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目的 探讨γ射线照射后小鼠DNA双链断裂修复缺陷细胞 (SCID)的剂量率效应和潜在致死性损伤的修复。方法 采用低剂量率和高剂量率以及间隔 2 4h的 2次γ射线照射正常细胞(CB .17+/ +)和SCID细胞 ,通过成克隆分析法观察被照射细胞的存活分数。结果 应用间隔 2 4h的2次γ射线照射CB .17+/ +细胞时 ,其存活分数明显高于相同剂量的单次照射 ,而SCID细胞二者无明显差异。在高剂量率单次和 2次γ射线照射时 ,SCID细胞均比CB .17+/ +细胞更敏感。在低剂量率γ射线照射时 ,SCID细胞亦显示比CB .17+/ +细胞更敏感。低剂量率γ射线照射CB .17+/ +细胞和SCID细胞后 ,二者的存活分数均明显高于高剂量率照射。结论 SCID细胞不具有DNA双链断裂的修复能力。SCID细胞和CB .17+/ +细胞均具有剂量率效应。
Objective To investigate the dose-rate effect and potential lethal injury repair of DNA double-strand break repair defective cells (SCID) in mice after γ-ray irradiation. Methods The normal cells (CB17 + / +) and SCID cells were irradiated with low dose rate and high dose rate as well as secondary γ ray irradiation at an interval of 24 hours. The viability of irradiated cells was observed by clonogenic assay. Results The survival rate of CB17 + / + cells irradiated by 2 γ-rays at 24 h intervals was significantly higher than that of the single irradiation at the same dose, but there was no significant difference in SCID cells. SCID cells were more sensitive than CB17 + / + cells at both high and single dose gamma irradiation. At low dose rate gamma irradiation, SCID cells also showed more sensitivity than CB17 + / + cells. Low dose rate γ-ray irradiation CB. 17 + / + cells and SCID cells, the survival of both were significantly higher than the high dose irradiation. Conclusion SCID cells do not have the ability to repair DNA double-strand breaks. Both SCID cells and CB17 + / + cells have dose-rate effects.