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Objective: To explore the relationship between beta-actin mRNA degradation in SD rat's brain, heart and kidney and early postmortem interval (PMI) in order to find new markers for estimating early PMI., Methods: Rats were sacrificed and kept in the place at a temperature of 20 degrees C. The total RNA were extracted from the brain, heart and kidney at different PMI points. Real time RT-PCR was applied to determine beta-actin mRNA levels in total RNA and the results were given in the form of Ct values. Linear relationships between PMI and Ct values were obtained and the functions of linear regression were established., Results: The great decrease of beta-actin mRNA level were observed in the three organs. The degradation rate was obviously higher in 24 hours after death in the heart and kidney. However, there were no significant changes in the brain. The changes of Ct values and PMI showed a good linear relationship., Conclusion: beta-actin mRNA in rat's brain, heart and kidney degrades obviously after death and can be used for estimating early PMI by its degradation rules.

Objective: To explore the relationship between the time-dependent level changes of microRNA and 18S rRNA and the different postmortem interval (PMI) in rat cardiac muscle., Methods: SD rats were sacrificed by cervical dislocation and placed at ambient temperature 25 degrees C with a humidity of 50%. Total RNA was extracted from the rat cardiac muscle at different time points after death. The levels of miR-1-2 and 18S rRNA were examined using real-time PCR in rat cardiac muscle. The results were expressed by cycle threshold (Ct) value to explore relationship between PMI and Ct value, and the regression functions were established to estimate PMI., Results: The miR-1-2 level in rat myocardial tissue showed no significant changes within 120 h after death, and then began to decline. The 18S rRNA level increased gradually within 96 h after death, and then declined slowly. The nonlinear relationships were established between Ct value (18S rRNA), deltaCt value (difference between 18S rRNA and miR-1-2) and PMI. The R2 of conics fitting were 0.9487 and 0.8072, respectively., Conclusion: Ct value of 18S rRNA and deltaCt value present a good correlation with PMI, and can be markers for estimating early PMI.

Objective: To observe the degradation of myoglobin in skeletal and cardiac muscles after death and to explore its usefulness in estimation of postmortem interval., Methods: Human skeletal and cardiac muscles were collected at 0, 4, 8, 12, 24, 36, 48, 60, and 72 hours after death and stored at 25 degrees C. The protein was extracted and examined and analyzed by Western blot and imaging technique., Results: Myoglobin showed a continuously postmortem degradation in both skeletal and cardiac muscles. There was no observed difference in degradation between the two tissues., Conclusion: Changes in myoglobin degradation could be a useful parameter for estimation of the postmortem interval.

Objective: To study the relationship between postmortem interval and the myofibril fragmentation index of skeletal muscle., Methods: Rabbit skeletal muscle were left in the room temperature for different postmortem intervals, and the protein concentration of each sample was detected by using biuret method. Furthermore, the myofibril fragmentation index of each sample was measured under the protein concentration level of 0.5 mg/mL., Results: The myofibril fragmentation index increased obviously according to the postmortem interval prolongation., Conclusion: The myofibril fragmentation index may be used on the estimation of early postmortem interval.

Objective: To investigate the relationship between DNA degradeation and postmortem interval., Methods: dUTP was transferred to 3'terminal of DNA by using terminal deoxynucleotidyl transferase (TDT), then the reminders of dUTP after experimental reaction, as indicator of quantity of DNA degradation, were detected., Results: The reminders of dUTP were decreasing along with the postmortem interval., Conclusion: Postmortem DNA degradation may be used in postmortem interval judgment.