| Objective:In order to investigate the effect and the possible mechanism ofγ-rays on neurodevelopment of fetal brain tissue as bystander effect organ.Methods:Pregnant Kunming mice were randomly divided into blank control group, 0.5 Gy whole-body exposed group, 0.5 Gy head exposed group, 1.0 Gy whole-body exposed group, 1.0 Gy head exposed group, 2.0 Gy whole-body exposed group and 2.0 Gy head exposed group. The mice were exposed with a vertical single acute dose using 60Co therapy apparatus on the 9th day of pregnancy, and cesarean operation was performed to gain fetal mice on the 18 th day of pregnancy. The number, the size, stillbirth, birth defects and abortion, and get fetal brains from live births were observed.Western-blot assay was used to detect the expression of MeCP2 protein and ELISA was used to measure the levels of AchE and Ach in fetal brain. The NO concentration and the levels of SOD were detected using NO kit and SOD kit. SAS 8.0 software was used for statistical analysis.Results:1. When the pregnant mice heads were exposed to ionizing radiation in the first trimester, the rates of stillbirth and birth defects were ascend, and the incidence of abnormal Pregnant mice became decline as the increase of doses. There was no significant difference between head exposed groups and whole-body exposed groups.2. Compared with the blank control group, the expression of MeCP2 were upregulated in the three head exposed groups,and in 1.0 Gy,2.0 Gy whole-body exposed group, there were no significant differences in 1.0 Gy,2.0 Gy groups.3. Compared with the blank control group, the overall decline in the amount of AchE and Ach were found as the increased dose. The levels of Ach in 0.5 Gy and 1.0 Gy head exposed groups were decreased (p<0.05); the levels of AchE and Ach were decreased in 2.0 Gy head exposed groups (p<0.05); the level of Ach in 0.5 Gy head exposed group was lower than the 0.5 Gy whole-body exposed group (p<0.05) and of the levels of AchE and Ach were lower in 2.0 Gy whole-body irradiation groups (p<0.05).4. The overall increase in the amount of NO was found as the increase dose. Compared with the blank control group, the content of NO in fetal brain of the 2.0Gy head exposed group was increased (P<0.05), the activity of SOD was decresed (P<0.05); the NO content of the 1.0Gy head exposed group was significantly less than the 1.0 Gy whole-body irradiation group (P <0.05); the SOD content of the 1.0Gy head exposed group was significantly more than the 1.0Gy whole-body group (P <0.05); while the NO content of the 2.0Gy head exposed group was significantly increased than the 2.0Gy whole-body group (P <0.05);the content of NO in fetal brain of the 1.0Gy and the 2.0Gy whole-body irradiation group was increased (P<0.05), the activity of SOD was decreased (P<0.05) .Conclusions:1. Bystander effect in vivo was induced by ionizing radiation.2. When the pregnant mice heads were exposed in the first trimester, there were no significant differences between head exposed groups and whole-body irradiation groups, and the effects were positively correlated with the doses within a certain range.3. The incidences of stillbirth, birth defects and abortion were ascend with dose ofγ-rays to the head of pregnant mice on the 9th day of pregnancy.4. The expression of MeCP2 in embryonic brain tissue was upregulated when the mice heads received ionizing radiation on the 9th day of pregnancy, which would promote DNA demethylation, change genomes and induce increas of the probability of stochastic effects, such as cancer.5. Fetal brain neuro development was affected when the mice head received ionizing radiation on the 9th day of pregnancy, which might be stimulated at lower doses and suppressed at higher doses.6. A large number of NO had produced, SOD activity had decreased in the embryonic brain tissues when the pregnant mice head was exposed in the first trimester, while this change as one of the mechanisms for the bystander effect in vivo needs further studied. |
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