title: Effects of equilibration time, precooling and developmental stage on the survival of mouse embryos cryopreserved by vitrification.
abstract: Factorial experiments were carried out to examine the effects of equilibration time, precooling and developmental stage on the postthaw in vitro survival of vitrified mouse embryos. Eight-cell embryos, compacted morulae, or blastocysts were cryopreserved using vitrification Solution 1 (VS1; 10% glycerol + 20% propylene glycol), and vitrification Solution 2 (VS2; 25% glycerol + 25% propylene glycol) in phosphate buffered saline + 10% calf serum. Each embryo stage group was first equilibrated in VS1 for 5, 10 or 20 min and then exposed to either a precooled ( approximately 4 degrees C) or nonprecooled ( approximately 20 degrees C) VS2 in a 0.25-ml straw before they were plunged directly into liquid nitrogen. Results of this study showed an interaction between precooling, equilibration time and developmental stage which affect significantly post-thaw embryo survival (P< 0.05). High survival rates were obtained after 10 min equilibration in VS1 irrespective of the embryo developmental stage. Precooling of the VS2 significantly improved the survival mainly of blastocysts. However, eight-cell and morula-stage embryos also showed high survival rates when they were exposed to precooled VS2 after 5 min equilibration in VS1. It was further observed that morulae usually exhibit high survival rates, and vitrification conditions are more critical for early and advanced stage embryo development.
authors.affiliation: Department of Theriogenology Faculty of Veterinary Medicine Hokkaido University, Sapporo 060, Japan.
authors.forename: C A
authors.initials: CA
authors.lastname: Valdez
authors.forename: O
authors.initials: O
authors.lastname: Abas Mazni
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: M
authors.initials: M
authors.lastname: Hishinuma
authors.forename: H
authors.initials: H
authors.lastname: Kanagawa