The Study On The Relationship Between Neuronal Apoptosis, DNA Fragmentation And Quantity With The Time Of Brain Contusion

Objective To look for a new method for estimating the time ofinjury by studying the changes of neuronal apoptosis, DNA fragmentationand quantity after brain contusion. Methods①The animal model of braincontusion caused by free drop hammer was established.②The injuredtissue of rat brain were stained by TUNEL for apoptosis,immunohistochemistry for Caspase-3 and Feulgen's for DNA. Image analysistechnique and the statistical method were employed to explorate thetemporal changes of injury time.③The DNA was extracted from ratcontusive tissue of brain and assayed by gel electrophoresis toinvestigate the relationship between the DNA fragmentation and injurytime.④One handred and seventeen cases of death from traumatic braininjury were retrospective researched to investigate the characteristicof TBI in forensic medicine.⑤The contusive tissue of human brain werestained by TUNEL, Caspase-3 immunohistochemistry and Feulgen's methodsin the same way to analyze and disclose the linear relationship betweentemporal changes with injury time. Results①The changes of cerebralcontusion made by established animal model were similar to those ofaccelerative brain injury in forensic medcine and had practical valuein TBI experiment and forensic studies.②There were linearrelationship between neuronal apoptosis, DNA fragmentation and quantitywith time of injury in the number of positive cells and intensity(IOD)of the cells. Linear formulae could be deduced from the results and applied to forensic study.③The DNA fragmentation of contusive tissuein rat presented a ladder break in electrophoresis after 6 hours. Thedegree and length of DNA fragmentation changed with injury time butwithout linear relationship.④The death of traumatic brain injury inforensic medicine had characteristics in sex, age, cause of injury(vulnerant), types of injury in head, pathological change, et al.⑤TheIOD of Feulgen's staining in central area of human brain contusion wassharply decreasing after injury within 24 hours. It had linearrelationship with injury time. R was 0.96. The rate of positive cellsand the mean of integral optical density, both of TUNEL and Caspase-3immunohistochemistry staining increased linearly in penumbra area ofhuman brain contusion in 48 hours after injury. R was 0.89,0.93 and0.92,0.90 respectively. Linear formulae could be deduced.⑥TUNEL andCaspase-3 immunohistochemistry staining might be used to locate theposition of brain contusion. Conclusion To observe the changes ofneuronal apoptosis, DNA fragmentation and quantity could be utilized intiming of brain contusion and locating the position of brain contusion.