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Sample records for comet assay analysis

  1. OpenComet: an automated tool for comet assay image analysis.

    PubMed

    Gyori, Benjamin M; Venkatachalam, Gireedhar; Thiagarajan, P S; Hsu, David; Clement, Marie-Veronique

    2014-01-01

    Reactive species such as free radicals are constantly generated in vivo and DNA is the most important target of oxidative stress. Oxidative DNA damage is used as a predictive biomarker to monitor the risk of development of many diseases. The comet assay is widely used for measuring oxidative DNA damage at a single cell level. The analysis of comet assay output images, however, poses considerable challenges. Commercial software is costly and restrictive, while free software generally requires laborious manual tagging of cells. This paper presents OpenComet, an open-source software tool providing automated analysis of comet assay images. It uses a novel and robust method for finding comets based on geometric shape attributes and segmenting the comet heads through image intensity profile analysis. Due to automation, OpenComet is more accurate, less prone to human bias, and faster than manual analysis. A live analysis functionality also allows users to analyze images captured directly from a microscope. We have validated OpenComet on both alkaline and neutral comet assay images as well as sample images from existing software packages. Our results show that OpenComet achieves high accuracy with significantly reduced analysis time.

  2. Aspects of design and statistical analysis in the Comet assay.

    PubMed

    Wiklund, Stig Johan; Agurell, Eva

    2003-03-01

    Some aspects of the statistical design and analysis of the Comet (single cell gel electrophoresis) assay have been evaluated by means of a simulation study. The tail length and tail moment were selected for the quantification of DNA migration. Results from the simulation study showed that the choice of measure to summarize the cells on each slide is extremely important in order to facilitate an efficient analysis. For tail moment, the mean of log transformed data is clearly superior to the other evaluated measures, whereas using the mean of raw data without transformation can lead to very inefficient analyses. The 90th percentile, capturing the upper tail of the distribution, performs well for the tail length, with a slight improvement obtained by applying a log transformation prior to calculations. Furthermore, the simulation study has been used to assess the appropriateness of some models for statistical analysis and to address the issue of design (i.e. number of cultures or animals in each group, number of slides per animal/culture and number of cells scored per slide). Combining the results from the simulations with practical experience from the pharmaceutical industry, we conclude the paper by providing concise recommendations regarding the design and statistical analysis in the Comet assay.

  3. Inter-laboratory comparison of the in vivo comet assay including three image analysis systems.

    PubMed

    Plappert-Helbig, Ulla; Guérard, Melanie

    2015-12-01

    To compare the extent of potential inter-laboratory variability and the influence of different comet image analysis systems, in vivo comet experiments were conducted using the genotoxicants ethyl methanesulfonate and methyl methanesulfonate. Tissue samples from the same animals were processed and analyzed-including independent slide evaluation by image analysis-in two laboratories with extensive experience in performing the comet assay. The analysis revealed low inter-laboratory experimental variability. Neither the use of different image analysis systems, nor the staining procedure of DNA (propidium iodide vs. SYBR® Gold), considerably impacted the results or sensitivity of the assay. In addition, relatively high stability of the staining intensity of propidium iodide-stained slides was found in slides that were refrigerated for over 3 months. In conclusion, following a thoroughly defined protocol and standardized routine procedures ensures that the comet assay is robust and generates comparable results between different laboratories.

  4. Quantification of applied dose in irradiated citrus fruits by DNA Comet Assay together with image analysis.

    PubMed

    Cetinkaya, Nurcan; Ercin, Demet; Özvatan, Sümer; Erel, Yakup

    2016-02-01

    The experiments were conducted for quantification of applied dose for quarantine control in irradiated citrus fruits. Citrus fruits exposed to doses of 0.1 to 1.5 kGy and analyzed by DNA Comet Assay. Observed comets were evaluated by image analysis. The tail length, tail moment and tail DNA% of comets were used for the interpretation of comets. Irradiated citrus fruits showed the separated tails from the head of the comet by increasing applied doses from 0.1 to 1.5 kGy. The mean tail length and mean tail moment% levels of irradiated citrus fruits at all doses are significantly different (p < 0.01) from control even for the lowest dose at 0.1 kGy. Thus, DNA Comet Assay may be a practical quarantine control method for irradiated citrus fruits since it has been possible to estimate the applied low doses as small as 0.1 kGy when it is combined with image analysis.

  5. DNA Damage Analysis in Children with Non-syndromic Developmental Delay by Comet Assay

    PubMed Central

    Chand, Parkash; Ballambattu, Vishnu Bhat; Hanumanthappa, Nandeesha; Veeramani, Raveendranath

    2016-01-01

    Introduction Majority of the developmental delays in children are non-syndromic and they are believed to have an underlying DNA damage, though not well substantiated. Hence the present study was carried out to find out if there is any increased DNA damage in children with non-syndromic developmental delay by using the comet assay. Aim The present case-control study was undertaken to assess the level of DNA damage in children with non syndromic developmental delay and compare the same with that of age and sex matched controls using submarine gel electrophoresis (Comet Assay). Materials and Methods The blood from clinically diagnosed children with non syndromic developmental delay and controls were subjected for alkaline version of comet assay – Single cell gel electrophoresis using lymphocytes isolated from the peripheral blood. The comets were observed under a bright field microscope; photocaptured and scored using the Image J image quantification software. Comet parameters were compared between the cases and controls and statistical analysis and interpretation of results was done using the statistical software SPSS version 20. Results The mean comet tail length in cases and control was 20.77+7.659μm and 08.97+4.398μm respectively which was statistically significant (p<0.001). Other comet parameters like total comet length and % DNA in tail also showed a statistically significant difference (p < 0.001) between cases and controls. Conclusion The current investigation unraveled increased levels of DNA damage in children with non syndromic developmental delay when compared to the controls. PMID:27437200

  6. Comprehensive analysis of sperm DNA fragmentation by five different assays: TUNEL assay, SCSA, SCD test and alkaline and neutral Comet assay.

    PubMed

    Ribas-Maynou, J; García-Peiró, A; Fernández-Encinas, A; Abad, C; Amengual, M J; Prada, E; Navarro, J; Benet, J

    2013-09-01

    Sperm DNA fragmentation (SDF) is becoming an important test to assess male infertility. Several different tests are available, but no consensus has yet been reached as to which tests are most predictive of infertility. Few publications have reported a comprehensive analysis comparing these methods within the same population. The objective of this study was to analyze the differences between the five most common methodologies, to study their correlations and to establish their cut-off values, sensitivity and specificity in predicting male infertility. We found differences in SDF between fertile donors and infertile patients in TUNEL, SCSA, SCD and alkaline Comet assays, but none with the neutral Comet assay. The alkaline COMET assay was the best in predicting male infertility followed by TUNEL, SCD and SCSA, whereas the neutral COMET assay had no predictive power. For our patient population, threshold values for infertility were 20.05% for TUNEL assay, 18.90% for SCSA, 22.75% for the SCD test, 45.37% for alkaline Comet and 34.37% for neutral Comet. This work establishes in a comprehensive study that the all techniques except neutral Comet are useful to distinguish fertile and infertile men.

  7. The Comet-FISH assay for the analysis of DNA damage and repair.

    PubMed

    Spivak, Graciela

    2010-01-01

    In this chapter, I describe the alkaline single-cell gel electrophoresis (Comet assay) combined with fluorescence in situ hybridization (FISH) technology, used in our laboratory, to study the incidence and repair of lesions induced in human cells by ultraviolet light. The Comet-FISH method permits the simultaneous and comparative analysis of DNA damage and its repair throughout the genome and in defined chromosomal regions. This very sensitive approach can be applied to any lesion, such as those induced by chemical carcinogens and products of cellular metabolism that can be converted to DNA single- or double-strand breaks. The unique advantages and limitations of the method for particular applications are discussed.

  8. In vivo Comet assay--statistical analysis and power calculations of mice testicular cells.

    PubMed

    Hansen, Merete Kjær; Sharma, Anoop Kumar; Dybdahl, Marianne; Boberg, Julie; Kulahci, Murat

    2014-11-01

    The in vivo Comet assay is a sensitive method for evaluating DNA damage. A recurrent concern is how to analyze the data appropriately and efficiently. A popular approach is to summarize the raw data into a summary statistic prior to the statistical analysis. However, consensus on which summary statistic to use has yet to be reached. Another important consideration concerns the assessment of proper sample sizes in the design of Comet assay studies. This study aims to identify a statistic suitably summarizing the % tail DNA of mice testicular samples in Comet assay studies. A second aim is to provide curves for this statistic outlining the number of animals and gels to use. The current study was based on 11 compounds administered via oral gavage in three doses to male mice: CAS no. 110-26-9, CAS no. 512-56-1, CAS no. 111873-33-7, CAS no. 79-94-7, CAS no. 115-96-8, CAS no. 598-55-0, CAS no. 636-97-5, CAS no. 85-28-9, CAS no. 13674-87-8, CAS no. 43100-38-5 and CAS no. 60965-26-6. Testicular cells were examined using the alkaline version of the Comet assay and the DNA damage was quantified as % tail DNA using a fully automatic scoring system. From the raw data 23 summary statistics were examined. A linear mixed-effects model was fitted to the summarized data and the estimated variance components were used to generate power curves as a function of sample size. The statistic that most appropriately summarized the within-sample distributions was the median of the log-transformed data, as it most consistently conformed to the assumptions of the statistical model. Power curves for 1.5-, 2-, and 2.5-fold changes of the highest dose group compared to the control group when 50 and 100 cells were scored per gel are provided to aid in the design of future Comet assay studies on testicular cells.

  9. Validation of freezing tissues and cells for analysis of DNA strand break levels by comet assay

    PubMed Central

    Jackson, Petra

    2013-01-01

    The comet analysis of DNA strand break levels in tissues and cells has become a common method of screening for genotoxicity. The large majority of published studies have used fresh tissues and cells processed immediately after collection. However, we have used frozen tissues and cells for more than 10 years, and we believe that freezing samples improve efficiency of the method. We compared DNA strand break levels measured in fresh and frozen bronchoalveolar cells, and lung and liver tissues from mice exposed to the known mutagen methyl methanesulphonate (0, 25, 75, 112.5mg/kg). We used a high-throughput comet protocol with fully automated scoring of DNA strand break levels. The overall results from fresh and frozen samples were in agreement [R 2 = 0.93 for %DNA in tail (%TDNA) and R 2 = 0.78 for tail length (TL)]. A slightly increased %TDNA was observed in lung and liver tissue from vehicle controls; and TL was slightly reduced in bronchoalveolar lavage cells from the high-dose group. In our comet protocol, a small block of tissue designated for comet analysis is frozen immediately at tissue collection and kept deep frozen until rapidly homogenised and embedded in agarose. To demonstrate the feasibility of long-term freezing of samples, we analysed the day-to-day variation of our internal historical negative and positive comet assay controls collected over a 10-year period (1128 observations, 11 batches of frozen untreated and H2O2-treated A549 lung epithelial cells). The H2O2 treatment explained most of the variation 57–77% and the day-to-day variation was only 2–12%. The presented protocol allows analysis of samples collected over longer time span, at different locations, with reduced variation by reducing number of electrophoreses and is suitable for both toxicological and epidemiological studies. The use of frozen tissues; however, requires great care during preparation before analysis, with handling as a major risk factor. PMID:24136994

  10. Comet Assay in Cancer Chemoprevention.

    PubMed

    Santoro, Raffaela; Ferraiuolo, Maria; Morgano, Gian Paolo; Muti, Paola; Strano, Sabrina

    2016-01-01

    The comet assay can be useful in monitoring DNA damage in single cells caused by exposure to genotoxic agents, such as those causing air, water, and soil pollution (e.g., pesticides, dioxins, electromagnetic fields) and chemo- and radiotherapy in cancer patients, or in the assessment of genoprotective effects of chemopreventive molecules. Therefore, it has particular importance in the fields of pharmacology and toxicology, and in both environmental and human biomonitoring. It allows the detection of single strand breaks as well as double-strand breaks and can be used in both normal and cancer cells. Here we describe the alkali method for comet assay, which allows to detect both single- and double-strand DNA breaks.

  11. The Comet Assay: Automated Imaging Methods for Improved Analysis and Reproducibility

    PubMed Central

    Braafladt, Signe; Reipa, Vytas; Atha, Donald H.

    2016-01-01

    Sources of variability in the comet assay include variations in the protocol used to process the cells, the microscope imaging system and the software used in the computerized analysis of the images. Here we focus on the effect of variations in the microscope imaging system and software analysis using fixed preparations of cells and a single cell processing protocol. To determine the effect of the microscope imaging and analysis on the measured percentage of damaged DNA (% DNA in tail), we used preparations of mammalian cells treated with etoposide or electrochemically induced DNA damage conditions and varied the settings of the automated microscope, camera, and commercial image analysis software. Manual image analysis revealed measurement variations in percent DNA in tail as high as 40% due to microscope focus, camera exposure time and the software image intensity threshold level. Automated image analysis reduced these variations as much as three-fold, but only within a narrow range of focus and exposure settings. The magnitude of variation, observed using both analysis methods, was highly dependent on the overall extent of DNA damage in the particular sample. Mitigating these sources of variability with optimal instrument settings facilitates an accurate evaluation of cell biological variability. PMID:27581626

  12. Analysis of DNA damage using the comet assay in infants fed cow's milk.

    PubMed

    Dündaröz, Ruşen; Ulucan, Hakan; Aydin, Halil Ibrahim; Güngör, Tayfun; Baltaci, Volkan; Denli, Metin; Sanisoğlu, Yavuz

    2003-01-01

    It has been hypothesized that non-human milk feeding may increase the risk for cancer or for a specific cancer or group of cancers as well as the risk for diseases such as type-1 diabetes mellitus and Crohn's disease. Regarding DNA damage leading to cancer development in the absence of human milk protection, a comparison between infants fed human milk and cow's milk has been performed. Each group consisted of 35 infants, whose ages ranged from 9 to 12 months. The level of DNA damage in the peripheral blood lymphocytes of infants has been studied by the comet assay. A significant increase has been found in the number of limited DNA-damaged (p < 0.001) and extensive DNA-damaged (p < 0.001) cells of infants fed cow's milk. To our knowledge, this is the first study using the comet assay on infants not breast-fed. Supporting our previous SCE study, these results suggest that there is some level of DNA damage in the lymphocytes of infants not breast-fed and this may lead to malignancy in childhood or later in life.

  13. Systematic random sampling of the comet assay.

    PubMed

    McArt, Darragh G; Wasson, Gillian R; McKerr, George; Saetzler, Kurt; Reed, Matt; Howard, C Vyvyan

    2009-07-01

    The comet assay is a technique used to quantify DNA damage and repair at a cellular level. In the assay, cells are embedded in agarose and the cellular content is stripped away leaving only the DNA trapped in an agarose cavity which can then be electrophoresed. The damaged DNA can enter the agarose and migrate while the undamaged DNA cannot and is retained. DNA damage is measured as the proportion of the migratory 'tail' DNA compared to the total DNA in the cell. The fundamental basis of these arbitrary values is obtained in the comet acquisition phase using fluorescence microscopy with a stoichiometric stain in tandem with image analysis software. Current methods deployed in such an acquisition are expected to be both objectively and randomly obtained. In this paper we examine the 'randomness' of the acquisition phase and suggest an alternative method that offers both objective and unbiased comet selection. In order to achieve this, we have adopted a survey sampling approach widely used in stereology, which offers a method of systematic random sampling (SRS). This is desirable as it offers an impartial and reproducible method of comet analysis that can be used both manually or automated. By making use of an unbiased sampling frame and using microscope verniers, we are able to increase the precision of estimates of DNA damage. Results obtained from a multiple-user pooled variation experiment showed that the SRS technique attained a lower variability than that of the traditional approach. The analysis of a single user with repetition experiment showed greater individual variances while not being detrimental to overall averages. This would suggest that the SRS method offers a better reflection of DNA damage for a given slide and also offers better user reproducibility.

  14. Acellular comet assay: a tool for assessing variables influencing the alkaline comet assay.

    PubMed

    Kennedy, Erin K; McNamee, James P; Prud'homme Lalonde, Louise; Jones, Trevor; Wilkinson, Diana

    2012-01-01

    In this study, an acellular modification to the alkaline comet assay to further evaluate key variables within the assay that may influence the outcome of genotoxicity studies is described. This acellular comet assay can detect differences of 0.2 Gy of (60)Co gamma-ray radiation between 0 and 1 Gy and differences of 1 Gy between 0 and 8 Gy; thus, this assay is applicable for a wide range of DNA damage levels. It is also shown that DNA damage from different radiation energies was not significantly different from (60)Co gamma-ray. This assay displayed a statistical increase in DNA damage due to uncontrolled exposure to natural light; however, the slope of the dose-response curve for light-exposed samples was similar to that for samples protected from light. A comparison of the alkaline comet assay with the acellular comet assay allowed for the intrinsic repair capacity of the alkaline comet assay to be quantified.

  15. ANALYSIS OF DNA DAMAGE AND REPAIR IN SKIN FIBROBLASTS OF INFANT AND OLDER CHILDREN USING THE IN VITRO ALKALINE COMET ASSAY

    EPA Science Inventory

    ANALYSIS OF DNA DAMAGE AND REPAIR IN SKIN FIBROBLASTS OF INFANT AND OLDER CHILDREN USING THE IN VITRO ALKALINE COMET ASSAY, Alan H. Tennant1, Geremy W. Knapp1 and Andrew D. Kligerman1, 1Environmental Carcinogenesis Division, National Health and Environmental Effects Research Lab...

  16. Reference cells and ploidy in the comet assay.

    PubMed

    Brunborg, Gunnar; Collins, Andrew; Graupner, Anne; Gutzkow, Kristine B; Olsen, Ann-Karin

    2015-01-01

    In the comet assay single cells are analyzed with respect to their level of DNA damage. Discrimination of the individual cell or cell type based on DNA content, with concomitant scoring of the DNA damage, is useful since this may allow analysis of mixtures of cells. Different cells can then be characterized based on their ploidy, cell cycle stage, or genome size. We here describe two applications of such a cell type-specific comet assay: (i) Testicular cell suspensions, analyzed on the basis of their ploidy during spermatogenesis; and (ii) reference cells in the form of fish erythrocytes which can be included as internal standards to correct for inter-assay variations. With standard fluorochromes used in the comet assay, the total staining signal from each cell - whether damaged or undamaged - was found to be associated with the cell's DNA content. Analysis of the fluorescence intensity of single cells is straightforward since these data are available in scoring systems based on image analysis. The analysis of testicular cell suspensions provides information on cell type specific composition, susceptibility to genotoxicants, and DNA repair. Internal reference cells, either untreated or carrying defined numbers of lesions induced by ionizing radiation, are useful for investigation of experimental factors that can cause variation in comet assay results, and for routine inclusion in experiments to facilitate standardization of methods, and comparison of comet assay data obtained in different experiments or in different laboratories. They can also be used - in combination with a reference curve - to quantify the DNA lesions induced by a certain treatment. Fish cells of a range of genome sizes, both greater and smaller than human, are suitable for this purpose, and they are inexpensive.

  17. The comet assay in human biomonitoring.

    PubMed

    Anderson, Diana; Dhawan, Alok; Laubenthal, Julian

    2013-01-01

    Human biomonitoring studies aim to identify potential exposures to environmental, occupational, or lifestyle toxicants in human populations and are commonly used by public health decision makers to predict disease risk. The Comet assay measures changes in genomic stability and is one of the most reliable biomarkers to indicate early biological effects, and therefore accepted by various governmental regulatory agencies. The appeal of the Comet assay lies in its relative simplicity, rapidity, sensitivity, and economic efficiency. Furthermore, the assay is known for its broad versatility, as it can be applied to virtually any human cell and easily adapted in order to detect particular biomarkers of interest, such as DNA repair capacity or single- and double-strand breaks. In a standard experiment, isolated single cells are first embedded in agarose, and then lysed in high-salt solutions in order to remove all cellular contents except the DNA attached to a nuclear scaffold. Subsequent electrophoresis results in accumulation of undamaged DNA sequences at the proximity of the nuclear scaffold, while damaged sequences migrate towards the anode. When visualized with fluorochromes, these migrated DNA fragments resemble a comet tail and can be quantified for their intensity and shape according to internationally drafted guidelines.

  18. Toxicity effect of dichlorvos on loach (Misgurnus anguillicaudatus) assessed by micronucleus test, hepatase activity analysis and comet assay.

    PubMed

    Nan, Ping; Yan, Shuaiguo; Li, Li; Chen, Jianjun; Du, Qiyan; Chang, Zhongjie

    2015-06-01

    Pesticides and other chemicals at environmental concentrations often have detrimental effects. Many aquatic species are particularly threatened because of their susceptibility and also because water environment are often polluted. This study preliminarily evaluated the toxicity effect of dichlorvos (DDVP) on loach (Misgurnus anguillicaudatus) using the methods of micronucleus (MN) test, hepatase activity and comet assay. The tested results showed that indeed very little DDVP had strong toxicity effect on loach and its 50% lethal concentration (LC50) at 24 h, 48 h and 96 h was 8.38 μg l(-1), 7.168 μg l(-1) and 6.411 μg l(-1), respectively; The glutamic-pyruvic transaminase (GPT) and glutamic-oxalacetic transaminase (GOT) activity of loach liver decreased; meanwhile, the GPT and GOT activity of loach serum, the MN rate (‰) and three comet parameters of tested fish increased with the increase in the treatment concentration and treatment time of DDVP, and there was significant difference between control group and each treatment group (p < 0.05). These results suggested that DDVP residues might become toxic chemical contaminant in environment and would threaten aquatic and other organisms.

  19. The next three decades of the comet assay: a report of the 11th International Comet Assay Workshop.

    PubMed

    Koppen, Gudrun; Azqueta, Amaya; Pourrut, Bertrand; Brunborg, Gunnar; Collins, Andrew R; Langie, Sabine A S

    2017-03-04

    The International Comet Assay Workshops are a series of scientific conferences dealing with practical and theoretical aspects of the Comet Assay (single-cell gel electrophoresis)-a simple method for detecting DNA strand breaks. The first paper describing such an assay was published over 30 years ago in 1984 by Swedish researchers O. Ostling and K. J. Johanson. Appropriately, the theme for the 2015 meeting was looking to the future: 'The Next 3 Decades of the Comet Assay'. The programme included 25 oral and 43 poster presentations depicting the latest advances in technical developments as well as applications of the comet assay in genotoxicity testing (in vitro and in vivo) and biomonitoring of both humans and the environment. Open discussion sessions based on questions from the participants allowed exchange of practical details on current comet assay protocols. This report summarises technical issues of high importance which were discussed during the sessions. We provide information on ways to improve the assay performance, by testing for cytotoxicity, by using reference samples to reduce or allow for inter-experimental variation, and by standardising quantification of the damage, including replicates and scoring enough comets to ensure statistical validity. After 30 years of experimentation with the comet assay, we are in a position to control the important experimental parameters and make the comet assay a truly reliable method with a wealth of possible applications.

  20. A Comprehensive Review on Clinical Applications of Comet Assay

    PubMed Central

    Gunasekarana, Vidya; Chand, Parkash

    2015-01-01

    Increased levels of DNA damage and ineffective repair mechanisms are the underlying bio-molecular events in the pathogenesis of most of the life-threatening diseases like cancer and degenerative diseases. The sources of DNA damage can be either exogenous or endogenous in origin. Imbalance between the oxidants and antioxidants resulting in increased reactive oxygen species mostly accounts for the endogenously derived attacks on DNA. Among the various methods employed in the estimation of DNA damage, alkaline comet assay is proven to be a relatively simple and versatile tool in the assessment of DNA damage and also in determining the efficacy of DNA repair mechanism. The aim of this article is to review the application of comet assay in the field of medicine towards human biomonitoring, understanding the pathogenesis of cancer and progression of chronic and degenerative diseases, prediction of tumour radio & chemosensitivity and in male infertility. A standardized protocol and analysis system of various variants of comet assay in different types of cells, across the labs will be of useful and reliable clinical tool in the field of Medicine for the estimation of levels of DNA damage and repair mechanisms. PMID:25954633

  1. Random, double- and single-strand DNA breaks can be differentiated in the method of Comet assay by the shape of the comet image.

    PubMed

    Georgieva, Milena; Zagorchev, Plamen; Miloshev, George

    2015-10-01

    Comet assay is an invaluable tool in DNA research. It is widely used to detect DNA damage as an indicator of exposure to genotoxic stress. A canonical set of parameters and specialized software programs exist for Comet assay data quantification and analysis. None of them so far has proven its potential to employ a computer-based algorithm for assessment of the shape of the comet as an indicator of the exact mechanism by which the studied genotoxins cut in the molecule of DNA. Here, we present 14 unique measurements of the comet image based on the comet morphology. Their mathematical derivation and statistical analysis allowed precise description of the shape of the comet image which in turn discriminated the cause of genotoxic stress. This algorithm led to the development of the "CometShape" software which allowed easy discrimination among different genotoxins depending on the type of DNA damage they induce.

  2. Recommendations for safety testing with the in vivo comet assay.

    PubMed

    Vasquez, Marie Z

    2012-08-30

    While the in vivo comet assay increases its role in regulatory safety testing, deliberations about the interpretation of comet data continue. Concerns can arise regarding comet assay publications with limited data from non-blind testing of positive control compounds and using protocols (e.g. dose concentrations, sample times, and tissues) known to give an expected effect. There may be a tendency towards bias when the validation or interpretation of comet assay data is based on results generated by widely accepted but non-validated assays. The greatest advantages of the comet assay are its sensitivity and its ability to detect genotoxicity in tissues and at sample times that could not previously be evaluated. Guidelines for its use and interpretation in safety testing should take these factors into account. Guidelines should be derived from objective review of data generated by blind testing of unknown compounds dosed at non-toxic concentrations and evaluated in a true safety-testing environment, where the experimental design and conclusions must be defensible. However, positive in vivo comet findings with such compounds are rarely submitted to regulatory agencies and this data is typically unavailable for publication due to its proprietary nature. To enhance the development of guidelines for safety testing with the comet assay, and with the permission of several sponsors, this paper presents and discusses relevant data from multiple GLP comet studies conducted blind, with unknown pharmaceuticals and consumer products. Based on these data and the lessons we have learned through the course of conducting these studies, I suggest significant adjustments to the current conventions, and I provide recommendations for interpreting in vivo comet assay results in situations where risk must be evaluated in the absence of carcinogenicity or clinical data.

  3. Alkaline Comet Assay for Assessing DNA Damage in Individual Cells.

    PubMed

    Pu, Xinzhu; Wang, Zemin; Klaunig, James E

    2015-08-06

    Single-cell gel electrophoresis, commonly called a comet assay, is a simple and sensitive method for assessing DNA damage at the single-cell level. It is an important technique in genetic toxicological studies. The comet assay performed under alkaline conditions (pH >13) is considered the optimal version for identifying agents with genotoxic activity. The alkaline comet assay is capable of detecting DNA double-strand breaks, single-strand breaks, alkali-labile sites, DNA-DNA/DNA-protein cross-linking, and incomplete excision repair sites. The inclusion of digestion of lesion-specific DNA repair enzymes in the procedure allows the detection of various DNA base alterations, such as oxidative base damage. This unit describes alkaline comet assay procedures for assessing DNA strand breaks and oxidative base alterations. These methods can be applied in a variety of cells from in vitro and in vivo experiments, as well as human studies.

  4. Micropatterned comet assay enables high throughput and sensitive DNA damage quantification.

    PubMed

    Ge, Jing; Chow, Danielle N; Fessler, Jessica L; Weingeist, David M; Wood, David K; Engelward, Bevin P

    2015-01-01

    The single cell gel electrophoresis assay, also known as the comet assay, is a versatile method for measuring many classes of DNA damage, including base damage, abasic sites, single strand breaks and double strand breaks. However, limited throughput and difficulties with reproducibility have limited its utility, particularly for clinical and epidemiological studies. To address these limitations, we created a microarray comet assay. The use of a micrometer scale array of cells increases the number of analysable comets per square centimetre and enables automated imaging and analysis. In addition, the platform is compatible with standard 24- and 96-well plate formats. Here, we have assessed the consistency and sensitivity of the microarray comet assay. We showed that the linear detection range for H2O2-induced DNA damage in human lymphoblastoid cells is between 30 and 100 μM, and that within this range, inter-sample coefficient of variance was between 5 and 10%. Importantly, only 20 comets were required to detect a statistically significant induction of DNA damage for doses within the linear range. We also evaluated sample-to-sample and experiment-to-experiment variation and found that for both conditions, the coefficient of variation was lower than what has been reported for the traditional comet assay. Finally, we also show that the assay can be performed using a 4× objective (rather than the standard 10× objective for the traditional assay). This adjustment combined with the microarray format makes it possible to capture more than 50 analysable comets in a single image, which can then be automatically analysed using in-house software. Overall, throughput is increased more than 100-fold compared to the traditional assay. Together, the results presented here demonstrate key advances in comet assay technology that improve the throughput, sensitivity, and robustness, thus enabling larger scale clinical and epidemiological studies.

  5. The study of comets, part 1. [conference on photometry and spectrum analysis of Kohoutek comet and comet tails

    NASA Technical Reports Server (NTRS)

    Donn, B. (Editor); Mumma, M. J. (Editor); Jackson, W. M. (Editor); Ahearn, M. (Editor); Harrington, R. (Editor)

    1976-01-01

    Papers are presented dealing with observations of comets. Topic discussed include: photometry, polarimetry, and astrometry of comets; detection of water and molecular transitions in comets; ion motions in comet tails; determination of comet brightness and luminosity; and evolution of cometary orbits. Emphasis is placed on analysis of observations of comet Kohoutek.

  6. The use of comet assay in plant toxicology: recent advances

    PubMed Central

    Santos, Conceição L. V.; Pourrut, Bertrand; Ferreira de Oliveira, José M. P.

    2015-01-01

    The systematic study of genotoxicity in plants induced by contaminants and other stress agents has been hindered to date by the lack of reliable and robust biomarkers. The comet assay is a versatile and sensitive method for the evaluation of DNA damages and DNA repair capacity at single-cell level. Due to its simplicity and sensitivity, and the small number of cells required to obtain robust results, the use of plant comet assay has drastically increased in the last decade. For years its use was restricted to a few model species, e.g., Allium cepa, Nicotiana tabacum, Vicia faba, or Arabidopsis thaliana but this number largely increased in the last years. Plant comet assay has been used to study the genotoxic impact of radiation, chemicals including pesticides, phytocompounds, heavy metals, nanoparticles or contaminated complex matrices. Here we will review the most recent data on the use of this technique as a standard approach for studying the genotoxic effects of different stress conditions on plants. Also, we will discuss the integration of information provided by the comet assay with other DNA-damage indicators, and with cellular responses including oxidative stress, cell division or cell death. Finally, we will focus on putative relations between transcripts related with DNA damage pathways, DNA replication and repair, oxidative stress and cell cycle progression that have been identified in plant cells with comet assays demonstrating DNA damage. PMID:26175750

  7. Re-analysis results using medians of the data from the JaCVAM-organized international validation study of the in vivo rat alkaline comet assay.

    PubMed

    Uno, Yoshifumi; Omori, Takashi

    2015-07-01

    The data from the JaCVAM-organized international validation study of the in vivo rat alkaline comet assay were reported and analyzed statistically using the simple means of % tail DNA. However, OECD test guideline TG 489 recommends use of the median for data analysis due to the hierarchical nature of the data. Comparison between the simple mean approach and the median based approach for positive/negative/equivocal chemical calls was conducted using the % tail DNA data for the 40 chemicals tested in the JaCVAM-organized international validation study of the in vivo rat alkaline comet assay, using liver and stomach as target organs. In the liver, two genotoxic chemicals, o-anisidine and 9-aminoacridine hydrochloride monohydrate, were positive using the median based approach but negative using the simple mean approach, and two genotoxic chemicals, 2-acetylaminofluorene and busulfan were equivocal using the median based approach but negative using the simple mean approach. In contrast, cadmium chloride (genotoxic carcinogen) was equivocal in both organs using the median based approach, while positive and equivocal in liver and stomach, respectively, using the simple mean approach. Two data sets of sodium arsenite showed equivocal and negative results for liver using the median based approach, although both data sets were equivocal using the simple mean approach. Overall, there are no large differences in terms of the genotoxic call between both approaches. However, the median based approach recommended in OECD TG 489 has an advantage toward higher precision within the groups treated with a test chemical, whereas the approach might show the lower values for the effect.

  8. Epithelial cells as alternative human biomatrices for comet assay

    PubMed Central

    Rojas, Emilio; Lorenzo, Yolanda; Haug, Kristiane; Nicolaissen, Bjørn; Valverde, Mahara

    2014-01-01

    The comet assay is a valuable experimental tool aimed at mapping DNA damage in human cells in vivo for environmental and occupational monitoring, as well as for therapeutic purposes, such as storage prior to transplant, during tissue engineering, and in experimental ex vivo assays. Furthermore, due to its great versatility, the comet assay allows to explore the use of alternative cell types to assess DNA damage, such as epithelial cells. Epithelial cells, as specialized components of many organs, have the potential to serve as biomatrices that can be used to evaluate genotoxicity and may also serve as early effect biomarkers. Furthermore, 80% of solid cancers are of epithelial origin, which points to the importance of studying DNA damage in these tissues. Indeed, studies including comet assay in epithelial cells have either clear clinical applications (lens and corneal epithelial cells) or examine genotoxicity within human biomonitoring and in vitro studies. We here review improvements in determining DNA damage using the comet assay by employing lens, corneal, tear duct, buccal, and nasal epithelial cells. For some of these tissues invasive sampling procedures are needed. Desquamated epithelial cells must be obtained and dissociated prior to examination using the comet assay, and such procedures may induce varying amounts of DNA damage. Buccal epithelial cells require lysis enriched with proteinase K to obtain free nucleosomes. Over a 30 year period, the comet assay in epithelial cells has been little employed, however its use indicates that it could be an extraordinary tool not only for risk assessment, but also for diagnosis, prognosis of treatments and diseases. PMID:25506353

  9. Epithelial cells as alternative human biomatrices for comet assay.

    PubMed

    Rojas, Emilio; Lorenzo, Yolanda; Haug, Kristiane; Nicolaissen, Bjørn; Valverde, Mahara

    2014-01-01

    The comet assay is a valuable experimental tool aimed at mapping DNA damage in human cells in vivo for environmental and occupational monitoring, as well as for therapeutic purposes, such as storage prior to transplant, during tissue engineering, and in experimental ex vivo assays. Furthermore, due to its great versatility, the comet assay allows to explore the use of alternative cell types to assess DNA damage, such as epithelial cells. Epithelial cells, as specialized components of many organs, have the potential to serve as biomatrices that can be used to evaluate genotoxicity and may also serve as early effect biomarkers. Furthermore, 80% of solid cancers are of epithelial origin, which points to the importance of studying DNA damage in these tissues. Indeed, studies including comet assay in epithelial cells have either clear clinical applications (lens and corneal epithelial cells) or examine genotoxicity within human biomonitoring and in vitro studies. We here review improvements in determining DNA damage using the comet assay by employing lens, corneal, tear duct, buccal, and nasal epithelial cells. For some of these tissues invasive sampling procedures are needed. Desquamated epithelial cells must be obtained and dissociated prior to examination using the comet assay, and such procedures may induce varying amounts of DNA damage. Buccal epithelial cells require lysis enriched with proteinase K to obtain free nucleosomes. Over a 30 year period, the comet assay in epithelial cells has been little employed, however its use indicates that it could be an extraordinary tool not only for risk assessment, but also for diagnosis, prognosis of treatments and diseases.

  10. Worldwide interest in the comet assay: a bibliometric study.

    PubMed

    Neri, Monica; Milazzo, Daniele; Ugolini, Donatella; Milic, Mirta; Campolongo, Alessandra; Pasqualetti, Patrizio; Bonassi, Stefano

    2015-01-01

    The comet assay is a rapid, sensitive and relatively simple method for measuring DNA damage. A bibliometric study was performed to evaluate temporal and geographical trends, research quality and main areas of interest in scientific production in this field. A PubMed search strategy was developed and 7674 citations were retrieved in the period 1990-2013. Notably, the MeSH (Medical Subject Headings) term 'comet assay', officially introduced in 2000, is used by indexers only in two thirds of papers retrieved. Articles on the comet assay were published in 78 countries, spread over the 5 continents. The EU contributed the greatest output, producing >2900 articles with IF (42.0%) and totalling almost 10000 IF points, and was followed by USA. In the new millennium, research with this assay reached a plateau or slow decline in the most industrialised areas (USA, Germany, UK, Italy), while its use has boomed in emerging countries, with increases of 5- to 7-fold in the last 10 years in China, India and Brazil, for instance. This transition resulted in a slow decrease of scientific production quality, as the countries that increased their relative weight typically had lower mIFs. The most common MeSH terms used in papers using the comet assay referred to wide areas of interest, such as DNA damage and repair, cell survival and apoptosis, cancer and oxidative stress, occupational and environmental health. Keywords related to humans, rodents and cell culture were also frequently used. The top journal for the comet assay articles was found to be Mutation Research, followed by Mutagenesis. Most papers using the comet assay as a biomarker were published in genetic and toxicology journals, with a stress on environmental and occupational disciplines.

  11. Further characterization of benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects.

    PubMed

    Bausinger, Julia; Schütz, Petra; Piberger, Ann Liza; Speit, Günter

    2016-03-01

    The present study aims to further characterize benzo[a]pyrene diol-epoxide (BPDE)-induced comet assay effects. Therefore, we measured DNA effects by the comet assay and adduct levels by high-performance liquid chromatography (HPLC) in human lymphocytes and A549 cells exposed to (±)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(±)-anti-BPDE] or (+)-anti-benzo[a]pyrene-7,8-diol 9,10-epoxide [(+)-anti-BPDE]. Both, the racemic form and (+)-anti-BPDE, which is the most relevant metabolite with regard to mutagenicity and carcinogenicity, induced DNA migration in cultured lymphocytes in the same range of concentrations to a similar extent in the alkaline comet assay after exposure for 2h. Nevertheless, (+)-anti-BPDE induced significantly enhanced DNA migration after 16 and 18h post-cultivation which was not seen in response to (±)-anti-BPDE. Combination of the comet assay with the Fpg (formamidopyrimidine-DNA glycosylase) protein did not enhance BPDE-induced effects and thus indicated the absence of Fpg-sensitive sites (oxidized purines, N7-guanine adducts, AP-sites). The aphidicolin (APC)-modified comet assay suggested significant excision repair activity of cultured lymphocytes during the first 18h of culture after a 2 h-exposure to BPDE. In contrast to these repair-related effects measured by the comet assay, HPLC analysis of stable adducts did not reveal any significant removal of (+)-anti-BPDE-induced adducts from lymphocytes during the first 22h of culture. On the other hand, HPLC measurements indicated that A549 cells repaired about 70% of (+)-anti-BPDE-induced DNA-adducts within 22h of release. However, various experiments with the APC-modified comet assay did not indicate significant repair activity during this period in A549 cells. The conflicting results obtained with the comet assay and the HPLC-based adduct analysis question the real cause for BPDE-induced DNA migration in the comet assay and the reliability of the APC-modified comet assay for the

  12. Comet assay: an essential tool in toxicological research.

    PubMed

    Glei, M; Schneider, T; Schlörmann, W

    2016-10-01

    The comet assay is a versatile, reliable, cost-efficient, and fast technique for detecting DNA damage and repair in any tissue. It is useable in almost any cell type and applicable to both eukaryotic and prokaryotic organisms. Instead of highlighting one of the numerous specific aspects of the comet assay, the present review aims at giving an overview about the evolution of this widely applicable method from the first description by Ostling and Johanson to the OECD Guideline 489 for the in vivo mammalian comet assay. In addition, methodical aspects and the influence of critical steps of the assay as well as the evaluation of results and improvements of the method are reviewed. Methodical aspects regarding oxidative DNA damage and repair are also addressed. An overview about the most recent works and relevant cutting-edge reviews based on the comet assay with special regard to, e.g., clinical applications, nanoparticles or environmental risk assessment concludes this review. Taken together, the presented overview raises expectations to further decades of successful applications and enhancements of this excellent method.

  13. Assessment of gamma ray-induced DNA damage in Lasioderma serricorne using the comet assay

    NASA Astrophysics Data System (ADS)

    Kameya, Hiromi; Miyanoshita, Akihiro; Imamura, Taro; Todoriki, Setsuko

    2012-03-01

    We attempted a DNA comet assay under alkaline conditions to verify the irradiation treatment of pests. Lasioderma serricorne (Fabricius) were chosen as test insects and irradiated with gamma rays from a 60Co source at 1 kGy. We conducted the comet assay immediately after irradiation and over time for 7 day. Severe DNA fragmentation in L. serricorne cells was observed just after irradiation and the damage was repaired during the post-irradiation period in a time-dependent manner. The parameters of the comet image analysis were calculated, and the degree of DNA damage and repair were evaluated. Values for the Ratio (a percentage determined by fluorescence in the damaged area to overall luminance, including intact DNA and the damaged area of a comet image) of individual cells showed that no cells in the irradiated group were included in the Ratio<0.1 category, the lowest grade. This finding was observed consistently throughout the 7-day post-irradiation period. We suggest that the Ratio values of individual cells can be used as an index of irradiation history and conclude that the DNA comet assay under alkaline conditions, combined with comet image analysis, can be used to identify irradiation history.

  14. The comet assay as a tool for human biomonitoring studies: the ComNet project.

    PubMed

    Collins, Andrew; Koppen, Gudrun; Valdiglesias, Vanessa; Dusinska, Maria; Kruszewski, Marcin; Møller, Peter; Rojas, Emilio; Dhawan, Alok; Benzie, Iris; Coskun, Erdem; Moretti, Massimo; Speit, Günter; Bonassi, Stefano

    2014-01-01

    The comet assay is widely used in human biomonitoring to measure DNA damage as a marker of exposure to genotoxic agents or to investigate genoprotective effects. Studies often involve small numbers of subjects, and design may be sub-optimal in other respects. In addition, comet assay protocols in use in different laboratories vary significantly. In spite of these difficulties, it is appropriate to carry out a pooled analysis of all available comet assay biomonitoring data, in order to establish baseline parameters of DNA damage, and to investigate associations between comet assay measurements and factors such as sex, age, smoking status, nutrition, lifestyle, etc. With this as its major objective, the ComNet project has recruited almost 100 research groups willing to share datasets. Here we provide a background to this project, discussing the history of the comet assay and practical issues that can critically affect its performance. We survey its diverse applications in biomonitoring studies, including environmental and occupational exposure to genotoxic agents, genoprotection by dietary and other factors, DNA damage associated with various diseases, and intrinsic factors that affect DNA damage levels in humans. We examine in depth the quality of data from a random selection of studies, from an epidemiological and statistical point of view.

  15. Hummingbird Comet Nucleus Analysis Mission

    NASA Technical Reports Server (NTRS)

    Kojiro, Daniel; Carle, Glenn C.; Lasher, Larry E.

    2000-01-01

    Hummingbird is a highly focused scientific mission, proposed to NASA s Discovery Program, designed to address the highest priority questions in cometary science-that of the chemical composition of the cometary nucleus. After rendezvous with the comet, Hummingbird would first methodically image and map the comet, then collect and analyze dust, ice and gases from the cometary atmosphere to enrich characterization of the comet and support landing site selection. Then, like its namesake, Hummingbird would carefully descend to a pre-selected surface site obtaining a high-resolution image, gather a surface material sample, acquire surface temperature and then immediately return to orbit for detailed chemical and elemental analyses followed by a high resolution post-sampling image of the site. Hummingbird s analytical laboratory contains instrumentation for a comprehensive molecular and elemental analysis of the cometary nucleus as well as an innovative surface sample acquisition device.

  16. Detection of Irradiation Treatment of Foods Using DNA `Comet Assay'

    NASA Astrophysics Data System (ADS)

    Khan, Hasan M.; Delincée, Henry

    1998-06-01

    Microgel electrophoresis of single cells (DNA comet assay) has been investigated to detect irradiation treatment of some food samples. These samples of fresh and frozen rainbow trout, red lentil, gram and sliced almonds were irradiated to 1 or 2 kGy using 10 MeV electron beam from a linear accelerator. Rainbow trout samples yielded good results with samples irradiated to 1 or 2 kGy showing fragmentation of DNA and, therefore, longer comets with no intact cells. Unirradiated samples showed shorter comets with a significant number of intact cells. For rainbow trout stored in a freezer for 11 days the irradiated samples can still be discerned by electrophoresis from unirradiated samples, however, the unirradiated trouts also showed some longer comets besides some intact cells. Radiation treatment of red lentils can also be detected by this method, i.e. no intact cells in 1 or 2 kGy irradiated samples and shorter comets and some intact cells in unirradiated samples. However, the results for gram and sliced almond samples were not satisfactory since some intact DNA cells were observed in irradiated samples as well. Probably, incomplete lysis has led to these deviating results.

  17. Sperm DNA damage output parameters measured by the alkaline Comet assay and their importance.

    PubMed

    Simon, L; Aston, K I; Emery, B R; Hotaling, J; Carrell, D T

    2017-03-01

    The alkaline Comet assay has shown high diagnostic value to determine male reproductive health and prognostic ability to predict ART success. Here, spermatozoon was analysed in 47 fertile donors and 238 patients, including 132 couples undergoing ART [semen was collected: Group I - within 3 months of their treatment (n = 79); and Group II - 3 months prior to their treatment (n = 53)]. We introduce four Comet distribution plots (A, B1, B2 and C) by plotting the level of DNA damage (x-axis) and percentage of comets (y-axis). Fertile donors had low mean DNA damage, olive tail moment and per cent of spermatozoa with damage and increased type A plots. Comet parameters were associated with clinical pregnancies in Group I. About 66% of couples with type A distribution plot were successful after ART, whereas couples with type B1, B2 and C distribution plots achieved 56%, 44% and 33% pregnancies respectively. The efficiency of the Comet assay was due to complete decondensation process, where the compact sperm nuclear DNA (28.2 ± 0.2 μm(3) ) is decondensed to ~63 μm(3) (before lysis) and ~1018 μm(3) (after lysis). A combinational analysis of all the Comet output parameters may provide a comprehensive evaluation of patient's reproductive health as these parameters measure different aspects of DNA damage within the spermatozoa.

  18. The comet assay: Reflections on its development, evolution and applications.

    PubMed

    Singh, Narendra P

    2016-01-01

    The study of DNA damage and its repair is critical to our understanding of human aging and cancer. This review reflects on the development of a simple technique, now known as the comet assay, to study the accumulation of DNA damage and its repair. It describes my journey into aging research and the need for a method that sensitively quantifies DNA damage on a cell-by-cell basis and on a day-by-day basis. My inspirations, obstacles and successes on the path to developing this assay and improving its reliability and sensitivity are discussed. Recent modifications, applications, and the process of standardizing the technique are also described. What was once untried and unknown has become a technique used around the world for understanding and monitoring DNA damage. The comet assay's use has grown exponentially in the new millennium, as emphasis on studying biological phenomena at the single-cell level has increased. I and others have applied the technique across cell types (including germ cells) and species (including bacteria). As it enters new realms and gains clinical relevance, the comet assay may very well illuminate human aging and its prevention.

  19. DNA ``comet assay'' for rapid detection of irradiated food

    NASA Astrophysics Data System (ADS)

    Delincée, H.

    1996-09-01

    Since treatment with ionizing radiation causes DNA fragmentation, microgel electrophoresis of single cell (``comet assay'') can be applied as a simple and rapid tool for identification of irradiated foods. The DNA ``comet assay'' has been employed successfully in the past to frozen meats (chicken, pork, beef) and its application is now being extended to a variety of other food items, such as fish, fruits, legumes, seeds and even spices. The electrophoretic separation requires only a few minutes, and after visualising DNA by silver staining, the DNA fragmentation pattern observed in a simple transmission microscope may indicate a possible irradiation treatment. Suspected samples may subsequently be analyzed by the more sophisticated (expensive) and validated techniques.

  20. DNA Damage among Wood Workers Assessed with the Comet Assay.

    PubMed

    Bruschweiler, Evin Danisman; Wild, Pascal; Huynh, Cong Khanh; Savova-Bianchi, Dessislava; Danuser, Brigitta; Hopf, Nancy B

    2016-01-01

    Exposure to wood dust, a human carcinogen, is common in wood-related industries, and millions of workers are occupationally exposed to wood dust worldwide. The comet assay is a rapid, simple, and sensitive method for determining DNA damage. The objective of this study was to investigate the DNA damage associated with occupational exposure to wood dust using the comet assay (peripheral blood samples) among nonsmoking wood workers (n = 31, furniture and construction workers) and controls (n = 19). DNA damage was greater in the group exposed to composite wood products compared to the group exposed to natural woods and controls (P < 0.001). No difference in DNA damage was observed between workers exposed to natural woods and controls (P = 0.13). Duration of exposure and current dust concentrations had no effect on DNA damage. In future studies, workers' exposures should include cumulative dust concentrations and exposures originating from the binders used in composite wood products.

  1. DNA Damage among Wood Workers Assessed with the Comet Assay

    PubMed Central

    Bruschweiler, Evin Danisman; Wild, Pascal; Huynh, Cong Khanh; Savova-Bianchi, Dessislava; Danuser, Brigitta; Hopf, Nancy B.

    2016-01-01

    Exposure to wood dust, a human carcinogen, is common in wood-related industries, and millions of workers are occupationally exposed to wood dust worldwide. The comet assay is a rapid, simple, and sensitive method for determining DNA damage. The objective of this study was to investigate the DNA damage associated with occupational exposure to wood dust using the comet assay (peripheral blood samples) among nonsmoking wood workers (n = 31, furniture and construction workers) and controls (n = 19). DNA damage was greater in the group exposed to composite wood products compared to the group exposed to natural woods and controls (P < 0.001). No difference in DNA damage was observed between workers exposed to natural woods and controls (P = 0.13). Duration of exposure and current dust concentrations had no effect on DNA damage. In future studies, workers’ exposures should include cumulative dust concentrations and exposures originating from the binders used in composite wood products. PMID:27398027

  2. Genotoxicity of environmental agents assessed by the alkaline comet assay.

    PubMed

    Møller, Peter

    2005-01-01

    Generation of DNA damage is considered to be an important initial event in carcinogenesis. A considerable battery of assays exists for the detection of different genotoxic effects of compounds in experimental systems, or for investigations of exposure to genotoxic agents in environmental or occupational settings. Some of the tests may have limited use because of complicated technical setup or because they only are applicable to a few cell types. The single cell gel electrophoresis (comet) assay is technically simple, relatively fast, cheap, and DNA damage can be investigated in virtually all mammalian cell types without requirement for cell culture. The aim of this thesis was to evaluate the comet assay as a genotoxicity test in genetic toxicology of environmental agents, encompassing both experimental animal models and biomonitoring. The comet assay detects strand breaks (SB). The cells are embedded in agarose and lysed, generating nucleus-like structures in the gel (referred to as nucleoids). Following alkaline electrophoresis, the DNA strands migrate toward the anode, and the extent of migration depends on the number of SB in the nucleoid. The migration is visualized and scored in a fluorescence microscope after staining. Broad classes of oxidative DNA damage can be detected as additional SB if nucleoids are incubated with bacterial DNA glycosylase/endonuclease enzymes. Oxidized pyrimidines and purines can be detected by incubation with endonuclease III and formamidopyrimidine DNA glycosylase, respectively. The animal experimental studies indicated that the comet assay was able to detect genotoxic effects of diesel exhaust particles in lung tissue, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ)-induced DNA damage in colon epithelial cells and liver tissue, and benzene-induced damage in bone marrow and liver cells. The strength of the comet assay was further outlined by application of repair enzymes, indicating no oxidative DNA base damage following IQ treatment

  3. Bovine Papillomavirus Clastogenic Effect Analyzed in Comet Assay

    PubMed Central

    Araldi, R. P.; Melo, T. C.; Diniz, N.; Mazzuchelli-de-Souza, J.; Carvalho, R. F.; Beçak, W.; Stocco, R. C.

    2013-01-01

    Bovine papillomavirus (BPV) is an oncogenic virus related to serious livestock diseases. Oncoproteins encoded by BPV are involved in several steps of cellular transformation and have been reported as presenting clastogenic effects in peripheral lymphocytes and primary culture cells. The aim of this study was to evaluate the clastogenic potential of BPV types 1, 2, and 4 by comet assay. Peripheral blood was collected from 37 bovines, 32 infected with different levels of papillomatosis (12 animals have no affection) and five calves, virus free (negative control). The viral identification showed presence of more than one virus type in 59.375% of the infected animals. Comet assay was performed according to alkaline technique. The Kruskal-Wallis test showed statistical difference between the negative control group and infected animals (P = 0.0015). The Dunn post hoc test showed difference comparing the infected animals with calves. Mann-Whitney U test verified no difference between animals infected with only one viral type and animals presenting more than one viral type. The comet assay is considered an efficient tool for assessment of damage in the host chromatin due to viral action, specifically highlighting viral activity in blood cells. PMID:23956996

  4. Drosophila comet assay: insights, uses, and future perspectives

    PubMed Central

    Gaivão, Isabel; Sierra, L. María

    2014-01-01

    The comet assay, a very useful tool in genotoxicity and DNA repair testing, is being applied to Drosophila melanogaster since around 15 years ago, by several research groups. This organism is a valuable model for all kind of processes related to human health, including DNA damage response. The assay has been performed mainly in vivo using different larvae cell types (from brain, midgut, hemolymph, and imaginal disk), but also in vitro with the S2 cell line. Since its first application, it has been used to analyze the genotoxicity and action mechanisms of different chemicals, demonstrating good sensitivity and proving its usefulness. Moreover, it is the only assay that can be used to analyze DNA repair in somatic cells in vivo, comparing the effects of chemicals in different repair strains, and to quantitate repair activities in vitro. Additionally, the comet assay in Drosophila, in vivo and in vitro, has been applied to study the influence of protein overexpression on genome integrity and degradation. Although the assay is well established, it could benefit from some research to determine optimal experimental design to standardize it, and then to allow comparisons among laboratories independently of the chosen cell type. PMID:25221574

  5. Detection of radiation treatment of beans using DNA comet assay

    NASA Astrophysics Data System (ADS)

    Khan, Ashfaq A.; Khan, Hasan M.; Delincée, Henry

    2002-03-01

    A simple technique of microgel electrophoresis of single cells (DNA Comet Assay) enabled a quick detection of radiation treatment of several kinds of leguminous beans (azuki, black, black eye, mung, pinto, red kidney and white beans). Each variety was exposed to radiation doses of 0.5, 1 and 5kGy covering the permissible limits for insect disinfestation. The cells or nuclei from beans were extracted in cold PBS, embedded in agarose on microscope slides, lysed between 15 and 60min in 2.5% SDS and electrophoresis was carried out at a voltage of 2V/cm for 2-2.5min. After silver staining, the slides were evaluated through an ordinary transmission microscope. In irradiated samples, fragmented DNA stretched towards the anode and the damaged cells appeared as a comet. The density of DNA in the tails increased with increasing radiation dose. However, in non-irradiated samples, the large molecules of DNA remained relatively intact and there was only minor or no migration of DNA; the cells were round or had very short tails only. Hence, the DNA comet assay provides an inexpensive, rapid and relatively simple screening method for the detection of irradiated beans.

  6. Automated detection of irradiated food with the comet assay.

    PubMed

    Verbeek, F; Koppen, G; Schaeken, B; Verschaeve, L

    2008-01-01

    Food irradiation is the process of exposing food to ionising radiation in order to disinfect, sanitise, sterilise and preserve food or to provide insect disinfestation. Irradiated food should be adequately labelled according to international and national guidelines. In many countries, there are furthermore restrictions to the product-specific maximal dose that can be administered. Therefore, there is a need for methods that allow detection of irradiated food, as well as for methods that provide a reliable dose estimate. In recent years, the comet assay was proposed as a simple, rapid and inexpensive method to fulfil these goals, but further research is required to explore the full potential of this method. In this paper we describe the use of an automated image analysing system to measure DNA comets which allow the discrimination between irradiated and non-irradiated food as well as the set-up of standard dose-response curves, and hence a sufficiently accurate dose estimation.

  7. Evaluation of environmental genotoxicity by comet assay in Columba livia.

    PubMed

    González-Acevedo, Anahi; García-Salas, Juan A; Gosálvez, Jaime; Fernández, José Luis; Dávila-Rodríguez, Martha I; Cerda-Flores, Ricardo M; Méndez-López, Luis F; Cortés-Gutiérrez, Elva I

    2016-01-01

    The concentrations of recognized or suspected genotoxic and carcinogenic agents found in the air of large cities and, in particular, developing countries, have raised concerns about the potential for chronic health effects in the populations exposed to them. The biomonitoring of environmental genotoxicity requires the selection of representative organisms as "sentinels," as well as the development of suitable and sensitive assays, such as those aimed at assessing DNA damage. The aim of this study was to evaluate DNA damage levels in erythrocytes from Columba livia living in the metropolitan area of Monterrey, Mexico, compared with control animals via comet assay, and to confirm the results via Micronuclei test (MN) and DNA breakage detection-fluorescence in situ hybridization (DBD-FISH). Our results showed a significant increase in DNA migration in animals from the area assayed compared with that observed in control animals sampled in non-contaminated areas. These results were confirmed by MN test and DBD-FISH. In conclusion, these observations confirm that the examination of erythrocytes from Columba livia via alkaline comet assay provides a sensitive and reliable end point for the detection of environmental genotoxicants.

  8. Comet Assay on Daphnia magna in eco-genotoxicity testing.

    PubMed

    Pellegri, Valerio; Gorbi, Gessica; Buschini, Annamaria

    2014-10-01

    Detection of potentially hazardous compounds in water bodies is a priority in environmental risk assessment. For the evaluation and monitoring of water quality, a series of methodologies may be applied. Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the most powerful. In recent years, some attempts were made to utilize Daphnia magna in genotoxicity testing as many of the new environmental contaminants are described as DNA-damaging agents in aquatic organisms. The aim of this research was to develop a highly standardized protocol of the Comet Assay adapted for D. magna, especially regarding the isolation of cells derived from the same tissue (haemolymph) from newborn organisms exposed in vivo. Several methods for haemolymph extraction and different Comet Assay parameters were compared. Electrophoretic conditions were adapted in order to obtain minimum DNA migration in cells derived from untreated organisms and, at the same time, maximum sensitivity in specimens treated with known genotoxicants (CdCl2 and H2O2). Additional tests were performed to investigate if life-history traits of the cladoceran (such as the age of adult organisms that provide newborns, the clutch size of origin, the number of generations reared in standard conditions) and the water composition as well, might influence the response of the assay. This study confirms the potential application of the Comet Assay in D. magna for assessing genotoxic loads in aqueous solution. The newly developed protocol could integrate the acute toxicity bioassay, thus expanding the possibility of using this model species in freshwater monitoring (waters, sediment and soil elutriates) and is in line with the spirit of the EU Water Framework Directive in reducing the number of bioassays that involve medium-sized species.

  9. Observation of DNA damage of human hepatoma cells irradiated by heavy ions using comet assay

    PubMed Central

    Qiu, Li-Mei; Li, Wen-Jian; Pang, Xin-Yue; Gao, Qing-Xiang; Feng, Yan; Zhou, Li-Bin; Zhang, Gao-Hua

    2003-01-01

    AIM: Now many countries have developed cancer therapy with heavy ions, especially in GSI (Gesellschaft fürSchwerionenforschung mbH, Darmstadt, Germany), remarkable results have obtained, but due to the complexity of particle track structure, the basic theory still needs further researching. In this paper, the genotoxic effects of heavy ions irradiation on SMMC-7721 cells were measured using the single cell gel electrophoresis (comet assay). The information about the DNA damage made by other radiations such as X-ray, γ-ray, UV and fast neutron irradiation is very plentiful, while little work have been done on the heavy ions so far. Hereby we tried to detect the reaction of liver cancer cells to heavy ion using comet assay, meanwhile to establish a database for clinic therapy of cancer with the heavy ions. METHODS: The human hepatoma cells were chosen as the test cell line irradiated by 80Mev/u 20Ne10+ on HIRFL (China), the radiation-doses were 0, 0.5, 1, 2, 4 and 8 Gy, and then comet assay was used immediately to detect the DNA damages, 100-150 cells per dose-sample (30-50 cells were randomly observed at constant depth of the gel). The tail length and the quantity of the cells with the tail were put down. EXCEL was used for statistical analysis. RESULTS: We obtained clear images by comet assay and found that SMMC-7721 cells were all damaged apparently from the dose 0.5 Gy to 8 Gy (t-test: P < 0.001, vs control). The tail length and tail moment increased as the doses increased, and the number of cells with tails increased with increasing doses. When doses were higher than 2 Gy, nearly 100% cells were damaged. Furthermore, both tail length and tail moment, showed linear equation. CONCLUSION: From the clear comet assay images, our experiment proves comet assay can be used to measure DNA damages by heavy ions. Meanwhile DNA damages have a positive correlation with the dose changes of heavy ions and SMMC-7721 cells have a great radiosensitivity to 20Ne10+. Different

  10. First application of comet assay in blood cells of Mediterranean loggerhead sea turtle (Caretta caretta).

    PubMed

    Caliani, Ilaria; Campani, Tommaso; Giannetti, Matteo; Marsili, Letizia; Casini, Silvia; Fossi, Maria Cristina

    2014-05-01

    The aim of this study was to validate the comet assay in erythrocytes of Caretta caretta, a species never investigated for genotoxicity. We studied 31 loggerhead sea turtles from three Italian marine rescue centres. Peripheral blood samples were collected from all the animals and the comet assay applied. All comet cells were analysed using two methods: visual scoring and computer image analysis. The % DNA in tail mean value ± SD and Damage Index were 21.56 ± 15.41 and 134.83 ± 94.12, respectively. A strong and statistically significant statistically correlation between the two analytical methods was observed (r = 0.95; p < 0.05). These results demonstrate that the comet assay is a useful method to detect the possible effects of genotoxic agents in loggerhead sea turtle and to increase the knowledge about the ecotoxicological health status of this threatened species.

  11. Identification of irradiated refrigerated pork with the DNA comet assay

    NASA Astrophysics Data System (ADS)

    Araújo, M. M.; Marin-Huachaca, N. S.; Mancini-Filho, J.; Delincée, H.; Villavicencio, A. L. C. H.

    2004-09-01

    Food irradiation can contribute to a safer and more plentiful food supply by inactivating pathogens, eradicating pests and by extending shelf-life. Particularly in the case of pork meat, this process could be a useful way to inactivate harmful parasites such as Trichinella and Taenia solium. Ionizing radiation causes damage to the DNA of the cells (e.g. strand breaks), which can be used to detect irradiated food. Microelectrophoresis of single cells (``Comet Assay'') is a simple and rapid test for DNA damage and can be used over a wide dose range and for a variety of products. Refrigerated pork meat was irradiated with a 60Co source, Gammacell 220 (A.E.C.L.) installed in IPEN (Sa~o Paulo, Brazil). The doses given were 0, 1.5, 3.0 and 4.5kGy for refrigerated samples. Immediately after irradiation the samples were returned to the refrigerator (6°C). Samples were kept in the refrigerator after irradiation. Pork meat was analyzed 1, 8 and 10 days after irradiation using the DNA ``Comet Assay''. This method showed to be an inexpensive and rapid technique for qualitative detection of irradiation treatment.

  12. ISO's analysis of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    1997-03-01

    of the comet's dust and vapour, and also rates of escape of vapour, which will help in assessing the loss of material from Comet Hale-Bopp during this visit to the Sun's vicinity. "Watch out for some fascinating news," says Thijs de Graauw of Groningen University, who is in charge of the SWS instrument used in this study. "What excites me is the opportunity we shall have to compare dusty Comet Hale-Bopp, seen in the Solar System, with dusty objects far away among the stars which seem to be made of similar materials. Infrared astronomy has a special ability to unify cosmic chemistry at all scales from little dust grains in the Earth's vicinity to vast and distant galaxies." The dust itself interests the infrared astronomers, not least because their view of the Universe at large is spoiled to some extent by dust left behind by comets. Together with fine debris from asteroids, the comet dust makes a bright infrared band around the sky, which corresponds with the zodiacal light sometimes seen by eye, slanting above the horizon at twilight. ISO's predecessor, the US-Dutch-UK infrared astronomical satellite IRAS, found trails of comet dust much longer and more persistent than the familiar comet tails. ISO has seen a trail from Comet Kopff. By detecting dust grains that are typically much larger than those seen by visible light, ISO scientists hope to learn more about the dust's long-term behaviour in the Solar System. A series of images of Comet Hale-Bopp, obtained by the camera ISOCAM in October 1996, is the subject of continuing analysis. Leading this work in progress is Philippe Lamy of Marseille, France. "We hope to unveil the nucleus of the comet," Professor Lamy explains. "In principle, the Hubble Space Telescope can see finer details by visible light, but the contrast of the nucleus against the bright surrounding coma is superior at infrared wavelengths. This is because the thermal emission from the nucleus is very large and can be detected thanks to the high

  13. Alkaline comet assay in liver and stomach, and micronucleus assay in bone marrow, from rats treated with 2-acetylaminofluorene, azidothymidine, cisplatin, or isobutyraldehyde.

    PubMed

    Kraynak, A R; Barnum, J E; Cunningham, C L; Ng, A; Ykoruk, B A; Bennet, B; Stoffregen, D; Merschman, M; Freeland, E; Galloway, S M

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined the ability of the assay to determine the genotoxicity of 2-acetylaminofluorene (AAF), azidothymidine (AZT), cisplatin (CPN), and isobutyraldehyde (IBA) in liver and glandular stomach of male Sprague-Dawley rats. Rats were given oral doses of test compound or control once daily for three days. High dose levels were approximately maximum tolerated doses and were based on preliminary range-finding studies. Tissues were harvested 3h after the final dose (48h after the initial dose). A bone marrow micronucleus assay (MN) was also conducted on the rats treated with AZT, CPN, and IBA. Acute toxic effects of treatment were determined primarily through histomorphologic analysis of liver and stomach but also by body weight and serum liver enzyme changes. The comet assay was conducted on fresh tissue preparations but frozen samples from two studies were also assayed. Statistically significant dose-related differences in comet % DNA in tail were found in liver and stomach for the genotoxin AZT and in liver for the genotoxin CPN, but not in liver or stomach for the non-genotoxin IBA. Statistically significant differences in % DNA in tail were measured in liver for the low and mid dose of the genotoxin AAF, but not the high dose. The comet assays of frozen liver suspensions from CPN- and AAF-treated rats yielded comparable results to the assays of fresh preparations. There were no indications of significant toxicity induced by any treatment. The micronucleus assay was positive for CPN and AZT and negative for IBA. In conclusion, the in vivo comet assay is capable of detecting genotoxic effects of a variety of chemicals and may fill an important role in the genotoxicity test battery.

  14. Inter-laboratory variation in DNA damage using a standard comet assay protocol.

    PubMed

    Forchhammer, Lykke; Ersson, Clara; Loft, Steffen; Möller, Lennart; Godschalk, Roger W L; van Schooten, Frederik J; Jones, George D D; Higgins, Jennifer A; Cooke, Marcus; Mistry, Vilas; Karbaschi, Mahsa; Collins, Andrew R; Azqueta, Amaya; Phillips, David H; Sozeri, Osman; Routledge, Michael N; Nelson-Smith, Kirsty; Riso, Patrizia; Porrini, Marisa; Matullo, Giuseppe; Allione, Alessandra; Stępnik, Maciej; Steepnik, Maciej; Komorowska, Magdalena; Teixeira, João Paulo; Costa, Solange; Corcuera, Laura-Ana; López de Cerain, Adela; Laffon, Blanca; Valdiglesias, Vanessa; Møller, Peter

    2012-11-01

    There are substantial inter-laboratory variations in the levels of DNA damage measured by the comet assay. The aim of this study was to investigate whether adherence to a standard comet assay protocol would reduce inter-laboratory variation in reported values of DNA damage. Fourteen laboratories determined the baseline level of DNA strand breaks (SBs)/alkaline labile sites and formamidopyrimidine DNA glycosylase (FPG)-sensitive sites in coded samples of mononuclear blood cells (MNBCs) from healthy volunteers. There were technical problems in seven laboratories in adopting the standard protocol, which were not related to the level of experience. Therefore, the inter-laboratory variation in DNA damage was only analysed using the results from laboratories that had obtained complete data with the standard comet assay protocol. This analysis showed that the differences between reported levels of DNA SBs/alkaline labile sites in MNBCs were not reduced by applying the standard assay protocol as compared with the laboratory's own protocol. There was large inter-laboratory variation in FPG-sensitive sites by the laboratory-specific protocol and the variation was reduced when the samples were analysed by the standard protocol. The SBs and FPG-sensitive sites were measured in the same experiment, indicating that the large spread in the latter lesions was the main reason for the reduced inter-laboratory variation. However, it remains worrying that half of the participating laboratories obtained poor results using the standard procedure. This study indicates that future comet assay validation trials should take steps to evaluate the implementation of standard procedures in participating laboratories.

  15. Can the comet assay be used reliably to detect nanoparticle-induced genotoxicity?

    PubMed

    Karlsson, Hanna L; Di Bucchianico, Sebastiano; Collins, Andrew R; Dusinska, Maria

    2015-03-01

    The comet assay is a sensitive method to detect DNA strand breaks as well as oxidatively damaged DNA at the level of single cells. Today the assay is commonly used in nano-genotoxicology. In this review we critically discuss possible interactions between nanoparticles (NPs) and the comet assay. Concerns for such interactions have arisen from the occasional observation of NPs in the "comet head", which implies that NPs may be present while the assay is being performed. This could give rise to false positive or false negative results, depending on the type of comet assay endpoint and NP. For most NPs, an interaction that substantially impacts the comet assay results is unlikely. For photocatalytically active NPs such as TiO2 , on the other hand, exposure to light containing UV can lead to increased DNA damage. Samples should therefore not be exposed to such light. By comparing studies in which both the comet assay and the micronucleus assay have been used, a good consistency between the assays was found in general (69%); consistency was even higher when excluding studies on TiO2 NPs (81%). The strong consistency between the comet and micronucleus assays for a range of different NPs-even though the two tests measure different endpoints-implies that both can be trusted in assessing the genotoxicity of NPs, and that both could be useful in a standard battery of test methods.

  16. Experiences with the in vivo and in vitro comet assay in regulatory testing.

    PubMed

    Frötschl, Roland

    2015-01-01

    The in vivo comet assay has recently been implemented into regulatory genotoxicity testing of pharmaceuticals with inclusion into the ICH S2R1 guidance. Regulatory genotoxicity testing aims to detect DNA alterations in form of gene mutations, larger scale chromosomal damage and recombination and aneuploidy. The ICH S2R1 guideline offers two options of standard batteries of tests for the detection of these endpoints. Both options start with an AMES assay and option 1 includes an in vitro mammalian cell assay and an in vivo micronucleus assay in rodent, whereas option 2 includes an in vivo micronucleus assay in bone marrow in rodent and a second in vivo assay in a second tissue with a second endpoint. The test recommended as second in vivo test is the comet assay in rat liver. The in vivo comet assay is considered as mature enough to ensure reliable detection of relevant in vivo genotoxicants in combination with the micronucleus test in bone marrow and the AMES assay. Although lots of research papers have been published using the in vitro comet assay, the in vitro version has not been implemented into official regulatory testing guidelines. A survey of the years 1999-2014 revealed 27 in vivo comet assays submitted to BfArM with market authorisation procedures, European and national advice procedures and clinical trial applications. In three procedures, in vitro comet assays had been submitted within the genetic toxicology packages.

  17. Comet assay to assess the genotoxicity of Persian walnut (Juglans regia L.) husks with statistical evaluation.

    PubMed

    Petriccione, Milena; Ciniglia, Claudia

    2012-07-01

    The aim of this study was to confirm the utility of the Comet assay as a genotoxicity screening test for evaluating the impact of walnut husk aqueous extract. Phytotoxicity assays using diluted and undiluted walnut husk aqueous extracts were performed on young roots of Raphanus sativus (radish), and the Comet assay was used to evaluate DNA integrity in isolated radish radicle nuclei. The results reveal a dose-dependent accumulation of DNA damage in radish radicles treated with walnut husks water extract and that the Kolmogorov-Smirnov test combined with Johnson SB distribution was the best approach for describing Comet assay data.

  18. A simple and novel modification of comet assay for determination of bacteriophage mediated bacterial cell lysis.

    PubMed

    Khairnar, Krishna; Sanmukh, Swapnil; Chandekar, Rajshree; Paunikar, Waman

    2014-07-01

    The comet assay is the widely used method for in vitro toxicity testing which is also an alternative to the use of animal models for in vivo testing. Since, its inception in 1984 by Ostling and Johansson, it is being modified frequently for a wide range of application. In spite of its wide applicability, unfortunately there is no report of its application in bacteriophages research. In this study, a novel application of comet assay for the detection of bacteriophage mediated bacterial cell lysis was described. The conventional methods in bacteriophage research for studying bacterial lysis by bacteriophages are plaque assay method. It is time consuming, laborious and costly. The lytic activity of bacteriophage devours the bacterial cell which results in the release of bacterial genomic material that gets detected by ethidium bromide staining method by the comet assay protocol. The objective of this study was to compare efficacy of comet assay with different assay used to study phage mediated bacterial lysis. The assay was performed on culture isolates (N=80 studies), modified comet assay appear to have relatively higher sensitivity and specificity than other assay. The results of the study showed that the application of comet assay can be an economical, time saving and less laborious alternative to conventional plaque assay for the detection of bacteriophage mediated bacterial cell lysis.

  19. The comet assay: assessment of in vitro and in vivo DNA damage.

    PubMed

    Bajpayee, Mahima; Kumar, Ashutosh; Dhawan, Alok

    2013-01-01

    Rapid industrialization and pursuance of a better life have led to an increase in the amount of chemicals in the environment, which are deleterious to human health. Pesticides, automobile exhausts, and new chemical entities all add to air pollution and have an adverse effect on all living organisms including humans. Sensitive test systems are thus required for accurate hazard identification and risk assessment. The Comet assay has been used widely as a simple, rapid, and sensitive tool for assessment of DNA damage in single cells from both in vitro and in vivo sources as well as in humans. Already, the in vivo comet assay has gained importance as the preferred test for assessing DNA damage in animals for some international regulatory guidelines. The advantages of the in vivo comet assay are its ability to detect DNA damage in any tissue, despite having non-proliferating cells, and its sensitivity to detect genotoxicity. The recommendations from the international workshops held for the comet assay have resulted in establishment of guidelines. The in vitro comet assay conducted in cultured cells and cell lines can be used for screening large number of compounds and at very low concentrations. The in vitro assay has also been automated to provide a high-throughput screening method for new chemical entities, as well as environmental samples. This chapter details the in vitro comet assay using the 96-well plate and in vivo comet assay in multiple organs of the mouse.

  20. Performance and data interpretation of the in vivo comet assay in pharmaceutical industry: EFPIA survey results.

    PubMed

    van der Leede, Bas-Jan; Doherty, Ann; Guérard, Melanie; Howe, Jonathan; O'Donovan, Mike; Plappert-Helbig, Ulla; Thybaud, Véronique

    2014-12-01

    In genotoxicity testing of pharmaceuticals the rodent alkaline comet assay is being increasingly used as a second in vivo assay in addition to the in vivo micronucleus assay to mitigate in vitro positive results as recommended by the ICH S2(R1) guideline. This paper summarizes a survey suggested by the Safety Working Party of European Medicines Agency (EMA), and conducted by the European Federation of Pharmaceutical Industries and Associations (EFPIA) to investigate the experience among European pharmaceutical companies by conducting the in vivo comet assay for regulatory purpose. A special focus was given on the typology of the obtained results and to identify potential difficulties encountered with the interpretation of study data. The participating companies reported a total of 147 studies (conducted in-house or outsourced) and shared the conclusion on the comet assay response for 136 studies. Most of the studies were negative (118/136). Only about 10% (14/136 studies) of the comet assays showed a positive response. None of the positive comet assay results were clearly associated with organ toxicity indicating that the positive responses are not due to cytotoxic effects of the compound in the tissue examined. The number of comet assays with an equivocal or inconclusive response was rare, respectively <1% (1/147 studies) and 2% (3/147 studies). In case additional information (e.g. repeat assay, organ toxicity, metabolism, tissue exposure) would have been available for evaluation, a final conclusion could most probably have been drawn for most or all of these studies. All (46) negative in vivo comet assays submitted alongside with a negative in vivo micronucleus assay were accepted by the regulatory authorities to mitigate a positive in vitro mammalian cell assay following the current ICH S2 guidance. The survey results demonstrate the robustness of the comet assay and the regulatory acceptance of the current ICH S2 guidance.

  1. Identification of irradiated refrigerated poultry with the DNA comet assay

    NASA Astrophysics Data System (ADS)

    Villavicencio, A. L. C. H.; Araújo, M. M.; Marin-Huachaca, N. S.; Mancini-Filho, J.; Delincée, H.

    2004-09-01

    Food irradiation could make a significant contribution to the reduction of food-borne diseases caused by harmful bacteria such as Salmonella and parasites. In fact these organisms cause an increasing number of diseases and eventually deaths all over the world, also in industrialized countries. Radiation processing has the advantage that in addition to eliminating pathogens, thereby enhancing food safety, it also extends shelf life through destruction of spoilage organisms. The DNA molecule because of its big size is an easy target for ionizing radiation, therefore, changes in DNA offer potential to be used as a detection method for the irradiation treatment. In our study, poultry has been irradiated and changes in DNA analyzed by the Comet Assay. Samples were packed in plastic bags and irradiated. Doses were 0, 1.5, 3.0 and 4.5kGy. Immediately after irradiation the samples were returned to the refrigerator (4°C). Samples were analyzed 1 and 10 days after irradiation. This method proved to be an inexpensive and rapid screening technique for qualitative detection of irradiation treatment.

  2. Two-Tailed Comet Assay (2T-Comet): Simultaneous Detection of DNA Single and Double Strand Breaks.

    PubMed

    Cortés-Gutiérrez, Elva I; Fernández, José Luis; Dávila-Rodríguez, Martha I; López-Fernández, Carmen; Gosálvez, Jaime

    2017-01-01

    A modification of the original comet assay was developed for the simultaneous evaluation of DNA single strand breaks (SSBs) and double strand breaks (DSBs) in human spermatozoa. The two-dimensional perpendicular tail comet assay (2T-comet) combines non-denaturing and denaturant conditions to the same sperm nucleoid. In this case, the species-specific deproteinized sperm is first subjected to an electrophoretic field under non-denaturing conditions to mobilize isolated free discrete DNA fragments produced from DSBs; this is then followed by a second electrophoresis running perpendicular to the first one but under alkaline conditions to produce DNA denaturation, exposing SSBs on the same linear DNA chain or DNA fragments flanked by DSBs. This procedure results in a two dimensional comet tail emerging from the core where two types of original DNA affected molecule can be simultaneously discriminated. The 2T-comet is a fast, sensitive, and reliable procedure to distinguish between single and double strand DNA damage within the same cell. It is an innovative method for assessing sperm DNA integrity, which has important implications for human fertility and andrological pathology. This technique may be adapted to assess different DNA break types in other species and other cell types.

  3. Combination of physico-chemical analysis, Allium cepa test system and Oreochromis niloticus erythrocyte based comet assay/nuclear abnormalities tests for cyto-genotoxicity assessments of treated effluents discharged from textile industries.

    PubMed

    Hemachandra, Chamini K; Pathiratne, Asoka

    2016-09-01

    Bioassays for cyto-genotoxicity assessments are generally not required in current textile industry effluent discharge management regulations. The present study applied in vivo plant and fish based toxicity tests viz. Allium cepa test system and Oreochromis niloticus erythrocyte based comet assay and nuclear abnormalities tests in combination with physico-chemical analysis for assessing potential cytotoxic/genotoxic impacts of treated textile industry effluents reaching a major river (Kelani River) in Sri Lanka. Of the treated effluents tested from two textile industries, color in the Textile industry 1 effluents occasionally and color, biochemical oxygen demand and chemical oxygen demand in the Textile industry 2 effluents frequently exceeded the specified Sri Lankan tolerance limits for discharge of industrial effluents into inland surface waters. Exposure of A. cepa bulbs to 100% and 12.5% treated effluents from both industries resulted in statistically significant root growth retardation, mito-depression, and induction of chromosomal abnormalities in root meristematic cells in comparison to the dilution water in all cases demonstrating cyto-genotoxicity associated with the treated effluents. Exposure of O. niloticus to the 100% and 12.5% effluents, resulted in erythrocytic genetic damage as shown by elevated total comet scores and induction of nuclear abnormalities confirming the genotoxicity of the treated effluents even with 1:8 dilution. The results provide strong scientific evidence for the crucial necessity of incorporating cyto-genotoxicity impact assessment tools in textile industry effluent management regulations considering human health and ecological health of the receiving water course under chronic exposure.

  4. The low molecular weight DNA diffusion assay as an indicator of cytotoxicity for the in vitro comet assay.

    PubMed

    Speit, Günter; Vesely, Alexandra; Schütz, Petra; Linsenmeyer, Regina; Bausinger, Julia

    2014-07-01

    The low molecular weight DNA diffusion assay (LMW assay) has been recommended as a measure for cytotoxicity for the in vivo comet assay. To better understand the relationship between effects in the LMW assay, DNA migration in the comet assay and effects in established cytotoxicity tests, we performed in vitro experiments with cultured human cell lines (TK6, A549) and comparatively investigated five test substances (methyl methanesulfonate, (±)-benzo[a]pyrene diol epoxide, sodium dodecyl sulphate, menthol and sodium arsenite). We measured DNA migration (tail intensity) in the comet assay and the frequency of 'hedgehogs' (cells with almost all DNA in the tail), DNA diffusion in the LMW assay, cell viability (trypan blue and fluorescein diacetate/ethidium bromide staining) and inhibition of proliferation (relative cell counts). Our in vitro experiments indicate that effects in the LMW assay occur independently from DNA effects in the comet assay and are not related to the occurrence of hedgehogs. Results from the LMW assay are in good agreement with results from viability assays and seem to allow discriminating genotoxic from non-genotoxic substances when appropriate preparation times are considered. Measurements of cytotoxicity by these methods only at an early preparation time after exposure to genotoxic substances may lead to erroneous results.

  5. Assessment of genotoxic effects of flumorph by the comet assay in mice organs.

    PubMed

    Zhang, T; Zhao, Q; Zhang, Y; Ning, J

    2014-03-01

    The present study investigated the genotoxic effects of flumorph in various organs (brain, liver, spleen, kidney and sperm) of mice. The DNA damage, measured as comet tail length (µm), was determined using the alkaline comet assay. The comet assay is a sensitive assay for the detection of genotoxicity caused by flumorph using mice as a model. Statistically significant increases in comet assay for both dose-dependent and duration-dependent DNA damage were observed in all the organs assessed. The organs exhibited the maximum DNA damage in 96 h at 54 mg/kg body weight. Brain showed maximum DNA damage followed by spleen > kidney > liver > sperm. Our data demonstrated that flumorph had induced systemic genotoxicity in mammals as it caused DNA damage in all tested vital organs, especially in brain and spleen.

  6. The relationship between environmental exposures to phthalates and DNA damage in human sperm using the neutral comet assay.

    PubMed Central

    Duty, Susan M; Singh, Narendra P; Silva, Manori J; Barr, Dana B; Brock, John W; Ryan, Louise; Herrick, Robert F; Christiani, David C; Hauser, Russ

    2003-01-01

    Phthalates are industrial chemicals widely used in many commercial applications. The general population is exposed to phthalates through consumer products as well as through diet and medical treatments. To determine whether environmental levels of phthalates are associated with altered DNA integrity in human sperm, we selected a population without identified sources of exposure to phthalates. One hundred sixty-eight subjects recruited from the Massachusetts General Hospital Andrology Laboratory provided a semen and a urine sample. Eight phthalate metabolites were measured in urine by using high-performance liquid chromatography and tandem mass spectrometry; data were corrected for urine dilution by adjusting for specific gravity. The neutral single-cell microgel electrophoresis assay (comet assay) was used to measure DNA integrity in sperm. VisComet image analysis software was used to measure comet extent, a measure of total comet length (micrometers); percent DNA in tail (tail%), a measure of the proportion of total DNA present in the comet tail; and tail distributed moment (TDM), an integrated measure of length and intensity (micrometers). For an interquartile range increase in specific gravity-adjusted monoethyl phthalate (MEP) level, the comet extent increased significantly by 3.6 micro m [95% confidence interval (95% CI), 0.74-6.47]; the TDM also increased 1.2 micro m (95% CI, -0.05 to 2.38) but was of borderline significance. Monobutyl, monobenzyl, monomethyl, and mono-2-ethylhexyl phthalates were not significantly associated with comet assay parameters. In conclusion, this study represents the first human data to demonstrate that urinary MEP, at environmental levels, is associated with increased DNA damage in sperm. PMID:12842768

  7. The comet assay, DNA damage, DNA repair and cytotoxicity: hedgehogs are not always dead.

    PubMed

    Lorenzo, Yolanda; Costa, Solange; Collins, Andrew R; Azqueta, Amaya

    2013-07-01

    DNA damage is commonly measured at the level of individual cells using the so-called comet assay (single-cell gel electrophoresis). As the frequency of DNA breaks increases, so does the fraction of the DNA extending towards the anode, forming the comet tail. Comets with almost all DNA in the tail are often referred to as 'hedgehog' comets and are widely assumed to represent apoptotic cells. We review the literature and present theoretical and empirical arguments against this interpretation. The level of DNA damage in these comets is far less than the massive fragmentation that occurs in apoptosis. 'Hedgehog' comets are formed after moderate exposure of cells to, for example, H2O2, but if the cells are incubated for a short period, 'hedgehogs' are no longer seen. We confirm that this is not because DNA has degraded further and been lost from the gel, but because the DNA is repaired. The comet assay may detect the earliest stages of apoptosis, but as it proceeds, comets disappear in a smear of unattached DNA. It is clear that 'hedgehogs' can correspond to one level on a continuum of genotoxic damage, are not diagnostic of apoptosis and should not be regarded as an indicator of cytotoxicity.

  8. Novel method for the high-throughput processing of slides for the comet assay

    PubMed Central

    Karbaschi, Mahsa; Cooke, Marcus S.

    2014-01-01

    Single cell gel electrophoresis (the comet assay), continues to gain popularity as a means of assessing DNA damage. However, the assay's low sample throughput and laborious sample workup procedure are limiting factors to its application. “Scoring”, or individually determining DNA damage levels in 50 cells per treatment, is time-consuming, but with the advent of high-throughput scoring, the limitation is now the ability to process significant numbers of comet slides. We have developed a novel method by which multiple slides may be manipulated, and undergo electrophoresis, in batches of 25 rather than individually and, importantly, retains the use of standard microscope comet slides, which are the assay convention. This decreases assay time by 60%, and benefits from an electrophoresis tank with a substantially smaller footprint, and more uniform orientation of gels during electrophoresis. Our high-throughput variant of the comet assay greatly increases the number of samples analysed, decreases assay time, number of individual slide manipulations, reagent requirements and risk of damage to slides. The compact nature of the electrophoresis tank is of particular benefit to laboratories where bench space is at a premium. This novel approach is a significant advance on the current comet assay procedure. PMID:25425241

  9. Novel method for the high-throughput processing of slides for the comet assay.

    PubMed

    Karbaschi, Mahsa; Cooke, Marcus S

    2014-11-26

    Single cell gel electrophoresis (the comet assay), continues to gain popularity as a means of assessing DNA damage. However, the assay's low sample throughput and laborious sample workup procedure are limiting factors to its application. "Scoring", or individually determining DNA damage levels in 50 cells per treatment, is time-consuming, but with the advent of high-throughput scoring, the limitation is now the ability to process significant numbers of comet slides. We have developed a novel method by which multiple slides may be manipulated, and undergo electrophoresis, in batches of 25 rather than individually and, importantly, retains the use of standard microscope comet slides, which are the assay convention. This decreases assay time by 60%, and benefits from an electrophoresis tank with a substantially smaller footprint, and more uniform orientation of gels during electrophoresis. Our high-throughput variant of the comet assay greatly increases the number of samples analysed, decreases assay time, number of individual slide manipulations, reagent requirements and risk of damage to slides. The compact nature of the electrophoresis tank is of particular benefit to laboratories where bench space is at a premium. This novel approach is a significant advance on the current comet assay procedure.

  10. Genotoxicity evaluation of drinking water sources in human peripheral blood lymphocytes using the comet assay.

    PubMed

    Wu, Yulin; Chen, Haigang; Li, Zhaoli; Sun, Liwei; Qu, Mengmeng; Li, Mei; Kong, Zhiming

    2008-01-01

    The potential harm of organic pollutants in drinking water to human health is widely focused on in the world; more and more pollutants with genotoxic substances are released into the aquatic environment. Water source samples were collected from 7 different localities of Nanjing City. The potential genotoxicity of organic extracts from drinking water sources were investigated by means of the comet assay in human peripheral lymphocytes. The results showed that all the organic extracts from all the water source samples could induce DNA damages of human peripheral blood lymphocytes at different levels. A significant difference (P < 0.01) was observed when compared with the solvent control. The DNA damage increased with the increase of the dosage of the original water source. Significant differences of DNA damage were observed in different drinking water sources, as shown by the multiple comparisons analysis at the dosage of 100x; the degree of DNA damage treated by Hushu waterworks (at town level) was the most serious, the arbitrary units (AU) was 141.62 +/- 6.96, however, that of Shangyuanmen waterworks (at city level) was only 109.64 +/- 2.97. The analysis also revealed that the genotoxicity of town's water sources was higher than that of the city. The results demonstrated that the comet assay can be successfully applied to the genotoxicity monitoring programs of drinking water sources.

  11. DNA damage in birds after the mining waste spill in southwestern Spain: a Comet assay evaluation.

    PubMed

    Pastor, N; López-Lázaro, M; Tella, J L; Baos, R; Forrero, M G; Hiraldo, F; Cortés, F

    2001-01-01

    In April 1998, an ecological disaster resulting from a massive toxic spill of mining acid waste rich in heavy metals posed a serious threat to the Doñana National Park in southwestern Spain. This especially important protected area is the nesting and breeding site for many endangered bird species; white storks (Ciconia ciconia) and black kites (Milvus migrans) are considered the more representative. The suitability of the Comet assay as a biomarker for genotoxic analysis in environmental biomonitoring has been recently validated in studies using different sentinel organisms such as fish, amphibians, rodents, or mollusks. Birds preying on a variety of invertebrate and vertebrate species in the marshlands are appropriate for evaluating the potential deleterious effects of the toxic spill on wildlife of the Dofiana area. Our study on wetland birds high on the aquatic trophic chain sampled within a few months after the toxic spill in the area around Doñana National Park has shown the accumulation of heavy metals. Fourteen months after the mine waste spill, blood samples from white storks and kites collected in the neighborhood of the park and from control birds at reference areas for comparison were examined by fluorescence image analysis after lymphocyte isolation, and by subsequent alkaline single-cell gel (SCG) electrophoresis, known as the Comet assay. Our results indicate that the exposed birds had a significantly increased level of genotoxic damage compared with control animals from noncontaminated locations.

  12. Critical issues with the in vivo comet assay: A report of the comet assay working group in the 6th International Workshop on Genotoxicity Testing (IWGT).

    PubMed

    Speit, Günter; Kojima, Hajime; Burlinson, Brian; Collins, Andrew R; Kasper, Peter; Plappert-Helbig, Ulla; Uno, Yoshifumi; Vasquez, Marie; Beevers, Carol; De Boeck, Marlies; Escobar, Patricia A; Kitamoto, Sachiko; Pant, Kamala; Pfuhler, Stefan; Tanaka, Jin; Levy, Dan D

    2015-05-01

    As a part of the 6th IWGT, an expert working group on the comet assay evaluated critical topics related to the use of the in vivo comet assay in regulatory genotoxicity testing. The areas covered were: identification of the domain of applicability and regulatory acceptance, identification of critical parameters of the protocol and attempts to standardize the assay, experience with combination and integration with other in vivo studies, demonstration of laboratory proficiency, sensitivity and power of the protocol used, use of different tissues, freezing of samples, and choice of appropriate measures of cytotoxicity. The standard protocol detects various types of DNA lesions but it does not detect all types of DNA damage. Modifications of the standard protocol may be used to detect additional types of specific DNA damage (e.g., cross-links, bulky adducts, oxidized bases). In addition, the working group identified critical parameters that should be carefully controlled and described in detail in every published study protocol. In vivo comet assay results are more reliable if they were obtained in laboratories that have demonstrated proficiency. This includes demonstration of adequate response to vehicle controls and an adequate response to a positive control for each tissue being examined. There was a general agreement that freezing of samples is an option but more data are needed in order to establish generally accepted protocols. With regard to tissue toxicity, the working group concluded that cytotoxicity could be a confounder of comet results. It is recommended to look at multiple parameters such as histopathological observations, organ-specific clinical chemistry as well as indicators of tissue inflammation to decide whether compound-specific toxicity might influence the result. The expert working group concluded that the alkaline in vivo comet assay is a mature test for the evaluation of genotoxicity and can be recommended to regulatory agencies for use.

  13. Assessment of DNA interstrand crosslinks using the modified alkaline comet assay.

    PubMed

    Wu, Jian Hong; Jones, Nigel J

    2012-01-01

    The single cell gel electrophoresis (SCGE) assay, more commonly known as the comet assay, due to the "comet-like" appearance of the cells, was originally developed as a technique to measure the presence of DNA single-strand breaks. The assay is performed on single cells embedded in agar and placed in an electrical field at alkaline pH, so that fragments of negatively charged single-stranded DNA move through the gel toward the positively charged anode. Undamaged DNA moves relatively slowly, forming the head of the comet, while DNA fragmented due to the presence of single-strand breaks, moves more quickly giving the appearance of the tail. The extent of DNA migration is a measure of the DNA damage present. Since it was first developed, the comet assay has been adapted for measuring other types of DNA damage. The neutral comet assay has been employed for DNA double-strand breaks, while techniques using DNA repair enzymes to cleave specific adducts, UvrABC for ultraviolet radiation induced adducts, for example, have also been described. Here, we describe a modified version of the comet assay for the measurement of interstrand crosslinks (ICLs). Interstrand crosslinking agents include the chemotherapeutic agents mitomycin C and cis-platin, psoralen plus UVA light (PUVA) used to treat hyperproliferative skin disorders and diepoxybutane, a metabolite of 1,3-butadiene used in industrial processes and an environmental pollutant. ICLs are a potent and cytotoxic form of DNA damage as they prevent DNA strand separation, thereby preventing DNA replication. Their removal requires several different DNA repair processes including translesion synthesis and homologous recombination. As ICLs prevent separation of the DNA strands, their presence results in less DNA migration in the comet assay. To successfully measure ICLs, it is necessary to incorporate a step that induces single-strand breaks (using a defined dose of ionizing radiation) that allows the crosslinked DNA to migrate.

  14. Using a medium-throughput comet assay to evaluate the global DNA methylation status of single cells.

    PubMed

    Lewies, Angélique; Van Dyk, Etresia; Wentzel, Johannes F; Pretorius, Pieter J

    2014-01-01

    The comet assay is a simple and cost effective technique, commonly used to analyze and quantify DNA damage in individual cells. The versatility of the comet assay allows introduction of various modifications to the basic technique. The difference in the methylation sensitivity of the isoschizomeric restriction enzymes HpaII and MspI are used to demonstrate the ability of the comet assay to measure the global DNA methylation level of individual cells when using cell cultures. In the experiments described here, a medium-throughput comet assay and methylation sensitive comet assay are combined to produce a methylation sensitive medium-throughput comet assay to measure changes in the global DNA methylation pattern in individual cells under various growth conditions.

  15. Cytotoxicity and genotoxicity assessment of Euphorbia hirta in MCF-7 cell line model using comet assay

    PubMed Central

    Ping, Kwan Yuet; Darah, Ibrahim; Chen, Yeng; Sasidharan, Sreenivasan

    2013-01-01

    Objective To evaluate the cytotoxicity and genotoxicity activity of Euphorbia hirta (E. hirta) in MCF-7 cell line model using comet assay. Methods The cytotoxicity of E. hirta extract was investigated by employing brine shrimp lethality assay and the genotoxicity of E. hirta was assessed by using Comet assay. Results Both toxicity tests exhibited significant toxicity result. In the comet assay, the E. hirta extract exhibited genotoxicity effects against MCF-7 DNA in a time-dependent manner by increasing mean percentage of DNA damage. The extract of E. hirta showed significant toxicity against brine shrimp with an LC50 value of 620.382 µg/mL (24 h). Comparison with positive control potassium dichromate signifies that cytotoxicity exhibited by the methanol extract might have moderate activity. Conclusion The present work confirmed the cytotoxicity and genotoxicity of E. hirta. However, the observed toxicity of E. hirta extracts needs to be confirmed in additional studies. PMID:23998008

  16. What is Comet assay not telling us: AFLP reveals wider aspects of genotoxicity.

    PubMed

    Šrut, Maja; Štambuk, Anamaria; Klobučar, Göran I V

    2013-06-01

    DNA damage detected by genotoxicity biomarkers such as the Comet assay is not always a reliable indicator of the consequences that genotoxic agents can have on the genome integrity of the exposed organisms. Therefore, to reveal the existence of more permanent alterations of DNA structure after genotoxic stress, the RTG-2 rainbow trout cell line was exposed for 3 days to benzo[a]pyrene (B[a]P, 0.1-10 μM) and ethyl methanesulfonate (EMS, 0.1-1mM) followed by 3 days of recovery period. Primary DNA damage was evaluated by the Comet assay and DNA alterations were assessed using AFLP (amplified fragment length polymorphism). Qualitative and quantitative modifications in AFLP profiles were analyzed in order to detect genetic alterations arising from mutation events and/or DNA damage. Significant induction in DNA damage measured by the Comet assay was noticed after B[a]P treatment at all concentrations but values returned to the control level after recovery. Exposure to EMS induced significant DNA damage only at the highest concentration and damage persisted after the recovery period. AFLP profiles detected DNA alterations even when Comet assay indicated complete DNA repair, revealing more persistent damage. Since such DNA damage can impair its structure and function, Comet assay results should preferably be supplemented with other methods in order to predict the consequences of genotoxic insult more accurately.

  17. Cytogenetic status of healthy children assessed with the alkaline comet assay and the cytokinesis-block micronucleus cytome assay.

    PubMed

    Gajski, Goran; Gerić, Marko; Oreščanin, Višnja; Garaj-Vrhovac, Vera

    2013-01-20

    In the present study the alkaline comet assay and the cytokinesis-block micronucleus cytome (CBMN Cyt) assay were used to evaluate the baseline frequency of cytogenetic damage in peripheral blood lymphocytes (PBLs) of 50 healthy children from the general population in Croatia (age, 11.62±1.81 years). Mean values of tail length, tail intensity and tail moment, as comet assay parameters, were 12.92±0.10, 0.73±0.06 and 0.08±0.01, respectively. The mean frequency of micronuclei (MN) for all subjects was 2.32±0.28 per 1000 bi-nucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 1.72±0.24 and of nuclear buds (NBUDs) 1.44±0.19. The mean nuclear division index (NDI) was 1.70±0.05. When comet-assay parameters were considered, higher mean values for all three were found for the female population. According to the Mann-Whitney U test applied on the results of the comet assay, the only statistically significant difference between the male and female populations was found for tail length. Similar to the results obtained by the comet assay, girls showed higher mean values of all three measured parameters of the CBMN Cyt assay. This difference was statistically significant for total number of NPBs only. In the case of the NDI, a higher mean value was also obtained in girls, but this difference was not statistically significant. The results obtained present background data that could be considered as normal values for healthy children living in urban areas, and can later on serve as baseline values for further toxicological monitoring. Additionally, the usefulness of both techniques in measuring cytogenetic damage during bio-monitoring of children is confirmed.

  18. Different sensitivities of cultured mammalian cells towards aphidicolin-enhanced DNA effects in the comet assay.

    PubMed

    Speit, Günter; Schütz, Petra; Bausinger, Julia

    2016-06-01

    The comet assay in combination with the polymerase inhibitor aphidicolin (APC) has been used to measure DNA excision repair activity, DNA repair kinetics and individual DNA repair capacity. Since APC can enhance genotoxic effects of mutagens measured by the comet assay, this approach has been proposed for increasing the sensitivity of the comet assay in human biomonitoring. The APC-modified comet assay has mainly been performed with human blood and it was shown that it not only enhances the detection of DNA damage repaired by nucleotide excision repair (NER) but also damage typically repaired by base excision repair (BER). Recently, we reported that in contrast to blood leukocytes, A549 cells (a human lung adenocarcinoma cell line) seem to be insensitive towards the repair-inhibiting action of APC. To further elucidate the general usefulness of the APC-modified comet assay for studying repair in cultured mammalian cells, we comparatively investigated further cell lines (HeLa, TK6, V79). DNA damage was induced by BPDE (benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide) and MMS (methyl methanesulfonate) in the absence and presence of APC (3 or 15μM). APC was either added for 2h together with the mutagen or cells were pre-incubated for 30min with APC before the mutagen was added. The results indicate that the cell lines tested differ fundamentally with regard to their sensitivity and specificity towards the repair-inhibiting effect of APC. The actual cause for these differences is still unclear but potential molecular explanations are discussed. Irrespective of the underlying mechanism(s), our study revealed practical limitations of the use of the APC-modified comet assay.

  19. The Comet assay in insects--Status, prospects and benefits for science.

    PubMed

    Augustyniak, Maria; Gladysz, Marcin; Dziewięcka, Marta

    2016-01-01

    The Comet assay has been recently adapted to investigate DNA damage in insects. The first reports of its use in Drosophila melanogaster appeared in 2002. Since then, the interest in the application of the Comet assay to studies of insects has been rapidly increasing. Many authors see substantial potential in the use of the Comet assay in D. melanogaster for medical toxicology studies. This application could allow the testing of drugs and result in an understanding of the mechanisms of action of toxins, which could significantly influence the limited research that has been performed on vertebrates. The possible perspectives and benefits for science are considered in this review. In the last decade, the use of the Comet assay has been described in insects other than D. melanogaster. Specifically, methods to prepare a cell suspension from insect tissues, which is a difficult task, were analyzed and compared in detail. Furthermore, attention was paid to any differences and modifications in the research protocols, such as the buffer composition and electrophoresis conditions. Various scientific fields in addition to toxicological and ecotoxicological research were considered. We expect the Comet assay to be used in environmental risk assessments and to improve our understanding of many important phenomena of insect life, such as metamorphosis, molting, diapause and quiescence. The use of this method to study species that are of key importance to humans, such as pests and beneficial insects, appears to be highly probable and very promising. The use of the Comet assay for DNA stability testing in insects will most likely rapidly increase in the future.

  20. Comet assays to assess DNA damage and repair in grass shrimp embryos exposed to phototoxicants.

    PubMed

    Lee, R; Kim, G B

    2002-01-01

    Exposure of grass shrimp (Palaemonetes pugio) embryos to four compounds (anthracene, pyrene, alpha-terthienyl, methylene blue) along with solar exposure resulted in extensive DNA strand damage using the comet assay. DNA tail moments of embryos exposed to these chemicals in the dark ranged from 1.8 to 4.3, while exposure to chemicals and solar resulted in tail moments of 14.3-15.3. Reduction of DNA tail moments when solar exposed embryos were transferred to the dark, suggested DNA repair systems were active. The comet assay can be used to follow both DNA damage and repair following exposure to phototoxic chemicals.

  1. Estimates of DNA strand breakage in bottlenose dolphin (Tursiops truncatus) leukocytes measured with the Comet and DNA diffusion assays

    PubMed Central

    2009-01-01

    The analysis of DNA damage by mean of Comet or single cell gel electrophoresis (SCGE) assay has been commonly used to assess genotoxic impact in aquatic animals being able to detect exposure to low concentrations of contaminants in a wide range of species. The aims of this work were 1) to evaluate the usefulness of the Comet to detect DNA strand breakage in dolphin leukocytes, 2) to use the DNA diffusion assay to determine the amount of DNA strand breakage associated with apoptosis or necrosis, and 3) to determine the proportion of DNA strand breakage that was unrelated to apoptosis and necrosis. Significant intra-individual variation was observed in all of the estimates of DNA damage. DNA strand breakage was overestimated because a considerable amount (~29%) of the DNA damage was derived from apoptosis and necrosis. The remaining DNA damage in dolphin leukocytes was caused by factors unrelated to apoptosis and necrosis. These results indicate that the DNA diffusion assay is a complementary tool that can be used together with the Comet assay to assess DNA damage in bottlenose dolphins. PMID:21637693

  2. Genotoxicity evaluation of hydroalcoholic and aqueous extracts of Dorema aucheri by the comet assay

    PubMed Central

    Etebari, Mahmoud; Sajjadi, Seyed Ebrahim; Jafarian-Dehkordi, Abbas; Nazmakanipour, Sajjad

    2016-01-01

    Background: Dorema aucheri is a plant of Apiaceae family which is used widely in some states of Iran. Different extracts and essential oil of Dorema species contain flavonoids and cumarin compounds which have anti-hypertensive, cholesterol- and triglycerides-lowering properties. This study was undertaken to evaluate the genotoxic properties of hydroalcoholic and aqueous extracts of D. aucheri on human hepatoma cells using the comet assay method for safety evaluation. Materials and Methods: In this method, after incubation of cells with different concentrations of extracts, cell suspensions were added to pre-coated normal agarose slides. After lysis, electrophoresis and neutralization process, staining was done by ethidium bromide and comets were observed using a fluorescence microscope. Tail length, percentage of DNA in tail and tail moment parameters were measured. Results: Statistical analysis of the results demonstrated that concentrations more than 500 μg/ml of hydroalcoholic and aqueous extract of D. aucheri were genotoxic. Conclusion: It can be concluded from the results that taking the concentrations less than these dosages of extracts are safe but more studies are required to determine genotoxic mechanisms of this plant. PMID:28217637

  3. The Comet Assay for the Evaluation of Genotoxic Potential of Landfill Leachate

    PubMed Central

    Widziewicz, Kamila; Kalka, Joanna; Skonieczna, Magdalena; Madej, Paweł

    2012-01-01

    Genotoxic assessment of landfill leachate before and after biological treatment was conducted with two human cell lines (Me45 and NHDF) and Daphnia magna somatic cells. The alkali version of comet assay was used to examine genotoxicity of leachate by DNA strand breaks analysis and its repair dynamics. The leachate samples were collected from Zabrze landfill, situated in the Upper Silesian Industrial District, Poland. Statistically significant differences (Kruskal-Wallice ANOVA rank model) were observed between DNA strand breaks in cells incubated with leachate before and after treatment (P < 0.001). Nonparametric Friedman ANOVA confirmed time-reliable and concentration-reliable cells response to leachate concentration. Examinations of chemical properties showed a marked decrease in leachate parameters after treatment which correlate to reduced genotoxicity towards tested cells. Obtained results demonstrate that biological cotreatment of leachate together with municipal wastewater is an efficient method for its genotoxic potential reduction; however, treated leachate still possessed genotoxic character. PMID:22666120

  4. Earthworm Comet Assay for Assessing the Risk of Weathered Petroleum Hydrocarbon Contaminated Soils: Need to Look Further than Target Contaminants.

    PubMed

    Ramadass, Kavitha; Palanisami, Thavamani; Smith, Euan; Mayilswami, Srinithi; Megharaj, Mallavarapu; Naidu, Ravi

    2016-11-01

    Earthworm toxicity assays contribute to ecological risk assessment and consequently standard toxicological endpoints, such as mortality and reproduction, are regularly estimated. These endpoints are not enough to better understand the mechanism of toxic pollutants. We employed an additional endpoint in the earthworm Eisenia andrei to estimate the pollutant-induced stress. In this study, comet assay was used as an additional endpoint to evaluate the genotoxicity of weathered hydrocarbon contaminated soils containing 520 to 1450 mg hydrocarbons kg(-1) soil. Results showed that significantly higher DNA damage levels (two to sixfold higher) in earthworms exposed to hydrocarbon impacted soils. Interestingly, hydrocarbons levels in the tested soils were well below site-specific screening guideline values. In order to explore the reasons for observed toxicity, the contaminated soils were leached with rainwater and subjected to earthworm tests, including the comet assay, which showed no DNA damage. Soluble hydrocarbon fractions were not found originally in the soils and hence no hydrocarbons leached out during soil leaching. The soil leachate's Electrical Conductivity (EC) decreased from an average of 1665 ± 147 to 204 ± 20 µS cm(-1). Decreased EC is due to the loss of sodium, magnesium, calcium, and sulphate. The leachate experiment demonstrated that elevated salinity might cause the toxicity and not the weathered hydrocarbons. Soil leaching removed the toxicity, which is substantiated by the comet assay and soil leachate analysis data. The implication is that earthworm comet assay can be included in future eco (geno) toxicology studies to assess accurately the risk of contaminated soils.

  5. Sperm DNA quality evaluated by comet assay and sperm chromatin structure assay in stallions after unilateral orchiectomy.

    PubMed

    Serafini, R; Varner, D D; Bissett, W; Blanchard, T L; Teague, S R; Love, C C

    2015-09-15

    Unilateral orchiectomy (UO) may interfere with thermoregulation of the remaining testis caused by inflammation surrounding the incision site, thus altering normal spermatogenesis and consequently sperm quality. Two measures of sperm DNA quality (neutral comet assay and the sperm chromatin structure assay [SCSA]) were compared before UO (0 days) and at 14, 30, and 60 days after UO to determine whether sperm DNA changed after a mild testis stress (i.e., UO). The percent DNA in the comet tail was higher at 14 and 60 days compared to 0 days (P < 0.05) after UO. All other comet tail measures (i.e., length, moment, migration) were higher at all time periods after UO compared to 0 days (P < 0.05). Two SCSA measures (mean-αt, mode-αt) increased at 14 days after UO (P < 0.05), whereas two measures (SD-αt and COMP-αt) did not change. This study identified a decrease in sperm DNA quality using both the neutral comet assay and the SCSA, which was not identified using traditional measures of sperm quality.

  6. Comets

    NASA Video Gallery

    Did you know that comets seen streaking across the night sky may have brought the building blocks of life to our planet billions of years ago? Join NASA in learning more about these fascinating obj...

  7. Lymphocyte DNA damage in Turkish asphalt workers detected by the comet assay.

    PubMed

    Bacaksiz, Aysegul; Kayaalti, Zeliha; Soylemez, Esma; Tutkun, Engin; Soylemezoglu, Tulin

    2014-01-01

    Asphalt has a highly complex structure and it contains several organic compounds including polycyclic aromatic hydrocarbons and heterocyclic compounds. In this study, comet assay was used to detect the DNA damage in blood lymphocytes of 30 workers exposed to asphalt fumes and 30 nonexposed controls. This is the first report on Turkish asphalt workers' investigated DNA damage using the alkaline single cell gel electrophoresis (SCGE). The DNA damage was evaluated by the percentage of DNA in the comet tail (% tail DNA) for each cell. According to our results, workers exposed to asphalt fumes had higher DNA damage than the control group (p < 0.01). The present study showed that asphalt fumes caused a significant increase in DNA damage and the comet assay is a suitable method for determining DNA damage in asphalt workers.

  8. Cryopreservation of human blood for alkaline and Fpg-modified comet assay.

    PubMed

    Pu, Xinzhu; Wang, Zemin; Klaunig, James E

    2016-01-01

    The Comet assay is a reproducible and sensitive assay for the detection of DNA damage in eukaryotic cells and tissues. Incorporation of lesion specific, oxidative DNA damage repair enzymes (for example, Fpg, OGG1 and EndoIII) in the standard alkaline Comet assay procedure allows for the detection and measurement of oxidative DNA damage. The Comet assay using white blood cells (WBC) has proven useful in monitoring DNA damage from environmental agents in humans. However, it is often impractical to performance Comet assay immediately after blood sampling. Thus, storage of blood sample is required. In this study, we developed and tested a simple storage method for very small amount of whole blood for standard and Fpg-modified modified Comet assay. Whole blood was stored in RPMI 1640 media containing 10% FBS, 10% DMSO and 1 mM deferoxamine at a sample to media ratio of 1:50. Samples were stored at -20 °C and -80 °C for 1, 7, 14 and 28 days. Isolated lymphocytes from the same subjects were also stored under the same conditions for comparison. Direct DNA strand breakage and oxidative DNA damage in WBC and lymphocytes were analyzed using standard and Fpg-modified alkaline Comet assay and compared with freshly analyzed samples. No significant changes in either direct DNA strand breakage or oxidative DNA damage was seen in WBC and lymphocytes stored at -20 °C for 1 and 7 days compared to fresh samples. However, significant increases in both direct and oxidative DNA damage were seen in samples stored at -20 °C for 14 and 28 days. No changes in direct and oxidative DNA damage were observed in WBC and lymphocytes stored at -80 °C for up to 28 days. These results identified the proper storage conditions for storing whole blood or isolated lymphocytes to evaluate direct and oxidative DNA damage using standard and Fpg-modified alkaline Comet assay.

  9. Genotoxicity evaluation of titanium dioxide nanoparticles using the Ames test and Comet assay.

    PubMed

    Woodruff, Robert S; Li, Yan; Yan, Jian; Bishop, Michelle; Jones, M Yvonne; Watanabe, Fumiya; Biris, Alexandru S; Rice, Penelope; Zhou, Tong; Chen, Tao

    2012-11-01

    Titanium dioxide nanoparticles (TiO2-NPs) are being used increasingly for various industrial and consumer products, including cosmetics and sunscreens because of their photoactive properties. Therefore, the toxicity of TiO2-NPs needs to be thoroughly understood. In the present study, the genotoxicity of 10nm uncoated sphere TiO2-NPs with an anatase crystalline structure, which has been well characterized in a previous study, was assessed using the Salmonella reverse mutation assay (Ames test) and the single-cell gel electrophoresis (Comet) assay. For the Ames test, Salmonella strains TA102, TA100, TA1537, TA98 and TA1535 were preincubated with eight different concentrations of the TiO2-NPs for 4 h at 37 °C, ranging from 0 to 4915.2 µg per plate. No mutation induction was found. Analyses with transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) showed that the TiO2-NPs were not able to enter the bacterial cell. For the Comet assay, TK6 cells were treated with 0-200 µg ml(-1) TiO2-NPs for 24 h at 37 °C to detect DNA damage. Although the TK6 cells did take up TiO2-NPs, no significant induction of DNA breakage or oxidative DNA damage was observed in the treated cells using the standard alkaline Comet assay and the endonuclease III (EndoIII) and human 8-hydroxyguanine DNA-glycosylase (hOGG1)-modified Comet assay, respectively. These results suggest that TiO2-NPs are not genotoxic under the conditions of the Ames test and Comet assay.

  10. Influence of experimental conditions on data variability in the liver comet assay.

    PubMed

    Guérard, M; Marchand, C; Plappert-Helbig, U

    2014-03-01

    The in vivo comet assay has increasingly been used for regulatory genotoxicity testing in recent years. While it has been demonstrated that the experimental execution of the assay, for example, electrophoresis or scoring, can have a strong impact on the results; little is known on how initial steps, that is, from tissue sampling during necropsy up to slide preparation, can influence the comet assay results. Therefore, we investigated which of the multitude of steps in processing the liver for the comet assay are most critical. All together eight parameters were assessed by using liver samples of untreated animals. In addition, two of those parameters (temperature and storage time of liver before embedding into agarose) were further investigated in animals given a single oral dose of ethyl methanesulfonate at dose levels of 50, 100, and 200 mg/kg, 3 hr prior to necropsy. The results showed that sample cooling emerged as the predominant influence factor, whereas variations in other elements of the procedure (e.g., size of the liver piece sampled, time needed to process the liver tissue post-mortem, agarose temperature, or time of lysis) seem to be of little relevance. Storing of liver samples of up to 6 hr under cooled conditions did not cause an increase in tail intensity. In contrast, storing the tissue at room temperature, resulted in a considerable time-dependent increase in comet parameters.

  11. Identification of low level gamma-irradiation of meats by high sensitivity comet assay

    NASA Astrophysics Data System (ADS)

    Miyahara, Makoto; Saito, Akiko; Ito, Hitoshi; Toyoda, Masatake

    2002-03-01

    The detection of low levels of irradiation in meats (pork, beef, and chicken) using the new comet assay was investigated in order to assess the capability of the procedure. The new assay includes a process that improves its sensitivity to irradiation and a novel evaluation system for each slide (influence score and comet-type distribution). Samples used were purchased at retailers and were irradiated at 0.5 and 2kGy at 0°C. The samples were processed to obtain comets. Slides were evaluated by typing comets, calculating the influence score and analyzing the comet-type distribution chart of shown on the slide. Influence scores of beef, pork, and chicken at 0kGy were 287(SD=8.0), 305 (SD=12.9), and 320 (SD=21.0), respectively. Those at 500Gy, were 305 (SD=5.3), 347 (SD=10.6), and 364 (12.6), respectively. Irradiation levels in food were successfully determined. Sensitivity to irradiation differed among samples (chicken>pork>beef).

  12. Application of the comet and micronucleus assays to butterfish (Pholis gunnellus) erythrocytes from the Firth of Forth, Scotland.

    PubMed

    Bombail, V; Aw, D; Gordon, E; Batty, J

    2001-07-01

    This report describes an investigation of genotoxic effects in an inter-tidal fish species sampled along a pollution gradient in the Firth of Forth, Scotland, UK. The comet assay is an electrophoretic technique for measuring DNA breakage in nuclei from individual cells and has only recently been applied to field investigations of genotoxicity. The measurement of nuclear anomalies (NA), such as the presence of micronuclei (MN) and 'lobes', has been successfully utilised in many field studies of genotoxic effects of contaminated sediments. These two techniques were applied to nucleated red blood cells (RBC) from the butterfish, Pholis gunnellus. The comet assay was adapted and validated for use in this species. Fish were sampled from the inner Firth of Forth, which has a legacy of industrial contamination and the outer Firth of Forth which is comparatively clean. The analysis of DNA strand breakage using this technique did not reveal any significant differences between animals sampled from inner and outer zones of the Firth. In contrast, MN and NA frequencies were elevated in the inner polluted zone of the Firth compared to the outer zone. This study suggests: (1) there are genotoxic effects associated with contaminants in the inner Firth of Forth, and (2) the comet assay may not be a suitable genotoxicity biomarker in fish.

  13. Genotoxicity of cadmium chloride in the marine gastropod Nerita chamaeleon using comet assay and alkaline unwinding assay.

    PubMed

    Sarkar, Anupam; Bhagat, Jacky; Ingole, Baban S; Rao, Durga P; Markad, Vijaykumar L

    2015-02-01

    This paper presents an evaluation of the genotoxic effects of cadmium chloride (CdCl2 ) on marine gastropod, Nerita chamaeleon following the technique of comet assay and the DNA alkaline unwinding assay (DAUA). In this study, the extent of DNA damage in gill cells of N. chamaeleon was measured after in vivo exposure to four different concentrations (10, 25, 50, and 75 µg/L) of CdCl2 . In vitro exposure of hydrogen peroxide (H2 O2 ; 1, 10, 25, and 50 µM) of the gill cells showed a significant increase in the percentage tail DNA, Olive tail moment, and tail length (TL). Significant changes in percentage tail DNA by CdCl2 exposure were observed in all exposed groups of snails with respect to those in control. Exposure to 75 µg/L of CdCl2 produced significant decrease in DNA integrity as measured by DAUA at all duration with respect to control. In vivo exposure to different concentrations of CdCl2 (10, 25, 50, and 75 µg/L) to N. chamaeleon showed considerable increase in DNA damage as observed by both alkaline comet assay and the DAUA. The extent of DNA damage in marine gastropods determined by the application of alkaline comet assay and DAUA clearly indicated the genotoxic responses of marine gastropod, N. chamaeleon to a wide range of cadmium concentration in the marine environment.

  14. Long-term biomonitoring of breast cancer patients under adjuvant chemotherapy: the comet assay as a possible predictive factor.

    PubMed

    Uriol, E; Sierra, M; Comendador, M A; Fra, J; Martínez-Camblor, P; Lacave, A J; Sierra, L M

    2013-01-01

    Most chemotherapy treatments induce DNA damage in the exposed patients. Using the comet assay and peripheral blood mononuclear cells (PBMC), we have quantified this induced DNA damage and studied its relationship with GSTM1 and GSTT1 polymorphisms, and clinical parameters. For this purpose, 29 Caucasian women, breast cancer patients under CMF or CEF adjuvant chemotherapy were included in the study. The clinical parameters considered were (i) therapies side effects, like haematological and biochemical toxicities, (ii) prognostic and predictive factors, like hormonal receptor expression, tumour differentiation degree, sickness stage, and nodal status, and (iii) the effectiveness of the chemotherapy measured as five years relapse probability. The results were also related to the confounding factor age. Comet assay results indicate that 13 patients were characterised by absence of induced DNA strand breaks, and 16 patients presented induced DNA strand breaks along the treatment. Relationships between comet variables and clinical parameters, found with principal component analysis, correlations, one-way ANOVA and multivariate logistic regression analyses revealed that: (1) baseline levels of DNA damage are related to GSTM1 genotype and to hormonal receptor expression; (2) GSTM1 genotype also influences comet results after chemotherapy, as it does the AST level; (3) the tail moment values of the cycle 6.1 and the sickness stage might predict cancer relapse at five years: for the Stage, OR = 13.8 (IIB versus I+IIA), 95% CI 0.80-238.97, and for 6.1 cycle TM, OR = 1.3, 95%, CI 0.97-1.79, with a potential model (10* Stage (I-IIA = 0, IIB = 1) + 6.1 cycle), that has a good predictive capacity, with an area under ROC curve of 0.872 (CI 0.62-1.00). To our knowledge, this is the first time such a predictive value is found for the comet assay. Nevertheless, before the comet assay could be used as a tool for oncologists, this relationship should be confirmed in more patients, and

  15. Comets

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.

    2006-01-01

    Spectroscopy of comets, in the X-ray and far-ultraviolet from space, and in the near infrared and millimeter from the ground, have revealed a wealth of new information, particularly about the molecular constituents that make up the volatile fraction of the comet s nucleus. Interpretation of these data requires not only proper wavelengths for identification but also information about the photolytic and excitation processes at temperatures typical of the inner coma (70-100 K) that lead to the observed spectral signatures. Several examples, mainly from Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope spectra of comets observed during the last few years, will be given to illustrate some of the current issues.

  16. Comets

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.

    2003-12-01

    Comets are surviving members of a formerly vast distribution of solid bodies that formed in the cold regions of the solar nebula. Cometary bodies escaped incorporation into planets and ejection from the solar system and they have been stored in two distant reservoirs, the Oort cloud and the Kuiper Belt, for most of the age of the solar system. Observed comets appear to have formed between 5 AU and 55 AU. From a cosmochemical viewpoint, comets are particularly interesting bodies because they are preserved samples of the solar nebula's cold ice-bearing regions that occupied 99% of the areal extent of the solar nebula disk. All comets formed beyond the "snow line" of the nebula, where the conditions were cold enough for water ice to condense, but they formed from environments that significantly differed in temperature. Some formed in the comparatively "warm" regions near Jupiter where the nebular temperature may have been greater than 120 K and others clearly formed beyond Neptune where temperatures may have been less than 30 K (Bell et al., 1997). Although comets are the best-preserved materials from the early solar system, they should be a mix of nebular and presolar materials that accreted over a vast range of distances from the Sun in environments that differed in temperature, pressure, and accretional conditions such as impact speed.Comets, by conventional definition, are unstable near the Sun; they contain highly volatile ices that vigorously sublime within 2-3 AU of the Sun. When heated, they release gas and solids due to "cometary activity," a series of processes usually detected from afar by the presence of a coma of gas and dust surrounding the cometary nucleus and or elongated tails composed of dust and gas. Active comets clearly have not been severely modified by the moderate to extreme heating that has affected all other solar system materials, including planets, moons, and even the asteroids that produced the most primitive meteorites. Comets have been

  17. Analysis of possible genotoxicity of the herbicide flurochloridone and its commercial formulations: Endo III and Fpg alkaline comet assays in Chinese hamster ovary (CHO-K1) cells.

    PubMed

    Soloneski, Sonia; Nikoloff, Noelia; Larramendy, Marcelo L

    2016-02-01

    Cytotoxic and genotoxic effects of flurochloridone (FLC) and its formulations Twin Pack Gold(®) and Rainbow(®) were evaluated in CHO-K1 cells. Using the alkaline single-cell gel electrophoresis (SCGE) assay, we observed that FLC (15 μg/ml), Twin Pack Gold(®) or Rainbow(®) induced primary DNA damage, increasing the frequency of damaged nucleoids. Vitamin E pretreatment did not modify the effect. Decreased cell viability was observed only in Twin Pack Gold(®)-treated cultures and was significantly ameliorated by vitamin E. Post-treatment of herbicide-damaged CHO-K1 cells with the enzymes Endo III or Fpg did not increase FLC-, Twin Pack Gold(®)-, or Rainbow(®)-induced DNA damage. These results demonstrate that neither FLC nor FLC-based formulations induce DNA damage through hydroxyl radical or lipid alkoxyl radical production, and that the induced DNA lesions were not related to oxidative damage at the purine/pyrimidine level. Our observations strongly suggest that the cytotoxic effects observed after Twin Pack Gold(®) exposure are due to the excipients contained within the technical formulation rather than FLC itself.

  18. Towards a more reliable comet assay: optimising agarose concentration, unwinding time and electrophoresis conditions.

    PubMed

    Azqueta, Amaya; Gutzkow, Kristine B; Brunborg, Gunnar; Collins, Andrew R

    2011-09-18

    The comet assay is now the method of choice for measuring most kinds of DNA damage in cells. However, due to the lack of a standardised protocol inter-laboratory comparisons are of limited value. The aim of this paper is to demonstrate how small changes in comet-assay variables may significantly affect the results. We examined the effect of varying agarose concentrations, alkaline unwinding time, electrophoresis time, voltage and current, by use of two cell types, viz. human peripheral blood lymphocytes and the lymphoblastoid cell line TK-6. All these variables have marked effects on assay performance and, therefore, on the determination of DNA damage. Here we identify factors of particular importance.

  19. Eco-genotoxicity of six anticancer drugs using comet assay in daphnids.

    PubMed

    Parrella, Alfredo; Lavorgna, Margherita; Criscuolo, Emma; Russo, Chiara; Isidori, Marina

    2015-04-09

    The eco-genotoxicity of six anti-neoplastic drugs, 5-fluorouracil, capecitabine, cisplatin, doxorubicin, etoposide, and imatinib, belonging to five classes of anatomical therapeutic classification (ATC), was studied applying the in vivo comet assay on cells from whole organisms of Daphnia magna and Ceriodaphnia dubia. For the first time, this test was performed in C. dubia. In addition, to have a wider genotoxic/mutagenic profile of the anticancer drugs selected, SOS chromotest and Salmonella mutagenicity assay were performed. The comet results showed that all drugs induced DNA damage, in both Cladocerans, with environmental concern; indeed Doxorubicin induced DNA damage in the order of tens of ng L(-1) in both crustaceans, as well as 5-flurouracil in C. dubia and cisplatin in D. magna. In the SOS Chromotest all drugs, except imatinib, were able to activate the repair system in Escherichia coli PQ37 while in the Salmonella mutagenicity assay, doxorubicin was the only drug able to cause direct and indirect frameshift and base-pair substitution mutations. Comet assay was the most sensitive tool of genotoxic exposure assessment, able to detect in vivo the adverse effects at concentration lower than those evaluated in vitro by bacterial assays.

  20. Antigenotoxicity of artepillin C in vivo evaluated by the micronucleus and comet assays.

    PubMed

    de Azevedo Bentes Monteiro Neto, Moacir; de Souza Lima, Ildercílio Mota; Furtado, Ricardo Andrade; Bastos, Jairo Kenupp; da Silva Filho, Ademar Alves; Tavares, Denise Crispim

    2011-11-01

    Artepillin C (3,5-diprenyl-p-coumaric acid), a major compound found in Brazilian green propolis and Baccharis dracunculifolia, shows anti-inflammatory, antibacterial, antiviral, antioxidant and antitumoral activities, among others. The aim of this study was to evaluate the genotoxic potential of artepillin C and its ability to prevent the chemically induced chromosome breakage or loss and the primary DNA damage using the micronucleus and comet assays in male Swiss mice, respectively. The animals were treated by gavage with different doses of artepillin C (0.4, 0.8 and 1.6 mg kg(-1) b.w.). For the antigenotoxicity assays, the different doses of artepillin C were administered simultaneously to doxorubicin (DXR; micronucleus test; 15 mg kg(-1) b.w.) and to methyl methanesulfonate (MMS; comet assay; 40 mg kg(-1) b.w.). The results showed that artepillin C itself was not genotoxic in the mouse micronucleus and comet assays. In the animals treated with artepillin C and DXR, the number of micronucleated reticulocytes was significantly lower in comparison with the animals treated only with DXR. Regarding antigenotoxicity, artepillin C at the tested doses significantly reduced the extent of DNA damage in liver cells induced by MMS.

  1. Does the duration of lysis affect the sensitivity of the in vitro alkaline comet assay?

    PubMed

    Enciso, José Manuel; Sánchez, Oscar; López de Cerain, Adela; Azqueta, Amaya

    2015-01-01

    The alkaline comet assay is now the method of choice for measuring different kinds of DNA damage in cells. Several attempts have been made to identify and evaluate the critical points affecting the comet assay outcome, highlighting the requirement of arriving at a standardised protocol in order to be able to compare the results obtained in different laboratories. However, reports on the effect of modifying the time of lysis are lacking. Here we tested different times of lysis (from no lysis to 1 week) in control HeLa cells and HeLa cells treated with different concentrations of methyl methanesulfonate (MMS) or H2O2. We also tested different times of lysis in the comet assay combined with formamidopyrimidine DNA glycosylase (FPG) in untreated and Ro 19-8022 plus light-treated HeLa cells. The same DNA damage levels were detected in the absence of lysis or after 1h of lysis when the standard comet assay was used to detect the MMS- and H2O2-induced lesions; the response increased when longer lysis was used, up to at least 1 week. When FPG was used, a minimum lysis period of 5 min was necessary to allow the enzyme to reach the DNA; the same DNA damage levels were detected after 5 min or 1h of lysis and the response increased up to 24h. In conclusion, the time of lysis can be varied depending on the sensitivity needed in both versions of the assay, and a constant time of lysis should be used if results from different experiments or laboratories are to be compared.

  2. Genotoxicity of nano/microparticles in in vitro micronuclei, in vivo comet and mutation assay systems

    PubMed Central

    Totsuka, Yukari; Higuchi, Takashi; Imai, Toshio; Nishikawa, Akiyoshi; Nohmi, Takehiko; Kato, Tatsuya; Masuda, Shuich; Kinae, Naohide; Hiyoshi, Kyoko; Ogo, Sayaka; Kawanishi, Masanobu; Yagi, Takashi; Ichinose, Takamichi; Fukumori, Nobutaka; Watanabe, Masatoshi; Sugimura, Takashi; Wakabayashi, Keiji

    2009-01-01

    Background Recently, manufactured nano/microparticles such as fullerenes (C60), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C60, CB and kaolin, an in vitro micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by in vivo assay systems using male C57BL/6J or gpt delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles. Results In in vitro genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C60, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C60 and kaolin, increased either or both of gpt and Spi- mutant frequencies in the lungs of gpt delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the gpt genes. The G:C to C:G transversion was commonly increased by these particle instillations. Conclusion Manufactured nano/microparticles, CB, C60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems. PMID:19725983

  3. Comets

    NASA Technical Reports Server (NTRS)

    Wilkening, L. L. (Editor); Matthews, M. S. (Editor)

    1982-01-01

    Vacuum ultraviolet observations from sounding rockets and satellite observatories of the gaseous comae of several comets are reviewed. The earliest of these led to discovery of the hydrogen envelope extending for millions of km from the nucleus. Subsequent observations of H I Lyman alpha, the OH (0,0 band and the oxygen resonance triplet provided strong evidence for the water-ice model of the cometary nucleus. Several species were discovered in the coma including C, C(+), CO, S, and CS. High resolution spectroscopy and the spatial variation of the observed emissions provide means to elucidate the production and excitation mechanisms of these species. The similarity of the spectra of the half dozen comets observed to date argues for a common, homogeneous composition (with the exception of dust and CO) of the cometary ice and a minimal effect on the neutral species due to molecular collisions in the inner coma.

  4. Modification of lung cancer susceptibility by green tea extract as measured by the comet assay.

    PubMed

    Zhang, Huifeng; Spitz, Margaret R; Tomlinson, Gail E; Schabath, Matthew B; Minna, John D; Wu, Xifeng

    2002-01-01

    Green tea is widely consumed throughout the world and is known to possess various beneficial properties that may affect carcinogen metabolism, free radical scavenging, or formation of DNA adducts. Therefore, it is plausible that green tea extract may modify BPDE-induced DNA damage. In this report, we utilized the comet assay to (1) evaluate BPDE-induced DNA damage as a potential marker of cancer susceptibility and (2) assess the ability of green tea to modify BPDE-induced DNA damage. DNA damage in individual comet cells was quantified by (1) visually measuring the proportion of cells exhibiting migration versus those without and (2) the length of damaged DNA migration (comet tail). We detected a dose-response between BDPE concentration and mean comet tail length in EBV-immortalized lymphoblastiod (lymphoid) cell lines. As the concentration of BPDE increased from 0.5 to 3 microM, the length of the mean comet tail length increased proportionally in the 3590P (derived from a healthy subject) and 3640P (derived from a patient with head and neck cancer) cell lines. In separate experiments using lymphoid cells from 21 lung cancer cases and 12 healthy subjects, the mean comet tail length was significantly higher in the lung cancer cases (80.19 +/- 15.55) versus the healthy subjects (59.94 +/- 14.23) (P < 0.01). Similar findings were observed when analyzing the mean percentage of comet induced cells (84.57 +/- 8.85 and 69.04 +/- 12.50, respectively) (P < 0.01). When green tea extract was added in conjunction with BPDE, there was a notable reduction of the mean comet tail length (13.29 +/- 0.97) as compared to BPDE treatment alone (80.19 +/- 15.55) (P < 0.01) in lung cancer cases. There were no statistical differences between the baseline (no treatments) (12.74 +/- 0.63) and the green tea extract treatment (13.06 +/- 0.97) (P = 0.21). These data suggest the modification of lung cancer susceptibility by the green tea extract. Similar results were observed for the percentage

  5. Lack of genotoxicity of formocresol, paramonochlorophenol, and calcium hydroxide on mammalian cells by comet assay.

    PubMed

    Ribeiro, Daniel Araki; Marques, Mariângela Esther Alencar; Salvadori, Daisy Maria Fávero

    2004-08-01

    Formocresol, paramonochlorophenol, and calcium hydroxide are widely used in dentistry because of their antibacterial activities in root canal disinfection. However, the results of genotoxicity studies using these materials are inconsistent in literature. The goal of this study was to examine the genotoxic potential of formocresol, paramonochlorophenol, and calcium hydroxide using mouse lymphoma cells and human fibroblasts cells in vitro by the comet assay. Data were assessed by Kruskal-Wallis nonparametric test. The results showed that all compounds tested did not cause DNA damage for the tail moment or tail intensity parameters. These findings suggest that formocresol, paramonochlorophenol, and calcium hydroxide do not promote DNA damage in mammalian cells and that the comet assay is a suitable tool to investigate genotoxicity.

  6. Genotoxic effects of Bismuth (III) oxide nanoparticles by Allium and Comet assay.

    PubMed

    Liman, Recep

    2013-09-01

    Genotoxic effects of Bismuth (III) oxide nanoparticles (BONPs) were investigated on the root cells of Allium cepa by Allium and Comet assay. A. cepa roots were treated with the aqueous dispersions of BONPs at five different concentrations (12.5, 25, 50, 75, and 100ppm) for 4h. Exposure of BONPs significantly increased mitotic index (MI) except 12.5ppm, total chromosomal aberrations (CAs) in Allium test. While stickiness chromosome laggards, disturbed anaphase-telophase and anaphase bridges were observed in anaphase-telophase cells, pro-metaphase and c-metaphase in other cells. A significant increase in DNA damage was also observed at all concentrations of BONPs except 12.5ppm by Comet assay. The results were also analyzed statistically by using SPSS for Windows; Duncan's multiple range test was performed. These results indicate that BONPs exhibit genotoxic activity in A. cepa root meristematic cells.

  7. Genotoxicity of Aflatoxin B1 and Ochratoxin A after simultaneous application of the in vivo micronucleus and comet assay.

    PubMed

    Corcuera, Laura-Ana; Vettorazzi, Ariane; Arbillaga, Leire; Pérez, Noemí; Gil, Ana Gloria; Azqueta, Amaya; González-Peñas, Elena; García-Jalón, Jose Antonio; López de Cerain, Adela

    2015-02-01

    Aflatoxin B1 (AFB1) and Ochratoxin A (OTA) are genotoxic mycotoxins that can contaminate a variety of foodstuffs, the liver and the kidney being their target organs, respectively. The micronucleus (MN) assay (bone marrow) and the comet assay (liver and kidney) were performed simultaneously in F344 rats, treated with AFB1 (0.25 mg/kg b.w.), OTA (0.5 mg/kg b.w.) or both mycotoxins. After AFB1 treatment, histopathology and biochemistry analysis showed liver necrosis, focal inflammation and an increase in Alanine Aminotransferase and Aspartate Aminotransferase. OTA alone did not cause any alteration. The acute hepatotoxic effects caused by AFB1 were less pronounced in animals treated with both mycotoxins. With regard to the MN assay, after 24 h, positive results were obtained for AFB1 and negative results were obtained for OTA, although both toxins caused bone marrow toxicity. In the combined treatment, OTA reduced the toxicity and the number of MN produced by AFB1. In the comet assay, after 3 h, positive results were obtained for AFB1 in the liver and for OTA in the kidney. The combined treatment reduced DNA damage in the liver and had no influence in the kidney. Altogether, these results may be indicative of an antagonistic relationship regarding the genotoxicity of both mycotoxins.

  8. Effects of seven chemicals on DNA damage in the rat urinary bladder: a comet assay study.

    PubMed

    Wada, Kunio; Yoshida, Toshinori; Takahashi, Naofumi; Matsumoto, Kyomu

    2014-07-15

    The in vivo comet assay has been used for the evaluation of DNA damage and repair in various tissues of rodents. However, it can give false-positive results due to non-specific DNA damage associated with cell death. In this study, we examined whether the in vivo comet assay can distinguish between genotoxic and non-genotoxic DNA damage in urinary bladder cells, by using the following seven chemicals related to urinary bladder carcinogenesis in rodents: N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), glycidol, 2,2-bis(bromomethyl)-1,3-propanediol (BMP), 2-nitroanisole (2-NA), benzyl isothiocyanate (BITC), uracil, and melamine. BBN, glycidol, BMP, and 2-NA are known to be Ames test-positive and they are expected to produce DNA damage in the absence of cytotoxicity. BITC, uracil, and melamine are Ames test-negative with metabolic activation but have the potential to induce non-specific DNA damage due to cytotoxicity. The test chemicals were administered orally to male Sprague-Dawley rats (five per group) for each of two consecutive days. Urinary bladders were sampled 3h after the second administration and urothelial cells were analyzed by the comet assay and subjected to histopathological examination to evaluate cytotoxicity. In the urinary bladders of rats treated with BBN, glycidol, and BMP, DNA damage was detected. In contrast, 2-NA induced neither DNA damage nor cytotoxicity. The non-genotoxic chemicals (BITC, uracil, and melamine) did not induce DNA damage in the urinary bladders under conditions where some histopathological changes were observed. The results indicate that the comet assay could distinguish between genotoxic and non-genotoxic chemicals and that no false-positive responses were obtained.

  9. The use of the comet assay in the study of human nutrition and cancer.

    PubMed

    Wasson, Gillian R; McKelvey-Martin, Valerie J; Downes, C Stephen

    2008-05-01

    The influence of diet on carcinogenesis is a hugely complex area; not only is the consumption of major dietary factors such as meat, fat and fruits and vegetables associated with increased or decreased risk of a range of cancers but also an increasing number of specific nutrients such as vitamins, minerals and phytochemicals are being proposed as the next 'superfoods' to combat the development of cancer. As well as epidemiological studies to determine the association of these dietary factors with cancer risk, it is also essential to investigate the underlying mechanisms through which these factors may causally influence carcinogenesis. The comet assay provides a relatively simple, cheap and rapid method to examine DNA damage and repair and is, therefore, an ideal biomarker for the study of the effects of nutrition on cancer. This review focuses on the use of the comet assay in studies involving human subjects or human cell lines, which investigate the effects of various nutrients on biomarkers relevant to carcinogenesis, and discusses the potential of the comet assay and its various modifications for use as cancer-related biomarkers suitable for use in nutritional studies.

  10. Genotoxicity evaluation of dental restoration nanocomposite using comet assay and chromosome aberration test

    NASA Astrophysics Data System (ADS)

    Musa, Marahaini; Thirumulu Ponnuraj, Kannan; Mohamad, Dasmawati; Rahman, Ismail Ab

    2013-01-01

    Nanocomposite is used as a dental filling to restore the affected tooth, especially in dental caries. The dental nanocomposite (KelFil) for tooth restoration used in this study was produced by the School of Dental Sciences, Universiti Sains Malaysia, Malaysia and is incorporated with monodispersed, spherical nanosilica fillers. The aim of the study was to determine the genotoxic effect of KelFil using in vitro genotoxicity tests. The cytotoxicity and genotoxicity of KelFil was evaluated using MTT assay, comet assay and chromosome aberration tests with or without the addition of a metabolic activation system (S9 mix), using the human lung fibroblast cell line (MRC-5). Concurrent negative and positive controls were included. In the comet assay, no comet formation was found in the KelFil groups. There was a significant difference in tail moment between KelFil groups and positive control (p < 0.05). Similarly, no significant aberrations in chromosomes were noticed in KelFil groups. The mitotic indices of treatment groups and negative control were significantly different from positive controls. Hence, it can be concluded that the locally produced dental restoration nanocomposite (KelFil) is non-genotoxic under the present test conditions.

  11. Orbital error analysis for comet Encke, 1980

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1976-01-01

    Before a particular comet is selected as a flyby target, the following criteria should be considered in determining its ephemeris uncertainty: (1) A target comet should have good observability during the apparition of the proposed intercept; and (2) A target comet should have a good observational history. Several well observed and consecutive apparitions allow an accurate determination of a comet's mean motion and nongravitational parameters. Using these criteria, along with statistical and empirical error analyses, it has been demonstrated that the 1980 apparition of comet Encke is an excellent opportunity for a cometary flyby space probe. For this particular apparition, a flyby to within 1,000 km of comet Encke seems possible without the use of sophisticated and expensive onboard navigation instrumentation.

  12. Evaluation of 4,4'-diaminodiphenyl ether in the rat comet assay: Part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of in vivo rat alkaline comet assay.

    PubMed

    Priestley, Catherine C; Walker, Joanne S; O'Donovan, Michael R; Doherty, Ann T

    2015-07-01

    As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay, 4,4'-diaminodiphenyl ether (DPE), a known rodent genotoxic carcinogen, was tested in this laboratory. Sprague Dawley rats (7-9 weeks of age) were given three oral doses of DPE, 24 and 21 h apart and liver or stomach sampled 3h after the final dose. Under the conditions of the test, no increases in DNA damage in liver and stomach were observed with DPE (up to 200 mg/kg/day). A dose-dependent decrease in DNA migration, compared to vehicle controls, was noted for DPE in rat stomach. Further analysis is required to elucidate fully whether this decrease is a consequence of the mode of action or due to the toxicity of DPE. What is perhaps surprising is the inability of the comet assay to detect a known rat genotoxic carcinogen in liver. Further investigation is needed to clarify whether this apparent lack of response results from limited tissue exposure or metabolic differences between species. This finding highlights a need for careful consideration of study design when evaluating assay performance as a measure of in vivo genotoxicity.

  13. Leucocytes DNA damage in mice exposed to JS-118 by the comet assay.

    PubMed

    Zhang, Tao; Hu, Jiye; Zhang, Yuchao; Zhao, Qianfei; Ning, Jun

    2011-09-01

    JS-118 is an extensively used insecticide in China. The present study investigated the genotoxic effect of JS-118 on whole blood at 24, 48, 72 and 96 h by using alkaline comet assay. Male Kunming mice were given 6.25, 12.5, 25, 50 and 100 mg/kg BW of JS-118 intraperitoneally. A statistically significant increase in all comet parameters indicating DNA damage was observed at 24 h post-treatment (p < 0.05). A clear concentration-dependent increase of DNA damage was revealed as evident by the OTM (arbitrary units), tail length (µm) and tail DNA (%). From 48 h post-treatment, a gradual decrease in mean comet parameters was noted. By 96 h of post-treatment, the mean comet tail length reached control levels indicating repair of damaged DNA. This study on mice showed different DNA damage depending on the concentration of JS-118 and the period of treatment. The present study provided further information of the potential risk of the genetic damage caused by JS-118.

  14. Measurement of DNA damage in individual cells using the Single Cell Gel Electrophoresis (Comet) assay.

    PubMed

    Hartley, Janet M; Spanswick, Victoria J; Hartley, John A

    2011-01-01

    The Single Cell Gel Electrophoresis (Comet) assay is a simple, versatile and sensitive method for measuring DNA damage in individual cells, allowing the determination of heterogeneity of response within a cell population. The basic alkaline technique described is for the determination of DNA strand break damage and its repair at a single cell level. Specific modifications to the method use a lower pH ('neutral' assay), or allow the measurement of DNA interstrand cross-links. It can be further adapted to, for example, study specific DNA repair mechanisms, be combined with fluorescent in situ hybridisation, or incorporate lesion specific enzymes.

  15. Interpreting sperm DNA damage in a diverse range of mammalian sperm by means of the two-tailed comet assay

    PubMed Central

    Cortés-Gutiérrez, Elva I.; López-Fernández, Carmen; Fernández, José Luis; Dávila-Rodríguez, Martha I.; Johnston, Stephen D.; Gosálvez, Jaime

    2014-01-01

    Key Concepts The two-dimensional Two-Tailed Comet assay (TT-comet) protocol is a valuable technique to differentiate between single-stranded (SSBs) and double-stranded DNA breaks (DSBs) on the same sperm cell.Protein lysis inherent with the TT-comet protocol accounts for differences in sperm protamine composition at a species-specific level to produce reliable visualization of sperm DNA damage.Alkaline treatment may break the sugar–phosphate backbone in abasic sites or at sites with deoxyribose damage, transforming these lesions into DNA breaks that are also converted into ssDNA. These lesions are known as Alkali Labile Sites “ALSs.”DBD–FISH permits the in situ visualization of DNA breaks, abasic sites or alkaline-sensitive DNA regions.The alkaline comet single assay reveals that all mammalian species display constitutive ALS related with the requirement of the sperm to undergo transient changes in DNA structure linked with chromatin packing.Sperm DNA damage is associated with fertilization failure, impaired pre-and post- embryo implantation and poor pregnancy outcome.The TT is a valuable tool for identifying SSBs or DSBs in sperm cells with DNA fragmentation and can be therefore used for the purposes of fertility assessment. Sperm DNA damage is associated with fertilization failure, impaired pre-and post- embryo implantation and poor pregnancy outcome. A series of methodologies to assess DNA damage in spermatozoa have been developed but most are unable to differentiate between single-stranded DNA breaks (SSBs) and double-stranded DNA breaks (DSBs) on the same sperm cell. The two-dimensional Two-Tailed Comet assay (TT-comet) protocol highlighted in this review overcomes this limitation and emphasizes the importance in accounting for the difference in sperm protamine composition at a species-specific level for the appropriate preparation of the assay. The TT-comet is a modification of the original comet assay that uses a two dimensional electrophoresis to

  16. Chaga mushroom extract inhibits oxidative DNA damage in human lymphocytes as assessed by comet assay.

    PubMed

    Park, Yoo Kyoung; Lee, Hyang Burm; Jeon, Eun-Jae; Jung, Hack Sung; Kang, Myung-Hee

    2004-01-01

    The Chaga mushroom (Inonotus obliquus) is claimed to have beneficial properties for human health, such as anti-bacterial, anti-allergic, anti-inflammatory and antioxidant activities. The antioxidant effects of the mushroom may be partly explained by protection of cell components against free radicals. We evaluated the effect of aqueous Chaga mushroom extracts for their potential for protecting against oxidative damage to DNA in human lymphocytes. Cells were pretreated with various concentrations (10, 50, 100 and 500 microg/mL) of the extract for 1 h at 37 degrees C. Cells were then treated with 100 microM of H2O2 for 5 min as an oxidative stress. Evaluation of oxidative damage was performed using single-cell gel electrophoresis for DNA fragmentation (Comet assay). Using image analysis, the degree of DNA damage was evaluated as the DNA tail moment. Cells pretreated with Chaga extract showed over 40% reduction in DNA fragmentation compared with the positive control (100 micromol H2O2 treatment). Thus, Chaga mushroom treatment affords cellular protection against endogenous DNA damage produced by H2O2.

  17. Analysis of Returned Comet Nucleus Samples

    NASA Astrophysics Data System (ADS)

    Chang, Sherwood

    1997-12-01

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  18. Analysis of Returned Comet Nucleus Samples

    NASA Technical Reports Server (NTRS)

    Chang, Sherwood (Compiler)

    1997-01-01

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  19. A modified alkaline Comet assay for in vivo detection of oxidative DNA damage in Drosophila melanogaster.

    PubMed

    Shukla, A K; Pragya, P; Chowdhuri, D Kar

    2011-12-24

    Modifications to the alkaline Comet assay by using lesion-specific endonucleases, such as formamidopyrimidine-DNA glycosylase (FPG) and endonuclease III (ENDOIII, also known as Nth), can detect DNA bases with oxidative damage. This modified assay can be used to assess the genotoxic/carcinogenic potential of environmental chemicals. The goal of this study was to validate the ability of this modified assay to detect oxidative stress-induced genotoxicity in Drosophila melanogaster (Oregon R(+)). In this study, we used three well known chemical oxidative stress inducers: hydrogen peroxide (H(2)O(2)), cadmium chloride (CdCl(2)) and copper sulfate (CuSO(4)). Third instar larvae of D. melanogaster were fed various concentrations of the test chemicals (50-200μM) mixed with a standard Drosophila food for 24h. Alkaline Comet assays with and without the FPG and ENDOIII enzymes were performed with midgut cells that were isolated from the control and treated larvae. Our results show a concentration-dependent increase (p<0.05-0.001) in the migration of DNA from the treated larvae. ENDOIII treatment detected more oxidative DNA damage (specifically pyrimidine damage) in the H(2)O(2) exposed larvae compared to FPG or no enzyme treatment (buffer only). In contrast, FPG treatment detected more oxidative DNA damage (specifically purine damage) in CuSO(4) exposed larvae compared to ENDOIII. Although previously reported to be a potent genotoxic agent, CdCl(2) did not induce more oxidative DNA damage than the other test chemicals. Our results show that the modified alkaline Comet assay can be used to detect oxidative stress-induced DNA damage in D. melanogaster and thus may be applicable for in vivo genotoxic assessments of environmental chemicals.

  20. A new approach for the oocyte genotoxicity assay: adaptation of comet assay on mouse cumulus-oocyte complexes.

    PubMed

    Greco, F; Perrin, J; Auffan, M; Tassistro, V; Orsière, T; Courbiere, B

    2015-07-01

    Conventional genotoxicity tests are technically difficult to apply to oocytes, and results obtained on somatic cells cannot be extrapolated to gametes. We have previously described a comet assay (original-CA) on denuded mouse oocytes, but, in vivo, oocytes are not isolated from their surrounding follicular cells. Our objective was to develop a comet assay on cumulus-oocyte complexes (COC-CA) for a more physiological approach to study the genotoxicity of environmental factors on oocytes. For COC-CA, whole COC were exposed directly to exogenous agents after ovulation and removal from oviducts. Three conditions were studied: a negative control group, and two positive control groups, one of which was exposed to hydrogen peroxide (H2O2) and the other group was incubated with cerium dioxide nanoparticles (CeO2 NPs). With both tests, DNA damage was significant in the presence of both H2O2 and CeO2 NPs compared with the negative control. COC-CA offers an interesting tool for assaying the genotoxicity of environmental agents towards germinal cells. Furthermore, COC-CA is less time-consuming and simplifies the protocol of the original-CA, because COC-CA is easier to perform without the washing-out procedure.

  1. Application of the comet assay in erythrocytes of Oreochromis niloticus (Pisces): A methodological comparison

    PubMed Central

    2009-01-01

    The present study applied the comet assay to erythrocytes of Oreochromis niloticus with the aim of improving protocols to detect DNA damage in these cells, by using two distinct pHs (pH = 12.1 and pH > 13) and evaluating whether there is a correspondence between silver and ethidium bromide staining. Comets were visually examined and, the frequency of cells with and without damage was obtained, as well as the distribution of classes and scores. By using the Kruskal-Wallis test, our results revealed that pH 12.1 is more effective, although both pHs can be used. Our findings also suggest that silver staining can substitute ethidium bromide, an expensive and highly toxic stain that requires specific equipment for examination. PMID:21637662

  2. The comet assay in higher terrestrial plant model: Review and evolutionary trends.

    PubMed

    Lanier, Caroline; Manier, Nicolas; Cuny, Damien; Deram, Annabelle

    2015-12-01

    The comet assay is a sensitive technique for the measurement of DNA damage in individual cells. Although it has been primarily applied to animal cells, its adaptation to higher plant tissues significantly extends the utility of plants for environmental genotoxicity research. The present review focuses on 101 key publications and discusses protocols and evolutionary trends specific to higher plants. General consensus validates the use of the percentage of DNA found in the tail, the alkaline version of the test and root study. The comet protocol has proved its effectiveness and its adaptability for cultivated plant models. Its transposition in wild plants thus appears as a logical evolution. However, certain aspects of the protocol can be improved, namely through the systematic use of positive controls and increasing the number of nuclei read. These optimizations will permit the increase in the performance of this test, namely when interpreting mechanistic and physiological phenomena.

  3. DNA damage in grasshoppers' larvae--comet assay in environmental approach.

    PubMed

    Augustyniak, Maria; Orzechowska, Helena; Kędziorski, Andrzej; Sawczyn, Tomasz; Doleżych, Bogdan

    2014-02-01

    The comet assay that provides a quantitative measure of the DNA-strand breaks may be used for assessing the 'genotoxic potential' of the environment. Young adults of Chorthippus brunneus (Orthoptera), collected at three sites in Southern Poland, differing in the level of pollution, particularly with heavy metals: Pilica (reference), Olkusz (moderately polluted) and Szopienice (heavily polluted) - were allowed to mate under laboratory conditions that were free from any pollution. Egg-pods were collected and, after diapause, brain cells from one-day old larvae were used for the comet assay. We compared the level of DNA damage in the larvae originating from these sites and also measured time-dependent DNA repair after single 10min. application of H2O2 (20μM final concentration). The DNA damage was relatively low in larval cells irrespectively of the site pollution their parents came from. However, measured comet parameters - tail DNA content (TDNA), tail length (TL), and olive tail moment (OTM) - were significantly higher in larvae originating from the Szopienice site than in those from the reference site. Incubation of cells with H2O2 resulted in significantly higher values of the comet parameters in the insects from all the study sites with the highest ones observed in the offspring of grasshoppers from Szopienice. Moreover, DNA repair, following the treatment, did not occur in the latter group. These data contribute to almost unexplored subject of genotoxic effects of environmental pollutants in insects. They are discussed in the light of the concept of adaptive strategies in energy allocation depending on the level of biotope pollution.

  4. Genotoxicity evaluation of carvacrol in rats using a combined micronucleus and comet assay.

    PubMed

    Llana-Ruiz-Cabello, María; Maisanaba, Sara; Puerto, María; Prieto, Ana I; Pichardo, Silvia; Moyano, Rosario; González-Pérez, José A; Cameán, Ana M

    2016-12-01

    Genotoxic data of substances which could be incorporated into food packaging are required by the European Food Safety Authority. Due to its antioxidant and antibacterial properties carvacrol is one of these compounds. This work aims to study for the first time the in vivo genotoxic effects produced in rats orally exposed to 81, 256 or 810 mg cavacrol/kg body weight (bw) at 0, 24 and 45 h. A combination of the micronucleus assay (OECD 474) in bone marrow and the standard (OECD 489) and enzyme-modified comet assay was used to determine the genotoxicity on cells isolated from stomach and liver of exposed animals. In addition, a histopathological study was performed on the assayed tissues, and also in the lungs due to the volatility of carvacrol. Direct analytical pyrolysis was used to search for carvacrol in viscera and to ensure that the compound reaches stomach and liver cells. Results from MN-comet assay revealed that carvacrol (81-810 mg/kg bw) did not induce in vivo genotoxicity or oxidative DNA damage in any of the tissues investigated. Moreover, no histopathological changes were observed. Altogether, these results suggest lack of genotoxicity of carvacrol and therefore its good profile for its potential application as food preservative.

  5. A combination of in vitro comet assay and micronucleus test using human lymphoblastoid TK6 cells.

    PubMed

    Kimura, Aoi; Miyata, Atsuro; Honma, Masamitsu

    2013-09-01

    The comet assay has been widely used as a genotoxicity test for detecting primary DNA damage in individual cells. The micronucleus (MN) test is also a well-established assay for detecting clastogenicity and aneugenicity. A combination of the comet assay (COM) and MN test is capable of detecting a variety of genotoxic potentials as an in vitro screening system. Although the in vitro MN test has a robust protocol and Organisation for Economic Co-operation and Development (OECD) test guideline, the in vitro COM does not. To establish a robust protocol for the COM and to compare its sensitivity with that of the MN, we conducted COM and MN concurrently for five genotoxic agents (ethyl methanesulfonate, methyl methanesulfonate, hydrogen peroxide, gamma-rays and mitomycin C) and one non-genotoxic agent (triton X-100), using human lymphoblastoid TK6 cells. Relative cell count (RCC), relative population doubling (RPD), relative increase in cell count (RICC) and relative cell viability determined by trypan blue dye-exclusion assay (TBDE) were employed as cytotoxic measurements. However, the relative cell viability determined by TBDE just after the treatment was not an appropriate parameter of cytotoxicity for the genotoxic agents because it remained constant even at the highest doses, which showed severe cytotoxicity by RCC, RPD and RICC. The results of the COM showed qualitative agreement (positive or negative) with those of the MN except for mitomycin C, which is an interstrand cross-linker. The COM always required higher doses than the MN to detect the genotoxic potential of the genotoxic agents under the test conditions applied here. The doses that induced a comet tail always yielded <50% RICC, and do not accord to the OECD test guideline for MN because of their high cytotoxicity. These results are helpful for interpreting the results of the COM and MN in in vitro genotoxic hazard assessments. Further investigation is required to standardise the COM.

  6. Combination comet/micronucleus assay validation performed by BioReliance under the JaCVAM initiative.

    PubMed

    Pant, Kamala; Krsmanovic, Ljubica; Bruce, Shannon Wilson; Kelley, Tawney; Arevalo, Mirna; Atta-Safoh, Samuel; Debelie, Fekadu; La Force, Michelle L Klug; Springer, Sandra; Sly, Jamie; Paranjpe, Madhav; Lawlor, Timothy; Aardema, Marilyn

    2015-07-01

    In the international validation study of the in vivo rat alkaline comet assay (comet assay), the Japanese Center for the Validation of Alternative Methods (JaCVAM) provided three coded chemicals to BioReliance, 1,3-dichloropropene, ethionamide and busulfan, to be tested in a combined in vivo comet/micronucleus assay. Induction of DNA damage (comet) in liver, stomach and jejunum (1,3-dichloropropene only) cells, and induction of MNPCEs in bone marrow, were examined in male Sprague-Dawley (Hsd:SD) rats following oral administration of the test chemical for three consecutive days. A dose range finding (DRF) test was performed with each chemical to determine the maximum tolerated dose (MTD). Based on the results of the DRF test; 1,3-dichloropropene was tested at 50, 100 and 200 mg/kg/day; ethionamide was tested at 125, 250 and 500 mg/kg/day, and busulfan was tested at 10, 20 and 40 mg/kg/day. The results indicated that 1,3-dichloropropene induced DNA damage only in liver cells at all three test article doses, while no effects were observed in the stomach and jejunum cells. Additionally, it did not increase MNPCEs in the bone marrow. 1,3-Dichloropropene was concluded to be negative in the MN assay but positive in the comet assay. Ethionamide did not induce DNA damage in liver. However, in stomach, statistically significant decreases (although still within historical range) in % tail DNA at all test article doses compared to the vehicle control were observed. There was no increase in MNPCEs in the bone marrow. Thus, ethionamide was concluded to be negative in the comet/MN combined assay. Busulfan did not induce DNA damage in any of the organs tested (liver and stomach) but it did induce a significant increase in MNPCEs in the bone marrow. Busulfan was concluded to be negative in the comet assay but positive in the MN assay.

  7. In vitro mutagenicity and genotoxicity study of a number of short-chain chlorinated hydrocarbons using the micronucleus test and the alkaline single cell gel electrophoresis technique (Comet assay) in human lymphocytes: a structure-activity relationship (QSAR) analysis of the genotoxic and cytotoxic potential.

    PubMed

    Tafazoli, M; Baeten, A; Geerlings, P; Kirsch-Volders, M

    1998-03-01

    Using the micronucleus (MN) test and the alkaline single cell gel electrophoresis (Comet) assay, potential mutagenicity (MN formation), genotoxicity (DNA breakage capacity) and cytotoxicity (cell proliferation reduction) of five chlorinated hydrocarbons (carbon tetrachloride, hexachloroethane, 1,2-dichloroethane, 1-chlorohexane and 2,3-dichlorobutane) have been evaluated in isolated human lymphocytes. With the MN test a low but statistically significant mutagenic activity was detected for all tested substances (except 2,3-dichlorobutane) with one out of the two donors and in the presence or absence of an exogenous metabolic activation system (S9 mix). However, at the concentration ranges tested none of the positive compounds induced a clear dose-dependent mutagenic effect. The Comet assay detected a strong DNA damaging effect for 1-chlorohexane, 2,3-dichlorobutane and 1,2-dichloroethane, but not for carbon tetrachloride and hexachloroethane. The influence of metabolism on the genotoxic activity of the chemicals was more clear in the Comet assay than in the MN test. The experimental genotoxicity and cytotoxicity data obtained in this study, together with data on five more related chemicals previously investigated, and their physico-chemical descriptors or electronic parameters have been used for QSAR analysis. The QSAR analysis high-lighted that the toxicity of the tested compounds was influenced by different parameters, like lipophilicity (logP), electron donor ability (charge) and longest carbon-chlorine (LBC-Cl) bond length. In addition, steric parameters, like molar refractivity (MR) and LBC-Cl, and electronic parameters, like ELUMO (energy of the lowest unoccupied molecular orbital, indicating electrophilicity), were predominant factors discriminating genotoxins from non-genotoxins in the presence but not in the absence of S9 mix. Although a limited number of compounds have been examined and cytotoxicity and genotoxicity were identified in two different

  8. Comet assay evaluation of six chemicals of known genotoxic potential in rats.

    PubMed

    Hobbs, Cheryl A; Recio, Leslie; Streicker, Michael; Boyle, Molly H; Tanaka, Jin; Shiga, Atsushi; Witt, Kristine L

    2015-07-01

    As a part of an international validation of the in vivo rat alkaline comet assay (comet assay) initiated by the Japanese Center for the Validation of Alternative Methods (JaCVAM) we examined six chemicals for potential to induce DNA damage: 2-acetylaminofluorene (2-AAF), N-nitrosodimethylamine (DMN), o-anisidine, 1,2-dimethylhydrazine dihydrochloride (1,2-DMH), sodium chloride, and sodium arsenite. DNA damage was evaluated in the liver and stomach of 7- to 9-week-old male Sprague Dawley rats. Of the five genotoxic carcinogens tested in our laboratory, DMN and 1,2-DMH were positive in the liver and negative in the stomach, 2-AAF and o-anisidine produced an equivocal result in liver and negative results in stomach, and sodium arsenite was negative in both liver and stomach. 1,2-DMH and DMN induced dose-related increases in hedgehogs in the same tissue (liver) that exhibited increased DNA migration. However, no cytotoxicity was indicated by the neutral diffusion assay (assessment of highly fragmented DNA) or histopathology in response to treatment with any of the tested chemicals. Therefore, the increased DNA damage resulting from exposure to DMN and 1,2-DMH was considered to represent a genotoxic response. Sodium chloride, a non-genotoxic non-carcinogen, was negative in both tissues as would be predicted. Although only two (1,2-DMH and DMN) out of five genotoxic carcinogens produced clearly positive results in the comet assay, the results obtained for o-anisidine and sodium arsenite in liver and stomach cells are consistent with the known mode of genotoxicity and tissue specificity exhibited by these carcinogens. In contrast, given the known genotoxic mode-of-action and target organ carcinogenicity of 2-AAF, it is unclear why this chemical failed to convincingly increase DNA migration in the liver. Thus, the results of the comet assay validation studies conducted in our laboratory were considered appropriate for five out of the six test chemicals.

  9. Comparative evaluation of genotoxicity by micronucleus assay in the buccal mucosa over comet assay in peripheral blood in oral precancer and cancer patients.

    PubMed

    Katarkar, Atul; Mukherjee, Sanjit; Khan, Masood H; Ray, Jay G; Chaudhuri, Keya

    2014-09-01

    Early detection and quantification of DNA damage in oral premalignancy or malignancy may help in management of the disease and improve survival rates. The comet assay has been successfully utilised to detect DNA damage in oral premalignant or malignancy. However, due to the invasive nature of collecting blood, it may be painful for many unwilling patients. This study compares the micronucleus (MN) assay in oral buccal mucosa cells with the comet assay in peripheral blood cells in a subset of oral habit-induced precancer and cancer patients. For this, MN assay of exfoliated epithelial cells was compared with comet assay of peripheral blood leucocytes among 260 participants, including those with oral lichen planus (OLP; n = 52), leukoplakia (LPK; n = 51), oral submucous fibrosis (OSF; n = 51), oral squamous cell carcinoma (OSCC; n = 54) and normal volunteers (n = 52). Among the precancer groups, LPK patients showed significantly higher levels of DNA damage as reflected by both comet tail length (P < 0.0001) and micronuclei (MNi) frequency (P = 0.0009). The DNA damage pattern in precancer and cancer patients was OLP < OSF < LPK < OSCC, and with respective oral habits, it was multiple habits > cigarette + khaini > cigarette smokers > areca + khaini > areca. There was no significant difference in the comet length and MNi frequency between males and females who had oral chewing habits. An overall significant correlation was observed between MNi frequency and comet tail length with r = 0.844 and P < 0.0001. Thus, the extent of DNA damage evaluation by the comet assay in peripheral blood cells is perfectly reflected by the MN assay on oral exfoliated epithelial cells, and MNi frequency can be used with the same effectiveness and greater efficiency in early detection of oral premalignant conditions.

  10. The application of the comet assay to assess the genotoxicity of environmental pollutants in the nematode Caenorhabditis elegans.

    PubMed

    Imanikia, Soudabeh; Galea, Francesca; Nagy, Eszter; Phillips, David H; Stürzenbaum, Stephen R; Arlt, Volker M

    2016-07-01

    This study aimed to establish a protocol for cell dissociation from the nematode Caenorhabditis elegans (C. elegans) to assess the genotoxicity of the environmental pollutant benzo[a]pyrene (BaP) using the alkaline version of the single cell electrophoresis assay (comet assay). BaP genotoxicity was assessed in C. elegans (wild-type [WT]; N2, Bristol) after 48h exposure (0-40μM). Induction of comets by BaP was concentration-dependent up to 20μM; comet% tail DNA was ∼30% at 20μM BaP and ∼10% in controls. Similarly, BaP-induced DNA damage was evaluated in C. elegans mutant strains deficient in DNA repair. In xpa-1 and apn-1 mutants BaP-induced comet formation was diminished to WT background levels suggesting that the damage formed by BaP that is detected in the comet assay is not recognised in cells deficient in nucleotide and base excision repair, respectively. In summary, our study provides a protocol to evaluate DNA damage of environmental pollutants in whole nematodes using the comet assay.

  11. Optimal dose selection of N-methyl-N-nitrosourea for the rat comet assay to evaluate DNA damage in organs with different susceptibility to cytotoxicity.

    PubMed

    Kitamoto, Sachiko; Matsuyama, Ryoko; Uematsu, Yasuaki; Ogata, Keiko; Ota, Mika; Yamada, Toru; Miyata, Kaori; Funabashi, Hitoshi; Saito, Koichi

    2015-07-01

    The in vivo rodent alkaline comet assay (comet assay) is a promising technique to evaluate DNA damage in vivo. However, there is no agreement on a method to evaluate DNA damage in organs where cytotoxicity is observed. As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the comet assay, we examined DNA damage in the liver, stomach, and bone marrow of rats given three oral doses of N-methyl-N-nitrosourea (MNU) up to the maximum tolerated dose based on systemic toxicity. MNU significantly increased the % tail DNA in all the organs. Histopathological analysis showed no cytotoxic effect on the liver, indicating clearly that MNU has a genotoxic potential in the liver. In the stomach, however, the cytotoxic effects were very severe at systemically non-toxic doses. Low-dose MNU significantly increased the % tail DNA even at a non-cytotoxic dose, indicating that MNU has a genotoxic potential also in the stomach. Part of the DNA damage at cytotoxic doses was considered to be a secondary effect of severe cell damage. In the bone marrow, both the % tail DNA and incidence of micronucleated polychromatic erythrocytes significantly increased at non-hematotoxic doses, which were different from the non-cytotoxic doses for liver and stomach. These findings indicate that an optimal dose for detecting DNA damage may vary among organs and that careful attention is required to select an optimum dose for the comet assay based on systemic toxicity such as mortality and clinical observations. The present study shows that when serious cytotoxicity is suggested by increased % hedgehogs in the comet assay, histopathological examination should be included for the evaluation of a positive response.

  12. Comet assay: a reliable tool for the assessment of DNA damage in different models.

    PubMed

    Dhawan, Alok; Bajpayee, Mahima; Parmar, Devendra

    2009-02-01

    New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.

  13. Genotoxicity evaluation of benzene, di(2-ethylhexyl) phthalate, and trisodium ethylenediamine tetraacetic acid monohydrate using a combined rat comet/micronucleus assays.

    PubMed

    Kitamoto, Sachiko; Matsuyama, Ryoko; Uematsu, Yasuaki; Ogata, Keiko; Ota, Mika; Yamada, Toru; Miyata, Kaori; Kimura, Juki; Funabashi, Hitoshi; Saito, Koichi

    2015-07-01

    As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo alkaline comet assay (comet assay), we examined DNA damage in the liver, stomach, and bone marrow of rats dosed orally three times with up to 2000 mg/kg of benzene, di(2-ethylhexyl) phthalate, and trisodium ethylenediamine tetraacetic acid monohydrate. All three compounds gave negative results in the liver and stomach. In addition, a bone marrow comet and micronucleus analysis revealed that benzene, but not di(2-ethylhexyl) phthalate or trisodium ethylenediamine tetraacetic acid monohydrate induced a significant increase in the median % tail DNA and micronucleated polychromatic erythrocytes, compared with the respective concurrent vehicle control. These results were in good agreement with the previously reported genotoxicity findings for each compound. The present study has shown that combining the micronucleus test with the comet assay and carrying out these analyses simultaneously is effective in clarifying the mechanism of action of genotoxic compounds such as benzene.

  14. In vivo genotoxicity assessment of sertraline by using alkaline comet assay and the cytokinesis-block micronucleus assay.

    PubMed

    Battal, Dilek; Aktas, Ayca; Sungur, Mehmet Ali; Kadioglu, Ela; Eker, Ebru Derici; Sahin, Nefise Ozlen; Saygi, Sahan

    2013-11-01

    Sertraline, a leading antidepressant in the selective serotonin reuptake inhibitor (SSRI) group of medicine, is the most frequently prescribed drug. In this study, the alkaline comet assay and the cytokinesis-block micronucleus (CBMN) assay were used to investigate genotoxicity potential of sertraline in the peripheral blood lymphocytes (PBLs) of acute and chronic sertraline-treated Wistar albino rats. Male Wistar albino rats (n = 48) were administered low, medium and high doses of sertraline (10, 40, 80 mg/kg) for acute and chronic treatment by employing the gavage method to investigate genotoxicity of the administered drug. The data (tail length, tail intensity and tail moment) were analysed and indicated that there was no statistically significant difference between sertraline-treated groups and the negative control group with respect to DNA damage (p > 0.05). However, it was observed that acute sertraline administration had caused much more DNA damage in comparison with chronic treatment (p < 0.05). According to the data obtained from the CBMN test, an increase in the micronucleus (MN) frequency was detected at chronic and high-dose acute sertraline treatment. Based on the outcome of comet assay, detection of statistically insignificant DNA damage may be due to the fact that sertraline did not cause damage on DNA. Also, increase in frequency of MN in chronic sertraline treatment suggests that chronic sertraline administration might influence some mechanisms of cell division. Therefore, dose adjustment in depressed patients seems significant as it may help prevent further prognosis of the diseases.

  15. Autonomous Onboard Science Data Analysis for Comet Missions

    NASA Technical Reports Server (NTRS)

    Thompson, David R.; Tran, Daniel Q.; McLaren, David; Chien, Steve A.; Bergman, Larry; Castano, Rebecca; Doyle, Richard; Estlin, Tara; Lenda, Matthew

    2012-01-01

    Coming years will bring several comet rendezvous missions. The Rosetta spacecraft arrives at Comet 67P/Churyumov-Gerasimenko in 2014. Subsequent rendezvous might include a mission such as the proposed Comet Hopper with multiple surface landings, as well as Comet Nucleus Sample Return (CNSR) and Coma Rendezvous and Sample Return (CRSR). These encounters will begin to shed light on a population that, despite several previous flybys, remains mysterious and poorly understood. Scientists still have little direct knowledge of interactions between the nucleus and coma, their variation across different comets or their evolution over time. Activity may change on short timescales so it is challenging to characterize with scripted data acquisition. Here we investigate automatic onboard image analysis that could act faster than round-trip light time to capture unexpected outbursts and plume activity. We describe one edge-based method for detect comet nuclei and plumes, and test the approach on an existing catalog of comet images. Finally, we quantify benefits to specific measurement objectives by simulating a basic plume monitoring campaign.

  16. Results of the International Validation of the in vivo rodent alkaline comet assay for the detection of genotoxic carcinogens: Individual data for 1,2-dibromoethane, p-anisidine, and o-anthranilic acid in the 2nd step of the 4th phase Validation Study under the JaCVAM initiative.

    PubMed

    Takasawa, Hironao; Takashima, Rie; Narumi, Kazunori; Kawasako, Kazufumi; Hattori, Akiko; Kawabata, Masayoshi; Hamada, Shuichi

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative International Validation Study of an in vivo rat alkaline comet assay, we examined 1,2-dibromoethane (DBE), p-anisidine (ASD), and o-anthranilic acid (ANT) to investigate the effectiveness of the comet assay in detecting genotoxic carcinogens. Each of the three test chemicals was administered to 5 male Sprague-Dawley rats per group by oral gavage at 48, 24, and 3h before specimen preparation. Single cells were collected from the liver and glandular stomach at 3h after the final dosing, and the specimens prepared from these two organs were subjected to electrophoresis under alkaline conditions (pH>13). The percentage of DNA intensity in the comet tail was then assessed using an image analysis system. A micronucleus (MN) assay was also conducted using these three test chemicals with the bone marrow (BM) cells collected from the same animals simultaneously used in the comet assay, i.e., combination study of the comet assay and BM MN assay. A genotoxic (Ames positive) rodent carcinogen, DBE gave a positive result in the comet assay in the present study, while a genotoxic (Ames positive) non-carcinogen, ASD and a non-genotoxic (Ames negative) non-carcinogen, ANT showed negative results in the comet assay. All three chemicals produced negative results in the BM MN assay. While the comet assay findings in the present study were consistent with those obtained from the rodent carcinogenicity studies for the three test chemicals, we consider the positive result in the comet assay for DBE to be particularly meaningful, given that this chemical produced a negative result in the BM MN assay. Therefore, the combination study of the comet assay and BM MN assay is a useful method to detect genotoxic carcinogens that are undetectable with the BM MN assay alone.

  17. Cytogenetic status and oxidative DNA-damage induced by atorvastatin in human peripheral blood lymphocytes: Standard and Fpg-modified comet assay

    SciTech Connect

    Gajski, Goran Garaj-Vrhovac, Vera; Orescanin, Visnja

    2008-08-15

    To investigate the genotoxic potential of atorvastatin on human lymphocytes in vitro standard comet assay was used in the evaluation of basal DNA damage and to investigate possible oxidative DNA damage produced by reactive oxygen species (ROS) Fpg-modified version of comet assay was also conducted. In addition to these techniques the new criteria for scoring micronucleus test were applied for more complete detection of baseline damage in binuclear lymphocytes exposed to atorvastatin 80 mg/day in different time periods by virtue of measuring the frequency of micronuclei, nucleoplasmic bridges and nuclear buds. All parameters obtained with the standard comet assay and Fpg-modified comet assay were significantly higher in the treated than in control lymphocytes. The Fpg-modified comet assay showed a significantly greater tail length, tail intensity, and tail moment in all treated lymphocytes than did the standard comet assay, which suggests that oxidative stress is likely to be responsible for DNA damage. DNA damage detected by the standard comet assay indicates that some other mechanism is also involved. In addition to the comet assay, a total number of micronuclei, nucleoplasmic bridges and nuclear buds were significantly higher in the exposed than in controlled lymphocytes. Regression analyses showed a positive correlation between the results obtained by the comet (Fpg-modified and standard) and micronucleus assay. Overall, the study demonstrated that atorvastatin in its highest dose is capable of producing damage on the level of DNA molecule and cell.

  18. Dose-response relationship of temozolomide, determined by the Pig-a, comet, and micronucleus assay.

    PubMed

    Guérard, M; Johnson, G; Dertinger, S; Duran-Pacheco, G; Funk, J; Zeller, A

    2017-02-15

    Temozolomide (TMZ), a monofunctional alkylating agent, was selected as a model compound to determine its quantitative genotoxic dose-response relationship in different tissues (blood, liver, and jejunum) and endpoints [Pig-a-, comet-, and micronucleus assay (MNT)] in male rats. TMZ was administered p.o. over 5 consecutive days (day 1-5), followed by a treatment-free period of 50 days (day 6-56) and a final administration prior to necropsy (day 57-59). TMZ showed a dose-dependent increase in DNA damage in all interrogated endpoints. A statistically significant increase in Pig-a mutant phenotypes was observed on day 44 starting at 7.5 mg/kg/day for mutant reticulocytes (for RET(CD59-)) and at 3.75 mg/kg/day for mutant red blood cells (RBC(CD59-)), respectively. In addition, a statistically significant increase in cytogenetic damage, as measured by micronucleated reticulocytes, was observed starting at 3.75 mg/kg/day on day 3 and 1.5 mg/kg/day on day 59. DNA strand breaks, as detected by the comet assay, showed a dose-dependent and statistically significant increase in liver, blood, and jejunum starting at doses of 3.75, 3.75, and 7.5 mg/kg/day, respectively. The dose-response relationships of the Pig-a, MNT, and comet data were analyzed for possible points of departure (PoD) using the benchmark-dose (BMD) software PROAST with different critical effect sizes (CES) (BMD0.1, BMD0.5, BMD1, and BMD1SD). Overall, PoD values show a high concordance between different tissues and endpoints, underlining the suitability of this experimental design to explore quantitative dose-response relationships in a variety of different tissues and endpoints, while minimizing animal use.

  19. Recent advances in in vivo genotoxicity testing: prediction of carcinogenic potential using comet and micronucleus assay in animal models.

    PubMed

    Kang, Seung Hun; Kwon, Jee Young; Lee, Jong Kwon; Seo, Young Rok

    2013-12-01

    Genotoxic events have been known as crucial step in the initiation of cancer. To assess the risk of cancer, genotoxicity assays, including comet, micronucleus (MN), chromosomal aberration, bacterial reverse, and sister chromatid exchange assay, can be performed. Compared with in vitro genotoxicity assay, in vivo genotoxicity assay has been used to verify in vitro assay result and definitely provide biological significance for certain organs or cell types. The comet assay can detect DNA strand breaks as markers of genotoxicity. Methods of the in vivo comet assay have been established by Japanese Center for the Validation of Alternative Methods (JaCVAM) validation studies depending on tissue and sample types. The MN can be initiated by segregation error and lagging acentric chromosome fragment. Methods of the in vivo MN assay have been established by Organization for Economic Co-operation and Development (OECD) test guidelines and many studies. Combining the in vivo comet and MN assay has been regarded as useful methodology for evaluating genetic damage, and it has been used in the assessment of potential carcinogenicity by complementarily presenting two distinct endpoints of the in vivo genotoxicity individual test. Few studies have investigated the quantitative relation between in vivo genotoxicity results and carcinogenicity. Extensive studies emphasizes that positive correlation is detectable. This review summarizes the results of the in vivo comet and MN assays that have investigated the genotoxicity of carcinogens as classified by the International Agency for Research on Cancer (IARC) carcinogenicity database. As a result, these genotoxicity data may provide meaningful information for the assessment of potential carcinogenicity and for implementation in the prevention of cancer.

  20. Identification of DNA damage in marine fish Therapon jarbua by comet assay technique.

    PubMed

    Nagarani, N; Devi, V Janaki; Kumaraguru, A K

    2012-07-01

    The marine fish Therapon jarbua was exposed to acute concentration of mercuric chloride (HgCl2). In static acute toxicity bioassays at 24, 48, 72 and 96 hr LC50 values were estimated for each concentrations such as control, 2, 1, 0.5, 0.25 and 0.125 ppm, respectively. DNAdamage (single-strand break) was also studied in gill, kidney and blood tissues at single-cell levels in the specimens exposed to different acute doses of HgCl2, by applying single-cell electrophoresis (comet assay). Dose-dependent responses were observed in DNA damage in all tissues. A comparison of DNA damage in all tissue at two concentration namely, 0.125 and 0.25 ppm indicated that the gill cells (maximum damage as 249.3 and 289.7 AU) were more sensitive to the heavy metal exposure than kidney (maximum 225.17 AU) and blood cells (maximum 200.3 AU). This study explored the utility of the comet assay for in vivo laboratory studies using fish for screening the genotoxic potential for various agents.

  1. An evaluation of the relative sensitivity of two marine bivalve mollusc species using the Comet assay.

    PubMed

    Cheung, Victoria V; Depledge, Michael H; Jha, Awadhesh N

    2006-07-01

    The aim of this study was to (a) evaluate the potential for the 'Comet assay' to be used as a method for detecting genetic damage in the common cockle Cerastoderma edule; and (b) to compare the relative sensitivity with Mytilus edulis as the bivalve widely used as a sentinel species in biomonitoring studies. In vitro validation studies were carried out on haemocytes from each species using hydrogen peroxide (H2O2), a known oxidant and the induced DNA damage was measured using the Comet assay. On exposure to 0, 100, 500 and 1000 microM H2O2, a significant concentration-dependent increase was observed in both species. Use of an additional concentration of 5000 microM H2O2 showed that while DNA damage could be assessed in M. edulis at this concentration, only a few cells from C. edule were amenable to measurements owing to extensive DNA damage ("hedgehog cells"). The evidence also suggested that the cells from C. edule are more sensitive to oxidative damage induced by H2O2 when compared with M. edulis. Bearing in mind that sediments are the ultimate sink for many contaminants, this study demonstrates the potential application of sediment-dwelling C. edule as a useful biomonitoring species.

  2. Genotoxicity of glyphosate assessed by the comet assay and cytogenetic tests.

    PubMed

    Mañas, Fernando; Peralta, Laura; Raviolo, José; Ovando, Hugo García; Weyers, Alicia; Ugnia, Laura; Cid, Marcela Gonzalez; Larripa, Irene; Gorla, Nora

    2009-07-01

    It was evaluated the genotoxicity of glyphosate which up to now has heterogeneous results. The comet assay was performed in Hep-2 cells. The level of DNA damage in the control group (5.42±1.83 arbitrary units) for tail moment (TM) measurements has shown a significant increase (p<0.01) with glyphosate at a range concentration from 3.00 to 7.50mM. In the chromosome aberrations (CA) test in human lymphocytes the herbicide (0.20-6.00mM) showed no significant effects in comparison with the control group. In vivo, the micronucleus test (MNT) was evaluated in mice at three doses rendering statistical significant increases at 400mg/kg (13.0±3.08 micronucleated erythrocytes/1000 cells, p<0.01). In the present study glyphosate was genotoxic in the comet assay in Hep-2 cells and in the MNT test at 400mg/kg in mice. Thiobarbituric acid reactive substances (TBARs) levels, superoxide dismutase (SOD) and catalase (CAT) activities were quantified in their organs. The results showed an increase in these enzyme activities.

  3. Assessment of DNA integrity (COMET assay) in sperm cells of boron-exposed workers.

    PubMed

    Duydu, Yalçin; Başaran, Nurşen; Ustündağ, Aylin; Aydin, Sevtap; Undeğer, Ulkü; Ataman, Osman Yavuz; Aydos, Kaan; Düker, Yalçin; Ickstadt, Katja; Waltrup, Britta Schulze; Golka, Klaus; Bolt, Hermann M

    2012-01-01

    An extension of a male reproductive study conducted in a boric acid/borate production zone at Bandırma, Turkey, is presented. The relation between DNA-strand breaks (COMET assay, neutral and alkaline version) in sperm cells and previously described sperm quality parameters was investigated in boron-exposed males. A correlation between blood boron levels and mean DNA-strand breaks in sperm was weak, and DNA-strand breaks in sperm were statistically not different between control and exposed groups. Therefore, increasing boron exposures had no additional contribution in addition to already pre-existing DNA-strand breaks in the sperm cells. Weak but statistically significant correlations between DNA-strand breaks and motility/morphology parameters of sperm samples were observed in the neutral version of the COMET assay, while correlations between the same variables were statistically not significant in the alkaline version. A likely reason for these negative results, even in highly exposed humans, is that experimental exposures that had led to reproductive toxicity in animals were significantly higher than any boron exposures, which may be reached under realistic human conditions.

  4. Modified in vivo comet assay detects the genotoxic potential of 14-hydroxycodeinone, an α,β-unsaturated ketone in oxycodone.

    PubMed

    Pant, Kamala; Roden, Nicholas; Zhang, Charles; Bruce, Shannon; Wood, Craig; Pendino, Kimberly

    2015-12-01

    14-Hydroxycodeinone (14-HC) is an α,β-unsaturated ketone impurity found in oxycodone drug substance and has a structural alert for genotoxicity. 14-HC was tested in a combined Modified and Standard Comet Assay to determine if the slight decrease in % Tail DNA noted in a previously conducted Standard Comet Assay with 14-HC could be magnified to clarify if the response was due to cross-linking activity. One limitation of the Standard Comet Assay is that DNA cross-links cannot be reliably detected. However, under certain modified testing conditions, DNA cross-links and chemical moieties that elicit such cross-links can be elucidated. One such modification involves the induction of additional breakages of DNA strands by gamma or X-ray irradiation. To determine if 14-HC is a DNA crosslinker in vivo, a Modified Comet Assay was conducted using X-ray irradiation as the modification to visualize crosslinking activity. In this assay, 14-HC was administered orally to mice up to 320 mg/kg/day. Results showed a statistically significant reduction in percent tail DNA in duodenal cells at 320 mg/kg/day, with a nonstatistically significant but dose-related reduction in percent tail DNA also observed at the mid dose of 160 mg/kg/day. Similar decreases were not observed in cells from the liver or stomach, and no increases in percent tail DNA were noted for any tissue in the concomitantly conducted Standard Comet Assay. Taken together, 14-HC was identified as a cross-linking agent in the duodenum in the Modified Comet Assay.

  5. Combining the in vivo comet and micronucleus assays: a practical approach to genotoxicity testing and data interpretation.

    PubMed

    Vasquez, Marie Z

    2010-03-01

    Despite regulatory directives requiring the reduction of animal use in safety testing, recent modifications to genotoxicity testing guidelines now propose the use of two in vivo genotoxicity assays as a follow-up to an in vitro positive (International Conference on Harmonization Consensus Draft Guidance S2[R1] released March, 2008). To address both goals, the in vivo comet and micronucleus (MN) assays can be successfully combined into one informative study. Combining these two assays with such differences in sensitivity, endpoints measured and the type of data generated significantly improves upon the current standard capabilities for detecting genotoxicity without requiring additional animals. But to take full advantage of the benefits of incorporating the comet assay in safety testing, these same differences must be recognized and considered. Developed from over 15 years experience using the in vivo comet and MN assays in genotoxicity testing of chemicals and pharmaceuticals, this paper presents guidelines for the appropriate experimental design, dose selection and data interpretation for combined in vivo comet/MN assay studies. To illustrate the approach, data from combined assay studies are presented and discussed.

  6. Genotoxicity evaluation of dimethoate to experimental mice by micronucleus, chromosome aberration tests, and comet assay.

    PubMed

    Ayed-Boussema, Imen; Rjiba, Karima; Mnasri, Nourhène; Moussa, Amal; Bacha, Hassen

    2012-01-01

    Dimethoate (DM) is an organophosphate insecticide with numerous uses on field and agricultural crops and ornamentals. Data concerning DM-acute genotoxicity are controversial and knowledge on its delayed effect is limited. For this reason, we aimed to further explore DM genotoxicity resulting from subchronic intoxication of experimental mice. Thus, DM was administered to mice at doses ranging from 1 to 30 mg/kg body weight for a period of 30 consecutive days. There was a significant increase (P < .05) in the frequency of micronucleated bone marrow cells following DM administration. Furthermore, the chromosome aberration assay revealed a significant increase in the percentage of chromosome abnormalities in a dose-dependent manner. Dimethoate was also found to induce significant DNA damage in mouse bone marrow cells as assessed by the comet assay. Altogether, our results showed that, after a subchronic exposure, DM was a genotoxic compound in experimental mice.

  7. The 15 years of comet photometry: A comparative analysis of 80 comets

    NASA Technical Reports Server (NTRS)

    Osip, David J.; Schleicher, David G.; Millis, Robert L.; Ahearn, Michael F.; Birch, Peter V.

    1991-01-01

    In 1976, a program of narrowband photometry of comets was initiated that has encompassed well over 400 nights of observations. To date, the program has provided detailed information on 80 comets, 11 of which were observed during multiple apparitions. The filters (initially isolating CN, C2, and continuum and later including C3, OH, and NH) as well as the detectors used for the observations were changed over time, and the parameters adopted in the reduction and modeling of the data have likewise evolved. Accordingly, we have re-reduced the entire database and have derived production rates using current values for scalelengths and fluorescence efficiencies. Having completed this task, the results for different comets can now be meaningfully compared. The general characteristics that are discussed include ranges in composition (molecular production rate ratios) and dustiness (gas production compared with Af(rho)). Additionally an analysis of trends on how the production rates vary with heliocentric distance and on pre- and post-perihelion asymmetries in the production rates of individual comets. Possible taxonomic groupings are also described.

  8. Evaluation of the Comet Assay for Assessing the Dose-Response Relationship of DNA Damage Induced by Ionizing Radiation

    PubMed Central

    Wang, Yan; Xu, Chang; Du, Li Qing; Cao, Jia; Liu, Jian Xiang; Su, Xu; Zhao, Hui; Fan, Fei-Yue; Wang, Bing; Katsube, Takanori; Fan, Sai Jun; Liu, Qiang

    2013-01-01

    Dose- and time-response curves were combined to assess the potential of the comet assay in radiation biodosimetry. The neutral comet assay was used to detect DNA double-strand breaks in lymphocytes caused by γ-ray irradiation. A clear dose-response relationship with DNA double-strand breaks using the comet assay was found at different times after irradiation (p < 0.001). A time-response relationship was also found within 72 h after irradiation (p < 0.001). The curves for DNA double-strand breaks and DNA repair in vitro of human lymphocytes presented a nice model, and a smooth, three-dimensional plane model was obtained when the two curves were combined. PMID:24240807

  9. In vivo assessment of DNA damage and protective effects of extracts from Miconia species using the comet assay and micronucleus test.

    PubMed

    Serpeloni, Juliana Mara; Bisarro dos Reis, Mariana; Rodrigues, Juliana; Campaner dos Santos, Lourdes; Vilegas, Wagner; Varanda, Eliana A; Dokkedal, Anne L; Cólus, Ilce Mara S

    2008-11-01

    The genus Miconia comprises approximately 1000 species belonging to the Melastomataceae family. Several crude plant extracts from Miconia and their isolated compounds have shown biological activities, such as analgesic and anti-neoplastic action; however, no studies concerning their effects on DNA are available. The present study aimed to evaluate, in vivo, the genotoxic and mutagenic effects of four species of plants from Miconia genus using the comet assay and micronucleus test. Their possible protective effects were also evaluated in experiments associating the plant extracts with cyclophosphamide (CPA). The methanolic extracts of Miconia albicans, Miconia cabucu, Miconia rubiginosa, Miconia stenostachya and the chloroformic extract of M. albicans were investigated. For genotoxic and mutagenic evaluations, three concentrations were tested, 200, 400 and 540 mg/kg body weight (bw), based on the solubility limit of the extract in distilled water. For the protective effects, only the highest dose was evaluated against 40 mg/kg bw of CPA. Blood was removed from mice tails pre- (T0) and post-treatment (T1-30 h) for the micronucleus test and 24 h post-treatment for the comet assay. The Student's t-test was used to compare data obtained at T0 and T1, the analysis of variance-Tukey test was used to compare between groups in the micronucleus test and the Kruskal-Wallis and Dunn's test were used to compare different groups in the comet assay. All the extracts induced alterations in DNA migration (comet assay); however, no mutagenic effect was observed in the micronucleus assay. All extracts showed a protective effect against CPA in both assays. Our study showed that the use of crude extracts could be more advantageous than the use of isolated compounds. The interaction between phytochemicals in the extracts showed efficacy in reducing mutagenicity and improving the protective effects.

  10. [Use of comet assay for the risk assessment of oil- and chemical-industry workers].

    PubMed

    Megyesi, János; Biró, Anna; Wigmond, László; Major, Jenő; Tompa, Anna

    2014-11-23

    Bevezetés: A comet assay a DNS száltöréseinek kimutatására alkalmas fluoreszcens mikroszkópos módszer. Jelentősége az alacsony sejtszámú mintáknál mutatkozik, képes számokban kifejezni a DNS-károsodást a nem proliferáltatható sejtekben. Célkitűzés: Genotoxikus, illetve oxidatív DNS-károsodásokat mértünk foglalkozásuk során benzollal, policiklusos aromás szénhidrogénekkel, illetve sztirollal exponált csoportokban. Célunk volt annak megvizsgálása, hogy a módszer használható-e genotoxikológiai monitorhatás markereként. Módszer: A comet assay alaplépései mellett az enzimkezelt mintát formamido-pirimidin-DNS glikoláz restrikciós enzimmel kezeljük, ami az oxidatív DNS-károsodás mértékére utal. Eredmények: A kezeletlen (genotoxikus DNS-károsodás) és a kezelt (oxidatív DNS-károsodás) minták esetében emelkedés volt tapasztalható a csóvahosszokat illetően minden csoporton belül a kontrollhoz képest. Következtetések: Megállapítható, hogy a környezeti (munkahelyi) expozíció valószínűsíthető a vizsgált csoportokban. A comet assay kitűnő hatásmarker, illetve kiegészítő módszer lehet egy monitorrendszerben, amelynek adatai tájékoztatást adhatnak a munkahelyeken emelkedett genotoxikus hatások jelenlétéről vagy hiányáról. Orv. Hetil., 2014, 155(47), 1872–1875.

  11. Tiagabine treatment and DNA damage in rat astrocytes: an in vitro study by comet assay.

    PubMed

    Cardile, V; Palumbo, M; Renis, M; Pavone, A; Maci, T; Perciavalle, V

    2001-06-22

    We studied in vitro the effects of Tiagabine on genomic DNA of cortical rat astrocytes. To evaluate DNA damage, we used a relatively simple technique called Single Cell Gel Electrophoresis or Comet assay. Tiagabine was dissolved in culture medium and added at concentration of 1, 10, 20 and 50 microg/ml on 12-day old cultured astrocytes. In presence of 1 and 10 microg/ml of Tiagabine, no DNA damage was observed after 48 h of treatment. A moderate DNA damage was instead observed for cells exposed to 20 microg/ml of antiepileptic drug. Finally, DNA fragmentation was more evident after treatment with 50 microg/ml of Tiagabine. We conclude that Tiagabine, at the usual recommended doses, does not appear to influence negatively the cortical rat astrocytes, inducing DNA fragmentation only at very high concentrations.

  12. Alkaline single-cell gel (comet) assay and genotoxicity monitoring using two species of tadpoles.

    PubMed

    Ralph, S; Petras, M; Pandrangi, R; Vrzoc, M

    1996-01-01

    Small bodies of water (e.g., creeks, ponds, and drainage ditches) have received very little attention in genotoxicity studies, yet these areas are important because they are often the first to be affected by industrial effluents, sewage contaminants, accidental spills, internal combustion engine emissions, landfill runoffs, and pesticide uses. To address this deficiency, we examined erythrocytes in two species of tadpoles, Rana clamitans and Bufo americanus, using the alkaline single-cell gel (SCG) ("comet") assay. This approach involves detection, under alkaline conditions, of cell DNA fragments, which on electrophoresis migrate from the nuclear core, resulting in a "comet-with-tail" formation. Exposure of R. clamitans todpoles to a range of concentrations of methyl methanesulfonate (MMS) produced a linear increase in DNA length to DNA core width ratios. This is consistent with findings in a number of other species. Time-dose experiments using MMS suggest that the peak level of DNA damage in R. clamitans todpoles occurred 42 hr after exposure. B. americanus tadpoles exposed to 6.25 mg/l of MMS for 12 hours had a significant increase in DNA damage over that seen in the controls. Freshly caught R. clamitans tadpoles from Highgate and B. americanus tadpoles from Duart, both on the north shore of Lake Erie, gave ratios of 2.78 and 2.07, respectively. This region of Ontario is a prime agricultural area and pesticide use is extensive. Tadpoles from Highgate and Duart, maintained in the laboratory for 4 months and 6 weeks, respectively, gave ratios of 1.29 and 1.44. The results of the SCG procedure in tadpoles indicate that this assay is extremely sensitive and suitable for detecting genotoxicity in the environment.

  13. Double-face activity of resveratrol in voluntary runners: assessment of DNA damage by comet assay.

    PubMed

    Tomasello, Barbara; Grasso, Salvatore; Malfa, Giuseppe; Stella, Stefania; Favetta, Marco; Renis, Marcella

    2012-05-01

    Voluntary runners are subjected to a massive increase in reactive oxygen/nitrogen species production, which can promote different oxidative stress-related diseases such as premature aging, neurodegenerative disorders, and cancer. The aims of this work were to evaluate the following in peripheral blood cells of voluntary runners: (i) DNA status; (ii) susceptibility to the in vitro insult induced by hydrogen peroxide (H(2)O(2)) as a breaking agent; (iii) capabilities of 3,5,4'-trihydroxystilbene (RESV) in counteracting DNA damage. Twenty-five male voluntary runners were compared with 20 sedentary men, as age-matched controls, and DNA status was evaluated with different versions of comet assay: alkaline, neutral, and Fpg enzyme-modified version to measure 8-OH-deoxyguanosine (8-oxo-dG) levels. The H(2)O(2) and/or RESV treatments were performed directly on agarose-embedded cells (atypical comet assay). The results evidenced DNA damage and levels of 8-oxo-dG higher in runners than in sedentary control subjects. The runners' DNA was more prone to the in vitro-induced oxidative insult (200 μM H(2)O(2)) than that of the control group. Resveratrol (100 μM), depending on the individual basal DNA status, was able to switch from antioxidant to pro-oxidant. Our results, on the one hand, validated the proposed in vitro experimental protocol in order to measure individual DNA status. On the other hand, our data point out the importance of monitoring the athletes' redox status before subjecting them to dietary supplementation treatment.

  14. Induction and repair of DNA damage measured by the comet assay in human T lymphocytes separated by immunomagnetic cell sorting.

    PubMed

    Bausinger, Julia; Speit, Günter

    2014-11-01

    The comet assay is widely used in human biomonitoring to measure DNA damage in whole blood or isolated peripheral blood mononuclear cells (PBMC) as a marker of exposure to genotoxic agents. Cytogenetic assays with phytohemagglutinin (PHA)-stimulated cultured T lymphocytes are also frequently performed in human biomonitoring. Cytogenetic effects (micronuclei, chromosome aberrations, sister chromatid exchanges) may be induced in vivo but also occur ex vivo during the cultivation of lymphocytes as a consequence of DNA damage present in lymphocytes at the time of sampling. To better understand whether DNA damage measured by the comet assay in PBMC is representative for DNA damage in T cells, we comparatively investigated DNA damage and its repair in PBMC and T cells obtained by immunomagnetic cell sorting. PBMC cultures and T cell cultures were exposed to mutagens with different modes of genotoxic action and DNA damage was measured by the comet assay after the end of a 2h exposure and after 18h post-incubation. The mutagens tested were methyl methanesulfonate (MMS), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), 4-nitroquinoline-1-oxide (4NQO), styrene oxide and potassium bromate. MMS and potassium bromate were also tested by the modified comet assay with formamido pyrimidine glycosylase (FPG) protein. The results indicate that the mutagens tested induce DNA damage in PBMC and T cells in the same range of concentrations and removal of induced DNA lesions occurs to a comparable extent. Based on these results, we conclude that the comet assay with PBMC is suited to predict DNA damage and its removal in T cells.

  15. Reference control data obtained from an in vivo comet-micronucleus combination assay using Sprague Dawley rats.

    PubMed

    Kasamoto, Sawako; Masumori, Shoji; Tanaka, Jin; Ueda, Maya; Fukumuro, Masahito; Nagai, Miho; Yamate, Jyoji; Hayashi, Makoto

    2017-04-04

    According to the International Conference on Harmonization Guidance on Genotoxicity Testing and Data Interpretation for Pharmaceuticals Intended for Human Use (ICH S2(R1)), a positive response in any in vitro assay necessitates additional in vivo test(s) (other tissue/endpoint) in addition to the erythrocyte micronucleus test when Option 1 of the test battery is selected. When Option 2 of the test battery is selected, a bacterial gene mutation test and two in vivo tests with different tissues/endpoint are required. The in vivo alkaline comet assay is recommended as the second in vivo test because it can detect a broad spectrum of DNA damage in any tissue and can be combined with the erythrocyte micronucleus test. Considering animal welfare, a combination assay is preferable to an individual assay. Thus, we validated the protocol for the in vivo comet-micronucleus combination assay in rats with three daily administrations and determined the dose of the positive control (ethyl methanesulfonate; EMS, 200mg/kg/day). We also collected the negative control (vehicle) and positive control (EMS) data from the comet (liver, stomach, and kidney) and micronucleus (bone marrow) combination assay using male Sprague Dawley (SD) rats. The negative control data were comparable to our historical control data obtained from stand-alone assays. The positive control data showed clear and consistent positive responses in both endpoints.

  16. EVALUATION OF DNA INTEGRITY USING TUNEL AND COMET ASSAY IN HUMAN SEMEN: IMMEDIATE- VERSUS DELAYED-FREEZING

    EPA Science Inventory

    EVALUATION OF DNA INTEGRITY USING TUNEL AND COMET ASSAY IN HUMAN SEMEN: IMMEDIATE- VERSUS DELAYED-FREEZING
    K. Young,* L. Xun,* S. Rothmann,? S. Perreault, ? W. Robbins*
    *University of California, Los Angeles, Los Angeles, California; ?Fertility Solutions Inc., Cleveland, ...

  17. Adaptation of the neutral bacterial comet assay to assess antimicrobial-mediated DNA double-strand breaks in Escherichia coli

    PubMed Central

    SOLANKY, DIPESH; HAYDEL, SHELLEY E.

    2012-01-01

    This study aimed to determine the mechanism of action of a natural antibacterial clay mineral mixture, designated CB, by investigating the induction of DNA double-strand breaks (DSBs) in Escherichia coli. To quantify DNA damage upon exposure to soluble antimicrobial compounds, we modified a bacterial neutral comet assay, which primarily associates the general length of an electrophoresed chromosome, or comet, with the degree of DSB-associated DNA damage. To appropriately account for antimicrobial-mediated strand fragmentation, suitable control reactions consisting of exposures to water, ethanol, kanamycin, and bleomycin were developed and optimized for the assay. Bacterial exposure to the CB clay resulted in significantly longer comet lengths, compared to water and kanamycin exposures, suggesting that the induction of DNA DSBs contributes to the killing activity of this antibacterial clay mineral mixture. The comet assay protocol described herein provides a general technique for evaluating soluble antimicrobial-derived DNA damage and for comparing DNA fragmentation between experimental and control assays. PMID:22940101

  18. Workshop on Analysis of Returned Comet Nucleus Samples

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This volume contains abstracts that were accepted by the Program Committee for presentation at the workshop on the analysis of returned comet nucleus samples held in Milpitas, California, January 16 to 18, 1989. The abstracts deal with the nature of cometary ices, cryogenic handling and sampling equipment, origin and composition of samples, and spectroscopic, thermal and chemical processing methods of cometary nuclei. Laboratory simulation experimental results on dust samples are reported. Some results obtained from Halley's comet are also included. Microanalytic techniques for examining trace elements of cometary particles, synchrotron x ray fluorescence and instrument neutron activation analysis (INAA), are presented.

  19. Role of recombinant human erythropoietin loading chitosan-tripolyphosphate nanoparticles in busulfan-induced genotoxicity: Analysis of DNA fragmentation via comet assay in cultured HepG2 cells.

    PubMed

    Ghassemi-Barghi, Nasrin; Varshosaz, Jaleh; Etebari, Mahmoud; Jafarian Dehkordi, Abbas

    2016-10-01

    -treatment conditions, significantly decreased the level of DNA damage induced by busulfan, measured with the comet assay, in HepG2 cells compared to the regular rhEPO group.

  20. Estimates of DNA damage by the comet assay in the direct-developing frog Eleutherodactylus johnstonei (Anura, Eleutherodactylidae)

    PubMed Central

    Valencia, Laura Carolina; García, Adriana; Ramírez-Pinilla, Martha Patricia; Fuentes, Jorge Luis

    2011-01-01

    The aim of this study was to use the Comet assay to assess genetic damage in the direct-developing frog Eleutherodactylus johnstonei. A DNA diffusion assay was used to evaluate the effectiveness of alkaline, enzymatic and alkaline/enzymatic treatments for lysing E. johnstonei blood cells and to determine the amount of DNA strand breakage associated with apoptosis and necrosis. Cell sensitivity to the mutagens bleomycin (BLM) and 4-nitro-quinoline-1-oxide (4NQO) was also assessed using the Comet assay, as was the assay reproducibility. Alkaline treatment did not lyse the cytoplasmic and nuclear membranes of E. johnstonei blood cells, whereas enzymatic digestion with proteinase K (40 μg/mL) yielded naked nuclei. The contribution of apoptosis and necrosis (assessed by the DNA diffusion assay) to DNA damage was estimated to range from 0% to 8%. BLM and 4NQO induced DNA damage in E. johnstonei blood cells at different concentrations and exposure times. Dose-effect curves with both mutagens were highly reproducible and showed consistently low coefficients of variation (CV ≤ 10%). The results are discussed with regard to the potential use of the modified Comet assay for assessing the exposure of E. johnstonei to herbicides in ecotoxicological studies. PMID:22215974

  1. Biomonitoring of agricultural workers exposed to pesticide mixtures in Guerrero state, Mexico, with comet assay and micronucleus test.

    PubMed

    Carbajal-López, Yolanda; Gómez-Arroyo, Sandra; Villalobos-Pietrini, Rafael; Calderón-Segura, María Elena; Martínez-Arroyo, Amparo

    2016-02-01

    The aim of this study was to evaluate the genotoxic effect of pesticides in exfoliated buccal cells of workers occupationally exposed in Guerrero, Mexico, using the comet assay and the micronucleus test. The study compared 111 agricultural workers in three rural communities (Arcelia 62, Ajuchitlan 13, and Tlapehuala 36), with 60 non-exposed individuals. All the participants were males. The presence of DNA damage was investigated in the exfoliated buccal cells of study participants with the comet assay and the micronucleus (MN) test; comet tail length was evaluated in 100 nuclei and 3000 epithelial cells of each individual, respectively; other nuclear anomalies such as nuclear buds, karyolysis, karyorrhexis, and binucleate cells were also evaluated. Study results revealed that the tail migration of DNA and the frequency of MN increased significantly in the exposed group, which also showed nuclear anomalies associated with cytotoxic or genotoxic effect. No positive correlation was noted between exposure time and tail length and micronuclei frequencies. No significant effect on genetic damage was observed as a result of age, smoking, and alcohol consumption. The MN and comet assay in exfoliated buccal cells are useful and minimally invasive methods for monitoring genetic damage in individuals exposed to pesticides. This study provided valuable data for establishing the possible risk to human health associated with pesticide exposure.

  2. Evaluation of genotoxicity of the acute gamma radiation on earthworm Eisenia fetida using single cell gel electrophoresis technique (Comet assay).

    PubMed

    Sowmithra, K; Shetty, N J; Jha, S K; Chaubey, R C

    2015-12-01

    Earthworms (Eisenia fetida) most suitable biological indicators of radioactive pollution. Radiation-induced lesions in DNA can be considered to be molecular markers for early effects of ionizing radiation. Gamma radiation produces a wide spectrum of DNA. Some of these lesions, i.e., DNA strand breaks and alkali labile sites can be detected by the single-cell gel electrophoresis (SCGE) or comet assay by measuring the migration of DNA from immobilized nuclear DNA. E. fetida were exposed to different doses of gamma radiation, i.e., 1, 5, 10, 20, 30, 40 and 50Gy, and comet assay was performed for all the doses along with control at 1, 3 and 5h post irradiation to evaluate the genotoxicity of gamma radiation in this organism. The DNA damage was measured as percentage of comet tail DNA. A significant increase in DNA damage was observed in samples exposed to 5Gy and above, and the increase in DNA damage was dose dependent i.e., DNA damage was increased with increased doses of radiation. The highest DNA damage was noticed at 1h post irradiation and gradually decreased with time, i.e., at 3 and 5h post irradiation. The present study reveals that gamma radiation induces DNA damage in E. fetida and the comet assay is a sensitive and rapid method for its detection to detect genotoxicity of gamma radiation.

  3. Antigenotoxic activity of watercress extract in an in vitro mammalian system using comet assay.

    PubMed

    Casanova, Natalia A; Carballo, Marta A

    2011-12-01

    Watercress (Cruciferae), an integral part of Mediterranean diets, is a nutritive food which is used in the treatment of several diseases. Oxidative DNA damage seems to play a crucial role in chronic, aging-related diseases and it is considered an important and probably carcinogenic factor. The aim of this work was to determine the impact of watercress extract on cell viability and its potential antigenotoxic properties against induced oxidative damage, using a comet assay and peripheral blood cells as an in vitro model. An aqueous extract of the leaves was prepared using a juice processor, centrifuged, filtered and preserved at -20 °C. Two concentrations of the aqueous extract (13.2 and 26.4 mg/mL) were assayed. No differences were found in cell viability between the control and treated groups at any time. Significant antigenotoxic effects were observed for both concentrations, expressed as the damage index (p = 0.005 at 30 min; p < 0.001 at 60 and 90 min), the percentage reductions in damage being similar between them (67.1-75.2% respectively). These results suggest that the consumption watercress in the diet is a powerful tool for improving health and the quality of life.

  4. Genotoxicity assessment of deoxynivalenol in the Caco-2 cell line model using the Comet assay.

    PubMed

    Bony, Sylvie; Carcelen, Monique; Olivier, Laurence; Devaux, Alain

    2006-09-30

    The genotoxic risk associated with deoxynivalenol (DON), a prevalent trichothecene mycotoxin which contaminates cereal-based products has not yet been deeply explored. In this work, the alkaline version of the Comet assay was used to evaluate DNA damage stemming from DON exposure in both dividing and differentiated Caco-2 cells, an epithelial intestinal cell line. To avoid false positive results, cytotoxic and apoptotic thresholds were firstly established using the MTS and neutral red assays and the Hoestch staining method, respectively. Dividing cells were found to be more sensitive to DON than differentiated cells and the lowest IC(10) (0.5 microM) obtained for dividing cells exposed for 72 h was used as the highest working concentration in the genotoxicity study. Both differentiated and dividing cells responded with a dose-dependent relationship to DON in terms of DNA damage in the 0.01-0.5 microM range. These results demonstrated the existence of a genotoxic potential for DON at low concentrations compatible with actual exposure situations and calls for additional studies to determine the functional consequences which could be taken into account for the risk assessment of this food contaminant.

  5. Genotoxic effects of environmental endocrine disruptors on the aquatic insect Chironomus riparius evaluated using the comet assay.

    PubMed

    Martínez-Paz, Pedro; Morales, Mónica; Martínez-Guitarte, José Luis; Morcillo, Gloria

    2013-12-12

    Genotoxicity is one of the most important toxic endpoints in chemical toxicity testing and environmental risk assessment. The aim of this study was to evaluate the genotoxic potential of various environmental pollutants frequently found in aquatic environments and characterized by their endocrine disrupting activity. Monitoring of DNA damage was undertaken after in vivo exposures of the aquatic larvae of the midge Chironomus riparius, a model organism that represents an abundant and ecologically relevant macroinvertebrate, widely used in freshwater toxicology. DNA-induced damage, resulting in DNA fragmentation, was quantified by the comet assay after short (24 h) and long (96 h) exposures to different concentrations of the selected toxicants: bisphenol A (BPA), nonylphenol (NP), pentachlorophenol (PCP), tributyltin (TBT) and triclosan (TCS). All five compounds were found to have genotoxic activity as demonstrated by significant increases in all the comet parameters (%DNA in tail, tail length, tail moment and Olive tail moment) at all tested concentrations. Persistent exposure did not increase the extent of DNA damage, except for TCS at the highest concentration, but generally there was a reduction in DNA damage thought to be associated with the induction of the detoxification processes and repairing mechanisms. Comparative analysis showed differences in the genotoxic potential between the chemicals, as well as significant time and concentration-dependent variations, which most likely reflect differences in the ability to repair DNA damage under the different treatments. The present report demonstrates the sensitivity of the benthic larvae of C. riparius to these environmental genotoxins suggesting its potential as biomonitor organism in freshwater ecosystems. The results obtained about the DNA-damaging potential of these environmental pollutants reinforce the need for additional studies on the genotoxicity of endocrine active substances that, by linking genotoxic

  6. Evaluation of γ-radiation-induced DNA damage in two species of bivalves and their relative sensitivity using comet assay.

    PubMed

    Praveen Kumar, M K; Shyama, S K; Sonaye, B S; Naik, U Roshini; Kadam, S B; Bipin, P D; D'costa, A; Chaubey, R C

    2014-05-01

    Ionizing radiation is known to induce genetic damage in diverse groups of organisms. Under accidental situations, large quantities of radioactive elements get released into the environment and radiation emitted from these radionuclides may adversely affect both the man and the non-human biota. The present study is aimed (a) to know the genotoxic effect of gamma radiation on aquatic fauna employing two species of selected bivalves, (b) to evaluate the possible use of 'Comet assay' for detecting genetic damage in haemocytes of bivalves as a biomarker for environmental biomonitoring and also (c) to compare the relative sensitivity of two species of bivalves viz. Paphia malabarica and Meretrix casta to gamma radiation. The comet assays was optimized and validated using different concentrations (18, 32 and 56 mg/L) of ethyl methanesulfonate (EMS), a direct-acting reference genotoxic agent, to which the bivalves were exposed for various times (24, 48 and 72 h). Bivalves were irradiated (single acute exposure) with 5 different doses (viz. 2, 4, 6, 8 and 10 Gy) of gamma radiation and their genotoxic effects on the haemocytes were studied using the comet assay. Haemolymph was collected from the adductor muscle at 24, 48 and 72 h of both EMS-exposed and irradiated bivalves and comet assay was carried out using standard protocol. A significant increase in DNA damage was observed as indicated by an increase in % tail DNA damage at different concentrations of EMS and all the doses of gamma radiation as compared to controls in both bivalve species. This showed a dose-dependent increase of genetic damage induced in bivalves by EMS as well as gamma radiation. Further, the highest DNA damage was observed at 24h. The damage gradually decreased with time, i.e. was smaller at 48 and 72 h than at 24h post irradiation in both species of bivalves. This may indicate repair of the damaged DNA and/or loss of heavily damaged cells as the post irradiation time advanced. The present study

  7. Measurements of the genotoxic potential of (xeno-)oestrogens in the bivalve mollusc Scrobicularia plana, using the Comet assay.

    PubMed

    Petridis, Panos; Jha, Awadhesh N; Langston, William J

    2009-08-13

    There is increasing concern about the fate and effects of (geno)toxic and endocrine disrupting chemicals in sediments, highlighting the need to develop suitable monitoring tools. The deposit-feeding bivalve mollusc Scrobicularia plana has been put forward as a promising bioindicator of sediment contamination in estuaries. The recent demonstration of intersex in S. plana populations has been attributed to the feminisation of male clams following exposure to (xeno-)oestrogens, yet the mode of action of these endocrine disrupting chemicals (EDCs) remains largely unclear. One hypothesis that warrants further investigation is the possible involvement of genotoxicity. The first objective of this study was to assess whether the blood cells of S. plana are suitable for genotoxicity screening, using the alkaline single cell gel electrophoresis (Comet) assay. This was demonstrated successfully by exposing blood cells under in vitro conditions to a range of concentrations of the reference genotoxin hydrogen peroxide (H(2)O(2)): strong correlations between H(2)O(2) concentration and various comet parameters were found. Subsequently, the Comet assay was used to test whether the natural oestrogen 17beta-oestradiol (E2) and the synthetic (xeno)oestrogens ethinyloestradiol (EE2) and nonylphenol (NP) can produce genotoxic effects in S. plana, which might indicate possible involvement of mutagenicity in the mode of action of intersex development. In these short-term tests, clear genotoxic effects (significantly more DNA in the comet tail) were demonstrated by all EDCs, albeit only at high doses: 100 ng/L E2, 1 microg/L EE2 and 100 microg/L NP in vitro; and 1 microg/L E2 and 1mg/L NP after a 6-day in vivo exposure. Nevertheless, this study provides valuable preliminary data on the application and sensitivity of S. plana blood cells and suggests that the Comet assay is a useful tool, to screen for genotoxicity in in faunal clams and to examine further the links with higher order

  8. Evaluation of a multi-endpoint assay in rats, combining the bone-marrow micronucleus test, the Comet assay and the flow-cytometric peripheral blood micronucleus test.

    PubMed

    Bowen, Damian E; Whitwell, James H; Lillford, Lucinda; Henderson, Debbie; Kidd, Darren; Mc Garry, Sarah; Pearce, Gareth; Beevers, Carol; Kirkland, David J

    2011-05-18

    With the publication of revised draft ICH guidelines (Draft ICH S2), there is scope and potential to establish a combined multi-end point in vivo assay to alleviate the need for multiple in vivo assays, thereby reducing time, cost and use of animals. Presented here are the results of an evaluation trial in which the bone-marrow and peripheral blood (via MicroFlow(®) flow cytometry) micronucleus tests (looking at potential chromosome breakage and whole chromosome loss) in developing erythrocytes or young reticulocytes were combined with the Comet assay (measuring DNA strand-breakage), in stomach, liver and blood lymphocytes. This allowed a variety of potential target tissues (site of contact, site of metabolism and peripheral distribution) to be assessed for DNA damage. This combination approach was performed with minimal changes to the standard and regulatory recommended sampling times for the stand-alone assays. A series of eight in vivo genotoxins (2-acetylaminofluorene, benzo[a]pyrene, carbendazim, cyclophosphamide, dimethylnitrosamine, ethyl methanesulfonate, ethyl nitrosourea and mitomycin C), which are known to act via different modes of action (direct- and indirect-acting clastogens, alkylating agents, gene mutagens, cross-linking and aneugenic compounds) were tested. Male rats were dosed at 0, 24 and 45 h, and bone marrow and peripheral blood (micronucleus endpoint), liver, whole blood and stomach (Comet endpoint) were sampled at three hours after the last dose. Comet and micronucleus responses were as expected based on available data for conventional (acute) stand-alone assays. All compounds were detected as genotoxic in at least one of the endpoints. The importance of evaluating both endpoints was highlighted by the uniquely positive responses for certain chemicals (benzo[a]pyrene and 2-acetylaminofluorene) with the Comet endpoint and certain other chemicals (carbendazim and mitomycin C) with the micronucleus endpoint. The data generated from these

  9. Measurement of oxidatively-induced clustered DNA lesions using a novel adaptation of single cell gel electrophoresis (comet assay).

    PubMed

    Georgakilas, Alexandros G; Holt, Stewart M; Hair, Jessica M; Loftin, Charles W

    2010-12-01

    The two basic groups of complex DNA damage are double-strand breaks (DSBs) and non-DSB oxidatively-induced clustered DNA lesions (OCDLs). The single-cell gel electrophoresis (SCGE) or comet assay has been widely used for the detection of low levels of various types of DNA lesions including single-strand breaks (SSBs), DSBs, and oxidized bases per individual cell. There are limited data on the use of the comet assay for the detection of non-DSB clustered DNA lesions using different repair enzymes as enzymatic probes. This unit discusses a novel adaptation of the comet assay used to measure these unique types of lesions. Until now OCDL yields have been measured using primarily pulsed-field agarose gel electrophoresis. The advantages offered by the current approach are: (1) measurement of OCDL levels per individual cell; (2) use of a small number of cells (∼10,000) and relatively low doses of ionizing radiation (1 to 2 Gy) or low levels of oxidative stress, which are not compatible with standard agarose gel electrophoresis; and finally, (3) the assay is fast and allows direct comparison with pulsed-field gel electrophoresis results.

  10. Investigation of sodium arsenite, thioacetamide, and diethanolamine in the alkaline comet assay: Part of the JaCVAM comet validation exercise.

    PubMed

    Beevers, Carol; Henderson, Debbie; Lillford, Lucinda

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined sodium arsenite, thioacetamide, and diethanolamine. Using the JaCVAM approved study protocol version 14.2, each chemical was tested in male rats up to maximum tolerated dose levels and DNA damage in the liver and stomach was assessed approximately 3h after the final administration by gavage. Histopathology assessments of liver and stomach sections from the same animals were also examined for evidence of cytotoxicity or necrosis. No evidence of DNA damage was observed in the stomach of animals treated with sodium arsenite at 7.5, 15, or 30 mg/kg/day. However, equivocal findings were found in the liver, where increases in DNA migration were observed in two independent experiments, but not in all treated animals and not at the same dose levels. Thioacetamide caused an increase in DNA migration in the stomach of rats treated at 19, 38, and 75 mg/kg/day, but not in the liver, despite evidence of marked hepatotoxicity following histopathology assessments. No evidence of DNA damage was observed in the stomach or liver of animals treated with diethanolamine at 175, 350, or 700 mg/kg/day.

  11. Genotoxic effects of boric acid and borax in zebrafish, Danio rerio using alkaline comet assay

    PubMed Central

    Gülsoy, Nagihan; Yavas, Cüneyd; Mutlu, Özal

    2015-01-01

    The present study is conducted to determine the potential mechanisms of Boron compounds, boric acid (BA) and borax (BX), on genotoxicity of zebrafish Danio rerio for 24, 48, 72 and 96-hours acute exposure (level:1, 4, 16, 64 mg/l BA and BX) in semi-static bioassay experiment. For that purpose, peripheral erythrocytes were drawn from caudal vein and Comet assay was applied to assess genotoxicity. Acute (96 hours) exposure and high concentrations of boric acid and borax increases % tail DNA and Olive tail moment. Genotoxicity was found for BA as concentration-dependent and BX as concentration and time dependent manner. In general, significant effects (P < 0,05) on both concentrations and exposure times were observed in experimental groups. DNA damage was highest at 96 h and 24 h for all BX and BA concentrations, respectively in peripheral blood of D. rerio. For the first time, our study demonstrates the effect of waterborne BA and BX exposure on genotoxicity at the molecular level, which may contribute to understanding the mechanism of boric acid and borax-induced genotoxicity in fish. PMID:26862320

  12. Genotoxic effects of boric acid and borax in zebrafish, Danio rerio using alkaline comet assay.

    PubMed

    Gülsoy, Nagihan; Yavas, Cüneyd; Mutlu, Özal

    2015-01-01

    The present study is conducted to determine the potential mechanisms of Boron compounds, boric acid (BA) and borax (BX), on genotoxicity of zebrafish Danio rerio for 24, 48, 72 and 96-hours acute exposure (level:1, 4, 16, 64 mg/l BA and BX) in semi-static bioassay experiment. For that purpose, peripheral erythrocytes were drawn from caudal vein and Comet assay was applied to assess genotoxicity. Acute (96 hours) exposure and high concentrations of boric acid and borax increases % tail DNA and Olive tail moment. Genotoxicity was found for BA as concentration-dependent and BX as concentration and time dependent manner. In general, significant effects (P < 0,05) on both concentrations and exposure times were observed in experimental groups. DNA damage was highest at 96 h and 24 h for all BX and BA concentrations, respectively in peripheral blood of D. rerio. For the first time, our study demonstrates the effect of waterborne BA and BX exposure on genotoxicity at the molecular level, which may contribute to understanding the mechanism of boric acid and borax-induced genotoxicity in fish.

  13. Geosmin induces genomic instability in the mammalian cell microplate-based comet assay.

    PubMed

    Silva, Aline Flor; Lehmann, Mauricio; Dihl, Rafael Rodrigues

    2015-11-01

    Geosmin (GEO) (trans-1,10-dimethyl-trans-9-decalol) is a metabolite that renders earthy and musty taste and odor to water. Data of GEO genotoxicity on mammalian cells are scarce in the literature. Thus, the present study assessed the genotoxicity of GEO on Chinese hamster ovary (CHO) cells in the microplate-based comet assay. The percent of tail DNA (tail intensity (TI)), tail moment (TM), and tail length (TL) were used as parameters for DNA damage assessment. The results demonstrated that concentrations of GEO of 30 and 60 μg/mL were genotoxic to CHO cells after 4- and 24-h exposure periods, in all parameters evaluated, such as TI, TM, and TL. Additionally, GEO 15 μg/mL was genotoxic in the three parameters only in the 24-h exposure time. The same was observed for GEO 7.5 μg/mL, which induced significant DNA damage observed as TI in the 24-h treatment. The results present evidence that exposure to GEO may be associated with genomic instability in mammalian cells.

  14. Genotoxicity assessment of cobalt chloride in Eisenia hortensis earthworms coelomocytes by comet assay and micronucleus test.

    PubMed

    Ciğerci, İbrahim Hakkı; Ali, Muhammad Muddassir; Kaygısız, Şöhret Yüksek; Liman, Recep

    2016-02-01

    Cobalt and its different compounds are extensively used worldwide and considered as possible environmental pollutant. Earthworms are useful model organism and its different species are used to monitor soil pollution. No study has been found to detect cobalt chloride (CoCl2) genotoxicity in earthworms. So, current study aimed to evaluate CoCl2 induced genotoxicity in Eisenia hortensis earthworms coelomocytes by alkaline comet assay (CA) and micronucleus (MN) test. The earthworms (n = 10 for each group) were exposed to different series of CoCl2 concentrations (100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm) to find LD50. The LD50 for CoCl2 was found at 226 ppm. Then, doses of LD50/2, LD50 and 2XLD50 for 48 h were used. CA and MN demonstrated the significant increase (P < 0.05) in DNA damage and chromosomal aberrations. Dose dependent relationship was found. Highest DNA damage and chromosomal aberrations were noticed at 2XLD50. The results concluded that CoCl2 induced DNA damage, cytokinesis failure and chromosomal aberrations in E. hortensis earthworms.

  15. In vitro comet and micronucleus assays do not predict morphological transforming effects of silica particles in Syrian Hamster Embryo cells.

    PubMed

    Darne, Christian; Coulais, Catherine; Terzetti, Francine; Fontana, Caroline; Binet, Stéphane; Gaté, Laurent; Guichard, Yves

    2016-01-15

    Crystalline silica particles and asbestos have both been classified as carcinogenic by the International Agency for Research on Cancer (IARC). However, because of the limited data available, amorphous silica was not classifiable. In vitro, the carcinogenic potential of natural crystalline and amorphous silica particles has been revealed by the Syrian Hamster Embryo (SHE) cell transformation assay. On the other hand, the genotoxic potential of those substances has not been investigated in SHE cells. And yet, genotoxicity assays are commonly used for hazard evaluation and they are often used as in vitro assays of reference to predict a possible carcinogenic potential. The main objective of this study was to compare the genotoxic potential and the carcinogenic potential of different crystalline and amorphous silica particles in SHE cells. Three silica samples of different crystallinity were used: natural amorphous silica, partially crystallized silica and quartz silica particles. Their genotoxicity were tested through the in vitro micronucleus assay and the comet assay in SHE, and their carcinogenic potential through the SHE transformation assay. In addition, silica samples were also tested with the same genotoxicity assays in V79 hamster-lung cells, a common in vitro model for particle exposure. Results obtained in the micronucleus and the comet assays show that none of the silica was capable of inducing genotoxic effects in SHE cells and only the amorphous silica induced genotoxic effects in V79 cells. However in the SHE cell transformation assays, the partially crystallized and quartz silica were able to induce morphological cell transformation. Together, these data suggest that, in vitro, the short-term genotoxic assays alone are not sufficient to predict the hazard and the carcinogenic potential of this type of particles; SHE transformation assay appears a more reliable tool for this purpose and should be included in the "in vitro battery assays" for hazard

  16. Baseline values of micronuclei and comet assay in the lizard Tupinambis merianae (Teiidae, Squamata).

    PubMed

    Schaumburg, Laura G; Poletta, Gisela L; Siroski, Pablo A; Mudry, Marta D

    2012-10-01

    The Micronucleus test (MN) and Comet assay (CA) are currently the most widely used methods that allow the characterization of DNA damage induced by physical and chemical agents in wild species. The continuous expansion of the cultivated areas in Argentina, since the introduction of transgenic crops, mainly soy, in association with the increased use of pesticides, transformed deeply the natural environments where the lizard Tupinambis merianae (tegu lizard) occurs. Despite the fact that reptiles have shown to be excellent bioindicators of environmental contaminants, there is no record of genotoxicity studies in T. merianae. The aim of the present study was to adjust the MN test and CA protocols to be applied in erythrocytes of T. merianae, and determine the baseline values of DNA damage in this species. We used 20 adult lizards (10 males: 10 females) from Estación Zoológica Experimental "Granja La Esmeralda" (Santa Fe, Argentina). Peripheral blood samples were collected from all animals and the MN test and CA applied according to the protocols established for other reptilian species. We test critical parameters of CA protocol (cell density, unwinding and electrophoresis times) using increasing concentrations of H2O2 (10, 25 and 50 μM) as a known genotoxic agent to induce DNA damage. Based on this, we determined the most suitable conditions for the CA in this species: a cell density of 4×10(3) erythrocytes per slide, 10 min of unwinding and 15 min of electrophoresis at 0.90 V/cm approximately. The baseline frequency of micronuclei (BFMN=MN/1000 erythrocytes counted) determined for this species was 0.95±0.27 and the basal damage index (BDI: calculated from 100 comet images classified in arbitrary units)=103.85±0.97. No differences were observed between sexes in the BFMN or BDI (p>0.05), and no relation was found between baseline values and length or weight of the analyzed animals (p>0.05). These results demonstrated the sensitivity of both biomarkers of

  17. Evaluation of genotoxicity of coal fly ash in Allium cepa root cells by combining comet assay with the Allium test.

    PubMed

    Chakraborty, Rajarshi; Mukherjee, Ashit Kumar; Mukherjee, Anita

    2009-06-01

    Fly ash is a by-product of coal-fired electricity generation plants. Its utilization and disposal is of utmost importance. Using onion (Allium cepa) root tip system, the present study was carried out to evaluate the potential toxic and genotoxic effects of fly ash, collected from a thermal power plant in West Bengal, India. Prior to testing, the collected fly ash sample was mixed with sand in different proportions. Allium bulbs were allowed to germinate directly in fly ash and after five days the germinating roots were processed for the Allium test. Additionally, the Allium test was adapted for detecting DNA damage through comet assay. The results from the Allium test indicate that fly ash at 100% concentration inhibits root growth and mitotic indices; induces binucleated cells as a function of the proportion, but is not toxic at very low concentration. In the comet assay, a statistical increase for DNA strand breaks was found only at higher concentrations. The sample was analyzed by flame atomic absorption spectrometer for Zn, Pb, Cu, Ni, Cd and As, whose presence could partly be responsible for the toxicity of fly ash. The study concludes that the classical Allium test can give a more comprehensive data when done in combination with the comet assay, which is faster, simpler and independent of mitosis. Also when fly ash is used for other purposes in combination with soils, it should be judiciously used at very low concentrations in order to protect the ecosystem health from any potential adverse effects.

  18. Genotoxicity of Thermopsis turcica on Allium cepa L. roots revealed by alkaline comet and random amplified polymorphic DNA assays.

    PubMed

    Ciğerci, İbrahim Hakkı; Cenkci, Süleyman; Kargıoğlu, Mustafa; Konuk, Muhsin

    2016-08-01

    This study was undertaken to evaluate genotoxic potential of Thermopsis turcica aqueous extracts on the roots of onion bulb (Allium cepa L.) by comet assay and random amplified polymorphic DNA technique. The Allium root growth inhibition test indicated that the EC50 and 2×EC50 values were 8 and 16 mg/ml concentrations of T. turcica aqueous extracts, respectively. The negative control (distilled water), positive control (methyl methane sulfonate, 10 mg/l) and 8 and 16 mg/ml concentrations of T. turcica extracts were introduced to the roots of onion bulbs for 24 and 96 h. The root growth, DNA damage in root cells and randomly amplified polymorphic DNA (RAPD) profiles of root tissue were used as endpoints of the genotoxicity. The comet assay clearly indicated that dose-dependent single strand DNA breaks in the root nuclei of onions were determined for the treatment concentrations of T. turcica extracts. In comparison to RAPD profile of negative control group, RAPD polymorphisms became evident as disappearance and/or appearance of RAPD bands in treated roots. The diagnostic and phenetic numerical analyses of RAPD profiles obviously indicated dose-dependent genotoxicity induced by Thermopsis extracts. In conclusion, the results clearly indicated that water extract of T. turcica has genotoxic potential on the roots of onion bulbs as shown by comet assay and RAPD technique.

  19. Assessment of DNA damage in car spray painters exposed to organic solvents by the high-throughput comet assay.

    PubMed

    Londoño-Velasco, Elizabeth; Martínez-Perafán, Fabián; Carvajal-Varona, Silvio; García-Vallejo, Felipe; Hoyos-Giraldo, Luz Stella

    2016-05-01

    Occupational exposure as a painter is associated with DNA damage and development of cancer. Comet assay has been widely adopted as a sensitive and quantitative tool for DNA damage assessment at the individual cell level in populations exposed to genotoxics. The aim of this study was to assess the application of the high-throughput comet assay, to determine the DNA damage in car spray painters. The study population included 52 car spray painters and 52 unexposed subjects. A significant increase in the %TDNA median (p <  0.001) was observed in the exposed group in comparison to the unexposed group. Neither age (%TDNA: p =  0.913) nor time of exposure (%TDNA: p = 0.398) were significantly correlated with DNA damage. The car spray painters who consumed alcohol did not show a significant increase in DNA damage compared to nonalcohol consumers (p  > 0.05). The results showed an increase in DNA breaks in car spray painters exposed to organic solvents and paints; furthermore, they demonstrated the application of high-throughput comet assay in an occupational exposure study to genotoxic agents.

  20. Use of a standardized JaCVAM in vivo rat comet assay protocol to assess the genotoxicity of three coded test compounds; ampicillin trihydrate, 1,2-dimethylhydrazine dihydrochloride, and N-nitrosodimethylamine.

    PubMed

    McNamee, J P; Bellier, P V

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), our laboratory examined ampicillin trihydrate (AMP), 1,2-dimethylhydrazine dihydrochloride (DMH), and N-nitrosodimethylamine (NDA) using a standard comet assay validation protocol (v14.2) developed by the JaCVAM validation management team (VMT). Coded samples were received by our laboratory along with basic MSDS information. Solubility analysis and range-finding experiments of the coded test compounds were conducted for dose selection. Animal dosing schedules, the comet assay processing and analysis, and statistical analysis were conducted in accordance with the standard protocol. Based upon our blinded evaluation, AMP was not found to exhibit evidence of genotoxicity in either the rat liver or stomach. However, both NDA and DMH were observed to cause a significant increase in % tail DNA in the rat liver at all dose levels tested. While acute hepatoxicity was observed for these compounds in the high dose group, in the investigators opinion there were a sufficient number of consistently damaged/measurable cells at the medium and low dose groups to judge these compounds as genotoxic. There was no evidence of genotoxicity from either NDA or DMH in the rat stomach. In conclusion, our laboratory observed increased DNA damage from two blinded test compounds in rat liver (later identified as genotoxic carcinogens), while no evidence of genotoxicity was observed for the third blinded test compound (later identified as a non-genotoxic, non-carcinogen). This data supports the use of a standardized protocol of the in vivo comet assay as a cost-effective alternative genotoxicity assay for regulatory testing purposes.

  1. Determination of genotoxic effects of Imazethapyr herbicide in Allium cepa root cells by mitotic activity, chromosome aberration, and comet assay.

    PubMed

    Liman, Recep; Ciğerci, İbrahim Hakkı; Öztürk, Nur Serap

    2015-02-01

    Imazethapyr (IM) is an imidazolinone herbicide that is currently used for broad-spectrum weed control in soybean and other legume crops. In this study, cytotoxic and genotoxic effects of IM were investigated by using mitotic index (MI), mitotic phases, chromosomal abnormalities (CAs) and DNA damage on the root meristem cells of Allium cepa. In Allium root growth inhibition test, EC50 value was determined as 20 ppm, and 0.5xEC50, EC50 and 2xEC50 concentrations of IM herbicide were introduced to onion tuber roots. Distilled water and methyl methane sulfonate (MMS, 10 mg/L) were used as a negative and positive control, respectively. As A. cepa cell cycle is 24 hours, so, application process was carried out for 24, 48, 72 and 96 hours. All the applied doses decreased MIs compared to control group and these declines were found to be statistically meaningful. Analysis of the chromosomes showed that 10 ppm IM except for 48 h induced CAs but 40 ppm IM except for 72 h decreased CAs. DNA damage was found significantly higher in 20 and 40 ppm of IM compared to the control in comet assay. These results indicated that IM herbicide exhibits cytotoxic activity but not genotoxic activity (except 10 ppm) and induced DNA damage in a dose dependent manner in A. cepa root meristematic cells.

  2. Monitoring of DNA breakage in embryonic stages of the African catfish Clarias gariepinus (Burchell, 1822) after exposure to lead nitrate using alkaline comet assay.

    PubMed

    Osman, Alaa G M; Mekkawy, Imam A; Verreth, Johan; Wuertz, Sven; Kloas, Werner; Kirschbaum, Frank

    2008-12-01

    Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead-caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 microg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post-fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA < or = 10%), low damaged (10% < %TDNA < or = 25%), median damaged (25 < %TDNA < or = 50%), highly damaged (50 < %TDNA < or = 75%), and extremely damaged (%TDNA > 75%) nuclei confirming a dose and time-dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h-PFS and 48 h-PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects.

  3. The potential value of the neutral comet assay and the expression of genes associated with DNA damage in assessing the radiosensitivity of tumor cells.

    PubMed

    Jayakumar, Sundarraj; Bhilwade, Hari N; Pandey, Badri N; Sandur, Santosh K; Chaubey, Ramesh C

    2012-10-09

    The assessment of tumor radiosensitivity would be particularly useful in optimizing the radiation dose during radiotherapy. Therefore, the degree of correlation between radiation-induced DNA damage, as measured by the alkaline and the neutral comet assays, and the clonogenic survival of different human tumor cells was studied. Further, tumor radiosensitivity was compared with the expression of genes associated with the cellular response to radiation damage. Five different human tumor cell lines were chosen and the radiosensitivity of these cells was established by clonogenic assay. Alkaline and neutral comet assays were performed in γ-irradiated cells (2-8Gy; either acute or fractionated). Quantitative PCR was performed to evaluate the expression of DNA damage response genes in control and irradiated cells. The relative radiosensitivity of the cell lines assessed by the extent of DNA damage (neutral comet assay) immediately after irradiation (4Gy or 6Gy) was in agreement with radiosensitivity pattern obtained by the clonogenic assay. The survival fraction of irradiated cells showed a better correlation with the magnitude of DNA damage measured by the neutral comet assay (r=-0.9; P<0.05; 6Gy) than evaluated by alkaline comet assay (r=-0.73; P<0.05; 6Gy). Further, a significant correlation between the clonogenic survival and DNA damage was observed in cells exposed to fractionated doses of radiation. Of 15 genes investigated in the gene expression study, HSP70, KU80 and RAD51 all showed significant positive correlations (r=0.9; P<0.05) with tumor radiosensitivity. Our study clearly demonstrated that the neutral comet assay was better than alkaline comet assay for assessment of radiosensitivities of tumor cells after acute or fractionated doses of irradiation.

  4. Analysis of IUE observations of hydrogen in comets

    NASA Technical Reports Server (NTRS)

    Combi, Michael R.; Feldman, Paul D.

    1993-01-01

    The large body of hydrogen Lyman-alpha observations of cometary comae obtained with the International Ultraviolet Explorer satellite has gone generally unanalyzed because of two main modeling complications. First, the inner comae of many bright (gas productive) comets are often optically thick to solar Lyman-alpha radiation. Second, even in the case of a small comet (low gas production) the large IUE aperture is quite small as compared with the immense size of the hydrogen coma, so an accurate model which properly accounts for the spatial distribution of the coma is required to invert the inferred brightnesses to column densities and finally to H atom production rates. Our Monte Carlo particle trajectory model (MPTM), which for the first time provides the realistic full phase space distribution of H atoms throughout the coma was used as the basis for the analysis of IUE observations of the inner coma. The MCPTM includes the effects of the vectorial ejection of the H atoms upon dissociation of their parent species (H2O and OH) and of their partial collisional thermalization. Both of these effects are crucial to characterize the velocity distribution of the H atoms. A new spherical radiative transfer calculation based on our MCPTM was developed to analyze IUE observations of optically thick H comae. The models were applied to observations of comets P/Giacobini-Zinner and P/Halley.

  5. Comet Tempel 2: Orbit, ephemerides and error analysis

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1978-01-01

    The dynamical behavior of comet Tempel 2 is investigated and the comet is found to be very well behaved and easily predictable. The nongravitational forces affecting the motion of this comet are the smallest of any comet that is affected by nongravitational forces. The sign and time history of these nongravitational forces imply (1) a direct rotation of the comet's nucleus and (2) the comet's ability to outgas has not changed substantially over its entire observational history. The well behaved dynamical motion of the comet, the well observed past apparitions, the small nongravitational forces and the excellent 1988 ground based observing conditions all contribute to relatively small position and velocity errors in 1988 -- the year of a proposed rendezvous space mission to this comet. To assist in planned ground based and earth orbital observations of this comet, ephemerides are given for the 1978-79, 1983-84 and 1988 apparitions.

  6. The comet assay in Environmental Risk Assessment of marine pollutants: applications, assets and handicaps of surveying genotoxicity in non-model organisms.

    PubMed

    Martins, Marta; Costa, Pedro M

    2015-01-01

    Determining the genotoxic effects of pollutants has long been a priority in Environmental Risk Assessment (ERA) for coastal ecosystems, especially of complex areas such as estuaries and other confined waterbodies. The acknowledged link between DNA damage, mutagenicity and carcinogenicity to the exposure to certain toxicants has been responsible to the growing interest in determining the genotoxic effects of xenobiotics to wildlife as a measure of environmental risk. The comet assay, although widely employed in in vivo and in vitro toxicology, still holds many constraints in ERA, in large part owing to difficulties in obtaining conclusive cause-effect relationships from complex environments. Nevertheless, these challenges do not hinder the attempts to apply the alkaline comet assay on sentinel organisms, wild or subjected to bioassays in or ex situ (from fish to molluscs) as well to standardise protocols and establish general guidelines to the interpretation of findings. Fish have been regarded as an appealing subject due to the ease of performing the comet assay in whole blood. However, the application of the comet assay is becoming increasingly common in invertebrates (e.g. in molluscan haemocytes and solid tissues such as gills). Virtually all sorts of results have been obtained from the application of the comet assay in ERA (null, positive and inconclusive). However, it has become clear that interpreting DNA damage data from wild organisms is particularly challenging due to their ability to adapt to continuous environmental stressors, including toxicants. Also, the comet assay in non-model organisms for the purpose of ERA implies different constraints, assumptions and interpretation of findings, compared with the in vitro procedures from which most guidelines have been derived. This paper critically reviews the application of the comet assay in ERA, focusing on target organisms and tissues; protocol developments, case studies plus data handling and

  7. Genotoxicity of cyanobacterial extracts containing microcystins from Polish water reservoirs as determined by SOS chromotest and comet assay.

    PubMed

    Mankiewicz, Joanna; Walter, Zofia; Tarczynska, Malgorzata; Palyvoda, Olena; Wojtysiak-Staniaszczyk, Magdalena; Zalewski, Maciej

    2002-01-01

    Toxicity of cyanobacterial blooms, an increasing problem around the world, is connected to the increase in bloom samples containing microcystins, caused by excessive eutrophication of drinking- and recreational water reservoirs. Microcystins are the most common group of cyanobacterial hepatotoxins. In Poland they are produced mainly by the Microcystis genus. The toxicity of microcystins has been well documented, but investigation into their genotoxicity has been insufficient relative to the study of their overall toxicity. Therefore, the aim of this study was the estimation and comparison of the genotoxicity of cyanobacterial extracts with microcystins (CEMs) using the SOS chromotest (bacterial test) with Escherichia coli PQ37 and the comet assay with human lymphocytes. Cyanobacterial bloom samples were collected in the summer months from two Polish water reservoirs, one at Sulejów and one at Jeziorsko. The SOS chromotest, which used prokaryotic cells (without metabolic activation), and the comet assay, which used eukaryotic cells, both indicated the potential genotoxic effect of CEMs. Cyanobacterial extracts caused DNA damage in human lymphocytes in vitro. The maximum level of DNA damage was observed after 12 h incubation with CEMs. The bacterial test indicated a dependence of the degree of CEM genotoxicity, the composition, and the concentration of microcystins in each bloom sample examined with the time of exposure. Differences between the genotoxicity of cyanobacterial extract and the standard microcystin-LR were noticeable. This was probably caused by the interaction of different microcystin variants. The results showed that CEMs from Polish water reservoirs were genotoxic, which was reflected by the stimulation of the SOS repair system in bacterial cells (SOS chromotest) and by the damage induced in DNA in human lymphocytes (comet assay).

  8. Measurement of X-ray-induced DNA double-strand breaks at various stages of the cell cycle using the total fluorescence as a comet assay parameter

    NASA Astrophysics Data System (ADS)

    Attia, Atef M. M.; Nabil, Ghada M.; Frankenberg, Dieter; Frankenberg-Schwager, M.

    2011-11-01

    The aim of the study was to develop a protocol for both estimating cell cycle position and the level of ionizing radiation-induced DNA dsb using the neutral comet assay. Using DNA histograms, cell cycle positions were determined for human dermal fibroblasts. The tail intensity was used to estimate the level of DNA damage induced by X-rays, at different positions of the cell cycle. The results of tail intensity versus DNA content bivariate analysis of exponentially growing cells showed a remarkable decrease in tail intensity with transition of cells from G1 to S-phase and increases 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 is not relevant to measure DNA damage at various stages of the cell cycle. The results of dose response curves showed a linear decrease in the comet fluorescence with the X-ray dose. 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 new approach 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/G1 cells.These results suggest that G0 and G2/M cells are the most sensitive to X-rays among all phases of the cell cycle and suggest synchronization of cells at these phases to increase the cellular radiosensitivity during radiotherapy.

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

    PubMed

    Martín-Cameán, Ana; Puerto, María; Jos, Ángeles; Azqueta, Amaya; Iglesias-Linares, Alejandro; Solano, Enrique; Cameán, Ana M

    2015-01-01

    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.

  10. Genotoxicity evaluation of locally produced dental porcelain--an in vitro study using the Ames and Comet assays.

    PubMed

    Noushad, Mohammed; Kannan, Thirumulu Ponnuraj; Husein, Adam; Abdullah, Haswati; Ismail, Abdul Rashid

    2009-09-01

    The aim of this study was to determine the genotoxicity of a locally produced dental porcelain (Universiti Sains Malaysia, Malaysia) using the Ames and Comet assays. In the Ames assay, four genotypic variants of the Salmonella strains (TA98, TA100, TA1537 and TA1535) carrying mutations in several genes were used. The dental porcelain was incubated with these four strains in five different doses both in the presence and absence of metabolic activation (S9) and the result was assessed based on the number of revertant colonies. Concurrently, appropriate positive controls were used so as to validate the test. The average number of revertant colonies per plate treated with locally produced dental porcelain was less than double as compared to that of negative control. In the Comet assay, L929 (CCL-1 ATCC, USA) mouse fibroblast cells were treated with the dental porcelain in three different concentrations along with concurrent negative and positive controls. The tail moment which was used as a measurement of DNA damage was almost equal to that of the negative control, suggesting that the locally produced dental porcelain did not induce any DNA damage. The results indicated that the locally produced dental porcelain is non-genotoxic under the present test conditions.

  11. DNA damage induced by coal dust, fly and bottom ash from coal combustion evaluated using the micronucleus test and comet assay in vitro.

    PubMed

    Matzenbacher, Cristina Araujo; Garcia, Ana Letícia Hilario; Dos Santos, Marcela Silva; Nicolau, Caroline Cardoso; Premoli, Suziane; Corrêa, Dione Silva; de Souza, Claudia Telles; Niekraszewicz, Liana; Dias, Johnny Ferraz; Delgado, Tânia Valéria; Kalkreuth, Wolfgang; Grivicich, Ivana; da Silva, Juliana

    2017-02-15

    Coal mining and combustion generating huge amounts of bottom and fly ash are major causes of environmental pollution and health hazards due to the release of polycyclic aromatic hydrocarbons (PAH) and heavy metals. The Candiota coalfield in Rio Grande do Sul, is one of the largest open-cast coal mines in Brazil. The aim of this study was to evaluate genotoxic and mutagenic effects of coal, bottom ash and fly ash samples from Candiota with the comet assay (alkaline and modified version) and micronucleus test using the lung fibroblast cell line (V79). Qualitative and quantitative analysis of PAH and inorganic elements was carried out by High Performance Liquid Chromatography (HPLC) and by Particle-Induced X-ray Emission (PIXE) techniques respectively. The samples demonstrated genotoxic and mutagenic effects. The comet assay modified using DNA-glicosilase formamidopirimidina (FPG) endonuclease showed damage related to oxidative stress mechanisms. The amount of PAHs was higher in fly ash followed by pulverized coal. The amount of inorganic elements was highest in fly ash, followed by bottom ash. It is concluded that the samples induce DNA damage by mechanisms that include oxidative stress, due to their complex composition, and that protective measures have to be taken regarding occupational and environmental hazards.

  12. Comet assay with gill cells of Mytilus galloprovincialis end point tools for biomonitoring of water antibiotic contamination: Biological treatment is a reliable process for detoxification.

    PubMed

    Mustapha, Nadia; Zouiten, Amina; Dridi, Dorra; Tahrani, Leyla; Zouiten, Dorra; Mosrati, Ridha; Cherif, Ameur; Chekir-Ghedira, Leila; Mansour, Hedi Ben

    2016-04-01

    This article investigates the ability of Pseudomonas peli to treat industrial pharmaceuticals wastewater (PW). Liquid chromatography-mass spectrometry (MS)/MS analysis revealed the presence, in this PW, of a variety of antibiotics such as sulfathiazole, sulfamoxole, norfloxacine, cloxacilline, doxycycline, and cefquinome.P. peli was very effective to be grown in PW and inducts a remarkable increase in chemical oxygen demand and biochemical oxygen demand (140.31 and 148.51%, respectively). On the other hand, genotoxicity of the studied effluent, before and after 24 h of shaking incubation with P. peli, was evaluated in vivo in the Mediterranean wild mussels Mytilus galloprovincialis using comet assay for quantification of DNA fragmentation. Results show that PW exhibited a statistically significant (p< 0.001) genotoxic effect in a dose-dependent manner; indeed, the percentage of genotoxicity was 122.6 and 49.5% after exposure to 0.66 ml/kg body weight (b.w.); 0.33 ml/kg b.w. of PW, respectively. However, genotoxicity decreased strongly when tested with the PW obtained after incubation with P. peli We can conclude that using comet assay genotoxicity end points are useful tools to biomonitor the physicochemical and biological quality of water. Also, it could be concluded that P. peli can treat and detoxify the studied PW.

  13. Analysis of organic compounds in returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.

    1989-01-01

    Techniques for analysis of organic compounds in returned comet nucleus samples are described. Interstellar, chondritic and transitional organic components are discussed. Appropriate sampling procedures will be essential to the success of these analyses. It will be necessary to return samples that represent all the various regimes found in the nucleus, e.g., a complete core, volatile components (deep interior), and crustal components (surface minerals, rocks, processed organics such as macromolecular carbon and polymers). Furthermore, sampling, storage, return, and distribution of samples must be done under conditions that preclude contamination of the samples by terrestrial matter.

  14. The effects on DNA migration of altering parameters in the comet assay protocol such as agarose density, electrophoresis conditions and durations of the enzyme or the alkaline treatments.

    PubMed

    Ersson, Clara; Möller, Lennart

    2011-11-01

    The single cell gel electrophoresis (comet assay) is a popular method for measuring DNA migration as an estimate of DNA damage. No standardised comet assay protocol exists, which make comparisons between studies complicated. In a previous inter-laboratory validation study of the comet assay, we identified important parameters in the protocol that might affect DNA migration. The aim of this study was to assess how different comet assay protocols affect DNA migration. The results in this study suggest that (i) there is a significant linear dose-response relationship between the agarose gel's density and DNA migration and that damaged cells are more sensitive to the agarose gel's density; (ii) incubation with formamidopyrimidine DNA glycosylase for 10 min is inadequate, whereas 30 min is sufficient; (iii) the typically used 20 min of alkaline treatment might be to short when analysing samples that contain particular alkali-labile sites (ALS) and (iv) the duration of electrophoresis as well as the strength of the electric field applied affects the DNA migration. By using protocol-specific calibration curves, it is possible to reduce the variation in DNA migration caused by differences in comet assay protocols. This does, however, not completely remove the impact of the durations of alkaline treatment and electrophoresis when analysing cells containing ALS that are relatively resistant to high alkaline treatment.

  15. Assessment of DNA damage by comet assay and fast halo assay in buccal epithelial cells of Indian women chronically exposed to biomass smoke.

    PubMed

    Mondal, Nandan Kumar; Bhattacharya, Purba; Ray, Manas Ranjan

    2011-07-01

    Genotoxicity of indoor air pollution from biomass burning was evaluated in buccal epithelial cells (BECs) of 85 pre-menopausal Indian women who were engaged in cooking with biomass (wood, dung, crop residues) and 76 age-matched control women who were cooking with cleaner fuel liquefied petroleum gas (LPG). DNA damage was evaluated by comet assay and fast halo assay (FHA). The concentrations of particulate matter with aerodynamic diameters of less than 10 and 2.5 μm (PM(10) and PM(2.5), respectively) in indoor air were measured by real-time aerosol monitor. Generation of reactive oxygen species (ROS) was measured by flow cytometry and the level of superoxide dismutase (SOD) by spectrophotometry. Compared with control, BEC of biomass users illustrated 2.6-times higher comet tail % DNA (32.2 vs. 12.4, p < 0.001), 2.7-times greater comet tail length (37.8 μm vs. 14.2 μm, p < 0.001) and 2.2-times more olive tail moment (7.1 vs. 3.2, p < 0.001), suggesting marked increase in DNA damage. FHA also showed 5-times more mean nuclear diffusion factor (9.2 vs. 1.8, p < 0.0001) in BEC of biomass users, confirming sharp rise in DNA single strand breaks. Airway cells of biomass-using women showed 51% rise in ROS generation but 28% reduction in SOD, suggesting oxidative stress in the airways. Indoor air of biomass-using households had 3-times more PM(10) and PM(2.5) than LPG-using families, and DNA damage showed positive association with PM(10) and PM(2.5) levels controlling education, kitchen location and family income as potential confounders. In summary, chronic inhalation of biomass smoke elicits oxidative stress and extensive DNA damage in BEC.

  16. Assessing the genotoxic potentials of roxarsone in V79 cells using the alkaline Comet assay and micronucleus test.

    PubMed

    Zhang, Yumei; Ying, Jun; Chen, Jun; Hu, Chenyun

    2012-01-24

    Until recently, knowledge about the genotoxicity of roxarsone in vitro or in vivo was limited. This study assessed the genotoxicity of roxarsone in an in vitro system. Roxarsone was tested for potential genotoxicity on V79 cells by a Comet assay and a micronucleus (MN) test, exposing the cells to roxarsone (1-500 μM) and to sodium arsenite (NaAsO₂, 20 μM) solutions for 3-48 h. Roxarsone was found to be cytotoxic when assessed with a commercial cell counting kit (CCK-8) used to evaluate cell viability, and moderately genotoxic in the Comet assay and micronucleus test used to assess DNA damage. The Comet metrics (percentages TDNA, TL, TM) increased significantly in a time- and concentration-dependent manner in roxarsone-treated samples compared with PBS controls (P<0.05), while the data from samples treated with 20 μM NaAsO₂ were comparable to those from 500 μM roxarsone-treated samples. The MN frequency of V79 cells treated with roxarsone was higher than that in the negative control but lower than the frequency in cells treated with 20 μM NaAsO₂. A dose- and time-dependent response in MN induction was observed at 10, 50, 100 and 500 μM doses of roxarsone after 12-48 h exposure time. The DNA damage in V79 cells treated with 500 μM roxarsone was similar to cells exposed to 20 μM NaAsO₂. The uptake of cells was correlated with the DNA damage caused by roxarsone. This investigation depicts the genotoxic potentials of roxarsone to V79 cells, which could lead to further advanced studies on the genotoxicity of roxarsone.

  17. Double-stranded DNA breaks hidden in the neutral Comet assay suggest a role of the sperm nuclear matrix in DNA integrity maintenance.

    PubMed

    Ribas-Maynou, J; Gawecka, J E; Benet, J; Ward, W S

    2014-04-01

    We used a mouse model in which sperm DNA damage was induced to understand the relationship of double-stranded DNA (dsDNA) breaks to sperm chromatin structure and to the Comet assay. Sperm chromatin fragmentation (SCF) produces dsDNA breaks located on the matrix attachment regions, between protamine toroids. In this model, epididymal sperm induced to undergo SCF can religate dsDNA breaks while vas deferens sperm cannot. Here, we demonstrated that the conventional neutral Comet assay underestimates the epididymal SCF breaks because the broken DNA ends remain attached to the nuclear matrix, causing the DNA to remain associated with the dispersion halo, and the Comet tails to be weak. Therefore, we term these hidden dsDNA breaks. When the Comet assay was modified to include an additional incubation with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) after the conventional lysis, thereby solubilizing the nuclear matrix, the broken DNA was released from the matrix, which resulted in a reduction of the sperm head halo and an increase in the Comet tail length, exposing the hidden dsDNA breaks. Conversely, SCF-induced vas deferens sperm had small halos and long tails with the conventional neutral Comet assay, suggesting that the broken DNA ends were not tethered to the nuclear matrix. These results suggest that the attachment to the nuclear matrix is crucial for the religation of SCF-induced DNA breaks in sperm. Our data suggest that the neutral Comet assay identifies only dsDNA breaks that are released from the nuclear matrix and that the addition of an SDS treatment can reveal these hidden dsDNA breaks.

  18. Evaluation of DNA damage induced by environmental exposure to mercury in Liza aurata using the comet assay.

    PubMed

    Pereira, Carla Sofia Alves; Guilherme, Sofia Isabel Antunes Gomes; Barroso, Carlos Miguel Miguez; Verschaeve, Luc; Pacheco, Mário Guilherme Garcês; Mendo, Sónia Alexandra Leite Velho

    2010-01-01

    Mercury (Hg) is one of the major aquatic contaminants even though emissions have been reduced over the years. Despite the relative abundance of investigations carried out on Hg toxicity, there is a scarcity of studies on its DNA damaging effects in fish under realistic exposure conditions. This study assessed the Hg genotoxicity in Golden grey mullets (Liza aurata) at Laranjo basin, a particularly contaminated area of Ria de Aveiro (Portugal) well known for its Hg contamination gradient. (1) Fish were seasonally caught at Laranjo basin and at a reference site (S. Jacinto), and (2) animals from the reference site were transplanted and caged (at bottom and surface), for 3 days, in two different locations within Laranjo basin. Using the comet assay, blood was analyzed for genetic damage and apoptotic cell frequency. The seasonal survey showed greater DNA damage in the Hg-contaminated area for all sampling seasons excluding winter. The temporal variation pattern of DNA lesions was: summer approximately autumn > winter > spring. Fish caged at Laranjo also exhibited greater DNA damage than those caged at the reference site, highlighting the importance of gill uptake on the toxicity of this metal. No increased susceptibility to apoptosis was detected in either wild or caged fish, indicating that mercury damages DNA of blood cells by a nonapoptotic mechanism. Both L. aurata and the comet assay proved to be sensitive and suitable for genotoxicity biomonitoring in mercury-contaminated coastal systems.

  19. Construction and validation of a dose-response curve using the comet assay to determine human radiosensitivity to ionizing radiation.

    PubMed

    Güerci, A; Zúñiga, L; Marcos, R

    2011-01-01

    Individual radiosensitivity is an individual characteristic associated with an increased reaction to ionizing radiation. The purpose of our work is to establish a dose-response curve useful to classify individuals as radiosensitive or radioresistant. Thus, a dose-response curve was constructed by measuring in vitro responses to increasing doses (0 to 8 Gy) of gamma radiation in the comet assay. The obtained curve fit well with a linear equation in the range of 0 to 8 Gy. The overall dose-response curve was constructed for percent DNA in tail, as a measure of the genetic damage induced by irradiation. To probe the goodness of the constructed curve, a validation study was carried out with whole blood from two donors in a blind study. Results show that, for the two applied doses (2 and 6 Gy), the obtained values fit well inside the interval of confidence of the curve. In conclusion, our results demonstrate the usefulness of the comet assay in determining individual responses to defined doses of gamma radiation. The standard dose-response curve constructed may be used to detect individuals departing from reference values.

  20. In vitro assessment of genotoxic effects of electric arc furnace dust on human lymphocytes using the alkaline comet assay.

    PubMed

    Garaj-Vrhovac, Vera; Orescanin, Visnja; Ruk, Damir; Gajski, Goran

    2009-02-15

    In vitro genotoxic effects of leachates of electric arc furnace dust (EAFD) on human peripheral lymphocytes, assessed prior and following the treatment with a strong alkaline solution were investigated using the alkaline comet assay. Prior and following the treatment, lymphocytes were incubated with leachate of EAFD for 6 and 24 hours at 37 degrees C. Negative controls were also included. Mean values of the tail lengths established in the samples treated with the leachate stemming from the original dust for 6 and 24 hours, were 15.70 microm and 16.78 microm, respectively, as compared to 12.33 microm found in the control sample. Slight, but significant increase in the tail length was also found with the dust treated with a strong alkaline solution (13.37 microm and 13.60 microm). In case of high heavy metal concentrations (the extract of the original furnace dust), the incubation period was revealed to be of significance as well. The obtained results lead to the conclusion that alkaline comet assay could be used as a rapid, sensitive and low-cost tool when assessing genotoxicity of various waste materials, such as leachates of the electric arc furnace dust.

  1. DNA damage detected by the comet assay in the white blood cells of workers in a wooden furniture plant.

    PubMed

    Palus, J; Dziubałtowska, E; Rydzyński, K

    1999-07-21

    The study was aimed at the assessment of genotoxic effects in workers of a wooden furniture manufacture, based on the level of DNA damage in white blood cells (WBC). The alkaline single cell gel electrophoresis assay (known as the comet assay) in individual cells was adapted for detecting damaged DNA in WBC. The level of DNA damage was determined as the percentage of cells with comets. It was assessed in cells before and after incubation in RPMI 1640 medium and CO(2) at 37 degrees C for 1 h to repair DNA breaks. Thirty-five woodworkers and 41 control subjects were studied. In the woodworkers, significantly more cells with DNA damage (21.5%) were observed than in the control persons (9.7%). A slight but significant decrease in the level of DNA damage was found in the WBC of woodworkers after incubation (17.2%). Significantly higher levels of damaged DNA was observed in woodworkers who either smoked (22.1%) or did not smoke cigarettes (20.8%) than in smokers (13.2%) and non-smokers (7.0%) from the control group. After incubation, a slight decrease in the level of DNA damage was found in both smoking and non-smoking woodworkers compared to the respective subjects in the control group. The increased levels of DNA damage observed in the woodworkers could be associated with the occupational exposure to wood dust in the furniture manufacture.

  2. Genotoxicity Assessment of Volatile Organic Compounds in Landfill Gas Emission Using Comet Assay in Higher Terrestrial Plant.

    PubMed

    Na Roi-Et, Veerapas; Chiemchaisri, Wilai; Chiemchaisri, Chart

    2017-02-01

    Genotoxicity model is developed to assess the individual subacute toxicity of benzene, toluene, ethylbenzene, and xylene (BTEX) at very low levels as in a landfill gas. Golden Pothos (Epipremnum aureum), a higher plant, was tested under variation of benzene 54-5656 ng/L, toluene 10-4362 ng/L, ethylbenzene 28-4997 ng/L, xylene 53-4845 ng/L, for 96 h. DNA fragmentation in plant leaves were investigated via comet assay. The results show that DNA migration ratio increased with the BTEX concentrations, but at different rates. The 50% effective concentration (EC50) of DNA fragmentation from the dose-response relationships indicated toluene has the highest EC50 value and followed by benzene, xylene and ethylbenzene. Alternatively, ethylbenzene has the highest toxicity unit and followed by xylene, benzene and toluene as described by toxicity unit (TU). In conclusion, comet assay of Pothos can be used in differentiating DNA fragmentation against very low levels of BTEX in the atmosphere. Pothos is recommended for genotoxicity assessment of a low BTEX contaminated atmosphere.

  3. Vehicle and positive control values from the in vivo rodent comet assay and biomonitoring studies using human lymphocytes: historical database and influence of technical aspects.

    PubMed

    Pant, Kamala; Springer, S; Bruce, S; Lawlor, T; Hewitt, N; Aardema, M J

    2014-10-01

    There is increased interest in the in vivo comet assay in rodents as a follow-up approach for determining the biological relevance of chemicals that are genotoxic in in vitro assays. This is partly because, unlike other assays, DNA damage can be assessed in this assay in virtually any tissue. Since background levels of DNA damage can vary with the species, tissue, and cell processing method, a robust historical control database covering multiple tissues is essential. We describe extensive vehicle and positive control data for multiple tissues from rats and mice. In addition, we report historical data from control and genotoxin-treated human blood. Technical issues impacting comet results are described, including the method of cell preparation and freezing. Cell preparation by scraping (stomach and other GI tract organs) resulted in higher % tail DNA than mincing (liver, spleen, kidney etc) or direct collection (blood or bone marrow). Treatment with the positive control genotoxicant, ethyl methanesulfonate (EMS) in rats and methyl methanesulfonate in mice, resulted in statistically significant increases in % tail DNA. Background DNA damage was not markedly increased when cell suspensions were stored frozen prior to preparing slides, and the outcome of the assay was unchanged (EMS was always positive). In conclusion, historical data from our laboratory for the in vivo comet assay for multiple tissues from rats and mice, as well as human blood show very good reproducibility. These data and recommendations provided are aimed at contributing to the design and proper interpretation of results from comet assays.

  4. Assessment of the in vivo genotoxicity of cadmium chloride, chloroform, and D,L-menthol as coded test chemicals using the alkaline comet assay.

    PubMed

    Wada, Kunio; Fukuyama, Tomoki; Nakashima, Nobuaki; Matsumoto, Kyomu

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) international validation study of in vivo rat alkaline comet assays, we examined cadmium chloride, chloroform, and D,L-menthol under blind conditions as coded chemicals in the liver and stomach of Sprague-Dawley rats after 3 days of administration. Cadmium chloride showed equivocal responses in the liver and stomach, supporting previous reports of its poor mutagenic potential and non-carcinogenic effects in these organs. Treatment with chloroform, which is a non-genotoxic carcinogen, did not induce DNA damage in the liver or stomach. Some histopathological changes, such as necrosis and degeneration, were observed in the liver; however, they did not affect the comet assay results. D,L-Menthol, a non-genotoxic non-carcinogen, did not induce liver or stomach DNA damage. These results indicate that the comet assay can reflect genotoxic properties under blind conditions.

  5. Assessment of genotoxic damage by the comet assay in white storks (Ciconia ciconia) after the Doñana Ecological Disaster.

    PubMed

    Pastor, N; López-Lázaro, M; Tella, J L; Baos, R; Hiraldo, F; Cortés, F

    2001-05-01

    Single cell gel electrophoresis, the so-called "Comet" assay, was performed as a genotoxicity test in white storks sampled in an area heavily contaminated after the ecological disaster in south western Spain. This disaster occurred as a consequence of a massive toxic spillage of acid waste rich in heavy metals that impacted on the Doñana National Park. The importance of this protected area as a breeding and wintering site for many endangered bird species makes this analysis of DNA damage of special interest. Our results clearly show that white storks born in the contaminated area 1 year after the toxic spill bear a high burden of genetic damage as compared with control individuals. The possible implications for future survival as well as reproductive rate are discussed.

  6. The JaCVAM international validation study on the in vivo comet assay: Selection of test chemicals.

    PubMed

    Morita, Takeshi; Uno, Yoshifumi; Honma, Masamitsu; Kojima, Hajime; Hayashi, Makoto; Tice, Raymond R; Corvi, Raffaella; Schechtman, Leonard

    2015-07-01

    The Japanese Center for the Validation of Alternative Methods (JaCVAM) sponsored an international prevalidation and validation study of the in vivo rat alkaline pH comet assay. The main objective of the study was to assess the sensitivity and specificity of the assay for correctly identifying genotoxic carcinogens, as compared with the traditional rat liver unscheduled DNA synthesis assay. Based on existing carcinogenicity and genotoxicity data and chemical class information, 90 chemicals were identified as primary candidates for use in the validation study. From these 90 chemicals, 46 secondary candidates and then 40 final chemicals were selected based on a sufficiency of carcinogenic and genotoxic data, differences in chemical class or genotoxic or carcinogenic mode of action (MOA), availability, price, and ease of handling. These 40 chemicals included 19 genotoxic carcinogens, 6 genotoxic non-carcinogens, 7 non-genotoxic carcinogens and 8 non-genotoxic non-carcinogens. "Genotoxicity" was defined as positive in the Ames mutagenicity test or in one of the standard in vivo genotoxicity tests (primarily the erythrocyte micronucleus assay). These chemicals covered various chemicals classes, MOAs, and genotoxicity profiles and were considered to be suitable for the purpose of the validation study. General principles of chemical selection for validation studies are discussed.

  7. Protective activity of cedron (Aloysia triphylla) infusion over genetic damage induced by cisplatin evaluated by the comet assay technique.

    PubMed

    Zamorano-Ponce, Enrique; Fernández, Julia; Vargas, Gilda; Rivera, Pilar; Carballo, Marta A

    2004-08-30

    Using the comet assay technique, this paper examines the protection from the cisplatin-induced genetic damage in mouse bone marrow cells provided by cedron-leaf infusion. Animals were separated into six groups: (I) untreated, (II) negative control, (III) treated with cedron-leaf infusion (5%), (IV) treated with cisplatin (6 mg/kg b.w.), (V) pretreated with infusion and treated with cisplatin and (VI) positive control (cyclophosphamide, 20 mg/kg b.w.). Based on the tail moment values found, four types of comets were distinguished. No statistical differences (P<0.01) were found between untreated animals, negative control and infusion treated mice. As expected, treatment of mice with a single dose of cis-DDP-induced genetic damage and the pretreatment with infusion prior to cis-DDP injection inhibited the capacity of cisplatin to induce genetic damage. Cell viability was up to 90% in all cases. The results suggest that infusion could exert its in vivo antigenotoxic action by enhancing the antioxidant status of bone marrow cells. The found could be attributed to its scavenging potency towards free radicals.

  8. An investigation of the DNA-damaging ability of benzene and its metabolites in human lymphocytes, using the Comet assay

    SciTech Connect

    Anderson, D.; Yu, T.W.; Schmezer, P. |

    1995-12-31

    Benzene and five of its known metabolites-muconic acid, hydroquinone, catechol, p-benzoquinone, and benzentriol-were examined for DNA damage in human lymphocytes using the alkaline Comet assay, and conditions were optimised to determine responses. When comets were measured by eye after treatment with hydrogen peroxide (H{sup 2}O{sup 2}), the positive control, and each compound for 0.5 hr, only H{sup 2}O{sup 2} and benzenetrial induced pronounced DNA damage without metabolic activation. The effect of catechol was moderate compared, with that of benzenetriol. There was a very weak effect of benzene in the absence of rat liver S-9 mix. In the presence of S-9 mix, benzene was not activated. The effect of benzenetriol was greatly reduced by the external metabolishing system, but p-benzoquinone became activated o some extent. Catalase abolished the effect of benzenetriol, suggesting that H{sup 2}O{sup 2} formed during autoxidation may be responsible for the DNA-damaging ability of this metabolite. Mitogen-stimulated cycling cells were less sensitive to H{sup 2}O{sup 2} and benzenetrial than unstimulated G{sub O} lymphocytes. Effects tended to become more pronounced at high doses and after longer exposures, although this was not always consistent from experiment to experiment. In conclusion, benzene and all metabolites investigated gave positive responses. Where altered responses were observed, they were significantly different from the corresponding controls. 46 refs., 7 tabs.

  9. Workshop on Analysis of Returned Comet Nucleus Samples

    NASA Astrophysics Data System (ADS)

    Chang, Sherwood

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  10. Genotoxicity of field-collected inter-tidal sediments from Cork Harbor, Ireland, to juvenile turbot (Scophthalmus maximus L.) as measured by the Comet assay.

    PubMed

    Kilemade, M F; Hartl, M G J; Sheehan, D; Mothersill, C; Van Pelt, F N A M; O'Halloran, J; O'Brien, N M

    2004-01-01

    The alkaline single cell gel electrophoresis (SCGE) or Comet assay was employed to test the potential of surficial sediment collected from Cork Harbor, Ireland, to induce DNA damage in turbot (Scophthalmus maximus L.) in a laboratory exposure experiment. Turbot were exposed for 21 days to field-collected sediment from Cork Harbor and from a relatively clean reference site at Ballymacoda and sampled at 0, 7, 14, and 21 days. As a positive control for the sediment exposure experiment, a subsample of the turbot was exposed to cadmium chloride-spiked seawater. DNA damage analysis was performed on epidermal, gill, spleen, liver, and whole blood cell preparations. Liver, gill, and blood were the most sensitive tissues while a lower level of damage was detected in the epidermis and spleen. The blood was determined to be a suitable predictor of DNA damage in the whole organism. Chemical analysis of the sediment indicated that polycyclic aromatic hydrocarbons formed the bulk of the contaminants, with the harbor sites having almost double the levels of those from the reference site. The data indicated that turbot exposed to sediments from Cork Harbor elicited a significant increase in DNA damage in comparison with those exposed to sediment from the reference site and that exposure to the contaminated sediments caused a multi-organ genotoxic response. Results from the study indicate a relationship between the presence of genotoxicants in sediment and DNA damage. This finding was encouraging with regard to the potential use of the Comet assay as part of a marine biomonitoring strategy.

  11. Effects of freezing-thawing on DNA integrity of boar spermatozoa assessed by the neutral comet assay.

    PubMed

    Fraser, L; Strzezek, J

    2005-12-01

    A modified version of the neutral comet assay was employed to evaluate the effect of the freezing-thawing process on boar-sperm DNA integrity. The sperm-rich fractions were collected from four mature boars and frozen into aluminium tubes and straws after extension in lactose-hen egg yolk-glycerol extender (lactose-HEY-G) or an extender containing lactose, lyophilized lipoprotein fractions extracted from ostrich egg yolk and glycerol (lactose-LPFo-G). The semen samples were also frozen in a standard boar semen extender (Kortowo-3), without the addition of cryoprotective substances. Post-thaw sperm motility and plasma membrane integrity, assessed by SYBR-14/PI and Hoechst 33258 stains, declined (p < or = 0.05) with a corresponding increase (p < or = 0.05) in sperm DNA damage, regardless of the extender type and packaging material. Spermatozoa frozen in lactose-HEY-G or lactose-LPFo-G extender showed lower (p < or = 0.05) DNA damage than those frozen in the absence of cryoprotective substances. The addition of HEY or LPFo to the freezing extender helped reduce the rate of cryo-damage to sperm DNA, which varied among the boars. Inter-boar variations in post-thaw DNA damage were more pronounced in sperm samples frozen in lactose-HEY-G or lactose-LPFo-G extender. The results of this study show that the freezing-thawing process affects the DNA integrity of boar spermatozoa, irrespective of the extender type and packaging material. Furthermore, the use of whole hen egg yolk and ostrich lyophilized lipoprotein fractions in the freezing extender gave similar results regarding sperm DNA integrity. It can be concluded that the neutral comet assay can be used in conjunction with routine sperm parameters for assessment of post-thaw quality of boar semen.

  12. Genotoxicity of chlorpyrifos in freshwater fish Labeo rohita using Alkaline Single-cell Gel Electrophoresis (Comet) assay.

    PubMed

    Ismail, Muhammad; Khan, Qaiser Mahmood; Ali, Rahat; Ali, Tayyaba; Mobeen, Ameena

    2014-10-01

    Chlorpyrifos is a widely used insecticide of organophosphate group, which causes severe toxicological effects in non target aquatic organisms especially in fish. In the present study the genotoxic effects of sublethal concentrations of chlorpyrifos were observed in the erythrocytes and gill cells of Labeo rohita (commonly known as rohu) using the Alkaline Single-Cell Gel Electrophoresis (Comet) assay. Effects of chlorpyrifos on the behavior of the fish were also investigated. The 96 h LC50 value of chlorpyrifos, estimated by Trimmed Spearman-Karber (TSK) in static bioassay, was found to be 442.8 µg/L. On the basis of LC50 value, the fish were exposed to three sublethal concentrations of chlorpyrifos (SL-I ∼221.4 µg/L, SL- II ∼110.7 µg/L and SL-III ∼73.8 µg/L) for 96 h. Blood and gill samples were collected at every 24 h and were subjected to the Comet assay. The observed DNA damage was concentration dependent and time dependent and those levels of DNA damage in between the tested concentrations and times were significantly different (p < 0.01). It was also found that the gill cells are more sensitive to chlorpyrifos, though; it revealed more DNA damage as compared to the erythrocytes of fish. Fish exposed to different concentrations of chlorpyrifos showed different neurotoxic behavioral responses. It was concluded that chlorpyrifos is a genotoxic and neurotoxic insecticide causing DNA damage and neurotoxic effects in Labeo rohita.

  13. Effect of electromagnetic radiofrequency radiation on the rats' brain, liver and kidney cells measured by comet assay.

    PubMed

    Trosić, Ivancica; Pavicić, Ivan; Milković-Kraus, Sanja; Mladinić, Marin; Zeljezić, Davor

    2011-12-01

    The goal of study was to evaluate DNA damage in rat's renal, liver and brain cells after in vivo exposure to radiofrequency/microwave (Rf/Mw) radiation of cellular phone frequencies range. To determine DNA damage, a single cell gel electrophoresis/comet assay was used. Wistar rats (male, 12 week old, approximate body weight 350 g) (N = 9) were exposed to the carrier frequency of 915 MHz with Global System Mobile signal modulation (GSM), power density of 2.4 W/m2, whole body average specific absorption rate SAR of 0.6 W/kg. The animals were irradiated for one hour/day, seven days/week during two weeks period. The exposure set-up was Gigahertz Transversal Electromagnetic Mode Cell (GTEM--cell). Sham irradiated controls (N = 9) were apart of the study. The body temperature was measured before and after exposure. There were no differences in temperature in between control and treated animals. Comet assay parameters such as the tail length and tail intensity were evaluated. In comparison with tail length in controls (13.5 +/- 0.7 microm), the tail was slightly elongated in brain cells of irradiated animals (14.0 +/- 0.3 microm). The tail length obtained for liver (14.5 +/- 0.3 microm) and kidney (13.9 +/- 0.5 microm) homogenates notably differs in comparison with matched sham controls (13.6 +/- 0.3 microm) and (12.9 +/- 0.9 microm). Differences in tail intensity between control and exposed animals were not significant. The results of this study suggest that, under the experimental conditions applied, repeated 915 MHz irradiation could be a cause of DNA breaks in renal and liver cells, but not affect the cell genome at the higher extent compared to the basal damage.

  14. Leucocytes isolated from simply frozen whole blood can be used in human biomonitoring for DNA damage measurement with the comet assay.

    PubMed

    Akor-Dewu, Maryam B; El Yamani, Naouale; Bilyk, Olena; Holtung, Linda; Tjelle, Torunn E; Blomhoff, Rune; Collins, Andrew R

    2014-04-01

    Preservation of human blood cells for DNA damage analysis with the comet assay conventionally involves the isolation of mononuclear cells by centrifugation, suspension in freezing medium and slow freezing to -80 °C-a laborious process. A recent publication (Al-Salmani et al. Free Rad Biol Med 2011; 51: 719-725) describes a simple method in which small volumes of whole blood are frozen to -20 or -80 °C; on subsequent thawing, the comet assay is performed, with no indication of elevated DNA strand breakage resulting from the rapid freezing. However, leucocytes in whole blood (whether fresh or frozen) are abnormally resistant to damage by H2 O2 , and so a common test of antioxidant status (resistance to strand breakage by H2 O2 ) cannot be used. We have refined this method by separating the leucocytes from the thawed blood; we find that, after three washes, the cells respond normally to H2 O2 . In addition, we have measured specific endogenous base damage (oxidized purines) in the isolated leucocytes, using the enzyme formamidopyrimidine DNA glycosylase. In a study of blood samples from 10 subjects, H2 O2 sensitivity and endogenous damage-both reflecting the antioxidant status of the cells-correlated significantly. This modified approach to sample collection and storage is particularly applicable when the available volume of blood is limited and has great potential in biomonitoring and ecogenotoxicology studies where samples are obtained in the field or at sites remote from the testing laboratory.

  15. Differences in quantification of DNA double-strand breaks assessed by 53BP1/γH2AX focus formation assays and the comet assay in mammalian cells treated with irradiation and N-acetyl-L-cysteine.

    PubMed

    Kurashige, Tomomi; Shimamura, Mika; Nagayama, Yuji

    2016-06-01

    The biological effect of ionizing radiation (IR) on genomic DNA is thought to be either direct or indirect; the latter is mediated by IR induction of free radicals and reactive oxygen species (ROS). This study was designed to evaluate the effect of N-acetyl-L-cysteine (NAC), a well-known ROS-scavenging antioxidant, on IR induction of genotoxicity, cytotoxicity and ROS production in mammalian cells, and aimed to clarify the conflicting data in previous publications. Although we clearly demonstrate the beneficial effect of NAC on IR-induced genotoxicity and cytotoxicity (determined using the micronucleus assay and cell viability/clonogenic assays), the data on NAC's effect on DNA double-strand break (DSB) formation were inconsistent in different assays. Specifically, mitigation of IR-induced DSBs by NAC was readily detected by the neutral comet assay, but not by the γH2AX or 53BP1 focus assays. NAC is a glutathione precursor and exerts its effect after conversion to glutathione, and presumably it has its own biological activity. Assuming that the focus assay reflects the biological responses to DSBs (detection and repair), while the comet assay reflects the physical status of genomic DNA, our results indicate that the comet assay could readily detect the antioxidant effect of NAC on DSB formation. However, NAC's biological effect might affect the detection of DSB repair by the focus assays. Our data illustrate that multiple parameters should be carefully used to analyze DNA damage when studying potential candidates for radioprotective compounds.

  16. Evaluation of genetic damage in tobacco and arsenic exposed population of Southern Assam, India using buccal cytome assay and comet assay.

    PubMed

    Roy, Prasenjit; Mukherjee, Anita; Giri, Sarbani

    2016-02-01

    Ground water is the principal source of drinking water in Assam. Ground water contamination of arsenic in drinking water is a great concern for human health and considered as a human carcinogen. The present cytogenetic biomonitoring study was undertaken to investigate the genotoxic effects associated with people of southern Assam consuming arsenic contaminated water and chewing tobacco. Employing the buccal cytome assay, exfoliated cells were analyzed in 138 individuals of age range 22-42 years and divided into four groups. Group I (n=54) are participants residing in localities where ground water contains arsenic concentration below the permissible limit (<10μg/l) and without any tobacco chewing history. Group II (n=32) participants from the same area but they are tobacco chewers. Group III (n=24) participants from localities where significantly high arsenic contamination in ground water were observed. Whereas the Group IV (n=28) consists of participants from the arsenic contaminated area and also tobacco chewers. Body mass index (BMI) in all the groups are found to be nearly same and in normal range. Statistically significant (P<0.001) increase in genotoxic, cell death parameters and cell proliferation biomarkers were observed in the Group IV compared to other groups. In the comet assay, percent of tail DNA gradually increases among the groups and has statistical significance. Spearman correlation revealed strong positive correlation between the arsenic exposed peoples and the binucleated cells (r=0.4763; P<0.001). Amount of chewing tobacco had significant positive correlation with micronucleus frequency (r=0.268; P<0.05) and karyolitic cells (r=0.217; P<0.05) and also in the percentage of tail DNA (r=0.5532, P<0.001). A statistically significant increase in glucose content and decrease in hemoglobin content as well as acetylcholine esterase in the blood of exposed individuals was observed. Our preliminary study indicate that population exposed to arsenic through

  17. Ephemeris data and error analysis in support of a Comet Encke intercept mission

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1974-01-01

    Utilizing an orbit determination based upon 65 observations over the 1961 - 1973 interval, ephemeris data were generated for the 1976-77, 1980-81 and 1983-84 apparitions of short period comet Encke. For the 1980-81 apparition, results from a statistical error analysis are outlined. All ephemeris and error analysis computations include the effects of planetary perturbations as well as the nongravitational accelerations introduced by the outgassing cometary nucleus. In 1980, excellent observing conditions and a close approach of comet Encke to the earth permit relatively small uncertainties in the cometary position errors and provide an excellent opportunity for a close flyby of a physically interesting comet.

  18. Genotoxicity of doxorubicin in F344 rats by combining the comet assay, flow-cytometric peripheral blood micronucleus test, and pathway-focused gene expression profiling.

    PubMed

    Manjanatha, Mugimane G; Bishop, Michelle E; Pearce, Mason G; Kulkarni, Rohan; Lyn-Cook, Lascelles E; Ding, Wei

    2014-01-01

    Doxorubicin (DOX) is an antineoplastic drug effective against many human malignancies. DOX's clinical efficacy is greatly limited because of severe cardiotoxicity. To evaluate if DOX is genotoxic in the heart, ~7-week-old, male F344 rats were administered intravenously 1, 2, and 3 mg/kg bw DOX at 0, 24, 48, and 69 hr and the Comet assays in heart, liver, kidney, and testis and micronucleus (MN) assay in the peripheral blood (PB) erythrocytes using flow cytometry were conducted. Rats were euthanized at 72 hr and PB was removed for the MN assay and single cells were isolated from multiple tissues for the Comet assays. None of the doses of DOX induced a significant DNA damage in any of the tissues examined by the alkaline Comet assay. Contrastingly, the glycosylase enzymes-modified Comet assay showed a significant dose dependent increase in the oxidative DNA damage in the cardiac tissue (P ≤ 0.05). In the liver, only the top dose induced significant increase in the oxidative DNA damage (P ≤ 0.05). The histopathology showed no severe cardiotoxicity but non-neoplastic lesions were present in both untreated and treated samples. A severe toxicity likely occurred in the bone marrow because no viable reticulocytes could be screened for the MN assay. Gene expression profiling of the heart tissues showed a significant alteration in the expression of 11 DNA damage and repair genes. These results suggest that DOX is genotoxic in the heart and the DNA damage may be induced primarily via the production of reactive oxygen species.

  19. Application of the micronucleus test and comet assay in Trachemys callirostris erythrocytes as a model for in situ genotoxic monitoring.

    PubMed

    Zapata, Lina M; Bock, Brian C; Orozco, Luz Yaneth; Palacio, Jaime A

    2016-05-01

    Trachemys callirostris is a turtle species endemic to northern South America. In northern Colombia it occurs in the middle and lower Magdalena River drainage and its principal tributaries (lower Cauca and San Jorge rivers) and in other minor drainages such as the lower Sinú River. In recent years, industrial, agricultural, and mining activities have altered natural habitats in Colombia where this species occurs, and many of the pollutants released there are known to induce genetic alterations in wildlife species. The micronucleus test and comet assay are two of the most widely used methods to characterize DNA damage induced by physical and chemical agents in wildlife species, but have not been employed previously for genotoxic evaluations in T. callirostris. The goal of this study was to optimize these genotoxic biomarkers for T. callirostris erythrocytes in order to establish levels of DNA damage in this species and thereby evaluate its potential as a sentinel species for monitoring genotoxic effects in freshwater environments in northern Colombia. Both genotoxic techniques were applied on peripheral blood erythrocytes from 20 captive-reared T. callirostris individuals as a negative control, as well as from samples obtained from 49 individuals collected in Magangué (Magdalena River drainage) and 24 individuals collected in Lorica (Sinú River drainage) in northern Colombia. Negative control individuals exhibited a baseline frequency of micronuclei of 0.78±0.58 and baseline values for comet tail length and tail moment of 3.34±0.24µm and 10.70±5.5, respectively. In contrast, samples from both field sites exhibited significantly greater evidence of genotoxic effects for both tests. The mean MN frequencies in the samples from Magangué and Lorica were 8.04±7.08 and 12.19±12.94, respectively. The mean tail length for samples from Magangué and Lorica were 5.78±3.18 and 15.46±7.39, respectively. Finally, the mean tail moment for samples from Magangué and

  20. The Comet Assay and its applications in the field of ecotoxicology: a mature tool that continues to expand its perspectives.

    PubMed

    de Lapuente, Joaquín; Lourenço, Joana; Mendo, Sónia A; Borràs, Miquel; Martins, Marta G; Costa, Pedro M; Pacheco, Mário

    2015-01-01

    Since Singh and colleagues, in 1988, launched to the scientific community the alkaline Single Cell Gel Electrophoresis (SCGE) protocol, or Comet Assay, its uses and applications has been increasing. The thematic areas of its current employment in the evaluation of genetic toxicity are vast, either in vitro or in vivo, both in the laboratory and in the environment, terrestrial or aquatic. It has been applied to a wide range of experimental models: bacteria, fungi, cells culture, arthropods, fishes, amphibians, reptiles, mammals, and humans. This document is intended to be a comprehensive review of what has been published to date on the field of ecotoxicology, aiming at the following main aspects: (i) to show the most relevant experimental models used as bioindicators both in the laboratory and in the field. Fishes are clearly the most adopted group, reflecting their popularity as bioindicator models, as well as a primary concern over the aquatic environment health. Amphibians are among the most sensitive organisms to environmental changes, mainly due to an early aquatic-dependent development stage and a highly permeable skin. Moreover, in the terrestrial approach, earthworms, plants or mammalians are excellent organisms to be used as experimental models for genotoxic evaluation of pollutants, complex mix of pollutants and chemicals, in both laboratory and natural environment. (ii) To review the development and modifications of the protocols used and the cell types (or tissues) used. The most recent developments concern the adoption of the enzyme linked assay (digestion with lesion-specific repair endonucleases) and prediction of the ability to repair of oxidative DNA damage, which is becoming a widespread approach, albeit challenging. For practical/technical reasons, blood is the most common choice but tissues/cells like gills, sperm cells, early larval stages, coelomocytes, liver or kidney have been also used. (iii) To highlight correlations with other biomarkers

  1. The Comet Assay and its applications in the field of ecotoxicology: a mature tool that continues to expand its perspectives

    PubMed Central

    de Lapuente, Joaquín; Lourenço, Joana; Mendo, Sónia A.; Borràs, Miquel; Martins, Marta G.; Costa, Pedro M.; Pacheco, Mário

    2015-01-01

    Since Singh and colleagues, in 1988, launched to the scientific community the alkaline Single Cell Gel Electrophoresis (SCGE) protocol, or Comet Assay, its uses and applications has been increasing. The thematic areas of its current employment in the evaluation of genetic toxicity are vast, either in vitro or in vivo, both in the laboratory and in the environment, terrestrial or aquatic. It has been applied to a wide range of experimental models: bacteria, fungi, cells culture, arthropods, fishes, amphibians, reptiles, mammals, and humans. This document is intended to be a comprehensive review of what has been published to date on the field of ecotoxicology, aiming at the following main aspects: (i) to show the most relevant experimental models used as bioindicators both in the laboratory and in the field. Fishes are clearly the most adopted group, reflecting their popularity as bioindicator models, as well as a primary concern over the aquatic environment health. Amphibians are among the most sensitive organisms to environmental changes, mainly due to an early aquatic-dependent development stage and a highly permeable skin. Moreover, in the terrestrial approach, earthworms, plants or mammalians are excellent organisms to be used as experimental models for genotoxic evaluation of pollutants, complex mix of pollutants and chemicals, in both laboratory and natural environment. (ii) To review the development and modifications of the protocols used and the cell types (or tissues) used. The most recent developments concern the adoption of the enzyme linked assay (digestion with lesion-specific repair endonucleases) and prediction of the ability to repair of oxidative DNA damage, which is becoming a widespread approach, albeit challenging. For practical/technical reasons, blood is the most common choice but tissues/cells like gills, sperm cells, early larval stages, coelomocytes, liver or kidney have been also used. (iii) To highlight correlations with other biomarkers

  2. Evaluation of drinking water treatment combined filter backwash water recycling technology based on comet and micronucleus assay.

    PubMed

    Chen, Ting; Xu, Yongpeng; Liu, Zhiquan; Zhu, Shijun; Shi, Wenxin; Cui, Fuyi

    2016-04-01

    Based on the fact that recycling of combined filter backwash water (CFBW) directly to drinking water treatment plants (WTP) is considered to be a feasible method to enhance pollutant removal efficiency, we were motivated to evaluate the genotoxicity of water samples from two pilot-scale drinking water treatment systems, one with recycling of combined backwash water, the other one with a conventional process. An integrated approach of the comet and micronucleus (MN) assays was used with zebrafish (Danio rerio) to investigate the water genotoxicity in this study. The total organic carbon (TOC), dissolved organic carbon (DOC), and trihalomethane formation potential (THMFP), of the recycling process were lower than that of the conventional process. All the results showed that there was no statistically significant difference (P>0.05) between the conventional and recycling processes, and indicated that the genotoxicity of water samples from the recycling process did not accumulate in 15 day continuous recycling trial. It was worth noting that there was correlation between the concentrations of TOC, DOC, UV254, and THMFPs in water and the DNA damage score, with corresponding R(2) values of 0.68, 0.63, 0.28, and 0.64. Nevertheless, both DNA strand breaks and MN frequency of all water samples after disinfection were higher than that of water samples from the two treatment units, which meant that the disinfection by-products (DBPs) formed by disinfection could increase the DNA damage. Both the comet and MN tests suggest that the recycling process did not increase the genotoxicity risk, compared to the traditional process.

  3. Induction and repair of DNA cross-links induced by sulfur mustard in the A-549 cell line followed by a comet assay.

    PubMed

    Jost, Petr; Svobodova, Hana; Stetina, Rudolf

    2015-07-25

    Sulfur mustard is a highly toxic chemical warfare agent with devastating impact on intoxicated tissues. DNA cross-links are probably the most toxic DNA lesions induced in the cell by sulfur mustard. The comet assay is a very sensitive method for measuring DNA damage. In the present study using the A-549 lung cell line, the comet assay protocol was optimized for indirect detection of DNA cross-links induced by sulfur mustard. The method is based on the additional treatment of the assayed cells containing cross-links with the chemical mutagen, styrene oxide. Alkali-labile adducts of styrene oxide cause DNA breaks leading to the formation of comets. A significant dose-dependent reduction of DNA migration of the comet's tail was found after exposing cells to sulfur mustard, indicative of the amount of sulfur mustard induced cross-links. The remarkable decrease of % tail DNA could be observed as early as 5min following exposure to sulfur mustard and the maximal effect was found after 30min, when DNA migration was reduced to the minimum. Sulfur mustard preincubated in culture medium without cells lost its ability to induce cross-links and had a half-life of about 15min. Pre-incubation longer than 30min does not lead to a significant increase in cross-links when applied to cells. However, the amount of cross-links is decreased during further incubation due to repair. The current modification of the comet assay provides a useful tool for detecting DNA cross-links induced by sulfur mustard and could be used for detection of other DNA cross-linking agents such as chemotherapeutic drugs.

  4. Genotoxic effects of the alkaloids harman and harmine assessed by comet assay and chromosome aberration test in mammalian cells in vitro.

    PubMed

    Boeira, J M; da Silva, J; Erdtmann, B; Henriques, J A

    2001-12-01

    Harman and harmine are beta-carboline alkaloids which are present in plants widely used in medical practice, in beverages used for religious purposes in Brazil, as well as in tobacco smoke and over cooked food. In view of the controversial results observed in the literature about the mutagenic effects of these alkaloids, we studied their cytotoxic and genotoxic effects in V79 Chinese hamster lung fibroblasts in vitro using single-cell gel assay, Comet assay, either in the presence or in absence of an exogenous metabolic activation system (S9-mix), and by the chromosome aberration test without S9-mix. Harmine was more cytotoxic than harman. Both harman and harmine increased aberrant cell frequency and induced DNA damage by the Comet assay. These results suggest that harman and harmine are genotoxic in V79 cells, probably as a consequence of their ability to induce DNA strand breaks.

  5. New osculating orbits for 110 comets and analysis of original orbits for 200 comets

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.; Sekanina, Z.; Everhart, E.

    1978-01-01

    Osculating orbits are presented for 110 nearly parabolic comets. Combining these with selected orbit determinations from other sources, a total of 200 orbits are considered where the available observations yield a result of very good (first-class) or good (second-class) quality. For each of these, the original and future orbits (referred to the barycenter of the solar system) are calculated. The Oort effect (a tendency for original reciprocal semimajor axis values to range from zero to +100 millionths per AU) is clearly seen among the first-class orbits but not among the second-class orbits. Modifications in original reciprocal semimajor axis values due to the effects of nongravitational forces are considered.

  6. Aerothermodynamic Analysis of Commercial Experiment Transporter (COMET) Reentry Capsule

    NASA Technical Reports Server (NTRS)

    Wood, William A.; Gnoffo, Peter A.; Rault, Didier F. G.

    1996-01-01

    An aerothermodynamic analysis of the Commercial Experiment Transporter (COMET) reentry capsule has been performed using the laminar thin-layer Navier-Stokes solver Langley Aerothermodynamic Upwind Relaxation Algorithm. Flowfield solutions were obtained at Mach numbers 1.5, 2, 5, 10, 15, 20, 25, and 27.5. Axisymmetric and 5, 10, and 20 degree angles of attack were considered across the Mach-number range, with the Mach 25 conditions taken to 90 degrees angle of attack and the Mach 27.5 cases taken to 60 degrees angle of attack. Detailed surface heat-transfer rates were computed at Mach 20 and 25, revealing that heating rates on the heat-shield shoulder ,can exceed the stagnation-point heating by 230 percent. Finite-rate chemistry solutions were performed above Mach 10, otherwise perfect gas computations were made. Drag, lift, and pitching moment coefficients are computed and details of a wake flow are presented. The effect of including the wake in the solution domain was investigated and base pressure corrections to forebody drag coefficients were numerically determined for the lower Mach numbers. Pitching moment comparisons are made with direct simulation Monte Carlo results in the more rarefied flow at the highest Mach numbers, showing agreement within two-percent. Thin-layer Navier-Stokes computations of the axial force are found to be 15 percent higher across the speed range than the empirical/Newtonian based results used during the initial trajectory analyses.

  7. Genotoxicity of a thiosulfonate compound derived from Allium sp. intended to be used in active food packaging: In vivo comet assay and micronucleus test.

    PubMed

    Mellado-García, Pilar; Puerto, María; Prieto, Ana I; Pichardo, Silvia; Martín-Cameán, Ana; Moyano, Rosario; Blanco, Alfonso; Cameán, Ana M

    2016-04-01

    Components of Allium species have antimicrobial and antioxidant properties. A commercial Allium sp. extract (Proallium AP(®)), of which the main constituent is propyl thiosulphinate oxide (PTSO), is being used in the development of active food packaging. In previous in vitro genotoxicity studies, PTSO, in the presence of metabolic activation, increased the appearance of micronuclei (MN). We assessed the genotoxicity PTSO in rats following oral administration (doses: 5.5, 17.4, and 55mg/kg). The comet assay in liver and stomach (OECD 489) and the MN assay in bone marrow (OECD 474) were carried out. After necropsy, histopathological examinations of the liver and the stomach were performed. The results revealed no in vivo genotoxicity and the histopathological analysis showed only slight modifications, such as increased glycogen storage in the liver and a degenerative process in stomach, with vacuolization of cell membranes, only at the highest dose. Therefore, the present work confirms that this compound is not genotoxic and could be considered as a natural alternative to synthetic preservatives used in the food packaging industry.

  8. Comparative study of the comet assay and the micronucleus test in amphibian larvae (Xenopus laevis) using benzo(a)pyrene, ethyl methanesulfonate, and methyl methanesulfonate: establishment of a positive control in the amphibian comet assay.

    PubMed

    Mouchet, F; Gauthier, L; Mailhes, C; Ferrier, V; Devaux, A

    2005-02-01

    The present investigation explored the potential use of the comet assay (CA) as a genotoxicity test in the amphibian Xenopus laevis and compared it with the French standard micronucleus test (MNT). Benzo[a]pyrene (B[a]P), methyl methanesulfonate (MMS), and ethyl methanesulfonate (EMS) were used as model compounds for assessing DNA damage. Damage levels were measured as DNA strand breaks after alkaline electrophoresis of nuclei isolated from larval amphibian erythrocytes using the CA in order to establish a positive control for further ecotoxicological investigations. The results led to the selection of MMS as a positive control on the basis of the higher sensitivity of Xenopus laevis to this compound. The CA and MNT were compared for their ability to detect DNA damage with the doses of chemical agents and exposure times applied. EMS and MMS were shown to increase micronucleus and DNA strand break formation in larval erythrocytes concurrently. However, B[a]P increased micronucleus formation but not that of DNA strand breaks. Time-dose experiments over 12 days of exposure suggest that the CA provides an earlier significant response to genotoxicants than does the MNT. In Xenopus the CA appears to be a sensitive and suitable method for detecting genotoxicity like that caused by EMS and MMS. It can be considered a genotoxicity-screening tool. The results for B[a]P show that both tests should be used in a complementary manner on Xenopus.

  9. DNA damage in hemodialysis patients with chronic kidney disease; a test of the role of diabetes mellitus; a comet assay investigation.

    PubMed

    Mamur, Sevcan; Unal, Fatma; Altok, Kadriye; Deger, Serpil Muge; Yuzbasioglu, Deniz

    2016-04-01

    The incidence of chronic kidney disease (CKD) is increasing rapidly. Diabetes mellitus (DM) is the most important cause of CKD. We studied the possible role of DM in CKD patients with respect to DNA damage, as assessed by the comet assay in 60 CKD patients (with or without DM) undergoing hemodialysis and in 26 controls. Effects of other factors, such as age, sex, hypertension, duration of hemodialysis, body mass index (BMI), and levels of hemoglobin (HB), intact parathormone (iPTH), and ferritin (FER), were also examined. Primary DNA damage measured by the comet assay was significantly higher in CKD patients than in controls. Among CKD patients, the following correlations were observed. (1) There was no difference in comet tail length or tail intensity between diabetic and non-diabetic individuals. (2) Age, sex, hemoglobin, hypertension, duration of hemodialysis, and ferritin levels affected neither tail length nor intensity. (3) BMI values above 25kg/m(2) and iPTH levels above 300pg/ml were associated with significantly greater comet tail length. Our results indicate that primary DNA damage is increased in CKD patients undergoing hemodialysis, compared to controls; however, DM had no additional effect.

  10. DNA alkylation lesions and their repair in human cells: modification of the comet assay with 3-methyladenine DNA glycosylase (AlkD).

    PubMed

    Hašplová, Katarína; Hudecová, Alexandra; Magdolénová, Zuzana; Bjøras, Magnar; Gálová, Eliška; Miadoková, Eva; Dušinská, Mária

    2012-01-05

    3-methyladenine DNA glycosylase (AlkD) belongs to a new family of DNA glycosylases; it initiates repair of cytotoxic and promutagenic alkylated bases (its main substrates being 3-methyladenine and 7-methylguanine). The modification of the comet assay (single cell gel electrophoresis) using AlkD enzyme thus allows assessment of specific DNA alkylation lesions. The resulting baseless sugars are alkali-labile, and under the conditions of the alkaline comet assay they appear as DNA strand breaks. The alkylating agent methyl methanesulfonate (MMS) was used to induce alkylation lesions and to optimize conditions for the modified comet assay method with AlkD on human lymphoblastoid (TK6) cells. We also studied cellular and in vitro DNA repair of alkylated bases in DNA in TK6 cells after treatment with MMS. Results from cellular repair indicate that 50% of DNA alkylation is repaired in the first 60 min. The in vitro repair assay shows that while AlkD recognises most alkylation lesions after 60 min, a cell extract from TK6 cells recognises most of the MMS-induced DNA adducts already in the first 15 min of incubation, with maximum detection of lesions after 60 min' incubation. Additionally, we tested the in vitro repair capacity of human lymphocyte extracts from 5 individuals and found them to be able to incise DNA alkylations in the same range as AlkD. The modification of the comet assay with AlkD can be useful for in vitro and in vivo genotoxicity studies to detect alkylation damage and repair and also for human biomonitoring and molecular epidemiology studies.

  11. Use of the comet assay to measure DNA damage in cells exposed to photosensitizers and gamma radiation

    NASA Astrophysics Data System (ADS)

    Pouget, J.-P.; Ravanat, J.-L.; Douki, T.; Richard, M.-J.; Cadet, J.

    1999-01-01

    We used the comet assay associated with DNA-glycosylases to estimate DNA damage in cells exposed to gamma irradiation or photosensitized either with methylene blue or orange acridine. A calibration performed using irradiation allowed the measurement of the steady-state level and the yield of 8-oxodGuo as well as strand breaks and alkali-labile sites. Nous avons utilisé la méthode des comètes associée à des ADN-glycosylases, pour estimer les dommages de l'ADN dans des cellules après l'exposition à un rayonnement gamma ou après photosensibilisation par le bleu de méthylène ou l'acridine orange. Une calibration de la méthode des comètes a permis de mesurer le niveau basal et les taux de formation de 8-oxodGuo ainsi que le nombre de cassures de brins et de sites alcali labiles.

  12. Genotoxicity of marine sediments in the fish hepatoma cell line PLHC-1 as assessed by the Comet assay.

    PubMed

    Šrut, Maja; Traven, Luka; Štambuk, Anamaria; Kralj, Sonja; Žaja, Roko; Mićović, Vladimir; Klobučar, Göran I V

    2011-02-01

    The main goal of this study was to test the usefulness of the Comet assay in the PLHC-1 hepatoma fish cell line as a tool for detecting the presence of genotoxic compounds in contaminated marine sediments. The system has been tested using both model chemicals (benzo[a]pyrene (B[a]P) and ethyl methanesulfonate (EMS)) and extracts of sediment samples obtained with solvent dichloromethane/methanol. For all of the analysed sediment extracts as well as for the model chemicals a concentration dependent genotoxic effect was observed. The sediment with the highest observed genotoxic potential was additionally extracted using various solvents in order to test which class of compounds, according to their polarity, is most responsible for the observed genotoxic effect. Non-polar solvents (cyclohexane and dichloromethane) yielded stronger genotoxic effect but the highest level of DNA damage was determined after exposure to sediment extract obtained with the solvent mixture dichloromethane/methanol which extracts a wide range of contaminants. Our results indicate that the PLHC-1 cell line is a suitable in vitro model in sediment genotoxicity assessment and encourage the use of fish cell lines as versatile tools in ecogenotoxicology.

  13. An improved method for the isolation of rat alveolar type II lung cells: Use in the Comet assay to determine DNA damage induced by cigarette smoke.

    PubMed

    Dalrymple, Annette; Ordoñez, Patricia; Thorne, David; Dillon, Debbie; Meredith, Clive

    2015-06-01

    Smoking is a cause of serious diseases, including lung cancer, emphysema, chronic bronchitis and heart disease. DNA damage is thought to be one of the mechanisms by which cigarette smoke (CS) initiates disease in the lung. Indeed, CS induced DNA damage can be measured in vitro and in vivo. The potential of the Comet assay to measure DNA damage in isolated rat lung alveolar type II epithelial cells (AEC II) was explored as a means to include a genotoxicity end-point in rodent sub-chronic inhalation studies. In this study, published AEC II isolation methods were improved to yield viable cells suitable for use in the Comet assay. The improved method reduced the level of basal DNA damage and DNA repair in isolated AEC II. CS induced DNA damage could also be quantified in isolated cells following a single or 5 days CS exposure. In conclusion, the Comet assay has the potential to determine CS or other aerosol induced DNA damage in AEC II isolated from rodents used in sub-chronic inhalation studies.

  14. JaCVAM-organized international validation study of the in vivo rodent alkaline comet assay for detection of genotoxic carcinogens: II. Summary of definitive validation study results.

    PubMed

    Uno, Yoshifumi; Kojima, Hajime; Omori, Takashi; Corvi, Raffaella; Honma, Masamistu; Schechtman, Leonard M; Tice, Raymond R; Beevers, Carol; De Boeck, Marlies; Burlinson, Brian; Hobbs, Cheryl A; Kitamoto, Sachiko; Kraynak, Andrew R; McNamee, James; Nakagawa, Yuzuki; Pant, Kamala; Plappert-Helbig, Ulla; Priestley, Catherine; Takasawa, Hironao; Wada, Kunio; Wirnitzer, Uta; Asano, Norihide; Escobar, Patricia A; Lovell, David; Morita, Takeshi; Nakajima, Madoka; Ohno, Yasuo; Hayashi, Makoto

    2015-07-01

    The in vivo rodent alkaline comet assay (comet assay) is used internationally to investigate the in vivo genotoxic potential of test chemicals. This assay, however, has not previously been formally validated. The Japanese Center for the Validation of Alternative Methods (JaCVAM), with the cooperation of the U.S. NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)/the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), the European Centre for the Validation of Alternative Methods (ECVAM), and the Japanese Environmental Mutagen Society/Mammalian Mutagenesis Study Group (JEMS/MMS), organized an international validation study to evaluate the reliability and relevance of the assay for identifying genotoxic carcinogens, using liver and stomach as target organs. The ultimate goal of this exercise was to establish an Organisation for Economic Co-operation and Development (OECD) test guideline. The study protocol was optimized in the pre-validation studies, and then the definitive (4th phase) validation study was conducted in two steps. In the 1st step, assay reproducibility was confirmed among laboratories using four coded reference chemicals and the positive control ethyl methanesulfonate. In the 2nd step, the predictive capability was investigated using 40 coded chemicals with known genotoxic and carcinogenic activity (i.e., genotoxic carcinogens, genotoxic non-carcinogens, non-genotoxic carcinogens, and non-genotoxic non-carcinogens). Based on the results obtained, the in vivo comet assay is concluded to be highly capable of identifying genotoxic chemicals and therefore can serve as a reliable predictor of rodent carcinogenicity.

  15. The comets of 1999

    NASA Astrophysics Data System (ADS)

    Shanklin, J.

    2009-12-01

    This report is the tenth in the annual series which gives for each comet: the discovery details, orbital data and general information, magnitude parameters and BAA Comet Section observations. Further details of the analysis techniques used in this report are given in an earlier paper. Ephemerides for the comets predicted to return during the year can be found in the BAA or ICQ Handbooks.

  16. The comets of 2000

    NASA Astrophysics Data System (ADS)

    Shanklin, J. D.

    2010-08-01

    This report is the eleventh in the annual series which gives for each comet: the discovery details, orbital data and general information, magnitude parameters and BAA Comet Section observations. Further details of the analysis techniques used in this report are given in an earlier paper. Ephemerides for the comets predicted to return during the year can be found in the BAA or ICQ Handbooks.

  17. Integration of Pig-a, micronucleus, chromosome aberration and comet assay endpoints in a 28-day rodent toxicity study with urethane

    PubMed Central

    Stankowski, Leon F.; Aardema, Marilyn J.; Lawlor, Timothy E.; Pant, Kamala; Roy, Shambhu; Xu, Yong; Elbekai, Reem

    2015-01-01

    As part of the international Pig-a validation trials, we examined the induction of Pig-a mutant reticulocytes and red blood cells (RETCD59− and RBCCD59−, respectively) in peripheral blood of male Sprague Dawley® rats treated with urethane (25, 100 and 250mg/kg/day) or saline by oral gavage for 29 days. Additional endpoints integrated into this study were: micronucleated reticulocytes (MN-RET) in peripheral blood; chromosome aberrations (CAb) and DNA damage (%tail intensity via the comet assay) in peripheral blood lymphocytes (PBL); micronucleated polychromatic erythrocytes (MN-PCE) in bone marrow; and DNA damage (comet) in various organs at termination (the 29th dose was added for the comet endpoint at sacrifice). Ethyl methanesulfonate (EMS; 200mg/kg/day on Days 3, 4, 13, 14, 15, 27, 28 and 29) was evaluated as the concurrent positive control (PC). All animals survived to termination and none exhibited overt toxicity, but there were significant differences in body weight and body weight gain in the 250-mg/kg/day urethane group, as compared with the saline control animals. Statistically significant, dose-dependent increases were observed for urethane for: RETCD59− and RBCCD59− (on Days 15 and 29); MN-RET (on Days 4, 15 and 29); and MN-PCE (on Day 29). The comet assay yielded positive results in PBL (Day 15) and liver (Day 29), but negative results for PBL (Days 4 and 29) and brain, kidney and lung (Day 29). No significant increases in PBL CAb were observed at any sample time. Except for PBL CAb (likely due to excessive cytotoxicity), EMS-induced significant increases in all endpoints/tissues. These results compare favorably with earlier in vivo observations and demonstrate the utility and sensitivity of the Pig-a in vivo gene mutation assay, and its ability to be easily integrated, along with other standard genotoxicity endpoints, into 28-day rodent toxicity studies. PMID:25934985

  18. Protective effect of dry olive leaf extract in adrenaline induced DNA damage evaluated using in vitro comet assay with human peripheral leukocytes.

    PubMed

    Cabarkapa, Andrea; Zivković, Lada; Zukovec, Dijana; Djelić, Ninoslav; Bajić, Vladan; Dekanski, Dragana; Spremo-Potparević, Biljana

    2014-04-01

    Excessive release of stress hormone adrenaline is accompanied by generation of reactive oxygen species which may cause disruption of DNA integrity leading to cancer and age-related disorders. Phenolic-rich plant product dry olive leaf extract (DOLE) is known to modulate effects of various oxidants in human cells. The aim was to evaluate the effect of commercial DOLE against adrenaline induced DNA damage in human leukocytes by using comet assay. Peripheral blood leukocytes from 6 healthy subjects were treated in vitro with three final concentrations of DOLE (0.125, 0.5, and 1mg/mL) for 30 min at 37°C under two different protocols, pretreatment and post-treatment. Protective effect of DOLE was assessed from its ability to attenuate formation of DNA lesions induced by adrenaline. Compared to cells exposed only to adrenaline, DOLE displayed significant reduction (P<0.001) of DNA damage at all three concentrations and under both experimental protocols. Pearson correlation analysis revealed a significant positive association between DOLE concentration and leukocytes DNA damage (P<0.05). Antigenotoxic effect of the extract was more pronounced at smaller concentrations. Post-treatment with 0.125 mg/mL DOLE was the most effective against adrenaline genotoxicity. Results indicate genoprotective and antioxidant properties in dry olive leaf extract, strongly supporting further explorations of its underlying mechanisms of action.

  19. Detection of DNA strand breaks by comet assay in sputum leucocytes of bitumen-exposed workers: a pilot study.

    PubMed

    Marczynski, B; Raulf-Heimsoth, M; Pesch, B; Kendzia, B; Käfferlein, H U; Vosshans, B; Borowitzki, G; Lee, E-H; Bramer, R; Brüning, T

    2010-09-01

    DNA strand breaks were determined in leucocytes of induced sputum (IS) and compared with DNA strand breaks in blood lymphocytes from 42 bitumen-exposed workers pre and post shift. Comet assay results were expressed in arbitrary units based on visual scoring (sputum leucocytes) and Olive tail moment (OTM, blood lymphocytes). DNA damage in IS leucocytes was overall high but did not change during shift. Level of DNA strand breaks in IS samples correlated with total cell count and neutrophil content (Spearman rank correlation coefficient r(s) = 0.47, p = 0.001, r(s)= 0.48, p = 0.001, respectively) and with IL-8 concentration before and after shift (r(s) = 0.31, P = 0.048, and r(s) = 0.43, P = 0.005). DNA damage in IS was not associated with DNA strand breaks in blood lymphocytes (r(s) = -0.04, p = 0.802 before shift, r(s) = 0.27, p = 0.088 after shift). A higher level of DNA strand breaks was measured in blood lymphocytes before shift (median OTM 1.7 before and 1.3 after shift, p = 0.023). A strong correlation was found between the number of neutrophils and IL-8 concentration in IS before and after shift (r(s) = 0.77 and r(s)= 0.75, p < 0.001). This study showed an association between genotoxic and inflammatory effects in the lower airways and compared simultaneously DNA strand breaks in IS and blood of bitumen-exposed workers.

  20. Shortening of alkaline DNA unwinding time does not interfere with detecting DNA damage to mouse and human spermatozoa in the comet assay.

    PubMed

    Kusakabe, Hirokazu; Tateno, Hiroyuki

    2011-01-01

    The comet assay was performed on mouse and human spermatozoa to examine the effect of alkaline DNA unwinding time. The spermatozoa were treated in vitro with the DNA-damaging agents, methyl methanesulfonate (MMS) or hydrogen peroxide (H₂O₂), and then embedded in agarose gel on glass slides. The slides were immersed in alkaline solution (> pH 13) for 1, 5, 10 and 20 min, and then subjected to the electrophoresis under neutral conditions. In mouse spermatozoa, comet tails seen in solvent controls became brighter and longer as the alkaline DNA unwinding time increased. However, in the MMS-treated mouse spermatozoa, a smaller difference in the damage from that in the solvent control was seen with time within a dose. DNA damage induced by H₂O₂ could also be detected accurately after alkali treatment for 1-20 min. In human spermatozoa, DNA damage induced by MMS and H₂O₂ could be detected in a dose-dependent manner after alkali treatment for 1 min. The ability of the comet assay to detect DNA damage was not adversely affected by the short period (1 min) of the alkaline DNA unwinding time.

  1. Assessment of status of three water bodies in Serbia based on tissue metal and metalloid concentration (ICP-OES) and genotoxicity (comet assay).

    PubMed

    Sunjog, Karolina; Kolarević, Stoimir; Kračun-Kolarević, Margareta; Višnjić-Jeftić, Željka; Skorić, Stefan; Gačić, Zoran; Lenhardt, Mirjana; Vasić, Nebojša; Vuković-Gačić, Branka

    2016-06-01

    Metals and metalloids are natural components of the biosphere, which are not produced per se by human beings, but whose form and distribution can be affected by human activities. Like all substances, they are a contaminant if present in excess compared to background levels and/or in a form that would not normally occur in the environment. Samples of liver, gills, gonads and muscle from European chub, Squalius cephalus, were analyzed for Al, As, B, Ba, Cr, Cu, Fe, Hg, Mn, Mo, Sr and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES) to highlight the importance of tissue selection in monitoring research. The comet assay or single cell gel electrophoresis (SCGE) was selected as an in vivo genotoxicity assay, a rapid and sensitive method for measuring genotoxic effects in blood, liver and gills of the European chub. Microscopic images of comets were scored using Comet IV Computer Software (Perceptive Instruments, UK). The objective of our study was to investigate two reservoirs, Zlatar and Garasi, and one river, Pestan by: (i) determining and comparing metal and metalloid concentrations in sediment, water and tissues of European chub: liver, gills, muscle and gonads (ii) comparing these findings with genotoxicity of water expressed through DNA damage of fish tissues. A clear link between the level of metals in water, sediment and tissues and between metal and genotoxicity levels at examined sites was not found. This suggests that other xenobiotics (possibly the organic compounds), contribute to DNA damage.

  2. Identification of irradiated wheat by germination test, DNA comet assay and electron spin resonance

    NASA Astrophysics Data System (ADS)

    Barros, Adilson C.; Freund, Maria Teresa L.; Villavicencio, Ana Lúcia C. H.; Delincée, Henry; Arthur, Valter

    2002-03-01

    In several countries, there has been an increase in the use of radiation for food processing thus improving the quality and sanitary conditions, inhibiting pathogenic microorganisms, delaying the natural aging process and so extending product lifetime. The need to develop analytical methods to detect these irradiated products is also increasing. The goal of this research was to identify wheat irradiated using different radiation doses. Seeds were irradiated with a gamma 60Co source (Gammacell 220 GC) in the Centro de Energia Nuclear na Agricultura and the Instituto de Pesquisas Energéticas e Nucleares. Dose rate used were 1.6 and 5.8kGy/h. Applied doses were 0.0, 0.10, 0.25, 0.50, 0.75, 1.0, and 2.0kGy. After irradiation, seeds were analysed over a 6 month period. Three different detection methods were employed to determine how irradiation had modified the samples. Screening methods consisted of a germination test measuring the inhibition of shooting and rooting and analysis of DNA fragmentation. The method of electron spin resonance spectroscopy allowed a better dosimetric evaluation. These techniques make the identification of irradiated wheat with different doses possible.

  3. Meteoroid streams and comet disintegration

    NASA Astrophysics Data System (ADS)

    Guliyev, A.

    2016-01-01

    The results of the statistical analysis of the dynamic parameters of 114 comets that have undergone nuclear splitting are presented in the article. The list of the objects contains: comets that have split in the period of the observation; data of twin-comets; lost comets with designation D; comets with large-scale structure in the coma. We will describe these comets as "splitted". Some aspects of the following hypothesis are studied: disintegration of comet nuclei happens as the result of their collision with meteoroid streams. For the verification of this hypothesis, the position of splitted comet orbits relatively to 125 meteor streams from Kronk's list is analyzed. It was found that the total number of comet orbit nodes located close to the meteor stream planes (for the distances up to 0.1 AU) is N = 1041. It is shown that if these comets are replaced by randomly selected different comets, N will be reduced by a factor of approximately three.

  4. Assessment by Ames test and comet assay of toxicity potential of polymer used to develop field-capable rapid-detection device to analyze environmental samples

    NASA Astrophysics Data System (ADS)

    Hebert, Amanda; Bishop, Michelle; Bhattacharyya, Dhiman; Gleason, Karen; Torosian, Stephen

    2015-08-01

    There is need for devices that decrease detection time of food-borne pathogens from days to real-time. In this study, a rapid-detection device is being developed and assessed for potential cytotoxicity. The device is comprised of melt-spun polypropylene coupons coated via oxidative chemical vapor deposition (oCVD) with 3,4-Ethylenedioxythiophene (EDOT), for conductivity and 3-Thiopheneethanol (3TE), allowing antibody attachment. The Ames test and comet assay have been used in this study to examine the toxicity potentials of EDOT, 3TE, and polymerized EDOT-co-3TE. For this study, Salmonella typhimurium strain TA1535 was used to assess the mutagenic potential of EDOT, 3TE and the copolymer. The average mutagenic potential of EDOT, 3TE and copolymer was calculated to be 0.86, 0.56, and 0.92, respectively. For mutagenic potential, on a scale from 0 to 1, close to 1 indicates low potential for toxicity, whereas a value of 0 indicates a high potential for toxicity. The comet assay is a single-cell gel electrophoresis technique that is widely used for this purpose. This assay measures toxicity based on the area or intensity of the comet-like shape that DNA fragments produce when DNA damage has occurred. Three cell lines were assessed; FRhK-4, BHK-21, and Vero cells. After averaging the results of all three strains, the tail intensity of the copolymer was 8.8 % and tail moment was 3.0, and is most similar to the untreated control, with average tail intensity of 5.7 % and tail moment of 1.7. The assays conducted in this study provide evidence that the copolymer is non-toxic to humans.

  5. Navigation accuracy analysis for the Halley flyby phase of a dual comet mission using ion drive

    NASA Technical Reports Server (NTRS)

    Wood, L. J.; Hast, S. L.

    1980-01-01

    A dual comet (Halley Flyby/Tempel 2 Rendezvous) mission, making use of the solar electric propulsion system, is under consideration for a 1985 launch. This paper presents navigation accuracy analysis results for the Halley flyby phase of this mission. Orbit determination and guidance accuracies are presented for the baseline navigation strategy, along with the results of a number of sensitivity studies involving parameters such as data frequencies, data accuracies, ion drive thrust vector errors, comet ephemeris uncertainties, time lags associated with data processing and command sequence generation, probe release time, and navigation coast arc duration.

  6. The interactive astronomical data analysis facility - image enhancement techniques to Comet Halley

    NASA Technical Reports Server (NTRS)

    Kinglesmith, D. A., III

    1981-01-01

    PDP 11/40 computer is at the heart of a general purpose interactive data analysis facility designed to permit easy access to data in both visual imagery and graphic representations. The major components consist of: the 11/40 CPU and 256 K bytes of 16-bit memory; two TU10 tape drives; 20 million bytes of disk storage; three user terminals; and the COMTAL image processing display system. The application of image enhancement techniques to two sequences of photographs of Comet Halley taken in Egypt in 1910 provides evidence for eruptions from the comet's nucleus.

  7. The interactive astronomical data analysis facility - image enhancement techniques to Comet Halley

    NASA Astrophysics Data System (ADS)

    Klinglesmith, D. A.

    1981-10-01

    PDP 11/40 computer is at the heart of a general purpose interactive data analysis facility designed to permit easy access to data in both visual imagery and graphic representations. The major components consist of: the 11/40 CPU and 256 K bytes of 16-bit memory; two TU10 tape drives; 20 million bytes of disk storage; three user terminals; and the COMTAL image processing display system. The application of image enhancement techniques to two sequences of photographs of Comet Halley taken in Egypt in 1910 provides evidence for eruptions from the comet's nucleus.

  8. Comet deflection by directed energy: a finite element analysis

    NASA Astrophysics Data System (ADS)

    Madajian, Jonathan; Griswold, Janelle; Gandra, Anush; Hughes, Gary B.; Zhang, Qicheng; Rupert, Nic; Lubin, Philip

    2016-09-01

    Comets and Asteroids are viable threats to our planet; if these space rocks are smaller than 25 meters, they burn up in the atmosphere, but if they are wider than 25 meters they can cause damage to the impact area. Anything more than one to two kilometers can have worldwide effects, furthermore a mile-wide asteroid travelling at 30,000 miles per hour has the energy equal to a megaton bomb and is very likely to wipe out most of the life on Earth. Residents near Chelyabinsk, Russia experienced the detrimental effects of a collision with a Near-Earth Asteroid (NEA) on 15 February 2013 as a 20 m object penetrated the atmosphere above that city. The effective yield from this object was approximately 1/2 Megaton TNT equivalent (Mt), or that of a large strategic warhead. The 1908 Tunguska event, also over Russia, is estimated to have had a yield of approximately 15 Mt and had the potential to kill millions of people had it come down over a large city1. In the face of such danger a planetary defense system is necessary and this paper proposes a design for such a system. DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) is a phased array laser system that can be used to oblate, deflect and de-spin asteroids and comets.

  9. Comets. [IUE

    NASA Technical Reports Server (NTRS)

    Ahearn, Michael F.

    1988-01-01

    The IUE was used to study comets including the first dynamically new comet to approach closer than 3 AU. Differences between old and new comets are studied. Results relevant to the nature of cometary nuclei are discussed. Identification of species in the spectra; relative abundances; variability of comets; and comet mass are considered.

  10. Assessment of DNA damage of Lewis lung carcinoma cells irradiated by carbon ions and X-rays using alkaline comet assay

    NASA Astrophysics Data System (ADS)

    Li, Ping; Zhou, Li-Bin; Jin, Xiao-Dong; He, Jing; Dai, Zhong-Ying; Zhou, Guang-Ming; Gao, Qing-Xiang; Li, Sha; Li, Qiang

    2008-01-01

    DNA damage and cell reproductive death determined by alkaline comet and clonogenic survival assays were examined in Lewis lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. Based on the survival data, Lewis lung carcinoma cells were verified to be more radiosensitive to the carbon ion beam than to the X-ray irradiation. The relative biological effectiveness (RBE) value, which was up to 1.77 at 10% survival level, showed that the DNA damage induced by the high-LET carbon ion beam was more remarkable than that induced by the low-LET X-ray irradiation. The dose response curves of “Tail DNA (%)” (TD) and “Olive tail moment” (OTM) for the carbon ion irradiation showed saturation beyond about 8 Gy. This behavior was not found in the X-ray curves. Additionally, the carbon ion beam produced a lower survival fraction at 2 Gy (SF2) value and a higher initial Olive tail moment 2 Gy (OTM2) than those for the X-ray irradiation. These results suggest that carbon ion beams having high-LET values produced more severe cell reproductive death and DNA damage in Lewis lung carcinoma cells in comparison with X-rays and comet assay might be an effective predictive test even combining with clonogenic assay to assess cellular radiosensitivity.

  11. Comet assay study of DNA damage and repair of tumour cells following boron neutron capture irradiation with fast d(14) + Be neutrons.

    PubMed

    Pöller, F; Bauch, T; Sauerwein, W; Böcker, W; Wittig, A; Streffer, C

    1996-11-01

    We compared the amount of radiation-induced DNA damage and the extent of DNA repair in human melanoma cells (MeWo) using the 'comet assay' after neutron, boron neutron capture and X-irradiation. Using a colony-forming assay it was shown earlier that lethal effects in tumour cells treated with fast neutrons may be increased by the neutron capture reaction 10B(n, alpha)7Li. The effectiveness of boron neutron capture in killing tumour cells depends on the number of 10B atoms delivered to the tumour, the subcellular distribution of 10B and the thermal neutron fluence at the side of the tumour. Using the 'comet assay' the DNA damage of fast neutrons (mean energy 5.8 MeV) was shown to be significantly greater than for the same absorbed dose of X-rays. The presence of 600 ppm 10B (boric acid H5 10BO3) in the cell medium during irradiation with d(14) + Be neutrons in a phantom enhances the DNA damage by 20% compared with neutron irradiation alone. After DNA damage induction by neutrons and neutron capture of boron, the DNA repair capacity of the MeWo cells is significantly reduced in comparison with X-irradiation resulting in proportionally more residual DNA damage after 180 min of repair time.

  12. An investigation of the potential effect of sperm nuclear vacuoles in human spermatozoa on DNA fragmentation using a neutral and alkaline Comet assay.

    PubMed

    Pastuszek, E; Kiewisz, J; Skowronska, P; Liss, J; Lukaszuk, M; Bruszczynska, A; Jakiel, G; Lukaszuk, K

    2017-03-01

    Presence of vacuoles and degree of sperm DNA damage are considered to be the basic factors used for the assessment of sperm fertilization capacity. We aimed to investigate the link between these two parameters. According to our knowledge, this is the first study where the Comet assay was used to assess the degree of DNA fragmentation of sperm categorized by Motile Sperm Organelle Morphology Examination (MSOME) Grades. Semen samples from 10 patients were assessed. Spermatozoa were graded into four MSOME groups according to the Vanderzwalmen's criteria. A total of 3930 motile spermatozoa were selected one-by-one using an inverted microscope and transferred onto two different slides. The degree of DNA fragmentation was analyzed by alkaline and neutral Comet assay. Results of the neutral Comet assay showed that Grade I spermatozoa (absence of vacuoles) presented significantly lower dsDNA fragmentation level (mean: 3.13 ± 1.17%) than Grade II (maximum of two small vacuoles; mean: 10.34 ± 2.65%), Grade III (more than two small vacuoles or at least one large vacuole; mean: 23.88 ± 8.37%), and Grade IV (large vacuoles associated with abnormal head shapes or other abnormalities; mean: 36.94 ± 7.78%; p < 0.05). Results of the alkaline Comet assay showed that Grade I spermatozoa had significantly lower DNA (ssDNA + dsDNA) fragmentation level (mean: 8.33 ± 3.62%) than Grade III (mean: 25.64 ± 9.15%) and Grade IV (mean: 40.10 ± 9.10%, p < 0.05), but not significantly lower than Grade II (mean: 12.73 ± 5.06%; p > 0.05). Probably, the vacuoles may be responsible for double strand DNA breaks rather than single strand DNA breaks (only 2.39% spermatozoa in MSOME Grade II, 1.76% in III, and 3.16% in IV has single strand breaks). The results demonstrate that lower MSOME grading correlates with lower sperm DNA fragmentation. Therefore, the observation of sperm nuclear vacuoles using real-time optical microscopy without precise DNA fragmentation

  13. Evaluation of p-phenylenediamine, o-phenylphenol sodium salt, and 2,4-diaminotoluene in the rat comet assay as part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiated international validation study of in vivo rat alkaline comet assay.

    PubMed

    De Boeck, Marlies; van der Leede, Bas-jan; De Vlieger, Kathleen; Geys, Helena; Vynckier, An; Van Gompel, Jacky

    2015-07-01

    As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiated international validation study of in vivo rat alkaline comet assay (comet assay), p-phenylenediamine dihydrochloride (PPD), o-phenylphenol sodium salt (OPP), and 2,4-diaminotoluene (2,4-DAT), were analyzed in this laboratory as coded test chemicals. Male Sprague-Dawley rats (7-9 weeks of age) were given three oral doses of the test compounds, 24 and 21 h apart and liver and stomach were sampled 3h after the final dose administration. Under the conditions of the test, no increases in DNA damage were observed in liver and stomach with PPD and OPP up to 100 and 1000 mg/kg/day, respectively. 2,4-DAT, a known genotoxic carcinogen, induced a weak but reproducible, dose-related and statistically significant increase in DNA damage in liver cells while no increases were observed in stomach cells.

  14. Trajectory analysis and performance for SEP Comet Encke missions

    NASA Technical Reports Server (NTRS)

    Sauer, C. G., Jr.

    1973-01-01

    A summary of the performance of Solar Electric Propulsion spacecraft for Comet Encke missions for the 1980, 1984 and 1987 mission opportunities is presented together with a description of the spacecraft trajectory for each opportunity. Included is data for rendezvous trajectories for all three opportunities and data for a slow flyby mission during the 1980 opportunity. A range of propulsion system input powers of 10 to 20 kW are considered together with a constant spacecraft power requirement of 400 watts. The performance presented in this paper is indicative of that using 30 cm Mercury electron bombardment thrusters that are currently being developed. Performance is given in terms of final spacecraft mass and is thus independent of any particular spacecraft design concept.

  15. Characterization of the Fine Component of Comet Wild 2: Analysis of 11 Stardust Craters from Foil C2010W

    NASA Astrophysics Data System (ADS)

    Haas, B. A.; Croat, T. K.; Floss, C.

    2016-08-01

    NASA's Stardust mission returned cometary material from comet Wild 2 in Al foil collectors. We report on SEM-EDX and Auger elemental analysis as well as FIB-TEM analysis performed on 11 craters from foil C2010W.

  16. Comet Odyssey: Comet Surface Sample Return

    NASA Astrophysics Data System (ADS)

    Weissman, Paul R.; Bradley, J.; Smythe, W. D.; Brophy, J. R.; Lisano, M. E.; Syvertson, M. L.; Cangahuala, L. A.; Liu, J.; Carlisle, G. L.

    2010-10-01

    Comet Odyssey is a proposed New Frontiers mission that would return the first samples from the surface of a cometary nucleus. Stardust demonstrated the tremendous power of analysis of returned samples in terrestrial laboratories versus what can be accomplished in situ with robotic missions. But Stardust collected only 1 milligram of coma dust, and the 6.1 km/s flyby speed heated samples up to 2000 K. Comet Odyssey would collect two independent 800 cc samples directly from the surface in a far more benign manner, preserving the primitive composition. Given a minimum surface density of 0.2 g/cm3, this would return two 160 g surface samples to Earth. Comet Odyssey employs solar-electric propulsion to rendezvous with the target comet. After 180 days of reconnaissance and site selection, the spacecraft performs a "touch-and-go” maneuver with surface contact lasting 3 seconds. A brush-wheel sampler on a remote arm collects up to 800 cc of sample. A duplicate second arm and sampler collects the second sample. The samples are placed in a return capsule and maintained at colder than -70 C during the return flight and at colder than -30 C during re-entry and for up to six hours after landing. The entire capsule is then refrigerated and transported to the Astromaterials Curatorial Facility at NASA/JSC for initial inspection and sample analysis by the Comet Odyssey team. Comet Odyssey's planned target was comet 9P/Tempel 1, with launch in December 2017 and comet arrival in June 2022. After a stay of 300 days at the comet, the spacecraft departs and arrives at Earth in May 2027. Comet Odyssey is a forerunner to a flagship Cryogenic Comet Sample Return mission that would return samples from deep below the nucleus surface, including volatile ices. This work was supported by internal funds from the Jet Propulsion Laboratory.

  17. Study of DNA damage via the comet assay and base excision repair activities in rat brain neurons and astrocytes during aging.

    PubMed

    Swain, Umakanta; Subba Rao, Kalluri

    2011-08-01

    Earlier we have used biochemical approach to assess the number of single (SSBs) and double (DSBs) strand breaks in brain cellular DNA. However, a quick method to obtain a reliable measure of DNA damage in cells was in need for population studies. Therefore, single cell gel electrophoresis technique (popularly known as "comet" assay) has been standardized using the Trevigen protocol. DNA damage was assessed in isolated neurons and astrocytes from the cortex of young (7 days), adult (6 months) and old (2 years). Marked increase is seen in DNA damage in terms SSBs and DSBs in both types of cells by 6 months of age, which increased further by 2 years of age. The number of 8-oxoguanine DNA glycosylase (OGG1) and uracil DNA glycosylase (UDG) sensitive sites also increased in DNA with age with the simultaneous decrease in OGG1, UDG and AP endonuclease (APE1) activities. Thus the comet assay adapted to our lab conditions has proven to be useful for a quick assessment of DNA damage in a large number of samples that constitute our future studies.

  18. Evolution of DNA strand-breaks in cultured spermatocytes: the Comet Assay reveals differences in normal and gamma-irradiated germ cells.

    PubMed

    Perrin, J; Lussato, D; De Méo, M; Durand, P; Grillo, J-M; Guichaoua, M-R; Botta, A; Bergé-Lefranc, J-L

    2007-02-01

    In reproductive toxicity assessment, in vitro systems can be used to determine mechanisms of action of toxicants. However, they generally investigate the immediate effects of toxicants, on isolated germ cells or spermatozoa. We report here the usefulness of in vitro cultures of rat spermatocytes and Sertoli cells, in conjunction with the Comet Assay to analyze the evolution of DNA strand-breaks and thus to determine DNA damage in germ cells. We compared cultures of normal and gamma-irradiated germ cells. In non-irradiated spermatocytes, the Comet Assay revealed the presence of DNA strand-breaks, which numbers decreased with the duration of the culture, suggesting the involvement of DNA repair mechanisms related to the meiotic recombination. In irradiated cells, the evolution of DNA strand-breaks was strongly modified. Thus our model is able to detect genotoxic lesions and/or DNA repair impairment in cultured spermatocytes. We propose this model as an in vitro tool for the study of genotoxic injuries on spermatocytes.

  19. Detection of in vivo DNA damage induced by ethanol in multiple organs of pregnant mice using the alkaline single cell gel electrophoresis (Comet) assay.

    PubMed

    Kido, Ryoko; Sato, Itaru; Tsuda, Shuji

    2006-01-01

    Ethanol is principal ingredient of alcohol beverage, but considered as human carcinogen, and has neurotoxicity. Alcohol consumption during pregnancy often causes fetal alcohol syndrome. The DNA damage is one of the important factors in carcinogenicity or teratogenicity. To detect the DNA damage induced by ethanol, we used an in vivo alkaline single cell gel electrophoresis (Comet) assay in pregnant mice organs and embryos. Pregnant ICR mice on Day 7 of gestation were treated with 2, 4 or 8 g/kg ethanol, and maternal organs/tissues and embryos were subjected to the Comet assay at 4, 8, 12 and 24 hr after ethanol treatment. Four and 8 g/kg ethanol induced DNA damage in brain, lung and embryos at 4 or 8 hr after the treatment. Two g/kg ethanol did not cause any DNA damage, and 8 g/kg ethanol only increased the duration of DNA damage without distinct increase in the degree of the damage. No significant DNA damage was observed in the liver. To detect the effect of acetaldehyde, disulfiram, acetaldehyde dehydrogenase inhibitor, was administered before 4 g/kg ethanol treatment. No significant increase of DNA damage was observed in the disulfiram pre-treated group. These data indicate that ethanol induces DNA damage, which might be related to ethanol toxicity. Since pre-treatment of disulfiram did not increase DNA damage, DNA damage observed in this study might not be the effect of acetaldehyde.

  20. Determination of genotoxic effects of copper sulphate and cobalt chloride in Allium cepa root cells by chromosome aberration and comet assays.

    PubMed

    Yildiz, Mustafa; Ciğerci, Ibrahim Hakki; Konuk, Muhsin; Fidan, A Fatih; Terzi, Hakan

    2009-05-01

    We used the anaphase-telophase chromosome aberration and comet (Single Cell Gel Electrophoresis, SCGE) assays to evaluate the genotoxic effects of copper sulphate (CS) and cobalt chloride (CC) chemicals prepared in two concentrations (EC(50), 2xEC(50)), using methyl methanesulfonate (MMS) as a positive control and untreated cells as a negative control. In Allium root growth inhibition test, EC(50) values for CS and CC are 1.5 and 5.5 ppm, respectively. Mitotic index (MI) decreased in all concentrations tested of CS and CC compared to the control at each exposure time. The bridge, stickiness, vagrant chromosomes, fragments, c-anaphase and multipolarity chromosome aberrations were observed in anaphase-telophase cells. The total chromosome aberrations were more frequent with an increasing in the exposure time and the concentrations of both chemicals. The genotoxicity of CS and CC in Allium cepa root cells was analyzed using a mild alkaline comet assay at pH 12.3, which allows the detection of single strand breaks. In all the concentrations, CS and CC induced a significant increase (P<0.05) in DNA damage. No significant difference was found between positive control (300+/-5.81) and 3 ppm CS (280+/-4.61). The methods used are applicable for biological monitoring of environmental pollutants.

  1. Expression of Inflammatory and Cell Death Program Genes and Comet DNA Damage Assay Induced by Escherichia coli in Layer Hens

    PubMed Central

    Mehaisen, Gamal M. K.; Eshak, Mariam G.; El Sabry, M. I.; Abass, Ahmed O.

    2016-01-01

    Modern methods of industrial poultry and egg production systems involve stressful practices that stimulate Escherichia coli (E. coli) activity causing endotoxic shock. This investigation was conducted to evaluate the expression of pro-inflammatory cytokines and cell death program genes and DNA damage induced by E. coli in the brain and liver tissues of laying hens. A total of two hundred and ten H&N brown layer hens with 20 week age, were used in this research. First, preliminary experiments were designed (60 hens in total) to establish the optimal exposure dose of E. coli and to determine the nearest time of notable response to be used in the remainder studies of this research. At 35-wk of age, 150 hens were randomly assigned into 2 groups with 3 replicates of 25 birds each; the first group was injected in the brachial wing vein with 107 E. coli colony/hen, while the second group was injected with saline and served as a control. The body temperature and plasma corticosterone concentration were measured 3 hr after injection. Specimens of liver and brain were obtained from each group and the gene expression of p38 mitogen-activated protein kinase, interlukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), Bax, and caspase-3 genes were measured by quantitative real-time PCR. DNA damage in the brain and liver tissues were also measured by comet assay. Hens treated with E. coli showed significant (P<0.05) increase of body temperature and plasma corticosterone (42.6°C and 14.5 ng/ml, respectively) compared to the control group (41.1°C and 5.5 ng/ml, respectively). Additional remarkable over-inflammation gene expression of p38, IL-1β and TNF-α.genes were also detected in the brain (2.2-fold, 2.0-fold and 3.3-fold, respectively) and the liver (2.1-fold, 1.9-fold and 3.0-fold, respectively) tissues of the infected chickens. It is also important to note that hens injected with E. coli showed an increase in DNA damage in the brain and liver cells (P<0.05). These

  2. Cordyceps sinensis: Genotoxic Potential in Human Peripheral Blood Cells and Antigenotoxic Properties Against Hydrogen Peroxide by Comet Assay.

    PubMed

    Vasiljevic, Jovana D; Zivkovic, Lada P; Cabarkapa, Andrea M; Bajic, Vladan P; Djelic, Ninoslav J; Spremo-Potparevic, Biljana M

    2016-06-01

    Context • Cordyceps sinensis (C sinensis) is a well-known, traditional, Chinese medicinal mushroom, valued for its beneficial properties for human health. C sinensis has been reported to have immunomodulatory, anticancer, antiaging, antioxidant and anti-inflammatory activity. Despite potential medicinal benefits, no previously published reports are available about the genotoxicity or antigenotoxicity of C sinensis, as detected by comet assay. Objective • The objective of the study was to evaluate both the genotoxic and antigenotoxic potential of an extract of C sinensis (CS extract) in human peripheral blood cells. Design • The research team designed a pilot study. Setting •The study was conducted at the Center for Biological Research, University of Belgrade, in Belgrade, Serbia. Participants • Participants were 6 healthy individuals (2 males and 4 females), between the ages of 20 and 45 y, recruited on a voluntary basis, who provided heparinized, peripheral blood samples. Intervention • Four concentrations of the CS extract-125 μg/mL, 250 μg/mL, 500 μg/mL, and 1000 μg/mL-were used in the treatment of tested blood cells from the blood samples. Three independent procedures were performed: (1) a genotoxicity assessment, (2) an antigenotoxicity assessment for pretreatment of human cells with the CS extract prior to their exposure to hydrogen peroxide (H2O2) (ie, an evaluation of the benefits of the CS extract as a preventive agent); and (3) posttreatment of human cells with the CS extract after their exposure to H2O2 (ie, an evaluation of the benefits of the CS extract as an interventional agent). Outcome Measures • Cells were graded by eye inspection into 5 classes, depending on the extent of DNA damage, representing: (1) class A-undamaged cells with no tail (<5% damaged DNA); (2) class B-low-level damage (5%-20%); (3) class C-medium-level damage (20%-40%); (4) class D-high-level damage (40%-95%), and (5) class E-total destruction (>95%).Results

  3. Nicotine derived genotoxic effects in human primary parotid gland cells as assessed in vitro by comet assay, cytokinesis-block micronucleus test and chromosome aberrations test.

    PubMed

    Ginzkey, Christian; Steussloff, Gudrun; Koehler, Christian; Burghartz, Marc; Scherzed, Agmal; Hackenberg, Stephan; Hagen, Rudolf; Kleinsasser, Norbert H

    2014-08-01

    Genotoxic effects of nicotine were described in different human cells including salivary gland cells. Based on the high nicotine concentration in saliva of smokers or patients using therapeutic nicotine patches, the current study was performed to evaluate the genotoxic potential of nicotine in human salivary gland cells. Therefore, primary salivary gland cells from 10 patients undergoing parotid gland surgery were exposed to nicotine concentrations between 1 μM and 1000 μM for 1 h in the absence of exogenous metabolic activation. The acinar phenotype was proven by immunofluorescent staining of alpha-amylase. Genotoxic effects were evaluated using the Comet assay, the micronucleus test and the chromosome aberration test. Cytotoxicity and apoptosis were determined by trypan blue exclusion test and Caspase-3 assay. Nicotine was able to induce genotoxic effects in all three assays. The chromosome aberration test was the most sensitive and increases in numerical and structural (chromatid-type and chromosome-type) aberrations were seen at ≥1 μM, whereas increases in micronuclei frequency were detected at 10 μM and DNA damage as measured in the Comet assay was noted at >100 μM. No cytotoxic damage or influence of apoptosis could be demonstrated. Nicotine as a possible risk factor for tumor initiation in salivary glands is still discussed controversially. Our results demonstrated the potential of nicotine to induce genotoxic effects in salivary gland cells. These results were observed at saliva nicotine levels similar to those found after oral or transdermal exposure to nicotine and suggest the necessity of careful monitoring of the use of nicotine in humans.

  4. Relative sensitivity of fish and mammalian cells to the antibiotic, trimethoprim: cytotoxic and genotoxic responses as determined by neutral red retention, Comet and micronucleus assays.

    PubMed

    Papis, Elena; Davies, Simon J; Jha, Awadhesh N

    2011-01-01

    Relative cytotoxicity and genotoxicity of a widely used antibiotic, trimethoprim (TRIMP) was evaluated under in vitro conditions using rainbow trout gonad-2 (RTG-2) and Chinese hamster ovary-K1 (CHO-K1) cells. Whilst cytotoxicity was determined using neutral red retention (NRR) assay, the genotoxicity was determined using single cell gel electrophoresis or the Comet assay and cytokinesis-block micronucleus (CBMN) assay. For NRR assay, concentration-dependent cytotoxic effect was observed for both the cell lines (estimated EC(50) values: 671.82 ± 21.78 and 611.6 ± 20.4 μg ml(-1) for RTG-2 and CHO-K1 cells, respectively). There was no statistically significant difference between the two cell lines for this assay. For the Comet assay, standard 6 h exposure to TRIMP did not show any positive response for any of the cell types used. However, 48 h exposure to RTG-2 cells showed a concentration-dependent induction of DNA damage (r = 0.86). The highest concentration of TRIMP used (i.e. 100 μg ml(-1)) showed relatively higher DNA damage, compared to ethyl methane sulfonate (EMS; 1 μg ml(-1) or 8 mM), a reference genotoxic agent, used concurrently. In contrast, 24 h exposure time for CHO-K1 cells did not show any concentration-dependent increase for this assay. For MN assay, a significant correlation was found between the MN induction and TRIMP concentration for both the cell lines (RTG-2: r = 0.68; CHO-K1: r = 0.79), although only the highest concentration used showed a significant increase for binucleated (BN) cell with micronuclei (BNMN). The study suggests that whilst the cells of different origin could exhibit similar cytotoxicity, they could display differential genotoxic effects. Furthermore, genotoxic effects of TRIMP are primarily exposure period dependent phenomena and, in addition to inhibiting the action of dihydrofolate reductase, oxidative stress could also contribute for the observed toxic effects, fish cells in general being more sensitive for genotoxic

  5. DNA staining with the fluorochromes EtBr, DAPI and YOYO-1 in the comet assay with tobacco plants after treatment with ethyl methanesulphonate, hyperthermia and DNase-I.

    PubMed

    Gichner, Tomás; Mukherjee, Anita; Velemínský, Jirí

    2006-06-16

    We applied the alkaline version of the single-cell gel electrophoresis (comet) assay to roots and leaves of tobacco (Nicotiana tabacum var. xanthi) seedlings or isolated leaf nuclei treated with: (1) the alkylating agent ethyl methanesulphonate, (2) necrotic heat treatments at 50 degrees C, and (3) DNase-I. All three treatments induced a dose-dependent increase in DNA migration, expressed as percentage of tail DNA. A comparison of the fluorochrome DNA dyes ethidium bromide, DAPI and YOYO-1 demonstrated that for the alkaline version of the comet assay in plants, the commonly used fluorescent dye ethidium bromide can be used with the same efficiency as DAPI or YOYO-1.

  6. Evaluation of DNA Single and Double Strand Breaks in Women with Cervical Neoplasia Based on Alkaline and Neutral Comet Assay Techniques

    PubMed Central

    Cortés-Gutiérrez, Elva I.; Hernández-Garza, Fernando; García-Pérez, Jorge O.; Dávila-Rodríguez, Martha I.; Aguado-Barrera, Miguel E.; Cerda-Flores, Ricardo M.

    2012-01-01

    A hospital-based unmatched case-control study was performed in order to determine the relation of DNA single (ssb) and double (dsb) strand breaks in women with and without cervical neoplasia. Cervical epithelial cells of 30 women: 10 with low grade squamous intraepithelial lesions (LG-SIL), 10 with high-grade SIL (HG-SIL), and 10 without cervical lesions were evaluated using alkaline and neutral comet assays. A significant increase in global DNA damage (ssb + dsb) and dsb was observed in patients with HG-SIL (48.90 ± 12.87 and 23.50 ± 13.91), patients with LG-SIL (33.60 ± 14.96 and 11.20 ± 5.71), and controls (21.70 ± 11.87 and 5.30 ± 5.38; resp.). Pearson correlation coefficient reveled a strong relation between the levels ssb and dsb (r2 = 0.99, P = 0.03, and r2 = 0.94, P = 0.16, resp.) and progression of neoplasia. The increase of dsb damage in patients with HG-SIL was confirmed by DNA breakage detection-FISH (DBD-FISH) on neutral comets. Our results argue in favor of a real genomic instability in women with cervical neoplasia, which was strengthened by our finding of a higher proportion of DNA dsb. PMID:23093842

  7. Measurement Protocols for In situ Analysis of Organic Compounds at Mars and Comets

    NASA Technical Reports Server (NTRS)

    Mahaffy, P. R.; Brinckerhuff, W. B.; Buch, A.; Cabane, M.; Coll, P.; Demick, J.; Glavin, D. P.; Navarro-Gonzalez, R.

    2005-01-01

    The determination of the abundance and chemical and isotopic composition of organic molecules in comets and those that might be found in protected environments at Mars is a first step toward understanding prebiotic chemistries on these solar system bodies. While future sample return missions from Mars and comets will enable detailed chemical and isotopic analysis with a wide range of analytical techniques, precursor insitu investigations can complement these missions and facilitate the identification of optimal sites for sample return. Robust automated experiments that make efficient use of limited spacecraft power, mass, and data volume resources are required for use by insitu missions. Within these constraints we continue to explore a range of instrument techniques and measurement protocols that can maximize the return from such insitu investigations.

  8. Measurement Protocols for In Situ Analysis of Organic Compounds at Mars and Comets

    NASA Technical Reports Server (NTRS)

    Mahaffy, P. R.; Brinckerhoff, W. B.; Buch, A.; Cabane, M.; Coll, P.; Demick, J.; Glavin, D. P.; Navarro-Gonzalez, R.

    2005-01-01

    The determination of the abundance and chemical and isotopic composition of organic molecules in comets and those that might be found in protected environments at Mars is a first step toward understanding prebiotic chemistries on these solar system bodies. While future sample return missions from Mars and comets will enable detailed chemical and isotopic analysis with a wide range of analytical techniques, precursor insitu investigations can complement these missions and facilitate the identification of optimal sites for sample return. Robust automated experiments that make efficient use of limited spacecraft power, mass, and data volume resources are required for use by insitu missions. Within these constraints we continue to explore a range of instrument techniques and measurement protocols that can maximize the return from such insitu investigations.

  9. In vitro cytotoxic and non-genotoxic effects of gutta-percha solvents on mouse lymphoma cells by single cell gel (comet) assay.

    PubMed

    Ribeiro, Daniel Araki; Marques, Mariângela Esther Alencar; Salvador, Daisy Maria Fávero

    2006-01-01

    Chloroform and eucalyptol are widely used in clinical dentistry as gutta-percha solvents. However, these compounds may represent a hazard to human health, especially by causing injury to genetic apparatus and/or inducing cellular death. In this study, the genotoxic and cytotoxic potentials associated with exposure to chloroform and eucalyptol were assessed on mouse lymphoma cells in vitro by the single cell gel (comet) assay and trypan blue exclusion test, respectively. Both gutta-percha solvents proved to be cytotoxic at the same levels in concentrations of 2.5, 5 and 10 microL/mL (p<0.05). On the other hand, neither of the solvents induced DNA breakage. Taken together, these results suggest that although both tested compounds (chloroform and eucalyptol) are strong cytotoxicants, it seems that they are not likely to increase the level of DNA damage on mammalian cells.

  10. Analysis of Gold Ores by Fire Assay

    ERIC Educational Resources Information Center

    Blyth, Kristy M.; Phillips, David N.; van Bronswijk, Wilhelm

    2004-01-01

    Students of an Applied Chemistry degree course carried out a fire-assay exercise. The analysis showed that the technique was a worthwhile quantitative analytical technique and covered interesting theory including acid-base and redox chemistry and other concepts such as inquarting and cupelling.

  11. Analysis of dust in the coma of comet 67P using VIRTIS-M observations

    NASA Astrophysics Data System (ADS)

    Rinaldi, G.; Tozzi, G. P.; Fink, U.; Doose, L.; Capaccioni, F.; Filacchione, G.; Bockelée-Morvan, D.; Leyrat, C.; Piccioni, G.; Blecka, M.; Ciarniello, M.; Irwin, P.; Combi, M.; Palomba, E.; Migliorini, A.; Capria, M. T.; Faggi, S.; Tosi, F.

    2015-10-01

    We present a preliminary overview of the analysis on the dust spectrophotometry in the inner coma of comet 67/P that was obtained during the escort phase (started on December 2014) with the imaging spectrometer VIRTIS-M onboard the Rosetta mission [1]. The morphology and behavior of the dust coma has been monitored by VIRTIS-M from the arrival at the comet (~August 2014) throughout the early escort phase. The data reveal intricate details and numerous radial jets coming from different regions on the surface. On March 15, 2015, VIRTIS-M performed a set of 22 coma observations, each about 23 minutes in duration and offset from the nucleus by about 1 km. The 22 observations lasted about 12 hours and thus covered a complete rotation of the comet. The maps of the dust distribution in the coma reveal three major structures: a roughly uniform background dusty coma, several enhanced radiance jet features and a region that shows a thermal radiation component between 3.5 and 5.0 μm. (Figure 1 and Figure 2) The jets features can be traced back to several region of the comet, neck,body and head. We shall analyse the three major structures to provide the basis to understand coma composition and properties and the relation between gas and dust. We will discuss the morphology of the background coma, the jet and the enhanced thermal radiation. We will also examine correlations between the water vapor column density and the coma/ jet /thermal radiation intensity. For the thermal radiation component there are several explanations, viz: stray instrumental scattered light or instrumental ghosts from heated part of the nucleus, or thermal rad iation emanating from the nucleus and scattered by the dust in closest proximity or a region of small particles in the coma heated by solar radiation.

  12. BENZO[A]PYRENE AND ITS K-REGION DIOL INDUCE DNA DAMAGE IN C3H10T1/2C18 CELLS AS MEASURED BY THE ALKALINE SINGLE CELL GEL (COMET) ASSAY

    EPA Science Inventory


    160. Benzo[a]pyrene and its K-region diol induce DNA damage in C3HlOTl/2Cl8 cells as measured by the alkaline single cell gel (Comet) assay

    In a continuing series of studies on the genotoxicity ofK-region dihydrodiols of polycyclic aromatic hydrocarbons, we have repo...

  13. Atlas of Great Comets

    NASA Astrophysics Data System (ADS)

    Stoyan, Ronald; Dunlop, Storm

    2015-01-01

    Foreword; Using this book; Part I. Introduction: Cometary beliefs and fears; Comets in art; Comets in literature and poetry; Comets in science; Cometary science today; Great comets in antiquity; Great comets of the Middle Ages; Part II. The 30 Greatest Comets of Modern Times: The Great Comet of 1471; Comet Halley 1531; The Great Comet of 1556; The Great Comet of 1577; Comet Halley, 1607; The Great Comet of 1618; The Great Comet of 1664; Comet Kirch, 1680; Comet Halley, 1682; The Great Comet of 1744; Comet Halley, 1759; Comet Messier, 1769; Comet Flaugergues, 1811; Comet Halley, 1835; The Great March Comet of 1843; Comet Donati, 1858; Comet Tebbutt, 1861; The Great September Comet of 1882; The Great January Comet of 1910; Comet Halley, 1910; Comet Arend-Roland, 1956; Comet Ikeya-Seki, 1965; Comet Bennett, 1970; Comet Kohoutek, 1973-4; Comet West, 1976; Comet Halley, 1986; Comet Shoemaker-Levy 9, 1994; Comet Hyakutake, 1996; Comet Hale-Bopp, 1997; Comet McNaught, 2007; Part III. Appendices; Table of comet data; Glossary; References; Photo credits; Index.

  14. Automated Protein Assay Using Flow Injection Analysis

    NASA Astrophysics Data System (ADS)

    Wolfe, Carrie A. C.; Oates, Matthew R.; Hage, David S.

    1998-08-01

    The technique of flow injection analysis (FIA) is a common instrumental method used in detecting a variety of chemical and biological agents. This paper describes an undergraduate laboratory that uses FIA to perform a bicinchoninic acid (BCA) colorimetric assay for quantitating protein samples. The method requires less than 2 min per sample injection and gives a response over a broad range of protein concentrations. This method can be used in instrumental analysis labs to illustrate the principles and use of FIA, or as a means for introducing students to common methods employed in the analysis of biological agents.

  15. Giotto data analysis: Electron plasma and heavy ion composition measurements at Comet Halley

    NASA Technical Reports Server (NTRS)

    Lin, Robert P.

    1992-01-01

    This investigation involved the analysis of electron plasma and heavy ion composition measurements made by the COPERNIC (COmplete Positive ion, Electron, and Ram Negative Ion measurements near Comet Halley) plasma experiment during the close fly-by of Halley by the European Space Agency's Giotto spacecraft. The experiment provided measurements of the full 3-dimensional distribution of 10 eV-30 keV electrons, and mass analysis of cold cometary ions from 10-210 amu. The analysis of the COPERNIC data has yielded some remarkable results, including: The discovery of negatively charged ions in the inner coma; the discovery of far heavier (mass is greater than 50 amu) ions than predicted, dominated by complex molecular ions made up of C, H, O, and N; the discovery of an adiabatic heating effect on electrons from the compression of the solar wind plasma; the identification of several organic and sulfur bearing ions; and the discovery of a new 'mystery region' where electrons are accelerated to high energies. These discoveries were in addition to the detailed analysis of 'expected' features at Comet Halley. Although this grant has expired, analysis continues on the data at a low (unfunded) level, and it is expected that more significant results will be obtained. A bibliography of the papers resulting from this research is attached, and a copy of each paper is included.

  16. Genotoxicity study with special reference to DNA damage by comet assay in fission yeast, Schizosaccharomyces pombe exposed to drinking water.

    PubMed

    Banerjee, Pamela; Talapatra, Soumendra N; Mandal, Nivedita; Sundaram, Geetanjali; Mukhopadhyay, Aniruddha; Chattopadhyay, Dhrubajyoti; Banerjee, Sudip K

    2008-01-01

    The objective of this study was to investigate genotoxicity, especially DNA damage, in drinking water samples collected from tap by using fission yeast Schizosaccharomyces pombe as a model organism. Generally raw water potabolization is done by treatment with polymeric coagulant, alum, chlorine, etc. In the comet test, highly significant (P<0.001) effects of DNA damage were detected in treated water (tap water) when compared to negative control (raw water) as well as laboratory control (distilled water) samples for both 1 h and 2 h exposure. In the water treatment plant, raw water treatment is done by the process of prechlorination, alum and polymeric coagulant (CatflocT) dosing, postchlorination, filtration and final discharge for consumption. In conclusion it can be stated from the results that chlorinated disinfectant, alum and polymeric coagulant (CatflocT) mixture used in drinking water has a potent cumulative genotoxic effect in the eukaryotic cells and may pose potential genotoxic risk for human health following long-term consumption.

  17. Radiation-induced DNA damage in canine hemopoietic cells and stromal cells as measured by the comet assay

    SciTech Connect

    Kreja, L.; Selig, C.; Plappert, U.; Nothdurft, W.

    1996-12-31

    Stromal cell progenitors (fibroblastoid colony-forming unit; CFU-Fs) are representative of the progenitor cell population of the hemopoietic microenvironment in bone marrow (BM). Previous studies of the radiation dose-effect relationships for colony formation have shown that canine CFU-Fs are relatively radioresistant as characterized by a D{sub 0} value of about 2.4 Gy. In contrast, hemopoietic progenitors are particularly radiosensitive (D{sub 0} values = 0.12-0.60 Gy). In the present study, the alkaline single-cell gel electrophoresis technique for the in situ quantitation of DNA strand breaks and alkalilabile site was employed. Canine buffy coat cells from BM aspirates and cells harvested from CFU-F colonies or from mixed populations of adherent BM stromal cell (SC) layers were exposed to increasing doses of X-rays, embedded in agarose gel on slides, lysed with detergents, and placed in an electric field. DNA migrating from single cells in the gel was made visible as {open_quotes}comets{close_quotes} by ethidium bromide staining. Immediate DNA damage was much less in cultured stromal cells than in hemopoietic cells in BM aspirates. These results suggest that the observed differences in clonogenic survival could be partly due to differences in the type of the initial DNA damage between stromal cells and hemopoietic cells. 37 refs., 2 figs., 1 tab.

  18. Advanced analysis techniques for uranium assay

    SciTech Connect

    Geist, W. H.; Ensslin, Norbert; Carrillo, L. A.; Beard, C. A.

    2001-01-01

    Uranium has a negligible passive neutron emission rate making its assay practicable only with an active interrogation method. The active interrogation uses external neutron sources to induce fission events in the uranium in order to determine the mass. This technique requires careful calibration with standards that are representative of the items to be assayed. The samples to be measured are not always well represented by the available standards which often leads to large biases. A technique of active multiplicity counting is being developed to reduce some of these assay difficulties. Active multiplicity counting uses the measured doubles and triples count rates to determine the neutron multiplication (f4) and the product of the source-sample coupling ( C ) and the 235U mass (m). Since the 35U mass always appears in the multiplicity equations as the product of Cm, the coupling needs to be determined before the mass can be known. A relationship has been developed that relates the coupling to the neutron multiplication. The relationship is based on both an analytical derivation and also on empirical observations. To determine a scaling constant present in this relationship, known standards must be used. Evaluation of experimental data revealed an improvement over the traditional calibration curve analysis method of fitting the doubles count rate to the 235Um ass. Active multiplicity assay appears to relax the requirement that the calibration standards and unknown items have the same chemical form and geometry.

  19. Cosima - Cometary Dust Analysis Next to Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Hilchenbach, M.; Kissel, J.; Briois, C.; Henkel, H.; Langevin, Y.; Schulz, R.; Silen, J. V.; Altwegg, K.; Colangeli, L.; Cottin, H.; Engrand, C.; Glasmachers, A.; Grün, E.; Haerendel, G.; Höfner, H.; Hornung, K.; Jessberger, E.; Koch, A.; Lehto, H.; Lehto, K.; Raulin, F.; Le Roy, L.; Rynö, J.; Steiger, W.; Stephan, T.; Thirkell, L.; Thomas, R.; Torkar, K.; Varmuza, K.; Wanczek, K. P.

    2014-12-01

    After a long journey through the inner solar system, ESA's corner stone mission ROSETTA has arrived at comet 67P/Churyumov-Gerasimenko. COSIMA or the COmetary Secondary Ion Mass Analyzer onboard ROSETTA is a secondary ion mass spectrometer focussing on in-situ measurements of the composition of cometary grains collected next to the nucleus and inner coma. High resolution mass spectra will contain complex mixtures of mineral and organic elements and molecules as well as molecular fragments representing the elements and molecules on the surface of the cometary grains. We will report on first results of the in-situ analysis of cometary grains as captured, imaged and analysed by COSIMA .

  20. Great Comets

    NASA Astrophysics Data System (ADS)

    Burnham, Robert

    2000-05-01

    Spectacular and mysterious objects that come and go in the night sky, comets have dwelt in our popular culture for untold ages. As remnants from the formation of the Solar system, they are objects of key scientific research and space missions. As one of nature's most potent and dramatic dangers, they pose a threat to our safety--and yet they were the origin of our oceans and perhaps even life itself. This beautifully illustrated book tells the story of the biggest and most awe-inspiring of all comets: those that have earned the title "Great." Robert Burnham focuses on the Great comets Hyakutake in 1996 and Hale-Bopp in 1997, which gripped attention worldwide because, for many, they were the first comets ever seen. He places these two recent comets in the context of their predecessors from past ages, among them the famous Comet Halley. Great Comets explains the exciting new discoveries that have come from these magnificent objects and profiles the spaceprobes to comets due for launch in the next few years. The book even takes a peek behind Hollywood's science-fiction fantasies to assess the real risks humanity faces from potential impacts of both comets and asteroids. For everyone interested in astronomy, this exciting book reveals the secrets of the Great Comets and provides essential tools for keeping up to date with comet discoveries in the future. Robert Burnham has been an amateur astronomer since the mid-1950s. He has been a senior editor of Astronomy magazine (1986-88) and is the author of many books and CD-ROMS, including Comet Hale-Bopp: Find and Enjoy the Great Comet and Comet Explorer.

  1. Entry Dispersion Analysis for the Stardust Comet Sample Return Capsule

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Mitcheltree, Robert A.; Cheatwood, F. McNeil

    1997-01-01

    Stardust will be the first mission to return samples from beyond the Earth-Moon system. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study analyzes the entry, descent, and landing of the returning sample capsule. The effects of two aerodynamic instabilities are revealed (one in the high altitude free molecular regime and the other in the transonic/subsonic flow regime). These instabilities could lead to unacceptably large excursions in the angle-of-attack near peak heating and main parachute deployment, respectively. To reduce the excursions resulting from the high altitude instability, the entry spin rate of the capsule is increased. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by an accelerometer and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) shows that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust program limits. Additionally, the size of the resulting 3-sigma landing ellipse is 83.5 km in downrange by 29.2 km in crossrange, which is within the Utah Test and Training Range boundaries.

  2. JaCVAM-organized international validation study of the in vivo rodent alkaline comet assay for the detection of genotoxic carcinogens: I. Summary of pre-validation study results.

    PubMed

    Uno, Yoshifumi; Kojima, Hajime; Omori, Takashi; Corvi, Raffaella; Honma, Masamistu; Schechtman, Leonard M; Tice, Raymond R; Burlinson, Brian; Escobar, Patricia A; Kraynak, Andrew R; Nakagawa, Yuzuki; Nakajima, Madoka; Pant, Kamala; Asano, Norihide; Lovell, David; Morita, Takeshi; Ohno, Yasuo; Hayashi, Makoto

    2015-07-01

    The in vivo rodent alkaline comet assay (comet assay) is used internationally to investigate the in vivo genotoxic potential of test chemicals. This assay, however, has not previously been formally validated. The Japanese Center for the Validation of Alternative Methods (JaCVAM), with the cooperation of the U.S. NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)/the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), the European Centre for the Validation of Alternative Methods (ECVAM), and the Japanese Environmental Mutagen Society/Mammalian Mutagenesis Study Group (JEMS/MMS), organized an international validation study to evaluate the reliability and relevance of the assay for identifying genotoxic carcinogens, using liver and stomach as target organs. The ultimate goal of this validation effort was to establish an Organisation for Economic Co-operation and Development (OECD) test guideline. The purpose of the pre-validation studies (i.e., Phase 1 through 3), conducted in four or five laboratories with extensive comet assay experience, was to optimize the protocol to be used during the definitive validation study.

  3. The nucleus of Comet 67P/Churyumov-Gerasimenko. A new shape model and thermophysical analysis

    NASA Astrophysics Data System (ADS)

    Lowry, S.; Duddy, S. R.; Rozitis, B.; Green, S. F.; Fitzsimmons, A.; Snodgrass, C.; Hsieh, H. H.; Hainaut, O.

    2012-12-01

    Context. Comet 67P/Churyumov-Gerasimenko is the target of the European Space Agency Rosetta spacecraft rendez-vous mission. Detailed physical characteristation of the comet before arrival is important for mission planning as well as providing a test bed for ground-based observing and data-analysis methods. Aims: To conduct a long-term observational programme to characterize the physical properties of the nucleus of the comet, via ground-based optical photometry, and to combine our new data with all available nucleus data from the literature. Methods: We applied aperture photometry techniques on our imaging data and combined the extracted rotational lightcurves with data from the literature. Optical lightcurve inversion techniques were applied to constrain the spin state of the nucleus and its broad shape. We performed a detailed surface thermal analysis with the shape model and optical photometry by incorporating both into the new Advanced Thermophysical Model (ATPM), along with all available Spitzer 8-24 μm thermal-IR flux measurements from the literature. Results: A convex triangular-facet shape model was determined with axial ratios b/a = 1.239 and c/a = 0.819. These values can vary by as much as 7% in each axis and still result in a statistically significant fit to the observational data. Our best spin state solution has Psid = 12.76137 ± 0.00006 h, and a rotational pole orientated at Ecliptic coordinates λ = 78°(±10°), β = + 58°(±10°). The nucleus phase darkening behaviour was measured and best characterized using the IAU HG system. Best fit parameters are: G = 0.11 ± 0.12 and HR(1,1,0) = 15.31 ± 0.07. Our shape model combined with the ATPM can satisfactorily reconcile all optical and thermal-IR data, with the fit to the Spitzer 24 μm data taken in February 2004 being exceptionally good. We derive a range of mutually-consistent physical parameters for each thermal-IR data set, including effective radius, geometric albedo, surface thermal inertia

  4. Stable isotope dilution assays in mycotoxin analysis.

    PubMed

    Rychlik, Michael; Asam, Stefan

    2008-01-01

    The principle and applications of stable isotope dilution assays (SIDAs) in mycotoxin analysis are critically reviewed. The general section includes historical aspects of SIDAs, the prerequisites and limitations of the use of stable isotopically labelled internal standards, and possible calibration procedures. In the application section actual SIDAs for the analysis of trichothecenes, zearalenone, fumonisins, patulin, and ochratoxin A are presented. The syntheses and availability of labelled mycotoxins for use as internal standards is reviewed and specific advances in food analysis and toxicology are demonstrated. The review indicates that LC-MS applications, in particular, require the use of stable isotopically labelled standards to compensate for losses during clean-up and for discrimination due to ion suppression. As the commercial availability of these compounds continues to increase, SIDAs can be expected to find expanding use in mycotoxin analysis.

  5. Evaluation of the mutagenicity and genotoxic potential of carvacrol and thymol using the Ames Salmonella test and alkaline, Endo III- and FPG-modified comet assays with the human cell line Caco-2.

    PubMed

    LLana-Ruiz-Cabello, Maria; Maisanaba, Sara; Puerto, Maria; Prieto, Ana I; Pichardo, Silvia; Jos, Ángeles; Cameán, Ana M

    2014-10-01

    Currently, direct antimicrobial and antioxidant additives derived from essential oils are used in food packaging and are perceived by consumers as low-health-risk compounds. In this study, we investigated the potential mutagenicity and genotoxicity of carvacrol and thymol, major compounds in several essential oils, using the Ames Salmonella test and the alkaline, Endo III- and formamidopyrimidine glycosylase (FPG)-modified comet assays, respectively. Thymol did not show any mutagenic activity at any concentration assayed (0-250 μM), whereas carvacrol exhibited mutagenic potential, displaying greater activity in presence of the metabolic fraction (29-460 μM). The genotoxic effects were evaluated in the human colon carcinoma cell line Caco-2, and the standard comet assay revealed that neither carvacrol (0-460 μM) nor thymol (0-250 μM) had any affects at 24 and 48 h. The FPG-modified comet assay showed that the highest concentration of carvacrol (460 μM) caused DNA damage, indicating damage to the purine bases. These results should be used to identify the appropriate concentrations of carvacrol and thymol as additives in food packaging. Moreover, further studies are necessary to explore the safety and/or the toxicity mechanisms of these compounds.

  6. Trajectory analysis for the nucleus and dust of comet C/2013 A1 (Siding Spring)

    SciTech Connect

    Farnocchia, Davide; Chesley, Steven R.; Chodas, Paul W.; Tricarico, Pasquale; Kelley, Michael S. P.; Farnham, Tony L.

    2014-08-01

    Comet C/2013 A1 (Siding Spring) will experience a high velocity encounter with Mars on 2014 October 19 at a distance of 135,000 km ± 5000 km from the planet center. We present a comprehensive analysis of the trajectory of both the comet nucleus and the dust tail. The nucleus of C/2013 A1 cannot impact on Mars even in the case of unexpectedly large nongravitational perturbations. Furthermore, we compute the required ejection velocities for the dust grains of the tail to reach Mars as a function of particle radius and density and heliocentric distance of the ejection. A comparison between our results and the most current modeling of the ejection velocities suggests that impacts are possible only for millimeter to centimeter size particles released more than 13 AU from the Sun. However, this level of cometary activity that far from the Sun is considered extremely unlikely. The arrival time of these particles spans a 20-minute time interval centered at 2014 October 19 at 20:09 TDB, i.e., around the time that Mars crosses the orbital plane of C/2013 A1. Ejection velocities larger than currently estimated by a factor >2 would allow impacts for smaller particles ejected as close as 3 AU from the Sun. These particles would reach Mars from 19:13 TDB to 20:40 TDB.

  7. Use of DNA strand damage (Comet assay) and embryo hatching effects to assess contaminant exposure in blue crab (Callinectes sapidus) embryos

    SciTech Connect

    Lee, R.F.; Steinert, S.A.; Nakayama, K.; Oshima, Y.

    1999-07-01

    After fertilization, blue crab eggs are embedded in a sponge which is attached to the female abdomen during embryo development. Embryos after 9 stages in the egg sac hatch into a swimming zoea stage (stage 10). The authors have developed a bioassay where embryo development is monitored in culture plates with and without toxicants in the water. Toxicant effects are based on determining the percentage of embryos which hatch to zoea. Hatching EC{sub 50} (toxicant concentration at which 50% of the embryos fail to hatch) for a number of pesticides, organometallics and metals were determined. The test takes from 2 to 6 days depending on the embryo stage selected for the study. In addition to embryo development effects the prevalence of DNA single-strand breaks in individual embryo cells were determined using the single cell gel electrophoresis method (Comet assay). A good correlation between DNA strand breakage and embryo defects was found after exposure to genotoxic contaminants. Thus, the bioassay linking DNA damage to embryo hatching effects is rapid, sensitive and mechanistically relevant.

  8. Genotoxicity of the herbicide imazethapyr in mammalian cells by oxidative DNA damage evaluation using the Endo III and FPG alkaline comet assays.

    PubMed

    Soloneski, Sonia; Ruiz de Arcaute, Celeste; Nikoloff, Noelia; Larramendy, Marcelo L

    2017-03-07

    We evaluated the role of oxidative stress in the genotoxic damage induced by imazethapyr (IMZT) and its formulation Pivot® in mammalian CHO-K1 cell line. Using the alkaline comet assay, we observed that a concentration of 0.1 μg/mL of IMZT or Pivot® was able to induce DNA damage by increasing the frequency of damaged nucleoids. To test whether the DNA lesions were caused by oxidative stress, the DNA repair enzymes endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg), which convert base damage to strand breaks, were used. Our results demonstrate that after treatment of CHO-K1 cells with the pure active ingredient as well as the commercial formulation Pivot®, an increase in DNA strand breaks was observed after incubation of both Endo III and Fpg enzymes, indicating that both compounds induce DNA damage involving both pyrimidine and purine-based oxidations, at least in CHO-K1 cells. Our findings confirm the genotoxic potential of IMZT and suggest that this herbicide formulation must be employed with great caution, especially not only for exposed occupational workers but also for other living species.

  9. Validation of Comet assay in Oregon-R and Wild type strains of Drosophila melanogaster exposed to a natural radioactive environment in Brazilian semiarid region.

    PubMed

    Verçosa, Cícero Jorge; Moraes Filho, Aroldo Vieira de; Castro, Ícaro Fillipe de Araújo; Santos, Robson Gomes Dos; Cunha, Kenya Silva; Silva, Daniela de Melo E; Garcia, Ana Cristina Lauer; Navoni, Julio Alejandro; Amaral, Viviane Souza do; Rohde, Claudia

    2017-03-21

    Natural radiation of geological origin is a common phenomenon in Brazil, a country where radioactive agents such as uranium may be often found. As an unstable atom, uranium undergoes radioactive decay with the generation of a series of decay by-products, including radon, which may be highly genotoxic and trigger several pathological processes, among which cancer. Because it is a gas, radon may move freely between cracks and gaps in the ground, seeping upwards into the buildings and in the environment. In this study, two Drosophila melanogaster Meigen (Diptera, Drosophilidae) strains called Oregon-R and Wild (collected in a non-radioactive environment) were exposed to atmospheric radiation in the Lajes Pintadas city, in the semiarid zone of northeastern Brazil. After six days of environmental exposure, the organisms presented genetic damage significantly higher than that of the negative control group. The genotoxic effects observed reinforce the findings of other studies carried out in the same region, which warn about the environmental risks related to natural radioactivity occurrence. The results also validate the use of the Comet assay in hemocytes of D. melanogaster as a sensitive test to detect genotoxicity caused by natural radiation, and the use of a recently collected D. melanogaster strain in the environmental of radon.

  10. Assessment of the genotoxic potential along the Danube River by application of the comet assay on haemocytes of freshwater mussels: The Joint Danube Survey 3.

    PubMed

    Kolarević, Stoimir; Kračun-Kolarević, Margareta; Kostić, Jovana; Slobodnik, Jaroslav; Liška, Igor; Gačić, Zoran; Paunović, Momir; Knežević-Vukčević, Jelena; Vuković-Gačić, Branka

    2016-01-01

    In this study we assessed the level of genotoxic pollution along the Danube River by measuring the level of DNA damage in the haemocytes of freshwater mussels of Unio sp. (Unio pictorum/Unio tumidus) and Sinanodonta woodiana. The comet assay was used for the assessment of DNA damage. The research was performed on 34 out of 68 sites analysed within the Joint Danube Survey 3 - the world's biggest river research expedition of its kind in 2013. During research, 2285 river kilometres were covered with an average distance of 68 km between the sites. The complex data set on concentrations of various substances present in water, suspended particulate matter and sediment on investigated sites gave the opportunity to identify the groups of xenobiotics which mostly affect the studied biomarker - DNA damage. The highest levels of DNA damage were recorded in the section VI (Panonnian Plain), which is under the impact of untreated wastewater discharges. Both positive and negative influences of the large tributaries on the level of genotoxicity in the Danube River were evident. Significant correlation in response was detected between the studied species of freshwater mussels. The level of DNA damage in mussels correlated with concentrations of compounds from the group of hazardous priority substances (polycyclic aromatic hydrocarbons), persistent organic pollutants (dioxins) and emerging pollutants (Oxazepam, Chloridazon-desphenyl).

  11. Comparison of post-thaw DNA integrity of boar spermatozoa assessed with the neutral comet assay and Sperm-Sus Halomax test kit.

    PubMed

    Fraser, L; Parda, A; Filipowicz, K; Strzeżek, J

    2010-10-01

    In this study, we tested the hypothesis whether the neutral Comet assay (NCA) and the Sperm-Sus-Halomax (SSH) test kit could provide similar measurements of post-thaw DNA fragmentation of boar spermatozoa. Whole ejaculates or sperm-rich fractions of boar semen were frozen in an extender containing lactose, lipoprotein fractions isolated from ostrich egg yolk (LPFo), glycerol (lactose-LPFo-G) or in a standard boar semen extender (K3), without the addition of cryoprotective substances. In all boars, both the NCA and SSH test showed similar levels of post-thaw sperm DNA fragmentation in samples of the same ejaculates, regardless of the ejaculate collection procedure and extender. Yet, the levels of post-thaw sperm DNA damage, detected by the NCA and SSH test, were more accentuated in spermatozoa frozen in the absence of cryoprotective substances. Both the NCA and SSH detected variations among individual boars in terms of post-thaw sperm DNA fragmentation. Agreement between the measurements of the NCA and SSH was confirmed by scatter plots of differences, suggesting that the DNA integrity tests could detect the same sperm populations, which were susceptible to cryo-induced DNA damage. The findings of this study indicate that the NCA and the SSH test are effective in detecting similar levels of sperm DNA fragmentation and reinforce their importance in the assessment of frozen-thawed boar semen quality.

  12. Iron oxide nanoparticles show no toxicity in the comet assay in lymphocytes: A promising vehicle as a nitric oxide releasing nanocarrier in biomedical applications

    NASA Astrophysics Data System (ADS)

    de Lima, R.; Oliveira, J. L.; Murakami, P. S. K.; Molina, M. A. M.; Itri, R.; Haddad, P.; Seabra, A. B.

    2013-04-01

    This work reports the synthesis and toxicological evaluation of surface modified magnetic iron oxide nanoparticles as vehicles to carry and deliver nitric oxide (NO). The surface of the magnetic nanoparticles (MNPs) was coated with two thiol-containing hydrophilic ligands: mercaptosuccinic acid (MSA) or dimercaptosuccinic acid (DMSA), leading to thiolated MNPs. Free thiols groups on the surface of MSA- or DMSA-MNPs were nitrosated leading to NO-releasing MNPs. The genotoxicity of thiolated-coated MNPs was evaluated towards human lymphocyte cells by the comet assay. No genotoxicity was observed due to exposure of human lymphocytes to MSA- or DMSA-MNPs, indicating that these nanovectors can be used as inert vehicles in drug delivery, in biomedical applications. On the other hand, NO-releasing MPNs showed genotoxicity and apoptotic activities towards human lymphocyte cell cultures. These results indicate that NO-releasing MNPs may result in important biomedical applications, such as the treatment of tumors, in which MNPs can be guided to the target site through the application of an external magnetic field, and release NO directly to the desired site of action.

  13. Radiation-induced DNA double-strand breaks produced in histone-depleted tumor cell nuclei measured using the neutral comet assay

    SciTech Connect

    Olive, P.L.; Banath, J.P.

    1995-05-01

    Removal of histones and other nuclear proteins greatly enhances the sensitivity of mammalian cells to DNA damage by ionizing radiation. We examined the possibility that the ease of dissociation of histones, or the association of other nuclear proteins with DNA, may differ between radioresistant and sensitive human tumor cells. Cells embedded in agarose were exposed to increasing salt concentrations prior to irradiation and examination using a microscopic gel electrophoresis method, the neutral comet assay. Induction of double-strand breaks increased by a factor of about 20 when cells of four human tumor cell line HT144 melanoma, HT29 adenocarcinoma, DU145 prostate carcinoma and U87 glioma, were exposed to 2 M NaCl; however, no correlation with radiosensitivity was apparent. While a significant number of histone and non-histone proteins are present after extraction with 1.2 M NaCL, these proteins apparently have only a minor influence on radiosensitivity. However, if they are allowed to remain with DNA during electrophoresis, about 15 times more strand breaks are required to produce a similar amount of DNA migration in both DU145 and HT144 cells. These results suggest that the association between proteins and DNA within the nucleus, as probed by extraction with sodium chloride, does not help to explain differences in intrinsic radiosensitivity among cells of these diverse tumor cell lines. 33 refs., 11 figs.

  14. Evaluation of methyl methanesulfonate, 2,6-diaminotoluene and 5-fluorouracil: Part of the Japanese center for the validation of alternative methods (JaCVAM) international validation study of the in vivo rat alkaline comet assay.

    PubMed

    Plappert-Helbig, Ulla; Junker-Walker, Ursula; Martus, Hans-Joerg

    2015-07-01

    As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined methyl methanesulfonate, 2,6-diaminotoluene, and 5-fluorouracil under coded test conditions. Rats were treated orally with the maximum tolerated dose (MTD) and two additional descending doses of the respective compounds. In the MMS treated groups liver and stomach showed significantly elevated DNA damage at each dose level and a significant dose-response relationship. 2,6-diaminotoluene induced significantly elevated DNA damage in the liver at each dose and a statistically significant dose-response relationship whereas no DNA damage was obtained in the stomach. 5-fluorouracil did not induce DNA damage in either liver or stomach.

  15. Comet composition and Lab

    NASA Astrophysics Data System (ADS)

    Bockelée-Morvan, Dominique; Biver, Nicolas

    2016-10-01

    Comet composition and properties provide information on chemical and physical processes that occurred in the early Solar system, 4.6 Gyr ago. The study of comets and of star-forming regions both help for a better understanding of the formation of planetary systems. A review of our present knowledge of cometary composition is presented. We also discuss laboratory studies that would be helpful for data analysis.

  16. Halley's Comet.

    ERIC Educational Resources Information Center

    Carey, Tom

    1985-01-01

    Provides tips for viewing Comet Halley in the Northeast including best viewing dates from November 1985-January 1986. Discusses going south to view the comet in March-April 1986 and gives specific information about accommodations for the Halley Rally in Everglades National Park, southernmost site in the contiguous 48 states. (JHZ)

  17. A new analysis of Spitzer observations of Comet 29P/Schwassmann-Wachmann 1

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles A.; Fernández, Yanga R.; Lisse, Carey M.; Samarasinha, Nalin; Woodney, Laura M.

    2015-11-01

    We present a new analysis of Spitzer observations of Comet 29P/Schwassmann-Wachmann 1 taken on UT 2003 November 21, 23, and 24, similar to a previous investigation of the observations (Stansberry et al., 2004), but using the most recent Spitzer data pipeline products and intensive image processing techniques. Analysis of images from the IRAC 5.8 and 8.0 μ m bands and the MIPS 24.0 and 70.0 μ m bands resulted in photometry measurements of the nucleus after a suite of coma modeling and removal processes were implemented. SW1 was not identified in the 5.8 μ m image from the previous work so its incorporation into this analysis is entirely new. Using the Near Earth Asteroid Thermal Model (Harris, 1998) resulted in a nucleus radius measurement of R =30.2-2.9+3.7 km and an infrared beaming parameter value of η =0.99-0.19+0.26 . We also measured an infrared geometric albedo, p5.8 = 0.5 ± 0.5 . Extrapolating a 0.04 V-band albedo and using a normalized reflectivity gradient S‧ = 14.94 ± 1.09 [% (1000 Å)-1] (Duffard, R., et al. [2014]. Astron. Astrophys. 564, A92) we recover an infrared albedo of p5.8 = 0.31 in the near infrared consistent with the value recovered from thermal modeling. The dust composition extracted from IRS spectra are very comet-like, containing mainly amorphous ferromagnesian silicates (but with a minority of crystalline silicates as well), water ice, and metal sulfides.

  18. Podosome reformation in macrophages: assays and analysis.

    PubMed

    Cervero, Pasquale; Panzer, Linda; Linder, Stefan

    2013-01-01

    Podosomes are multifunctional organelles of invasive cells that combine several key abilities including cell-matrix adhesion, extracellular matrix degradation, and mechanosensing. In combination with their high turnover rates that allow quick adaptation to the pericellular environment, podosomes are likely to play important roles during invasive migration of cells. Primary human macrophages constitutively form numerous podosomes and are thus an ideal system for the quantitative study of podosome dynamics. This protocol describes assays for the study of podosome dynamics, namely, reformation of podosomes, in fixed and living cells, with subsequent software-based analyses allowing the extraction of quantitative parameters such as the number of podosomes per cell, podosome density, and half times for podosome disruption and reformation. Moreover, we describe the preparation of podosome-enriched cell fractions and their analysis by immunoblotting.

  19. Comet fluorescence in situ hybridization analysis for oxidative stress-induced DNA damage in colon cancer relevant genes.

    PubMed

    Glei, Michael; Schaeferhenrich, Anja; Claussen, Uwe; Kuechler, Alma; Liehr, Thomas; Weise, Anja; Marian, Brigitte; Sendt, Wolfgang; Pool-Zobel, Beatrice L

    2007-04-01

    Our objective was to study whether products of oxidative stress, such as hydrogen peroxide (H(2)O(2)), trans-2-hexenal, and 4-hydroxy-2-nonenal (HNE), cause DNA damage in genes, relevant for human colon cancer. For this, total DNA damage was measured in primary human colon cells and colon adenoma cells (LT97) using the single-cell gel electrophoresis assay, known as "Comet Assay." APC, KRAS, and TP53 were marked in the comet images using fluorescence in situ hybridization (Comet FISH). The migration of APC, KRAS, or TP53 signals into the comet tails was quantified and compared to total DNA damage. All three substances were clearly genotoxic for APC, KRAS, and TP53 genes and total DNA in both types of cells. In primary colon cells, TP53 gene was more sensitive toward H(2)O(2), trans-2-hexenal, and HNE than total DNA was. In LT97 cells, the TP53 gene was more sensitive only toward trans-2-hexenal and HNE. APC and KRAS genes were more susceptible than total DNA to both lipid peroxidation products but only in primary colon cells. This suggests genotoxic effects of lipid peroxidation products in APC, KRAS, and TP53 genes. In LT97 cells, TP53 was more susceptible than APC and KRAS toward HNE. Based on the reported gatekeeper properties of TP53, which in colon adenoma is frequently altered to yield carcinoma, this implies that HNE is likely to contribute to cancer progression. This new experimental approach facilitates studies on effects of nutrition-related carcinogens in relevant target genes.

  20. Photometrical analysis of the neck-line structure of Comet Halley

    SciTech Connect

    Cremonese, G.; Fulle, M.; Osservatorio Astronomico, Trieste )

    1989-08-01

    The Fulle and Sedmak (1988) quantitative analysis of Neck-Line Structures (NLSs) is presently applied to the dust streamer and the real antitail noted in images obtained for Comet Halley during April-June, 1986. Results for the dust size distribution at very large sizes, the time-dependent dust velocity ejection velocity from the inner coma, and the anisotropy of dust are related to the January 10-18, 1986 interval. The power index of the size distribution fitting the NLS isophotes is -4.0 for 0.2-2.0 mm, and -0.4 for 2-10 mm; the strong excess of large dust suggested by McDonnell, et al. (1987) to account for the Giotto data is therefore confirmed. 18 refs.

  1. COSIMA - Cometary Dust Analysis in the inner coma of Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Hilchenbach, Martin; Kissel, Jochen; Briois, Christelle; von Hoerner, Hanna; Langevin , Yves; Schulz, Rita; Silen, Johan; Altwegg, Kathrin; Colangeli, Luigi; Cottin, Herve; Engrand, Cecile; Glasmachers, Albrecht; Gruen, Eberhard; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus; Jessberger, Elmar; Koch, Andreas; Letho, Harry; Letho, Kirsi; Raulin, Francois; Le Roy, Lena; Rynö, Jouni; Steiger , Wolfgang; Stephan , Thomas; Laurent, Thirkell; Thomas, Roger.; Torkar, Klaus; Varmuza, Kurt; Wanczek, Klaus Peter

    2014-11-01

    After a long journey through the inner solar system, ESA’s corner stone mission ROSETTA has arrived at comet 67P/Churyumov-Gerasimenko. COSIMA or the COmetary Secondary Ion Mass Analyzer onboard ROSETTA is a secondary ion mass spectrometer focussing on in-situ measurements of the composition of cometary grains collected near the nucleus and inner coma. High resolution mass spectra will contain ions of complex mixtures of mineral compounds and organic molecules as well as molecular fragments representing the elements and molecules on the surface of the cometary grains. We will report on our envisaged in-situ analysis goals of cometary grains as captured, imaged and analysed by COSIMA.

  2. Low-thrust mission risk analysis, with application to a 1980 rendezvous with the comet Encke

    NASA Technical Reports Server (NTRS)

    Yen, C. L.; Smith, D. B.

    1973-01-01

    A computerized failure process simulation procedure is used to evaluate the risk in a solar electric space mission. The procedure uses currently available thrust-subsystem reliability data and performs approximate simulations of the thrust sybsystem burn operation, the system failure processes, and the retargeting operations. The method is applied to assess the risks in carrying out a 1980 rendezvous mission to the comet Encke. Analysis of the results and evaluation of the effects of various risk factors on the mission show that system component failure rates are the limiting factors in attaining a high mission relability. It is also shown that a well-designed trajectory and system operation mode can be used effectively to partially compensate for unreliable thruster performance.

  3. Effects of motexafin gadolinium on DNA damage and X-ray-induced DNA damage repair, as assessed by the Comet assay

    SciTech Connect

    Donnelly, Erling T.; Liu Yanfeng; Paul, Tracy K.; Rockwell, Sara . E-mail: sara.rockwell@yale.edu

    2005-07-15

    Purpose: To investigate the effects of motexafin gadolinium (MGd) on the levels of reactive oxygen species (ROS), glutathione (GSH), and DNA damage in EMT6 mouse mammary carcinoma cells. The ability of MGd to alter radiosensitivity and to inhibit DNA damage repair after X-ray irradiation was also evaluated. Methods and Materials: Reactive oxygen species and GSH levels were assessed by 2,7-dichlorofluorescein fluorescence flow cytometry and the Tietze method, respectively. Cellular radiosensitivity was assessed by clonogenic assays. Deoxyribonucleic acid damage and DNA damage repair were assessed in plateau-phase EMT6 cells by the Comet assay and clonogenic assays. Results: Cells treated with 100 {mu}mol/L MGd plus equimolar ascorbic acid (AA) had significantly increased levels of ROS and a 58.9% {+-} 3.4% decrease in GSH levels, relative to controls. Motexafin gadolinium plus AA treatment increased the hypoxic, but not the aerobic, radiosensitivity of EMT6 cells. There were increased levels of single-strand breaks in cells treated with 100 {mu}mol/L MGd plus equimolar AA, as evidenced by changes in the alkaline tail moment (MGd + AA, 6 h: 14.7 {+-} 1.8; control: 2.8 {+-} 0.9). The level of single-strand breaks was dependent on the length of treatment. Motexafin gadolinium plus AA did not increase double-strand breaks. The repair of single-strand breaks at 2 h, but not at 4 h and 6 h, after irradiation was altered significantly in cells treated with MGd plus AA (MGd + AA, 2 h: 15.8 {+-} 3.4; control: 5.8 {+-} 0.6). Motexafin gadolinium did not alter the repair of double-strand breaks at any time after irradiation with 10 Gy. Conclusions: Motexafin gadolinium plus AA generated ROS, which in turn altered GSH homeostasis and induced DNA strand breaks. The MGd plus AA-mediated alteration of GSH levels increased the hypoxic, but not aerobic, radiosensitivity of EMT6 cells. Motexafin gadolinium altered the kinetics of single-strand break repair soon after irradiation but

  4. A Comet's Missing Light

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    On 28 November 2013, comet C/2012 S1 better known as comet ISON should have passed within two solar radii of the Suns surface as it reached perihelion in its orbit. But instead of shining in extreme ultraviolet (EUV) wavelengths as it grazed the solar surface, the comet was never detected by EUV instruments. What happened to comet ISON?Missing EmissionWhen a sungrazing comet passes through the solar corona, it leaves behind a trail of molecules evaporated from its surface. Some of these molecules emit EUV light, which can be detected by instruments on telescopes like the space-based Solar Dynamics Observatory (SDO).Comet ISON, a comet that arrived from deep space and was predicted to graze the Suns corona in November 2013, was expected to cause EUV emission during its close passage. But analysis of the data from multiple telescopes that tracked ISON in EUV including SDO reveals no sign of it at perihelion.In a recent study, Paul Bryans and DeanPesnell, scientists from NCARs High Altitude Observatory and NASA Goddard Space Flight Center, try to determine why ISON didnt display this expected emission.Comparing ISON and LovejoyIn December 2011, another comet dipped into the Suns corona: comet Lovejoy. This image, showingthe orbit Lovejoy took around the Sun, is a composite of SDO images of the pre- and post-perihelion phases of the orbit. Click for a closer look! The dashed part of the curve represents where Lovejoy passed out of view behind the Sun. [Bryans Pesnell 2016]This is not the first time weve watched a sungrazing comet with EUV-detecting telescopes: Comet Lovejoy passed similarly close to the Sun in December 2011. But when Lovejoy grazed the solar corona, it emitted brightly in EUV. So why didnt ISON? Bryans and Pesnell argue that there are two possibilities:the coronal conditions experienced by the two comets were not similar, orthe two comets themselves were not similar.To establish which factor is the most relevant, the authors first demonstrate that both

  5. Sensitive field assays for water analysis

    SciTech Connect

    Douglas, W.L.

    1984-08-01

    The goal of the project is to develop a rapid, simple, and inexpensive dry-film assay device for detection of environmental contaminants using the compound geosmin as a model. Phase I activities centered upon the immunochemical reagents necessary for the assay, development of an enzyme-cycling system that makes possible detection of substances in the parts per billion (PPB) range or lower, and demonstration of how the Immuno-Replacement-Assay can be used to detect geosmin.

  6. Assessment of DNA damage in coal open-cast mining workers using the cytokinesis-blocked micronucleus test and the comet assay.

    PubMed

    León-Mejía, Grethel; Espitia-Pérez, Lyda; Hoyos-Giraldo, Luz Stella; Da Silva, Juliana; Hartmann, Andreas; Henriques, João Antônio Pêgas; Quintana, Milton

    2011-01-15

    Coal mining is one of the most important causes of environmental pollution, as large quantities of coal dust particles are emitted. Colombia-South America has large natural coal reserves and "El Cerrejón" is the world's largest open-cast mine located in the northern department of Guajira. The aim of the present study was to evaluate genotoxic effects in a population exposed to coal residues from the open-cast mine "El Cerrejón". 100 exposed workers and 100 non-exposed control individuals were included in this study. The exposed group was divided according to different mining area activities: (i). Transport of extracted coal, (ii). Equipment field maintenance, (iii). Coal stripping and, (iv). Coal embarking. Blood samples were taken to investigate biomarkers of genotoxicity, specifically, primary DNA damage as damage index (DI), tail length and% of tail DNA using the Comet assay (alkaline version) and chromosome damage as micronucleus (MN) frequency in lymphocytes. Both biomarkers showed statistically significantly higher values in the exposed group compared to the non-exposed control group. No difference was observed between the exposed groups executing different mining activities. These results indicate that exposure to coal mining residues may result in an increased genotoxic exposure in coal mining workers. We did not find a correlation between age, alcohol consumption and service time with the biomarkers of genotoxicity. Our results are the first data of genotoxic effects induced by coal mining exposure in Colombia, and thus, contribute to the exploration of test batteries use for monitoring of exposed populations and may stimulate designing control, hygiene and prevention strategies for occupational health risk assessment in developing countries.

  7. SiO2 Nanoparticule-induced size-dependent genotoxicity - an in vitro study using sister chromatid exchange, micronucleus and comet assay.

    PubMed

    Battal, Dilek; Çelik, Ayla; Güler, Gizem; Aktaş, Ayça; Yildirimcan, Saadet; Ocakoglu, Kasim; Çömelekoǧlu, Ülkü

    2015-04-01

    Fine particles with a characteristic size smaller than 100 nm (i.e. nanoparticlesspread out in nowadays life. Silicon or Si, is one of the most abundant chemical elements found on the Earth. Its oxide forms, such as silicate (SiO4) and silicon dioxide, also known as silica (SiO2), are the main constituents of sand and quartz contributing to 90% of the Earth's crust. In this work, three genotoxicity systems "sister chromatid exchange, cytokinesis block micronucleus test and single cell gel electrophoresis (comet) assay" were employed to provide further insight into the cytotoxic and mutagenic/genotoxic potential of SiO2 nanoparticules (particle size 6 nm, 20 nm, 50 nm) in cultured peripheral blood lymphocytes as in vitro. It was observed that there is a significant decrease in Mitotic index (MI), Cytokinesis block proliferation index (CBPI), proliferation index (PRI) values expressed as Cell Kinetic parameters compared with negative control (p < 0.05). There is a statistically significant difference between negative control culture and culture exposed to SiO2 (6 nm, 20 nm, 50 nm) (p < 0.01, p < 0.01, p < 0.05, respectively). It is found that SiO2 nanoparticles at different size (6, 20, 50 nm) progressively increased the SCE frequency and DNA damage on the basis the AU values compared with negative control (p < 0.05). Results showed that the genotoxic/mutagenic and cytotoxic effects of SiO2 nanoparticules is dependent to particule size.

  8. Genotoxicity evaluation of the herbicide Garlon(®) and its active ingredient (triclopyr) in fish (Anguilla anguilla L.) using the comet assay.

    PubMed

    Guilherme, Sofia; Santos, Maria A; Gaivão, Isabel; Pacheco, Mário

    2015-09-01

    Triclopyr-based herbicides are broadly used worldwide for site preparation and forest vegetation management. Thus, following application, these agrochemicals can inadvertently reach the aquatic ecosystems. Garlon(®) is one of the most popular commercial denominations of this group of herbicides, considered as highly toxic to fish, even by its manufacturer. Although DNA is frequently regarded as a target of pesticide toxicity, the genotoxic potential of Garlon(®) to fish remains completely unknown. Hence, the main goal of this study was to evaluate the genotoxicity of Garlon(®) and its active ingredient (triclopyr), clarifying the underlying mechanisms. Therefore, the comet assay, implemented as the standard procedure, with an extra step involving DNA lesion-specific repair enzymes (formamidopyrimidine DNA glycosylase and endonuclease III), was used to identify DNA damage in blood cells of Anguilla anguilla L. Short-term exposures (1 and 3 days) to Garlon(®) and triclopyr were carried out, adopting environmentally realistic concentrations (67.6 and 270.5 µg L(-1) Garlon(®) and 30 and 120 µg L(-1) triclopyr). The results concerning the nonspecific DNA damage proved the risk of the herbicide Garlon(®) and its active ingredient triclopyr in both tested concentrations and exposure lengths. In addition, the higher genotoxic potential of the formulation, in comparison with the active ingredient, was demonstrated. When the additional breaks corresponding to net enzyme-sensitive sites were considered, none of the conditions revealed significant levels of oxidative damage. This identification of the genotoxic properties of triclopyr-based herbicides to fish highlights the need to develop less hazardous formulations, as well as the adoption of mitigation measures related to the application of these agrochemicals in the framework of forestry and agriculture sustainable management.

  9. Sublethal toxicity of esbiothrin relationship with total antioxidant status and in vivo genotoxicity assessment in fish (Cyprinus carpio L., 1758) using the micronucleus test and comet assay.

    PubMed

    Selvi, Mahmut; Cavaş, Tolga; Cağlan Karasu Benli, A; Koçak Memmi, Burcu; Cinkılıç, Nilüfer; Dinçel, Aylin Sepici; Vatan, Ozgür; Yılmaz, Dilek; Sarıkaya, Rabia; Zorlu, Tolga; Erkoç, Figen

    2013-11-01

    Esbiothrin, synthetic pyrethroid with quick activity against insects, is widely used against household pests and in public health. Despite widespread use, data on ecotoxicity and genotoxic effects are extremely scarce. The aim of the present study is to evaluate the genotoxic potential of esbiothrin on a model fish species Cyprinus carpio L., 1758 (Pisces: Cyprinidae, koi) using the micronucleus test and comet assay in peripheral blood erythrocytes. Effects of two sublethal exposure concentrations on plasma total antioxidant status (TAS mmol/L), and Hct values were examined. On the basis of the 96 h LC50 data from U.S. EPA ecotox database (32 μg/L) two sublethal exposure concentrations (5 and 10 μg/L) were used together with ethyl methanesulfonate (EMS) (5 mg/L) as positive control. Five fish were used for each dose/duration group (24, 48, and 72 h) under controlled laboratory conditions. The fish showed behavioral changes at the higher dose. Plasma TAS (mmol/L) levels decreased in 24 h; an increase was observed slightly for 48 and obviously for 72 h in both exposure doses. Similarly, hematocrit (Hct) values differed between exposure duration but no significant differences in mean values were found between groups of the same exposure time. The general trend was a rise after 48 h, which decreased afterwards. Our results revealed significant increases in the frequencies of micronuclei and levels of DNA strand breaks and thus demonstrated the genotoxic potential of this pesticide on fish, a nontarget organism of the aquatic ecosystem. To our knowledge this is the first study to report observable genotoxic effects of esbiothrin on fish.

  10. In vitro genotoxicity of neutral red after photo-activation and metabolic activation in the Ames test, the micronucleus test and the comet assay.

    PubMed

    Guérard, Melanie; Zeller, Andreas; Singer, Thomas; Gocke, Elmar

    2012-07-04

    Neutral red (Nr) is relatively non-toxic and is widely used as indicator dye in many biological test systems. It absorbs visible light and is known to act as a photosensitizer, involving the generation of reactive oxygen species (type-I reaction) and singlet oxygen (type-II reaction). The mutagenicity of Nr was determined in the Ames test (with Salmonella typhimurium strains TA1535, TA97, TA98, TA98NR, TA100, and TA102) with and without metabolic activation, and with and without photo-activation on agar plates. Similarly to the situation following metabolic activation, photo-mutagenicity of Nr was seen with all Salmonella strains tested, albeit with different effects between these strains. To our knowledge, Nr is the only photo-mutagen showing such a broad action. Since the effects are also observed in strains not known to be responsive to ROS, this indicates that ROS production is not the sole mode of action that leads to photo-genotoxicity. The reactive species produced by irradiation are short-lived as pre-irradiation of an Nr solution did not produce mutagenic effects when added to the bacteria. In addition, mutagenicity in TA98 following irradiation was stronger than in the nitroreductase-deficient strain TA98NR, indicating that nitro derivatives that are transformed by bacterial nitroreductase to hydroxylamines appear to play a role in the photo-mutagenicity of Nr. Photo-genotoxicity of Nr was further investigated in the comet assay and micronucleus test in L5178Y cells. Concentration-dependent increases in primary DNA damage and in the frequency of micronuclei were observed after irradiation.

  11. Carbon in comet dust

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.

    1990-01-01

    The association of Halley particle results with data from existing meteoritic materials that can be analyzed in the laboratory is discussed. Comet samples must exist in present collections of meteoritic materials and the Halley results provide clues for identifying them. Although it is not presently possible to positively identify cometary meteorites or cometary interplanetary dust (IDP) samples, it is possible to determine which materials are similar to Halley dust and which ones are distinctly unlike Halley. The properties of these existing Halley-compatible samples provide insight into the possible properties of cometary material. Positive identification of meteoritic comet samples or direct samples returned from a comet nucleus would of course revolutionize our ability to study carbonaceous matter in comets. Modern analytical techniques are very powerful and it is possible to perform elemental, chemical, mineralogical and even limited isotopic analysis on micron-size particles. There is an important synergism between the laboratory studies of collected samples and astronomical data from comets and interstellar grains. To fully interpret results there must be convincing methods for associating a particular class or classes of meteoritic material with comets. Ultimately this will be done by direct comet sample return such as the Rosetta mission under development by ESA. At the present time the only links that can be made involve comparison with sample properties and measurable properties of comets. Unfortunately there is at present no known unique property of cometary dust that allows its absolute identification in the laboratory. The results from Halley encounters and observation do provide much new information on cometary grains. The Halley grain compositions, density, size distribution and scattering properties all provide a basis for future investigations. Other Halley properties such as the presence of polyoxymethylene and the 3.4um emission feature could

  12. Analysis of the morphological structures of comet 1P/Halley in their perihelion passages in 1910 and 1986

    NASA Astrophysics Data System (ADS)

    Voelzke, Marcos Rincon

    2015-08-01

    This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km/s ; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km/s .The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 106 km and in 1986 is (2.2 ± 0.2) x 106 km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 105 km and in 1986 it is equal to (2.8 ± 0.5) x 105 km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work.

  13. Analysis of the perihelic passages of the comet 1P/Halley in 1910 and in 1986

    NASA Astrophysics Data System (ADS)

    Voelzke, Marcos Rincon

    2016-07-01

    This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km/s; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km/s. The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 10 ^{6} km and in 1986 is (2.2 ± 0.2) x 10 ^{6} km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 10 ^{5} km and in 1986 it is equal to (2.8 ± 0.5) x 10 ^{5} km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work.

  14. Sketching Comets

    NASA Astrophysics Data System (ADS)

    Perez, Jeremy

    Comets add a sense of surprise and freshness to the predictability and seeming timelessness of the visible cosmos. Some of these mists of dust and fl uorescing gas sail through the inner solar system at regular intervals, such as the famous comet 1P/Halley. Many other comets are discovered yearly as they make their first observed descent to our vicinity. Depending on their distance, composition, and intrinsic brightness, comets can present a variety of appearances—from almost stellar objects, to soft round patches, to majestic, tailed plumes that are sometimes visible to the naked eye. Because these are fl eeting, transitory objects, time spent observing and sketching them is all the more precious.

  15. Comet culture

    NASA Astrophysics Data System (ADS)

    Lusher, Rebekah

    2011-10-01

    Rebekah Lusher describes an exhibition in the new Caroline Lucretia Gallery at the Herschel Museum of Astronomy in Bath: Omens and Inspirations: Ice, Dust and Fire - the Story of the Great Comet of 1811.

  16. IRAS observations of comets

    NASA Technical Reports Server (NTRS)

    Walker, R. G.; Matson, D. L.; Veeder, G. J.

    1986-01-01

    The moderate spatial resolution and high sensitivity of the Infrared Astronomical Satellite (IRAS), which surveyed the celestial sphere during 1983 at wavelengths of 12, 25, 60, and 100 microns, were particularly well suited to detecting extended thermal emission from cometary dust. Sources with infrared color temperatures characteristic of solar system bodies, and at the ephemerides position of known comets were selected for analysis by the IRAS Asteroid Data Analysis System (ADAS). The data base is now available for use by researchers. This paper describes the development of the data base, details its entries, and presents a statistical analysis of its contents. The IRAS survey contains multiple observations of many periodic comets. A brief description and analysis is given of the observed infrared and derived physical properties for several comets of special interest.

  17. Anti-genotoxic effect of Aloysia triphylla infusion against acrylamide-induced DNA damage as shown by the comet assay technique.

    PubMed

    Zamorano-Ponce, E; Morales, C; Ramos, D; Sepúlveda, C; Cares, S; Rivera, P; Fernández, J; Carballo, M A

    2006-02-28

    Aloysia triphylla a perennial, bushy plant originally from South America has long been used in traditional medicine. Its aqueous extract contains considerable amounts of polyphenolic compounds, namely flavonoids and phenolic acids. In view of the interest in natural phenolic compounds as antioxidant in preventive medicine, this study was undertaken to investigate the chemoprotective effects of cedron leaves infusion against the genetic damage induced by acrylamide (AA) by using the alkaline version of the comet assay technique. Mice were separated in nine groups (eight animals each): (I) untreated, (II) negative control, (III) treated with infusion of cedron leaves 5%, 20 days twice a day, (IV) treated with AA (5 mg/kg b.w.), (V) treated with AA (20 mg/kg b.w.), (VI) treated with AA (30 mg/kg b.w.), (VII) treated with AA (50 mg/kg b.w.), (VIII) pretreated with infusion and treated with AA (50 mg/kg b.w.) and (IX) positive control (cyclophosphamide, 20 mg/kg b.w.). Three hundred blast cells were digitally evaluated per animal from three different slides (100 each). Media of tail moment (TM) values were analyzed by ANOVA test. No statistical differences (p>0.05) were found between untreated animals, negative control and infusion-treated mice. A single dose of AA-induced genetic damage as revealed by a statistically significant increase in TM values (p<0.01). Pretreatment with infusion prior to AA injection significantly reduces the capacity of AA to induce genetic damage. In these conditions, tail moments values did not differ from data obtained in negative control (p>0.05) and exhibit statistical differences from animals treated only with AA (p<0.01). Cell viability was at least 90% in all cases as measured by the trypan blue exclusion method. The ferric reducing ability of plasma (FRAP) method reveals that the plasma of infusion-treated mice has a significantly higher antioxidant capacity than plasma from controls (p<0.01). The results suggest that the infusion

  18. Effects of co-exposure to extremely low frequency (50 Hz) magnetic fields and xenobiotics determined in vitro by the alkaline comet assay.

    PubMed

    Villarini, Milena; Moretti, Massimo; Scassellati-Sforzolini, Giuseppina; Boccioli, Bruno; Pasquini, Rossana

    2006-05-15

    In the present study, we used human peripheral blood leukocytes from 4 different donors, to investigate in vitro the possible genotoxic and/or co-genotoxic activity of extremely low frequency magnetic fields (ELF-MF) at 3 mT intensity. Two model mutagens were used to study the possible interaction between ELF-MF and xenobiotics: N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and 4-nitroquinoline N-oxide (4NQO). Primary DNA damage was evaluated by the alkaline single-cell microgel-electrophoresis ("comet") assay. Control cells (leukocytes not exposed to ELF-MF, nor treated with genotoxins) from the different blood donors showed a comparable level of basal DNA damage, whereas the contribution of individual susceptibility toward ELF-MF and the tested genotoxic compounds led to differences in the extent of DNA damage observed following exposure to the genotoxins, both in the presence and in the absence of an applied ELF-MF. A 3 mT ELF-MF alone was unable to cause direct primary DNA damage. In leukocytes exposed to ELF-MF and genotoxins, the extent of MNNG-induced DNA damage increased with exposure duration compared to sham-exposed cells. The opposite was observed in cells treated with 4NQO. In this case the extent of 4NQO-induced DNA damage was somewhat reduced in leukocytes exposed to ELF-MF compared to sham-exposed cells. Moreover, in cells exposed to ELF-MF an increased concentration of GSH was always observed, compared to sham-exposed cells. Since following GSH conjugation the genotoxic pattern of MNNG and 4NQO is quite different, an influence of ELF-MF on the activity of the enzyme involved in the synthesis of GSH leading to different activation/deactivation of the model mutagens used was hypothesized to explain the different trends observed in MNNG and 4NQO genotoxic activity in the presence of an applied ELF-MF. The possibility that ELF-MF might interfere with the genotoxic activity of xenobiotics has important implications, since human populations are likely to be

  19. CCD imaging of Comet Wilson (1987VII) - A quantitative coma analysis

    NASA Technical Reports Server (NTRS)

    Schulz, Rita; A'Hearn, Michael F.; Birch, Peter V.; Bowers, Craig; Kempin, Mark; Martin, Ralph

    1993-01-01

    Distinctive cometary components (dust, ions, and radicals) are studied on the basis of 2D, narrow-band CCD images of Comet Wilson (1987VII). The fact that Comet Wilson showed no significant structures in the neutral coma during its first perihelion passage is additional evidence for the hypothesis that dynamically new comets do not show a heterogeneous nucleus, but still have a relatively uniform surface. The deviations from the 1/rho law for the decrease of surface brightness as a function of nuclear distance are explained by a combination of short-term variations in the dust production and the effects of solar radiation pressure. The C2 production rate remains basically constant during the whole observational period, while the CN production rate decreases with increasing heliocentric distance. It is inferred that the formation of C2 might be due both to photolytic destruction of some parent molecules as well as to chemical reactions between other species.

  20. Curation and Analysis of Samples from Comet Wild-2 Returned by NASA's Stardust Mission

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, Keiko; Walker, Robert M.

    2015-01-01

    The NASA Stardust mission returned the first direct samples of a cometary coma from comet 81P/Wild-2 in 2006. Intact capture of samples encountered at 6 km/s was enabled by the use of aerogel, an ultralow dense silica polymer. Approximately 1000 particles were captured, with micron and submicron materials distributed along mm scale length tracks. This sample collection method and the fine scale of the samples posed new challenges to the curation and cosmochemistry communities. Sample curation involved extensive, detailed photo-documentation and delicate micro-surgery to remove particles without loss from the aerogel tracks. This work had to be performed in highly clean facility to minimize the potential of contamination. JSC Curation provided samples ranging from entire tracks to micrometer-sized particles to external investigators. From the analysis perspective, distinguishing cometary materials from aerogel and identifying the potential alteration from the capture process were essential. Here, transmission electron microscopy (TEM) proved to be the key technique that would make this possible. Based on TEM work by ourselves and others, a variety of surprising findings were reported, such as the observation of high temperature phases resembling those found in meteorites, rarely intact presolar grains and scarce organic grains and submicrometer silicates. An important lesson from this experience is that curation and analysis teams must work closely together to understand the requirements and challenges of each task. The Stardust Mission also has laid important foundation to future sample returns including OSIRIS-REx and Hayabusa II and future cometary nucleus sample return missions.

  1. Analysis of hydrogen H-alpha observations of the coma of Comet P/Halley

    NASA Technical Reports Server (NTRS)

    Smyth, William H.; Marconi, M. L.; Scherb, Frank; Roesler, Fred L.

    1993-01-01

    The Monte Carlo Particle Trajectory Model of Combi and Smyth (1988) is used here to analyze observations of the H-alpha coma of Comet Halley. The solar excitation mechanism for the H-alpha emissions line is described. The H2O production rates derived for the H-alpha brightness measurements are shown to be very consistent with the H2O production rates determined from other Comet Halley observations of the H, O, and OH comae. Revised H2O production rates determined from 6300 A brightness measurements are presented.

  2. Evaluation of the genotoxic potential of 3-monochloropropane-1,2-diol (3-MCPD) and its metabolites, glycidol and beta-chlorolactic acid, using the single cell gel/comet assay.

    PubMed

    El Ramy, R; Ould Elhkim, M; Lezmi, S; Poul, J M

    2007-01-01

    3-monochloropropane-1,2-diol (3-MCPD) is a member of a group of chemicals known as chloropropanols. It is found in many foods and food ingredients as a result of food processing. 3-MCPD is regarded as a rat carcinogen known to induce Leydig-cell and mammary gland tumours in males and kidney tumours in both genders. The aim of our study was to clarify the possible involvement of genotoxic mechanisms in 3-MCPD induced carcinogenicity at the target organ level. For that purpose, we evaluated DNA damages in selected target (kidneys and testes) and non-target (blood leukocytes, liver and bone marrow) male rat organs by the in vivo alkaline single cell gel electrophoresis (comet) assay, 3 and 24 h after 3-MCPD oral administration to Sprague-Dawley and Fisher 344 adult rats. 3-MCPD may be metabolised to a genotoxic intermediate, glycidol, whereas the predominant urinary metabolite in rats following 3-MCPD administration is beta-chlorolactic acid. Therefore, we also studied the DNA damaging effects of 3-MCPD and its metabolites, glycidol and beta-chlorolactic acid, in the in vitro comet assay on CHO cells. Our results show the absence of genotoxic potential of 3-MCPD in vivo in the target as well as in the non-target organs. Glycidol, the epoxide metabolite, induced DNA damages in CHO cells. beta-Chlorolactic acid, the main metabolite of 3-MCPD in rats, was shown to be devoid of DNA-damaging effects in vitro in mammalian cells.

  3. Small Bodies, Big Concepts: Engaging Teachers and Their Students in Visual Analysis of Comets and Asteroids

    NASA Astrophysics Data System (ADS)

    Cobb, W. H.; Buxner, S.; Lebofsky, L. A.; Ristvey, J.; Weeks, S.; Zolensky, M.

    2011-12-01

    Small Bodies, Big Concepts is a multi-disciplinary, professional development project that engages 5th - 8th grade teachers in high end planetary science using a research-based pedagogical framework, Designing Effective Science Instruction (DESI). In addition to developing sound background knowledge with a focus on visual analysis, teachers' awareness of the process of learning new content is heightened, and they use that experience to deepen their science teaching practice. Culling from NASA E/PO educational materials, activities are sequenced to enhance conceptual understanding of big ideas in space science: what do we know, how do we know it, why do we care? Helping teachers develop a picture of the history and evolution of our understanding of the solar system, and honing in on the place of comets and asteroids in helping us answer old questions and discover new ones, teachers see the power and excitement underlying planetary science as human endeavor. Research indicates that science inquiry is powerful in the classroom and mission scientists are real-life models of science inquiry in action. Using guest scientist facilitators from the Planetary Science Institute, NASA Johnson Space Center, Lockheed Martin, and NASA E/PO professionals from McREL and NASA AESP, teachers practice framing scientific questions, using current visual data, and adapting NASA E/PO activities related to current exploration of asteroids and comets in our Solar System. Cross-curricular elements included examining research-based strategies for enhancing English language learners' ability to engage in higher order questions and a professional astronomy artist's insight into how visual analysis requires not just our eyes engaged, but our brains: comparing, synthesizing, questioning, evaluating, and wondering. This summer we pilot tested the SBBC curriculum with thirteen 5th- 10th grade teachers modeling a variety of instructional approaches over eight days. Each teacher developed lesson plans

  4. Analysis of CCD images of the coma of comet P/Halley

    NASA Technical Reports Server (NTRS)

    Combi, Michael R.

    1992-01-01

    The modeling analysis objective of this project is to make use of the skill acquired in the development of Monte Carlo particle trajectory models for the distributions of gas species in cometary comae as a basis for a new dust coma model. This model will include a self-consistent picture of the time-dependent dusty-gas dynamics of the inner coma and the three-dimensional time-dependent trajectories of the dust particles under the influence of solar gravity and solar radiation pressure in the outer coma. Our purpose is to use this model as a tool to analyze selected images from two sets of data of the comet P/Halley with the hope that we can help to understand the effects of a number of important processes on the spatial morphology of the observed dust coma. The study will proceed much in the same way as our study of the spatially extended hydrogen coma where we were able to understand the spatial morphology of the Lyman-alpha coma in terms of the partial thermalization of the hot H atoms produced by the photodissociation of cometary H2O and OH. The processes of importance to the observed dust coma include: (1) the dust particle size distribution function; (2) the terminal velocities of various sized dust particles in the inner coma; (3) the radiation scattering properties of dust particles, which are important both in terms of the observed scattered radiation and the radiation pressure acceleration on dust particles; (4) the fragmentation and/or vaporization of dust particles; (5) the relative importance of CHON and silicate dust particles as they contribute both to the dusty-gas dynamics in the inner coma (that produce the dust particle terminal velocities) and to the observed spatial morphology of the outer dust coma; and (6) the time and direction dependence of the source of dust.

  5. Use of long-term models for analysis of comet Encke's motion

    NASA Astrophysics Data System (ADS)

    Usanin, V.; Nefedyev, Y.; Andreev, A.

    2016-12-01

    This paper is focused on the problem of the reactive non-gravitational effects change in the cometary motion caused by the comet's activity fading. The modern researches have been reviewed. The necessity of a new model compatible with Marsden's model of non-gravitational forces is shown. Modifications of Marsden's model for the cases in which the main factors of the parameters change are the deposition of the significant non-volatile mass and the growth of the superficial crust are developed. They contain besides the usual Marsden's parameters two and three additional values correspondingly. The developed equations have been used to explain the known change of Marsden's non-gravitational parameters for the comet Encke during 225 years of its observational interval. Although the model with significant non-volatile mass contains less free values, it explains the characteristic features of the comet's non-gravitational parameters behavior better. The model can be further applied for the comet's observed astrometric positions fitting.

  6. Comet formation

    NASA Astrophysics Data System (ADS)

    Blum, J.

    2014-07-01

    There has been vast progress in our understanding of planetesimal formation over the past decades, owing to a number of laboratory experiments as well as to refined models of dust and ice agglomeration in protoplanetary disks. Coagulation rapidly forms cm-sized ''pebbles'' by direct sticking in collisions at low velocities (Güttler et al. 2010; Zsom et al. 2010). For the further growth, two model approaches are currently being discussed: (1) Local concentration of pebbles in nebular instabilities until gravitational instability occurs (Johansen et al. 2007). (2) A competition between fragmentation and mass transfer in collisions among the dusty bodies, in which a few ''lucky winners'' make it to planetesimal sizes (Windmark et al. 2012a,b; Garaud et al. 2013). Predictions of the physical properties of the resulting bodies in both models allow a distinction of the two formation scenarios of planetesimals. In particular, the tensile strength (i.e, the inner cohesion) of the planetesimals differ widely between the two models (Skorov & Blum 2012; Blum et al. 2014). While model (1) predicts tensile strengths on the order of ˜ 1 Pa, model (2) results in rather compactified dusty bodies with tensile strengths in the kPa regime. If comets are km-sized survivors of the planetesimal-formation era, they should in principle hold the secret of their formation process. Water ice is the prime volatile responsible for the activity of comets. Thermophysical models of the heat and mass transport close to the comet-nucleus surface predict water-ice sublimation temperatures that relate to maximum sublimation pressures well below the kPa regime predicted for formation scenario (2). Model (1), however, is in agreement with the observed dust and gas activity of comets. Thus, a formation scenario for cometesimals involving gravitational instability is favored (Blum et al. 2014).

  7. The First International Halley Watch: guiding the worldwide search for comet Halley, 1755 - 1759.

    NASA Astrophysics Data System (ADS)

    Waff, C. B.

    Contents: Edmond Halley's "Synopsis of the astronomy of comets". One comet or two? Some early ephemerides. Finding the comet the illustrated way. "Comet" sightings. The ephemerides of the Boston-Gazette and Lalande. The perturbational analysis of Clairaut. Delisle. The recovery of the comet. Conclusion.

  8. Low-Energy Asteroid and Comet Transit Analysis using Isolating Blocks

    NASA Astrophysics Data System (ADS)

    Anderson, Rodney L.; Chodas, Paul; Easton, Robert W.; Lo, Martin W.

    2016-05-01

    It is well known that asteroids and comets typically capture or transit near a planet by traveling through the L1 and L2 libration point gateways. These regions are therefore key to understanding the mechanism by which these captures, transits, and potential impacts occur. Recently, Anderson, Easton, and Lo (2015) explored the L2 region in the Earth-Moon system using isolating blocks in the circular restricted three-body problem (CRTBP). Isolating blocks provide a theoretically rigorous method for computing the invariant manifolds of libration point periodic orbits and all possible transit trajectories at a particular Jacobi constant in the CRTBP. Using isolating block methods allows us to directly compute and study the transit trajectories used by comets and asteroids in the low-energy regimes common for these types of bodies. In this study, both L1 and L2 isolating blocks are computed for the Sun-Earth and Sun-Jupiter CRTBP systems to compute trajectories transiting near the Earth and Jupiter. Statistics based on transit time, periapse passages, and exit location are first computed. Then individual trajectory solutions corresponding to different trajectory types are analyzed. The transit trajectories are also characterized using their orbital elements and compared to known comets and asteroids. These results show that the invariant manifolds of the orbits in the isolating block control and guide the dynamics of comets and asteroids as they temporarily capture between the L1 and L2 region of a planet or satellite.Reference: Anderson, R. L., R. W. Easton, M. W. Lo (2015), AAS/AIAA Astrodynamics Conf., AAS 15-615.

  9. Jet morphology and coma analysis of comet 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Vaughan, Charles M.

    In 2010, comet 103P/Hartley 2 was observed pre- and post-perihelion using the George and Cynthia Mitchell Integral Field Spectrometer on the 2.7-m telescope at McDonald Observatory in Texas. Data for gaseous radicals C2, C3, CH, CN, and NH2 were collected over six nights from 15 July to 10 November. The spectral data were used to create coma maps for each of the observed species, and the maps were processed using radial and azimuthal mean division techniques to create enhanced images of the coma, revealing subtle morphological features. 340 enhanced coma images were created for each observation and species. Visual inspection reveals that the coma is heterogeneous between the five detected radicals, and statistical analyses verify this result. To compliment the ongoing investigation of Hartley 2 as studied by the EPOXI flyby mission, findings from other researchers (Belton et al., 2012; Syal et al., 2012; and Thomas et al., 2012) are used to characterize the nucleus spin state and identify dust jet locations on the nucleus. With rotational period measurements from EPOXI, dust jet vectors on the nucleus surface are rotated to relevant observation times in November to compare the computed jet directions with the radical densities in the coma. Dust jet sites on the smaller nucleus lobe show a stronger correlation with high radical concentrations than the dust sites on the larger nucleus lobe. Production rates for potential parentage of radical species are calculated using the radial outflow Haser model (Haser, 1957), which are compared to mixing ratios relative to water from separate campaigns to constrain parentage. NH3 is likely the sole producer of NH2, whereas CN may be produced from a combination of HCN, C2N2, and CH3CN. Traditional parentage of C2, C3, and CH do not yield acceptable fits or suitable mixing ratios with the Haser model, and it is possible that extended coma ices having relatively short scale lengths greatly contribute to production of these

  10. Rosetta/COSIMA: High Resolution In-Situ Dust Analysis at Comet 67P/Churyumov-Gerasimenkov

    NASA Astrophysics Data System (ADS)

    Krueger, Harald; Engrand, C.; Fischer, H.; Hilchenbach, M.; Hornung, K.; Kissel, J.; Stephan, T.; Thirkell, L.; Trieloff, M.; Thomas, R.; Tubiana, C.; Varmuza, K.

    2006-09-01

    The COmetary Secondary Ion Mass Analyser (COSIMA) instrument on board ESA's Rosetta spacecraft is a high-resolution time-of-flight mass spectrometer dedicated to the in-situ analysis of cometary dust. Rosetta was launched in 2004 and will reach comet 67P/Churyumov-Gerasimenkov in 2014. The COSIMA instrument will collect cometary dust on metal targets and identify grains with sizes 10 micron and bigger with an optical camera. Material from the grain surface is sputtered with an indium ion beam and the generated secondary ions are accelerated in an electric field. Time-of-flight secondary ion mass spectra are obtained with a mass resolution of approximately 2000 at m = 100 amu. The goal of the COSIMA investigation is the in-situ characterisation of the elemental, molecular, mineralogic, and isotopic composition of dust in the coma of comet 67P/C-G. To reach this goal, we perform an extensive laboratory measurement program with a COSIMA reference instrument (RM), a twin of the flight instrument, located at Max-Planck-Institut fuer Sonnensystemforschung (MPS). Cometary dust analogues are prepared from natural and synthetic minerals (pyroxene, olivine, hydrous silicates, sulfides, etc.) with known composition and, which are believed to exist in comets. Reference spectra of these samples are obtained with the COSIMA RM instrument and with laboratory time-of-flight secondary ion mass spectrometer (TOF-SIMS) instruments located at the University of Muenster/Germany and the Laboratoire de Physique & Chimie de L'Environment in Orleans/France. We will present first results on the calibration of the COSIMA RM instrument and the identification of the elemental and mineralogic composition of reference samples.

  11. Comet radar explorer

    NASA Astrophysics Data System (ADS)

    Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

    will enjoy significant simplifying benefits compared to using the same instrument for Mars or lunar radar science: (1) The proximity of operations leads to a much higher signal to noise, as much as +30 dB. (2) The lack of an ionosphere simplifies data modeling and analysis. (3) The body is globally illuminated during every data acquisition, minimizing ambiguity or 'clutter' and allowing for tomographic reconstruction. What is novel is the data processing, where instead of a planar radargram approach we coherently process the data into an image of the deep interior. CORE thus uses a MARSIS-SHARAD heritage radar to make coherent reflection sounding measurements, a 'CAT SCAN' of a comet nucleus. What is unique about this mission compared to the Mars radars mentioned above, is that the target is a finite mass of dirty ice in free space, rather than a sheet of dirty ice draped on a planet surface. The depth of penetration (kilometers), attainable resolution (decameters), and the target materials, are more or less the same. This means that the science story is robust, and the radar implementation is robust. The target is comet 10P/Tempel 2, discovered by Wilhelm Tempel in 1873 and observed on most apparitions since. It has been extensively studied, in part because of interest as a CRAF target in the mid-1980s, and much is known about it. Tempel 2 is one of the largest known comet nuclei, 16×8×8 km (about the same size as Halley) [1] and has rotation period 8.9 hours [3,5,6,7,9]. The spin state is evolving with time, spinning up by ˜10 sec per perihelion pass [5,7]. The comet is active, but not exceedingly so, especially given its size. The water production is measured at ˜ 4 × 1028 mol/sec at its peak [2], a factor of 25 lower than comet Halley, and it is active over only ˜2% of its surface. The dust environment is well known, producing a factor of ˜100 less dust than Halley. Comet References: [1] A'Hearn et al., ApJ 347, 1155, 1989 [2] Feldman and Festou, ACM 1991, p

  12. Evaluation of the genotoxic and antigenotoxic effects after acute and subacute treatments with açai pulp (Euterpe oleracea Mart.) on mice using the erythrocytes micronucleus test and the comet assay.

    PubMed

    Ribeiro, Juliana Carvalho; Antunes, Lusânia Maria Greggi; Aissa, Alexandre Ferro; Darin, Joana D'arc Castania; De Rosso, Veridiana Vera; Mercadante, Adriana Zerlotti; Bianchi, Maria de Lourdes Pires

    2010-01-01

    Açai, the fruit of a palm native to the Amazonian basin, is widely distributed in northern South America, where it has considerable economic importance. Whereas individual polyphenolics compounds in açai have been extensively evaluated, studies of the intact fruit and its biological properties are lacking. Therefore, the present study was undertaken to investigate the in vivo genotoxicity of açai and its possible antigenotoxicity on doxorubicin (DXR)-induced DNA damage. The açai pulp doses selected were 3.33, 10.0 and 16.67g/kg b.w. administered by gavage alone or prior to DXR (16mg/kg b.w.) administered by intraperitoneal injection. Swiss albino mice were distributed in eight groups for acute treatment with açai pulp (24h) and eight groups for subacute treatment (daily for 14 consecutive days) before euthanasia. The negative control groups were treated in a similar way. The results of chemical analysis suggested the presence of carotenoids, anthocyanins, phenolic, and flavonoids in açai pulp. The endpoints analyzed were micronucleus induction in bone marrow and peripheral blood cells polychromatic erythrocytes, and DNA damage in peripheral blood, liver and kidney cells assessed using the alkaline (pH >13) comet assay. There were no statistically significant differences (p>0.05) between the negative control and the groups treated with the three doses of açai pulp alone in all endpoints analyzed, demonstrating the absence of genotoxic effects. The protective effects of açai pulp were observed in both acute and subacute treatments, when administered prior to DXR. In general, subacute treatment provided greater efficiency in protecting against DXR-induced DNA damage in liver and kidney cells. These protective effects can be explained as the result of the phytochemicals present in açai pulp. These results will be applied to the developmental of food with functional characteristics, as well as to explore the characteristics of açai as a health promoter.

  13. VIRTIS on board Rosetta: cryocoolers usage analysis in support of Comet phases observations

    NASA Astrophysics Data System (ADS)

    Giuppi, Stefano; Politi, Romolo; Capria, Maria Teresa; Piccioni, Giuseppe; De Sanctis, Maria Cristina; Erard, Stéphane; Tosi, Federico; Capaccioni, Fabrizio; Filacchione, Gianrico

    Rosetta is a planetary cornerstone mission of the European Space Agency (ESA). It is devoted to the study of minor bodies of our solar system and it will be the first mission ever to land on a comet (the Jupiter-family comet 67P/Churyumov-Gerasimenko). VIRTIS-M is a sophisticated imaging spectrometer that combines two data channels in one compact instrument, respectively for the visible and the infrared range (0.25-5.0 μm). VIRTIS-H is devoted to infrared spectroscopy (2.5-5.0 μm) with high spectral resolution. Since the satellite will be inside the tail of the comet during one of the most important phases of the mission, it would not be appropriate to use a passive cooling system, due to the high flux of contaminants on the radiator. Therefore the IR sensors are cooled by two Stirling cycle cryocoolers. This paper focuses on the usage of VIRTIS cryocoolers from the beginning of the Rosetta mission till spacecraft hibernation in order to optimize their usage. After a description of the cryocooler used in the mission, a detailed information about time usage and power consumption is provided. On the basis of previous experiences with this kind of cryocoolers it has been made an estimation of the remaining working life of the VIRTIS coolers operating in Rosetta mission. Moreover an estimation of the minimum time between a cryocooler switch off and on again has been carried out in order to preserve the coolers working life.

  14. Gas chromatography for space exploration : application to the in situ analysis of Titan's atmosphere, comets nucleus and martian soil

    NASA Astrophysics Data System (ADS)

    Sternberg, R.; Szopa, C.; Buch, A.; Mettetal, F.; Coscia, D.; Coll, P.; Cabane, M.; Rodier, C.; Vidal-Madjar, C.; Raulin, F.

    Gas chromatography is one of the most powerful technique for the in situ chemical investigation of extraterrestrial environments Its successful use in past planetary missions to Mars 1976-78 and Venus 1978-85 made it the main method selected for the in situ molecular characterization of the Titan s atmosphere comets and the Martian soil Indeed gas chromatography fully meet the severe constraints required in space instrumentation such as small weight and size low power consumption high mechanical strength and resistance to deep space conditions vacuum cosmic rays This paper presents the gas chromatographic subsystems which have been developed at LISA and SA respectively for the Huygens probe of the Cassini-Huygens mission to Titan 1 the Philae probe of the Rosetta mission to a comet 2 and the future landing probe of the MSL 2009 mission to Mars 3 The coupling of these GC subsystems with pyrolysis and chemical derivatization techniques allows the chemical analysis of a wide range of molecules including non-volatiles complex organics such as aminoacides and nucleobases the search of wich is of particular interest for exobiology The analytical capabilities of these subsystems with a particular emphasis of their exobiological aspects and implications are described 1 G Israel C Szopa F Raulin M Cabane P Coll R Sternberg et al Nature vol438 796-799 2005 2 C Szopa R Sternberg F Raulin and H Rosenbauer PSS 863-877 2003 3 Cabane M P Coll C Szopa G Isra e l F Raulin

  15. Analysis of photopolarimetric data of comets at small phase angles by rough surface scattering

    NASA Astrophysics Data System (ADS)

    Mukai, S.; Mukai, T.

    1990-07-01

    A comparison of cometary rough surface scattering model calculation results with observations has indicated that negative polarization is produced, over a phase-angle range of less than 20 deg, by the variation of polarization angle of reflected light due to a contribution from (1) different sites on large, rough particles, and/or (2) multiple internal reflection within small dielectric particles. The opposition effect in cometary comas is caused by large, rough particle reflection. The mixing model for cometary grains, encompassing small particles and large rough ones composed in both cases of slightly absorbing material, is seen as explaining the photopolarimetric data of comets in the backward-scattering region.

  16. Activity in distant comets

    NASA Technical Reports Server (NTRS)

    Luu, Jane X.

    1992-01-01

    Activity in distant comets remains a mystery in the sense that we still have no complete theory to explain the various types of activity exhibited by different comets at large distances. This paper explores the factors that should play a role in determining activity in a distant comet, especially in the cases of comet P/Tempel 2, comet Schwassmann-Wachmann 1, and 2060 Chiron.

  17. Numerical and probabilistic analysis of asteroid and comet impact hazard mitigation

    SciTech Connect

    Plesko, Catherine S; Weaver, Robert P; Huebner, Walter F

    2010-09-09

    The possibility of asteroid and comet impacts on Earth has received significant recent media and scientific attention. Still, there are many outstanding questions about the correct response once a potentially hazardous object (PHO) is found. Nuclear munitions are often suggested as a deflection mechanism because they have a high internal energy per unit launch mass. However, major uncertainties remain about the use of nuclear munitions for hazard mitigation. There are large uncertainties in a PHO's physical response to a strong deflection or dispersion impulse like that delivered by nuclear munitions. Objects smaller than 100 m may be solid, and objects at all sizes may be 'rubble piles' with large porosities and little strength. Objects with these different properties would respond very differently, so the effects of object properties must be accounted for. Recent ground-based observations and missions to asteroids and comets have improved the planetary science community's understanding of these objects. Computational power and simulation capabilities have improved such that it is possible to numerically model the hazard mitigation problem from first principles. Before we know that explosive yield Y at height h or depth -h from the target surface will produce a momentum change in or dispersion of a PHO, we must quantify energy deposition into the system of particles that make up the PHO. Here we present the initial results of a parameter study in which we model the efficiency of energy deposition from a stand-off nuclear burst onto targets made of PHO constituent materials.

  18. Image analysis and data management of ELISPOT assay results.

    PubMed

    Lehmann, Paul Viktor

    2005-01-01

    The recent renaissance of enzyme-linked immunospot (ELISPOT) assays largely is the result of advances in image analysis. Information on the frequency of antigen-specific T-cells and also on the secretion rate of the individual cells is captured in spots generated using this technique. Although the overall assessment of ELISPOT results can be conducted visually, this is inevitably subjective, inaccurate, and cumbersome. In contrast, objective, and accurate measurements are fundamental to good science. Validated image analysis algorithms and procedures, therefore, have become critical for elevating the quality of ELISPOT assays results. As cytokine and granzyme B ELISPOT assays become the gold standard for monitoring antigen-specific T-cell immunity in clinical trials, the pressure increases to make ELISPOT analysis transparent, reproducible and tamperproof, complying with Good Laboratory Practice and Code for Federal Regulations Part 11 guidelines. In addition, ELISPOT assays in clinical and basic science settings frequently require high degrees of throughput, thus further raising the need for advanced data management and statistical analysis. The ImmunoSpot software portfolio has been specifically designed to meet all these needs, using the techniques described in this chapter.

  19. Prompt Gamma Activation Analysis (PGAA): Technique of choice for nondestructive bulk analysis of returned comet samples

    NASA Technical Reports Server (NTRS)

    Lindstrom, David J.; Lindstrom, Richard M.

    1989-01-01

    Prompt gamma activation analysis (PGAA) is a well-developed analytical technique. The technique involves irradiation of samples in an external neutron beam from a nuclear reactor, with simultaneous counting of gamma rays produced in the sample by neutron capture. Capture of neutrons leads to excited nuclei which decay immediately with the emission of energetic gamma rays to the ground state. PGAA has several advantages over other techniques for the analysis of cometary materials: (1) It is nondestructive; (2) It can be used to determine abundances of a wide variety of elements, including most major and minor elements (Na, Mg, Al, Si, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni), volatiles (H, C, N, F, Cl, S), and some trace elements (those with high neutron capture cross sections, including B, Cd, Nd, Sm, and Gd); and (3) It is a true bulk analysis technique. Recent developments should improve the technique's sensitivity and accuracy considerably.

  20. Kalman filter analysis of delayed neutron nondestructive assay measurements.

    SciTech Connect

    Aumeier, S. E.

    1998-04-29

    The ability to nondestructively determine the presence and quantity of fissile and fertile nuclei in various matrices is important in several nuclear applications including international and domestics safeguards, radioactive waste characterization and nuclear facility operations. Material irradiation followed by delayed neutron counting is a well known and useful nondestructive assay technique used to determine the fissile-effective content of assay samples. Previous studies have demonstrated the feasibility of using Kalman filters to unfold individual isotopic contributions to delayed neutron measurements resulting from the assay of mixes of uranium and plutonium isotopes. However, the studies in question used simulated measurement data and idealized parameters. We present the results of the Kalman filter analysis of several measurements of U/Pu mixes taken using Argonne National Laboratory's delayed neutron nondestructive assay device. The results demonstrate the use of Kalman filters as a signal processing tool to determine the fissile and fertile isotopic content of an assay sample from the aggregate delayed neutron response following neutron irradiation.

  1. Transient DNA damage induced by high-frequency electromagnetic fields (GSM 1.8 GHz) in the human trophoblast HTR-8/SVneo cell line evaluated with the alkaline comet assay.

    PubMed

    Franzellitti, Silvia; Valbonesi, Paola; Ciancaglini, Nicola; Biondi, Carla; Contin, Andrea; Bersani, Ferdinando; Fabbri, Elena

    2010-01-05

    One of the most controversial issue regarding high-frequency electromagnetic fields (HF-EMF) is their putative capacity to affect DNA integrity. This is of particular concern due to the increasing use of HF-EMF in communication technologies, including mobile phones. Although epidemiological studies report no detrimental effects on human health, the possible disturbance generated by HF-EMF on cell physiology remains controversial. In addition, the question remains as to whether cells are able to compensate their potential effects. We have previously reported that a 1-h exposure to amplitude-modulated 1.8 GHz sinusoidal waves (GSM-217 Hz, SAR=2 W/kg) largely used in mobile telephony did not cause increased levels of primary DNA damage in human trophoblast HTR-8/SVneo cells. Nevertheless, further investigations on trophoblast cell responses after exposure to GSM signals of different types and durations were considered of interest. In the present work, HTR-8/SVneo cells were exposed for 4, 16 or 24h to 1.8 GHz continuous wave (CW) and different GSM signals, namely GSM-217 Hz and GSM-Talk (intermittent exposure: 5 min field on, 10 min field off). The alkaline comet assay was used to evaluate primary DNA damages and/or strand breaks due to uncompleted repair processes in HF-EMF exposed samples. The amplitude-modulated signals GSM-217 Hz and GSM-Talk induced a significant increase in comet parameters in trophoblast cells after 16 and 24h of exposure, while the un-modulated CW was ineffective. However, alterations were rapidly recovered and the DNA integrity of HF-EMF exposed cells was similar to that of sham-exposed cells within 2h of recovery in the absence irradiation. Our data suggest that HF-EMF with a carrier frequency and modulation scheme typical of the GSM signal may affect the DNA integrity.

  2. Radioreceptor assay analysis of tamsulosin and terazosin pharmacokinetics

    PubMed Central

    Taguchi, Katsunari; Schäfers, Rafael F; Michel, Martin C

    1998-01-01

    Aims A radioreceptor assay has been developed for α1-adrenoceptor subtypes and applied to a pharmacokinetic analysis of tamsulosin and terazosin. Methods Young, male, healthy volunteers received 0.4 mg tamsulosin (as Omnic® modified release capsules) or 5 mg terazosin (as Flotrin® tablets) in a randomized, cross-over design. Before and after 1, 3, 5, 7, 10 and 23.5 h plasma was analyzed by radioreceptor assay using cloned human α1A-, α1B- and α1D-adrenoceptors and specific h.p.l.c. analysis. Results Following ingestion of tamsulosin median peak plasma levels of 16 ng ml−1 were reached after 5 h and declined to 2 ng ml−1 at 23.5 h. The time course in the radioreceptor assay was similar, and at most time points binding to α1A-adrenoceptors was significantly greater than to α1B- and α1D-adrenoceptors. Following ingestion of terazosin median peak plasma levels of 91 ng ml−1 were reached after 1 h and declined to 11 ng ml−1 at 23.5 h. In the radioreceptor assay binding also peaked at 1 h and declined thereafter, but even after 23.5 h considerable binding activity remained detectable at all three subtypes. At most time points binding to the α1A- and α1D-adrenoceptor was significantly greater than to the α1B-adrenoceptor. Conclusions We conclude that α1-adrenoceptor antagonist pharmacokinetics can be monitored by radioreceptor assays in a subtype-selective manner. Tamsulosin and terazosin exhibit subtype selective receptor binding ex vivo. The discordance between terazosin blood levels as determined by h.p.l.c. and radioreceptor assay at late time points indicates the possible involvement of metabolites in in vivo terazosin effects. PMID:9489594

  3. Dynamical analysis on the transitivity of Jupiter Family Comets to Near-Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Erece, Orhan; Aslan, Gürkan; Eker, Zeki; Kaplan, Murat

    2016-07-01

    The purpose of this research is to identify the contribution of JFC (Jupiter Family Comet) population to NEA (Near-Earth Asteroid) region by integrating their orbits forward in time. To test and compare the statistics we also integrated NEAs having Tisserand parameters from 2 to 3 and their clones backward in time. As a result, 31.9% of orbits turned out to be Earth-crossing orbits for forward integrations while 66.7% of NEAs reached JFC region for backward integrations. From another point of view, when the number of chosen body population is considered; 304 JFC region body is possibly going to reach NEA orbits, 254 NEA region body look like come from JFC region in a comparable time interval. These results substantially support each other.

  4. ROSETTA/COSIMA at comet 67P/Churyumov-Gerasimenko - 2 years of in-situ dust analysis

    NASA Astrophysics Data System (ADS)

    Schulz, Rita; Hilchenbach, Martin; Kissel, Jochen; Langevin, Yves; Briois, Christelle; Koch, Andreas; Silen, Johan; Baklouti, Donia; Bardyn, Anais; Cottin, Herve'; Engrand, Cecile; Fischer, Henning; Fray, Nicolas; Glasmachers, Albrecht; Gruen, Eberhard; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Hervig; Hornung, Klaus; Jessberger, Elmar; Lehto, Harry J.; Letho, Kirsi; Ligier, Nicolas; Merouane, Sihane; Orthous-Daunay, Francois-Regis; Paquette, John; Raulin, F.; Le Roy, Léna; Rynö, Jouni; Siljeström, Sandra; Steiger, Wolfgang; Stenzel, Oliver; Stephan, Thomas; Thirkell, Laurent; Thomas, Roger; Torkar, Klaus; Varmuza, Kurt; Wanczek, Karl-Peter; Zaprudin, Boris

    2016-10-01

    In August 2014 the ROSETTA spacecraft rendezvoused with comet 67P/Churyumov-Gerasimenko and escorted it for more than 2 years along its orbit around the Sun from 4 AU preperihelion to 4 AU postperihelion. During this time the COSIMA instrument (COmetary Secondary Ion Mass Analyser) onboard ROSETTA collected more than 25,000 dust particles in the vicinity of the comet nucleus. All these particles were collected on a number of specially designed metal target plates which were regularly imaged with a microscope (14 µm pixel/pixel resolution, 14mm x 14mm FOV) enabling the analysis of their individual morphologies, certain physical properties, e.g. tensile strength, albedo, as well as the overall flux and size distribution of the dust entering the COSIMA instrument. The images were also used to choose which of the particles shall go through compositional measurements with the time-of-flight mass spectrometer (sometimes repeated at a later time). All these investigations were done over 2 years. This allows to study the compositional and morphological differences of the particles collected at the various sections of the pre- and postperihelion orbit, the evolution of the morphology of the particles on the target plate with time, and the search for spatial heterogeneity of the composition within a particle by taking mass spectra at different locations on the same particle. An overview will be given on the available data and the results obtained so far in view to the analysis of dust composition and morphology, as well as dust flux and size distribution along the orbit.

  5. Comet explorer spacecraft design project

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The small, chemically primitive objects of the solar system, comets and asteroids, are one of the most important frontiers remaining for future planetary exploration. So stated the Solar System Exploration Committee of the NASA Advisory Council in its 1986 report 'Planetary Exploration Through the Year 2000.' The Halley's comet flyby missions completed last spring raised more questions than were answered about the nature of comets. The next mission to a comet must be able to explore some of these questions. In the late 1990's, a spacecraft might be built to explore the hazardous area surrounding a comet nucleus. Rigorous pointing requirements for remote sensing instruments will place a considerable burden on their attendant control systems. To meet these requirements we have pursued the initial design and analysis of a multi-bodied comet explorer spacecraft. Sized so as to be built on-orbit after the space station is operational, the spacecraft is comprised of Orbit Replaceable Unit (ORU) subsystems, packaged into two major components: a three-axis controlled instrument platform and a spinning, detached comet dust shield. Such a configuration decouples the dynamics of dust impaction from the stringent pointing out requirements of the imaging experiments. At the same time, it offers an abundance of simple analysis problems that may be carried out by undergraduates. These problems include the following: Selection of subsystem components, sizing trade studies, investigation of three-axis and simple spin dynamics, design of simple control systems, orbit determination, and intercept trajectory generation. Additionally, such topics as proposal writing project management, human interfacing, and costing have been covered. A new approach to design teaching has been taken, whereby students will 'learn by teaching.' They are asked to decompose trade options into a set of 'if-then' rules, which then 'instruct' the Mechanically Intelligent Designer (MIND) expert design system

  6. PRELIMINARY ANALYSIS OF SOHO/STEREO OBSERVATIONS OF SUNGRAZING COMET ISON (C/2012 S1) AROUND PERIHELION

    SciTech Connect

    Knight, Matthew M.; Battams, Karl

    2014-02-20

    We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in Solar and Heliospheric Observatory (SOHO) and Solar TErrestrial RElations Observatory (STEREO) images around its perihelion on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a superimposed outburst on November 21.3-23.5. The slope of brightening changed about November 26.7 and was significantly steeper in SOHO's orange and clear filter images until November 27.9 when it began to flatten out, reaching a peak about November 28.1 (r {sub H} ≈ 17 R {sub ☉}), then fading before brightening again from November 28.6 (r {sub H} ≈ 5 R {sub ☉}) until disappearing behind the occulting disk. ISON brightened continuously as it approached perihelion while visible in all other telescopes/filters. The central condensation disappeared about November 28.5 and the leading edge became progressively more elongated until perihelion. These photometric and morphological behaviors are reminiscent of the tens of meter-sized Kreutz comets regularly observed by SOHO and STEREO and strongly suggest that the nucleus of ISON was destroyed prior to perihelion. This is much too small to support published gas production rates and implies significant mass loss and/or disruption in the days and weeks leading up to perihelion. No central condensation was seen post-perihelion. The post-perihelion lightcurve was nearly identical in all telescopes/filters and fell slightly steeper than r{sub H}{sup −2}. This implies that the brightness was dominated by reflected solar continuum off of remnant dust in the coma/tail and that any remaining active nucleus was <10 m in radius.

  7. Use of the comet assay to investigate possible interactions of nitric oxide and reactive oxygen species in the induction of DNA damage and inhibition of function in an insulin-secreting cell line.

    PubMed

    Delaney, C A; Green, I C; Lowe, J E; Cunningham, J M; Butler, A R; Renton, L; D'Costa, I; Green, M H

    1997-04-29

    We have previously used the comet assay to demonstrate that the nitric oxide donor 3-morpholinosydnonimine (SIN-1) produces DNA damage in rat islets of Langerhans and in the SV40-transformed insulin-secreting hamster cell line, HIT-T15. Damage is not prevented by the addition of superoxide dismutase (SOD). In the present study, we have compared SIN-1, which generates nitric oxide, superoxide anion and hydrogen peroxide, with two other nitric oxide donors, S-nitrosoglutathione (GSNO) and the tetra-iron-sulphur cluster nitrosyl, Roussin's black salt (RBS). We have used the comet assay as a highly sensitive method to measure DNA-damaging ability, and also measured inhibition of DNA synthesis and inhibition of insulin secretion. We have examined the effect of SOD and catalase on each of these endpoints in HIT-T15 cells following a 30-min exposure to the compounds (24 h for DNA synthesis). All compounds produced a significant dose-dependent increase in strand-breakage formation and all inhibited DNA synthesis and glucose-stimulated insulin secretion. RBS was the most potent. SOD did not reduce the responses observed with any of the compounds. Catalase largely prevented DNA strand breakage, inhibition of DNA synthesis and inhibition of insulin secretion by SIN-1, but had no effect on responses to GSNO or RBS. Addition of SOD together with catalase gave no greater protection against SIN-1 than catalase alone. The nitric oxide and superoxide anion produced by SIN-1 are though to combine to form highly reactive peroxynitrite. In addition, H2O2 may be formed in the presence of SIN-1 and may form hydroxyl radical in the presence of a transition metal, such as Fe2+. It appears that in insulin-secreting cells, the effects of SIN-1 are largely mediated by this latter mechanism. In contrast, GSNO and RBS appear to act by a different mechanism, not overtly involving reactive oxygen species. GSNO and H2O2 show no significant interaction in the induction of DNA strand breaks. Both

  8. Nongravitational forces on comets

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.

    1976-01-01

    Methods are presented and discussed for determining the effects of nongravitational forces on the orbits of comets. These methods are applied to short-period and long-period comets. Results are briefly described.

  9. Flight of the Comet

    NASA Video Gallery

    This video clip was compiled from images taken by NASA's EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. During the encounter, the spacecraft and comet whisked past ea...

  10. Bye, Bye Comet

    NASA Video Gallery

    SOHO watched as a fairly bright comet dove towards the Sun in a white streak and was not seen again after its close encounter (May 10-11, 2011). The comet, probably part of the Kreutz family of com...

  11. A Million Comet Pieces

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] A Million Comet Pieces (poster version)

    This infrared image from NASA's Spitzer Space Telescope shows the broken Comet 73P/Schwassman-Wachmann 3 skimming along a trail of debris left during its multiple trips around the sun. The flame-like objects are the comet's fragments and their tails, while the dusty comet trail is the line bridging the fragments.

    Comet 73P /Schwassman-Wachmann 3 began to splinter apart in 1995 during one of its voyages around the sweltering sun. Since then, the comet has continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believe the icy comet cracked due the thermal stress from the sun.

    The Spitzer image provides the best look yet at the trail of debris left in the comet's wake after its 1995 breakup. The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlight and glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earth passes near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky in meteor showers. In 2022, Earth is expected to cross close to the comet's trail, producing a noticeable meteor shower.

    Astronomers are studying the Spitzer image for clues to the comet's composition and how it fell apart. Like NASA's Deep Impact experiment, in which a probe smashed into comet Tempel 1, the cracked Comet 73P/Schwassman-Wachmann 3 provides a perfect laboratory for studying the pristine interior of a comet.

    This image was taken from May 4 to May 6 by Spitzer's multi-band imaging photometer, using its 24-micron wavelength channel.

  12. Analysis of the Touch-And-Go Surface Sampling Concept for Comet Sample Return Missions

    NASA Technical Reports Server (NTRS)

    Mandic, Milan; Acikmese, Behcet; Bayard, David S.; Blackmore, Lars

    2012-01-01

    This paper studies the Touch-and-Go (TAG) concept for enabling a spacecraft to take a sample from the surface of a small primitive body, such as an asteroid or comet. The idea behind the TAG concept is to let the spacecraft descend to the surface, make contact with the surface for several seconds, and then ascend to a safe location. Sampling would be accomplished by an end-effector that is active during the few seconds of surface contact. The TAG event is one of the most critical events in a primitive body sample-return mission. The purpose of this study is to evaluate the dynamic behavior of a representative spacecraft during the TAG event, i.e., immediately prior, during, and after surface contact of the sampler. The study evaluates the sample-collection performance of the proposed sampling end-effector, in this case a brushwheel sampler, while acquiring material from the surface during the contact. A main result of the study is a guidance and control (G&C) validation of the overall TAG concept, in addition to specific contributions to demonstrating the effectiveness of using nonlinear clutch mechanisms in the sampling arm joints, and increasing the length of the sampling arms to improve robustness.

  13. COSAC prepares for sampling and in situ analysis of cometary matter from comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Goesmann, F.; Raulin, F.; Bredehöft, J. H.; Cabane, M.; Ehrenfreund, P.; MacDermott, A. J.; McKenna-Lawlor, S.; Meierhenrich, U. J.; Muñoz Caro, G. M.; Szopa, C.; Sternberg, R.; Roll, R.; Thiemann, W. H.-P.; Ulamec, S.

    2014-11-01

    The comet rendezvous mission Rosetta will be the first mission to encounter and land on a comet nucleus. After a 10-year journey Rosetta is set for rendezvous with Comet 67P/Churyumov-Gerasimenko. The mission goal is: to study the origin of comets; the relationship between cometary and interstellar material and its implications for the origin of the solar system. The Rosetta spacecraft with an overall mass of about 3000 kg was launched in March 2004 and brought into cometary orbit towards comet 67P/Churyumov-Gerasimenko with 4 gravity assist maneuvers. On its way Rosetta passed and observed two asteroids, (2867) Šteins in 2008 and (21) Lutetia in 2010, respectively. In June 2011 Rosetta entered into hibernation and woke up - as planned - on January 20, 2014. In November 2014 Rosetta's Philae lander and 10 science instruments will be deployed onto the surface of comet 67P/Churyumov-Gerasimenko. This will be followed by the first ever in situ investigation of a comet nucleus. Onboard Philae is the COmetary SAmpling and Composition experiment (COSAC), one of two evolved gas analysers that will investigate organic compounds within the material of the nucleus. Data from the COSAC instrument are expected to provide important insights into the early history of our solar system and contribute to our knowledge of small bodies that may have seeded the early Earth through impacts. In this paper we review recent developments in cometary science, including data on target comet 67P/Churyumov-Gerasimenko. We report on laboratory measurements and the calibration of the COSAC instrument as well as the preparation for operations on the nucleus of comet 67P/Churyumov-Gerasimenko.

  14. Newton and comets

    NASA Astrophysics Data System (ADS)

    Bork, Alfred

    1987-12-01

    The publication of Isaac Newton's ``notions about motion'' 300 years ago was a major moment in the history of science. In the period just before 1687 Newton's correspondence was much concerned with comets. In this period two bright comets were seen. These comets appear to have been a major stimulation to Newton's work on mechanics.

  15. Analytical study of comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Albee, A. L.

    1989-01-01

    Analytical procedures for studying and handling frozen (130 K) core samples of comet nuclei are discussed. These methods include neutron activation analysis, x ray fluorescent analysis and high resolution mass spectroscopy.

  16. Retrieving samples from comet nuclei

    NASA Astrophysics Data System (ADS)

    Stuhlinger, Ernst; Bassner, Helmut; Fechtig, Hugo; Igenbergs, Eduard; Kuczera, Heribert; Loeb, Horst; Schobert, Detlef

    1987-09-01

    A comet nucleus sampling scenario is proposed. Material samples for analysis in earth-based laboratories should be collected continuously to a depth of 3 m below the surface, and at a solar distance of at least 2.5 AU where the comet surface is inactive. The spacecraft is propelled by chemical and electric thrusters. While hovering above the comet nucleus at an altitude of 500 to 1000 m, the spacecraft will dispatch a rotating drill on a tether. The drill pipe will be driven into the nucleus by a rocket-powered reaction wheel. The inner pipe of the drill, when filled with cometary material, will be withdrawn by the tether, stored on the spacecraft, and transported back to Earth.

  17. Analysis of Hubble Space Telescope Observations of an Outburst of Comet 29P/Schwassmann-Wachmann 1

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles Alfred; Fernandez, Yanga R.; Samarasinha, Nalin H.; Kundu, Arunav

    2016-10-01

    We present results of a continuing analysis on the spin state of the enigmatic Comet 29P/Schwassmann-Wachmann 1 (SW1). Previous works have reported possible constraints on the spin state including a non-principal axis state [1] or a rotation period of tens of days [2]. This diversity of published answers highlights the complexity of determining the spin state of an active comet nucleus. Previous work by our group using 3D Monte Carlo coma modeling of ground-based outburst observations from 2008 [3] has placed constraints on the spin period for a set of assumed spin-pole orientations. Due to the nature of the 2008 outburst morphology no constraints on the spin-pole orientation could be found.We present here an analysis of Hubble Space Telescope WFPC2 observations of SW1 shortly after a 1996 outburst [4] with which we have further constrained the spin state. The 0.046-arcsec/pixel scale (176 km/pixel at SW1) of the PC detector gives an order-of-magnitude improvement in spatial resolution over our ground-based observations. Two sets of observations from UT 1996 Mar. 11.3 and 12.1 show the ejected dust forming an asymmetric outflow contained on the sunward side of the coma. A projected outflow velocity of 0.15 ± 0.02 km/s was measured, similar to our measured value from the 2008 observations. Enhancements of the images were performed [5] to bring out subtle variations in coma brightness (i.e., jets) and to allow us to search for signatures of the nucleus' rotation during the outburst. Three curved features are seen in both sets of observations and were modeled using the 3D Monte Carlo coma model [6]. We find a spin period on the order of several days, in agreement with our earlier 2008 analysis.[1] Meech, K. J., et al.: 1993, Astron. J., 106, 1222. [2] Miles, R., et al.: 2016, Icarus, 272, 327. [3] Schambeau, C. A., et al.: 2016, Icarus, submitted. [4] Feldman, P. D., et al.: 1996, AAS/DPS Meeting Abstracts, 28, 1084. [5] Samarasinha, N. and Larson, S.: 2014, Icarus

  18. Reality of comet nucleus.

    NASA Technical Reports Server (NTRS)

    Lyttleton, R. A.

    1972-01-01

    The prime problem of a comet mission must be to settle whether the cometary nucleus has an actual tangible material existence, or whether it arises from some optical effect present only at times within comets. The absence of any large particles in a comet seems to be demonstrated by certain meteor showers. A feature that would seem to indicate that a comet consists primarily of a swarm of particles is that the coma in general contracts as the comet approaches the sun, roughly in proportion within the distance, and then expands again as it recedes.

  19. Disintegration of comet nuclei

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid V.

    2012-02-01

    The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies.

  20. The TRAPPIST comet survey

    NASA Astrophysics Data System (ADS)

    Jehin, E.; Opitom, C.; Manfroid, J.; Hutsemékers, D.; Gillon, M.

    2014-07-01

    distribution of several species among which OH, NH, CN, C2 and C3 as well as ions like CO+. The dust production rates (Afrho) and color of the dust are determined through four dust continuum bands (UC, BC, GC, RC). Such regular measurements are rare because of the lack of observing time on larger telescopes. Yet they are very valuable as they show how the gas production rate of each species evolves with respect to the distance to the Sun. Those observations allow to determine the composition of the comets and the chemical class to which they belong (rich or poor in carbon for instance [3]), possibly revealing the origin of those classes but also if there are some changes of the abundance ratios along the orbit (evolutionary effects). Indeed with half a dozen of comets observed each year --- and as long as possible along their orbit --- this program will provide a good statistical sample after a few years. We will present the results of this monitoring after three years of operations. Thanks to the way the telescope is operated, follow-up of split comets and of special outburst events is possible right after an alert is given and can bring important information on the nature of comets. In addition to providing the productions rates of the different species through a proper photometric calibration, image analysis can reveal coma features (jets, fans, tails), that can lead to the detection of active regions and measure the rotation period of the nucleus. The monitoring is also useful to assess the gas and dust activity of a given comet in order to prepare more detailed observations with larger telescopes. Such data can be obtained at any time under request. Finally a dozen of faint comets (V < 20) are monitored once a week through B, V, Rc, Ic filters and magnitudes and positions are sent to the MPC.

  1. In vivo osteogenesis assay: a rapid method for quantitative analysis.

    PubMed

    Dennis, J E; Konstantakos, E K; Arm, D; Caplan, A I

    1998-08-01

    A quantitative in vivo osteogenesis assay is a useful tool for the analysis of cells and bioactive factors that affect the amount or rate of bone formation. There are currently two assays in general use for the in vivo assessment of osteogenesis by isolated cells: diffusion chambers and porous calcium phosphate ceramics. Due to the relative ease of specimen preparation and reproducibility of results, the porous ceramic assay was chosen for the development of a rapid method for quantitating in vivo bone formation. The ceramic cube implantation technique consists of combining osteogenic cells with 27-mm3 porous calcium phosphate ceramics, implanting the cell-ceramic composites subcutaneously into an immuno-tolerant host, and, after 2-6 weeks, harvesting and preparing the ceramic implants for histologic analysis. A drawback to the analysis of bone formation within these porous ceramics is that the entire cube must be examined to find small foci of bone present in some samples; a single cross-sectional area is not representative. For this reason, image analysis of serial sections from ceramics is often prohibitively time-consuming. Two alternative scoring methodologies were tested and compared to bone volume measurements obtained by image analysis. The two subjective scoring methods were: (1) Bone Scale: the amount of bone within pores of the ceramic implant is estimated on a scale of 0-4 based on the degree of bone fill (0=no bone, 1=up to 25%, 2=25 to 75%, 4=75 to 100% fill); and (2) Percentage Bone: the amount of bone is estimated by determining the percentage of ceramic pores which contain bone. Every tenth section of serially sectioned cubes was scored by each of these methods under double-blind conditions, and the Bone Scale and Percentage Bone results were directly compared to image analysis measurements from identical samples. Correlation coefficients indicate that the Percentage Bone method was more accurate than the Bone Scale scoring method. The Bone Scale

  2. Infrared spectroscopy of comets

    NASA Technical Reports Server (NTRS)

    Disanti, Michael A.; Mumma, M. J.; Hoban, S. M.; Reuter, D.; Espenak, F.; Storrs, A. D.; Lacy, J.; Parmar, R.; Joyce, R.

    1990-01-01

    An observational search for cometary parent molecules using infrared spectroscopy was conducted in the 1 to 5 micron region. The investigation involved two different observing programs, one at moderate spectral resolution and one at fairly high resolution. The lower resolution was used to study cometary spectra in the vicinity of 3.5 micron at wavelength/change in wavelength is approximately or equal to 10(exp 3). Comets P/Brorsen-Metcalf (1989o), Okazaki-Levy-Rudenko (1989r), and Austin (1990c1) were observed with the Cryogenic Spectrometer (CRSP) at Kitt Peak. The detector incorporated an InSb array with 58 spatial elements, each 2.7 min on the sky, and 62 spectral channels per spatial element. An, as yet, unidentified feature was detected at approximately 3.52 micron in Comet Austin (on 1990 May 4, 5, and 6). The feature is possibly present in P/Brorsen-Metcalf (observed on 1989 August 23 and 25), as well. Comet Okazaki-Levy-Rudenko exhibited continuum emission only in this spectral region at the time of the observations (1989 November 14 and 16). The data are presented, and the relationship between the 3.52 micron feature and cometary activity (e.g., water production rate, visibility of the 3.4 micron emission feature) are discussed. The high resolution program probed comet Austin in the 4.8 micron region. These observations were used to search for emission lines comprising the (1-0) vibration-rotation band of the ground electronic state of CO. Retrieval of the lines allows a probe of the population distribution of levels J' = 1 through 4 of the excited (v' = 1) vibrational state within the ground electronic state of CO. Knowledge of this distribution can be used to constrain the rotational temperature. Preliminary analysis suggests the P3 line was present UT May 16 at roughly the 5 sigma level. Results concerning the existence of other lines, and physical conditions inferred therefrom are discussed.

  3. Observations and analysis of O(1D) and NH2 line profiles for the coma of comet P/Halley

    NASA Technical Reports Server (NTRS)

    Smyth, William H.; Combi, Michael R.; Roesler, Fred L.; Scherb, Frank

    1995-01-01

    A set of high-resolution Fabry-Perot measurements of the coma of comet P/Halley was acquired in the (O I) 6300 A and NH2 6298.62 A emission lines. These high-resolution measurements provide the first optical observations capable of studying directly the photochemical kinetics and dynamic outflow of the coma. The observations were analyzed by a Monte Carlo Particle Trajectory Model. The agreement of the model and observed line profiles was excellent and verified the underlying dynamics, exothermic photodissociative chemistry, and collisional thermalization in the coma. The somewhat wider intrinsic line profile width for the O(1D) emission in 1986 January compared to 1986 May, is, for example, produced by the larger outflow speeds and gas temperatures nearer perihelion in January. The January O(1D) profile, which is wider than the January NH2 profile, is indicative of the photochemical kinetics in the dissociation of the parent molecules H2O and OH in the coma. The absolute calibration of the observations in 1986 January allowed the production rates for H2O and the NH2-parent molecules to be determined. The average daily water production rates derived from the O(1D) emission data for January 16 and 17 are presented. These very large water production rates are consistent with the extrapolated (and 7.6 day time variable) water production rates determined from the analysis of lower spectral resolution observations for O(1D) and H-alpha emissions that covered the time period up to January 13. The large production rates on January 16 and 17 establish that the maximum water production rate for comet Halley accurred pre-perihelion in January. Implications drawn from comparison with 18 cm radio emission data in January suggest that the peak water production rate was even larger. The average production rate for NH3 determined from the NH2 emission data for January 17 was (1.48 +/- 0.10) x 10(exp 28) molecules/s, yielding an NH3/H2O production rate ratio of 0.55%.

  4. Total Gamma Count Rate Analysis Method for Nondestructive Assay Characterization

    SciTech Connect

    Cecilia R. Hoffman; Yale D. Harker

    2006-03-01

    A new approach to nondestructively characterize waste for disposal, based on total gamma response, has been developed at the Idaho Cleanup Project by CH2M-WG Idaho, LLC and Idaho State University, and is called the total gamma count rate analysis method. The total gamma count rate analysis method measures gamma interactions that produce energetic electrons or positrons in a detector. Based on previous experience with waste assays, the radionuclide content of the waste container is then determined. This approach potentially can yield minimum detection limits of less than 10 nCi/g. The importance of this method is twofold. First, determination of transuranic activity can be made for waste containers that are below the traditional minimum detection limits. Second, waste above 10 nCi/g and below 100 nCi/g can be identified, and a potential path for disposal resolved.

  5. Statistical analysis of dust signals observed by ROSINA/COPS onboard of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Tzou, Chia-Yu; altwegg, kathrin; Bieler, Andre; Calmonte, Ursina; Gasc, Sébastien; Le Roy, Léna; Rubin, Martin

    2016-10-01

    ROSINA is the in situ Rosetta Orbiter Spectrometer for Ion and Neutral Analysis on board of Rosetta, one of the corner stone missions of the European Space Agency (ESA) to land and orbit the Jupiter family comet 67P/Churyumov-Gerasimenko (67P). ROSINA consists of two mass spectrometers and a pressure sensor. The Reflectron Time of Flight Spectrometer (RTOF) and the Double Focusing Mass Spectrometer (DFMS) complement each other in mass and time resolution.The Comet Pressure Sensor (COPS) provides density measurements of the neutral molecules in the cometary coma of 67P. COPS has two gauges, a nude gauge that measures the total neutral density and a ram gauge that measures the dynamic pressure from the comet. Combining the two COPS is also capable of providing gas dynamic information such as gas velocity and gas temperature of the coma.While Rosetta started orbiting around 67P in August 2014, COPS observed diurnal and seasonal variations of the neutral gas density in the coma. Surprisingly, additional to these major density variation patterns, COPS occasionally observed small spikes in the density that are associated with dust. These dust signals can be interpreted as a result of cometary dust releasing volatiles while heated up near COPS. A statistical analysis of dust signals detected by COPS will be presented.

  6. Ultraviolet observations of comets

    NASA Technical Reports Server (NTRS)

    Code, A. D.; Houck, T. E.; Lillie, C. F.

    1972-01-01

    The first observations of a comet in the vacuum ultraviolet were obtained on January 14, 1970, when OAO-2 recorded the spectrum of the bright comet Tago-Sato-Kosaka (1969g). The observations revealed, among other things, the predicted extensive hydrogen Lyman alpha halo. OAO-2 continued to collect spectrophotometric measurements of this comet throughout January of that year; a photograph of the nucleus in Lyman alpha revealed finer scale structures. In February of 1970, the bright comet Bennet (1969i) became favorable for space observations. On the basis of the OAO discovery, OGO-V made several measurements of comet Bennet with low spatial resolution photometers. Comet Enke was detected by OGO in January of 1971 at a large heliocentric distance from its Lyman alpha emission.

  7. Ammonia abundances in comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S.; Engel, L.

    The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

  8. Comet Dead Ahead

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 26, 2005, when the spacecraft was 7,118,499.4 kilometers (4,423,435 miles) away from the comet. Eight images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  9. Ballistic intercept missions to Comet Encke

    NASA Technical Reports Server (NTRS)

    Mumma, M. (Compiler)

    1975-01-01

    The optimum ballistic intercept of a spacecraft with the comet Encke is determined. The following factors are considered in the analysis: energy requirements, encounter conditions, targeting error, comet activity, spacecraft engineering requirements and restraints, communications, and scientific return of the mission. A baseline model is formulated which includes the basic elements necessary to estimate the scientific return for the different missions considered. Tradeoffs which have major impact on the cost and/or scientific return of a ballistic mission to comet Encke are identified and discussed. Recommendations are included.

  10. Comet or Asteroid?

    NASA Astrophysics Data System (ADS)

    1997-11-01

    , Institute of Planetary Exploration) soon thereafter obtained seven unfiltered CCD images on three consecutive nights with the 60-cm `Bochum telescope' at La Silla, Uri Carsenty found a tail extending 15 arcseconds in the WSE direction from the point source, cf. ESO Press Photo 31b/97. The (red) magnitude was about 19, or 150,000 times fainter than what is visible to the naked eye. More observations were obtained at La Silla during the following nights, confirming the persistent presence of this tail. NTT observations confirm the cometary nature of P/1997 T3 ESO Press Photo 31c/97 ESO Press Photo 31c/97 [JPG, 52k] Caption: Deep NTT image of P/1997 T3. This image covers a field of 105 x 60 arcsec and is a composite of several CCD exposures. It was taken with the ESO New Technology Telescope (NTT) and the EMMI multi-mode instrument by ESO astronomers Hermann Boehnhardt and Olivier Hainaut on different days between 21 and 25 October 1997. By computer processing, the images of P/1997 T3 are aligned to the same pixel position and co-added in order to increase the visibility of the comet. Due to the motion of the comet, multiple images of several galaxies and stars appear in this photo. At the time of the observations, the comet was about 3.34 AU from Earth and about 4.30 AU from the Sun. A larger version [JPG, 384k] is also available. In late October 1997, further images of the new object and its tail were taken with the ESO 3.5-m New Technology Telescope (NTT) at La Silla, cf. ESO Press Photo 31c/97. On these, the narrow tail was seen to be at least 90 arcsec long and pointing roughly in the Sun direction . The steady appearance and the sunward orientation of the tail indicates that it consists of dust. Moreover, a preliminary image analysis shows the presence of a weak and very condensed coma of dust grains around the nucleus. Interestingly, a series of images through several broadband filters with a total of almost 30 min exposure time did not show any trace of a normal, anti

  11. Special Report: Chemistry of Comets.

    ERIC Educational Resources Information Center

    A'Hearn, Michael F.

    1984-01-01

    Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

  12. A quantitative analysis of OH prompt emission in three comets: the 3046 cm-1 quadruplet and its use in determining cometary water production rates.

    NASA Astrophysics Data System (ADS)

    Bonev, B. P.; Mumma, M. J.; Dello Russo, N.; Gibb, E. L.; DiSanti, M. A.; Magee-Sauer, K.

    2003-05-01

    Multiplets from OH in the 1-0 band were seen in prompt emission in several comets observed with NIRSPEC at the W. M. Keck Observatory (1, 2). These lines originate from vibrationally-excited rotationally-hot states of OH, produced by dissociative excitation of water. The various OH quadruplets span the L-band atmospheric window (2.9 - 3.7 μ m); here, we report results for the quadruplet falling near 3046 cm-1, including the effective g-factors in comets C/1999 H1 (Lee), C/2001 A2 (LINEAR), and C/2000 WM1 (LINEAR). The resulting spatial distribution of OH peaks at the nucleus and it traces that of the parent, H2O. (By contrast, OH fluorescent emission tracks the spatial distribution of OH itself.) OH prompt emission can provide an alternative way to determine water production rates in future comets, providing a convenient means for quantifying H2O simultaneously with several other parent species of "key" interest observed in the near-infrared. We discuss the significance of this approach, present our first quantitative results, and outline the direction of this work towards analysis of other OH multiplets. This work was supported by a grant to M. J. Mumma (RTOP 344-32-30-07) from the Planetary Astronomy Program. [1] M. J. Mumma et al., Ap. J. 546:1183-1193 (2001). [2] M. J. Mumma et al., Science 292:1334-1339 (2001).

  13. Comet composition and density analyzer

    NASA Technical Reports Server (NTRS)

    Clark, B. C.

    1982-01-01

    Distinctions between cometary material and other extraterrestrial materials (meteorite suites and stratospherically-captured cosmic dust) are addressed. The technique of X-ray fluorescence (XRF) for analysis of elemental composition is involved. Concomitant with these investigations, the problem of collecting representative samples of comet dust (for rendezvous missions) was solved, and several related techniques such as mineralogic analysis (X-ray diffraction), direct analysis of the nucleus without docking (electron macroprobe), dust flux rate measurement, and test sample preparation were evaluated. An explicit experiment concept based upon X-ray fluorescence analysis of biased and unbiased sample collections was scoped and proposed for a future rendezvous mission with a short-period comet.

  14. Observing chemical abundances in comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1981-01-01

    The atomic resonance lines of the major elements were observed in the atmospheres of a few comets, by using vacuum ultraviolet spectrographs on board rockets or orbiting observatories. Dust-to-gas ratios were also deduced for two comets through a Finson-Probstein's analysis of their dust-tail isophotes. The geometric albedo of the dust for the phase angle alpha of the observations is not accurately known but, the dust-to-gas ratio is not overly sensitive to the actual value of this albedo. Infrared observations of the dust head of some comets show that the bulk of cometary dust must be silicates, although a minor component (5-10 percent) of carbon compounds is rather likely, because of poor dielectric properties of the grains. This interpretation is confirmed by the fact that interplanetary dust probably of cometary origin, that was collected in the stratosphere by NASA-U2 Spacecraft, is chondritic in nature. Metal abundances in the head of a sungrazing comet support the chondritic hypothesis.

  15. Neutron Resonance Transmission Analysis (NRTA): A Nondestructive Assay Technique for the Next Generation Safeguards Initiative’s Plutonium Assay Challenge

    SciTech Connect

    J. W. Sterbentz; D. L. Chichester

    2010-12-01

    This is an end-of-year report for a project funded by the National Nuclear Security Administration's Office of Nuclear Safeguards (NA-241). The goal of this project is to investigate the feasibility of using Neutron Resonance Transmission Analysis (NRTA) to assay plutonium in commercial light-water-reactor spent fuel. This project is part of a larger research effort within the Next-Generation Safeguards Initiative (NGSI) to evaluate methods for assaying plutonium in spent fuel, the Plutonium Assay Challenge. The first-year goals for this project were modest and included: 1) developing a zero-order MCNP model for the NRTA technique, simulating data results presented in the literature, 2) completing a preliminary set of studies investigating important design and performance characteristics for the NRTA measurement technique, and 3) documentation of this work in an end of the year report (this report). Research teams at Los Alamos National Laboratory (LANL), Lawrence Berkeley National Laboratory (LBNL), Pacific Northwest National Laboratory (PNNL), and at several universities are also working to investigate plutonium assay methods for spent-fuel safeguards. While the NRTA technique is well proven in the scientific literature for assaying individual spent fuel pins, it is a newcomer to the current NGSI efforts studying Pu assay method techniques having just started in March 2010; several analytical techniques have been under investigation within this program for two to three years or more. This report summarizes a nine month period of work.

  16. Studying comets with NEOWISE

    NASA Astrophysics Data System (ADS)

    Stevenson, R.; Bauer, J.; Kramer, E.; Fernández, Y.; Mainzer, A.; Grav, T.; Masiero, J.

    2014-07-01

    The Wide-Field Infrared Survey Explorer (WISE) mission detected more than 150 comets during its all-sky survey between January 2010 and February 2011. The comets were imaged at 4 infrared wavelengths (3.4, 4.6, 12, and 22 microns). The large sample of both long-period and Jupiter-family comets observed at a range of heliocentric distances allows for systematic comparison of the properties of both dynamical families. Nucleus diameters and albedos, dust comae temperatures, CO and CO_{2} emission rates, and dust tail and trail morphologies are some of the properties studied with the WISE data. This work is being continued by the reactivated NEOWISE mission [1]. In 2013, the WISE spacecraft was brought out of hibernation to resume discovering, tracking, and characterizing small bodies in the Solar System by imaging the sky at solar elongations of ˜90° at wavelengths of 3.4 and 4.6 microns. Since NEOWISE resumed its all-sky survey on December 23, 2013, 10 comets have been observed, including one previously-unknown long-period comet -- C/2014 C3 (NEOWISE). Of particular interest are the NEOWISE observations of comet C/2013 A1 (Siding Spring), which will have a close encounter with Mars in October 2014. NEOWISE observed this comet in January 2014 and will observe it twice more before the comet's close approach to Mars. NEOWISE will continue to operate until early 2017, greatly enhancing our understanding of cometary properties as studied in the infrared.

  17. Changing Speed of Comets

    ERIC Educational Resources Information Center

    Follows, Mike

    2003-01-01

    It is shown that highly elliptical orbits, such as those of comets, can be explained well in terms of energy rather than forces. The principle of conservation of energy allows a comet's velocity to be calculated at aphelion and perihelion. An example asks students to calculate whether they can run fast enough to escape from a small asteroid.…

  18. Asteroids, Comets, Meteors 1991

    NASA Technical Reports Server (NTRS)

    Harris, Alan W. (Editor); Bowell, Edward (Editor)

    1992-01-01

    Papers from the conference are presented and cover the following topics with respect to asteroids, comets, and/or meteors: interplanetary dust, cometary atmospheres, atmospheric composition, comet tails, astronomical photometry, chemical composition, meteoroid showers, cometary nuclei, orbital resonance, orbital mechanics, emission spectra, radio astronomy, astronomical spectroscopy, photodissociation, micrometeoroids, cosmochemistry, and interstellar chemistry.

  19. The evolution of comet orbits

    NASA Technical Reports Server (NTRS)

    Everhart, E.

    1976-01-01

    The origin of comets and the evolution of their orbits are discussed. Factors considered include: the law of survival of comets against ejection on hyperbolic orbits; short-period comets are not created by single close encounters of near-parabolic comets with Jupiter; observable long-period comets do not evolve into observable short-period comets; unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets; long-period comets cannot have been formed or created within the planetary region of the solar system (excluding the effects of stellar perturbations); it is possible that some of the short-period comets could have been formed inside the orbit of Neptune; circularly-restricted three-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.

  20. Sulfur and Oxygen Isotopic Analysis of a Cosmic Symplectite from a Comet Wild 2 Stardust Terminal Particle

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Berger, E. L.; Nakamura-Messenger, K.; Messenger, S.

    2015-01-01

    Introduction: Analyses of comet 81P/Wild 2 samples re-turned from the Stardust mission have uncovered surprising simi-larities to meteoritic material, including the identification of inner solar system grains [1-3]. The TEM characterization of terminal particle (TP) 4 from Stardust track #147 revealed an assemblage consisting of symplectically intergrown pentlandite and nanocrys-talline maghemite coexisting with high-Ca pyroxene [4]. Mineral-ogically similar cosmic symplectites (COS) containing pentlandite and magnetite in the primitive Acfer 094 meteorite are highly de-pleted in 16O (?17O, ?18O 180 per mille) [5-7]. This isotopic signature is proposed to record alteration with primordial solar nebula water. Conversely, the normal O isotopic composition of the Stardust COS indicates alteration by a different aqueous reservoir, perhaps on the comet [8]. In this study, we analyzed the Wild 2 COS for S isotopes to further constrain its origin. Experimental: Thin sections of TP4 (12 ?m) were produced and their mineralogy was thoroughly characterized by TEM. Two of the sections were analyzed for O isotopes by isotopic imaging in the JSC NanoSIMS 50L. The sample in one of the slices was completely consumed. The remaining material in the adjacent slice was analyzed simultaneously for 16O, 32S, 33S, 34S, and 56Fe16O in electron multipliers using a Cs+ primary ion beam. Quasi-simulta-neous arrival (QSA) can have a significant effect on S isotopic ra-tios when using electron multipliers, resulting in undercounting of 32S [9]. Canyon Diablo troilite (CDT) was measured numerous times to deduce a correction factor for QSA and ensure measure-ment reproducibility. Isotopic ratios are reported relative to CDT. Results and Discussion: The Wild 2 COS is enriched in the heavy S isotopes relative to CDT (?33S = 6.5 +/- 1.6 per mille; ?34S = 5.1 +/- 0.7 per mille; 1?). The degree of 33S enrichment indicates mass-inde-pendent fractionation (MIF) with ?33S = 3.9 +/- 1.7 per mille. MIF of

  1. The chemistry of comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1988-01-01

    Comets appear to represent a population of rather homogeneous objects. In particular, the original size distribution peaks at a mean diameter of the order of 10 km. Cometary dust grains appear to be made of clusters of extremely fine particles (0.1-1.0 micron) sintered by heat at a variable degree during their perihelion passages. The brightness laws of comets appear to be derived only by the sublimation of water ice or at least of gas hydrates of the clathrate type. Pristine nuclei are likely to be radially undifferentiated; only their crustal surface must be outgassed and sintered by the heat of perihelion passages. Comet Halley is confirmed to be in the same general class as the bright comets of the 1970s. With an organic fraction of 33 percent in the cometary dust, the carbon of Comet Halley is close to cosmic abundances.

  2. Newly developed techniques for the analysis of micrometer-sized interplanetary dust particles and comet grains

    NASA Astrophysics Data System (ADS)

    Bradley, J. P.

    1991-04-01

    Electron transparent sections (30-100 nm thick) of interplanetary dust particles and other fine-grained meteoric materials are produced using an ultramicrotome equipped with a diamond knife. An analytical electron microscope (AEM) is employed to examine indigenous physical properties (e.g., porosity), mineralogy, and petrography. Large data sets of quantitative point count analysis obtained from thin sections enable direct mineralogical comparison of IDPs and Halley.

  3. Fully Bayesian Analysis of High-throughput Targeted Metabolomics Assays

    EPA Science Inventory

    High-throughput metabolomic assays that allow simultaneous targeted screening of hundreds of metabolites have recently become available in kit form. Such assays provide a window into understanding changes to biochemical pathways due to chemical exposure or disease, and are usefu...

  4. The comet disintegration and meteor streams

    NASA Astrophysics Data System (ADS)

    Guliyev, A. S.; Poladova, U. J.

    2015-03-01

    Possibility of disintegration of proto-comet nucleus of sungraser comets in three zones of Solar System predicted by one of authors is considered. Testing of parameters of 118 split comets confirms the basic idea. Results of the statistical analysis of comet outbursts gave us additional argument in favor of this assumption. Almost twenty years have passed since, as a result of the search for host phases of isotopically unusual noble gases, the first discovery in 1987 of surviving pre-solar minerals (diamond and silicon carbide) in primitive meteorites. These were followed by others (graphite, refractory oxides, silicon nitride, and finally silicates) in the years since. Pre-solar grains occur in even higher abundance than in meteorites in interplanetary dust particles (IDPs). The result is a kind of `new astronomy' based on the study of pre-solar condensates with all the methods available in modern analytical laboratories.

  5. A Comparative Analysis of Acyl-Homoserine Lactone Synthase Assays.

    PubMed

    Shin, Daniel; Frane, Nicole D; Brecht, Ryan M; Keeler, Jesse; Nagarajan, Rajesh

    2015-12-01

    Quorum sensing is cell-to-cell communication that allows bacteria to coordinate attacks on their hosts by inducing virulent gene expression, biofilm production, and other cellular functions, including antibiotic resistance. AHL synthase enzymes synthesize N-acyl-l-homoserine lactones, commonly referred to as autoinducers, to facilitate quorum sensing in Gram-negative bacteria. Studying the synthases, however, has proven to be a difficult road. Two assays, including a radiolabeled assay and a colorimetric (DCPIP) assay are well-documented in literature to study AHL synthases. In this paper, we describe additional methods that include an HPLC-based, C-S bond cleavage and coupled assays to investigate this class of enzymes. In addition, we compare and contrast each assay for both acyl-CoA- and acyl-ACP-utilizing synthases. The expanded toolkit described in this study should facilitate mechanistic studies on quorum sensing signal synthases and expedite discovery of antivirulent compounds.

  6. The location of Asteroidal Belt Comets (ABCs), in a comet's evolutionary diagram: The Lazarus Comets

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio; Zuluaga, Jorge; Cuartas, Pablo

    2013-09-01

    There is a group of newly recognized asteroids in the main belt that are exhibiting cometary characteristics. We will call them Asteroidal Belt Comets or ABCs for short. The surprising property of these objects is that their orbits are entirely asteroidal while their behaviour is entirely cometary, with Tisserand invariants larger than 3.0, while all Jupiter family comets have Tisserand invariants smaller than 3.0. An analysis of their orbital and physical properties has resulted in the following conclusion. (1) We define the `detached group (DG)' as those objects that exhibit cometary characteristics (sublimating water) and have aphelion distances Q < 4.5 au. The DG contains all the ABCs traditionally recognized, plus a few other members not traditionally recognized like 2P and 107P. With the above definition there are 11 members of the ABC group: 2P, 107P, 133P, 176P, 233P, 238P, C/2008 R1, C/2010 R2, 2011 CR42, 3200 and 300163 = 2006 VW139. And there are three members of the collisioned asteroids, CA, P/2010 A2, 596 Scheila and P/2012 F5 Gibbs. (2) In the literature a common reason for activity is interplanetary collisions. Active objects sublimate ices except for the CA that have exhibited dust tails due to collisions and 3200 Phaethon activated by solar wind sputtering. In this work, we will trace the origin of activity to a diminution of their perihelion distances, a hypothesis that has not been previously explored in the literature. (3) We have calibrated the blackbody (colour) temperature of comets versus perihelion distance, R, regardless of class. We find T = 325 ± 5 K/√R. (4) Using a mathematical model of the thermal wave we calculate the thickness of the crust or dust layer on comet nuclei. We find a thickness of 2.0 ± 0.5 m for comet 107P, 4.7 ± 1.2 m for comet 133P and 1.9 ± 0.5 m for a sample of nine comets. Note the small errors. (5) We have located three ABCs in an evolutionary diagram of Remaining Revolutions (RR) versus Water-Budget Age (WB

  7. Laboratory intercomparison of the dicentric chromosome analysis assay.

    PubMed

    Beinke, C; Barnard, S; Boulay-Greene, H; De Amicis, A; De Sanctis, S; Herodin, F; Jones, A; Kulka, U; Lista, F; Lloyd, D; Martigne, P; Moquet, J; Oestreicher, U; Romm, H; Rothkamm, K; Valente, M; Meineke, V; Braselmann, H; Abend, M

    2013-08-01

    The study design and obtained results represent an intercomparison of various laboratories performing dose assessment using the dicentric chromosome analysis (DCA) as a diagnostic triage tool for individual radiation dose assessment. Homogenously X-irradiated (240 kVp, 1 Gy/min) blood samples for establishing calibration data (0.25-5 Gy) as well as blind samples (0.1-6.4 Gy) were sent to the participants. DCA was performed according to established protocols. The time taken to report dose estimates was documented for each laboratory. Additional information concerning laboratory organization/characteristics as well as assay performance was collected. The mean absolute difference (MAD) was calculated and radiation doses were merged into four triage categories reflecting clinical aspects to calculate accuracy, sensitivity and specificity. The earliest report time was 2.4 days after sample arrival. DCA dose estimates were reported with high and comparable accuracy, with MAD values ranging between 0.16-0.5 Gy for both manual and automated scoring. No significant differences were found for dose estimates based either on 20, 30, 40 or 50 cells, suggesting that the scored number of cells can be reduced from 50 to 20 without loss of precision of triage dose estimates, at least for homogenous exposure scenarios. Triage categories of clinical significance could be discriminated efficiently using both scoring procedures.

  8. Quantitative Analysis of Filament Branch Orientation in Listeria Actin Comet Tails.

    PubMed

    Jasnin, Marion; Crevenna, Alvaro H

    2016-02-23

    Several bacterial and viral pathogens hijack the host actin cytoskeleton machinery to facilitate spread and infection. In particular, Listeria uses Arp2/3-mediated actin filament nucleation at the bacterial surface to generate a branched network that will help propel the bacteria. However, the mechanism of force generation remains elusive due to the lack of high-resolution three-dimensional structural data on the spatial organization of the actin mother and daughter (i.e., branch) filaments within this network. Here, we have explored the three-dimensional structure of Listeria actin tails in Xenopus laevis egg extracts using cryo-electron tomography. We found that the architecture of Listeria actin tails is shared between those formed in cells and in cell extracts. Both contained nanoscopic bundles along the plane of the substrate, where the bacterium lies, and upright filaments (also called Z filaments), both oriented tangentially to the bacterial cell wall. Here, we were able to identify actin filament intersections, which likely correspond to branches, within the tails. A quantitative analysis of putative Arp2/3-mediated branches in the actin network showed that mother filaments lie on the plane of the substrate, whereas daughter filaments have random deviations out of this plane. Moreover, the analysis revealed that branches are randomly oriented with respect to the bacterial surface. Therefore, the actin filament network does not push directly toward the surface but rather accumulates, building up stress around the Listeria surface. Our results favor a mechanism of force generation for Listeria movement where the stress is released into propulsive motion.

  9. Quantitative Analysis of Filament Branch Orientation in Listeria Actin Comet Tails

    PubMed Central

    Jasnin, Marion; Crevenna, Alvaro H.

    2016-01-01

    Several bacterial and viral pathogens hijack the host actin cytoskeleton machinery to facilitate spread and infection. In particular, Listeria uses Arp2/3-mediated actin filament nucleation at the bacterial surface to generate a branched network that will help propel the bacteria. However, the mechanism of force generation remains elusive due to the lack of high-resolution three-dimensional structural data on the spatial organization of the actin mother and daughter (i.e., branch) filaments within this network. Here, we have explored the three-dimensional structure of Listeria actin tails in Xenopus laevis egg extracts using cryo-electron tomography. We found that the architecture of Listeria actin tails is shared between those formed in cells and in cell extracts. Both contained nanoscopic bundles along the plane of the substrate, where the bacterium lies, and upright filaments (also called Z filaments), both oriented tangentially to the bacterial cell wall. Here, we were able to identify actin filament intersections, which likely correspond to branches, within the tails. A quantitative analysis of putative Arp2/3-mediated branches in the actin network showed that mother filaments lie on the plane of the substrate, whereas daughter filaments have random deviations out of this plane. Moreover, the analysis revealed that branches are randomly oriented with respect to the bacterial surface. Therefore, the actin filament network does not push directly toward the surface but rather accumulates, building up stress around the Listeria surface. Our results favor a mechanism of force generation for Listeria movement where the stress is released into propulsive motion. PMID:26497103

  10. Realm of the comets

    SciTech Connect

    Weissman, P.R.

    1987-03-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  11. Realm of the comets

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    1987-01-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  12. Meteor showers on Earth from sungrazing comets

    NASA Astrophysics Data System (ADS)

    Sekhar, A.; Asher, D. J.

    2014-01-01

    Sungrazing comets have always captured a lot of interest and curiosity among the general public as well as scientists since ancient times. The perihelion passage of comet C/2012 S1 (ISON) at the end of this year (on 2013 November 28) is an eagerly awaited event. In this work, we do a mathematical study to check whether meteoroids ejected from this comet during its journey around the Sun can produce spectacular meteor phenomena on Earth. Our calculations show that although the orbital elements of this comet are much more favourable than for most sungrazers to have its descending node near the Earth's orbit, even ejection velocities as high as 1 km s-1 do not induce sufficient nodal dispersion to bring meteoroids to Earth intersection during present times. A similar result applies to Newton's comet C/1680 V1 which has surprisingly similar orbital elements, although it is known to be a distinct comet from C/2012 S1. Our analysis also shows that for meteoroids ejected from all known sungrazing groups during recent epochs, only the Marsden family (with required ejection velocities of some hundreds of m s-1) can produce meteor phenomena during present times. In a broader sense, we indicate why we do not observe visually brilliant meteor showers from frequently observed sungrazers.

  13. The vicinity of Jupiter: A region to look for comets

    NASA Technical Reports Server (NTRS)

    Tancredi, Gonzalo; Lindgren, Mats

    1992-01-01

    Low-relative velocity and long-lasting encounters can dramatically change the orbital elements of a comet; the object could be temporarily bound to Jupiter for a period of several years. It is well stated that most of the discoveries of comets occurred just after a close encounter with the planet and a decrease of the perihelion distance of the comet. So, why don't we look for comets during close encounters with Jupiter rather than waiting to find them afterwards? To estimate the feasibility of this proposal, dynamical computations and observational analysis of the Jupiter family of comets were made. A criterion to distinguish comets during an encounter from other moving objects in the field is discussed.

  14. Space missions to comets

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (Editor); Yeomans, D. K. (Editor); Brandt, J. C. (Editor); Hobbs, R. W. (Editor)

    1979-01-01

    The broad impact of a cometary mission is assessed with particular emphasis on scientific interest in a fly-by mission to Halley's comet and a rendezvous with Tempel 2. Scientific results, speculations, and future plans are discussed.

  15. Comets: Search and Discovery

    NASA Astrophysics Data System (ADS)

    Shanklin, J.; Murdin, P.

    2003-04-01

    Comet discovery in the traditional sense by an amateur astronomer may be a thing of the past. The development of increasing numbers of professional all-sky survey programs, many specifically designed to spot moving or changing objects, means that the future prospects for visual discovery of a comet by an amateur astronomer are bleak. In the near future the professional programs are likely to cover...

  16. Comet coma sample return instrument

    NASA Technical Reports Server (NTRS)

    Albee, A. L.; Brownlee, Don E.; Burnett, Donald S.; Tsou, Peter; Uesugi, K. T.

    1994-01-01

    The sample collection technology and instrument concept for the Sample of Comet Coma Earth Return Mission (SOCCER) are described. The scientific goals of this Flyby Sample Return are to return to coma dust and volatile samples from a known comet source, which will permit accurate elemental and isotopic measurements for thousands of individual solid particles and volatiles, detailed analysis of the dust structure, morphology, and mineralogy of the intact samples, and identification of the biogenic elements or compounds in the solid and volatile samples. Having these intact samples, morphologic, petrographic, and phase structural features can be determined. Information on dust particle size, shape, and density can be ascertained by analyzing penetration holes and tracks in the capture medium. Time and spatial data of dust capture will provide understanding of the flux dynamics of the coma and the jets. Additional information will include the identification of cosmic ray tracks in the cometary grains, which can provide a particle's process history and perhaps even the age of the comet. The measurements will be made with the same equipment used for studying micrometeorites for decades past; hence, the results can be directly compared without extrapolation or modification. The data will provide a powerful and direct technique for comparing the cometary samples with all known types of meteorites and interplanetary dust. This sample collection system will provide the first sample return from a specifically identified primitive body and will allow, for the first time, a direct method of matching meteoritic materials captured on Earth with known parent bodies.

  17. Comet coma sample return instrument

    NASA Astrophysics Data System (ADS)

    Albee, A. L.; Brownlee, Don E.; Burnett, Donald S.; Tsou, Peter; Uesugi, K. T.

    The sample collection technology and instrument concept for the Sample of Comet Coma Earth Return Mission (SOCCER) are described. The scientific goals of this Flyby Sample Return are to return to coma dust and volatile samples from a known comet source, which will permit accurate elemental and isotopic measurements for thousands of individual solid particles and volatiles, detailed analysis of the dust structure, morphology, and mineralogy of the intact samples, and identification of the biogenic elements or compounds in the solid and volatile samples. Having these intact samples, morphologic, petrographic, and phase structural features can be determined. Information on dust particle size, shape, and density can be ascertained by analyzing penetration holes and tracks in the capture medium. Time and spatial data of dust capture will provide understanding of the flux dynamics of the coma and the jets. Additional information will include the identification of cosmic ray tracks in the cometary grains, which can provide a particle's process history and perhaps even the age of the comet. The measurements will be made with the same equipment used for studying micrometeorites for decades past; hence, the results can be directly compared without extrapolation or modification. The data will provide a powerful and direct technique for comparing the cometary samples with all known types of meteorites and interplanetary dust. This sample collection system will provide the first sample return from a specifically identified primitive body and will allow, for the first time, a direct method of matching meteoritic materials captured on Earth with known parent bodies.

  18. Comet Stepping Stones

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image from NASA's Spitzer Space Telescope shows three of the many fragments making up Comet 73P /Schwassman-Wachmann 3. The infrared picture also provides the best look yet at the crumbling comet's trail of debris, seen here as a bridge connecting the larger fragments.

    The comet circles around our sun every 5.4 years. In 1995, it splintered apart into four pieces, labeled A through D, with C being the biggest. Since then, the comet has continued to fracture into dozens of additional pieces. This image is centered about midway between fragments C and B; fragment G can be seen in the upper right corner.

    The comet's trail is made of dust, pebbles and rocks left in the comet's wake during its numerous journeys around the sun. Such debris can become the stuff of spectacular meteor showers on Earth.

    This image was taken on April 1, 2006, by Spitzer's multi-band imaging photometer using the 24-micron wavelength channel.

  19. Comets: Data, problems, and objectives

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1977-01-01

    A highly abridged review of new relevant results from the observations of Comet Kohoutek is followed by an outline summary of our basic knowledge concerning comets, both subjects being confined to data related to the nature and origin of comets rather than the phenomena (for example, plasma phenomena are omitted). The discussion then centers on two likely places of cometary origin in the developing solar system, the proto-Uranus-Neptune region versus the much more distant fragmented interstellar cloud region, now frequented by comets of the Opik-Oort cloud. The Comet Kohoutek results add new insights, particularly with regard to the parent molecules and the nature of meteoric solids in comets, to restrict the range of the physical circumstances of comet formation. A few fundamental and outstanding questions are asked, and a plea made for unmanned missions to comets and asteroids in order to provide definitive answers as to the nature and origin of comets, asteroids, and the solar system generally.

  20. Outbursts and cavities in comets

    NASA Astrophysics Data System (ADS)

    Ipatov, Sergei

    Based on analysis of the images made during the first 13 minutes after the collision of the impact module of the Deep Impact (DI) spacecraft with Comet 9P/Tempel 1, Ipatov & A'Hearn [1] studied time variations of ejection of material after this impact. They showed that, besides the normal ejection, at time t_{e} after the DI collision between 8 s and 60 s there was a considerable additional ejection (a triggered outburst) of small (micron size) particles. It increased the mean velocities of observed small ejected particles (compared with the normal ejection). The outburst could be caused by excavation of a large cavity with dust and gas under pressure. The largest cavity excavated after the collision could be relatively deep because a considerable excess ejection lasted during about 50 s. Schultz et al. [2] concluded that the diameter d_{tc} of the DI transient crater was about 200 m. Some authors support smaller values of d_{tc}. The depth of the DI crater at t_{e}=8 s was estimated in [3] to be about 6 m for d_{tc}=200 m and 4 m for d_{tc}=100 m. The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest excavated cavity equal to about 4-6 m, and sizes of particles inside the cavities of a few microns are in good agreement with the results obtained by Kossacki & Szutowicz [4]. In their models of the explosion of Comet 17P/Holmes, the initial sublimation front of the CO ice was located at a depth of 4 m, 10 m, or 20 m, and calculations were finished when the CO pressure exceeded the threshold value 10 kPa. It was shown that the pressure of CO vapor can rise to this value only when the nucleus is composed of very fine grains, a few microns in radius. The porous structure of comets provides enough space for sublimation. The projection of the velocity of the leading edge of the DI cloud (onto the plane perpendicular to the line of sight) was about 100-200 m/s and is typical for outburst particles ejected from comets

  1. Limited variance control in statistical low thrust guidance analysis. [stochastic algorithm for SEP comet Encke flyby mission

    NASA Technical Reports Server (NTRS)

    Jacobson, R. A.

    1975-01-01

    Difficulties arise in guiding a solar electric propulsion spacecraft due to nongravitational accelerations caused by random fluctuations in the magnitude and direction of the thrust vector. These difficulties may be handled by using a low thrust guidance law based on the linear-quadratic-Gaussian problem of stochastic control theory with a minimum terminal miss performance criterion. Explicit constraints are imposed on the variances of the control parameters, and an algorithm based on the Hilbert space extension of a parameter optimization method is presented for calculation of gains in the guidance law. The terminal navigation of a 1980 flyby mission to the comet Encke is used as an example.

  2. Comets and the Stardust Mission

    ScienceCinema

    LLNL - University of California Television

    2016-07-12

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  3. Comets and the Stardust Mission

    SciTech Connect

    LLNL - University of California Television

    2008-05-16

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  4. Comets in Australian Aboriginal Astronomy

    NASA Astrophysics Data System (ADS)

    Hamacher, Duane W.; Norris, Ray P.

    2011-03-01

    We present 25 accounts of comets from 40 Australian Aboriginal communities, citing both supernatural perceptions of comets and historical accounts of historically bright comets. Historical and ethnographic descriptions include the Great Comets of 1843, 1861, 1901, 1910, and 1927. We describe the perceptions of comets in Aboriginal societies and show that they are typically associated with fear, death, omens, malevolent spirits, and evil magic, consistent with many cultures around the world. We also provide a list of words for comets in 16 different Aboriginal languages.

  5. The Comet With a Broken Heart

    NASA Astrophysics Data System (ADS)

    2006-04-01

    ). Fragment B seems to have fragmented again, bringing the total of fragments close to 40, some being most probably very small, boulder-sized objects with irregular and short-lived activity. The new observations reveal that this new small fragment has split again! The image clearly reveals that below the main B fragment, there is a small fragment that is divided into two and a careful analysis reveals five more tiny fragments almost aligned. Thus, this image alone shows at least 7 fragments. The comet has thus produced a whole set of mini-comets! ESO PR Photo 15b/06 ESO PR Photo 15b/06 Broken Fragments of Comet SW-3 Will the process continue? Will more and more fragments form and will the comet finally disintegrate? How bright will the fragments be when the comet will be the closest to the Earth, on 11 to 14 May, and how many new fragments will have appeared before the comet reaches its closest approach to the Sun, around 7 June? Fragment C of the comet should be the closest to Earth on 11 May, when it will be about 12 million km away, while fragment B will come as 'close' as 10 million km from Earth on 14 May. Although this is the closest a comet ever approached Earth in more than twenty years - even Comet Hyakutake's smallest distance was 15 million km - this is still 26 times the distance between the Earth and the Moon and therefore does not pose any threat to our planet. ESO PR Photo 15/06 ESO PR Photo 15c/06 Mini-Comets coming off Comet SW-3 If nothing else happens, at the time of closest approach, fragment B will be just visible with unaided eye by experienced observers. It should be an easy target however to observe with binoculars. If we are lucky, however, fragment B presents another outburst, becoming a magnificent sight in the night sky. On the other hand, it could just as well fade away into oblivion. But then, the main fragment C should still be visible, even possibly with the unaided eye. ESO telescopes will observe the comet in the greatest detail at the end of

  6. Pseudotype-Based Neutralization Assays for Influenza: A Systematic Analysis

    PubMed Central

    Carnell, George William; Ferrara, Francesca; Grehan, Keith; Thompson, Craig Peter; Temperton, Nigel James

    2015-01-01

    The use of vaccination against the influenza virus remains the most effective method of mitigating the significant morbidity and mortality caused by this virus. Antibodies elicited by currently licensed influenza vaccines are predominantly hemagglutination-inhibition (HI)-competent antibodies that target the globular head of hemagglutinin (HA) thus inhibiting influenza virus entry into target cells. These antibodies predominantly confer homosubtypic/strain specific protection and only rarely confer heterosubtypic protection. However, recent academia or pharma-led R&D toward the production of a “universal vaccine” has centered on the elicitation of antibodies directed against the stalk of the influenza HA that has been shown to confer broad protection across a range of different subtypes (H1–H16). The accurate and sensitive measurement of antibody responses elicited by these “next-generation” influenza vaccines is, however, hampered by the lack of sensitivity of the traditional influenza serological assays HI, single radial hemolysis, and microneutralization. Assays utilizing pseudotypes, chimeric viruses bearing influenza glycoproteins, have been shown to be highly efficient for the measurement of homosubtypic and heterosubtypic broadly neutralizing antibodies, making them ideal serological tools for the study of cross-protective responses against multiple influenza subtypes with pandemic potential. In this review, we will analyze and compare literature involving the production of influenza pseudotypes with particular emphasis on their use in serum antibody neutralization assays. This will enable us to establish the parameters required for optimization and propose a consensus protocol to be employed for the further deployment of these assays in influenza vaccine immunogenicity studies. PMID:25972865

  7. Analysis of HIV Using a High Resolution Melting (HRM) Diversity Assay: Automation of HRM Data Analysis Enhances the Utility of the Assay for Analysis of HIV Incidence

    PubMed Central

    Cousins, Matthew M.; Swan, David; Magaret, Craig A.; Hoover, Donald R.; Eshleman, Susan H.

    2012-01-01

    Background HIV diversity may be a useful biomarker for discriminating between recent and non-recent HIV infection. The high resolution melting (HRM) diversity assay was developed to quantify HIV diversity in viral populations without sequencing. In this assay, HIV diversity is expressed as a single numeric HRM score that represents the width of a melting peak. HRM scores are highly associated with diversity measures obtained with next generation sequencing. In this report, a software package, the HRM Diversity Assay Analysis Tool (DivMelt), was developed to automate calculation of HRM scores from melting curve data. Methods DivMelt uses computational algorithms to calculate HRM scores by identifying the start (T1) and end (T2) melting temperatures for a DNA sample and subtracting them (T2–T1 = HRM score). DivMelt contains many user-supplied analysis parameters to allow analyses to be tailored to different contexts. DivMelt analysis options were optimized to discriminate between recent and non-recent HIV infection and to maximize HRM score reproducibility. HRM scores calculated using DivMelt were compared to HRM scores obtained using a manual method that is based on visual inspection of DNA melting curves. Results HRM scores generated with DivMelt agreed with manually generated HRM scores obtained from the same DNA melting data. Optimal parameters for discriminating between recent and non-recent HIV infection were identified. DivMelt provided greater discrimination between recent and non-recent HIV infection than the manual method. Conclusion DivMelt provides a rapid, accurate method of determining HRM scores from melting curve data, facilitating use of the HRM diversity assay for large-scale studies. PMID:23240016

  8. Thermal structure analyses for CSM testbed (COMET)

    NASA Technical Reports Server (NTRS)

    Xue, David Y.; Mei, Chuh

    1994-01-01

    This document is the final report for the project entitled 'Thermal Structure Analyses for CSM Testbed (COMET),' for the period of May 16, 1992 - August 15, 1994. The project was focused on the investigation and development of finite element analysis capability of the computational structural mechanics (CSM) testbed (COMET) software system in the field of thermal structural responses. The stages of this project consisted of investigating present capabilities, developing new functions, analysis demonstrations, and research topics. The appendices of this report list the detailed documents of major accomplishments and demonstration runstreams for future references.

  9. Unidentified ions in comets

    NASA Technical Reports Server (NTRS)

    Engel, Lisa

    1990-01-01

    Optical spectra were taken of comets Halley, West, and Brorsen-Metcalf in the wavelength region 3200 to 6400 A. These spectra were offset approximately 10(exp -5) to 10(exp -6) km tailward from the nucleus so that the features detected were all ions with the exception of a very small residual C2 emission at 5165 A. The full labeled tail spectrum of comet Halley is given. While most of the features detected are attributable to CO(+), H2O(+), CO2(+), CH(+), and OH(+), there are three moderately strong bands in the spectra of comets Halley and Brorsen-Metcalf which remain unidentified. These features were not detected in comet West. All three spectra in the 4800 to 5400 A region are presented, Brorsen-Metcalf is the gassiest of the three. The central wavelengths of the unidentified features are 4930, 5300, and 6000 A. In an effort to identify the ions responsible for these features as well as to confirm previous identifications, laboratory spectra of ions were compared with the comet spectra. H2O(+) and CO(+) are known to have extensive emission in the 4800 to 6200 A region. Therefore, the possibility that these unidentified features are due to H2O(+) and CO(+) was investigated. A search for the following bands was conducted: H2O(+) (11-0), H2O(+) (12-0), H2O(+) (13-1), CO(+) (1-1), and CO(+) (0-0). CO(+) (1-1) and CO(+) (0-0) were previously identified and are present in all the spectra examined. The H2O(+) (11-0) band was identified. Comparison of the H2O(+) (11-0) synthetic spectrum with comet Brorsen-Metcalf data is presented. The relative fluxes of the blended H2O(+) lines in the synthetic spectrum match those of the cometary data. After eliminating H2O(+) and CO(+) as significant contributors to the stronger unidentified features, spectra of ions which are not yet identified in the optical region of comets were compared to the data. These ions are NH(+), CS(+), and C2(+). None of these ions appears to be a significant contributor to the optical spectra of these

  10. Geologic analysis of the Rosetta NavCam, Osiris and ROLIS images of the comet 67P/Churyumov-Gerasimenko nucleus

    NASA Astrophysics Data System (ADS)

    Basilevsky, A. T.; Mall, U.; Keller, H. U.; Skorov, Yu. V.; Hviid, S. F.; Mottola, S.; Krasilnikov, S. S.; Dabrowski, B.

    2017-03-01

    This paper is based on geologic analysis of the surface morphology of nucleus of the Jupiter family comet 67P. This comet was visited by the ESA mission Rosetta, which escorted the comet since May 2014 till the end of September 2016 and studied it by 11 instruments of the mission orbiter and 10 instruments of the lander. The nucleus is 4 km in diameter, has a bilobate shape with the smaller (Head) and larger (Body) lobes, and the narrow neck between them. For the analysis, primarily images taken by the Rosetta Navigation camera (NavCam) were used and then complemented by selected images from the ROLIS and OSIRIS cameras. Two major types of the nucleus material are distinguished by us and other researchers: 1) the consolidated nucleus material and 2) the loose material, a kind of cometary regolith, covering the nucleus consolidated material. On the surface of the consolidated material rather long (up to hundreds meters) straight lineaments are distinguishable. They probably correspond to fractures and in some cases to strata. Their presence suggests that the consolidated material is rather compact and lacks voids larger than tens of meters across. Surfaces of consolidated nucleus material typically show knobby appearance at the scales from tens of meters and meters to centimeters and millimeters. This suggests that this material is grainy, consisting of more and less resistant (to surface weathering) ;particles; on the scale of the visible knobs. The geometric analysis of steep slopes based on the nucleus shape model allowed us to estimate a tensile, shear and compressive strength of the consolidated material. It was shown that the 67P consolidated nucleus material is very fragile, and taking into account the scale effect one can conclude that it is as fragile as fresh fallen snow and maybe even more fragile. In addition, estimates of the compressive strength of the surface material were considered at the sites of the first and the last contacts of the Philae lander

  11. Hubble View of Comet ISON

    NASA Video Gallery

    This time-lapse sequence of images from the Hubble Space Telescope shows comet ISON as it appeared on May 8, 2013. At the time the images were taken, the comet was 403 million miles from the Earth,...

  12. P31comet, a member of the synaptonemal complex, participates in meiotic DSB formation in rice.

    PubMed

    Ji, Jianhui; Tang, Ding; Shen, Yi; Xue, Zhihui; Wang, Hongjun; Shi, Wenqing; Zhang, Chao; Du, Guijie; Li, Yafei; Cheng, Zhukuan

    2016-09-20

    The human mitotic arrest-deficient 2 (Mad2) binding protein p31(comet) participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31(comet) as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31(comet), homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31(comet), together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31(comet) and radiation sensitive 51c (rad51c) p31(comet) double mutants, indicates that P31(comet) plays an essential role in double-strand break (DSB) formation. Interestingly, the dynamic colocalization pattern between P31(comet) and ZEP1 (a transverse filament protein of SC) by immunostaining, as well as the interaction between P31(comet) and CENTRAL REGION COMPONENT 1 (CRC1) in yeast two-hybrid assays, suggests possible involvement of P31(comet) in SC installation. Together, these data indicate that P31(comet) plays a key role in DSB formation and SC installation, mainly through its cooperation with CRC1.

  13. P31comet, a member of the synaptonemal complex, participates in meiotic DSB formation in rice

    PubMed Central

    Ji, Jianhui; Tang, Ding; Shen, Yi; Xue, Zhihui; Wang, Hongjun; Shi, Wenqing; Zhang, Chao; Du, Guijie; Li, Yafei; Cheng, Zhukuan

    2016-01-01

    The human mitotic arrest-deficient 2 (Mad2) binding protein p31comet participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31comet as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31comet, homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31comet, together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31comet and radiation sensitive 51c (rad51c) p31comet double mutants, indicates that P31comet plays an essential role in double-strand break (DSB) formation. Interestingly, the dynamic colocalization pattern between P31comet and ZEP1 (a transverse filament protein of SC) by immunostaining, as well as the interaction between P31comet and CENTRAL REGION COMPONENT 1 (CRC1) in yeast two-hybrid assays, suggests possible involvement of P31comet in SC installation. Together, these data indicate that P31comet plays a key role in DSB formation and SC installation, mainly through its cooperation with CRC1. PMID:27601671

  14. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  15. Astrobiology of Comets

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Wickramasinghe, Nalin C.; Wallis, Max K.; Sheldon, Robert B.

    2004-01-01

    We review the current state of knowledge concerning microbial extremophiles and comets and the potential significance of comets to Astrobiology. We model the thermal history of a cometary body, regarded as an assemblage of boulders, dust, ices and organics, as it approaches a perihelion distance of - IAU. The transfer of incident energy from sunlight into the interior leads to the melting of near surface ices, some under stable porous crust, providing possible habitats for a wide range of microorganisms. We provide data concerning new evidence for indigenous microfossils in CI meteorites, which may be the remains of extinct cometary cores. We discuss the dominant microbial communities of polar sea-ice, Antarctic ice sheet, and cryoconite environments as possible analogs for microbial ecosystems that may grow in sub-crustal pools or in ice/water films in comets.

  16. Infrared observations of comets

    NASA Technical Reports Server (NTRS)

    Hanner, Martha S.

    1991-01-01

    Selected comets are observed in the near infrared (1 to 2.2 micron) and thermal infrared (3.5 to 20 micron) with the NASA Infrared Telescope Facility (IRTF) and other telescopes as appropriate, in order to characterize the physical properties of the dust grains; their composition, size distribution, emissivity, and albedo. Systematic variations in these properties among comets are looked for, in order to understand the heterogeneity of comet nuclei. Spectrophotometry of the 10 micron silicate emission feature is particularly emphasized. The rate of dust production from the nucleus and its temporal variability are also determined. Knowledge of the dust environment is essential to S/C design and mission planning for NASA's CRAF mission.

  17. A Continuing Analysis of Possible Activity Drivers for the Enigmatic Comet 29P/Schwassmann-Wachmann 1

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles; Fernández, Yanga; Samarasinha, Nalin H.; Mueller, Beatrice E. A.; Sarid, Gal; Meech, Karen Jean; Woodney, Laura

    2016-01-01

    We present results from our effort to understand activity drivers in Comet 29P/Schwassmann-Wachmann 1 (SW1). In a nearly circular orbit around 6 AU, outside of the water-sublimation zone, SW1 is continuously active and experiences frequent outbursts. Our group's effort is focusing on finding constraints on physical and dynamical properties of SW1's nucleus and their incorporation into a thermophysical model [1,2] to explain this behavior. We are currently analyzing coma morphology of SW1 before, during, and after outburst placing constraints on the spin-pole direction, spin period, and surface areas of activity. In addition, we are using the thermal model to investigate if the continuous activity comes from one or multiple processes, such as the release of trapped supervolatiles during the amorphous to crystalline (A-C) water ice phase transition and/or the direct sublimation of pockets of supervolatile ices. The supervolatile ices may be primordial or from the condensation of gases released during the A-C phase transition. To explain the possibly quasi-periodic but frequent outbursts, we are looking into subsurface cavities where internal pressures can build, reaching and exceeding surrounding material strengths [3,4] and/or thermal waves reaching a pocket of supervolatile ices, causing a rapid increase in the sublimation rate. For all these phenomena, the model is constrained by comparing the output dust mass loss rate and its variability with what has been observed through optical imaging of the comet at various points in its orbit. We will present preliminary thermal modeling of a homogeneous progenitor nucleus that evolves into a body showing internal material layering, the generation of CO and CO2 ice pockets, and the production of outbursts, thus bringing us closer to explaining the behavior of this intriguing comet. [1] Sarid, G., et al.: 2005, PASP, 117, 843. [2] Sarid, G.: 2009, PhD Thesis, Tel Aviv Univ. [3] Gronkowski, P., 2014, Astron. Nachr./AN 2, No

  18. A Continuing Analysis of Possible Activity Drivers for the Enigmatic Comet 29P/Schwassmann-Wachmann 1

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles Alfred; Fernandez, Yanga; Samarasinha, Nalin; Sarid, Gal; Mueller, Beatrice; Meech, Karen; Woodney, Laura

    2015-11-01

    We present results from our continuing effort to understand activity drivers in Comet 29P/Schwassmann-Wachmann 1 (SW1). While being in a nearly circular orbit around 6 AU, SW1 is continuously active and experiences frequent outbursts. Our group’s effort is focusing on finding constraints on physical and dynamical properties of SW1’s nucleus and their incorporation into a thermophysical model [1,2] to explain this behavior. Now we are analyzing coma morphology of SW1 before, during, and after outburst to place constraints on the spin-pole direction, spin period, and surface areas of activity (a spin period lower limit has been measured). Also, we are using the thermal model to investigate if the continuous activity comes from one or multiple processes, such as the release of trapped supervolatiles during the amorphous to crystalline (A-C) water ice phase transition and/or the direct sublimation of pockets of supervolatile ices, which may be primordial or from the condensation of gases released during the A-C phase transition. To explain the possibly quasi-periodic but frequent outbursts, we are looking into subsurface cavities where internal pressures can build, reaching and exceeding surrounding material strengths [3,4] and/or thermal waves reaching a pocket of supervolatile ices, causing a rapid increase in the sublimation rate. For all these phenomena, the model is constrained by comparing the output dust mass loss rate and its variability with what has been observed through optical imaging of the comet at various points in its orbit. We will present preliminary thermal modeling of a homogeneous progenitor nucleus that evolves into a body showing internal material layering, the generation of CO and CO2 ice pockets, and the production of outbursts, thus bringing us closer to explaining the behavior of this intriguing comet.[1] Sarid, G., et al.: 2005, PASP, 117, 843. [2] Sarid, G.: 2009, PhD Thesis, Tel Aviv Univ. [3] Gronkowski, P., 2014, Astron. Nachr./AN 2

  19. Look--It's a Comet!

    ERIC Educational Resources Information Center

    Berglund, Kay

    1997-01-01

    Describes a classroom lesson on comets that uses modeling and guided imagery to spark students' curiosity. Comet models are built using chunks of rock salt, polystyrene balls, and tinsel. Abstract ideas are made more concrete with a guided imagery story called Comet Ride! Includes an introduction to the use of parallax to measure the distance of…

  20. Term Projects on Interstellar Comets

    ERIC Educational Resources Information Center

    Mack, John E.

    1975-01-01

    Presents two calculations of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. Proposes three problems, each of which would be a reasonable term project for a motivated undergraduate. (Author/MLH)

  1. Discovering the Nature of Comets.

    ERIC Educational Resources Information Center

    Whipple, Fred L.

    1986-01-01

    "The Mystery of Comets" by Dr. Fred Whipple provides an introduction to the modern picture of comets and his personal reminiscences of how his model of comets came to be. An adaptation of several sections of the book is presented. (JN)

  2. The Organic Matter of Comet P/Halley as Inferred by Joint Gas and Solid Phase Analysis

    NASA Astrophysics Data System (ADS)

    Krueger, F. R.; Korth, A.; Kissel, J.

    1997-12-01

    During the encounters with comet Halley, PICCA on GIOTTO measured the gas phase organic ion composition of the coma, and PUMA on VEGA 1 measured the dust composition. Joining those results a consistent picture of the parent organic matter from which dust and gas is produced can be obtained. One recognizes a complex unsaturated polycondensate, which splits during coma-formation into the more refractory C=C,C-N-containing dust part, and the more volatile C=C,C-O-containing gas part. The responsible exothermal chemical reactions, triggered by the sun light may play a major role in the dynamics of coma formation. The latent heat and reactivity may cause problems regarding a sample return mission.

  3. Observations and analysis of a curved jet in the coma of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Lin, Z.-Y.; Lai, I.-L.; Su, C.-C.; Ip, W.-H.; Lee, J.-C.; Wu, J.-S.; Vincent, J.-B.; La Forgia, F.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Güttler, C.; Hviid, S. F.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Lowry, S.; Marzari, F.; Michalik, H.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Rożek, A.; Thomas, N.; Tubiana, C.

    2016-04-01

    Aims: We analyze the physical properties and dynamical origin of a curved jet of comet 67P/Churyumov-Gerasimenko that was observed repeatedly in several nucleus rotations starting on May 30 and persisting until early August, 2015. Methods: We simulated the motion of dust grains ejected from the nucleus surface under the influence of the gravity and viscous drag effect of the expanding gas flow from the rotating nucleus. Results: The formation of the curved jet is a combination of the size of the dust particles (~0.1-1 mm) and the location of the source region near the nucleus equator. This enhances the spiral feature of the collimated dust stream after the dust is accelerated to a terminal speed on the order of m s-1.

  4. First analysis of the size-frequency distribution of boulders ge 7m on comet 67P

    NASA Astrophysics Data System (ADS)

    Pajola, M.; Vincent, J. B.; Güttler, C.; Lee, J.-C.; Massironi, M.; Bertini, I.; Simioni, E.; Marzari, F.; Giacomini, L.; Barbieri, C.; Cremonese, G.; Naletto, G.; Pommerol, A.; El Maarry, M. R.; Besse, S.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Thomas, N.; Auger, A. T.; Ip, W.-H.; Lin, Z.-Y.; Sierks, H.; OSIRIS Team; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J.-L.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hviid, S. F.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Koschny, D.; Kramm, J.-R.; Kürt, E.; Lamy, P.; Lara, L. M.; Lopez Moreno, J. J.; Magrin, S.; Michalik, H.; Moissl, R.; Mottola, S.; Oklay, N.; Preusker, F.; Rickman, H.; Rodrigo, R.; Scholten, F.; Tubiana, C.

    Images of the surface of comet 67P Churyumov-Gerasimenko taken by the OSIRIS camera on board the Rosetta spacecraft have been used to study the statistical distribution and morphological properties of both cluster and isolated roundish structures ('boulders') scattered all over the surface. We used NAC images taken on Aug 5-6, 2014, at a distance between 131.45 - 109.76 km, with a spatial resolution ranging from 2.44 - 2.03 m/px (Fig. 1). Such data cover a full rotation of 67P, providing the first ever full size frequency distribution coverage of boulders ≥ 7m visible on a cometary illuminated side. Boulders are ubiquitous on the head, neck, and body of 67P \\citep{thomas15}. The initial count of 4,976 boulders was reduced to 3,546 for statistical purposes taking into consideration only those with a diameter larger than 7 m \\citep{pajola15}.

  5. Comet LINEAR Splits Further

    NASA Astrophysics Data System (ADS)

    2001-05-01

    Third Nucleus Observed with the VLT Summary New images from the VLT show that one of the two nuclei of Comet LINEAR (C/2001 A2), now about 100 million km from the Earth, has just split into at least two pieces . The three fragments are now moving through space in nearly parallel orbits while they slowly drift apart. This comet will pass through its perihelion (nearest point to the Sun) on May 25, 2001, at a distance of about 116 million kilometres. It has brightened considerably due to the splitting of its "dirty snowball" nucleus and can now be seen with the unaided eye by observers in the southern hemisphere as a faint object in the southern constellation of Lepus (The Hare). PR Photo 18a/01 : Three nuclei of Comet LINEAR . PR Photo 18b/01 : The break-up of Comet LINEAR (false-colour). Comet LINEAR splits and brightens ESO PR Photo 18a/01 ESO PR Photo 18a/01 [Preview - JPEG: 400 x 438 pix - 55k] [Normal - JPEG: 800 x 875 pix - 136k] ESO PR Photo 18b/01 ESO PR Photo 18b/01 [Preview - JPEG: 367 x 400 pix - 112k] [Normal - JPEG: 734 x 800 pix - 272k] Caption : ESO PR Photo 18a/01 shows the three nuclei of Comet LINEAR (C/2001 A2). It is a reproduction of a 1-min exposure in red light, obtained in the early evening of May 16, 2001, with the 8.2-m VLT YEPUN (UT4) telescope at Paranal. ESO PR Photo 18b/01 shows the same image, but in a false-colour rendering for more clarity. The cometary fragment "B" (right) has split into "B1" and "B2" (separation about 1 arcsec, or 500 km) while fragment "A" (upper left) is considerably fainter. Technical information about these photos is available below. Comet LINEAR was discovered on January 3, 2001, and designated by the International Astronomical Union (IAU) as C/2001 A2 (see IAU Circular 7564 [1]). Six weeks ago, it was suddenly observed to brighten (IAUC 7605 [1]). Amateurs all over the world saw the comparatively faint comet reaching naked-eye magnitude and soon thereafter, observations with professional telescopes indicated

  6. Multiple birth concordance of street drug assays of meconium analysis.

    PubMed

    Lewis, D; Moore, C; Leikin, J B; Kechavarz, L

    1995-08-01

    To determine the prevalence of maternal drug usage in a mid-size midwestern city (population 250,000), we analyzed 1,175 consecutive meconium samples from the neonatal intensive care unit from March 1991 through December 1993. We focused on meconium assays from multiple births as a quality control method. Meconium specimens were analyzed using fluorescence polarization immunoassay (FPIA-Abbott Diagnostics) with confirmation done by gas chromatography/mass spectrometry (GC/MS). Cutoff concentrations of 5 ng/g were utilized for all analytes. A total of 151 samples (12.9%) tested positive. Cocaine-exposed neonates had the highest positive rate (63 or 5.4%), followed by marijuana (52 cases or 4.4%), cocaethylene (12 cases or 1%), and amphetamine (1 case or 0.1%). Nine patients (0.8%) had multiple drugs present. There were a total of 23 sets of multiple births (21 twins, 2 triplets); 20 sets of multiple births (42 patients) had concordance with all births testing negative. Three sets of twins had concordance in testing positive, with 1 twin testing positive for cocaine while the other twin tested positive for cocaine and marijuana. No absolute discordance of twins assays were noted. The rate of maternal drug use through measurement of meconium is about 12.95% in this mid-sized midwestern city. Twin studies provide an excellent method for verifying fetal drug exposure. The use of sets of multiple births provides a unique internal quality control mechanism in determining fetal drug exposure.

  7. There is no 'cometopause' at comet Halley

    NASA Astrophysics Data System (ADS)

    Reme, H.; Mazelle, C.; D'Uston, C.; Korth, A.; Lin, R. P.; Chaizy, P.

    1994-02-01

    Immediately after the flybys at comet Halley by a fleet of spacecraft in 1986, Gringauz et al. (1986a) reported the detection by the Vega-2 spacecraft of a chemical and sharp plasma boundary, which they named the 'cometopause,' at a distance of about 1.6 x 105 km from the nucleus. Gringauz and Verigin (1991) presented the 'cometopause' as a permanent feature of the solar wind - Halley type comet interaction at about 1 UA from the Sun. This permanent boundary presumably separates an upstream region dominated by the solar wind from the downstream region where heavy cometary ions dominate. We present here the analysis of the results of the Giotto positive ion cluster composition analyzer - Reme plasma analyzer (PICCA-RPA2) ion mass spectrometer and electron electrostatic analyzer - Reme plasma analyzer (EESA-RPA1) electron spectrometer data, which clearly show that there is no such boundary at comet Halley.

  8. Observations of comets with the IUE

    NASA Technical Reports Server (NTRS)

    Feldman, Paul D.

    1995-01-01

    This is the final report for Observation of Comets with the IUE, which began in December 1992 and was completed in January 1995. This grant continued our IUE program which began in July 1979 and was terminated in September 1992. Attached in Appendix A is a complete list of publications related to IUE observations of comets from 1980 to the present. Publication numbers 51-53 appeared during the December 1992 - January 1995 period and copies of these are being forwarded to the NSSDC along with this report. Papers presented at recent scientific meetings are listed in Appendix B. During this period we have concentrated our effort into two distinct areas: new observations of comets of interest and continuing analysis of the data from previous observations.

  9. Mid-infrared spectra of comet nuclei

    NASA Astrophysics Data System (ADS)

    Kelley, Michael S. P.; Woodward, Charles E.; Gehrz, Robert D.; Reach, William T.; Harker, David E.

    2017-03-01

    Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 μm thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 ± 0.11, derived from 16- and 22-μm photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 μm. When the spectra are normalized by the NEATM model, a weak 10-μm silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well

  10. Analysis of R-band observations of an outburst of Comet 29P/Schwassmann-Wachmann 1 to place constraints on the nucleus' rotation state

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles A.; Fernández, Yanga R.; Samarasinha, Nalin H.; Mueller, Beatrice E. A.; Woodney, Laura M.

    2017-03-01

    We present analysis of five nights of R-band observations of Comet 29P/Schwassmann-Wachmann 1 (SW1) taken on September 2008 which show the comet undergoing an outburst. Coma morphology shows a projected asymmetric shell of material expanding radially and four linear features on the northern side of the coma at position angles 37°, 78°, 300°, and 353°. Using the measured projected radial outflow velocity of 0.11 ±0.02 km/s for the shell material, we calculate an outburst time of UT 2008-09-21.03 ±0.95 days. By tracking the inner and outer extent of the northern linear features, we found that the features are fully contained within the expanding shell of material. This suggested both shell and linear features originated during the same event and activity originating from different regions on the nuclear surface are not necessary to generate both types of morphological structure observed. A 3-D Monte Carlo coma model was used to model the outburst. Morphological features present in the observations were modeled allowing constraints to be placed on the spin state of SW1's nucleus. The evolution of morphological features allows constraints on the rotation period P assuming an outburst duration Δt and the spin period constraints are expressed in terms of their ratio P/Δt. Since the spin-pole orientation could not be constrained, four spin-pole orientations were chosen for modeling the coma. Spin-period constraints for each assumed pole orientation are discussed. Overall, modeling suggested either a spin period on the order of days, a spin-pole orientation nearly along the sub-Earth direction, or a combination of both. To place an independent constraint on the outburst duration, radial surface-brightness profiles of the observations were compared with profiles from synthetic models, giving an upper-limit of Δt ≤ 1.5 days. Longer outbursts resulted in a higher number of dust grains in close proximity to the nucleus during the observations and a profile slope too

  11. Fire hazards analysis of transuranic waste storage and assay facility

    SciTech Connect

    Busching, K.R., Westinghouse Hanford

    1996-07-31

    This document analyzes the fire hazards associated with operations at the Central Waste Complex. It provides the analysis and recommendations necessary to ensure compliance with applicable fire codes.

  12. DIRBE Comet Trails

    NASA Technical Reports Server (NTRS)

    Arendt, Richard G.

    2015-01-01

    Re-examination of the COBE DIRBE data reveals the thermal emission of several comet dust trails.The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported.The known trails of 2P/Encke, and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 microns surface brightnesses of <0.1 and <0.15 MJy/sr, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals one additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  13. Rendezvous with a comet

    NASA Astrophysics Data System (ADS)

    Taylor, Matt

    2014-10-01

    After making a successful rendezvous with Comet 67P/Churyumov-Gerasimenko earlier this year, Europe's Rosetta craft is now riding alongside this celestial body and next month is set to land a probe on its surface. Matt Taylor describes the excitement of this unique project and the scientific insights that it hopes to achieve.

  14. Halley's Comet: A Bibliography.

    ERIC Educational Resources Information Center

    Freitag, Ruth S., Comp.

    Included in this bibliography are over 3,200 references to publications on Halley's Comet, its history, orbital motion, and physical characteristics, meteor streams associated with it, preparations for space missions to study it in 1986, and popular reaction to its appearances. Also cited are a few papers that, although they devote little…

  15. Comets in Indian Scriptures

    NASA Astrophysics Data System (ADS)

    Das Gupta, P.

    2016-01-01

    The Indo-Aryans of ancient India observed stars and constellations for ascertaining auspicious times in order to conduct sacrificial rites ordained by the Vedas. Naturally, they would have sighted comets and referred to them in the Vedic texts. In Rigveda (circa 1700-1500 BC) and Atharvaveda (circa 1150 BC), there are references to dhumaketus and ketus, which stand for comets in Sanskrit. Rigveda speaks of a fig tree whose aerial roots spread out in the sky (Parpola 2010). Had this imagery been inspired by the resemblance of a comet's tail with long and linear roots of a banyan tree (ficus benghalensis)? Varahamihira (AD 550) and Ballal Sena (circa AD 1100-1200) described a large number of comets recorded by ancient seers, such as Parashara, Vriddha Garga, Narada, and Garga, to name a few. In this article, we propose that an episode in Mahabharata in which a radiant king, Nahusha, who rules the heavens and later turns into a serpent after he kicked the seer Agastya (also the star Canopus), is a mythological retelling of a cometary event.

  16. DRBE comet trails

    SciTech Connect

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann–Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of <0.1 and <0.15 MJy sr{sup −1}, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  17. Imaging studies of comets

    NASA Technical Reports Server (NTRS)

    Niedner, Malcolm B., Jr.; Klinglesmith, Daniel A., III; Westpfahl, David J.

    1991-01-01

    The Joint Observatory for Cometary Research's (JOCR) historical mission has been to provide understanding of large-scale interactions between bright comets and solar wind using wide-angle (Schmidt) imagery and spacecraft data; in this pursuit the JOCR has excelled. The 16 inch Newtonian/Cassegrain telescope was upgraded to permit filtered, narrow-field charge coupled device (CCD) imaging of both bright and faint comets. Thus, the goal of obtaining narrow-band imagery of the near-nuclear region of bright comets was added to JOCR's original mission with emphasis on ionization processes and total gas production. A 300 mm lens/CCD system exists with 3 degree field of view (FOV) which uses comet filters; this system bridges the gap between the wide-field (8 x 10 deg) Schmidt plates and the several-arcmin. field of the 16 inch telescope. JOCR is located under dark skies on South Baldy Mountain (el. 10,600 ft.) near Socorro, NM, and is one of the last truly dark sites in the continental U.S.

  18. Finding Comet Halley.

    ERIC Educational Resources Information Center

    Glenn, William H.

    1985-01-01

    Provides background information and references on Comet Halley (which will be observable by telescope in October 1985 and reach its most brilliant appearance in March and April of 1986). Suggestions for equipment and maps of its path through the sky are included. (DH)

  19. Ammonia abundances in four comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S. C.; Engel, L.

    1991-02-01

    NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses.

  20. Comet Kohoutek - Ultraviolet images and spectrograms

    NASA Technical Reports Server (NTRS)

    Opal, C. B.; Carruthers, G. R.; Prinz, D. K.; Meier, R. R.

    1974-01-01

    Emissions of atomic oxygen (1304 A), atomic carbon (1657 A), and atomic hydrogen (1216 A) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on Jan. 8, 1974. Analysis of the Lyman alpha halo at 1216 A gave an atomic hydrogen production rate of 4.5 x 10 to the 29th atoms per second.

  1. Comet kohoutek: ultraviolet images and spectrograms.

    PubMed

    Opal, C B; Carruthers, G R; Prinz, D K; Meier, R R

    1974-08-23

    Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 x 10(29) atoms per second.

  2. Forensically relevant SNaPshot(®) assays for human DNA SNP analysis: a review.

    PubMed

    Mehta, Bhavik; Daniel, Runa; Phillips, Chris; McNevin, Dennis

    2017-01-01

    Short tandem repeats are the gold standard for human identification but are not informative for forensic DNA phenotyping (FDP). Single-nucleotide polymorphisms (SNPs) as genetic markers can be applied to both identification and FDP. The concept of DNA intelligence emerged with the potential for SNPs to infer biogeographical ancestry (BGA) and externally visible characteristics (EVCs), which together enable the FDP process. For more than a decade, the SNaPshot(®) technique has been utilised to analyse identity and FDP-associated SNPs in forensic DNA analysis. SNaPshot is a single-base extension (SBE) assay with capillary electrophoresis as its detection system. This multiplexing technique offers the advantage of easy integration into operational forensic laboratories without the requirement for any additional equipment. Further, the SNP panels from SNaPshot(®) assays can be incorporated into customised panels for massively parallel sequencing (MPS). Many SNaPshot(®) assays are available for identity, BGA and EVC profiling with examples including the well-known SNPforID 52-plex identity assay, the SNPforID 34-plex BGA assay and the HIrisPlex EVC assay. This review lists the major forensically relevant SNaPshot(®) assays for human DNA SNP analysis and can be used as a guide for selecting the appropriate assay for specific identity and FDP applications.

  3. Temperatures within comet nuclei.

    PubMed

    Squyres, S W; McKay, C P; Reynolds, R T

    1985-12-10

    We have performed a theoretical study of temperatures beneath the surface of a comet's nucleus. We solve the one-dimensional heat conduction equation for the outer portion of the comet. The upper boundary condition of the model is given by energy balance at the surface of the nucleus, including conduction of heat inward, radiation, insolation as modified by the coma, and sublimation. Our coma model assumes single scattering and includes attenuation of direct sunlight by dust grains, scattering of light onto the nucleus, and infrared radiation by dust grains. The lower boundary condition is zero net heat flux around an orbit. The thermal conductivity expression for the nucleus includes direct conduction at grain boundaries, radiative conduction, and Knudsen flow vapor diffusion. The thermal diffusivity of the nucleus and the resultant temperature profiles are shown to be strongly dependent on the physical properties of the material, including porosity, pore size, and compaction. The temperature profiles and the equilibrium temperature deep within the comet also depend on the functional relationship between thermal conductivity and temperature; the highest deep equilibrium temperatures are found for models where the thermal conductivity increases strongly with increasing temperature. The dependence of temperatures on the albedo and thermal emissivity of the nucleus is also calculated, as well as the variation of temperature with latitude for a variety of pole orientations. The effect of a dust mantle on subsurface temperatures is also investigated. All calculations are presented for short-period comets with orbits that make them accessible for exploration by spacecraft rendezvous. In situ measurements of the thermal profile in the upper meter of a comet nucleus can substantially constrain the thermal diffusivity of the material, which in turn can provide significant information about the physical properties of the nucleus.

  4. New developments in comet-FISH.

    PubMed

    Spivak, Graciela

    2015-01-01

    The comet assay combined with fluorescence in-situ hybridisation (FISH) is a powerful technique for comparative analyses of damage induction and repair in genomes and in specific DNA sequences within single cells. Recent advances in the methodology of comet-FISH will be considered here, with particular attention to the design and generation of fluorescent probes. In general, all the approaches must fulfil a few basic requirements: the probes should be no longer than ~300 nucleotides in length (single or double stranded) to be able to penetrate the gel in which the target genomic DNA is embedded, they should be sequence-specific, and their signal should be detectable and distinct from the background fluorescence and the dye used to stain the DNA.

  5. A complementation assay for in vivo protein structure/function analysis in Physcomitrella patens (Funariaceae)

    DOE PAGES

    Scavuzzo-Duggan, Tess R.; Chaves, Arielle M.; Roberts, Alison W.

    2015-07-14

    Here, a method for rapid in vivo functional analysis of engineered proteins was developed using Physcomitrella patens. A complementation assay was designed for testing structure/function relationships in cellulose synthase (CESA) proteins. The components of the assay include (1) construction of test vectors that drive expression of epitope-tagged PpCESA5 carrying engineered mutations, (2) transformation of a ppcesa5 knockout line that fails to produce gametophores with test and control vectors, (3) scoring the stable transformants for gametophore production, (4) statistical analysis comparing complementation rates for test vectors to positive and negative control vectors, and (5) analysis of transgenic protein expression by Westernmore » blotting. The assay distinguished mutations that generate fully functional, nonfunctional, and partially functional proteins. In conclusion, compared with existing methods for in vivo testing of protein function, this complementation assay provides a rapid method for investigating protein structure/function relationships in plants.« less

  6. Infrared Imaging, Spectroscopic, and Photometric Studies of Comets

    NASA Technical Reports Server (NTRS)

    Gehrz, Robert D.

    1997-01-01

    We have continued our program of infrared (IR) photometric, imaging, spectroscopic, and polarimetric temporal observations of comets to study the properties of comet dust and comet nuclei. During the first two years we digitized our IR data base on P/Halley and other recent comets to facilitate further analysis and comparison with other data bases, and found compelling evidence for the emission of a burst of small grains from P/Halley's nucleus at perihelion. We reported imaging and photometric observations of Comets Austin 1990 V and Swift-Tuttle 1992. The Swift-Tuttle 1992t observations included IR photometry, several 7-14 micron long-slit spectra of the coma and a time-sequence of more than 150 10 micron broadband images of the coma. An analysis of near-IR images of the inner coma of P/Halley obtained on three consecutive nights in 1986 March showed sunwardjets. We completed our analysis of IR imaging spectrosco-photometric data on comets. We also obtained observations of Comets Hyakutake 1996 B2 and Hale/Bopp 1995 01. We obtained infrared imaging, photometric, spectroscopic and polarimetric temporal observations of bright comets using a network of five telescopes, with emphasis on simultaneous observations of comets at many wavelengths with different instruments. Our program offers several unique advantages: 1) rapid observational response to new comets with dedicated infrared telescopes; 2) observations within a few degrees of the sun when comets are near perihelion and 3) access to advanced infrared array imagers and spectrometers. In particular, reduction, analysis, publication and archiving of our Jupiter/sl-9 and Comet Hyakutake infrared data received special emphasis. Instrumentation development included installation of the latest version of the innovative FORTH telescope control and a data acquisition system that enables us to control three telescopes remotely by telephone from anywhere in the world for comet observations in broad daylight. We have

  7. Use of Cause-and-Effect Analysis to Design a High-Quality Nanocytotoxicology Assay.

    PubMed

    Rösslein, Matthias; Elliott, John T; Salit, Marc; Petersen, Elijah J; Hirsch, Cordula; Krug, Harald F; Wick, Peter

    2015-01-20

    An important consideration in developing standards and regulations that govern the production and use of commercial nanoscale materials is the development of robust and reliable measurements to monitor the potential adverse biological effects of such products. These measurements typically require cell-based and other biological assays that provide an assessment of the risks associated with the nanomaterial of interest. In this perspective, we describe the use of cause-and-effect (C&E) analysis to design robust, high quality cell-based assays to test nanoparticle-related cytotoxicity. C&E analysis of an assay system identifies the sources of variability that influence the test result. These sources can then be used to design control experiments that aid in establishing the validity of a test result. We demonstrate the application of C&E analysis to the commonly used 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) cell-viability assay. This is the first time to our knowledge that C&E analysis has been used to characterize a cell-based toxicity assay. We propose the use of a 96-well plate layout which incorporates a range of control experiments to assess multiple factors such as nanomaterial interference, pipetting accuracy, cell seeding density, and instrument performance, and demonstrate the performance of the assay using the plate layout in a case study. While the plate layout was formulated specifically for the MTS assay, it is applicable to other cytotoxicity, ecotoxicity (i.e., bacteria toxicity), and nanotoxicity assays after assay-specific modifications.

  8. Analysis of hydrogen Lyman-alpha observations of the coma of Comet P/Halley near the perihelion

    NASA Technical Reports Server (NTRS)

    Smyth, William H.; Marconi, M. L.; Combi, Michael R.

    1995-01-01

    The pioneer Venus Orbiter Ultraviolet Spectrometer measurements of the Lyman-alpha intensity of atomic hydrogen excited by solar resonance scattering in the coma of Comet P/Halley acquired from December 28, 1985, to January 6, 1986, and from January 31, 1986, to March 6, 1986, are simulated with the Monte Carlo Particle Trajectory Model corrected for optical depth effects. Spatially detailed comparisons between data and model show excellent agreement and are used to infer that the highest cometary activity may not be at perihelion, but about 2 1/2 weeks before. An improved set of H2O production rates is presented for the period of time that the spectrometer was observing and is found to be consistent with the rates from other types of measurements. The apparent discrepancy between Stewart (1987) in early March and International Ultraviolet Explorer OH derived rates is resolved. The problem with the conversion of 18-cm OH radio brightness to H2O production rates is also discussed.

  9. Interaction of Comets and the Solar Wind

    NASA Technical Reports Server (NTRS)

    Wagner, William (Technical Monitor); Raymond, John C.

    2004-01-01

    The analysis of Comet Kudo-Fujikawa at perihelion was published and picked up by Der Spiegel. Besides a large and rapidly increasing water outgassing rate, we detected a bright tail in doubly ionized carbon. The amount of carbon was greater than could be accounted for by CO photodissociation, and we attribute it to evaporation of organics from dust. A spectacular disconnection event was apparent in the C III tail, and it coincides within the uncertainties to the position of the heliospheric current sheet. The analysis of the sungrazing comet C2001 C2 is in press. It showed evidence for subfragments and for a very long lasting source of neutrals, which we identify as evaporation of pyroxene dust grains. Results were also presented at COSPAR. We are working on observations of another sungrazer, comet C2002 S2, which shows a sudden 2 magnitude drop in optical brightness and an equally sudden recovery. UVCS observations during that time show a steadily increasing outgassing rate. We have derived solar wind densities for both comets, but we are still sorting out the ambiguities involving the fragmentation and optical behavior.

  10. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe.

  11. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1977-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of the evolution of cometary dust. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tails is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  12. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of evolution. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tail is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  13. Carbon isotopes in comets

    NASA Technical Reports Server (NTRS)

    Wehinger, Peter A.

    1990-01-01

    The progress is reported of high resolution spectra of selected bright comets with the aim of determining the carbon isotope abundance ratio, C-12/C-13. The ratio was determined for various Solar System objects (in the atmospheres of the giant planets, meteorites, the Earth, and the solar photosphere), where the C-12/C-13 = 89/1. In the interstellar medium, optical and radio observations give a range of C-12/C-13 = 43-67/1 depending on the observing techniques used and the specific interstellar cloud observed. The echelle spectra is presented of the CN(0,0) violet system in three comets: P/Brorsen-Metcalf, C/Okazaki-Levy-Rudenko, and C/Austin. P/Brorsen-Metcalf has a period of 70 y (prograde) compared with P/Halley which is 76 y (retrograde). The similar periods made P/Brorsen-Metcalf of special interest for comparison with P/Halley.

  14. Diatoms in comets

    NASA Technical Reports Server (NTRS)

    Hoover, R.; Hoyle, F.; Wallis, M. K.; Wickramasinghe, N. C.

    1986-01-01

    The fossil record of the microscopic algae classified as diatoms suggests they were injected to earth at the Cretaceous boundary. Not only could diatoms remain viable in the cometary environment, but also many species might replicate in illuminated surface layers or early interior layers of cometary ice. Presumably they reached the solar system on an interstellar comet as an already-evolved assemblage of organisms. Diatoms might cause color changes to comet nuclei while their outgassing decays and revives around highly elliptical orbits. Just as for interstellar absorption, high-resolution IR observations are capable of distinguishing whether the 10-micron feature arises from siliceous diatom material or mineral silicates. The 10-30-micron band and the UV 220-nm region can also provide evidence of biological material.

  15. Analysis of the dust jet imaged by Rosetta VIRTIS-M in the coma of comet 67P/Churyumov–Gerasimenko on 2015 April 12

    NASA Astrophysics Data System (ADS)

    Tenishev, V.; Fougere, N.; Borovikov, D.; Combi, M. R.; Bieler, A.; Hansen, K. C.; Gombosi, T. I.; Migliorini, A.; Capaccioni, F.; Rinaldi, G.; Filacchione, G.; Kolokolova, L.; Fink, U.

    2016-11-01

    This work is a part of a more global effort aimed at understanding and interpreting in situ and remote sensing data acquired by instruments on board Rosetta. This study aims at deriving the dust mass source rate and the location of the dust jet source observed by Rosetta VIRTIS-M on 2015 April 12. The analysis is performed by means of the coupled kinetic modelling of gas and dust in the coma of comet 67P/Churyumov-Gerasimenko, which were used for calculating the coma brightness as it would be seen from the Rosetta spacecraft. The dust mass production rate and a possible location of the jet origin needed to explain the Rosetta VIRTIS-M dust brightness image were inferred by comparing the calculated brightness with VIRTIS-M data. Our analysis suggests that the dust mass production rate needed to maintain the observed jet is about 1.9 kg s-1. According to our analysis, the location of the observed jet surface footprint is outside of the nucleus area characterized by the highest gas production rate, which suggests that gas and dust source rates are not necessarily proportional to each other across the entire nucleus surface. The inferred location of the possible jet origin is consistent with that of the observed active pits. In this paper, we show that the jet intensity is variable in time, and has a lifetime of at least 10 h.

  16. Analysis of hexazinone in soil by enzyme linked immunosorbent assay

    SciTech Connect

    Bushway, R.J.; Perkins, L.B.; Reed, A.W.

    1996-10-01

    A tube enzyme immunoassay (ELA) procedure was developed for the determination of the triazine herbicide hexazinone in soil. The antibody was polyclonal and was prepared by employing metabolite A (3-(4-hydroxycyclohexyl)-6-dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione of hexazinone conjugated to bovine serum albumin as the immunogen. Hexazinone was extracted from soil by shaking with methanol-water 80/20 for 10 min and allowed to set overnight before reshaking for 5 min. Aliquots for EIA analysis were diluted in such a way as to always contain 8% methanol. Reproducibility results for both standards and samples were good. A correlation coefficient of 0.9562 was obtained for 76 soil samples run by EIA vs. HPLC. Of the eight known metabolites of hexazinone, 7 were tested for cross-reactivity and 5 were shown to be cross-reactive.

  17. The SNPforID Assay as a Supplementary Method in Kinship and Trace Analysis

    PubMed Central

    Schwark, Thorsten; Meyer, Patrick; Harder, Melanie; Modrow, Jan-Hendrick; von Wurmb-Schwark, Nicole

    2012-01-01

    Objective Short tandem repeat (STR) analysis using commercial multiplex PCR kits is the method of choice for kinship testing and trace analysis. However, under certain circumstances (deficiency testing, mutations, minute DNA amounts), STRs alone may not suffice. Methods We present a 50-plex single nucleotide polymorphism (SNP) assay based on the SNPs chosen by the SNPforID consortium as an additional method for paternity and for trace analysis. The new assay was applied to selected routine paternity and trace cases from our laboratory. Results and Conclusions Our investigation shows that the new SNP multiplex assay is a valuable method to supplement STR analysis, and is a powerful means to solve complicated genetic analyses. PMID:22851934

  18. Optical Detection of Anomalous Nitrogen in Comets

    NASA Astrophysics Data System (ADS)

    2003-12-01

    that causes glowing teeth and shirts in a Disco. The upper panel displays the "raw" spectrum; the lower is the "extracted" spectrum, now clearly displaying the individual emission lines. Observations of Comet LINEAR (C/2000 WM1) were carried out with the UV-Visual Echelle Spectrograph (UVES) mounted on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile) on four occasions during March 2002. At that time, the comet had moved past its perihelion and was by far the faintest comet for which such a detailed spectral analysis had ever been attempted. A number of 25-min exposures were secured, resulting in a total observing time of about 4 hours. The final spectrum covers the entire visual region (330 - 670 nm) and is one of the most detailed and information-rich cometary spectra ever obtained. PR Photo 28b/03 displays a small part of this spectrum. These observations are the first high resolution spectra of a comet taken with the VLT. Identification of nitrogen-15 ESO PR Photo 28c/03 ESO PR Photo 28c/03 [Preview - JPEG: 400 x 524 pix - 109k [Normal - JPEG: 800 x 1047 pix - 285k] Captions : PR Photo 28c/03 is an enlarged view of a small section of the high-resolution UVES spectrum of Comet LINEAR ( PR Photo 28b/03 ) with emission lines from CN-molecules (blue line), compared to the "synthetic" spectrum based on theoretical calculations and laboratory measurements (black line ; some of the lines are labeled with quantum numbers). In the upper panel, the synthetic spectrum has been produced on the basis of the most abundant isotopic species ( 12 C 14 N). The lower panel shows that the observed spectrum is in nearly perfect agreement with a synthetic spectrum which includes contributions from two other isotopic species, 13 C 14 N (emission lines at wavelengths indicated by red ticks) and 12 C 15 N (blue ticks); they are added in proportions of 1/115 and 1/140, respectively. The isotopic abundances of carbon-13 and nitrogen-15 are measured accordingly

  19. Physical aging in comets

    NASA Technical Reports Server (NTRS)

    Meech, Karen J.

    1991-01-01

    The question of physical aging in cometary nuclei is addressed in order to elucidate the relationship between the past conditions in the protosolar nebula and the present state of the cometary nucleus, and to understand the processes that will physically and chemically alter the nucleus as a function of time. Attention is given to some of the processes that might be responsible for causing aging in comets, namely, radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, processing from heating and collisions within the Oort cloud, loss of highly volatile species from the nucleus on the first passage through the inner solar system, buildup of a dusty mantle, which can eventually prohibit further sublimation, and a change in the porosity, and hence the thermal properties, of the nucleus. Recent observations suggest that there are distinct differences between 'fresh' Oort cloud comets and thermally processed periodic comets with respect to intrinsic brightness and rate of change of activity as a function of distance.

  20. Kitt Peak Observes Comet

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The Kitt Peak National Observatory's 2.1-meter telescope observed comet Tempel 1 on April 11, 2005, when the comet was near its closest approach to the Earth. A pinkish dust jet is visible to the southwest, with the broader neutral gas coma surrounding it. North is up, East is to the left, and the field of view is about 80,000 km (50,000 miles) wide. The Sun was almost directly behind the observer at this time. The red, green and blue bars in the background are stars that moved between the individual images.

    This pseudo-color picture was created by combining three black and white images obtained with different filters. The images were obtained with the HB Narrowband Comet Filters, using CN (3870 A - shown in blue), C2 (5140 A - shown in green) and RC (7128 A - shown in red). The CN and C2 filters capture different gas species (along with the underlying dust) while the RC filter captures just the dust.

  1. Analysis of Midlatitude Auroral Emissions Observed During the Impact of Comet Shoemaker-Levy 9 with Jupiter

    NASA Technical Reports Server (NTRS)

    Bauske, Rainer; Combi, Michael R.; Clarke, John T.

    1999-01-01

    During the impact of Comet Shoemaker-Levy 9 fragment K on Jupiter observers detected aurora-like emissions near the impact region as well as in the other hemisphere at approximately magnetic conjugate positions equatorward of aurorae latitudes. A number of generation mechanisms were suggested, but investigations of their significance have been hampered by a lack of knowledge about the jovian internal magnetic field, the exact timing, and the geometry of the impact and emission sites. We use the VIP 4 model of the internal magnetic field, high-time-resolution calculations of the fragment K trajectory, and images from the Hubble Space Telescope Wide Field Planetary Camera 2 with advanced processing to reanalyze the relationship between these emissions. The impact location is enclosed to the north and south by two regions of enhanced far-ultraviolet emissions reaching a maximum distance of 18,000 km south of the impact site roughly along the line of the incoming fragment's trajectory. The southern region can be further divided into two subregions, which partly overlap with magnetic projections of two brighter emission regions observed in the northern hemisphere close to the line of footprints of Amalthea. The area of the southern region approximates the area of these projections. No enhanced emissions are found conjugate to the impact site and the northward emission region. The magnetic projections suggest that the Gossamer ring scattered particles coming from the region southward of the impact site and prevented precipitation from the northward region into the northern hemisphere. Particle acceleration by upward accelerating shocks seems feasible to explain the geometry of the southern and northern hemispheric emission regions if we assume that a part of the plume bounced twice and provided enough energy at its second bounce to also generate shock waves.

  2. Analysis of histamine release assays using the Bootstrap.

    PubMed

    Coberly, William A; Price, Joseph A

    2005-01-01

    The data from several types of bioassays is usually presented as a quotient as an intuitive parameter and a means of comparing results between experiments. For the example we considered here, we look at experiments with an experiment-wide negative control used to generate percent activity quotients from each experimental group. We asked if there was a valid means to statistically evaluate the transformed rather than the raw data. The experimental system chosen was a dose response of the agonist compound 48/80, which causes release of histamine from mast cells, thus providing test data from replicates of n=24. Descriptive statistics, the Ryan-Joiner test for normality of distribution of data, and normal probability plots confirm the normality of the distribution of data at each dose level. In parametric analysis, when the control group was treated as an errorless constant, there was a distinct consistent bias in the standard error of the data of 10% or less, which was not present if the control group's mean was treated as a variable with experimental error. This would be of minor interest in qualitative studies and might be safely ignored, but might be of considerable importance in quantitative assessments of activity using confidence intervals. When using Bootstrap estimates of standard error and probability plots of the bootstrap samples, the transformed data does not deviate significantly from normality. The standard, bias-corrected percentile limits (BCa), and empirical percentile methods gave very similar results when using resampling statistics to generate the transformed data from groups of n=6. Sample size can be as low as n=4 and still provide useful results. Thus, we have shown that resampling (i.e., bootstrap, Monte Carlo method, computer-intensive methods) can produce the data transform as well as provide confidence intervals using this type of raw data in small groups (n=4 to 6), giving improved statistical analysis of the transformed data (ratio

  3. A study of ion composition and dynamics at Comet Halley

    NASA Technical Reports Server (NTRS)

    Shelley, E. G.; Fuselier, S. A.

    1991-01-01

    This report details the participation by Lockheed co-investigators in the reduction, analysis, and interpretation of data obtained by the Ion Mass Spectrometer onboard the Giotto mission to Comet Halley. The data analysis activities and much of the scientific collaboration was shared by this team. One objective of the effort under this contract was to use data obtained by the Giotto Ion Mass Spectrometer (IMS) during the encounter with comet Halley for the purpose of advancing our understanding of the chemistry and physics of the interaction of the solar wind with comets and obtaining new information on the comet's composition. An additional objective was to make this unique data set available in a format which can be easily used by the reset of the cometary science community for other analysis in the future. The IMS has two sensors: the High Intensity Spectrometer (HIS) and the High Energy Range Spectrometer (HERS).

  4. Mutational analysis of NF2 by in vitro expression assay

    SciTech Connect

    Pulaski, K.; Pettingell, W.; MacCollin, M.; Gusella, J.F.

    1994-09-01

    Neurofibromatosis 2 (NF2) is an autosomal dominant disorder characterized by the development of multiple nervous system tumors. The recently cloned NF2 tumor suppressor gene encodes a novel member of a family of cytoskeleton associated proteins. Because the majority of germline mutational events of the NF2 gene cause gross truncation of the protein product, we investigated the feasibility of a single step protein-based screen for mutation. Total cellular RNA extracted from blood or cell lines was used to synthesize cDNA from mRNA using reverse transcriptase. Two rounds of PCR amplification were carried out. The 5{prime} primer contained an in-frame T7 promoter followed by an initiation methionine within a Kozak consensus sequence. The antisense 3{prime} primer contained the native stop codon followed by a poly (A) tail. The resulting product was used in a cell-free coupled transcription/translation reaction which was visualized on a standard protein separating gel. We were able to amplify 95% of the coding sequence of the NF2 gene with a single set of primers which produced a 1724 basepair product. Normal transcripts produced an approximately 66 KDa protein product while transcripts which contained known nonsense or splice site mutations produced truncated protein products in addition to the normal sized product. Estimation of the location of the mutation could be determined by the extent of the protein shift. This system may improve both efficiency and sensitivity of mutational analysis of the NF2 gene.

  5. On the composition of the dust component of comet nuclei

    NASA Astrophysics Data System (ADS)

    Iavnel', A. A.

    1988-11-01

    This paper considers the composition of the dust component of comet nuclei, with special attention given to Vega mass-spectrometry data on the Comet Halley nucleus and neutron-activation analysis data on magnetite spherules found at the Tungusk site. A comparison of these data with those on the carbonaceous chondrites of the Ornans (CO) and the Ivuna (CI) types and on the particles from the Draconid meteoritic shower suggest that Comet Halley, whose dust-particle composition corresponded to that of the CI type except for a higher content of volatiles, was formed at a greater distance from the sun than the asteroids.

  6. Small-size dust particles near Halley's Comet

    NASA Astrophysics Data System (ADS)

    Sagdeev, R. Z.; Evlanov, E. N.; Fomenkova, M. N.; Prilutskii, O. F.; Zubkov, B. V.

    Dust-impact PUMA mass-analyzers aboard the spacecrafts VEGA-1 and VEGA-2 allow to conduct the first direct measurements of mass-spectra of comet Halley's dust envelope particles with masses higher than 10 to the -17th g. The analysis of spectra measured by the PUMA instruments showed that unindentified peaks in this spectra could be associated with very small particles. Detection of small-size particles in the dust envelope of comet Halley agrees with the idea that the comet's nucleus is an interstellar dust aggregate which contains very small particles.

  7. AN UPPER BOUND TO THE SPACE DENSITY OF INTERSTELLAR COMETS

    SciTech Connect

    Jura, M.

    2011-05-15

    Two well-studied white dwarfs with helium-dominated atmospheres (DBs) each possess less hydrogen than carried by a single average-mass comet. Plausibly, the wind rates from these stars are low enough that most accreted hydrogen remains with the star. If so, and presuming their nominal effective temperatures, then these DBs have faced minimal impact by interstellar comets during their 50 Myr cooling age; interstellar iceballs with radii between 10 m and 2 km contain less than 1% of all interstellar oxygen. This analysis suggests that most stars do not produce comets at the rate predicted by 'optimistic' scenarios for the formation of the Oort Cloud.

  8. SPR-based assays enable the full functional analysis of bispecific molecules.

    PubMed

    Meschendoerfer, W; Gassner, C; Lipsmeier, F; Regula, J T; Moelleken, J

    2017-01-05

    The increasing complexity of novel biotherapeutics such as bispecific antibodies or fusion proteins raises new challenges for functional characterization. When compared to standard antibodies, two individual interactions and the inter-dependency of binding events need to be considered for bispecific antibodies. We have previously described an SPR-based assay setup, which enables us to assess the binding activity of a bivalent-bispecific molecule to both targets simultaneously and - in addition to one individual target - in a single setup. However, there might be some pitfalls when applying the bridging assay, e.g. change of antigen activity upon immobilization. Therefore, we have developed an alternative SPR-based assay principle, which allows the individual assessment of both targets in solution. Comparison of data between the assays showed that simultaneous binding can be calculated based on both individual readouts, and revealed a good correlation. Hence, both SPR-based assay principles allow a "full" functional analysis of a bispecific CrossMab in only one assay. The assay principles can be qualified and enable an efficient drug development.

  9. An Introduction to Comets and Their Origin.

    ERIC Educational Resources Information Center

    Chapman, Robert D.; Brandt, John C.

    1985-01-01

    Presents excerpts from "The Comet Book," a nontechnical primer on comets. Various topics discusses in these excerpts include such basic information about comets as their components, paths, and origins. (DH)

  10. Sulfides and oxides in comets

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1988-01-01

    Metal abundances associated with Sun-grazing P/comet Ikeya-Seki 1965f, the mineralogy of chrondritic interplanetary dust particles and cosmochemical affinities of Co, V, Cr, and Ni in extraterrestrial materials and probable vaporization data for nonsilicate minerals are used to evaluate the putative dearth of nonsilicates in short-period comets. It is concluded that sulfides and oxides are common, albeit minor, constituents of these comets. Sulfides and oxides can form in situ during perihelion passage in the nucleus of active short-period comets by sulfidation of Mg, Fe-silicates.

  11. Elimination of "hook-effect" in two-site immunoradiometric assays by kinetic rate analysis.

    PubMed

    Hoffman, K L; Parsons, G H; Allerdt, L J; Brooks, J M; Miles, L E

    1984-09-01

    Two-site or sandwich immunoradiometric assays (IRMAs) offer theoretical advantages over competitive immunoassay systems for sensitivity, precision, and rapid incubation. The practical realization of these advantages has been limited by the phenomenon of the "high-dose hook effect," such that high concentrations of an analyte give similar responses to those of much lower concentrations. We have developed a kinetic rate monitoring IRMA system for use with the Kineti-Count 48TM, an automated kinetic radioassay analyzer, which eliminates "hook-effect" interference, thereby permitting optimal assay design for increasing sensitivity and reducing incubation time. Practical illustration of these concepts is demonstrated by a 10-min, automated, quantitative assay we developed for human choriogonadotropin. The assay can detect as little as 1.2 int. units/L and kinetically screens for the hook effect. Kinetic rate analysis of the two-site IRMA and potentially of nonisotopic counterparts permits improvements in the speed and reliability of these immunoassays.

  12. Metallic atoms and ions in comets: Comet Halley 1986 3

    NASA Technical Reports Server (NTRS)

    Ibadov, S.

    1992-01-01

    The origin of metallic atoms and ions in the cometary comae is investigated theoretically. Two effects are revealed in the comas of bright comets: (1) the Na anomalous type effect is possible within the gas-dust jets of comet P/Halley 1986 3 due to cooling cometary dust by cryogenic gas flow from the nucleus; and (2) the production of ions of refractory elements (Fe(+), Si(+), etc.) at large heliocentric distances is possible in the comas of the Halley type dusty comets due to high-velocity impacts between cometary and zodiacal dust particles. Spectral observations of comets with high sensitivity and spatial resolution are important for studying both comets and interplanetary dust.

  13. Melt analysis of mismatch amplification mutation assays (Melt-MAMA): a functional study of a cost-effective SNP genotyping assay in bacterial models.

    PubMed

    Birdsell, Dawn N; Pearson, Talima; Price, Erin P; Hornstra, Heidie M; Nera, Roxanne D; Stone, Nathan; Gruendike, Jeffrey; Kaufman, Emily L; Pettus, Amanda H; Hurbon, Audriana N; Buchhagen, Jordan L; Harms, N Jane; Chanturia, Gvantsa; Gyuranecz, Miklos; Wagner, David M; Keim, Paul S

    2012-01-01

    Sing