(a) Female rats treated with 5-Azacytidine (Aza; i.p., 2mg/kg BW/day) from PND22 onwards have delayed vaginal opening. At the time when vaginal opening has occurred in all control animals (PND32), vaginal patency was not apparent in any of the Aza-treated rats. (b) Estrous cycle profiles showing that Aza treatment markedly disrupts estrous cyclicity. The phases of the estrous cycle depicted on the Y axis are proestrous (P), estrous (E), a transitional stage estrous-diestrous (ED), and diestrous (D). (c) Microphotographs illustrating the delay in ovarian maturation caused by Aza treatment during the juvenile phase of prepubertal development (PND 22 to 28) and the absence of ovulation, assessed by the lack of corpora lutea (CL) in ovaries from young adult (PND day 44) rats. Arrows point to examples of antral follicles. Scale bars = 100 μm.