Expression Of INOS On Brain Tissue In Rats Model Of Axphyxia Death And Forensic Significance

Backgrounds and Objectives: Mechanical asphyxia death is one of the most common cases in homicidal cases. Most can be identified by scene inspection and internal or external body signs. However, a few cases can not be of assurance for scene damage, unclear traces or unspecific external signs of corpses. According to the mechanism of mechanical asphyxia death, brain injury is the most serious for internal organs, and the integrity of the brain tissue is not easy to undermine. Detecting specific changes of certain substances in mechanical asphyxia death in brain tissue provides a scientific basis for estimation of mechanical asphyxia death.iNOS is a subtype of the nitric oxide synthetase with micro-expression or no expression in physiological state. When the body is stimulated by inflammation, injury, ischemia, ultraviolet or other stimulations, INOS will express largely in the corresponding diseased tissue or organs, and has certain time regularity. The main objectives of this experiment is to study the expression of iNOS in brain tissue in Group mechanical asphyxia death and the other death groups, therefore to investigate its forensic significance for estimating causes of death in mechanical asphyxia. Methods:(1)Animal Model: experimental animals from the Animal Experimental Center of Chongqing Medical University, healthy clean grade SD rats 80, were randomly divided into mechanical asphyxia death group, hemorrhagic shock and death group, brain contusion death group and broken neck death group. Methods: mechanical asphyxia death group: With a nylon rope (diameter 3 mm) to make a sliding loop and its top fixed in a bar, rats were put in the loop causing suffocation death for their own gravities; Brain contusion death group: 10g weight from 20CM height within the vertical catheter freely fell hitting the dura; Hemorrhagic shock death group: Isolated bilateral carotid artery, bleeding cut to shock death;Cut off neck to death group: the thumb and index finger of one hand held the rats'head, the other hand grasped the tail pulling by force , resulting in spinal cord transaction to death ; (2) drawing materials: cut 0.4 CM brain tissue in the central part transversally in each group at different time points; (3) the brain tissue sections embedded in paraffin were stained by HE and observed under light microscope; (4) The expression of iNOS at different time were detected by immunohistochemical staining.(5) using SPSS 13.0 software for the data for statistical analysis.Results: In each group positive staining at 0h was less slightly than other time points, and had no obvious difference at 6h,12h and 24h. In mechanical asphyxia death group neurons in the brain gray matter were deep stained in cytoplasm, showing brown, basically involving all neurons in the entire field of vision, and had more significant differences than other groups. In hemorrhagic shock and death group, brain contusion death group, the staining involved most neurons, but there were no significant differences between the two groups. In broken neck death group there were no obvious staining, occasionally few neurons with slight staining.Conclusions: The iNOS expression after mechanical asphyxia death had high specificity with certain regularity. At 6h, 12h, 24h, the expression of iNOS tended to be at the same level which was higher than 0h. In mechanical asphyxia death group iNOS expression levels were significantly higher than the other two groups at different time points. Thus, iNOS can be used as a supplementary indicator for forensic suffocation death.