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Application of the Premature Chromosome Condensation Assay in Simulated Partial-Body Radiation Exposures: Evaluation of the Use of an Automated Metaphase-Finder

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The premature chromosome condensation PCC assay has been proposed as a useful and rapid end point for biological dosimetry following accidental high-dose radiation overexposures. A major benefit of the PCC assay is that it does not require cells to divide for evaluation of cytogenetic damage. The PCC assay was performed on isolated human peripheral lymphocytes exposed in vitro to doses from 1 to 9 Gy of 250 kVp x-rays. The dose-response relationships of the frequency distribution and the yield of PCC fragments in cells were determined after one day of repair at 37 deg C. A Qpcc approach, which involves the analysis of the yield of excess PCC fragments in damaged cells, was used to establish a dose-response calibration curve. This method is identical in concept to the Qdr technique introduced by Sasaki for partial-body exposure dose-estimates using asymmetrical chromosome aberrations i.e., dicentrics and rings in metaphase spreads of human lymphocytes. A simulated in vitro test of a partial-body exposure to a 6-Gy dose was performed. The results from this test provided dose estimates of 5.3 or 0.6, 4.7 or 0.6,5.0 or 0.6 and 4.7 or 0.8 Gy for the 20,30,50 and 75 percent component of 6-Gy irradiated cells, respectively. An automated metaphase-finding system was evaluated for use with the PCC assay. This system helped to locate PCC spreads among the mitotic inducer Chinese hamster ovary CHO metaphase spreads, thereby facilitating rapid scoring of samples. We conclude that the measurement of excess PCC fragments in Giemsa-stained preparations provides useful biological dosimetry information on the size of the irradiated fraction in cases of acute radiation exposures. Use of Qpcc analysis is recommended for partial-body exposures to determine dose estimates for the irradiated fraction. Automated metaphasc finding significantly enhances the spced of the PCC assay.

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  • Radiobiology
  • Genetic Engineering and Molecular Biology

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