Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences


Biomedical Sciences

Committee Director

Gary D. Hodgen

Committee Member

Keith Carson

Committee Member

Joseph C. Daniel

Committee Member

Lloyd Wolfinbarger, Jr.


Microsurgical fertilization is the technique in which a spermatozoon or sperm nucleus is injected into the cytoplasm of an egg. To establish a foundation for the use of microsurgical fertilization as a means of treating infertility, this study evaluated the procedure in hamster and human eggs. Hamster sperm nuclei were microinjected into hamster eggs to determine the rate of abnormal fertilization and to ultrastructurally assess cellular damage by transmission electron microscopy. Hamster eggs were also injected with human spermatozoa obtained from fertile and infertile men to evaluate the fertilizing potential of the sperm cells. In addition, human eggs donated by patients undergoing in vitro fertilization were injected with human spermatozoa to perform a preliminary evaluation of the human egg's ability to survive the sperm microinjection procedure and participate in the early events of fertilization. This study found no evidence of ultrastructural damage to either hamster or human eggs surviving the microinjection procedure although abnormal fertilization events were found to occur in surgically fertilized hamster eggs at an incidence of six percent. In the study of human spermatozoa, no significant difference was found in the rate of pronuclear formation following microinjection between spermatozoa differing in motility and maturational status. Spermatozoa found incapable of penetrating an egg by normal fertilization were shown to be capable of sperm decondensation and pronuclear formation following their direct injection into the cytoplasm of an egg. In addition, human eggs were found to be capable of surviving the mechanical insertion of a spermatozoon directly into the ooplasm with subsequent development to the pronuclear stage of fertilization.