通过脑形态及生物力学特性时序性变化推断死亡时间

Postmortem interval estimation by time-dependent changes of morphology and biomechanical properties in brain tissues

目的探讨家猪脑组织形态学及生物力学特性时序性变化规律及其推断死亡时间(postmortem interval,PMI)的可行性。方法采集42个家猪脑组织,25℃恒温、75%恒湿气候箱内放置,每12 h(0、12、24、36、48、60 h;n=6)按照定时、定位、定向、定比、定量、定形"六定"规范切取额叶脑组织,甲醛固定,生物力学检测仪检测各组试件的生物力学参数并制备组织形态切片。结果 PMI 60 h内脑组织大体呈自溶腐败变色、瘫软、泥化、液化等趋势;PMI0~48 h脑白质间隙总面积及其累积光密度均明显增高;PMI 12~60 h极限载荷、平均力、弹性模量、断裂能量均呈下降趋势,其中极限载荷组间差异高度显著;平均力、弹性模量和断裂能量组间比较均差异显著。结论脑组织形态结构与生物力学性状变化之间呈明显负相关构效关系,死后0~60 h脑组织极限载荷"窗口期"最佳,可作为推断PMI的新方法。

Objective To explore the regularity of time-dependent changes in morphology and biomechanical prop- erties of brain tissues in pigs, and value the feasibility of deducing the postmortem interval （PMI）. Methods Brain tissues were taken from 42 pigs and kept in an artificial climate chamber with the temperature of 25 ℃ and humidity of 75%. The samples were collected from telencephalon at sequential time intervals （0, 12, 24, 36, 48, 60 h;n = 6） according to the principle of predefined time, position, direction, ratio, quantity and shape. The sam- ples fixed with formaldehyde were then immediately tested by mechanical testing machine to obtain their biome- chanical parameters and the histological sections were prepared. Results With the extension of PMI （0-60 h）, brain tissues gradually became discolored, weak, mudding and liquefied under the influence of autolysis and pu- trefaction. Both clearance area of the white matter and its integrated optical density （IOD） significantly increased during 0-48 h. Biomechanical properties of brain tissues including the limit load, average force, elastic modulus and fracture energy all presented a declining tendency at the interval of ：12-60 h. The limit load was considered highly statistically significant, and statistical differences were found in average force, elastic modulus and fracture energy. Conclusions There exists a significantly negative structure-activity relationship between the morphology of brain tissues and biomechanical properties. The limit load of postmortem brain tissues in 60 h is the optimum inthe window period, which can be used as a new method for estimating PMI.