FIG. 4.

Typical micrographs showing the development of the early secondary preantral follicle retrieved mechanically from deer mouse ovaries during in vitro culture in MD of the nonconditioned medium: ∼8% of the early secondary preantral follicle (A) could develop through the nonphysiologically diffused stage (B) to antral stage (C). After further IVM, COC (D) was obtained from the antral follicle by follicular puncture. Cumulus cells in the COC were removed using hyaluronidase to obtain clean oocytes, shown in Figure 3. Only 2.7% of the primary oocytes in the early secondary preantral follicle developed to the MII stage using this conventional MD method. Scale bars: 100 μm. COC, cumulus–oocyte complex.