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Retrospective analysis of DSB rejoining data
collected using warm-lysis PFGE protocols
Published erratum in
Int. J Radiat. Biol. 82(2), 139 (2006) |
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Purpose: Sample preparation procedures for the PFGE assay sometimes involve a lysis step at temperatures as high as 50°C. During this warm-lysis procedure, multiply damaged sites containing heat-labile sites (HLS) can be converted into DSBs. Once formed, these DSBs cannot be distinguished from the DSBs formed directly by ionizing radiation. In this work, we develop a method to correct DSB estimates for the effects of HLS in warm-lysis protocols. Material and methods: A first-order repair model is used to predict the number of HLS available for conversion into DSBs as a function of the time available for repair before initiating warm-lysis. A mathematical expression is derived to separate prompt DSBs from those formed through the artefactul conversion of HLS into DSBs. The proposed formalism only requires the specification of two adjustable parameters, both of which can be estimated from measured data. Results: Estimates of prompt DSB yields obtained by correcting warm-lysis data are in good agreement with estimates obtained using cold-lysis protocols, which do not include the effect of HLS. The retrospective analyses of two published datasets suggest that corrections for HLS have a substantial impact on DSB yields within the first 20 to 30 min after irradiation. Bi-exponential fits to the DSB data for CHO cells suggest that corrections for HLS reduce the half-time for fast DSB rejoining by about 15%, whereas the half-time for the slow DSB rejoining only decreases by 4%. Conclusions: The proposed formalism can be used to characterize trends and uncertainties in DSB rejoining kinetics associated with the artefactual conversion of HLS into DSBs. The retrospective application of the methodology to warm-lysis data enhances their relevance and usefulness for studies of DSB rejoining kinetics. |
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Last updated: July 22, 2006 |
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