Experimental investigations in post-mortem protein degradation

Comparison of post-mortem metabolic changes in sheep brain tissue in isolated heads and whole animals using 1H-MR spectroscopy--preliminary results

By means of in situ proton magnetic resonance spectroscopy ((1)H-MRS) time-dependent metabolic changes in brain are measured for the estimation of post-mortem intervals (PMIs). An isolated whole head and a whole young sheep from an abattoir with known time of death were stored at approximately 21°C, and localized (1)H-MRS (TR/TE 2,500/25 ms) of the brain was performed at various PMIs with a clinical 1.5 T whole-body scanner using a quadratur head coil. In the isolated head, additional metabolites including free trimethylammonium (fTMA), propionate, and butyrate, and especially acetate, could be detected as described in previous studies. In the head of the whole animal, especially fTMAs and lactate were found in the late PMI but no further metabolites of relevance. These preliminary findings support the hypothesis that in a whole-body corpse, the distribution of bacteria from the gastrointestinal tract up to the brain in the late post-mortem interval can influence the metabolic decomposition of brain tissues. In further studies, it should be kept in mind that an isolated head does not represent authentic circumstances and is, therefore, not an ideal model for brain decomposition in intact corpses.

Comparison of morphological changes in white blood cells after death and in vitro storage of blood for the estimation of postmortem interval

Estimation of the time of death is one of the most important problems for forensic medicine and law. Physical and chemical postmortem changes are evaluated together while estimating the time of death. In this study, in vitro storage and postmortem changes of white blood cells were aimed to be compared within the given postmortem interval, and a follow-up study was carried out. Blood smears which were obtained from 10 non-refrigerated cadavers (experimental group) and from 40 hospital patients (control group) have been evaluated to observe and compare changes during the in vitro storage and postmortem degenerative morphological changes that white blood cells undergo throughout the given postmortem intervals. The samples were examined by using a light microscope, and blood cells were differentiated by staining blood films with May-Grunwald stain, followed by Giemsa stain. Identifiable degenerated eosinophils and monocytes were first examined at 6h of death and the in vitro storage, and they were unidentifiable beyond 72 h of storage. Identifiable degeneration of neutrophils were first examined at 6h of death and storage while unidentifiable beyond 96 h of storage. Identifiable degeneration of lymphocytes were first examined at 24h of death, and they were still identifiable beyond 120 h. Cellular changes of leukocytes can be useful in the 6-120 h for estimating the time of in vitro storage, and the findings match during the first 21 h for both experimental and control groups. Finally, this follow-up study and the comparison will also be carried out for a longer postmortem interval, and other specific hypothesis that relate cellular changes in tissues other than blood with time since death are various points that needs to be studied.

[Investigations to determine the time of death, late post mortem, by means of electrophoresis of inner organs (author's transl)]

In CAF-electrophoresis, extracts of cardiac muscle and of kidney tissue, after storage at 4 degrees C, show a roughly linear increase of the equivalent to the Albumin fraction. This increase depends on the time elapsed and is explained by the relatively high stability of this fraction compared to organ proteins, which appear in the globulin region. Thus, a sort of internal standard exists and can be used as a parameter for the determination of the post mortem period. Hepatic tissue is less suitable for this kind of investigations as the relation of the post mortem period and the values of the relative concentration of the fraction do not show the linearity found in cardiac muscle and kidney tissue. Splenic tissue shows no distinct trend and the findings are of little value. The present investigations were arranged in such a way that taking the order of magnitude for the equivalent of the Albumin fraction as a guideline led to a determination of the maximum post mortem period, i.e., the maximum period of time the body lay after the hour of death. The tables of this paper show the figures for the individual organs.

[Identification and significance of delta-aminovaleric acid in putrefaction materials (author's transl)]

During former putrefaction experiments regularly a proteogenic substance has been found which by means of modern analytical methods now was identified as delta-aminovaleric acid (DAVA). DAVA seems to appear in guinea pig as well as human organs and some body fluids under experimental conditions never before the 3rd (20 degrees C) to 5th day (10 degrees C). It is characterized by statistically significant increases until the end of the 2nd (20 degrees C) to 5th week (10 degrees C) and relatively stable values thereafter. Considering storage temperature measurement of DAVA concentration can be of relevance for the estimation of the time of death in cases of putrescent corpses.