Equine oocyte competence for nuclear and cytoplasmic in vitro maturation: effect of follicle size and hormonal environment
Equine oocyte competence after in vitro maturation (IVM) was investigated in terms of the diameter of the follicle of origin and the stage of the estrous cycle, with three criteria of maturation: nuclear stage after DNA Hoechst staining, meiotic spindle morphology after tubulin immunocytochemical st...
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Published in | Biology of reproduction Vol. 57; no. 2; pp. 232 - 245 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Madison, WI
Society for the Study of Reproduction
01.08.1997
Society for the Study of Reproduction - Oxford Academic |
Subjects | |
Online Access | Get full text |
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Summary: | Equine oocyte competence after in vitro maturation (IVM) was investigated in terms of the diameter of the follicle of origin
and the stage of the estrous cycle, with three criteria of maturation: nuclear stage after DNA Hoechst staining, meiotic spindle
morphology after tubulin immunocytochemical staining, and cortical granule localization after lectin labeling. Seven successive
in vivo ultrasound-guided follicular punctures were performed on 10 cyclic saddle mares, alternatively at the end of the follicular
phase (after induction of ovulation with a gonadotropin injection) and in midluteal phase (with or without a gonadotropin
injection). Expanded cumulus-oocyte complexes (COCs) were stained at collection, and compact COCs were stained after in vitro
culture. They were observed under a confocal microscope. Successive punctures on one mare provided 0.9 preovulatory COCs and
8 immature COCs per 22 days. Among the preovulatory oocytes, 55% had completed nuclear and cytoplasmic maturation, 86% of
which displayed a normal meiotic spindle. Of the 262 oocytes cultured in vitro, 37% completed nuclear maturation. The nuclear
and cytoplasmic maturation rate significantly increased with follicle diameter. The IVM rate tended to be higher in follicular
phase and tended to increase in luteal phase with the gonadotropin injection. The meiotic spindle morphology was not significantly
different between the classes of follicular diameters. This study provided the opportunity to increase the number of characterized
oocytes collected per cycle and per mare. This is the first report showing the progressive acquisition of meiotic competence
in the equine oocyte during antral follicle growth and is the only description of the equine meiotic spindle. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod57.2.232 |