ABSTRACT
[Objective] To study the correlation between kidney cell DNA degradation and postmortem interval within the span of 6-48 hour after the subject rats′ death.[Methods] To select 18 healthy mature female SD rats and equally divide them into 6 groups.To execute the rats with cervical spine articulation and put the rats under the incubator temperature of 25.1℃ (the average temperature of the 5 previous Decembers in Guangzhou prefecture).Sample kidney tissue from the rat separately 0 hour,6 hours,12 hours,24 hours,36 hours,48 hours,and 60 hours after the rats′ execution to prepare monoplast suspension,which is committed to comet assay.The comet images were captured by fluorescence CCD.Kinetic Comet 4.0 software was used to analyze images.Relevant data were collected by kinetic Comet 4.0 software and were subjected to Kruskal-Wallis test.[Results] Within the postmortem interval of 6-48 h,the number of SD rat kidney cell DNA fragments increased as the postmortem interval lengthens.So did the comet tail length.The Oliver tail moment and tail DNA of comet also showed sign of increase in positive proportion to the postmortem interval (their values corresponding to 60-hour-postmortem-interval were not obtainable.Kruskal-Wallis test indicated:the discrepancies of TL among the 6 groups were all significant (P ＜ 0.01).The difference of TM between 6 h group and 12 h group was not significant (P ＞ 0.05).The difference of TM between 24 h and 36 h was significant (P ＜ 0.05).The difference of TDNA among 6 h,12 h,and 36 h groups were not significant (P ＞ 0.05).The difference of TDNA between 36 h and 48 h was significant (P ＜ 0.05).[Conclusion] Degradation of nuclear DNA of the rat kidney cells increases as the postmortem interval lengthens and comet assay may provide important empirical evidence for determining the postmortem interval.
ABSTRACT
Objective To study the relationship between the DNA content of chondrocytes in the costal cartilage and postmortem interval in putrefactive rat cadavers.Methods Nuclear DNA wag visualized by modified Feulgen's staining method.DNA content of ehondrocytes in the costal cartilage was semi-quantita tively determined by a computerized image analysis system in rats within 35d postmortem.Results Staining intensity of the nuclei was gradually reduced within from 1d to 28d postmortem.The nuclej could not be detected at 35d.The DNA content of chondrocytes decreased time-dependently within 28 days after death as determined semi-quantitatively,which revealed a linear relationship between DNA content and postmortem interval.Conclusion DNA content of chondrocytes in the costal cartilage reduces time-dependently with the extension of postmortem interval.