Figure 2

General morphology and organelle microtopography in adult ovine cumulus-oocyte-complexes (COCs) at sampling (IVM: 0 hours). a) Representative LM image showing the eccentric profile of an irregularly shaped nucleus (N), flattened against the ZP. Arrows indicate “spikes” of the oolemma. Many layers of compact CCs adhere to a round ZP. The ooplasm is rich of vacuoles (in white), lipid droplets (in grey) and organelles (in violet). Bar: 25 μm. b) Representative TEM micrograph showing the oocyte and CC ultrastructure. Cumulus expansion starts as indicated by the reduction of CC coupling. The oolemma is anchored to the ZP only in correspondence of focal adhesions (arrows) established with trans-zonal projections still present. ZP: zona pellucida; PVS: perivitelline space; CC: cumulus cell. Mitochondria (m), are interspersed to electron-negative vacuoles (Va), electron-dense lipid droplets (LD). Bar: 5 μm.