Estimation of postmortem interval by changes in brain lipids : Application to estimate the time after brain death

为了研究死亡后时间的估计，研究了死后脑脂的变化。本文对44例法医尸检病例进行了脑脂分析。测定总脂、总磷脂和总游离脂肪酸，计算游离脂肪酸组成百分比。随着死后时间的延长，磷脂在总脂中所占的百分比逐渐降低，而总游离脂肪酸的百分比逐渐增加。游离脂肪酸中16：0和18：0的比例较高，但前者随死后时间的延长有下降的趋势。比较了杀菌方式和贮藏温度对脂肪变化的影响。采用氮气窒息、断头或腹腔注射戊巴比妥钠的方法处死大鼠。这些身体在孵化器中保持在15ﾟC、23ﾟC和30ﾟC长达120小时。在游离脂肪酸中，18：0和20：4的组成随时间的延长而减少，22：6的组成随时间的延长而增加，但戊巴比妥中毒死亡大鼠的总游离脂肪酸含量略低于氮窒息和断头死亡大鼠。杀人方式对血脂变化影响不大，可能是因为其死亡时间较短。大鼠体内储存温度对血脂变化有影响，30ﾟC时的影响大于15ﾟC和23ﾟC时的变化。采用戊巴比妥中毒的方法研究了死亡时间对血脂变化的影响。注射戊巴比妥后断头处死大鼠的总游离脂肪酸含量低于未注射戊巴比妥的断头处死大鼠。注射戊巴比妥钠15分钟或30分钟后死亡大鼠的总游离脂肪酸含量低于注射戊巴比妥钠后5分钟死亡大鼠的总游离脂肪酸含量。

For the study of estimation of the time after death, postmortem changes in brain lipids were investigated. Brain lipids in 44 forensic autopsy cases were examined. Total lipids, total phospholipids and total free fatty acids were measured, and percentage of free fatty acid composition was calculated. Percentage of phospholipid to total lipid decreased, whereas that of total free fatty acids increased in accordance with postmortem interval. Percentages of 16 : 0 and 18 : 0 in the free fatty acid were high, although the former tended to decrease in accordance with postmortem interval.The influence of modes of killing and storage temperature on the changes of lipids was compared. Rats were killed by either nitrogen asphyxiation, decapitation, or intraperitoneal injection of sodium pentobarbital. The bodies were maintained at 15ﾟC,23ﾟC and 30ﾟC in incubator up to 120 hours. Among the free fatty acid, the composition of 18 : 0 and 20 : 4 decreased, whereas that of 22 : 6 increased with time, although the amounts of total free fatty acid of rats died of pentobarbital intoxication were somewhat lower than those of nitrogen asphyxiation and decapitation. The modes of killing did not significantly affect the changes of lipids presumably because of short duration of agonal stage inherent in them. The storage temperature of rat bodies influenced the changes of lipids, which were greater at 30ﾟC than at 15ﾟC and 23ﾟC.The influence of duration of agonal stage on the change of lipids was investigated by pentobarbital intoxication. The amounts of total free fatty acid of rats killed by decapitation after injection of pentobarbital were lower than those of rats killed by decapitation without pentobarbital injection. The amounts of total free fatty acid in rats died 15 or 30 minutes after pentobarbital injection were lower than those of 5 minutes.We intend to investigate the changes of brain lipids for estimation of the time after brain death.