Representative examples of anti-BrdU immunohistochemistry in the ovaries of IO and BR mice. A. BrdU immuno-positive cells in the OSE (arrows) adjacent to a follicle (foll) and a corpus luteum in a 9-month IO ovary on the afternoon of estrous. Note the labeled cells in the theca and stroma just beneath the OSE. B. Negative control (no primary antibody added) of an adjacent section to A. C. Numerous BrdU immuno-positive nuclei (arrows) in the OSE at the base of a recently ovulated follicle (rof) in a 6-month BR ovary. D. A single BrdU immuno-positive cell (arrow) is present in this group of three rete ovarii tubules from a 9-month BR ovary. E. BrdU incorporation in cells present in a hilar cyst (c) in a 12-month BR ovary. F. BrdU incorporation in cells, including hobnail cells with clear cytoplasm, lining a cortical cyst in a 12-month IO ovary. Bars = 75 μm; original magnification 200 ×.