title: Effects of cooling and warming rates during vitrification on fertilization of in vitro-matured bovine oocytes.
abstract: The purpose of this study was to clarify the relationship of cooling rates (CR) and warming rates (WR) during vitrification with postwarming viability of in vitro-matured bovine oocytes. In Experiment 1, oocytes were vitrified in a solution containing 7.2 M ethylene glycol and 1.0 M sucrose by use of open-pulled glass capillaries with five different outer diameters and were warmed by placement of the capillaries into 0.25 M sucrose solution. The capillaries of 2000-, 1400-, 1000-, 630-, and 440-mm diameters provided CR of 2000, 3000, 5000, 8000, and 12,000 degrees C/min and WR of 5000, 8000, 17,000, 33,000, and 62,000 degrees C/min, respectively. In oocytes vitrified in capillaries of 1400-mm diameter (CR, 3000 degrees C/min; WR, 8000 degrees C/min), the morphological survival rate (86% of vitrified), penetration rate (79% of inseminated), and normal fertilization rate (69% of penetrated) were higher or tended to be higher than those in the other vitrification groups. In Experiment 2, oocytes cooled at 2000, 3000, or 12,000 degrees C/min were warmed at 8000 degrees C/min, and oocytes cooled at 3000 degrees C/min were warmed at 5000, 8000, or 33,000 degrees C/min. Among these CR-WR combinations, cooling of oocytes at 3000 degrees C/min regardless of the WR resulted in higher postwarming survival. These results indicate that survival of in vitro-matured bovine oocytes after vitrification and subsequent warming is improved by a slightly rapid cooling rate in open-pulled glass capillaries compared to that obtained in conventional straws.
authors.affiliation: Faculty of Textile Science and Technology, Ueda, Nagano, 386-8567, Japan.shochi@giptc.shinshu-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Hochi
authors.forename: M
authors.initials: M
authors.lastname: Akiyama
authors.forename: G
authors.initials: G
authors.lastname: Minagawa
authors.forename: K
authors.initials: K
authors.lastname: Kimura
authors.forename: A
authors.initials: A
authors.lastname: Hanada
mesh_terms: D000818:Animals; D002417:Cattle; D002454:Cell Differentiation; D002470:Cell Survival; D015925:Cryopreservation / Q000379:methods*; D005260:Female; D005307:Fertilization in Vitro; D066298:In Vitro Techniques; D009865:Oocytes / Q000166:cytology