Time since death: The histological chronotanatognostic

The time since death is an important aspect of forensic medicine; however, there is not an accurate single method to determine this data. Therefore, this research aimed to evaluate parameters and procedures based on the morphological analysis of cells and tissues to determine the time since death, using animal models. Pigs were chosen in this research because of their similarities with human anatomy, physiology, and pathophysiology. We identified the cells and tissue alterations in the viscera of pig cadavers according to the time since death, also describing the changes in the temperature of the organs and the bodies. The environmental temperature during the sample collection was also registered. The viscera analysis was performed for 24 h, with a 2-h variation period. After the sample collection, microscope slides were prepared for optical microscopy analysis. Through this 24-h analysis, we observed that the pancreas, small intestine, and large intestine presented more cellular alterations than the other organs. The alterations observed in the other viscera have significance when analyzed in combination. The meninges presented higher stability and few changes in 24 h, which could be relevant in an investigation of the time since death in a period greater than 24 h. Our results showed that histological evaluation is an excellent method to determine the time since death.

Implication of High-mobility group box-1 and skin post mortem changes in estimation of time passed since death: Animal and human study

Determination of postmortem interval (PMI) is one of the goals of the forensic autopsy. The study aimed to correlate the postmortem skin changes and High-mobility group box-1 (HMGB1) alterations in serum and skin immunohistochemical staining with time since death. We used animal and human specimens; forty adult male albino rats were dissected to obtain samples at PMI (0, 3, 6, 12, 24 h); forty human medicolegal autopsy cases with a known time of death (within the first 24 h PMI). Cases were classified into 5 groups according to the PMI: I (0 h); II (≤3h); III (4 to 6); IV (7 to 12); V (13 to 24) hour intervals after death; blood and full-thickness skin samples were collected from both models. Results showed a significant time-dependent elevation in serum HMGB1 levels along with its overexpression in immunohistochemically stained skin tissue. Also, the degree of histopathological changes in epidermis, dermis, and hypodermis progressively increased with PMI in both models. The timetable of postmortem skin histological changes, serum HMGB1 concentration, and immunoexpression for HMGB1 proteins in skin tissues has a profile that could serve as actual and simply convenient parameters for accurate determination of postmortem intervals in both models. HMGB1 displayed a pivotal role in the estimation of PMI at the examined periods.

The frequently dismissed importance of properly sampling skin bruises

The correct interpretation of skin lesions is a crucial issue in forensic medicine. Many macroscopic and microscopic vital reaction markers and molecules have been studied in the past years in order to estimate the timing of injuries. However, literature lacks information regarding how to perform sampling to obtain a more reliable and accurate response. The present study investigates 25 bruises and analyses the different histological asset in different areas (central or marginal) and the different layers (epidermis, dermis, hypodermis and muscle) of the wound. All wounds were sampled in several areas and analysed under a 200× magnification optical microscope, simply counting the degree of haemorrhaging (i.e hematic infiltration) visible in each optical field (0 = 0%-5%; 1 = 6%-25%; 2 = 26%-50%; 3 = 51%-75%; 4 = 76%-100%). All the injuries presented some kind of infiltration in at least one area, nonetheless only 56% of the wounds were infiltrated in the entirety of the areas. Finally, in 28% the dermal layer did not show any trace of infiltration. Therefore, considering such results it seems that depth or area of sampling of a bruise may largely influence the evaluation of vitality and hence of age of a wound. Though this may seem intuitive, no studies have examined this issue in depth.

Are animal models predictive for human postmortem muscle protein degradation?

A most precise determination of the postmortem interval (PMI) is a crucial aspect in forensic casework. Although there are diverse approaches available to date, the high heterogeneity of cases together with the respective postmortal changes often limit the validity and sufficiency of many methods. Recently, a novel approach for time since death estimation by the analysis of postmortal changes of muscle proteins was proposed. It is however necessary to improve the reliability and accuracy, especially by analysis of possible influencing factors on protein degradation. This is ideally investigated on standardized animal models that, however, require legitimization by a comparison of human and animal tissue, and in this specific case of protein degradation profiles. Only if protein degradation events occur in comparable fashion within different species, respective findings can sufficiently be transferred from the animal model to application in humans. Therefor samples from two frequently used animal models (mouse and pig), as well as forensic cases with representative protein profiles of highly differing PMIs were analyzed. Despite physical and physiological differences between species, western blot analysis revealed similar patterns in most of the investigated proteins. Even most degradation events occurred in comparable fashion. In some other aspects, however, human and animal profiles depicted distinct differences. The results of this experimental series clearly indicate the huge importance of comparative studies, whenever animal models are considered. Although animal models could be shown to reflect the basic principles of protein degradation processes in humans, we also gained insight in the difficulties and limitations of the applicability of the developed methodology in different mammalian species regarding protein specificity and methodic functionality.