TEMPERATURE VARIATION IN MARQUETTE, MICHIGAN, CONCERNING SKELETAL MUSCLE DEGRADATION PATTERNS FOR POSTMORTEM INTERVAL DETERMINATION

Author

Julia G. Emery, Northern Michigan UniversityFollow

Date of Award

8-2025

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Integrated Biosciences (MS)

First Advisor/Chairperson

Dr. Josh Sharp

Abstract

Postmortem interval (PMI), or time since death, is regularly estimated in criminal investigations. Biochemistry methods can estimate PMI by analyzing changes in protein breakdown within muscle tissue. Observing protein degradation has been proposed as a new method of PMI estimation due to specific proteins degrading in a predictable and time-dependent manner. This study examined the effect of temperature on the degradation patterns of vinculin, a skeletal protein, and the levels of essential metals in human skeletal muscle. Calcium concentrations were also observed for evidence of calpain activation, which degrades vinculin. Once observations of vinculin degradation and calpain activation were seen and the patterns of vinculin degradation were observed in the controlled temperature studies, the controlled temperature data were used to identify the PMI range of human muscle samples with unknown PMI. For the PMI estimation, human muscle samples were donated from the Paris Lodron Universität Salzburg and compared to controlled samples to evaluate the potential for PMI estimation. The study was conducted in three temperature-controlled lab environments and at the Forensic Research Outdoor Station (FROST) during spring/summer. Muscle samples underwent western blotting and ICP-MS analysis. Ambient temperatures were continuously recorded using the onsite weather station at FROST. Analysis of the western blot results showed that temperature affects the degradation rate of skeletal muscle and that it is possible to estimate PMI using controlled temperature data. Analysis of ICP-MS results indicated that metal concentration patterns vary between spring and summer, along with evidence of calpain activation related to calcium concentrations.

Recommended Citation

Emery, Julia G., "TEMPERATURE VARIATION IN MARQUETTE, MICHIGAN, CONCERNING SKELETAL MUSCLE DEGRADATION PATTERNS FOR POSTMORTEM INTERVAL DETERMINATION" (2025). All NMU Master's Theses. 896.
https://commons.nmu.edu/theses/896

Access Type

Open Access

Justification for Restricting Access

I want to submit this data/thesis for publishing in the American Academy of Forensic Science.