role of vitreous humor biochemistry in forensic pathology - CiteSeerX

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ROLE OF VITREOUS HUMOR BIOCHEMISTRY IN FORENSIC PATHOLOGY

A Thesis Submitted to the College of Graduate Studies and Research in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in the Department of Pathology, College of Medicine University of Saskatchewan

By AMITH MULLA Saskatoon, Saskatchewan

© Copyright Amith Mulla, July, 2005. All rights reserved.

In presenting this thesis in partial fulfillment of the requirements for a postgraduate degree from the University of Saskatchewan, I agree that the libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by Dr. J. Kalra who supervised my thesis work or in his absence, by the Head of the Department of Pathology or the Dean of the College of Medicine in which my thesis work was done. It is understood that any copying or publication or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis. Requests for permission to copy or to make other use of material in this thesis in whole or part should be addressed to:

Head of the Department of Pathology University of Saskatchewan Saskatoon, Saskatchewan, S7N 0W8

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ABSTRACT Vitreous humor is a fluid that is relatively well protected from postmortem degradation and contamination. Due to its postmortem stability, vitreous humor has high utility in forensic pathology. Vitreous humor biochemical constituents, especially potassium, have been widely used in the postmortem interval (PMI) estimations. The time dependant rise of vitreous potassium levels in the postmortem period has been considered to be helpful in PMI determinations. The relative stability of vitreous biochemistry is useful in assessing the antemortem metabolic status and in predicting the antemortem serum biochemistry of an individual. However, the validity of vitreous biochemistry in forensic applications has been questioned in light of the reported concentration differences of various biochemical constituents in the same pair of eyes at identical PMI. This study hypothesized that the concentration of vitreous biochemical constituents in the same pair of eyes change at the same rate and this change that occurs in a time dependent fashion may be utilized in accurately estimating the PMI. It was further hypothesized that postmortem vitreous humor biochemistry closely mimics antemortem serum biochemistry and may be a useful aid in establishing a postmortem diagnoses of hyperglycemia. To test these hypotheses, vitreous humor samples were collected from a total of 103 autopsies (Female, 35 and Male, 68; Mean Age ± SD, 60.6 ± 17.6) conducted at Royal University Hospital morgue between January 2003 to February 2005. In 61 of these subjects, the precise time of death was known. Right and left eye vitreous humor samples were collected separately through a scleral puncture at the lateral

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canthus. Most of the biochemical analyses were carried out immediately postextraction. After centrifugation, the supernatant of the fluid were analyzed for sodium, potassium, chloride, calcium, magnesium, urea, creatinine, glucose and lactate on an LX-20 Analyzer (Beckman-Coulter). Osmolality was measured on an Osmometer model 3900 (Advanced Instruments Inc.).

Vitreous humor

hypoxanthine and xanthine were analyzed using a colorimetric method (Amplex® Red Xanthine/ Xanthine Oxidase Assay Kit, Molecular Probes Inc.). Vitreous humor lipid hydroperoxides were measured using the Ferrous Oxidation in Xylenol Orange assay version 2 (FOX 2). The data was statistically analyzed by paired t-test, linear regression analysis and Mann-Whitney test using Statistical Package for Social Sciences (SPSS) for Windows™ version 13.0. The results of this study indicated that there were no significant between-eye differences for all of the vitreous biochemical constituents that were studied. It was observed that there was a significant correlation between vitreous potassium (R, 0.731; P,