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Sample records for alkaline comet assay

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

    Science.gov (United States)

    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. Copyright © 2015 John Wiley & Sons, Inc.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. © 2013 American Society of Andrology and European Academy of Andrology.

  4. In Vivo Alkaline Comet Assay and Enzyme-modified Alkaline Comet Assay for Measuring DNA Strand Breaks and Oxidative DNA Damage in Rat Liver.

    Science.gov (United States)

    Ding, Wei; Bishop, Michelle E; Lyn-Cook, Lascelles E; Davis, Kelly J; Manjanatha, Mugimane G

    2016-05-04

    Unrepaired DNA damage can lead to genetic instability, which in turn may enhance cancer development. Therefore, identifying potential DNA damaging agents is important for protecting public health. The in vivo alkaline comet assay, which detects DNA damage as strand breaks, is especially relevant for assessing the genotoxic hazards of xenobiotics, as its responses reflect the in vivo absorption, tissue distribution, metabolism and excretion (ADME) of chemicals, as well as DNA repair process. Compared to other in vivo DNA damage assays, the assay is rapid, sensitive, visual and inexpensive, and, by converting oxidative DNA damage into strand breaks using specific repair enzymes, the assay can measure oxidative DNA damage in an efficient and relatively artifact-free manner. Measurement of DNA damage with the comet assay can be performed using both acute and subchronic toxicology study designs, and by integrating the comet assay with other toxicological assessments, the assay addresses animal welfare requirements by making maximum use of animal resources. Another major advantage of the assays is that they only require a small amount of cells, and the cells do not have to be derived from proliferating cell populations. The assays also can be performed with a variety of human samples obtained from clinically or occupationally exposed individuals.

  5. Benzene-induced genotoxicity in mice in vivo detected by the alkaline comet assay

    DEFF Research Database (Denmark)

    Tuo, J; Loft, S; Thomsen, M S

    1996-01-01

    was further increased to 5.4-fold and 6.6-fold of the control values, respectively (p propylene glycol (5 microliters/g b.wt., twice with a 60-min interval), a selective CYP2E1 inhibitor, reduced the increase in the tail length by about half at all doses in both cell types (p ...The myelotoxic and genotoxic effects of benzene have been related to oxidative DNA damage after metabolism by CYP2E1. Single cell gel electrophoresis (alkaline comet assay) detects DNA damage and may thus be a convenient method for the study of benzene genotoxicity. Benzene exposure to NMRI mice.......01). By comparing our data with those from genotoxicity studies on benzene using other methods, we conclude that the 'alkaline comet assay' is a sensitive method to detect DNA damage induced by benzene. We also infer that CYP2E1 contributes, at least partly, to the formation of the 'comet'-inducing metabolites...

  6. Genotoxicity of cadmium in marine diatom Chaetoceros tenuissimus using the alkaline Comet assay

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, S.R.; Verlecar, X.N.; Nagarajappa; Goswami, U.

    of Cd increased growth of the diatom decreased. Alkaline single-cell gel electrophoresis (Comet assay) method, which is highly sensitive in detection of DNA damage in eukaryotic cells, was used to observe genomic changes in marine diatom cells. DNA...

  7. Genotoxicity testing: Comparison of the γH2AX focus assay with the alkaline and neutral comet assays.

    Science.gov (United States)

    Nikolova, Teodora; Marini, Federico; Kaina, Bernd

    2017-10-01

    Genotoxicity testing relies on the quantitative measurement of adverse effects, such as chromosome aberrations, micronuclei, and mutations, resulting from primary DNA damage. Ideally, assays will detect DNA damage and cellular responses with high sensitivity, reliability, and throughput. Several novel genotoxicity assays may fulfill these requirements, including the comet assay and the more recently developed γH2AX assay. Although they are thought to be specific for genotoxicants, a systematic comparison of the assays has not yet been undertaken. In the present study, we compare the γH2AX focus assay with the alkaline and neutral versions of the comet assay, as to their sensitivities and limitations for detection of genetic damage. We investigated the dose-response relationships of γH2AX foci and comet tail intensities at various times following treatment with four prototypical genotoxicants, methyl methanesulfonate (MMS), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), mitomycin C, and hydrogen peroxide (H 2 O 2 ) and we tested whether there is a correlation between the endpoints, i.e., alkali-labile sites and DNA strand breaks on the one hand and the cell's response to DNA double-strand breaks and blocked replication forks on the other. Induction of γH2AX foci gave a linear dose response and all agents tested were positive in the assay. The increase in comet tail intensity was also a function of dose; however, mitomycin C was almost completely ineffective in the comet assay, and the doses needed to achieve a significant effect were somewhat higher for some treatments in the comet assay than in the γH2AX foci assay, which was confirmed by threshold analysis. There was high correlation between tail intensity and γH2AX foci for MMS and H 2 O 2 , less for MNNG, and none for mitomycin C. From this we infer that the γH2AX foci assay is more reliable, sensitive, and robust than the comet assay for detecting genotoxicant-induced DNA damage. Copyright © 2017 Elsevier

  8. OpenComet: An automated tool for comet assay image analysis

    Directory of Open Access Journals (Sweden)

    Benjamin M. Gyori

    2014-01-01

    Full Text Available 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.

  9. Assessment and reduction of comet assay variation in relation to DNA damage: studies from the European Comet Assay Validation Group

    DEFF Research Database (Denmark)

    Møller, Peter; Möller, Lennart; Godschalk, Roger W L

    2010-01-01

    The alkaline single cell gel electrophoresis (comet) assay has become a widely used method for the detection of DNA damage and repair in cells and tissues. Still, it has been difficult to compare results from different investigators because of differences in assay conditions and because the data...... are reported in different units. The European Comet Assay Validation Group (ECVAG) was established for the purpose of validation of the comet assay with respect to measures of DNA damage formation and its repair. The results from this inter-laboratory validation trail showed a large variation in measured level...... reliability for the measurement of DNA damage by the comet assay but there is still a need for further validation to reduce both assay and inter-laboratory variation....

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. The Comet Assay: Tails of the (Unexpected. Use of the comet assay in pharmaceutical development.

    Directory of Open Access Journals (Sweden)

    Bas-jan Van Der Leede

    2015-08-01

    Full Text Available 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 regulatory guidance. In this presentation we want to give insight into the circumstances in vivo comet assay is deployed in a Genetic Toxicology Department of a pharmaceutical company. As the in vivo comet assay is a salvage assay, it means that some events have occurred in an in vitro assay and that the compound (or metabolite responsible for this signal is potentially deselected for further development. More than often the decision to perform an in vivo comet assay is at a very early stage in development and the first time that the compound will be tested in vivo at high/toxic dose levels. As almost no toxicokinetic data and tissue distribution data are available a careful design with maximizes the chances for successful mitigation is necessary. Decisions on acute or repeated dosing need to be made and arrangements for combining the in vivo comet assay with the in vivo micronucleus assay are to be considered. Often synthesis methods need to be scaled up fast to provide the required amount of compound and information on suitable formulations needs to be in place. As exposure data is crucial for interpretation of results, analytical methods need to be brought in place rapidly. An experienced multi skilled and communicative team needs to be available to deploy successfully this kind of assays at an early stage of development. We will present a few scenarios on study conduct and demonstrate how this assay can make a difference for the further development of a new drug.

  12. Lack of genotoxicity of potassium iodate in the alkaline comet assay and in the cytokinesis-block micronucleus test. Comparison to potassium bromate.

    Science.gov (United States)

    Poul, J M; Huet, S; Godard, T; Sanders, P

    2004-02-01

    Iodine could be added to the diet of human population in the form of iodide or iodate but iodate had not been adequately tested for genotoxicity and carcinogenicity. In the present study, genotoxic effects of potassium iodate were evaluated in vitro using the alkaline comet assay and the cytokinesis-block micronucleus assay on CHO cells and compared to halogenate salt analogues potassium bromate and chlorate and also to their respective reduced forms (potassium iodide, bromide and chloride). The results showed that the comet assay failed to detect the presence of DNA damage after a treatment of cells by potassium iodate for concentrations up to 10 mM. This absence of primary DNA damage was confirmed in the cytokinesis-block micronucleus assay. In the same way, results showed that potassium chlorate as well as potassium iodide, bromide and chloride did not induced DNA damage in the alkaline comet assay for doses up to 10 mM. By contrast, potassium bromate exposure led to an increase in both DNA damage and frequency of micronucleated cells. The repair of bromate-induced DNA damage was incomplete 24 h after the end of treatment. These results seem to indicate that potassium bromate would induce DNA damage by several mechanisms besides oxidative stress.

  13. New Application of the Comet Assay

    Science.gov (United States)

    Cortés-Gutiérrez, Elva I.; Dávila-Rodríguez, Martha I.; Fernández, José Luís; López-Fernández, Carmen; Gosálbez, Altea; Gosálvez, Jaime

    2011-01-01

    The comet assay is a well-established, simple, versatile, visual, rapid, and sensitive tool used extensively to assess DNA damage and DNA repair quantitatively and qualitatively in single cells. The comet assay is most frequently used to analyze white blood cells or lymphocytes in human biomonitoring studies, although other cell types have been examined, including buccal, nasal, epithelial, and placental cells and even spermatozoa. This study was conducted to design a protocol that can be used to generate comets in subnuclear units, such as chromosomes. The new technique is based on the chromosome isolation protocols currently used for whole chromosome mounting in electron microscopy, coupled to the alkaline variant of the comet assay, to detect DNA damage. The results show that migrant DNA fragments can be visualized in whole nuclei and isolated chromosomes and that they exhibit patterns of DNA migration that depend on the level of DNA damage produced. This protocol has great potential for the highly reproducible study of DNA damage and repair in specific chromosomal domains. PMID:21540337

  14. Biomonitoring of genotoxic risk in radar facility workers: comparison of the comet assay with micronucleus assay and chromatid breakage assay

    International Nuclear Information System (INIS)

    Garaj-Vrhovac, V.; Kopjar, N.

    2003-01-01

    Genotoxic risks of occupational exposure in a radar facility were evaluated by using alkaline comet assay, micronucleus assay and chromatid breakage assay on peripheral blood leukocytes in exposed subjects and corresponding controls. Results show that occupational exposure to microwave radiation correlates with an increase of genome damage in somatic cells. The levels of DNA damage in exposed subjects determined by using alkaline comet assay were increased compared to control and showed interindividual variations. Incidence of micronuclei was also significantly increased compared to baseline control values. After short exposure of cultured lymphocytes to bleomycin, cells of occupationally exposed subjects responded with high numbers of chromatid breaks. Although the level of chromosome damage generated by bleomycin varied greatly between individuals, in exposed subjects a significantly elevated number of chromatid breaks was observed. Our results support data reported in literature indicating that microwave radiation represents a potential DNA-damaging hazard. Alkaline comet assay is confirmed as a sensitive and highly reproducible technique for detection of primary DNA damage inflicted in somatic cells. Micronucleus assay was confirmed as reliable bio-markers of effect and chromatid breakage assay as sensitive bio-marker of individual cancer susceptibility. The results obtained also confirm the necessity to improve measures and to perform accurate health surveillance of individuals occupationally exposed to microwave radiation

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

    Science.gov (United States)

    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. The alkaline comet assay as a biomarker of primary DNA damage in peripheral blood leukocytes of nuclear medicine personnel

    International Nuclear Information System (INIS)

    Kopjar, N.; Garaj-Vrhovac, V.

    2003-01-01

    The aim of this study was to assess whether occupational exposure to chronic low doses of ionizing radiation in nuclear medicine departments may lead to genotoxicity. The alkaline comet assay was selected as a bio-marker of exposure to evaluate the levels of primary DNA damage in peripheral blood leukocytes of exposed and corresponding control subjects. Statistically significant differences were found between comet tail length and tail moment values measured in leukocytes from the exposed and control groups. Within exposed group significant inter-individual differences in DNA damage were assessed, indicating different genome sensitivity. In majority of exposed subjects the levels of DNA damage were in positive correlation with the duration of occupational exposure, while the influences of age and dosimeter readings could be excluded. However, the levels of primary DNA damage detected both in control and exposed subjects were significantly influenced by smoking. The present study indicates the possibility of genotoxic risks related to occupational exposure in nuclear medicine departments. Therefore, the exposed personnel should carefully apply the radiation protection procedures to minimize, as low as possible, radiation exposure to avoid possible genotoxic effects. According to results obtained, the alkaline comet assay could be usefully applied as a sensitive additional bio-marker in the regular health screening of workers occupationally exposed to low doses of ionizing radiation. (authors)

  17. Development of cultures of the marine sponge Hymeniacidon perleve for genotoxicity assessment using the alkaline comet assay.

    Science.gov (United States)

    Akpiri, Rachael U; Konya, Roseline S; Hodges, Nikolas J

    2017-12-01

    Sponges are a potential alternative model species to bivalves in pollution biomonitoring and environmental risk assessment in the aquatic ecosystem. In the present study, a novel in vivo exposure sponge culture model was developed from field-collected and cryopreserved sponge (Hymeniacidon perleve) cells to investigate the genotoxic effects of environmentally relevant metals in the laboratory. Sponge cell aggregates were cultured and exposed to noncytotoxic concentrations (0-0.4 mg/L) of cadmium chloride, nickel chloride, and sodium dichromate as quantified by the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and DNA-strand breaks assessed by the comet assay. Reactive oxygen species (ROS) formation was quantified by oxidation of 2',7'-dichlorofluorescin diacetate in sponge cell aggregates exposed to the same concentrations of Cd, Cr, and Ni. There was a statistically significant (p sponge cells and demonstrated that exposure to noncytotoxic concentrations of Cd, Cr, and Ni for 12 h results in a concentration-dependent increase in DNA damage and levels of ROS production. In conclusion, we have developed a novel in vivo model based on culture of cryopreserved sponge cells that is compatible with the alkaline comet assay. Genotoxicity in marine sponges measured by the comet assay technique may be a useful tool for biomonitoring research and risk assessment in aquatic ecosystems. Environ Toxicol Chem 2017;36:3314-3323. © 2017 SETAC. © 2017 SETAC.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    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 60 Co 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. - Highlights: ► We investigated the DNA comet assay to verify the irradiation of pests. ► Ratio and Tail Moment were higher in irradiated groups than in the control group. ► The DNA comet assay can be used to identify irradiation history.

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

    NARCIS (Netherlands)

    Osman, A.G.M.; Mekkawy, Imam A.; Verreth, J.A.J.; Wuertz, S.; Kloas, W.; Kirschbaum, Frank

    2008-01-01

    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

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Construction of dose-effect curves by irradiating peripheral blood mononuclear cells analyzed with the alkaline comet assay

    International Nuclear Information System (INIS)

    Rueda, Lenin; Rosales Jaime; Leon, Kety; Espinoza, Marco

    2015-01-01

    The suitability of the alkaline comet assay to detect levels of DNA damage in human monocytes and lymphocytes under radiation was tested. For this purpose, four dose-effect curves by irradiation of cells isolated from blood samples of 4 young, health and non-smoker donors. A gamma ray source of "6"0Co was used and doses of 0, 2.5, 5 and 7 Gy were delivered to blood cells. The results show good correlation (R2 = 0.973, SD = 0.009) between the radiation dose and DNA damage as measured by the parameter Tail Intensity (percentage of DNA in the tail of the 'comet'). Furthermore, we observe the variability in predicting DNA damage by Gy (7.59, SD = 1.5). Potential use of this technique in the biological dosimetry of ionizing radiations is being evaluated. (author)

  3. Comet assay optimization for assessment of DNA damage due to radiation exposure

    International Nuclear Information System (INIS)

    Dwi Ramadhani; Devita Tetriana; Viria Agesti Suvifan

    2016-01-01

    Comet assay can be used to measure the deoxyribonucleic acid (DNA) damage level caused by ionizing radiation exposure in peripheral blood lymphocytes. The principle of the comet assay is based on the amount of denatured DNA fragments that migrated out of the cell nucleus during electrophoresis. There are several aspects that must be concerned when doing the comet assay. For example the agarose concentration, duration of alkaline incubation, electrophoresis conditions (time, temperature, and voltage gradient), and the measurement parameters that used in analyze the comet. Percentage of DNA in the comet tail (% tail DNA) is strongly recommended as a parameter when analyze the comet because it can be converted to lesions per 106 base pairs (bp) using calibration curve that show relationship between the dose of ionizing radiation and % tail DNA. To obtain an accurate result, the calibration curve must be made and comet should be analyzing using image processing analysis software since it can be increase the precision and reduce the subjectivity of the measurement process. (author)

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Laura Carolina Valencia

    2011-01-01

    Full Text Available 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-nitroquinoline-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 !g/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.

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

    Science.gov (United States)

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

    2011-10-01

    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.

  7. A Comprehensive Review on Clinical Applications of Comet Assay

    Science.gov (United States)

    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

  8. 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.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. 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.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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; Pcomet assay (r=-0.73; Pcomet assay was better than alkaline comet assay for assessment of radiosensitivities of tumor cells after acute or fractionated doses of irradiation. © 2012 Elsevier B.V. All rights reserved.

  11. Evaluation of the neutral comet assay for detection of alpha-particle induced DNA-double-strand-breaks

    International Nuclear Information System (INIS)

    Hofbauer, Daniela

    2010-01-01

    Aim of this study was to differentiate DNA-double-strand-breaks from DNA-single-strand-breaks on a single cell level, using the comet assay after α- and γ-irradiation. Americium-241 was used as a alpha-irradiation-source, Caesium-137 was used for γ-irradiation. Because of technical problems with both the neutral and alkaline comet assay after irradiation of gastric cancer cells and human lymphocytes, no definite differentiation of DNA-damage was possible.

  12. Controlling variation in the comet assay

    Directory of Open Access Journals (Sweden)

    Andrew Richard Collins

    2014-10-01

    Full Text Available Variability of the comet assay is a serious issue, whether it occurs from experiment to experiment in the same laboratory, or between different laboratories analysing identical samples. Do we have to live with high variability, just because the comet assay is a biological assay rather than analytical chemistry? Numerous attempts have been made to limit variability by standardising the assay protocol, and the critical steps in the assay have been identified; agarose concentration, duration of alkaline incubation, and electrophoresis conditions (time, temperature and voltage gradient are particularly important. Even when these are controlled, variation seems to be inevitable. It is helpful to include in experiments reference standards, i.e. cells with a known amount of specific damage to the DNA. They can be aliquots frozen from a single large batch of cells, either untreated (negative controls or treated with, for example, H2O2 or X-rays to induce strand breaks (positive control for the basic assay, or photosensitiser plus light to oxidise guanine (positive control for Fpg- or OGG1-sensitive sites. Reference standards are especially valuable when performing a series of experiments over a long period - for example, analysing samples of white blood cells from a large human biomonitoring trial - to check that the assay is performing consistently, and to identify anomalous results necessitating a repeat experiment. The reference values of tail intensity can also be used to iron out small variations occurring from day to day. We present examples of the use of reference standards in human trials, both within one laboratory and between different laboratories, and describe procedures that can be used to control variation.

  13. The alkaline comet assay used in evaluation of genotoxic damage of drinking water disinfection by-products (bromoform and chloroform

    Directory of Open Access Journals (Sweden)

    Messaouda Khallef

    2015-06-01

    Full Text Available The alkaline comet assay (pH 12.3 is a useful method for monitoring genotoxic effects of environmental pollutants in the root nuclei of Allium cepa and various plants; it allows the detection of single- and double-strand breaks, incomplete excision-repair sites and cross-links. It has been introduced to detect even small changes in DNA structure. It is a technically simple, highly sensitive, fast and economic test which detects in vitro and in vivo genotoxicity (DNA integrity and packing mode in any cell types examined, and requires just a few cells for its execution (Liman et al., 2011; Yıldız et al., 2009. Chloroform and bromoform are the most important trihalomethanes found in drinking water. Different concentrations of bromoform (25, 50, 75and 100µg/ml and chloroform (25, 50, 100 and 200 µg/ml were introduced to onion tuber roots. Distilled water was used as a negative control and methyl methansulfonate (MMS-10 µg/ml as positive control. All obtained data were subjected to statistical analyses by using SPSS 15.0 for Windows software. For comparison purposes, Duncan multiple range tests using one-way analysis of variance (ANOVA were employed and p<0.05 was accepted as the test of significance. Comet assay results showed that DNA damage was significant at p <0.05 for the different concentrations of chloroform and bromoform compared to the negative control which has a damage rate equal to 3.5 ± 0.7 and the positive control which has damage rate equal to 13.5 ± 2.12. The exposure of root tip cells to these disinfection by-products increases DNA damage. All concentrations examined in this study of bromoform and chloroform cause significant harm, which could be due to DNA damage induced by oxidative stress. The measurement of DNA damage in the nuclei of higher plant tissues is a new area of study with SCGE. This assay could be incorporated into in situ monitoring of atmosphere, water and soil: the comet assay allows a fast detection without

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

    Science.gov (United States)

    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

  15. Assessment of radiation induced cytogenetic damage in human keratinocytes by comet assay

    International Nuclear Information System (INIS)

    Joseph, Praveen; Sanjeev Ganesh; Narayana, Y.; Puthali, Abhay; Bhat, N.N.

    2010-01-01

    In the present study the effect of gamma radiation on normal human keratinocytes (HaCaT) cells has been analyzed using alkaline comet assay and a comparative study over the sensitivity of different comet parameters such as tail length (TL), olive tail moment (OTM) and percentage tail DNA (TDNA) has also been made. Human keratinocytes (HaCaT) cells were grown in Dulbecco's modified essential medium (DMEM) (10% FCS) at 37 °C in a humidified atmosphere containing 5% CO 2 . Cultured cells were harvested with 0.025 % trypsin EDTA. The sample (2 X 10 cells/ml) was exposed to gamma radiation of different dose using a 60 Co gamma source at dose rate of 2 Gy min -1 and the dosimetry has been carried out using Fricke and FBX dosimeters. After irradiation, to quantify the DNA damage the comet assay (single cell gel electrophoresis) was carried out under alkaline conditions, by the methods outlined by Singh et al. The quantification of the DNA strand breaks in each cells were performed using CASP software. The DNA damage quantification can be accomplished by measuring those comet parameters which exhibit a linear dependence on the amount of DNA damage. In the present study, comet parameters such as OTM, TL and TDNA were recorded and the variation of these parameters and their correlation coefficients for different doses of gamma radiation is plotted. The OTM value is normalized with control value and control for TL and TDNA is adjusted to zero to avoid initial variations in different experiments

  16. An ECVAG trial on assessment of oxidative damage to DNA measured by the comet assay

    DEFF Research Database (Denmark)

    Johansson, Clara; Møller, Peter; Forchhammer, Lykke

    2010-01-01

    The increasing use of single cell gel electrophoresis (the comet assay) highlights its popularity as a method for detecting DNA damage, including the use of enzymes for assessment of oxidatively damaged DNA. However, comparison of DNA damage levels between laboratories can be difficult due...... to differences in assay protocols (e.g. lysis conditions, enzyme treatment, the duration of the alkaline treatment and electrophoresis) and in the end points used for reporting results (e.g. %DNA in tail, arbitrary units, tail moment and tail length). One way to facilitate comparisons is to convert primary comet...... assay end points to number of lesions/10(6) bp by calibration with ionizing radiation. The aim of this study was to investigate the inter-laboratory variation in assessment of oxidatively damaged DNA by the comet assay in terms of oxidized purines converted to strand breaks with formamidopyrimidine DNA...

  17. Biomonitoring of genotoxicity of industrial fertilizer pollutants in Aiolopus thalassinus (Orthoptera: Acrididae) using alkaline comet assay.

    Science.gov (United States)

    Abdelfattah, Eman A; Augustyniak, Maria; Yousef, Hesham A

    2017-09-01

    Phosphate fertilizer industry is considered as one of the main sources of environmental pollutants. Besides solid waste products, e.g. phosphates, sulphates, and heavy metals, also atmospheric pollutants, such as hydrofluoric acid fumes (HF), sulphur dioxide (SO 2 ), nitrogen oxides (NO 2 ), and particulate matter with diameter up to 10 μm (PM 10 ) can be dangerous. Genotoxic effect of these pollutants was monitored by assessing the DNA damage using alkaline comet assay on cells from brain, thoracic muscles and gut of Aiolopus thalassinus collected at three sites (A-C) located at 1, 3, and 6 km away from Abu-Zaabal Company for Fertilizers and Chemical Industries. Control site was established 32 km from the source of pollution, at the Cairo University Campus. The level of the DNA damage was significantly higher in insects from polluted sites comparing to that from the control site. A strong negative correlation between percentage of cells with visible DNA damage (% of severed cells) and the distance of the sites from Abu-Zaabal Company was found. The best parameter for monitoring of fertilizer pollutants is % of severed cells. Possible impact of Abu-Zaabal Company (extremely high concentration of phosphates and sulphates in all the polluted sites) on DNA integrity in A. thalassinus tissues was discussed. The potential use of the comet assay as a biomonitoring method of the environmental pollution caused by fertilizer industry was proposed. Specific pollution resulting from the activity of the fertilizer industry can cause comparable adverse effects in the organisms inhabiting areas up to 6 km from the source of contamination. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. 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.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Comet Assay: A Method to Evaluate Genotoxicity of Nano-Drug Delivery System

    Science.gov (United States)

    Vandghanooni, Somayeh; Eskandani, Morteza

    2011-01-01

    Introduction Drug delivery systems could induce cellular toxicity as side effect of nanomaterials. The mechanism of toxicity usually involves DNA damage. The comet assay or single cell gel electrophoresis (SCGE) is a sensitive method for detecting strand damages in the DNA of a cell with applications in genotoxicity testing and molecular epidemiology as well as fundamental research in DNA damage and repair. Methods In the current study, we reviewed recent drug delivery researches related to SCGE. Results We found that one preference for choosing the assay is that comet images may result from apoptosis-mediated nuclear fragmentation. This method has been widely used over the last decade in several different areas. Overall cells, such as cultured cells are embedded in agarose on a microscope slide, lysed with detergent, and treated with high salt. Nucleoids are supercoiled DNA form. When the slide is faced to alkaline electrophoresis any breakages present in the DNA cause the supercoiling to relax locally and loops of DNA extend toward the anode as a ‘‘comet tail’’. Conclusion This article provides a relatively comprehensive review upon potentiality of the comet assay for assessment of DNA damage and accordingly it can be used as an informative platform in genotoxicity studies of drug delivery systems. PMID:23678412

  20. A quantitative comet infection assay for influenza virus

    Science.gov (United States)

    Lindsay, Stephen M.; Timm, Andrea; Yin, John

    2011-01-01

    Summary The virus comet assay is a cell-based virulence assay used to evaluate an antiviral drug or antibody against a target virus. The comet assay differs from the plaque assay in allowing spontaneous flows in 6-well plates to spread virus. When implemented quantitatively the comet assay has been shown to have an order-of-magnitude greater sensitivity to antivirals than the plaque assay. In this study, a quantitative comet assay for influenza virus is demonstrated, and is shown to have a 13-fold increase in sensitivity to ribavirin. AX4 cells (MDCK cells with increased surface concentration of α2–6 sialic acid, the influenza virus receptor) have reduced the comet size variability relative to MDCK cells, making them a better host cell for use in this assay. Because of enhanced antiviral sensitivity in flow-based assays, less drug is required, which could lead to lower reagent costs, reduced cytotoxicity, and fewer false-negative drug screen results. The comet assay also serves as a readout of flow conditions in the well. Observations from comets formed at varying humidity levels indicate a role for evaporation in the mechanism of spontaneous fluid flow in wells. PMID:22155578

  1. Variation in assessment of oxidatively damaged DNA in mononuclear blood cells by the comet assay with visual scoring

    DEFF Research Database (Denmark)

    Forchhammer, Lykke; Bräuner, Elvira Vaclavik; Folkmann, Janne Kjaersgaard

    2008-01-01

    The comet assay is popular for assessments of genotoxicity, but the comparison of results between studies is challenging because of differences in experimental procedures and reports of DNA damage in different units. We investigated the variation of DNA damage in mononuclear blood cells (MNBCs......) measured by the comet assay with focus on the variation related to alkaline unwinding and electrophoresis time, number of cells scored, as well as the putative benefits of transforming the primary end points to common units by the use of reference standards and calibration curves. Eight experienced......, our results indicate that inter-investigator difference in scoring is a strong determinant of DNA damage levels measured by the comet assay....

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

    Science.gov (United States)

    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.

  3. 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.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Comet assay on mice testicular cells

    Directory of Open Access Journals (Sweden)

    Anoop Kumar Sharma

    2015-05-01

    Full Text Available Heritable mutations may result in a variety of adverse outcomes including genetic disease in the offspring. In recent years the focus on germ cell mutagenicity has increased and the “Globally Harmonized System of Classification and Labelling of Chemicals (GHS” has published classification criteria for germ cell mutagens (Speit et al., 2009. The in vivo Comet assay is considered a useful tool for investigating germ cell genotoxicity. In the present study DNA strand breaks in testicular cells of mice were investigated. Different classes of chemicals were tested in order to evaluate the sensitivity of the comet assay in testicular cells. The chemicals included environmentally relevant substances such as Bisphenol A, PFOS and Tetrabrombisphenol A. Statistical power calculations will be presented to aid in the design of future Comet assay studies on testicular cells. Power curves were provided with different fold changes in % tail DNA, different number of cells scored and different number of gels (Hansen et al., 2014. An example is shown in Figure 1. A high throughput version of the Comet assay was used. Samples were scored with a fully automatic comet assay scoring system that provided faster scoring of randomly selected cells.

  5. Detection of radiation-induced apoptosis using the comet assay

    International Nuclear Information System (INIS)

    Wada, Seiichi; Kobayashi, Yasuhiko; Funayama, Tomoo; Yamamoto, Kazuo; Khoa, Tran Van; Natsuhori, Masahiro; Ito, Nobuhiko

    2003-01-01

    The electrophoresis pattern of apoptotic cells detected by the comet assay has a characteristic small head and spread tail. This image has been referred to as an apoptotic comet, but it has not been previously proven to be apoptotic cells by any direct method. In order to identify this image obtained by the comet assay as corresponding to an apoptotic cell, the frequency of appearance of apoptosis was examined using CHO-K1 and L5178Y cells which were exposed to gamma irradiation. As a method for detecting apoptosis, the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay was used. When the frequency of appearance of apoptotic cells following gamma irradiation was observed over a period of time, there was a significant increase in appearance of apoptosis when using the TUNEL assay. However, there was only a slight increase when using the comet assay. In order to verify the low frequency of appearance of apoptosis when using the comet assay, we attempted to use the TUNEL assay to satin the apoptotic comets detected in the comet assay. The apoptotic comets were TUNEL positive and the normal comets were TUNEL negative. This indicates that the apoptotic comets were formed from DNA fragments with 3'-hydroxy ends that are generated as cells undergo apoptosis. Therefore, it was understood that the characteristic pattern of apoptotic comets detected by the comet assay corresponds to cells undergoing apoptosis. (author)

  6. 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

    Science.gov (United States)

    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...

  7. 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).

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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 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.

  9. Cutaneous radiation syndrome: applicability of comet assay for early assessment of irradiation consequences

    International Nuclear Information System (INIS)

    Di Giorgio, Marina; Taja, Maria R.; Bolgiani, A.; Bustos, N.; Cavalieri, H.

    2002-01-01

    Many accidental overexposures to ionizing radiation lead to an inhomogeneous irradiation of the body. Skin and mucous membranes resulted exposed to very high local radiation doses, which may be survivable because bone marrow is less severely exposed. Under these circumstances, the skin becomes an important organ in determining clinical prognosis, being dosimetric assessment a necessary requirement. There is increasing interest in the assessment of biological markers that permit the detection of radiation induced damage in the localized irradiations. The 'Comet Assay' (single cell gel electrophoresis) is a sensitive, rapid and relatively inexpensive method for measuring DNA damage in individual cells. Single cells are embedded in agarose on microscope slides, lysed to remove the majority of the proteins, electrophoreses, then stained with ethidium bromide in order to visualize the DNA. Following radiation damage, the smaller the fragment size and the grater the number of fragments of DNA, the grater the percentage of DNA that it is able to migrate in an electric field, forming a comet image. The assay can be performed under alkaline conditions to examine DNA single strand breaks (SSBs), or in non denaturing (neutral) conditions to measure double strand breaks (DSBs) in individual cells. In order to get information to be applied on the evaluation of skin biopsies without culture for an early assessment of irradiation consequences in locally irradiated individuals, we have evaluated the alkaline comet assay (for doses 5 Gy), neutral comet assay has been applied to keratinocytes from primary and secondary cultures and to a suspension of epidermal cells obtained from biopsies irradiated in vitro and afterwards processed to obtain the mentioned cellular suspension, in order to reproduce the closest condition to in vivo overexposure. Our results suggest that comet assay can be applied for the early assessment of gamma radiation induced damage in skin biopsies without

  10. The comet assay: ready for 30 more years.

    Science.gov (United States)

    Møller, Peter

    2018-02-24

    During the last 30 years, the comet assay has become widely used for the measurement of DNA damage and repair in cells and tissues. A landmark achievement was reached in 2016 when the Organization for Economic Co-operation and Development adopted a comet assay guideline for in vivo testing of DNA strand breaks in animals. However, the comet assay has much more to offer than being an assay for testing DNA strand breaks in animal organs. The use of repair enzymes increases the range of DNA lesions that can be detected with the assay. It can also be modified to measure DNA repair activity. Still, despite the long-term use of the assay, there is a need for studies that assess the impact of variation in specific steps of the procedure. This is particularly important for the on-going efforts to decrease the variation between experiments and laboratories. The articles in this Special Issue of Mutagenesis cover important technical issues of the comet assay procedure, nanogenotoxicity and ionising radiation sensitivity on plant cells. The included biomonitoring studies have assessed seasonal variation and certain predictors for the basal level of DNA damage in white blood cells. Lastly, the comet assay has been used in studies on genotoxicity of environmental and occupational exposures in human biomonitoring studies and animal models. Overall, the articles in this Special Issue demonstrate the versatility of the comet assay and they hold promise that the assay is ready for the next 30 years.

  11. The development and validation of EpiComet-Chip, a modified high-throughput comet assay for the assessment of DNA methylation status.

    Science.gov (United States)

    Townsend, Todd A; Parrish, Marcus C; Engelward, Bevin P; Manjanatha, Mugimane G

    2017-08-01

    DNA damage and alterations in global DNA methylation status are associated with multiple human diseases and are frequently correlated with clinically relevant information. Therefore, assessing DNA damage and epigenetic modifications, including DNA methylation, is critical for predicting human exposure risk of pharmacological and biological agents. We previously developed a higher-throughput platform for the single cell gel electrophoresis (comet) assay, CometChip, to assess DNA damage and genotoxic potential. Here, we utilized the methylation-dependent endonuclease, McrBC, to develop a modified alkaline comet assay, "EpiComet," which allows single platform evaluation of genotoxicity and global DNA methylation [5-methylcytosine (5-mC)] status of single-cell populations under user-defined conditions. Further, we leveraged the CometChip platform to create an EpiComet-Chip system capable of performing quantification across simultaneous exposure protocols to enable unprecedented speed and simplicity. This system detected global methylation alterations in response to exposures which included chemotherapeutic and environmental agents. Using EpiComet-Chip on 63 matched samples, we correctly identified single-sample hypermethylation (≥1.5-fold) at 87% (20/23), hypomethylation (≥1.25-fold) at 100% (9/9), with a 4% (2/54) false-negative rate (FNR), and 10% (4/40) false-positive rate (FPR). Using a more stringent threshold to define hypermethylation (≥1.75-fold) allowed us to correctly identify 94% of hypermethylation (17/18), but increased our FPR to 16% (7/45). The successful application of this novel technology will aid hazard identification and risk characterization of FDA-regulated products, while providing utility for investigating epigenetic modes of action of agents in target organs, as the assay is amenable to cultured cells or nucleated cells from any tissue. Environ. Mol. Mutagen. 58:508-521, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  12. [Endonuclease modified comet assay for oxidative DNA damage induced by detection of genetic toxicants].

    Science.gov (United States)

    Zhao, Jian; Li, Hongli; Zhai, Qingfeng; Qiu, Yugang; Niu, Yong; Dai, Yufei; Zheng, Yuxin; Duan, Huawei

    2014-03-01

    The aim of this study was to investigate the use of the lesion-specific endonucleases-modified comet assay for analysis of DNA oxidation in cell lines. DNA breaks and oxidative damage were evaluated by normal alkaline and formamidopyrimidine-DNA-glycosylase (FPG) modified comet assays. Cytotoxicity were assessed by MTT method. The human bronchial epithelial cell (16HBE) were treated with benzo (a) pyrene (B(a)P), methyl methanesulfonate (MMS), colchicine (COL) and vincristine (VCR) respectively, and the dose is 20 µmol/L, 25 mg/ml, 5 mg/L and 0.5 mg/L for 24 h, respectively. Oxidative damage was also detected by levels of reactive oxygen species in treated cells. Four genotoxicants give higher cytotoxicity and no significant changes on parameters of comet assay treated by enzyme buffer. Cell survival rate were (59.69 ± 2.60) %, (54.33 ± 2.81) %, (53.11 ± 4.00) %, (51.43 ± 3.92) % in four groups, respectively. There was the direct DNA damage induced by test genotoxicants presented by tail length, Olive tail moment (TM) and tail DNA (%) in the comet assay. The presence of FPG in the assays increased DNA migration in treated groups when compared to those without it, and the difference was statistically significant which indicated that the clastogen and aneugen could induce oxidative damage in DNA strand. In the three parameters, the Olive TM was changed most obviously after genotoxicants treatment. In the contrast group, the Olive TM of B(a) P,MMS, COL,VCR in the contrast groups were 22.99 ± 17.33, 31.65 ± 18.86, 19.86 ± 9.56 and 17.02 ± 9.39, respectively, after dealing with the FPG, the Olive TM were 34.50 ± 17.29, 43.80 ± 10.06, 33.10 ± 12.38, 28.60 ± 10.53, increased by 58.94%, 38.48%, 66.86% and 68.21%, respectively (t value was 3.91, 3.89, 6.66 and 3.87, respectively, and all P comet assay appears more specific for detecting oxidative DNA damage induced by genotoxicants exposure, and the application of comet assay will be expanded. The endonuclease

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

    Science.gov (United States)

    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 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. 2008 Wiley Periodicals, Inc.

  14. OpenComet: An automated tool for comet assay image analysis

    OpenAIRE

    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 ...

  15. Dose-Response Assessment of Four Genotoxic Chemicals in a Combined Mouse and Rat Micronucleus and Comet Assay Protocol

    Science.gov (United States)

    Recio, Leslie; Hobbs, Cheryl; Caspary, William; Witt, Kristine L.

    2012-01-01

    The in vivo micronucleus (MN) assay has proven to be an effective measure of genotoxicity potential. However, sampling a single tissue (bone marrow) for a single indicator of genetic damage using the MN assay provides a limited genotoxicity profile. The in vivo alkaline (pH>13) Comet assay, which detects a broad spectrum of DNA damage, can be applied to a variety of rodent tissues following administration of test agents. To determine if the Comet assay is a useful supplement to the in vivo MN assay, a combined test protocol (MN/Comet assay) was conducted in male B6C3F1 mice and F344/N rats using four model genotoxicants: ethyl methanesulfonate (EMS), acrylamide (ACM), cyclophosphamide (CP), and vincristine sulfate (VS). Test compounds were administered on 4 consecutive days at 24-hour intervals (VS was administered to rats for 3 days); animals were euthanized 4 hours after the last administration. All compounds induced significant increases in micronucleated reticulocytes (MN-RET) in the peripheral blood of mice, and all but ACM induced MN-RET in rats. EMS and ACM induced significant increases in DNA damage, measured by the Comet assay, in multiple tissues of mice and rats. CP-induced DNA damage was detected in leukocytes and duodenum cells. VS, a spindle fiber disrupting agent, was negative in the Comet assay. Based on these results, the MN/Comet assay holds promise for providing more comprehensive assessments of potential genotoxicants, and the National Toxicology Program is presently using this combined protocol in its overall evaluation of the genotoxicity of substances of public health concern. PMID:20371966

  16. Correlation between the genotoxicity endpoints measured by two different genotoxicity assays: comet assay and CBMN assay

    Directory of Open Access Journals (Sweden)

    Carina Ladeira

    2015-06-01

    The results concerning of positive findings by micronuclei and non significant ones by comet assay, are corroborated by Deng et al. (2005 study performed in workers occupationally exposed to methotrexate, also a cytostatic drug. According to Cavallo et al. (2009, the comet assay seems to be more suitable for the prompt evaluation of the genotoxic effects, for instance, of polycyclic aromatic hydrocarbons mixtures containing volatile substances, whereas the micronucleus test seems more appropriate to evaluate the effects of exposure to antineoplastic agents. However, there are studies that observed an increase in both the comet assay and the micronucleus test in nurses handling antineoplastic drugs, although statistical significance was only seen in the comet assay, quite the opposite of our results (Maluf & Erdtmann, 2000; Laffon et al. 2005.

  17. Increased DNA damage in blood cells of rat treated with lead as assessed by comet assay

    Directory of Open Access Journals (Sweden)

    Mohammad Arif

    2008-06-01

    Full Text Available A growing body of evidence suggests that oxidative stress is the key player in the pathogenesis of lead-induced toxicity. The present study investigated lead induced oxidative DNA damage, if any in rat blood cells by alkaline comet assay. Lead was administered intraperitoneally to rats at doses of 25, 50 and 100 mg/kg body weight for 5 days consecutively. Blood collected on day six from sacrificed lead-treated rats was used to assess the extent of DNA damage by comet assay which entailed measurement of comet length, olive tail moment, tail DNA (% and tail length. The results showed that treatment with lead significantly increased DNA damage in a dose-dependent manner. Therefore, our data suggests that lead treatment is associated with oxidative stress-induced DNA damage in rat blood cells which could be used as an early bio-marker of lead-toxicity.

  18. Comet assay as a procedure for detecting possible genotoxicity induced by non-ionizing radiation

    Directory of Open Access Journals (Sweden)

    Zsuzsanna Nemeth

    2015-05-01

    In our laboratory we use comet assay for testing genotoxicity of non-ionizing radiation for more than ten years. In the experiments we use whole blood samples (human or dog, cell lines (e.g. H295R cell line or 3 dimensional in vitro skin tissue (epidermis models. In our protocol a slightly modified alkaline Comet assay method of Singh et al. (1988 is used. On our poster there will be presented a brief summary of our experiments with exposure to different types of radiation (ELF, RF, and intermediate frequency. In our protocols the non-ionizing radiation was often combined with ionizing radiation to see whether the non-ionizing radiation can influence the repair of the DNA damage induced by ionizing radiation. For the evaluation of the slides mainly Komet 4.0 image analysis system software (Kinetic Imaging, Liverpool, UK was used, but as we got familiarized with other methods for slide evaluation like grading the comets by visual scoring into 5 categories or the CaspLab software, the comparison of these three methods will be also presented.

  19. Applicability of the comet assay in evaluation of DNA damage in healthcare providers' working with antineoplastic drugs: a systematic review and meta-analysis.

    Science.gov (United States)

    Zare Sakhvidi, Mohammad Javad; Hajaghazadeh, Mohammad; Mostaghaci, Mehrdad; Mehrparvar, Amir Houshang; Zare Sakhvidi, Fariba; Naghshineh, Elham

    2016-01-01

    Unintended occupational exposure to antineoplastic drugs (ANDs) may occur in medical personnel. Some ANDs are known human carcinogens and exposure can be monitored by genotoxic biomarkers. To evaluate the obstacles to obtaining conclusive results from a comet assay test to determine DNA damage among AND exposed healthcare workers. We systematically reviewed studies that used alkaline comet assay to determine the magnitude and significance of DNA damage among health care workers with potential AND exposure. Fifteen studies were eligible for review and 14 studies were used in the meta-analysis. Under random effect assumption, the estimated standardized mean difference (SMD) in the DNA damage of health care workers was 1.93 (95% CI: 1.15-2.71, p comet moment, I2 test results, as a measure of heterogeneity, dropped to zero. Heterogeneity analysis showed that date of study publication was a possible source of heterogeneity (B = -0.14; p comet assay methodological variables, and exposure characteristics may be responsible for heterogenic data from comet assay studies and interfere with obtaining conclusive results. Lack of quantitative environmental exposure measures and variation in comet assay protocols across studies are important obstacles in generalization of results.

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

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.; Bhagat, J.; Ingole, B.S.; Rao, P.V.S.S.D.P.; Markad, V.L.

    cell lines. Toxicology 126:103–114. Mitchelmore CL, Birmelin C, Chipman JK, Livingstone DR. 1998. Evidence for cytochrome P-450 catalysis and free radical involvement in the production of DNA strand breaks by benzo[a]pyrene and nitroaromatics... Lymnaea luteola L. Aquat Toxicol 124:83-90. Anderson D, Yu TW, Phillips BJ, Schmezer P. 1994. The effect of various antioxidants and other modifying agents on oxygen-radical-generated DNA damage in human lymphocytes in the Comet assay. Mutat Res...

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

    Science.gov (United States)

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Localized irradiations, Evaluation through ''comet assay''

    International Nuclear Information System (INIS)

    Giorgio, M.D.; Taja, M.R.; Nasazzi, N.B.; Bustos, N.; Cavalieri, H.; Bolgiani, A.

    2000-01-01

    During the last 50 years various radiation accidents involving localized irradiations occurred, resulting mainly from improper handling of sealed sources Co 60 , Cs 137 or Ir 192 at workplaces for industrial gammagraphy. Severe skin reaction may develop at the contact sites. Such inhomogeneous irradiations lead to a differential exposure of lymphocytes in lymphatic tissues or other organs that may recirculate into the peripheral blood producing a mixed irradiated and unirradiated population of lymphocytes. Applying the mathematical models ''Contaminated Poisson'' of Dolphin and Qdr method of Sasaki, a mean dose in the irradiated body area and its size can be estimated from unstable chromosome aberration scoring. This give an indication of the proportion of haemopoietic stem cell compartment involved in the overexposure. There are also different biophysical techniques that can give responses in biological dosimetry. The ''Comet Assay'' (single cell gel electrophoresis) is a sensitive and rapid method for DNA strand break detection in individual cells. The advantages of the technique include: collection of data at the level of individual cell; the need for small numbers of cells per sample; its sensitivity for detecting DNA damage and that virtually any eukaryote cell population is amenable to analysis. The objective of this work is to apply ''Comet Assay'' method to evaluate the effect of radiation on skin and subcutaneous tissues, differentiating irradiated from unirradiated body areas. It could provide a useful tool to estimate the extension and the dose in the irradiated region, contributing with the current techniques. In this first study, we evaluate the alkaline comet assay as a method for detection of DNA radiation induced damage in keratinocytes from primary culture obtained from full thickness skin biopsies of patients requiring grafts. Skin and, particularly, keratinocytes were selected as an appropriate cellular system due to: Skin, the first barrier

  3. CometQ: An automated tool for the detection and quantification of DNA damage using comet assay image analysis.

    Science.gov (United States)

    Ganapathy, Sreelatha; Muraleedharan, Aparna; Sathidevi, Puthumangalathu Savithri; Chand, Parkash; Rajkumar, Ravi Philip

    2016-09-01

    DNA damage analysis plays an important role in determining the approaches for treatment and prevention of various diseases like cancer, schizophrenia and other heritable diseases. Comet assay is a sensitive and versatile method for DNA damage analysis. The main objective of this work is to implement a fully automated tool for the detection and quantification of DNA damage by analysing comet assay images. The comet assay image analysis consists of four stages: (1) classifier (2) comet segmentation (3) comet partitioning and (4) comet quantification. Main features of the proposed software are the design and development of four comet segmentation methods, and the automatic routing of the input comet assay image to the most suitable one among these methods depending on the type of the image (silver stained or fluorescent stained) as well as the level of DNA damage (heavily damaged or lightly/moderately damaged). A classifier stage, based on support vector machine (SVM) is designed and implemented at the front end, to categorise the input image into one of the above four groups to ensure proper routing. Comet segmentation is followed by comet partitioning which is implemented using a novel technique coined as modified fuzzy clustering. Comet parameters are calculated in the comet quantification stage and are saved in an excel file. Our dataset consists of 600 silver stained images obtained from 40 Schizophrenia patients with different levels of severity, admitted to a tertiary hospital in South India and 56 fluorescent stained images obtained from different internet sources. The performance of "CometQ", the proposed standalone application for automated analysis of comet assay images, is evaluated by a clinical expert and is also compared with that of a most recent and related software-OpenComet. CometQ gave 90.26% positive predictive value (PPV) and 93.34% sensitivity which are much higher than those of OpenComet, especially in the case of silver stained images. The

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

    Science.gov (United States)

    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. Copyright © 2015

  5. How to best freeze liver samples to perform the in vivo mammalian alkaline comet assay

    Directory of Open Access Journals (Sweden)

    José Manuel Enciso Gadea

    2015-06-01

    None of the different methods used was capable of giving good results, except immersing the liver samples in liquid nitrogen, followed by Jackson’s et al. (2013 thawing protocol, suggesting that the thawing process may be as critical as the freezing process. To sum up, these results highlight the importance of deepening the possibility to perform the comet assay with frozen tissue.

  6. Comet Assay in Cancer Chemoprevention.

    Science.gov (United States)

    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.

  7. Applicability of the comet assay in evaluation of DNA damage in healthcare providers’ working with antineoplastic drugs: a systematic review and meta-analysis

    Science.gov (United States)

    Zare Sakhvidi, Mohammad Javad; Hajaghazadeh, Mohammad; Mostaghaci, Mehrdad; Mehrparvar, Amir houshang; Zare Sakhvidi, Fariba; Naghshineh, Elham

    2016-01-01

    Background Unintended occupational exposure to antineoplastic drugs (ANDs) may occur in medical personnel. Some ANDs are known human carcinogens and exposure can be monitored by genotoxic biomarkers. Objective To evaluate the obstacles to obtaining conclusive results from a comet assay test to determine DNA damage among AND exposed healthcare workers. Methods We systematically reviewed studies that used alkaline comet assay to determine the magnitude and significance of DNA damage among health care workers with potential AND exposure. Fifteen studies were eligible for review and 14 studies were used in the meta-analysis. Results Under random effect assumption, the estimated standardized mean difference (SMD) in the DNA damage of health care workers was 1.93 (95% CI: 1.15–2.71, p comet moment, I2 test results, as a measure of heterogeneity, dropped to zero. Heterogeneity analysis showed that date of study publication was a possible source of heterogeneity (B = −0.14; p comet assay methodological variables, and exposure characteristics may be responsible for heterogenic data from comet assay studies and interfere with obtaining conclusive results. Lack of quantitative environmental exposure measures and variation in comet assay protocols across studies are important obstacles in generalization of results. PMID:27110842

  8. 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.

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

    Science.gov (United States)

    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. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Localized irradiations, evaluation through 'Comet Assay'

    International Nuclear Information System (INIS)

    Di Giorgio, Marina; Taja, Maria R.; Nasazzi, Nora B.; Bustos, N.; Cavalieri, H.; Bolgiani, A.

    2000-01-01

    During the last 50 years various radiation accidents involving localized irradiations occurred, resulting mainly from improper handling of sealed sources of Cobalt 60, Cesium 137 or Iridium 192 at work placed for industrial gammagraphy and other radiation sources. Severe skin reaction may developed at the contact sites. Such inhomogeneous irradiations lead to a differential exposure of lymphocytes in lymphatic tissues or other organs that may recirculate into the peripheral blood producing a mixed irradiated and unirradiated population of lymphocytes. Applying the mathematical models 'Contaminated Poisson' of Dolphin and Qdr method of Sasaki, a mean dose in the irradiated body area and its size can be estimated from unstable chromosome aberration scoring. There are also different biophysical techniques that can give response in localized irradiations. Biological dosimetry is a necessary complement to physical and clinical dosimetries. Thus, there is increasing interest in the assessment of biological markers that permit the detection of radiation induced damage in the localized irradiations. The 'Comet Assay' (single cell gel electrophoresis) is a sensitive, rapid and relatively inexpensive method for measuring DNA damage in individual cells. Single cells are embedded in agarose on microscope slides, lysed to remove the majority of the proteins, electrophoresed, then stained with ethidium bromide in order to visualize the DNA. When visualized using a fluorescent microscope, DNA of undamaged cells appears as a spherical mass occupying the cavity formed by the lysed cell. Following radiation damage, the smaller the fragment size and the grater the number of fragments of DNA, the grater the percentage of DNA that it is able to migrate in an electric field, forming a comet image. The assay can be performed under alkaline conditions to examine DNA single strand breaks (SSBs), or in non denaturing (neutral) conditions to measure double strand breaks (DSBs) in individual

  12. Irradiation detection of food by DNA Comet Assay

    International Nuclear Information System (INIS)

    Khan, A.A.; Delincee, H.

    1999-01-01

    Microgel electrophoresis of single cells or nuclei (DNA Comet Assay) has been investigated to detect irradiation treatment of more than 50 food commodities e.g. meats, seafood, cereals, pulses, nuts, fruits and vegetables, and spices. The foodstuffs have been exposed to radiation doses covering the range of potential commercial irradiation for inactivation of pathogenic and spoilage micro-organisms, for insect disinfestation and for shelf-life extension. The Comet Assay is based on detection of DNA fragments presumptive to irradiation. For most of the food items investigated, the assay can be applied successfully for irradiation detection by working out different conditions of the assay. However, with some of the foods difficulties arose due to - lack of discrimination between the irradiated and unirradiated food samples due to the presence of the same kinds of comets in both cases and the total absence of the typical intact cells in unirradiated samples. - Sufficient DNA material was not available from some of the foods. - Insufficient lysis of the cell walls in case of some plant foods. In conclusion, the DNA Comet Assay can help to detect the irradiation treatment of several varieties of foods using low-cost equipment in a short time of analysis. (orig.)

  13. Comparison of DNA comet assay and germination test (half-embryo-test) in gamma-irradiated cherry seeds

    International Nuclear Information System (INIS)

    Todoroki, Setsuko; Hayashi, Toru

    2002-01-01

    Cherry fruits were irradiated with gamma-rays at doses up to 200Gy (effective dose for disinfestation of codling moth), and DNA strand break in seed embryos was investigated by using alkaline comet assay. Immediately after irradiation (≥100Gy), DNA from embryos produced comets with a long and wide tail due to fragmentation. In control cells, DNA relaxed and produced comet with very short tail (with few strand break). After 72h storage, DNA from fruits irradiated at 200 Gy showed comets with little tail and tail moment of comets was same as un-irradiated control. These results indicate that the strand breaks of DNA caused by irradiation in fresh seed embryo are repaired during storage. On the contrary, the ability of germination lost by irradiation did not restored, a dose of 100Gy and more retarded shoot elongation. In cherries irradiated at 100Gy, the shooting percentage was less than 50% at 4th day after incubation. Germination test (Half embryo test) can be discriminate between irradiated and un-irradiated cherries. (author)

  14. Standardizing electrophoresis conditions: how to eliminate a major source of error in the comet assay.

    Directory of Open Access Journals (Sweden)

    Gunnar Brunborg

    2015-06-01

    Full Text Available In the alkaline comet assay, cells are embedded in agarose, lysed, and then subjected to further processing including electrophoresis at high pH (>13. We observed very large variations of mean comet tail lengths of cell samples from the same population when spread on a glass or plastic substrate and subjected to electrophoresis. These variations might be cancelled out if comets are scored randomly over a large surface, or if all the comets are scored. The mean tail length may then be representative of the population, although its standard error is large. However, the scoring process often involves selection of 50 – 100 comets in areas selected in an unsystematic way from a large gel on a glass slide. When using our 96-sample minigel format (1, neighbouring sample variations are easily detected. We have used this system to study the cause of the comet assay variations during electrophoresis and we have defined experimental conditions which reduce the variations to a minimum. We studied the importance of various physical parameters during electrophoresis: (i voltage; (ii duration of electrophoresis; (iii electric current; (iv temperature; and (v agarose concentration. We observed that the voltage (V/cm varied substantially during electrophoresis, even within a few millimetres of distance between gel samples. Not unexpectedly, both the potential ( V/cm and the time were linearly related to the mean comet tail, whereas the current was not. By measuring the local voltage with microelectrodes a few millimetres apart, we observed substantial local variations in V/cm, and they increased with time. This explains the large variations in neighbouring sample comet tails of 25% or more. By introducing simple technology (circulation of the solution during electrophoresis, and temperature control, these variations in mean comet tail were largely abolished, as were the V/cm variations. Circulation was shown to be particularly important and optimal conditions

  15. Reference cells and ploidy in the comet assay

    Directory of Open Access Journals (Sweden)

    Gunnar eBrunborg

    2015-02-01

    Full Text Available 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.

  16. Evaluating In Vitro DNA Damage Using Comet Assay.

    Science.gov (United States)

    Lu, Yanxin; Liu, Yang; Yang, Chunzhang

    2017-10-11

    DNA damage is a common phenomenon for each cell during its lifespan, and is defined as an alteration of the chemical structure of genomic DNA. Cancer therapies, such as radio- and chemotherapy, introduce enormous amount of additional DNA damage, leading to cell cycle arrest and apoptosis to limit cancer progression. Quantitative assessment of DNA damage during experimental cancer therapy is a key step to justify the effectiveness of a genotoxic agent. In this study, we focus on a single cell electrophoresis assay, also known as the comet assay, which can quantify single and double-strand DNA breaks in vitro. The comet assay is a DNA damage quantification method that is efficient and easy to perform, and has low time/budget demands and high reproducibility. Here, we highlight the utility of the comet assay for a preclinical study by evaluating the genotoxic effect of olaparib/temozolomide combination therapy to U251 glioma cells.

  17. An alkaline comet assay study on the antimalarial drug atovaquone in human peripheral blood lymphocytes: a study based on clinically relevant concentrations.

    Science.gov (United States)

    Dinter, Domagoj; Gajski, Goran; Garaj-Vrhovac, Vera

    2013-01-01

    Atovaquone, a hydroxynaphthoquinone, is an anti-parasite drug, selectively targeting the mitochondrial respiratory chain of malaria parasite. It is used for both the treatment and prevention of malaria, usually in a fixed combination with proguanil. Although atovaquone has not often been associated with severe adverse reactions in the recommended dosages and has a relatively favorable side effect profile, the present study was undertaken to evaluate its cytogenotoxic potential towards human peripheral blood lymphocytes. Two different concentrations of atovaquone found in plasma when used in fixed-dose combination with proguanile hydrochloride were used with and without S9 metabolic activation: 2950 ng ml(-1) used for prophylactic treatment and 11 800 ng ml(-1) used in treatment of malaria. The results showed that lymphocyte viability was not affected after the treatment, suggesting that atovaquone was not cytotoxic in the given concentrations. With the alkaline comet assay we demonstrated that in human peripheral blood lymphocytes no significant changes in comet parameters occurred after the treatment. There were no differences in tested parameters with the addition of S9 metabolic activation, indicating that atovaquone either has no metabolite or it is not toxic in the given concentrations. Since no effects were observed after the treatment, it is to be concluded that atovaquone is safe from the aspect of genototoxicity in the recommended dosages. Copyright © 2011 John Wiley & Sons, Ltd.

  18. Impaired DNA repair as assessed by the ``comet`` assay in patients developing thyroid carcinoma after radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Leprat, F.; Sarasin, A.; Suarez, H.G. [Institut de Recherches sur le Cancer, 94 - Villesuif (France); Leprat, F.; Alapetite, C.; Rosselli, F.; Ridet, A.; Moustacch, E.; Alapetite, C. [Institut Curie, 75 - Paris (France); Schlumberger, M. [Institut Gustave Roussy, 94 - Villejuif (France)

    1997-03-01

    A defective cellular response to DNA lesions induced be genotoxic agents may be associated to an increased cancer proneness. This has been clearly identified in some rare but extensively studied genetic diseases such as xeroderma pigmentosum (XP), ataxia telangiectasia (AT) and Fanconi anemia (FA). In practical oncology, most patients receive genotoxic therapeutic agents and the presence of so far unidentified sensitive genotypes could account for an increased susceptibility to cancer in a subgroup of exposed patients. The thyroid gland of children is especially sensitive to the carcinogenic effect of ionizing radiation. Evidence for risk is reported even at doses as low as 0.1 Gy, and the excess relative risk to develop a thyroid tumor following a radiation dose of 1 Gy in childhood is of 7.7 [l]. In order to determine if a defect in repair of DNA strand breaks could be involved, as an early step, in the development of secondary thyroid tumors after radiotherapy, we examined, using the alkaline single cell gel electrophoresis assay (SCGE or `comet`), the response to in vitro {gamma}-rays exposure of lymphocytes of a small group of patients who developed thyroid carcinoma after radiotherapy for a primary tumor. Because of its practical advantages, the alkaline comet assay offers the opportunity to question the role of DNA strand beaks rejoining capacity of the individual in the radiation induced carcinogenesis of thyroid tumors. This preliminary study of a small group of patients with therapeutic irradiation at childhood for a primary tumor indicates that, at the time of blood sampling, lymphocytes of some of these patients demonstrated reduced rejoining capacity. These results suggest that the comet assay might help to distinguish a subgroup of individuals at risk for radiation induced genomic instability and encourage further investigation. (authors)

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

    Science.gov (United States)

    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. © 2014 Wiley Periodicals, Inc.

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

    Science.gov (United States)

    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. © The Author 2014. Published by

  1. Assessment of Genotoxicity of Ionizing radiation using Tradescantia-Comet assay

    Energy Technology Data Exchange (ETDEWEB)

    Han, Min; Ryu, Tae Ho; Hyun, Kyung Man; Kim, Jin Kyu [Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of); Wilhelmova, Nad [Institute of Experimental Botany, Prague (Czech Republic)

    2010-05-15

    Over the last two decades, several new methodologies for the detection of DNA damage have been developed. The comet assay is currently used in different areas of biological sciences to detect DNA damage. The comet assay, also called the single cell gel electrophoresis (SCGE) was first introduced by Ostling and Johanson as a microelectrophoretic technique for the direct visualization of DNA damage in individual cells. The comet assay, due to its simplicity, sensitivity and need of a few cells, is ideal as a short-term genotoxicity test. The comet assay can theoretically be applied to every type of eukaryotic cell, including plant cells. Plants are very useful as monitors of genetic effects caused by pollution in the atmosphere, water and soil. Although the genotoxic effects detected by Tradescantia tests cannot be associated with mutagenesis or even carcinogenesis in humans, these bioassays are very useful tools for screening the mutagenic potential in the environment. Experiments were conducted to study the genotoxic effects of ionizing radiations on the genome integrity, particularly of Tradescantia. The increasingly frequent use of Tradescantia as a sensitive environmental bioindicator of genotoxic effects. This study was designed to assess the genotoxicity of ionizing radiation using Tradescnatia-comet assay

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  4. Comet assay on tetraploid yeast cells

    DEFF Research Database (Denmark)

    Rank, Jette; Syberg, Kristian; Jensen, Klara

    2009-01-01

    Tetraploid yeast cells (Saccharomyces cerevisiae) were used in the comet assay with the intention of developing a new, fast and easy assay for detecting environmental genotoxic agents without using higher organisms. Two DNA-damaging chemicals, H2O2 and acrylamide, together with wastewater from...... three municipal treatment plants were tested for their effect on the yeast-cell DNA. The main problem with using yeast in the comet assay is the necessity to degrade the cell wall. This was achieved by using Zymolase 100 T twice during the procedure, since Zymolase 20 T did not open the cell wall....... Analytical problems that arose due to the small amount of DNA in the yeast nuclei in haploid and diploid cells, which contain 13 Mbp and 26 Mbp DNA per cell, respectively, were solved by using tetraploid yeast cells (52 Mbp) instead. DNA damage was shown after exposure to H2O2 and acrylamide. The lowest dose...

  5. Use of statistical analysis to validate ecogenotoxicology findings arising from various comet assay components.

    Science.gov (United States)

    Hussain, Bilal; Sultana, Tayyaba; Sultana, Salma; Al-Ghanim, Khalid Abdullah; Masoud, Muhammad Shahreef; Mahboob, Shahid

    2018-04-01

    Cirrhinus mrigala, Labeo rohita, and Catla catla are economically important fish for human consumption in Pakistan, but industrial and sewage pollution has drastically reduced their population in the River Chenab. Statistics are an important tool to analyze and interpret comet assay results. The specific aims of the study were to determine the DNA damage in Cirrhinus mrigala, Labeo rohita, and Catla catla due to chemical pollution and to assess the validity of statistical analyses to determine the viability of the comet assay for a possible use with these freshwater fish species as a good indicator of pollution load and habitat degradation. Comet assay results indicated a significant (P comet head diameter, comet tail length, and % DNA damage. Regression analysis and correlation matrices conducted among the parameters of the comet assay affirmed the precision and the legitimacy of the results. The present study, therefore, strongly recommends that genotoxicological studies conduct appropriate analysis of the various components of comet assays to offer better interpretation of the assay data.

  6. Ecotoxicological Assessment of Aquatic Genotoxicity Using the Comet Assay

    Directory of Open Access Journals (Sweden)

    KHUSNUL YAQIN

    2006-09-01

    Full Text Available Comet assay is a novel biological analysis, which is a sensitive, flexible, simple, rapid, and inexpensive method to assess aquatic genotoxicant. Since Singh and co-workers developed the method in 1988, its use has increased exponentially in various fields. This review discourses on the application of this assay in aquatic ecosystems. Various types of cells from various aquatic organisms have been tested by various genotoxicant both direct- and indirect-acting using the comet assay. The applications of this assay suggest that it is a useful assay to assess aquatic genotoxicants. However, there are some factors, which should be taken into account when using this assay as aquatic ecotoxicological assessment device such as inter-animal and cell variability.

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

    Directory of Open Access Journals (Sweden)

    Conceição LV Santos

    2015-06-01

    Full Text Available 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.

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

    Science.gov (United States)

    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

  9. Detection of hypoxic fractions in murine tumors by comet assay: Comparison with other techniques

    International Nuclear Information System (INIS)

    Hu, Q.; Kavanagh, M.C.; Newcombe, D.

    1995-01-01

    The alkaline comet assay was used to detect the hypoxic fractions of murine tumors. A total of four tumor types were tested using needle aspiration biopsies taken immediately after a radiation dose of 15 Gy. Initial studies confirmed that the normalized tail moment, a parameter reflecting single-strand DNA breaks induced by the radiation, was linearly related to radiation dose. Further, it was shown that for a mixed population (1:1) of cells irradiated under air-breathing or hypoxic conditions, the histogram of normal tail moment values obtained from analyzing 400 cells in the population had a double peak which, when fitted with two Gaussian distributions, gave a good estimate of the proportion of the two subpopulations. For the four tumor types, the means of the calculated hypoxic fractions from four or five individual tumors were 0.15 ± 0.04 for B16F1, 0.08 ± 0.04 for KHT-LP1, 0.17 ± 0.04 for RIF-1 and 0.04 ± 0.01 for SCCVII. Analysis of variance showed that the hypoxic fraction in KHT-LP1 tumors is significantly lower than those of the other three tumors (P = 0.026) but that there is no significant difference in hypoxic fraction between B16F1, RIF-1 and SCCVII tumors (P = 0.574). Results from multiple samples taken from each of five RIF-1 tumors showed that the intertumor heterogeneity of hypoxic fractions was greater than that within the same tumor. The mean hypoxic fraction obtained using the comet assay for the four tumor types was compared with the hypoxic fraction determined by the clonogenic assay, or median pO 2 values, or [ 3 H]misonidazole binding in the same tumor types. The values of hypoxic fraction obtained with the comet assay were two to four times lower than those measured by the paired survival method. Preliminary results obtained with a dose of 5 Gy were consistent with those obtained using 15 Gy. These results suggest the further development of the comet assay for clinical studies. 21 refs., 7 figs., 5 tabs

  10. Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

    International Nuclear Information System (INIS)

    Mattos, Jose Carlos Pelielo de; Motta, Ellen Serri da; Oliveira, Marcia Betania Nunes de; Dantas, Flavio Jose da Silva; Araujo, Adriano Caldeira de

    2008-01-01

    Reactive oxygen species (ROS) can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl 2 ) is a ROS generator, leading to lethality in Escherichia coli (E. coli), with the base excision repair (BER) mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl 2 in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl 2 was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms. (author)

  11. Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Mattos, Jose Carlos Pelielo de; Motta, Ellen Serri da; Oliveira, Marcia Betania Nunes de; Dantas, Flavio Jose da Silva; Araujo, Adriano Caldeira de [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Dept. de Biofisica e Biometria. Lab. de Radio e Fotobiologia]. E-mail: jcmattos@uerj.br

    2008-12-15

    Reactive oxygen species (ROS) can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl{sub 2}) is a ROS generator, leading to lethality in Escherichia coli (E. coli), with the base excision repair (BER) mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl{sub 2} in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl{sub 2} was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms. (author)

  12. Reasonable threshold value used to segment the individual comet from the comet assay image

    International Nuclear Information System (INIS)

    Yan Xuekun; Chen Ying; Du Jie; Zhang Xueqing; Luo Yisheng

    2009-01-01

    Reasonable segmentation of the individual comet contour from the Comet Assay (CA) images is the precondition for all of parameters analysis during the automatic analyzing for the CA. The Otsu method and several arithmetic operators for image segmentation, such as Sobel, Prewitt, Roberts and Canny were used to segment the comet contour, and characters of the CA images were analyzed firstly. And then the segmentation methods which had been adopted in the software for CA automatic analysis, such as the CASP, the TriTek CometScore TM , were put for-ward and compared. At last, a two-step procedure for threshold calculation based on image-content analysis is adopted to segment the individual comet from the CA images, and several principles for the segmentation are put forward too.(authors)

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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 comet tail measures (i.e., length, moment, migration) were higher at all time periods after UO compared to 0 days (P comet assay and the SCSA, which was not identified using traditional measures of sperm quality. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Evaluation of irradiation in foods using DNA comet assay

    International Nuclear Information System (INIS)

    Khawar, Affaf; Bhatti, Ijaz Ahmad; Khan, Q.M.; Ali, T.; Khan, A.I.; Asi, M.R.

    2011-01-01

    Comet assay is a rapid, inexpensive and sensitive biological technique to detect DNA damage in food stuffs by irradiation. In this study the Comet assay is applied on foods of plant and animal origins. Samples were irradiated by using 60 Co gamma-radiation source. The applied doses were 2, 6 and 10 kGy for food of plant origin and 0.5, 1 and 2 kGy for meat items. The un-irradiated and irradiated samples were clearly differentiated on the basis of DNA fragmentation. During the electrophoresis study, it was found that in un-irradiated cells DNA remained intact and appeared as Comets without tail whereas in irradiated cells Comets with tails were visible due to stretching of fragmented DNA. Moreover, it was also revealed that the DNA tail length was dose dependent. Dry food stuffs (seeds) showed good results as compared to moist foods (meat, fruits and vegetables) due to the absence of background damage. (author)

  16. Alkaline Comet Assay and Micronucleus Test Parameters in Children Exposed to Diagnostic X-Ray Examination

    International Nuclear Information System (INIS)

    Gajski, G.; Geric, M.; Garaj-Vrhovac, V.; Milkovic, Dj.; Beck, N.; Ranogajec-Komor, M.; Miljanic, S.; Knezevic, Z.

    2011-01-01

    Chest radiograms represent the basic radiological examination of thorax and are the most frequently performed radiological diagnostic procedure in the child population. Understanding the risks of low doses of radiation is an important aspect in the risk benefit analysis in paediatric populations. To provide the best care for the young patients the effects of radiation should be minimized thus chest X-rays must be performed by highest standards to ensure that the young patient has the lowest risk possible. Since children are the most sensitive to radiation, there is a need for follow up of the young populations that receive these X-ray diagnostic examinations. Follow up would be especially advisable for children that are at higher risk of radiation induced damage, for example children with a predisposition to DNA damage, or for children that are constantly exposed to numerous radiological examinations due to their illness. In that manner, present study was undertaken to evaluate application of different dosimetry systems in conjunction with alkaline comet assay and micronucleus test for the assessment of different types of DNA and chromosomal alterations in child population exposed to acute diagnostic X-rays examination. For that purpose doses were measured using thermoluminescence (TL) and radiophotoluminescent (RPL) dosimetry systems. The study demonstrated that immediately after exposure to diagnostic X-irradiation, mean percentage of DNA in tail of the comets, which is indirect measures of DNA damage, was significantly changed. The same was noticed for mean total number of micronuclei as well. It was shown that children with pulmonary diseases subjected to diagnostic procedure develop a significant increase in mean total number of each measured parameter which are the biomarkers of genetic damage for carcinogenesis, than prior to diagnostic procedure and that interindividual differences exist for each monitored child. Our results show that genetic damage arises

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

    Science.gov (United States)

    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.

  18. Comet assay as a cold chain control tool

    International Nuclear Information System (INIS)

    Duarte, Renato Cesar

    2009-01-01

    Bearing in mind an ever more demanding market regarding the quality of food, it has been necessary to develop processes that meet the demands of consumers. Within the existing processes the cold chain and irradiation stand out. The cold chain comprises all the stages of conserving food from production, cooling, freezing, storing and transportation to the final consumer. Irradiation, as a means of conserving food, prolongs the shelf life, inhibits budding and reduces pathogenic contamination among other benefits. Is very important the identification of food degradation in function of failure on the processes which they were subjected. The comet assay is a screening test widely studied, considerate fast and with low cost. By the fact of the test identify breaks on the DNA, may be possible use the comet test on the control of cold chain failures that degrade de food. The labels and stamp, do not consider the previous food situation and indicate failures from the moment where they be placed in contact with the product. With the comet assay is possible to check the degradation that has occurred in liver chicken samples until the moment of comet's test realization. (author)

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

    Science.gov (United States)

    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. PMID:25071840

  20. The comet assay in testing the potential genotoxicity of nanomaterials

    Directory of Open Access Journals (Sweden)

    Amaya Azqueta

    2015-06-01

    Full Text Available In the last two decades the production and use of nanomaterials (NMs has impressively increased. Their small size, given a mass equal to that of the corresponding bulk material, implies an increase in the surface area and consequently in the number of atoms that can be reactive. They possess different physical, chemical and biological properties compared to bulk materials of the same composition, which makes them very interesting and valuable for many different applications in technology, energy, construction, electronics, agriculture, optics, paints, textiles, food, cosmetics, medicine... Toxicological assessment of NMs is crucial; the same properties that make them interesting also make them potentially harmful for health and the environment. However, the term NM covers many different kinds of particle , and so there is no simple, standard approach to assessing their toxicity. NMs can enter the cell, interact with cell components and even penetrate the nucleus and interfere with the genetic material. Among the different branches of toxicology, genotoxicity is a main area of concern since it is closely related with the carcinogenic potential of compounds. The Organisation for Economic Co-operation and Development (OECD has published internationally agreed in vitro and in vivo validated test methods to evaluate different genotoxic endpoints of chemicals, including chromosome and gene mutations, and DNA breaks. However not all the assays are suitable to study the genotoxic potential of NMs as has been shown by the OECD Working Party on Manufactured Nanomaterials (WPMN. Moreover, alterations to DNA bases, which are precursors to mutations and of great importance in elucidating the mechanism of action of NMs, are not covered by the OECD guidelines. The in vivo standard comet assay (which measures DNA breaks and alkali-labile sites was included in the OECD assays battery in September 2014 while the in vitro standard comet assay is currently under

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

    Science.gov (United States)

    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 borax-induced genotoxicity in fish.

  2. Identification of irradiated pepper with comet assay

    International Nuclear Information System (INIS)

    Prieto Miranda, Enrique Fco.; Moreno Alvarez, Damaris L.; Carro Palacio, Sandra; Iglesia Enriquez, Isora

    2007-01-01

    The treatment of foods with ionizing radiations is a technological process utilized in order to increase the hygienic quality and the storage time of the foods. Several methods of detection of irradiated foods have been recommended. The comet assay of DNA is one fast and economical technique for the qualitative identification of irradiated foods. The objective of the present paper was to identify with the comet assay technique the modifications of the DNA molecule of irradiated pepper storage at environment and refrigeration temperatures and different post-irradiation times for different absorbed dose values, (0.1, 0.3 and 0.5 kGy). It was demonstrated that for the high absorbed dose values was observed a greater break into fragments of the DNA molecule, which shows the application of this technique for the identification of irradiated foods. (author)

  3. Detection of garlic gamma-irradiated by assay comet

    International Nuclear Information System (INIS)

    Moreno Alvarez, Damaris L.; Miranda, Enrique F. Prieto; Carro, Sandra; Iglesias Enrique, Isora; Matos, Wilberto

    2009-01-01

    The garlic samples were irradiated in a facility with 60 Co sources, at absorbed dose values of 0-0,15 kGy. The detection method utilized for the identification of the irradiated garlic was biological comet assay. The samples were classified post-irradiation several times. The irradiated samples showed high strand breaks of DNA exhibiting comets of several forms, while the not irradiated and lower dose samples showed a behavior like round shape and light comets. Significant differences were found for higher absorbed dose values at 0.06 kGy, this absorbed dose value is corresponding with the applied dose value at this food in order to avoid the germination. (author)

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

    International Nuclear Information System (INIS)

    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.

    2014-01-01

    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 24 h. The damage gradually decreased with time, i.e. was smaller at 48 and 72 h than at 24 h 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 reveals that gamma radiation induces single strand breaks in DNA as measured by alkaline comet assay in bivalves and comet assay serves as a sensitive and rapid method to detect genotoxicity of gamma radiation. This study further indicates that both M. casta and P. malabarica exhibit almost identical sensitivity to gamma radiation as measured by DNA damage

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

    Energy Technology Data Exchange (ETDEWEB)

    Praveen Kumar, M.K., E-mail: here.praveen@gmail.com [Department of Zoology, Goa University, Goa 403206 (India); Shyama, S.K., E-mail: skshyama@gmail.com [Department of Zoology, Goa University, Goa 403206 (India); Sonaye, B.S. [Department of Radiation Oncology, Goa Medical College, Goa (India); Naik, U Roshini; Kadam, S.B.; Bipin, P.D.; D’costa, A. [Department of Zoology, Goa University, Goa 403206 (India); Chaubey, R.C. [Radiation Biology and Health Science Division, Bhabha Atomic Research Centre, Mumbai (India)

    2014-05-01

    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 24 h. The damage gradually decreased with time, i.e. was smaller at 48 and 72 h than at 24 h 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 reveals that gamma radiation induces single strand breaks in DNA as measured by alkaline comet assay in bivalves and comet assay serves as a sensitive and rapid method to detect genotoxicity of gamma radiation. This study further indicates that both M. casta and P. malabarica exhibit almost identical sensitivity to gamma radiation as measured by DNA damage.

  6. Application of the DNA comet assay for detection of irradiated meat

    International Nuclear Information System (INIS)

    Kruszewski, M.; Iwanenko, T.; Wojewodzka, M.; Malec-Czechowska, K.; Dancewicz, A. M.; Szot, Z.

    1998-01-01

    Radiation induces damage to the DNA. This damage (fragmentation) can be assessed in the irradiated food using Single Cell Gel Electrophoresis (SCGE), known as DNA comet assay. Fragmentation of DNA may also be caused by improper storage of meat and repeated freezing and thawing. This makes identification of irradiated meat by this assay not reliable enough. In order to know the scale of the processes imitating radiation effects in DNA of the comets, their shape and lengths were examined in both irradiated and unirradiated fresh meat (D = 1.5 or 3.0 kGy) stored at 4 o C or frozen (-21 o ) up to 5 months. Comets formed upon SCGE were stained with DAPI or silver and examined in fluorescent or light microscope. They were divided arbitrarily into 4 classes. Comets of IV class were found quite often in fresh meat stored at 4 o C. In meat samples that were irradiated and stored frozen, comets of class I, II and III were observed. The negative comet test is univocal. Positive comet test, however, needs confirmation. The meat should be subjected to further analysis with other validated methods. (author)

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

    Science.gov (United States)

    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. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  8. DNA Comet Assay. A simple screening technique for identification of some irradiated foods

    International Nuclear Information System (INIS)

    Khan, A.A.; Khan, H.M.

    2008-01-01

    DNA Comet Assay method was carried out to detect irradiation treatment of some foods like meat, spices, beans and lentils. The fresh meat of cow and duck were irradiated up to radiation doses of 3 kGy, the spices (cardamoms and cumin black) were irradiated to radiation doses of 5, 10, 15 and 20 kGy while the beans (black beans and white beans) and lentils (red and green lentils) were irradiated to 0.5 and 1 kGy. All the foods were then analyzed for radiation treatment using simple microgel electrophoresis of single cells or nuclei (DNA Comet Assay). Sedimentation, lysis and staining times were adjusted to get optimized conditions for correct and easy analysis of each food. Using these optimized conditions, it was found out that radiation damaged DNA showed comets in case of irradiated food samples, whereas in non-treated food samples, round or conical spots of stained DNA were visible. Shape, length and intensity of these comets were also radiation dose dependent. Screening of unirradiated and irradiated samples by Comet Assay was successful in the case of all the foods under consideration under the optimized conditions of assay. Therefore, for different kinds of irradiated foods studied in the present study, the DNA Comet Assay can be used as a rapid, simple and inexpensive screening test. (author)

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

    Science.gov (United States)

    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

    reveals that gamma radiation induces single strand breaks in DNA as measured by alkaline comet assay in bivalves and comet assay serves as a sensitive and rapid method to detect genotoxicity of gamma radiation. This study further indicates that both M. casta and P. malabarica exhibit almost identical sensitivity to gamma radiation as measured by DNA damage. Copyright © 2014 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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

  11. Detection of garlic gamma-irradiated by assay comet

    Energy Technology Data Exchange (ETDEWEB)

    Moreno Alvarez, Damaris L.; Miranda, Enrique F. Prieto; Carro, Sandra; Iglesias Enrique, Isora; Matos, Wilberto [Centro de Aplicaciones Tecnologicas y Desarrollo Nuclear (CEADEN), Ciudad de La Habana (Cuba)], e-mail: damaris@ceaden.edu.cu

    2009-07-01

    The garlic samples were irradiated in a facility with {sup 60}Co sources, at absorbed dose values of 0-0,15 kGy. The detection method utilized for the identification of the irradiated garlic was biological comet assay. The samples were classified post-irradiation several times. The irradiated samples showed high strand breaks of DNA exhibiting comets of several forms, while the not irradiated and lower dose samples showed a behavior like round shape and light comets. Significant differences were found for higher absorbed dose values at 0.06 kGy, this absorbed dose value is corresponding with the applied dose value at this food in order to avoid the germination. (author)

  12. Assessment of the predictive capacity of the optimized in vitro comet assay using HepG2 cells.

    Science.gov (United States)

    Hong, Yoon-Hee; Jeon, Hye Lyun; Ko, Kyung Yuk; Kim, Joohwan; Yi, Jung-Sun; Ahn, Ilyoung; Kim, Tae Sung; Lee, Jong Kwon

    2018-03-01

    Evaluation of DNA damage is critical during the development of new drugs because it is closely associated with genotoxicity and carcinogenicity. The in vivo comet assay to assess DNA damage is globally harmonized as OECD TG 489. However, a comet test guideline that evaluates DNA damage without sacrificing animals does not yet exist. The goal of this study was to select an appropriate cell line for optimization of the in vitro comet assay to assess DNA damage. We then evaluated the predictivity of the in vitro comet assay using the selected cell line. In addition, the effect of adding S9 was evaluated using 12 test chemicals. For cell line selection, HepG2, Chinese hamster lung (CHL/IU), and TK6 cell lines were evaluated. We employed a method for the in vitro comet assay based on that for the in vivo comet assay. The most appropriate cell line was determined by% tail DNA increase after performing in vitro comet assays with 6 test chemicals. The predictivity of the in vitro comet assay using the selected cell line was measured with 10 test chemicals (8 genotoxins and 2 non-genotoxic chemicals). The HepG2 cell line was found to be the most appropriate, and in vitro comet assays using HepG2 cells exhibited a high accuracy of 90% (9/10). This study suggests that HepG2 is an optimal cell line for the in vitro comet assay to assess DNA damage. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Individual sensitivity to radiations and DNA repair proficiency: the comet assay contribution; Sensibilite individuelle aux radiations et reparation de l`ADN: apport du test des cometes

    Energy Technology Data Exchange (ETDEWEB)

    Alapetite, C. [Institut Curie, 75 - Paris (France)

    1998-09-01

    Some are hereditary syndromes demonstrate high cancer risk and hypersensitivity in response to exposures to agents such as ultraviolet or ionising radiation, and are characterized by a defective processing of DNA damage. They highlight the importance of the individual risk associated to exposures. The comet assay, a simple technique that detects DNA strand breaks, requires few cells and allows examination of DNA repair capacities in established cell lines, in blood samples or biopsies. The assay has been validated on cellular systems with known repair defects such as xeroderma pigmentosum defective in nucleotide excision repair, on mutant rodent cell lines defective in DNA single strand breaks rejoining (XRCC5/Ku80 and XRCC7/DNAPKcs) (neutral conditions). This assay does not allow to distinguish a defective phenotype in ataxia telangiectasia cells. It shows in homozygous mouse embryo fibroblasts Brca2-/- an impaired DNA double strand break rejoining. Simplicity, rapidity and sensitivity of the alkaline comet assay allow to examine the response of lymphocytes. It has been applied to the analysis of the role of DNA repair in the pathogenesis of collagen diseases, and the involvement of individual DNA repair proficiency in the thyroid tumorigenesis induced in some patients after therapeutic irradiation at childhood has been questioned. Preliminary results of these studies suggest that this type of approach could help for adapting treatment modalities and surveillance in subgroups of patients defective in DNA repair process. It could also have some incidence in the radioprotection field. (author)

  14. Reliability of plant root comet assay in comparison with human leukocyte comet assay for assessment environmental genotoxic agents.

    Science.gov (United States)

    Reis, Gabriela Barreto Dos; Andrade-Vieira, Larissa Fonseca; Moraes, Isabella de Campos; César, Pedro Henrique Souza; Marcussi, Silvana; Davide, Lisete Chamma

    2017-08-01

    Comet assay is an efficient test to detect genotoxic compounds based on observation of DNA damage. The aim of this work was to compare the results obtained from the comet assay in two different type of cells extracted from the root tips from Lactuca sativa L. and human blood. For this, Spent Pot Liner (SPL), and its components (aluminum and fluoride) were applied as toxic agents. SPL is a solid waste generated in industry from the aluminum mining and processing with known toxicity. Three concentrations of all tested solutions were applied and the damages observed were compared to negative and positive controls. It was observed an increase in the frequency of DNA damage for human leukocytes and plant cells, in all treatments. On human leukocytes, SPL induced the highest percentage of damage, with an average of 87.68%. For root tips cells of L. sativa the highest percentage of damage was detected for aluminum (93.89%). Considering the arbitrary units (AU), the average of nuclei with high levels of DNA fragmentation was significant for both cells type evaluated. The tested cells demonstrated equal effectiveness for detection of the genotoxicity induced by the SPL and its chemical components, aluminum and fluoride. Further, using a unique method, the comet assay, we proved that cells from root tips of Lactuca sativa represent a reliable model to detect DNA damage induced by genotoxic pollutants is in agreement of those observed in human leukocytes as model. So far, plant cells may be suggested as important system to assess the toxicological risk of environmental agents. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    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. Copyright © 2016. Published by Elsevier B.V.

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

    Science.gov (United States)

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Effect of chronic low dose natural radiation in human peripheral blood mononuclear cells: Evaluation of DNA damage and repair using the alkaline comet assay

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P.R. Vivek, E-mail: prvkumar06@gmail.com [Low Level Radiation Research Laboratory, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, IRE Campus, Beach Road, Kollam 691 001, Kerala (India); Seshadri, M. [Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Jaikrishan, G. [Low Level Radiation Research Laboratory, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, IRE Campus, Beach Road, Kollam 691 001, Kerala (India); Das, Birajalaxmi [Low Level Radiation Research Section, Radiation Biology and Health Sciences Division, Bio-Science Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2015-05-15

    Highlights: • Effect of chronic low dose natural radiation in radio adaptive response studied. • PBMCs of subjects from NLNRA and HLNRA were challenged with gamma radiation. • DNA damage and repair in PBMCs was compared using the alkaline comet assay. • Significant reduction in DNA damage in subjects of high dose group from HLNRA noted. • Probable induction of an in vivo radio adaptive response in subjects from HLNRA. - Abstract: This study investigates whether peripheral blood mononuclear cells (PBMCs) from inhabitants of Kerala in southwest India, exposed to chronic low dose natural radiation in vivo (>1 mSv year{sup −1}), respond with a radioadaptive response to a challenging dose of gamma radiation. Toward this goal, PBMCs isolated from 77 subjects from high-level natural radiation areas (HLNRA) and 37 subjects from a nearby normal level natural radiation area (NLNRA) were challenged with 2 Gy and 4 Gy gamma radiation. Subjects from HLNRA were classified based on the mean annual effective dose received, into low dose group (LDG) and high dose group (HDG) with mean annual effective doses of 2.69 mSv (N = 43, range 1.07 mSv year{sup −1} to 5.55 mSv year{sup −1}) and 9.62 mSv (N = 34, range 6.07 mSv year{sup −1} to17.41 mSv year{sup −1}), respectively. DNA strand breaks and repair kinetics (at 7 min, 15 min and 30 min after 4 Gy) were evaluated using the alkaline single cell gel electrophoresis (comet) assay. Initial levels of DNA strand breaks observed after either a 2 Gy or a 4 Gy challenging dose were significantly lower in subjects of the HDG from HLNRA compared to subjects of NLNRA (2 Gy, P = 0.01; 4 Gy, P = 0.02) and LDG (2 Gy P = 0.01; 4 Gy, P = 0.05). Subjects of HDG from HLNRA showed enhanced rejoining of DNA strand breaks (HDG/NLNRA, P = 0.06) during the early stage of repair (within 7 min). However at later times a similar rate of rejoining of strand breaks was observed across the groups (HDG, LDG and NLNRA). Preliminary results from

  18. Ecogenotoxicity testing of aquatic environment by comet assay in plants

    Directory of Open Access Journals (Sweden)

    Anita Mukherjee

    2015-05-01

    Full Text Available One of the goals of environmental monitoring is the detection of potentially hazardous compounds in water. We have set up a standard method to apply the Comet assay in aquatic plants that could be of great interest to evaluate cytotoxicity, genotoxicity and oxidative stress on the same species regarded as most sensitive to environmental pollutants. The aim of the present study was to set up of standardized procedure to evaluate genotoxicity in aquatic plants- Ceratophyllum demersum one that is submerged free floating and the other is Lemna minor - a fresh water floating plant by Comet assay. Electrophoresis and unwinding times were adapted to obtain minimum DNA migration evaluated as tail intensity % or tail moment in the control group and, at the same time maximum sensitivity for DNA damage with known genotoxicants. We further investigated the cytotoxicity and oxidative stress induced in the same species. Based on the repeatability of results obtained we suggest that Ceratophyllum, Lemna can serve as model species and Comet assay could be adopted to monitor the eco-genotoxicity of water pollutants.

  19. Fluorescence in situ hybridization in combination with the comet assay and micronucleus test in genetic toxicology

    Directory of Open Access Journals (Sweden)

    Hovhannisyan Galina G

    2010-09-01

    Full Text Available Abstract Comet assay and micronucleus (MN test are widely applied in genotoxicity testing and biomonitoring. While comet assay permits to measure direct DNA-strand breaking capacity of a tested agent MN test allows estimating the induced amount of chromosome and/or genome mutations. The potential of these two methods can be enhanced by the combination with fluorescence in situ hybridization (FISH techniques. FISH plus comet assay allows the recognition of targets of DNA damage and repairing directly. FISH combined with MN test is able to characterize the occurrence of different chromosomes in MN and to identify potential chromosomal targets of mutagenic substances. Thus, combination of FISH with the comet assay or MN test proved to be promising techniques for evaluation of the distribution of DNA and chromosome damage in the entire genome of individual cells. FISH technique also permits to study comet and MN formation, necessary for correct application of these methods. This paper reviews the relevant literature on advantages and limitations of Comet-FISH and MN-FISH assays application in genetic toxicology.

  20. ASTRO Research Fellow Presentation - A comparison of the comet assay and pulsed-field gel electrophoresis as a predictive assay for radiosensitivity in human fibroblasts

    International Nuclear Information System (INIS)

    Sarkaria, Jann N.; Eady, John J.; Peacock, John H.; Steel, G. Gordon

    1996-01-01

    Purpose/Objective: To determine whether neutral lysis single-cell gel electrophoresis (comet assay) or pulsed-field gel electrophoresis (PFGE) can be used as a predictive assay for tissue response to radiotherapy as an alternative to clonogenic survival measurements. Materials and Methods: The comet assay has been widely used to measure DNA double strand breaks (dsb) in individual cells, and it has been suggested that it could be used as an alternative to clonogenic assays to measure radiosensitivity. Previous studies in this lab have demonstrated the ability of pulsed-field gel electrophoresis, which also measures DNA dsb, to accurately predict the radiosensitivity of a panel of fibroblasts based on determination of residual DNA dsb. As part of an ongoing study examining the relationship between fibroblast radiosensitivity and normal-tissue radiation reactions, we have compared the sensitivity and accuracy of the comet assay and PFGE on a different panel of non-transformed fibroblasts derived from breast cancer patients who developed severe radiation late effects and from case-matched controls. For the measurement of initial damage, cells were suspended in PBS and irradiated on ice for the comet assay and irradiated in agarose plugs on ice for pFGE. Residual damage was measured following irradiation of confluent cultures at 37 degree sign C and subsequent incubation for four hours prior to preparation of agarose slides and plugs. All irradiations were performed with a 59 TBq 60 Co source at a dose rate of 1.7 Gy/min. Electrophoresis was performed following neutral pH cell lysis. Comet images were captured and analyzed using Optimas software with DNA damage quantitated by the comet moment. PFGE gels were analyzed using a phosphor-image analysis system and damage was quantitated based on the percent of activity released from the well. Results: The comet assay was able to detect initial DNA damage at a threshold of 5 Gy and exhibited a linear dose

  1. Systematic random sampling of the comet assay.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2014-11-23

    The comet assay is a fluorescent microscopic method that is able to detect DNA strand-breaks even in non-proliferative cells in samples with low cell counts. The aim of the authors was to measure genotoxic DNA damage and assess oxidative DNA damage caused by occupational exposure in groups exposed to benzene, polycyclic aromatic carbohydrates and styrene at the workplace in order to clarify whether the comet assay can be used as an effect marker tool in genotoxicology monitoring. In addition to the basic steps of the comet assay, one sample was treated with formamido-pirimidine-DNA-glycolase restriction-enzyme that measures oxidative DNA damage. An increase was observed in tail moments in each group of untreated and Fpg-treated samples compared to the control. It can be concluded that occupational exposure can be detected with the method. The comet assay may prove to be an excellent effect marker and a supplementary technique for monitoring the presence or absence of genotoxic effects.

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

    Science.gov (United States)

    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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Comet assay. Pt.1. Theory and practice

    International Nuclear Information System (INIS)

    Kruszewski, M.; Wojewodzka, M.; Iwanenko, T.

    1996-01-01

    Comet assay is a new method for measuring DNA breakage in a single cell. The main applications of the method are estimation of DNA single and double strand breaks, oxidative damage, pyrimidine dimers and (6-4)photoproducts, DNA-DNA and DNA-protein crosslinks. The method is used for studying DNA damage and its repair. (author).19 refs, 9 figs

  5. Detection of Hypoxia in Human Brain Tumor Xenografts Using a Modified Comet Assay

    Directory of Open Access Journals (Sweden)

    Jingli Wang

    2003-07-01

    Full Text Available We used the standard comet assay successfully to generate in vitro dose-response curves under oxic and hypoxic conditions. We then made mixtures of cells that had been irradiated with 3 and 9 Gy of X-rays to simulate two subpopulations in a tumor, but efforts to accurately detect and quantify the subpopulations using the standard comet assay were unsuccessful. Therefore, we investigated a modified comet assay to determine whether it could be used for measuring hypoxia in our model systems. U251 MG cells were grown as subcutaneous tumors in athymic mice; U251 MG and U87 MG cells were grown as intracerebral (i.c. tumors in athymic rats. Animals were injected with RSU 1069, irradiated, and euthanized. Tumors and normal brains were removed, and the cells were analyzed using a modified comet assay. Differences in comet tail moment distributions between tumor and contralateral normal brain, using tail moments at either the 25th or 50th percentile in each distribution, were taken as measures of the degree of tumor hypoxia. For U251 MG tumors, there was a positive relationship between tumor size and the degree of hypoxia, whereas preliminary data from U87 MG i.c. tumors showed less hypoxia and no apparent relationship between tumor size and hypoxia.

  6. Measuring oxidative damage to DNA and its repair with the comet assay.

    Science.gov (United States)

    Collins, Andrew R

    2014-02-01

    Single cell gel electrophoresis, or the comet assay, was devised as a sensitive method for detecting DNA strand breaks, at the level of individual cells. A simple modification, incorporating a digestion of DNA with a lesion-specific endonuclease, makes it possible to measure oxidised bases. With the inclusion of formamidopyrimidine DNA glycosylase to recognise oxidised purines, or Nth (endonuclease III) to detect oxidised pyrimidines, the comet assay has been used extensively in human biomonitoring to monitor oxidative stress, usually in peripheral blood mononuclear cells. There is evidence to suggest that the enzymic approach is more accurate than chromatographic methods, when applied to low background levels of base oxidation. However, there are potential problems of over-estimation (because the enzymes are not completely specific) or under-estimation (failure to detect lesions that are close together). Attempts have been made to improve the inter-laboratory reproducibility of the comet assay. In addition to measuring DNA damage, the assay can be used to monitor the cellular or in vitro repair of strand breaks or oxidised bases. It also has applications in assessing the antioxidant status of cells. In its various forms, the comet assay is now an invaluable tool in human biomonitoring and genotoxicity testing. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn. Copyright © 2013 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Antioxidants and the Comet assay.

    Science.gov (United States)

    Cemeli, Eduardo; Baumgartner, Adolf; Anderson, Diana

    2009-01-01

    It is widely accepted that antioxidants, either endogenous or from the diet, play a key role in preserving health. They are able to quench radical species generated in situations of oxidative stress, either triggered by pathologies or xenobiotics, and they protect the integrity of DNA from genotoxicants. Nevertheless, there are still many compounds with unclear or unidentified prooxidant/antioxidant activities. This is of concern since there is an increase in the number of compounds synthesized or extracted from vegetables to which humans might be exposed. Despite the well-established protective effects of fruit and vegetables, the antioxidant(s) responsible have not all been clearly identified. There might also be alternative mechanisms contributing to the protective effects for which a comprehensive description is lacking. In the last two decades, the Comet assay has been extensively used for the investigation of the effects of antioxidants and many reports can be found in the literature. The Comet assay, a relatively fast, simple, and sensitive technique for the analysis of DNA damage in all cell types, has been applied for the screening of chemicals, biomonitoring and intervention studies. In the present review, several of the most well-known antioxidants are considered. These include: catalase, superoxide dismutase, glutathione peroxidase, selenium, iron chelators, melatonin, melanin, vitamins (A, B, C and E), carotenes, flavonoids, isoflavones, tea polyphenols, wine polyphenols and synthetic antioxidants. Investigations showing beneficial as well as non-beneficial properties of the antioxidants selected, either at the in vitro, ex vivo or in vivo level are discussed.

  9. Slight hypercalcemia is not associated with positive responses in the Comet Assay in male rat liver.

    Science.gov (United States)

    Thiel, Anette; Hamel, Annie; Schaefer, Katrien; Cardoso, Renato; Beilstein, Paul

    2017-08-01

    Maintenance of physiological levels of intracellular and extracellular calcium is essential for life. Increased intracellular calcium levels are involved in cell death (apoptosis and necrosis) and are associated with positive responses in the Comet assay in vitro. In addition, high calcium and vitamin D intakes were reported to induce apoptosis in adipose tissue in obese mice and to increase DNA-migration in the Comet assay. To investigate increased serum concentration of calcium as a potential confounding factor in the regulatory Comet assay in vivo, we induced mild hypercalcemia in male Wistar rats by 3-day continuous intravenous infusion of calcium gluconate and performed the Comet assay in the liver in line with regulatory guidelines. The results of the study showed that mild increases in serum calcium concentration (up to 1.4 times above the concurrent control) and increased urinary calcium concentration (up to 27.8 times above the concurrent control) results in clinical signs like mild tremor, faster respiration rate and decreased activity in a few animals. However, under the conditions of the study, no increase in the %Tail DNA in the Comet assay and no indication of liver damage as determined by histopathological means were observed. Thus, mild increases in plasma calcium did not lead to positive results in a genotoxicity assessment by the Comet assay in the rat liver. This result is important as it confirms the reliability of this assay for regulatory evaluation of safety. Copyright © 2017 DSM Nutritional Products AG. Published by Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    2008-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Gajski, Goran [Institute for Medical Research and Occupational Health, Mutagenesis Unit, 10000 Zagreb (Croatia); Garaj-Vrhovac, Vera [Institute for Medical Research and Occupational Health, Mutagenesis Unit, 10000 Zagreb (Croatia); Orescanin, Visnja [Ruder Boskovic Institute, 10000 Zagreb (Croatia)

    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.

  12. The Role Of Sevoflurane And Ionising Radiation On THE Level Of Primary DNA Damage Measured In Blood And Different Organs Of Swiss Albino Mice By THE Alkaline Comet Assay

    International Nuclear Information System (INIS)

    Benkovic, V.; Milic, M.; Horvat Knezevic, A.; Halovanovic, S.; Borojevic, N.; Orsolic, N.

    2015-01-01

    Sevoflurane is general anaesthetic suitable for short surgical procedures due to its quick induction of anaesthesia, maintaining spontaneous breathing frequency and hemodynamic stability of patients. However, it can directly trigger the formation of peroxynitrite, significantly increase intracellular levels of H2O2, peroxide, superoxide anion and nitric oxide in peripheral polymorphonuclear neutrophils 1h after the treatment; lowering the levels of intracellular glutathione, and increase radiosensitivity of cells also exposed to ionising radiation (IR). We wanted to evaluate the level of sinergistic effect and possible radiosensitivity DNA damage in blood, and different organs of Swiss albino mice after exposure to both sevoflurane (2.4 percent, 50:50) and the 1Gy gamma-ray radiation generally used in diagnostic purposes after 0, 2, 6 and 24 hours from the combined treatment with alkaline comet assay. Combined exposure to sevoflurane and IR has demonstrated synergistic effect. Due to metabolising of the sevoflurane, there was different sensitivity between blood, liver, kidney and brain cells. (author).

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

    Science.gov (United States)

    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. Copyright © 2013 Wiley Periodicals, Inc.

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

    Science.gov (United States)

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. 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.

    Science.gov (United States)

    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. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

  16. The effect of different methods and image analyzers on the results of the in vivo comet assay.

    Science.gov (United States)

    Kyoya, Takahiro; Iwamoto, Rika; Shimanura, Yuko; Terada, Megumi; Masuda, Shuichi

    2018-01-01

    The in vivo comet assay is a widely used genotoxicity test that can detect DNA damage in a range of organs. It is included in the Organisation for Economic Co-operation and Development Guidelines for the Testing of Chemicals. However, various protocols are still used for this assay, and several different image analyzers are used routinely to evaluate the results. Here, we verified a protocol that largely contributes to the equivalence of results, and we assessed the effect on the results when slides made from the same sample were analyzed using two different image analyzers (Comet Assay IV vs Comet Analyzer). Standardizing the agarose concentrations and DNA unwinding and electrophoresis times had a large impact on the equivalence of the results between the different methods used for the in vivo comet assay. In addition, there was some variation in the sensitivity of the two different image analyzers tested; however this variation was considered to be minor and became negligible when the test conditions were standardized between the two different methods. By standardizing the concentrations of low melting agarose and DNA unwinding and electrophoresis times between both methods used in the current study, the sensitivity to detect the genotoxicity of a positive control substance in the in vivo comet assay became generally comparable, independently of the image analyzer used. However, there may still be the possibility that other conditions, except for the three described here, could affect the reproducibility of the in vivo comet assay.

  17. Validation of the 3D Skin Comet assay using full thickness skin models: Transferability and reproducibility.

    Science.gov (United States)

    Reisinger, Kerstin; Blatz, Veronika; Brinkmann, Joep; Downs, Thomas R; Fischer, Anja; Henkler, Frank; Hoffmann, Sebastian; Krul, Cyrille; Liebsch, Manfred; Luch, Andreas; Pirow, Ralph; Reus, Astrid A; Schulz, Markus; Pfuhler, Stefan

    2018-03-01

    Recently revised OECD Testing Guidelines highlight the importance of considering the first site-of-contact when investigating the genotoxic hazard. Thus far, only in vivo approaches are available to address the dermal route of exposure. The 3D Skin Comet and Reconstructed Skin Micronucleus (RSMN) assays intend to close this gap in the in vitro genotoxicity toolbox by investigating DNA damage after topical application. This represents the most relevant route of exposure for a variety of compounds found in household products, cosmetics, and industrial chemicals. The comet assay methodology is able to detect both chromosomal damage and DNA lesions that may give rise to gene mutations, thereby complementing the RSMN which detects only chromosomal damage. Here, the comet assay was adapted to two reconstructed full thickness human skin models: the EpiDerm™- and Phenion ® Full-Thickness Skin Models. First, tissue-specific protocols for the isolation of single cells and the general comet assay were transferred to European and US-American laboratories. After establishment of the assay, the protocol was then further optimized with appropriate cytotoxicity measurements and the use of aphidicolin, a DNA repair inhibitor, to improve the assay's sensitivity. In the first phase of an ongoing validation study eight chemicals were tested in three laboratories each using the Phenion ® Full-Thickness Skin Model, informing several validation modules. Ultimately, the 3D Skin Comet assay demonstrated a high predictive capacity and good intra- and inter-laboratory reproducibility with four laboratories reaching a 100% predictivity and the fifth yielding 70%. The data are intended to demonstrate the use of the 3D Skin Comet assay as a new in vitro tool for following up on positive findings from the standard in vitro genotoxicity test battery for dermally applied chemicals, ultimately helping to drive the regulatory acceptance of the assay. To expand the database, the validation will

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

    Science.gov (United States)

    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 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. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. DNA damage and repair assessed by comet assay in workers exposed to lead in a battery recycling.

    Directory of Open Access Journals (Sweden)

    Mahara Valverde

    2015-05-01

    In addition to these findings, DNA damage determined by comet assay was sensible to reflect lead exposure levels related to specific activities inside this factory. Human biomonitoring studies through comet assay could be robust when additional biomarkers are determined at time.

  20. High throughput comet assay to study genotoxicity of nanomaterials

    Directory of Open Access Journals (Sweden)

    Naouale El Yamani

    2015-06-01

    Full Text Available The unique physicochemical properties of engineered nanomaterials (NMs have accelerated their use in diverse industrial and domestic products. Although their presence in consumer products represents a major concern for public health safety, their potential impact on human health is poorly understood. There is therefore an urgent need to clarify the toxic effects of NMs and to elucidate the mechanisms involved. In view of the large number of NMs currently being used, high throughput (HTP screening technologies are clearly needed for efficient assessment of toxicity. The comet assay is the most used method in nanogenotoxicity studies and has great potential for increasing throughput as it is fast, versatile and robust; simple technical modifications of the assay make it possible to test many compounds (NMs in a single experiment. The standard gel of 70-100 μL contains thousands of cells, of which only a tiny fraction are actually scored. Reducing the gel to a volume of 5 μL, with just a few hundred cells, allows twelve gels to be set on a standard slide, or 96 as a standard 8x12 array. For the 12 gel format, standard slides precoated with agarose are placed on a metal template and gels are set on the positions marked on the template. The HTP comet assay, incorporating digestion of DNA with formamidopyrimidine DNA glycosylase (FPG to detect oxidised purines, has recently been applied to study the potential induction of genotoxicity by NMs via reactive oxygen. In the NanoTEST project we investigated the genotoxic potential of several well-characterized metal and polymeric nanoparticles with the comet assay. All in vitro studies were harmonized; i.e. NMs were from the same batch, and identical dispersion protocols, exposure time, concentration range, culture conditions, and time-courses were used. As a kidney model, Cos-1 fibroblast-like kidney cells were treated with different concentrations of iron oxide NMs, and cells embedded in minigels (12

  1. Detection of irradiation treatment of foods using DNA 'comet assay'

    International Nuclear Information System (INIS)

    Khan, Hasan M.; Delincee, Henry

    1998-01-01

    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

  2. Evaluation through comet assay of DNA damage induced in human lymphocytes by alpha particles. Comparison with protons and Co-60 gamma rays

    International Nuclear Information System (INIS)

    Di Giorgio, M.; Kreiner, A. J.; Schuff, J. A.; Vallerga, M. B.; Taja, M. R.; Lopez, F. O.; Alvarez, D. E.; Saint Martin, G.; Burton, A.; Debray, M. E.; Kesque, J. M.; Somacal, H.; Stoliar, P.; Valda, A.; Davidson, J.; Davidson, M.; Ozafran, M. J.; Vazquez, M. E.

    2004-01-01

    Several techniques with different sensitivity to single-strand breaks and/or double strand breaks were applied to detect DNA breaks generated by high LET particles. Tests that assess DNA damage in single cells might be the appropriate tool to estimate damage induced by particles, facilitating the assessment of heterogeneity of damage in a cell population. The microgel electrophoresis (comet) assay is a sensitive method for measuring DNA damage in single cells. The objective of this work was to evaluate the proficiency of comet assay to assess the effect of high LET radiation on peripheral blood lymphocytes, compared to protons and Co-60 gamma rays. Materials and methods: Irradiations of blood samples were performed at TANDAR laboratory (Argentina). Thin samples of human peripheral blood were irradiated with different doses (0-2.5 Gy) of 20.2 MeV helium-4 particles in the track segment mode, at nearly constant LET. Data obtained were compared with the effect induced by a MeV protons and Co-60 gamma rays. Alkaline comet assay was applied. Comets were quantified by the Olive tail moment. Distribution of the helium-4 particle and protons were evaluated considering Poisson distribution in lymphocyte nuclei. The mean dose per nucleus per particle result 0.053 Gy for protons and 0.178 Gy for helium-4 particles. When cells are exposed to a dose of 0.1 Gy, the hit probability model predicts that 43% of the nuclei should have experienced and alpha traversal while with protons, 85% of the nuclei should be hit. The experimental results show a biphasic response for helium-4 particles (0.1 Gy), indicating the existence of two subpopulations: unhit and hit. Distributions of tail moment as a function of fluence and experimental dose for comets induced by helium-4 particles, protons and Co-60 gamma rays were analyzed. With helium-4 irradiations, lymphocyte nuclei show an Olive tail moment distribution flattened to higher tail moments a dose increase. However, for irradiations with

  3. DNA damage in isolated rat hepatocytes exposed to C.I. pigment orange 5 and C.I. pigment yellow 12 by the alkaline comet assay

    DEFF Research Database (Denmark)

    Møller, P; Wallin, Håkan; Grunnet, N

    1998-01-01

    The induction of DNA damage by commonly used printing ink pigments, C.I. pigment orange 5 (C.I. 12075) and C.I. pigment yellow 12 (C.I. 21090), was investigated in freshly isolated rat hepatocytes with the comet assay. C.I. pigment yellow 12 is a 3,3'-dichlorobenzidine-based diarylide pigment...

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

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    Musa, Marahaini; Ponnuraj, Kannan Thirumulu; 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. (paper)

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

    Science.gov (United States)

    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. © 2015 Wiley Periodicals, Inc.

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

    Science.gov (United States)

    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

  8. Detection of irradiated onion by means of the comet assay

    International Nuclear Information System (INIS)

    Moreno Alvarez, Damaris L.; Prieto Miranda, Enrique Fco.; Carro Palacio, Sandra; Iglesia Enriquez, Isora

    2007-01-01

    The ionizing radiations are used as a harmless alternative treatment that it substitutes the employment of chemical treatments, which after their application in the food products can remain residuals not desired that they come to be carcinogenic. With the food irradiation is eliminated microorganisms and the storage time is prolonged, which produces benefits for the Food Industry and the consumers. In many countries the search of sensitive detecting methods of irradiated foods is promoted by the necessity of the assurance of the consumption of foods with nutritional quality and to test directly the radiation processing, for which several techniques have been developed, these are based on the changes that induce the ionizing radiations in the food products. A recommended method is the Comet Assay of DNA, it is approved by the European Committee of Standardization (EN 13784). The DNA molecule is very sensitive to gamma radiations even at low radiation dose, where the modifications produced in the molecule can be monitored for this analytical technique well-known as Comet Assay of DNA or Single Cell Gel Electrophoresis. The objective of the present paper was to evaluate the modifications of the DNA molecule of irradiated onions with the Comet Assay for several dose values, the onions were conserved at environment and refrigeration temperatures. The samples were irradiated in a self-shielding irradiator with 60 Co source, dose rate of 20.45 Gy/min and absorbed dose values of 0.5; 0.6; 0.8 and 1.0 kGy. This detection method demonstrates to be one sensitive and quick technique for the qualitative detection of irradiated onions. (author)

  9. Detection of DNA damage in mussels and sea urchins exposed to crude oil using comet assay

    International Nuclear Information System (INIS)

    Taban, I.C.; Bechmann, R.K.; Torgrimsen, S.; Baussant, T.; Sanni, S.

    2004-01-01

    The single-cell microgel electrophoresis assay or the comet assay was used to evaluate DNA damage of dispersed crude oil on sea urchins (Strongylocentrotus droebachiensis) and mussels (Mytilus edulis L.). Sea urchins were exposed to 0.06 and 0.25 mg/L dispersed crude oil in a continuous flow system, while the mussels were exposed to 0.015, 0.06 and 0.25 mg/L dispersed crude oil. Sea urchin coelomocytes and mussel haemocytes were sampled after 4 and 5 weeks exposure, respectively. In the sea urchin coelomocytes, there was a significant concentration-related increase in the percentage of DNA in comet tail. In mussel haemocytes, there was a significantly higher percentage of DNA in comet tail for all treatments compared to the control. The responses were concentration-related up to 0.06 mg/L oil. The two highest exposure concentrations of mussels were not significantly different from each other. These results indicate that the comet assay can be used for biomonitoring of DNA damage in marine invertebrates following oil contamination. (author)

  10. A Bayesian, generalized frailty model for comet assays.

    Science.gov (United States)

    Ghebretinsae, Aklilu Habteab; Faes, Christel; Molenberghs, Geert; De Boeck, Marlies; Geys, Helena

    2013-05-01

    This paper proposes a flexible modeling approach for so-called comet assay data regularly encountered in preclinical research. While such data consist of non-Gaussian outcomes in a multilevel hierarchical structure, traditional analyses typically completely or partly ignore this hierarchical nature by summarizing measurements within a cluster. Non-Gaussian outcomes are often modeled using exponential family models. This is true not only for binary and count data, but also for, example, time-to-event outcomes. Two important reasons for extending this family are for (1) the possible occurrence of overdispersion, meaning that the variability in the data may not be adequately described by the models, which often exhibit a prescribed mean-variance link, and (2) the accommodation of a hierarchical structure in the data, owing to clustering in the data. The first issue is dealt with through so-called overdispersion models. Clustering is often accommodated through the inclusion of random subject-specific effects. Though not always, one conventionally assumes such random effects to be normally distributed. In the case of time-to-event data, one encounters, for example, the gamma frailty model (Duchateau and Janssen, 2007 ). While both of these issues may occur simultaneously, models combining both are uncommon. Molenberghs et al. ( 2010 ) proposed a broad class of generalized linear models accommodating overdispersion and clustering through two separate sets of random effects. Here, we use this method to model data from a comet assay with a three-level hierarchical structure. Although a conjugate gamma random effect is used for the overdispersion random effect, both gamma and normal random effects are considered for the hierarchical random effect. Apart from model formulation, we place emphasis on Bayesian estimation. Our proposed method has an upper hand over the traditional analysis in that it (1) uses the appropriate distribution stipulated in the literature; (2) deals

  11. In vitro mutagenicity and genotoxicity study of 1,2-dichloroethylene, 1,1,2-trichloroethane, 1,3-dichloropropane, 1,2,3-trichloropropane and 1,1,3-trichloropropene, using the micronucleus test and the alkaline single cell gel electrophoresis technique (comet assay) in human lymphocytes.

    Science.gov (United States)

    Tafazoli, M; Kirsch-Volders, M

    1996-12-20

    The main objective of this study was to compare the cytotoxic genotoxic and mutagenic activity of a number of chlorinated aliphatic hydrocarbons, which are widely used as chemical intermediates, solvents, degreasing agents etc. in industry, and to establish the structure-toxicity relationship of the chemicals by using the most adequate determinants in estimating their toxicity. The mutagenicity and cytotoxicity of some of the candidate chemicals, namely 1,2-dichloroethylene, 1,1,2-trichloroethane, 1,3-dichloropropane, 1,2,3-trichloropropane and 1,1,3-trichloropropene were evaluated in an in vitro micronucleus assay. The cytokinesis-block methodology was applied on human lymphocytes in the presence or absence of an external metabolic activation system (S9-mix). In the micronucleus assay, all test substances, except 1,2,3-trichloropropane with and without S9-mix and 1,1,2-trichloroethane without S9-mix in the repeated experiment, exhibited a low but statistically significant mutagenic activity, compared to the concurrent control. However, none of the five chemicals was able to induce a clear and reproducible linear dose-dependent increase in micronucleus frequencies in this assay. Generally, mutagenic activity of the chemicals was found in the absence of severe cytotoxicity and/or cell cycle delay. The DNA breakage capacity and the cytotoxicity of these chemicals were also assessed in the alkaline single cell gel (SCG) electrophoresis test (comet assay) with and without S9-mix in isolated human lymphocytes. All chemical compounds induced DNA breakage, in the presence or absence of the metabolic activation system, at the doses tested. The data showed that the DNA reactivity of the chemicals increased with increasing degree of halogenation. The results of the present work suggested that the comet assay might be a more suitable and sensitive screening method than the micronucleus test for this particular class of compound. However, both assays do detect different

  12. Hepatocytes, rather than leukocytes reverse DNA damage in vivo induced by whole body y-irradiation of mice, as shown by the alkaline comet assay

    Directory of Open Access Journals (Sweden)

    JUANA PINCHEIRA

    2008-01-01

    Full Text Available DNA damage repair was assessed in quiescent (G0 leukocytes and in hepatocytes of mice, after 1 and 2 hours recovery from a single whole body y-irradiation with 0.5, 1 or 2 Gy. Evaluation of single-strand breaks (SSB and alkali-labile sites together were carried out by a single-cell electrophoresis at pH>13.0 (alkaline comet assay. In non-irradiated (control mice, the constitutive, endogenous DNA damage (basal was around 1.5 times higher in leukocytes than in hepatocytes. Irradiation immediately increased SSB frequency in both cell types, in a dose-dependent manner. Two sequential phases took place during the in vivo repair of the radio-induced DNA lesions. The earliest one, present in both hepatocytes and leukocytes, further increased the SSB frequency, making evident the processing of some primary lesions in DNA bases into the SSB repair intermediates. In a second phase, SSB frequency decreased because of their removal. In hepatocytes, such a frequency regressed to the constitutive basal level after 2 hours recovery from either 0.5 orí Gy. On the other hand, the SSB repair phase was specifically abrogated in leukocytes, at the doses and recovery times analyzed. Thus, the efficiency of in vivo repair of radio-induced DNA damage in dormant cells (lymphocytes is quite different from that in hepatocytes whose low proliferation activity accounts only for cell renewal.

  13. Factors influencing heterogeneity of radiation-induced DNA-damage measured by the alkaline comet assay

    International Nuclear Information System (INIS)

    Seidel, Clemens; Lautenschläger, Christine; Dunst, Jürgen; Müller, Arndt-Christian

    2012-01-01

    To investigate whether different conditions of DNA structure and radiation treatment could modify heterogeneity of response. Additionally to study variance as a potential parameter of heterogeneity for radiosensitivity testing. Two-hundred leukocytes per sample of healthy donors were split into four groups. I: Intact chromatin structure; II: Nucleoids of histone-depleted DNA; III: Nucleoids of histone-depleted DNA with 90 mM DMSO as antioxidant. Response to single (I-III) and twice (IV) irradiation with 4 Gy and repair kinetics were evaluated using %Tail-DNA. Heterogeneity of DNA damage was determined by calculation of variance of DNA-damage (V) and mean variance (Mvar), mutual comparisons were done by one-way analysis of variance (ANOVA). Heterogeneity of initial DNA-damage (I, 0 min repair) increased without histones (II). Absence of histones was balanced by addition of antioxidants (III). Repair reduced heterogeneity of all samples (with and without irradiation). However double irradiation plus repair led to a higher level of heterogeneity distinguishable from single irradiation and repair in intact cells. Increase of mean DNA damage was associated with a similarly elevated variance of DNA damage (r = +0.88). Heterogeneity of DNA-damage can be modified by histone level, antioxidant concentration, repair and radiation dose and was positively correlated with DNA damage. Experimental conditions might be optimized by reducing scatter of comet assay data by repair and antioxidants, potentially allowing better discrimination of small differences. Amount of heterogeneity measured by variance might be an additional useful parameter to characterize radiosensitivity

  14. Inhibition of nucleotide excision repair by fludarabine in normal lymphocytes in vitro, measured by the alkaline single cell gel electrophoresis (comet) assay

    Energy Technology Data Exchange (ETDEWEB)

    Yamauchi, Takahiro; Kawai, Yasukazu; Ueda, Takanori [Fukui Medical Univ., Matsuoka (Japan)

    2002-05-01

    Alkylating agents or platinum analogues initiate several excision repair mechanisms, which involve incision of the DNA strand, excision of the damaged nucleotide, gap filling by DNA resynthesis, and rejoining by ligation. The previous study described that nucleotide excision repair permitted incorporation of fludarabine nucleoside (F-area-A) into the repair patch, thereby inhibiting the DNA resynthesis. In the present study, to clarify the repair kinetics in view of the inhibition by F-ara-A, normal lymphocytes were stimulated to undergo nucleotide excision repair by ultraviolet C (UV) irradiation in the presence or absence of F-ara-A. The repair kinetics were determined as DNA single strand breaks resulting from the incision and the rejoining using the alkaline single cell gel electrophoresis (comet) assay. DNA resynthesis was evaluated in terms of the uptake of tritiated thymidine into DNA. The lymphocytes initiated the incision step maximally at 1 h, and completed the rejoining process within 4 h after UV exposure. UV also initiated thymidine uptake, which increased time-dependently and reached a plateau at 4 h. A 2-h pre-incubation with F-ara-A inhibited the repair in a concentration-dependent manner, with the maximal inhibition by 5 {mu}M. This inhibitory effect was demonstrated by the reduction of the thymidine uptake and by the inhibition of the rejoining. A DNA polymerase inhibitor, aphidicolin, and a ribonucleotide reductase inhibitor, hydroxyurea, were not so inhibitory to the repair process as F-ara-A at equimolar concentrations. The present findings suggest that inhibition of nucleotide excision repair may represent a novel therapeutic strategy against cancer, especially in the context of resistant cells with an increased repair capacity. (author)

  15. Identification of radiation treatment of foods using novel technique of 'DNA comet assay'

    International Nuclear Information System (INIS)

    Khan, A.A.; Khan, H.M.; Wasim, M.A.

    2005-01-01

    Treatment of food using ionizing radiation is being progressively used in many countries to inactivate food pathogens, to eradicate pests and to extend shelf life thereby contributing to safer and more plentiful food supply. Food control agencies throughout the world need some reliable, simple and rapid methods for the detection foods to ensure free choice of consumer and to enforce labeling. The DNA comet assay offers great potential as a rapid tool to screen irradiated and unirradiated samples of several kinds of foods. In the present study samples of fresh and frozen beef has investigated for the detection of irradiation treatment. The samples were subjected to radiation doses of 0,4.5 and 7 KGy and were stored in freezer before analysis. The cells were extracted into cold PBS solutions, embedded into agarose gel on microscope slides, lysed and eletrophoressed at a voltage of 2V/cm for 2 minutes. The fragmented DNA as a irradiation treatment was stretched in the gel producing the dose dependent comets. These comets were visible using a simple transmission microscope after silver staining. The controlled and irradiation samples of meat were clearly distinguishable on the basis of the stained patterns of DNA in from of round or conical intact cells for unirradiated samples or in from of comets for irradiated samples. It is therefore concluded that DNA comet Assay offers a potential to screen unirradiated and irradiated meat samples. (author)

  16. Detection of radiation treatment of meat by novel techniques of DNA comet assay

    International Nuclear Information System (INIS)

    Khan, A.A.; Khan, H.M.

    2002-01-01

    Treatment of food to ionizing radiation is being progressively used in many countries to inactivate food pathogens, to eradicate pests and to extend shelf life; thereby contributing to safer and more plentiful food supply. Food control agencies throughout the world need some reliable, simple and rapid methods for detection of irradiated foods to ensure free choice of consumer and to enforce labeling. The DNA comet assay offers great potential as a rapid tool to screen irradiated and unirradiated samples of several kinds of foods. In the present study, frozen beef has been investigated for detection of irradiation treatment. The samples were subjected to radiation doses of 0,4,5 and 7.0 kGy and were stored in freezer before analysis. The cells were extracted into cold PBS solutions, embedded into the agarose gel on microscope slides, lysed and electrophoressed at a voltage of 2v/cm for 2 min. The fragmented DNA as a result of irradiation treatment was stretched in the gel producing the dose dependent comets. These comets were visible using a simple transmission microscope after silver staining. The controlled and irradiated samples of meat were clearly distinguishable on the basis of the stained patterns of DNA in form of round or conical intact cells for unirradiated samples or in form of comets for irradiated samples. It is therefore, concluded that 'DNA Comet Assay' offers a potential to screen unirradiated and irradiated meat samples. (author)

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

    Science.gov (United States)

    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 earthworms. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    Qiang Liu

    2013-11-01

    Full Text Available 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.

  20. Protective effects of aqueous and ethanolic extracts of Portulaca oleracea L. aerial parts on H2O2-induced DNA damage in lymphocytes by comet assay.

    Science.gov (United States)

    Behravan, Javad; Mosafa, Fatemeh; Soudmand, Negar; Taghiabadi, Elahe; Razavi, Bibi Marjan; Karimi, Gholamreza

    2011-09-01

    The comet assay is a standard method for measuring DNA damage. In this study, the protective effects of ethanolic and aqueous extracts of Portulaca oleracea L. (P. oleracea) on human lymphocyte DNA lesions were evaluated with the comet assay. Lymphocytes were isolated from blood samples taken from healthy volunteers. Human lymphocytes were incubated in H(2)O(2) (50,100, and 200 μM), aqueous extract (0.05, 0.1, 0.5, 1, and 2.5mg/ml), and ethanolic extracts (0.05, 0.1, 0.5, 1, and 2.5mg/ml) of P. oleraceae aerial parts alone with a combination of H(2)O(2) (100 μM) with either 1 or 2.5mg/ml of both extracts at 4°C for 30 minutes. The extent of DNA migration was measured using the alkaline single cell gel electrophoresis approach assay, and DNA damage was expressed as percentage tail DNA. We found that the aqueous extract of P. oleracea significantly inhibited DNA damage, while there was no effect of the ethanolic extract. These data suggest that the aqueous extract of P. oleracea can prevent oxidative DNA damage to human lymphocytes, which is likely due to antioxidant constituents in the extract. Copyright © 2011. Published by Elsevier B.V.

  1. Detection of irradiation treatment of foods using DNA 'comet assay'

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Hasan M.; Delincee, 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.

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

    Science.gov (United States)

    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  0.05). 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.

  3. Single Cell Analysis of Human RAD18-Dependent DNA Post-Replication Repair by Alkaline Bromodeoxyuridine Comet Assay

    Science.gov (United States)

    Mórocz, Mónika; Gali, Himabindu; Raskó, István; Downes, C. Stephen; Haracska, Lajos

    2013-01-01

    Damage to DNA can block replication progression resulting in gaps in the newly synthesized DNA. Cells utilize a number of post-replication repair (PRR) mechanisms such as the RAD18 controlled translesion synthesis or template switching to overcome the discontinuities formed opposite the DNA lesions and to complete DNA replication. Gaining more insights into the role of PRR genes promotes better understanding of DNA damage tolerance and of how their malfunction can lead to increased genome instability and cancer. However, a simple and efficient method to characterise gene specific PRR deficiencies at a single cell level has not been developed. Here we describe the so named BrdU comet PRR assay to test the contribution of human RAD18 to PRR at a single cell level, by which we kinetically characterized the consequences of the deletion of human RAD18 on the replication of UV-damaged DNA. Moreover, we demonstrate the capability of our method to evaluate PRR at a single cell level in unsynchronized cell population. PMID:23936422

  4. Factors influencing heterogeneity of radiation-induced DNA-damage measured by the alkaline comet assay

    Directory of Open Access Journals (Sweden)

    Seidel Clemens

    2012-04-01

    Full Text Available Abstract Background To investigate whether different conditions of DNA structure and radiation treatment could modify heterogeneity of response. Additionally to study variance as a potential parameter of heterogeneity for radiosensitivity testing. Methods Two-hundred leukocytes per sample of healthy donors were split into four groups. I: Intact chromatin structure; II: Nucleoids of histone-depleted DNA; III: Nucleoids of histone-depleted DNA with 90 mM DMSO as antioxidant. Response to single (I-III and twice (IV irradiation with 4 Gy and repair kinetics were evaluated using %Tail-DNA. Heterogeneity of DNA damage was determined by calculation of variance of DNA-damage (V and mean variance (Mvar, mutual comparisons were done by one-way analysis of variance (ANOVA. Results Heterogeneity of initial DNA-damage (I, 0 min repair increased without histones (II. Absence of histones was balanced by addition of antioxidants (III. Repair reduced heterogeneity of all samples (with and without irradiation. However double irradiation plus repair led to a higher level of heterogeneity distinguishable from single irradiation and repair in intact cells. Increase of mean DNA damage was associated with a similarly elevated variance of DNA damage (r = +0.88. Conclusions Heterogeneity of DNA-damage can be modified by histone level, antioxidant concentration, repair and radiation dose and was positively correlated with DNA damage. Experimental conditions might be optimized by reducing scatter of comet assay data by repair and antioxidants, potentially allowing better discrimination of small differences. Amount of heterogeneity measured by variance might be an additional useful parameter to characterize radiosensitivity.

  5. Detection of xenobiotic-induced DNA damage by the comet assay applied to human and rat precision-cut liver slices

    NARCIS (Netherlands)

    Plazar, Janja; Hrejac, Irena; Pirih, Primoz; Filipic, Metka; Groothuis, Geny M. M.

    The comet assay is a simple and sensitive method for measuring DNA damage at the level of individual cells and is extensively used in genotoxicity studies. It is commonly applied to cultured cells. The aim of this study was to apply the comet assay for use in fresh liver tissue, where metabolic

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

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, M.M. E-mail: villavic@net.ipen.br; Marin-Huachaca, N.S.; Mancini-Filho, J. E-mail: jmancini@usp.br; Delincee, H.; Villavicencio, A.L.C.H. E-mail: henry.delincee@bfe.uni-karlsruhe.de

    2004-10-01

    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 {sup 60}Co source, Gammacell 220 (A.E.C.L.) installed in IPEN (Sao Paulo, Brazil). The doses given were 0, 1.5, 3.0 and 4.5 kGy for refrigerated samples. Immediately after irradiation the samples were returned to the refrigerator (6 deg. 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.

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

    Science.gov (United States)

    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.

  8. The DNA comet assay and the germination test in detection of food treated by ionizing radiation

    International Nuclear Information System (INIS)

    Huachaca, Nelida Simona Marin

    2002-01-01

    Two methods of irradiated food detection, one biochemical, the comet assay and, other biological, the germination test, were applied in bovine meat and fruit samples. The comet assay detects the damage on DNA caused by ionizing radiation. The germination test evaluates the sensitivity to radiation of seeds as for germination ability, shooting and, rooting. The samples were irradiated in gamma font and electron accelerator. For bovine meat samples, the doses were 0.0; 2.5; 4.5 e 7.0 kGy at chilled condition and, 0.0; 2.5; 4.5; 7.0 e 8.5 kGy at frozen conditions. For fruit samples such as melon, watermelon, apple, orange, papaya and, tomato, the doses were: 0.0; 0.5; 0.75; 1.0; 2.0 e 4.0 kGy. The differences between the gamma rays and the electron beam effects on extent of DNA migration and, on shooting and rooting, showed to be similar. The comet assay, under neutral conditions, permitted to discriminate between irradiated and unirradiated bovine meat samples, until one month of storage. Also, it was possible to distinguish, by the comet assay, the control sample with regard to irradiated fruit, at doses as low as 0,5 kGy. In the germination test, the root length was the best parameter to discriminate irradiated and unirradiated samples of melon, watermelon and tomato, while the germination percent was the best parameter for apple and orange. (author)

  9. Capability for identification of gamma-irradiated bovine liver by new high sensitivity comet assay

    International Nuclear Information System (INIS)

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

    2000-01-01

    DNA in food will sustain damage by gamma radiation. The detection capability of the high sensitivity comet assay was studied using fluorescence-microscopy. Beef liver was irradiated at a range of 1 Gy to 8 kGy. Single cells were obtained from the irradiated liver, then analyzed by agaros-gel electrophoresis. The pH of the buffer for electrophoresis was pH 13, which is generally utilized for sensitive detection of DNA damage. The pattern formed by DNA was visualized by staining with ethidium bromide. The resulting comets were evaluated with a scale we developed, and Influence Scores were calculated based on the Tice method. It is possible to detect irradiation damage to beef liver at 10 Gy. Together with Influence Score, histogram of comet type is used for detection of irradiation. We elucidated those histograms were useful for distinguishing damage caused by irradiation from that of others. DNA damage can be caused not only by irradiation, but also by the other treatments. Therefore, the respective influences of freezing, preservation, irradiating temperature, atmosphere of irradiation, cooking, and homogenizing devices were also examined. This new comet assay will be a useful method of detecting DNA damage to identify irradiated foods. (author)

  10. DNA comet assay for rice seeds treated with low energy electrons ('soft-electrons')

    International Nuclear Information System (INIS)

    Todoriki, Setsuko; Hayashi, Toru

    1999-01-01

    As rice seeds are sometimes contaminated with phytopathogenic organisms such as blast disease fungi and nematodes, a novel non-chemical disinfection method for rice seeds is highly required. In order to develop a disinfection method, the effect of low energy electron ('soft-electrons') on seed DNA was examined by using the neutral comet assay. Rice seeds (whole grain) were treated with electrons of different acceleration voltages (180 kV to 1 MV) at a dose of 5 kGy. Nucleus suspensions were prepared from whole brown rice and subjected to electrophoresis. DNA from un-irradiated (control) seeds relaxed and produced comets with a short tail, most of the comets distributed within the range of comet length between 30 μm to 70 μm. In the case of seeds treated with electrons at acceleration voltages up to 190 kV, cells without seed coats were not damaged and the frequency histograms of comet length showed almost the same pattern as that for control. At acceleration voltages higher than 200 kV, the cells were distributed into two categories; DNA comets with a short tail (with little DNA damages, less than 70 μm in the comet length) and DNA comets with long tails (with sever strand breaks, more than 130 μm in the comet length). The ratios of damaged cells increased with increasing acceleration voltage. The growths of rice seedlings were not affected by the treatment with electrons at up to 200 kV. On the contrary, the cells of gamma-irradiated seed showed small variations in the comet length, and which were depending on radiation dose. The individual cells of gamma-irradiated seeds at 1 kGy showed shorter comet than the damaged cells with soft electron, seed treated with gamma rays (1-5 kGy) did not shoot nor root. (author)

  11. The comet assay as a dosimetric tool in evaluation of overexposure localized irradiation; El ensayo de cometa como herramienta de la dosimetria biologica en la evaluacion de sobreexposiciones fuertemente localizadas

    Energy Technology Data Exchange (ETDEWEB)

    Giorgio, Marina Di; Taja, Maria R.; Nasazzi, Nora [Autoridad Regulatoria Nuclear, Buenos Aires (Argentina); Bustos, Norma; Cavalieri, Hernan; Bolgiani, Alberto [Fundacion Fortunato Benaim, Buenos Aires (Argentina)

    2001-07-01

    With inhomogeneous exposures, as is characteristic in accidents, the skin may be an important organ in determining clinical prognosis, being dosimetric assessment a necessary requirement. In order to get information to be applied on the evaluation of skin biopsies without culture for an early assessment of irradiation consequences in locally irradiated individuals, contributing with the biophysical techniques, we evaluate the alkaline comet assay (for doses < 5 Gy) as a method for the detection of DNA radiation induced damage in keratinocytes from primary and secondary cultures obtained from medium thickness skin biopsies and epidermal cells, without culture, derived from the same sample of skin biopsies of patients requiring grafts. To extend the dose range (> 5 Gy), neutral comet assay was applied to keratinocytes from primary and secondary cultures and to a suspension of epidermal cells obtained from biopsies irradiated in vitro an afterwards processed to obtain the mentioned cellular suspension, in order to reproduce the closest condition to in vivo overexposure. The correlation of the obtained data with factors of the patient and the corresponding skin graft response, were evaluated. (author)

  12. Comet assay for rapid detection of base damage in foods

    International Nuclear Information System (INIS)

    Al-Zubaidi, I. A.; Abdullah, T. S.; Qasim, S. R.

    2012-12-01

    Single cell gel electrophoresis (SCGE) or comet assay technique a sensitive, reliable and rapid method for DNA double and single strand break, alkali- labile site and delayed repair site detection in individual cells. In recent years, this method has been widely used for studies of DNA repair, genetic toxicology, and environmental biomontoring, however, this technique serves as an important tool for detection of DNA damage in living organism and is increasing being used in genetic testing of industrial chemicals, environmental agent's contaminations. This research paper helps to evaluate the oxidant agent's effects of exposure to organic pollutants by using comet assay techniques. This study used five samples of each food sample (Meat, Chicken, Rice, Fruits, Vegetables and Tea) to evaluate the genotoxic effects of exposure, to environmental agent's pollutants. The experimental data suggest that the DNA damage parameters ( Tail length, Tail width 1 ) were found higher value in exposed population when compared with the ratio of the length to width that cells exhibiting no migration having a ratio of 1. The percentage and distribution of cells in exposed population of cells also increases with the increase in values. This study demonstrates that, using sensitive techniques, it is possible to detect environmental agent's risks at an early stage. (Author)

  13. Genotoxicity of waterpipe smoke in buccal cells and peripheral blood leukocytes as determined by comet assay.

    Science.gov (United States)

    Al-Amrah, Hadba Jar-Allah; Aboznada, Osama Abdullah; Alam, Mohammad Zubair; ElAssouli, M-Zaki Mustafa; Mujallid, Mohammad Ibrahim; ElAssouli, Sufian Mohamad

    2014-12-01

    Waterpipe smoke causes DNA damage in peripheral blood leukocytes and in buccal cells of smokers. To determine the exposure effect of waterpipe smoke on buccal cells and peripheral blood leukocytes in regard to DNA damage using comet assay. The waterpipe smoke condensates were analyzed by gas chromatography-mass spectrometry (GC-MS). The study was performed on 20 waterpipe smokers. To perform comet assay on bucaal cells of smokers, 10 µl of cell suspension was mixed with 85 µl of pre-warmed 1% low melting agarose, applied to comet slide and electrophoresed. To analyze the effect of smoke condensate in vitro, 1 ml of peripheral blood was mixed with 10 µl of smoke condensate and subjected for comet assay. The GC-MS analysis revealed the presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4on, nicotine, hydroxymethyl furancarboxaldehyde and 3-ethoxy-4-hydroxybenzaldehyde in the smoke condensates. Waterpipe smoking caused DNA damage in vivo in buccal cells of smokers. The tail moment and tail length in buccal cells of smokers were 186 ± 26 and 456 ± 71, respectively, which are higher than control. The jurak and moassel smoke condensates were found to cause DNA damage in peripheral blood leukocytes. The moassel smoke condensate was more damaging. There is wide misconception that waterpipe smoking is not as harmful as cigarette smoking. This study demonstrated that waterpipe smoke induced DNA damage in exposed cells. Waterpipe smokes cause DNA damage in buccal cells. The smoke condensate of both jurak and moassel caused comet formation suggesting DNA damage in peripheral blood leukocytes.

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

    Directory of Open Access Journals (Sweden)

    Adriana Díaz

    2009-01-01

    Full Text Available 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.

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

    Science.gov (United States)

    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. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Effect of low dose tritium on mouse lymphocyte DNA estimated by comet assay

    International Nuclear Information System (INIS)

    Ichimasa, Yusuke; Otsuka, Kensuke; Maruyama, Satoko; Tauchi, Hiroshi; Ichimasa, Michiko; Uda, Tatsuhiko

    2003-01-01

    This paper deals with low dose effect of HTO on mouse lymphocytes DNA (in vitro irradiation) estimated by the comet assay using ICR male mouse of 20 to 23 weeks old. Lymphocytes were isolated by centrifugation of whole blood sample on Ficoll-Paque solution and embedded in agarose gel just after mixed with HTO. After lymphocytes were exposed to 17-50 mGy of HTO, the agarose gel slides were washed to remove HTO and cell lysis treatment on the slides was conducted before electrophoresis. The individual comets on stained slides after electrophoresis were analyzed using imaging software. No significant DNA damages were observed. (author)

  17. Impaired DNA repair as assessed by the 'comet' assay in patients with thyroid tumors after a history of radiation therapy: A preliminary study

    International Nuclear Information System (INIS)

    Leprat, Frederic; Alapetite, Claire; Rosselli, Filippo; Ridet, Agnes; Schlumberger, Martin; Sarasin, Alain; Suarez, Horacio G.; Moustacchi, Ethel

    1998-01-01

    Purpose: Patients with a history of head and neck irradiation in childhood are at risk to develop thyroid tumors. The aim of this study was to determine if an impairment of DNA strand breaks repair could account for this observation. Methods and Materials: Circulating unstimulated lymphocytes of a group of 13 patients who developed thyroid tumors after radiotherapy were submitted to the alkaline single-cell gel electrophoresis assay (SCGE or 'comet' assay) after in vitro exposure to 2 and 5 Gy of γ-rays. A control group of 8 healthy donors and 2 cases with a history of neck irradiation who did not develop a thyroid tumor were also analysed. The immediate response was compared to that observed after 15, 30, and 60 min of postexposure incubation periods. Results: Induction of DNA strand breaks is a dose-dependent process. The SCGE assay parameters did not differ significantly between patients and controls immediately (t = 0) after irradiation at the two doses used. As compared to healthy donors, a slower kinetics of repair was found in the patients. The proportion of residual damage at 60 min postirradiation was significantly (p < 0.01) higher in patients than in controls, at both doses analysed. Flow cytometric analysis of apoptosis and p53 protein status studied before and after irradiation showed no apparent relationship with the repair capacity. Conclusion: This preliminary study suggests that a subgroup of patients who develop thyroid tumors after a history of irradiation are partially defective in the late restitution of in vitro radiation-induced DNA strand breaks. This deficiency could be a predisposing factor to radiation-associated thyroid tumorigenesis. Detection of susceptible individuals using the simple and rapid comet assay, especially children receiving radiotherapeutic treatment, may allow a preventive surveillance for radiation-associated epithelial thyroid tumor development

  18. The comet assay as a rapid test in biomonitoring occupational exposure to DNA-damaging agents and effect of confounding factors

    DEFF Research Database (Denmark)

    Møller, P; Knudsen, Lisbeth E.; Loft, S

    2000-01-01

    appeared to have less power than the positive studies. Also, there were poor dose-response relationships in many of the biomonitoring studies. Many factors have been reported to produce effects by the comet assay, e.g., age, air pollution exposure, diet, exercise, gender, infection, residential radon...... be used as criteria for the selection of populations and that data on exercise, diet, and recent infections be registered before blood sampling. Samples from exposed and unexposed populations should be collected at the same time to avoid seasonal variation. In general, the comet assay is considered...... exposure, smoking, and season. Until now, the use of the comet assay has been hampered by the uncertainty of the influence of confounding factors. We argue that none of the confounding factors are unequivocally positive in the majority of the studies. We recommend that age, gender, and smoking status...

  19. Application of the comet assay in studies of programmed cell death (PCD in plants

    Directory of Open Access Journals (Sweden)

    Maria Charzyńska

    2014-01-01

    Full Text Available Programmed cell death (PCD in plants is an intensively investigated process. One of the main characteristics of PCD in both animal and plant organisms is the non-random, internucleosomal fragmentation of nuclear DNA, usually analysed using total DNA gel electrophoresis or TUNEL method. In this paper we present application of the "comet assay" (Single Cell Gel Electrophoresis for detection of nDNA degradation in studies of PCD during plant life cycle. We analyzed three types of tissue: anther tapetum, endosperm and mesophyll which were prepared in different ways to obtain a suspension of viable cells (without cell walls. The comet assay gives a possibility of examination of the nDNA degradation in individual cell. This method is significant for studies of the plant tissue differentiation and senescence especially in the cases when it is not possible to isolate large number of cells at the same developmental stage.

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

    Science.gov (United States)

    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.

  1. The effect of gamma radiation on the Common carp (Cyprinus carpio): In vivo genotoxicity assessment with the micronucleus and comet assays.

    Science.gov (United States)

    M K, Praveen Kumar; Soorambail K, Shyama; Bhagatsingh Harisingh, Sonaye; D'costa, Avelyno; Ramesh Chandra, Chaubey

    2015-10-01

    Radioactive wastes may be leached into freshwater, either accidentally or in industrial effluents. We have studied gamma radiation-induced DNA damage in the freshwater fish Cyprinus carpio. Fish were irradiated with 2-10Gy gamma radiation and genotoxic effects in blood cells were studied with the micronucleus (MN) and comet assays. Micronuclei and a dose-dependent increase in comet-tail DNA were seen in dose- and time-dependent studies. The highest % tail DNA was observed at 24h, declining until 72h, which may indicate the repair of radiation-induced DNA single-strand breaks after gamma radiation. However, double-stranded DNA damage may not have been repaired, as indicated by increased micronuclei at later periods. A positive correlation was observed between the comet and micronucleus assay results. This study confirms the mutagenic/genotoxic potential of gamma radiation in the Common carp, as well as the possible combined use of the micronucleus and comet assays for in vivo laboratory studies with fresh-water fish for screening the genotoxic potential of radioactive pollution. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Genotoxic effects of bismuth (III oxide nanoparticles by comet assay

    Directory of Open Access Journals (Sweden)

    Reecep Liman

    2015-06-01

    Full Text Available Bismuth oxide is one of the important transition metal oxides and it has been intensively studied due to their peculiar characteristics (semiconductor band gap, high refractive index, high dielectric permittivity, high oxygen conductivity, resistivity, photoconductivity and photoluminescence etc.. Therefore, it is used such as microelectronics, sensor technology, optical coatings, transparent ceramic glass manufacturing, nanoenergetic gas generator, biosensor for DNA hybridization, potential immobilizing platforms for glucose oxidase and polyphenol oxidase, fuel cells, a additive in paints, an astringent in a variety of medical creams and topical ointments, and for the determination of heavy metal ions in drinking water, mineral water and urine. In addition this, Bismuth (III oxide nanoparticles (BONPs are favorable for the biomolecules adsorption than regular sized particles because of their greater advantages and novel characteristics (much higher specific surface, greater surface free energy, and good electrochemical stability etc.. Genotoxic effects of BONPs were investigated on the root cells of Allium cepa by Comet assay. A. cepa roots were treated with the aqueous dispersions of BONPs at 5 different concentrations (12.5, 25, 50, 75, and 100 ppm for 4 h. A significant increase in DNA damage was also observed at all concentrations of BONPs except 12.5 ppm by Comet assay. The results were also analyzed statistically by using SPSS for Windows; Duncan’s multiple range test was performed. These result indicate that BONPs exhibit genotoxic activity in A. cepa root meristematic cells.

  3. Assessing genotoxicity of diuron on Drosophila melanogaster by the wing-spot test and the wing imaginal disk comet assay.

    Science.gov (United States)

    Peraza-Vega, Ricardo I; Castañeda-Sortibrán, América N; Valverde, Mahara; Rojas, Emilio; Rodríguez-Arnaiz, Rosario

    2017-05-01

    The aim of this study was to evaluate the genotoxicity of the herbicide diuron in the wing-spot test and a novel wing imaginal disk comet assay in Drosophila melanogaster. The wing-spot test was performed with standard (ST) and high-bioactivation (HB) crosses after providing chronic 48 h treatment to third instar larvae. A positive dose-response effect was observed in both crosses, but statistically reduced spot frequencies were registered for the HB cross compared with the ST. This latter finding suggests that metabolism differences play an important role in the genotoxic effect of diuron. To verify diuron's ability to produce DNA damage, a wing imaginal disk comet assay was performed after providing 24 h diuron treatment to ST and HB third instar larvae. DNA damage induced by the herbicide had a significantly positive dose-response effect even at very low concentrations in both strains. However, as noted for the wing-spot test, a significant difference between strains was not observed that could be related to the duration of exposure between both assays. A positive correlation between the comet assay and the wing-spot test was found with regard to diuron genotoxicity.

  4. Evaluation of gamma radiation induced genetic damage in the fish Cyprinus carpio using comet assay

    International Nuclear Information System (INIS)

    Praveen Kumar, M.K.; Shyama, S.K.; Bhagat, S.S.; Chaubey, R.C.

    2013-01-01

    Radionuclides released from various sources including the industries, as well as, accidental release during a nuclear disaster can contaminate inland water bodies. Suitable bio-monitoring methods/biomarkers are the need of the day to assess the impact of high/low levels of radiation exposure in aquatic environment. Fishes are very important as a group of ecologically and commercially important non-human biota and are often used as a bioindicators of aquatic pollution. Present work was carried out to assess the genotoxic effect of gamma radiation on fresh water fish Cyprinus carpio (common carp) in vivo using comet assay. Fishes were irradiated with 2, 4, 6, 8 and 10 Gy of gamma rays using a teletherapy machine and comet assay was performed on nucleated erythrocytes after 24, 48 and 72 h of irradiation . A significant increase in % tail DNA was observed at all the doses of gamma radiation as compared to controls indicating radiation induced DNA damage in a dose-dependent manner. Maximum % tail DNA was observed at 24 h which gradually declined till 72 h, in a time-dependent manner. This decrease in damage may indicate repair of the damaged DNA and or loss of heavily damaged cells, over a period of time. The study reveals that the comet assay may be used as a sensitive and rapid method to detect genotoxicity of gamma radiation and other environmental pollutants in sentinel species. (author)

  5. Application of the microbiological method DEFT/APC and DNA comet assay to detect ionizing radiation processing of minimally processed vegetables

    International Nuclear Information System (INIS)

    Araujo, Michel Mozeika

    2008-01-01

    Marketing of minimally processed vegetables (MPV) are gaining impetus due to its convenience, freshness and apparent healthy. However, minimal processing does not reduce pathogenic microorganisms to safe levels. Food irradiation is used to extend the shelf life and inactivation of food-borne pathogens, Its combination with minimal processing could improve the safety and quality of MPV. Two different food irradiation detection methods, a biological, the DEFT/APC, and another biochemical, the DNA Comet Assay were applied to MPV in order to test its applicability to detect irradiation treatment. DEFT/APC is a microbiological screening method based on the use of the direct epi fluorescent filter technique (DEFT) and the aerobic plate count (APC). DNA Comet Assay detects DNA damage due to ionizing radiation. Samples of lettuce, chard, watercress, dandelion, kale, chicory, spinach, cabbage from retail market were irradiated O.5 kGy and 1.0 kGy using a 60 Co facility. Irradiation treatment guaranteed at least 2 log cycle reduction for aerobic and psychotropic microorganisms. In general, with increasing radiation doses, DEFT counts remained similar independent of irradiation processing while APC counts decreased gradually. The difference of the two counts gradually increased with dose increment in all samples. It could be suggested that a DEFT/APC difference over 2.0 log would be a criteria to judge if a MPV was treated by irradiation. DNA Comet Assay allowed distinguishing non-irradiated samples from irradiated ones, which showed different types of comets owing to DNA fragmentation. Both DEFT/APC method and DNA Comet Assay would be satisfactorily used as a screening method for indicating irradiation processing. (author)

  6. The comet assay in Folsomia candida: A suitable approach to assess genotoxicity in collembolans.

    Science.gov (United States)

    Cardoso, Diogo N; Silva, Ana Rita R; Cruz, Andreia; Lourenço, Joana; Neves, Joana; Malheiro, Catarina; Mendo, Sónia; Soares, Amadeu M V M; Loureiro, Susana

    2017-09-01

    The present study shows the comet assay technique being successfully applied for the first time to one of the most widely used soil organisms in standardized ecotoxicological tests, Folsomia candida, providing a step forward in assessing the genotoxicity induced by xenobiotics. Because collembolans have a high content of chitin, a new methodology was developed in which the heads of the collembolans were separated from the rest of the body, allowing the hemolymph to leak out. This procedure allows the cells to be released, and after lysis the genetic material is available for the comet assay. Among other key procedures, the use of 30 organisms (20- to 22-d-old adults) per replicate and the correct amount of cells with genetic material (translated as 10 μL of suspension) applied on the agarose gel were determinants for the success of the results obtained. The methodology was validated by exposing F. candida to a representative metallic element (cadmium) and a representative of organophosphates, the insecticide dimethoate, for a shorter time period of 10 d, compared with the 28 d for the International Organization for Standardization 11267 method. Within this method, the relatively low percentage of DNA damage (30%) observed in controls and the significant increase in terms of percentage of DNA damage for almost all the concentrations of dimethoate and Cd (reaching 52% and 56% of damage in the highest concentrations, respectively) confirmed the genotoxic effect of both compounds and validated this technique. The comet assay proved to be a sensitive technique to detect DNA strand breaks in collembolans' cells. Environ Toxicol Chem 2017;36:2514-2520. © 2017 SETAC. © 2017 SETAC.

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

    Science.gov (United States)

    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.

  8. The influence of the number of cells scored on the sensitivity in the comet assay

    DEFF Research Database (Denmark)

    Sharma, Anoop Kumar; Soussaline, Françoise; Sallette, Jerome

    2012-01-01

    The impact on the sensitivity of the in vitro comet assay by increasing the number of cells scored has only been addressed in a few studies. The present study investigated whether the sensitivity of the assay could be improved by scoring more than 100 cells. Two cell lines and three different che...... of the assay. A two-way ANOVA analysis of variance showed that the contribution from the two variables “the number of cells scored” and “concentration” on the total variation in the coefficients of variance dataset was statistically significant (p...

  9. Assessment of DNA damage in blood lymphocytes of bakery workers by comet assay.

    Science.gov (United States)

    Kianmehr, Mojtaba; Hajavi, Jafar; Gazeri, Javad

    2017-09-01

    The comet assay is widely used in screening and identification of genotoxic effects of different substances on people in either their working or living environment. Exposure to fuel smoke leads to DNA damage and ultimately different types of cancer. Using a comet assay, the present study aimed to assess peripheral blood lymphocyte DNA damage in people working in bakeries using natural gas, kerosene, diesel, or firewood for fuel compared to those in the control group. The subjects of this study were 55 people in total who were divided into four experimental groups, each of which comprised of 11 members (based on the type of fuel used), and one control group comprised of 11 members. Using CometScore, the subjects' peripheral blood lymphocytes were examined for DNA damage. All bakers, that is, experimental subjects, showed significantly greater peripheral blood lymphocyte DNA damage compared to the individuals in the control group. There was greater peripheral blood lymphocyte DNA damage in bakers who had been using firewood for fuel compared to those using other types of fuel to such an extent that tail moments (µm) for firewood-burning bakers was 4.40 ± 1.98 versus 1.35 ± 0.84 for natural gas, 1.85 ± 1.33 for diesel, and 2.19 ± 2.20 for kerosene. The results indicated that burning firewood is the greatest inducer of peripheral blood lymphocytes DNA damage in bakers. Nonetheless, there was no significant difference in peripheral blood lymphocyte DNA damage among diesel and kerosene burning bakers.

  10. Radiosensitivity evaluation of human tumor cell lines by detecting 4977 bp deletion in mitochondrial DNA and comet assay

    International Nuclear Information System (INIS)

    Chu Liping; Liu Qiang; Wang Qin; Li Jin; Yue Jingyin; Mu Chuanjie; Fan Feiyue

    2008-01-01

    Objective: To explore the feasibility of determining radiosensitivity of human tumor cell lines in vitro using the assay of mtDNA 4977 bp deletion and comet assay. Methods: Three human tumor cell lines were selected in this study, HepG 2 , EC-9706 and MCF-7. The surviving fraction(SF), the ratio of mtDNA 4977 bp deletion and DNA damage were detected by MTY assay, nested PCR technique and comet assay, respectively. Results: The results of MTT assay showed that the radiosensitivity of HepG 2 and EC-9706 was higher than that of MCF-7. The ratio of mtDNA 4977 bp deletion of HepG 2 and EC-9706 was higher significantly than that of MCF-7 (P 2 and EC-9706 was higher than that of MCF-7. The difference of radiosensitivity among these three tumor cell lines was significant after 8 Gy γ-ray irradiation. Conclusions: Combination of many biological parameter is helpful to evaluate the radiosensitivity of tumor cells more accurately. (authors)

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

    Science.gov (United States)

    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, ...

  12. Comet assay as a human biomonitoring tool: application in occupational exposure to antineoplastic drugs

    Directory of Open Access Journals (Sweden)

    Carina Ladeira

    2015-05-01

    Occupational exposure to antineoplastic drugs is associated with genotoxic effects, although comet assay analyzed parameters were higher in exposed comparing with controls, were not significant. Also the study of the susceptibility biomarkers did not show statistical significant differences, the small size of our sample hampered the finding of a possible association, let alone a causality relationship.

  13. A buccal cell model comet assay: Development and evaluation for human biomonitoring and nutritional studies

    International Nuclear Information System (INIS)

    Szeto, Y.T.; Benzie, I.F.F.; Collins, A.R.; Choi, S.W.; Cheng, C.Y.; Yow, C.M.N.; Tse, M.M.Y.

    2005-01-01

    The comet assay is a widely used biomonitoring tool for DNA damage. The most commonly used cells in human studies are lymphocytes. There is an urgent need to find an alternative target human cell that can be collected from normal subjects with minimal invasion. There are some reports of buccal cells, collected easily from the inside of the mouth, being used in studies of DNA damage and repair, and these were of interest. However, our preliminary studies following the published protocol showed that buccal cells sustained massive damage and disintegrated at the high pH [O. Ostling, K.J. Johanson. Microelectrophoretic study of radiation-induced DNA damages in individual mammalian cells. Biochem. Biophys. Res. Commun. 123 (1984) 291-298] used, but that at lower pH were extremely resistant to lysis, an essential step in the comet assay. Therefore, the aims of this study were to develop a protocol than enabled buccal cell lysis and DNA damage testing in the comet assay, and to use the model to evaluate the potential use of the buccal cell model in human biomonitoring and nutritional study. Specifically, we aimed to investigate intra- and inter-individual differences in buccal cell DNA damage (as strand breaks), the effect of in vitro exposure to both a standard oxidant challenge and antioxidant treatment, as well as in situ exposure to an antioxidant-rich beverage and supplementation-related effects using a carotenoid-rich food. Successful lysis was achieved using 0.25% trypsin for 30 min followed by proteinase K (1 mg/ml) treatment for 60 min. When this procedure was performed on cells pre-embedded in agarose on a microscope slide, followed by electrophoresis (in 0.01 M NaOH, 1 mM EDTA, pH 9.1, 18 min at 12 V), a satisfactory comet image was obtained, though inter-individual variation was quite wide. Pre-lysis exposure of cells to a standard oxidant challenge (induced by H 2 O 2 ) increased DNA strand breaks in a dose related manner, and incubation of cells in Trolox

  14. A buccal cell model comet assay: Development and evaluation for human biomonitoring and nutritional studies

    Energy Technology Data Exchange (ETDEWEB)

    Szeto, Y.T. [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); School of Health Sciences, Macao Polytechnic Institute, Macao (China); Benzie, I.F.F. [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China)]. E-mail: iris.benzie@inet.polyu.edu.hk; Collins, A.R. [Department of Nutrition, University of Oslo, Oslo (Norway); Choi, S.W. [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Cheng, C.Y. [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Yow, C.M.N. [Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Tse, M.M.Y. [School of Nursing, Hong Kong Polytechnic University, Kowloon, Hong Kong (China)

    2005-10-15

    The comet assay is a widely used biomonitoring tool for DNA damage. The most commonly used cells in human studies are lymphocytes. There is an urgent need to find an alternative target human cell that can be collected from normal subjects with minimal invasion. There are some reports of buccal cells, collected easily from the inside of the mouth, being used in studies of DNA damage and repair, and these were of interest. However, our preliminary studies following the published protocol showed that buccal cells sustained massive damage and disintegrated at the high pH [O. Ostling, K.J. Johanson. Microelectrophoretic study of radiation-induced DNA damages in individual mammalian cells. Biochem. Biophys. Res. Commun. 123 (1984) 291-298] used, but that at lower pH were extremely resistant to lysis, an essential step in the comet assay. Therefore, the aims of this study were to develop a protocol than enabled buccal cell lysis and DNA damage testing in the comet assay, and to use the model to evaluate the potential use of the buccal cell model in human biomonitoring and nutritional study. Specifically, we aimed to investigate intra- and inter-individual differences in buccal cell DNA damage (as strand breaks), the effect of in vitro exposure to both a standard oxidant challenge and antioxidant treatment, as well as in situ exposure to an antioxidant-rich beverage and supplementation-related effects using a carotenoid-rich food. Successful lysis was achieved using 0.25% trypsin for 30 min followed by proteinase K (1 mg/ml) treatment for 60 min. When this procedure was performed on cells pre-embedded in agarose on a microscope slide, followed by electrophoresis (in 0.01 M NaOH, 1 mM EDTA, pH 9.1, 18 min at 12 V), a satisfactory comet image was obtained, though inter-individual variation was quite wide. Pre-lysis exposure of cells to a standard oxidant challenge (induced by H{sub 2}O{sub 2}) increased DNA strand breaks in a dose related manner, and incubation of cells in

  15. Comet assay in reconstructed 3D human epidermal skin models—investigation of intra- and inter-laboratory reproducibility with coded chemicals

    Science.gov (United States)

    Pfuhler, Stefan

    2013-01-01

    Reconstructed 3D human epidermal skin models are being used increasingly for safety testing of chemicals. Based on EpiDerm™ tissues, an assay was developed in which the tissues were topically exposed to test chemicals for 3h followed by cell isolation and assessment of DNA damage using the comet assay. Inter-laboratory reproducibility of the 3D skin comet assay was initially demonstrated using two model genotoxic carcinogens, methyl methane sulfonate (MMS) and 4-nitroquinoline-n-oxide, and the results showed good concordance among three different laboratories and with in vivo data. In Phase 2 of the project, intra- and inter-laboratory reproducibility was investigated with five coded compounds with different genotoxicity liability tested at three different laboratories. For the genotoxic carcinogens MMS and N-ethyl-N-nitrosourea, all laboratories reported a dose-related and statistically significant increase (P 30% cell loss), and the overall response was comparable in all laboratories despite some differences in doses tested. The results of the collaborative study for the coded compounds were generally reproducible among the laboratories involved and intra-laboratory reproducibility was also good. These data indicate that the comet assay in EpiDerm™ skin models is a promising model for the safety assessment of compounds with a dermal route of exposure. PMID:24150594

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  17. Genotoxic Potential of Two Herbicides and their Active Ingredients Assessed with Comet Assay on a Fish Cell Line, Epithelioma Papillosum Cyprini (EPC)

    DEFF Research Database (Denmark)

    Syberg, Kristian; Rank, Jette; Jensen, Klara

    2013-01-01

    The aim of this study was to optimize the epithelioma papillosum cyprini (EPC) cell line handling procedure for the comet assay to investigate the genotoxic potential of widely used pesticides. The effects of various media and handling of the EPC cell line were examined. Results indicated......-(2,4-dichlorophenoxy)propionic acid) individually and in a ternary mixture were examined with the comet assay. Data showed that among the active ingredients only 2,4-D andMCPA induced DNA damage, while both herbicides were genotoxic at high concentrations....

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

    Science.gov (United States)

    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. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Hemocytes of zebra mussels (Dreissena polymorpha are relevant cells for the monitoring of environmental genotoxicity by the comet assay.

    Directory of Open Access Journals (Sweden)

    Marc Bonnard

    2015-06-01

    Full Text Available The measure of DNA integrity by the single cell gel electrophoresis (SCGE or comet assay is especially recommended for its sensitivity and its capacity for detecting different types of damages. Therefore, it has been applied in environmental genotoxicity in a variety of organisms. It appears today necessary to define both reference and threshold levels of DNA damage, for their application in in situ biomonitoring. However, little is known about the influence of both biological (sex, reproduction status or external (temperature… confounding factors on the measure of DNA damage by the comet assay. These variables need to be taken into account if the robustness of the assay is to be established (Jha, 2008. In the zebra mussel Dreissena polymorpha (recommended as a sentinel species in the evaluation of freshwater quality the measure of DNA damage by the comet assay is mainly performed on hemocytes, which are circulating cells involved in key physiological functions such as immunity, homeostasis, detoxication…. This communication will present and discuss results from an innovative study about the variability of the baseline level of DNA damage in hemocytes of mussels encaged for one year in the canal de l’Aisne à la Marne (Reims, according to their sex and their reproductive status. The sensitivity and the suitability of hemocytes in the evaluation of environmental genotoxicity will also be discussed, referring to observations during a 6 month-exposure of mussels in mesocosms to environmentally realistic concentrations of carbamazepine.

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

    Science.gov (United States)

    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. DNA Comet Assay and Changes in Microflora Load as Screening Methods to Detect Irradiated Food in Egypt

    International Nuclear Information System (INIS)

    Hammad, A.A.; Abo El Nour, S.A.; Ibrahim, H.M.; Osman, M.E.; Abo El- Nasr, A.

    2014-01-01

    In the present study the microgel electrophoresis of single cells (DNA Comet Assay), and changes in microflora load were applied to detect irradiation treatment of strawberries and fresh-deboned chicken produced in Egypt. Strawberry samples were irradiated at 1.0, 2.0, 3.0 and 4.0 kGy, stored at 4 degree C±1 and analyzed at 0 and 7 days post.-irradiation. Fresh- deboned chicken meat samples were exposed to 2.0, 3.0, 4.0 and 5.0 kGy, stored at 4 degree C±1 and analyzed at 0, 7, 14 and 21 days post-irradiation. After electrophoresis performance, the accridine orange stain slides were seen under fluorescent microscope and the DNA comets were evaluated by photographic and image analysis. Changes in microflora load of irradiated samples were also evaluated. In all irradiated samples, the DNA fragments stretched or migrated out of the cells towards the anode of the agrose gel and appeared as a “comets” with tail. Whereas, DNA comets of all non-irradiated samples were almost intact, round without tail or had very short tail. Values of DNA % in tails and the tail length increased with increasing irradiation dose and storage times. The DNA comet assay could successfully be used to detect radiation treatment of strawberry and deboned-chicken meat samples up to 7 and 21 days post-irradiation, respectively. The absence of gram-negative bacteria and enterobacteriaceae group as well as the very low count of fungi (mostly yeasts) might be considered another evidence of radiation treatment of strawberries and fresh-deboned chicken.

  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.

    Science.gov (United States)

    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. A high sensitivity, high throughput, automated single-cell gel electrophoresis ('Comet') DNA damage assay

    International Nuclear Information System (INIS)

    Vojnovic, B.; Barber, P.R.; Johnston, P.J.; Gregory, H.C.; Locke, R.J.

    2003-01-01

    A fully automated microscopy machine vision image capture and analysis system for the collection of data from slides of 'comets' has been developed. The novel image processing algorithms employed in delineating the 'comet head' from the 'comet tail' allow us to determine accurately very low levels of damage. In conjunction with calibrated and automated image capture methods, we are able to eliminate operator subjectivity and analyse large numbers of cells (>2500) in a short time (<1 hour). The image processing algorithm is designed to handle particularly difficult nuclei containing a high degree of structure, due to DNA clumping. We also present techniques used to extend the assay's dynamic range by removing interfering background fluorescence and to define a region of interest. If subtle biological variations are to be quantified (e.g. cell cycle dependant damage), then the use of large cell populations is dictated. Under those circumstances, the use of a fully automated system is particularly advantageous providing that the manner in which data is extracted does not introduce any inadvertent bias. In practice, it is essential that the image processing steps are geared towards the correct recognition of an acceptable cell nucleus, i.e. comet 'head'. We acknowledge the financial support of CRUK, Programme Grant C133/A1812 - SP 2195-01/02 and the US Department of Energy Low Dose Radiation Research Program grant DE-FG07-99ER62878

  4. Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

    Directory of Open Access Journals (Sweden)

    José Carlos Pelielo de Mattos

    2008-12-01

    Full Text Available Reactive oxygen species (ROS can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl2 is a ROS generator, leading to lethality in Escherichia coli (E. coli, with the base excision repair (BER mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl2 in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl2 was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms.Espécies reativas de oxigênio (ERO podem induzir lesões em diferentes alvos celulares, incluindo o DNA. O cloreto estanoso (SnCl2 é um gerador de ERO que induz letalidade em E. coli, sendo o reparo por excisão de bases (BER um mecanismo importante neste processo. Técnicas como o ensaio cometa (em eucariotos e a eletroforese de DNA plasmidial em gel de agarose têm sido utilizadas para detectar genotoxicidade. No presente estudo, uma adaptação do método de eletroforese em gel alcalino de agarose foi usada para verificar a indução de quebras, pelo SnCl2, no DNA de E. coli, bem como a participação de enzimas do BER na restauração das lesões. Os resultados mostraram que o SnCl2 induziu quebras no DNA de todas as cepas testadas. Além disso, endonuclease IV e exonuclease III estão envolvidas na reparação dos danos. Em resumo, os dados obtidos indicam que a metodologia de eletroforese em gel alcalino de agarose pode ser empregada tanto para o estudo de quebras no DNA, quanto para avaliação dos

  5. 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

    International Nuclear Information System (INIS)

    Kurashige, Tomomi; Shimamura, Mika; Nagayama, Yuji

    2016-01-01

    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

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

    Science.gov (United States)

    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. Copyright © 2016. Published by Elsevier B.V.

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

    Science.gov (United States)

    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 (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; Pcomet assay. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. The use of comet assay to assess DNA integrity of boar spermatozoa following liquid preservation at 5 degrees C and 16 degrees C.

    Directory of Open Access Journals (Sweden)

    J Strzezek

    2004-03-01

    Full Text Available The comet assay, under neutral conditions, allows the assessment of DNA integrity influenced by sperm ageing, which is manifested in DNA double-strand breaks. Here, we attempted to use a modified neutral comet assay test (single-cell gel electrophoresis, to our knowledge for the first time, to assess DNA integrity of boar spermatozoa during liquid storage for 96 h at 5 degrees C and 16 degrees C. In this comet assay protocol we used 2% beta-mercaptoethanol prior to the lysis procedure, to aid in removing nuclear proteins. Ejaculates from 3 boars (designated A, C and G were diluted with a standard semen extender, Kortowo-3 (K-3, which was supplemented with lipoprotein fractions extracted from hen egg yolk (LPFh or ostrich egg yolk (LPFo. Irrespective of the extender type, the percentage of comet-detected spermatozoa with damaged DNA increased gradually during prolonged storage at 5 degrees C and 16 degrees C. Spermatozoa stored in K-3 extender exhibited elevated levels of DNA damage at both storage temperatures. Significant differences in DNA damage among the boars were more pronounced during storage in LPF-based extenders at 5 degrees C: spermatozoa of boars A and G were less susceptible to DNA damage. The percent of tail DNA in comets was lower in LPF-based extenders, and there were individual variations among the boars. We observed that changes in DNA integrity were dependent on the extender type and storage temperature. A higher level of DNA instability was observed in K-3 extended semen compared with K-3/LPFh or K-3/LPFo extended semen during storage at 5 degrees C. No significant difference in the level of DNA damage between K-3/LPFh and K-3/LPFo was observed. It seems that a long-term storage can affect genomic integrity of boar spermatozoa. The modified neutral comet assay can be used to detect low levels of DNA damage in boar spermatozoa during liquid preservation. Therefore, screening for sperm DNA damage may be used as an additional

  9. The use of comet assay to assess DNA integrity of boar spermatozoa following liquid preservation at 5 degrees C and 16 degrees C.

    Science.gov (United States)

    Fraser, L; Strzezek, J

    2004-01-01

    The comet assay, under neutral conditions, allows the assessment of DNA integrity influenced by sperm ageing, which is manifested in DNA double-strand breaks. Here, we attempted to use a modified neutral comet assay test (single-cell gel electrophoresis), to our knowledge for the first time, to assess DNA integrity of boar spermatozoa during liquid storage for 96 h at 5 degrees C and 16 degrees C. In this comet assay protocol we used 2% beta-mercaptoethanol prior to the lysis procedure, to aid in removing nuclear proteins. Ejaculates from 3 boars (designated A, C and G) were diluted with a standard semen extender, Kortowo-3 (K-3), which was supplemented with lipoprotein fractions extracted from hen egg yolk (LPFh) or ostrich egg yolk (LPFo). Irrespective of the extender type, the percentage of comet-detected spermatozoa with damaged DNA increased gradually during prolonged storage at 5 degrees C and 16 degrees C. Spermatozoa stored in K-3 extender exhibited elevated levels of DNA damage at both storage temperatures. Significant differences in DNA damage among the boars were more pronounced during storage in LPF-based extenders at 5 degrees C: spermatozoa of boars A and G were less susceptible to DNA damage. The percent of tail DNA in comets was lower in LPF-based extenders, and there were individual variations among the boars. We observed that changes in DNA integrity were dependent on the extender type and storage temperature. A higher level of DNA instability was observed in K-3 extended semen compared with K-3/LPFh or K-3/LPFo extended semen during storage at 5 degrees C. No significant difference in the level of DNA damage between K-3/LPFh and K-3/LPFo was observed. It seems that a long-term storage can affect genomic integrity of boar spermatozoa. The modified neutral comet assay can be used to detect low levels of DNA damage in boar spermatozoa during liquid preservation. Therefore, screening for sperm DNA damage may be used as an additional test of sperm

  10. The agricultural impact of pesticides on Physalaemus cuvieri tadpoles (Amphibia: Anura ascertained by comet assay

    Directory of Open Access Journals (Sweden)

    Macks W. Gonçalves

    2017-10-01

    Full Text Available ABSTRACT Amphibians inhabiting agricultural areas are constantly exposed to large amounts of chemicals, which reach the aquatic environment during the rainy season through runoff, drainage, and leaching. We performed a comet assay on the erythrocytes of tadpoles found in the surroundings of agricultural fields (soybean and corn crops, where there is an intense release of several kinds of pesticides in different quantities. We aimed to detect differences in the genotoxic parameters between populations collected from soybeans and cornfields, and between them and tadpoles sampled from non-agricultural areas (control group. Tadpoles collected from ponds located at soybean fields had significantly more DNA damage, followed by tadpoles collected from cornfields. In contrast, animals sampled from non-agricultural areas had the lowest incidence of DNA damage. In addition, we found a negative correlation between the parameters of the comet assay and the area of the ponds surrounding soybean. This correlation indicates a possible dilution effect in the concentration of pesticides. Finally, Physalaemus cuvieri Fitzinger, 1826 seems to be a good bioindicator for detecting the genotoxic effects of field agricultural insecticides; therefore, we suggest that this species should be used in environmental biomonitoring studies, since it is common and abundant where it occurs.

  11. 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.

    Science.gov (United States)

    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. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  12. Genotoxicity determinations of coriander drop and extract of Coriander Sativum cultured fibroblast of rat embryo by comet assay

    International Nuclear Information System (INIS)

    Heibatullah, K.; Marzieh, P.; Arefeh, I.; Ebrahim, M.

    2008-01-01

    The single cell gel electrophoresis (SCGE) or comet assay is a quick, simple and sensitive technique for measuring DNA damage in cell nucleus. It is well known that medicinal herbs play an important role in the life of human beings, thus it is essential to determine their safety as public health is concerned. In this study the genotoxicity of Coriander drop, herbal pharmaceutical product, and the extract of Coriander sativum were examined in cultured fibroblast of rat embryo using comet assay. The thirteen to fifteen days old rat embryos were lysed with tripsin and after certain steps it was centrifuged and then cultured. After three to five passages, different concentrations of each product were applied to the fibroblasts. Lysing, electrophoresis, neutralization and staining were carried out. Finally the slides were analyzed with fluorescence microscope. In the test groups the results indicated that coriander drop at different doses showed some fragmentation of DNA but this damage as a result was deemed to be not significant. However, in the case of Coriander sativum extract the results showed no mutagenic effects in comparison with the positive control group (p<0.05). In conclusion, these herbal products did not show any magnetic effect according to our test, but further genotoxicity assays are recommended. (author)

  13. Comet assay in the detection of irradiated garlic

    International Nuclear Information System (INIS)

    Villavicencio, Anna Lucia C.H.; Marin-Huachaca, Nelida Simona; Romanelli, Maria Fernanda; Delincee, Henry

    2002-01-01

    The increased claim for fresh produce has forced a consensus between nations to pay more attention to the phytosanitary regulations. Inhibition of sprouting of bulbs and tubers by applying ionising radiation is authorised by the National Food Codes in Brazil. The availability of methods for detection of irradiated food will contribute to increase consumers' confidence. A quick and simple screening test to indicate whether a food product has been irradiated or not was utilised in this study. The DNA comet assay was applied to verify whether garlic imported from China had been irradiated or not. This test has already been adopted as a European Standard (EN 13784), for detection of irradiated food. Non-irradiated control samples of garlic and garlic treated with maleic hydrazide were compared with garlic samples irradiated in our department. The unirradiated samples exhibited only limited DNA migration. If samples were irradiated, an increased DNA fragmentation was observed which permitted the discrimination between non-irradiated and irradiated samples. Since the garlic samples from China showed only very limited DNA fragmentation, they were deemed non-irradiated. Thus, this simple screening test was shown to be successful for identification of an irradiation treatment. (author)

  14. Comparative antioxidant activity of cultivated and wild Vaccinium species investigated by EPR, human neutrophil burst and COMET assay.

    Science.gov (United States)

    Braga, P C; Antonacci, R; Wang, Y Y; Lattuada, N; Dal Sasso, M; Marabini, L; Fibiani, M; Lo Scalzo, R

    2013-01-01

    The Vaccinium (V.) spp. berries are considered a source of antioxidants, mainly belonging to polyphenols, specifically flavonoids and anthocyanins. Wild genotypes generally contain more antioxidants than cultivated counterparts. So, seven different antioxidants assays on extracts from cultivated and wild Vaccinium berries were performed, to evaluate their difference in terms of bioactivity on oxidative protection and minimum dosage to have a significant action. Four cell-free antioxidant assays (ABTS radical scavenging and electronic paramagnetic resonance using Fremy's salt, superoxide anion and hydroxyl radical), and three assays on human cells (two luminol amplified chemiluminescence, LACL, one on DNA damage, COMET) were used to measure the effects of cultivated blueberry (V. corymbosum) and wild bilberry (V. myrtillus) on the differently induced oxidative stress. Concentrations vs activity patterns were obtained by successive dilutions of extracts in order to identify both EC50 and minimum significant activity (MSA). All the assays (except for the hydroxyl radical scavenging) showed a good relationship mainly with anthocyanin and polyphenol content and the significant greater activity of wild Vaccinium extracts. In fact, LACL data gave an EC50 of 11.8 and an MSA of 5.2 g were calculated as fresh weight dosage in cultivated berries, compared with lower doses in wild berries, EC50 of 5.7 g and MSA of 3.4 g. Wild Vaccinium extracts averaged 3.04 and 2.40 fold more activity than cultivated extracts by EC50 and MSA, respectively. COMET assay confirmed the stronger action on DNA protection in wild samples.

  15. DNA-repair measurements by use of the modified comet assay

    DEFF Research Database (Denmark)

    Godschalk, Roger W L; Ersson, Clara; Riso, Patrizia

    2013-01-01

    The measurement of DNA-repair activity by extracts from cells or tissues by means of the single-cell gel electrophoresis (comet) assay has a high potential to become widely used in biomonitoring studies. We assessed the inter-laboratory variation in reported values of DNA-repair activity...... on substrate cells that had been incubated with Ro19-8022 plus light to generate oxidatively damaged DNA. Eight laboratories assessed the DNA-repair activity of three cell lines (i.e. one epithelial and two fibroblast cell lines), starting with cell pellets or with cell extracts provided by the coordinating...... laboratory. There was a large inter-laboratory variation, as evidenced by the range in the mean level of repair incisions between the laboratory with the lowest (0.002incisions/10(6)bp) and highest (0.988incisions/10(6)bp) incision activity. Nevertheless, six out of eight laboratories reported the same cell...

  16. DNA damage evaluation of hydroxyapatite on fibroblast cell L929 using the single cell gel electrophoresis assay.

    Science.gov (United States)

    Rajab, N F; Yaakob, T A; Ong, B Y; Hamid, M; Ali, A M; Annuar, B O; Inayat-Hussain, S H

    2004-05-01

    Hydroxyapatite is the main component of the bone which is a potential biomaterial substance that can be applied in orthopaedics. In this study, the biocompatibility of this biomaterial was assessed using an in vitro technique. The cytotoxicity and genotoxicity effect of HA2 and HA3 against L929 fibroblast cell was evaluated using the MTT Assay and Alkaline Comet Assay respectively. Both HA2 and HA3 compound showed low cytotoxicity effect as determined using MTT Assay. Cells viability following 72 hours incubation at maximum concentration of both HA2 and HA3 (200 mg/ml) were 75.3 +/- 8.8% and 86.7 +/- 13.1% respectively. However, the cytotoxicity effect of ZnSO4.7H2O as a positive control showed an IC50 values of 46 mg/ml (160 microM). On the other hand, both HA2 and HA3 compound showed a slight genotoxicity effect as determined using the Alkaline Comet Assay following incubation at the concentration 200 mg/ml for 72 hours. This assay has been widely used in genetic toxicology to detect DNA strand breaks and alkali-labile site. The percentage of the cells with DNA damage for both substance was 27.7 +/- 1.3% and 15.6 +/- 1.0% for HA2 and HA3 respectively. Incubation of the cells for 24 hours with 38 microg/ml (IC25) of positive control showed an increase in percentage of cells with DNA damage (67.5 +/- 0.7%). In conclusion, our study indicated that both hydroxyapatite compounds showed a good biocompatibility in fibroblast cells.

  17. Robotic implementation of assays: tissue-nonspecific alkaline phosphatase (TNAP) case study.

    Science.gov (United States)

    Chung, Thomas D Y

    2013-01-01

    Laboratory automation and robotics have "industrialized" the execution and completion of large-scale, enabling high-capacity and high-throughput (100 K-1 MM/day) screening (HTS) campaigns of large "libraries" of compounds (>200 K-2 MM) to complete in a few days or weeks. Critical to the success these HTS campaigns is the ability of a competent assay development team to convert a validated research-grade laboratory "benchtop" assay suitable for manual or semi-automated operations on a few hundreds of compounds into a robust miniaturized (384- or 1,536-well format), well-engineered, scalable, industrialized assay that can be seamlessly implemented on a fully automated, fully integrated robotic screening platform for cost-effective screening of hundreds of thousands of compounds. Here, we provide a review of the theoretical guiding principles and practical considerations necessary to reduce often complex research biology into a "lean manufacturing" engineering endeavor comprising adaption, automation, and implementation of HTS. Furthermore we provide a detailed example specifically for a cell-free in vitro biochemical, enzymatic phosphatase assay for tissue-nonspecific alkaline phosphatase that illustrates these principles and considerations.

  18. Introducing a true internal standard for the Comet assay to minimize intra- and inter-experiment variability in measures of DNA damage and repair

    Science.gov (United States)

    Zainol, Murizal; Stoute, Julia; Almeida, Gabriela M.; Rapp, Alexander; Bowman, Karen J.; Jones, George D. D.

    2009-01-01

    The Comet assay (CA) is a sensitive/simple measure of genotoxicity. However, many features of CA contribute variability. To minimize these, we have introduced internal standard materials consisting of ‘reference’ cells which have their DNA substituted with BrdU. Using a fluorescent anti-BrdU antibody, plus an additional barrier filter, comets derived from these cells could be readily distinguished from the ‘test’-cell comets, present in the same gel. In experiments to evaluate the reference cell comets as external and internal standards, the reference and test cells were present in separate gels on the same slide or mixed together in the same gel, respectively, before their co-exposure to X-irradiation. Using the reference cell comets as internal standards led to substantial reductions in the coefficient of variation (CoV) for intra- and inter-experimental measures of comet formation and DNA damage repair; only minor reductions in CoV were noted when the reference and test cell comets were in separate gels. These studies indicate that differences between individual gels appreciably contribute to CA variation. Further studies using the reference cells as internal standards allowed greater significance to be obtained between groups of replicate samples. Ultimately, we anticipate that development will deliver robust quality assurance materials for CA. PMID:19828597

  19. DNA damage and repair in Arabidopsis thaliana as measured by the comet assay after treatment with different classes of genotoxins

    Czech Academy of Sciences Publication Activity Database

    Menke, M.; Chen, P.; Angelis, Karel; Schubert, I.

    2001-01-01

    Roč. 493, - (2001), s. 87-93 ISSN 0027-5107 R&D Projects: GA ČR GA521/01/1418 Institutional research plan: CEZ:AV0Z5038910 Keywords : Arabidopsis thaliana * Comet assay * Monofunctioal alkylating agents Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.545, year: 2001

  20. Evaluation of radio-induced DNA damage and their repair in human lymphocytes by comet assay or single cell gel electrophoresis

    International Nuclear Information System (INIS)

    Nascimento, Patricia A. do; Suzuki, Miriam F.; Okazaki, Kayo

    1997-01-01

    The comet assay, also called single cell gel electrophoresis technique, permits to evaluate quantitatively DNA breakage induced by chemical and physical agents at the level of the single cell. The present paper refers to the construction of dose-response curves to DNA damage and repair studies in human peripheral lymphocytes, utilizing the comet assay for the radiosensitivity analysis. So, the blood samples were obtained from healthy donors (40-50 year old), irradiated in a 60 Co source (GAMMACEL 220) with doses of 0.17, 0.25, 0.57, 1.10, 2.12 and 4.22 Gy (0.59 Gy/min.) and processed 1 and 24 hours after the exposition. Results obtained showed a increase in the total lenght of comet (DNA migration) as a function of radiation dose in samples processed 1 and 24 hours after the treatment. The DNA lesion in irradiated lymphocytes with 4.22 Gy (means value of 101.4 μm) were 3.4 times higher than in the untreated lymphocytes (mean value of 30 μm) instead of 24 hours after the irradiation were 1.5 times higher (mean value of 46.3 μm). This reduction on DNA repair occurred in these cells. It was also possible visualized the presence of subpopulations of the cells with different sensitivity and repair capacity to ionizing radiation in these donors. (author). 8 refs., 3 figs

  1. Cr(VI) induces DNA damage, cell cycle arrest and polyploidization: a flow cytometric and comet assay study in Pisum sativum.

    Science.gov (United States)

    Rodriguez, Eleazar; Azevedo, Raquel; Fernandes, Pedro; Santos, Conceição

    2011-07-18

    Chromium(VI) is recognized as the most toxic valency of Cr, but its genotoxicity and cytostaticity in plants is still poorly studied. In order to analyze Cr(VI) cyto- and gentotoxicity, Pisum sativum L. plants were grown in soil and watered with solutions with different concentrations of Cr up to 2000 mg/L. After 28 days of exposure, leaves showed no significant variations in either cell cycle dynamics or ploidy level. As for DNA damage, flow cytometric (FCM) histograms showed significant differences in full peak coefficient of variation (FPCV) values, suggesting clastogenicity. This is paralleled by the Comet assay results, showing an increase in DNA damage for 1000 and 2000 mg/L. In roots, exposure to 2000 mg/L resulted in cell cycle arrest at the G(2)/M checkpoint. It was also verified that under the same conditions 40% of the individuals analyzed suffered polyploidization having both 2C and 4C levels. DNA damage analysis by the Comet assay and FCM revealed dose-dependent increases in DNA damage and FPCV. Through this, we have unequivocally demonstrated for the first time in plants that Cr exposure can result in DNA damage, cell cycle arrest, and polyploidization. Moreover, we critically compare the validity of the Comet assay and FCM in evaluating cytogenetic toxicity tests in plants and demonstrate that the data provided by both techniques complement each other and present high correlation levels. In conclusion, the data presented provides new insight on Cr effects in plants in general and supports the use of the parameters tested in this study as reliable endpoints for this metal toxicity in plants. © 2011 American Chemical Society

  2. DNA comet assay as a rapid detection method of irradiated bovine meat by electron beam

    International Nuclear Information System (INIS)

    Marin-Huachaca, Nelida Simona; Villavicencio, Anna Lucia C.H.

    2001-01-01

    Full text: Introduction: The presence in food of pathogenic microorganisms, such as Salmonella species, Escherichia coli 0157:H7, Listeria Monocytogenes or Yersinia enterolitica, is a problem of growing concern to public health authorities all over the world. Thus, irradiation of certain prepackaged meat products such as ground beef, minced meat, and hamburgers may help in controlling meatborne pathogens and parasites. Pathogenic microorganisms and parasites in meat products, which are commonly consumed raw, are of particular importance, Up to now, only electron-beam accelerators and gamma-ray cells have been used for commercial applications. At the international conference on 'The Acceptance, Control of, and Trade in Irradiated Food', it was recommended that governments should encourage research into detection methods (Anon, 1989), Already five international standards are available to food control agencies. A number of physical, chemical, and biological techniques of detection of irradiated foods have been discussed in the literature. A rapid and inexpensive screening test employing DNA Comet Assay to identify radiation treatment of food has been described by Cerda et al. (1997). This method is restricted to foods that have not been subjected to heat or other treatments, which also induce DNA fragmentation. Advantages are its simplicity, low cost and speed of measurement. This method was proposed to the European Committee for Standardization (CEN) as a screening protocol (presumptive) and not as a proof (definitive). The DNA comet assay have been yielded good results with chicken, pork, fish meat, exotic meat, hamburgers, fruits and cereals. In this work we studied a DNA fragmentation of bovine meat irradiated by electron beam. Experimental: Bovine meat was purchased in local shops in Sao Paulo. Irradiation was performed with electron beam of accelerator facility of Radiation Dynamics Inc., USA (E=1,5 MeV, l=25 mA). The irradiation doses were 3,5; 4,5, 5,5, and 7

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

    Science.gov (United States)

    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

  4. Measurement of DNA base and nucleotide excision repair activities in mammalian cells and tissues using the comet assay - A methodological overview

    Czech Academy of Sciences Publication Activity Database

    Azqueta, A.; Langie, S. A. S.; Slyšková, Jana; Collins, A. R.

    2013-01-01

    Roč. 12, č. 11 (2013), s. 1007-1010 ISSN 1568-7864 Grant - others:EU FP6(XE) LSHB-CT-2006-037575 Institutional support: RVO:68378041 Keywords : comet assay * base excision repair * nucleotide excision repair Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.362, year: 2013

  5. DNA Strand Breaks in Mitotic Germ Cells of Caenorhabditis elegans Evaluated by Comet Assay

    Science.gov (United States)

    Park, Sojin; Choi, Seoyun; Ahn, Byungchan

    2016-01-01

    DNA damage responses are important for the maintenance of genome stability and the survival of organisms. Such responses are activated in the presence of DNA damage and lead to cell cycle arrest, apoptosis, and DNA repair. In Caenorhabditis elegans, double-strand breaks induced by DNA damaging agents have been detected indirectly by antibodies against DSB recognizing proteins. In this study we used a comet assay to detect DNA strand breaks and to measure the elimination of DNA strand breaks in mitotic germline nuclei of C. elegans. We found that C. elegans brc-1 mutants were more sensitive to ionizing radiation and camptothecin than the N2 wild-type strain and repaired DNA strand breaks less efficiently than N2. This study is the first demonstration of direct measurement of DNA strand breaks in mitotic germline nuclei of C. elegans. This newly developed assay can be applied to detect DNA strand breaks in different C. elegans mutants that are sensitive to DNA damaging agents. PMID:26903030

  6. Genotoxic and teratogenic potential of marine sediment extracts investigated with comet assay and zebrafish test

    International Nuclear Information System (INIS)

    Kammann, Ulrike; Biselli, Scarlett; Huehnerfuss, Heinrich; Reineke, Ninja; Theobald, Norbert; Vobach, Michael; Wosniok, Werner

    2004-01-01

    Organic extracts of marine sediments from the North Sea and the Baltic Sea were investigated with two toxicity assays. The comet assay based on the fish cell line Epithelioma papulosum cyprini (EPC) was applied to determine the genotoxic potential; zebrafish embryos (Danio rerio) were used to quantify the teratogenic potential of the samples. EC 50 values were calculated from dose-response curves for both test systems. Highest teratogenic and genotoxic effects normalised to total organic carbon (TOC) content were detected in sediment samples of different origins. Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) are not likely to be the causes of the observed effects, as demonstrated by a two-step fractionation procedure of selected extracts. The toxic potential was more pronounced in fractions having polarity higher than those possessed by PAHs and PCBs. The suitability of the two in vitro test systems for assessing genotoxic and teratogenic effects of marine sediment extracts could be demonstrated. - Capsule: In vitro toxicity assays are used to assess genotoxic and teratogenic effects of environmental extracts

  7. HT-COMET: a novel automated approach for high throughput assessment of human sperm chromatin quality

    Science.gov (United States)

    Albert, Océane; Reintsch, Wolfgang E.; Chan, Peter; Robaire, Bernard

    2016-01-01

    STUDY QUESTION Can we make the comet assay (single-cell gel electrophoresis) for human sperm a more accurate and informative high throughput assay? SUMMARY ANSWER We developed a standardized automated high throughput comet (HT-COMET) assay for human sperm that improves its accuracy and efficiency, and could be of prognostic value to patients in the fertility clinic. WHAT IS KNOWN ALREADY The comet assay involves the collection of data on sperm DNA damage at the level of the single cell, allowing the use of samples from severe oligozoospermic patients. However, this makes comet scoring a low throughput procedure that renders large cohort analyses tedious. Furthermore, the comet assay comes with an inherent vulnerability to variability. Our objective is to develop an automated high throughput comet assay for human sperm that will increase both its accuracy and efficiency. STUDY DESIGN, SIZE, DURATION The study comprised two distinct components: a HT-COMET technical optimization section based on control versus DNAse treatment analyses (n = 3–5), and a cross-sectional study on 123 men presenting to a reproductive center with sperm concentrations categorized as severe oligozoospermia, oligozoospermia or normozoospermia. PARTICIPANTS/MATERIALS, SETTING, METHODS Sperm chromatin quality was measured using the comet assay: on classic 2-well slides for software comparison; on 96-well slides for HT-COMET optimization; after exposure to various concentrations of a damage-inducing agent, DNAse, using HT-COMET; on 123 subjects with different sperm concentrations using HT-COMET. Data from the 123 subjects were correlated to classic semen quality parameters and plotted as single-cell data in individual DNA damage profiles. MAIN RESULTS AND THE ROLE OF CHANCE We have developed a standard automated HT-COMET procedure for human sperm. It includes automated scoring of comets by a fully integrated high content screening setup that compares well with the most commonly used semi

  8. Analysis of DNA damage in lizards D.raddei, from areas with different levels of soil contamination using comet assay

    International Nuclear Information System (INIS)

    Simonyan, A.E.; Gevorgyan, A.L.; Sargsyan, A.A.; Arakelyan, M.S.; Minasyan, S.H.

    2015-01-01

    The levels of DNA damage in erythrocytes of rock lizards Darevskia raddei from reserve Shikahogh and Kajaran (Republic of Armenia) and Zuar (Nagorno-Karabakh Republic), were assessed using the comet assay. Female lizards were more sensitive to environmental pollutants than males. Significant positive correlation was found between DNA damage in female lizards and content of Cu, Mo, Pb, Cd, V and As in soil

  9. Assessment of genotoxicity of methyl-tert-butyl ether, benzene, toluene, ethylbenzene, and xylene to human lymphocytes using comet assay

    International Nuclear Information System (INIS)

    Chen, Colin S.; Hseu, You C.; Liang, Shih H.; Kuo, J.-Y.; Chen, Ssu. C.

    2008-01-01

    Methyl-tert-butyl ether (MTBE) is a gasoline oxygenate and antiknock additive substituting for lead alkyls currently in use worldwide. Benzene, toluene, ethylbenzene, and xylene (BTEX) are volatile monoaromatic hydrocarbons which are commonly found together in crude petroleum and petroleum products such as gasoline. The aim of this study is to evaluate the genotoxic effects of these tested chemicals in human lymphocytes. Using the alkaline comet assay, we showed that all of the tested chemicals induce DNA damage in isolated human lymphocytes. This effect could follow from the induction of DNA strands breaks. The neutral version of the test revealed that MTBE, benzene, and xylenes induce DNA double-strand breaks at 200 μM. Apart from MTBE, the spin traps, 5,5-dimethyl-pyrroline-N-oxide (DMPO) and N-tert-butyl-α-phenylnitrone (PBN) can decrease the level of DNA damage in BTEX at 200 μM. This indicated that DNA damage could result from the participation of free radicals in DNA-damaging effect, which was further supported by the fact that post-treatment of formamidopyrimidine-DNA glycosylase (Fpg), enzyme recognizing oxidized DNA purines, gave rise to a significant increase in the extent of DNA damage in cells treated with benzene, and xylene at 200 μM. The results obtained suggested that MTBE and BTEX could induce a variety type of DNA damage such as single-strand breaks (SSBs), double-strand breaks (DSBs), and oxidative base modification

  10. Mutagenic effects of tributyltin and inorganic lead (Pb II on the fish H. malabaricus as evaluated using the comet assay and the piscine micronucleus and chromosome aberration tests

    Directory of Open Access Journals (Sweden)

    Ferraro Marcos Vinícius M.

    2004-01-01

    Full Text Available Genotoxicity studies on toxic metals and their organic compounds are very important, especially so in the investigation of the effects of these compounds on the aquatic environments where they tend to accumulate. The use of endemic aquatic organisms as biological sentinels has proved useful to environmental monitoring. We assessed the mutagenic potential of tributyltin (TBT and inorganic lead (PbII using samples of the fish Hoplias malabaricus (commonly called traíra using the comet assay and the piscine micronucleus and chromosome aberration tests. Eighteen H. malabaricus were acclimatized in three individual aquariums, each containing six fish, six fish being exposed to 0.3 mg/g of body weight (bw of TBT, six to 21 mg/g bw of PbII and six being used as controls. Exposure to TBT and PbII was achieved by feeding the fish every five days with Astyanax (a small fish that is part of the normal diet of H. malabaricus which had been injected with solutions of TBT, PbII or with water (the control group. After two months the H. malabaricus were sacrificed and their peripheral blood collected and subjected to the comet and micronucleus assays, the chromosome aberration assay being conducted using kidney-tissue. Although the comet assay showed now mutagenic effects at the lead concentrations used but encountered results with TBT, the micronucleus and chromosome aberrations assays both indicated that TBT and PbII are potentially mutagenic (p < 0.01, the micronucleus assay showing morphological alterations of the nucleus.

  11. Gene polymorphisms against DNA damage induced by hydrogen peroxide in leukocytes of healthy humans through comet assay: a quasi-experimental study

    Directory of Open Access Journals (Sweden)

    Klautau-Guimarães Maria N

    2010-05-01

    Full Text Available Abstract Background Normal cellular metabolism is well established as the source of endogenous reactive oxygen species which account for the background levels of oxidative DNA damage detected in normal tissue. Hydrogen peroxide imposes an oxidative stress condition on cells that can result in DNA damage, leading to mutagenesis and cell death. Several potentially significant genetic variants related to oxidative stress have already been identified, and angiotensin I-converting enzyme (ACE inhibitors have been reported as possible antioxidant agents that can reduce vascular oxidative stress in cardiovascular events. Methods We investigate the influences of haptoglobin, manganese superoxide dismutase (MnSOD Val9Ala, catalase (CAT -21A/T, glutathione peroxidase 1 (GPx-1 Pro198Leu, ACE (I/D and gluthatione S-transferases GSTM1 and GSTT1 gene polymorphisms against DNA damage and oxidative stress. These were induced by exposing leukocytes from peripheral blood of healthy humans (N = 135 to hydrogen peroxide (H2O2, and the effects were tested by comet assay. Blood samples were submitted to genotyping and comet assay (before and after treatment with H2O2 at 250 μM and 1 mM. Results After treatment with H2O2 at 250 μM, the GPx-1 polymorphism significantly influenced results of comet assay and a possible association of the Pro/Leu genotype with higher DNA damage was found. The highest or lowest DNA damage also depended on interaction between GPX-1/ACE and Hp/GSTM1T1 polymorphisms when hydrogen peroxide treatment increased oxidative stress. Conclusions The GPx-1 polymorphism and the interactions between GPX-1/ACE and Hp/GSTM1T1 can be determining factors for DNA oxidation provoked by hydrogen peroxide, and thus for higher susceptibility to or protection against oxidative stress suffered by healthy individuals.

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

    Directory of Open Access Journals (Sweden)

    Joaquin ede Lapuente

    2015-06-01

    Full Text Available 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

  13. In vitro genotoxicity of microcystin-RR on primary cultured rat hepatocites and Hep G2 cell line detected by Comet assay

    International Nuclear Information System (INIS)

    Zegura, B.; Filipic, M.; Lah Turnsek, T.; Sedmak, B.; Suput, D.

    2002-01-01

    Microcystins are hepatotoxic cyclic heptapeptides produced by different species of bloom forming cyanobacteria (Microcystis, Anabaena, Nostoc Oscillatoria). The primary target of the toxin is the liver. The uptake of microcystins into the hepatocites occurs via carrier-mediated transport system. Microcystins cause cytoskeletal damage, necrosis and pooling of blood in the liver, with a consequent increase in the liver weight. The cause of death is a massive hepatic haemorrhage. Microcystins are inhibitors of serine/threonine protein phosphatases 1 and 2A and act as tumor-promoters. Ito and coworkers demonstrated that microcystins induced neoplastic nodules in the liver after repeated injections without an initiator, which indicates that they might act also as tumor initiators. The aim of our studies was to elucidate possible genotoxic effects of microcystin-RR (MCYST-RR) at molecular level using Comet assay. The Comet assay is a sensitive method for detection of DNA strand breaks at the level of a single cell. DNA single-strand breaks can lead to mutations, which are the first step in carcinogensis. (author)

  14. Human sperm sex chromosome disomy and sperm DNA damage assessed by the neutral comet assay.

    Science.gov (United States)

    McAuliffe, M E; Williams, P L; Korrick, S A; Dadd, R; Marchetti, F; Martenies, S E; Perry, M J

    2014-10-10

    Is there an association between human sperm sex chromosome disomy and sperm DNA damage? An increase in human sperm XY disomy was associated with higher comet extent; however, there was no other consistent association of sex chromosome disomies with DNA damage. There is limited published research on the association between sex chromosome disomy and sperm DNA damage and the findings are not consistent across studies. We conducted a cross-sectional study of 190 men (25% ever smoker, 75% never smoker) from subfertile couples presenting at the Massachusetts General Hospital Fertility Clinic from January 2000 to May 2003. Multiprobe fluorescence in situ hybridization for chromosomes X, Y and 18 was used to determine XX, YY, XY and total sex chromosome disomy in sperm nuclei using an automated scoring method. The neutral comet assay was used to measure sperm DNA damage, as reflected by comet extent, percentage DNA in the comet tail, and tail distributed moment. Univariate and multiple linear regression models were constructed with sex chromosome disomy (separate models for each of the four disomic conditions) as the independent variable, and DNA damage parameters (separate models for each measure of DNA damage) as the dependent variable. Men with current or past smoking history had significantly greater comet extent (µm: regression coefficients with 95% CI) [XX18: 15.17 (1.98, 28.36); YY18: 14.68 (1.50, 27.86); XY18: 15.41 (2.37, 28.45); Total Sex Chromosome Disomy: 15.23 (2.09, 28.38)], and tail distributed moment [XX18: 3.01 (0.30, 5.72); YY18: 2.95 (0.24, 5.67); XY18: 3.04 (0.36, 5.72); Total Sex Chromosome Disomy: 3.10 (0.31, 5.71)] than men who had never smoked. In regression models adjusted for age and smoking, there was a positive association between XY disomy and comet extent. For an increase in XY disomy from 0.56 to 1.47% (representing the 25th to 75th percentile), there was a mean increase of 5.08 µm in comet extent. No other statistically significant

  15. A direct view by immunofluorescent comet assay (IFCA) of DNA damage induced by nicking and cutting enzymes, ionizing (137)Cs radiation, UV-A laser microbeam irradiation and the radiomimetic drug bleomycin.

    Science.gov (United States)

    Grigaravicius, Paulius; Rapp, Alexander; Greulich, Karl Otto

    2009-03-01

    In DNA repair research, DNA damage is induced by different agents, depending on the technical facilities of the investigating researchers. A quantitative comparison of different investigations is therefore often difficult. By using a modified variant of the neutral comet assay, where the histone H1 is detected by immunofluorescence [immunofluorescent comet assay (IFCA)], we achieve previously unprecedented resolution in the detection of fragmented chromatin and show that trillions of ultraviolet A photons (of a few eV), billions of bleomycin (BLM) molecules and thousands of gamma quanta (of 662 keV) generate, in first order, similar damage in the chromatin of HeLa cells. A somewhat more detailed inspection shows that the damage caused by 20 Gy ionizing radiation and by a single laser pulse of 10 microJ are comparable, while the damage caused by 12 microg/ml BLM depends highly on the individual cell. Taken together, this work provides a detailed view of DNA fragmentation induced by different treatments and allows comparing them to some extent, especially with respect to the neutral comet assay.

  16. Evaluating the genotoxic effects of workers exposed to lead using micronucleus assay, comet assay and TCR gene mutation test

    International Nuclear Information System (INIS)

    Chen Zhijian; Lou Jianlin; Chen Shijie; Zheng Wei; Wu Wei; Jin Lifen; Deng Hongping; He Jiliang

    2006-01-01

    To evaluate the genotoxic effects of lead (Pb) exposure, 25 workers in a workplace producing storage battery were monitored for three genetic end-points using micronucleus (MN) assay, comet assay and TCR gene mutation test. Twenty-five controls were matched with workers according to age, gender and smoking. The air Pb concentration in the workplace was 1.26 mg/m 3 . All subjects were measured for Pb concentration of blood by atom absorption spectrophotometry. The mean Pb concentration of blood in workers (0.32 mg/l) was significantly higher than that in controls (0.02 mg/l). The results of MN test showed that the mean micronuclei rate (MNR) and mean micronucleated cells rate (MCR) in workers were 9.04 ± 1.51 per mille and 7.76 ± 1.23 per mille , respectively, which were significantly higher than those (2.36 ± 0.42 per mille and 1.92 ± 0.31 per mille ) in controls (P -4 and 1.74 ± 0.17 x 10 -4 , respectively, there was no significant difference between workers and controls (P > 0.05). The results of our study indicated that the genetic damage was detectable in 25 workers occupationally exposed to lead

  17. The DNA comet assay and the germination test in detection of food treated by ionizing radiation; Teste do cometa e teste de germinacao na deteccao do tratamento de alimentos com a radiacao ionizante

    Energy Technology Data Exchange (ETDEWEB)

    Huachaca, Nelida Simona Marin

    2002-07-01

    Two methods of irradiated food detection, one biochemical, the comet assay and, other biological, the germination test, were applied in bovine meat and fruit samples. The comet assay detects the damage on DNA caused by ionizing radiation. The germination test evaluates the sensitivity to radiation of seeds as for germination ability, shooting and, rooting. The samples were irradiated in gamma font and electron accelerator. For bovine meat samples, the doses were 0.0; 2.5; 4.5 e 7.0 kGy at chilled condition and, 0.0; 2.5; 4.5; 7.0 e 8.5 kGy at frozen conditions. For fruit samples such as melon, watermelon, apple, orange, papaya and, tomato, the doses were: 0.0; 0.5; 0.75; 1.0; 2.0 e 4.0 kGy. The differences between the gamma rays and the electron beam effects on extent of DNA migration and, on shooting and rooting, showed to be similar. The comet assay, under neutral conditions, permitted to discriminate between irradiated and unirradiated bovine meat samples, until one month of storage. Also, it was possible to distinguish, by the comet assay, the control sample with regard to irradiated fruit, at doses as low as 0,5 kGy. In the germination test, the root length was the best parameter to discriminate irradiated and unirradiated samples of melon, watermelon and tomato, while the germination percent was the best parameter for apple and orange. (author)

  18. DNA damage in leukocytes from fanconi anemia patients and heterozygotes induced by mitomycin C and ionizing radiation as assessed by the comet and comet - FISH assay

    International Nuclear Information System (INIS)

    Mohseni Meybodi, A.; Mozdarani, H.

    2009-01-01

    Lymphocytes of Fanconi anemia (FA) show an increased sensitivity to the alkylating agents such as mitomycin C (MMC), but their responses to gamma-irradiation is controversial. The extent of DNA damage in leukocytes of FA patients following irradiation and MMC treatment was studied at cellular and single chromosome level. Methods: DNA damage induced by gamma-rays and MMC was measured in leukocytes of FA patients and carriers at whole genome level using the comet assay. Also, at the DNA level of specific chromosome involved in this disease using a modified comet-FISH protocol with whole chromosome painting probes (chromosomes 16 and 13), DNA damage in leukocytes of FA patients and heterozygotes were compared to healthy individuals. Results: Baseline DNA damage in leukocytes of patients and heterozygotes was higher than in controls. Net induced DNA damage by gamma-rays in leukocytes of FA cases was not significantly different from that of healthy donors and heterozygotes. Net induced DNA damage by MMC was statistically higher and significantly different (P<0.05) in patients than other groups. Hybridization of chromosome 16 reveals more signals in the tail but the number of spots in the tail was not significantly higher than the hybridization spots for chromosome 13 in both gamma-irradiated and MMC treated samples. Conclusion: Results indicate that DNA damage induced by MMC could be a better index for diagnosis of FA patients compared to gamma-rays. Results of comet-FISH showed no difference between the sensitivity of chromosome 16 and 13 to MMC and radiation. It may indicate that, although the FA-A gene is located on chromosome 16, this chromosome might have a similar sensitivity as other chromosomes

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

    International Nuclear Information System (INIS)

    Donnelly, Erling T.; Liu Yanfeng; Paul, Tracy K.; Rockwell, Sara

    2005-01-01

    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 μmol/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 μmol/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 did not

  20. Neutralization potential as an assay of alkalinity of environmental solids

    International Nuclear Information System (INIS)

    Grube, W.E.Jr.; Ammons, J.T.

    1993-01-01

    The method to determine neutralizing equivalence of agricultural limestone has been applied to quantify the amount of bases present in a broad diversity of mineral materials, solid reagents, and products involved in environmental processes. The capacity to neutralize native or imposed acidity must be known in many processes in order to preserve near-neutral material. The standard method for assaying agricultural limestones was adapted to quantify native alkalinity in calcareous rocks exposed by coal surface mining. Data from these analyses continue to provide the surface mining industry and regulating agencies with a measure of the extent to which acidic mine drainage may be neutralized by the natural components of surrounding rock strata and disturbed materials. This approach to determine base content has also been applied to commercially available industrial byproducts added to soils or wastes. Kiln dust, fly ash, sludge, and other additives have been evaluated routinely to measure their alkalinity contribution and also batch-to-batch uniformity. The application of this technique to monitor amounts of reagents added to neutralize acid waste materials by adding alkalis is discussed. Use of this procedure to evaluate different materials is documented with exemplary data. Results of analyses of a broad variety of rock and soil materials, amended soils, soil additives or amendments, industrial waste byproducts, sludge, and treated wastes are presented. Utility of the procedure for routine quality control in soil treatment, amendment uniformity, and product analysis is discussed

  1. Variation in the measurement of DNA damage by comet assay measured by the ECVAG dagger inter-laboratory validation trial

    DEFF Research Database (Denmark)

    Forchhammer, Lykke; Johansson, Clara; Loft, Steffen

    2010-01-01

    the level of DNA damage in monocyte-derived THP-1 cells by either visual classification or computer-aided image analysis of pre-made slides, coded cryopreserved samples of cells and reference standard cells (calibration curve samples). The reference standard samples were irradiated with ionizing radiation...... by the different laboratories as evidenced by an inter-laboratory coefficient of variation (CV) of 47%. Adjustment of the primary comet assay end points by a calibration curve prepared in each laboratory reduced the CV to 28%, a statistically significant reduction (P test). A large fraction...

  2. Environmental exposure to human carcinogens in teenagers and the association with DNA damage

    International Nuclear Information System (INIS)

    Franken, Carmen; Koppen, Gudrun; Lambrechts, Nathalie; Govarts, Eva; Bruckers, Liesbeth; Den Hond, Elly; Loots, Ilse; Nelen, Vera; Sioen, Isabelle; Nawrot, Tim S.; Baeyens, Willy; Van Larebeke, Nicolas; Boonen, Francis; Ooms, Daniëlla; Wevers, Mai; Jacobs, Griet; Covaci, Adrian; Schettgen, Thomas; Schoeters, Greet

    2017-01-01

    Background: We investigated whether human environmental exposure to chemicals that are labeled as (potential) carcinogens leads to increased (oxidative) damage to DNA in adolescents. Material and methods: Six hundred 14–15-year-old youngsters were recruited all over Flanders (Belgium) and in two areas with important industrial activities. DNA damage was assessed by alkaline and formamidopyrimidine DNA glycosylase (Fpg) modified comet assays in peripheral blood cells and analysis of urinary 8-hydroxydeoxyguanosine (8-OHdG) levels. Personal exposure to potentially carcinogenic compounds was measured in urine, namely: chromium, cadmium, nickel, 1-hydroxypyrene as a proxy for exposure to other carcinogenic polycyclic aromatic hydrocarbons (PAHs), t,t-muconic acid as a metabolite of benzene, 2,5-dichlorophenol (2,5-DCP), organophosphate pesticide metabolites, and di(2-ethylhexyl) phthalate (DEHP) metabolites. In blood, arsenic, polychlorinated biphenyl (PCB) congeners 118 and 156, hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and perfluorooctanoic acid (PFOA) were analyzed. Levels of methylmercury (MeHg) were measured in hair. Multiple linear regression models were used to establish exposure-response relationships. Results: Biomarkers of exposure to PAHs and urinary chromium were associated with higher levels of both 8-OHdG in urine and DNA damage detected by the alkaline comet assay. Concentrations of 8-OHdG in urine increased in relation with increasing concentrations of urinary t,t-muconic acid, cadmium, nickel, 2,5-DCP, and DEHP metabolites. Increased concentrations of PFOA in blood were associated with higher levels of DNA damage measured by the alkaline comet assay, whereas DDT was associated in the same direction with the Fpg-modified comet assay. Inverse associations were observed between blood arsenic, hair MeHg, PCB 156 and HCB, and urinary 8-OHdG. The latter exposure biomarkers were also associated with higher fish intake. Urinary nickel

  3. Environmental exposure to human carcinogens in teenagers and the association with DNA damage

    Energy Technology Data Exchange (ETDEWEB)

    Franken, Carmen, E-mail: carmen.franken@vito.be [Flemish Institute for Technological Research (VITO), Mol (Belgium); Department of Biomedical Sciences, University of Antwerp, Antwerp (Belgium); Koppen, Gudrun; Lambrechts, Nathalie; Govarts, Eva [Flemish Institute for Technological Research (VITO), Mol (Belgium); Bruckers, Liesbeth [Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Hasselt (Belgium); Den Hond, Elly [Flemish Institute for Technological Research (VITO), Mol (Belgium); Loots, Ilse [Political and Social Sciences, University of Antwerp, Antwerp (Belgium); Nelen, Vera [Provincial Institute for Hygiene, Antwerp (Belgium); Sioen, Isabelle [Department of Public Health, Ghent University, Ghent (Belgium); Department of Food Safety and Food Quality, Ghent University, Ghent (Belgium); Nawrot, Tim S. [Centre for Environmental Sciences, Hasselt University, Diepenbeek (Belgium); Department of Public Health & Primary Care, Leuven University, Leuven (Belgium); Baeyens, Willy [Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Brussels (Belgium); Van Larebeke, Nicolas [Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Brussels (Belgium); Department of Radiotherapy and Experimental Cancerology, Ghent University, Ghent (Belgium); Boonen, Francis; Ooms, Daniëlla; Wevers, Mai; Jacobs, Griet [Flemish Institute for Technological Research (VITO), Mol (Belgium); Covaci, Adrian [Toxicological Centre, Department of Pharmaceutical Sciences, University of Antwerp, Antwerp (Belgium); Schettgen, Thomas [Department of Occupational and Social Medicine, RWTH Aachen University, Aachen (Germany); Schoeters, Greet [Flemish Institute for Technological Research (VITO), Mol (Belgium); Department of Biomedical Sciences, University of Antwerp, Antwerp (Belgium); University of Southern Denmark, Institute of Public Health, Department of Environmental Medicine, Odense (Denmark)

    2017-01-15

    Background: We investigated whether human environmental exposure to chemicals that are labeled as (potential) carcinogens leads to increased (oxidative) damage to DNA in adolescents. Material and methods: Six hundred 14–15-year-old youngsters were recruited all over Flanders (Belgium) and in two areas with important industrial activities. DNA damage was assessed by alkaline and formamidopyrimidine DNA glycosylase (Fpg) modified comet assays in peripheral blood cells and analysis of urinary 8-hydroxydeoxyguanosine (8-OHdG) levels. Personal exposure to potentially carcinogenic compounds was measured in urine, namely: chromium, cadmium, nickel, 1-hydroxypyrene as a proxy for exposure to other carcinogenic polycyclic aromatic hydrocarbons (PAHs), t,t-muconic acid as a metabolite of benzene, 2,5-dichlorophenol (2,5-DCP), organophosphate pesticide metabolites, and di(2-ethylhexyl) phthalate (DEHP) metabolites. In blood, arsenic, polychlorinated biphenyl (PCB) congeners 118 and 156, hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT) and perfluorooctanoic acid (PFOA) were analyzed. Levels of methylmercury (MeHg) were measured in hair. Multiple linear regression models were used to establish exposure-response relationships. Results: Biomarkers of exposure to PAHs and urinary chromium were associated with higher levels of both 8-OHdG in urine and DNA damage detected by the alkaline comet assay. Concentrations of 8-OHdG in urine increased in relation with increasing concentrations of urinary t,t-muconic acid, cadmium, nickel, 2,5-DCP, and DEHP metabolites. Increased concentrations of PFOA in blood were associated with higher levels of DNA damage measured by the alkaline comet assay, whereas DDT was associated in the same direction with the Fpg-modified comet assay. Inverse associations were observed between blood arsenic, hair MeHg, PCB 156 and HCB, and urinary 8-OHdG. The latter exposure biomarkers were also associated with higher fish intake. Urinary nickel

  4. The single-cell gel electrophoresis assay to determine apoptosis ...

    African Journals Online (AJOL)

    When the frequency of appearance of apoptotic cells following was observed over a period of time, there was a significant increase in appearance of apoptosis when using single cell gel electrophoresis assay. The present report demonstrates that the characteristic pattern of apoptotic comets detected by the comet assay ...

  5. Fish eco-genotoxicology: Comet and micronucleus assay in fish erythrocytes as in situ biomarker of freshwater pollution

    Directory of Open Access Journals (Sweden)

    Bilal Hussain

    2018-02-01

    Full Text Available Owing to white meat production Labeo rohita have vast economic importance, but its population has been reduced drastically in River Chenab due to pollution. Atomic absorption spectrophotometry showed a merciless toxicity level of Cd, Cu, Mn, Zn, Pb, Cr, Sn and Hg. Comet assay results indicated significant (p < .05 DNA fragmentation in Labeo rohita as 42.21 ± 2.06%, 31.26 ± 2.41% and 21.84 ± 2.21% DNA in comet tail, tail moment as 17.71 ± 1.79, 10.30 ± 1.78 and 7.81 ± 1.56, olive moment as 13.58 ± 1.306, 8.10 ± 1.04 and 5.88 ± 0.06, respectively, from three different polluted sites on the river. Micronucleus assay showed similar findings of single micronucleus induction (MN as 50.00 ± 6.30‰, double MN 14.40 ± 2.56‰, while nuclear abnormalities (NA were found as 150.00 ± 2.92‰. These higher frequencies of MN induction and NA were found to be the cause of reduction of 96% of the population of this fish species in an experimental area of the River Chenab. This fish species has been found near extinction through the length of the river Chenab and few specimens in rainy seasons if restored by flood, may die in sugarcane mill season. Due to sweeping extinction Labeo rohita showed the highest sensitivity for pollution and could be used as bioindicator and DNA fragmentation in this column feeder fish species as a biomarker of the pollution load in freshwater bodies.

  6. DNA comet assay to identify different freezing temperatures of irradiated liver chicken

    International Nuclear Information System (INIS)

    Duarte, Renato C.; Mozeika, Michel A.; Fanaro, Gustavo B.; Villavicencio, Anna L.C.H.; Marchioni, Eric

    2009-01-01

    The cold chain is a succession of steps which maintain the food at low temperature. The thawed food never be frozen again and the best solution being to consume it quickly to avoid the microorganism growth which causes decay and nutrients damage. One of most important point is that freezing process, unlike irradiation, do not destroy microorganisms, only inactive them as long as they remain in a frozen state. The Comet Assay is an original test used to detect irradiated foods that's recognize the DNA damage and can then be used to control the overall degradation of the food and in a certain extend to evaluate the damage caused by irradiation, different forms of freeze and storage time on liver chicken cells. Different freezing temperatures were used, deep freeze -196 deg C and slow freeze -10 deg C. Samples were irradiated in a 60 Co irradiator with 1.5, 3.0 and 4.5 kGy radiation doses. Fast freezing technique induces a low percent of DNA degradation comparing to slow freezing technique. This procedure could be a good choose to chicken freezing processing. (author)

  7. DNA comet assay to identify different freezing temperatures of irradiated liver chicken

    Energy Technology Data Exchange (ETDEWEB)

    Duarte, Renato C.; Mozeika, Michel A.; Fanaro, Gustavo B.; Villavicencio, Anna L.C.H. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)], e-mail: renatocduarte@yahoo.com.br; Marchioni, Eric [Universite de Strasbourg, Illkirch (France). Faculte de Pharmacie. Lab. de Chimie Analytique et Sciences de l' Aliment

    2009-07-01

    The cold chain is a succession of steps which maintain the food at low temperature. The thawed food never be frozen again and the best solution being to consume it quickly to avoid the microorganism growth which causes decay and nutrients damage. One of most important point is that freezing process, unlike irradiation, do not destroy microorganisms, only inactive them as long as they remain in a frozen state. The Comet Assay is an original test used to detect irradiated foods that's recognize the DNA damage and can then be used to control the overall degradation of the food and in a certain extend to evaluate the damage caused by irradiation, different forms of freeze and storage time on liver chicken cells. Different freezing temperatures were used, deep freeze -196 deg C and slow freeze -10 deg C. Samples were irradiated in a {sup 60}Co irradiator with 1.5, 3.0 and 4.5 kGy radiation doses. Fast freezing technique induces a low percent of DNA degradation comparing to slow freezing technique. This procedure could be a good choose to chicken freezing processing. (author)

  8. Observing comets

    CERN Document Server

    James, Nick

    2003-01-01

    Since comet Shoemaker-Levy collided with the planet Jupiter with stupendous force in 1994 there has been an upsurge of amateur interest in comets Most comets are first discovered by amateur astronomers because there are so many amateurs looking for them, and techniques and instruments have improved dramatically in the past few years After a short but detailed introduction to the comets themselves Nick James and Gerald North describe comet hunting, photographing and imaging comets, and digital image processing The use of computers for orbital calculations and even helping to discover new comets is given a full chapter, as are advanced techniques including comet photometry and spectroscopy This comprehensive book has an accompanying CD-ROM and is at once a "primer" for comet hunters and a reference text for more advanced amateur astronomers

  9. Optimization of Neutral Comet Assay for studying DNA double-strand breaks in pea and wheat

    Directory of Open Access Journals (Sweden)

    Ivelina Nikolova

    2013-01-01

    Full Text Available This study describes an adaptation of the Comet assay under neutral conditions for mono- and dicotyledonous plants pea (Pisum sativum L. and wheat (Triticum aestivum L.. Modifications concern lysis and electrophoresis steps, respectively. Electrophoresis was carried out varying the intensity of the electric field. A linear relationship between the percentages of DNA in the tail from control background with alteration of intensity was found. Trypan blue dye exclusion test was used in order to determine the intactness of nuclear membrane of the isolated nuclei from both plant model systems. Assessment was conducted on non-irradiated and irradiated nuclei on a monolayer with three doses of UVC. It was found that the share of intact nuclei (trypan blue negative ones is about 95% in controls. Gradual dose-related increase of damaged nuclei was observed in both species, reaching statistical significance only at the higher dose applied.

  10. 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.

    Science.gov (United States)

    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 (pbody 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. © The Author(s) 2013.

  11. Comet assay and micronucleus tests on Oreochromis niloticus (Perciforme: Cichlidae) exposed to raw sugarcane vinasse and to phisicochemical treated vinasse by pH adjustment with lime (CaO).

    Science.gov (United States)

    Correia, Jorge E; Christofoletti, Cintya Ap; Ansoar-Rodríguez, Yadira; Guedes, Thays A; Fontanetti, Carmem S

    2017-04-01

    In Brazil vinasse, a main sugarcane distillery residue, stands out because every liter of alcohol generates 10-15 L of vinasse as waste. An alternative for the disposal of this waste is the fertirrigation of the sugarcane culture itself. However, the high amount released can saturate the soil and through leaching/percolation contaminate water resources. The aim of this study is verifying the toxic potential of vinasse in tilapias and effectiveness of the physicalchemical treatment of this waste with pH adjustment with lime (CaO). The comet assay and the micronucleus test were applied on animals exposed to dilutions of raw vinasse and vinasse adjusted to neutral pH. Bioassays with raw vinasse dilutions indicated a toxic and genotoxic potential; fish exposed to the highest concentration died less than 48 h after the exposure; the incidence of micronucleus was significantly higher when compared to negative control for all dilutions. For the comet assay, the scores of damage were statistically higher for all dilutions, with the exception of the 1% dillution. However, in the bioassay with the chemically treated vinasse (neutral pH), most fish in the 10% dilution survived and there was no significant difference when compared to the control. Damage scores in the comet assay were similar to the results of the untreated vinasse. The chemical treatment of vinasse with lime to neutralize the pH proved to be an effective alternative for the toxicity reduction of this residue, since it reduced the mortality of fish at higher concentrations and the incidence of damage to DNA. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Application of the microbiological method DEFT/APC and DNA comet assay to detect ionizing radiation processing of minimally processed vegetables; Aplicacao do metodo microbiologico DEFT/APC e do teste do cometa na deteccao do tratamento com radiacao ionizante de hortalicas minimamente processadas

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Michel Mozeika

    2008-07-01

    Marketing of minimally processed vegetables (MPV) are gaining impetus due to its convenience, freshness and apparent healthy. However, minimal processing does not reduce pathogenic microorganisms to safe levels. Food irradiation is used to extend the shelf life and inactivation of food-borne pathogens, Its combination with minimal processing could improve the safety and quality of MPV. Two different food irradiation detection methods, a biological, the DEFT/APC, and another biochemical, the DNA Comet Assay were applied to MPV in order to test its applicability to detect irradiation treatment. DEFT/APC is a microbiological screening method based on the use of the direct epi fluorescent filter technique (DEFT) and the aerobic plate count (APC). DNA Comet Assay detects DNA damage due to ionizing radiation. Samples of lettuce, chard, watercress, dandelion, kale, chicory, spinach, cabbage from retail market were irradiated O.5 kGy and 1.0 kGy using a {sup 60} Co facility. Irradiation treatment guaranteed at least 2 log cycle reduction for aerobic and psychotropic microorganisms. In general, with increasing radiation doses, DEFT counts remained similar independent of irradiation processing while APC counts decreased gradually. The difference of the two counts gradually increased with dose increment in all samples. It could be suggested that a DEFT/APC difference over 2.0 log would be a criteria to judge if a MPV was treated by irradiation. DNA Comet Assay allowed distinguishing non-irradiated samples from irradiated ones, which showed different types of comets owing to DNA fragmentation. Both DEFT/APC method and DNA Comet Assay would be satisfactorily used as a screening method for indicating irradiation processing. (author)

  13. Mixture Genotoxicity of 2,4-Dichlorophenoxyacetic Acid, Acrylamide, and Maleic Hydrazide on Human Caco-2 Cells Assessed with Comet Assay

    DEFF Research Database (Denmark)

    Syberg, Kristian; Binderup, Mona-Lise; Cedergreen, Nina

    2015-01-01

    Assessment of genotoxic properties of chemicals is mainly conducted only for single chemicals, without taking mixture genotoxic effects into consideration. The current study assessed mixture effects of the three known genotoxic chemicals, 2,4-dichlorophenoxyacetic acid (2,4-D), acrylamide (AA......), and maleic hydrazide (MH), in an experiment with a fixed ratio design setup. The genotoxic effects were assessed with the single-cell gel electrophoresis assay (comet assay) for both single chemicals and the ternary mixture. The concentration ranges used were 0-1.4, 0-20, and 0-37.7 mM for 2,4-D, AA, and MH......, respectively. Mixture toxicity was tested with a fixed ratio design at a 10:23:77% ratio for 2.4-D:AA:MH. Results indicated that the three chemicals yielded a synergistic mixture effect. It is not clear which mechanisms are responsible for this interaction. A few possible interactions are discussed...

  14. In vivo Comet assay – statistical analysis and power calculations of mice testicular cells

    DEFF Research Database (Denmark)

    Hansen, Merete Kjær; Sharma, Anoop Kumar; Dybdahl, Marianne

    2014-01-01

    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....... 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....

  15. Genotoxicity of indium tin oxide by comet test

    Directory of Open Access Journals (Sweden)

    İbrahim Hakkı Ciğerci

    2015-06-01

    Full Text Available Indium tin oxide (ITO is used for liquid crystal display (LCDs, electrochromic displays, flat panel displays, field emission displays, touch or laptop computer screens, cell phones, energy conserving architectural windows, defogging aircraft and automobile windows, heat-reflecting coatings to increase light bulb efficiency, gas sensors, antistatic window coatings, wear resistant layers on glass, nanowires and nanorods because of its unique properties of high electrical conductivity, transparency and mechanical resistance.Genotoxic effects of ITO were investigated on the root cells of Allium cepa by Comet assay. A. cepa roots were treated with the aqueous dispersions of ITO at 5 different concentrations (12.5, 25, 50, 75, and 100 ppm for 4 h. A significant increase in DNA damage was a observed at all concentrations of ITO by Comet assay. These result indicate that ITO exhibit genotoxic activity in A. cepa root meristematic cells.

  16. Use of molecular cytogenetic analysis as bio marker in assessment of DNA damage in radiation workers at Al-Twuathia site Iraq

    International Nuclear Information System (INIS)

    Abdulsahib, K. A.; Amel, J. M.; Abdullah, A.K.; Haider, Y.L.; Ali, H.F.; Khawla, A.B.

    2012-12-01

    The present study aims to use the biological techniques in a genotoxicity assessment of low doses of radiation in samples of workers in Al-Tuwatha site due to decommissioning to radioactive contamination as a result of work. Used three molecular genetic techniques as included micronuclei in cytoplasm of reticulocytes cells, buccal micronuclei cymate assay and alkaline comet assay. this study including 50 blood samples, aged (35 - 63) as well as 50 blood samples which are not smokers and alcohol as control group which including (35 and 15) aged (25 - 57 year) for the test of micronuclei in cytoplasm of reticulocytes. While the comet assay and buccal micronuclei cymate assay which including blood and cheek swab samples from 25 aged (30 - 56), as well as 25 blood and cheek swab samples which are not smokers and alcohol as control group which including (15 and 10) aged (25 - 57 year). The frequencies of micronuclei in cytoplasm of reticulocytes observed for the radiation workers at Tl-Tuwaith site were significantly (P<0.05) higher than in the control group. Similarly, the comet parameter were statistically higher (P<0.05) in the radiation workers group in comparison with the control group. Also, the results obtained showed statistically significant differences (P-<0.05 between comet tail length and tail moment values measured in radiation worker and control groups. In the case of buccal micronuclei assay, no significant (P<0.05) differences between both group was found. In conclusion, the results indicated that there is a possibility of using the changes in the levels of micronuclei in cytoplasm of reticulocytes, and comet assay useful as results obtained confirmed usefulness of the alkaline comet assay as a sensitive additional bio marker in the regular health screening of workers occupationally exposed to low doses of ionizing radiation.(Author)

  17. Evaluation of DNA Damage in Common Carp (Cyprinus carpio L. by Comet Assay for Determination of Possible Pollution in Lake Mogan (Ankara

    Directory of Open Access Journals (Sweden)

    İsmet Çok

    2011-01-01

    Full Text Available Contamination of the aquatic environment with various concentrations of pollutants results in unexpected threats to humans and wildlife. The consequences of exposure and metabolism of pollutants/xenobiotics, especially carcinogens and mutagens, can be suitably assessed by investigating severe events, such as DNA damage; for example, DNA adducts and DNA strand breaks. One of the commonly used techniques to detect DNA damage in aquatic organisms is single-cell gel electrophoresis (comet assay. This study was carried out using Cyprinus carpio in order to identify the possible pollution in Lake Mogan, near Ankara, Turkey, where the city's sewer system and pesticides used in agriculture are believed to be the common causes of pollution. From the comet assay, the tail length (μm, tail intensity (%, and tail moment values of fish caught from Lake Mogan were found to be 31.10 ± 10.39, 7.77 ± 4.51, 1.50 ± 1.48, respectively, whereas for clean reference sites they were found to be 22.80 ± 1.08, 3.47 ± 1.59, 0.40 ± 0.51, respectively. The values are statistically different from each other (p < 0.0001, p < 0.0001, and p < 0.0013, respectively. These results indicate that Lake Mogan may be polluted with substances that have genotoxic effects and constitute an early warning for the lake system. Further detailed research is needed to establish the source of the pollution and the chemicals responsible.

  18. Indoor and outdoor genotoxic load detected by the Comet assay in leaves of Nicotiana tabacum cultivars Bel B and Bel W3.

    Science.gov (United States)

    Restivo, Francesco Maria; Laccone, Maria Concetta; Buschini, Annamaria; Rossi, Carlo; Poli, Paola

    2002-03-01

    Environmental pollution assessment and control are priority issues for both developed and developing countries of the world. The use of plant material for a more complete picture of environmental health appears to be particularly appealing. Here we validate a previous plant-adapted Comet assay on leaf tissues of Nicotiana tabacum cultivars Bel B and Bel W3. The effects of H(2)O(2) on DNA damage in Bel B and Bel W3 agree with the hypothesis that some component of the machinery that protects DNA integrity from oxidative stress may be impaired in cv. Bel W3. Exposure in the field on sunny summer days (peak ozone concentration >80 p.p.b.) showed significantly higher DNA damage in cv. Bel W3 if plants were collected and subjected to the Comet assay when the air ozone concentration was reaching its peak value, but not when plants were sampled early in the morning and hence after a period of low ozone concentration. The different results suggest that Bel W3 possesses a less efficient recovery apparatus that requires a longer period of activity to be effective and/or is less protected against reactive oxygen species production during exposure to ozone. However, it cannot be excluded that the increase in mean DNA damage is the result of the presence of a genotoxic agent(s) other than ozone. Interestingly, Bel W3 also appears to be more responsive, compared with Bel B, when exposed to ambient indoor pollutants. The use of cv. Bel W3 increases the sensitivity of the assay under both indoor and field conditions. However, different classes of mutagens should be tested to define the range of profitable utilization of this tobacco cultivar for environmental genotoxicity detection.

  19. Comets

    International Nuclear Information System (INIS)

    Hughes, D.W.

    1982-01-01

    Comets are objects of considerable fascination and this paper reviews the present knowledge of the physical structure of the cometary nucleus, coma and tail, the orbits of comets in the Solar System, the proposed mechanisms of cometary origin, the decay processes suffered by comets, and the ways in which they can be observed from Earth and by spacecraft. (author)

  20. Photochemistry of comets

    International Nuclear Information System (INIS)

    Huebner, W.F.

    1985-01-01

    The classification of comets, chemically rich mixtures of volatile materials and refractory grains, is described. The developments of coma and tails, and the composition and structure of coma, plasma tails, dust, and nucleus are examined. The differences between comets and planetary atmospheres are investigated. Three hypotheses on the origin of comets are proposed; one states that comets formed in the region of the giant planets, the second theory has the development of comets occuring in the outer parts of the solar nebula, and the third states that comets formed in a companion fragment of the nebula. The use of radar, photometric, spectral, and laboratory measurements for modeling comets is discussed. The physics and main photolytic and chemical reaction processes of a collision-dominated coma are analyzed; the influence of the solar wind on the coma is studied. A comparison of the model with observed data is presented; good correlation of data is observed. The features of Halley's Comet and other comets with distinctive characteristics are examined. Future comet exploration missions and the need to improve comet models are discussed. 31 references

  1. Visually observing comets

    CERN Document Server

    Seargent, David A J

    2017-01-01

    In these days of computers and CCD cameras, visual comet observers can still contribute scientifically useful data with the help of this handy reference for use in the field. Comets are one of the principal areas for productive pro-amateur collaboration in astronomy, but finding comets requires a different approach than the observing of more predictable targets. Principally directed toward amateur astronomers who prefer visual observing or who are interested in discovering a new comet or visually monitoring the behavior of known comets, it includes all the advice needed to thrive as a comet observer. After presenting a brief overview of the nature of comets and how we came to the modern understanding of comets, this book details the various types of observations that can usefully be carried out at the eyepiece of a telescope. Subjects range from how to search for new comets to visually estimating the brightness of comets and the length and orientation of tails, in addition to what to look for in comet heads a...

  2. Testing the genotoxicity of some perfumes with high diethylphthalate (DEP levels using comet assay

    Directory of Open Access Journals (Sweden)

    Iman Al-Saleh

    2015-05-01

    Full Text Available The presence of phthalates in perfumes has gained recently some attention since these chemicals are added sometimes intentionally as a fixative. Our previous study tested 47 branded perfumes sold in Saudi market and found 68% of tested samples had diethylphthalate (DEP, above reported threshold limit of 1 ppm. Of these phthalates, DEP was found to have the highest mean value (1621.63 ppm. These results enticed us to test the potential genotoxicity of 7 brands in which their DEP contents were in the range of 1.06 ppm to 23649.3 ppm in human TK-6 cells using single cell gel electrophoresis assay (comet assay. Cells were exposed to 400 µl perfume for 2 hrs, at room temperature. Tail moment was (TM used as a metric measure for DNA damage and 25 cells per sample were determined by image analysis software. Four perfumes with DEP above 40 ppm produced significant DNA damage in TK-6 cells with TM of 54.27 ± 1.04, n=500 compare to the other 3 perfumes with DEP < 2 ppm (21.94 ± 1.09, n=300, untreated cells (2.99 ± 0.17, n=250 and cells induced with ethanol (33.76 ± 1.4, n=75 or methanol (23.82 ± 1.84, n=100 which are the vehicles used in perfume's preparations. The results suggest that DEP in perfumes might be one of the ingredients that provoked DNA damage; however, further investigation is required confirming our observation.

  3. Radioprotection of Wistar Rat Lymphocytes Against Microwave Radiation Mediated by Bee Venom

    International Nuclear Information System (INIS)

    Garaj-Vrhovac, V.; Gajski, G.

    2011-01-01

    Microwave radiation is a type of non-ionising electromagnetic radiation present in the environment, and is a potential threat to human health. Cytogenetic studies of microwave radiation conducted in vitro and in vivo, yielded contradictory and often intriguing experimental results. Some reports suggest that exposure of human cells to radiofrequency radiation does not result in increased cytogenetic damage. On the other hand, there is a range of studies showing that radiofrequency radiation can indeed induce genetic alteration after exposure to electric field. Bee venom is used in traditional medicine to treat variety of conditions, such as arthritis, rheumatism, back pain and skin disease. In recent years it has been reported that bee venom possesses antimutagenic, proinflammatory, anti-inflammatory, antinociceptive, and anticancer effects. In addition to the wide range of the bee venom's activities, it also possesses a radioprotective capacity that was noted against X-ray and gamma radiation in various test systems. The aim of the present study was assessment of the radioprotective effect of bee venom against 915 MHz microwave radiation-induced DNA damage in the Wistar rat's lymphocytes in vitro. The possible genotoxic effect of bee venom alone was also assessed on non-irradiated lymphocytes. The alkaline comet assay was used as a sensitive tool in The assessment of DNA damage was performed using the alkaline comet assay and the Fpg-modified comet assay that is more specific technique in detection of DNA strand breaks and oxidative stress. Whole blood was collected from adult male Wistar rats (11 weeks old, approximate body weight 350 g)by cardiac puncture under sterile conditions in heparinized vacutainer tubes. After collection, blood was divided into 1 ml aliquots and placed into 24-well culture plates according to the exposure conditions. Bee venom was added to lymphocyte cultures in final concentration of 1 μg/ml, 4 h prior to irradiation and immediately

  4. Investigation of genotoxic potential of various sizes Fe2O3 nanoparticles with comet assay

    Directory of Open Access Journals (Sweden)

    İbrahim Hakkı Ciğerci

    2015-06-01

    In this study, genotoxic potential of <50 nm and <100 nm Fe2O3 nanoparticles were investigated by using Comet Assay. Allium cepa root meristems were exposed with five doses (0.001, 0.01, 0.1, 1, 10 mM of <50 nm for 4 hour and three doses (2.5, 5 (EC50, 10 mM for <100 nm of Fe2O3 nanoparticle for 24 and 96 h. Methyl methanesulfonate -MMS (10 ppm was used as a positive control. The results were also analyzed statistically by using SPSS by Windows, 18.0. It was determined that different doses of <50 nm Fe2O3 nanoparticle have no genotoxic effect of DNA. Different doses of <100 nm Fe2O3 have no genotoxic but only 10 mM dose have genotoxic effect on DNA. When compared <50 nm with <100 nm of Fe2O3 nanoparticle; <50 nm have more effects than <100 nm of Fe2O3 on DNA damage.

  5. Assessment of genotoxicity and depuration of anthracene in the juvenile coastal fish Trachinotus carolinus using the comet assay

    Directory of Open Access Journals (Sweden)

    Fabio Matsu Hasue

    2013-12-01

    Full Text Available In the environment, anthracene is characterized as being persistent, bioaccumulative and toxic to aquatic organisms. Biotransformation of xenobiotic substances, such as anthracene, produces reactive oxygen species that may induce DNA strand breaks. The aim of the present study was to evaluate the DNA damage in juvenile T. carolinus exposed to different concentrations (8, 16 and 32 µg.L-1 of anthracene for 24 h in the dark then subsequently allowed to depurate in clean water for different periods of time (48, 96 or 144 h using the comet assay. Our results show that anthracene is genotoxic to T. carolinus and that DNA damage was dose- and depuration/time- dependent. Anthracenegenotoxicity was observed in all experimental concentrations. Depuration seemed to be more efficient in fish exposed to thelowest anthracene concentration and maintained in clean water for 96 h.

  6. Carbon quantum dots-based recyclable real-time fluorescence assay for alkaline phosphatase with adenosine triphosphate as substrate.

    Science.gov (United States)

    Qian, Zhaosheng; Chai, Lujing; Tang, Cong; Huang, Yuanyuan; Chen, Jianrong; Feng, Hui

    2015-03-03

    A convenient, reliable, and highly sensitive real-time assay for alkaline phosphatase (ALP) activity in the continuous and recyclable way is established on the basis of aggregation and disaggregation of carbon quantum dots (CQDs) through the competitive assay approach. CQDs and adenosine triphosphate (ATP) were used as the fluorescent indicator and substrate for ALP activity assessment, respectively. Richness of carboxyl groups on the surface of CQDs enables their severe aggregation triggered by cerium ions, which results in effective fluorescence quenching. Under the catalytic hydrolysis of ALP, ATP can be rapidly transformed to phosphate ions. Stronger affinity of phosphate ions to cerium ions than carboxyl groups is taken advantage of to achieve fluorescence recovery induced by redispersion of CQDs in the presence of ALP and ATP. Quantitative evaluation of ALP activity in a broad range from 4.6 to 383.3 U/L with the detection limit of 1.4 U/L can be realized in this way, which endows the assay with high enough sensitivity for practical detection in human serum. The assay can be used in a recyclable way for more than three times since the generated product CePO4 as a precipitate can be easily removed from the standard assay system. This strategy broadens the sensing application of fluorescent CQDs with excellent biocompatibility and provides an example based on disaggregation in optical probe development.

  7. Patient pools and the use of "patient means" are valuable tools in quality control illustrated by a bone-specific alkaline phosphatase assay

    DEFF Research Database (Denmark)

    Hinge, Maja; Lund, Erik D.; Brandslund, Ivan

    2016-01-01

    BACKGROUND: Quality control (QC) is an essential part of clinical biochemistry to ensure that laboratory test results are reliable and correct. Those tests without a defined reference method constitute a special challenge, as is the case with bone-specific alkaline phosphatase (BAP). METHODS...... AND RESULTS: The present study reports an example where a shift in a BAP assay was detected by use of a patient pool and supported by a retrospective calculation of "patient mean", while the external QC and specific assay control material were unaffected by the shift. CONCLUSIONS: Patient pools and the use...

  8. Assay format as a critical success factor for identification of novel inhibitor chemotypes of tissue-nonspecific alkaline phosphatase from high-throughput screening.

    Science.gov (United States)

    Chung, Thomas D Y; Sergienko, Eduard; Millán, José Luis

    2010-04-27

    The tissue-nonspecific alkaline phosphatase (TNAP) isozyme is centrally involved in the control of normal skeletal mineralization and pathophysiological abnormalities that lead to disease states such as hypophosphatasia, osteoarthritis, ankylosis and vascular calcification. TNAP acts in concert with the nucleoside triphosphate pyrophosphohydrolase-1 (NPP1) and the Ankylosis protein to regulate the extracellular concentrations of inorganic pyrophosphate (PP(i)), a potent inhibitor of mineralization. In this review we describe the serial development of two miniaturized high-throughput screens (HTS) for TNAP inhibitors that differ in both signal generation and detection formats, but more critically in the concentrations of a terminal alcohol acceptor used. These assay improvements allowed the rescue of the initially unsuccessful screening campaign against a large small molecule chemical library, but moreover enabled the discovery of several unique classes of molecules with distinct mechanisms of action and selectivity against the related placental (PLAP) and intestinal (IAP) alkaline phosphatase isozymes. This illustrates the underappreciated impact of the underlying fundamental assay configuration on screening success, beyond mere signal generation and detection formats.

  9. Comparative Detection of Alkaline Protease Production in Exiguobacterium acetylicum

    International Nuclear Information System (INIS)

    Gomaa, O.M.; EI Shafey, H.M.

    2009-01-01

    Alkaline protease is one of the most important enzymes in industry, medicine, and research. In the present work, a comparative detection for alkaline protease activity was established for instant detection of enzyme activity. Eight different alkalophilic bacterial isolates were compared based on the clear zone they produced on skim milk agar. One strain gave an absolute clear zone in 16 hours and was used for alkaline protease detection. The result of Phenotypic identification using Biology Microlog 3 identified the isolate as Exiguobacterium acetylicum. The isolate under study showed slightly different characteristics from a known Exiguobacterium acetylicum strain. The isolate tolerated alkaline conditions up to ph 11, while good growth was evident at ph 7, the maximum alkaline protease activity was observed at ph 9 which reached up to 109.01 U/ml. The alkaline activity assay using alkaline protease enzyme assay were coordinating with those obtained by conductivity; there was a relevant decrease in conductivity at the maximum increase in enzyme activity, which proved the cell membrane conductivity has a close relation to alkaline protease production. This isolate has tolerated gamma radiation, the increase in dose (up to 4 Gy) gave wider clear zones in terms of diameter and this was relevant to the conductivity measurements

  10. Mystery of comets

    International Nuclear Information System (INIS)

    Whipple, F.L.

    1985-01-01

    An account is given of the growth of human understanding of comets with emphasis initially placed on theories developed before the twentieth century and subsequently on information regarding the nature of comets, their origin and possible relation to life on earth. Special consideration is given to a description of how the author arrived at his own model of the origin and nature of comets, the dirty snowball theory. The significance of comets (i.e. the hazards they may represent) is assessed and space missions to Halley's comet together with the first landing on a comet (tentatively planned for 1995) are described. It is noted that this growth of cometary understanding is presented as an integral part of the growth of science and technology. 14 references

  11. Genotoxicity and antigenotoxicity assessment of shiitake (Lentinula edodes (Berkeley Pegler using the Comet assay

    Directory of Open Access Journals (Sweden)

    CK Miyaji

    2004-01-01

    Full Text Available The mushroom shiitake (Lentinula edodes (Berkeley Pegler is been widely consumed in many countries, including Brazil, because of its pleasant flavor and reports of its therapeutic properties, although there is little available information on the genotoxicity and/or antigenotoxicity of this mushroom. We used the Comet assay and HEp-2 cells to evaluate the in vitro genotoxic and antigenotoxic activity of aqueous extracts of shiitake prepared in three different concentrations (0.5, 1.0 and 1.5 mg/mL and three different temperatures (4, 22 and 60 °C, using methyl methanesulfonate (MMS as a positive control and untreated cells as a negative control. Two concentrations (1.0 and 1.5 mg/mL of extract prepared at 4 °C and all of the concentrations prepared at 22 ± 2 and 60 °C showed moderate genotoxic activity. To test the protective effect of the three concentrations of the extracts against the genotoxicity induced by methyl methanesulfonate, three protocols were used: pre-treatment, simultaneous-treatment and post-treatment. Treatments were repeated for all combinations of preparation temperature and concentration. Two extracts (22 ± 2 °C 1.0 mg/mL (simultaneous-treatment and 4 °C 0.5 mg/mL (post-treatment showed antigenotoxic activity.

  12. Physics of comets

    CERN Document Server

    Krishna Swamy, K S

    1997-01-01

    The study of Comet Halley in 1986 was a tremendous success for cometary science. In March of that year, six spacecrafts passed through Comet Halley as close as 600 km from the nucleus and made the in situ measurements of various kinds. These space missions to Comet Halley and that of the ICE spacecraft to Comet Giacobini-Zinner combined with studies, both ground-based and above the atmosphere, have increased our knowledge of cometary science in a dramatic way.This new edition of Physics of Comets incorporates these new and exciting findings. The emphasis of the book is on the physical processe

  13. Utilization of DNA comet assay and half embryo test to identify irradiated lentil

    International Nuclear Information System (INIS)

    Romanelli, Maria Fernanda; Villavicencio, Anna Lucia C.H.

    2001-01-01

    Full text: Legumes make an important contribution to human nutrition on a worldwide basis. Insect infestation cause extensive damage to stored grains. Over the last few decades some countries adopted food irradiation as a safe food process. Radiation's processing on foods improves hygienic quality and extends their shelf life. The use of radiation treatment to reduce the microbial population and thereby extend the shelf life in legumes has been reported in many papers. Irradiation has been shown to be an effective pest control method for these commodities and a good alternative to prohibited methyl bromide. Radiation disinfestation can facilitate trade in foods that often harbor insect pests of quarantine importance. Although the wholesomeness of irradiated food is no longer a question there is a need for irradiation control in the international trade of foods, in order to enhance the consumer confidence in the regulation. As a screening methods to identify irradiated lentils, processed by e-beam as a food treatment to disinfestation, the DNA Comet Assay and Half Embryo tests were performed. The methodologies used in this work are based upon biological changes that occur in Brazilian lentils. The samples were irradiated in an electron beam accelerator facility of Radiation Dynamics Inc., USA (E=1,5 MeV, l=25 mA). The irradiation doses were 0,7; 1,4 and 3,0 kGy at dry conditions. The thickness of samples was less than 0,5 cm. A sensitive technique to detect DNA fragmentation is the microgel electrophoresis of single cells or nuclei, also called 'comet assay'. Since the large molecule of DNA is an easy target for ionizing radiation, changes in DNA offer potential as a detection method. It is restricted to foods that have not been subjected to heat or other treatments, which also cause DNA fragmentation. Lentil samples were crushed with a mortar and pestle and was transferred to 3ml ice-cold PBS. This suspension was stirred for 5 minutes and filtered. 100μl cell

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

    Science.gov (United States)

    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

  15. Comets and their origin the tools to decipher a comet

    CERN Document Server

    Meierhenrich, Uwe

    2014-01-01

    Divided into two parts, the first four chapters of Comets and their Origin refer to comets and their formation in general, describing cometary missions, comet remote observations, astrochemistry, artificial comets, and the chirality phenomenon.The second part covers the cometary Rosetta mission, its launch, journey, scientific objectives, and instrumentations, as well as the landing scenario on a cometary nucleus. Along the way, the author presents general questions concerning the origin of terrestrial water and the molecular beginnings of lifeon Earth, as well as how the instruments used on

  16. Comparative genotoxicity testing of Rhine river sediment extracts using the comet assay with permanent fish cell lines (RTG-2 and RTL-W1) and the Ames test

    Energy Technology Data Exchange (ETDEWEB)

    Kosmehl, T.; Braunbeck, T.; Hollert, H. [Dept. of Zoology, Aquatic Ecology and Toxicology Section, Univ. of Heidelberg (Germany); Krebs, F.; Manz, W. [German Federal Inst. of Hydrology, Koblenz (Germany); Erdinger, L. [Dept. for Hygiene and Medical Microbiology, Inst. for Hygiene, Univ. of Heidelberg (Germany)

    2004-07-01

    Whilst at least in Germany assessment strategies on the basis of chemical analysis and acute toxicity data dominated the last decades, the development of more specific biological endpoints and biomarkers in ecotoxicology is required in order to arrive at a good ecological potential and good chemical status of surface waters in the European river basins until the year 2015, as required by the European Water Framework Directive. Since sediments have for long been known to function both as a sink and as a source of pollutants in aquatic systems, and since part of the particle-associated substances have frequently been demonstrated to cause mutagenic and carcinogenic effects in aquatic organisms, particularly in fish, there is, among other requirements, an urgent need to develop, standardize and implement integrated vertebrate-based test systems addressing genotoxicity into recent sediment investigation strategies. Thus, the present study was designed to compare the suitability of two commonly used test systems, the comet assay and the Ames test, for the evaluation of the ecotoxicological burden of surface and core sediment samples from the river Rhine. Methods (or main features). In order to determine the importance of inherent enzymatic activities, two permanent fish cell lines with different biotransformation capacities, RTL-W1 and RTG-2, were compared with respect to their capability of detecting genotoxic effects in 18 surface and core sediment samples from 9 locations along the river Rhine in the comet assay with and without exogenous bioactivation. For further comparison, as a prokaryotic mutagenicity assay, the Salmonella plate incorporation assay (Ames test) with the test strains TA98 and TA100 with and without exogenous metabolic activation was used. Results and discussion. Whereas all sediment extracts induced genotoxic effects in the comet assay with RTL-W1 cells, only 12 out of 18 sediment extracts revealed significant genotoxicity in the tests with the

  17. Comet Giacobini-Zinner - a normal comet?

    International Nuclear Information System (INIS)

    Cochran, A.L.; Barker, E.S.

    1987-01-01

    Observations of Comet Giacobini-Zinner were obtained during its 1985 apparition using an IDS spectrograph at McDonald Observatory. Column densities and production rates were computed. The production rates were compared to observations of other normal comets. Giacobini-Zinner is shown to be depleted in C2 and C3 relative to CN. These production rates are down by a factor of 5. 12 references

  18. The DNA 'comet assay' as a rapid screening technique to control irradiated food

    International Nuclear Information System (INIS)

    Cerda, H.; Delincee, H.; Haine, H.; Rupp, H.

    1997-01-01

    The exposure of food to ionizing radiation is being progressively used in many countries to inactivate food pathogens, to eradicate pests, and to extend shelf-life, thereby contributing to a safer and more plentiful food supply. To ensure free consumer choice, irradiated food will be labelled as such, and to enforce labelling, analytical methods to detect the irradiation treatment in the food product itself are desirable. In particular, there is a need for simple and rapid screening methods for the control of irradiated food. The DNA comet assay offers great potential as a rapid tool to detect whether a wide variety of foodstuffs have been radiation processed. In order to simplify the test, the agarose single-layer set-up has been chosen, using a neutral protocol. Interlaboratory blind trials have been successfully carried out with a number of food products, both of animal and plant origin. This paper presents an overview of the hitherto obtained results and in addition the results of an intercomparison test with seeds, dried fruits and spices are described. In this intercomparison, an identification rate of 95% was achieved. Thus, using this novel technique, an effective screening of radiation-induced DNA fragmentation is obtained. Since other food treatments also may cause DNA fragmentation, samples with fragmented DNA suspected to have been irradiated should be analyzed by other validated methods for irradiated food, if such treatments which damage DNA cannot be excluded

  19. Study of niobium corrosion in alkaline medium

    International Nuclear Information System (INIS)

    Almeida, S.H. de.

    1987-01-01

    A comparative study of niobium electrochemical behaviour in NaOH and KOH solution, with concentrations between 0,5 and 6,1M is presented. The studies were done through electrochemicals assays, consisting in the corrosion potential and anodic and cathodic polarization curves, complemented by loss of mass experiments. The niobium anodic behaviour in alkaline medium is characterized by passivation occurrence, with a stable film formation. The Na oH solution in alkaline medium are more corrosible to niobium than the KOH solution. The loss of mass assays showed that the corrosion velocit is more dependente of hydroxide concentration in KOH medium than the NaOH medium. (C.G.C.) [pt

  20. Origin and development of comets

    International Nuclear Information System (INIS)

    Kresak, L.

    1989-01-01

    The comets are the most primitive and probably also the oldest members of the solar system. Comet cores are brittle bodies of an irregular shape and of a size of 1 to 10 km whose main component is ice. Around 130 comets move along short-period paths whose aphelia are concentrated in the area of Jupiter. They are in the last stage of development. About 20 comets have periods of 20 to 200 years and feature higher motion stability. Roughly 180 comets have elliptical orbits of a period exceeding 200 years, 200 comets have parabolic and 120 comets have hyperbolic orbits. The most distant comets form the Oort cloud around the solar system consisting of about one billion comets. Comets originated roughly 4.6 thousand million years ago together with planets, probably inside the Oort cloud. (M.D.). 11 figs

  1. Spectrophotometry of 25 comets - Post-Halley updates for 17 comets plus new observations for eight additional comets

    Science.gov (United States)

    Newburn, Ray L., Jr.; Spinrad, Hyron

    1989-01-01

    The best possible production figures within the current post-Halley framework and available observations are given for H2O, O(1D), CN, C3, C2 and dust in 25 comets. Of these, the three objects with the smallest mixing ratios of all minor species have moderate to little or no dust and appear 'old'. Comets with large amounts of CN are very dusty, and there is a clear correlation of CN with dust, although comets with little or no dust still have some CN. Thus, CN appears to have at least two sources, dust and one or more parent gases. Also, the C2/CN production ratio changes continuously with heliocentric distance in every comet considered, suggesting that C2 production may be a function of coma density as well as parental abundance. Dust production ranges from essentially zero in Comet Sugano-Saigusa-Fujikawa up to 67,000 kg/s for Halley on March 14, 1986.

  2. Spectrophotometry of 25 comets - Post-Halley updates for 17 comets plus new observations for eight additional comets

    International Nuclear Information System (INIS)

    Newburn, R.L. Jr.; Spinrad, H.

    1989-01-01

    The best possible production figures within the current post-Halley framework and available observations are given for H2O, O(1D), CN, C3, C2 and dust in 25 comets. Of these, the three objects with the smallest mixing ratios of all minor species have moderate to little or no dust and appear 'old'. Comets with large amounts of CN are very dusty, and there is a clear correlation of CN with dust, although comets with little or no dust still have some CN. Thus, CN appears to have at least two sources, dust and one or more parent gases. Also, the C2/CN production ratio changes continuously with heliocentric distance in every comet considered, suggesting that C2 production may be a function of coma density as well as parental abundance. Dust production ranges from essentially zero in Comet Sugano-Saigusa-Fujikawa up to 67,000 kg/s for Halley on March 14, 1986. 61 references

  3. Numerical simulations of comets - predictions for Comet Giacobini-Zinner

    International Nuclear Information System (INIS)

    Fedder, J.A.; Lyon, J.G.; Giuliani, J.L. Jr.

    1986-01-01

    Simulations of Comet Giacobini-Zinner's interaction with solar wind are described and results are presented. The simulations are carried out via the numerical solution of the ideal MHD equations as an initial value problem in a uniform solar wind. The calculations are performed on a Cartesian mesh centered at the comet. Results reveal that the first significant modifications of the solar wind along the ISEE/ICE trajectory will occur 100,000 km from the solar wind comet axis. 6 references

  4. Comet assay to determine genetic damage by the use of ivermectin in zebu cows (Bos taurus indicus

    Directory of Open Access Journals (Sweden)

    Donicer Montes-Vergara

    2017-05-01

    Full Text Available Objective. The objective of the work was evaluate the damage genetic caused by the use of ivermectin (IVM in cows zebu to concentrations of 1% and 3.15% through the test comet. Material and methods. 15 cows, were taken with age between 3 and 4 years old, average weight of 350 kg, body condition between 3 and 3.5. Three experimental groups with five animals per group, which were exposed to the concentration of IVM to 1% to 3.15% more group control (without application of IVM were used. Animal blood sample was performed by venipuncture jugular or medial flow with vacutainer® needle, extracting 8 ml of blood. The blood samples it was collected at 9, 18 and 27 days post-treatment. Results. The display of the comets is made by using fluorescence microscope, the cells were evaluated by means of visual log and the Comet image software. Evidenced the presence of nuclei with DNA migration in all analyzed plates. The values of classification of comets indicate cells with high levels of damage (grade 3: cells with high damage. The rate of DNA damage of the treatment to 1% to 3.15% was significant, to relate to the control group. Conclusions. The results obtained in this study demonstrate the likely genotoxic potential of the use of IVM in cattle.

  5. Mission to the comets

    International Nuclear Information System (INIS)

    Hughes, D.

    1980-01-01

    The plans of space agencies in the United States and Europe for an exploratory comet mission including a one year rendezvous with comet Temple-2 and a fast fly-by of comet Halley are discussed. The mission provides an opportunity to make comparative measurements on the two different types of comets and also satisfies the three major scientific objectives of cometary missions namely: (1) To determine the chemical nature and the physical structure of cometary nuclei, and the changes that occur with time and orbital position. (2) To study the chemical and physical nature of the atmospheres and ionospheres of comets, the processes that occur in them, and their development with time and orbital position. (3) To determine the nature of the tails of comets and the processes by which they are formed, and to characterise the interaction of comets with solar wind. (UK)

  6. Comet assay in the detection of irradiated garlic; Teste do cometa na deteccao de alho irradiado

    Energy Technology Data Exchange (ETDEWEB)

    Villavicencio, Anna Lucia C.H.; Marin-Huachaca, Nelida Simona; Romanelli, Maria Fernanda [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: villavic@net.ipen.br; Delincee, Henry [Federal Research Centre for Nutrition - BFE, Karlsruhe (Germany)]. E-mail: henry.delincee@bfe.uni-karlsruhe.de

    2002-07-01

    The increased claim for fresh produce has forced a consensus between nations to pay more attention to the phytosanitary regulations. Inhibition of sprouting of bulbs and tubers by applying ionising radiation is authorised by the National Food Codes in Brazil. The availability of methods for detection of irradiated food will contribute to increase consumers' confidence. A quick and simple screening test to indicate whether a food product has been irradiated or not was utilised in this study. The DNA comet assay was applied to verify whether garlic imported from China had been irradiated or not. This test has already been adopted as a European Standard (EN 13784), for detection of irradiated food. Non-irradiated control samples of garlic and garlic treated with maleic hydrazide were compared with garlic samples irradiated in our department. The unirradiated samples exhibited only limited DNA migration. If samples were irradiated, an increased DNA fragmentation was observed which permitted the discrimination between non-irradiated and irradiated samples. Since the garlic samples from China showed only very limited DNA fragmentation, they were deemed non-irradiated. Thus, this simple screening test was shown to be successful for identification of an irradiation treatment. (author)

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

    Science.gov (United States)

    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

  8. Ammonia abundances in comets

    Science.gov (United States)

    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.

  9. Comets in Australian Aboriginal Astronomy

    Science.gov (United States)

    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.

  10. Comet showers and the steady-state infall of comets from the Oort cloud

    International Nuclear Information System (INIS)

    Hills, J.G.

    1981-01-01

    The appearance of an inner edge to the Oort comet cloud at a semimajor axis of a = (1--2) x 10 4 AU is an observational artifact. Stellar perturbations are frequent enough and strong enough to assure that a constant fraction of the comets with semimajor axes greater than this are in orbits which bring them within the planetary region. Only infrequent, close stellar encounters are able to repopulate the planet-crossing orbits of comets with smaller semimajor axes. Owing to their relatively short orbital periods which return them frequently to the planetary system, the comets in these more tightly bound orbits will be deflected by Jupiter into drastically different orbits or be destroyed by solar heating before another close stellar passage repopulates their numbers. Comets with semimajor axes less than 2 x 10 4 AU appear in the inner solar system only in intense bursts or showers which last for a few orbital periods after the close passage of a star to the Sun. This is followed by a much longer span of time during which only comets with a>2 x 10 4 AU enter the planetary system. The theoretically determined location of the boundary between the semimajor axes of those comets which enter the planetary system only in bursts or showers and those which arrive in a steady stream is very abrupt and falls at the observed inner edge of the Oort cloud. We propose that the comets formed in the outer parts of the collapsing protosun, which had a radius of less than 5 x 10 3 AU. If this produced a first-generation comet cloud with a radius of 10 3 AU or greater, the coupled dynamical perturbations of passing stars and Jupiter will, of necessity, lead to the formation of a comet cloud similar that of the observed Oort comet cloud

  11. Ammonia abundances in four comets

    International Nuclear Information System (INIS)

    Wickoff, S.; Tegler, S.C.; Engel, L.

    1991-01-01

    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. 64 refs

  12. Realm of the comets

    International Nuclear Information System (INIS)

    Weissman, P.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

  13. Posttranslational heterogeneity of bone alkaline phosphatase in metabolic bone disease.

    Science.gov (United States)

    Langlois, M R; Delanghe, J R; Kaufman, J M; De Buyzere, M L; Van Hoecke, M J; Leroux-Roels, G G

    1994-09-01

    Bone alkaline phosphatase is a marker of osteoblast activity. In order to study the posttranscriptional modification (glycosylation) of bone alkaline phosphatase in bone disease, we investigated the relationship between mass and catalytic activity of bone alkaline phosphatase in patients with osteoporosis and hyperthyroidism. Serum bone alkaline phosphatase activity was measured after lectin precipitation using the Iso-ALP test kit. Mass concentration of bone alkaline phosphatase was determined with an immunoradiometric assay (Tandem-R Ostase). In general, serum bone alkaline phosphatase mass and activity concentration correlated well. The activity : mass ratio of bone alkaline phosphatase was low in hyperthyroidism. Activation energy of the reaction catalysed by bone alkaline phosphatase was high in osteoporosis and in hyperthyroidism. Experiments with neuraminidase digestion further demonstrated that the thermodynamic heterogeneity of bone alkaline phosphatase can be explained by a different glycosylation of the enzyme.

  14. Comet thermal modeling

    International Nuclear Information System (INIS)

    Weissman, P.R.; Kieffer, H.H.

    1987-01-01

    The past year was one of tremendous activity because of the appearance of Halley's Comet. Observations of the comet were collected from a number of sources and compared with the detailed predictions of the comet thermal modeling program. Spacecraft observations of key physical parameters for cometary nucleus were incorporated into the thermal model and new cases run. These results have led to a much better understanding of physical processes on the nucleus and have pointed the way for further improvements to the modeling program. A model for the large-scale structure of cometary nuclei was proposed in which comets were envisioned as loosely bound agglomerations of smaller icy planetesimals, essentially a rubble pile of primordial dirty snowballs. In addition, a study of the physical history of comets was begun, concentrating on processes during formation and in the Oort cloud which would alter the volatile and nonvolatile materials in cometary nuclei from their pristine state before formation

  15. DNA Damage Following Pulmonary Exposure by Instillation to Low Doses of Carbon Black (Printex 90) Nanoparticles in Mice

    DEFF Research Database (Denmark)

    Kyjovska, Zdenka O.; Jacobsen, Nicklas R.; Saber, Anne T.

    2015-01-01

    of 0.67, 2, 6, and 162 mu g Printex 90 NPCB and vehicle. Cellular composition and protein concentration was evaluated in BAL fluid as markers of inflammatory response and cell damage. DNA strand breaks in BAL cells, lung, and liver tissue were assessed using the alkaline comet assay. The pulmonary...... the comet assay. We interpret the increased DNA strand breaks occurring following these low exposure doses of NPCB as DNA damage caused by primary genotoxicity in the absence of substantial inflammation, cell damage, and acute phase response. Environ. Mol. Mutagen. 56:41-49, 2015. (c) 2014 The Authors...

  16. Radiomodifying effect of resveratrol in human rhabdomyosarcoma (RD) cell culture applying the comet assay

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes, Vanessa D.; Rogero, Sizue O.; Vieira, Daniel P.; Okazaki, Kayo; Rogero, Jose R., E-mail: van.biologa@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Cruz, Aurea S., E-mail: aurcruz@ial.sp.gov.br [Instituto Adolfo Lutz (IAL-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    Cancer is considered a worldwide public health problem. Resveratrol is a defense polyphenol, synthesized naturally by a wide variety of plants according to response of ultraviolet radiation (UV) exposition or according to mechanical stress resulting of pathogens or chemical and physical agents. In vines this substance is found in elevated concentration. Thus, resveratrol is present in grape juice and wines, especially red wine. Red wines are the best dietary source of resveratrol.The protective effects performed by resveratrol during the process of cell damage, produced by oxidative effects of free radicals, are anti-inflammatory, anti-platelet and anti-carcinogenic activity, prevent or inhibit degenerative diseases, decrease incidence of cardiovascular diseases. Moreover, resveratrol is considered as a cell radioprotector. On the other hand, in some elevated concentrations resveratrol is considered as a radiosensitizing compound. The aim of this work was study in vitro the radiomodifying effect of resveratrol in human rhabdomyosarcoma (RD) cells applying the comet assay to evaluate the cellular damage and its repair capacity. In this study RD cells culture was irradiated by gamma radiation at 50 Gy and 100 Gy doses and the used resveratrol concentrations was from 15 μM to 60 μM. The protective and radioprotective effects were observed at 15 μM and 30 μM resveratrol concentrations. The resveratrol concentration of 60 μM showed cytotoxic effect to RD tumor cells and with gamma radiation presence this concentration showed no statistically significant radiosensitizing effects. (author)

  17. Radiomodifying effect of resveratrol in human rhabdomyosarcoma (RD) cell culture applying the comet assay

    International Nuclear Information System (INIS)

    Magalhaes, Vanessa D.; Rogero, Sizue O.; Vieira, Daniel P.; Okazaki, Kayo; Rogero, Jose R.; Cruz, Aurea S.

    2013-01-01

    Cancer is considered a worldwide public health problem. Resveratrol is a defense polyphenol, synthesized naturally by a wide variety of plants according to response of ultraviolet radiation (UV) exposition or according to mechanical stress resulting of pathogens or chemical and physical agents. In vines this substance is found in elevated concentration. Thus, resveratrol is present in grape juice and wines, especially red wine. Red wines are the best dietary source of resveratrol.The protective effects performed by resveratrol during the process of cell damage, produced by oxidative effects of free radicals, are anti-inflammatory, anti-platelet and anti-carcinogenic activity, prevent or inhibit degenerative diseases, decrease incidence of cardiovascular diseases. Moreover, resveratrol is considered as a cell radioprotector. On the other hand, in some elevated concentrations resveratrol is considered as a radiosensitizing compound. The aim of this work was study in vitro the radiomodifying effect of resveratrol in human rhabdomyosarcoma (RD) cells applying the comet assay to evaluate the cellular damage and its repair capacity. In this study RD cells culture was irradiated by gamma radiation at 50 Gy and 100 Gy doses and the used resveratrol concentrations was from 15 μM to 60 μM. The protective and radioprotective effects were observed at 15 μM and 30 μM resveratrol concentrations. The resveratrol concentration of 60 μM showed cytotoxic effect to RD tumor cells and with gamma radiation presence this concentration showed no statistically significant radiosensitizing effects. (author)

  18. The effect of obstructive sleep apnea on DNA damage and oxidative stress.

    Science.gov (United States)

    Kang, Il Gyu; Jung, Joo Hyun; Kim, Seon Tae

    2013-06-01

    Obstructive sleep apnea syndrome (OSAS) is associated with repeated hypoxia and re-oxygenation. This characteristic of OSAS may cause oxidative stress and DNA damage. However, the link of OSAS with oxidative stress and DNA damage is still controversial. In the current study, we investigated whether OSAS causes DNA damage using alkaline single-cell gel electrophoresis (comet assay) and measuring oxidative stress by monitoring serum malondialdehyde (MDA) levels. From March 2009 to August 2010, 51 patients who underwent polysomnography (PSG) during the night were enrolled in this study. We obtained serum from the patients at 6 AM. DNA damage and oxidative stress were evaluated using a comet assay and measuring serum MDA, respectively. We divided the patients into two groups according to the existence of comets appearing in the comet assay. Group 1 included 44 patients with negative assay results and group 2 consisted of seven patients with positive comet assay findings. We compared the age, gender proportion, PSG data (respiratory disturbance index [RDI], lowest O2 saturation level, and arousal index [AI]), time of disease onset, smoking habits, and serum MDA levels between the two groups. The average age and gender proportion of the two groups were not statistically different (P>0.05). The average of RDI for group 1 was 30.4±18.4 and 8.0±7.7 (P0.05). No relationship between positive comet assay results and OSAS severity was identified. Results of the current study showed that OSAS was not associated with DNA damage as measured by comet assays or oxidative stress according to serum MDA levels.

  19. The McDonald Observatory Faint Comet Survey - Gas production in 17 comets

    Science.gov (United States)

    Cochran, Anita L.; Barker, Edwin S.; Ramseyer, Tod F.; Storrs, Alex D.

    1992-01-01

    The complete Intensified Dissector Scanner data set on 17 comets is presented, and production rates are derived and analyzed. It is shown that there is a strong degree of homogenization in the production rate ratios of many comets. It also appears that the ratio of the production rates of the various species has no heliocentric distance dependence, except for the case of NH2. When speaking of the gas in the coma of a comet, it appears that comets must have been formed under remarkably uniform conditions, and that they must have evolved and formed their comae in a similar manner. The data presented here constitute strong evidence that the minor species must be bound up in a lattice and that the interior of a comet must be reasonably uniform.

  20. Disintegration of comet nuclei

    International Nuclear Information System (INIS)

    Ksanfomality, Leonid V

    2012-01-01

    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. (physics of our days)

  1. Disintegration of comet nuclei

    Science.gov (United States)

    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.

  2. High-throughput screening platform for engineered nanoparticle-mediated genotoxicity using CometChip technology.

    Science.gov (United States)

    Watson, Christa; Ge, Jing; Cohen, Joel; Pyrgiotakis, Georgios; Engelward, Bevin P; Demokritou, Philip

    2014-03-25

    The likelihood of intentional and unintentional engineered nanoparticle (ENP) exposure has dramatically increased due to the use of nanoenabled products. Indeed, ENPs have been incorporated in many useful products and have enhanced our way of life. However, there are many unanswered questions about the consequences of nanoparticle exposures, in particular, with regard to their potential to damage the genome and thus potentially promote cancer. In this study, we present a high-throughput screening assay based upon the recently developed CometChip technology, which enables evaluation of single-stranded DNA breaks, abasic sites, and alkali-sensitive sites in cells exposed to ENPs. The strategic microfabricated, 96-well design and automated processing improves efficiency, reduces processing time, and suppresses user bias in comparison to the standard comet assay. We evaluated the versatility of this assay by screening five industrially relevant ENP exposures (SiO2, ZnO, Fe2O3, Ag, and CeO2) on both suspension human lymphoblastoid (TK6) and adherent Chinese hamster ovary (H9T3) cell lines. MTT and CyQuant NF assays were employed to assess cellular viability and proliferation after ENP exposure. Exposure to ENPs at a dose range of 5, 10, and 20 μg/mL induced dose-dependent increases in DNA damage and cytotoxicity. Genotoxicity profiles of ZnO>Ag>Fe2O3>CeO2>SiO2 in TK6 cells at 4 h and Ag>Fe2O3>ZnO>CeO2>SiO2 in H9T3 cells at 24 h were observed. The presented CometChip platform enabled efficient and reliable measurement of ENP-mediated DNA damage, therefore demonstrating the efficacy of this powerful tool in nanogenotoxicity studies.

  3. Optical observation of comets

    International Nuclear Information System (INIS)

    Tanabe, Hiroyoshi

    1974-01-01

    The observation of comets is proposed to study the state of interplanetary space. The behavior of the tails of comets shows the state of solar wind. On July 4, 1964, large bending was seen in the tail of the Tomita-Gerber-Handa comet. Then, on July 7, 1964, geomagnetic disturbance was observed. Disturbance in the tail of Kohoutek comet was seen on Jan. 19, 1974, and Ksub(p)--5 on the ground on Jan. 25. The effort for the quantitative measurement of the parameters of solar wind has been continued in various countries. Recently, the large scale observation of the Kohoutek comet was carried out in the world. Preliminary report is presented in this paper. Waving in the type 1 tail of the comet was seen, and this phenomenon may show some instability due to the interaction between the tail and the solar wind. Periodic variation of the direction of the tail has been reported. The present result also confirmed this report. In case of small comets, flare-up occurs and original luminous intensity is regained after several days. Measurement of the spectrum at the time of flare-up may show information concerning temporary variation of the state of interplanetary space. For the tracking of time variation of comets, cooperation of a number of stations at different positions is required. (Kato, T.)

  4. Disappearance and disintegration of comets

    Science.gov (United States)

    Sekanina, Z.

    1984-01-01

    The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.

  5. Radio response of human lymphocytes pretreated with boron and gadoliniums assessed by the, comet assay

    International Nuclear Information System (INIS)

    Kim, J. K.; Park, T. W.; Cebulska-Wasiewska, A.; Nili, M.

    2009-01-01

    Boron and gadolinium are among the nuclides that hold a unique property of being a neutron capture therapy agent. Neutron beams have often a considerable portion of gamma rays with fast neutrons. Gamma rays, as beam contaminants, can cause considerable damage to normal tissues even if such tissues do contain high boron concentrations. Materials and Methods: The modification of radio response in human lymphocytes pretreated with boron or gadolinium compound was studied by assessing the DNA damage using single cell gel electrophoresis, the comet assay. The lymphocytes from the human peripheral blood were irradiated with 0, 1, 2 and 4 Gy of gamma rays from a 60 Co isotopic source with or without pretreatment of boron or gadolinium compound for 10 minutes at 4 d egree C . Post-irradiation procedures included slide preparation, cell-lysing, unwinding and electrophoresis, neutralization, staining, and analytic steps, gel electrophoresis. Results: The results indicate that pretreatment with boron compound (50 n M or 250 n M of 10 B) is effective in reducing the radiosensitivity of the lymphocyte DNA. Conversely, pretreatment with gadolinium compound (50 n M) led to a dose-dependent increase in the radiosensitivity, most prominently with a dose of 4 Gy (P<0.001). Furthermore, when the lymphocytes were pretreated with a Combined mixture (1:1) of boron (250 n M) and gadolinium (50 n M) compounds, the reduced radiosensitivity was also observed.

  6. Physical processes in comets

    International Nuclear Information System (INIS)

    Newburn, R.L. Jr.

    1988-01-01

    When this program began in 1975 only limited photometry had been carried out on comets at any wavelength. Program goals were to observe many comets, including faint periodic comets, at a range of heliocentric distances in order to begin to understand the range of behavior among comets and in a given comet during its approach and departure from the sun. Then a study of the continuum of scattered light from dust was added. More recently the value of joint team observations in visible and infrared light has been recognized and utilized as often as possible. All 1978 to 1982 data was reanalyzed and 1983 to 1986 data analyzed in the framwork of the post-Halley paradigm, covering 25 comets in all. Four observing runs (June, July, Sept., and Jan.) with Hanner produced excellent results on Wilson, Bradfield, P/Klemola, and P/Borrelly and lesser data on other objects, including the last reported IR photometry of P/Halley. The Wilson and Halley data have been reduced

  7. Genotoxicity of Water Contaminants from the Basin of Lake Sevan, Armenia Evaluated by the Comet Assay in Gibel Carp (Carassius auratus gibelio) and Tradescantia Bioassays.

    Science.gov (United States)

    Simonyan, Anna; Gabrielyan, Barduch; Minasyan, Seyran; Hovhannisyan, Galina; Aroutiounian, Rouben

    2016-03-01

    Combination of bioassays and chemical analysis was applied to determine the genotoxic/mutagenic contamination in four different sites of the basin of Lake Sevan in Armenia. Water genotoxicity was evaluated using the single cell gel electrophoresis technique (comet assay) in erythrocytes of gibel carp (Carassius auratus gibelio), Tradescantia micronucleus (Trad-MCN) and Tradescantia stamen hair mutation (Trad-SHM) assays. Significant inter-site differences in the levels of water genotoxicity according to fish and Trad-MCN bioassays have been revealed. Two groups of locations with lower (south-southwest of the village Shorzha and Peninsula of Lake Sevan) and higher (estuaries of Gavaraget and Dzknaget rivers) levels of water genotoxicity were distinguished. Correlation analysis support the hypothesis that the observed genetic alterations in fish and plant may be a manifestation of the effects of water contamination by nitrate ions, Si, Al, Fe, Mn and Cu. Increase of DNA damage in fish also correlated with content of total phosphorus.

  8. CO2 Orbital Trends in Comets

    Science.gov (United States)

    Kelley, Michael; Feaga, Lori; Bodewits, Dennis; McKay, Adam; Snodgrass, Colin; Wooden, Diane

    2014-12-01

    Spacecraft missions to comets return a treasure trove of details of their targets, e.g., the Rosetta mission to comet 67P/Churyumov-Gerasimenko, the Deep Impact experiment at comet 9P/Tempel 1, or even the flyby of C/2013 A1 (Siding Spring) at Mars. Yet, missions are rare, the diversity of comets is large, few comets are easily accessible, and comet flybys essentially return snapshots of their target nuclei. Thus, telescopic observations are necessary to place the mission data within the context of each comet's long-term behavior, and to further connect mission results to the comet population as a whole. We propose a large Cycle 11 project to study the long-term activity of past and potential future mission targets, and select bright Oort cloud comets to infer comet nucleus properties, which would otherwise require flyby missions. In the classical comet model, cometary mass loss is driven by the sublimation of water ice. However, recent discoveries suggest that the more volatile CO and CO2 ices are the likely drivers of some comet active regions. Surprisingly, CO2 drove most of the activity of comet Hartley 2 at only 1 AU from the Sun where vigorous water ice sublimation would be expected to dominate. Currently, little is known about the role of CO2 in comet activity because telluric absorptions prohibit monitoring from the ground. In our Cycle 11 project, we will study the CO2 activity of our targets through IRAC photometry. In conjunction with prior observations of CO2 and CO, as well as future data sets (JWST) and ongoing Earth-based projects led by members of our team, we will investigate both long-term activity trends in our target comets, with a particular goal to ascertain the connections between each comet's coma and nucleus.

  9. [Comet assay of DNA fragmentation: modification of silver staining for obtaining permanent preparations].

    Science.gov (United States)

    Kamins'kyĭ, V O; Lutsyk, M D; Stoĭka, R S

    2005-01-01

    Modification of comet analysis is proposed for obtaining permanent preparations by DNA staining with silver compounds. The sensitivity of staining is similar to that observed at the treatment by ethidium bromide and other fluorochromes. The advantages of the method are stability of slides and possibility of their reinvestigation by light microscopy. The method does not need expensive fluorescent microscope and lacks contacting with carcinogenic compounds and UV light irradiation.

  10. Evaluation of radio-induced DNA damage and their repair in human lymphocytes by comet assay or single cell gel electrophoresis; Avaliacao do dano radioinduzido no DNA e reparo em linfocitos humanos pelo metodo do cometa (single cell gel electrophoresis)

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Patricia A. do; Suzuki, Miriam F.; Okazaki, Kayo [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1997-12-01

    The comet assay, also called single cell gel electrophoresis technique, permits to evaluate quantitatively DNA breakage induced by chemical and physical agents at the level of the single cell. The present paper refers to the construction of dose-response curves to DNA damage and repair studies in human peripheral lymphocytes, utilizing the comet assay for the radiosensitivity analysis. So, the blood samples were obtained from healthy donors (40-50 year old), irradiated in a {sup 60} Co source (GAMMACEL 220) with doses of 0.17, 0.25, 0.57, 1.10, 2.12 and 4.22 Gy (0.59 Gy/min.) and processed 1 and 24 hours after the exposition. Results obtained showed a increase in the total lenght of comet (DNA migration) as a function of radiation dose in samples processed 1 and 24 hours after the treatment. The DNA lesion in irradiated lymphocytes with 4.22 Gy (means value of 101.4 {mu}m) were 3.4 times higher than in the untreated lymphocytes (mean value of 30 {mu}m) instead of 24 hours after the irradiation were 1.5 times higher (mean value of 46.3 {mu}m). This reduction on DNA repair occurred in these cells. It was also possible visualized the presence of subpopulations of the cells with different sensitivity and repair capacity to ionizing radiation in these donors. (author). 8 refs., 3 figs.

  11. Cometography a catalog of comets

    CERN Document Server

    Kronk, Gary W; Seargent, David A J

    2017-01-01

    Cometography is a multi-volume catalog of every comet observed from ancient times up to the 1990s, when the internet took off as a medium of scientific record. It uses the most reliable orbits known to determine the distances from the Earth and Sun at the time of discovery and last observation, as well as the largest and smallest angular distance to the Sun, most northerly and southerly declination, closest distance to the Earth, and other details, to enable the reader to understand each comet's physical appearance. Volume 6, the final volume in the catalog, covers the observations and pertinent calculations for every comet seen between 1983 and 1993. The comets are listed in chronological order, with complete references to publications relating to each comet and physical descriptions of each comet's development throughout its apparition. Cometography is the definitive reference on comets through the ages, for astronomers and historians of science.

  12. Genotoxic potential of the perfluorinated chemicals PFOA, PFOS, PFBS, PFNA and PFHxA in human HepG2 cells

    DEFF Research Database (Denmark)

    Eriksen, Kirsten Thorup; Raaschou-Nielsen, Ole; Sørensen, Mette

    2010-01-01

    , the increase in ROS production was not concentration-dependent and the compounds did not generate DNA damage that could be detected by the alkaline comet assay as strand breakage and alkali-labile sites or formamidopyrimidine-DNA-glycosylase (FPG) sites. Perfluorobutane sulfonate (PFBS) and perfluorohexanoic...

  13. Detecting active comets with SDSS

    Energy Technology Data Exchange (ETDEWEB)

    Solontoi, Michael; Ivezic, Zeljko; /Washington U., Seattle, Astron. Dept.; West, Andrew A.; /MIT, MKI; Claire, Mark; /Washington U., Seattle, Astron. Dept.; Juric, Mario; /Princeton U. Observ.; Becker, Andrew; Jones, Lynne; /Washington U., Seattle, Astron. Dept.; Hall, Patrick B.; /York U., Canada; Kent, Steve; /Fermilab; Lupton, Robert H.; /Princeton U. Observ.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

    2010-12-01

    Using a sample of serendipitously discovered active comets in the Sloan Digital Sky Survey (SDSS), we develop well-controlled selection criteria for greatly increasing the efficiency of comet identification in the SDSS catalogs. After follow-up visual inspection of images to reject remaining false positives, the total sample of SDSS comets presented here contains 19 objects, roughly one comet per 10 million other SDSS objects. The good understanding of selection effects allows a study of the population statistics, and we estimate the apparent magnitude distribution to r {approx} 18, the ecliptic latitude distribution, and the comet distribution in SDSS color space. The most surprising results are the extremely narrow range of colors for comets in our sample (e.g. root-mean-square scatter of only {approx}0.06 mag for the g-r color), and the similarity of comet colors to those of jovian Trojans. We discuss the relevance of our results for upcoming deep multi-epoch optical surveys such as the Dark Energy Survey, Pan-STARRS, and the Large Synoptic Survey Telescope (LSST), and estimate that LSST may produce a sample of about 10,000 comets over its 10-year lifetime.

  14. Postencounter view of comets

    International Nuclear Information System (INIS)

    Mendis, D.A.

    1988-01-01

    Ground-based and space observations of Comet Halley during its 1986 perihelion passage are reviewed, with an emphasis on their implications for theoretical models. Consideration is given to the shape, surface morphology, and composition of the comet nucleus; the shape, dynamics, and composition of the dust tail; neutral and ionic gas species in the head and plasma tail; and the comet/solar-wind interaction. Extensive diagrams, graphs, and sample images are provided, and the potential value of the new kinds of data to be obtained with the NASA Comet-Rendezvous/Asteroid-Flyby spacecraft is discussed. 139 references

  15. Composition of faint comets

    International Nuclear Information System (INIS)

    Brown, L.W.

    1986-01-01

    The study uses an emission line, differential imaging camera built by the Science Operations Branch. This instrument allows photometric data to be obtained over a large area of a comet in a large number of resolution elements. The detector is a 100x100 Reticon array which with interchangeable optics can give resolutions from 2'' to 30'' over a field of 1' to 15'. The camera through its controlling computer can simultaneously take images in on-line and continuum filters and through computer subtraction and calibration present a photometric image of the comet produced by only the emission of the molecule under study. Initial work has shown two significant problems. First the auxiliary equipment of the telescope has not allowed the unambiguous location of faint comets so that systematic observations could be made, and secondly initial data has not shown much molecular emission from the faint comets which were located. Work last year on a software and hardware display system and this year on additional guide motors on the 36-inch telescope has allowed the differential camera to act as its own finder and guide scope. Comet IRAS was observed in C2 and CO+, as well as an occultation by the comet of SAO029103. The perodic comet Giacobini-Zinner was also observed in C2

  16. ISO's analysis of Comet Hale-Bopp

    Science.gov (United States)

    1997-03-01

    The European Space Agency's Infrared Space Observatory ISO inspected Comet Hall-Bopp during the spring and autumn of 1996. The need to keep ISO's telescope extremely cold restricts the spacecraft's pointing in relation to the Sun and the Earth and it ruled out observations at other times. The analyses of the 1996 observations are not yet complete, but already they give new insight into the nature of comets. Comet Hale-Bopp is believed to be a large comet with a nucleus up to 40 kilometres wide. It was discovered in July 1995 by two American astronomers working independently, Alan Hale and Thomas Bopp. At that time, the comet was a billion kilometres away from the Sun, but 200 times brighter than Halley's Comet was, when at a comparable distance. Comet Hale-Bopp will make its closest approach to the Earth on 22 March, and its closest approach to the Sun (perihelion) on 1 April 1997. Some scientific results from ISO The discovery of Comet Hale-Bopp occurred before ISO's launch in November 1995. When first observed by ISO in March and April 1996, the comet was still 700 million kilometres from the Sun, and almost as far from the Earth and ISO. With its privileged view of infrared wavebands inaccessible from the Earth's surface, ISO's photometer ISOPHOT discovered that carbon dioxide was an important constituent of the comet's emissions of vapour.ISOPHOT measured the temperature of the dust cloud around Comet Hale-Bopp. In March 1996, when the comet was still more than 700 million kilometres from the Sun, the dust cloud was at minus 120 degrees C. When ISOPHOT made similar observations in October 1996, the comet was 420 million kilometres from the Sun, and the dust cloud had warmed to about minus 50 degrees C. Intensive observations of Comet Hale-Bopp were also made by ISO's Short-Wave Spectrometer SWS, the Long-Wave Spectrometer LWS, and the ISOPHOT spectrometer PHOT-S. Results are due for publication at the end of March. They will give details about the composition

  17. Physics of comets

    CERN Document Server

    Krishna Swamy, K S

    2010-01-01

    This revised edition places a unique emphasis on all the new results from ground-based, satellites and space missions - detection of molecule H2 and prompt emission lines of OH for the first time; discovery of X-rays in comets; observed diversity in chemical composition among comets; the puzzle of the constancy of spin temperature; the well-established mineralogy of cometary dust; extensive theoretical modeling carried out for understanding the observed effects; and, the similarity in the mineralogy of dust in circumstellar shell of stars, comets, meteorites, asteroids and IDPs, thus indicatin

  18. Comets in UV

    Science.gov (United States)

    Shustov, B.; Sachkov, M.; Gómez de Castro, A. I.; Vallejo, J. C.; Kanev, E.; Dorofeeva, V.

    2018-04-01

    Comets are important "eyewitnesses" of Solar System formation and evolution. Important tests to determine the chemical composition and to study the physical processes in cometary nuclei and coma need data in the UV range of the electromagnetic spectrum. Comprehensive and complete studies require additional ground-based observations and in situ experiments. We briefly review observations of comets in the ultraviolet (UV) and discuss the prospects of UV observations of comets and exocomets with space-borne instruments. A special reference is made to the World Space Observatory-Ultraviolet (WSO-UV) project.

  19. Comet radar explorer

    Science.gov (United States)

    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

    The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet

  20. Periodic Comet Machholz and its idiosyncrasies

    International Nuclear Information System (INIS)

    Sekanina, Z.

    1990-01-01

    The dynamics and physical characteristics of Comet P/Machholz are analyzed. The discovery of the comet (Machholz, 1986) is discussed, including the observational conditions and the theory that the comet is inactive over extensive periods of time. Consideration is given to observations of the two tails of Comet P/Machholz (Emerson, 1986), the brightness variations and light curve of the comet, and nuclear photometry of the comet (Green, 1987). It is suggested that the increase in activity beginning one day after perihelion was triggered by a discrete source within 15 deg of the rotation pole that became sunlit after perihelion. Also, the possibility that Comet P/Machholz is associated with a meteor stream is examined. 45 refs

  1. The Protective Effect of Whole Honey and Phenolic Extract on Oxidative DNA Damage in Mice Lymphocytes Using Comet Assay.

    Science.gov (United States)

    Cheng, Ni; Wang, Yuan; Cao, Wei

    2017-12-01

    In this study, the antioxidant activity and the protective effect against hydrogen peroxide-induced DNA damage were assessed for five honeys of different botanical origin. Seven phenolic acids were detected in the honey samples. Ferulic acid was the most abundant phenolic acid detected in longan honey, jujube honey and buckwheat honey. Ellagic acid, p-hydroxybenzoic acid and protocatechuic acid were the main phenolic acids detected in vitex honey. Of all honey samples tested, the highest total phenolic content and antioxidant activity were found in buckwheat honey, whereas the lowest total phenolic content and antioxidant activity were found in locust honey. Treatment with hydrogen peroxide induced a 62% increase in tail DNA in mice lymphocytes, and all studied honeys significantly inhibited this effect (P Phenolic extracts of honey displayed greater protective effects than whole honey in comet assay. The hydrogen peroxide-generated increase in 8-hydroxy-2-deoxyguanosine (8-OHdG) was effectively inhibited by the honeys studied (P phenolic acids of honey can penetrate into lymphocytes and protect DNA from oxidative damage by scavenging hydrogen peroxide and/or chelating ferrous ions.

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

    Science.gov (United States)

    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

  3. Direct human DNA protection by Coriolus versicolor (Yunzhi) extract.

    Science.gov (United States)

    Szeto, Yim Tong; Lau, Po Chun; Kalle, Wouter; Pak, Sok Cheon

    2013-07-01

    Scientific evidence has shown Coriolus versicolor (L. ex Fr.) Quel (also known as Yunzhi) has the role of immunomodulator in therapeutic effect. The aim of this in vitro study was to investigate the antioxidative effect of Yunzhi and to explore the mechanisms behind its DNA protection. Commercial Yunzhi extract was dissolved in water and diluted in five concentrations (10(1)-10(5) μg/L) with appropriate buffers. Lymphocytes harvested from three healthy subjects were incubated with Yunzhi extract for 30 min. Cells were then subjected to 5 min oxidant challenge by 45 μM hydrogen peroxide. The standard alkaline comet (SAC) assay and lysed cell comet (LCC) assay were performed in parallel. DNA damage of each treatment was scored under a fluorescence microscope and compared with the cells without Yunzhi pretreatment. U-shaped dose-response was seen in both versions of the comet assay. Yunzhi at 10(4) μg/L demonstrated a genoprotective effect against oxidative damage in the SAC assay (25% decrease in comet score). In the LCC assay, a trend of protection in lymphocytes was observed but it did not reach statistical significance. A direct antioxidant effect of Yunzhi against oxidant challenge on the DNA of lymphocytes was evidenced. The active component in Yunzhi was likely to be membrane permeable.

  4. Comet assay in gill cells of Prochilodus lineatus exposed in vivo to cypermethrin.

    Science.gov (United States)

    Poletta, G L; Gigena, F; Loteste, A; Parma, M J; Kleinsorge, E C; Simoniello, M F

    2013-11-01

    Agricultural chemicals can induce genetic alterations on aquatic organisms that have been associated with effects on growth, reproduction and population dynamics. The evaluation of DNA damage in fish using the comet assay (CA) frequently involves the utilization of erythrocytes. However, epithelial gill cells (EGC) can be more sensitive, as they are constantly dividing and in direct contact with potentially stressing compounds from the aquatic environment. The aim of the present study was to evaluate (1) the sensitivity and suitability of epithelial gill cells of Prochilodus lineatus in response to different genotoxic agents through the application of the CA, (2) the induction of DNA damage in this cell population after in vivo exposure to cypermethrin. Baseline value of the CA damage index (DI) for EGC of juvenile P. lineatus was 144.68±5.69. Damage increased in a dose-dependent manner after in vitro exposure of EGC to methyl methanesulfonate (MMS) and H2O2, two known genotoxic agents. In vivo exposure of fish to cypermethrin induced a significant increase in DNA DI of EGC at 0.150μg/l (DI: 239.62±6.21) and 0.300μg/l (270.63±2.09) compared to control (150.25±4.38) but no effect was observed at 0.075μg/l (168.50±10.77). This study shows that EGC of this species are sensitive for the application of the CA, demonstrating DNA damage in response to alkylation (MMS), oxidative damage (H2O2), and to the insecticide cypermethryn. These data, together with our previous study on DNA damage induction on erythrocytes of this species, provides useful information for future work involving biomonitoring in regions where P. lineatus is naturally exposed to pesticides and other genotoxic agents. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis during anoxic stress and aerobic recovery

    Science.gov (United States)

    Slobodskova, Valentina V.; Zhukovskaya, Avianna F.; Chelomin, Victor P.

    2012-06-01

    Anoxia-induced DNA damage in the gill cells of the marine scallop Mizuhopecten yessoensis was assessed with the alkaline comet assay (single-cell gel electrophoresis). The alkaline comet assay method for detecting DNA strand breaks and alkali labile sites in individual cells. DNA damage was determened in the scallops ( M. yessoensis) gill cells. The scallops were exposed to air for 8 h showing a clear increase in the levels of DNA damage. After the air exposure, M. yessoensis were re-submersed for a period of 12 h, leading values to return to a pre-aerial exposure level. Control animals were kept immersed during the whole period. The resulting data demonstrate that natural influences, such as oxygen depletion (anoxia) in seawater, can be responsible for the induction of DNA damage. If the scallops were re-immersed in oxic conditions, the anoxically induced breaks were repaired. The main mechanisms influencing the integrity of the DNA structure are discussed in this paper.

  6. Molecular ions in comet tails

    International Nuclear Information System (INIS)

    Wyckoff, S.; Wehinger, P.A.

    1976-01-01

    Band intensities of the molecular ions CH + , CO + , N 2 + , and H 2 O + have been determined on an absolute scale from tail spectra of comet Kohoutek (1973f) and comet Bradfield (1974b). Photoionization and photodissociation rates have been computed for CH, CO, and N 2 . Also emission rate excitation g-factors for (1) photoionization plus excitation and (2) resonance fluorescence have been computed for the observed ions. It is shown that resonance fluorescence is the dominant excitation mechanism for observed comet tail ions at rapprox. =1 AU. Band system luminosities and molecular ion abundances within a projected nuclear distance rho 4 km have been determined for CH + , CO + , N 2 + , and H 2 O + in comet Kohoutek, and for H 2 O + in comet Bradfield. Estimates are also given for column densities of all observed ions at rhoapprox. =10 4 km on the tailward side of the coma. The observed H 2 O + column densities were found to be roughly the same in comet Kohoutek and comet Bradfield et equal heliocentric distances, while CO + was found to be approximately 100 times more abundant than H 2 O + , N 2 + , and CH + at rhoapprox. =10 4 km in comet Kohoutek. Finally, the relative abundances of the observed ions and of the presumed parent neutral species are briefly discussed

  7. Comets and their composition

    International Nuclear Information System (INIS)

    Spinrad, H.

    1987-01-01

    Recent theoretical and observational studies of comets are reviewed, with an emphasis on in situ data from spacecraft encounters with P/Giacobini-Zinner (September 1985) and P/Halley (March 1986). Topics addressed include clues on the origin and permanence of the Oort cometary cloud, observations of cometary nuclei far from the sun, the Halley nucleus, compositional and physical data from comae studies, and the parent molecules in comet ices. Also discussed are quantitative analyses of coma production; special features in the tail of P/Giacobini-Zinner; and proposals for (1) observations to detect distant giant comets, (2) high-resolution spectroscopic studies of comae, and (3) additional spacecraft missions such as the NASA Comet Rendezvous and Asteroid Flyby. 121 references

  8. DIRBE Comet Trails

    Science.gov (United States)

    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 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.

  9. Singing comet changes its song

    Science.gov (United States)

    Volwerk, M.; Goetz, C.; Delva, M.; Richter, I.; Tsurutani, B. T.; Eriksson, A.; Odelstad, E.; Meier, P.; Nilsson, H.; Glassmeier, K.-H.

    2017-09-01

    The singing comet was discovered at the beginning of the Rosetta mission around comet 67P/Churyumov-Gerasimenko. Large amplitude compressional waves with frequencies between 10 and 100 mHz were observed. When the comet became more active this signal was no longer measured. During the so-called tail excursion, late in the mission after perihelion, with again a less active comet, the singing was observed again and interestingly, going from 26 March to 27 March 2016 the character of the singing changed.

  10. Nature and origin of comets

    International Nuclear Information System (INIS)

    Fernandez, J.A.; Jockers, K.

    1983-01-01

    The review examines basic history and morphology, motion, dynamic evolution, physical properties of neutral gaseous matter, vaporization of gases and outflow from the nucleus, chemistry of the coma gases, the comet nucleus, dust particles, solar wind-comet interactions and tail formation and the origin of comets. (U.K.)

  11. A New Orbit for Comet C/1865 B1 (Great Southern Comet of 1865)

    Science.gov (United States)

    Branham, Richard L., Jr.

    2018-04-01

    Comet C/1865 B1 (Great southern comet of 1865), observed only in the southern hemisphere, is one of a large number of comets with parabolic orbits. Given that there are 202 observations in right ascension and 165 in declination it proves possible to calculate a better orbit than that Körber published in 1887, the orbit used in various catalogs and data bases. C/1865 B1's orbit is hyperbolic and statistically distinguishable from a parabola. This object, therefore, cannot be considered an NEO. The comet has a small perihelion distance of 0.026 AU.

  12. Halley comet, implication on the origin

    International Nuclear Information System (INIS)

    Festou, M.C.

    1990-01-01

    One will first give a rapid description of the different parts that compose a comet coma. Then one will describe the spectrum of comets from the UV to the IR regions with special emphasis on how information relative to the physico-chemistry of comet atmospheres can be retrieved. Our basic knowledge about the composition of comets before 1985 will be summarized and the input of the 1985-86 observing campaign of comet Halley will be shown (in situ, ground-based and space borne observations). One will see then that the chemical composition of comets appears as of today completely compatible with a formation from pre-solar matter that condensed inside the solar system [fr

  13. A Comet Engulfs Mars: MAVEN Observations of Comet Siding Spring's Influence on the Martian Magnetosphere

    Science.gov (United States)

    Espley, Jared R.; Dibraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper S.; Combi, Michael; Luhmann, Janet; Ma, Yingjuan

    2015-01-01

    The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000?km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

  14. The Usefulness Cytogenetic Biomarkers in Assessment of Occupational Exposure to Microwave Radiation

    International Nuclear Information System (INIS)

    Garaj-Vrhovac, V.; Kopjar, N.

    2003-01-01

    In recent years there has been growing interest in the health effects of the electromagnetic radiation's designated extremely low frequency (ELF) and radiofrequency radiation (RFR). Available data on cytogenetic consequences of microwave exposure on the induction of chromosome damage are contradictory, mostly because of different experimental conditions of in vitro and in vivo studies. It has been suggested that exposure to radiofrequency radiation may have genetic effects, which predispose to the development of cancer or birth defects. For the detection of early biological effects of DNA-damaging agents, well-established cytogenetic biomarkers are used. Comet assay was also successfully introduced detection of primary DNA damage and micronucleus assay for simultaneous detection of chromosome damage and spindle disfunction. The chromatid breakage assay, allowing selection of persons with a defect in DNA repair, is also an additional marker in human biomonitoring. Susceptibility to bleomycin-induced chromatid breaks in cultured peripheral blood lymphocytes may reflect the way a person deals with carcinogenic challenges. The objective of the present study the assessment of primary DNA damage, chromosome and spindle disfunctions as well as the mutagen sensitivity in peripheral blood leukocytes in radar-facility workers daily exposed to microwave radiation and corresponding control. As sensitive biomarkers three endpoints were chosen: the alkaline comet assay, micronucleus assay and chromatid breakage assay (bleomycin sensitivity test). A large number of experimental and epidemiological studies have been carried out to elucidate the possible health hazards associated with human exposure to ELF or RF electromagnetic fields. The results presented here indicate that the alkaline comet assay, as reliable biomarker of exposure, can be successfully applied in study of DNA damaging effects in microwave exposed subjects. The fact that the comet assay is a microdosimetric

  15. DRBE comet trails

    International Nuclear Information System (INIS)

    Arendt, Richard G.

    2014-01-01

    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 −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.

  16. DRBE comet trails

    Energy Technology Data Exchange (ETDEWEB)

    Arendt, Richard G., E-mail: Richard.G.Arendt@nasa.gov [CREST/UMBC, Code 665, NASA/GSFC, Greenbelt, MD 20771 (United States)

    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. Studying Short-Period Comets and Long-Period Comets Detected by WISE/NEOWISE

    Science.gov (United States)

    Kramer, Emily A.; Fernández, Yanga R.; Bauer, James M.; Stevenson, Rachel; Mainzer, Amy K.; Grav, Tommy; Masiero, Joseph; Walker, Russell G.; Lisse, Carey M.

    2014-11-01

    The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22-micron) between January 2010 and February 2011 [1, 2]. During the mission, WISE serendipitously observed 160 comets, including 21 newly discovered objects. About 89 of the comets observed by WISE displayed a significant dust tail in the 12 and 22-micron (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal evolution that each of these populations has undergone. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method [3, 4]. For a selection of 40 comets, we have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the dust tail particle properties were estimated separately, and then compared. We find that the dust tails of both LPCs and SPCs are primarily comprised of ~mm to cm sized particles, which were the result of emission that occurred several months to several years prior to the observations. The LPCs nearly all have strong dust emission close to the comet's perihelion distance, and the SPCs mostly have strong dust emission close to perihelion, but some have strong dust emission well before perihelion. Acknowledgments: This publication makes use of data products from (1) WISE, which is a joint project of UCLA and JPL/Caltech, funded by NASA; and (2) NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA. EK was supported by a NASA Earth and Space Sciences Fellowship. RS gratefully acknowledges support from the NASA

  18. Inside look at Halley's comet

    International Nuclear Information System (INIS)

    Beatty, J.K.

    1986-01-01

    The 1985-1986 emergence of Halley's comet, the first since the advent of the space age, was explored by a variety of spacecraft. The Vega 1, launched by the USSR together with the Eastern-block alliance, passed 5523 miles from the comet's nucleus at 7:20:06 Universal time. It indicated that the comet was about 300 miles closer to the sun than had been predicted. The Japanese spacecraft, Suisei, was created to map the distribution of neutral hydrogen atoms outside Halley's visible coma. Its pictures indicated that the comet's output of water varied between 25 and 60 tons per second. Five days after the Vega 2's passage through the comet, the Giotto (sponsored by the European Space Agency) probe appeared. Giotto's close approach took place 3.1 minutes after midnight UT on March 14th; the craft had passed 376 miles from its target. Giotto's data indicated that the nucleus was bigger than expected, and that the comet was composed primarily of water, CO2 and N2. The Vegas and Giotto found that as the solar wind approaches Halley, it slows gradually and the solar magnetic lines embedded in the wind begin to pile up. Pick-up ions, from the comet's halo of neutral hydrogen, were found in this solar wind. Sensors on the Vega spacecraft found a variety of plasma waves propagating inside the bow wave. In order to synthesize all the results, a conference on the exploration of Halley's comet will be held this October

  19. Comet Mineralogy as Inferred from Infrared Spectra of Comets

    Science.gov (United States)

    Wooden, Diane H.

    2006-01-01

    For most comets, infrared (IR) spectroscopy (remote sensing) is the method through which we diagnose the mineralogy and size distribution of dust in their comae. The shape and contrast of the IR spectral features depend on the particle size: optically active minerals (absorbing of visible and near-IR solar photons) and submicron solid grains or highly porous (> 90% vacuum) grains primarily contribute to the shapes of the observed resonances. Comet mineralogies typically are determined by fitting thermal emission models of ensembles of discrete mineral grains to observed IR spectral energy distributions. The absorptivities (Q-abs) and scattering efficiencies (Q-scat) of the discrete mineral grains are computed using Mie scattering, Maxwell-Garnet mixing, Discrete Dipole Approximation, and Multi-Layered Sphere codes. These techniques when applied to crystalline minerals, specifically olivine (Mg_x, Fe_1-x)2 Si04, x>0.9, require the use of ellipsoidal shaped particles with elongated axial ratios or hollow spheres to produce the shapes of the resonances observed both from comet comae and laboratory samples. The wavelength positions of the distinct resonances from submicron-radii crystalline silicates, as well as their thermal equilibrium temperatures, constrain the crystalline olivine to have a relatively high Mg-content (x>0.9, or Fo>90). Only resonances computed for submicron Mg-rich crystalline olivine and crystalline orthopyroxene match the observed IR spectral features. However, this has led to the interpretation that micron-radii and larger crystals are absent from comet comae. Furthermore, the mass fraction of silicate crystals is dependent upon whether just the submicron portion of the size distribution is being compared or the submicron crystals compare to the aggregates of porous amorphous silicates that are computationally tractable as porous spheres. We will discuss the Deep Impact results as examples of these challenges to interpreting mid-IR spectra of

  20. Journal of Biosciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Amitraz is formamidine pesticide widely used as insecticide and acaricide. In veterinary medicine, amitraz has important uses against ticks, mites and lice on animals. Also, amitraz is used in apiculture to control Varroa destructor. It this study, the alkaline Comet assay was used to evaluate DNA damaging effects of amitraz ...

  1. Comet Halley and interstellar chemistry

    International Nuclear Information System (INIS)

    Snyder, L.E.

    1989-01-01

    How complex is the chemistry of the interstellar medium? How far does it evolve and how has it interacted with the chemistry of the solar system? Are the galactic chemical processes destroyed, preserved, or even enhanced in comets? Are biogenic molecules formed in space and have the formation mechanisms interacted in any way with prebiotic organic chemical processes on the early earth? Radio molecular studies of comets are important for probing deep into the coma and nuclear region and thus may help answer these questions. Comets are believed to be pristine samples of the debris left from the formation of the solar system and may have been the carrier between interstellar and terrestrial prebiotic chemistries. Recent observations of Comet Halley and subsequent comets have given the author an excellent opportunity to study the relationship between interstellar molecular chemistry and cometary chemistry

  2. Origin of Short-Perihelion Comets

    Science.gov (United States)

    Guliyev, A. S.

    2011-01-01

    New regularities for short-perihelion comets are found. Distant nodes of cometary orbits of Kreutz family are concentrated in a plane with ascending node 76 and inclination 267 at the distance from 2 up to 3 a.u. and in a very narrow interval of longitudes. There is a correlation dependence between q and cos I concerning the found plane (coefficient of correlation 0.41). Similar results are received regarding to cometary families of Meyer, Kracht and Marsden. Distant nodes of these comets are concentrated close three planes (their parameters are discussed in the article) and at distances 1.4; 0.5; 6 a.u. accordingly. It is concluded that these comet groups were formed as a result of collision of parent bodies with meteoric streams. One more group, consisting of 7 comets is identified. 5 comet pairs are selected among sungrazers.

  3. X-rays from comets - a surprising discovery

    CERN Document Server

    CERN. Geneva

    2000-01-01

    Comets are kilometre-size aggregates of ice and dust, which remained from the formation of the solar system. It was not obvious to expect X-ray emission from such objects. Nevertheless, when comet Hyakutake (C/1996 B2) was observed with the ROSAT X-ray satellite during its close approach to Earth in March 1996, bright X-ray emission from this comet was discovered. This finding triggered a search in archival ROSAT data for comets, which might have accidentally crossed the field of view during observations of unrelated targets. To increase the surprise even more, X-ray emission was detected from four additional comets, which were optically 300 to 30 000 times fainter than Hyakutake. For one of them, comet Arai (C/1991 A2), X-ray emission was even found in data which were taken six weeks before the comet was optically discovered. These findings showed that comets represent a new class of celestial X-ray sources. The subsequent detection of X-ray emission from several other comets in dedicated observations confir...

  4. Effects of the anti-malarial compound cryptolepine and its analogues in human lymphocytes and sperm in the Comet assay.

    Science.gov (United States)

    Gopalan, Rajendran C; Emerce, Esra; Wright, Colin W; Karahalil, Bensu; Karakaya, Ali E; Anderson, Diana

    2011-12-15

    Malaria is a mosquito-borne infectious disease caused by the genus Plasmodium. It causes one million deaths per year in African children under the age of 5 years. There is an increasing development of resistance of malarial parasites to chloroquine and other currently used anti-malarial drugs. Some plant products such as the indoloquinoline alkaloid cryptolepine have been shown to have potent activity against P. falciparum in vitro. On account of its toxicity, cryptolepine is not suitable for use as an antimalarial drug but a number of analogues of cryptolepine have been synthesised in an attempt to find compounds that have reduced cytotoxicity and these have been investigated in the present study in human sperm and lymphocytes using the Comet assay. The results suggest that cryptolepine and the analogues cause DNA damage in lymphocytes, but appear to have no effect on human sperm at the assessed doses. In the context of antimalarial drug development, the data suggest that all cryptolepine compounds and in particular 2,7-dibromocryptolepine cause DNA damage and therefore may not be suitable for pre clinical development as antimalarial agents. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  5. The Halley comet

    International Nuclear Information System (INIS)

    Encrenaz, T.; Festou, M.

    1985-01-01

    The conspicuous part of a comet, made of tenuous gas and dusts, represents only a tiny part of its mass. The main information is hidden in the central part: a solid nucleus, ice and rock blocks with a radius less than 10 km, completely invisible from the Earth. The knowledge of the nucleus structure and its composition could give the key of the planet creation mechanisms. That is a reason why it has been decided to send an automatic device to penetrate the Halley comet atmosphere and that two Soviet probes, Vega 1 and 2, one European probe Giotto, and two Japanese, Planet-A and MS-TS, will explore in-situ in March 1986, for the first time, a comet at atmosphere [fr

  6. Comet prospects for 2004

    Science.gov (United States)

    Shanklin, J. D.

    2003-12-01

    2004 sees the return of 18 periodic comets. None are particularly bright and the best are likely to be 78P/Gehrels and 88P/Howell. Three new long period comets are likely to put on a good show: 2001 Q4 (NEAT) reaches perihelion in May, when it could make at least 3rd magnitude. Northern hemisphere observers will first pick it up just after perihelion as it rapidly moves north. 2002 T7 (LINEAR) could also reach 3rd magnitude at closest approach in May, however northern hemisphere observers will have lost it as a binocular object in mid-March. Observers at far southern latitudes may be able to see these two naked eye comets at the same time. 2003 K4 (LINEAR) could reach 6th magnitude as it brightens on its way to perihelion. Several other long period comets discovered in previous years are also still visible.

  7. Meteoroid Streams from Sunskirter Comet Breakup

    Science.gov (United States)

    Jenniskens, P. M.

    2012-12-01

    In its first year of operations, the CAMS project (Cameras for Allsky Meteor Surveillance) has measured 47,000 meteoroid orbits at Earth, including some that pass the Sun as close as 0.008 AU. The population density increases significantly above perihelion distance q = 0.037 AU. Meteoroid streams are known with q about 0.1 AU. The Sun has a profound effect on comets that pass at 0.04-0.16 AU distance, called the sunskirter comets. SOHO and STEREO see families of small comets called the Marsden and Kracht groups. Sunlight is efficiently scattered by small 10-m sized fragments, making those fragments visible even when far from Earth. These comet groups are associated with meteor showers on Earth, in particular the Daytime Arietids and Delta Aquariids. All are related to 96P/Machholz, a highly inclined short-period (5.2 year) Jupiter family comet that comes to within 0.12 AU from the Sun, the smallest perihelion distance known among numbered comets. The proximity of the Sun speeds up the disintegration process, providing us a unique window on this important decay mechanism of Jupiter family comets and creating meteoroid streams. These are not the only sunskirting comets, however. In this presentation, we will present CAMS observations of the complete low-q meteoroid population at Earth and review their association with known parent bodies.

  8. X-ray emission from comets

    International Nuclear Information System (INIS)

    Dennerl, Konrad

    1999-01-01

    When comet Hyakutake (C/1996 B2) encountered Earth in March 1996 at a minimum distance of only 15 million kilometers (40 times the distance of the moon), x-ray and extreme ultraviolet emission was discovered for the first time from a comet. The observations were performed with the astronomy satellites ROSAT and EUVE. A systematic search for x-rays from comets in archival data, obtained during the ROSAT all-sky survey in 1990/91, resulted in the discovery of x-ray emission from four additional comets. They were detected at seven occasions in total, when they were optically 300 to 30 000 times fainter than Hyakutake. These findings indicated that comets represent a new class of celestial x-ray sources. Subsequent detections of x-ray emission from additional comets with the satellites ROSAT, EUVE, and BeppoSAX confirmed this conclusion. The x-ray observations have obviously revealed the presence of a process in comets which had escaped attention until recently. This process is most likely charge exchange between highly charged heavy ions in the solar wind and cometary neutrals. The solar wind, a stream of particles continuously emitted from the sun with ≅ 400 km s -1 , consists predominantly of protons, electrons, and alpha particles, but contains also a small fraction (≅0.1%) of highly charged heavier ions, such as C 6+ ,O 6+ ,Ne 8+ ,Si 9+ ,Fe 11+ . When these ions capture electrons from the cometary gas, they attain highly excited states and radiate a large fraction of their excitation energy in the extreme ultraviolet and x-ray part of the spectrum. Charge exchange reproduces the intensity, the morphology and the spectrum of the observed x-ray emission from comets very well

  9. Comets and How to Observe Them

    CERN Document Server

    Schmude, Richard

    2010-01-01

    Comets have inspired wonder, excitement and even fear ever since they were first observed. They contain material from early in the life of the Solar System, held in deep-freeze. This makes them key in our understanding of the formation and evolution of many Solar System bodies. Recent ground- and space-based observations have changed much in our understanding of comets. Comets and How to Observe Them gives a summary of our current knowledge and describes how amateur astronomers can contribute to the body of scientific knowledge of comets. This book contains many practical examples of how to construct comet light-curves, measure how fast a comet’s coma expands, and determine the rotation period of the nucleus. All these examples are illustrated with drawings and photographs.

  10. Explanation for excessive DNA single-strand breaks and endogenous repair foci in pluripotent mouse embryonic stem cells.

    Science.gov (United States)

    Banáth, J P; Bañuelos, C A; Klokov, D; MacPhail, S M; Lansdorp, P M; Olive, P L

    2009-05-01

    Pluripotent mouse embryonic stem cells (mES cells) exhibit approximately 100 large gammaH2AX repair foci in the absence of measurable numbers of DNA double-strand breaks. Many of these cells also show excessive numbers of DNA single-strand breaks (>10,000 per cell) when analyzed using the alkaline comet assay. To understand the reasons for these unexpected observations, various methods for detecting DNA strand breaks were applied to wild-type mES cells and to mES cells lacking H2AX, ATM, or DNA-PKcs. H2AX phosphorylation and expression of other repair complexes were measured using flow and image analysis of antibody-stained cells. Results indicate that high numbers of endogenous gammaH2AX foci and single-strand breaks in pluripotent mES cells do not require ATM or DNA-PK kinase activity and appear to be associated with global chromatin decondensation rather than pre-existing DNA damage. This will limit applications of gammaH2AX foci analysis in mES cells to relatively high levels of initial or residual DNA damage. Excessive numbers of single-strand breaks in the alkaline comet assay can be explained by the vulnerability of replicating chromatin in mES cells to osmotic shock. This suggests that caution is needed in interpreting results with the alkaline comet assay when applied to certain cell types or after treatment with agents that make chromatin vulnerable to osmotic changes. Differentiation of mES cells caused a reduction in histone acetylation, gammaH2AX foci intensity, and DNA single-strand breakage, providing a link between chromatin structural organization, excessive gammaH2AX foci, and sensitivity of replicating mES cell chromatin to osmotic shock.

  11. Facile colorimetric assay of alkaline phosphatase activity using Fe(II)-phenanthroline reporter.

    Science.gov (United States)

    Hu, Qiong; Zhou, Baojing; Dang, Pengyun; Li, Lianzhi; Kong, Jinming; Zhang, Xueji

    2017-01-15

    We report a versatile approach for the colorimetric assay of alkaline phosphatase (ALP) activity based on the distinctive metal-to-ligand charge-transfer (MLCT) absorption properties of Fe(II)-phenanthroline reporter. In the presence of ALP, the applied substrate ascorbic acid 2-phosphate is enzymatically hydrolyzed to produce ascorbic acid, which then reduces Fe 3+ to Fe 2+ . The complexation of Fe 2+ with the bathophenanthroline disulfonate (BPS) ligand generates a blood-red Fe(BPS) 3 4- reporter, which is characterized by an intense MLCT absorption band at 535 nm in the visible range. Under optimal conditions, the spectral output exhibits a good quantitative relationship with ALP activity over the range of 0-220 mU mL -1 with a detection limit of 0.94 mU mL -1 . Moreover, the activity of ALP can also be conveniently judged through naked-eye observations. Results indicate that it is highly selective and can be applied to the screening of ALP inhibitors. In addition, it has been successfully employed to detect the endogenous ALP level of undiluted human serum samples, with a detection limit of 1.05 mU mL -1 being achieved. This approach avoids any elaborately designed substrates and holds considerable simplicity and flexibility for reporter design. This study broadens the horizon of the applications of phenanthroline-based transition metal complexes. Furthermore, an efficient and practical method like this has the potential to be widely used in clinical applications and in the point-of-care testing. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Astrobiology of Comets

    Science.gov (United States)

    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.

  13. Characterization of Human Bone Alkaline Phosphatase in Pichia Pastoris

    Science.gov (United States)

    Malone, Christine C.; Ciszak, Eva; Karr, Laurel J.

    1999-01-01

    A soluble form of human bone alkaline phosphatase has been expressed in a recombinant strain of the methylotrophic yeast Pichia pastoris. We constructed a plasmid containing cDNA encoding for human bone alkaline phosphatase, with the hydrophobic carboxyl terminal portion deleted. Alkaline phosphatase was secreted into the medium to a level of 32mg/L when cultured in shake flasks, and enzyme activity was 12U/mg, as measured by a spectrophotometric assay. By conversion to a fermentation system, a yield of 880mg/L has been achieved with an enzyme activity of 968U/mg. By gel electrophoresis analysis, it appears that greater than 50% of the total protein in the fermentation media is alkaline phosphatase. Although purification procedures are not yet completely optimized, they are expected to include filtration, ion exchange and affinity chromatography. Our presentation will focus on the purification and crystallization results up to the time of the conference. Structural data should provide additional information on the role of alkaline phosphatase in normal bone mineralization and in certain bone mineralization anomalies.

  14. COMET concept; COMET-Konzept

    Energy Technology Data Exchange (ETDEWEB)

    Alsmeyer, H.; Tromm, W.

    1995-08-01

    Studies of the COMET core catcher concept developed for a future PWR have been continued. The concept is based on the spreading of a core melt on a sacrificial layer and its erosion, until a subsequent addition of water from below causes a fragmentation of the melt. A porous solidification of the melt would then admit a complete flooding within a short period. (orig.)

  15. Evaluation of the genotoxic and antigenotoxic potential of Baccharis dracunculifolia extract on V79 cells by the comet assay.

    Science.gov (United States)

    Munari, Carla Carolina; Alves, Jacqueline Morais; Bastos, Jairo Kenupp; Tavares, Denise Crispim

    2010-01-01

    Baccharis dracunculifolia (Asteraceae), the main botanical source of green propolis, is a shrub of the Brazilian 'cerrado'. In folk medicine it is used as an anti-inflammatory agent, mainly for the treatment of gastrointestinal diseases. The aim of the present study was to evaluate the genotoxic and antigenotoxic effects of B. dracunculifolia ethyl acetate extract (Bd-EAE) on Chinese hamster lung fibroblasts (V79 cells) by the comet assay. Methyl methanesulfonate (MMS; 200 microM) was used as an inducer of DNA damage. Genotoxicity was evaluated using four different concentrations of Bd-EAE: 12.5, 25.0, 50.0 and 100.0 microg ml(-1). Antigenotoxicity was assessed before, simultaneously, and after treatment with the mutagen. The results showed a significant increase in the frequency of DNA damage in cultures treated with 50.0 and 100.0 microg ml(-1) Bd-EAE. Regarding its antigenotoxic potential, Bd-EAE reduced the frequency of DNA damage induced by MMS. However, this chemopreventive activity depended on the concentrations and treatment regimens used. The antioxidant activity of phenolic components present in Bd-EAE may contribute to reduce the alkylation damage induced by MMS. In conclusion, our findings confirmed the chemopreventive activity of Bd-EAE and showed that this effect occurs under different mechanism.

  16. Comets in Indian Scriptures

    Science.gov (United States)

    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.

  17. Jupiter Laser Facility - COMET Laser

    Data.gov (United States)

    Federal Laboratory Consortium — COMET has 4 beam configurations with uncompressed pulse lengths from 500 ps to 6 ns, compressed pulses to 0.5 ps, and beam energies up to 20 J. COMET can fire every...

  18. DNA strand breaks, acute phase response and inflammation following pulmonary exposure by instillation to the diesel exhaust particle NIST1650b in mice

    DEFF Research Database (Denmark)

    Kyjovska, Zdenka O.; Jacobsen, Nicklas R.; Saber, Anne T.

    2015-01-01

    by the alkaline comet assay as DNA strand breaks in BAL cells, lung and liver tissue. The pulmonary acute phase response was analysed by Saa3 mRNA levels by real-time quantitative polymerase chain reaction. Instillation of DEP induced a strong neutrophil influx 1 and 3 days, but not 28 days post-exposure. Saa3 m...

  19. 12038_2018_9736_MOESM7_ESM.docx

    Indian Academy of Sciences (India)

    Disha

    Lower Panel: Representative images of p53 positive nuclei (C) Representative images for Alkaline (a,c,e) and Neutral Comet assay (b,d,f) performed with NHDF cells, either left untreated (“No Treatment”) or treated with HU for 2h or 24h. Supplementary figure 4: DDR during short replication stress is ATR kinase dependent: ...

  20. Comet-Narval acquisition notice

    International Nuclear Information System (INIS)

    Le Bris, J.; Sellem, R.; Artiges, J.C.; Clavelin, J.F.; Du, S.; Grave, X.; Hubert, O.; Sauvage, J.; Roussiere, B.

    2006-01-01

    The COMET cards (encoding and time marking) serve to determine the energies and the time correlations of radiations detected during a multiparameter experiment while avoiding any extra specific module like coincidence circuits or delays) to set this time correlation. For each detected radiation, the arrival time information as well as the amplitude of the detected signal, are encoded. The results of these amplitude and time coding are associated to create an event. In this way, each detector is an independent source which provides a building block of the general information obtained by all the detectors. The COMET cards are associated with a NARVAL data acquisition system. This document is the instruction booklet of the COMET-NARVAL acquisition system

  1. Comet: Multifunction VOEvent broker

    Science.gov (United States)

    Swinbank, John

    2014-04-01

    Comet is a Python implementation of the VOEvent Transport Protocol (VTP). VOEvent is the IVOA system for describing transient celestial events. Details of transients detected by many projects, including Fermi, Swift, and the Catalina Sky Survey, are currently made available as VOEvents, which is also the standard alert format by future facilities such as LSST and SKA. The core of Comet is a multifunction VOEvent broker, capable of receiving events either by subscribing to one or more remote brokers or by direct connection from authors; it can then both process those events locally and forward them to its own subscribers. In addition, Comet provides a tool for publishing VOEvents to the global VOEvent backbone.

  2. Comets in the space age

    International Nuclear Information System (INIS)

    Whipple, F.L.

    1989-01-01

    The historical development of the study of the nature of comets and their origin is discussed, emphasizing the use of aerospace technology in cometary science. The use of satellites to study the Comet Kohoutek 1973 XII, advances between Kohoutek and P/Halley, and studies of P/Halley during its 1986 return are examined. Consideration is given to data from ground, air, and space sensors, and from the Giotto and Vega spacecraft missions. Also, the physical structure of the nucleus of Comet Halley is described. 136 refs

  3. Report of Some Comets: The Discovery of Uranus and Comets by William, Caroline, and John Herschel

    Science.gov (United States)

    Pasachoff, Jay M.; Olson, R. J. M.

    2011-01-01

    We report on the discovery and drawings of comets by William, Caroline, and John Herschel. The first discovery, by William Herschel, in 1781 from Bath, published in the Philosophical Transactions of the Royal Society with the title "Report of a Comet," turned out to be Uranus, the first planet ever discovered, Mercury through Saturn having been known since antiquity. William's sister Caroline was given duties of sweeping the skies and turned out to be a discoverer of 8 comets in her own right, in addition to keeping William's notes. Caroline's comets were discovered from Slough between 1786 and 1797. In the process, we also discuss original documents from the archives of the Royal Society and of the Royal Astronomical Society. We conclude by showing comet drawings that we have recently attributed to John Herschel, including Halley's Comet from 1836, recently located in the Ransom Center of the University of Texas at Austin. Acknowledgments: Planetary astronomy at Williams College is supported in part by grant NNX08AO50G from NASA Planetary Astronomy. We thank Peter Hingley of the Royal Astronomical Society and Richard Oram of the Harry Ransom Center of The University of Texas at Austin for their assistance.

  4. Nucleus of Comet IRAS-Araki-Alcock (1983 VII)

    International Nuclear Information System (INIS)

    Sekanina, Z.

    1988-01-01

    Optical, radar, infrared, UV, and microwave-continuum observations of Comet IRAS-Araki-Alcok were obtained in May 1983, the week of the comet's close approach to earth. The comet has a nucleus dimension and a rotation period which are similar to those of Comet Halley, but a different morphological signature (a persisting sunward fan-shaped coma). Time variations are noted in the projected nucleus cross section. Results suggest significant limb-darkening effects in the relevant domains of radio waves, and that the comet's interior must be extremely cold. It is found that the thermal-infrared fluxes from the inner coma of the comet are dominated by the nucleus. 63 references

  5. EPOXI at comet Hartley 2.

    Science.gov (United States)

    A'Hearn, Michael F; Belton, Michael J S; Delamere, W Alan; Feaga, Lori M; Hampton, Donald; Kissel, Jochen; Klaasen, Kenneth P; McFadden, Lucy A; Meech, Karen J; Melosh, H Jay; Schultz, Peter H; Sunshine, Jessica M; Thomas, Peter C; Veverka, Joseph; Wellnitz, Dennis D; Yeomans, Donald K; Besse, Sebastien; Bodewits, Dennis; Bowling, Timothy J; Carcich, Brian T; Collins, Steven M; Farnham, Tony L; Groussin, Olivier; Hermalyn, Brendan; Kelley, Michael S; Kelley, Michael S; Li, Jian-Yang; Lindler, Don J; Lisse, Carey M; McLaughlin, Stephanie A; Merlin, Frédéric; Protopapa, Silvia; Richardson, James E; Williams, Jade L

    2011-06-17

    Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.

  6. Repair of UVC induced DNA lesions in erythrocytes from Carassius auratus gibelio

    International Nuclear Information System (INIS)

    Bagdonas, E.; Zukas, K.

    2004-01-01

    The kinetics of UVC (254 nm) irradiation induced DNA single-strand breaks generated during the excision repair of UV induced DNA damage in erythrocytes from Carassius auratus gibelio were studied using alkaline comet assay. Nucleotide excision repair recognised DNA lesions such as UVC induced cyclobutane pyrimidine dimers and 6-4 pyrimidine-pyrimidone photoproducts and produced DNA single-stranded breaks that were easily detected by comet assay. After irradiation of erythrocytes with 58 j/m 2 UVC dose, there was an increase in comet tail moment (CTM) at 2 hours post-radiation, whereas at 4 hours post-radiation CTM decreased and did not differ significantly from the control level (P=0,127). When erythrocytes were exposed to 173 J/m 2 UVC dose, the excision repair delayed in the beginning (0 hours), reached maximum level at 2 hours post-radiation (CTM-54,8) and showed slightly decreased level at 4 hours post-radiation (CTM=18,5). (author)

  7. Abundant Solar Nebula Solids in Comets

    Science.gov (United States)

    Messenger, S.; Keller, L. P.; Nakamura-Messenger, K.; Nguyen, A. N.; Clemett, S.

    2016-01-01

    Comets have been proposed to consist of unprocessed interstellar materials together with a variable amount of thermally annealed interstellar grains. Recent studies of cometary solids in the laboratory have shown that comets instead consist of a wide range of materials from across the protoplanetary disk, in addition to a minor complement of interstellar materials. These advances were made possible by the return of direct samples of comet 81P/Wild 2 coma dust by the NASA Stardust mission and recent advances in microscale analytical techniques. Isotopic studies of 'cometary' chondritic porous interplanetary dust particles (CP-IDPs) and comet 81P/Wild 2 Stardust samples show that preserved interstellar materials are more abundant in comets than in any class of meteorite. Identified interstellar materials include sub-micron-sized presolar silicates, oxides, and SiC dust grains and some fraction of the organic material that binds the samples together. Presolar grain abundances reach 1 weight percentage in the most stardust-rich CP-IDPs, 50 times greater than in meteorites. Yet, order of magnitude variations in presolar grain abundances among CP-IDPs suggest cometary solids experienced significant variations in the degree of processing in the solar nebula. Comets contain a surprisingly high abundance of nebular solids formed or altered at high temperatures. Comet 81P/Wild 2 samples include 10-40 micron-sized, refractory Ca- Al-rich inclusion (CAI)-, chondrule-, and ameboid olivine aggregate (AOA)-like materials. The O isotopic compositions of these refractory materials are remarkably similar to their meteoritic counterparts, ranging from 5 percent enrichments in (sup 16) O to near-terrestrial values. Comet 81P/Wild 2 and CP-IDPs also contain abundant Mg-Fe crystalline and amorphous silicates whose O isotopic compositions are also consistent with Solar System origins. Unlike meteorites, that are dominated by locally-produced materials, comets appear to be composed of

  8. A biological evaluation of DNA damage detected by comet assay in healthy populations residing in areas that differ in lung cancer incidence.

    Science.gov (United States)

    Heepchantree, Worapa; Paratasilpin, Thipmani; Kangwanpong, Daoroong

    2006-06-01

    The comet assay was performed to evaluate the effect of environmental exposure between human populations residing in two areas that differ in lung cancer incidence, Saraphi (n = 91) and Chom Thong (n = 94). Three parameters, the tail length, tail intensity, and tail moment, were used to detect DNA damage in peripheral blood and stimulated lymphocytes with and without the DNA repair inhibitor, aphidicolin. Internal standards, cryopreserved isolated lymphocytes, and isolated lymphocytes irradiated with 2 Gy gamma rays, were used to correct the interexperimental variability. Results revealed a significant difference between two populations only when the tail length was used to measure DNA damage. The evaluation of various potential confounding factors, such as gender, pesticide exposure, smoking, alcohol drinking, and fermented tea leaf or betel nut chewing, indicated no significant influence in DNA damage. In conclusion, significant difference in DNA damage, detected only by tail length between the two populations residing in the areas with different incidence of lung cancer, may reflect a nonhazardous level of exposure to toxic substances.

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

    Science.gov (United States)

    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 (Padrenaline genotoxicity. Results indicate genoprotective and antioxidant properties in dry olive leaf extract, strongly supporting further explorations of its underlying mechanisms of action. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Application of the Single Cell Gel Electrophoresis (SCGE) Assay to Genotoxicity Evaluation in Plants and Animals

    International Nuclear Information System (INIS)

    Kim, Jin Kyu

    2007-10-01

    Application of the Single Cell Gel Electrophoresis (SCGE) Assay to Genotoxicity Evaluation in Plants and Animals. Recently, the importance of ionizing radiation and chemicals has been recognized since radio- and chemical therapy is directly related to the control of various diseases such as cancer. Radiation and the chemicals can cause biological damages while they have great applicability. It is of necessity to analyze rapidly, easily and accurately the biological effects, especially DNA damage due to those factors. Recently SCGE (single cell gel electrophoresis assay, alias comet assay) has been developed for the efficient evaluation of DNA damage. In this report, the comprehensive review will be given on the rationale, the technical applications and the advantages and shortcomings of SCGE assay. This method can be directly applied to study on toxicity, cancer, and aging in terms of the evaluation of DNA damages due to radiation and chemicals on human cellular level. It is also suggested that comet assay be used for testing genotoxicity of suspected substances, detecting irradiated foods, screening radioprotective candidates, and studying DNA repair process in various biological systems

  11. Application of the Single Cell Gel Electrophoresis (SCGE) Assay to Genotoxicity Evaluation in Plants and Animals

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Kyu

    2007-10-15

    Application of the Single Cell Gel Electrophoresis (SCGE) Assay to Genotoxicity Evaluation in Plants and Animals. Recently, the importance of ionizing radiation and chemicals has been recognized since radio- and chemical therapy is directly related to the control of various diseases such as cancer. Radiation and the chemicals can cause biological damages while they have great applicability. It is of necessity to analyze rapidly, easily and accurately the biological effects, especially DNA damage due to those factors. Recently SCGE (single cell gel electrophoresis assay, alias comet assay) has been developed for the efficient evaluation of DNA damage. In this report, the comprehensive review will be given on the rationale, the technical applications and the advantages and shortcomings of SCGE assay. This method can be directly applied to study on toxicity, cancer, and aging in terms of the evaluation of DNA damages due to radiation and chemicals on human cellular level. It is also suggested that comet assay be used for testing genotoxicity of suspected substances, detecting irradiated foods, screening radioprotective candidates, and studying DNA repair process in various biological systems.

  12. Overexpression of Human Bone Alkaline Phosphatase in Pichia Pastoris

    Science.gov (United States)

    Karr, Laurel; Malone, Christine, C.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The Pichiapastoris expression system was utilized to produce functionally active human bone alkaline phosphatase in gram quantities. Bone alkaline phosphatase is a key enzyme in bone formation and biomineralization, yet important questions about its structural chemistry and interactions with other cellular enzymes in mineralizing tissues remain unanswered. A soluble form of human bone alkaline phosphatase was constructed by deletion of the 25 amino acid hydrophobic C-terminal region of the encoding cDNA and inserted into the X-33 Pichiapastoris strain. An overexpression system was developed in shake flasks and converted to large-scale fermentation. Alkaline phosphatase was secreted into the medium to a level of 32mgAL when cultured in shake flasks. Enzyme activity was 12U/mg measured by a spectrophotometric assay. Fermentation yielded 880mgAL with enzymatic activity of 968U/mg. Gel electrophoresis analysis indicates that greater than 50% of the total protein in the fermentation is alkaline phosphatase. A purification scheme has been developed using ammonium sulfate precipitation followed by hydrophobic interaction chromatography. We are currently screening crystallization conditions of the purified recombinant protein for subsequent X-ray diffraction analyses. Structural data should provide additional information on the role of alkaline phosphatase in normal bone mineralization and in certain bone mineralization anomalies.

  13. Comet formation

    Science.gov (United States)

    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).

  14. Comet Halley Returns. A Teacher's Guide, 1985-1986.

    Science.gov (United States)

    Chapman, Robert D.; Bondurant, R. Lynn, Jr.

    This booklet was designed as an aid for elementary and secondary school teachers. It is divided into two distinct parts. Part I is a brief tutorial which introduces some of the most important concepts about comets. Areas addressed include: the historical importance of Comet Halley; how comets are found and names; cometary orbits; what Comet Halley…

  15. Comets and the origin and evolution of life

    CERN Document Server

    McKay, Christopher P

    2006-01-01

    Nine years after the publication of Comets and the Origin and Evolution of Life, one of the pioneering books in Astrobiology, this second edition revisits the role comets may have played in the origins and evolution of life. Recent analyses of Antarctic micrometeorites and ancient rocks in Australia and South Africa, the continuing progress in discovering complex organic macromolecules in comets, protostars and interstellar clouds, new insights into organic synthesis in comets, and numerical simulations of comet impacts on the Earth and other members of the solar system yield a spectacular wea

  16. Tungsten carbide-cobalt as a nanoparticulate reference positive control in in vitro genotoxicity assays.

    Science.gov (United States)

    Moche, Hélène; Chevalier, Dany; Barois, Nicolas; Lorge, Elisabeth; Claude, Nancy; Nesslany, Fabrice

    2014-01-01

    With the increasing human exposure to nanoparticles (NP), the evaluation of their genotoxic potential is of significant importance. However, relevance for NP of the routinely used in vitro genotoxicity assays is often questioned, and a nanoparticulate reference positive control would therefore constitute an important step to a better testing of NP, ensuring that test systems are really appropriate. In this study, we investigated the possibility of using tungsten carbide-cobalt (WC-Co) NP as reference positive control in in vitro genotoxicity assays, including 2 regulatory assays, the mouse lymphoma assay and the micronucleus assay, and in the Comet assay, recommended for the toxicological evaluation of nanomedicines by the French Agency of Human Health Products (Afssaps). Through these assays, we were able to study different genetic endpoints in 2 cell types commonly used in regulatory genotoxicity assays: the L5178Y mouse lymphoma cell line and primary cultures of human lymphocytes. Our results showed that the use of WC-Co NP as positive control in in vitro genotoxicity assays was conceivable, but that different parameters have to be considered, such as cell type and treatment schedule. L5178Y mouse lymphoma cells did not provide satisfactory results in the 3 performed tests. However, human lymphocytes were more sensitive to genotoxic effects induced by WC-Co NP, particularly after a 24-h treatment in the in vitro micronucleus assay and after a 4-h treatment in the in vitro Comet assay. Under such conditions, WC-Co could be used as a nanoparticulate reference positive control in these assays.

  17. Comets - cosmic 'snowballs'

    International Nuclear Information System (INIS)

    Luest, R.

    1979-01-01

    Non-periodic comets come from regions at the limit of our solar system and have conserved their original structure and composition since they have originated from a pre-solar nebuly together with the sun and the planets about 4.5 x 10 9 years ago. They are icy bodies of kilometer size whose structure and chemical composition is of great interest also with respect to the origin of the solar system. It is hoped to send a space craft to comet Halley in 1986 to get more detailed informations. (orig.) [de

  18. Nitrogen abundance in Comet Halley

    International Nuclear Information System (INIS)

    Wyckoff, S.; Tegler, S.C.; Engel, L.

    1991-01-01

    Data on the nitrogen-containing compounds that observed spectroscopically in the coma of Comet Halley are summarized, and the elemental abundance of nitrogen in the Comet Halley nucleus is derived. It is found that 90 percent of elemental nitrogen is in the dust fraction of the coma, while in the gas fraction, most of the nitrogen is contained in NH3 and CN. The elemental nitrogen abundance in the ice component of the nucleus was found to be deficient by a factor of about 75, relative to the solar photosphere, indicating that the chemical partitioning of N2 into NH3 and other nitrogen compounds during the evolution of the solar nebula cannot account completely for the low abundance ratio N2/NH3 = 0.1, observed in the comet. It is suggested that the low N2/NH3 ratio in Comet Halley may be explained simply by physical fractionation and/or thermal diffusion. 88 refs

  19. Comet nuclei and Trojan asteroids - A new link and a possible mechanism for comet splittings

    International Nuclear Information System (INIS)

    Hartmann, W.K.; Tholen, D.J.

    1990-01-01

    Relatively elongated shapes, implied by recent evidence of a greater incidence of high amplitude lightcurves for comet nuclei and Trojan asteroids than for similarly scaled main belt asteroids, are suggested to have evolved among comet nuclei and Trojans due to volatile loss. It is further suggested that such an evolutionary course may account for observed comet splitting; rotational splitting may specifically occur as a result of evolution in the direction of an elongated shape through sublimation. Supporting these hypotheses, the few m/sec separation velocities projected for rotationally splitting elongated nuclei are precisely in the observed range. 40 refs

  20. The Assessment of Primary DNA Damage in Medical Personnel Occupationally Exposed to Ionizing Radiation

    International Nuclear Information System (INIS)

    Kopjar, N.; Garaj-Vrhovac, V.

    2003-01-01

    alkaline comet assay was selected. Working in the presence of ionizing radiation is one of many managed risks within a hospital. Among individuals occupationally exposed to ionizing radiation different cytogenetic changes, for example increased frequencies of chromosome aberrations and micronuclei are well known. Lesions induced by ionizing radiation in DNA can be also detected by comet assay. The increased comet values measured in peripheral blood leukocytes of exposed subjects indicate highly significant levels of primary radiation-induced DNA damage compared to control. However, the influences of the different occupational settings and doses absorbed on the levels of DNA damage in majority of subjects might be excluded. In the present study smoking habit did not significantly increased the levels of primary DNA damage both in control and exposed subjects. Cigarette smoking was not a very potent confounding factor on the comet parameters measured. The results indicate that the alkaline comet assay might be useful additional complement to standard biodosimetric methods. By detection of momentary DNA damage and/or repair activity, it reflects the concurrent exposure and the actual levels of DNA damage present in peripheral blood leukocytes of the radiological workers at the moment of blood sampling.(author)

  1. Assessment of the colorimetric and fluorometric assays for alkaline phosphatase activity in cow's, goat's, and sheep's milk.

    Science.gov (United States)

    Klotz, V; Hill, Art; Warriner, K; Griffiths, M; Odumeru, J

    2008-09-01

    Raw milk is a well-established vehicle for the carriage of human pathogens, and many regulatory bodies have consequently mandated compulsory pasteurization as a food safety intervention. The residual activity of alkaline phosphatase (ALP) has historically been used to verify the adequacy of pasteurization of cow's milk. However, there is uncertainty on how the current ALP standards and methods of analysis can be applied to sheep's and goat's milk, which naturally contain different levels of the enzyme than that found in cow's milk. The official ALP methods applied in Canada (colorimetric assay; MFO-3) and in the United States (Fluorophos) were assessed for their ability to detect enzyme activity in raw and pasteurized milk derived from cows, sheep, and goats. The detection limit and the limit of quantitation were 0.8 and 2.02 microg/ml phenol, respectively, for the MFO-3 method and 43 and 85 mU/liter, respectively, for the Fluorophos method. The average ALP levels in raw goat's, cow's, and sheep's milk were 165, 1,562, and 3,512 microg/ml phenol, respectively. Raw milk detection limits, which correspond to raw milk phosphatase levels, were 0.051, 0.485, and 0.023% in cow's, goat's, and sheep's milk, respectively, for the MFO-3 method and 0.007, 0.070, and 0.004%, respectively, for the Fluorophos method. Although both methods can be used for ALP determination in cow's, goat's, and sheep's milk, the Fluorophos assay was superior to the colorimetric MFO-3 method based on sensitivity and time required to complete the analysis.

  2. Solar wind interaction with type-1 comet tails

    International Nuclear Information System (INIS)

    Ershkovich, A.I.

    1977-01-01

    A comet tail is considered as a plasma cylinder separated by a tangential discontinuity surface from the solar wind. Under typical conditions a comet tail boundary is shown to undergo the Kelvin-Helmholtz instability. With infinite amplitude the stabilizing effect of the magnetic field increases, and waves become stable. The proposed model supplies the detailed quantitative description of helical waves observed in type-1 comet tails. This theory enables the evaluation of the comet tail magnetic field by means of the observations of helical waves. The magnetic field in the comet tail turns out to be of the order of the interplanetary field. This conclusion seems to be in accordance with Alfven's idea that the magnetic field in type-1 comet tails is a captured interplanetary field. (Auth.)

  3. Where are the mini Kreutz-family comets?

    International Nuclear Information System (INIS)

    Ye, Quan-Zhi; Wiegert, Paul A.; Hui, Man-To; Kracht, Rainer

    2014-01-01

    The Kreutz family of sungrazing comets contains over 2000 known members, many of which are believed to be under ∼100 m sizes (mini comets) and have only been studied at small heliocentric distances (r H ) with space-based SOHO/STEREO spacecraft. To understand the brightening process of mini Kreutz comets, we conducted a survey using CFHT/MegaCam at moderate r H guided by SOHO/STEREO observations. We identify two comets that should be in our search area but are not detected, indicating that the comets have either followed a steeper brightening rate within the previously reported rapid brightening stage (the brightening burst), or the brightening burst starts earlier than expected. We present a composite analysis of the pre-perihelion light curves of five Kreutz comets that cover to ∼1 AU. We observe significant diversity in the light curves that can be used to grossly classify them into two types: C/Ikeya-Seki and C/SWAN follow the canonical r H −4 while the others follow r H −7 . In particular, C/SWAN seems to have undergone an outburst (Δm > 5 mag) or a rapid brightening (n ≳ 11) between r H = 1.06 AU and 0.52 AU, and shows hints of structural/compositional differences compared to other bright Kreutz comets. We also find evidence that the Kreutz comets as a population lose their mass less efficiently than the dynamically new comet, C/ISON, and are relatively devoid of species that drive C/ISON's activity at large r H . Concurrent observations of C/STEREO in different wavelengths also suggest that a blueward species such as CN may be the main driver for brightening bursts, instead of sodium as previously thought

  4. COLOR SYSTEMATICS OF COMETS AND RELATED BODIES

    Energy Technology Data Exchange (ETDEWEB)

    Jewitt, David, E-mail: jewitt@ucla.edu [Department of Earth, Planetary and Space Sciences, UCLA, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States)

    2015-12-15

    Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived “small body” populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-period comets, Jovian Trojans and Kuiper belt objects to examine the color systematics of the comet-related populations. We find that the mean optical colors of the dust in short-period and long-period comets are identical within the uncertainties of measurement, as are the colors of the dust and of the underlying nuclei. These populations show no evidence for scattering by optically small particles or for compositional gradients, even at the largest distances from the Sun, and no evidence for ultrared matter. Consistent with earlier work, ultrared surfaces are common in the Kuiper belt and on the Centaurs, but not in other small body populations, suggesting that this material is hidden or destroyed upon entry to the inner solar system. The onset of activity in the Centaurs and the disappearance of the ultrared matter in this population begin at about the same perihelion distance (∼10 AU), suggesting that the two are related. Blanketing of primordial surface materials by the fallback of sub-orbital ejecta, for which we calculate a very short timescale, is the likely mechanism. The same process should operate on any mass-losing body, explaining the absence of ultrared surface material in the entire comet population.

  5. Theories of comets to the age of Laplace

    Science.gov (United States)

    Heidarzadeh, Tofigh

    Although the development of ideas about cometary motion has been investigated in several projects, a comprehensive and detailed survey of physical theories of comets has not been conducted. The available works either illustrate relatively short periods in the history of physical cometology or portray a landscape view without adequate details. The present study is an attempt to depict the details of the major physical theories of comets from Aristotle to the age of Laplace. The basic question from which this project originated was simple: how did natural philosophers and astronomers define the nature and place of a new category of celestial objects--the comets--after Brahe's estimation of cometary distances? However, a study starting merely from Brahe without covering classical and medieval thought about comets would be incomplete. Thus, based on the fundamental physical characteristics attributed to comets, the history of cometology may be divided into three periods: from Aristotle to Brahe, in which comets were assumed to be meteorological phenomena; from Brahe to Newton, when comets were admitted as celestial bodies but with unknown trajectories; and from Newton to Laplace, in which they were treated as members of the solar system having more or less the same properties of the planets. By estimating the mass of comets in the 1800s, Laplace diverted cometology into a different direction wherein they were considered among the smallest bodies in the solar system and deprived of the most important properties that had been used to explain their physical constitution during the previous two millennia. Ideas about the astrological aspects of comets are not considered in this study. Also, topics concerning the motion of comets are explained to the extent that is helpful in illustrating their physical properties. The main objective is to demonstrate the foundations of physical theories of comets, and the interaction between observational and mathematical astronomy, and

  6. THE PLASMA ENVIRONMENT IN COMETS OVER A WIDE RANGE OF HELIOCENTRIC DISTANCES: APPLICATION TO COMET C/2006 P1 (MCNAUGHT)

    Energy Technology Data Exchange (ETDEWEB)

    Shou, Y.; Combi, M.; Gombosi, T.; Toth, G. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI (United States); Jia, Y.-D. [IGPP, and EPSS, University of California, Los Angeles, CA 90095 (United States); Rubin, M. [Physikalisches Institut, University of Bern, Sidlerstrasse. 5, CH-3012 Bern (Switzerland)

    2015-08-20

    On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses.

  7. THE PLASMA ENVIRONMENT IN COMETS OVER A WIDE RANGE OF HELIOCENTRIC DISTANCES: APPLICATION TO COMET C/2006 P1 (MCNAUGHT)

    International Nuclear Information System (INIS)

    Shou, Y.; Combi, M.; Gombosi, T.; Toth, G.; Jia, Y.-D.; Rubin, M.

    2015-01-01

    On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses

  8. To Catch A Comet...Learning From Halley's.

    Science.gov (United States)

    National Aeronautics and Space Administration, Washington, DC.

    Comet chronicles and stories extend back over thousands of years. A common theme has been that comets are a major cause of catastrophe and tragedy here on earth. In addition, both Aristotle and Ptolemy believed that comets were phenomena within the earth's atmosphere, and it wasn't until the 16th century, when Danish astronomer Tycho Brache…

  9. Autonomous Onboard Science Data Analysis for Comet Missions

    Science.gov (United States)

    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.

  10. Reservoirs for Comets: Compositional Differences Based on Infrared Observations

    Science.gov (United States)

    Disanti, Michael A.; Mumma, Michael J.

    Tracing measured compositions of comets to their origins continues to be of keen interest to cometary scientists and to dynamical modelers of Solar System formation and evolution. This requires building a taxonomy of comets from both present-day dynamical reservoirs: the Kuiper Belt (hereafter KB), sampled through observation of ecliptic comets (primarily Jupiter Family comets, or JFCs), and the Oort cloud (OC), represented observationally by the long-period comets and by Halley Family comets (HFCs). Because of their short orbital periods, JFCs are subjected to more frequent exposure to solar radiation compared with OC comets. The recent apparitions of the JFCs 9P/Tempel 1 and 73P/Schwassmann-Wachmann 3 permitted detailed observations of material issuing from below their surfaces—these comets added significantly to the compositional database on this dynamical class, which is under-represented in studies of cometary parent volatiles. This chapter reviews the latest techniques developed for analysis of high-resolution spectral observations from ˜2-5 μm, and compares measured abundances of native ices among comets. While no clear compositional delineation can be drawn along dynamical lines, interesting comparisons can be made. The sub-surface composition of comet 9P, as revealed by the Deep Impact ejecta, was similar to the majority of OC comets studied. Meanwhile, 73P was depleted in all native ices except HCN, similar to the disintegrated OC comet C/1999 S4 (LINEAR). These results suggest that 73P may have formed in the inner giant planets' region while 9P formed farther out or, alternatively, that both JFCs formed farther from the Sun but with 73P forming later in time.

  11. What's Causing the Activity on Comet 67P?

    Science.gov (United States)

    Kohler, Susanna

    2015-09-01

    Comet 67P/ChuryumovGerasimenko made famous by the explorations of the Rosetta mission has been displaying puzzling activity as it hurtles toward the Sun. However, recent modeling of the comet by a group of scientists from the Cte dAzur University may now explain whats causing 67Ps activity.Shadowed ActivityA model of comet 67P, with the colors indicating the rate of change of the temperature on the comets surface. The most rapid temperature changes are seen at the comets neck, in the same locations as the early activity seen in the Rosetta images. [Al-Lagoa et al. 2015] Between June and September of 2014, Rosetta observed comet 67P displaying early activity in the form of jets of dust emitted from near the neck of the comet (its narrowest point). Such activity is usually driven by the sublimation of volatiles from the comets surface as a result of sun exposure. But the neck of the comet is frequently shadowed as the comet rotates, and it receives significantly less sunlight than the rest of the comet. So why would the early activity originate from the comets neck?The authors of a recent study, led by Victor Al-Lagoa, hypothesize that its precisely because the neck is receiving alternating sunlight/shadows that its displaying activity. They suggest that thermal cracking of the surface of the comet is happening faster in this region, due to the rapid changes in temperature that result from the shadows cast by the surrounding terrain. The cracking exposes subsurface ices in the neck faster than in other regions, and the ensuing sublimation of that ice is what creates the activity were seeing.Temperature Models: To test their hypothesis, the authors study the surface temperatures on comet 67P by means of a thermophysical model a model used to calculate the temperatures on an airless body, both on and below the surface. The model takes into account factors like thermal inertia (how quickly the bodys temperature responds to changes in the incident energy), shadowing, and

  12. Modeling Formaldehyde Emission in Comets

    Science.gov (United States)

    Disanti, M. A.; Reuter, D. C.; Bonev, B. P.; Mumma, M. J.; Villanueva, G. L.

    Modeling fluorescent emission from monomeric formaldehyde (H2CO) forms an integral part of our overall comprehensive program of measuring the volatile composition of comets through high-resolution (RP ~ 25,000) infrared spectroscopy using CSHELL at the IRTF and NIRSPEC at Keck II. The H2CO spectra contain lines from both the nu1 (symmetric CH2 stretch) and nu5 (asymmetric CH2 stretch) bands near 3.6 microns. We have acquired high-quality spectra of twelve Oort cloud comets, and at least six of these show clear emission from H2CO. We also detected H2CO with NIRSPEC in one Jupiter Family comet, 9P/Tempel 1, during Deep Impact observations. Our H2CO model, originally developed to interpret low-resolution spectra of comets Halley and Wilson (Reuter et al. 1989 Ap J 341:1045), predicts individual line intensities (g-factors) as a function of rotational temperature for approximately 1300 lines having energies up to approximately 400 cm^-1 above the ground state. Recently, it was validated through comparison with CSHELL spectra of C/2002 T7 (LINEAR), where newly developed analyses were applied to obtain robust determinations of both the rotational temperature and abundance of H2CO (DiSanti et al. 2006 Ap J 650:470). We are currently in the process of extending the model to higher rotational energy (i.e., higher rotational quantum number) in an attempt to improve the fit to high-J lines in our spectra of C/T7 and other comets. Results will be presented, and implications discussed.Modeling fluorescent emission from monomeric formaldehyde (H2CO) forms an integral part of our overall comprehensive program of measuring the volatile composition of comets through high-resolution (RP ~ 25,000) infrared spectroscopy using CSHELL at the IRTF and NIRSPEC at Keck II. The H2CO spectra contain lines from both the nu1 (symmetric CH2 stretch) and nu5 (asymmetric CH2 stretch) bands near 3.6 microns. We have acquired high-quality spectra of twelve Oort cloud comets, and at least six of

  13. The COMET Sleep Research Platform.

    Science.gov (United States)

    Nichols, Deborah A; DeSalvo, Steven; Miller, Richard A; Jónsson, Darrell; Griffin, Kara S; Hyde, Pamela R; Walsh, James K; Kushida, Clete A

    2014-01-01

    The Comparative Outcomes Management with Electronic Data Technology (COMET) platform is extensible and designed for facilitating multicenter electronic clinical research. Our research goals were the following: (1) to conduct a comparative effectiveness trial (CET) for two obstructive sleep apnea treatments-positive airway pressure versus oral appliance therapy; and (2) to establish a new electronic network infrastructure that would support this study and other clinical research studies. The COMET platform was created to satisfy the needs of CET with a focus on creating a platform that provides comprehensive toolsets, multisite collaboration, and end-to-end data management. The platform also provides medical researchers the ability to visualize and interpret data using business intelligence (BI) tools. COMET is a research platform that is scalable and extensible, and which, in a future version, can accommodate big data sets and enable efficient and effective research across multiple studies and medical specialties. The COMET platform components were designed for an eventual move to a cloud computing infrastructure that enhances sustainability, overall cost effectiveness, and return on investment.

  14. Comet Halley and its historic passages during the past millennium

    International Nuclear Information System (INIS)

    Legrand, J.P.

    1986-01-01

    The March 12, 1759 return of Comet Halley verified Halley's hypothesis on the existence of periodic comets and supported Newton's principle of universal attraction. Comet Halley's appearances before the 16th century are traced and it is noted that the length of the comet's tail has varied greatly. The comet's rendezvous with ESA's satellite Giotto is discussed briefly

  15. The Comet Halley Handbook: An Observer's Guide. Second Edition.

    Science.gov (United States)

    Yeomans, Donald K.

    This handbook contains information on: (1) the orbit of comet Halley; (2) the expected physical behavior of comet Halley in 1985-1986, considering brightness estimates, coma diameters, and tail lengths; (3) observing conditions for comet Halley in 1985-1986; and (4) observing conditions for the dust tail of comet Halley in 1985-1986. Additional…

  16. 67P, Singing Comet

    Science.gov (United States)

    Smirnova, Ekaterina

    2017-04-01

    I would like to propose to present a short science-art-music collaboration film called "67P, Singing Comet" (5:27 min). If time of the session will allow, prior to the film I would like to make a slide show introduction to this project, highlighting the inspiration - the mission Rosetta by the European Space Agency (ESA) - and the artistic collaboration that took place in creating this piece. Inspired by the ESA Rosetta mission to the comet 67P, Ekaterina Smirnova (artist and project director, New York), Lee Mottram (clarinetist, Wales), Takuto Fukuda (composer, Japan) and Brian Hekker (video editor, New York) collaborated to create a unique atmospheric piece. Water and the origins of life throughout the Universe (specifically the Earth) is an element of the mission and the focus of Ekaterina's artistic vision. Ekaterina literally and figuratively paints a sensory assemblage using a combination of synthetic and natural elements to shape this artistic creation. To paint her watercolor works she is using a replica of the water found on the comet and implementing her own heartbeat into the music to create a recognizable inward sound of life. The Electro-Acoustic composition by Takuto Fukuda features an electronically manipulated performance by clarinetist Lee Mottram. The piece ceremoniously begins with reverberant bursts of low-register atonal bells transporting the listener to their ethereal inner origins of body and mind. The imagination takes the experience to an unknown destination as it gains speed gliding through the visual and audible textures of space and time. The comet's water similarly reacts with an ebb and flow thawing ice to potentially give life a chance as it is thrust along an orbit around the Sun. Near then far from the heat the comet forms frozen particles from vapors as it reaches it's furthest stretches creating an aerodynamic tail of icicles that slowly dissipate in a cycle that repeats itself until the comet's ultimate collision with an

  17. Study of Comets Composition and Structure

    Science.gov (United States)

    Khalaf, S. Z.; Selman, A. A.; Ali, H. S.

    2008-12-01

    The present paper focuses on the nature of the different interactions between cometary nucleus and tail with solar wind. The dynamics of the comet will impose many features that provide unique behavior of the comet when entering the solar system. These features are reviewed in this paper and few investigations are made. The calculations made in this work represent the analysis and interpretation of the different features of the comet, such as perihelion and eccentricity dependence on the gas production rate, and the dependence of the latter on the composition of the comet nucleus. The dependences of the heliocentric, bow shock, contact surface, and stand-off distances with gas production rate for many types of comets that cover linear and non-linear types are studied in this work. Important results are obtained which indicated the different physical interactions between cometary ions and solar wind. Furthermore, the important relation between mean molecular weight and gas production rate are analyzed and studied in this work and a conclusion is made that, as the gas production rate increases, the mean molecular weight will decrease exponentially. A detailed discussion for this unique relation is given.

  18. A GREAT search for Deuterium in Comets

    Science.gov (United States)

    Mumma, Michael

    2013-10-01

    Comets are understood to be the most pristine bodies in the Solar System. Their compositions reflect the chemical state of materials at the very earliest evolutionary stages of the protosolar nebula and, as such, they provide detailed insight into the physical and chemical processes operating in planet-forming disks. Isotopic fractionation ratios of the molecular ices in the nucleus are regarded as signatures of formation processes. These ratios provide unique information on the natal heritage of those ices, and can also test the proposal that Earth's water and other volatiles were delivered by cometary bombardment. Measurement of deuterium fractionation ratios is thus a major goal in contemporary cometary science and the D/H ratio of water - the dominant volatile in comets - holds great promise for testing the formation history of cometary matter. The D/H ratio in cometary water has been measured in only eight comets. Seven were from the Oort Cloud reservoir and the D/H ratio was about twice that of the Earth's oceans. However, the recent Herschel measurement of HDO/H2O in 103P/Hartley-2 (the first from the Kuiper Belt) was consistent with exogenous delivery of Earth's water by comets. Outstanding questions remain: are cometary HDO/H2O ratios consistent with current theories of nebular chemical evolution or with an interstellar origin? Does the HDO/H2O ratio vary substantially among comet populations? Hartley-2 is the only Kuiper Belt comet with measured HDO/H2O, are there comets with similar ratios in the Oort cloud? These questions can only be addressed by measuring HDO/H2O ratios in many more suitable bright comets. We therefore propose to measure the D/H ratio in water in a suitable target-of-opportunity comet by performing observations of HDO and OH with the GREAT spectrometer on SOFIA. A multi-wavelength, ground-based observing campaign will also be conducted in support of the airborne observations.

  19. CLATHRATE HYDRATES FORMATION IN SHORT-PERIOD COMETS

    International Nuclear Information System (INIS)

    Marboeuf, Ulysse; Mousis, Olivier; Petit, Jean-Marc; Schmitt, Bernard

    2010-01-01

    The initial composition of current models of cometary nuclei is only based on two forms of ice: crystalline ice for long-period comets and amorphous ice for short-period comets. A third form of ice, i.e., clathrate hydrate, could exist within the short-period cometary nuclei, but the area of formation of this crystalline structure in these objects has never been studied. Here, we show that the thermodynamic conditions in the interior of short-period comets allow the existence of clathrate hydrates in Halley-type comets. We show that their existence is viable in the Jupiter family comets only when the equilibrium pressure of CO clathrate hydrate is at least 1 order of magnitude lower than the usually assumed theoretical value. We calculate that the amount of volatiles that could be trapped in the clathrate hydrate layer may be orders of magnitude greater than the daily amount of gas released at the surface of the nucleus at perihelion. The formation and the destruction of the clathrate hydrate cages could then explain the diversity of composition of volatiles observed in comets, as well as some pre-perihelion outbursts. We finally show that the potential clathrate hydrate layer in comet 67P/Churyumov-Gerasimenko would, unfortunately, be deep inside the nucleus, out of reach of the Rosetta lander. However, such a clathrate hydrate layer would show up by the gas composition of the coma.

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

    DEFF Research Database (Denmark)

    Forchhammer, Lykke; Ersson, Clara; Loft, Steffen

    2012-01-01

    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...... 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...

  1. The "silent world" of Comet 15P/Finlay

    CERN Document Server

    Beech, M; Jones, J

    1999-01-01

    Comet 15P/Finlay is unusual in that, contrary to ab initio expectations, it demonstrates no apparent linkage to any known meteor shower. Using data contained within the Electronic Atlas of Dynamical Evolutions of Short-Period Comets, the authors evaluate theoretical shower radiants for Comet 15P/Finlay, but find no evidence to link it to any meteoric anomalies in recorded antiquity. This result, however, must be tempered by the fact that any Comet 15P/Finlay- derived meteoroids will have a low, 16 km s/sup -1/, encounter velocity with Earth's atmosphere. Typically, therefore, one would expect mostly faint meteors to be produced during an encounter with a Comet 15P/Finlay-derived meteoroid stream. they have conducted a D- criterion survey of meteoroid orbits derived from three southern hemisphere meteor radar surveys conducted during the 1960s, and again they find no evidence for any Comet 15P/Finlay-related activity. Numerical calculations following the orbital evolution of hypothetical meteoroids ejected fro...

  2. Stardust: Catching a Comet and Bringing it Home

    Science.gov (United States)

    Brownlee, Donald E.

    2007-01-01

    The NASA STARDUST mission collected thousands of particles from Comet Wild 2 that are now being studied by two hundred scientists around the world. The spacecraft captured the samples during a close flyby of the comet in 2004 and returned them to Earth with a dramatic entry into the atmosphere early in 2006. The precious cargo of comet dust is being studied to determine new information about the origin of the Sun and planets. The comet formed at the edge of the solar system, beyond the orbit of Neptune, and is a sample of the material from which the solar system was formed. One of the most dramatic early findings from the mission was that a comet that formed in the coldest place in the solar system contained minerals that formed in the hottest place in the solar system. The comet samples are telling stories of fire and ice and they providing fascinating and unexpected information about our origins.

  3. Comets, Asteroids, and the Origin of the Biosphere

    Science.gov (United States)

    Hoover, Richard B.

    2006-01-01

    During the past few decades, the role of comets in the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment has become more widely accepted. However comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are entirely devoid of liquid water and consequently unsuitable for life in any form. Complex organic compounds have been observed comets and on the water rich asteroid 1998 KY26, which has color and radar reflectivity similar to the carbonaceous meteorites. Near infrared observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar with resurfacing that may indicate cryovolcanic outgassing and the Cassini spacecraft has detected water-ice geysers on Saturn s moon Enceladus. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have now firmly established that comets contain a suite of complex organic chemicals; water is the predominant volatile; and that extremely high temperatures (approx.350-400 K) can be reached on the surface of the very black (albedo-0.03) nuclei when the comets are with 1.5 AU from the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust and episodic outbursts and jets observed on the nuclei of several comets are interpreted as indications that localized regimes of liquid water and water vapor can periodically exist beneath the crust of some comets. The Deep Impact observations indicate that the temperature on the nucleus of of comet Tempel 1 at 1.5 AU varied from 330K on the sunlit side to a minimum of 280+/-8 K. It is interesting that even the coldest region of the comet surface was slightly above the ice/liquid water phase transition temperature. These results suggest that pools and films of liquid water can exist in a wide

  4. ACTIVITY OF 50 LONG-PERIOD COMETS BEYOND 5.2 au

    Energy Technology Data Exchange (ETDEWEB)

    Sárneczky, K.; Szabó, Gy. M.; Csák, B.; Kelemen, J.; Pál, A.; Szakáts, R.; Szegedi-Elek, E.; Vida, K.; Vinkó, J.; Kiss, L. L. [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Budapest, Konkoly Thege Miklós út 15-17 (Hungary); Marschalkó, G. [Eötvös Loránd Tudományegyetem, H-1117 Pázmány Péter sétány 1/A, Budapest (Hungary); Szalai, T. [Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9 (Hungary); Székely, P. [Department of Experimental Physics, University of Szeged, Szeged H-6720, Dóm tér 9 (Hungary)

    2016-12-01

    Remote investigations of ancient matter in the solar system have traditionally been carried out through observations of long-period (LP) comets, which are less affected by solar irradiation than their short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the data set is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by Afρ values >3–4, higher than those for our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. In contrast to this, the comae of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, which suggest sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, tenuous tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.

  5. ACTIVITY OF 50 LONG-PERIOD COMETS BEYOND 5.2 au

    International Nuclear Information System (INIS)

    Sárneczky, K.; Szabó, Gy. M.; Csák, B.; Kelemen, J.; Pál, A.; Szakáts, R.; Szegedi-Elek, E.; Vida, K.; Vinkó, J.; Kiss, L. L.; Marschalkó, G.; Szalai, T.; Székely, P.

    2016-01-01

    Remote investigations of ancient matter in the solar system have traditionally been carried out through observations of long-period (LP) comets, which are less affected by solar irradiation than their short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the data set is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by Afρ values >3–4, higher than those for our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. In contrast to this, the comae of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, which suggest sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, tenuous tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.

  6. ESA Unveils Its New Comet Chaser.

    Science.gov (United States)

    1999-07-01

    The objective is to study one of these primordial objects at close quarters by placing a lander on its surface and chasing, with an orbiter, the comet for millions of kilometres through space. Comets - among the oldest (4.6 billion years!) and last altered objects in the solar system - are regarded as the building blocks from which the planets formed. Thus the Rosetta's discoveries will allow the scientists to learn more about birth and evolution of the planets and about the origin of life on the Earth. The final design of the Rosetta orbiter will be revealed for the first time at the Royal Society in London on 1 July when a 1:4 scale model will be unveiled by ESA's Director of Science, Prof.. Roger Bonnet. (The full size version of the spacecraft is 32 metres across, so large that it would stretch the entire width of a football pitch. Almost 90 of this is accounted for by the giant solar panels which are needed to provide electrical power in the dark depths of the Solar System). "Rosetta is a mission of major scientific importance," said Prof. Bonnet. "It will build on the discoveries made by Giotto and confirm ESA's leading role in the exploration of the Solar System and the Universe as a whole." The timing of this event has been chosen to coincide with the London meeting of the Rosetta Science Working Team and the second Earth flyby of the now non-operational Giotto spacecraft. In addition, the opening of the British Museum's 'Cracking Codes' Exhibition, for which the Rosetta Stone is the centrepiece, is set to take place on 10 July. The Rosetta mission. Rosetta is the third Cornerstone in ESA's 'Horizon 2000' long-term scientific programme. It will be launched by Ariane 5 rocket from Kourou spaceport in French Guiana in January 2003. In order to gain sufficient speed to reach the distant comet, Rosetta will require gravity assists from the Earth (twice) and Mars. After swinging around Mars in May 2005, Rosetta will return to Earth's vicinity in October 2005 and

  7. Giacobini-Zinner comet: polarimetric and physical observations

    International Nuclear Information System (INIS)

    Martel, M.T.; Maines, P.; Grudzinska, S.; Stawikowski, A.

    1984-10-01

    The results of observations of the Giacobini-Zinner comet on 25 and 31 October 1959 are presented. The magnitude of the comet was measured photoelectrically in two spectral regions. The radius is on the order of one kilometer. The photoelectric measurements of comets 1959b and 1957c were used to measure the abundances of the CN and C2 radicals and of solid particles in the heads

  8. Constraints on Comet 332P/Ikeya-Murakami

    Science.gov (United States)

    Hui, Man-To; Ye, Quan-Zhi; Wiegert, Paul

    2017-01-01

    Encke-type comet 332P/Ikeya-Murakami is experiencing cascading fragmentation events during its 2016 apparition. It is likely the first splitting Encke-type comet ever observed. A nongravitational solution to the astrometry reveals a statistical detection of the radial and transverse nongravitational parameters, {A}1=(1.54+/- 0.39)× {10}-8 au day‑2 and {A}2=(7.19+/- 1.92)× {10}-9 au day‑2, respectively, which implies a nucleus erosion rate of (9.1+/- 1.7)‰ per orbital revolution. The mass-loss rate likely has to be supported by a much larger fraction of an active surface area than known cases of short-period comets; it may be relevant to the ongoing fragmentation. We failed to detect any serendipitous pre-discovery observations of the comet in archival data from major sky surveys, whereby we infer that 332P used to be largely inactive, and is perhaps among the few short-period comets that have been reactivated from weakly active or dormant states. We therefore constrain an upper limit to the nucleus size as 2.0 ± 0.2 km in radius. A search for small bodies in similar orbits to that of 332P reveals comet P/2010 B2 (WISE) to be the best candidate. From an empirical generalized Jupiter-family (Encke-type included) comet population model, we estimate the likelihood of a chance alignment of the 332P–P/2010 B2 pair to be 1 in 33, a small number indicative of a genetic linkage between the two comets on a statistical basis. The pair possibly originated from a common progenitor, which underwent a disintegration event well before the twentieth century.

  9. In vitro antioxidation activity and genoprotective effect of selected Chinese medicinal herbs.

    Science.gov (United States)

    Szeto, Yim Tong; Wong, Shirley Ching Yee; Wong, Julia Wai Ming; Kalle, Wouter; Pak, Sok Cheon

    2011-01-01

    Some traditional Chinese medicinal seeds and fruits are well known for their antioxidant properties. This research aims to investigate whether Fructus Lycii, Fructus Schisandrae Chinensis, Fructus Ligustri Lucidi and Semen Cuscutae protect DNA from oxidant challenge by hydrogen peroxide (H(2)O(2)). The standard comet assay was used to assess the genoprotective effect of these medicinal herbs. Blood was taken from three healthy adults, aged from 36 to 42. Lymphocytes were isolated and treated with different concentrations of aqueous herbal extracts, while controls were treated with phosphate buffered saline. The lymphocytes were stressed with 50 μM H(2)O(2). Treated cells were embedded in agarose and layered on slides. These sandwiched lymphocytes were lysed and afterwards subjected to an electric field in an alkaline environment. Damaged DNA was pulled out from the nucleus towards the positive electrode as a comet tail; its density was related to the degree of DNA damage. Finally, the slides were stained with fluorescence dye and tails were visually scored for 100 cells. The experiment was repeated three times and DNA damage in treated cells was compared to the controls. There was no statistical difference in DNA damage among the herb treated cells and untreated cells in the comet assay. Our data demonstrated that the selected medicinal herbs did not show in vitro DNA protection in the comet assay against oxidant challenge.

  10. On the origin of comets

    Science.gov (United States)

    Mendis, A.; Alfven, H.

    1976-01-01

    Physico-chemical processes leading to the dynamic formation and physical evolution of comets are reviewed in relationship to the various theories that propose solar origins, protoplanetary origins, planetary origins and interstellar origins. Evidence points to the origins of comets by the growth and agglomeration of small particles from gas and dust at very low temperatures at undetermined regions in space.

  11. Planetary perturbations and the origins of short-period comets

    International Nuclear Information System (INIS)

    Quinn, T.; Tremaine, S.; Duncan, M.

    1990-01-01

    To investigate the dynamical plausibility of possible sources for the short-period comets, a representative sample of comet orbits in the field of the sun and the giant planets was integrated, with the aim to determine whether the distribution of orbits from a proposed source that reach observable perihelia (q less than 2.5 AU) matches the observed distribution of short-period orbits. It is found that the majority of the short-period comets, those with orbital period P less than 20 yr (the Jupiter family), cannot arise from isotropic orbits with perihelia near Jupiter's orbit, because the resulting observable comet orbits have the wrong distribution in period, inclination, and argument of perihelion. The simulations also show that Jupiter-family comets cannot arise from isotropic orbits with perihelia in the Uranus-Neptune region. On the other hand, a source of low-inclination Neptune-crossing orbits yields a distribution of observable Jupiter-family comets that is consistent with the data in all respects. These results imply that the Jupiter-family comets arise from a disk source in the outer solar system rather than from the Oort comet cloud. 30 refs

  12. Cytogenetic monitoring of personnel occupationally exposed to microwave radiation of GEM radar

    International Nuclear Information System (INIS)

    Garaj-Vrhovac, Vera; Gajski, Goran; Brumen, Vlatka

    2008-01-01

    In the present study we analyzed and followed-up on the DNA damaging effects of microwave radiation of GEM radar equipment within microwave field of 10 μW/cm 2 to 10 mW/cm 2 in personnel occupationally exposed to frequency range of 1.5 GHz to 10.9 GHz. The single cell gel electrophoresis (SCGE)/comet assay as a tool for the bio monitoring of individuals accidentally, environmentally or occupationally exposed to physical or chemical agents was used to evaluate possible genotoxic effect on peripheral human blood lymphocytes. The comet assay is a method that allows efficient determination of single strand breaks (SSB) and double-strand breaks (DSB), as well as alkali-labile sites in the DNA of single cells. The comet assay was carried out under alkaline conditions. We measured the baseline comet assay effect in whole blood samples. Parameter of the comet assay was studied in workers occupationally exposed to microwave radiation of GEM radar and in corresponding unexposed control subjects. It was found that in the subjects who were occupationally exposed to microwave radiation, the levels of DNA damage increased compare to control group and showed interindividual variations. As a measure of DNA damage tail length was used, calculated from the centre of the head and presented in micrometers (μm). Mean value of exposed group was 13.54±1.44 as opposed to control mean value that was 13.15±1.39. Differences between mean tail lengths were statistically significant (P<0.05, ANOVA). The results of this study indicate that individuals occupationally exposed to microwave frequency of GEM radar equipment may experience an increased genotoxic risk, emphasizing the importance of individual bio monitoring, limiting exposure and radiation safety programs. (author)

  13. Comet Tempel 1 Went Back to Sleep

    Science.gov (United States)

    2005-07-01

    Astronomers Having Used ESO Telescopes Start Analysing Unique Dataset on the Comet Following the Deep Impact Mission Ten days after part of the Deep Impact spacecraft plunged onto Comet Tempel 1 with the aim to create a crater and expose pristine material from beneath the surface, astronomers are back in the ESO Offices in Santiago, after more than a week of observing at the ESO La Silla Paranal Observatory. In this unprecedented observing campaign - among the most ambitious ever conducted by a single observatory - the astronomers have collected a large amount of invaluable data on this comet. The astronomers have now started the lengthy process of data reduction and analysis. Being all together in a single place, and in close contacts with the space mission' scientific team, they will try to assemble a clear picture of the comet and of the impact. The ESO observations were part of a worldwide campaign to observe this unique experiment. During the campaign, ESO was connected by phone, email, and videoconference with colleagues in all major observatories worldwide, and data were freely exchanged between the different groups. This unique collaborative spirit provides astronomers with data taken almost around the clock during several days and this, with the largest variety of instruments, making the Deep Impact observing campaign one of the most successful of its kind, and thereby, ensuring the greatest scientific outcome. From the current analysis, it appears most likely that the impactor did not create a large new zone of activity and may have failed to liberate a large quantity of pristine material from beneath the surface. ESO PR Photo 22/05 ESO PR Photo 22/05 Evolution of Comet Tempel 1 (FORS2/VLT) [Preview - JPEG: 400 x 701 pix - 128k] [Normal - JPEG: 800 x 1401 pix - 357k] ESO PR Photo 22/05 Animated Gif Caption: ESO PR Photo 22/05 shows the evolution of Comet Tempel 1 as observed with the FORS2 instrument on Antu (VLT). The images obtained at the VLT show that

  14. A dynamical study on extrasolar comets

    Science.gov (United States)

    Loibnegger, B.; Dvorak, R.

    2017-09-01

    Since the detection of absorption features in spectra of beta Pictoris varying on short time scales it is known that comets exist in other stellar systems. We investigate the dynamics of comets in two differently build systems (HD 10180 and HIP 14810). The outcomes of the scattering process, as there are collisions with the planets, captures and ejections from the systems are analysed statistically. Collisions and close encounters with the planets are investigated in more detail in order to conclude about transport of water and organic material. We will also investigate the possibility of detection of comets in other planetary systems.

  15. Vaporization of comet nuclei: Light curves and life times

    Energy Technology Data Exchange (ETDEWEB)

    Cowan, J J [Harvard Univ., Cambridge, MA (USA). Center for Astrophysics; A' Hearn, M F [Maryland Univ., College Park (USA)

    1979-10-01

    The authors have examined the effects of vaporization from the nucleus of a comet and show that a latitude dependence of vaporization can, in some cases, explain asymmetries in commetary light curves. They also find that a non-uniform distribution of solar radiation over a comet can considerably shorten the vaporization lifetime compared to the results normally obtained by assuming that the nuclear surface is isothermal. Independent of any latitude effects, comets with CO/sub 2/-dominated nuclei and with periherlion distances less than 0.5 AU have vaporization lifetimes less than or comparable to their dynamical ejection times. This may explain the observed deficit of comets with small perihelion distances. Similarly comets with CO/sub 2/-dominated nuclei and perihelia near Jupiter's orbit have vaporization lifetimes that are shorter than the time for capture into short-period orbits. They suggest, therefore, that at least some new comets are composed in large part of CO/sub 2/, while only H/sub 2/O-dominated comets, with lower vaporization rates, can survive to be captured into short-period orbits.

  16. Catastrophic Disruption of Comet ISON

    Science.gov (United States)

    Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

    2016-01-01

    We report submillimeter 450 and 850 microns dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (rh?=?0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60? (greater than 10(exp 5) km in the anti-solar direction. Deconvolution of the November 28.04 850 microns image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing approximately 5.2?×?10(exp 10) kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

  17. Hyakutake, Hale-Bopp and the chemistry of comets

    International Nuclear Information System (INIS)

    Bachiller, R.; Planesas, P.

    1997-01-01

    Comets can be regarded as messengers from the primitive solar system which can provide precious pieces of information on the composition of the protosolar nebula. Physical and chemical phenomena within comets (shock waves, photodissociation caused by solar radiation, some endothermic chemical reactions, etc) are of the highest interest and cannot be reproduced at terrestrial laboratories in many cases. The passage of Hyakutake in 1996 and that of Hale-Bopp in 1997 are allowing remarkable progress in the understanding of the physico-chemistry of comets. Observations of such comets can be crucial in the study of the origin of life on Earth. (Author)

  18. Comparison between sensitivity of a viscometric method and sensitivity of the alkaline elution assay for the determination of DNA damage induced by dimethylsulfate in vitro.

    Science.gov (United States)

    Parodi, S; Balbi, C; Taningher, M; Abelmoschi, M L; Pala, M; Parodi, G; Santi, L

    1982-03-01

    DNA damage induced by dimethylsulfate (DMS) was measured with a new oscillating crucible viscometer, having a U-shaped circular channel. Rat liver nuclei were treated in vitro. Viscosity was measured by lysing nuclei in an aklaline lysing solution (pH 12.5; 25 degrees C). Nuclei were lysed immediately in the viscometer and released DNA started to uncoil. In control samples the viscosity increased very slowly with time, reaching a maximum only after about 8 h. A progressively more rapid increase in viscosity was seen with increasing concentrations of DMS. The time of DNA disentanglement was sensitive to about 30 times less breaks than the alkaline elution assay.

  19. Optical Detection of Anomalous Nitrogen in Comets

    Science.gov (United States)

    2003-12-01

    VLT Opens New Window towards Our Origins Summary A team of European astronomers [1] has used the UVES spectrograph on the 8.2-m VLT KUEYEN telescope to perform a uniquely detailed study of Comet LINEAR (C/2000 WM1) . This is the first time that this powerful instrument has been employed to obtain high-resolution spectra of a comet. At the time of the observations in mid-March 2002, Comet LINEAR was about 180 million km from the Sun, moving outwards after its perihelion passage in January. As comets are believed to carry "pristine" material - left-overs from the formation of the solar system, about 4,600 million years ago - studies of these objects are important to obtain clues about the origins of the solar system and the Earth in particular. The high quality of the data obtained of this moving 9th-magnitude object has permitted a determination of the cometary abundance of various elements and their isotopes [2]. Of particular interest is the unambiguous detection and measurement of the nitrogen-15 isotope. The only other comet in which this isotope has been observed is famous Comet Hale-Bopp - this was during the passage in 1997, when it was much brighter than Comet LINEAR. Most interestingly, Comet LINEAR and Comet Hale-Bopp display the same isotopic abundance ratio, about 1 nitrogen-15 atom for each 140 nitrogen-14 atoms ( 14 N/ 15 N = 140 ± 30) . That is about half of the terrestrial value (272). It is also very different from the result obtained by means of radio measurements of Comet Hale-Bopp ( 14 N/ 15 N = 330 ± 75). Optical and radio measurements concern different molecules (CN and HCN, respectively), and this isotopic anomaly must be explained by some differentiation mechanism. The astronomers conclude that part of the cometary nitrogen is trapped in macromolecules attached to dust particles . The successful entry of UVES into cometary research now opens eagerly awaited opportunities for similiar observations in other, comparatively faint comets. These

  20. The spacecraft encounters of Comet Halley

    Science.gov (United States)

    Asoka Mendis, D.; Tsurutani, Bruce T.

    1986-01-01

    The characteristics of the Comet Halley spacecraft 'fleet' (VEGA 1 and VEGA 2, Giotto, Suisei, and Sakigake) are presented. The major aims of these missions were (1) to discover and characterize the nucleus, (2) to characterize the atmosphere and ionosphere, (3) to characterize the dust, and (4) to characterize the nature of the large-scale comet-solar wind interaction. While the VEGA and Giotto missions were designed to study all four areas, Suisei addressed the second and fourth. Sakigake was designed to study the solar wind conditions upstream of the comet. It is noted that NASA's Deep Space Network played an important role in spacecraft tracking.

  1. Ensemble Properties of Comets in the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Solontoi, Michael; /Adler Planetarium, Chicago; Ivezic, Zeljko; /Washington U., Seattle, Astron. Dept.; Juric, Mario; /Harvard Coll. Observ.; Becker, Andrew C.; /Washington U., Seattle, Astron. Dept.; Jones, Lynne; /Washington U., Seattle, Astron. Dept.; West, Andrew A.; /Boston U.; Kent, Steve; /Fermilab; Lupton, Robert H.; /Princeton U. Observ.; Claire, Mark; /Washington U., Seattle, Astron. Dept.; Knapp, Gillian R.; /Princeton U. Observ.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

    2012-02-01

    We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u, g, r, i, z) photometry is used to determine the comets colors, sizes, surface brightness profiles, and rates of dust production in terms of the Afp formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(comets. The resolved comets show an extremely narrow distribution of colors (0.57 {+-} 0.05 in g - r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.

  2. Unveiling the formation and evolution of comets

    Science.gov (United States)

    Lasue, J.; Levasseur-Regourd, A. C.; Botet, R.; Coradini, A.; Desanctis, M. C.; Kofman, W.

    2007-08-01

    Comet nuclei are considered as the most pristine bodies of the solar system and consequently their study sheds an important light on the processes occurring during the initial stages of the solar system formation. The analysis of the porosity and bulk density of such primordial bodies is especially important to understand their capacity to retain volatile components (organics and ices) present in the early solar nebula. Typical tensile strengths deduced for comet nuclei range from below 102N.m-2 from the Deep Impact mission [1] up to 104N.m-2 from the study of comet C/1999 S4 LINEAR breakup [2] and meteoroids [3]. A bulk density of about 350 kg/m3 has been obtained for 9P/Tempel 1 from the Deep Impact mission [4]. Moreover the properties of dust released from the comets strongly confirm such values. Instruments flying-by comet 1P/Halley had discovered the presence of organics, and pointed out the dust low albedo and extremely low density while analyses of Interplanetary Dust Particles collected in the stratosphere and remote spectroscopic observations have indicated that cometary dust consists of an un-equilibrated heterogeneous mixture of organic refractory materials and of amorphous and crystalline silicate minerals [5], as recently confirmed by Stardust [6]. Observations of the solar scattered light, together with elaborate simulations, give an estimation of the mass ratio between silicates and absorbing organics, the size distribution and the structure of the dust particles, suggesting that a fair amount consists in fluffy aggregates built up from submicronic grains [7,8], as recently confirmed by the analysis of dust craters and aerogel tracks on Stardust collector showing for some large particles (up to 100 μm) an extraordinary fluffy structure [9]. Simulations have been developed in our teams to describe the aspects of comet aggregation and evolution that have not been thoroughly explained yet. Particle aggregation simulations taking into account cohesive

  3. Comet 67P Through the Lens of Art

    Science.gov (United States)

    Smirnova, Ekaterina

    2017-04-01

    My proposal is to share my artistic exploration of a comet through the bodily senses, while finding inspiration in scientific data. I will present my artwork as a slideshow, showcasing: large scale paintings, ceramic sculptures, music and interactive augmented reality. The Rosetta mission of the European Space Agency (ESA) to comet 67P/ Churyumov-Gerasimenko is remarkable. The scientific investigation of the comet's composition, atmosphere, dust, vapor, surface and internal structure are crucial to help researchers understand the origin of the solar system and our own planet. Sight: Paintings Rosetta mission discovered that the water on the comet is different from the water on Earth; as measured with the ROSINA-DFMS instrument on Rosetta, water on 67P contains approximately 3 times more hydrogen­deuterium oxide - HDO, than found in Earth's oceans. In the art studio I re-create water that is close in composition to the water on the comet, by concentrating the level of HDO. With this water I paint large scale watermedia paintings, based on the photographs by Rosetta (OSIRIS, Nav. Cam.). Touch: Sculptures While exploring the comet's three-dimensional form, I focus more deeply on the composition of the comet. Stoneware clay and my choice of a glaze both include iron oxide, a common constituent of meteorites and comets. Hearing: Music An audio piece "A Singing Comet", by Manuel Senfft, based on the Rosetta Plasma Consortium data, inspired me to make a musical piece. In collaboration with clarinetist Lee Mottram (Wales) and composer Takuto Fukuda (Japan) we created an electro­acoustic composition in which we tell the story of comets visiting our Solar System, repeating their cycle, curving around the sun and releasing water, carrying away dust to form their tails. Smell In collaboration with The Open University, UK, postcards with a smell of the comet were created, introducing the chemical components of the comet. The smell was recreated by combining several molecules

  4. Migration of Interplanetary Dust and Comets

    Science.gov (United States)

    Ipatov, S. I.; Mather, J. C.

    Our studies of migration of interplanetary dust and comets were based on the results of integration of the orbital evolution of 15,000 dust particles and 30,000 Jupiter-family comets (JFCs) [1-3]. For asteroidal and cometary particles, the values of the ratio β between the radiation pressure force and the gravitational force varied from 1000 and 1 microns. The probability of a collision of a dust particle started from an asteroid or JFC with the Earth during a lifetime of the particle was maximum at diameter d ˜100 microns. For particles started from asteroids and comet 10P, this maximum probability was ˜0.01. Different studies of migration of dust particles and small bodies testify that the fraction of cometary dust particles of the overall dust population inside Saturn's orbit is considerable and can be dominant: (1) Cometary dust particles produced both inside and outside Jupiter's orbit are needed to explain the observed constant number density of dust particles at 3-18 AU. The number density of migrating trans-Neptunian particles near Jupiter's orbit is smaller by a factor of several than that beyond Saturn's orbit. Only a small fraction of asteroidal particles can get outside Jupiter's orbit. (2) Some (less than 0.1%) JFCs can reach typical near-Earth object orbits and remain there for millions of years. Dynamical lifetimes of most of the former JFCs that have typical near-Earth object orbits are about 106 -109 yr, so during most of these times they were extinct comets. Such former comets could disintegrate and produce a lot of mini-comets and dust. (3) Comparison of the velocities of zodiacal dust particles (velocities of MgI line) based on the distributions of particles over their orbital elements obtained in our runs [3-4] with the velocities obtained at the WHAM observations shows that only asteroidal dust particles cannot explain these observations, and particles produced by comets, including high-eccentricity comets, are needed for such explanation

  5. On the existence of a comet belt beyond Neptune

    International Nuclear Information System (INIS)

    Fernandez, J.A.

    1980-01-01

    The possible existence of a comet belt in connection with the origin of the short-period comets is analysed. It is noted that the current theory - that these comets originate as near-parabolic comets captured by Jupiter and the other giant planets - implies an excessive wastage of comets lost in hyperbolic orbits, which is avoided in the present model. The following picture is predicted. Solid conglomerates up to approximately 10 18 g were formed by gravitational instabilities in the belt region (about 35 to 50 AU). A further fragmentation-accretion process led to a power-law mass distribution similar to that observed in the asteroids. Since then, close encounters between members of the belt have provoked the diffusion of some of them with the effect that they have become subject to the strong perturbations of Neptune. Of these a small number pass from one planet to the next inside and end as short-period comets. By means of a Monte Carlo method, the influence of close encounters between belt comets is then studied in relation to the diffusion of their orbits. It is concluded that if such a belt contains members with masses equal to or greater than that of Ceres, the orbital diffusion could proceed fast enough to maintain the number of observed short-period comets in a steady state. (author)

  6. CATASTROPHIC DISRUPTION OF COMET ISON

    Energy Technology Data Exchange (ETDEWEB)

    Keane, Jacqueline V.; Kleyna, Jan T.; Riesen, Timm-Emmanuel; Meech, Karen J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Milam, Stefanie N.; Charnley, Steven B. [Astrochemistry Laboratory, NASA GSFC, MS 690, Greenbelt, MD 20771 (United States); Coulson, Iain M. [Joint Astronomy Center, 660 North Aohoku Place, Hilo, HI 96720 (United States); Sekanina, Zdenek [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Kracht, Rainer, E-mail: keane@ifa.hawaii.edu [Ostlandring 53, D-25335 Elmshorn, Schleswig-Holstein (Germany)

    2016-11-10

    We report submillimeter 450 and 850 μ m dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 ( r {sub h} = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>10{sup 5} km) in the anti-solar direction. Deconvolution of the November 28.04 850 μ m image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ∼5.2 × 10{sup 10} kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

  7. Evolution of comets into asteroids

    International Nuclear Information System (INIS)

    Weissman, P.R.; A'hearn, M.F.; Rickman, H.; Mcfadden, L.A.

    1989-01-01

    This paper presents observational evidence, together with recent theoretical developments, supporting the hypothesis that at least some asteroids might be extinct or dormant cometary nuclei. The observations include the discovery of a number of apparent asteroids in chaotic Jupiter-crossing orbits; the IRAS discovery of 1983 TB, an asteroid in the same orbit as the Geminid meteor shower; the apparent low activity levels determined for several short-period comet nuclei including Comet Halley; and observations of possible cometary activity in some earth-crossing asteroids. Theoretical developments include explorations of dynamical mechanisms capable of delivering main-belt asteroids into earth-crossing orbits, and an understanding of possible processes which may affect comets during their long residence in the Oort cloud and lead to the formation of nonvolatile crusts before and after they enter the planetary system. 143 refs

  8. Comet showers and Nemesis, the death star

    International Nuclear Information System (INIS)

    Hills, J.G.

    1984-01-01

    The recently proposed hypothesis that the periodic extinctions of terrestrial species are the result of comet showers catalyzed by a hypothetical distant solar companion, Nemesis, a tale of global death by comet bombardment of the earth, is discussed

  9. Comments on comet shapes and aggregation processes

    International Nuclear Information System (INIS)

    Hartmann, W.K.

    1989-01-01

    An important question for a comet mission is whether comet nuclei preserve information clarifying aggregation processes of planetary matter. New observational evidence shows that Trojan asteroids, as a group, display a higher fraction of highly-elongated objects than the belt. More recently evidence has accumulated that comet nuclei, as a group, also display highly-elongated shapes at macro-scale. This evidence comes from the several comets whose nuclear lightcurves or shapes have been well studied. Trojans and comet nuclei share other properties. Both groups have extremely low albedos and reddish-to neutral-black colors typical of asteroids of spectral class D, P, and C. Both groups may have had relatively low collision frequencies. An important problem to resolve with spacecraft imaging is whether these elongated shapes are primordial, or due to evolution of the objects. Two hypotheses that might be tested by a combination of global-scale and close-up imaging from various directions are: (1) The irregular shapes are primordial and related to the fact that these bodies have had lower collision frequencies than belt asteroids; or (2) The irregular shapes may be due to volatile loss

  10. COMET SHOWERS ARE NOT INDUCED BY INTERSTELLAR CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Morris, D.E.

    1985-11-01

    Encounters with interstellar clouds (IC) have been proposed by Rampino and Stothers as a cause of quasi-periodic intense comet showers leading to earth impacts, in order to explain the periodicity in marine mass extinctions found by Raup and Sepkoski. The model was described further, criticized and defended. The debate has centered on the question of whether the scale height of the clouds is small enough (in comparison to the amplitude of the oscillation of the solar system about the plane of the Galaxy) to produce a modulation in the rate of encounters. We wish to point out another serious, we believe fatal, defect in this model - the tidal fields of ICs are not strong enough to produce intense comet showers leading to earth impacts by bringing comets of the postulated inner Oort cloud into earth crossing orbits, except possibly during very rare encounters with very dense clouds. We will show that encounters with abundant clouds of low density cannot produce comet showers; cloud density N > 10{sup 3} atoms cm{sup -3} is needed to produce an intense comet shower leading to earth impacts. Furthermore, the tidal field of a dense cloud during a distant encounter is too weak to produce such showers. As a consequence, comet showers induced by ICs will be far less frequent than showers caused by passing stars. This conclusion is independent of assumptions about the radial distribution of comets in the inner Oort cloud.

  11. Comet LINEAR C/1999 S4 - an absolutely well-behaved comet before breakup

    Science.gov (United States)

    Peschke, S. B.; Lisse, C. M.; Fernandez, Y. R.; Ressler, M.; Stickel, M.; Kaminski, C.; Golish, B.

    2000-10-01

    We present results from infrared imaging of comet LINEAR C/1999 S4 on June 17 - 19, 2000 (pre-breakup), using the near-IR camera NSFCAM and the mid-IR camera MIRLIN at the 3m NASA/IRTF. Images and multi-wavelength spectroscopy were obtained in the zJHK'L'MNQ bands, and were used to create a 1.0 - 25 μ m SED of the comet's dust and nucleus. The coma's contribution at each wavelength was modeled using spatial fitting (Fernandez 1999, PhD thesis; Lisse et al. 1999, Icarus 140, 189). The resulting comatic and nuclear SEDs were then modeled using modified Mie theory (Lisse et al. 1998, ApJ 496, 971) and the standard nuclear thermal models (Lebofsky and Spencer 1989, Asteroids II, 128), respectively. We report the resulting dust PSD, mass loss rate, and albedo, as well as the nuclear radius, and we compare these results to those obtained by others from optical data both before and after the comet's breakup in late July 2000.

  12. The shortage of long-period comets in elliptical orbits

    International Nuclear Information System (INIS)

    Everhart, E.

    1979-01-01

    Based on the number of 'new' comets seen on near-parabolic orbits, one can predict the number of comets that should be found on definitely elliptical orbits on their subsequent returns. The author shows that about three out of four of these returning comets are not observed. (Auth.)

  13. Real-time fluorescence assay of alkaline phosphatase in living cells using boron-doped graphene quantum dots as fluorophores.

    Science.gov (United States)

    Chen, Li; Yang, Guancao; Wu, Ping; Cai, Chenxin

    2017-10-15

    This work reports a convenient and real-time assay of alkaline phosphatase (ALP) in living cells based on a fluorescence quench-recovery process at a physiological pH using the boron-doped graphene quantum dots (BGQDs) as fluorophore. The fluorescence of BGQDs is found to be effectively quenched by Ce 3+ ions because of the coordination of Ce 3+ ions with the carboxyl group of BGQDs. Upon addition of adenosine triphosphate (ATP) into the system, the quenched fluorescence can be recovered by the ALP-positive expressed cells (such as MCF-7 cells) due to the removal of Ce 3+ ions from BGQDs surface by phosphate ions, which are generated from ATP under catalytic hydrolysis of ALP that expressed in cells. The extent of fluorescence signal recovery depends on the level of ALP in cells, which establishes the basis of ALP assay in living cells. This approach can also be used for specific discrimination of the ALP expression levels in different type of cells and thus sensitive detection of those ALP-positive expressed cells (for example MCF-7 cells) at a very low abundance (10±5 cells mL -1 ). The advantages of this approach are that it has high sensitivity because of the significant suppression of the background due to the Ce 3+ ion quenching the fluorescence of BGQDs, and has the ability of avoiding false signals arising from the nonspecific adsorption of non-target proteins because it operates via a fluorescence quench-recovery process. In addition, it can be extended to other enzyme systems, such as ATP-related kinases. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. UVA/UVB-induced genotoxicity and lesion repair in Colossoma macropomum and Arapaima gigas Amazonian fish.

    Science.gov (United States)

    Groff, Aline Aparecida; da Silva, Juliana; Nunes, Emilene A; Ianistcki, Martus; Guecheva, Temenouga N; de Oliveira, Alzira Miranda; de Oliveira, Christiane Patrícia Feitosa; Val, Adalberto Luis; Henriques, João A P

    2010-05-03

    Ultraviolet radiation is known to cause adverse effects to aquatic species and aquatic environments. The fish Colossoma macropomum (tambaqui) and Arapaima gigas (pirarucu) live in the Amazon basin, near the Equator, and thus receive high intensity of ultraviolet radiation. Deforestation further aggravates the situation by reducing shade at ground level. The aim of this study was to evaluate the genotoxic effects of UVA and UVB radiation on erythrocytes of tambaqui and pirarucu fish using Micronuclei test and Comet assay. Our study showed that UV radiation caused DNA damage in both species as detected by Comet assay. In addition, there were differences in response to genotoxicity between both species, which are possibly related to their evolutionary history. Tambaqui fish exposed to ultraviolet radiation for different periods presented clear dose-response in DNA damage profile. Significant damage repair was observed 24h after cessation of ultraviolet radiation exposure. At the test conditions used, no significant increase in micronucleated cells was observed in tambaqui and pirarucu fish. Tambaqui proved to be more sensitive to ultraviolet radiation than Pirarucu, as detected by Comet assay, showing statistically higher baseline DNA damage. The present results demonstrated that alkaline Comet assay was very sensitive for detecting the UV-induced genotoxicity during the short exposure period in our study. In addition, the present study also suggests that tambaqui and pirarucu fish are useful sentinel organisms, as their UV sensitivity allows them to be effective monitors of biological hazards in the Amazon region. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Comet Shoemaker-Levy 9 meets Jupiter.

    Science.gov (United States)

    Levy, D. H.; Shoemaker, E. M.; Shoemaker, C. S.

    1995-08-01

    The impact of comet D/1993 F2 (Shoemaker-Levy 9) with Jupiter was unforgettable, an event probably not to be repeated for millennia to come. One year later the astronomers who first spotted the comet reflect on their discovery, on the anxious months of anticipation before the collision and on what has been learned since.

  16. Comet West: a view from the HELIOS zodiacal light photometers

    International Nuclear Information System (INIS)

    Benensohn, R.M.; Jackson, B.V.

    1987-01-01

    Comet West passed through perihelion on February 25, 1976. The comet crossed the HELIOS A and B spacecraft zodiacal light photometer fields of view as the spacecraft orbited the Sun, allowing them to record the brightness, polarization, and color of the comet and its surrounding interplanetary medium. Data from the U, B, and V photometers across the tail shows a distinct bluing followed by a slight reddening corresponding to the ion and dust tails, respectively, entering the field of view. The non-Earth perspective of the HELIOS photometers allows a comparison of the tail with Earth observations at the same time. Precise location of the nucleus and tail allow the photometer data to be searched for evidence of the comet bow shock and orbital dust. A brightness bump present in the data before the comet reaches some photometer positions, can be shown to approximately form a parabolic shape Sunward and ahead of the orbital motion of the Comet West nucleus. If this is the comet bow shock or bow compression, then it corresponds to a density enhancement of the ambient medium by 1.5 to 2 times in the vicinity of the comet. The distance of the brightness increase from the nucleus by comparison with Comet Halley implies a neutral gas production rate of approximately 3 times that of Halley

  17. The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko

    Science.gov (United States)

    Buratti, Bonnie J.

    2017-06-01

    As remnant bodies left over from the formation of the Solar System, comets offer clues to the physical conditions and architecture of the protosolar nebula. The Rosetta spacecraft, which included an orbiter and a lander that were built and managed by the European Space Agency with NASA contributing four instruments and scientific expertise, was the first mission to orbit and study a comet through a perihelion passage. The targeted Jupiter-family comet 67P/ Churyumov-Gerasimenko, is seemingly two distinct planetesimals stuck together. The comet has not melted or been processed substantially, except for its outer layers, which consist of reaccreted dust and a crust of heated, devolatized, and annealed refractory materials and organics. The exceptionally low density (0.53 gm/cc) of 67P/ implies it is a rubble pile. The comet also appears to contain a hierarchy of building blocks: smaller spherically shaped meter-sized bodies can be seen in its interior, and even smaller cm-sized pebbles were imaged by the camera as the spacecraft made a soft crash landing on the comet’s surface on 30 September 2016. The unexpected discovery of molecular oxygen, nitrogen, and hydrogen imply that 67P/ was formed under cold conditions not exceeding 30K. The discovery of many organic compounds, including the amino acid glycine, lends support to the idea that comets, which originate in the Kuiper Belt and the Oort Cloud, brought the building blocks of life to Earth. More laboratory data on organic compounds would help to identify additional organic compounds on the comet. The differences between cometary and terrestrial D/H ratios suggest that comets are not the primary source of terrestrial water, although data on more comets is needed to confirm this result.Besides being primordial objects offering a window into the formation of solar systems, comets are astrophysical laboratories, ejecting dust and charged particles into the plasma comprising the solar wind. Several unusual phenomena

  18. The comet rendezvous asteroid flyby mission

    International Nuclear Information System (INIS)

    Morrison, D.; Neugebauer, M.; Weissman, P.R.

    1989-01-01

    The Comet Rendezvous Asteroid Flyby (CRAF) mission is designed to answer the many questions raised by the Halley missions by exploring a cometary nucleus in detail, following it around its orbit and studying its changing activity as it moves closer to and then away from the Sun. In addition, on its way to rendezvous with the comet, CRAF will fly by a large, primitive class main belt asteroid and will return valuable data for comparison with the comet results. The selected asteroid is 449 Hamburga with a diameter of 88 km and a surface composition of carbonaceous chondrite meteorites. The expected flyby date is January, 1998. The CRAF spacecraft will continue to make measurements in orbit around the cometary nucleus as they both move closer to the Sun, until the dust and gas hazard becomes unsafe. At that point the spacecraft will move in and out between 50 and 2,500 kilometers to study the inner coma and the cometary ionosphere, and to collect dust and gas samples for onboard analysis. Following perihelion, the spacecraft will make a 50,000 km excursion down the comet's tail, further investigating the solar wind interaction with the cometary atmosphere. The spacecraft will return to the vicinity of the nucleus about four months after perihelion to observe the changes that have taken place. If the spacecraft remains healthy and adequate fuel is still onboard, an extended mission to follow the comet nucleus out to aphelion is anticipated

  19. Hummingbird Comet Nucleus Analysis Mission

    Science.gov (United States)

    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.

  20. Rocket Detection of Argon in Comet Hale-Bopp

    Science.gov (United States)

    Stern, S. A.; Festou, M. C.; Parker, J. Wm.; Slater, D. C.; Gladstone, G. R.; A'Hearn, M. F.

    1998-12-01

    The EUVS planetary sounding rocket spectrograph was flown on 30.2 March 1997 (UT) from White Sands, New Mexico to observe comet Hale-Bopp in the bandpass from 830--1120 A. At the time of launch the comet was near perihelion, 0.915 AU from the Sun, 1.340 AU from Earth, and traveling at a heliocentric radial velocity of +0.70 km/s. EUVS obtained its primary spectra of the comet at resolution near 12 A, collecting 9340 counts over approximately 330 seconds of integration time. To our knowledge, the resulting dataset is both the most sensitive and the highest spectral resolution probe of a comet in the UV below 1200 A as yet achieved, and contains signatures of both the 1048.2 A and 1066.7 A Ar I resonance lines. These features represent the first-ever detections of any noble gas in a comet. The spectrum also includes significant detections which we tentatively attribute to due to 834 A 0 II, 972 A Lyman gamma, 989 A O I, the 1026 A H I Lyman beta/O I. We will discuss the Ar features, retrieve the Ar column in the coma, and discuss the implications of the total Ar/O abundance ratio in Hale-Bopp for the comet's origin.

  1. 100 and counting : SOHO's score as the world's top comet finder

    Science.gov (United States)

    2000-02-01

    Like nearly all of SOHO's discoveries, the 100th comet showed up in images from the LASCO instrument. This is a set of coronagraphs that view the space around the Sun out to 20 million kilometres, while blotting out the bright solar disk with masks. Developed for SOHO by a multinational team led by the US Naval Research Laboratory, LASCO watches for mass ejections from the Sun that threaten to disturb the Earth's space environment. The comet discoveries are a big bonus. SOHO's experts spot many of the comets as soon as the images come in. But still pictures and movies from LASCO are freely available on the Internet to astronomers around the world, who can discover less obvious comets without leaving their desks. This was the case when Kazimieras Cernis of the Institute of Theoretical Physics and Astronomy in Vilnius, Lithuania, found SOHO-100. "On 4 February I saw the comet as a small speck of light in the previous day's LASCO images," Cernis explained. "It had no visible tail, but it was too fuzzy to be an asteroid. By the time I had seen the object moving steadily across the sky in six successive images, I was convinced it was a comet and I sent the details to the SOHO scientists for verification." The competition to find SOHO's 100th comet was keen. An amateur astronomer, Maik Meyer of Frauenstein, Germany, discovered SOHO-98 and 99. On 5 February, less than 24 hours after Cernis reported the candidate SOHO-100, Meyer found the candidate SOHO-101. On the same day and in the same LASCO images Douglas Biesecker, a member of the SOHO science team, spotted the candidate SOHO-102 travelling ahead of 101. Computations have now validated the orbits for all three candidates, and shown them to be bona fide comet discoveries. Other amateur astronomers have used the LASCO images to find comets. In the summer of 1999 Terry Lovejoy in Australia found five, and since September 1999 an amateur in England, Jonathan Shanklin, has spotted three more. "SOHO is a special chance for

  2. Rosetta - a comet ride to solve planetary mysteries

    Science.gov (United States)

    2003-01-01

    Comets are very interesting objects for scientists, since their composition reflects how the Solar System was when it was very young and still 'unfinished', more than 4600 million years ago. Comets have not changed much since then. By orbiting Comet Wirtanen and landing on it, Rosetta will collect essential information to understand the origin and evolution of our Solar System. It will also help discover whether comets contributed to the beginnings of life on Earth. In fact comets are carriers of complex organic molecules, that - delivered to Earth through impacts - perhaps played a role in the origin of living forms. Furthermore, “volatile” light elements carried by comets may have also played an important role in forming the Earth’s oceans and atmopshere. “Rosetta is one of the most challenging missions ever undertaken so far”, says Prof. David Southwood, ESA Director of Science, “No one before attempted a similar mission, unique for its scientific implications as well as for its complex and spectacular interplanetary space manoeuvres”. Before reaching its target in 2011, Rosetta will circle the Sun almost four times on wide loops in the inner Solar System. During its long trek, the spacecraft will have to endure some extreme thermal conditions. Once it is close to Comet Wirtanen, scientists will take it through a delicate braking manoeuvre; then the spacecraft will closely orbit the comet, and gently drop a lander on it. It will be like landing on a small, fast-moving cosmic bullet that still has - at present - an almost unknown 'geography'. An amazing 8-year interplanetary trek Rosetta is a 3-tonne box-type spacecraft about 3 metres high, with two 14-metre long solar panels. It consists of an orbiter and a lander. The lander is approximately 1 metre across and 80 centimetres high. It will be attached to the side of the Rosetta orbiter during the journey to Comet Wirtanen. Rosetta carries 21 experiments in total, 10 of them on the lander. They will

  3. Outbursting comet P/2010 V1 (Ikeya-Murakami): A miniature comet Holmes

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, Gwanak, Seoul 151-742 (Korea, Republic of); Jewitt, David [Department of Earth, Planetary and Space Sciences, University of California at Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States); Hanayama, Hidekazu; Miyaji, Takeshi; Fukushima, Hideo; Watanabe, Jun-ichi [Ishigakijima Astronomical Observatory, National Astronomical Observatory of Japan, Ishigaki, Okinawa 907-0024 (Japan); Usui, Fumihiko [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sekiguchi, Tomohiko [Department of Teacher Training, Hokkaido University of Education, 9 Hokumon, Asahikawa 070-8621 (Japan); Yanagisawa, Kenshi; Kuroda, Daisuke [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asaguchi, Okayama 719-0232 (Japan); Yoshida, Michitoshi [Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ohta, Kouji [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Kawai, Nobuyuki [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2014-05-20

    The short-period comet P/2010 V1 (Ikeya-Murakami, hereafter {sup V}1{sup )} was discovered visually by two amateur astronomers. The appearance of the comet was peculiar, consisting of an envelope, a spherical coma near the nucleus and a tail extending in the anti-solar direction. We investigated the brightness and the morphological development of the comet by taking optical images with ground-based telescopes. Our observations show that V1 experienced a large-scale explosion between UT 2010 October 31 and November 3. The color of the comet was consistent with the Sun (g' – R {sub C} = 0.61 ± 0.20, R {sub C} – I {sub C} = 0.20 ± 0.20, and B – R {sub C} = 0.93 ± 0.25), suggesting that dust particles were responsible for the brightening. We used a dynamical model to understand the peculiar morphology, and found that the envelope consisted of small grains (0.3-1 μm) expanding at a maximum speed of 500 ± 40 m s{sup –1}, while the tail and coma were composed of a wider range of dust particle sizes (0.4-570 μm) and expansion speeds 7-390 m s{sup –1}. The total mass of ejecta is ∼5 × 10{sup 8} kg and kinetic energy ∼5 × 10{sup 12} J. These values are much smaller than in the historic outburst of 17P/Holmes in 2007, but the energy per unit mass (1 × 10{sup 4} J kg{sup –1}) is comparable. The energy per unit mass is about 10% of the energy released during the crystallization of amorphous water ice suggesting that crystallization of buried amorphous ice can supply the mass and energy of the outburst ejecta.

  4. Time-dependent injection of Oort Cloud comets into earth-crossing orbits

    International Nuclear Information System (INIS)

    Fernandez, J.A.; Ip, W.H.; Max-Planck-Institut fuer Aeronomie, Katlenburg-Lindau, West Germany)

    1987-01-01

    The present consideration of close stellar encounter-induced modulations of the influx rate of Oort Cloud comets notes that comet showers sufficiently intense for emergence in cratering statistics are produced at 80-Myr intervals, on the assumption of an Oort Cloud heavy comet core. Numerical simulations of the time evolution of comet showers or bursts indicate that a long tail of residual shower comets follows the major event with an intensity of about 0.01 of the peak rate after 20-30 Myr, thereby suggesting that residual comet showers are primarily clustered in certain areas of the sky, rendering them observable at virtually any time. 33 references

  5. Dynamical evolution and disintegration of comets

    Science.gov (United States)

    Kresak, L.

    Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members, limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed.

  6. Rapid colorimetric assay for gentamicin injection.

    Science.gov (United States)

    Tarbutton, P

    1987-01-01

    A rapid colorimetric method for determining gentamicin concentration in commercial preparations of gentamicin sulfate injection was developed. Methods currently available for measuring gentamicin concentration via its colored complex with cupric ions in alkaline solution were modified to reduce the time required for a single analysis. The alkaline copper tartrate (ACT) reagent solution was prepared such that each milliliter contained 100 mumol cupric sulfate, 210 mumol potassium sodium tartrate, and 1.25 mmol sodium hydroxide. The assay involves mixing 0.3 mL gentamicin sulfate injection 40 mg/mL (of gentamicin), 1.0 mL ACT reagent, and 0.7 mL water; the absorbance of the resulting solution at 560 nm was used to calculate the gentamicin concentration in the sample. For injections containing 10 mg/mL of gentamicin, the amount of the injection was increased to 0.5 mL and water decreased to 0.5 mL. The concentration of gentamicin in samples representing 11 lots of gentamicin sulfate injection 40 mg/mL and 8 lots of gentamicin sulfate injection 10 mg/mL was determined. The specificity, reproducibility, and accuracy of the assay were assessed. The colored complex was stable for at least two hours. Gentamicin concentration ranged from 93.7 to 108% and from 95 to 109% of the stated label value of the 40 mg/mL and the 10 mg/mL injections, respectively. No components of the preservative system present in the injections interfered with the assay. Since other aminoglycosides produced a colored complex, the assay is not specific for gentamicin. The assay was accurate and reproducible over the range of 4-20 mg of gentamicin. This rapid and accurate assay can be easily applied in the hospital pharmacy setting.

  7. Observations of faint comets at McDonald Observatory: 1978-1980

    Science.gov (United States)

    Barker, E. S.; Cochran, A. L.; Rybski, P. M.

    1981-01-01

    Modern observational techniques, developed for spectroscopy and photometry of faint galaxies and quasars, successfully applied to faint comets on the 2.7 m telescope. The periodic comets Van Biesbrock, Ashbrook-Jackson, Schwassmann-Wachmann 1, Tempel 2, Encke, Forbes, Brooks 2, Stephan-Oterma and the new comets Bradfield (19791), Bowell (1980b), Chernis-Petrauskas (1980k) were observed. The comets ranged in magnitude from 10th to 20th magnitude. For comets fainter than 19th magnitude, reflectance spectra at 100A resolution and area photometry were obtained. On comets of 17th or 18th magnitude, spectrometric scans (6A resolution) of the nucleus or inner coma region. On those comets which are brighter than 16th magnitude spatial spectrophotometric (6A resolution) studies of the inner and extended comae were done. An extensive spatial study of the comae of P/Encke and P/Stephen-Oterma, correlated with heliocentric distance is taking place. The observing process used is described and examples of the results obtained to date are discussed.

  8. Localization of specific sequences and DNA single-strand breaks in individual UV-A-irradiated human lymphocytes by COMET FISH

    Science.gov (United States)

    Bock, Claudia; Rapp, Alexander; Dittmar, Heike; Monajembashi, Shamci; Greulich, Karl-Otto

    1999-01-01

    The COMET assay, a single cell electrophoresis technique which allows to separate electrophoretically fractionated DNA according to size has been combined with fluorescence in situ hybridization (FISH) which allows to localize specific genes or gene regions. This combination (COMET FISH) allows the detection of DNA single strand breaks in specific regions of the genome of human lymphocytes at the single cell level. Various types of DNA probes, e.g. centromere-, (alpha) - satellite-, telomere-, whole chromosome-, single copy- and region specific DNA probes have been used to investigate whether the UV-A induced DNA single strand breaks are distributed randomly all over the human genome or induced at specific sites ('hot spots'). In the investigated human peripheral blood lymphocytes all but one centromere reveal low sensitivity for UV-A irradiation (500 kJ/m2), while telomeres are randomly distributed over COMET heads and tails. The human chromosome 1 is fractionated by irradiation, but remains in the COMET head, indicating an only moderate degree of fractionation. Among three tested single copy probes, c- myc, p53 and p58, the p53 gene located on chromosome 17p13.1 and the p58 gene (1p36) appear to be located in UV-A stable regions of the human genome in 95% of 65 investigated lymphocytes. In contrast, the c-myc proto-oncogene (8q24) is found in the COMET tail in 90% of the 27 investigated lymphocytes and thus appears to be more sensitive to UV-A irradiation.

  9. Comets, Asteroids, Meteorites, and the Origin of the Biosphere

    Science.gov (United States)

    Hoover, Richard B.

    2006-01-01

    During the past few decades, the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment by comets and asteroids has become more widely accepted. Comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are devoid of liquid water and therefore unsuitable for life. Complex organic compounds have been observed in comets and on the water-rich asteroid 1998 KY26 and near IR observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar that has resurfacing suggesting cryovolcanic outgassing. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have shown that comets contain complex organic chemicals; that water is the predominant volatile; and that extremely high temperatures (approx. 350-400 K) can be reached on the surfae of the very black (albedo approx. 0.03) nuclei of comets when they approach the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust. Episodic outbursts and jets from the nuclei of several comets indicate that localized regimes of liquid water and water vapor can periodically exist beneath the comet crust. The Deep Impact mission found the temperature of the nucleus of comet Tempel 1 at 1.5 AU varied from a minimum of 280 plus or minus 8 K the 330K (57 C) on the sunlit side. In this paper it is argued that that pools and films of liquid water exist (within a wide range of temperatures) in cavities and voids just beneath the hot, black crust. The possibility of liquid water existing over a wide range of temperatures significantly enhances the possibility that comets might contain niches suitable for the growth of microbial communities and ecosystems. These regimes would be ideal for the growth of psychrophilic, mesophilic, and thermophilic

  10. The Composition of Comet C/2012 K1 (PanSTARRS) and the Distribution of Primary Volatile Abundances Among Comets

    Energy Technology Data Exchange (ETDEWEB)

    Roth, Nathan X.; Gibb, Erika L. [Department of Physics and Astronomy, University of Missouri-St. Louis, 503 Benton Hall, One University Blvd., St. Louis, MO 63121 (United States); Bonev, Boncho P.; DiSanti, Michael A.; Mumma, Michael J.; Villanueva, Geronimo L.; Paganini, Lucas, E-mail: nxrq67@mail.umsl.edu [Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Mail Stop 690, Greenbelt, MD 20771 (United States)

    2017-04-01

    On 2014 May 22 and 24 we characterized the volatile composition of the dynamically new Oort cloud comet C/2012 K1 (PanSTARRS) using the long-slit, high resolution ( λ /Δ λ  ≈ 25,000) near-infrared echelle spectrograph (NIRSPEC) at the 10 m Keck II telescope on Maunakea, Hawaii. We detected fluorescent emission from six primary volatiles (H{sub 2}O, HCN, CH{sub 4}, C{sub 2}H{sub 6}, CH{sub 3}OH, and CO). Upper limits were derived for C{sub 2}H{sub 2}, NH{sub 3}, and H{sub 2}CO. We report rotational temperatures, production rates, and mixing ratios (relative to water). Compared with median abundance ratios for primary volatiles in other sampled Oort cloud comets, trace gas abundance ratios in C/2012 K1 (PanSTARRS) for CO and HCN are consistent, but CH{sub 3}OH and C{sub 2}H{sub 6} are enriched while H{sub 2}CO, CH{sub 4}, and possibly C{sub 2}H{sub 2} are depleted. When placed in context with comets observed in the near-infrared to date, the data suggest a continuous distribution of abundances of some organic volatiles (HCN, C{sub 2}H{sub 6}, CH{sub 3}OH, CH{sub 4}) among the comet population. The level of “enrichment” or “depletion” in a given comet does not necessarily correlate across all molecules sampled, suggesting that chemical diversity among comets may be more complex than the simple organics-enriched, organics-normal, and organics-depleted framework.

  11. Disintegration phenomena in Comet West

    Science.gov (United States)

    Sekanina, Z.

    1976-01-01

    Two peculiarities of Comet West, the multiple splitting of the nucleus as seen in telescope observations and the complex structure of the dust tail, are discussed. A method of analysis based on the premise that the observed rate of separation of a fragment from the principal nucleus is determined by the difference in effective solar attraction acting on the bodies is applied to investigate the motion of the four fragments that separated from the nucleus of Comet West. The predicted motion of the fragments is in good agreement with available observations. It is suggested that the 'synchronic' bands of the dust tail consist of tiny fragments from relatively large particles that burst after release from the comet. The unusual orientation of these bands and their high surface brightness relative to the diffuse tail are explained by a sudden increase in the particle acceleration and in the total scattering surface as the result of the disintegration of the larger particles.

  12. Origin of comets - implications for planetary formation

    International Nuclear Information System (INIS)

    Weissman, P.R.; Arizona Univ., Tucson)

    1985-01-01

    Primordial and episodic theories for the origin of comets are discussed. The implications of the former type for the origin of the solar system are considered. Candidate sites for the formation of comets are compared. The possible existence of a massive inner Oort cloud is discussed

  13. Asteroid Family Associations of Main-Belt Comets

    Science.gov (United States)

    Hsieh, Henry H.; Novakovic, Bojan; Kim, Yoonyoung; Brasser, Ramon

    2016-10-01

    We present a population-level analysis of the asteroid family associations of known main-belt comets or main-belt comet candidates (which, to date, have largely just been analyzed on individual bases as they have been discovered). In addition to family associations that have already been reported in the literature, we have identified dynamical relationships between 324P/La Sagra and the Alauda family, P/2015 X6 (PANSTARRS) and the Aeolia family, and P/2016 G1 (PANSTARRS) and the Adeona family. We will discuss the overall implications of these family associations, particularly as they pertain to the hypothesis that members of primitive asteroid family members may be more susceptible to producing observable sublimation-driven dust emission activity, and thus becoming main-belt comets. We will also discuss the significance of other dynamical and physical properties of a family or sub-family as they relate to the likelihood of that family containing one or more currently active main-belt comets.

  14. Learned modesty and the first lady's comet: a commentary on Caroline Herschel (1787) 'An account of a new comet'.

    Science.gov (United States)

    Winterburn, Emily

    2015-04-13

    Long before women were allowed to become Fellows of the Royal Society, or obtain university degrees, one woman managed to get her voice heard, her discovery verified and her achievement celebrated. That woman was Caroline Herschel, who, as this paper will discuss, managed to find ways to fit comet discoveries into her domestic life, and present them in ways that were socially acceptable. Caroline lived in a time when strict rules dictated how women (and men) should behave and present themselves and their work. Caroline understood these rules, and used them carefully as she announced each discovery, starting with this comet which she found in 1786. Caroline discovered her comets at a time when astronomers were mainly concerned with position, identifying where things were and how they were moving. Since her discoveries, research has moved on, as astronomers, using techniques from other fields, and most recently sending experiments into space, have learned more about what comets are and what they can tell us about our solar system. Caroline's paper marks one small, early step in this much bigger journey to understand comets. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

  15. Biological effects of radiation and dosimetry in X-ray diagnostics of children

    International Nuclear Information System (INIS)

    Milkovic, Durdica; Beck, Natko; Kovac, Kornelija; Garaj-Vrhovac, Vera; Gajski, Goran

    2008-01-01

    The chest radiograms represent the basic radiological examinations of thorax. The basis for radiation protection especially in pediatrics is the exact determination of doses. The risk estimation of genome damages can be received in human peripheral blood lymphocytes using alkaline version of Comet Assay. The aim of this work was assessment and quantification of the level of DNA damage in peripheral blood lymphocytes of children during airways X-ray examinations of chest and to compare data to the dose of exposure. Doses were determined using thermoluminescence (TL) dosimetry and radiophotoluminescent (RPL) glass dosimetry system. Twenty children with pulmonary diseases, ages between 5 and 14 years were assessed. Dose measurements were conducted for poster-anterior (PA) projection on the forehead, thyroid gland, gonads, chest and back. We used a 150 kV Shimadzu CH-200 M X-ray unit. Peripheral blood samples were taken from children after and prior to X-ray exposure and were examined with the alkaline Comet Assay. Comet Assay is one of the standard techniques for assessing genome damage with variety applications in genotoxicity testing as well as fundamental research in DNA damage and repair. As a measure of DNA damage tail length was used, calculated from the centre of the head and presented in micrometers (μm). Mean value of group after irradiation was 14.04 ± 1.74 as opposed to mean value of group before irradiation that was 13.15 ± 1.33. Differences between mean tail lengths were statistically significant (P<0.05, ANOVA). In addition, correlation was found between doses in primary beam (measured on the back) and the ratio of tail length (DNA damage) before and after irradiation. Doses measured with TL and RPL dosimeters showed satisfactory agreement and both dosimetry methods are suitable for dosimetric measurements in X-ray diagnostics. (author)

  16. The C-12/C-13 abundance ratio in Comet Halley

    International Nuclear Information System (INIS)

    Wyckoff, S.; Lindholm, E.; Wehinger, P.A.; Peterson, B.A.; Zucconi, J.M.

    1989-01-01

    The individual (C-13)N rotational lines in Comet Halley are resolved using high-resolution spectra of the CN B2Sigma(+)-X2Sigma(+) (0,0) band. The observe C-12/C-13 abundance ratio excludes a site of origin for the comet near Uranus and Neptune and suggests a condensation environment quite distinct from other solar system bodies. Two theories are presented for the origin of Comet Halley. One theory suggest that the comet originated 4.5 Gyr ago in an inner Oort cloud at a heliocentric distance greater than 100 AU where chemical fractionation led to the C-13 enrichment in the CN parent molecule prior to condensation of the comet nucleus. According to the other, more plausible theory, the comet nucleus condensed relatively recently from the interstellar medium which has become enriches in C-13 and was subsequently gravitationally captured by the solar system. 107 refs

  17. On the nature of the Halley comet

    International Nuclear Information System (INIS)

    Dobrovol'skij, O.V.; Ioffe, Z.M.

    1987-01-01

    The results of study of the Halley comet by means of the ''Vega'', ''Suisej'', ''Sakigaki'' and ''Jotton'' space probes are presented in the popular form. The form and composition of the comet nucleus, its atmosphere and processes ocurring when moving in the near-the-solar space are described

  18. Establishing Quantitative Standards for Residual Alkaline Phosphatase in Pasteurized Milk.

    Science.gov (United States)

    Kim, Dong-Hyeon; Chon, Jung-Whan; Lim, Jong-Soo; Kim, Hong-Seok; Kang, Il-Byeong; Jeong, Dana; Song, Kwang-Young; Kim, Hyunsook; Kim, Kwang-Yup; Seo, Kun-Ho

    2016-01-01

    The alkaline phosphatase (ALP) assay is a rapid and convenient method for verifying milk pasteurization. Since colorimetric ALP assays rely on subjective visual assessments, their results are especially unreliable near the detection limits. In this study, we attempted to establish quantitative criteria for residual ALP in milk by using a more objective method based on spectrophotometric measurements. Raw milk was heat-treated for 0, 10, 20, 30, and 40 min and then subjected to ALP assays. The quantitative criteria for residual ALP in the milk was determined as 2 μg phenol/mL of milk, which is just above the ALP value of milk samples heat-treated for 30 min. These newly proposed methodology and criteria could facilitate the microbiological quality control of milk.

  19. The exploration of Halley's comet - An example of international cooperation

    Science.gov (United States)

    Rahe, Jurgen H.; Newburn, Ray L., Jr.

    1987-01-01

    The history of international cooperation in studies of comets started with observations in 1577 and 1680, when Tycho Brahe and Newton, respectively, collected position measurements made in different countries to determine the paths of the comets observed. In the fall of 1979, a worldwide Comet Halley watch was proposed. As a result of international cooperation, Comet Halley was explored during its recent appearance from the ground, earth orbit, Venus orbit, interplanetary space, and from within the comet itself. The various activities in space were coordinated by the ESA, the USSR Intercosmos, the Japanese ISAS, and NASA, through the Inter-Agency Consultative Group. The activities of the ground-based observers were coordinated by the International Halley Watch.

  20. Dynamical evolution and disintegration of comets

    International Nuclear Information System (INIS)

    Kresak, L.

    1982-01-01

    Current concepts of the origin and evolution of comets are reviewed. The place of their formation from which they have been delivered into the Oort reservoir is still an open problem, but the region of the outermost planets appears most probable. The interplay of stellar and planetary perturbations can be traced by model computations which reveal both the general trends and the variety of individual evolutionary paths. The present structure of the system of comets is controlled by the dynamical evolution of its individual members limited by their physical aging by disintegration. Where the lifetimes are short, as in the Jupiter family of short-period comets, an equilibrium between elimination and replenishment is established. The role of different destructive processes and the resulting survival times are discussed. (Auth.)

  1. AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO2 IN 18 COMETS

    International Nuclear Information System (INIS)

    Ootsubo, Takafumi; Kawakita, Hideyo; Hamada, Saki; Kobayashi, Hitomi; Yamaguchi, Mitsuru; Usui, Fumihiko; Nakagawa, Takao; Ueno, Munetaka; Ishiguro, Masateru; Sekiguchi, Tomohiko; Watanabe, Jun-ichi; Sakon, Itsuki; Shimonishi, Takashi; Onaka, Takashi

    2012-01-01

    We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 μm. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H 2 O) at 2.7 μm and carbon dioxide (CO 2 ) at 4.3 μm. The fundamental vibrational band of carbon monoxide (CO) around 4.7 μm and the broad emission feature, probably related to carbon-hydrogen-bearing molecules, can also be recognized around the 3.3-3.5-μm region in some of the comets. With respect to H 2 O, gas production rate ratios of CO 2 have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO 2 /H 2 O production rate ratios in comets obtained so far. The CO 2 /H 2 O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within ∼2.5 AU, since H 2 O ice fully sublimates there. The CO 2 /H 2 O ratio in cometary ice spans from several to ∼30% among the comets observed at 2 in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.

  2. MOLECULAR OXYGEN IN OORT CLOUD COMET 1P/HALLEY

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, M.; Altwegg, K. [Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Dishoeck, E. F. van [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Schwehm, G. [ESA (retired) Science Operations Department, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands)

    2015-12-10

    Recently, the ROSINA mass spectrometer suite on board the European Space Agency's Rosetta spacecraft discovered an abundant amount of molecular oxygen, O{sub 2}, in the coma of Jupiter family comet 67P/Churyumov–Gerasimenko of O{sub 2}/H{sub 2}O = 3.80 ± 0.85%. It could be shown that O{sub 2} is indeed a parent species and that the derived abundances point to a primordial origin. Crucial questions are whether the O{sub 2} abundance is peculiar to comet 67P/Churyumov–Gerasimenko or Jupiter family comets in general, and also whether Oort cloud comets such as comet 1P/Halley contain similar amounts of molecular oxygen. We investigated mass spectra obtained by the Neutral Mass Spectrometer instrument during the flyby by the European Space Agency's Giotto probe of comet 1P/Halley. Our investigation indicates that a production rate of O{sub 2} of 3.7 ± 1.7% with respect to water is indeed compatible with the obtained Halley data and therefore that O{sub 2} might be a rather common and abundant parent species.

  3. Trajectories for spacecraft encounters with Comet Honda-Mrkos-Pajdusakova in 1996

    Science.gov (United States)

    Dunham, David W.; Jen, Shao-Chiang; Farquhar, Robert W.

    1989-01-01

    Early in 1996, the relatively bright short-period Comet Honda-Mrkos-Pajdusakova (HMP) will pass only 0.17 astronomical unit from the earth, providing both an unusually favorable apparition for ground-based observers and an opportunity for a spacecraft to reach Comet HMP on relatively low-energy trajectories. The Japanense Institute of Space and Astronautical Sciences Sakigake spacecraft is expected to fly by Comet HMP on February 3, 1996, after utilizing four earth swingbys to modify its orbit. If the camera on the ESA Giotto spacecraft is inoperable, Giotto may also be sent to Comet HMP. In addition, 1-year earth-return trajectories to Comet HMP are described, along with some that can be extended to encounter Comet Giacobini-Zinner in 1998.

  4. On the observed excess of retrograde orbits among long-period comets

    International Nuclear Information System (INIS)

    Fernandez, J.A.

    1981-01-01

    The distribution of orbital inclinations of the observed long-period comets is analysed. An excess of retrograde orbits is found which increases with the perihelion distance, except for the range 1.1 10 3 A U) has the same behaviour as the total sample. It is thus suggested that the excess of retrograde orbits among long-period comets is related to an already existent excess among the incoming new comets (i.e. comets driven into the planetary region by stellar perturbations). Using theoretical considerations and a numerical model it is proposed that an important fraction of the so-called new comets are actually repeating passages through the planetary region. Nearly a half of the new comets with q > 2 A U may be repeating passages. An important consequence of the presence of comets repeating passages among the new ones is the production of an excess of retrograde orbits in the whole sample. (author)

  5. 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.

    Science.gov (United States)

    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. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. On the relationship between gas and dust in 15 comets: an application to Comet 103P/Hartley 2 target of the NASA EPOXI mission of opportunity

    Science.gov (United States)

    Sanzovo, G. C.; Sanzovo, D. Trevisan; de Almeida, A. A.

    After the success of Deep Impact mission to hit the nucleus of Comet 9P/Tempel 1 with an impactor, the concerns are turned now to the possible reutilization of this dormant flyby spacecraft in the study of another comet, for only about 10% of the cost of the original mission. Comet 103P/Hartley 2 on UT 2010 October 11 is the most attractive target in terms of available fuel at rendezvous and arrival time at the comet. In addition, the comet has a low inclination so that major orbital plane changes in the spacecraft trajectory are unnecessary. In an effort to provide information concerning the planning of this new NASA EPOXI space mission of opportunity, we use in this work, visual magnitudes measurements available from International Comet Quarterly (ICQ) to obtain, applying the Semi-Empirical Method of Visual Magnitudes - SEMVM (de Almeida, Singh, & Huebner 1997), the water production rates (in molecules/s) related to its perihelion passage of 1997. When associated to the water vaporization theory of Delsemme (1982), these rates allowed the acquisition of the minimum dimension for the effective nuclear radius of the comet. The water production rates were then converted into gas production rates (in g/s) so that, with the help of the strong correlation between gas and dust found for 12 periodic comets and 3 non-period comets (Trevisan Sanzovo 2006), we obtained the dust loss rates (in g/s), its behavior with the heliocentric distance and the dust-to-gas ratios in this physically attractive rendezvous target-comet to Deep Impact spacecraft at a closest approach of 700 km.

  7. Halley comet position in structure of the comet origin general scheme

    International Nuclear Information System (INIS)

    Davydov, V.D.

    1988-01-01

    Attempt to explain data on the Halley comet nucleus figure by photographes received from space probes in 1986 was undertaken. Peanut-like nucleus might be formed from two bodies former system under specific conditions. This hypothesis preliminary development is made; solution way for the problem about quantitative characteristics of collision and destruction is found. Quantitative assessments confirm retention possibility of two space icebergs original form after their ''docking'' within relative velocity range up to a few meters per second. Then complex with visible saddle point between two jointed fragments is formed. The hypothesis suggested is well inscribed in the origin general scheme of comets with nucleus different types, and from general scheme one may draw up the most important details to this hypothesis (for example, power mechanism of binary system formation and reasons of its destabilization)

  8. A neutral glyoxal gel electrophoresis method for the detection and semi-quantitation of DNA single-strand breaks.

    Science.gov (United States)

    Pachkowski, Brian; Nakamura, Jun

    2013-01-01

    Single-strand breaks are among the most prevalent lesions found in DNA. Traditional electrophoretic methods (e.g., the Comet assay) used for investigating these lesions rely on alkaline conditions to denature DNA prior to electrophoresis. However, the presence of alkali-labile sites in DNA can result in the introduction of additional single-strand breaks upon alkali treatment during DNA sample processing. Herein, we describe a neutral glyoxal gel electrophoresis assay which is based on alkali-free DNA denaturation and is suitable for qualitative and semi-quantitative analyses of single-strand breaks in DNA isolated from different organisms.

  9. The application of single cell gel electrophoresis or comet assay to human monitoring studies

    Directory of Open Access Journals (Sweden)

    Valverde Mahara

    1999-01-01

    Full Text Available Objective. In the search of new human genotoxic biomarkers, the single cell gel electrophoresis assay has been proposed as a sensible alternative. Material and methods. This technique detects principally single strand breaks as well as alkali-labile and repair-retarded sites. Results. Herein we present our experience using the single cell gel electrophoresis assay in human population studies, both occupationally and environmentally exposed. Conclusions. We discuss the assay feasibility as a genotoxic biomarker.

  10. Comet Kohoutek, 1973-1974, A Teachers' Guide with Student Activities.

    Science.gov (United States)

    Chapman, Robert D.

    This teacher's guide provides background information, curriculum source materials, and suggested class activities for class discussion and study. Information related to the discovery of the comet is presented as well as photographic and schematic pictures showing the sky through which the comet travels. Historical data regarding comets of the past…

  11. An analysis of the BVRI colors of 22 active comets

    Science.gov (United States)

    Betzler, A. S.; Almeida, R. S.; Cerqueira, W. J.; Araujo, L. A.; Prazeres, C. J. M.; Jesus, J. N.; Bispo, P. A. S.; Andrade, V. B.; Freitas, Y. A. S.; Betzler, L. B. S.

    2017-08-01

    Our aim was to analyze the variation of Johnson-Kron-Cousins BVRI color indexes of a sample with 22 active comets of various dynamic groups with the time, geometrical, observational and dynamical parameters. We performed photometric observations of 16 comets between 2010 and 2014, using robotic telescopes in three continents. In addition to the sample, we used data of six comets available in the literature. A statistical comparison between the distributions of color indexes was performed using the Kruskal-Wallis H-test. The color indexes of active comets can vary a few tenths up to a magnitude on time scales that range from hours to weeks. Using the B-V colors of the observed comets, we generated a relationship that correlates the cometary visual and CCD magnitudes. We did not identify any relationship between B-V and V-R colors with heliocentric distance and phase angle. The color B-V is correlated with the photometric aperture that can be described by a logarithmic function. We did not identify any differences in the distribution of B-V color among the comets analyzed at a confidence level equal to or greater than 95%. The mean color of active comets are B-R = 1.20 ± 0.24 , B-V = 0.76 ± 0.16 and V-R = 0.42 ± 0.16 . Active comets with V-R colors outside the three standard deviation interval can be considered objects with unusual physical characteristics.

  12. The Rotation Temperature of Methanol in Comet 103P/Hartley 2

    Science.gov (United States)

    Chuang, Yo-Ling; Kuan, Yi-Jehng; Milam, Stefanie; Charnley, Steven B.; Coulson, Iain M.

    2012-01-01

    Considered to be relics from Solar System formation, comets may provide the vital information connecting Solar Nebula and its parent molecular cloud. Study of chemical and physical properties of comets is thus important for our better understanding of the formation of Solar System. In addition, observing organic molecules in comets may provide clues fundamental to our knowledge on the formation of prebiotically important organic molecules in interstellar space, hence, may shed light on the origin of life on the early Earth. Comet 103PIHartley 2 was fIrst discovered in 1986 and had gone through apparitions in 1991, 1997, and 2004 with an orbital period of about 6 years, before its latest return in 2010. 2010 was also a special year for Comet 103PIHartley 2 because of the NASA EPOXI comet-flyby mission.

  13. Silicate emission feature in the spectrum of comet Mueller 1993a

    Science.gov (United States)

    Hanner, Martha S.; Hackwell, John A.; Russell, Ray W.; Lynch, David K.

    1994-01-01

    An 8- to 13-micron spectrum of comet Mueller 1993a, a dynamically new comet, was acquired when the comet was at R = 2 AU. Strong, structured silicate emission is present, closely resembling that seen in Comet P/Halley at smaller R. For the first time in a new comet, the 11.2-micron peak of crystalline olivine was detected, demonstrating that crystalline olivine particles were widespread in the solar nebula. Crystalline olivine particles could have formed in the inner protosolar nebula at temperatures greater than 1200 K; extensive radial mixing would have been required to transport these grains to the region of comet formation. Either there was more radial mixing in the solar nebula than some current theories predict or the olivine grains have a presolar origin.

  14. The persistent coma of Comet P/Schwassmann-Wachmann 1

    International Nuclear Information System (INIS)

    Jewitt, D.

    1990-01-01

    Time-series photometry of Comet P/Schwassmann-Wachmann 1 in both 1987 and 1988 shows that this comet is continually active despite its large heliocentric distance. The observed activity, upon which the famous outbursts of this comet are superposed, may be driven by the sublimation of crystalline water ice at the nucleus surface. A simple model which accounts for both the continuous activity and the sporadic outbursts is suggested. 34 refs

  15. The mass disruption of Jupiter Family comets

    Science.gov (United States)

    Belton, Michael J. S.

    2015-01-01

    I show that the size-distribution of small scattered-disk trans-neptunian objects when derived from the observed size-distribution of Jupiter Family comets (JFCs) and other observational constraints implies that a large percentage (94-97%) of newly arrived active comets within a range of 0.2-15.4 km effective radius must physically disrupt, i.e., macroscopically disintegrate, within their median dynamical lifetime. Additional observational constraints include the numbers of dormant and active nuclei in the near-Earth object (NEO) population and the slope of their size distributions. I show that the cumulative power-law slope (-2.86 to -3.15) of the scattered-disk TNO hot population between 0.2 and 15.4 km effective radius is only weakly dependent on the size-dependence of the otherwise unknown disruption mechanism. Evidently, as JFC nuclei from the scattered disk evolve into the inner Solar System only a fraction achieve dormancy while the vast majority of small nuclei (e.g., primarily those with effective radius <2 km) break-up. The percentage disruption rate appears to be comparable with that of the dynamically distinct Oort cloud and Halley type comets (Levison, H.F., Morbidelli, A., Dones, L., Jedicke, R., Wiegert, P.A., Bottke Jr., W.F. [2002]. Science 296, 2212-2215) suggesting that all types of comet nuclei may have similar structural characteristics even though they may have different source regions and thermal histories. The typical disruption rate for a 1 km radius active nucleus is ∼5 × 10-5 disruptions/year and the dormancy rate is typically 3 times less. We also estimate that average fragmentation rates range from 0.01 to 0.04 events/year/comet, somewhat above the lower limit of 0.01 events/year/comet observed by Chen and Jewitt (Chen, J., Jewitt, D.C. [1994]. Icarus 108, 265-271).

  16. Comet P/Machholtz and the Quadrantid meteor stream

    International Nuclear Information System (INIS)

    Mcintosh, B.A.

    1990-01-01

    Attention is drawn to the suggestive similarities between the calculated perturbation behavior of Comet P/Machholtz 1986 VIII, on the one hand, and on the other those of the Quadrantid, Delta Aquarid, and Arietid meteor streams. There appears to be adequate evidence for the formation by the Comets P/Machholtz and 1491-I, together with the three meteor streams, of a related complex controlled by Jupiter's gravitational perturbations; there is no comparably compelling information, however, bearing on the questions of parent-offspring or sibling relationships among these comets and meteor streams. 13 refs

  17. Plasma Waves Associated with Mass-Loaded Comets

    Science.gov (United States)

    Tsurutani, Bruce; Glassmeier, Karl-Heinz

    2015-01-01

    Plasma waves and instabilities are integrally involved with the plasma "pickup" process and the mass loading of the solar wind (thus the formation of ion tails and the magnetic tails). Anisotropic plasmas generated by solar wind-comet interactions (the bow shock, magnetic field pileup) cause the generation of plasma waves which in turn "smooth out" these discontinuities. The plasma waves evolve and form plasma turbulence. Comets are perhaps the best "laboratories" to study waves and turbulence because over time (and distance) one can identify the waves and their evolution. We will argue that comets in some ways are better laboratories than magnetospheres, interplanetary space and fusion devices to study nonlinear waves and their evolution.

  18. New Image of Comet Halley in the Cold

    Science.gov (United States)

    2003-09-01

    VLT Observes Famous Traveller at Record Distance Summary Seventeen years after the last passage of Comet Halley , the ESO Very Large Telescope at Paranal (Chile) has captured a unique image of this famous object as it cruises through the outer solar system. It is completely inactive in this cold environment. No other comet has ever been observed this far - 4200 million km from the Sun - or that faint - nearly 1000 million times fainter than what can be perceived with the unaided eye. This observation is a byproduct of a dedicated search [1] for small Trans-Neptunian Objects, a population of icy bodies of which more than 600 have been found during the past decade. PR Photo 27a/03 : VLT image (cleaned) of Comet Halley PR Photo 27b/03 : Sky field in which Comet Halley was observed PR Photo 27c/03 : Combined VLT image with star trails and Comet Halley The Halley image ESO PR Photo 27a/03 ESO PR Photo 27a/03 [Preview - JPEG: 546 x 400 pix - 207k] [Normal - JPEG: 1092 x 800 pix - 614k] [FullRes - JPEG: 1502 x 1100 pix - 1.1M] Caption : PR Photo 27a/03 shows the faint, star-like image of Comet Halley (centre), observed with the ESO Very Large Telescope (VLT) at the Paranal Observatory on March 6-8, 2003. 81 individual exposures from three of the four 8.2-m VLT telescopes with a total exposure time of about 9 hours were combined to show the magnitude 28.2 object. At this time, Comet Halley was about 4200 million km from the Sun (28.06 AU) and 4080 million km (27.26 AU) from the Earth. All images of stars and galaxies in the field were removed during the extensive image processing needed to produce this unique image. Due to the remaining, unavoidable "background noise", it is best to view the comet image from some distance. The field measures 60 x 40 arcsec 2 ; North is up and East is left. Remember Comet Halley - the famous "haired star" that has been observed with great regularity - about once every 76 years - during more than two millennia? Which was visited by an

  19. Alkaline phosphatase activity in gingival crevicular fluid during canine retraction.

    Science.gov (United States)

    Batra, P; Kharbanda, Op; Duggal, R; Singh, N; Parkash, H

    2006-02-01

    The aim of the study was to investigate alkaline phosphatase activity in the gingival crevicular fluid (GCF) during orthodontic tooth movement in humans. Postgraduate orthodontic clinic. Ten female patients requiring all first premolar extractions were selected and treated with standard edgewise mechanotherapy. Canine retraction was done using 100 g sentalloy springs. Maxillary canine on one side acted as experimental site while the contralateral canine acted as control. Gingival crevicular fluid was collected from mesial and distal of canines before initiation of canine retraction (baseline), immediately after initiation of retraction, and on 1st, 7th, 14th and 21st day and the alkaline phosphatase activity was estimated. The results show significant (p < 0.05) changes in alkaline phosphatase activity on the 7th, 14th and 21st day on both mesial and distal aspects of the compared experimental and control sides. The peak in enzyme activity occurred on the 14th day of initiation of retraction followed by a significant fall in activity especially on the mesial aspect. The study showed that alkaline phosphatase activity could be successfully estimated in the GCF using calorimetric estimation assay kits. The enzyme activity showed variation according to the amount of tooth movement.

  20. Results from the UMD physical properties of comets survey

    Science.gov (United States)

    Lisse, Carey M.; A'Hearn, Michael F.; Fernandez, Yanga R.

    2005-01-01

    We report on an ongoing statistical study of the emitted dust and exposed nuclei of a survey of the brightest near-Earth comets over the last 13 years. Combined thermal infrared and optical observations are analyzed using dynamical spectral and morphological coma models [123] to update and improve dust emission rates [4] and nucleus size estimates [5]. Using these results we show that 1) there is more than enough dust emitted from short period comets into bound solar system orbits to create and support the current interplanetary dust cloud (IPD); 2) that a population of dormant or extinct comets in the solar system is quite plausible; and 3) that the lifetime versus sublimation for the short period comets is much longer than their dynamical lifetime. [1] C.M. Lisse et al. (1998) Ap J 496 971. [2] C.M. Lisse et al. (1999) Icarus 140 189. [3] Y.R. Fernandez et al. (2000) Icarus 147 145 [4] L. Kresak and M. Kresakova (1987) in Symposium on Diversity and Similarity of Comets ESA SP-278 739 [5] D.C.Jewitt (1991) in Comets in the Post-Halley Era (R.L. Newburn M. Neugebauer and J. Rahe Eds.) Kluwer Academic Dordecht 19.

  1. Physical Mechanism of Comet Outbursts: The Movie

    Science.gov (United States)

    Hartmann, William K.

    2014-11-01

    During experiments conducted in 1976 at the NASA Ames Research Center’s Vertical Gun Facility (VGF), the author studied low velocity impacts into simulated regolith powders and gravels, in order to examine physics of low-velocity collisions during early solar system planetesimal formation. In one “accidental” experiment, the bucket of powder remained gas-charged during evacuation of the VGF vacuum chamber. The impactor, moving at 5.5 m/s, disturbed the surface, initiating eruptions of dust-charged gas, shooting in jets from multiple vents at speeds up to about 3 m/s, with sporadic venting until 17 seconds after the impact. This experiment was described in [1], which concluded that it simulated comet eruption phenomena. In this hypothesis, a comet nucleus develops a lag deposit of regolith in at least some regions. At a certain distance from the sun, the thermal wave penetrates to an ice-rich depth, causing sublimation. Gas rises into the regolith, collects in pore spaces, and creates a gas-charged powder, as in our experiment. Any surface disturbance, such as a meteoroid, may initiate a temporary eruption, or eventually the gas pressure becomes sufficient to blow off the overburden. Our observed ejection speed would be sufficient to launch dust off of a kilometer-scale comet nucleus.Film (100 frames/s) of the event was obtained, but was partially torn up in a projector. It has recently been reconstituted (Centric Photo Labs, Tucson) and dramatically illustrates various cometary phenomena. Parabolic curtains of erupted material resemble curtains of material photographed from earth in real comet comas, “falling back” under solar wind forces. In retrospect, the mechanism photographed here helps explain:*sporadic eruptions in Comet P/Schwassmann-Wachmann 1 (near-circular orbit at ~6 A.U., where repeated recharge may occur).*sporadic eruptions on “asteroid” 2060 Chiron (which stays beyond 8.5 A.U.). *the thicker dust curtain (and longer eruption?) than

  2. Competitive Memory Training (COMET) for OCD: a self-treatment approach to obsessions.

    Science.gov (United States)

    Schneider, Brooke C; Wittekind, Charlotte E; Talhof, Alina; Korrelboom, Kees; Moritz, Steffen

    2015-01-01

    Competitive Memory Training (COMET) is a cognitive intervention that aims to change the maladaptive cognitive-emotional networks underlying obsessive-compulsive disorder (OCD). COMET has not been previously tried as a self-help intervention. The present study tested the preliminary feasibility, acceptability, and effectiveness of COMET for OCD implemented as a self-help intervention. Sixty-five participants with OCD recruited through online OCD self-help fora completed an online baseline assessment including measures of OCD symptoms, self-esteem, and depression. Participants were randomly assigned to either COMET or a wait-list control group. All participants were approached 4 weeks later to complete an online post-assessment. There was no evidence for a greater decline of OCD symptoms or depression under COMET. When analyses were limited to only those participants who reported reading the entire manual at least once, self-esteem was higher at post-assessment in the COMET group. Although 78.1% of patients in the COMET group rated it as appropriate for self-administration, only 56.5% performed COMET exercises regularly and 26.4% read the entire manual at least once. The feasibility and effectiveness of COMET as a self-help internet intervention for OCD was not supported in this study. Further work is needed to better understand if modifications to our implementation of COMET may yield improved outcomes.

  3. Improved orbits of two periodic comets: Tsuchinshan 1 and Tsuchinshan 2

    International Nuclear Information System (INIS)

    Szutowicz, S.

    1986-01-01

    The observations made during four apparitions of two comets were collected and the orbits of the comets were improved; 86 observations of Comet Tsuchinshan 1 and 50 observations of Comet Tsuchinshan 2 made in the period 1965-1985 were used. The orbit of Comet Tsuchinshan 1 was improved taking into account nongravitational effects in its motion as well as a displacement of the photometric center from the center of mass. The following values of nongravitational parameters and of observational parameter D were obtained: A 1 = 0.75953 x 10 -8 , A 2 0.00375 x 10 -8 , D = 0.34698 x 10 -3 . To link all observations of Comet Tsuchinshan 2 by one system of elements it was sufficient to add observational effects as a displacement of the photometric center from the center of mass. The following value of parameter D was obtained: D = 1.00200 x 10 -3 . The equations of motion of both comets were integrated backwards and forwards till 1992. Ephemerides for their next returns were computed. 6 refs., 5 tabs. (author)

  4. Comets Nature, Dynamics, Origin, and their Cosmogonical Relevance

    CERN Document Server

    Fernández, Julio Angel

    2005-01-01

    The book covers the most recent ideas about the nature and dynamics of comets, including a thorough discussion on Oort cloud dynamics which has not received due attention in other books on the subject. It also discusses the most relevant aspects of the physics and chemistry of comet nuclei, highlighting their importance as relics of the protoplanetary disk and, perhaps, as carriers of water and organics that permitted the development of life on Earth. The book contains several tables with useful data, and an ample bibliography covering the most recent work as well as some historical key contributions to the subject. It may be suitable as a textbook for graduate students with some basic knowledge of celestial mechanics and astrophysics, as well as a consult book for comet researchers, or researchers from other related fields willing to start working on comets, or get an updated view of the subject.

  5. AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO{sub 2} IN 18 COMETS

    Energy Technology Data Exchange (ETDEWEB)

    Ootsubo, Takafumi [Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Kawakita, Hideyo; Hamada, Saki; Kobayashi, Hitomi; Yamaguchi, Mitsuru [Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555 (Japan); Usui, Fumihiko; Nakagawa, Takao; Ueno, Munetaka [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Ishiguro, Masateru [Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Sekiguchi, Tomohiko [Department of Teacher Training, Hokkaido University of Education, Asahikawa Campus, Hokumon 9, Asahikawa, Hokkaido 070-8621 (Japan); Watanabe, Jun-ichi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Sakon, Itsuki; Shimonishi, Takashi; Onaka, Takashi, E-mail: ootsubo@astr.tohoku.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2012-06-10

    We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 {mu}m. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H{sub 2}O) at 2.7 {mu}m and carbon dioxide (CO{sub 2}) at 4.3 {mu}m. The fundamental vibrational band of carbon monoxide (CO) around 4.7 {mu}m and the broad emission feature, probably related to carbon-hydrogen-bearing molecules, can also be recognized around the 3.3-3.5-{mu}m region in some of the comets. With respect to H{sub 2}O, gas production rate ratios of CO{sub 2} have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO{sub 2}/H{sub 2}O production rate ratios in comets obtained so far. The CO{sub 2}/H{sub 2}O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within {approx}2.5 AU, since H{sub 2}O ice fully sublimates there. The CO{sub 2}/H{sub 2}O ratio in cometary ice spans from several to {approx}30% among the comets observed at <2.5 AU (13 out of the 17 comets). Alternatively, the ratio of CO/CO{sub 2} in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.

  6. CINE: Comet INfrared Excitation

    Science.gov (United States)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  7. Spiral arms, comets and terrestrial catastrophism

    International Nuclear Information System (INIS)

    Clube, S.V.M.; Napier, W.M.

    1982-01-01

    A review is presented of an hypothesis of terrestrial catastrophism in which comets grow in molecular clouds and are captured by the Sun as it passes through the spiral arms of the Galaxy. Assuming that comets are a major supplier of the Earth-crossing (Appollo) asteroid population, the latter fluctuates correspondingly and leads to episodes of terrestrial bombardment. Changes in the rotational momentum of core and mantle, generated by impacts, lead to episodes of magnetic field reversal and tectonic activity, while surface phenomena lead to ice-ages and mass extinctions. An episodic geophysical history with an interstellar connection is thus implied. If comets in spiral arms are necessary intermediaries in the process of star formation, the theory also has implications relating to early solar system history and galactic chemistry. These aspects are briefly discussed with special reference to the nature of spiral arms. (author)

  8. Mission to a comet that could save earth

    CERN Multimedia

    Utton, T

    2003-01-01

    Scientists are going to attempt to land a probe on the comet Wirtanen. The GBP640million unmanned craft will travel four billion miles before catching up with the comet Wirtanen and launching a robotic lander called Rosetta, on to its surface (1/2 page).

  9. Terrestrial cometary tail and lunar corona induced by small comets: Predictions for Galileo

    International Nuclear Information System (INIS)

    Dessler, A.J.; Sandel, B.R.; Vasyliunas, V.M.

    1990-01-01

    A search for small comets near 1 AU is an objective of the Galileo mission. If small comets are as numerous and behave as has been proposed, two near-Earth signatures of small comets should be observable by the UVS experiment on the Earth flybys of Galileo; (1) a comet-like tail of Earth created by small comets that come close to Earth, break up and vaporize, but just miss the atmosphere and proceed back into interplanetary space, and (2) a corona surrounding the Moon induced by lunar impact of small comets

  10. Infrared imaging and photometry of Comet Giacobini-Zinner

    International Nuclear Information System (INIS)

    Campins, H.

    1986-01-01

    Infrared images and photometry were obtained to determine the spatial distribution and physical characteristics (temperature, albedo, size distribution, total mass, etc.) of the grains in the coma of Comet GZ. A 10.8 m image of Comet GZ obtained on August 4 represents the first ground-based thermal-infrared image of a Comet. Among the most significant results are: (1) an estimate of the number of grains that the ICE spacecraft must have encountered, which led the plasma wave team to conclude that they could only detect impacts on the antennae and not on the whole body of the ICE spacecraft; (2) the discovery of a population of large grains (radius > 100 micrometer), not observed in most other comets, which formed a curved tail near the nucleus (within 80 arcsec or 34,000 km); and (3) the detection of structure in the spatial distribution in the coma of the particle albedo, which was tentatively attributed to the presence of very fluffy grains which are likely to have multiple internal scattering of incident sunlight. The albedo map of Comet GZ was obtained by combining the 10.8 micrometer image shown with a simultaneous image taken at 0.68 micrometer, a bandpass which isolates the scattered continuum

  11. Catastrophic disruptions as the origin of bilobate comets

    Science.gov (United States)

    Schwartz, Stephen R.; Michel, Patrick; Jutzi, Martin; Marchi, Simone; Zhang, Yun; Richardson, Derek C.

    2018-05-01

    Several comets observed at close range have bilobate shapes1, including comet 67P/Churyumov-Gerasimenko (67P/C-G), which was imaged by the European Space Agency's Rosetta mission2,3. Bilobate comets are thought to be primordial because they are rich in supervolatiles (for example, N2 and CO) and have a low bulk density, which implies that their formation requires a very low-speed accretion of two bodies. However, slow accretion does not only occur during the primordial phase of the Solar System; it can also occur at later epochs as part of the reaccumulation process resulting from the collisional disruption of a larger body4, so this cannot directly constrain the age of bilobate comets. Here, we show by numerical simulation that 67P/C-G and other elongated or bilobate comets can be formed in the wake of catastrophic collisional disruptions of larger bodies while maintaining their volatiles and low density throughout the process. Since this process can occur at any epoch of our Solar System's history, from early on through to the present day5, there is no need for these objects to be formed primordially. These findings indicate that observed prominent geological features, such as pits and stratified surface layers4,5, may not be primordial.

  12. Comet mission hopes to uncover Earth's origins

    CERN Multimedia

    Henderson, M

    2004-01-01

    "A European spacecraft that will hunt down a comet in search of clues to the origin of life on Earth will blast off tomorrow from the Kourou spaceport in French Guiana. The Rosetta probe will take 12 years to catch up with Churyumov-Gerasimenko before becoming the first spacecraft to make a soft, controlled landing on a comet's nucleus" (1 page).

  13. Dynamics of comets: their origin and evolution

    International Nuclear Information System (INIS)

    Carusi, A.; Valsecchi, G.B.

    1985-01-01

    Comets can be considered as remnants of the original population of planetesimals and the study of their origin and dynamical histories can provide insight into the accretion phenomena; the original mass, energy and angular momentum distribution across the solar system; the collisional fragmentation of minor bodies; the impact rates on planets and the nature of impacting bodies. The interaction of comets with other solar system bodies certainly provides one of the best possibilities for a deeper understanding of the dynamics of the whole system, and a challenging test for all theories of celestial mechanics dealing with the gravitational behaviour of multiple-body systems. Comets could also be considered as the last footprints left by the interaction of the protosun and its original galactic environment. (orig.)

  14. Cytogenetic investigation of subjects professionally exposed to radiofrequency radiation.

    Science.gov (United States)

    Maes, Annemarie; Van Gorp, Urbain; Verschaeve, Luc

    2006-03-01

    Nowadays, virtually everybody is exposed to radiofrequency radiation (RFR) from mobile phone base station antennas or other sources. At least according to some scientists, this exposure can have detrimental health effects. We investigated cytogenetic effects in peripheral blood lymphocytes from subjects who were professionally exposed to mobile phone electromagnetic fields in an attempt to demonstrate possible RFR-induced genetic effects. These subjects can be considered well suited for this purpose as their RFR exposure is 'normal' though rather high, and definitely higher than that of the 'general population'. The alkaline comet assay, sister chromatid exchange (SCE) and chromosome aberration tests revealed no evidence of RFR-induced genetic effects. Blood cells were also exposed to the well known chemical mutagen mitomycin C in order to investigate possible combined effects of RFR and the chemical. No cooperative action was found between the electromagnetic field exposure and the mutagen using either the comet assay or SCE test.

  15. A biomarker model of sublethal genotoxicity (DNA single-strand breaks and adducts) using the sentinel organism Aporrectodea longa in spiked soil

    International Nuclear Information System (INIS)

    Martin, Francis L.; Piearce, Trevor G.; Hewer, Alan; Phillips, David H.; Semple, Kirk T.

    2005-01-01

    There is a need to develop risk biomarkers during the remediation of contaminated land. We employed the earthworm, Aporrectodea longa (Ude), to determine whether genotoxicity measures could be applied to this organism's intestinal tissues. Earthworms were added, for 24 h or 7 days, to soil samples spiked with benzo[a]pyrene (B[a]P) and/or lindane. After exposure, intestinal tissues (crop/gizzard or intestine) were removed prior to the measurement in disaggregated cells of DNA single-strand breaks (SSBs) by the alkaline comet assay. Damage was quantified by comet tail length (CTL, μm). B[a]P 24-h exposure induced dose-related increases (P 32 P-postlabelling, showed a two-adduct-spot pattern. This preliminary investigation suggests that earthworm tissues may be incorporated into genotoxicity assays to facilitate hazard identification within terrestrial ecosystems. - Sublethal genotoxicity in the sentinel organism A. longa can be used to monitor the effects of contaminants in soil

  16. Comet Hyakutake to Approach the Earth in Late March 1996

    Science.gov (United States)

    1996-03-01

    Astronomers Prepare for a Rare Event In the early morning of January 31, 1996, Japanese amateur astronomer Yuji Hyakutake made his second comet discovery within five weeks. He found the new comet near the border between the southern constellations of Hydra (The Water-Snake) and Libra (The Scales), amazingly just three degrees from the position where he detected another comet on December 26, 1995. After two weeks of hectic activity among amateur and professional astronomers all over the world, much interesting information has now been gathered about the new comet which has been designated C/1996 B2 (Hyakutake) . In particular, it has been found to move in a near-parabolic orbit that will bring it unusually close to the Earth next month. It is then expected to become bright enough to be seen with the unaided eye and to remain so during several weeks thereafter. Preparations are now made to observe the celestial visitor with a large number of telescopes, on the ground and in space. This event offers a rare opportunity to study the immediate surroundings of a cometary nucleus in detail and the specialists intend to make the most of it. Discovery and orbit Yuji Hyakutake, of profession photoengraver and a well-known amateur astronomer, announced his new discovery without delay, and within 24 hours, it had been sighted by several other observers in Japan and Australia. Experienced comet-watchers described its appearance as `diffuse with central condensation and of magnitude 11-12', i.e. a little more than 100 times fainter than what can be seen with the unaided eye. This brightness is not unusual for a comet discovered by an amateur, although it would probably have been missed, had it been just a little fainter. In the present case, the decisive factors for Hyakutake's success were undoubtedly his very powerful equipment (25 x 150 binoculars) and the advantageous combination of the comet's southern position in the sky and his location in Kagoshima, the southernmost

  17. The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

    Science.gov (United States)

    Jones, Geraint H.; Knight, Matthew M.; Battams, Karl; Boice, Daniel C.; Brown, John; Giordano, Silvio; Raymond, John; Snodgrass, Colin; Steckloff, Jordan K.; Weissman, Paul; Fitzsimmons, Alan; Lisse, Carey; Opitom, Cyrielle; Birkett, Kimberley S.; Bzowski, Maciej; Decock, Alice; Mann, Ingrid; Ramanjooloo, Yudish; McCauley, Patrick

    2018-02-01

    This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun's centre, equal to half of Mercury's perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and

  18. COMET concept

    International Nuclear Information System (INIS)

    Alsmeyer, H.; Tromm, W.

    1995-01-01

    Studies of the COMET core catcher concept developed for a future PWR have been continued. The concept is based on the spreading of a core melt on a sacrificial layer and its erosion, until a subsequent addition of water from below causes a fragmentation of the melt. A porous solidification of the melt would then admit a complete flooding within a short period. (orig.)

  19. Assessment in vitro of the genotoxicity, antigenotoxicity and antioxidant of Ceratonia siliqua L. extracts in murine leukaemia cells L1210 by comet assay.

    Science.gov (United States)

    Sassi, Aïcha; Bouhlel, Ines; Mustapha, Nadia; Mokdad-Bzeouich, Imen; Chaabane, Fadwa; Ghedira, Kamel; Chekir-Ghedira, Leila

    2016-06-01

    Genotoxicity of Ceratonia siliqua extracts, was investigated by assessing their capacity to induce nucleus DNA degradation of murine leukaemia cells L1210, using the "Comet assay". The ability of total oligomer flavonoids (TOF) and aqueous extracts to protect cell DNA against oxidative stress induced by H2O2, was performed by pre- co or post-treatment of cells with the before mentioned extracts for different periods preceding exposure to H2O2 stress. No significant genotoxic effect was detected at different exposure times, except at the lowest concentration of TOF extract (16.25 μg/ml). It appears that extracts decreased DNA damage, induced by H2O2. Both of TOF and aqueous extracts exhibited cellular antioxidant capacity, with EC50 values of respectively capacity against lipidperoxidation inducing using L1210 cells line as a cellular model. MDA inhibition percentages reached 88.43% and 90.52% with respectively 35.5 μg/ml of TOF extract and 70 μg/ml of aqueous extract. Antioxidant properties of carob leaf extracts revealed by our study make a good antioxidant protection and thus a good candidate as food addition component. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Kelvin-Helmholtz instability in type-1 comet tails and associated phenomena

    International Nuclear Information System (INIS)

    Ershkovich, A.I.

    1980-01-01

    Selected problems of the solar wind - comet tail coupling that are currently accessible to quantitative analysis are reviewed. The model of a comet tail as a plasma cylinder separated by a tangential discontinuity surface from the solar wind is discussed in detail. This model is compatible with the well-known Alfven mechanism of formation of the comet tail. The stability problem of the comet tail boundary (considered as a discontinuity surface) is solved. Under typical conditions a comet tail boundary can undergo the Kelvin-Helmholtz instability. With finite amplitude the stabilizing effect of the magnetic field increases, and waves become stabilized. This model supplies a detailed quantitative description of helical waves observed in type-1 comet tails. A more general model of the tail boundary as a transition layer with a continuous change of the plasma parameters within it is also considered. This theory, in principle, enables us to solve one of the fundamental problems of cometary physics: the magnetic field of the comet tail can be derived from the observations of helical waves. This field turns out to be of the order of the interplanetary field. Various other considerations, discussed in this review also support this conclusion. (orig.)