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

<p>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.</p>

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biology

Year dc:date.available

2025

Author dc:creator

• Emery, Julia G

Contributors dc:contributor

• Dr. Josh Sharp

• Skeletal Muscle
• PMI
• Time Since Death
• Human
• Calpain
• Vinculin
• Western Blot
• Biochemistry

Repository record dc:identifier

https://commons.nmu.edu/theses/896

OAI identifier oai:identifier

oai:commons.nmu.edu:theses-1958