Ritter S, Nasonova E, Scholz M, Kraft-Weyrather W, Kraft G
Gesellschaft fur Schwerionenforschung, Darmstadt, Germany.
Int J Radiat Biol. 1996 Feb;69(2):155-66. doi: 10.1080/095530096145986.
Synchronous V79 Chinese hamster cells were exposed in G1 to either X-rays or 4.6 MeV/u Ar-ions (LET = 1840 keV/micrometer) and the induction of chromosomal damage was measured at five sampling times ranging from 14 to 30 h after treatment. To distinguish between cells in the first and second post-irradiation cycle the fluorescence-plus-Giemsa technique was applied. The experiment showed that the time-course of the appearance of damaged cells was markedly influenced by radiation-induced cell cycle delays and depended on both radiation quality and dose. The yield of aberrant metaphases and the number of aberrations per metaphase was found to increase with sampling time, but this increase was more pronounced for Ar ions. These differences in yield-time profiles of X-ray and Ar ion induced chromosomal damage are particularly important for an accurate determination of the RBE for particles. Our data clearly indicate that meaningful RBEs can only be obtained if chromosomal damage is analysed at several post-irradiation sampling times and the complete time-course of the expression of chromosomal damage is taken into account. Besides these quantitative differences, differences in the spectrum of chromosomal lesions were observed for X-rays and Ar ions. Following particle exposure more breaks and less exchange-type aberrations were formed compared with X-irradiation and, despite irradiation in G(1), a significant number of chromatid-type aberrations occurred in Ar-irradiated samples. The experimental results are interpreted on the basis of the different pattern of energy deposition by sparsely and densely ionizing radiation. In addition, a statistical analysis based on the Neyman type A distribution is performed, which takes into account the specific stochastic properties of particle irradiation.
同步化的V79中国仓鼠细胞在G1期受到X射线或4.6 MeV/u的氩离子（线性能量传递=1840 keV/微米）照射，在处理后14至30小时的五个采样时间点测量染色体损伤的诱导情况。为了区分处于照射后第一个和第二个细胞周期的细胞，应用了荧光加吉姆萨技术。实验表明，受损细胞出现的时间进程受到辐射诱导的细胞周期延迟的显著影响，并且取决于辐射质量和剂量。发现异常中期的产率和每个中期的畸变数量随采样时间增加，但氩离子的这种增加更为明显。X射线和氩离子诱导的染色体损伤的产率-时间曲线的这些差异对于准确确定粒子的相对生物效应尤为重要。我们的数据清楚地表明，只有在照射后的几个采样时间点分析染色体损伤并考虑染色体损伤表达的完整时间进程，才能获得有意义的相对生物效应。除了这些数量差异外，还观察到X射线和氩离子在染色体损伤谱方面的差异。与X射线照射相比，粒子照射后形成的断裂更多，交换型畸变更少，并且尽管在G1期进行照射，但在氩离子照射的样本中仍出现了大量染色单体型畸变。基于稀疏和密集电离辐射的不同能量沉积模式对实验结果进行了解释。此外，还基于奈曼A型分布进行了统计分析，该分析考虑了粒子照射的特定随机特性。
