Changing expression of p16 in oocytes of follicles initiating growth. Original magnification 1000X. (A)Increased expression of p16 in primordial follicle oocytes (arrows); (B&C) Increased expression of p16 in primary follicles with unenlarged oocytes (arrows); (D) Diminished expression of p16 after enlargement of the oocyte in primary follicles. (E) Note the primordial follicle (arrow) with significantly higher expression of p16 in its oocyte compared to the adjacent primary follicle with an enlarged oocyte. Bar = 50 μm.