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PubMed2026

Genotoxicity  effects in Cancer Patients: Evaluation by Micronucleus and Comet Assays and Correlation with Biochemical and Hematological Indices.

BACKGROUND: Cancer is one of the most significant global health challenges. Cytogenetic techniques are used as biomarkers of cancer risk to detect DNA damage and chromosomal abnormalities. OBJECTIVE: This study aimed to evaluate the influence of chemotherapy on genetic stability in cancer patients by applying Micronucleus and Comet assays as indicators of DNA and chromosomal alterations. It also aimed to determine the possible links between these genotoxic changes and variations in biochemical and hematological parameters, providing insight into the cellular responses to chemotherapy exposure. METHODS: Buccal epithelial cells were collected from 190 individuals (90 controls and 100 cancer patients) and stained for micronucleus analysis. To observe DNA breakdown, cells from blood were subjected to an alkaline comet assay. Biochemical (urea, creatinine, calcium, and bilirubin) and hematopoietic (Hb, WBC, Plt, and HCT) parameters were also assessed. RESULTS: Cancer patients showed elevated Binucleated cells (27.50 ± 3.62 per 1000 cells, ~6.8-fold), Condensed chromatin (10.50 ± 2.87 per 1000 cells, ~1.3-fold), pyknotic cells (2.65 ± 1.53 per 1000 cells, ~1.6-fold), basal cells (4.65 ± 1.98 per 1000 cells, ~2.4-fold), Karyorrhectic cells (9.45 ± 1.73 per 1000 cells, ~189-fold), Karyolytic cells (85.10 ± 2.69 per 1000 cells, ~8.9-fold), Monoonucleated cell with Micronucleus (12.50 ± 1.43 per 1000 cells, ~8.3-fold), and Percentage of nuclear anomalies in total (152.8 ± 4.75 per 1000 cells) compared with controls. The comet assay results revealed pronounced DNA fragmentation in cancer cells, with variable tail lengths indicating heterogeneous damage. The biochemical results showed a significant increase in the mean levels of urea (50.600 ± 8.259) and creatinine (1.073 ± 0.173), and no significant increase in TSB (0.917 ± 0.143) and HCT(38.080 ± 2.311) in cancer patients compared to the control. Calcium (9.010 ± 0.680), Hb (8.322 ± 1.247), Plt (91.300 ± 24.495), and WBC (11.920 ± 2.833) levels were lower in the patient group than in the control group. CONCLUSION: The increased frequency of nuclear anomalies and DNA fragmentation in cancer patients highlights the potential of the buccal Micronucleus assay and comet assays as effective, non-invasive tools for early cancer detection and genotoxic monitoring. Alterations in the blood and biochemical parameters further support the systemic effects of malignancy.

Humans↗
PubMed2004

Detection of gamma-irradiation induced DNA damage and radioprotection of compounds in yeast using comet assay.

The single cell gel electrophoresis assay (SCGE), a very rapid and sensitive method, has been applied to follow gamma-irradiation induced DNA damage in budding yeast, Saccharomyces cerevisiae. Spheroplasting the gamma-irradiated yeast cells by enzyme glusulase, before subjecting them to electrophoresis, resulted in a well-defined appearance of comets. Yeast comets look quite different from mammalian comets. A linear relationship was observed between the doses of irradiation and the tail moments of comets. These studies were extended to follow the action of known radio-protectors, i.e., caffeine and disulfiram. The results revealed the usefulness SCGE as applied to yeast in studies of the gamma-irradiation-induced DNA breaks and also radio-protection by chemicals at doses that are not feasible with other eukaryotes.

Caffeine↗
PubMed2004

The comet assay for DNA damage and repair: principles, applications, and limitations.

The comet assay (single-cell gel electrophoresis) is a simple method for measuring deoxyribonucleic acid (DNA) strand breaks in eukaryotic cells. Cells embedded in agarose on a microscope slide are lysed with detergent and high salt to form nucleoids containing supercoiled loops of DNA linked to the nuclear matrix. Electrophoresis at high pH results in structures resembling comets, observed by fluorescence microscopy; the intensity of the comet tail relative to the head reflects the number of DNA breaks. The likely basis for this is that loops containing a break lose their supercoiling and become free to extend toward the anode. The assay has applications in testing novel chemicals for genotoxicity, monitoring environmental contamination with genotoxins, human biomonitoring and molecular epidemiology, and fundamental research in DNA damage and repair. The sensitivity and specificity of the assay are greatly enhanced if the nucleoids are incubated with bacterial repair endonucleases that recognize specific kinds of damage in the DNA and convert lesions to DNA breaks, increasing the amount of DNA in the comet tail. DNA repair can be monitored by incubating cells after treatment with damaging agent and measuring the damage remaining at intervals. Alternatively, the repair activity in a cell extract can be measured by incubating it with nucleoids containing specific damage.

Animals↗
PubMed2000

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

Within the last decade, the comet assay has been used with increasing popularity to investigate the level of DNA damage in terms of strand breaks and alkaline labile sites in biomonitoring studies. The assay is easily performed on WBCs and has been included in a wide range of biomonitoring studies of occupational exposures encompassing styrene, vinyl chloride, 1,3-butadiene, pesticides, hair dyes, antineoplastic agents, organic solvents, sewage and waste materials, wood dust, and ionizing radiation. Eleven of the occupational studies were positive, whereas seven were negative. Notably, the negative studies appeared to have less power than the positive studies. Also, there were poor dose-response relationships in many of the biomonitoring studies. Many factors have been reported to produce effects by the comet assay, e.g., age, air pollution exposure, diet, exercise, gender, infection, residential radon exposure, smoking, and season. Until now, the use of the comet assay has been hampered by the uncertainty of the influence of confounding factors. We argue that none of the confounding factors are unequivocally positive in the majority of the studies. We recommend that age, gender, and smoking status be used as criteria for the selection of populations and that data on exercise, diet, and recent infections be registered before blood sampling. Samples from exposed and unexposed populations should be collected at the same time to avoid seasonal variation. In general, the comet assay is considered a suitable and fast test for DNA-damaging potential in biomonitoring studies.

Adolescent↗
PubMed2000

Comet assay and cytokinesis-blocked micronucleus test for monitoring the genotoxic effects of X-ray radiation in humans.

OBJECTIVE: To assess the genotoxic effects of X-ray radiation on human populations. METHODS: The single cell gel electrophoresis (SCGE) and cytokinesis-blocked micronucleus (CBMN) test were applied as biological dosimeters to detect DNA damage and abnormalities in human peripheral lymphocytes of subpopulation exposed to X-ray radiation. The subjects were divided into four groups: 12 radiation-patients; 13 intervention-radiation-therapy doctors; 32 radiation-diagnostians; 28 controls. RESULTS: The average comet lengths of the four groups were 128.17 +/- 4.49 microns, 88.09 +/- 5.39 microns, 72.68 +/- 2.57 microns and 32.87 +/- 0.57 microns, respectively. The difference in average comet length between any two groups was highly significant (P < 0.01). The average micronucleated cell (MNC) rates (@1000) of the four groups were 12.33 +/- 0.85, 9.75 +/- 1.02, 8.48 +/- 0.66 and 3.18 +/- 0.36, respectively. The difference of MNC rates of Group 1 vs 3, 1 vs 4, 2 vs 4 and 3 vs 4 was highly significant (P < 0.01), and the difference of Group 1 vs 2 was significant (P < 0.05), but there was no difference of MNC rate in Group 2 vs 3 (P > 0.05). CONCLUSIONS: This study showed that both the comet assay and the CBMN test could be used to monitor populations exposed to X-ray radiation, but the comet assay seems to be more sensitive than the CBMN test.

Adult↗
PubMed2001

Standardization of the comet assay technique on FRTL5 cells.

The comet assay is a sensitive and rapid method for DNA strand break detection in individual cells. The principle of break detection, using either the alkaline or neutral version of the assay, makes it a good technique for studying both double and single strand DNA breaks. Furthermore, the possibility of following DNA damage at different time moments also makes it possible to investigate the cell repair mechanisms. This explains why in the last few years there has been a tremendous increase in the number of laboratories which started to use this technique. The technique was first created for lymphocyte cells and later on has been used on many other cell types, growing both in suspension and adherent. To date, no one has applied this technique on normal differentiated endocrine cells, such as FRTL5 cells (Fisher Rat Thyroid Cells). The aim of this study has been to standardize the alkaline version of the Comet Assay technique on FRTL5 cells by studying the kinetics of DNA-damage and DNA-repair after different doses of UV-C (254 nm). FRTL-5 cells not only resulted very sensitive to UV-C (p<0.05 at 5 J/m2), but were also able to repair most of their DNA damage very rapidly (within one hour) as shown by a significant exponential regression in comet length. Finally, the successful measurement of biomarkers of UV-C on thyroid cells established the comet assay as a valuable tool in measurement of DNA damage and repair. Any radiation, or other damaging agents, interacting with living organisms could cause DNA damages which, depending upon dosages and kinetics of exposure, may or may not be completely repaired.

Animals↗
PubMed2002

Characterization of Fanconi anemia fibroblasts in terms of clonogenic survival and DNA damage assessed by the Comet assay.

BACKGROUND: Response of Fanconi anemia (FA) cells to X-irradiation is controversial. Present study was undertaken to compare short-term and long-term responses of irradiated FA fibroblasts. MATERIAL/METHODS: Skin fibroblasts derived from FA patients were studied using the Comet assay, clonogenic survival, apoptosis and cell cycle checkpoint arrest. Fibroblasts derived from ataxia telangiectasia (AT) patients served as positive controls. RESULTS: The alkaline Comet assay showed that the initial DNA fragmentation in irradiated FA fibroblasts is similar to or even higher than in AT cells. Moreover, the DNA rejoining occurred slowly in FA fibroblasts than in AT cells. In contrast, the colony assay revealed that the survival of X-ray-irradiated FA fibroblasts is higher than that of irradiated AT cells. Unlike FA fibroblasts, which were arrested in the G1 phase of the cell cycle by X-irradiation, AT cells displayed a pronounced G2/M arrest after X-ray exposure. CONCLUSIONS: FA cells are shown to be radioresistant by clonogenic survival but display high tail moments in the Comet assay suggesting high initial DNA damage and reduced repair capacity. It is demonstrated that the colony assay can not explain the high radiosensitivity of FA patients. The Comet assay can help to obtain additional information on initial DNA damage and repair capacity.

Apoptosis↗
PubMed2001

[Distinguishing apoptotic cells from DNA strand-broken cells by comet assay].

Apoptosis of immature thymocyte of mice induced by dexamethasone and DNA strand-broken cells induced by K2Cr2O7 were tested by comet assay. The results showed that the morphology of apoptotic cells assayed by comet was special. Under the same condition, the time of apoptotic cells running on electrophoresis was shorter than DNA-broken cells. The length of comet tail of DNA strand-broken cells increased in a dose-response relation with the increase of K2Cr2O7, whereas, the apoptotic index increased with the dosage of dexamethasone. While DNA damage was repairing, apoptosis continued to process. The DNA strand-broken cells could be obviously seen while DNA damage was repairing. It was suggested that comet assay could be used to detect DNA strand break sensitively, but also could distinguish different grades of DNA damage, which is helpful for studies on the etiology, progressing and outcome of cancer.

Animals↗
PubMed2001

[The comet assay: principles of the method and clinical utilization].

BACKGROUND: Single cell gel electrophoresis or comet assay is used at present in the world to study of DNA damage, DNA repair and apoptosis. The aim of the work is to introduce the principle of comet assay to the medical community and to give a basic survey of its possible clinical applications. The article includes our first experience with this method in detection of apoptosis in bone marrow cells of patients with myelodysplastic syndrome (MDS). METHODS AND RESULTS: The whole bone marrow aspirates from 6 patients with MDS and 7 control persons were processed by alkaline version of comet assay and the degree of DNA fragmentation in individual cells was quantified using Image Analysis System. In comparison with controls, the patients with diagnosis RA and RARS exhibited in bone marrow significantly elevated number of cells with high level of DNA breaks, reflecting most probably the apoptotic cleavage of DNA. In contrast, the patient in proliferative stage of the disease (MDS-CMML-->AML) exhibited decreased frequency of apoptotic cells, well below the control level. CONCLUSION: Our results correspond with the data published on the occurrence of apoptosis in particular types of MDS. Comet assay represents a simple and cheap technique, applicable in clinical hematology to specify the diagnosis, to monitor the disease progress and efficacy of therapy not only in patients with MDS but also in other diseases resulting from an imbalance between proliferation and apoptosis.

Adult↗
PubMed2004

[Detecting DNA repair capacity of human lymphocytes exposed to ultraviolet C with comet assay].

OBJECTIVE: To assess DNA repair capacity of human lymphocytes with comet assay. METHODS: Fresh lymphocytes form twelve 26-year old donors (6 males, 6 females) were exposed to ultraviolet C (UVC, 254 nm) at the dose rate of 1.5 J/m(2). The lymphocytes of each donor were divided into three parts: UVC group, UVC + aphidicolin (APC) group, UVC + novobiocin (NOV) group. DNA single strand breaks were detected with comet assay in UVC-irradiated cells and unirradiated cells incubated for 30, 60, 90, 120, 180 and 240 min. DNA repair rate (DRR) was calculated and served as an indicator of DNA repair capacity. RESULTS: The maximum average comet tail length (MTL) in three groups appeared 90 min after UVC exposure. The DRR range of UVC group was 81.84% (62.84% - 98.71%); There was no significant difference in DRR between males and females (P > 0.05). However, the average DRRs of UVC + NOV group and UVC + APC group (52.98% and 39.57% respectively) were significantly lower than that of UVC group (P < 0.01). CONCLUSION: Comet assay is a rapid and simple screening test to assess DNA repair capacity. DRR, as an indicator, may express the individual DNA repair capacity.

Aphidicolin↗
PubMed2005

Fragility of telomeres after bleomycin and cisplatin combined treatment measured in human leukocytes with the Comet-FISH technique.

UNLABELLED: THE AIM of the present study was the comparative investigation of action of widely applied anticancer preparations: cisplatin (cis-DDP) and bleomycin (BLM) on total DNA and telomeres damage in human blood cells. METHODS: The "Comet-FISH technique" -- single cell gel electrophoresis ("comet assay") in combination with fluorescent in situ hybridization (FISH) was used for this purpose. This newly applied combined approach permits to detect on the same specimen the total DNA damage in individual cells and evaluate specific DNA sequences as well. Telomere -- specific -- PNA (peptide nucleic acid) probes were used for the localization of telomeres in the comet's head and their migration to the tail. THE RESULTS obtained indicate that in control variants, due to DNA metabolism and handling, approximately 7% of the DNA and 17% of the telomeres were found in the tail. In cells treated with BLM alone, telomeres leak out with equal probability as total DNA. In turn, the combination of cis-DDP with BLM reduces telomere migration more than the migration of total DNA due to cis-DDP crosslinking effect. Thus, preferentially telomeric action of the cis-DDP can be concluded. CONCLUSION: The Comet-FISH approach permitted us to reveal the induction of DNA breaks with BLM and its modification due to platinum-crosslink formation, using telomeric PNA probes.

Adult↗
PubMed2005

Assessment of human DNA repair (NER) capacity with DNA repair rate (DRR) by comet assay.

OBJECTIVE: Alkaline comet assay was used to evaluate DNA repair (nucleotide excision repair, NER) capacity of human fresh lymphocytes from 12 young healthy non-smokers (6 males and 6 females). METHODS: Lymphocytes were exposed to UV-C (254 nm) at the dose rate of 1.5 J/m2/sec. Novobiocin (NOV) and aphidicolin (APC), DNA repair inhibitors, were utilized to imitate the deficiency of DNA repair capacity at the incision and ligation steps of NER. Lymphocytes from each donor were divided into three grougs: UVC group, UVC plus NOV group, and UVC plus APC group. DNA single strand breaks were detected in UVC irradiated cells incubated for 0, 30, 60, 90, 120, 180, and 240 min after UVC irradiation. DNA repair rate (DRR) served as an indicator of DNA repair capacity. RESULTS: The results indicated that the maximum DNA damage (i.e. maximum tail length) in the UVC group mainly appeared at 90 min. The ranges of DRRs in the UVC group were 62.84%-98.71%. Average DRR value was 81.84%. The DRR difference between males and females was not significant (P < 0.05). However, the average DRR value in the UVC plus NOV group and the UVC plus APC group was 52.98% and 39.57% respectively, which were significantly lower than that in the UVC group (P < 0.01). CONCLUSION: The comet assay is a rapid, simple and sensitive screening test to assess individual DNA repair (NER) capacity. It is suggested that the time to detect DNA single strand breaks in comet assay should include 0 (before UV irradiation), 90 and 240 min after exposure to 1.5 J x m(-2) UVC at least. The DRR, as an indicator, can represent the individual DNA repair capacity in comet assay.

Adult↗
PubMed2005

[Genotoxicity effect of chronic lead exposure assessed using the comet assay].

BACKGROUND: Lead, an important xenobiotic, is globally well distributed. The IARC has classified inorganic lead compounds as possibly carcinogenic to humans. The study was designed to assess genotoxic effects in workers occupationally exposed to Pb. MATERIALS AND METHODS: The study comprised 62 male workers with chronic exposure to lead and 22 matched non-exposed men. DNA damage was assessed by single cell gel electrophoresis (known as comet assay) using peripheral blood lymphocytes. The level of DNA damage was determined as the percentage of cells with comets. RESULTS: Mean blood Pb (PbB) concentrations in workers exposed to lead were significantly higher than in controls (422.6 +/- 181.2 microg/l vs. 81.0 +/- 37.84 microg/; p< 0.01). The level and the grade of DNA damage were significantly higher in workers exposed to lead (total--12.55 +/- 7.93%; grade 1--9.05 +/- 5.78%; grade 3--1.05 +/- 1.28%; p < 0.05) than in controls (total--6.63 +/- 3.05%; grade 1--5.68 +/- 2.32%; grade 3--0.35 +/- 1.04%; p < 0.05). The highest level and the degree of DNA damage were observed in workers with PbB over 500 microg/l and the lowest in workers with PbB lower than 200 microg/l. CONCLUSIONS: Our results suggest that lead, particularly in people with chronic occupational Pb exposure and high PbB may induce DNA damage in peripheral lymphocytes detected by the comet assay, and thus should be regarded as a potential agent harmful to the human chromosome. The comet assay can be used to monitor and evaluate biological toxic effects in humans occupationally exposed to lead.

Adult↗
PubMed1998

Comparative biomonitoring study of workers at a waste disposal site using cytogenetic tests and the comet (single-cell gel) assay.

Workers exposed to environmental pollutants at a waste disposal site were studied for genotoxic effects with cytogenetic tests and the comet (alkaline single-cell gel) assay. Analyses were performed on peripheral blood samples of 44 workers at a waste disposal site (DM) and 47 subjects of a control group (VE) matched for gender, age, and smoking habits. Chromosomal aberrations were evaluated in 1,000 lymphocytes per individual, sister chromatid exchanges in 50 cells, and DNA migration (tail moment) was determined in 100 leukocytes. Structural chromosome aberrations were more frequent in DM than in VE, but only the frequency of acentric fragments and the percentage of aberrant cells (excluding gaps) was significantly increased. No significant difference was found for the mean frequency of SCE. A statistically significant difference was also seen with the comet assay. The mean tail moment was higher in DM than in VE. However, no correlation was found between cytogenetic data and the effects in the comet assay. The results of our study indicate that DNA effects in the comet assay represent an independent endpoint which might be useful for the biomonitoring of genotoxic effects in addition to established tests.

Adult↗
PubMed1994

DNA strand breakage and DNA structure influence staining with propidium iodide using the alkaline comet assay.

The alkaline comet assay is used to detect DNA single-strand breaks in individual cells embedded in agarose, lysed to denature DNA and remove proteins, and briefly exposed to an electric field to allow broken DNA to migrate. Total DNA fluorescence, measured by staining individual comets with propidium iodide, is reduced 30-40% by low doses of ionizing radiation, N-methyl-N-nitrosoguanidine (MNNG), etoposide, or hydrogen peroxide. Three possible explanations were examined: 1) these agents produce small fragments of DNA that are lost during lysis and electrophoresis, 2) the analysis of comet images is less efficient once the DNA is small enough to migrate in the electric field, and 3) DNA staining by propidium iodide is affected by changes in DNA structure caused by strand breaks and exposure to alkali. Our results indicate that the decrease in fluorescence after low doses is best explained by a change in ability of DNA, which has been denatured by alkali and subsequently renatured, to interact with fluorescent dyes. This change in fluorescence has the practical consequence of improving the ability of the alkaline comet assay to distinguish damaged from undamaged cells.

Alkalies↗
PubMed1995

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

Benzene and five of its known metabolites--muconic acid, hydroquinone, catechol, p-benzoquinone, and benzentriol--were examined for DNA damage in human lymphocytes using the alkaline Comet assay, and conditions were optimised to determine responses. Metabolic activation (S-9 mix) was included in the assay for varying times to try to enhance effects. In addition, the effects of catalase were investigated as it is known to be present in S-9 mix reducing oxidative damage, and some benzene metabolites are known to react through oxygen radical mechanisms. Effects were also examined in cycling cells to determine whether they were more sensitive to damage then noncycling cells. Comets were measured either by eye or by image analysis. Data have been presented according to length of treatments. When Comets were measured by eye after treatment with hydrogen peroxide (H2O2), the positive control, and each compound for 0.5 hr, only H2O2 and benzenetriol induced pronounced DNA damage without metabolic activation. The effect of catechol was moderate compared with that of benzenetriol. There was a very weak effect of benzene in the absence of rat liver S-9 mix. In the presence of S-9 mix, benzene was not activated. The effect of benzenetriol was greatly reduced by the external metabolising system, but p-benzoquinone became activated to some extent. Catalase abolished the effect of benzenetriol, suggesting that H2O2 formed during autoxidation may be responsible for the DNA-damaging ability of this metabolite. The presence of catalase in S-9 mix may explain the detoxification of benzenetriol and the failure to detect consistent benzene responses. Mitogen-stimulated cycling cells were less sensitive to H2O2 and benzenetriol than unstimulated G0 lymphocytes. When comets were measured by image analysis, a 0.5-hr treatment with H2O2 and benzenetriol and catechol confirmed results analysed by eye, with S-9 mix greatly reducing responses. When treatments were increased to 1 hr in the presence and absence of S-9 mix, benzene at a 5-fold increased dose produced a significant positive response but not at the lower dose. When treatment times were increased to 2 and 4 hr, doses were also increased, and muconic acid, hydroquinone, catechol, and benzoquinone in the presence of S-9 mix showed positive time and dose-related responses, and at the highest dose of benzoquinone the morphology of the nucleus was affected. Effects tended to become more pronounced at high doses and after longer exposures, although this was not always consistent from experiment to experiment. In conclusion, benzene and all metabolites investigated gave positive responses. Where altered responses were observed, they were significantly different from the corresponding controls.

Adult↗
PubMed1998

Detection of DNA strand breaks in isolated mussel (Mytilus edulis L. ) digestive gland cells using the "Comet" assay.

Isolated mussel (Mytilus edulis L.) digestive gland cells were analyzed using the single-cell gel electrophoresis or "comet" assay to assess the ability of potential aquatic contaminants to induce DNA strand breaks (SBs) and to investigate the potential application of this technique as part of an aquatic biomonitoring regime. Freshly prepared cell suspensions from digestive gland were exposed in vitro to hydrogen peroxide (H2O2, 0-200 microM), 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX, 0-200 microM), benzo[a]pyrene (BaP, 0-200 microM), 1-nitropyrene (1-NP, 0-250 microM) and nitrofurantoin (NF, 0-1000 microM) for 1 h in the dark at 15 degreesC in the presence of the DNA repair inhibitor cytosine-beta-D-arabinofuranoside (araC). DNA strand breakage was measured using the comet assay. There were significant concentration-dependent increases in the percentage of DNA in the comet tail (mean values+/-SD) for all doses compared with controls (P<0.05) with H2O2 (up to 61.4+/-5.1% at 100 microM), MX (up to 34. 3+/-2.2% at 200 microM), BaP (up to 24.7+/-5.1 at 100 microM), 1-NP (up to 54.7+/-5.0% at 200 microM), and NF (up to 68.1+/-4.5% at 500 microM). There was a decrease (P<0.05) in viability (eosin Y exclusion) of exposed compared with control cells at 200 microM H2O2 and BaP only. This study has demonstrated the potential of the comet assay to detect DNA strand breakage at subcytotoxic concentrations of a range of agents, some of which require metabolic activation. This may provide a sensitive, but nonspecific, molecular biomarker of genotoxicity.

Animals↗
PubMed1987

Observations of HCN in comet P/Halley.

We present observations of the HCN J = 1-0 rotational transition at 3.4 mm wavelength in comet P/Halley. The data were obtained during a total of 56 individual observing sessions between November 1985 and May 1986 and represent the first time that a cometary parent molecule has been so extensively monitored. The HCN production rate is well correlated with the total visual magnitude of the comet, and comparison of the HCN production to the total gas production of the comet indicates that it is a relatively minor constituent with 0.1% the abundance of H2O. Comparison of HCN and CN production suggests that HCN is a major parent molecule of CN, but probably not the sole parent. HCN spectra obtained by binning the data with heliocentric distance show that the line width, and thus the parent outflow velocity, increases with decreasing heliocentric distance, and that there is a tendency for the lines to be blue shifted due to anisotropic outgassing from the nucleus. Finally, there is evidence of day-to-day time variability in the total HCN emission and in the hyperfine ratios. The time variation of the total emission is consistent with the known time variable behavior of the comet, and detailed comparisons to optical data, where possible, confirm this interpretation. However, non-LTE values of the hyperfine ratios are not consistent with theoretical modeling of the excitation of these transitions.

Astronomical Phenomena↗