Investigating the Postmortem Molecular Biology of Cartilage and its Potential Forensic Applications

This study investigated the postmortem molecular changes that articular cartilage undergoes following burial. Fresh pig trotters were interred in 30‐cm‐deep graves at two distinct locations exhibiting dissimilar soil environments for up to 42 days. Extracts of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joint cartilage from trotters disinterred weekly over 6 weeks were analyzed by Western blot against the monoclonal antibody 2‐B‐6 to assess aggrecan degradation. In both soil conditions, aggrecan degradation by‐products of decreasing molecular size and complexity were observed up to 21 days postmortem. Degradation products were undetected after this time and coincided with MCP/MTP joint exposure to the soil environment. These results show that cartilage proteoglycans undergo an ordered molecular breakdown, the analysis of which may have forensic applications. This model may prove useful for use as a human model and for forensic investigations concerning crimes against animals and the mortality of endangered species.     

The Application of Flow Cytometry as a Rapid and Sensitive Screening Method to Detect Contamination of Vitreous Humor Samples and Avoid Miscalculation of the Postmortem Interval

Research into maximizing the speed, precision, and reliability of estimating the postmortem interval (PMI) has been a recurring object of investigation and methodologies based on the vitreous humor (VH) have provided good results. However, contamination from causes not readily apparent, such as blood, can occur, and thus lead not only to an erroneous estimation of PMI, but also interfere with the correct identification of other substances in the VH. We have developed a flow cytometry method which quantifies blood contamination and is able to detect erythrocytes in 1:750,000 dilution of contaminated VH which affects the results of hypoxanthine. It is an improvement on the previous more complex mass spectrometry method, being faster, more sensitive, and readily available. As such, it could be proposed for the rapid screening of appropriate samples by detecting and eliminating blood contaminated samples from PMI estimation.     

生前与死后电击伤皮肤NSE活性的观察

本实验采用非特异性酯酶Ｎｏｎ－ｓｐｅｃｉｆｉｃＥｓｔｅｒｓｅ（Ｎ．Ｓ．Ｅ）组织化学方法对生前与死后电损伤进行实验研究，发现生前与死后短时间内的电损伤皮肤胶原纤维上ＮＳＥ活性有显著差别（Ｐ＜０．０５），在相同实验条件控制下，电击后存活时间越长，电流斑皮肤周围的酯酶着色反应越深，范围越宽。实验结果表明，Ｎ．Ｓ．Ｅ对于鉴别生前电流斑与死后电流斑具有法医学意义。     

Influence of substrate tissue type on larval growth in Calliphora augur and Lucilia cuprina (Diptera: Calliphoridae)

The size of fly larvae is an important variable in the use of these insects to estimate postmortem interval. Furthermore, the nutritional intake of larvae is likely to vary subject to the part of a corpse on which they are feeding. A study was therefore conducted to investigate the effect of type of food substrate on larval growth in two species of forensically important Australian blowflies. After collection on sheep's liver in the laboratory, different groups of larvae of Lucilia cuprina (Wiedemann) and Calliphora augur (Fabricius) were grown on sheep's liver, meat, and brains, and their body lengths compared. Results indicated that the development of larvae fed sheep's liver was adversely affected compared with larvae fed meat and brain; they moulted later, reached maximum length more slowly and sometimes produced significantly smaller pupae. These findings, similar to those of another recent study, have obvious implications for postmortem interval determinations. Estimates may be considerably skewed if the site of collection of larvae at a death scene contains tissue types different to those used in reference experiments. We therefore recommend caution in forensic analyses that interpret crime scene data using developmental studies performed with a single type of larval food substrate.     

Reduction of postmortem angiography-induced tissue edema by using polyethylene glycol as a contrast agent dissolver

Postmortem investigation is increasingly supported by computed tomography (CT) and magnetic resonance imaging, in which postmortem minimal invasive angiography has become important. The newly introduced approach using an aqueous contrast agent solution provided excellent vessel visualization but was suspected to possibly cause tissue edema artifacts in histological investigations. The aim of this study was to investigate on a porcine heart model whether it is possible to influence the contrast agent distribution within the soft tissue by changing its viscosity by dissolving the contrast agent in polyethylene glycol (PEG) as a matrix medium. High-resolution CT scans after injection showed that viscosities above c. 15 mPa s (65% PEG) prevented a contrast agent distribution within the capillary bed of the left ventricular myocardium. Thereby, the precondition of edema artifacts could be reduced. Its minimal invasive application on human corpses needs to be further adapted as the flow resistance is expected to differ between different tissues.     

A forensic entomology case from the Amazon rain forest of Brazil

The first case of application of forensic entomology in the Brazilian Amazonia is described. The corpses of 26 men were found in the rainforest in Rondonia State, Brazil. Fly larvae collected on the bodies during autopsy were identified as Paralucilia fulvinota (Diptera, Calliphoridae). No data or specimens were collected at the crime scene. At the laboratory, the larvae developed into pupae in 58 h and into adults in 110.5 h. The total development time for P. fulvinota was measured in field experiments inside the forest. The age of the larvae when collected from the bodies was estimated as the difference between the time required for them to become adults and the total development time for this species. The estimated age of the maggots and the minimum postmortem interval was 5.7 days.     

肋软骨及牙髓细胞DNA含量与PMI的相关性

目的探讨人死后肋软骨及牙髓细胞平均DNA含量与死亡时间(PMI)的相关性,寻求推断PMI的新方法。方法应用细胞图像分析技术分析高温(30～35℃)及低温(15～20℃)环境下人死后0～15d两种组织细胞平均DNA含量的降解情况。结果两种组织细胞平均DNA含量随死后时间的延长而逐步降解,其中低温组牙髓细胞平均DNA含量的降解在死后0～4d内有一个降解平台期。统计分析两组温度下两种组织细胞平均DNA含量与PMI有显著的负相关性(P<0.01)。结论依据两种组织细胞平均DNA含量的降解可进行PMI推断。     

蛋白质降解与死亡时间推断的初步研究

目的观察大鼠肝脏肌动蛋白、微管蛋白在死后不同时间的降解情况,为死亡时间的推断寻找客观依据。方法大鼠麻醉致死后置于21℃温度控制系统模拟死后18d的改变,在不同时间点剪取肝脏组织抽提蛋白质,利用westernblot技术检测肌动蛋白、微管蛋白的降解变化并对产物进行半定量分析。结果大鼠肝脏肌动蛋白在死后8d尚可检测,死亡10d后检测不到;在死后2d,α微管蛋白已检测不到,但可检测到β微管蛋白,死亡4d后,β微管蛋白也检测不到。结论肌动蛋白、微管蛋白的死后降解存在差异,其在肝脏组织保存时间的不同可作为死亡时间推断的参数。     

应用DNA3’末端转移推测死亡时间

目的根据机体死后组织细胞DNA降解规律,研究其与死亡时间之间的关系.方法SD大鼠处死后,在不同死亡时间段取肝、肾、脾组织提取DNA.根据DNA3′末端转移的方法(TdT法)将dUTP结合到DNA的3′末端,检测反应剩余的dUTP量,从而推测机体死后不同时间段DNA的降解情况.结果经对剩余dUTP检测发现,dUTP的剩余量随死亡时间延长而减少,说明DNA降解与死亡时间存在一定的关系.结论根据机体死后DNA降解规律可用于早期死亡时间的推测.     

DNA含量变化与死亡时间推断的研究进展

在法医学实践中,死亡经历时间的推断具有重要的实践价值,但其准确推断却一直是法医学实践的难题,因而也一直是法医学研究的热点。法医DNA技术是近年来发展起来的在分子水平进行死亡时间推断的新技术、新方法,同传统方法相比,具有很大的优势,本文对该技术提出的背景、发展、优缺点以及发展前景进行综述,着重对DNA含量变化与其相关性的研究进展进行讨论。