The effects of the culture environment on gamete physiology

Jason R Herrick, Purdue University

Abstract

Throughout this dissertation, modifications to the culture environment were found to affect the physiology of both spermatozoa and oocytes, including motility, viability, and capacitation of spermatozoa and nuclear and cytoplasmic maturation of oocytes. Across studies, treatments resulting in optimal maturation and/or fertilization success were those treatments that were thought to more closely resemble the conditions within the follicle or the oviduct. In goat oocytes, high rates of cytoplasmic maturation (assessed by embryonic development) could be achieved in a physiological medium with a variety of macromolecules and carbohydrate concentrations. Both glucose and lactate interacted to alter the glycolytic activity of goat oocytes, but within a physiological range of concentrations the cumulus-oocyte complex and the oocyte appeared to be able to maintain a relatively constant metabolic activity. This demonstrated that goat oocytes matured under more optimal conditions were capable of adapting to changing environmental conditions without a loss of developmental competence. In porcine oocytes the pentose phosphate pathway was linked to both nuclear (meiosis) and cytoplasmic (embryonic development and glutathione synthesis) maturation. Inhibition of this pathway significantly inhibited oocyte maturation, highlighting the importance of this pathway and the interactions between several cellular pathways known to be critical components of maturation. A physiologically relevant medium for capacitation and fertilization is of particular importance because it must meet the needs of both gametes without compromising oocyte viability or inhibiting fertilization. The conditions used during coincubation of porcine gametes affected fertilization and subsequent development of the embryo. Among the nondomestic bovids studied, the most intriguing finding was that optimal culture conditions for sperm function varied between species. Although gamete and embryo culture are powerful tools for studying early development, the utility of these techniques is dependent on the normality of the physiology they support. The more normal the physiology of cultured gametes, the more useful the culture environment for physiological studies. Research on the interactions between gametes and their environment in culture also provides important knowledge regarding the control of physiological processes. In addition, this information can be used to further modify the culture environment, providing a more appropriate tool for future studies.

Degree

Ph.D.

Advisors

Krisher, Purdue University.

Subject Area

Anatomy & physiology|Animals

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