title: In vitro maturation of oocytes derived from the brown bear (Ursus arctos).
abstract: This study was conducted to determine whether meiotic maturation could be induced in ovarian oocytes from the American brown bear (Ursus arctos), a model for gamete "rescue" techniques for endangered ursids. The bears were euthanized, and their ovaries were transported to the laboratory within 4 h. The mean ovarian size was 2.4 x 1.8 cm (range: 2.0-3.3 x 1.5-2.2 cm). The ovaries obtained from the 2 brown bears yielded 97 oocytes (48.5/female), and 88 (90.7%) of them were morphologically classified as normal quality. Oocytes were in vitro matured at 38.5 C in 5% CO2 for 24 or 48 h in TCM-199 supplemented with 10% FBS, 1 microg/ml estradiol-17beta, and 10 microg/ml FSH. In Exp. 1, morphologic evaluation of matured oocytes was conducted by measuring the diameters of oocytes with a zona pellucida (ZP) or cytoplasm without a ZP. In Exp. 2, activation was induced by applying two 20 microsec DC pulses of 2.0 kV/cm delivered by an Electro Cell Fusion Generator. The activated oocytes were cultured in TCM-199 containing 2 mM of 6-dimethylaminopurine for 4 h, in Charles Rosenkrans (CR) 1 for 3 days and the in CR2 for another 4 days. The diameters of the matured bear oocytes with a ZP and with cytoplasm without a ZP (161.8 +/- 6.0 and 135.3 +/- 7.5 microm, respectively) were significantly (P<0.05) larger than those of bovine oocytes (150.7 +/- 4.9 and 118.7 +/- 7.5 microm). The maturation rates of the bear oocytes were 17.6 and 59.4% at 24 and 48 h of in vitro maturation, the percentage of activated oocytes that developed to the 2 or 4-cell stage was 31.6%; however, no blastocysts were observed. These results indicate that bear oocytes can develop to metaphase II in an in vitro culture system and that activated oocytes can develop to the 2 or 4-cell stages.
authors.affiliation: Department of Animal Science and Technology, Sunchon National University, Korea.
authors.forename: Xi-Jun
authors.initials: XJ
authors.lastname: Yin
authors.forename: Hyo-Sang
authors.initials: HS
authors.lastname: Lee
authors.forename: Eu-Gene
authors.initials: EG
authors.lastname: Choi
authors.forename: Xian-Feng
authors.initials: XF
authors.lastname: Yu
authors.forename: Gye-Young
authors.initials: GY
authors.lastname: Park
authors.forename: Inhyu
authors.initials: I
authors.lastname: Bae
authors.forename: Chul-Ju
authors.initials: CJ
authors.lastname: Yang
authors.forename: Dong-Hwan
authors.initials: DH
authors.lastname: Oh
authors.forename: Nam-Hung
authors.initials: NH
authors.lastname: Kim
authors.forename: Il-Keun
authors.initials: IK
authors.lastname: Kong
mesh_terms: D000818:Animals; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D008540:Meiosis / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000254:growth & development*; D010053:Ovary / Q000033:anatomy & histology; D001503:Ursidae / Q000196:embryology*