| Objective: To solve the problems about the radiation biological dosimetry, such as dose rate effect,prompt dose estimation and low dose estimation, human peripheral blood in vitro was irradiated by 60Coγradiation, the frequencies of dicentric chromosome aberrations were compared between different dose rates, the dose-response curves and equations were established respectively in order to estimate accurately the biological dose of the victims exposed to different dose rats exposure accidents; the feasibility of SCGE as a biological dosimeter was discussed; DDB2 and IER5 genes,the two radiation inducible genes,were screened and observed about the effect of 60Coγradiation on the expression of the two genes and the feasibility of them as novel molecular biological dosimeter was discussed.Methods: Human peripheral blood in vitro was irradiated by 60Coγradiation at low,moderate,high dose rates (0.35,1.94,4.4Gy min-1) respectively, then lymphocytes were cultured for 52h and harvested. The frequencies of dicentrics (multi-centrics) and rings were counted and compared between different dose rates, the dose-response curves and equations were established respectively; Mice peripheral blood cells were irradiated by 60Coγradiation at 2 Gy in vivo and DNA damage at different times was measured by Alkaline SCGE, human peripheral blood cells were irradiated by 60Coγradiation at different doses (0～5Gy),and the dose-response curves were established according to DNA damage measured by Alkaline SCGE; Using a model system of human lymphoblastoid AHH-1 cells, the effect of different doses (0 to 10Gy) 60Coγray radiation on the relative expression of two genes(DDB2,IER5) was examined by northern blot analysis at 4 h,12h and 24 h post-radiation.Results: (1) Human peripheral blood in vitro was irradiated to 60Coγradiation at three different dose rates of 0.35,1.94 and 4.4Gy min-1, at a certain dose rate the frequencies of dicentrics and rings in lymphocytes increased in a dose dependent manner, then the dose-response of equations were established respectively and all fitted to linear-square model, at a certain dose the frequencies of dicentrics and rings in lymphocytes decreased with decrease in the dose rate with a remarkable dose rate effect, the dose estimated by low rate curve was much higher than the one estimated by high dose rate.(2) The tail moment of comet , index of DNA damage in this experiment, in vivo , in mice peripheral blood cells the damage was the most serious immediately after irradiation, the TM value was 33.77, and decreased to 7.74 2 h after irradiation and had no statistically significant difference ( p > 0. 05) between irradiation and control groups 24h after irradiation. In vitro, TM value of human peripheral blood cells increased in a dose dependent manner, and an extremely statistically significant difference was observed between irradiation and control groups after irradiation immediately. The dose response relationship well fitted with linear model: Y = 0. 3619 + 2. 1834D (r=0. 9946). However, there has been no significant difference (p > 0. 05) between irradiation and control groups 6 h after irradiation.(3) A progressive dose dependent increase in mRNA levels was observed for DDB2 gene between 0.5 and 4Gy 4h and 12h after irradiation respectively; a progressive dose dependent increase in mRNA levels was observed for IER5 gene between 0.5 and 10Gy 4h after irradiation,between 0.5 and 6Gy 12h after irradiation and between 0.5 and 4Gy 24h after irradiation.Conclusion:The yield of dicentic chromosome aberrations induced by 60Coγradiation showed a dose rate effect, the dose estimated by low rate curve was much higher than the one estimated by high dose rate, to estimate biological dose of the victims exposed to radiation, it is advisable to choose the corresponding dose-response curve according to exposure accident; Alkaline SCGE is a rapid, sensitive method for examining radiation-induced DNA damages, and has showed a well linear dose-response relation although it can only measure in a limited time range as damages repaired more rapidly; A significant dose dependent increase in mRNA levels was observed for DDB2 mRNA and IER5 mRNA at certain doses and time ranges, changes in DDB2 gene and IER5gene expression could be a potential molecular radiation biodosimeter.
|
PDF Full Text Request