Ruthenium red staining of vaginal epithelial cells and adherent bacteria.

The vaginal epithelium of the rhesus monkey is a keratinized stratified squamous epithelium throughout the menstrual cycle and early pregnancy. The superficial cells have a thickened cell envelope, surface microridges, and numerous adherent bacteria. During later pregnancy the cells mucify and have a typical cell membrane, microvilli, and no adherent bacteria. In the present study we have extended these observations by examining vaginal surface structures after ruthenium red staining. Throughout the cycle, the superficial cells have a thin layer of stained material closely associated with the cell membrane, but in some cases a much thicker mucous blanket was observed. During later pregnancy the epithelial cells had a moderately thick, somewhat clumped ruthenium red-positive material associated with the cell membrane. Glycocalyx components of the surface of many bacteria also stained with ruthenium red. The adherence of many types of bacteria to the vaginal epithelial cells appears to be effected by the interaction of polyanionic components on the surface of both the bacterial and epithelial cells.