The Relation Of The Content Changes Of Cardiac Muscle Myoglobin(mb) MRNA To Degradation Time In Rats After Death

Study background and objctive: In forensic practice, the Postmortem interval(PMI )which has been being one of the focus and emphasis forensic study is very important .With the rapid development of the molecular biology and information technology, Forensic pathology research also gradually develop in the field of molecular biology information.Currently we has also achieved some encouraging research results. In recent years, with the growing number of criminal cases and the ever-changing methods of the cases, coupled with the complexity of the environment, many affecting factors, so looking for a more sensitive and reliable indicators becomes a serious problem in forensic field. The surface of the skin and other organs has been considered as the preferred object of study in PMI and injury time estimation.But in some cases, because most of the many external factors have lost value among a number of organs derived easilyWhen meet the decomposed and mutilated bodies. However, the heart of corruption preserved relatively intaction compared with the other body organs. Recently the heart becomes the focus of studies , many clinical research experts have confirmed that Mb can be highly sensitive in responsed to myocardial injury, which could be considered as a value diagnosis indicators of the early of AMI with important clinical diagnostic value, but now the research of Mb mainly concentrated on the clinical context, few study in forensic medicine.Mb is the low molecular weight oxygenation protein presented in the cardiac and skeletal muscles .The content is abundant in myocardium and its primary role is to uptake and stort oxygen for cells.In forensic practice , we often encounter with a number of mutilated murder case or cases.In view of the practice of forensic workers need, we build the experiment :the experimental animal models through the establishment of an independent randomized , extract myocardial tissue, using RT-PCR to detect every degree of degradation of Mb and observe the changes about the relative time and time regularity in two different states:in vivo and in vitro ,in hope to find a more effective scientific indicators of PMI which can be used in forensic practice.Method:In the study, the healthy and clean SD rats are obtained 100 (supplyed by the Experimental Animal Center of Chongqing Medical University), either sex,weighing 220g~240g,which are randomly divided into two experimental groups: vivo group and vitro group.Each experimental group was divided into 10 of time groups :0 h, lh, 2h, 4h, 6h, 8h, 12h, 24h, 48h, 72 h, and every time group has five rats.The rats were killed by cervical and placed immediately in (25±1)℃, 65% ~ 70% of temperature and humidity control system, and strictly operated in accordance with the requirements of experimental design.The perimer of PCR was designed by primer design software: Perimer 5.0 . We extract RNA using total RNA extraction kit , reverse transcription the extracted RNA,and amplify DNA by RT-PCR kit .The DNA products obtained were put in ultraviolet instrument on the observation, in gel imaging instrument . Finally we analyzed the data using statistical software spss17.0 .Retults: We use RT-PCRto reverse transcript Mb mRNA , and amplify it .we use agarose gel electrophoresis to show the band of DNA and then observed and analyzed the results in the gel imager:(1)The contents of Mb mRNA in dead heart in vitro group and vivo group decreased with dead time gradually. (2)The Mb mRNA in vivo group up to 72 hours from death could not be detected; Howere ,the band becoming gradually pale and thinner with the time death,could not be detected after 24 hours in vitro group.(3)Compare the degradation of Mb in two groups :vivo group and vitro group , the degradation rate was higher in vitro group. Conclusion: In this study, the degradation of myocardial Mb mRNA were detected by using RT-PCR technique after death.The results were analyzed by statistical software spss17.0. And draw the followingconclusions:(1)The degradation of cardiac myoglobin (Mb) mRNA has some correlation with the time of death, gradually decreasing with the time.It can be inferred as an important indicator for PMI .(2)The results show that Mb is only significant within the first 24 hours from the degradation trend, but there is no obvious change during 24 hours to 72 hours .So it is more suitable for the early time of PMI.(3)Mb mRNA was time-related degradation, but the degradationin is not entirely consistent in vivo group and in vitro group.