Experimental evaluation of rigor mortis. I. Histochemical analysis of rat skeletal muscle in the early post-mortem period

Influence of Rigor Mortis on Tendon Mobility in an Animal Fresh Cadaver Model

Simple Summary

In biomechanical research, fresh frozen cadaver material and embalmed specimens are often used to evaluate surgical approaches. Unlike, biomechanical research using fresh cadaver material is rare. There are no reliable data on the point of time when rigor mortis starts to have an impact on results with fresh cadaver material. In this study, the authors have conducted measurements using fresh porcine cadaver tendons of the supraspinatus muscle post mortem to determine the time of onset and the influence of rigor mortis on specimen tissue. 151 min post mortem, a significant decrease in tendon mobility was observed. Therefore, the authors of the presented study concluded that the onset of rigor mortis started 151 min post mortem and decreased the mobility of the tendon. Hence, biomechanical research using fresh cadaver material should ideally be conducted within 150 min post mortem to obtain in vivo-like results without being impacted by rigor mortis.

Abstract

(1) Many biomechanical studies are performed using fresh frozen cadavers or embalmed specimens, although the biomechanical characteristics do not match the characteristics of in vivo tendons. Therefore, a fresh in vivo-like cadaver model has been introduced recently. As a limitation for studies with fresh cadavers, rigor mortis must be considered. The aim of this study was to evaluate the impact of the biomechanical properties and time of occurrence of rigor mortis in a fresh cadaver model. (2) For this study, 15 fresh porcine cadaver shoulders were used in an established biomechanical in vitro model to evaluate the onset of rigor mortis. Measurements took place at ten points of time (t1–t10) beginning 103 min post mortem (pm). The mobility of the supraspinatus tendon was measured in Newton (N) with a modified sensor-enhanced arthroscopic grasper. (3) The mean load measured at the time point t1 was 28.0 ± 11.2 N. The first significant decrease of mobility occurred 151 min post mortem (t4) at a mean load of 30.2 ± 13.7 N. From 227 min pm to 317 min pm, there was no further significant increase. (4) Tendon mobility decreases significantly within the first three hours after the killing. Therefore, reliable results can be obtained within 150 min post mortem before the onset of rigor mortis alters the biomechanical properties.

Experimental estimation of postmortem interval using multivariate analysis of proton NMR metabolomic data

Nuclear magnetic resonance (NMR) spectroscopy has recently been applied to metabolic studies. In particular, metabolic profiles of tissues or of the whole body can easily be acquired through multivariate analysis of NMR spectra. The present study investigates metabolic changes after death in rat femoral muscles using pattern recognition of proton NMR spectra. Rats were killed by suffocation, cocaine overdose and induced respiratory failure, and then low molecular weight metabolites extracted using perchlorate from excised tissues were measured using proton NMR. All spectral data were processed and assessed by multivariate analysis to obtain metabolic profiles of the tissues. The results of principal component analysis (PCA) score plots soon after death showed that the metabolic profiles of the tissues differed according to the mode of death. The principal component (PC) scores of the data varied hourly and correlated with postmortem interval. The present results showed that NMR-based metabolic profiling could provide useful information with which to estimate postmortem intervals and causes of death.

1H-NMR studies of postmortem biochemical changes in rat skeletal muscle

1H-nuclear magnetic resonance (NMR) has been applied to the study of postmortem biochemical changes in perchloric acid extracts of rat skeletal muscle. Several metabolites have been detected and the dependence upon the postmortem time has been considered. The simultaneous quantitative determination of metabolites showing up at very low and very high fields has been suggested to yield a satisfactory delineation of the thanatochronology.

Study of postmortem blood circulation

The objective of this work was to study the postmortem redistribution of blood volumes and its influence of the distribution of substances of different molecular weight (194.2 and 150,000 Da). Lipiodol Ultrafluide, Omnitrast, or a radioisotopic mixture of aminohippuric acid and human IgG were injected into the left ventricle of a total of 20 rabbits divided into three groups. Our results demonstrate the importance of related factors, including left ventricular postmortem contraction, the arterial vascular bed, diffusion processes connected to the physicochemical characteristics of the substances, and the anatomical distribution of the vessels. Postmortem diffusion of aminohippuric acid to the urine was observed.

Postmortem changes in the level of calcium pumping adenosine triphosphatase in rat heart sarcoplasmic reticulum

The activity of calcium pumping adenosine triphosphatase (Ca2+-ATPase) in cardiac sarcoplasmic reticulum plays a pivotal role in myocardiac contraction-relaxation. The Ca2+-ATPase activity is controlled by phosphorylation and dephosphorylation of a sarcoplasmic reticulum protein "phospholamban" in response to neurotransmitters and drugs. To clarify the role of Ca2+-ATPase in the development of cardiac rigor mortis, we examined the changes of cardiac rigidity and cardiac sarcoplasmic reticulum Ca2+-ATPase activity up to 5 h after the decapitation of rats. Fifteen minutes after decapitation, the rats showed a cardiac rigidity on left ventricles. After 30 min, rigidity was obvious over the whole heart. After 1 h, the rigidity reached a high degree which was maintained for the rest of the observation period. On the other hand, the Ca2+-ATPase activity controlled by phosphorylation and dephosphorylation of phospholamban did not change for the whole observation period (5 h). Another Ca2+-ATPase activity representing the total amount of Ca2+-ATPase in sarcoplasmic reticulum gradually decreased. The data suggest that no significant phosphorylation or dephosphorylation of phospholamban occurs for a short time, at least for 5 h, after death and that the Ca2+-ATPase tends to relax the myocardium against the development of cardiac rigor mortis.

Experimental evaluation of rigor mortis. IV. Change in strength and evolution of rigor mortis in the case of physical exercise preceding death

Evolution of rigor mortis in rats exercised before death shows the following characteristics with respect to controls: (1) Its intensity is increased in the initial phase. (2) It reaches its maximum development at the same time. (3) Higher maximum values are reached (in our experiments 1.39 times the maximum values for controls). (4) Higher values are maintained from 100 minutes to 16 hours with statistically significant differences. (5) It attains resolution at the same time.