Human SFO and VO at MII stage. Presence of vacuoles. By TEM, numerous vacuoles (Va) are seen in the ooplasm of SFO (a,b), whereas only a few vacuoles are visible in VO (c). Vacuoles appear empty (a-c) or contain cell debris (a,b). Note some interruptions in the vacuole membrane (a-c). A close association between a vacuole and a lysosome (Ly) is seen in (c). A typical M-SER aggregate (b), isolated mitochondria (M) and MV complexes (c) are seen in the areas adjacent to vacuoles. Bar is: 1 μm (a-c).