Tissue changes in the FRT during the estrous cycle of the mouse.

<p>Vaginal smears were taken from naïve virgin C57BL/6 female mice (8–12 weeks old) over the course of one estrous cycle and used for determination of cycle stage. Mice were killed at PE (<b>A</b>), E (<b>B</b>), ME (<b>C</b>) and DE (<b>D</b>) and tissue sections of vagina were cut. Vaginal smears (top panel) and tissue sections (bottom panel) were stained with H&E. The insets in the top panel show typical cell types found in vaginal smears of each cycle stage. The inset in the bottom panel shows neutrophils present in vaginal epithelium. Representative images from conventional cycle stage assessments are shown. Top panel, 100× magnification; bottom panel, 400× magnification.