title: Effects of gas conditions, time of medium change, and ratio of medium to embryo on in vitro development of horse oocytes fertilized by intracytoplasmic sperm injection.
abstract: This study was conducted to evaluate the effects of two different gas conditions (5% CO(2) in air or 5% CO(2), 5% O(2), 90% N(2), mixed gas), time of medium change (Day 3 or 4) and ratio of medium to embryo (2, 5 or 10 microl per presumptive zygote) on the development of horse oocytes fertilized by intracytoplasmic sperm injection and cultured in G1.2/2.2 medium. Oocytes from slaughterhouse-derived ovaries were matured in vitro for 24 h and fertilized by injection of frozen-thawed sperm using micromanipulation with a Piezo drill. Presumptive zygotes were randomly assigned to 5% CO(2) in air or mixed gas and fixed after 96 h of culture. Cleavage rates between two gas conditions were similar (67 and 63%), but the mean nucleus number of embryos in the mixed gas treatment was significantly (P<0.05) higher than that of embryos cultured in 5% CO(2) in air (15.2 versus 7.0, respectively). Further experiments were done with mixed gas incubation. Development of embryos was compared after change from G1.2 to G2.2 medium at Day 3 or 4. There was no significant difference in cleavage rate (56 and 65%, respectively) or development to the blastocyst stage after 7 days of culture (5% and 46%, respectively) between embryos changed on different days. To evaluate the effect of the ratio of medium to embryo, zygotes were cultured at a ratio of 2, 5 or 10 microl medium per zygote. There were no significant differences among ratio treatments in rates of cleavage or development to blastocyst.
authors.affiliation: Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4466, USA.
authors.forename: Young-Ho
authors.initials: YH
authors.lastname: Choi
authors.forename: Charles C
authors.initials: CC
authors.lastname: Love
authors.forename: Dickson D
authors.initials: DD
authors.lastname: Varner
authors.forename: Linda B
authors.initials: LB
authors.lastname: Love
authors.forename: Katrin
authors.initials: K
authors.lastname: Hinrichs
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000502:physiology; D003470:Culture Media; D005314:Embryonic and Fetal Development / Q000502:physiology*; D005260:Female; D006736:Horses / Q000196:embryology*; D008297:Male; D009584:Nitrogen / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D010100:Oxygen / Q000502:physiology; D011897:Random Allocation; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods* / Q000662:veterinary*
chemical_list: D003470:Culture Media; D002245:Carbon Dioxide; D009584:Nitrogen; D010100:Oxygen