Comet assay: an essential tool in toxicological research.

PubMed

Glei, M; Schneider, T; Schlörmann, W

2016-10-01

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

Comet Assay in Cancer Chemoprevention.

PubMed

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

2016-01-01

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

Epithelial cells as alternative human biomatrices for comet assay.

PubMed

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

2014-01-01

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

Epithelial cells as alternative human biomatrices for comet assay

PubMed Central

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

2014-01-01

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

Systematic random sampling of the comet assay.

PubMed

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

2009-07-01

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

Recommendations for safety testing with the in vivo comet assay.

PubMed

Vasquez, Marie Z

2012-08-30

While the in vivo comet assay increases its role in regulatory safety testing, deliberations about the interpretation of comet data continue. Concerns can arise regarding comet assay publications with limited data from non-blind testing of positive control compounds and using protocols (e.g. dose concentrations, sample times, and tissues) known to give an expected effect. There may be a tendency towards bias when the validation or interpretation of comet assay data is based on results generated by widely accepted but non-validated assays. The greatest advantages of the comet assay are its sensitivity and its ability to detect genotoxicity in tissues and at sample times that could not previously be evaluated. Guidelines for its use and interpretation in safety testing should take these factors into account. Guidelines should be derived from objective review of data generated by blind testing of unknown compounds dosed at non-toxic concentrations and evaluated in a true safety-testing environment, where the experimental design and conclusions must be defensible. However, positive in vivo comet findings with such compounds are rarely submitted to regulatory agencies and this data is typically unavailable for publication due to its proprietary nature. To enhance the development of guidelines for safety testing with the comet assay, and with the permission of several sponsors, this paper presents and discusses relevant data from multiple GLP comet studies conducted blind, with unknown pharmaceuticals and consumer products. Based on these data and the lessons we have learned through the course of conducting these studies, I suggest significant adjustments to the current conventions, and I provide recommendations for interpreting in vivo comet assay results in situations where risk must be evaluated in the absence of carcinogenicity or clinical data. Copyright © 2012 Elsevier B.V. All rights reserved.

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

PubMed

Georgieva, Milena; Zagorchev, Plamen; Miloshev, George

2015-10-01

Comet assay is an invaluable tool in DNA research. It is widely used to detect DNA damage as an indicator of exposure to genotoxic stress. A canonical set of parameters and specialized software programs exist for Comet assay data quantification and analysis. None of them so far has proven its potential to employ a computer-based algorithm for assessment of the shape of the comet as an indicator of the exact mechanism by which the studied genotoxins cut in the molecule of DNA. Here, we present 14 unique measurements of the comet image based on the comet morphology. Their mathematical derivation and statistical analysis allowed precise description of the shape of the comet image which in turn discriminated the cause of genotoxic stress. This algorithm led to the development of the "CometShape" software which allowed easy discrimination among different genotoxins depending on the type of DNA damage they induce. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

PubMed

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 < 0.0001). The resulting SMD was reduced to 1.756 (95% CI: 0.992-2.52, p < 0.0001) when the analysis only included nurses. In subgroup analyses based on gender and smoking, heterogeneity was observed. Only for studies reporting 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 < 0.0001). A mixture of personal parameters, 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.

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

NASA Astrophysics Data System (ADS)

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

2012-03-01

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

The comet assay in human biomonitoring.

PubMed

Anderson, Diana; Dhawan, Alok; Laubenthal, Julian

2013-01-01

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

A Comprehensive Review on Clinical Applications of Comet Assay

PubMed Central

Gunasekarana, Vidya; Chand, Parkash

2015-01-01

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

Worldwide interest in the comet assay: a bibliometric study.

PubMed

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

2015-01-01

The comet assay is a rapid, sensitive and relatively simple method for measuring DNA damage. A bibliometric study was performed to evaluate temporal and geographical trends, research quality and main areas of interest in scientific production in this field. A PubMed search strategy was developed and 7674 citations were retrieved in the period 1990-2013. Notably, the MeSH (Medical Subject Headings) term 'comet assay', officially introduced in 2000, is used by indexers only in two thirds of papers retrieved. Articles on the comet assay were published in 78 countries, spread over the 5 continents. The EU contributed the greatest output, producing >2900 articles with IF (42.0%) and totalling almost 10000 IF points, and was followed by USA. In the new millennium, research with this assay reached a plateau or slow decline in the most industrialised areas (USA, Germany, UK, Italy), while its use has boomed in emerging countries, with increases of 5- to 7-fold in the last 10 years in China, India and Brazil, for instance. This transition resulted in a slow decrease of scientific production quality, as the countries that increased their relative weight typically had lower mIFs. The most common MeSH terms used in papers using the comet assay referred to wide areas of interest, such as DNA damage and repair, cell survival and apoptosis, cancer and oxidative stress, occupational and environmental health. Keywords related to humans, rodents and cell culture were also frequently used. The top journal for the comet assay articles was found to be Mutation Research, followed by Mutagenesis. Most papers using the comet assay as a biomarker were published in genetic and toxicology journals, with a stress on environmental and occupational disciplines. © The Author 2014. Published by Oxford University Press on behalf of the Mutagenesis Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Seasonal variations as predictive factors of the comet assay parameters: a retrospective study.

PubMed

Geric, Marko; Gajski, Goran; Orešcanin, Višnja; Garaj-Vrhovac, Vera

2018-02-24

Since there are several predicting factors associated with the comet assay parameters, we have decided to assess the impact of seasonal variations on the comet assay results. A total of 162 volunteers were retrospectively studied, based on the date when blood donations were made. The groups (winter, spring, summer and autumn) were matched in terms of age, gender, smoking status, body mass index and medical diagnostic exposure in order to minimise the impact of other possible predictors. Means and medians of the comet assay parameters were higher when blood was sampled in the warmer period of the year, the values of parameters being the highest during summer. Correlation of meteorological data (air temperature, sun radiation and sun insolation) was observed when data were presented as the median per person. Using multivariate analysis, sampling season and exposure to medical radiation were proved to be the most influential predictors for the comet assay parameters. Taken together, seasonal variation is another variable that needs to be accounted for when conducting a cohort study. Further studies are needed in order to improve the statistical power of the results related to the impact of sun radiation, air temperature and sun insolation on the comet assay parameters.

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

PubMed Central

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 < 0.0001). The resulting SMD was reduced to 1.756 (95% CI: 0.992–2.52, p < 0.0001) when the analysis only included nurses. In subgroup analyses based on gender and smoking, heterogeneity was observed. Only for studies reporting 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 < 0.0001). Conclusions A mixture of personal parameters, 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

Evaluating In Vitro DNA Damage Using Comet Assay.

PubMed

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.

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

PubMed

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

2015-03-01

The comet assay is a sensitive method to detect DNA strand breaks as well as oxidatively damaged DNA at the level of single cells. Today the assay is commonly used in nano-genotoxicology. In this review we critically discuss possible interactions between nanoparticles (NPs) and the comet assay. Concerns for such interactions have arisen from the occasional observation of NPs in the "comet head", which implies that NPs may be present while the assay is being performed. This could give rise to false positive or false negative results, depending on the type of comet assay endpoint and NP. For most NPs, an interaction that substantially impacts the comet assay results is unlikely. For photocatalytically active NPs such as TiO2 , on the other hand, exposure to light containing UV can lead to increased DNA damage. Samples should therefore not be exposed to such light. By comparing studies in which both the comet assay and the micronucleus assay have been used, a good consistency between the assays was found in general (69%); consistency was even higher when excluding studies on TiO2 NPs (81%). The strong consistency between the comet and micronucleus assays for a range of different NPs-even though the two tests measure different endpoints-implies that both can be trusted in assessing the genotoxicity of NPs, and that both could be useful in a standard battery of test methods. © 2014 Wiley Periodicals, Inc.

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

PubMed

Bajpayee, Mahima; Kumar, Ashutosh; Dhawan, Alok

2013-01-01

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

Alkaline Comet Assay for Assessing DNA Damage in Individual Cells.

PubMed

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

2015-08-06

Single-cell gel electrophoresis, commonly called a comet assay, is a simple and sensitive method for assessing DNA damage at the single-cell level. It is an important technique in genetic toxicological studies. The comet assay performed under alkaline conditions (pH >13) is considered the optimal version for identifying agents with genotoxic activity. The alkaline comet assay is capable of detecting DNA double-strand breaks, single-strand breaks, alkali-labile sites, DNA-DNA/DNA-protein cross-linking, and incomplete excision repair sites. The inclusion of digestion of lesion-specific DNA repair enzymes in the procedure allows the detection of various DNA base alterations, such as oxidative base damage. This unit describes alkaline comet assay procedures for assessing DNA strand breaks and oxidative base alterations. These methods can be applied in a variety of cells from in vitro and in vivo experiments, as well as human studies. Copyright © 2015 John Wiley & Sons, Inc.

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

PubMed Central

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

2016-01-01

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. PMID:27166647

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

PubMed

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.

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

PubMed

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

2014-01-01

The comet assay is widely used in human biomonitoring to measure DNA damage as a marker of exposure to genotoxic agents or to investigate genoprotective effects. Studies often involve small numbers of subjects, and design may be sub-optimal in other respects. In addition, comet assay protocols in use in different laboratories vary significantly. In spite of these difficulties, it is appropriate to carry out a pooled analysis of all available comet assay biomonitoring data, in order to establish baseline parameters of DNA damage, and to investigate associations between comet assay measurements and factors such as sex, age, smoking status, nutrition, lifestyle, etc. With this as its major objective, the ComNet project has recruited almost 100 research groups willing to share datasets. Here we provide a background to this project, discussing the history of the comet assay and practical issues that can critically affect its performance. We survey its diverse applications in biomonitoring studies, including environmental and occupational exposure to genotoxic agents, genoprotection by dietary and other factors, DNA damage associated with various diseases, and intrinsic factors that affect DNA damage levels in humans. We examine in depth the quality of data from a random selection of studies, from an epidemiological and statistical point of view. Copyright © 2013 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-01-01

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

The use of comet assay in plant toxicology: recent advances

PubMed Central

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

2015-01-01

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

Antioxidants and the Comet assay.

PubMed

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.

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

PubMed

Augustyniak, Maria; Gladysz, Marcin; Dziewięcka, Marta

2016-01-01

The Comet assay has been recently adapted to investigate DNA damage in insects. The first reports of its use in Drosophila melanogaster appeared in 2002. Since then, the interest in the application of the Comet assay to studies of insects has been rapidly increasing. Many authors see substantial potential in the use of the Comet assay in D. melanogaster for medical toxicology studies. This application could allow the testing of drugs and result in an understanding of the mechanisms of action of toxins, which could significantly influence the limited research that has been performed on vertebrates. The possible perspectives and benefits for science are considered in this review. In the last decade, the use of the Comet assay has been described in insects other than D. melanogaster. Specifically, methods to prepare a cell suspension from insect tissues, which is a difficult task, were analyzed and compared in detail. Furthermore, attention was paid to any differences and modifications in the research protocols, such as the buffer composition and electrophoresis conditions. Various scientific fields in addition to toxicological and ecotoxicological research were considered. We expect the Comet assay to be used in environmental risk assessments and to improve our understanding of many important phenomena of insect life, such as metamorphosis, molting, diapause and quiescence. The use of this method to study species that are of key importance to humans, such as pests and beneficial insects, appears to be highly probable and very promising. The use of the Comet assay for DNA stability testing in insects will most likely rapidly increase in the future. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

Frötschl, Roland

2015-01-01

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

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

PubMed

Karbaschi, Mahsa; Cooke, Marcus S

2014-11-26

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

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

PubMed

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

2014-05-01

The aim of this study was to validate the comet assay in erythrocytes of Caretta caretta, a species never investigated for genotoxicity. We studied 31 loggerhead sea turtles from three Italian marine rescue centres. Peripheral blood samples were collected from all the animals and the comet assay applied. All comet cells were analysed using two methods: visual scoring and computer image analysis. The % DNA in tail mean value ± SD and Damage Index were 21.56 ± 15.41 and 134.83 ± 94.12, respectively. A strong and statistically significant statistically correlation between the two analytical methods was observed (r = 0.95; p < 0.05). These results demonstrate that the comet assay is a useful method to detect the possible effects of genotoxic agents in loggerhead sea turtle and to increase the knowledge about the ecotoxicological health status of this threatened species. Copyright © 2013 Elsevier Ltd. All rights reserved.

Bovine Papillomavirus Clastogenic Effect Analyzed in Comet Assay

PubMed Central

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

2013-01-01

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

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

PubMed Central

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

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

PubMed Central

Karbaschi, Mahsa; Cooke, Marcus S.

2014-01-01

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

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

PubMed

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

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined the ability of the assay to determine the genotoxicity of 2-acetylaminofluorene (AAF), azidothymidine (AZT), cisplatin (CPN), and isobutyraldehyde (IBA) in liver and glandular stomach of male Sprague-Dawley rats. Rats were given oral doses of test compound or control once daily for three days. High dose levels were approximately maximum tolerated doses and were based on preliminary range-finding studies. Tissues were harvested 3h after the final dose (48h after the initial dose). A bone marrow micronucleus assay (MN) was also conducted on the rats treated with AZT, CPN, and IBA. Acute toxic effects of treatment were determined primarily through histomorphologic analysis of liver and stomach but also by body weight and serum liver enzyme changes. The comet assay was conducted on fresh tissue preparations but frozen samples from two studies were also assayed. Statistically significant dose-related differences in comet % DNA in tail were found in liver and stomach for the genotoxin AZT and in liver for the genotoxin CPN, but not in liver or stomach for the non-genotoxin IBA. Statistically significant differences in % DNA in tail were measured in liver for the low and mid dose of the genotoxin AAF, but not the high dose. The comet assays of frozen liver suspensions from CPN- and AAF-treated rats yielded comparable results to the assays of fresh preparations. There were no indications of significant toxicity induced by any treatment. The micronucleus assay was positive for CPN and AZT and negative for IBA. In conclusion, the in vivo comet assay is capable of detecting genotoxic effects of a variety of chemicals and may fill an important role in the genotoxicity test battery. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2014-03-01

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

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

PubMed

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 < 0.05), and the correlation between Olive TM and reactive oxygen species was better than other parameters (r = 0.77, P < 0.05). This study indicates that FPG-comet assay

Drosophila comet assay: insights, uses, and future perspectives

PubMed Central

Gaivão, Isabel; Sierra, L. María

2014-01-01

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

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

PubMed

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

2017-01-01

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

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

PubMed

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.

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

PubMed

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.

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

PubMed

Singh, Narendra P

2016-01-01

The study of DNA damage and its repair is critical to our understanding of human aging and cancer. This review reflects on the development of a simple technique, now known as the comet assay, to study the accumulation of DNA damage and its repair. It describes my journey into aging research and the need for a method that sensitively quantifies DNA damage on a cell-by-cell basis and on a day-by-day basis. My inspirations, obstacles and successes on the path to developing this assay and improving its reliability and sensitivity are discussed. Recent modifications, applications, and the process of standardizing the technique are also described. What was once untried and unknown has become a technique used around the world for understanding and monitoring DNA damage. The comet assay's use has grown exponentially in the new millennium, as emphasis on studying biological phenomena at the single-cell level has increased. I and others have applied the technique across cell types (including germ cells) and species (including bacteria). As it enters new realms and gains clinical relevance, the comet assay may very well illuminate human aging and its prevention. Copyright © 2016. Published by Elsevier B.V.

Application of cytogenetic endpoints and comet assay on human lymphocytes treated with atorvastatin in vitro.

PubMed

Gajski, Goran; Garaj-Vrhovac, Vera

2008-01-01

This study investigated the genotoxic potential of atorvastatin on human lymphocytes using comet assay, structural chromosome aberrations (CA) and sister-chromatid exchange (SCE) analysis. Lymphocyte cultures were treated with a single drug at a concentration of 30.21 ng/mL. For comet assay, cells exposed to atorvastatin for 24 h, 48 h and 72 h were embedded in agarose slides, lysed with alkaline lysis solution and exposed to an electric field. DNA migrated within the agarose and formed comets whose length depends on the amount of DNA damage. For analysis of structural CA, cells were grown on medium for 48 h and for SCE analysis for 72 h. Structural CA did not induce significant damage to the genome, although a higher CA frequency was observed in cells treated with atorvastatin for 3 h, 20 h and 48 h than in control samples. Results of the SCE analysis did show statistically significant differences in the mean SCE number between atorvastatin-exposed and control human lymphocytes and between different exposure times. Comet assay also showed increased DNA damage caused in atorvastatin-exposed human lymphocytes than in corresponding control cells for exposure times of 24 h, 48 h and 72 h for the tail length and for 72 h for the tail moment. Results obtained in this study point to the significance of biological indicators providing information on the primary genome damage after long-term exposure, which can help to establish drug therapeutic concentrations that do not put patients with high blood cholesterol to a greater treatment-related risk.

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

PubMed

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

2014-07-01

The comet assay is the widely used method for in vitro toxicity testing which is also an alternative to the use of animal models for in vivo testing. Since, its inception in 1984 by Ostling and Johansson, it is being modified frequently for a wide range of application. In spite of its wide applicability, unfortunately there is no report of its application in bacteriophages research. In this study, a novel application of comet assay for the detection of bacteriophage mediated bacterial cell lysis was described. The conventional methods in bacteriophage research for studying bacterial lysis by bacteriophages are plaque assay method. It is time consuming, laborious and costly. The lytic activity of bacteriophage devours the bacterial cell which results in the release of bacterial genomic material that gets detected by ethidium bromide staining method by the comet assay protocol. The objective of this study was to compare efficacy of comet assay with different assay used to study phage mediated bacterial lysis. The assay was performed on culture isolates (N=80 studies), modified comet assay appear to have relatively higher sensitivity and specificity than other assay. The results of the study showed that the application of comet assay can be an economical, time saving and less laborious alternative to conventional plaque assay for the detection of bacteriophage mediated bacterial cell lysis. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed Central

Jackson, Petra

2013-01-01

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

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

PubMed

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

2013-01-20

In the present study the alkaline comet assay and the cytokinesis-block micronucleus cytome (CBMN Cyt) assay were used to evaluate the baseline frequency of cytogenetic damage in peripheral blood lymphocytes (PBLs) of 50 healthy children from the general population in Croatia (age, 11.62±1.81 years). Mean values of tail length, tail intensity and tail moment, as comet assay parameters, were 12.92±0.10, 0.73±0.06 and 0.08±0.01, respectively. The mean frequency of micronuclei (MN) for all subjects was 2.32±0.28 per 1000 bi-nucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 1.72±0.24 and of nuclear buds (NBUDs) 1.44±0.19. The mean nuclear division index (NDI) was 1.70±0.05. When comet-assay parameters were considered, higher mean values for all three were found for the female population. According to the Mann-Whitney U test applied on the results of the comet assay, the only statistically significant difference between the male and female populations was found for tail length. Similar to the results obtained by the comet assay, girls showed higher mean values of all three measured parameters of the CBMN Cyt assay. This difference was statistically significant for total number of NPBs only. In the case of the NDI, a higher mean value was also obtained in girls, but this difference was not statistically significant. The results obtained present background data that could be considered as normal values for healthy children living in urban areas, and can later on serve as baseline values for further toxicological monitoring. Additionally, the usefulness of both techniques in measuring cytogenetic damage during bio-monitoring of children is confirmed. Copyright © 2012 Elsevier B.V. All rights reserved.

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

PubMed

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

2014-12-01

In genotoxicity testing of pharmaceuticals the rodent alkaline comet assay is being increasingly used as a second in vivo assay in addition to the in vivo micronucleus assay to mitigate in vitro positive results as recommended by the ICH S2(R1) guideline. This paper summarizes a survey suggested by the Safety Working Party of European Medicines Agency (EMA), and conducted by the European Federation of Pharmaceutical Industries and Associations (EFPIA) to investigate the experience among European pharmaceutical companies by conducting the in vivo comet assay for regulatory purpose. A special focus was given on the typology of the obtained results and to identify potential difficulties encountered with the interpretation of study data. The participating companies reported a total of 147 studies (conducted in-house or outsourced) and shared the conclusion on the comet assay response for 136 studies. Most of the studies were negative (118/136). Only about 10% (14/136 studies) of the comet assays showed a positive response. None of the positive comet assay results were clearly associated with organ toxicity indicating that the positive responses are not due to cytotoxic effects of the compound in the tissue examined. The number of comet assays with an equivocal or inconclusive response was rare, respectively <1% (1/147 studies) and 2% (3/147 studies). In case additional information (e.g. repeat assay, organ toxicity, metabolism, tissue exposure) would have been available for evaluation, a final conclusion could most probably have been drawn for most or all of these studies. All (46) negative in vivo comet assays submitted alongside with a negative in vivo micronucleus assay were accepted by the regulatory authorities to mitigate a positive in vitro mammalian cell assay following the current ICH S2 guidance. The survey results demonstrate the robustness of the comet assay and the regulatory acceptance of the current ICH S2 guidance. Copyright © 2014 The Authors

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

PubMed

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

2015-09-15

Unilateral orchiectomy (UO) may interfere with thermoregulation of the remaining testis caused by inflammation surrounding the incision site, thus altering normal spermatogenesis and consequently sperm quality. Two measures of sperm DNA quality (neutral comet assay and the sperm chromatin structure assay [SCSA]) were compared before UO (0 days) and at 14, 30, and 60 days after UO to determine whether sperm DNA changed after a mild testis stress (i.e., UO). The percent DNA in the comet tail was higher at 14 and 60 days compared to 0 days (P < 0.05) after UO. All other comet tail measures (i.e., length, moment, migration) were higher at all time periods after UO compared to 0 days (P < 0.05). Two SCSA measures (mean-αt, mode-αt) increased at 14 days after UO (P < 0.05), whereas two measures (SD-αt and COMP-αt) did not change. This study identified a decrease in sperm DNA quality using both the neutral comet assay and the SCSA, which was not identified using traditional measures of sperm quality. Copyright © 2015 Elsevier Inc. All rights reserved.

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

PubMed

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

2015-05-01

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

Estimation of serum malondialdehyde and assessment of DNA damage using comet assay in patients with oral submucous fibrosis.

PubMed

Paulose, Swetha; Rangdhol, Vishwanath; Ramesh, Ramasamy; Jeelani, Siccandar Ali; Brooklyin, Sivakumar

2016-08-01

To quantify the level of serum malondialdehyde and extent of DNA damage using comet assay in patients with oral submucous fibrosis (SMF) in comparison to normal individuals and to correlate the extent of DNA damage with MDA levels. Study included 30 cases of SMF (n = 30) and equal number of healthy volunteers. Serum malondialdehyde was measured using the thiobarbituric-trichloroacetitic acid (TBA-TCA) method. Comet assay was used to assess the DNA damage. Association between the extent of DNA damage and serum MDA levels was analyzed in SMF statistically. Comet assay results showed that there was an increase in tail length, percentage of tail DNA and tail moment among SMF subjects (P < 0.05). Serum MDA levels were elevated in SMF patients compared with healthy subjects. A significant positive correlation was observed between serum MDA levels and comet tail length in SMF group (r = 0.56; P < 0.05). Patients with SMF have increased DNA damage and elevated levels of lipid peroxidation compared with healthy controls. Evaluation of MDA levels as an oxidative biomarker along with comet assay analysis will serve as a diagnostic tool to identify patients with high risk of malignant potential in SMF. © 2015 Wiley Publishing Asia Pty Ltd.

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

PubMed

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

2017-03-01

The alkaline Comet assay has shown high diagnostic value to determine male reproductive health and prognostic ability to predict ART success. Here, spermatozoon was analysed in 47 fertile donors and 238 patients, including 132 couples undergoing ART [semen was collected: Group I - within 3 months of their treatment (n = 79); and Group II - 3 months prior to their treatment (n = 53)]. We introduce four Comet distribution plots (A, B1, B2 and C) by plotting the level of DNA damage (x-axis) and percentage of comets (y-axis). Fertile donors had low mean DNA damage, olive tail moment and per cent of spermatozoa with damage and increased type A plots. Comet parameters were associated with clinical pregnancies in Group I. About 66% of couples with type A distribution plot were successful after ART, whereas couples with type B1, B2 and C distribution plots achieved 56%, 44% and 33% pregnancies respectively. The efficiency of the Comet assay was due to complete decondensation process, where the compact sperm nuclear DNA (28.2 ± 0.2 μm 3 ) is decondensed to ~63 μm 3 (before lysis) and ~1018 μm 3 (after lysis). A combinational analysis of all the Comet output parameters may provide a comprehensive evaluation of patient's reproductive health as these parameters measure different aspects of DNA damage within the spermatozoa. © 2016 Blackwell Verlag GmbH.

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

PubMed

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

2014-11-23

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.

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

EPA Science Inventory

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

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

PubMed

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.

A Bayesian, generalized frailty model for comet assays.

PubMed

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

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

NASA Astrophysics Data System (ADS)

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

2002-03-01

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

Weak silica nanomaterial-induced genotoxicity can be explained by indirect DNA damage as shown by the OGG1-modified comet assay and genomic analysis.

PubMed

Pfuhler, Stefan; Downs, Thomas R; Allemang, Ashley J; Shan, Yuching; Crosby, Meredith E

2017-01-01

In a previous study, 15-nm silica nanoparticles (NPs) caused small increases in DNA damage in liver as measured in the in vivo comet and micronucleus assays after intravenous administration to rats at their maximum tolerated dose, a worst-case exposure scenario. Histopathological examination supported a particle-induced, tissue damage-mediated inflammatory response. This study used a targeted approach to provide insight into the mode of action (MoA) by examining transcriptional regulation of genes in liver in a time and dose-dependent manner at 1, 2, 4, 8 and 24 h after intravenous administration of 15-nm silica NPs. DNA damage was assessed using the standard comet assay and hOGG1 glycosylase-modified comet assay that also measures oxidative DNA damage. Potassium bromate, an IARC Class 2B carcinogen that specifically operates via an oxidative stress MoA, was used as a positive control for the hOGG1 comet assay and gave a strong signal in its main target organ, the kidney, while showing less activity in liver. Treatment of rats with silica NPs at 50 mg/kg body weight (bw) caused small, statistically insignificant increases in DNA damage in liver measured by the standard comet assay, while a statistically significant increase was observed at 4 h with the hOGG1 comet assay, consistent with a MoA involving reactive oxygen species. Histopathology showed liver damage and neutrophil involvement while genomic analysis and response pattern of key genes involved in inflammation and oxidative stress supported a tissue damage-mediated inflammatory response involving the complement system for removing/phagocytising damaged cells. No changes were observed for histopathology or gene array for the low-dose (5 mg/kg bw) silica NPs. The results of this study confirm our hypothesis that the weak DNA damage observed by silica NPs occurs secondary to inflammation/immune response, indicating that a threshold can be applied in the risk assessment of these materials. © The Author 2016

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

PubMed

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2008-08-15

To investigate the genotoxic potential of atorvastatin on human lymphocytes in vitro standard comet assay was used in the evaluation of basal DNA damage and to investigate possible oxidative DNA damage produced by reactive oxygen species (ROS) Fpg-modified version of comet assay was also conducted. In addition to these techniques the new criteria for scoring micronucleus test were applied for more complete detection of baseline damage in binuclear lymphocytes exposed to atorvastatin 80 mg/day in different time periods by virtue of measuring the frequency of micronuclei, nucleoplasmic bridges and nuclear buds. All parameters obtained with the standard comet assay andmore » 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.« less

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

PubMed

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

2008-08-15

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

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

PubMed Central

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

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

PubMed

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

2014-03-01

The in vivo comet assay has increasingly been used for regulatory genotoxicity testing in recent years. While it has been demonstrated that the experimental execution of the assay, for example, electrophoresis or scoring, can have a strong impact on the results; little is known on how initial steps, that is, from tissue sampling during necropsy up to slide preparation, can influence the comet assay results. Therefore, we investigated which of the multitude of steps in processing the liver for the comet assay are most critical. All together eight parameters were assessed by using liver samples of untreated animals. In addition, two of those parameters (temperature and storage time of liver before embedding into agarose) were further investigated in animals given a single oral dose of ethyl methanesulfonate at dose levels of 50, 100, and 200 mg/kg, 3 hr prior to necropsy. The results showed that sample cooling emerged as the predominant influence factor, whereas variations in other elements of the procedure (e.g., size of the liver piece sampled, time needed to process the liver tissue post-mortem, agarose temperature, or time of lysis) seem to be of little relevance. Storing of liver samples of up to 6 hr under cooled conditions did not cause an increase in tail intensity. In contrast, storing the tissue at room temperature, resulted in a considerable time-dependent increase in comet parameters. Copyright © 2013 Wiley Periodicals, Inc.

The Use of Bacterial Repair Endonucleases in the Comet Assay.

PubMed

Collins, Andrew R

2017-01-01

The comet assay is a sensitive electrophoretic method for measuring DNA breaks at the level of single cells, used widely in genotoxicity experiments, in biomonitoring, and in fundamental research. Its sensitivity and range of application are increased by the incorporation of an extra step, after lysis of agarose-embedded cells, in which the DNA is digested with lesion-specific endonucleases (DNA repair enzymes of bacterial or phage origin). Enzymes with specificity for oxidized purines, oxidized pyrimidines, alkylated bases, UV-induced cyclobutane pyrimidine dimers, and misincorporated uracil have been employed. The additional enzyme-sensitive sites, over and above the strand breaks detected in the standard comet assay, give a quantitative estimate of the number of specific lesions present in the cells.

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

PubMed

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

2014-01-01

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

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

PubMed

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.

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

PubMed

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

2014-09-01

Early detection and quantification of DNA damage in oral premalignancy or malignancy may help in management of the disease and improve survival rates. The comet assay has been successfully utilised to detect DNA damage in oral premalignant or malignancy. However, due to the invasive nature of collecting blood, it may be painful for many unwilling patients. This study compares the micronucleus (MN) assay in oral buccal mucosa cells with the comet assay in peripheral blood cells in a subset of oral habit-induced precancer and cancer patients. For this, MN assay of exfoliated epithelial cells was compared with comet assay of peripheral blood leucocytes among 260 participants, including those with oral lichen planus (OLP; n = 52), leukoplakia (LPK; n = 51), oral submucous fibrosis (OSF; n = 51), oral squamous cell carcinoma (OSCC; n = 54) and normal volunteers (n = 52). Among the precancer groups, LPK patients showed significantly higher levels of DNA damage as reflected by both comet tail length (P < 0.0001) and micronuclei (MNi) frequency (P = 0.0009). The DNA damage pattern in precancer and cancer patients was OLP < OSF < LPK < OSCC, and with respective oral habits, it was multiple habits > cigarette + khaini > cigarette smokers > areca + khaini > areca. There was no significant difference in the comet length and MNi frequency between males and females who had oral chewing habits. An overall significant correlation was observed between MNi frequency and comet tail length with r = 0.844 and P < 0.0001. Thus, the extent of DNA damage evaluation by the comet assay in peripheral blood cells is perfectly reflected by the MN assay on oral exfoliated epithelial cells, and MNi frequency can be used with the same effectiveness and greater efficiency in early detection of oral premalignant conditions. © The Author 2014. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comet Assay on Daphnia magna in eco-genotoxicity testing.

PubMed

Pellegri, Valerio; Gorbi, Gessica; Buschini, Annamaria

2014-10-01

Detection of potentially hazardous compounds in water bodies is a priority in environmental risk assessment. For the evaluation and monitoring of water quality, a series of methodologies may be applied. Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the most powerful. In recent years, some attempts were made to utilize Daphnia magna in genotoxicity testing as many of the new environmental contaminants are described as DNA-damaging agents in aquatic organisms. The aim of this research was to develop a highly standardized protocol of the Comet Assay adapted for D. magna, especially regarding the isolation of cells derived from the same tissue (haemolymph) from newborn organisms exposed in vivo. Several methods for haemolymph extraction and different Comet Assay parameters were compared. Electrophoretic conditions were adapted in order to obtain minimum DNA migration in cells derived from untreated organisms and, at the same time, maximum sensitivity in specimens treated with known genotoxicants (CdCl2 and H2O2). Additional tests were performed to investigate if life-history traits of the cladoceran (such as the age of adult organisms that provide newborns, the clutch size of origin, the number of generations reared in standard conditions) and the water composition as well, might influence the response of the assay. This study confirms the potential application of the Comet Assay in D. magna for assessing genotoxic loads in aqueous solution. The newly developed protocol could integrate the acute toxicity bioassay, thus expanding the possibility of using this model species in freshwater monitoring (waters, sediment and soil elutriates) and is in line with the spirit of the EU Water Framework Directive in reducing the number of bioassays that involve medium-sized species. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed

Speit, Günter; Schütz, Petra; Bausinger, Julia

2016-06-01

The comet assay in combination with the polymerase inhibitor aphidicolin (APC) has been used to measure DNA excision repair activity, DNA repair kinetics and individual DNA repair capacity. Since APC can enhance genotoxic effects of mutagens measured by the comet assay, this approach has been proposed for increasing the sensitivity of the comet assay in human biomonitoring. The APC-modified comet assay has mainly been performed with human blood and it was shown that it not only enhances the detection of DNA damage repaired by nucleotide excision repair (NER) but also damage typically repaired by base excision repair (BER). Recently, we reported that in contrast to blood leukocytes, A549 cells (a human lung adenocarcinoma cell line) seem to be insensitive towards the repair-inhibiting action of APC. To further elucidate the general usefulness of the APC-modified comet assay for studying repair in cultured mammalian cells, we comparatively investigated further cell lines (HeLa, TK6, V79). DNA damage was induced by BPDE (benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide) and MMS (methyl methanesulfonate) in the absence and presence of APC (3 or 15μM). APC was either added for 2h together with the mutagen or cells were pre-incubated for 30min with APC before the mutagen was added. The results indicate that the cell lines tested differ fundamentally with regard to their sensitivity and specificity towards the repair-inhibiting effect of APC. The actual cause for these differences is still unclear but potential molecular explanations are discussed. Irrespective of the underlying mechanism(s), our study revealed practical limitations of the use of the APC-modified comet assay. Copyright © 2016 Elsevier B.V. All rights reserved.

Comprehensive Profiling of Radiosensitive Human Cell Lines with DNA Damage Response Assays Identifies the Neutral Comet Assay as a Potential Surrogate for Clonogenic Survival

PubMed Central

Nahas, Shareef A.; Davies, Robert; Fike, Francesca; Nakamura, Kotoka; Du, Liutao; Kayali, Refik; Martin, Nathan T.; Concannon, Patrick; Gatti, Richard A.

2015-01-01

In an effort to explore the possible causes of human radiosensitivity and identify more rapid assays for cellular radiosensitivity, we interrogated a set of assays that evaluate cellular functions involved in recognition and repair of DNA double-strand breaks: (1) neutral comet assay, (2) radiation-induced γ-H2AX focus formation, (3) the temporal kinetics of structural maintenance of chromosomes 1 phosphorylation, (4) intra-S-phase checkpoint integrity, and (5) mitochondrial respiration. We characterized a unique panel of 19 “radiosensitive” human lymphoblastoid cell lines from individuals with undiagnosed diseases suggestive of a DNA repair disorder. Radiosensitivity was defined by reduced cellular survival using a clonogenic survival assay. Each assay identified cell lines with defects in DNA damage response functions. The highest concordance rate observed, 89% (17/19), was between an abnormal neutral comet assay and reduced survival by the colony survival assay. Our data also suggested that the neutral comet assay would be a more rapid surrogate for analyzing DNA repair/processing disorders. PMID:21962002

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

PubMed

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.

Detection of radiation treatment of beans using DNA comet assay

NASA Astrophysics Data System (ADS)

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

2002-03-01

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

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

PubMed

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

Evaluation of environmental genotoxicity by comet assay in Columba livia.

PubMed

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

2016-01-01

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

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

NASA Astrophysics Data System (ADS)

Khan, Hasan M.; Delincée, Henry

1998-06-01

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

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

PubMed

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.

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

PubMed Central

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

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

PubMed

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

2015-02-01

This paper presents an evaluation of the genotoxic effects of cadmium chloride (CdCl2 ) on marine gastropod, Nerita chamaeleon following the technique of comet assay and the DNA alkaline unwinding assay (DAUA). In this study, the extent of DNA damage in gill cells of N. chamaeleon was measured after in vivo exposure to four different concentrations (10, 25, 50, and 75 µg/L) of CdCl2 . In vitro exposure of hydrogen peroxide (H2 O2 ; 1, 10, 25, and 50 µM) of the gill cells showed a significant increase in the percentage tail DNA, Olive tail moment, and tail length (TL). Significant changes in percentage tail DNA by CdCl2 exposure were observed in all exposed groups of snails with respect to those in control. Exposure to 75 µg/L of CdCl2 produced significant decrease in DNA integrity as measured by DAUA at all duration with respect to control. In vivo exposure to different concentrations of CdCl2 (10, 25, 50, and 75 µg/L) to N. chamaeleon showed considerable increase in DNA damage as observed by both alkaline comet assay and the DAUA. The extent of DNA damage in marine gastropods determined by the application of alkaline comet assay and DAUA clearly indicated the genotoxic responses of marine gastropod, N. chamaeleon to a wide range of cadmium concentration in the marine environment. © 2013 Wiley Periodicals, Inc.

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

PubMed

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

2016-07-01

This study aimed to establish a protocol for cell dissociation from the nematode Caenorhabditis elegans (C. elegans) to assess the genotoxicity of the environmental pollutant benzo[a]pyrene (BaP) using the alkaline version of the single cell electrophoresis assay (comet assay). BaP genotoxicity was assessed in C. elegans (wild-type [WT]; N2, Bristol) after 48h exposure (0-40μM). Induction of comets by BaP was concentration-dependent up to 20μM; comet% tail DNA was ∼30% at 20μM BaP and ∼10% in controls. Similarly, BaP-induced DNA damage was evaluated in C. elegans mutant strains deficient in DNA repair. In xpa-1 and apn-1 mutants BaP-induced comet formation was diminished to WT background levels suggesting that the damage formed by BaP that is detected in the comet assay is not recognised in cells deficient in nucleotide and base excision repair, respectively. In summary, our study provides a protocol to evaluate DNA damage of environmental pollutants in whole nematodes using the comet assay. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1995-12-01

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 withmore » 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{sub 2} values, or [{sup 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.« less

Evaluation of sperm DNA quality in men presenting with testicular cancer and lymphoma using alkaline and neutral Comet assays.

PubMed

Kumar, K; Lewis, S; Vinci, S; Riera-Escamilla, A; Fino, M-G; Tamburrino, L; Muratori, M; Larsen, P; Krausz, C

2018-01-01

Despite more cancers in young men over the past two decades, improvements in therapies give a greater chance to live full lives following treatment. Sperm genomic quality is variable following cancer diagnosis, so its assessment is important if sperm cryopreservation is being considered. Here, we evaluated DNA damage using two DNA damage assays: an alkaline and for the first time, a neutral Comet assays in men presenting with testicular cancer (n = 19 for alkaline and 13 for neutral group) and lymphoma (n = 13 for alkaline and 09 for neutral group) compared with fertile donors (n = 20 for alkaline and 14 for neutral group). No significant differences were observed in any semen analysis parameters. In contrast, sperm DNA damage was higher in men with testicular cancer than in donors as assessed by both the alkaline (12.4% vs. 37.4%, p < 0.001) and neutral (7.5% vs. 13.4%; p < 0.05) Comet assays. Similar trends were observed in men with lymphoma. Here, sperm DNA damage was higher using both the alkaline (35.0% vs. 12.4%) and neutral (10.7% against 7.5% (p < 0.05) Comet assays. Moreover, the DNA strand breaks (particularly double-strand breaks) were significantly more prominent in men with cancer having abnormal seminal parameters than normozoospermic ones. This study showed that sperm DNA testing using alkaline and neutral Comet assays is more sensitive than semen analysis in detecting impaired sperm quality in men presenting with cancer. It may provide a useful adjunct when considering storage prior to cancer investigations and assisted reproductive techniques (ART)-based treatment. © 2017 American Society of Andrology and European Academy of Andrology.

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

PubMed Central

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

2014-01-01

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

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

PubMed

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

2015-07-01

As a part of an international validation of the in vivo rat alkaline comet assay (comet assay) initiated by the Japanese Center for the Validation of Alternative Methods (JaCVAM) we examined six chemicals for potential to induce DNA damage: 2-acetylaminofluorene (2-AAF), N-nitrosodimethylamine (DMN), o-anisidine, 1,2-dimethylhydrazine dihydrochloride (1,2-DMH), sodium chloride, and sodium arsenite. DNA damage was evaluated in the liver and stomach of 7- to 9-week-old male Sprague Dawley rats. Of the five genotoxic carcinogens tested in our laboratory, DMN and 1,2-DMH were positive in the liver and negative in the stomach, 2-AAF and o-anisidine produced an equivocal result in liver and negative results in stomach, and sodium arsenite was negative in both liver and stomach. 1,2-DMH and DMN induced dose-related increases in hedgehogs in the same tissue (liver) that exhibited increased DNA migration. However, no cytotoxicity was indicated by the neutral diffusion assay (assessment of highly fragmented DNA) or histopathology in response to treatment with any of the tested chemicals. Therefore, the increased DNA damage resulting from exposure to DMN and 1,2-DMH was considered to represent a genotoxic response. Sodium chloride, a non-genotoxic non-carcinogen, was negative in both tissues as would be predicted. Although only two (1,2-DMH and DMN) out of five genotoxic carcinogens produced clearly positive results in the comet assay, the results obtained for o-anisidine and sodium arsenite in liver and stomach cells are consistent with the known mode of genotoxicity and tissue specificity exhibited by these carcinogens. In contrast, given the known genotoxic mode-of-action and target organ carcinogenicity of 2-AAF, it is unclear why this chemical failed to convincingly increase DNA migration in the liver. Thus, the results of the comet assay validation studies conducted in our laboratory were considered appropriate for five out of the six test chemicals. Copyright © 2015

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

PubMed Central

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

2015-01-01

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. PMID:26212309

Evaluation of DNA damage in flight personnel by Comet assay.

PubMed

Cavallo, Delia; Tomao, Paola; Marinaccio, Alessandro; Perniconi, Barbara; Setini, Andrea; Palmi, Silvana; Iavicoli, Sergio

2002-04-26

There have been some suggestions that air-crew are at a higher-than-normal risk of developing cancer, since they are exposed to potential genotoxic factors. These include cosmic radiations, airborne pollutants such as the combustion products of jet propulsion, ozone, and electromagnetic fields. We used the Comet assay to investigate DNA damage in flight personnel with the aim of assessing potential health hazards in this occupational category. We studied 40 civil air-crew members who had been flying long-haul routes for at least 5 years, and compared them with a homogeneous control group of 40 healthy male ground staff. The Comet assay, or single-cell gel electrophoresis (SCGE), detects DNA single- and double-strand breaks (DSBs) and alkali-labile lesions in individual cells, and is a powerful and sensitive technique for detecting genetic damage induced by different genotoxic agents. Taking into consideration occupational risk and possible confounding factors, this assay showed a small increase, that did not reach statistical significance, of DNA damage in long-haul crew members compared to controls, indicating a lack of evident genotoxic effects. An association, although again not statistically significant, was found between reduced DNA damage and use of protective drugs (antioxidants).

DNA Damage among Wood Workers Assessed with the Comet Assay

PubMed Central

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

2016-01-01

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

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

PubMed

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

2015-12-01

14-Hydroxycodeinone (14-HC) is an α,β-unsaturated ketone impurity found in oxycodone drug substance and has a structural alert for genotoxicity. 14-HC was tested in a combined Modified and Standard Comet Assay to determine if the slight decrease in % Tail DNA noted in a previously conducted Standard Comet Assay with 14-HC could be magnified to clarify if the response was due to cross-linking activity. One limitation of the Standard Comet Assay is that DNA cross-links cannot be reliably detected. However, under certain modified testing conditions, DNA cross-links and chemical moieties that elicit such cross-links can be elucidated. One such modification involves the induction of additional breakages of DNA strands by gamma or X-ray irradiation. To determine if 14-HC is a DNA crosslinker in vivo, a Modified Comet Assay was conducted using X-ray irradiation as the modification to visualize crosslinking activity. In this assay, 14-HC was administered orally to mice up to 320 mg/kg/day. Results showed a statistically significant reduction in percent tail DNA in duodenal cells at 320 mg/kg/day, with a nonstatistically significant but dose-related reduction in percent tail DNA also observed at the mid dose of 160 mg/kg/day. Similar decreases were not observed in cells from the liver or stomach, and no increases in percent tail DNA were noted for any tissue in the concomitantly conducted Standard Comet Assay. Taken together, 14-HC was identified as a cross-linking agent in the duodenum in the Modified Comet Assay. © 2015 Wiley Periodicals, Inc.

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

PubMed Central

SOLANKY, DIPESH; HAYDEL, SHELLEY E.

2012-01-01

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

Recent Advances in In Vivo Genotoxicity Testing: Prediction of Carcinogenic Potential Using Comet and Micronucleus Assay in Animal Models

PubMed Central

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

2013-01-01

Genotoxic events have been known as crucial step in the initiation of cancer. To assess the risk of cancer, genotoxicity assays, including comet, micronucleus (MN), chromosomal aberration, bacterial reverse, and sister chromatid exchange assay, can be performed. Compared with in vitro genotoxicity assay, in vivo genotoxicity assay has been used to verify in vitro assay result and definitely provide biological significance for certain organs or cell types. The comet assay can detect DNA strand breaks as markers of genotoxicity. Methods of the in vivo comet assay have been established by Japanese Center for the Validation of Alternative Methods (JaCVAM) validation studies depending on tissue and sample types. The MN can be initiated by segregation error and lagging acentric chromosome fragment. Methods of the in vivo MN assay have been established by Organization for Economic Co-operation and Development (OECD) test guidelines and many studies. Combining the in vivo comet and MN assay has been regarded as useful methodology for evaluating genetic damage, and it has been used in the assessment of potential carcinogenicity by complementarily presenting two distinct endpoints of the in vivo genotoxicity individual test. Few studies have investigated the quantitative relation between in vivo genotoxicity results and carcinogenicity. Extensive studies emphasizes that positive correlation is detectable. This review summarizes the results of the in vivo comet and MN assays that have investigated the genotoxicity of carcinogens as classified by the International Agency for Research on Cancer (IARC) carcinogenicity database. As a result, these genotoxicity data may provide meaningful information for the assessment of potential carcinogenicity and for implementation in the prevention of cancer. PMID:25337557

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

PubMed

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

2016-11-01

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

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

PubMed Central

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

2013-01-01

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

Application of DNA comet assay for detection of radiation treatment of grams and pulses.

PubMed

Khan, Hasan M; Khan, Ashfaq A; Khan, Sanaullah

2011-12-01

Several types of whole pulses (green lentils, red lentils, yellow lentils, chickpeas, green peas, cowpeas and yellow peas) and grams (black grams, red grams and white grams) have been investigated for the identification of radiation treatment using microgel electrophoresis of single cells (DNA comet assay). Pulses and grams were exposed to the radiation doses of 0.5, 1.0 and 5 kGy covering the legalized commercial dose range for protection from insect/pest infestations. All irradiated samples showed comet like stretching of fragmented DNA toward anode, which is expected for irradiated samples. Unirradiated samples showed many intact cells/nuclei in form of round stains or with short faint tails, which is typical for unirradiated food samples. The study shows that DNA comet assay can be used as a rapid, inexpensive and highly effective screening test for the detection of radiation treatment of foods, like pulses and grams.

Genotoxicity of TiO2 nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry

PubMed Central

Di Bucchianico, Sebastiano; Cappellini, Francesca; Le Bihanic, Florane; Zhang, Yuning; Dreij, Kristian; Karlsson, Hanna L.

2017-01-01

The widespread production and use of nanoparticles calls for faster and more reliable methods to assess their safety. The main aim of this study was to investigate the genotoxicity of three reference TiO2 nanomaterials (NM) within the frame of the FP7-NANoREG project, with a particular focus on testing the applicability of mini-gel comet assay and micronucleus (MN) scoring by flow cytometry. BEAS-2B cells cultured under serum-free conditions were exposed to NM100 (anatase, 50–150nm), NM101 (anatase, 5–8nm) and NM103 (rutile, 20–28nm) for 3, 24 or 48h mainly at concentrations 1–30 μg/ml. In the mini-gel comet assay (eight gels per slide), we included analysis of (i) DNA strand breaks, (ii) oxidised bases (Fpg-sensitive sites) and (iii) light-induced DNA damage due to photocatalytic activity. Furthermore, MN assays were used and we compared the results of more high-throughput MN scoring with flow cytometry to that of cytokinesis-block MN cytome assay scored manually using a microscope. Various methods were used to assess cytotoxic effects and the results showed in general no or low effects at the doses tested. A weak genotoxic effect of the tested TiO2 materials was observed with an induction of oxidised bases for all three materials of which NM100 was the most potent. When the comet slides were briefly exposed to lab light, a clear induction of DNA strand breaks was observed for the anatase materials, but not for the rutile. This highlights the risk of false positives when testing photocatalytically active materials if light is not properly avoided. A slight increase in MN formation for NM103 was observed in the different MN assays at the lower doses tested (1 and 5 μg/ml). We conclude that mini-gel comet assay and MN scoring using flow cytometry successfully can be used to efficiently study cytotoxic and genotoxic properties of nanoparticles. PMID:27382040

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

PubMed

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

2008-05-01

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

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

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Identification of irradiated refrigerated pork with the DNA comet assay

NASA Astrophysics Data System (ADS)

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

2004-09-01

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

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

PubMed

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

2015-07-01

As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay, 4,4'-diaminodiphenyl ether (DPE), a known rodent genotoxic carcinogen, was tested in this laboratory. Sprague Dawley rats (7-9 weeks of age) were given three oral doses of DPE, 24 and 21 h apart and liver or stomach sampled 3h after the final dose. Under the conditions of the test, no increases in DNA damage in liver and stomach were observed with DPE (up to 200 mg/kg/day). A dose-dependent decrease in DNA migration, compared to vehicle controls, was noted for DPE in rat stomach. Further analysis is required to elucidate fully whether this decrease is a consequence of the mode of action or due to the toxicity of DPE. What is perhaps surprising is the inability of the comet assay to detect a known rat genotoxic carcinogen in liver. Further investigation is needed to clarify whether this apparent lack of response results from limited tissue exposure or metabolic differences between species. This finding highlights a need for careful consideration of study design when evaluating assay performance as a measure of in vivo genotoxicity. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2011-01-01

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

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

PubMed

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.

Centered reduced moments and associate density functions applied to alkaline comet assay.

PubMed

Castaneda, Roman; Pelaez, Alejandro; Marquez, Maria-Elena; Abad, Pablo

2005-01-01

The single cell gel electrophoresis assay is a sensitive, rapid, and visual technique for deoxyribonucleic acid (DNA) strand-break detection in individual mammalian cells, whose application has significantly increased in the past few years. The cells are embedded in agarose on glass slides followed by lyses of the cell membrane. Thereafter, damaged DNA strands are electrophoresed away from the nucleus towards the anode giving the appearance of a comet tail. Nowadays, charge coupled device cameras are attached at optical microscopes for recording the images of the cells, and digital image processing is applied for obtaining quantitative descriptors. However, the conventional software is usually expensive, inflexible and, in many cases, can only provide low-order descriptors based in image segmentation, determination of centers of mass, and Euclidean distances. Associated density functions and centered reduced moments offer an effective and flexible alternative for quantitative analysis of the comet cells. We will show how the position of the center of mass, the lengths and orientation of the main semiaxes, and the eccentricity of such images can be accurately determined by this method.

Automated detection of irradiated food with the comet assay.

PubMed

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

2008-01-01

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

Genotoxicity of TiO2 nanoparticles assessed by mini-gel comet assay and micronucleus scoring with flow cytometry.

PubMed

Di Bucchianico, Sebastiano; Cappellini, Francesca; Le Bihanic, Florane; Zhang, Yuning; Dreij, Kristian; Karlsson, Hanna L

2017-01-01

The widespread production and use of nanoparticles calls for faster and more reliable methods to assess their safety. The main aim of this study was to investigate the genotoxicity of three reference TiO 2 nanomaterials (NM) within the frame of the FP7-NANoREG project, with a particular focus on testing the applicability of mini-gel comet assay and micronucleus (MN) scoring by flow cytometry. BEAS-2B cells cultured under serum-free conditions were exposed to NM100 (anatase, 50-150nm), NM101 (anatase, 5-8nm) and NM103 (rutile, 20-28nm) for 3, 24 or 48h mainly at concentrations 1-30 μg/ml. In the mini-gel comet assay (eight gels per slide), we included analysis of (i) DNA strand breaks, (ii) oxidised bases (Fpg-sensitive sites) and (iii) light-induced DNA damage due to photocatalytic activity. Furthermore, MN assays were used and we compared the results of more high-throughput MN scoring with flow cytometry to that of cytokinesis-block MN cytome assay scored manually using a microscope. Various methods were used to assess cytotoxic effects and the results showed in general no or low effects at the doses tested. A weak genotoxic effect of the tested TiO 2 materials was observed with an induction of oxidised bases for all three materials of which NM100 was the most potent. When the comet slides were briefly exposed to lab light, a clear induction of DNA strand breaks was observed for the anatase materials, but not for the rutile. This highlights the risk of false positives when testing photocatalytically active materials if light is not properly avoided. A slight increase in MN formation for NM103 was observed in the different MN assays at the lower doses tested (1 and 5 μg/ml). We conclude that mini-gel comet assay and MN scoring using flow cytometry successfully can be used to efficiently study cytotoxic and genotoxic properties of nanoparticles. © The Author 2016. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society.

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

PubMed

Martins, Marta; Costa, Pedro M

2015-01-01

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

Monitoring regulation of DNA repair activities of cultured cells in-gel using the comet assay

PubMed Central

Nickson, Catherine M.; Parsons, Jason L.

2014-01-01

Base excision repair (BER) is the predominant cellular mechanism by which human cells repair DNA base damage, sites of base loss, and DNA single strand breaks of various complexity, that are generated in their thousands in every human cell per day as a consequence of cellular metabolism and exogenous agents, including ionizing radiation. Over the last three decades the comet assay has been employed in scientific research to examine the cellular response to these types of DNA damage in cultured cells, therefore revealing the efficiency and capacity of BER. We have recently pioneered new research demonstrating an important role for post-translational modifications (particularly ubiquitylation) in the regulation of cellular levels of BER proteins, and that subtle changes (∼20–50%) in protein levels following siRNA knockdown of E3 ubiquitin ligases or deubiquitylation enzymes can manifest in significant changes in DNA repair capacity monitored using the comet assay. For example, we have shown that the E3 ubiquitin ligase Mule, the tumor suppressor protein ARF, and the deubiquitylation enzyme USP47 modulate DNA repair by controlling cellular levels of DNA polymerase β, and also that polynucleotide kinase phosphatase levels are controlled by ATM-dependant phosphorylation and Cul4A–DDB1–STRAP-dependent ubiquitylation. In these studies we employed a modification of the comet assay whereby cultured cells, following DNA damage treatment, are embedded in agarose and allowed to repair in-gel prior to lysis and electrophoresis. Whilst this method does have its limitations, it avoids the extensive cell culture-based processing associated with the traditional approach using attached cells and also allows for the examination of much more precise DNA repair kinetics. In this review we will describe, using this modified comet assay, our accumulating evidence that ubiquitylation-dependant regulation of BER proteins has important consequences for overall cellular DNA repair

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

PubMed

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

2012-10-09

The assessment of tumor radiosensitivity would be particularly useful in optimizing the radiation dose during radiotherapy. Therefore, the degree of correlation between radiation-induced DNA damage, as measured by the alkaline and the neutral comet assays, and the clonogenic survival of different human tumor cells was studied. Further, tumor radiosensitivity was compared with the expression of genes associated with the cellular response to radiation damage. Five different human tumor cell lines were chosen and the radiosensitivity of these cells was established by clonogenic assay. Alkaline and neutral comet assays were performed in γ-irradiated cells (2-8Gy; either acute or fractionated). Quantitative PCR was performed to evaluate the expression of DNA damage response genes in control and irradiated cells. The relative radiosensitivity of the cell lines assessed by the extent of DNA damage (neutral comet assay) immediately after irradiation (4Gy or 6Gy) was in agreement with radiosensitivity pattern obtained by the clonogenic assay. The survival fraction of irradiated cells showed a better correlation with the magnitude of DNA damage measured by the neutral comet assay (r=-0.9; P<0.05; 6Gy) than evaluated by alkaline comet assay (r=-0.73; P<0.05; 6Gy). Further, a significant correlation between the clonogenic survival and DNA damage was observed in cells exposed to fractionated doses of radiation. Of 15 genes investigated in the gene expression study, HSP70, KU80 and RAD51 all showed significant positive correlations (r=0.9; P<0.05) with tumor radiosensitivity. Our study clearly demonstrated that the neutral comet assay was better than alkaline comet assay for assessment of radiosensitivities of tumor cells after acute or fractionated doses of irradiation. © 2012 Elsevier B.V. All rights reserved.

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

PubMed

McNamee, J P; Bellier, P V

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), our laboratory examined ampicillin trihydrate (AMP), 1,2-dimethylhydrazine dihydrochloride (DMH), and N-nitrosodimethylamine (NDA) using a standard comet assay validation protocol (v14.2) developed by the JaCVAM validation management team (VMT). Coded samples were received by our laboratory along with basic MSDS information. Solubility analysis and range-finding experiments of the coded test compounds were conducted for dose selection. Animal dosing schedules, the comet assay processing and analysis, and statistical analysis were conducted in accordance with the standard protocol. Based upon our blinded evaluation, AMP was not found to exhibit evidence of genotoxicity in either the rat liver or stomach. However, both NDA and DMH were observed to cause a significant increase in % tail DNA in the rat liver at all dose levels tested. While acute hepatoxicity was observed for these compounds in the high dose group, in the investigators opinion there were a sufficient number of consistently damaged/measurable cells at the medium and low dose groups to judge these compounds as genotoxic. There was no evidence of genotoxicity from either NDA or DMH in the rat stomach. In conclusion, our laboratory observed increased DNA damage from two blinded test compounds in rat liver (later identified as genotoxic carcinogens), while no evidence of genotoxicity was observed for the third blinded test compound (later identified as a non-genotoxic, non-carcinogen). This data supports the use of a standardized protocol of the in vivo comet assay as a cost-effective alternative genotoxicity assay for regulatory testing purposes. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

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

PubMed

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

2011-09-01

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

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

PubMed

Bausinger, Julia; Speit, Günter

2014-11-01

The comet assay is widely used in human biomonitoring to measure DNA damage in whole blood or isolated peripheral blood mononuclear cells (PBMC) as a marker of exposure to genotoxic agents. Cytogenetic assays with phytohemagglutinin (PHA)-stimulated cultured T lymphocytes are also frequently performed in human biomonitoring. Cytogenetic effects (micronuclei, chromosome aberrations, sister chromatid exchanges) may be induced in vivo but also occur ex vivo during the cultivation of lymphocytes as a consequence of DNA damage present in lymphocytes at the time of sampling. To better understand whether DNA damage measured by the comet assay in PBMC is representative for DNA damage in T cells, we comparatively investigated DNA damage and its repair in PBMC and T cells obtained by immunomagnetic cell sorting. PBMC cultures and T cell cultures were exposed to mutagens with different modes of genotoxic action and DNA damage was measured by the comet assay after the end of a 2h exposure and after 18h post-incubation. The mutagens tested were methyl methanesulfonate (MMS), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), 4-nitroquinoline-1-oxide (4NQO), styrene oxide and potassium bromate. MMS and potassium bromate were also tested by the modified comet assay with formamido pyrimidine glycosylase (FPG) protein. The results indicate that the mutagens tested induce DNA damage in PBMC and T cells in the same range of concentrations and removal of induced DNA lesions occurs to a comparable extent. Based on these results, we conclude that the comet assay with PBMC is suited to predict DNA damage and its removal in T cells. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2014-01-01

We used a mouse model in which sperm DNA damage was induced to understand the relationship of double-stranded DNA (dsDNA) breaks to sperm chromatin structure and to the Comet assay. Sperm chromatin fragmentation (SCF) produces dsDNA breaks located on the matrix attachment regions, between protamine toroids. In this model, epididymal sperm induced to undergo SCF can religate dsDNA breaks while vas deferens sperm cannot. Here, we demonstrated that the conventional neutral Comet assay underestimates the epididymal SCF breaks because the broken DNA ends remain attached to the nuclear matrix, causing the DNA to remain associated with the dispersion halo, and the Comet tails to be weak. Therefore, we term these hidden dsDNA breaks. When the Comet assay was modified to include an additional incubation with sodium dodecyl sulfate (SDS) and dithiothreitol (DTT) after the conventional lysis, thereby solubilizing the nuclear matrix, the broken DNA was released from the matrix, which resulted in a reduction of the sperm head halo and an increase in the Comet tail length, exposing the hidden dsDNA breaks. Conversely, SCF-induced vas deferens sperm had small halos and long tails with the conventional neutral Comet assay, suggesting that the broken DNA ends were not tethered to the nuclear matrix. These results suggest that the attachment to the nuclear matrix is crucial for the religation of SCF-induced DNA breaks in sperm. Our data suggest that the neutral Comet assay identifies only dsDNA breaks that are released from the nuclear matrix and that the addition of an SDS treatment can reveal these hidden dsDNA breaks. PMID:24282283

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

PubMed

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

2014-04-01

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

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

PubMed

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

2015-07-01

The in vivo rodent alkaline comet assay (comet assay) is a promising technique to evaluate DNA damage in vivo. However, there is no agreement on a method to evaluate DNA damage in organs where cytotoxicity is observed. As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the comet assay, we examined DNA damage in the liver, stomach, and bone marrow of rats given three oral doses of N-methyl-N-nitrosourea (MNU) up to the maximum tolerated dose based on systemic toxicity. MNU significantly increased the % tail DNA in all the organs. Histopathological analysis showed no cytotoxic effect on the liver, indicating clearly that MNU has a genotoxic potential in the liver. In the stomach, however, the cytotoxic effects were very severe at systemically non-toxic doses. Low-dose MNU significantly increased the % tail DNA even at a non-cytotoxic dose, indicating that MNU has a genotoxic potential also in the stomach. Part of the DNA damage at cytotoxic doses was considered to be a secondary effect of severe cell damage. In the bone marrow, both the % tail DNA and incidence of micronucleated polychromatic erythrocytes significantly increased at non-hematotoxic doses, which were different from the non-cytotoxic doses for liver and stomach. These findings indicate that an optimal dose for detecting DNA damage may vary among organs and that careful attention is required to select an optimum dose for the comet assay based on systemic toxicity such as mortality and clinical observations. The present study shows that when serious cytotoxicity is suggested by increased % hedgehogs in the comet assay, histopathological examination should be included for the evaluation of a positive response. Copyright © 2015 Elsevier B.V. All rights reserved.

Comet assay: a prognostic tool for DNA integrity assessment in infertile men opting for assisted reproduction.

PubMed

Shamsi, M B; Venkatesh, S; Tanwar, M; Singh, G; Mukherjee, S; Malhotra, N; Kumar, R; Gupta, N P; Mittal, S; Dada, R

2010-05-01

The growing concern on transmission of genetic diseases in assisted reproduction technique (ART) and the lacunae in the conventional semen analysis to accurately predict the semen quality has led to the need for new techniques to identify the best quality sperm that can be used in assisted procreation techniques. This study analyzes the sperm parameters in the context of DNA damage in cytogenetically normal, AZF non deleted infertile men for DNA damage by comet assay. Seventy infertile men and 40 fertile controls were evaluated for the semen quality by conventional semen parameters and the sperms were also analyzed for DNA integrity by comet assay. The patients were classified into oligozoospermic (O), asthenozoospermic (A), teratozoospermic (T), oligoasthenoteratozoospermic (OAT) categories and infertile men with normal semen profile. The extent of DNA damage was assessed by visual scoring method of comets. Idiopathic infertile men with normal semen profile (n=18) according to conventional method and patients with history of spontaneous abortions and normal semen profile (n=10) had high degree of DNA damage (29 and 47% respectively) as compared to fertile controls (7%). The O, A, T and OAT categories of patients had a variably higher DNA damage load as compared to fertile controls. The normal range and threshold for DNA damage as a predictor of male fertility potential and technique which could assess the sperm DNA damage are necessary to lower the trauma of couples experiencing recurrent spontaneous abortion or failure in ART.

Genotoxicity of citrate-coated silver nanoparticles to human keratinocytes assessed by the comet assay and cytokinesis blocked micronucleus assay.

PubMed

Bastos, V; Duarte, I F; Santos, C; Oliveira, H

2017-02-01

Silver nanoparticles (AgNPs) are widely used in industrial, cosmetic, and biomedical products, and humans are frequently exposed to these products through the skin. It is widely recognized that the characteristics of AgNPs (e.g., size, coating) may influence their cytotoxic effects, but their correlation with DNA damage and mitotic disorders remains poorly explored. In this study, human keratinocytes (HaCaT cell line) were exposed to well-characterized 30 nm AgNPs coated with citrate, and their effects on viability, DNA fragmentation (assessed by the comet assay), and micronuclei (MNi) induction (assessed by the cytokinesis-block micronucleus cytome assays, CBMN) were investigated. The results showed that 10 and 40 μg/mL AgNPs decreased cell proliferation and viability, and induced a significant genetic damage. This was observed by an increase of DNA amount in comet tail, which linearly correlated with dose and time of exposure. Also, cytostaticity (increase of mononucleated cells) and MNi rates increased in treated cells. In contrast, no significant changes were observed in nucleoplasmatic bridges (NPBs) or nuclear buds (NBUDs), although NBUDs tended to increase in all conditions and periods. The cytostatic effects on HaCaT cells were also shown by the decrease of their nuclear division index. Thus, both comet and CBMN assays supported the observation that citrate-AgNPs induced genotoxic effects on HaCaT cells. Considering that AgNPs are present in a vast number of consumer products and also in multiple nanomedicine skin applications and formulations, more research is needed to determine the properties that confer less toxicity of AgNPs to different cell lines.

15 years of comet photometry: A comparative analysis of 80 comets

NASA Technical Reports Server (NTRS)

Osip, David J.; Schleicher, David G.; Millis, Robert L.; Hearn, M. F. A.; Birch, P. V.

1992-01-01

In 1976 we began a program of narrowband photometry of comets that has encompassed well over 400 nights of observations. To date, the program has provided detailed information on 80 comets, 11 of which have been observed on multiple apparitions. In this paper we present the observed range of compositions (molecular production rate ratios) and dustiness (gas production compared with AF-rho) for a well sampled group of comets. Based on these results we present preliminary analysis of taxonomic groupings as well as the abundance ratios we associate with a 'typical' comet.

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

PubMed

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

2014-07-15

The in vivo comet assay has been used for the evaluation of DNA damage and repair in various tissues of rodents. However, it can give false-positive results due to non-specific DNA damage associated with cell death. In this study, we examined whether the in vivo comet assay can distinguish between genotoxic and non-genotoxic DNA damage in urinary bladder cells, by using the following seven chemicals related to urinary bladder carcinogenesis in rodents: N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), glycidol, 2,2-bis(bromomethyl)-1,3-propanediol (BMP), 2-nitroanisole (2-NA), benzyl isothiocyanate (BITC), uracil, and melamine. BBN, glycidol, BMP, and 2-NA are known to be Ames test-positive and they are expected to produce DNA damage in the absence of cytotoxicity. BITC, uracil, and melamine are Ames test-negative with metabolic activation but have the potential to induce non-specific DNA damage due to cytotoxicity. The test chemicals were administered orally to male Sprague-Dawley rats (five per group) for each of two consecutive days. Urinary bladders were sampled 3h after the second administration and urothelial cells were analyzed by the comet assay and subjected to histopathological examination to evaluate cytotoxicity. In the urinary bladders of rats treated with BBN, glycidol, and BMP, DNA damage was detected. In contrast, 2-NA induced neither DNA damage nor cytotoxicity. The non-genotoxic chemicals (BITC, uracil, and melamine) did not induce DNA damage in the urinary bladders under conditions where some histopathological changes were observed. The results indicate that the comet assay could distinguish between genotoxic and non-genotoxic chemicals and that no false-positive responses were obtained. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-12-01

Genotoxic data of substances which could be incorporated into food packaging are required by the European Food Safety Authority. Due to its antioxidant and antibacterial properties carvacrol is one of these compounds. This work aims to study for the first time the in vivo genotoxic effects produced in rats orally exposed to 81, 256 or 810 mg cavacrol/kg body weight (bw) at 0, 24 and 45 h. A combination of the micronucleus assay (OECD 474) in bone marrow and the standard (OECD 489) and enzyme-modified comet assay was used to determine the genotoxicity on cells isolated from stomach and liver of exposed animals. In addition, a histopathological study was performed on the assayed tissues, and also in the lungs due to the volatility of carvacrol. Direct analytical pyrolysis was used to search for carvacrol in viscera and to ensure that the compound reaches stomach and liver cells. Results from MN-comet assay revealed that carvacrol (81-810 mg/kg bw) did not induce in vivo genotoxicity or oxidative DNA damage in any of the tissues investigated. Moreover, no histopathological changes were observed. Altogether, these results suggest lack of genotoxicity of carvacrol and therefore its good profile for its potential application as food preservative. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

PubMed

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 < 0.05) concentration-dependent increase in the level of DNA-strand breaks and ROS formation in all of the metals investigated. To the best of our knowledge, we have utilized for the first time the alkaline comet assay to detect DNA-strand breaks in marine 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.

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

PubMed

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

2016-05-01

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

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

PubMed

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

2016-02-01

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

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

PubMed

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

2014-05-01

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

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

PubMed

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.

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

PubMed

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.

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

PubMed

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

2011-05-18

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

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

PubMed

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.

The impact of lymphocyte isolation on induced DNA damage in human blood samples measured by the comet assay.

PubMed

Bausinger, Julia; Speit, Günter

2016-09-01

The comet assay is frequently used in human biomonitoring for the detection of exposure to genotoxic agents. Peripheral blood samples are most frequently used and tested either as whole blood or after isolation of lymphocytes (i.e. peripheral blood mononuclear cells, PBMC). To investigate a potential impact of lymphocyte isolation on induced DNA damage in human blood samples, we exposed blood ex vivo to mutagens with different modes of genotoxic action. The comet assay was performed either directly with whole blood at the end of the exposure period or with lymphocytes isolated directly after exposure. In addition to the recommended standard protocol for lymphocyte isolation, a shortened protocol was established to optimise the isolation procedure. The results indicate that the effects of induced DNA strand breaks and alkali-labile sites induced by ionising radiation and alkylants, respectively, are significantly reduced in isolated lymphocytes. In contrast, oxidative DNA base damage (induced by potassium bromate) and stable bulky adducts (induced by benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide; BPDE) seem to be less affected. Our findings suggest that in vivo-induced DNA damage might also be reduced in isolated lymphocytes in comparison with the whole blood depending of the types of DNA damage induced. Because only small genotoxic effects can generally be expected in human biomonitoring studies with the comet assay after occupational and environmental exposure to genotoxic agents, any loss might be relevant and should be avoided. The possibility of such effects and their potential impact on variability of comet assay results in human biomonitoring should be considered when performing or evaluating such kind of studies. © The Author 2016. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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

PubMed

Dhawan, Alok; Bajpayee, Mahima; Parmar, Devendra

2009-02-01

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

Measurement of DNA damage in rat urinary bladder transitional cells: improved selective harvest of transitional cells and detailed Comet assay protocols.

PubMed

Wang, Amy; Robertson, John L; Holladay, Steven D; Tennant, Alan H; Lengi, Andrea J; Ahmed, S Ansar; Huckle, William R; Kligerman, Andrew D

2007-12-01

Urinary bladder transitional epithelium is the main site of bladder cancer, and the use of transitional cells to study carcinogenesis/genotoxicity is recommended over the use of whole bladders. Because the transitional epithelium is only a small fraction of the whole bladder, the alkaline single cell gel electrophoresis assay (Comet assay), which requires only a small number of cells per sample, is especially suitable for measuring DNA damage in transitional cells. However, existed procedures of cell collection did not yield transitional cells with a high purity, and pooling of samples was needed for Comet assay. The goal of this study was to develop an optimized protocol to evaluate DNA damage in the urinary bladder transitional epithelium. This was achieved by an enzymatic stripping method (trypsin-EDTA incubation plus gentle scraping) to selectively harvest transitional cells from rat bladders, and the use of the alkaline Comet assay to detect DNA strand breaks, alkaline labile sites, and DNA-protein crosslinks. Step by step procedures are reported here. Cells collected from a single rat bladder were sufficient for multiple Comet assays. With this new protocol, increases in DNA damage were detected in transitional cells after in vitro exposure to the positive control agents, hydrogen peroxide or formaldehyde. Repair of the induced DNA damage occurred within 4h. This indicated the capacity for DNA repair was maintained in the harvested cells. The new protocol provides a simple and inexpensive method to detect various types of DNA damage and to measure DNA damage repair in urinary bladder transitional cells.

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

EPA Science Inventory

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

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

PubMed Central

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

2016-01-01

-manual analysis software. Using this method, a cross-sectional study on 123 men showed no significant correlation between sperm concentration and sperm DNA damage, confirming the existence of hidden chromatin damage in men with apparently normal semen characteristics, and a significant correlation between percentage DNA in the tail and percentage of progressively motile spermatozoa. Finally, the use of DNA damage profiles helped to distinguish subjects between and within sperm concentration categories, and allowed a determination of the proportion of highly damaged cells. LIMITATIONS, REASONS FOR CAUTION The main limitations of the HT-COMET are the high, yet indispensable, investment in an automated liquid handling system and heating block to ensure accuracy, and the availability of an automated plate reading microscope and analysis software. WIDER IMPLICATIONS OF THE FINDINGS This standardized HT-COMET assay offers many advantages, including higher accuracy and evenness due to automation of sensitive steps, a 14.4-fold increase in sample analysis capacity, and an imaging and scoring time of 1 min/well. Overall, HT-COMET offers a decrease in total experimental time of more than 90%. Hence, this assay constitutes a more efficient option to assess sperm chromatin quality, paves the way to using this assay to screen large cohorts, and holds prognostic value for infertile patients. STUDY FUNDING/COMPETING INTEREST(S) Funded by the CIHR Institute of Human Development, Child and Youth Health (IHDCYH; RHF 100625). O.A. is a fellow supported by the Fonds de la Recherche du Québec - Santé (FRQS) and the CIHR Training Program in Reproduction, Early Development, and the Impact on Health (REDIH). B.R. is a James McGill Professor. The authors declare no conflicts of interest. PMID:26975326

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

PubMed

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

2016-05-01

Can we make the comet assay (single-cell gel electrophoresis) for human sperm a more accurate and informative high throughput assay? 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. 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. The study comprised two distinct components: a HT-COMET technical optimization section based on control versus DNAse treatment analyses ( ITALIC! 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. 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. 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-manual analysis software. Using this method, a cross-sectional study on 123 men showed no significant correlation between sperm concentration and sperm DNA

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

PubMed

Beevers, Carol; Henderson, Debbie; Lillford, Lucinda

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined sodium arsenite, thioacetamide, and diethanolamine. Using the JaCVAM approved study protocol version 14.2, each chemical was tested in male rats up to maximum tolerated dose levels and DNA damage in the liver and stomach was assessed approximately 3h after the final administration by gavage. Histopathology assessments of liver and stomach sections from the same animals were also examined for evidence of cytotoxicity or necrosis. No evidence of DNA damage was observed in the stomach of animals treated with sodium arsenite at 7.5, 15, or 30 mg/kg/day. However, equivocal findings were found in the liver, where increases in DNA migration were observed in two independent experiments, but not in all treated animals and not at the same dose levels. Thioacetamide caused an increase in DNA migration in the stomach of rats treated at 19, 38, and 75 mg/kg/day, but not in the liver, despite evidence of marked hepatotoxicity following histopathology assessments. No evidence of DNA damage was observed in the stomach or liver of animals treated with diethanolamine at 175, 350, or 700 mg/kg/day. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

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

PubMed

Jost, Petr; Svobodova, Hana; Stetina, Rudolf

2015-07-25

Sulfur mustard is a highly toxic chemical warfare agent with devastating impact on intoxicated tissues. DNA cross-links are probably the most toxic DNA lesions induced in the cell by sulfur mustard. The comet assay is a very sensitive method for measuring DNA damage. In the present study using the A-549 lung cell line, the comet assay protocol was optimized for indirect detection of DNA cross-links induced by sulfur mustard. The method is based on the additional treatment of the assayed cells containing cross-links with the chemical mutagen, styrene oxide. Alkali-labile adducts of styrene oxide cause DNA breaks leading to the formation of comets. A significant dose-dependent reduction of DNA migration of the comet's tail was found after exposing cells to sulfur mustard, indicative of the amount of sulfur mustard induced cross-links. The remarkable decrease of % tail DNA could be observed as early as 5min following exposure to sulfur mustard and the maximal effect was found after 30min, when DNA migration was reduced to the minimum. Sulfur mustard preincubated in culture medium without cells lost its ability to induce cross-links and had a half-life of about 15min. Pre-incubation longer than 30min does not lead to a significant increase in cross-links when applied to cells. However, the amount of cross-links is decreased during further incubation due to repair. The current modification of the comet assay provides a useful tool for detecting DNA cross-links induced by sulfur mustard and could be used for detection of other DNA cross-linking agents such as chemotherapeutic drugs. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

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

PubMed

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

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative International Validation Study of an in vivo rat alkaline comet assay, we examined 1,2-dibromoethane (DBE), p-anisidine (ASD), and o-anthranilic acid (ANT) to investigate the effectiveness of the comet assay in detecting genotoxic carcinogens. Each of the three test chemicals was administered to 5 male Sprague-Dawley rats per group by oral gavage at 48, 24, and 3h before specimen preparation. Single cells were collected from the liver and glandular stomach at 3h after the final dosing, and the specimens prepared from these two organs were subjected to electrophoresis under alkaline conditions (pH>13). The percentage of DNA intensity in the comet tail was then assessed using an image analysis system. A micronucleus (MN) assay was also conducted using these three test chemicals with the bone marrow (BM) cells collected from the same animals simultaneously used in the comet assay, i.e., combination study of the comet assay and BM MN assay. A genotoxic (Ames positive) rodent carcinogen, DBE gave a positive result in the comet assay in the present study, while a genotoxic (Ames positive) non-carcinogen, ASD and a non-genotoxic (Ames negative) non-carcinogen, ANT showed negative results in the comet assay. All three chemicals produced negative results in the BM MN assay. While the comet assay findings in the present study were consistent with those obtained from the rodent carcinogenicity studies for the three test chemicals, we consider the positive result in the comet assay for DBE to be particularly meaningful, given that this chemical produced a negative result in the BM MN assay. Therefore, the combination study of the comet assay and BM MN assay is a useful method to detect genotoxic carcinogens that are undetectable with the BM MN assay alone. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2014-01-01

Doxorubicin (DOX) is an antineoplastic drug effective against many human malignancies. DOX's clinical efficacy is greatly limited because of severe cardiotoxicity. To evaluate if DOX is genotoxic in the heart, ~7-week-old, male F344 rats were administered intravenously 1, 2, and 3 mg/kg bw DOX at 0, 24, 48, and 69 hr and the Comet assays in heart, liver, kidney, and testis and micronucleus (MN) assay in the peripheral blood (PB) erythrocytes using flow cytometry were conducted. Rats were euthanized at 72 hr and PB was removed for the MN assay and single cells were isolated from multiple tissues for the Comet assays. None of the doses of DOX induced a significant DNA damage in any of the tissues examined by the alkaline Comet assay. Contrastingly, the glycosylase enzymes-modified Comet assay showed a significant dose dependent increase in the oxidative DNA damage in the cardiac tissue (P ≤ 0.05). In the liver, only the top dose induced significant increase in the oxidative DNA damage (P ≤ 0.05). The histopathology showed no severe cardiotoxicity but non-neoplastic lesions were present in both untreated and treated samples. A severe toxicity likely occurred in the bone marrow because no viable reticulocytes could be screened for the MN assay. Gene expression profiling of the heart tissues showed a significant alteration in the expression of 11 DNA damage and repair genes. These results suggest that DOX is genotoxic in the heart and the DNA damage may be induced primarily via the production of reactive oxygen species. Copyright © 2013 Wiley Periodicals, Inc.

Genotoxic effects of the water-soluble fraction of heavy oil in the brackish/freshwater amphipod Quadrivisio aff. lutzi (Gammaridea) as assessed using the comet assay.

PubMed

Weber, Laura; Carvalho, Ligia; Sá, Natália; Silva, Viviane; Beraldini, Nathalia; Souza, Valderes; Conceição, Moisés

2013-05-01

Amphipod crustaceans have been widely used as invertebrate models in ecotoxicology due to their importance in the food chain. However, few studies have evaluated the genotoxic effects of pollutants in this model using the comet assay. The main obstacle to using amphipods in the comet assay is the difficulty in obtaining enough blood cells from a single individual. In this study, we evaluated the genotoxic effects of the water-soluble fraction (WSF) of heavy oil on the brackish/freshwater amphipod Quadrivisio aff. lutzi, which is common in the coastal lagoons of southeastern Brazil, using hemocytes obtained from single amphipods (without pooling) after optimizing hemolymph extraction. The comet assay revealed significantly higher DNA damage levels (2- to 6-fold higher) in treated amphipods compared to untreated ones with a sublethal concentration of 17.6 % of the WSF within 72 h of treatment. Two independent experiments confirmed an "up and down" pattern of DNA damage, measured as the % of DNA contained in the tail of the comets. Elevations in DNA damage levels were observed at the 6 and 48 h time points, while very low levels of DNA damage were observed at the 24 and 72 h time points. Furthermore, the comet assay revealed gender variability in the levels of DNA damage after short-term exposure.

DNA comet Giemsa staining for conventional bright-field microscopy.

PubMed

Osipov, Andreyan; Arkhangelskaya, Ekaterina; Vinokurov, Alexei; Smetaninа, Nadezhda; Zhavoronkov, Alex; Klokov, Dmitry

2014-04-10

This study was undertaken to evaluate the compatibility of Giemsa staining protocol with the comet assay. We showed, for the first time, that DNA comets can be visualized and analyzed using Giemsa staining. We generated DNA damage dose response curves for human peripheral blood lymphocytes exposed to X-ray radiation using the comet assay with either SybrGreen I or Giemsa stain. The dose response curves were fitted by linear regressions (R2>0.977). The SybrGreen I results showed only ~1.2-fold higher slope coefficient (method sensitivity) compared to the Giemsa results. The unexpectedly high sensitivity of Giemsa staining for the comet assay is due to the Romanowsky-Giemsa effect, the stain photo-stability and the higher resolution of bright-field imaging compared to fluorescence imaging. Our results demonstrate that Giemsa staining can effectively be used for measuring DNA damage by the comet assay. The low cost and availability of Giemsa stain makes this method affordable for any low budget research and will facilitate new applications of the comet assay in biology and medicine.

Sister chromatid exchange rate and alkaline comet assay scores in patients with ovarian cancer.

PubMed

Baltaci, Volkan; Kayikçioğlu, Fulya; Alpas, Idil; Zeyneloğlu, Hulusi; Haberal, Ali

2002-01-01

Sister chromatid exchange (SCE) frequencies were studied in patients with different types of ovarian malignancies and in healthy volunteers. The level of DNA damage in patients with ovarian malignancy and control subjects has also been studied by alkaline single cell gel electrophoresis (SCGE), also known as the comet assay. Peripheral blood was collected from 30 patients after histological confirmation of malignancy and 20 healthy female volunteers. The cells were evaluated according to their grade of damage. We found that the sister chromatid exchange frequencies of cancer cases were significantly greater than that of controls (P < 0.001). The frequency of exchange in chromosomal groups A, B, and C, which include chromosomes 1-12, was higher than that of the other chromosomal groups in both groups. Comparison of the results of the alkaline comet assay in patient and control subjects showed a significant difference in the number of damaged cells. The frequency of limited migrated and extensive migrated cells in the women with ovarian malignancies was higher than that of control women (P < 0.001). SCE and SCGE can be used successfully to monitor DNA damage in women with ovarian cancer.

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

PubMed

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

2015-12-01

Earthworms (Eisenia fetida) most suitable biological indicators of radioactive pollution. Radiation-induced lesions in DNA can be considered to be molecular markers for early effects of ionizing radiation. Gamma radiation produces a wide spectrum of DNA. Some of these lesions, i.e., DNA strand breaks and alkali labile sites can be detected by the single-cell gel electrophoresis (SCGE) or comet assay by measuring the migration of DNA from immobilized nuclear DNA. E. fetida were exposed to different doses of gamma radiation, i.e., 1, 5, 10, 20, 30, 40 and 50Gy, and comet assay was performed for all the doses along with control at 1, 3 and 5h post irradiation to evaluate the genotoxicity of gamma radiation in this organism. The DNA damage was measured as percentage of comet tail DNA. A significant increase in DNA damage was observed in samples exposed to 5Gy and above, and the increase in DNA damage was dose dependent i.e., DNA damage was increased with increased doses of radiation. The highest DNA damage was noticed at 1h post irradiation and gradually decreased with time, i.e., at 3 and 5h post irradiation. The present study reveals that gamma radiation induces DNA damage in E. fetida and the comet assay is a sensitive and rapid method for its detection to detect genotoxicity of gamma radiation. Copyright © 2015 Elsevier B.V. All rights reserved.

Genotoxicity of AMPA, the environmental metabolite of glyphosate, assessed by the Comet assay and cytogenetic tests.

PubMed

Mañas, F; Peralta, L; Raviolo, J; García Ovando, H; Weyers, A; Ugnia, L; Gonzalez Cid, M; Larripa, I; Gorla, N

2009-03-01

Formulations containing glyphosate are the most widely used herbicides in the world. AMPA is the major environmental breakdown product of glyphosate. The purpose of this study is to evaluate the in vitro genotoxicity of AMPA using the Comet assay in Hep-2 cells after 4h of incubation and the chromosome aberration (CA) test in human lymphocytes after 48h of exposition. Potential in vivo genotoxicity was evaluated through the micronucleus test in mice. In the Comet assay, the level of DNA damage in exposed cells at 2.5-7.5mM showed a significant increase compared with the control group. In human lymphocytes we found statistically significant clastogenic effect AMPA at 1.8mM compared with the control group. In vivo, the micronucleus test rendered significant statistical increases at 200-400mg/kg. AMPA was genotoxic in the three performed tests. Very scarce data are available about AMPA potential genotoxicity.

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

PubMed

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.

Assessment of DNA damage and repair efficiency in drug naïve schizophrenia using comet assay.

PubMed

Muraleedharan, Aparna; Menon, Vikas; Rajkumar, Ravi Philip; Chand, Parkash

2015-09-01

The etiology of schizophrenia continues to be confounding and elusive. Some knowledge gaps exist in the neurodegenerative theory of schizophrenia. Oxidative DNA damage and repair deficits are relevant to the mechanisms of neurodegeneration but have not been studied in drug naïve schizophrenia. The present study used the comet assay technique to study the extent of DNA damage in circulating peripheral lymphocytes of patients with drug naïve schizophrenia (n = 40) along with an age and gender matched control group (n = 40). We also assessed the DNA repair efficiency in cases following incubation in a nutrient medium. All the assayed comet parameters demonstrated significantly greater baseline DNA damage in cases in comparison to the controls except for head diameter (p < 0.001 for all significant results, p = 0.32 for head diameter). Gender, age and duration of illness (p = 0.21, 0.69 and 0.12 respectively for tail length) did not influence any of the parameters significantly. Significant decrease was noted in the comet tail length and percentage of DNA in comet tail (p < 0.001 for both) in cases following incubation suggesting that the DNA repair machinery was preserved. No difference in DNA repair efficiency was noted between the genders (p = 0.23 for tail length). Our findings confirm the presence of significant baseline DNA damage in schizophrenia even prior to the initiation of anti-psychotic treatment. Additionally, intact genomic repair efficiency was noted in this group as a whole. These results provide some evidence for oxidative DNA damage as molecular link underpinning neurodegeneration in drug naïve schizophrenia. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

PubMed

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

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM) international validation study of in vivo rat alkaline comet assays, we examined cadmium chloride, chloroform, and D,L-menthol under blind conditions as coded chemicals in the liver and stomach of Sprague-Dawley rats after 3 days of administration. Cadmium chloride showed equivocal responses in the liver and stomach, supporting previous reports of its poor mutagenic potential and non-carcinogenic effects in these organs. Treatment with chloroform, which is a non-genotoxic carcinogen, did not induce DNA damage in the liver or stomach. Some histopathological changes, such as necrosis and degeneration, were observed in the liver; however, they did not affect the comet assay results. D,L-Menthol, a non-genotoxic non-carcinogen, did not induce liver or stomach DNA damage. These results indicate that the comet assay can reflect genotoxic properties under blind conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2014-10-01

There is increased interest in the in vivo comet assay in rodents as a follow-up approach for determining the biological relevance of chemicals that are genotoxic in in vitro assays. This is partly because, unlike other assays, DNA damage can be assessed in this assay in virtually any tissue. Since background levels of DNA damage can vary with the species, tissue, and cell processing method, a robust historical control database covering multiple tissues is essential. We describe extensive vehicle and positive control data for multiple tissues from rats and mice. In addition, we report historical data from control and genotoxin-treated human blood. Technical issues impacting comet results are described, including the method of cell preparation and freezing. Cell preparation by scraping (stomach and other GI tract organs) resulted in higher % tail DNA than mincing (liver, spleen, kidney etc) or direct collection (blood or bone marrow). Treatment with the positive control genotoxicant, ethyl methanesulfonate (EMS) in rats and methyl methanesulfonate in mice, resulted in statistically significant increases in % tail DNA. Background DNA damage was not markedly increased when cell suspensions were stored frozen prior to preparing slides, and the outcome of the assay was unchanged (EMS was always positive). In conclusion, historical data from our laboratory for the in vivo comet assay for multiple tissues from rats and mice, as well as human blood show very good reproducibility. These data and recommendations provided are aimed at contributing to the design and proper interpretation of results from comet assays. © 2014 Wiley Periodicals, Inc.

The comet assay for the evaluation of genotoxic potential of landfill leachate.

PubMed

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

2012-01-01

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

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

PubMed Central

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

2012-01-01

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

ISO's analysis of Comet Hale-Bopp

NASA Astrophysics Data System (ADS)

1997-03-01

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

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

PubMed

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

2016-04-01

The incidence of chronic kidney disease (CKD) is increasing rapidly. Diabetes mellitus (DM) is the most important cause of CKD. We studied the possible role of DM in CKD patients with respect to DNA damage, as assessed by the comet assay in 60 CKD patients (with or without DM) undergoing hemodialysis and in 26 controls. Effects of other factors, such as age, sex, hypertension, duration of hemodialysis, body mass index (BMI), and levels of hemoglobin (HB), intact parathormone (iPTH), and ferritin (FER), were also examined. Primary DNA damage measured by the comet assay was significantly higher in CKD patients than in controls. Among CKD patients, the following correlations were observed. (1) There was no difference in comet tail length or tail intensity between diabetic and non-diabetic individuals. (2) Age, sex, hemoglobin, hypertension, duration of hemodialysis, and ferritin levels affected neither tail length nor intensity. (3) BMI values above 25kg/m(2) and iPTH levels above 300pg/ml were associated with significantly greater comet tail length. Our results indicate that primary DNA damage is increased in CKD patients undergoing hemodialysis, compared to controls; however, DM had no additional effect. Copyright © 2016. Published by Elsevier B.V.

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

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Hummingbird Comet Nucleus Analysis Mission

NASA Technical Reports Server (NTRS)

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

2000-01-01

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

Autonomous Onboard Science Data Analysis for Comet Missions

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Evaluation of genotoxic effects of lead in pottery-glaze workers using micronucleus assay, alkaline comet assay and DNA diffusion assay.

PubMed

Kašuba, V; Rozgaj, R; Milić, M; Zelježić, D; Kopjar, N; Pizent, A; Kljaković-Gašpić, Z; Jazbec, A

2012-10-01

We investigated genotoxic effects of occupational exposure to lead acetate in pottery-glaze ceramic workers. The study was carried out in 30 exposed workers and 30 matched controls, to whom several biochemical parameters-the blood lead (B-Pb; range: exposed, 41.68-404.77; controls, 12-52) and cadmium (B-Cd) level, the activity of delta-aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin (EP), the level of vitamin B(12) and folate in serum-were measured. The genotoxic effects were evaluated by the alkaline comet assay, the DNA diffusion assay and micronucleus test in peripheral blood lymphocytes. Subjects exposed to lead had significantly higher B-Pb level and, consequently, increased values of tail intensity (TI), frequency of apoptotic and necrotic cells, and frequency of micronuclei (MN). In contrast, their activity of ALAD, the level of vitamin B(12) and folate in serum were significantly lower compared to controls. Poisson regression analysis showed a significant correlation of profession, duration of exposure, smoking, level of cadmium in blood, ALAD and EP with primary DNA damage. A majority of primary damage repairs in a short period after exposure to a genotoxic agent. In addition, the influence of gender and level of vitamin B(12) and folate in serum MN frequency in exposed group was observed. In this study, DNA diffusion and micronucleus test showed higher influence of tested parameters to DNA damage. The results indicate a need for concomitant use of at least two different biomarkers of exposure when estimating a genetic risk of lead exposure.

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

PubMed

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

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

PubMed

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

2017-02-01

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

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

PubMed

Kurashige, Tomomi; Shimamura, Mika; Nagayama, Yuji

2016-06-01

The biological effect of ionizing radiation (IR) on genomic DNA is thought to be either direct or indirect; the latter is mediated by IR induction of free radicals and reactive oxygen species (ROS). This study was designed to evaluate the effect of N-acetyl-L-cysteine (NAC), a well-known ROS-scavenging antioxidant, on IR induction of genotoxicity, cytotoxicity and ROS production in mammalian cells, and aimed to clarify the conflicting data in previous publications. Although we clearly demonstrate the beneficial effect of NAC on IR-induced genotoxicity and cytotoxicity (determined using the micronucleus assay and cell viability/clonogenic assays), the data on NAC's effect on DNA double-strand break (DSB) formation were inconsistent in different assays. Specifically, mitigation of IR-induced DSBs by NAC was readily detected by the neutral comet assay, but not by the γH2AX or 53BP1 focus assays. NAC is a glutathione precursor and exerts its effect after conversion to glutathione, and presumably it has its own biological activity. Assuming that the focus assay reflects the biological responses to DSBs (detection and repair), while the comet assay reflects the physical status of genomic DNA, our results indicate that the comet assay could readily detect the antioxidant effect of NAC on DSB formation. However, NAC's biological effect might affect the detection of DSB repair by the focus assays. Our data illustrate that multiple parameters should be carefully used to analyze DNA damage when studying potential candidates for radioprotective compounds. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Comet Odyssey: Comet Surface Sample Return

NASA Astrophysics Data System (ADS)

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

2010-10-01

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

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

PubMed

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

2015-07-01

As part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiated international validation study of in vivo rat alkaline comet assay (comet assay), p-phenylenediamine dihydrochloride (PPD), o-phenylphenol sodium salt (OPP), and 2,4-diaminotoluene (2,4-DAT), were analyzed in this laboratory as coded test chemicals. Male Sprague-Dawley rats (7-9 weeks of age) were given three oral doses of the test compounds, 24 and 21 h apart and liver and stomach were sampled 3h after the final dose administration. Under the conditions of the test, no increases in DNA damage were observed in liver and stomach with PPD and OPP up to 100 and 1000 mg/kg/day, respectively. 2,4-DAT, a known genotoxic carcinogen, induced a weak but reproducible, dose-related and statistically significant increase in DNA damage in liver cells while no increases were observed in stomach cells. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-07-01

The in vivo rodent alkaline comet assay (comet assay) is used internationally to investigate the in vivo genotoxic potential of test chemicals. This assay, however, has not previously been formally validated. The Japanese Center for the Validation of Alternative Methods (JaCVAM), with the cooperation of the U.S. NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)/the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), the European Centre for the Validation of Alternative Methods (ECVAM), and the Japanese Environmental Mutagen Society/Mammalian Mutagenesis Study Group (JEMS/MMS), organized an international validation study to evaluate the reliability and relevance of the assay for identifying genotoxic carcinogens, using liver and stomach as target organs. The ultimate goal of this validation effort was to establish an Organisation for Economic Co-operation and Development (OECD) test guideline. The purpose of the pre-validation studies (i.e., Phase 1 through 3), conducted in four or five laboratories with extensive comet assay experience, was to optimize the protocol to be used during the definitive validation study. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

Roy, Prasenjit; Mukherjee, Anita; Giri, Sarbani

2016-02-01

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

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

PubMed

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.

Rapid communications: antiperspirant induced DNA damage in canine cells by comet assay.

PubMed

Yiu, Gloria

2004-01-01

Abstract Millions of people around the world use antiperspirants to decrease or eliminate body odors. Most antiperspirants contain aluminum zirconium or another form of aluminum as its active ingredient. The present investigation applied Comet assay to detect if Secret Platinum for women, Old Spice for men, or Crystal Natural produced DNA damage in Madin-Darby canine kidney cells (MDCKII). This study has shown that antiperspirants cause DNA damage on a single-cell level. Additionally, our data showed us that in general, Secret Platinum for women and Old Spice for men, produced equivalent damage. Crystal Natural, marketed as being safer or less damaging, induced the most extensive damage of all three antiperspirants tested.

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

PubMed

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

2009-06-01

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

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

PubMed

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

2008-12-01

Increasing lead contamination in Egyptian ecosystems and high lead concentrations in food items have raised concern for human health and stimulated studies on monitoring ecotoxicological impact of lead-caused genotoxicity. In this work, the alkaline comet assay was modified for monitoring DNA strand breakage in sensitive early life stages of the African catfish Clarias gariepinus. Following exposure to 100, 300, and 500 microg/L lead nitrate, DNA strand breakage was quantified in embryos at 30, 48, 96, 144, and 168 h post-fertilization (PFS). For quantitative analysis, four commonly used parameters (tail % DNA, %TDNA; head % DNA, %HDNA; tail length, TL; tail moment, TM) were analyzed in 96 nuclei (in triplicates) at each sampling point. The parameter %TDNA revealed highest resolution and lowest variation. A strong correlation between lead concentration, time of exposure, and DNA strand breakage was observed. Here, genotoxicity detected by comet assay preceded the manifested malformations assessed with conventional histology. Qualitative evaluation was carried out using five categories are as follows: undamaged (%TDNA < or = 10%), low damaged (10% < %TDNA < or = 25%), median damaged (25 < %TDNA < or = 50%), highly damaged (50 < %TDNA < or = 75%), and extremely damaged (%TDNA > 75%) nuclei confirming a dose and time-dependent shift towards increased frequencies of highly and extremely damaged nuclei. A protective capacity provided by a hardened chorion is a an interesting finding in this study as DNA damage in the prehatching stages 30 h-PFS and 48 h-PFS was low in all treatments (qualitative and quantitative analyses). These results clearly show that the comet assay is a sensitive tool for the detection of genotoxicity in vulnerable early life stages of the African catfish and is a method more sensitive than histological parameters for monitoring genotoxic effects. 2008 Wiley Periodicals, Inc.

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

PubMed Central

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

Primary DNA damage assessed with the comet assay and comparison to the absorbed dose of diagnostic X-rays in children.

PubMed

Milkovic, Durdica; Garaj-Vrhovac, Vera; Ranogajec-Komor, Mária; Miljanic, Saveta; Gajski, Goran; Knezevic, Zeljka; Beck, Natko

2009-01-01

The aim of this work is to assess DNA damage in peripheral blood lymphocytes of children prior to and following airway X-ray examinations of the chest using the alkaline comet assay and to compare data with the measured absorbed dose. Twenty children with pulmonary diseases, between the ages of 5 and 14 years, are assessed. Absorbed dose measurements are conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest, and back. Doses are measured using thermoluminescent and radiophotoluminescent dosimetry systems. Differences between tail lengths, tail intensity, and tail moments as well as for the long-tailed nuclei before and after exposures are statistically significant and are dependent on the individual. The results demonstrate the usefulness of the comet assay as a measure of X-ray damage to lymphocytes in a clinical setting. Doses measured with both dosimeters show satisfactory agreement (0.01 mSv) and are suitable for dosimetric measurements in X-ray diagnostics.

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

PubMed

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

2017-02-15

Coal mining and combustion generating huge amounts of bottom and fly ash are major causes of environmental pollution and health hazards due to the release of polycyclic aromatic hydrocarbons (PAH) and heavy metals. The Candiota coalfield in Rio Grande do Sul, is one of the largest open-cast coal mines in Brazil. The aim of this study was to evaluate genotoxic and mutagenic effects of coal, bottom ash and fly ash samples from Candiota with the comet assay (alkaline and modified version) and micronucleus test using the lung fibroblast cell line (V79). Qualitative and quantitative analysis of PAH and inorganic elements was carried out by High Performance Liquid Chromatography (HPLC) and by Particle-Induced X-ray Emission (PIXE) techniques respectively. The samples demonstrated genotoxic and mutagenic effects. The comet assay modified using DNA-glicosilase formamidopirimidina (FPG) endonuclease showed damage related to oxidative stress mechanisms. The amount of PAHs was higher in fly ash followed by pulverized coal. The amount of inorganic elements was highest in fly ash, followed by bottom ash. It is concluded that the samples induce DNA damage by mechanisms that include oxidative stress, due to their complex composition, and that protective measures have to be taken regarding occupational and environmental hazards. Copyright © 2016 Elsevier B.V. All rights reserved.

Application of micronucleus test and comet assay to evaluate BTEX biodegradation.

PubMed

Mazzeo, Dânia Elisa Christofoletti; Matsumoto, Silvia Tamie; Levy, Carlos Emílio; de Angelis, Dejanira de Franceschi; Marin-Morales, Maria Aparecida

2013-01-01

The BTEX (benzene, toluene, ethylbenzene and xylene) mixture is an environmental pollutant that has a high potential to contaminate water resources, especially groundwater. The bioremediation process by microorganisms has often been used as a tool for removing BTEX from contaminated sites. The application of biological assays is useful in evaluating the efficiency of bioremediation processes, besides identifying the toxicity of the original contaminants. It also allows identifying the effects of possible metabolites formed during the biodegradation process on test organisms. In this study, we evaluated the genotoxic and mutagenic potential of five different BTEX concentrations in rat hepatoma tissue culture (HTC) cells, using comet and micronucleus assays, before and after biodegradation. A mutagenic effect was observed for the highest concentration tested and for its respective non-biodegraded concentration. Genotoxicity was significant for all non-biodegraded concentrations and not significant for the biodegraded ones. According to our results, we can state that BTEX is mutagenic at concentrations close to its water solubility, and genotoxic even at lower concentrations, differing from some described results reported for the mixture components, when tested individually. Our results suggest a synergistic effect for the mixture and that the biodegradation process is a safe and efficient methodology to be applied at BTEX-contaminated sites. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

PubMed

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

2015-07-01

The in vivo rodent alkaline comet assay (comet assay) is used internationally to investigate the in vivo genotoxic potential of test chemicals. This assay, however, has not previously been formally validated. The Japanese Center for the Validation of Alternative Methods (JaCVAM), with the cooperation of the U.S. NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)/the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), the European Centre for the Validation of Alternative Methods (ECVAM), and the Japanese Environmental Mutagen Society/Mammalian Mutagenesis Study Group (JEMS/MMS), organized an international validation study to evaluate the reliability and relevance of the assay for identifying genotoxic carcinogens, using liver and stomach as target organs. The ultimate goal of this exercise was to establish an Organisation for Economic Co-operation and Development (OECD) test guideline. The study protocol was optimized in the pre-validation studies, and then the definitive (4th phase) validation study was conducted in two steps. In the 1st step, assay reproducibility was confirmed among laboratories using four coded reference chemicals and the positive control ethyl methanesulfonate. In the 2nd step, the predictive capability was investigated using 40 coded chemicals with known genotoxic and carcinogenic activity (i.e., genotoxic carcinogens, genotoxic non-carcinogens, non-genotoxic carcinogens, and non-genotoxic non-carcinogens). Based on the results obtained, the in vivo comet assay is concluded to be highly capable of identifying genotoxic chemicals and therefore can serve as a reliable predictor of rodent carcinogenicity. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-06-01

Smoking is a cause of serious diseases, including lung cancer, emphysema, chronic bronchitis and heart disease. DNA damage is thought to be one of the mechanisms by which cigarette smoke (CS) initiates disease in the lung. Indeed, CS induced DNA damage can be measured in vitro and in vivo. The potential of the Comet assay to measure DNA damage in isolated rat lung alveolar type II epithelial cells (AEC II) was explored as a means to include a genotoxicity end-point in rodent sub-chronic inhalation studies. In this study, published AEC II isolation methods were improved to yield viable cells suitable for use in the Comet assay. The improved method reduced the level of basal DNA damage and DNA repair in isolated AEC II. CS induced DNA damage could also be quantified in isolated cells following a single or 5 days CS exposure. In conclusion, the Comet assay has the potential to determine CS or other aerosol induced DNA damage in AEC II isolated from rodents used in sub-chronic inhalation studies. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

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

PubMed

Reus, Astrid A; Reisinger, Kerstin; Downs, Thomas R; Carr, Gregory J; Zeller, Andreas; Corvi, Raffaella; Krul, Cyrille A M; Pfuhler, Stefan

2013-11-01

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 < 0.05) in DNA damage in every experiment. For the genotoxic carcinogen, 2,4-diaminotoluene, the overall result from all laboratories showed a smaller, but significant genotoxic response (P < 0.05). For cyclohexanone (CHN) (non-genotoxic in vitro and in vivo, and non-carcinogenic), an increase compared to the solvent control acetone was observed only in one laboratory. However, the response was not dose related and CHN was judged negative overall, as was p-nitrophenol (p-NP) (genotoxic in vitro but not in vivo and non-carcinogenic), which was the only compound showing clear cytotoxic effects. For p-NP, significant DNA damage generally occurred only at doses that were substantially cytotoxic (>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

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

PubMed Central

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 < 0.05) in DNA damage in every experiment. For the genotoxic carcinogen, 2,4-diaminotoluene, the overall result from all laboratories showed a smaller, but significant genotoxic response (P < 0.05). For cyclohexanone (CHN) (non-genotoxic in vitro and in vivo, and non-carcinogenic), an increase compared to the solvent control acetone was observed only in one laboratory. However, the response was not dose related and CHN was judged negative overall, as was p-nitrophenol (p-NP) (genotoxic in vitro but not in vivo and non-carcinogenic), which was the only compound showing clear cytotoxic effects. For p-NP, significant DNA damage generally occurred only at doses that were substantially cytotoxic (>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

Workshop on Analysis of Returned Comet Nucleus Samples

NASA Technical Reports Server (NTRS)

1989-01-01

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

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

PubMed Central

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

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

PubMed Central

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

Identification of irradiated refrigerated poultry with the DNA comet assay

NASA Astrophysics Data System (ADS)

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

2004-09-01

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

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

PubMed

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

2009-02-15

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

Evaluation of cytotoxicity, genotoxicity and teratogenicity of marine sediments from Qingdao coastal areas using in vitro fish cell assay, comet assay and zebrafish embryo test.

PubMed

Yang, Fan; Zhang, Qianqian; Guo, Huarong; Zhang, Shicui

2010-10-01

Marine sediments are often a final sink for numerous anthropogenic contaminants and may impose serious effects on benthic organisms and ecosystem. An in vitro cell assay using a cell line derived from flounder gill (FG) cells, an in vitro comet assay in FG cells, and an in vitro zebrafish embryo assay were used to evaluate the in vitro cytotoxicity (measured by MTT reduction), genotoxicity and teratogenicity of crude sediment extracts of Li Cang (LC), Zhan Qiao (ZQ) and Olympic Sailing Center (OSC) from Qingdao coastal area. Sediments from the three sites displayed different cytotoxicity, genotoxicity and teratogenicity potencies; however, all three assays yielded similar LOECs (lowest observed effect concentration) for each site, suggesting that the assays were equally sensitive to and suitable for initial screening of the LOECs of marine sediments. The cytotoxicity, genotoxicity and teratogenicity for these three sampling sites were in the same order of LC>ZQ>OSC, indicating different degrees of contamination. Interestingly, trials with the three sediment extracts at the doses inducing a similar cytotoxicity as evaluated with MTT reduction did not produce similar genotoxicity and teratogenicity, with the genotoxic and teratogenic activities of LC and ZQ extracts being markedly higher than those of OSC sediments. These findings indicate that cytotoxicity does not form a fully equivalent toxicity index with that of genotoxicity and teratogenicity. Therefore, in order to assess the true toxic potential of marine sediments, all three assays should be performed. Analysis of 16 EPA (US Environmental Protection Agency) priority PAHs in these three sediment samples showed a clear correlation between PAH concentrations and sediment toxicities, with a higher PAH content corresponding to higher toxicity although PAHs are surely not the only cause. Copyright © 2010 Elsevier Ltd. All rights reserved.

MUTAGENICITY IN SALMONELLA AND DNA DAMAGE IN THE CHO/COMET ASSAY INDUCED BY NITROHALOMETHANES, A NOVEL CLASS OF DRINKING WATER DISINFECTION BY-PRODUCTS

EPA Science Inventory

Mutagenicity in Salmonella and DNA Damage in the CHO/Comet Assay Induced by Nitrohalomethanes, a Novel Class of Drinking Water Disinfection By-Products.

Halomethanes are a class of drinking water disinfection by-products (DBPs) whose genotoxicity has been studied extensi...

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

PubMed

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

2016-04-01

This article investigates the ability of Pseudomonas peli to treat industrial pharmaceuticals wastewater (PW). Liquid chromatography-mass spectrometry (MS)/MS analysis revealed the presence, in this PW, of a variety of antibiotics such as sulfathiazole, sulfamoxole, norfloxacine, cloxacilline, doxycycline, and cefquinome.P. peli was very effective to be grown in PW and inducts a remarkable increase in chemical oxygen demand and biochemical oxygen demand (140.31 and 148.51%, respectively). On the other hand, genotoxicity of the studied effluent, before and after 24 h of shaking incubation with P. peli, was evaluated in vivo in the Mediterranean wild mussels Mytilus galloprovincialis using comet assay for quantification of DNA fragmentation. Results show that PW exhibited a statistically significant (p< 0.001) genotoxic effect in a dose-dependent manner; indeed, the percentage of genotoxicity was 122.6 and 49.5% after exposure to 0.66 ml/kg body weight (b.w.); 0.33 ml/kg b.w. of PW, respectively. However, genotoxicity decreased strongly when tested with the PW obtained after incubation with P. peli We can conclude that using comet assay genotoxicity end points are useful tools to biomonitor the physicochemical and biological quality of water. Also, it could be concluded that P. peli can treat and detoxify the studied PW. © The Author(s) 2013.

Comet Tempel 2: Orbit, ephemerides and error analysis

NASA Technical Reports Server (NTRS)

Yeomans, D. K.

1978-01-01

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

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

PubMed

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

Analysis of IUE Observations of Hydrogen in Comets

NASA Technical Reports Server (NTRS)

Combi, Michael R.; Feldman, Paul D.

1998-01-01

The 15-years worth of hydrogen Lyman-alpha observations of cometary comae obtained with the International Ultraviolet Explorer (IUE) satellite had gone generally unanalyzed because of two main modeling complications. First, the inner comae of many bright (gas productive) comets are often optically thick to solar Lyman-alpha radiation. Second, even in the case of a small comet (low gas production) the large IUE aperture is quite small as compared with the immense size of the hydrogen coma, so an accurate model which properly accounts for the spatial distribution of the coma is required to invert the infrared brightnesses to column densities and finally to H atom production rates. Our Monte Carlo particle trajectory model (MCPTM), which for the first time provides the realistic full phase space distribution of H atoms throughout the coma has been used as the basis for the analysis of IUE observations of the inner coma. The MCPTM includes the effects of the vectorial ejection of the H atoms upon dissociation of their parent species (H2O and OH) and of their partial collisional thermalization. Both of these effects are crucial to characterize the velocity distribution of the H atoms. This combination of the MCPTM and spherical radiative transfer code had already been shown to be successful in understanding the moderately optically thick coma of comet P/Giacobini-Zinner and the coma of comet Halley that varied from being slightly to very optically thick. Both of these comets were observed during solar minimum conditions. Solar activity affects both the photochemistry of water and the solar Lyman-alpha radiation flux. The overall plan of this program here was to concentrate on comets observed by IUE at other time during the solar cycle, most importantly during the two solar maxima of 1980 and 1990. Described herein are the work performed and the results obtained.

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.

PubMed

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.

COMETS!

NASA Astrophysics Data System (ADS)

Eicher, David J.; Levy, David H.

2013-11-01

Foreword David H. Levy; Preface; Acknowledgments; 1. Strange lights in the sky; 2. Great comets of the past; 3. What are comets?; 4. Comets of the modern era; 5. Comets in human culture; 6. Where comets live; 7. The expanding science of comets; 8. Observing comets; 9. Imaging comets; Glossary; Bibliography; Index.

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

PubMed

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

2015-07-01

The Japanese Center for the Validation of Alternative Methods (JaCVAM) sponsored an international prevalidation and validation study of the in vivo rat alkaline pH comet assay. The main objective of the study was to assess the sensitivity and specificity of the assay for correctly identifying genotoxic carcinogens, as compared with the traditional rat liver unscheduled DNA synthesis assay. Based on existing carcinogenicity and genotoxicity data and chemical class information, 90 chemicals were identified as primary candidates for use in the validation study. From these 90 chemicals, 46 secondary candidates and then 40 final chemicals were selected based on a sufficiency of carcinogenic and genotoxic data, differences in chemical class or genotoxic or carcinogenic mode of action (MOA), availability, price, and ease of handling. These 40 chemicals included 19 genotoxic carcinogens, 6 genotoxic non-carcinogens, 7 non-genotoxic carcinogens and 8 non-genotoxic non-carcinogens. "Genotoxicity" was defined as positive in the Ames mutagenicity test or in one of the standard in vivo genotoxicity tests (primarily the erythrocyte micronucleus assay). These chemicals covered various chemicals classes, MOAs, and genotoxicity profiles and were considered to be suitable for the purpose of the validation study. General principles of chemical selection for validation studies are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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.

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.

PubMed

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.

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

PubMed Central

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

2014-01-01

STUDY QUESTION Is there an association between human sperm sex chromosome disomy and sperm DNA damage? SUMMARY ANSWER 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. WHAT IS KNOWN ALREADY There is limited published research on the association between sex chromosome disomy and sperm DNA damage and the findings are not consistent across studies. STUDY DESIGN, SIZE, AND DURATION 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. PARTICIPANTS/MATERIALS, SETTING, METHODS 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. MAIN RESULTS AND THE ROLE OF CHANCE 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

Terminal navigation analysis for the 1980 comet Encke slow flyby mission

NASA Technical Reports Server (NTRS)

Jacobson, R. A.; Mcdanell, J. P.; Rinker, G. C.

1973-01-01

The initial results of a terminal navigation analysis for the proposed 1980 solar electric slow flyby mission to the comet Encke are presented. The navigation technique employs onboard optical measurements with the scientific television camera, groundbased observations of the spacecraft and comet, and groundbased orbit determination and thrust vector update computation. The knowledge and delivery accuracies of the spacecraft are evaluated as a function of the important parameters affecting the terminal navigation. These include optical measurement accuracy, thruster noise level, duration of the planned terminal coast period, comet ephemeris uncertainty, guidance initiation time, guidance update frequency, and optical data rate.

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

PubMed

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

2016-06-01

Metals and metalloids are natural components of the biosphere, which are not produced per se by human beings, but whose form and distribution can be affected by human activities. Like all substances, they are a contaminant if present in excess compared to background levels and/or in a form that would not normally occur in the environment. Samples of liver, gills, gonads and muscle from European chub, Squalius cephalus, were analyzed for Al, As, B, Ba, Cr, Cu, Fe, Hg, Mn, Mo, Sr and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES) to highlight the importance of tissue selection in monitoring research. The comet assay or single cell gel electrophoresis (SCGE) was selected as an in vivo genotoxicity assay, a rapid and sensitive method for measuring genotoxic effects in blood, liver and gills of the European chub. Microscopic images of comets were scored using Comet IV Computer Software (Perceptive Instruments, UK). The objective of our study was to investigate two reservoirs, Zlatar and Garasi, and one river, Pestan by: (i) determining and comparing metal and metalloid concentrations in sediment, water and tissues of European chub: liver, gills, muscle and gonads (ii) comparing these findings with genotoxicity of water expressed through DNA damage of fish tissues. A clear link between the level of metals in water, sediment and tissues and between metal and genotoxicity levels at examined sites was not found. This suggests that other xenobiotics (possibly the organic compounds), contribute to DNA damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

Genotoxic effects of styrene-7,8-oxide in human white blood cells: comet assay in relation to the induction of sister-chromatid exchanges and micronuclei.

PubMed

Laffon, B; Pásaro, E; Méndez, J

2001-04-05

Styrene is used in the production of plastics, resins and rubber. The highest human exposures to styrene take place by inhalation during the production of fiberglass reinforced plastics. Styrene is metabolized mainly in the liver to styrene-7,8-oxide (SO), its principal in vivo mutagenic metabolite. In this study, human peripheral white blood cells were exposed to several SO concentrations (10-200 microM) in order to evaluate its genotoxic properties by means of comet assay, sister-chromatid exchanges (SCE) and cytokinesis-blocked micronucleus (MN) test, in addition to determine its clastogenic or aneugenic properties by combining MN with fluorescence in situ hybridization (FISH) procedures. Our results show that SO induces DNA damage, SCE and MN in human leukocytes in vitro at concentrations above 50 microM, and that there is a strong relationship between DNA damage, as measured by the comet assay, and cytogenetic damage induced by SO at the doses employed. SO shows preferentially a clastogenic activity and produces a cytostatic effect at high doses, reflected by the significant decrease of the calculated proliferation indices. A good dose-effect relationship is obtained in the three tests performed at the concentration range assayed.

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

NASA Technical Reports Server (NTRS)

Yeomans, D. K.

1974-01-01

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

Development and validation of a modified comet assay to phenotypically assess nucleotide excision repair.

PubMed

Langie, Sabine A S; Knaapen, Ad M; Brauers, Karen J J; van Berlo, Damien; van Schooten, Frederik-Jan; Godschalk, Roger W L

2006-03-01

There is an increasing need for simple and reliable approaches to phenotypically assess DNA repair capacities. Therefore, a modification of the alkaline comet assay was developed to determine the ability of human lymphocyte extracts to perform the initial steps of the nucleotide excision repair (NER) process, i.e. damage recognition and incision. Gel-embedded nucleoids from A549 cells, pre-exposed to 1 microM benzo[a]pyrene-diol-epoxide, were incubated with cell extracts from frozen or freshly isolated lymphocytes. The rate at which incisions are introduced and the subsequent increase in tail moment is indicative for the repair capacity of the extracts. Freshly prepared extracts from lymphocytes of human volunteers (n = 8) showed significant inter-individual variations in their DNA repair capacity, which correlated with the removal of bulky DNA lesions over a period of 48 h determined by (32)P-post-labelling (R(2) = 0.76, P = 0.005). Repeated measurements revealed a low inter-assay variation (11%). Storage of cell extracts for more than 3 weeks significantly reduced (up to 80%) the capacity to incise the damaged DNA as compared to freshly isolated extracts. This reduction was completely restored by addition of ATP to the extracts before use, as it is required for the incision step of NER. In contrast, extracts freshly prepared from frozen lymphocyte pellets can be used without loss of repair activity. DNA repair deficient XPA-/- and XPC-/- fibroblasts were used to further validate the assay. Although some residual capacity to incise the DNA was observed in these cells, the repair activity was restored to normal wild-type levels when a complementary mixture of both extracts (thereby restoring XPA and XPC deficiency) was used. These results demonstrate that this repair assay can be applied in molecular epidemiological studies to assess inter-individual differences in NER.

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

PubMed

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

2013-12-12

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

Development of a miniature scanning electron microscope for in-flight analysis of comet dust

NASA Technical Reports Server (NTRS)

Conley, J. M.; Bradley, J. G.; Giffin, C. E.; Albee, A. L.; Tomassian, A. D.

1983-01-01

A description is presented of an instrument which was developed with the original goal of being flown on the International Comet Mission, scheduled for a 1985 launch. The Scanning Electron Microscope and Particle Analyzer (SEMPA) electron miniprobe is a miniaturized electrostatically focused electron microscope and energy dispersive X-ray analyzer for in-flight analysis of comet dust particles. It was designed to be flown on board a comet rendezvous spacecraft. Other potential applications are related to asteroid rendezvous and planetary lander missions. According to the development objectives, SEMPA miniprobe is to have the capability for imaging and elemental analysis of particles in the size range of 0.25 microns and larger.

Evaluation the urban atmospheric conditions in different cities using comet and micronuclei assay in Tradescantia pallida.

PubMed

Sposito, Juliana Caroline Vivian; Crispim, Bruno do Amaral; Romãn, Amanda Izadora; Mussury, Rosilda Mara; Pereira, Joelson Gonçalves; Seno, Leonardo Oliveira; Grisolia, Alexeia Barufatti

2017-05-01

In the present study, genotoxicity and mutagenicity were investigated in Tradescantia pallida exposed to vehicular traffic at different sites in a high-altitude tropical climate. During March, May, July, September, and November 2014, a comet assay and micronucleus bioassays were conducted on young inflorescences and leaves of T. pallida collected from twelve towns in the southern region of Mato Grosso do Sul with different amounts of vehicular traffic. Weather parameters (temperature, relative humidity and rainfall) were measured and vehicles were counted to determine traffic levels in each town. A higher frequency of genotoxic and mutagenic damage was observed in the municipality of Dourados. The highest frequency of genetic damage was observed in September and November according to both assays. Relative humidity and rainfall were inversely proportional to the frequency of genetic damage in T. pallida during the collection period. Based on these results, we conclude that the bioassays are efficient for assessing the effects of vehicular traffic in these towns with respect to weather conditions over time. These bioassays can be applied to identify risk areas, which are determined by climatic conditions and air pollutants released. Copyright © 2017 Elsevier Ltd. All rights reserved.

Atlas of Great Comets

NASA Astrophysics Data System (ADS)

Stoyan, Ronald; Dunlop, Storm

2015-01-01

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

Comets. [IUE

NASA Technical Reports Server (NTRS)

Ahearn, Michael F.

1988-01-01

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

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).

PubMed

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.

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

PubMed

Hemachandra, Chamini K; Pathiratne, Asoka

2016-09-01

Bioassays for cyto-genotoxicity assessments are generally not required in current textile industry effluent discharge management regulations. The present study applied in vivo plant and fish based toxicity tests viz. Allium cepa test system and Oreochromis niloticus erythrocyte based comet assay and nuclear abnormalities tests in combination with physico-chemical analysis for assessing potential cytotoxic/genotoxic impacts of treated textile industry effluents reaching a major river (Kelani River) in Sri Lanka. Of the treated effluents tested from two textile industries, color in the Textile industry 1 effluents occasionally and color, biochemical oxygen demand and chemical oxygen demand in the Textile industry 2 effluents frequently exceeded the specified Sri Lankan tolerance limits for discharge of industrial effluents into inland surface waters. Exposure of A. cepa bulbs to 100% and 12.5% treated effluents from both industries resulted in statistically significant root growth retardation, mito-depression, and induction of chromosomal abnormalities in root meristematic cells in comparison to the dilution water in all cases demonstrating cyto-genotoxicity associated with the treated effluents. Exposure of O. niloticus to the 100% and 12.5% effluents, resulted in erythrocytic genetic damage as shown by elevated total comet scores and induction of nuclear abnormalities confirming the genotoxicity of the treated effluents even with 1:8 dilution. The results provide strong scientific evidence for the crucial necessity of incorporating cyto-genotoxicity impact assessment tools in textile industry effluent management regulations considering human health and ecological health of the receiving water course under chronic exposure. Copyright © 2016 Elsevier Inc. All rights reserved.

An analysis of the BVRI colors of 22 active comets

NASA Astrophysics Data System (ADS)

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.

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

PubMed Central

Çok, İsmet; Ulutaş, Onur Kenan; Okuşluk, Öncü; Durmaz, Emre; Demir, Nilsun

2011-01-01

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. PMID:21805014

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

PubMed

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.

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

PubMed

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

2012-04-20

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.

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

PubMed Central

2012-01-01

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. PMID:22520045

Sodium hypochlorite-, chlorine dioxide- and peracetic acid-induced genotoxicity detected by the Comet assay and Saccharomyces cerevisiae D7 tests.

PubMed

Buschini, Annamaria; Carboni, Pamela; Furlini, Mariangela; Poli, Paola; Rossi, Carlo

2004-03-01

Mutagenicity of drinking water is due not only to industrial, agricultural and urban pollution but also to chlorine disinfection by-products. Furthermore, residual disinfection is used to provide a partial safeguard against low level contamination and bacterial re-growth within the distribution system. The aims of this study were to further evaluate the genotoxic potential of the world wide used disinfectants sodium hypochlorite and chlorine dioxide in human leukocytes by the Comet assay and in Saccharomyces cerevisiae strain D7 (mitotic gene conversion, point mutation and mitochondrial DNA mutability, with and without endogenous metabolic activation) and to compare their effects with those of peracetic acid, proposed as an alternative disinfectant. All three disinfectants are weakly genotoxic in human leukocytes (lowest effective dose 0.2 p.p.m. for chlorine dioxide, 0.5 p.p.m. for sodium hypochlorite and peracetic acid). The results in S.cerevisiae show a genotoxic response on the end-points considered with an effect only at doses higher (5- to 10-fold) than the concentration normally used for water disinfection; sodium hypochlorite and peracetic acid are able to induce genotoxic effects without endogenous metabolic activation (in stationary phase cells) whereas chlorine dioxide is effective in growing cells. The Comet assay was more sensitive than the yeast tests, with effective doses in the range normally used for water disinfection processes. The biological effectiveness of the three disinfectants on S.cerevisiae proved to be strictly dependent on cell-specific physiological/biochemical conditions. All the compounds appear to act on the DNA and peracetic acid shows effectiveness similar to sodium hypochlorite and chlorine dioxide.

Long-term evolution of Oort Cloud comets: capture of comets

NASA Astrophysics Data System (ADS)

Nurmi, P.; Valtonen, M. J.; Zheng, J. Q.; Rickman, H.

2002-07-01

We test different possibilities for the origin of short-period comets captured from the Oort Cloud. We use an efficient Monte Carlo simulation method that takes into account non-gravitational forces, Galactic perturbations, observational selection effects, physical evolution and tidal splittings of comets. We confirm previous results and conclude that the Jupiter family comets cannot originate in the spherically distributed Oort Cloud, since there is no physically possible model of how these comets can be captured from the Oort Cloud flux and produce the observed inclination and Tisserand constant distributions. The extended model of the Oort Cloud predicted by the planetesimal theory consisting of a non-randomly distributed inner core and a classical Oort Cloud also cannot explain the observed distributions of Jupiter family comets. The number of comets captured from the outer region of the Solar system are too high compared with the observations if the inclination distribution of Jupiter family comets is matched with the observed distribution. It is very likely that the Halley-type comets are captured mainly from the classical Oort Cloud, since the distributions in inclination and Tisserand value can be fitted to the observed distributions with very high confidence. Also the expected number of comets is in agreement with the observations when physical evolution of the comets is included. However, the solution is not unique, and other more complicated models can also explain the observed properties of Halley-type comets. The existence of Jupiter family comets can be explained only if they are captured from the extended disc of comets with semimajor axes of the comets a<5000au. The original flattened distribution of comets is conserved as the cometary orbits evolve from the outer Solar system era to the observed region.

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

NASA Astrophysics Data System (ADS)

Klinglesmith, D. A.

1981-10-01

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

Comets

NASA Astrophysics Data System (ADS)

Brownlee, D. E.

2003-12-01

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

A Comet's Missing Light

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-05-01

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

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

PubMed Central

Gülsoy, Nagihan; Yavas, Cüneyd; Mutlu, Özal

2015-01-01

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

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

PubMed

Gülsoy, Nagihan; Yavas, Cüneyd; Mutlu, Özal

2015-01-01

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

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

PubMed

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

2015-07-01

As a part of the Japanese Center for the Validation of Alternative Methods (JaCVAM)-initiative international validation study of the in vivo rat alkaline comet assay (comet assay), we examined methyl methanesulfonate, 2,6-diaminotoluene, and 5-fluorouracil under coded test conditions. Rats were treated orally with the maximum tolerated dose (MTD) and two additional descending doses of the respective compounds. In the MMS treated groups liver and stomach showed significantly elevated DNA damage at each dose level and a significant dose-response relationship. 2,6-diaminotoluene induced significantly elevated DNA damage in the liver at each dose and a statistically significant dose-response relationship whereas no DNA damage was obtained in the stomach. 5-fluorouracil did not induce DNA damage in either liver or stomach. Copyright © 2015 Elsevier B.V. All rights reserved.

Infrared Imaging, Spectroscopic, and Photometric Studies of Comets

NASA Technical Reports Server (NTRS)

Gehrz, Robert D.

1997-01-01

We have continued our program of infrared (IR) photometric, imaging, spectroscopic, and polarimetric temporal observations of comets to study the properties of comet dust and comet nuclei. During the first two years we digitized our IR data base on P/Halley and other recent comets to facilitate further analysis and comparison with other data bases, and found compelling evidence for the emission of a burst of small grains from P/Halley's nucleus at perihelion. We reported imaging and photometric observations of Comets Austin 1990 V and Swift-Tuttle 1992. The Swift-Tuttle 1992t observations included IR photometry, several 7-14 micron long-slit spectra of the coma and a time-sequence of more than 150 10 micron broadband images of the coma. An analysis of near-IR images of the inner coma of P/Halley obtained on three consecutive nights in 1986 March showed sunwardjets. We completed our analysis of IR imaging spectrosco-photometric data on comets. We also obtained observations of Comets Hyakutake 1996 B2 and Hale/Bopp 1995 01. We obtained infrared imaging, photometric, spectroscopic and polarimetric temporal observations of bright comets using a network of five telescopes, with emphasis on simultaneous observations of comets at many wavelengths with different instruments. Our program offers several unique advantages: 1) rapid observational response to new comets with dedicated infrared telescopes; 2) observations within a few degrees of the sun when comets are near perihelion and 3) access to advanced infrared array imagers and spectrometers. In particular, reduction, analysis, publication and archiving of our Jupiter/sl-9 and Comet Hyakutake infrared data received special emphasis. Instrumentation development included installation of the latest version of the innovative FORTH telescope control and a data acquisition system that enables us to control three telescopes remotely by telephone from anywhere in the world for comet observations in broad daylight. We have

On the problem of origin of periodic comets.

NASA Astrophysics Data System (ADS)

Guliev, A. S.

The problem of origin of periodic comets is viewed under various aspects. A steady growth of the fraction of these comets in the overall population of comets is emphasized. The number of discovered periodic comets with small eccentricities and with the Jacobi constant close to 3 is also growing eventually. Comparison of maximum magnitudes of the same comets in different apparitions at the same elongations as well as the analysis of exhausted comets indicate that the age of these objects does not exceed 1000 years. Capture is considered as an efficient mechanism for preserving equilibrium over reasonable time intervals. The analysis of the data given by Everhart and the calculations of the evolution of cometary orbits reveal small efficiency of capture. Comparison of the number of well established capture cases with the corresponding time interval shows that the age of the system of periodic comets must be 17000 years within the framework of this mechanism. This is most unlikely. Secular variations in the distributions of semimajor axes, inclinations, longitudes of perihelia, eccentricities of orbits of periodic comets are analysed. On the average, the eccentricities tend to increase, but this conflicts with the capture mechanism. A conclusion is made that the concept of capture in its classical and modern versions is unable to solve the problem of the origin of periodic comets on the whole. Other, more effective sources and mechanisms seem to be also in operation in enlarging the cometary system.

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

PubMed Central

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

2015-01-01

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

Comet composition and density analyzer

NASA Technical Reports Server (NTRS)

Clark, B. C.

1982-01-01

Distinctions between cometary material and other extraterrestrial materials (meteorite suites and stratospherically-captured cosmic dust) are addressed. The technique of X-ray fluorescence (XRF) for analysis of elemental composition is involved. Concomitant with these investigations, the problem of collecting representative samples of comet dust (for rendezvous missions) was solved, and several related techniques such as mineralogic analysis (X-ray diffraction), direct analysis of the nucleus without docking (electron macroprobe), dust flux rate measurement, and test sample preparation were evaluated. An explicit experiment concept based upon X-ray fluorescence analysis of biased and unbiased sample collections was scoped and proposed for a future rendezvous mission with a short-period comet.

Airborne observations of methane in Comet Kohoutek

NASA Technical Reports Server (NTRS)

Roche, A. E.; Wells, W. C.

1974-01-01

The experiment is described for airborne observations of Comet Kohoutek using an infrared tilting-filter photometer. Preliminary analysis of the data established an upper limit to the Comet's fluorescence radiation in methane lines at 3.3 microns.

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

PubMed

Kido, Ryoko; Sato, Itaru; Tsuda, Shuji

2006-01-01

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

HUBBLE SEES MINI-COMET FRAGMENTS FROM COMET LINEAR

NASA Technical Reports Server (NTRS)

2002-01-01

[lower right] In one stunning Hubble picture the fate of the mysteriously vanished solid nucleus of Comet LINEAR has been settled. The Hubble picture shows that the comet nucleus has been reduced to a shower of glowing 'mini-comets' resembling the fiery fragments from an exploding aerial firework. This is the first time astronomers have ever gotten a close-up look at what may be the smallest building blocks of cometary nuclei, the icy solid pieces called 'cometesimals', which are thought to be less than 100 feet across. The farthest fragment to the left, which is now very faint, may be the remains of the parent nucleus that fragmented into the cluster of smaller pieces to the right. The comet broke apart around July 26, when it made its closest approach to the Sun. The picture was taken with Hubble's Wide Field Planetary Camera 2 on August 5, 2000, when the comet was at a distance of 64 million miles (102 million kilometers) from Earth. Credit: NASA, Harold Weaver (the Johns Hopkins University), and the HST Comet LINEAR Investigation Team [upper left] A ground-based telescopic view (2.2-meter telescope) of Comet LINEAR taken on August 5, at nearly the same time as the Hubble observations. The comet appears as a diffuse elongated cloud of debris without any visible nucleus. Based on these images, some astronomers had concluded that the ices in the nucleus had completely vaporized, leaving behind a loose swarm of dust. Hubble's resolution was needed to pinpoint the remaining nuclei (inset box shows HST field of view as shown in lower right). Credit: University of Hawaii

Mixture genotoxicity of 2,4-dichlorophenoxyacetic acid, acrylamide, and maleic hydrazide on human Caco-2 cells assessed with comet assay.

PubMed

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

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, but further investigations including in vivo studies are needed to clarify how important these more-than-additive effects are for risk assessment.

Basal damage and oxidative DNA damage in children with chronic kidney disease measured by use of the comet assay.

PubMed

Aykanat, Banu; Demircigil, Gonca Cakmak; Fidan, Kibriya; Buyan, Necla; Gulleroglu, Kaan; Baskin, Esra; Bayrakci, Umut Selda; Sepici, Aylin; Buyukkaragoz, Bahar; Karakayali, Hamdi; Haberal, Mehmet; Burgaz, Sema

2011-10-09

One consequence of chronic kidney disease (CKD) is an elevated risk for cancer. There is sufficient evidence to conclude that there is an increased incidence of at least some cancers in kidney-dialysis patients. Cancer risk after kidney transplantation has mainly been attributed to immunosuppressive therapy. There are no data evaluating DNA damage in children with CKD, in dialysis patients, or following kidney transplantation. In this study, the comet assay and the enzyme-modified comet assay - with the use of endonuclease III (Endo III) and formamidopyrimidine glycosylase (FPG) enzymes - were conducted to investigate the basal damage and the oxidative DNA damage as a result of treatment in peripheral blood lymphocytes of children. Children at various stages of treatment for kidney disease, including pre-dialysis patients (PreD) (n=17), regular hemodialysis patients (HD) (n=15), and those that received kidney transplants (Tx) (n=17), comprised the study group. They were compared with age- and gender-matched healthy children (n=20) as a control group. Our results show that the %DNA intensity, a measure of basal damage, was significantly increased in children with CKD (mean ± SD) (5.22 ± 1.57) and also in each of the PreD, HD, and Tx groups [(4.92 ± 1.23), (4.91 ± 1.35), and (5.79 ± 1.94), respectively, vs the healthy children (2.74 ± 2.91) (p<0.001). Significant increases in oxidative DNA damage were only found in the FPG-sensitive sites for the PreD and Tx groups, compared with control and HD groups (p<0.05), suggesting that basal DNA damage was more evident for the PreD, HD, and Tx groups. The findings of the present study indicate a critical need for further research on genomic damage with different endpoints and also for preventive measures and improvements in treatment of pediatric patients, in order to improve their life expectancy. 2011 Elsevier B.V. All rights reserved.

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

PubMed Central

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

2012-01-01

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

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

PubMed

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

2016-04-01

Based on the fact that recycling of combined filter backwash water (CFBW) directly to drinking water treatment plants (WTP) is considered to be a feasible method to enhance pollutant removal efficiency, we were motivated to evaluate the genotoxicity of water samples from two pilot-scale drinking water treatment systems, one with recycling of combined backwash water, the other one with a conventional process. An integrated approach of the comet and micronucleus (MN) assays was used with zebrafish (Danio rerio) to investigate the water genotoxicity in this study. The total organic carbon (TOC), dissolved organic carbon (DOC), and trihalomethane formation potential (THMFP), of the recycling process were lower than that of the conventional process. All the results showed that there was no statistically significant difference (P>0.05) between the conventional and recycling processes, and indicated that the genotoxicity of water samples from the recycling process did not accumulate in 15 day continuous recycling trial. It was worth noting that there was correlation between the concentrations of TOC, DOC, UV254, and THMFPs in water and the DNA damage score, with corresponding R(2) values of 0.68, 0.63, 0.28, and 0.64. Nevertheless, both DNA strand breaks and MN frequency of all water samples after disinfection were higher than that of water samples from the two treatment units, which meant that the disinfection by-products (DBPs) formed by disinfection could increase the DNA damage. Both the comet and MN tests suggest that the recycling process did not increase the genotoxicity risk, compared to the traditional process. Copyright © 2015. Published by Elsevier B.V.

Ballistic intercept missions to Comet Encke

NASA Technical Reports Server (NTRS)

Mumma, M. (Compiler)

1975-01-01

The optimum ballistic intercept of a spacecraft with the comet Encke is determined. The following factors are considered in the analysis: energy requirements, encounter conditions, targeting error, comet activity, spacecraft engineering requirements and restraints, communications, and scientific return of the mission. A baseline model is formulated which includes the basic elements necessary to estimate the scientific return for the different missions considered. Tradeoffs which have major impact on the cost and/or scientific return of a ballistic mission to comet Encke are identified and discussed. Recommendations are included.

Temporary satellite capture of comets by Jupiter

NASA Astrophysics Data System (ADS)

Emel'yanenko, N. Yu.

2012-05-01

This paper studies the dynamical evolution of 97 Jupiter-family comets over an 800-year time period. More than two hundred encounters with Jupiter are investigated, with the observed comets moving during a certain period of time in an elliptic jovicentric orbit. In most cases this is an ordinary temporary satellite capture of a comet in Everhart's sense, not associated with a transition of the small body into Jupiter's family of satellites. The phenomenon occurs outside the Hill sphere with comets with a high Tisserand constant relative to Jupiter; the comets' orbits have a small inclination to the ecliptic plane. An analysis of 236 encounters has allowed the determination within the planar pair two-body problem of a region of orbits in the plane ( a, e) whose semimajor axes and eccentricities contribute to the phenomenon under study. Comets with orbits belonging to this region experience a temporary satellite capture during some of their encounters; the jovicentric distance function has several minima; and the encounters are characterized by reversions of the line of apsides and some others features of their combination that are intrinsic to comets in this region. Therefore, this region is called a region of comets with specific features in their encounters with Jupiter. Twenty encounters (out of 236), whereby the comet enters an elliptic jovicentric orbit in the Hill sphere, are identified and investigated. The size and shape of the elliptic heliocentric orbits enabling this transition are determined. It is found that in 11 encounters the motion of small bodies in the Hill sphere has features the most important of which is multiple minima of the jovicentric distance function. The study of these 20 encounters has allowed the introduction of the concept of temporary gravitational capture of a small body into the Hill sphere. An analysis of variations in the Tisserand constant in these (20) encounters of the observable comets shows that their motion is unstable in

A Million Comet Pieces

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] A Million Comet Pieces (poster version)

This infrared image from NASA's Spitzer Space Telescope shows the broken Comet 73P/Schwassman-Wachmann 3 skimming along a trail of debris left during its multiple trips around the sun. The flame-like objects are the comet's fragments and their tails, while the dusty comet trail is the line bridging the fragments.

Comet 73P /Schwassman-Wachmann 3 began to splinter apart in 1995 during one of its voyages around the sweltering sun. Since then, the comet has continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believe the icy comet cracked due the thermal stress from the sun.

The Spitzer image provides the best look yet at the trail of debris left in the comet's wake after its 1995 breakup. The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlight and glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earth passes near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky in meteor showers. In 2022, Earth is expected to cross close to the comet's trail, producing a noticeable meteor shower.

Astronomers are studying the Spitzer image for clues to the comet's composition and how it fell apart. Like NASA's Deep Impact experiment, in which a probe smashed into comet Tempel 1, the cracked Comet 73P/Schwassman-Wachmann 3 provides a perfect laboratory for studying the pristine interior of a comet.

This image was taken from May 4 to May 6 by Spitzer's multi-band imaging photometer, using its 24-micron wavelength channel.

Use of sensitive methods for detection of DNA damage on human lymphocytes exposed to p,p'-DDT: Comet assay and new criteria for scoring micronucleus test.

PubMed

Gajski, Goran; Ravlic, Sanda; Capuder, Zeljka; Garaj-Vrhovac, Vera

2007-08-01

Wide distribution, stability and long persistence in the environment of dichlorodiphenyltrichloroethane (DDT), probably the best-known and most useful insecticide in the world, imposes the need for further examination of the effect of this chemical on human health and especially on the human genome. In this study, peripheral blood human lymphocytes from a healthy donor were exposed to 0.025 mg/L concentration of p,p'-DDT at different time periods (1, 2, 24 and 48 h). For the assessment of genotoxic effect, the new criteria for scoring micronucleus test and alkaline comet assay were used. Both methods showed that p,p'-DDT induces DNA damage in low concentration used in this research. Results of micronucleus test showed a statistically significant (p < 0.05) genotoxic effect of p,p'-DDT on human lymphocytes compared with corresponding control and a different exposure time. A comet assay also showed increased DNA damage caused in p,p'-DDT-exposed human lymphocytes than in corresponding control cells for the tail length. Results obtained by measuring the level of DNA migration and incidence of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) indicate the sensitivity of these tests and their application in detection of primary genome damage after long-term exposure to establish the effect of p,p'-DDT on human genome.

Comet ISON May Have Survived

NASA Image and Video Library

2013-11-30

This movie shows Comet ISON orbiting around the sun – represented by the white circle -- on Nov. 28, 2013. ISON looks smaller as it streams away, but scientists believe its nucleus may still be intact. The video covers Nov. 27, 2013, 3:30 p.m. EST to Nov. 29, 2013, 8:30 a.m. EST. Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun. The question remains whether it is merely debris from the comet, or if some portion of the comet's nucleus survived, but late-night analysis from scientists with NASA's Comet ISON Observing Campaign suggest that there is at least a small nucleus intact. Credit: ESA/NASA/SOHO/Jhelioviewer NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Oort spike comets with large perihelion distances

NASA Astrophysics Data System (ADS)

Królikowska, Małgorzata; Dybczyński, Piotr A.

2017-12-01

The complete sample of large-perihelion nearly-parabolic comets discovered during the period 1901-2010 is studied, starting with their orbit determination. Next, an orbital evolution that includes three perihelion passages (previous-observed-next) is investigated in which a full model of Galactic perturbations and perturbations from passing stars is incorporated. We show that the distribution of planetary perturbations suffered by actual large-perihelion comets during their passage through the Solar system has a deep, unexpected minimum around zero, which indicates a lack of 'almost unperturbed' comets. Using a series of simulations we show that this deep well is moderately resistant to some diffusion of the orbital elements of the analysed comets. It seems reasonable to assert that the observed stream of these large-perihelion comets experienced a series of specific planetary configurations when passing through the planetary zone. An analysis of the past dynamics of these comets clearly shows that dynamically new comets can appear only when their original semimajor axes are greater than 20 000 au. On the other hand, dynamically old comets are completely absent for semimajor axes longer than 40 000 au. We demonstrate that the observed 1/aori-distribution exhibits a local minimum separating dynamically new from dynamically old comets. Long-term dynamical studies reveal a wide variety of orbital behaviour. Several interesting examples of the action of passing stars are also described, in particular the impact of Gliese 710, which will pass close to the Sun in the future. However, none of the obtained stellar perturbations is sufficient to change the dynamical status of the analysed comets.

Genotoxicity assessment of nanomaterials: recommendations on best practices, assays and methods.

PubMed

Elespuru, Rosalie; Pfuhler, Stefan; Aardema, Marilyn; Chen, Tao; Doak, Shareen H; Doherty, Ann; Farabaugh, Christopher S; Kenny, Julia; Manjanatha, Mugimane; Mahadevan, Brinda; Moore, Martha M; Ouédraogo, Gladys; Stankowski, Leon F; Tanir, Jennifer Y

2018-04-26

Nanomaterials (NMs) present unique challenges in safety evaluation. An international working group, the Genetic Toxicology Technical Committee of the International Life Sciences Institute's Health and Environmental Sciences Institute, has addressed issues related to the genotoxicity assessment of NMs. A critical review of published data has been followed by recommendations on methods alterations and best practices for the standard genotoxicity assays: bacterial reverse mutation (Ames); in vitro mammalian assays for mutations, chromosomal aberrations, micronucleus induction, or DNA strand breaks (comet); and in vivo assays for genetic damage (micronucleus, comet and transgenic mutation assays). The analysis found a great diversity of tests and systems used for in vitro assays; many did not meet criteria for a valid test, and/or did not use validated cells and methods in the Organization for Economic Co-operation and Development Test Guidelines, and so these results could not be interpreted. In vivo assays were less common but better performed. It was not possible to develop conclusions on test system agreement, NM activity, or mechanism of action. However, the limited responses observed for most NMs were consistent with indirect genotoxic effects, rather than direct interaction of NMs with DNA. We propose a revised genotoxicity test battery for NMs that includes in vitro mammalian cell mutagenicity and clastogenicity assessments; in vivo assessments would be added only if warranted by information on specific organ exposure or sequestration of NMs. The bacterial assays are generally uninformative for NMs due to limited particle uptake and possible lack of mechanistic relevance, and are thus omitted in our recommended test battery for NM assessment. Recommendations include NM characterization in the test medium, verification of uptake into target cells, and limited assay-specific methods alterations to avoid interference with uptake or endpoint analysis. These

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

EPA Science Inventory

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

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

Extended atmospheres of outer planet satellites and comets

NASA Technical Reports Server (NTRS)

Smyth, W. H.; Combi, M. R.

1985-01-01

Model analysis of the extended atmospheres of outer planet satellites and comets are discussed. Understanding the neutral hydrogen distribution in the Saturn system concentrated on assessing the spatial dependence of the lifetime of hydrogen atoms and on obtaining appropriately sorted Lyman ALPHA data from the Voyager 1 UVS instrument. Progress in the area of the extended cometary atmospheres included analysis of Pioneer Venus Layman alpha observations of Comet P/Encke with the fully refined hydrogen cloud model, development of the basic carbon and oxygen models, and planning for the Pioneer Venus UVS observations of Comets P/Giacobini-Zinner and P/Halley.

The origin of comets

NASA Astrophysics Data System (ADS)

Bailey, M. E.; Clube, S. V. M.; Napier, W. M.

Theories of the nature and origin of comets are discussed in a historical review covering the period from ancient times to the present. Consideration is given to the ancient controversy as to the atmospheric or celestial nature of comets, Renaissance theories of comet orbits, superstitions regarding the effects of comets, Kant's (1755) theory of solar-system origin, the nineteenth-century discovery of the relationship between comets and meteor showers, and the continuing solar-system/interstellar debate. Oort's (1950) model of a comet swarm surrounding the solar system is examined in detail; arguments advanced to explain the formation of comets within this model are summarized; and the question of cometary catastrophism is addressed.

Biomonitoring of genotoxic risk in workers in a rubber factory: comparison of the Comet assay with cytogenetic methods and immunology.

PubMed

Somorovská, M; Szabová, E; Vodicka, P; Tulinská, J; Barancoková, M; Fábry, R; Lísková, A; Riegerová, Z; Petrovská, H; Kubová, J; Rausová, K; Dusinská, M; Collins, A

1999-09-30

Several substances used in rubber processing are known to be genotoxic. Workers in a rubber tyre factory, exposed to a broad spectrum of contaminants such as benzo[a]pyrene, benzo-fluoranthene, naphthalene, acetonaphthene, alkenes and 1,3-butadiene have been regularly examined for several years: chromosomal aberrations in lymphocytes, mutagenicity of urine (by use of the Ames test) and various parameters of blood and urine were assessed. An elevated level of mercapturic acid derivatives was found in the urine of employees, which is indicative of environmental exposure to toxicants with alkylating activity. We have now extended this study by examining genotoxicity with the modified Comet assay in parallel with chromosomal aberrations and micronucleus formation as well as immunological endpoints. Twenty-nine exposed workers from this factory were compared with 22 non-exposed administrative staff working in the same factory, as well as with 22 laboratory workers. The absolute numbers of peripheral leukocytes were significantly higher in the exposed group than in either of the control groups (p < 0.001). The erythrocyte mean cell volume was significantly higher in exposed workers in comparison with laboratory controls (p < 0.05). Percentages of lymphocytes, polymorphonuclear leukocytes, monocytes and eosinophils were not altered. The proliferative response of T- and B-cells to mitogen treatment when calculated per number of lymphocytes and adjusted for smoking, age and years of exposure did not differ between exposed and control groups. Endogenous strand breaks (including alkali-labile sites) and altered bases (formamidopyrimidine glycosylase- and endonuclease III-sensitive sites) were measured by the Comet assay in lymphocyte DNA. Exposed workers had significantly elevated levels of DNA breaks compared with office workers (p < 0.00001) or with laboratory controls (p < 0.00001). Micronuclei occurred at significantly higher frequencies in the exposed group than in

Activity in distant comets

NASA Technical Reports Server (NTRS)

Luu, Jane X.

1992-01-01

Activity in distant comets remains a mystery in the sense that we still have no complete theory to explain the various types of activity exhibited by different comets at large distances. This paper explores the factors that should play a role in determining activity in a distant comet, especially in the cases of comet P/Tempel 2, comet Schwassmann-Wachmann 1, and 2060 Chiron.

Comet assay and micronucleus test in circulating erythrocytes of Cyprinus carpio specimens exposed in situ to lake waters treated with disinfectants for potabilization.

PubMed

Buschini, A; Martino, A; Gustavino, B; Monfrinotti, M; Poli, P; Rossi, C; Santoro, M; Dörr, A J M; Rizzoni, M

2004-02-14

The detection of a possible genotoxic effect of surface water treated with disinfectants for potabilization is the aim of the present work. The Comet assay and the micronucleus test were applied in circulating erythrocytes of Cyprinus carpio. Young specimens (20-30 g) were exposed in experimental basins, built within the potabilization plant of Castiglione del Lago (Perugia, Italy). In this plant the water of the Trasimeno Lake is treated and disinfected for potabilization before it is distributed to the people in the net of drinkable water. A continuous flow of water at a constant rate was supplied to basins; the water was continuously treated at a constant concentration with one of the three tested disinfectants (sodium hypochlorite, peracetic acid and chloride dioxide), one control basin being supplied with untreated water. Three sampling campaigns were performed: October 2000, February 2001 and June 2001. Repeated blood samplings through intracardiac punctures allowed to follow the same fish populations after different exposure times: before introduction of the disinfectant, and 10 or 20 days afterwards. An additional blood sampling was performed 3 h after addition of the disinfectant in other, simultaneously exposed, fish populations. Genotoxic damage was shown in fish exposed to water disinfected with sodium hypochlorite and chloride dioxide. The Comet assay showed an immediate response, i.e. DNA damage that was induced directly in circulating erythrocytes, whereas micronuclei reached their highest frequencies at later sampling times, when a genotoxic damage in stem cells of the cephalic kidney is expressed in circulating erythrocytes. The quality of the untreated surface water seems to be the most important parameter for the long-term DNA damage in circulating erythrocytes.

COMET-AR User's Manual: COmputational MEchanics Testbed with Adaptive Refinement

NASA Technical Reports Server (NTRS)

Moas, E. (Editor)

1997-01-01

The COMET-AR User's Manual provides a reference manual for the Computational Structural Mechanics Testbed with Adaptive Refinement (COMET-AR), a software system developed jointly by Lockheed Palo Alto Research Laboratory and NASA Langley Research Center under contract NAS1-18444. The COMET-AR system is an extended version of an earlier finite element based structural analysis system called COMET, also developed by Lockheed and NASA. The primary extensions are the adaptive mesh refinement capabilities and a new "object-like" database interface that makes COMET-AR easier to extend further. This User's Manual provides a detailed description of the user interface to COMET-AR from the viewpoint of a structural analyst.

Suicide Comet HD Video

NASA Image and Video Library

2010-03-16

Captured March 12, 2010 The SOHO spacecraft captured a very bright, sungrazing comet as it rocketed towards the Sun (Mar. 12, 2010) and was vaporized. This comet is arguably the brightest comet that SOHO has observed since Comet McNaught in early 2007. The comet is believed to belong to the Kreutz family of comets that broke up from a much larger comet many hundreds of years ago. They are known to orbit close to the Sun. A coronal mass ejection (CME) burst away from the Sun during the bright comet’s approach. Interestingly, a much smaller comet that preceded this one can be seen about half a day earlier on just about the identical route. And another pair of small comets followed the same track into the Sun after the bright one. Such a string of comets has never been witnessed before by SOHO. SOHO's C3 coronagraph instrument blocks out the Sun with an occulting disk; the white circle represents the size of the Sun. The planet Mercury can also be seen moving from left to right just beneath the Sun. To learn more and to download the video and still images go here: sohowww.nascom.nasa.gov/pickoftheweek/old/15mar2010/ Credit: NASA/GSFC/SOHO

From the Cover: An Investigation of the Genotoxicity and Interference of Gold Nanoparticles in Commonly Used In Vitro Mutagenicity and Genotoxicity Assays.

PubMed

George, Jiya M; Magogotya, Millicent; Vetten, Melissa A; Buys, Antoinette V; Gulumian, Mary

2017-03-01

The suitability of 4 in vitro assays, commonly used for mutagenicity and genotoxicity assessment, was investigated in relation to treatment with 14 nm citrate-stabilized gold nanoparticles (AuNPs). Specifically, the Ames test was conducted without metabolic activation, where no mutagenic effects were observed. High resolution transmission electron microscopy and Cytoviva dark-field image analysis showed that AuNPs did not enter the bacterial cells, thus confirming the unreliability of the Ames test for nanoparticle mutagenicity studies. In addition, the Chinese hamster ovary (CHO) cell line was used for Comet, Chromosome aberration and Micronucleus assays. CHO cells were treated with AuNPs for 20 h at 37 °C. Cytotoxicity was not detected by cell impedance studies even though AuNP uptake was confirmed using Cytoviva image analysis. The DNA damage was statistically significant in treated cells when assessed by the Comet assay. However, minimal and nonstatistically significant chromosomal DNA damage was observed using the chromosome aberration and micronucleus assays. In this study, we showed that false positive results obtained with Comet assay may have been due to the possibility of direct contact between the residual, intracellular AuNPs and DNA during the assay procedure. Therefore, the chromosome aberration and micronucleus assays are better suited to assess the genotoxic effects of nanoparticles due to low probability of such direct contact occurring. Genotoxic effect of 14 and 20 nm citrate-stabilized, as well as, 14 nm PCOOH AuNPs were also investigated using chromosome aberration and micronucleus assays. Based on our acceptance criteria for a positive genotoxic response, none of the AuNPs were found to be genotoxic in either of these assays. © The Author 2017. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Double Stranded Sperm DNA Breaks, Measured by Comet Assay, Are Associated with Unexplained Recurrent Miscarriage in Couples without a Female Factor

PubMed Central

Ribas-Maynou, Jordi; García-Peiró, Agustín; Fernandez-Encinas, Alba; Amengual, Maria José; Prada, Elena; Cortés, Pilar; Navarro, Joaquima; Benet, Jordi

2012-01-01

It is known that sperm samples from recurrent pregnancy loss (RPL) couples have an increase in their sperm DNA fragmentation (SDF), but no studies have been performed in order to identify differences between single stranded SDF (ssSDF) and double stranded SDF (dsSDF) in these patients. This could be relevant because the type of DNA damage could have different effects. Semen samples were classified attending their clinical status: 25 fertile donors and 20 RPL patients with at least two unexplained first trimester miscarriages. SDF was analysed using alkaline and neutral Comet assay, SCD test and pulsed-field gel electrophoresis (PFGE), and ROC analysis including data from 105 more infertile patients (n = 150) was performed to establish predictive threshold values. SDF for alkaline and neutral Comet, and the SCD test was analysed in these categories of individuals. Data revealed the presence of two subgroups within fertile donors. The values obtained were 21.10±9.13, 23.35±10.45 and 12.31±4.31, respectively, for fertile donors with low values for both ssSDF and dsSDF; 27.86±12.64, 80.69±12.67 and 12.43±5.22, for fertile donors with low ssSDF and high dsSDF; and 33.61±15.50, 84.64±11.28 and 19.28±6.05, for unexplained RPL patients, also showing a low ssSDF and high dsSDF profile. This latter profile was seen in 85% of unexplained RPL and 33% of fertile donors, suggesting that it may be associated to a male risk factor for undergoing RPL. ROC analysis regarding recurrent miscarriage set the cut-off value at 77.50% of dsDNA SDF. PFGE for low ssSDF and high dsSDF profile samples and positive controls treated with DNase, to induce dsDNA breaks, showed a more intense band of about 48 kb, which fits the toroid model of DNA compaction in sperm, pointing out that some nuclease activity may be affecting their sperm DNA in RPL patients. This work identifies a very specific SDF profile related to the paternal risk of having RPL. PMID:23028579

Bright Comet ISON

NASA Image and Video Library

2013-11-22

Comet ISON shines brightly in this image taken on the morning of 19 Nov. 2013. This is a 10-second exposure taken with the Marshall Space Flight Center 20" telescope in New Mexico. The camera there is black and white, but the smaller field of view allows for a better "zoom in" on the comet's coma, which is essentially the head of the comet. Credit: NASA/MSFC/MEO/Cameron McCarty -------- More details on Comet ISON: Comet ISON began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- 28 Nov 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Catalogued as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012. This is ISON's very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Comet ISON is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide -- some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. NASA has been using a vast fleet of spacecraft, instruments, and space- and Earth-based telescope, in order to learn more about this time capsule from when the solar system first formed. The journey along the way for such a sun-grazing comet can be dangerous. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars -- at some 230 million miles away from the sun -- the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation

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

NASA Technical Reports Server (NTRS)

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.

Study of Comets Composition and Structure

NASA Astrophysics Data System (ADS)

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.

Analysis of the perihelic passages of the comet 1P/Halley in 1910 and in 1986

NASA Astrophysics Data System (ADS)

Voelzke, Marcos Rincon

2016-07-01

This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km/s; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km/s. The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 10 ^{6} km and in 1986 is (2.2 ± 0.2) x 10 ^{6} km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 10 ^{5} km and in 1986 it is equal to (2.8 ± 0.5) x 10 ^{5} km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work.

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

PubMed

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

2012-10-01

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

Extended atmospheres of outer planet satellites and comets

NASA Technical Reports Server (NTRS)

Smyth, W. H.; Combi, M. R.

1984-01-01

The cometary hydrogen particle-trajectory model was used successfully to analyze observations of Comet P/Encke. The Pioneer Venus Orbiter Ultraviolet Spectrometer observed the comet at 1216A (hydrogen Lyman-alpha) on 15 April 1984, when the comet was .58 AU from the Sun and 1.02 AU from Venus. The analysis implies a production rate at .58 AU of 3.3 x 10 to the 28th power/sec of the water molecules which photodissociate to produce the observed hydrogen.

Terrestrial analysis of the organic component of comet dust.

PubMed

Sandford, Scott A

2008-01-01

The nature of cometary organics is of great interest, both because these materials are thought to represent a reservoir of the original carbon-containing materials from which everything else in our solar system was made and because these materials may have played key roles in the origin of life on Earth. Because these organic materials are the products of a series of universal chemical processes expected to operate in the interstellar media and star-formation regions of all galaxies, the nature of cometary organics also provides information on the composition of organics in other planetary systems and, by extension, provides insights into the possible abundance of life elsewhere in the universe. Our current understanding of cometary organics represents a synthesis of information from telescopic and spacecraft observations of individual comets, the study of meteoritic materials, laboratory simulations, and, now, the study of samples collected directly from a comet, Comet P81/Wild 2.

Comparative analysis of three sperm DNA damage assays and sperm nuclear protein content in couples undergoing assisted reproduction treatment.

PubMed

Simon, L; Liu, L; Murphy, K; Ge, S; Hotaling, J; Aston, K I; Emery, B; Carrell, D T

2014-05-01

Is there an association between sperm DNA damage, measured by three different assays, sperm nuclear protein content and clinical outcomes in assisted reproduction treatment (ART)? Sperm DNA damage measured by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling (TUNEL) and the Comet assay were significantly associated with ART outcomes in our single institution study. Abnormal protamine expression is known to be associated with sperm DNA damage and male infertility. A number of studies have shown a significant relationship between sperm DNA damage and ART outcomes. To date, there are no large studies providing direct comparisons of DNA damage tests within the same study population. Thus, the prognostic value for each method remains unknown. Cross-sectional study of 238 men from infertile couples undergoing ART at the University Center for Reproductive Medicine, Utah, USA, between April 2011 and March 2013. Sperm from men undergoing ART were tested for DNA damage using the alkaline Comet assay, TUNEL and flow cytometric chromatin evaluation (FCCE) assays. Histone retention was analysed using the aniline blue staining method, whereas protamine content (proteins P1 and P2) and ratio were analysed using acid urea gel electrophoresis. The prognostic value of each sperm DNA test to predict clinical pregnancy was calculated. Histone retention was associated with sperm DNA damage (P < 0.001), reduced embryo quality (P = 0.005) and clinical pregnancies (P < 0.001). The mean percentage of sperm with DNA damage was significantly higher in sperm from non-pregnant couples compared with that from pregnant couples, as measured by TUNEL assay (15.04 ± 1.16% versus 8.79 ± 0.56%; P < 0.001) and alkaline Comet assay (72.79 ± 2.49% versus 55.86 ± 2.29%; P < 0.001). There was no association between clinical pregnancies and DNA fragmentation index measured by FCCE (12.97 ± 1.46 versus 14.93 ± 1.65; P = 0.379). Of the protamine parameters analysed, only the P1/P2

Comet rendezvous mission study

NASA Technical Reports Server (NTRS)

Friedlander, A. L.; Wells, W. C.

1971-01-01

Four periodic comets with perihelia between 1980 and 1986 (Encke, d'Arrest, Kipff, and Halley) are used as candidates for the comet rendezvous mission study. All these comet apparitions are especially favorable for rendezvous missions, because of early earth-based comet recovery, good opportunities to view their activity from earth, and reasonable launch vehicle and trajectory requirements for nominal payloads.

Development and characteristics of Mechanical Porous Ambient Comet Simulants as comet surface analogs

NASA Astrophysics Data System (ADS)

Carey, Elizabeth M.; Peters, Gregory H.; Choukroun, Mathieu; Chu, Lauren; Carpenter, Emma; Cohen, Brooklin; Panossian, Lara; Zhou, Yu Meng; Sarkissian, Ani; Moreland, Scott; Shiraishi, Lori R.; Backes, Paul; Zacny, Kris; Green, Jacklyn R.; Raymond, Carol

2017-11-01

Comets are icy remnants of the Solar System formation, and as such contain some of the most primitive volatiles and organic materials. Sampling the surface of a comet is a high priority for the New Frontiers program. Planetary simulants are crucial to the development of adequate in situ instruments and sample acquisition systems. A high-fidelity comet surface simulant has been developed to support hardware design and development for one Comet Surface Sample Return tool, the BiBlade Comet Sampler. Mechanical Porous Ambient Comet Simulants (MPACS) can be manufactured to cover a wide range of desired physical properties, such as density and cone penetration resistance, and exhibit a brittle fracture mode. The structure of the MPACS materials is an aggregated composite structure of weakly-bonded grains of very small size (diameter ≤ 40 μm) that are most relevant to the structure of the surface of a comet nucleus.

Analysis of Returned Comet Nucleus Samples

NASA Astrophysics Data System (ADS)

Chang, Sherwood

1997-12-01

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

Analysis of Returned Comet Nucleus Samples

NASA Technical Reports Server (NTRS)

Chang, Sherwood (Compiler)

1997-01-01

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

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

PubMed

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.

Comet ISON Enhanced

NASA Image and Video Library

2013-11-22

Taken on 19 Nov. 2013, this image shows a composite "stacked" image of comet ISON. These five stacked images of 10 seconds each were taken with the 20" Marshall Space Flight Center telescope in New Mexico. This technique allows the comet's sweeping tail to emerge with more detail. Credit: NASA/MSFC/MEO/Cameron McCarty -------- More details on Comet ISON: Comet ISON began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- 28 Nov 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Catalogued as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012. This is ISON's very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Comet ISON is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide -- some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. NASA has been using a vast fleet of spacecraft, instruments, and space- and Earth-based telescope, in order to learn more about this time capsule from when the solar system first formed. The journey along the way for such a sun-grazing comet can be dangerous. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars -- at some 230 million miles away from the sun -- the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation and pressure as it flies near the surface of the sun could

Comets: Data, problems, and objectives

NASA Technical Reports Server (NTRS)

Whipple, F. L.

1977-01-01

A highly abridged review of new relevant results from the observations of Comet Kohoutek is followed by an outline summary of our basic knowledge concerning comets, both subjects being confined to data related to the nature and origin of comets rather than the phenomena (for example, plasma phenomena are omitted). The discussion then centers on two likely places of cometary origin in the developing solar system, the proto-Uranus-Neptune region versus the much more distant fragmented interstellar cloud region, now frequented by comets of the Opik-Oort cloud. The Comet Kohoutek results add new insights, particularly with regard to the parent molecules and the nature of meteoric solids in comets, to restrict the range of the physical circumstances of comet formation. A few fundamental and outstanding questions are asked, and a plea made for unmanned missions to comets and asteroids in order to provide definitive answers as to the nature and origin of comets, asteroids, and the solar system generally.

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

NASA Technical Reports Server (NTRS)

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

2005-01-01

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

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

NASA Technical Reports Server (NTRS)

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

2005-01-01

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

Comparative study of icy patches on comet nuclei

NASA Astrophysics Data System (ADS)

Oklay, Nilda; Pommerol, Antoine; Barucci, Maria Antonietta; Sunshine, Jessica; Sierks, Holger; Pajola, Maurizio

2016-07-01

Cometary missions Deep Impact, EPOXI and Rosetta investigated the nuclei of comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko respectively. Bright patches were observed on the surfaces of each of these three comets [1-5]. Of these, the surface of 67P is mapped at the highest spatial resolution via narrow angle camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, [6]) on board the Rosetta spacecraft. OSIRIS NAC is equipped with twelve filters covering the wavelength range of 250 nm to 1000 nm. Various filters combinations are used during surface mapping. With high spatial resolution data of comet 67P, three types of bright features were detected on the comet surface: Clustered, isolated and bright boulders [2]. In the visible spectral range, clustered bright features on comet 67P display bluer spectral slopes than the average surface [2, 4] while isolated bright features on comet 67P have flat spectra [4]. Icy patches observed on the surface of comets 9P and 103P display bluer spectral slopes than the average surface [1, 5]. Clustered and isolated bright features are blue in the RGB composites generated by using the images taken in NIR, visible and NUV wavelengths [2, 4]. This is valid for the icy patches observed on comets 9P and 103P [1, 5]. Spectroscopic observations of bright patches on comets 9P and 103P confirmed the existence of water [1, 5]. There were more than a hundred of bright features detected on the northern hemisphere of comet 67P [2]. Analysis of those features from both multispectral data and spectroscopic data is an ongoing work. Water ice is detected in eight of the bright features so far [7]. Additionally, spectroscopic observations of two clustered bright features on the surface of comet 67P revealed the existence of water ice [3]. The spectral properties of one of the icy patches were studied by [4] using OSIRIS NAC images and compared with the spectral properties of the active regions observed

Comets in Australian Aboriginal Astronomy

NASA Astrophysics Data System (ADS)

Hamacher, Duane W.; Norris, Ray P.

2011-03-01

We present 25 accounts of comets from 40 Australian Aboriginal communities, citing both supernatural perceptions of comets and historical accounts of historically bright comets. Historical and ethnographic descriptions include the Great Comets of 1843, 1861, 1901, 1910, and 1927. We describe the perceptions of comets in Aboriginal societies and show that they are typically associated with fear, death, omens, malevolent spirits, and evil magic, consistent with many cultures around the world. We also provide a list of words for comets in 16 different Aboriginal languages.

Where are the mini Kreutz-family comets?

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 {sub 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 {sub 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),more » 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{sub H}{sup −4} while the others follow r{sub H}{sup −7}. In particular, C/SWAN seems to have undergone an outburst (Δm > 5 mag) or a rapid brightening (n ≳ 11) between r {sub 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 {sub 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.« less

Mid-infrared spectra of comet nuclei

NASA Astrophysics Data System (ADS)

Kelley, Michael S. P.; Woodward, Charles E.; Gehrz, Robert D.; Reach, William T.; Harker, David E.

2017-03-01

Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 μm thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 ± 0.11, derived from 16- and 22-μm photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 μm. When the spectra are normalized by the NEATM model, a weak 10-μm silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well

Analytical study of comet nucleus samples

NASA Technical Reports Server (NTRS)

Albee, A. L.

1989-01-01

Analytical procedures for studying and handling frozen (130 K) core samples of comet nuclei are discussed. These methods include neutron activation analysis, x ray fluorescent analysis and high resolution mass spectroscopy.

Comet Dead Ahead

NASA Technical Reports Server (NTRS)

2005-01-01

This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 26, 2005, when the spacecraft was 7,118,499.4 kilometers (4,423,435 miles) away from the comet. Eight images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

Reservoirs for Comets: Compositional Differences Based on Infrared Observations

NASA Astrophysics Data System (ADS)

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.

Reservoirs for Comets: Compositional Differences Based on Infrared Observations

NASA Astrophysics Data System (ADS)

Disanti, Michael A.; Mumma, Michael J.

2008-07-01

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.

Realm of the comets

NASA Technical Reports Server (NTRS)

Weissman, Paul R.

1987-01-01

Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

Realm of the comets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weissman, P.R.

1987-03-01

Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sendingmore » 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.« less

In vivo gamma-rays induced initial DNA damage and the effect of famotidine in mouse leukocytes as assayed by the alkaline comet assay.

PubMed

Mozdarani, Hossein; Nasirian, Borzo; Haeri, S Abolghasem

2007-03-01

Ionizing radiation induces a variety of lesions in DNA, each of which can be used as a bio-indicator for biological dosimetry or the study of the radioprotective effects of substances. To assess gamma ray-induced DNA damage in vivo in mouse leukocytes at various doses and the effect of famotidine, blood was collected from Balb/c male mice after irradiation with 4 Gy gamma-rays at different time intervals post-irradiation. To assess the response, mice were irradiated with doses of gamma-rays at 1 to 4 Grays. Famotidine was injected intra-peritoneally (i.p) at a dose of 5 mg/kg at various time intervals before irradiation. Four slides were prepared from each sample and alkaline comet assay was performed using standard protocols. Results obtained show that radiation significantly increases DNA damage in leukocytes in a dose dependent manner (p < 0.01) when using appropriate sampling time after irradiation, because increasing sampling time after irradiation resulted in a time dependent disappearance of DNA damage. Treatment with only 5 mg/kg famotidine before 4 Gy irradiation led to almost 50% reduction in DNA damage when compared with those animals which received radiation alone. The radioprotective capability of famotidine might be attributed to radical scavenging properties and an anti-oxidation mechanism.

A study of ion composition and dynamics at Comet Halley

NASA Technical Reports Server (NTRS)

Shelley, E. G.; Fuselier, S. A.

1991-01-01

This report details the participation by Lockheed co-investigators in the reduction, analysis, and interpretation of data obtained by the Ion Mass Spectrometer onboard the Giotto mission to Comet Halley. The data analysis activities and much of the scientific collaboration was shared by this team. One objective of the effort under this contract was to use data obtained by the Giotto Ion Mass Spectrometer (IMS) during the encounter with comet Halley for the purpose of advancing our understanding of the chemistry and physics of the interaction of the solar wind with comets and obtaining new information on the comet's composition. An additional objective was to make this unique data set available in a format which can be easily used by the reset of the cometary science community for other analysis in the future. The IMS has two sensors: the High Intensity Spectrometer (HIS) and the High Energy Range Spectrometer (HERS).

Interaction of Comets and the Solar Wind

NASA Technical Reports Server (NTRS)

Wagner, William (Technical Monitor); Raymond, John C.

2004-01-01

The analysis of Comet Kudo-Fujikawa at perihelion was published and picked up by Der Spiegel. Besides a large and rapidly increasing water outgassing rate, we detected a bright tail in doubly ionized carbon. The amount of carbon was greater than could be accounted for by CO photodissociation, and we attribute it to evaporation of organics from dust. A spectacular disconnection event was apparent in the C III tail, and it coincides within the uncertainties to the position of the heliospheric current sheet. The analysis of the sungrazing comet C2001 C2 is in press. It showed evidence for subfragments and for a very long lasting source of neutrals, which we identify as evaporation of pyroxene dust grains. Results were also presented at COSPAR. We are working on observations of another sungrazer, comet C2002 S2, which shows a sudden 2 magnitude drop in optical brightness and an equally sudden recovery. UVCS observations during that time show a steadily increasing outgassing rate. We have derived solar wind densities for both comets, but we are still sorting out the ambiguities involving the fragmentation and optical behavior.

Comet ISON Seen Coming and Going

NASA Image and Video Library

2013-11-30

"Timelapse" series of images of comet ISON as viewed by ESA/NASA's Solar and Heliospheric Observatory, or SOHO. This image is a composite, with the sun imaged by NASA's Solar Dynamics Observatory in the center, and SOHO's two coronagraphs showing the solar atmosphere, the corona. The most recent image in this is from 5:30 p.m. EST on Nov. 29, 2013. Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun. The question remains whether it is merely debris from the comet, or if some portion of the comet's nucleus survived, but late-night analysis from scientists with NASA's Comet ISON Observing Campaign suggest that there is at least a small nucleus intact. Image Credit:ESA&NASA/SOHO/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Comet flyby sample return

NASA Technical Reports Server (NTRS)

Tsou, P.; Albee, A.

1985-01-01

The results of a joint JPL/CSFC feasability study of a low-cost comet sample return flyby mission are presented. It is shown that the mission could be undertaken using current earth orbiter spacecraft technology in conjunction with pathfinder or beacon spacrcraft. Detailed scenarios of missions to the comets Honda-Mrkos-Pajdusakova (HMP), comet Kopff, and comet Giacobini-Zinner (GZ) are given, and some crossectional diagrams of the spacecraft designs are provided.

Comets

NASA Astrophysics Data System (ADS)

Festou, M. C.; Feldman, P. D.

Observations of comets obtained with the IUE satellite since its launch in 1978 are reviewed. The status of UV observation of comets prior to IUE is discussed, and particular attention is given to low-resolution UV spectroscopy of cometary comae, the detection of new species in the UV emission, high-dispersion spectroscopy, spatial mapping of the emissions, abundance determinations, and short-term variability. Diagrams, graphs, sample spectra, and tables of numerical data are provided.

First Comet Encounter

NASA Image and Video Library

2010-09-09

Dr. Michael A'Hearn, Principal Investigator, EPOXI Comet Encounter Mission, speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

Comets and the Stardust Mission

ScienceCinema

LLNL - University of California Television

2017-12-09

The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

Comets and the Stardust Mission

DOE Office of Scientific and Technical Information (OSTI.GOV)

LLNL - University of California Television

2008-05-16

The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

Physical processes in comets

NASA Technical Reports Server (NTRS)

Whipple, F. L.; Huebner, W. F.

1976-01-01

The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

Evaluation of the genotoxicity of waters impacted by domestic and industrial effluents of a highly industrialized region of São Paulo State, Brazil, by the comet assay in HTC cells.

PubMed

Manzano, Bárbara Cassu; Roberto, Matheus Mantuanelli; Hoshina, Márcia Miyuki; Menegário, Amauri Antônio; Marin-Morales, Maria Aparecida

2015-01-01

The problems that most affect the quality of the waters of rivers and lakes are associated with the discharges performed in these environments, mainly industrial and domestic effluents inappropriately treated or untreated. The comet assay is a sensitive tool and is recommended for studies of environmental biomonitoring, which aim to determine the genotoxicity potential of water pollutants. This study aimed to assess the genotoxic potential of the Ribeirão Tatu waters, region of Limeira, São Paulo (SP), by the comet assay with mammalian cells (hepatoma tissue culture (HTC)). Water samples were collected along the Ribeirão Tatu at three distinct periods: November 2008, February 2009 and August 2009, and five collection sites were established: P1, source of the stream; P2, site located downstream the urban perimeter of the municipality of Cordeirópolis and after receiving the pollution load of this city; P3, collection site located upstream the urban perimeter of the city of Limeira; P4, urban area of Limeira; and P5, rural area of Limeira, downstream the discharges of the city sewage. The results showed that for the November 2008 collection, there was no water sample-induced genotoxicity; for the February 2009 collection, the sites P1 and P2 were statistically significant in relation to the negative control (NC), and for the August 2009 collection, the site P5 was statistically significant. These results could be explained by the content of different metals during the different seasons that are under the influence of domestic, industrial and agricultural effluents and also due to the seasonality, since the water samples collected in the period of heavy rain (February 2009) presented a higher genotoxicity possibly due to the entrainment of contaminants into the bed of the stream promoted by the outflow of rainwaters. The comet assay showed to be a useful and sensitive tool in the evaluation of hydric resources impacted by pollutants of diverse origins, and a

Thermal structure analyses for CSM testbed (COMET)

NASA Technical Reports Server (NTRS)

Xue, David Y.; Mei, Chuh

1994-01-01

This document is the final report for the project entitled 'Thermal Structure Analyses for CSM Testbed (COMET),' for the period of May 16, 1992 - August 15, 1994. The project was focused on the investigation and development of finite element analysis capability of the computational structural mechanics (CSM) testbed (COMET) software system in the field of thermal structural responses. The stages of this project consisted of investigating present capabilities, developing new functions, analysis demonstrations, and research topics. The appendices of this report list the detailed documents of major accomplishments and demonstration runstreams for future references.

Comparative analysis of images of comet 1P/Halley in their perihelion passages in 1910 and 1986

NASA Astrophysics Data System (ADS)

Voelzke, Marcos Rincon

This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km s (-1) ; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km s (-1) .The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 10 (6) km and in 1986 is (2.2 ± 0.2) x 10 (6) km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 10 (5) km and in 1986 it is equal to (2.8 ± 0.5) x 10 (5) km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work.

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

NASA Technical Reports Server (NTRS)

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.

Disintegration of comet nuclei

NASA Astrophysics Data System (ADS)

Ksanfomality, Leonid V.

2012-02-01

The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies.

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

PubMed

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.

Disappearance and disintegration of comets

NASA Technical Reports Server (NTRS)

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.

Halley's Comet.

ERIC Educational Resources Information Center

Carey, Tom

1985-01-01

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

CometBoards Users Manual Release 1.0

NASA Technical Reports Server (NTRS)

Guptill, James D.; Coroneos, Rula M.; Patnaik, Surya N.; Hopkins, Dale A.; Berke, Lazlo

1996-01-01

Several nonlinear mathematical programming algorithms for structural design applications are available at present. These include the sequence of unconstrained minimizations technique, the method of feasible directions, and the sequential quadratic programming technique. The optimality criteria technique and the fully utilized design concept are two other structural design methods. A project was undertaken to bring all these design methods under a common computer environment so that a designer can select any one of these tools that may be suitable for his/her application. To facilitate selection of a design algorithm, to validate and check out the computer code, and to ascertain the relative merits of the design tools, modest finite element structural analysis programs based on the concept of stiffness and integrated force methods have been coupled to each design method. The code that contains both these design and analysis tools, by reading input information from analysis and design data files, can cast the design of a structure as a minimum-weight optimization problem. The code can then solve it with a user-specified optimization technique and a user-specified analysis method. This design code is called CometBoards, which is an acronym for Comparative Evaluation Test Bed of Optimization and Analysis Routines for the Design of Structures. This manual describes for the user a step-by-step procedure for setting up the input data files and executing CometBoards to solve a structural design problem. The manual includes the organization of CometBoards; instructions for preparing input data files; the procedure for submitting a problem; illustrative examples; and several demonstration problems. A set of 29 structural design problems have been solved by using all the optimization methods available in CometBoards. A summary of the optimum results obtained for these problems is appended to this users manual. CometBoards, at present, is available for Posix-based Cray and

OORT-Cloud and Kuiper-Belt Comets

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1998-01-01

This paper follows the broadly accepted theory that Oort-Cloud Comets originated in the Solar Nebula in the general region where the major planets, Jupiter and Saturn, were formed while the Kuiper-Belt Comets originated farther out where the temperatures were lower. The Oort-Cloud Comets are identified orbitally by long periods and random inclinations and, including the Halley-type comets, comets with a Tisserand Criterion less than 2.0. Kuiper-Belt comets are identified by short periods, usually much less than 200 years, and small inclinations to the ecliptic. Here two criteria for comet activity are found to separate the two classes of comets. These quantities NG1 and NG2, were intended to measure theoretical nongravitaional effects on comet orbits. They are only, mildly successful in correlations with observed cases of measured non-gravitational forces. But, in fact, their variations with perihelion distance separate the two classes of comets. The results are consistent with the theory that the activity or intrinsic brightness of Oort-Cloud Comets fall off faster with increasing perihelion distance that does the intrinsic brightness of short-period Kuiper-Belt Comets.

Evaluation of the genotoxic potential of 3-monochloropropane-1,2-diol (3-MCPD) and its metabolites, glycidol and beta-chlorolactic acid, using the single cell gel/comet assay.

PubMed

El Ramy, R; Ould Elhkim, M; Lezmi, S; Poul, J M

2007-01-01

3-monochloropropane-1,2-diol (3-MCPD) is a member of a group of chemicals known as chloropropanols. It is found in many foods and food ingredients as a result of food processing. 3-MCPD is regarded as a rat carcinogen known to induce Leydig-cell and mammary gland tumours in males and kidney tumours in both genders. The aim of our study was to clarify the possible involvement of genotoxic mechanisms in 3-MCPD induced carcinogenicity at the target organ level. For that purpose, we evaluated DNA damages in selected target (kidneys and testes) and non-target (blood leukocytes, liver and bone marrow) male rat organs by the in vivo alkaline single cell gel electrophoresis (comet) assay, 3 and 24 h after 3-MCPD oral administration to Sprague-Dawley and Fisher 344 adult rats. 3-MCPD may be metabolised to a genotoxic intermediate, glycidol, whereas the predominant urinary metabolite in rats following 3-MCPD administration is beta-chlorolactic acid. Therefore, we also studied the DNA damaging effects of 3-MCPD and its metabolites, glycidol and beta-chlorolactic acid, in the in vitro comet assay on CHO cells. Our results show the absence of genotoxic potential of 3-MCPD in vivo in the target as well as in the non-target organs. Glycidol, the epoxide metabolite, induced DNA damages in CHO cells. beta-Chlorolactic acid, the main metabolite of 3-MCPD in rats, was shown to be devoid of DNA-damaging effects in vitro in mammalian cells.

CO2 Orbital Trends in Comets

NASA Astrophysics Data System (ADS)

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.

Composition/Structure/Dynamics of comet and planetary satellite atmospheres

NASA Technical Reports Server (NTRS)

Combi, Michael R. (Principal Investigator)

1995-01-01

This research program addresses two cases of tenuous planetary atmospheres: comets and Io. The comet atmospheric research seeks to analyze a set of spatial profiles of CN in comet Halley taken in a 7.4-day period in April 1986; to apply a new dust coma model to various observations; and to analyze observations of the inner hydrogen coma, which can be optically thick to the resonance scattering of Lyman-alpha radiation, with the newly developed approach that combines a spherical radiative transfer model with our Monte Carlo H coma model. The Io research seeks to understand the atmospheric escape from Io with a hybrid-kinetic model for neutral gases and plasma given methods and algorithms developed for the study of neutral gas cometary atmospheres and the earth's polar wind and plasmasphere. Progress is reported on cometary Hydrogen Lyman-alpha studies; time-series analysis of cometary spatial profiles; model analysis of the dust comae of comets; and a global kinetic atmospheric model of Io.

David Levy's Guide to Observing and Discovering Comets

NASA Astrophysics Data System (ADS)

Levy, David H.

2003-05-01

Preface; Part I. Why Observe Comets?: 1. Of history, superstition, magic, and science; 2. Comet science progresses; Part II. Discovering Comets: 3. Comet searching begins; 4. Tails and trails; 5. Comet searching in the twentieth century; 6. How I search for comets; 7. Searching for comets photographically; 8. Searching for comets with CCDs; 9. Comet hunting by reading; 10. Hunting for sungrazers over the Internet; 11. What to do when you think you've found a comet; Part III. A New Way of Looking at Comets: 12. When comets hit planets; 13. The future of visual comet hunting; Part IV. How to Observe Comets: 14. An introduction to comet hunting; 15. Visual observing of comets; 16. Estimating the magnitude of a comet; 17. Taking a picture of a comet; 18. Measuring where a comet is in the sky; Part V. Closing Notes: 19. My passion for comets.

Disintegration phenomena in Comet West

NASA Technical Reports Server (NTRS)

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.

Comet nucleus sample return mission

NASA Technical Reports Server (NTRS)

1983-01-01

A comet nucleus sample return mission in terms of its relevant science objectives, candidate mission concepts, key design/technology requirements, and programmatic issues is discussed. The primary objective was to collect a sample of undisturbed comet material from beneath the surface of an active comet and to preserve its chemical and, if possible, its physical integrity and return it to Earth in a minimally altered state. The secondary objectives are to: (1) characterize the comet to a level consistent with a rendezvous mission; (2) monitor the comet dynamics through perihelion and aphelion with a long lived lander; and (3) determine the subsurface properties of the nucleus in an area local to the sampled core. A set of candidate comets is discussed. The hazards which the spacecraft would encounter in the vicinity of the comet are also discussed. The encounter strategy, the sampling hardware, the thermal control of the pristine comet material during the return to Earth, and the flight performance of various spacecraft systems and the cost estimates of such a mission are presented.

COMETS2: An advanced MATLAB toolbox for the numerical analysis of electric fields generated by transcranial direct current stimulation.

PubMed

Lee, Chany; Jung, Young-Jin; Lee, Sang Jun; Im, Chang-Hwan

2017-02-01

Since there is no way to measure electric current generated by transcranial direct current stimulation (tDCS) inside the human head through in vivo experiments, numerical analysis based on the finite element method has been widely used to estimate the electric field inside the head. In 2013, we released a MATLAB toolbox named COMETS, which has been used by a number of groups and has helped researchers to gain insight into the electric field distribution during stimulation. The aim of this study was to develop an advanced MATLAB toolbox, named COMETS2, for the numerical analysis of the electric field generated by tDCS. COMETS2 can generate any sizes of rectangular pad electrodes on any positions on the scalp surface. To reduce the large computational burden when repeatedly testing multiple electrode locations and sizes, a new technique to decompose the global stiffness matrix was proposed. As examples of potential applications, we observed the effects of sizes and displacements of electrodes on the results of electric field analysis. The proposed mesh decomposition method significantly enhanced the overall computational efficiency. We implemented an automatic electrode modeler for the first time, and proposed a new technique to enhance the computational efficiency. In this paper, an efficient toolbox for tDCS analysis is introduced (freely available at http://www.cometstool.com). It is expected that COMETS2 will be a useful toolbox for researchers who want to benefit from the numerical analysis of electric fields generated by tDCS. Copyright © 2016. Published by Elsevier B.V.

Asteroid Family Associations of Main-Belt Comets

NASA Astrophysics Data System (ADS)

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.

Anatomy of a Busted Comet

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Poster Version (Figure 1)

NASA's Spitzer Space Telescope captured the picture on the left of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced on the right to show the anatomy of the comet.

Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt. Astronomers still do not know the cause of these eruptions.

Spitzer's infrared picture at left hand side of figure 1, reveals fine dust particles that make up the outer shell, or coma, of the comet. The nucleus of the comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the comet in the explosion. The comet is headed away from the sun, which lies beyond the right-hand side of figure 1.

The contrast-enhanced picture on the right shows the comet's outer shell, and strange filaments, or streamers, of dust. The streamers and shell are a yet another mystery surrounding comet Holmes. Scientists had initially suspected that the streamers were small dust particles ejected from fragments of the nucleus, or from hyerpactive jets on the nucleus, during the October 2007 explosion. If so, both the streamers and the shell should have shifted their orientation as the comet followed its orbit around the sun. Radiation pressure from the sun should have swept the material back and away from it. But pictures of comet Holmes taken by Spitzer over time show the streamers and shell in the same configuration, and not pointing away from the sun. The observations have left astronomers stumped.

The horizontal line seen in the contrast-enhanced picture is a trail of debris

Ultrastructural Interactions and Genotoxicity Assay of Cerium Dioxide Nanoparticles on Mouse Oocytes

PubMed Central

Courbiere, Blandine; Auffan, Mélanie; Rollais, Raphaël; Tassistro, Virginie; Bonnefoy, Aurélie; Botta, Alain; Rose, Jérôme; Orsière, Thierry; Perrin, Jeanne

2013-01-01

Cerium dioxide nanoparticles (CeO2 ENPs) are on the priority list of nanomaterials requiring evaluation. We performed in vitro assays on mature mouse oocytes incubated with CeO2 ENPs to study (1) physicochemical biotransformation of ENPs in culture medium; (2) ultrastructural interactions with follicular cells and oocytes using Transmission Electron Microscopy (TEM); (3) genotoxicity of CeO2 ENPs on follicular cells and oocytes using a comet assay. DNA damage was quantified as Olive Tail Moment. We show that ENPs aggregated, but their crystal structure remained stable in culture medium. TEM showed endocytosis of CeO2 ENP aggregates in follicular cells. In oocytes, CeO2 ENP aggregates were only observed around the zona pellucida (ZP). The comet assay revealed significant DNA damage in follicular cells. In oocytes, the comet assay showed a dose-related increase in DNA damage and a significant increase only at the highest concentrations. DNA damage decreased significantly both in follicular cells and in oocytes when an anti-oxidant agent was added in the culture medium. We hypothesise that at low concentrations of CeO2 ENPs oocytes could be protected against indirect oxidative stress due to a double defence system composed of follicular cells and ZP. PMID:24185910

The intermediate comets and nongravitational effects

NASA Technical Reports Server (NTRS)

Yeomans, D. K.

1986-01-01

The motions of the intermediate-period comets Pons-Brooks, Olbers, Brorsen-Metcalf, and Westphal are investigated over their observed intervals. The three apparitions of comets Pons-Brooks and Olbers were successfully linked, using the now standard nongravitational-force model. The two apparitions of Comet Brorsen-Metcalf were successfully linked without the need for nongravitational effects. For the 1852 and 1913 apparitions of Comet Westphal, complete success was not achieved in modeling the comet's motion either with or without nongravitational effects. However, by including these effects, the comet's astrometric observations could be represented significantly better than if they were assumed inoperative. Comet Westphal's dynamic and photometric behavior suggests its complete disintegration before reaching perihelion in 1913. If the very large radial nongravitational parameter determined for Comet Westphal is due to the comet's disintegration into dust, then the resultant dust-particle size is of the order of 0.8 mm.

CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return): A New Frontiers Mission Concept to Collect Samples from a Comet and Return Them to Earth for Study

NASA Astrophysics Data System (ADS)

Sandford, S. A.; Chabot, N. L.; Dello Russo, N.; Leary, J. C.; Reynolds, E. L.; Weaver, H. A.; Wooden, D. H.

2017-07-01

CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return) is a mission concept submitted in response to NASA's New Frontiers 4 call. CORSAIR's proposed mission is to return comet nucleus samples to Earth for detailed analysis.

Collisional quenching of OH radio emission from comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Schloerb, F. P.; Devries, C. H.; Lovell, A. J.; Irvine, W. M.; Senay, M.; Wootten, H. A.; Ferris, J. P. (Principal Investigator)

1997-01-01

Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state A-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of approximately 500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.

Look--It's a Comet!

ERIC Educational Resources Information Center

Berglund, Kay

1997-01-01

Describes a classroom lesson on comets that uses modeling and guided imagery to spark students' curiosity. Comet models are built using chunks of rock salt, polystyrene balls, and tinsel. Abstract ideas are made more concrete with a guided imagery story called Comet Ride! Includes an introduction to the use of parallax to measure the distance of…

The natural history of Halley's comet

NASA Astrophysics Data System (ADS)

McLaughlin, W. I.

1981-07-01

The 1986 apparition of Halley's comet will be the subject of numerous space probes, planned to determine the chemical nature and physical structure of comet nuclei, atmospheres, and ionospheres, as well as comet tails. The problems of cometary origin remain inconclusive, with theories ranging from a purely interstellar origin to their being ejecta from the Galilean satellites of Jupiter. Comets can be grouped into one of two classes, depending on their periodicity, and statistical mechanics of the entire Jovian family of comets can be examined under the equilibrium hypothesis. Comet anatomy estimations have been determined, and there is speculation that comet chemistry may have been a factor in the origin of life on earth. Halley's comet was first noted using Newton's dynamical methods, and Brady (1972) attempted to use the comet as a gravitational probe in search of a trans-Plutonian planet. Halley's orbit is calculated by combination of ancient observations and modern scientific methods.

Analysis of the morphological structures of comet 1P/Halley in their perihelion passages in 1910 and 1986

NASA Astrophysics Data System (ADS)

Voelzke, Marcos Rincon

2015-08-01

This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km/s ; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km/s .The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 106 km and in 1986 is (2.2 ± 0.2) x 106 km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 105 km and in 1986 it is equal to (2.8 ± 0.5) x 105 km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work.

Comets in UV

NASA Astrophysics Data System (ADS)

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.

Special Report: Chemistry of Comets.

ERIC Educational Resources Information Center

A'Hearn, Michael F.

1984-01-01

Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

Fluffy comets

NASA Astrophysics Data System (ADS)

Greenberg, J. M.

The density of typical comet nuclei is estimated on the basis of published empirical and theoretical density data on meteors. The nuclei are assumed to consist of aggregated interstellar dust (silicate cores with complex organic refractory mantles) as proposed by Greenberg (1982 and 1983) and Van de Bult et al. (1985). The theoretical density (0.5 g/cu cm) of a compact nucleus of this type is contrasted with the observed densities of meteors associated with short-period comets (0.2 g/cu cm) and the Draconids associated with comet Giacobini-Zinner (0.01 g/cu cm), and it is inferred that the original comet debris was less than fully packed. A birdsnest structure comprising elongated crystals and about 60 percent empty space is proposed; its albedo is estimated as about 0.05 (in the range predicted by observations); and it is shown to undergo much less internal heating by the sun than a solid ice nucleus. The mean density of reconstituted cometary matter is found to be in the range 0.54-0.03 g/cu cm, consistent with the estimates (0.1 g/cu cm) of Lin (1966) and Donn (1963).

Analysis of Polarimetric, Photometric, and Spectroscopic Observations of Comet C/1996 Q1 (Tabur)

NASA Astrophysics Data System (ADS)

Kiselev, N. N.; Jockers, K.; Rosenbush, V. K.; Korsun, P. P.

2001-11-01

We present the imaging polarimetry and photometry of Comet C/1996 Q1 (Tabur) obtained on October 10, 1996, with a two-channel focal reducer attached to the 2-m Pik Terskol Observatory telescope through blue (λ4430/44 Å) and red (λ6420/26 Å) continuum filters and through a λ6620/59 Å filter that isolated the NH_2(0.7.0) band. We analyze the λ3600-9300 Å long-slit spectrograms of the comet taken on October 5-6, 1996, with the 2.6-m Crimean Astrophysical Observatory telescope. The NH_2(0.8.0) λ6408 Å emission and an unidentified λ6428 Å emission were found to fall within the pass band of the red filter. The blue filter transmits weak unidentified emissions at λ4424-4444 Å and partially C_2(λ4360 Å). Correction for the depolarizing effect of molecular emissions resulted in an increase of the dust polarization by 2-4% in the near-nucleus region and by almost a factor of 2 in the outer coma regions. However, the polarization and color differences between different coma regions remained even after correction for the contribution of emissions. We found no dust polarization difference between the gas comet Tabur and the dust comet C/1988 A1 (Liller), which are believed to be fragments of a common parent comet. The NH_2coma was found to be elongated perpendicular to the comet radius vector. The causes of the spatial asymmetry in the NH_2molecular distribution are yet to be established. We study the evolution of activity and the spatial distribution of dust brightness, polarization, and color in the comet. We consider a taxonomic classification of gas and dust comets according to dust polarization properties. The polarization differences between dust and gas comets at large phase angles are most likely related both to the actual differences in dust and to the effect of molecular emissions, nuclear gas- and dust-production rates and to the evolution of grain properties with distance from the nucleus.

Mechanical and SEM analysis of artificial comet nucleus samples

NASA Technical Reports Server (NTRS)

Thiel, K.; Kochan, H.; Roessler, K.; Gruen, E.; Schwehm, G.; Hellmann, H.; Hsiung, P.; Koelzer, G.

1989-01-01

Since 1987 experiments dealing with comet nucleus phenomena have been carried out in the DFVLR space simulation chambers. The main objective of these experiments is a better understanding of thermal behavior, surface phenomena and especially the gas dust interaction. As a function of different sample compositions and exposure to solar irradiation (xenon-bulbs) crusts of different hardness and thickness were measured. The measuring device consists of a motor driven pressure foot (5 mm diameter), which is pressed into the sample. The applied compressive force is electronically monitored. The microstructure of the crust and dust residuals is investigated by scanning electron microscopy (SEM) techniques. Stress-depth profiles of an unirradiated and an irradiated model comet are given.

A volatility index for comets

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1992-01-01

The variations in total brightness of a comet when it is most active, near perihelion, are presently used as the bases of a volatility index (VI) for short-period (SP) and long-period (LP) comets. Volatility does not correlate with period among the LP comets, and thereby shows no 'aging' effect; similarly, the VI measurements are the same for SP and for LP comets and exhibit no correlation with (1) absolute magnitude near perihelion, (2) orbital inclination, or (3) activity index measuring the intrinsic brightness change from great solar distances to the maximum near perihelion. Active comets are shown to be basically alike irrespective of their orbits or 'ages'.

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

PubMed

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

2016-05-01

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

Comet Hyakutake C/1996 B2

NASA Technical Reports Server (NTRS)

1998-01-01

These are two images of the inner coma of Comet Hyakutake made on April 3 and 4, 1996, using the NASA Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2). The first one, shown in red, was taken through a narrow-band red filter that shows only sunlight scattered by dust particles in the inner coma of the comet. The second one, shown in blue was taken with an ultraviolet 'Woods' filter image that shows the distribution of scattered ultraviolet radiation from hydrogen atoms in the inner coma. The coma is the head or dusty-gas atmosphere of a comet. The square field of view is 14,000 km on a side and the sun is toward the upper right corner of the image. Hydrogen atoms represent the most abundant gas in the whole coma of the comet. They are produced when solar ultraviolet light breaks up molecules of water, the major constituent of the nucleus of the comet. These images were taken as part of an observing program to study water photochemistry in comets. Measurements of hydrogen (H) and hydroxyl (OH) in the coma (or atmosphere) of Comet Hyakutake were also made using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS). A self-consistent analysis of all the data shows that the water production rate of the comet was between 7 and 8 tons per second on the April 3 and 4. A theoretical model was used in the analysis which accounts for the detailed physics and chemistry of the photochemical destruction of the water, the production of the H and OH, and their expansion in the coma (or atmosphere) of the comet. The model matched the velocity measurements of hydrogen atoms made using the high spectral resolution capabilities of the GHRS instrument. The importance of such a detailed model is that is permits the accurate calculation of the production rate of water from observations of H and OH.

The inner yellow region near the center of the red dust image is dominated by the contribution from the dust which shows sunward directed

Discovering the Nature of Comets.

ERIC Educational Resources Information Center

Whipple, Fred L.

1986-01-01

"The Mystery of Comets" by Dr. Fred Whipple provides an introduction to the modern picture of comets and his personal reminiscences of how his model of comets came to be. An adaptation of several sections of the book is presented. (JN)

Organics in comet 67P - a first comparative analysis of mass spectra from ROSINA-DFMS, COSAC and Ptolemy

NASA Astrophysics Data System (ADS)

Altwegg, Kathrin; Balsiger, H.; Berthelier, J. J.; Bieler, A.; Calmonte, U.; Fuselier, S. A.; Goesmann, F.; Gasc, S.; Gombosi, T. I.; Le Roy, L.; de Keyser, J.; Morse, A.; Rubin, M.; Schuhmann, M.; Taylor, M. G. G. T.; Tzou, C.-Y.; Wright, I.

2017-07-01

The ESA Rosetta spacecraft followed comet 67P at a close distance for more than 2 yr. In addition, it deployed the lander Philae on to the surface of the comet. The (surface) composition of the comet is of great interest to understand the origin and evolution of comets. By combining measurements made on the comet itself and in the coma, we probe the nature of this surface material and compare it to remote sensing observations. We compare data from the double focusing mass spectrometer (DFMS) of the ROSINA experiment on ESA's Rosetta mission and previously published data from the two mass spectrometers COSAC (COmetary Sampling And Composition) and Ptolemy on the lander. The mass spectra of all three instruments show very similar patterns of mainly CHO-bearing molecules that sublimate at temperatures of 275 K. The DFMS data also show a great variety of CH-, CHN-, CHS-, CHO2- and CHNO-bearing saturated and unsaturated species. Methyl isocyanate, propanal and glycol aldehyde suggested by the earlier analysis of the measured COSAC spectrum could not be confirmed. The presence of polyoxymethylene in the Ptolemy spectrum was found to be unlikely. However, the signature of the aromatic compound toluene was identified in DFMS and Ptolemy data. Comparison with remote sensing instruments confirms the complex nature of the organics on the surface of 67P, which is much more diverse than anticipated.

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

PubMed

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.

Comet 67P Seen by Kepler

NASA Image and Video Library

2016-10-07

The European Space Agency's Rosetta mission concluded its study of comet 67P/Churyumov-Gerasimenko on Sept. 30, 2016. NASA's planet-hunting Kepler spacecraft observed the comet during the final month of the Rosetta mission, while the comet was not visible from Earth. This animation is composed of images from Kepler of the comet. From Sept. 7 through Sept. 20, the Kepler spacecraft, operating in its K2 mission, fixed its gaze on comet 67P. From the distant vantage point of Kepler, the comet's nucleus and tail could be observed. The long-range view from Kepler complements the closeup view of the Rosetta spacecraft, providing context for the high-resolution investigation Rosetta performed as it descended closer and closer to the comet. During the two-week period of study, Kepler took a picture of the comet every 30 minutes. The animation shows a period of 29.5 hours of observation from Sept. 17 thru Sept. 18. The comet is seen passing through Kepler's field of view from top right to bottom left, as outlined by the diagonal strip. The white dots represent stars and other regions in space studied during K2's tenth observing campaign. As a comet travels through space it sheds a tail of gas and dust. The more material that is shed, the more surface area there is to reflect sunlight. A comet's activity level can be obtained by measuring the reflected sunlight. Analyzing the Kepler data, scientists will be able to determine the amount of mass lost each day as comet 67P travels through the solar system. An animation is available at http://photojournal.jpl.nasa.gov/catalog/PIA21072

Comet Tempel 1 Went Back to Sleep

NASA Astrophysics Data System (ADS)

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

William Herschel and Comets

NASA Astrophysics Data System (ADS)

Sullivan, Woodruff

2018-01-01

I examine the observational and theoretical researches of William Herschel on 21 comets that he observed over the period 1781 to 1812. Herschel's focus, unlike most contemporaries, was on their physical structure, not their orbits. He forged a strong connection between comets and his nebulae with a scheme of cometary "maturation" (1812) involved a comet traveling from star to star after its central "planetary body'; was born from gravitational collapse of a nebula. During close passages of a star, the comet brightened and lost mass from its atmosphere; at other times, when between stars, it encountered nebulae and was rejuvenated by picking up more mass. Laplace soon adopted these ideas to improve his nebula hypothesis for solar system formation.

Singing comet changes its song

NASA Astrophysics Data System (ADS)

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.

The Low Albedo of Comets

NASA Astrophysics Data System (ADS)

Buratti, B. J.; Choukroun, M.; Bauer, J. M.

2016-12-01

Comets are among the handful of objects with very low albedos, in the 0.02-0.06 range. Dark material is common in the outer Solar System, but analysis of the spectra and albedo of this material by spacecraft including Cassini and New Horizons shows that it is diverse, covering a range of compositions. Some is neutral-colored in the visible, such as that found on Phoebe, while some is very red, such as that on the surfaces of D-type asteroids or the low-albedo side of Iapetus. The different types of low-albedo material may reflect both compositional diversity, including contamination by volatiles or darkening agents, and divergent alteration histories. The key question is whether a particular sub-type of low albedo material is pristine - an unprocessed accumulation of interstellar dust - or an end product of polymerization and photolysis into ever more complex materials. Comets have albedos similar to the leading hemisphere of Iapetus, the surface of Titan, and the lowest-albedo C-type and D-type asteroids. Observations by the WISE and NEOWISE cameras show that comets have consistently low albedos (1). The first quantitative measurement of low-albedo material in the Kuiper Belt, from which comets such as Jupiter Family Comets including 67P/Churyumov-Gerasimenko come, shows that even this material is not as dark as that found on comets (2). Results from both Stardust (3) and more recently Rosetta (4, 5) show that cometary surfaces contain prebiotic molecules, including the amino acid glycine. Other very low albedo objects have also been connected to complex organic molecules: on Iapetus, PAHs have been detected (6), and Titan's surface is believed to be covered with hydrocarbons produced in its haze layer (7). The presence of organic molecules, including complex ones, could be the unique characteristic of the very darkest material. The delivery of pre-biotic material from comets to the young Earth could represent a key link in the origins of terrestrial life. (1

IUE observations of faint comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Feldman, P. D.; Festou, M. C.; Ahearn, M. F.; Keller, H. U.

1981-01-01

Ultraviolet spectra of seven comets taken with the same instrument are given. The comets P/Encke (1980), P/Tuttle (1980 h), P/Stephan-Oterma (1980 g), and Meier (1980 q) were observed in November and December 1980 with the IUE satellite, and comets P/Borrelly (1980 i) and Panther (1980 u) were observed with the IUE on March 6, 1981. The spectra of these comets are compared with one another, as well as with comet Bradfield (1978 X), which was extensively studied earlier in 1980 with the IUE. To simplify the interpretation of the data and to minimize the dependence upon a specific model, the spectra are compared at approximately the same value of heliocentric distance whenever possible. Effects arising from heliocentric velocity, geocentric distance, and optical depth are also discussed. All of the cometary spectra are found to be remarkably similar, suggesting that these comets may have a common composition and origin.

IUE observations of faint comets

NASA Astrophysics Data System (ADS)

Weaver, H. A.; Feldman, P. D.; Festou, M.; A'Hearn, M. F.; Keller, H. U.

1981-09-01

Ultraviolet spectra of seven comets taken with the same instrument are given. The comets P/Encke (1980), P/Tuttle (1980 h), P/Stephan-Oterma (1980 g), and Meier (1980 q) were observed in November and December 1980 with the IUE satellite, and comets P/Borrelly (1980 i) and Panther (1980 u) were observed with the IUE on March 6, 1981. The spectra of these comets are compared with one another, as well as with comet Bradfield (1978 X), which was extensively studied earlier in 1980 with the IUE. To simplify the interpretation of the data and to minimize the dependence upon a specific model, the spectra are compared at approximately the same value of heliocentric distance whenever possible. Effects arising from heliocentric velocity, geocentric distance, and optical depth are also discussed. All of the cometary spectra are found to be remarkably similar, suggesting that these comets may have a common composition and origin.

CoMET: Cost and Mass Evaluation Tool for Spacecraft and Mission Design

NASA Technical Reports Server (NTRS)

Bieber, Ben S.

2005-01-01

New technology in space exploration is often developed without a complete knowledge of its impact. While the immediate benefits of a new technology are obvious, it is harder to understand its indirect consequences, which ripple through the entire system. COMET is a technology evaluation tool designed to illuminate how specific technology choices affect a mission at each system level. COMET uses simplified models for mass, power, and cost to analyze performance parameters of technologies of interest. The sensitivity analysis that CoMET provides shows whether developing a certain technology will greatly benefit the project or not. CoMET is an ongoing project approaching a web-based implementation phase. This year, development focused on the models for planetary daughter craft, such as atmospheric probes, blimps and balloons, and landers. These models are developed through research into historical data, well established rules of thumb, and engineering judgment of experts at JPL. The model is validated by corroboration with JpL advanced mission studies. Other enhancements to COMET include adding launch vehicle analysis and integrating an updated cost model. When completed, COMET will allow technological development to be focused on areas that will most drastically improve spacecraft performance.

Term Projects on Interstellar Comets

ERIC Educational Resources Information Center

Mack, John E.

1975-01-01

Presents two calculations of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. Proposes three problems, each of which would be a reasonable term project for a motivated undergraduate. (Author/MLH)

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Technical Reports Server (NTRS)

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.

Temporal analysis of the morphological structures of comet 1P/Halley in the perihelion passages in 1910 and 1986

NASA Astrophysics Data System (ADS)

Voelzke, M. R.

2016-11-01

This work is based on a systematic analysis of images of 1P/Halley comet collected during its penultimate and ultimate approaches, i.e., in 1910 and in 1986. The present research basically characterised, identified, classified, measured and compared some of the tail structures of comet 1P/Halley like DEs, wavy structures and solitons. The images illustrated in the Atlas of Comet Halley 1910 II (Donn et al., 1986), which shows the comet in its 1910 passage, were compared with the images illustrated in The International Halley Watch Atlas of Large-Scale Phenomena (Brandt et al., 1992), which shows the comet in its 1986 passage. While two onsets of DEs were discovered after the perihelion passage in 1910, the average value of the corrected cometocentric velocity Vc was (57 ± 15) km/s; ten were discovered after the perihelion passage in 1986 with an average of corrected velocities equal to (130 ± 37) km/s. The mean value of the corrected wavelength of wavy structures, in 1910, is equal to (1.7 ± 0.1) x 10^6 km and in 1986 is (2.2 ± 0.2) x 10^6 km. The mean value of the amplitude A of the wave, in 1910, is equal to (1.4 ± 0.1) x 10^5 km and in 1986 it is equal to (2.8 ± 0.5) x 10^5 km. The goals of this research are to report the results obtained from the analysis of the P/Halleýs 1910 and 1986 images, to provide empirical data for comparison and to form the input for future physical/theoretical work. Referências [1] Brandt, J.C., Niedner Jr., M.B. & Rahe, J. 1992. International Halley Watch Atlas of Large-Scale Phenomena. University of Colorado-Boulder (printed by Johnson Printing Co., Boulder, CO) [2] Donn, B., Rahe, J. & Brandt, J.C. 1986. Atlas of Comet Halley 1910 II. NASA SP-488

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

PubMed

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

2014-04-01

Excessive release of stress hormone adrenaline is accompanied by generation of reactive oxygen species which may cause disruption of DNA integrity leading to cancer and age-related disorders. Phenolic-rich plant product dry olive leaf extract (DOLE) is known to modulate effects of various oxidants in human cells. The aim was to evaluate the effect of commercial DOLE against adrenaline induced DNA damage in human leukocytes by using comet assay. Peripheral blood leukocytes from 6 healthy subjects were treated in vitro with three final concentrations of DOLE (0.125, 0.5, and 1mg/mL) for 30 min at 37°C under two different protocols, pretreatment and post-treatment. Protective effect of DOLE was assessed from its ability to attenuate formation of DNA lesions induced by adrenaline. Compared to cells exposed only to adrenaline, DOLE displayed significant reduction (P<0.001) of DNA damage at all three concentrations and under both experimental protocols. Pearson correlation analysis revealed a significant positive association between DOLE concentration and leukocytes DNA damage (P<0.05). Antigenotoxic effect of the extract was more pronounced at smaller concentrations. Post-treatment with 0.125 mg/mL DOLE was the most effective against adrenaline genotoxicity. Results indicate genoprotective and antioxidant properties in dry olive leaf extract, strongly supporting further explorations of its underlying mechanisms of action. Copyright © 2014 Elsevier Ltd. All rights reserved.

Spectrophotometry of Dust in Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Witteborn, Fred C. (Technical Monitor)

1997-01-01

Comets, such as Hale-Bopp (C/1995 O1), are frozen reservoirs of primitive solar nebula dust grains and ices. Analysis of the composition of cometary dust grains from infrared spectroscopic techniques permits an estimation of the types of organic and inorganic materials that constituted the early primitive solar nebula. In addition, the cometary bombardment of the Earth (approximately 3.5 Gy ago) supplied the water for the oceans and brought organic materials to Earth which may have been biogenic. Spectroscopic observations of comet Hale-Bopp suggest the possible presence of organic hydrocarbon species, silicate and olivine dust grains, and water ice. Spectroscopy near 3 microns obtained in Nov 1996 r=2.393 AU, delta=3.034 AU) shows a feature which we attribute to PAH emission. The spatial morphology of the 3.28 microns PAH feature is also presented. Optical and infrared spectrophotometric observations of comets convey valuable information about the spatial distribution and properties of dust and gas within the inner coma. In the optical and NIR shortward of 2 microns, the observed light is primarily scattered sunlight from the dust grains. At longer wavelengths, particularly in the 10 gm window, thermal emission from these grains dominates the radiation allowing an accurate estimate of grain sizes and chemical composition. Here we present an initial analysis of spectra taken with the NASA HIFOGS at 7-14 microns as part of a multiwavelength temporal study of the "comet of the century".

Rosetta following a living comet

NASA Astrophysics Data System (ADS)

Accomazzo, Andrea; Ferri, Paolo; Lodiot, Sylvain; Pellon-Bailon, Jose-Luis; Hubault, Armelle; Porta, Roberto; Urbanek, Jakub; Kay, Ritchie; Eiblmaier, Matthias; Francisco, Tiago

2016-09-01

The International Rosetta Mission was launched on 2nd March 2004 on its 10 year journey to rendezvous with comet 67P Churyumov-Gerasimenko. Rosetta performed comet orbit insertion on the 6th of August 2014, after which it characterised the nucleus and orbited it at altitudes as low as a few kilometres. In November 2014 Rosetta delivered the lander Philae to perform the first soft landing ever on the surface of a comet. The critical landing operations have been conducted with remarkable accuracy and will constitute one of the most important achievements in the history of spaceflight. After this critical operation, Rosetta began the escort phase of the comet in its journey in the Solar System heading to the perihelion, reached in August 2015. Throughout this period, the comet environment kept changing with increasing gas and dust emissions. A first phase of bound orbits was followed by a sequence of complex flyby segments which allowed the scientific instruments to perform in depth investigation of the comet environment and nucleus. The unpredictable nature of the comet activity forced the mission control team to implement unplanned changes to the flight plan prepared for this mission phase and to plan the whole mission in a more dynamic way than originally conceived. This paper describes the details of the landing operations and of the main comet escort phase. It also includes the mission status as achieved after perihelion and the findings about the evolution of the comet and its environment from a mission operations point of view. The lessons learned from this unique and complex operations phase and the plans for the next mission phases, which include a mission extension into 2016, are also described.

Analysis of the tail structures of comet P/Halley 1910 II

NASA Astrophysics Data System (ADS)

Voelzke, M. R.; Izaguirre, L. S.

Eight hundred and eighty six images from September 1909 to May 1911 are analysed for the purpose of identifying, measuring and correlating the morphological structures along the plasma tail of P/Halley. These images are from the Atlas of Comet Halley 1910 II (Donn et al. 1986). A systematic visual analysis revealed 304 wavy structures along the main tail and 164 along the secondary tails, 41 solitary waves (solitons), 13 Swan-like tails, 26 disconnection events (DEs), 166 knots and six shells. While the wavy structures denote undulations or a train of waves, the solitons refer to the formations usually denominated kinks. In general, it is possible to associate the occurrence of a DE and/or a Swan-Tail with the occurrence of a knot, but the last one may occur independently. It is also possible to say that the solitons occur in association with the wavy structures, but the reverse is not true. The 26 DEs documented in 26 different images allowed the derivation of two onsets of DEs, i.e., the time when the comet supposedly crossed a frontier between magnetic sectors of the solar wind. Both onsets of DEs were determined after the perihelion passage with an average of the corrected velocities Vc equal to (57 ± 15) km s-1. The mean value of the corrected wavelength λ c measured in 70 different wavy structures is equal to (1.7 ± 0.1) × 106 km and the mean amplitude A of the wave (measured in the same 70 wavy structures cited above) is equal to (1.4 ± 0.1) × 105 km. The mean value of the corrected cometocentric phase velocity Vpc measured in 20 different wavy structures is equal to (168 ± 28) km s-1. The average value of the corrected velocities Vkc of the knots measured in 36 different images is equal to (128 ± 12) km s-1. There is a tendency for A and λ c to increase with increasing cometocentric distance. The preliminary results of this work agree with the earlier research from Voelzke and Matsuura (1998), which analysed comet P/Halley's tail structures in its

A new activity index for comets

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1992-01-01

An activity index, AI, is derived from observational data to measure the increase of activity in magnitudes for comets when brightest near perihelion as compared to their inactive reflective brightness at great solar distances. Because the observational data are still instrumentally limited in the latter case and because many comets carry particulate clouds about them at great solar distances, the application of the activity index is still limited. A tentative application is made for the comets observed by Max Beyer over a period of nearly 40 years, providing a uniform magnitude system for the near-perihelion observations. In all, 32 determinations are made for long-period (L-P) comets and 15 for short-period (S-P). Although the correlations are scarcely definitive, the data suggest that the faintest comets are just as active as the brightest and that the S-P comets are almost as active as those with periods (P) exceeding 10(exp 4) years or those with orbital inclinations of i less than 120 deg. Comets in the range 10(exp 2) less than P less than 10(exp 4) yr. or with i greater than 120 deg appear to be somewhat more active than the others. There is no evidence to suggest aging among the L-P comets or to suggest other than a common nature for comets generally.

DIRBE Comet Trails

NASA Technical Reports Server (NTRS)

Arendt, Richard G.

2015-01-01

Re-examination of the COBE DIRBE data reveals the thermal emission of several comet dust trails.The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported.The known trails of 2P/Encke, and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 microns surface brightnesses of <0.1 and <0.15 MJy/sr, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals one additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

Comets - Groundbased observations of spacecraft mission candidates

NASA Technical Reports Server (NTRS)

Osip, David J.; Schleicher, David G.; Millis, Robert L.

1992-01-01

Ground-based narrowband photometry results are presented for nine candidate comets for flyby and/or rendezvous missions. The comets include Churyumov-Gerasimenko, d'Arrest, Encke, Grigg-Skjellerup, Honda-Mrkos-Pajdusakova, Kopff, Tempel 1, Tempel 2, and Wild 2. On the basis of measured OH production rates and a model of the sublimation of water from the surface, limits are derived on the size of each cometary nucleus. A detailed analysis of the characteristics of these nine viable mission candidates can furnish the bases for the prioritization of targets of prospective missions.

Secular light curves of comets, II: 133P/Elst Pizarro, an asteroidal belt comet

NASA Astrophysics Data System (ADS)

Ferrín, Ignacio

2006-12-01

We present the secular light curve (SLC) of 133P/Elst-Pizarro, and show ample and sufficient evidence to conclude that it is evolving into a dormant phase. The SLC provides a great deal of information to characterize the object, the most important being that it exhibits outburst-like activity without a corresponding detectable coma. 133P will return to perihelion in July of 2007 when some of our findings may be corroborated. The most significant findings of this investigation are: (1) We have compiled from 127 literature references, extensive databases of visual colors (37 comets), rotational periods and peak-to-valley amplitudes (64 comets). 2-Dimensional plots are created from these databases, which show that comets do not lie on a linear trend but in well defined areas of these phase spaces. When 133P is plotted in the above diagrams, its location is entirely compatible with those of comets. (2) A positive correlation is found between cometary rotational periods and diameters. One possible interpretation suggest the existence of rotational evolution predicted by several theoretical models. (3) A plot of the historical evolution of cometary nuclei density estimates shows no trend with time, suggesting that perhaps a consensus is being reached. We also find a mean bulk density for comets of <ρ>=0.52±0.06 g/cm. This value includes the recently determined spacecraft density of Comet 9P/Tempel 1, derived by the Deep Impact team. (4) We have derived values for over 18 physical parameters, listed in the SLC plots, Figs. 6-9. (5) The secular light curve of 133P/Elst-Pizarro exhibits a single outburst starting at +42±4 d (after perihelion), peaking at LAG=+155±10 d, duration 191±11 d, and amplitude 2.3±0.2 mag. These properties are compatible with those of other low activity comets. (6) To explain the large time delay in maximum brightness, LAG, two hypothesis are advanced: (a) the existence of a deep ice layer that the thermal wave has to reach before sublimation

Flyby Comet Imaged By Radar

NASA Image and Video Library

2016-03-24

Radar data of comet P/2016 BA14 taken over three days (March 21-23, 2016), when the comet was between 2.5 million miles and 2.2 million miles (4.1 million kilometers and 3.6 million kilometers) from Earth. Radar images from the flyby indicated that the comet is about 3,000 feet (1 kilometer) in diameter.

Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Analysis and interpretation

NASA Technical Reports Server (NTRS)

Neubauer, Fritz M.; Glassmeier, Karl-Heinz; Coates, A. J.; Johnstone, A. D.

1993-01-01

The propagation and polarization characteristic of low-frequency electromagnetic wave fields near comet P/Grigg-Skjellerup (P/GS) are analyzed using magnetic field and plasma observations obtained by the Giotto magnetometer experiment and the Johnstone plasma analyzer during the encounter at the comet on July 10, 1992. The results have been physically interpreted.

Origin of Short-Perihelion Comets

NASA Technical Reports Server (NTRS)

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.

Flight of the Comet

NASA Image and Video Library

2010-11-05

Image taken by NASA EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. The spacecraft came within about 700 kilometers 435 miles of the comet nucleus at the time of closest approach.

Observations of faint comets with the IUE

NASA Astrophysics Data System (ADS)

Festou, M.

1982-06-01

Spectral observations of eight comets, including seven periodic comets, made in the range 1150-3400 A with the IUE satellite are presented. Comet Bradfield, the sole nonperiodic comet observed, is found to exhibit strong OH and atomic hydrogen emissions from the decomposition of water, along with oxygen, carbon, sulfur, carbon disulfide, C2 and CO2(plus) emissions and a faint continuum due to dust at longer wavelengths. Comets Encke, Tuttle and Stefan-Oterma appear to have identical spectra in the UV, showing evidence of much gas, little dust and few ions (only CO2(plus) detected), and differing from comet Bradfield only in the lack of C2 emission. All eight comets observed by IUE, including Seargent, Meier, Borrelly and Panther, had the same chemical composition, consisting mainly of water with a few per mil or per cent CN, C2, C3 and CS. The water production rates of the periodic comets range from levels 6 times less to 11 times more than that of Comet Bradfield, which may be related to nuclear size or cometary age.

Comet ISON Passes Through Virgo

NASA Image and Video Library

2013-11-22

Date: 8 Nov 2013 - Comet ISON shines in this five-minute exposure taken at NASA's Marshall Space Flight Center on Nov. 8, 2013.. The image was captured using a color CCD camera attached to a 14" telescope located at Marshall. At the time of this picture, comet ISON was 97 million miles from Earth, moving ever closer toward the sun. Credit: NASA/MSFC/Aaron Kingery -------- More details on Comet ISON: Comet ISON began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- 28 Nov 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Catalogued as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012. This is ISON's very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Comet ISON is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide -- some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. NASA has been using a vast fleet of spacecraft, instruments, and space- and Earth-based telescope, in order to learn more about this time capsule from when the solar system first formed. The journey along the way for such a sun-grazing comet can be dangerous. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars -- at some 230 million miles away from the sun -- the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation and pressure

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

PubMed

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.

On the Determination of the Orbits of Comets

NASA Astrophysics Data System (ADS)

Englefield, Henry

2013-06-01

Preface; 1. General view of the method; 2. On the motion of the point of intersection of the radius vector and cord; 3. On the comparison of the parabolic cord with the space which answers to the mean velocity of the earth in the same time; 4. Of the reduction of the second longitude of the comet; 5. On the proportion of the three curtate distances of the comet from the earth; 6. Of the graphical declination of the orbit of the earth; 7. Of the numerical quantities to be prepared for the construction or computation of the comet's orbit; 8. Determination of the distances of the comet from the earth and the sun; 9. Determination of the elements of the orbit from the determined distances; 10. Determination of the place of the comet from the earth and sun; 11. Determination of the distances of the comet from the earth and sun; 12. Determination of the comet's orbit; 13. Determination of the place of the comet; 14. Application of the graphical method to the comet of 1769; 15. Application of the distances found; 16. Determination of the place of the comet, for another given time; 17. Application of the trigonometrical method to the comet of 1769; 18. Determination of the elements of the orbit of the comet of 1769; Example of the graphical operation for the orbit of the comet of 1769; Example of the trigonometrical operation for the orbit of the comet of 1769; Conclusion; La Place's general method for determining the orbits of comets; Determination of the two elements of the orbit; Application of La Place's method of finding the approximate perihelion distance; Application of La Place's method for correcting the orbit of a comet, to the comet of 1769; Explanation and use of the tables; Tables; Appendix; Plates.

Comet 81P/Wild 2 under a microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brownlee, D; Tsou, P; Aleon, J

2006-10-12

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixingmore » on the grandest scales. Stardust was the first mission to return solid samples from a specific astronomical body other than the Moon. The mission, part of the NASA Discovery program, retrieved samples from a comet that is believed to have formed at the outer fringe of the solar nebula, just beyond the most distant planet. The samples, isolated from the planetary region of the solar system for billions of years, provide new insight into the formation of the solar system. The samples provide unprecedented opportunities both to corroborate astronomical (remote sensing) and sample analysis information (ground truth) on a known primitive solar system body and to compare preserved building blocks from the edge of the planetary system with sample-derived and astronomical data for asteroids, small bodies that formed more than an order of magnitude closer to the Sun. The asteroids, parents of most meteorites, formed by accretion of solids in warmer, denser, more collisionally evolved inner regions of the solar nebula where violent nebular events were capable of flash-melting millimeter-sized rocks, whereas comets formed in the coldest, least dense region. The samples collected by Stardust are the first primitive materials from a known body, and as such they provide contextual insight for all primitive meteoritic samples. About 200

Comet 67P's Pitted Surface

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-11-01

High-resolution imagery of comet 67P ChuryumovGerasimenko has revealed that its surface is covered in active pits some measuring hundreds of meters both wide and deep! But what processes caused these pits to form?Pitted LandscapeESAs Rosetta mission arrived at comet 67P in August 2014. As the comet continued its journey around the Sun, Rosetta extensively documented 67Ps surface through high-resolution images taken with the on-board instrument NavCam. These images have revealed that active, circular depressions are a common feature on the comets surface.In an attempt to determine how these pits formed, an international team of scientists led by Olivier Mousis (Laboratory of Astrophysics of Marseille) has run a series of simulations of a region of the comet the Seth region that contains a 200-meter-deep pit. These simulations include the effects of various phase transitions, heat transfer through the matrix of ices and dust, and gas diffusion throughout the porous material.Escaping VolatilesAdditional examples of pitted areas on 67Ps northern-hemisphere surface include the Ash region and the Maat region (both imaged September 2014 by NavCam) [Mousis et al. 2015]Previous studies have already eliminated two potential formation mechanisms for the pits: impacts (the sizes of the pits werent right) and erosion due to sunlight (the pits dont have the right shape). Mousis and collaborators assume that the pits are instead caused by the depletion of volatile materials chemical compounds with low boiling points either via explosive outbursts at the comets surface, or via sinkholes opening from below the surface. But what process causes the volatiles to deplete when the comet heats?The authors simulations demonstrate that volatiles trapped beneath the comets surface either in icy structures called clathrates or within amorphous ice can be suddenly released as the comet warms up. The team shows that the release of volatiles from these two structures can create 200-meter

Spectroscopic observations of comets

NASA Technical Reports Server (NTRS)

1982-01-01

Development of a spectrograph using a microchannel plate intensifier for observing faint comets is described. The spectrograph is capable of obtaining useful spectra of objects as faint as M(2) = 18. The increased guiding efficiency achieved by the optical coupling of the ISIT vidicon of the 154 cm telescope has resulted in a better signal to noise ratio. The ability to take a direct image of the comet aids in the interpretation of the spatial profile of the emissions. Spectra of comets Schwassmann-Wachmann 1, Bradfield, Encke, Tuttle, and Stephen-Oterma are discussed.

Rosetta - ESA's new comet chaser

NASA Astrophysics Data System (ADS)

1999-06-01

The Rosetta orbiter will literally chase comet Wirtanen for two years, sending back valuable data and ensuring Europe retains its lead in comet science. A lander will attach itself to this lump of frozen ice and dust, which is travelling through space at over 130,000 kilometres per hour, and analyse samples. Just as the re-discovery of the Rosetta Stone, 200 years ago, enabled the mysteries of ancient Egyptian hieroglyphics to be unrravelled, so the Rosetta mission will help scientists learn even more about comets, the most primitive objects in the solar system. In 1986, ESA's Giotto spacecraft flew into the tail of Halley's Comet. That was ESA's first interplanetary mission and it was hailed as an outstanding success. The pictures and scientific data that Giotto sent back placed Europe at the forefront of comet science. Notes for Editors : On the day of the press event, the now deactivated Giotto spacecraft will do an Earth flyby 13 years after its encounter with Halley's Comet. The British Museum is celebrating 200-years anniversary of the Rosetta Stone, with an exhibition that includes a model of its modern equivalent, the Rosetta spacecraft.

Comets and nongravitational forces. IV.

NASA Technical Reports Server (NTRS)

Marsden, B. G.; Sekanina, Z.

1971-01-01

Orbital elements and nongravitational parameters are derived from observations at every apparition of the periodic comets Honda-Mrkos-Pajdusakova, Faye, Tempel 2, Biela, Brorsen, and Tempel-Swift. For all except the first comet, the observations go back a century and more, although the last three comets have failed to reappear for some considerable time. The circumstances of the splitting of P/Biela are studied, and it is shown that the motion of the primary component was scarcely affected; it is also demonstrated that, if the primary still exists, it may pass only 0.05 AU from the earth in November 1971. An up-to-date list of mass-loss rates from comets is presented. It is found that, while most of the reliable determinations indicate that the cometary nongravitational effects decrease with time, there are a few cases where the effects increase slightly. The former situation is discussed in terms of a nuclear core-mantle model, implying that these comets will eventually evolve into inert, asteroidal objects, while the nuclei of the other comets are interpreted as coreless, eventually to disappear completely (or almost completely).

Assessment of occupational exposure to welding fumes by inductively coupled plasma-mass spectroscopy and by the alkaline Comet assay.

PubMed

Botta, Céline; Iarmarcovai, Gwenaëlle; Chaspoul, Florence; Sari-Minodier, Irène; Pompili, Jocelyne; Orsière, Thierry; Bergé-Lefranc, Jean-Louis; Botta, Alain; Gallice, Philippe; De Méo, Michel

2006-05-01

Welding fumes are classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer. In the current study, blood and urine concentrations of aluminum (Al), cadmium (Cd), cobalt (Co), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were monitored by inductively coupled plasma-mass spectrometry (ICP-MS) in 30 welders and in 22 controls. In addition, DNA damage was examined in the lymphocytes of these subjects by the alkaline Comet assay. Two biological samples were taken from the welders at the beginning (BW) and at the end (EW) of a work week. In controls, collection of samples was limited to BW. Blood concentrations of Cd, Co, Cr, Ni, and Pb were higher in the welders than in the control group while higher concentrations of Al, Cd, Co, Cr, Ni, and Pb were detected in welder urines. There was no significant difference in the metal concentrations for the BW and EW welder samples. Increased levels of DNA damage were found in lymphocytes from welders as compared to the controls, and 20/30 welders had higher levels of DNA lesions in the EW than in the BW samples. Age had a significant effect on DNA damage in the control group. Spearman's rank correlation analysis indicated that there were positive correlations between blood concentrations of Al, Co, Ni, and Pb and the levels of DNA damage. A negative correlation was found between DNA damage and Mn in blood, while there was a positive correlation between urinary Mn concentration and DNA damage. These data indicate that occupational exposure to welding fumes increases DNA damage in lymphocytes. Copyright (c) 2006 Wiley-Liss, Inc.

Multiwavelength Observations of Recent Comets

NASA Technical Reports Server (NTRS)

Milam, Stefanie N.; Charnley, Steven B.; Gicquel, Adeline; Cordiner, Martin; Kuan, Yi-Jehng; Chuang, Yo-Ling; Villanueva, Geronimo; DiSanti, Michael A.; Bonev, Boncho P.; Remijan, Anthony J.;

Nutritional value of ganoderma extract and assessment of its genotoxicity and antigenotoxicity using comet assays of mouse lymphocytes.

PubMed

Chiu, S W; Wang, Z M; Leung, T M; Moore, D

2000-01-01

The nutritive composition of a hot aqueous extract of wild Ganoderma fruit bodies was determined. This extract was assessed for cytotoxicity and in vivo genotoxicity by both acute and subchronic exposure of mice (given by mouth at a dose equivalent to extract of 220g fresh Ganoderma fruit body/kg body weight). To test any alleged protection against mutagens by Ganoderma treatments, the mice were injected intraperitoneally with the radiomimetic mutagen ethyl methanesulfonate (EMS), and after 24hr of treatment their lymphocytes were examined using the comet assay. Ganoderma extract consisted of Folin-positive material (68.9% of dry weight), but protein comprised only 7.3% of dry weight. Glucose accounted for 11. 1% and metals 10.2% of dry weight (K, Mg and Ca being the major components with Ge (often touted as being of value in sales literature for Ganoderma preparations) having the fifth highest metal concentration at 489 microg/g). In comparison to rodent chow, Ganoderma extract was a modest dietary supplement. No evidence was found for genotoxic chromosomal breakage nor cytotoxic effects by Ganoderma extract in the mouse, nor did it protect against the effects of ethyl methanesulfonate. We found no support in this study for the extract having any value in protecting against the test mutagen.

On Course for a Comet

NASA Technical Reports Server (NTRS)

2005-01-01

This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 27, 2005, when the spacecraft was 6,229,030.3 kilometers (3,870,719 miles) away from the comet. Three images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

Comets: Role and importance to exobiology

NASA Technical Reports Server (NTRS)

Delsemme, Armand H.

1992-01-01

The transfer of organic compounds from interstellar space to the outskirts of a protoplanetary disk, their accretion into cometary objects, and the transport of the latter into the inner solar system by orbital diffusion throw a new light on the central problem of exobiology. It suggests the existence of a cosmic mechanism, working everywhere, that can supply prebiotic compounds to ubiquitous rocky planets, in search of the proper environment to start life in many places in the Universe. Under the heading of chemistry of the cometary nucleus, the following topics are covered: radial homogeneity of the nucleus; the dust-to-ice ratio; nature of the dust grains; origin of the dust in comets; nature of the volatile fraction; the CO distribution in comet Halley; dust contribution to the volatile fraction; elemental balance sheet of comet Halley; quantitative molecular analysis of the volatile fraction; and isotopic ratios. Under the heading of exogenous origin of carbon on terrestrial planets the following topics are covered: evidence for a high-temperature phase; from planetesimals to planets; a veneer of volatile and organic material; and cometary contribution.

DRBE comet trails

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arendt, Richard G., E-mail: Richard.G.Arendt@nasa.gov

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 DIRBEmore » 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.« less

Comet Borrelly Varied Landscape

NASA Image and Video Library

2001-11-03

Sunlight illuminates the bowling-pin shaped nucleus from directly below comet Borrelly as seen by NASA Deep Space 1. At this distance, many features become vivid on the surface of the nucleus, including a jagged line between day and night on the comet.

The comet rendezvous asteroid flyby mission to Comet Kopff - Getting there is half the fun

NASA Technical Reports Server (NTRS)

Sweetser, Theodore H.; Kiedron, Krystyna

1990-01-01

The goal of the Comet Rendezvous Asteroid Flyby mission (CRAF) is to fly 'outward to the beginning', to examine closely what are thought to be remnants of the origins of the solar system. In particular, the CRAF spacecraft will use a two-year delta-V-earth-gravity-assist (delta-V-EGA) trajectory to reach a rendezvous point near the aphelion of the Comet Kopff, flying by the asteroid 449 Hamburga on the way. This paper discusses the trajectory used to get to the comet. Topics covered include the launch period, possible additional asteroid flybys, the earth flyby, the Hamburga flyby, and the rendezvous with Comet Kopff.

Comet prospects for 2004

NASA Astrophysics Data System (ADS)

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.

Book Review: The Origins of Comets

NASA Technical Reports Server (NTRS)

McKay, Christopher P.

1992-01-01

In The Origins of Comets, Bailey, Clube, and Napier propose that the answer to whether the ancient heavens were more interesting is a resounding "yes." The sky, in fact, has changed and is still changing. The authors trace the study of comets back to ancient Babylonian times with a focus on theories of the origins of these enigmatic visitors. The book is really of three distinct parts: the first six chapters provide an excellent and delightfully readable historical account of comet studies up to this century. The next few chapters give a rather detailed treatment of current models for comet origins. The last section treats the authors' own theories about the relationship between giant comets and extinctions on Earth.

Meteoroid Streams from Sunskirter Comet Breakup

NASA Astrophysics Data System (ADS)

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.

Perspectives on Comets, Comet-like Asteroids, and Their Predisposition to Provide an Environment That Is Friendly to Life

NASA Astrophysics Data System (ADS)

Bosiek, Katharina; Hausmann, Michael; Hildenbrand, Georg

2016-04-01

In recent years, studies have shown that there are many similarities between comets and asteroids. In some cases, it cannot even be determined to which of these groups an object belongs. This is especially true for objects found beyond the main asteroid belt. Because of the lack of comet fragments, more progress has been made concerning the chemical composition of asteroids. In particular, the SMASSII classification establishes a link between the reflecting spectra and chemical composition of asteroids and meteorites. To find clues for the chemical structure of comets, the parameters of all known asteroids of the SMASSII classification were compared to those of comet groups like the Encke-type comets, the Jupiter-family comets, and the Halley-type comets, as well as comet-like objects like the damocloids and the centaurs. Fifty-six SMASSII objects similar to comets were found and are categorized as comet-like asteroids in this work. Aside from the chemistry, it is assumed that the available energy on these celestial bodies plays an important role concerning habitability. For the determination of the available energy, the effective temperature was calculated. Additionally, the size of these objects was considered in order to evaluate the possibility of a liquid water core, which provides an environment that is more likely to support processes necessary to create the building blocks of life. Further study of such objects could be notable for the period of the Late Heavy Bombardment and could therefore provide important implications for our understanding of the inner workings of the prebiotic evolution within the Solar System since the beginning.

Perspectives on Comets, Comet-like Asteroids, and Their Predisposition to Provide an Environment That Is Friendly to Life.

PubMed

Bosiek, Katharina; Hausmann, Michael; Hildenbrand, Georg

2016-04-01

In recent years, studies have shown that there are many similarities between comets and asteroids. In some cases, it cannot even be determined to which of these groups an object belongs. This is especially true for objects found beyond the main asteroid belt. Because of the lack of comet fragments, more progress has been made concerning the chemical composition of asteroids. In particular, the SMASSII classification establishes a link between the reflecting spectra and chemical composition of asteroids and meteorites. To find clues for the chemical structure of comets, the parameters of all known asteroids of the SMASSII classification were compared to those of comet groups like the Encke-type comets, the Jupiter-family comets, and the Halley-type comets, as well as comet-like objects like the damocloids and the centaurs. Fifty-six SMASSII objects similar to comets were found and are categorized as comet-like asteroids in this work. Aside from the chemistry, it is assumed that the available energy on these celestial bodies plays an important role concerning habitability. For the determination of the available energy, the effective temperature was calculated. Additionally, the size of these objects was considered in order to evaluate the possibility of a liquid water core, which provides an environment that is more likely to support processes necessary to create the building blocks of life. Further study of such objects could be notable for the period of the Late Heavy Bombardment and could therefore provide important implications for our understanding of the inner workings of the prebiotic evolution within the Solar System since the beginning.

Determination of orbits of comets: P/Kearns-Kwee, P/Gunn, including nongravitational effects in the comets' motion

NASA Technical Reports Server (NTRS)

Todorovic-Juchniewicz, Bozenna; Sitarski, Grzegorz

1992-01-01

To improve the orbits, all the positional observations of the comets were collected. The observations were selected and weighted according to objective mathematical criteria and the mean residuals a priori were calculated for both comets. We took into account nongravitational effects in the comets' motion using Marsden's method applied in two ways: either determining the three constant parameters, A(sub 1), A(sub 2), A(sub 3) or the four parameters A, eta, I, phi connected with the rotating nucleus of the comet. To link successfully all the observations, we had to assume for both comets that A(t) = A(sub O)exp(-B x t) where B was an additional nongravitational parameter.

Triple F - A Comet Nucleus Sample Return Mission

NASA Technical Reports Server (NTRS)

Kueppers, Michael; Keller, Horst Uwe; Kuhrt, Ekkehard; A'Hearn, Michael; Altwegg, Kathrin; Betrand, Regis; Busemann, Henner; Capria, Maria Teresa; Colangeli, Luigi

2008-01-01

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three samples of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

Triple F - A Comet Nucleus Sample Return Mission

NASA Technical Reports Server (NTRS)

Kueppers, Michael; Keller, H. U.; Kuehrt, E.; A'Hearn, M. F.; Altwegg, K.; Bertrand, R.; Busemann, H.; Capria, M. T.; Colangeli, L.; Davidsson, B.;

First Comet Encounter

NASA Image and Video Library

2010-09-09

Dr. James L. Green, Director of Planetary Science at NASA, speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

Development and Testing of Harpoon-Based Approaches for Collecting Comet Samples

NASA Technical Reports Server (NTRS)

Purves, Lloyd (Compiler); Nuth, Joseph (Compiler); Amatucci, Edward (Compiler); Wegel, Donald; Smith, Walter; Church, Joseph; Leary, James; Kee, Lake; Hill, Stuart; Grebenstein, Markus;

An Introduction to Comets and Their Origin.

ERIC Educational Resources Information Center

Chapman, Robert D.; Brandt, John C.

1985-01-01

Presents excerpts from "The Comet Book," a nontechnical primer on comets. Various topics discusses in these excerpts include such basic information about comets as their components, paths, and origins. (DH)

Kohoutek - A great comet coming.

NASA Technical Reports Server (NTRS)

Maran, S. P.; Hobbs, R. W.

1973-01-01

Passing inside the earth's orbit in late November, the comet Kohoutek will travel through the inner solar system during a unique period in the history of the space program, when Skylab and Mariner Venus-Mercury are in operation and the new C-141 Airborne Infrared Observatory is ready for flight. It is planned to investigate comprehensively the nature and evolution of the coma and tails of the comet. The detailed goals of the investigation include the identification of the parent molecules of the gases observed in comets, the determination of the processes that break down the parent molecules, the study of the physical nature of transient events in the comet, and the measurement of the solar-wind velocity in the inner solar system.