Moiseenko V V, Edwards A A, Nikjoo H, Prestwich W V
McMaster University, Department of Physics and Astronomy, Hamilton, Ontario, Canada.
Radiat Res. 1997 Feb;147(2):208-14.
A biophysical model has been applied to describe the production of exchange chromosomal aberrations (dicentrics) in human lymphocytes by radiations of different qualities. The model includes a detailed description of the energy deposition pattern in the form of computer-generated tracks. Energy deposition events are further converted to DNA double-strand breaks (DSBs). Formation of chromosomal exchanges is modeled in competition with repair in a distance-dependent manner with breaks in proximity being most likely to interact. We demonstrate that an assumption of an RBE > 1 for production of DSBs at higher LET leads to a significant increase with LET of both the linear and the quadratic coefficients of the dose response for exchange formation. The latter is not supported experimentally and argues against high RBE values for production of DSBs, at least for those breaks involved in chromosomal exchanges. Assuming that the RBE for production of DSBs is unity, the calculated dose-response curves conformed to experimental data for 60Co gamma rays, 250 kVp X rays and 8.7 MeV protons. The linear coefficient for 23.5 MeV 3He ions is underpredicted. The model predicts that a quadratic term in the dose response for exchange aberrations should be observed at LET values of 20-30 keV/microm. The curvature is not observed experimentally, and the contradiction is discussed.
已应用一种生物物理模型来描述不同性质辐射在人淋巴细胞中产生交换型染色体畸变（双着丝粒）的情况。该模型以计算机生成的径迹形式详细描述了能量沉积模式。能量沉积事件进一步转化为DNA双链断裂（DSB）。染色体交换的形成以距离依赖的方式与修复竞争进行建模，相邻的断裂最有可能相互作用。我们证明，对于较高传能线密度（LET）下DSB产生的相对生物效应（RBE）>1的假设，会导致交换形成剂量响应的线性和二次系数均随LET显著增加。后者未得到实验支持，这表明至少对于参与染色体交换的那些断裂，DSB产生的RBE值不会很高。假设DSB产生的RBE为1，则计算出的剂量响应曲线与60Coγ射线、250 kVp X射线和8.7 MeV质子的实验数据相符。对于23.5 MeV 3He离子，线性系数预测不足。该模型预测，在LET值为20 - 30 keV/μm时，交换畸变的剂量响应中应观察到二次项。但实验未观察到这种曲率，对此矛盾进行了讨论。
