中文摘要：

目的探讨小鼠死后不同时间和温度下脑组织β-actin mRNA、18S rRNA的降解规律与死亡时间的关系。方法将24只健康成年C57BL/6小鼠随机分为2组,每组12只,断颈法处死后分别置于不同的环境温度中（4℃、37℃）,恒定环境湿度为80%。分别于死后即刻和0.5、2、6、24、48h取小鼠脑组织进行总RNA提取。利用RT-PCR技术和实时荧光定量PCR技术测定每一样本中β-actin mRNA和18S rRNA的Ct值,进一步计算每个样本中18S rRNA与β-actin mRNA的含量比值,对二者含量比值与死亡时间的关系进行统计学回归分析。结果 37℃下,RNA降解速度明显快于4℃,表明温度与死后RNA的降解速度呈正相关。与β-actin mRNA的稳定性相比,18S rRNA更为稳定。结论通过采用实时荧光定量PCR技术研究小鼠死后脑组织中β-actin mRNA和18S rRNA的降解规律,可为法医学死亡时间推断提供新的理论基础。

英文摘要：

Objective To investigate the degradation changes of β-actin mRNA and 18S rRNA in different time points and temperature after death,and to explore the relationship between the changes and postmortem interval（PMI） in the brain of mice.Methods Twenty-four health adult C57BL/6 mice were randomly divided into two groups（12 each group）.They were sacrificed by cervical dislocation and placed in chamber with two different temperature（4 ℃ and 37 ℃,humidity was 80%）.The mice brains were sampled at 6 different time points（immediately,0.5 h,2 h,6 h,24 h,48 h）,and total brain RNA were extracted.Ct value of each sample was obtained using RT-PCR and real-time PCR technology,and β-actin mRNA and 18S rRNA content ratio was calculated.The correlation between the content ratio and PMI was expressed using statistical regression analysis.Results At 37 ℃,RNA degradation rate was faster than 4 ℃,which showed that there was correlation between temperature and RNA degradation.Comparing with the stability of β-actin mRNA,18S rRNA was more stable.Conclusion The study on degradation of β-actin mRNA and 18S rRNA in mice brain using real time PCR technology could provide a new theoretical basis for estimation of PMI and would be supplementary to the traditional methods.