 h in rats and significant difference were found with those groups (P < 0.001).@*CONCLUSION@#The equations, which were concluded from our study, indicate the close relationship of degradation rate and degree of DNA in the nuclear with postmortem interval from 0 to 72 h, and provide an objective and exact new way to estimate the postmortem interval.

Detecting DNA damage of cell in rats using comet assay after tetramine poisoned / 法医学杂志

OBJECTIVE@#To study the damage of DNA in lymphocytes, brain cells and cardiac muscle cells of rats induced by different dose of tetramine and to speculate the toxicant mechanism of tetramine.@*METHODS@#The rat were poisoned by Tetramine, which was taken in by mouth. The rat poisoning models were used by 0.2, 0.1, 0.05, 0.01 mg x kg(-1) Tetramine, and comparison model was made by NS. Lymphocytes and brain cells and cardiac muscle cells of rats were separatd and collected form experimentation rat. DNA damages of cells which were exposed to different doses of tetramine were detected using the single cell gel electrophorresis (SCGE) or comet assay.@*RESULTS@#DNA damages have been observed in lymphocytes, brain cells and cardiac muscle cells of rats which exposed form 0.01mg x kg(-1) doses of tetramine to 0.2mg x kg(-1) doses of tetramine. The test groups are very significantly statistical different to the control group (P<0.01).@*CONCLUSION@#It is assumed that DNA damages of cells might be one of the toxicant mechanism of tetramine.

Genotoxic effects of rotenone on cultured lymphocytes

Rotenone is a heterocyclic compound widely used as an insecticide, acaricide and piscicide. Its toxicity is mainly caused by the inhibition of mitochondrial respiratory processes and ATP production, resulting in the generation of reactive oxygen species. Reactive oxygen species can interact with DNA, RNA and proteins, leading to cell damage, followed by death. We used the Comet assay, and we analyzed chromosome aberrations, in order to evaluate the genotoxic and clastogenic effects of rotenone on the different phases of the cell cycle. Cultured human lymphocytes were treated with 1.0, 1.5 and 2.0 microg/mL rotenone during the G1, G1/S, S (pulses of 1 and 6 h), and G2 phases of the cell cycle. Rotenone induced DNA damage and was clastogenic, but the clastogenicity was detected only with treatments conducted during the G1/S and S phases of the cell cycle. Rotenone also induced endoreduplication and polyploidy in treatments made during G1, while it significantly reduced the mitotic index in all phases of the cell cycle.