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Title: SEXUAL DIMORPHISM IN IVM-IVF BOVINE EMBRYOS PRODUCED FROM X AND Y CHROMOSOME BEARING SPERM SORTED BY HIGH SPEED FLOW CYTOMETRY

Author
item BEYHAN, Z - UNIV OF WISCONSIN-MADISON
item Johnson, Lawrence
item FIRST, N - UNIV OF WISCONSIN-MADISON

Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The utilization of sperm that has been sorted into separate X and Y populations can be useful for studying various mechanisms of fertilization. Improving reproductive efficiency is dependent on gaining a greater understanding of fertilization processes hitherto that could not be studied on separate populations of X and Y sperm. In this study sorted populations at purities of greater than 90% X or Y were used to fertilize oocytes with subsequent evaluation of the blastocyst formation. It was found that the sperm aster (associated with fertilization) was larger for the Y bearing population of sperm than for the X population. However, pronuclei size nor sperm aster quality did not differ between the sexes. It was concluded that though development was dimorphic between male and female embryos, the difference was probably not of major significance.

Technical Abstract: The objective of this study was to examine the preimplantation development and sperm aster charecteristics of bovine male and female embryos produced by using spermatozoa sorted for X- or Y-chromosome. In vitro matured oocytes were inseminated at 24 h of maturation with either sorted X- or Y- chromosome bearing spermatozoa, fresh or frozen spermatozoa. Samples were taken from each spermatozoa group 12 h post insemination (hpi), fixed and immunostained for microtubule cytoskeleton. Confocal microscopy enabled visualization of sperm aster formation and microtubule characteristics of each zygote during early fertilization. Cultured embryos were checked for cleavage at 30, 35, 40 and 45 hpi, embryo development was examined daily until day eight of culture. Blastocyst cell numbers were determined at the end of the experiments. Reanalysis of sorted sperm for DNA content showed purity rates of 90.1 and 92.1% for X- and Y-chromosome bearing sperm, respectively. Reduced fertilization and development rates were observed when sorted sperm were used as compared with fresh and frozen sperm. Penetration rates at 12 hpi were 39.5%, 44.7%, 55.9%, 79.0%, blastocyst formation rates at Day 8 were 26.7, 26.5, 31.7 and 40.7% for X-, Y- chromosome bearing spermatozoa, fresh and frozen spermatozoa groups, respectively. The sperm aster size was larger in males, while the size of pronuclei and subjective grade of sperm aster quality showed no difference between sexes. In this study, greater cleavage rate and sperm aster size in male embryos indicate a dimorphic pattern of development in male and female embryos during fertilization and first cleavage.