Morphology of detached and dying cells at 24 h involution.
(A) shows an H&E stained thin section of tissue from a 24 h involution mouse mammary gland; a single alveolus is shown. Black arrows point to cells that have detached from the alveolar epithelial wall but are still intact and exhibit two hypercondensed nuclei. Red arrows point to viable luminal cells that are still within the alveolar epithelial wall. The basal/myoepithelial cells are too thin to be detected. The insert shows the lack of nuclear condensation in glands deficient for caspase 3. (B) shows a single alveolus immunostained for cleaved (active) caspase 3 in green (white arrows) and nuclei with Hoechst in blue (red arrows). Note the large number of shed cells staining for cleaved caspase 3 in the lumen but none in the alveolar wall.