Title: Evaluation of chronic occupational radiation exposure by the measurement of residual/initial DNA strand breaks ratio

Authors: Tahereh Ziafazeli, Shahla Mohammadi, Mehdi Ghiassi-Nejad, Saeid Reza Khatami

Addresses: 33-Cote St. Catherine App. 1508, Montreal Quebec H2V 2A1; Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal PQ H3A 2B2, Canada; Radiation Molecular Genetic Laboratory, National Radiation Protection Department (NRPD), Iranian Nuclear Regulatory Authority (INRA), P.O. Box 14155–4494, Tehran, Iran. ' Radiation Molecular Genetic Laboratory, National Radiation Protection Department (NRPD), Iranian Nuclear Regulatory Authority, Tehran, Iran. ' Department of Biophysics, University of Tarbiat Modares, Iran. ' Shahid Chamran University of Ahvaz, Ahvaz, Iran

Abstract: The comet assay was used to examine radiation workers who deal with radioisotopes such as iodine-125, iodine-131 and technetium-99m. In this study, lymphocytes from test and control donors were exposed to γ-radiation at 0, 1, 2, 4 and 6 Gy. A significant difference (P < 0.05) between the test and the control group in the level of initial damage was observed immediately after exposure. In addition, the level of the residual damage of samples from the test group after 24 hours was slightly higher than the control group. The subsequent measurement of the ratio of residual/initial breaks, representing the fraction of remained DNA break, demonstrated a lower value in the test group. These results indicated an enhanced DNA repair in the test group that led to the decline in residual/initial ratio. However, the high initial damage might be due to the presence of fragile sites in the genome of the test group.

Keywords: chronic occupational radiation exposure; DNA strand breaks ratio; low radiation; lymphocytes; DNA repair; ionising radiation.

DOI: 10.1504/IJLR.2006.010008

International Journal of Low Radiation, 2006 Vol.3 No.1, pp.57 - 65

Published online: 08 Jun 2006 *

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