POSTNATAL-DEVELOPMENT OF THE VAGINAL EPITHELIUM IN THE MONGOLIAN GERBIL (MERIONES-UNGUICULATUS)

This study examines the normal postnatal (p.n.) development of the Mon golian gerbil's vagina from birth to the age when consistent cyclic ch anges of the estrus occur. At birth, the Mullerian vagina has a lumen and is lined by a pseudostratified or 2- to 3-layered epithelium. The cells contain large amounts of glycogen. The sinus vagina forms a soli d plate and contains hardly any glycogen. During the first few p.n. da ys the cell layers separate, and the newly formed lumen becomes contin uous with the Mullerian vagina. Only a vaginal closure membrane persis ts. Between p.n. days 10 and 15 the epithelium increases in height rea ching 2-5 cell layers. The amount of glycogen diminishes, but in the l uminal cells the first mucous granules develop. Leukocyte diapedesis s tarts, and immature Langerhans cells become discernible. Between p.n. days 18 and 30 the apical cells become mucified, and some shedding of these cells begins. Between p.n. days 36 and 45 bundles of keratin fil aments appear in many of the luminal mucous cells intermingled with th e mucous granules. In the middle layers keratin filaments, keratohyali n granules and membrane-coating granules indicate the beginning of the keratinization process. Diapedesis of leukocytes may lead to cell agg regations below top layers. By day 50 the shedding of the mucous cell layers reveals the underlying keratinized cell layers which then becom e exfoliated. The first steps of the estrous cycle show a heterogeneou s pattern. At about p.n. day 60 the cycle becomes established.