Geard C R
Center for Radiological Research, College of Physicians & Surgeons of Columbia University, New York, New York 10032.
Radiat Res. 1993 May;134(2):187-92.
Frequencies of sister chromatid exchanges (SCEs) were evaluated in chromosome spreads of CHO-AA8 cells at the second mitosis after irradiation with charged particles of 10, 40, 80, and 120 keV/microns. At each LET there was a dose-dependent increase in the frequency of SCEs. In contrast to the majority of end points where relative biological effectiveness increases as LET increases up to an optimum and then declines, it was found that the most biologically effective particles were protons at 10 keV/microns, followed by deuterons at 40 keV/microns, then alpha particles at 80 and 120 keV/microns. Nuclear cross-sectional areas of these cells were log-normally distributed with a mean of 77 microns 2. When induced SCEs per chromosome were related to charged particles per cell nucleus (down to a mean of 0.5 particles per nucleus), results at low fluences favored a linear relationship between SCEs and particles which was relatively independent of LET. These observations are not compatible with the origin of radiation-induced SCEs being DNA double-strand breaks and favor the notion that they may be consistent with DNA single-strand breaks.
在用能量为10、40、80和120 keV/μm的带电粒子照射后，在第二次有丝分裂时对CHO-AA8细胞的染色体铺展进行了姐妹染色单体交换（SCE）频率的评估。在每个传能线密度（LET）下，SCE频率均呈剂量依赖性增加。与大多数终点不同，在这些终点中，相对生物效能随着LET的增加而增加，直至达到最佳值然后下降，研究发现，生物效能最高的粒子是10 keV/μm的质子，其次是40 keV/μm的氘核，然后是80和120 keV/μm的α粒子。这些细胞的核横截面积呈对数正态分布，平均值为77μm²。当每条染色体诱导的SCE与每个细胞核的带电粒子相关时（低至每个细胞核平均0.5个粒子），低注量下的结果支持SCE与粒子之间存在线性关系，且该关系相对独立于LET。这些观察结果与辐射诱导的SCE起源于DNA双链断裂不相符，支持它们可能与DNA单链断裂一致的观点。
