title: Assessment of pronuclear formation following in vitro fertilization with bovine spermatozoa obtained after thermal insulation of the testis.
abstract: This study was conducted to follow the chronology of pronuclear formation in bovine zygotes after in vitro insemination with a population of spermatozoa having abnormal morphology. Semen samples were obtained and cryopreserved from four Holstein bulls before and after a scrotal insulation period of 48 h (Day 0). A pre-insult (Day 5) and a Day 20 post-insult semen sample were evaluated for morphology and used for IVF after standard swim-up sperm separation protocols. Pronuclear formation was scored on subpopulations of presumptive zygotes after they were fixed and stained at 3-h time intervals from 6 to 18 h post in vitro insemination (hpi). Post-thaw morphological evaluation of semen samples revealed a decrease in the percentages of normal spermatozoa in the post-insult samples compared with the pre-insult samples for Bull I (74-22%) and Bull III (68-1%). The sperm penetration rate decreased (P<0.05) between the pre- and post-insult samples for Bulls I (90-76%) and III (92-70%), but was not different for Bulls II (92-90%) and IV (78-85%). The pronuclear formation rates for post-insult zygotes for Bulls II and IV had comparable increases in development over time, whereas there was no increase in the pronuclear development for the zygotes from the post-insult samples for Bulls I and III, and generally a condensed sperm head was observed in the oolemma. At 18 hpi the fertilization rate between the pre- and post-insult samples for Bulls I (51-4%), II (88-75%) and III (94-2%) decreased (P<0.01), but there was no change for Bull IV (66%). In conclusion, we inferred that the failure in normal pronuclear formation was associated with an absence of normal decondensation of the penetrating spermatozoon; this suggested that the effect of morphologically abnormal spermatozoa occurred prior to cleavage, thus limiting early development.
authors.affiliation: Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0315, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Walters
authors.forename: R G
authors.initials: RG
authors.lastname: Saacke
authors.forename: R E
authors.initials: RE
authors.lastname: Pearson
authors.forename: F C
authors.initials: FC
authors.lastname: Gwazdauskas
mesh_terms: D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000648:ultrastructure; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D006358:Hot Temperature; D008297:Male; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology / Q000648:ultrastructure; D013737:Testis / Q000166:cytology*; D020858:Tissue and Organ Harvesting / Q000379:methods / Q000662:veterinary*; D015053:Zygote / Q000648:ultrastructure*