Date of Award

2011

Degree Type

Dissertation

Department

Chemistry

First Advisor

Bayachou, Mekki

Subject Headings

Human reproductive technology, Spermatozoa, Oxidative stress, Assisted reproduction, human spermatozoa, semen quality, reactive oxygen species, oxidative stress, antioxidants, L-carnitine, nitric oxide

Abstract

The necessary multi-step process to prepare human semen for assisted reproduction (AR) such as in vitro fertilization (IVF) is known to induce oxidative stress in human spermatozoa and subsequent damage to the integrity of their cell components and, thus, to their function. Literature reports have viewed this as a potential link with the high frequency of birth defects among the IVF babies. In this work, we studied the effect of incubation and centrifugation on human sperm quality using established AR protocols. We found that in vitro incubation and centrifugation (20 min at 220g) of sperm generally degrade sperm quality in terms of motility and DNA oxidation. The total antioxidant capacity of the semen significantly decreased upon raising the centrifugation force from 220g to 400g. We then studied the efficacy of supplements such as L-carnitine (LC) on remediating the oxidative stress. We found that supplementation with LC counteracts the overall damage of quality brought by the multi-step method of sperm processing. We determined the LC concentration range (0.1-1.0 mg/mL) with optimum oxidative stress remediation and which enhances qualities such as motility. Among the various oxidative stress species, we particularly focused on nitric oxide as a species with known dual functional and cytotoxic properties. We have demonstrated a method to monitor its dynamic concentrations in spermatozoa. The method enabled us to establish a link between motility and nitric oxide levels in spermatozoa. The method also allowed us to establish that the LC-induced enhancement of human sperm motility is also accompanied with a simultaneous increase in NO production

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