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目的研究DNA降解变化与死亡时间关系,探讨兔死后牙髓细胞核DNA的降解机理及寻找灵敏、实用的DNA降解监测指标,为死亡时间的法医学研究提供一种新的方法和技术。方法利用快速、灵敏的检测细胞DNA损伤的单细胞凝胶电泳(SCG)技术结合荧光显微镜和专业的计算机图像分析技术,以“彗星样”细胞出现率(计数一定量细胞其中彗星样细胞所占的比例)、头半径、尾长度、头/尾DNA含量比例、Oliver矩、尾矩、头面积和尾面积来评价死后兔牙髓细胞核DNA的降解程度。结果在个体死亡72h内,测定的8项参数指标中尾DNA含量比例、彗星尾长、尾矩、Olive矩、尾面积都呈增加趋势,头半径,头DNA含量比例,头面积均呈下降趋势。上述参数均与死亡时间具有高度的相关性。并将每个参数的测量值进行了多项式运算,获得了更能体现DNA降解趋势的二项式回归方程(P<0.001),具有显著的统计学意义。结论应用单细胞凝胶电泳技术,监测机体死后牙髓细胞核DNA降解变化,将会成为推断死亡时间精确、客观的新方法。
Objective To study the relationship between the changes of DNA degradation and the time of death, to explore the degradation mechanism of DNA in dental pulp after rabbits death, and to find a sensitive and practical indicator of DNA degradation monitoring, so as to provide a new method and technique for forensic research on death time. Methods Rapid and sensitive single cell gel electrophoresis (SCG) was used to detect the DNA damage of cells. Combined with fluorescence microscopy and professional computer image analysis technology, we used the “comet-like” The ratio of the head radius, the tail length, the ratio of the head / tail DNA content, the Oliver moment, the tail moment, the head area and the tail area. Results Within 72 hours after death, the ratio of tail DNA, tail length, tail moment, Olive moment and tail area of the 8 parameters were all increased. The head radius, head DNA content and head area showed a decreasing trend. The above parameters are highly correlated with the time of death. The polynomial operation of the measured values of each parameter was carried out. Binomial regression equation (P <0.001), which can better reflect the trend of DNA degradation, was obtained and had significant statistical significance. Conclusion Using single cell gel electrophoresis to monitor the changes of nuclear DNA degradation in pulp cells after death will be a new way to infer the exact and objective time of death.