Micrographs of CL obtained from rats killed on day 4 post-partum and stained with H&E. Panel (A) shows the structure of a an old CL of pregnancy obtained from an animal treated with vehicle, whereas panel (B) displays the structure of an old CL of pregnancy obtained from a rat treated with estradiol benzoate. Similar results were observed in newly formed CL after post-partum ovulation obtained from animals receiving vehicle or estradiol benzoate. The arrows indicate nuclei undergoing apoptosis displaying different features of chromatin condensation. Magnification × 400.