Nakano M, Kodama Y, Ohtaki K, Itoh M, Nakamura N
Department of Genetics, Radiation Effects Research Foundation, Hiroshima, Japan.
Int J Radiat Biol. 1999 Jan;75(1):47-9. doi: 10.1080/095530099140799.
It has been proposed previously that the ratio of complete to incomplete translocations as seen by fluorescence in situ hybridization (FISH), the S value, can be a cytogenetic fingerprint of exposure to radiation of different qualities. Results from a previous study suggested that the S value is approximately 10 for sparsely ionizing radiations such as X- and gamma-rays, and 2 for densely ionizing radiations. Based on FISH data of atomic-bomb (A-bomb) survivors, which showed an S value of 3.25, a significant neutron component to A-bomb radiation was suggested. To examine the possibility, the present in vitro study was conducted using X-rays.
Human blood lymphocytes were exposed to X-rays and first metaphases were examined with FISH using DNA probes for chromosomes 1, 2 and 4.
The S value was 3.16 for X-rays, which differs from approximately 10 as reported previously, and not larger than the 3.25 obtained from the blood lymphocytes of A-bomb survivors.
S values seem to vary among laboratories even after exposure of cells to sparsely ionizing radiations. Data from this study show that S values are not a signature for a significant contribution of neutrons to the radiation dose received by A-bomb survivors in Hiroshima.
先前有人提出，荧光原位杂交（FISH）检测到的完全易位与不完全易位的比例，即S值，可能是不同性质辐射暴露的细胞遗传学指纹。先前一项研究的结果表明，对于X射线和γ射线等低线性能量传递辐射，S值约为10；对于高线性能量传递辐射，S值为2。基于原子弹幸存者的FISH数据显示S值为3.25，提示原子弹辐射中有显著的中子成分。为了检验这种可能性，本研究使用X射线进行了体外实验。
将人血淋巴细胞暴露于X射线下，使用针对1号、2号和4号染色体的DNA探针，通过FISH检测首次分裂中期细胞。
X射线的S值为3.16，与先前报道的约10不同，且不大于从广岛原子弹幸存者血淋巴细胞中获得的3.25。
即使细胞暴露于低线性能量传递辐射后，S值在不同实验室之间似乎也存在差异。本研究数据表明，S值并非广岛原子弹幸存者所接受辐射剂量中中子显著贡献的特征标志。
