Fig. 3. Histological analysis of ovaries from postnatal Zp3-Foxo3a Tg mice and their WT littermates. Ovaries from 8-, 13- and 24-day-old, and 6-week-old Zp3-Foxo3a Tg mice and their WT littermates were isolated, fixed in 4% paraformaldehyde, dehydrated and embedded in paraffin. Serial 8 µm sections were prepared and stained with Hematoxylin for morphological observation. (A-C) Total numbers of follicles (mean±s.e.m.; ^*P<0.01) of type 3b, type 4, type 5 and types 6-7 per ovary in Tg mice (Tg) and WT littermates (WT) at PD8, PD13 and PD24. For each genotype and each age, ovaries from 3-5 mice were used. (D-M) Representative images of ovaries from Zp3-Foxo3a Tg mice (Tg) and WT littermates (WT) at PD8, PD13, PD24 and 6 weeks (6-wk). At PD13, in WT mice the first wave of follicular growth had reached the type 4 and 5 stages (H, arrows), whereas the majority of follicles in Tg ovaries were still at the stages of types 3b or 4 (I, arrows). In 6-week-old WT mice, corpus luteum (CL; L, arrow) and developing follicles (L, arrowhead) were seen, whereas, in Tg mice, most of the follicles were types 3b and 4 (M, arrow), with occasionally a few follicles of type 5 (M, arrowhead).