- Postmortem diagnostics play an important role in the ability to understand the cause of death of an animal. However, removal from oxygen supply, either by surgical excision or at death, leads to cell and tissue decomposition. Knowledge about factors impacting reliability of test results is extremely important for accurate diagnostics. This thesis examined two common diagnostic assays and the effect of environmental temperature and time ex vivo or postmortem on samples quality and assay performance. Chapter 1 examined the enzymatic properties of alkaline phosphatase (ALP), a diagnostic tissue marker of canine osteosarcoma. Samples known to express ALP (liver) or not (kidney and muscle tissues) were tested at both room temperature and 4 °C. Samples were obtained for both temperatures at 0 h, 24 h, 48 h and an additional sample was collected 96 h for the refrigerated sample. Liver samples produced the expected enzymatic response ex vivo up to 48 h, after which point degradation of the samples precluded proper visualization of intact hepatocytes with staining in the canaliculi. Chapter 2 examined staining intensity of commonly used immunohistological markers in formalin-fixed paraffin-embedded tissues samples collected at 3 different time points and 2 different storage temperatures postmortem. The staining for cytokeratin and vimentin diminished gradually both in intensity and percentage of cells staining; the 48 h 21 ˚C sample showed no staining. The PAX5 and CD79 stains showed some non-specific staining, and had weak intensities at early time points and lower temperatures, and little to no staining at later time points and higher temperatures. For all target molecules, there was a decrease in the amount and percentage of staining with increasing time, as well as increasing temperature; however, some markers were more sensitive to degradation.
- Key Words: Alkaline Phosphatase, Dogs, Osteosarcoma, Rabbits, Vimentin, Cytokeratin, PAX5, CD 79a, Immunohistochemistry