title: Ultrastructure of in vitro oocyte maturation in buffalo (Bubalus bubalis).
abstract: The objective of the present study was to describe ultrastructural changes in the nucleus and cytoplasmic organelles during in vitro maturation (IVM) of buffalo cumulus-oocyte complexes (COCs). The structures were collected by ovum pick-up (OPU). Some COCs, removed from maturation medium at 0, 6, 12, 18 and 24 h, were processed for transmission electron microscopy. The average number of COCs collected by OPU/animal/session was 6.4, and 44% of them were viable. Immature oocytes had a peripherally located nucleus, Golgi complex and mitochondrial clusters, as well as a large number of coalescent lipid vacuoles. After 6 h of IVM, the oocyte nucleus morphology changed from round to a flatter shape, and the granulosa cells (GC) lost most of their contact with zona pellucida (ZP). At 12 h the first polar body was extruded and the aspect of lipid droplet changed to dark, probably denoting lipid oxidation. Cortical granules were clearly visible at 18 h of maturation, always located along the oocyte periphery. At 24 h of IVM the number of cortical granules increased. Ultrastructure studies revealed that: (1) immature oocytes have a high lipid content; (2) the perivitelline space (PS) increases during IVM; (3) Golgi complexes and mitochondrial clusters migrate to oocyte periphery during IVM; (4) 6 h of IVM are enough to lose contact between GC and ZP; (5) the oocyte lipid droplets' appearance changes between 6 and 12 h of IVM.
authors.affiliation: Universidade Federal de Pelotas, Instituto de Biologia, Departamento de Morfologia, Pelotas-RS, Brazil. rmondadori@hotmail.com
authors.forename: Rafael Gianella
authors.initials: RG
authors.lastname: Mondadori
authors.forename: Tiago Rollemberg
authors.initials: TR
authors.lastname: Santin
authors.forename: Andrei Antonioni Guedes
authors.initials: AA
authors.lastname: Fidelis
authors.forename: Khesller Patrícia Olázia
authors.initials: KP
authors.lastname: Name
authors.forename: Juliana Souza
authors.initials: JS
authors.lastname: da Silva
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Rumpf
authors.forename: Sônia Nair
authors.initials: SN
authors.lastname: Báo
mesh_terms: D000818:Animals; D002020:Buffaloes / Q000033:anatomy & histology; D002467:Cell Nucleus / Q000648:ultrastructure; D054885:Cumulus Cells; D005260:Female; D066298:In Vitro Techniques; D054315:Oocyte Retrieval; D009865:Oocytes / Q000166:cytology / Q000648:ultrastructure*; D009866:Oogenesis