Dose-rate is one of the basic physical factors determining the effects of ionizing radiation on biological systems. Generally, observations of biological systems have revealed
Li Wen-jian, Wang Zhuan-zi, Wei Wei, Jing Xigang Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu Nanchang road 509
In this paper,we study the biological response induced by heavy ions irradiation of high dose,human peripheral blood lymphocytes are irradiated in vitro by the carbon ions of LET=35 keV/μm,and the chromosome aberrations at absorbed doses of 0-20 Gy are analyzed by the calyculin A-induced premature chromosome condensation(PCC).The frequencies of PCC-rings at the stage of G2/M-phase increase steeply with radiation doses up to 20 Gy at a rate of 0.017 Gy^(-1).The G2-PCC index remains more than 5%up to 15 Gy,and 3%after 20 Gy,this is high enough to score a substantial number of chromosome spreads without dose-rate effect.The results show that the calyculin A-induced PCC technique is suitable for analyzing the chromosome damage induced by carbon ions irradiation of high dose.
The relationship between deoxyribonucleic acid (DNA) damage and the cell death induced by 12C ions irradiation was examined in four kinds of cells, Melanoma B16, cervical squamous carcinoma HeLa, Chinese hamster V79 and hepatoma SMMC-7721. Cell survival was determined by a colonogenic assay, and the sensitivity was described by D50 (the dose of radiation necessary to reduce the survival to 50%). For all cell lines, D50 ranged from 0.74 Gy to 3.85 Gy, among them B16 was the most radiosensitive to 12C ions, and V79 and HeLa cells had almost the same radio-sensitivity, SMMC-7721 was the last. The induction of deproteinized DNA double-strand breaks induced by 12C ions were measured by pulsed-field gel electrophoresis (PFGE), and the initial yield of the deproteinized DNA dsbs per unit dose was expressed as the DNA double break level (L). A linear dose-response curve was seen for initial DNA dsbs for all cell lines (slopes range from 0.40-0.98 (DSBs/100Mbp/Gy)). V79 was the steepest, B16 was the last. There was an inverse relationship between the initial DNA dsb and D50 if the B16 cell line was not considered, but there was no relativity even excludes the B16 cell line. The present results indicate that there is no relationship between cellular sensitivity and initial DNA dsb, even exclude the effects of chromatin structure.
LI Wenjian ZHOU Guangming WANG Zhuanzi LI Qiang DANG Bingrong WANG Jufang
Measurements of chromosome aberrations in peripheral blood lymphocytes are currently the most sensitive and reliable indicator of radiation exposure that can be used for
Wang Zhuanzi, Li Wenjian, Wei Wei, Jing Xigang, Dang bingrong, Liu jinting Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu Nanchang road 509
