Document Detail

Ultrastructural aspects of oocyte maturation and fertilization in cattle.
MedLine Citation:
PMID:  2677348     Owner:  NLM     Status:  MEDLINE    
The preovulatory surge of LH triggers follicular and oocyte maturation in cattle. Oocyte maturation includes disruption of the gap junctions between cumulus-cell projections and oocyte and the breakdown of the envelope of the oocyte nucleus within 12 h after the LH peak; at approximately 15 h metaphase of the first meiotic division occurs and spatial rearrangements of mitochondria and vesicles are seen in the ooplasm; at approximately 19 h the first polar body is abstricted and the second metaphase appears; and at 21-22 h the cortical granules migrate to solitary positions along the oolemma, the Golgi compartment decreases, and the smooth endoplasmic reticulum (SER) transforms. Ovulations occur in unstimulated and superovulated cattle at approximately 24 h and 24-33 h, respectively. The acrosome reaction, which is preceded by swelling of and appearance of small vesicles in the acrosome, is completed on the surface of the zona pellucida. During the subsequent gamete fusion the microvilli of the ovum contact the equatorial segment of the sperm head, and the acrosomal region is subsequently internalized into the ooplasm surrounded by a vesicle. Within the following 2-3 h the formation of the maternal and paternal pronucleus is initiated, the cortical granules are released, conspicuous Golgi complexes develop, and the SER is transformed; at 5-7 h the pronuclei enlarge, and arrays of annulate lamellae develop. Subsequently, the pronuclei migrate close together; at approximately 20 h the envelopes of the pronuclei are broken down and synkaryosis is seen; and at approximately 24 h the 2-cell stage emerges. Artificial control of oocyte maturation and fertilization in cattle may lead to deviation in these processes. Superovulation may affect oocyte maturation adversely, and in-vitro fertilization may lead to increased frequencies of polyspermy due to deviations in cortical granule release and dispersal. Knowledge about these basal processes of oocyte maturation and fertilization are fundamental in the context of egg manipulation (oocyte enucleation at cloning, gene injection into pronuclei at specific stages etc.) in cattle.
P Hyttel; T Greve; H Callesen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Journal of reproduction and fertility. Supplement     Volume:  38     ISSN:  0449-3087     ISO Abbreviation:  J. Reprod. Fertil. Suppl.     Publication Date:  1989  
Date Detail:
Created Date:  1989-11-08     Completed Date:  1989-11-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0225652     Medline TA:  J Reprod Fertil Suppl     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  35-47     Citation Subset:  IM    
Department of Reproduction, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
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MeSH Terms
Cattle / physiology*
Oocytes / ultrastructure*

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