Radiation-induced versus endogenous DNA damage and assays that measure parameters reflecting DNA damage on cell by cell basis: comments on the article by Pollycove and Feinendegen

2003 ◽  
Vol 22 (6) ◽  
pp. 309-313 ◽  
Author(s):  
Joseph L Roti Roti

The article by Pollycove and Feinendegen raises important issues regarding the relative contributions of endogenous and radiation-induced DNA damage to the overall DNA damage burden following low level radiation exposures. Clearly, resolution of the issues raised in their article will have important implications regarding regulatory philosophy. Dose-limiting studies of DNA damage measured on a cell-by-cell basis was used to analyze available data in the context of the proposed model. If one proposes that significant numbers of oxidative DNA lesions are present in cells at a steady state level at any give time, then such damage will be included in the background measure of any DNA damage dependent parameter that is sensitive to these classes of DNA damage. Then the expected number of lesions per cell was compared, prior to X- or γ-ray exposure, at the dose that gives the minimum statistically significant difference from background, at the dose where the DNA damage dependent parameter is twice background (i.e., the doubling dose). The lesion frequencies predicted from the model by Pollycove and Feinendegen are reasonable for the micronucleus assay and the inhibition of DNA supercoil rewinding, but appear to be inconsistent with results from the comet assay. Possible explanations for the inconsistency between the comet assay dose) response data and the predicted levels of DNA damage predicted by the model are discussed, suggesting that the estimates of the radiation induced damage are too low and those for endogenous damage are too high. The goal in introducing these issues is not to be negative to the article but to present a basis for future discussions and more importantly future experimental work, by which the important issues raised can be resolved.

2019 ◽  
Vol 186 (2-3) ◽  
pp. 168-171
Author(s):  
Kateřina Pachnerová Brabcová ◽  
Zuzana Jamborová ◽  
Anna Michaelidesová ◽  
Marie Davídková ◽  
Satoshi Kodaira ◽  
...  

Abstract Plasmid DNA is commonly used as a simpler substitute for a cell in studies of early effects of ionizing radiation because it allows to determine yields of primary DNA lesions. Experimental studies often employ plasmids of different lengths, in different concentrations in the aqueous solution. Influence of these parameters on the heavy-ion induced yields of primary DNA damage has been studied, using plasmids pUC19 (2686 bp), pBR322 (4361 bp) and pKLAC2 (9107 bp) in 10 and 50 ng/μl concentration. Results demonstrate the impact of plasmid length, while no significant difference was observed between the two concentrations. The uncertainty of the results is discussed.


2003 ◽  
Vol 89 (3) ◽  
pp. 305-310 ◽  
Author(s):  
Volkan Baltaci ◽  
Semra Sardas ◽  
Bulent Aytac ◽  
Sami Cakar ◽  
Ali Esat Karakaya

Aims, Background and Study Design Few studies have investigated the karyotypes of colorectal carcinomas with emphasis on the correlation between cytogenetic findings and clinicopathologic features. The aim of our study involving 20 colorectal adenocarcinomas was to determine their genomic alterations at the chromosomal level by correlating the cytogenetic findings with the extent of DNA damage and clinicopathologic parameters and to compare the results with those of healthy controls. Results Cytogenetic evaluation of patients and controls revealed 10 abnormal karyotypes in patients with adenocarcinomas located in the rectum, sigmoid and rectosigmoid regions. Four had numerical and six had structural abnormalities. Conclusions Statistical analysis revealed a significant difference compared with controls (P <0.01). The karyotypes and the extent of DNA damage assessed by the comet assay were also significantly correlated with tumor stage (P <0.01) using the Kruskal-Wallis non-parametric test, while no statistical significance was observed in relation to patient age and smoking.


2013 ◽  
Vol 03 (03) ◽  
pp. 038-041
Author(s):  
Shobha S. Shetty ◽  
Hrishikesh Nachane

Abstract Background: Smoking has been shown to have a positive effect on DNA damage in almost all the cells of the body. Quantitative analysis of this damage will help in assessing the etiopathogenesis of various nicotine induced damage to the body. Comet assay has been an emerging tool in this regard and hence was applied by us to estimate the severity of DNA damage in smokers. Aims & Objectives: To evaluate the DNA genotoxicity in peripheral blood lymphocytes in smokers and their comparison with non smokers & assess the quantitative damage. Materials and methods: 30 smokers & 20 non smokers were recruited & their peripheral blood was taken for the comet assay to look for Olive moment & Tail moment to quantitatively assess the DNA damage due to cigarette smoking. Results: In our study there was no significant difference in the analysis of DNA damage (with regard to tail moment & olive moment) in smokers versus non smokers (P value: more than 0.05). Conclusions: Though smoking is known to cause DNA damage, we did not find significant differences between the two groups probably due to other multifactorial etiologies for genotoxicity.


2014 ◽  
Vol 150 ◽  
pp. 1-8 ◽  
Author(s):  
M.K. Praveen Kumar ◽  
S.K. Shyama ◽  
B.S. Sonaye ◽  
U Roshini Naik ◽  
S.B. Kadam ◽  
...  

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4353-4353
Author(s):  
Janusz Blasiak ◽  
Jozef Drzewoski ◽  
Tomasz Poplawski ◽  
Agnieszka Czechowska

Abstract Imatinib (STI571) is a 2-phenylaminopyrimidine derivative used mostly in the treatment of chronic myeloid leukaemia. It targets specifically the BCR/ABL oncogenic tyrosine kinase, inhibiting its activity. Using the alkaline comet assay we showed that STI571 at concentrations ranging from 0.05 to 2 μM induced DNA damage in human leukemic K562 cells expressing the BCR/ABL oncogene, whereas it had no effect in normal human lymphocytes. Because the extent of DNA damage observed in the neutral and pH 12.1 versions of the comet assay was much lesser than in the alkaline version, we concluded that the drug induced DNA alkali-labile sites rather than strand breaks. Imatinib did not induce DNA strand breaks in the direct interaction with DNA as examined by the plasmid relaxation assay. K562 cells were unable to repair H2O2-induced DNA damage during a 120-min incubation, if they had been preincubated with STI571, whereas normal lymphocytes did so within 60 min. Pre-treatment of K562 cells with vitamins A, C and E reduced the extent of DNA damage evoked by STI571. Similar results brought experiments with the nitrone spin traps POBN and PBN, suggesting that free radicals may be involved in the formation of DNA lesions induced by STI571 in K562 cells. These cells exposed to imatinib and treated with endonuclease III, formamidopyrimidine-DNA glycosylase and 3-methyladenine-DNA glycosylase II, the enzymes recognizing oxidized and alkylated bases, displayed greater extent of DNA damage than those not treated with these enzymes.


2003 ◽  
Vol 65 (4) ◽  
pp. 471-477 ◽  
Author(s):  
Seiichi WADA ◽  
Hidemitsu KURAHAYASHI ◽  
Yasuhiko KOBAYASHI ◽  
Tomoo FUNAYAMA ◽  
Kazuo YAMAMOTO ◽  
...  

2009 ◽  
Vol 60 (3) ◽  
pp. 307-315
Author(s):  
Bensu Karahalil ◽  
Tulin Gumus ◽  
Esra Emerce ◽  
Seval Izdes ◽  
Orhan Kanbak ◽  
...  

Comet Assay in Evaluating DNA Damage Associated With Ischaemia-Reperfusion Injury in Patients Undergoing Coronary SurgeryIschaemia-reperfusion (I/R) injury is responsible for a number of conditions such as coronary bypass and myocardial infarction, and deaths. Oxygen-free radicals formed during I/R have been proposed as the leading causes of tissue injury, and they play an important role in I/R injury. I/R induces oxidative DNA damage (such as purinic and pyrimidinic base lesions). Comet assay is a suitable and sensitive method for early detection of low-level DNA damage. We used modified alkaline comet assay in peripheral blood lymphocytes and evaluated I/R-induced DNA damage in patients undergoing coronary artery bypass graft (CABG) operation (in vivo model for I/R). No statistically significant difference in DNA damage levels was found before surgery, after anaesthesia, ischemia, reperfusion, and surgery. However, blood lactate levels (assessed in parallel with the comet assay) increased after I/R and did not return to the baseline level. Our findings showed that I/R injury did not induce DNA damage, but increased the lactate levels. This finding suggests that there might be reversible and uncommon necrosis that did not reflect on overall DNA base damage. Further studies are needed using this approach.


Genetika ◽  
2016 ◽  
Vol 48 (2) ◽  
pp. 617-627
Author(s):  
Stefan Dacic ◽  
Ninoslav Djelic ◽  
Milena Radakovic ◽  
Nada Lakic ◽  
Aleksandar Veselinovic ◽  
...  

Certain in vivo studies have shown that the application of adhesives directly onto the open pulp or on a thin layer of dentin causes inflammation and pulpal abscesses. This reaction is related to toxic effects of monomers from adhesives. It has been confirmed that after proper illumination the adhesives become less toxic. The aim of the study was to examine genotoxicity of non-polymerised, partly polymerised and polymerised adhesives on isolated human lymphocytes using the alkaline Comet assay. Adper Single bond2 and Adper Easy One/3M ESPE adhesive photopolymerisation was performed by Elipar Highlight 3M ESPE halogen lamp for 0, 10 and 40 sec, at final concentrations of 100, 200, 500 and 1000 ?g/mL. With both adhesives, photopolymerisation at 0 and 10 seconds showed statistically significant increase in DNA damage in comparision to the negative control (solvent). On the other hand, after 40 seconds of photopolymerisation of both adhesives in all tested concentrations, the degree of DNA damage in Comet assay had no significant difference (P>0.05, ?2 test) compared to the negative control. Therefore, only the 40 seconds of photopolymerisation prevented genotoxic effects of both adhesives in the Comet assay.


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