Meiotic competence of prepubertal goat oocytes.
ABSTRACT The object of this work was to evaluate in vitro maturation of follicular oocytes from the ovaries of prepubertal goats obtained from the slaughterhouse. To obtain the oocytes, follicles were dissected and classified according to their diameters. In the first experiment, oocytes were matured in vitro with granulosa cells. No significant differences were detected in the percentages of maturation between adult and prepubertal goat oocytes recovered from follicles of 2.5 to 6.0 mm in diameter (81.82 vs 72.47%, respectively). The percentage of maturation increased to 88.0% in prepubertal goat oocytes from 3.0 to 6.0-mm follicles. In the second experiment, the percentage of maturation of prepubertal goat oocytes was greater after 27 than after 24 h. In the third experiment, the maturational capacity of prepubertal goat oocytes according to follicular diameter was evaluated. The percentages of maturation after 27 h of culture with no granulosa cells were 24.14, 56.60 and 74.78%, respectively, for follicles 1.0 to 1.9 mm, 2.0 to 2.9 mm, and 3.0 to 6.0 mm in diameter. As the follicular diameter increased, growth of the oocyte as well as a greater number of oocytes with more cumulus cell layers were observed. A correlation between the diameter of the oocyte and its competence to complete in vitro maturation was also observed. Oocytes with more cumulus cell layers showed only a slight superiority in their capacity for maturation in large-size follicles (3.0 to 6.0 mm), but the difference was not significant. In conclusion, oocytes from prepubertal goats complete their growth and reach meiotic competence in follicles larger than 3.0 mm. With these oocytes it is possible to obtain in vitro maturation results similar to those from adult goats.
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ABSTRACT: This study was conducted to investigate 1) the capacity of in vitro-matured (IVM) marmoset oocytes to be fertilized and to support embryonic development in vitro and 2) oocyte meiotic maturation in relation to in vivo FSH administration, follicle size, and oocyte-cumulus cell status. Pairs of ovaries were collected on Day 4 of the follicular phase from adult females receiving either 1) human FSH (3 IU; n = 5) or 2) control (saline; n = 5) daily for 4 days. Antral follicles were excised from ovaries and separated into classes according to size: class 1 (660-840 microm), class 2 (> 840-1000 microm), class 3 (> 1000-1400 microm), and class 4 (> 1400 microm). A total of 823 partially naked and cumulus-enclosed oocytes (CEOs) were released from follicles and cultured in vitro. Cumulus cells remaining after 22 h were removed, metaphase II (MII) oocytes were inseminated with epididymal sperm, and resulting embryos were cultured until developmental arrest. Fluorescence microscopy was used to assess oocyte meiotic and embryo developmental progression. Oocyte germinal vesicle breakdown (GVB)- and MII-competencies increased significantly with follicular size (p < 0.01 and p < 0.0001, respectively), although they were independent of oocyte-cumulus cell associations. After 24 and 32 h in vitro, 69% and 93%, respectively, of CEOs with MII competence had completed meiotic maturation, and the rate of nuclear maturation increased progressively with follicle size (p < 0.01) and with the association of cumulus cells (p < 0.01). In vivo FSH priming slightly improved oocyte GVB- and MII-competencies (p < 0.01 and p < 0.05, respectively) and decreased the time required to achieve MII (p < 0.01). IVM oocytes from all follicle sizes fertilized (78-92%) in vitro, with 27% developing to morula- and 4% to blastocyst-stage embryos. This study demonstrates for the first time that IVM New World primate oocytes are able to support advanced preimplantation embryonic development in vitro. Oocyte meiotic competence and the time course of nuclear maturation are profoundly influenced by their follicular origin, and marginally by FSH treatment.Biology of Reproduction 01/1997; 56(1):238-46. · 4.01 Impact Factor