Suzuki M, Nakano K, Suzuki K, Watanabe M
International Space Radiation Laboratory, National Institute of Radiological Sciences, Chiba, Japan.
Int J Radiat Biol. 2000 Jun;76(6):815-21. doi: 10.1080/09553000050028977.
To investigate the time-course of chromosomal aberrations following radiations of differing LET.
Syrian hamster embryonic cells were irradiated with nitrogen ions (LET(infinity) = 530 keV/microm) and helium-ions (LET(infinity) = 36 and 77 keV/microm), also 137Cs gamma-rays as a reference radiation. The frequency of chromatid-type aberrations was determined after 0-6 h incubation in a 5% CO2 incubator at 37 degrees C.
The amount of chromosomal damage per cell for nitrogen ions detected immediately after irradiation was lower than induced by 137Cs gamma-rays. In contrast, helium ions were more effective than gamma rays in inducing chromatid type damage. The RBE values for the nitrogen-ion beams were 0.45 for gaps, 0.43 for deletions and 0.20 for exchanges. For helium-ion beams, the RBE values for the 36 keV/microm beams and the 77 keV/microm beams were 1.2 and 1.5 for gaps, 1.3 and 2.1 for deletions, and 1.5 and 1.9 for exchanges, respectively. The frequency of cells with chromosomal damage following exposure to gamma-rays and helium-ion beams showed a downward trend with increasing incubation period. In contrast, in the case of nitrogen-ion beams, there was an increase with the incubation period.
The results show that it is possible to underestimate chromosomal damage for different types of radiation by scoring aberrations at a single fixed sampling time.
研究不同传能线密度（LET）辐射后染色体畸变的时间进程。
用氮离子（LET(∞)=530keV/μm）、氦离子（LET(∞)=36和77keV/μm）辐照叙利亚仓鼠胚胎细胞，同时用137Csγ射线作为参考辐射。在37℃、5%二氧化碳培养箱中孵育0 - 6小时后，测定染色单体型畸变的频率。
辐照后立即检测到的氮离子所致每个细胞的染色体损伤量低于137Csγ射线诱导的损伤量。相比之下，氦离子在诱导染色单体型损伤方面比γ射线更有效。氮离子束的相对生物学效应（RBE）值，间隙为0.45，缺失为0.43，交换为0.20。对于氦离子束，36keV/μm束和77keV/μm束的RBE值，间隙分别为1.2和1.5，缺失分别为1.3和2.1，交换分别为1.5和1.9。γ射线和氦离子束照射后出现染色体损伤的细胞频率随孵育时间延长呈下降趋势。相比之下，对于氮离子束，随孵育时间则有所增加。
结果表明，在单一固定采样时间对畸变进行评分可能会低估不同类型辐射的染色体损伤。
