Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays. Export

@article{citeulike:2775885, abstract = {Single-color painting of whole chromosomes, or protocols in which only a few chromosomes are distinctively painted, will always fail to detect a proportion of complex exchanges because they frequently produce pseudosimple painting patterns that are indistinguishable from those produced by bona fide simple exchanges. When 24-color multi-fluor FISH (mFISH) was employed for the purpose of distinguishing (truly) simple from pseudosimple exchanges, it was confirmed that the acute low-LET radiation dose-response relationship for simple exchanges lacked significant upward curvature. This result has been interpreted to indicate that the formation of simple exchanges requires only one chromosome locus be damaged (e.g. broken) by radiation to initiate an exchange-not two, as classical cytogenetic theory maintains. Because a one-lesion mechanism implies single-track action, it follows that the production of simple exchanges should not be influenced by changes in dose rate. To examine this prediction, we irradiated noncycling primary human fibroblasts with graded doses of (137)Cs gamma rays at an acute dose rate of 1.10 Gy/min and compared, using mFISH, the yield of simple exchanges to that observed after exposure to the same radiation delivered at a chronic dose rate of 0.08 cGy/min. The shape of the dose response was found to be quasi-linear for both dose rates, but, counter to providing support for a one-lesion mechanism, the yield of simple aberrations was greatly reduced by protracted exposure. Although chronic doses were delivered at rates low enough to produce damage exclusively by single-track action, this did not altogether eliminate the formation of complex aberrations, an analysis of which leads to the conclusion that a single track of low-LET radiation is capable of inducing complex exchanges requiring up to four proximate breaks for their formation. For acute exposures, the ratio of simple reciprocal translocations to simple dicentrics was near unity.}, address = {Department of Radiation Oncology, University of Texas Medical Branch, Galveston, Texas 77555-0656, USA.}, author = {Loucas, Bradford D. and Eberle, Richard and Bailey, Susan M. and Cornforth, Michael N.}, citeulike-article-id = {2775885}, citeulike-linkout-0 = {http://view.ncbi.nlm.nih.gov/pubmed/15447049}, citeulike-linkout-1 = {http://www.hubmed.org/display.cgi?uids=15447049}, issn = {0033-7587}, journal = {Radiation research}, keywords = {complex, doserate, gamma-rays, lymphocytes, mfish}, month = {October}, number = {4}, pages = {339--349}, posted-at = {2008-05-09 14:43:02}, priority = {3}, title = {Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/15447049}, volume = {162}, year = {2004} }

TY - JOUR ID - citeulike:2775885 L3 - citeulike-article-id:2775885 N2 - Single-color painting of whole chromosomes, or protocols in which only a few chromosomes are distinctively painted, will always fail to detect a proportion of complex exchanges because they frequently produce pseudosimple painting patterns that are indistinguishable from those produced by bona fide simple exchanges. When 24-color multi-fluor FISH (mFISH) was employed for the purpose of distinguishing (truly) simple from pseudosimple exchanges, it was confirmed that the acute low-LET radiation dose-response relationship for simple exchanges lacked significant upward curvature. This result has been interpreted to indicate that the formation of simple exchanges requires only one chromosome locus be damaged (e.g. broken) by radiation to initiate an exchange-not two, as classical cytogenetic theory maintains. Because a one-lesion mechanism implies single-track action, it follows that the production of simple exchanges should not be influenced by changes in dose rate. To examine this prediction, we irradiated noncycling primary human fibroblasts with graded doses of (137)Cs gamma rays at an acute dose rate of 1.10 Gy/min and compared, using mFISH, the yield of simple exchanges to that observed after exposure to the same radiation delivered at a chronic dose rate of 0.08 cGy/min. The shape of the dose response was found to be quasi-linear for both dose rates, but, counter to providing support for a one-lesion mechanism, the yield of simple aberrations was greatly reduced by protracted exposure. Although chronic doses were delivered at rates low enough to produce damage exclusively by single-track action, this did not altogether eliminate the formation of complex aberrations, an analysis of which leads to the conclusion that a single track of low-LET radiation is capable of inducing complex exchanges requiring up to four proximate breaks for their formation. For acute exposures, the ratio of simple reciprocal translocations to simple dicentrics was near unity. IS - 4 JF - Radiation research SN - 0033-7587 AD - Department of Radiation Oncology, University of Texas Medical Branch, Galveston, Texas 77555-0656, USA. EP - 349 TI - Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays. VL - 162 SP - 339 KW - complex KW - doserate KW - gamma-rays KW - lymphocytes KW - mfish AU - Loucas, Bradford AU - Eberle, Richard AU - Bailey, Susan AU - Cornforth, Michael PY - 2004/10// UR - http://view.ncbi.nlm.nih.gov/pubmed/15447049 ER -