Date of Award

2005

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr Peter Roberts

Second Advisor

Dr Peter Burton

Abstract

Semen cryopreservation has an important role in assisted reproductive technology however, the cooling, freezing and thawing processes often result in a significant loss of sperm motility, viability and nuclear integrity. The destructive effects of cryopreservation are significantly exacerbated in samples exhibiting low sperm number and poor morphological characteristics. Recent research into infertility has focused on the correlation between excessive oxidation and subfertility, in particular radical induced lipid peroxidation within the phospholipid bilayer of the spermatozoon plasma membrane and the promotion of cellular damage as a result of antioxidant insufficiency. The aim of this study was to evaluate the effect of vitamin E on the survival and integrity of sperm from oligozoospermic and teratozoospermic men following cryo preservation. Ejaculated semen samples from 43 men undergoing assessment for infertility were identified as normal (n=23) or abnormal (n=20) according to WHO standards. Each semen sample was divided into 3 aliquots: The first fraction remained untreated and the second and third fractions were treated with cryomedia containing either 100µM or 200µM of the vitamin E analogue Trolox (6-hydroxy-2,5,7,8-teramethylchroman-2-carboxylic acid) prior to freezing. Post-thaw analysis included sperm survival rate, vitality staining, and assessment of DNA fragmentation using the TUNEL assay. Motile sperm concentration and morphological normality was significantly higher in normozoospermic semen compared to the abnormal samples (P<0.001: unpaired t-tests). Whole semen volume was significantly higher in abnormal samples (P<0.05: unpaired t-tests). Post-thaw analysis found significant differences in post-thaw vitality between the normozoospermic and abnormal samples (P<0.05: Unpaired t-tests). Post-thaw survival and DNA fragmentation assay revealed no differences between normal and abnormal semen groups. The addition of vitamin E at concentrations of 100µM and 200µM did not significantly improve survival rate, post-thaw vitality or the degree of DNA fragmentation in the normal or abnormal semen samples. However, the results obtained were highly variable and an improvement in post-thaw survival was seen in 12 of the 43 semen samples from both the normal and abnormal groups. The variable response to vitamin E treatment observed in this study, suggests that the antioxidant ability of vitamin E during cryopreservation may depend on the oxidative status of individual semen samples.

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