Volumetric alterations in tonofibrils during epithelial differentiation in hamster cheek pouch mucosa.

The present report describes the use of stereological procedures to evaluate the volume of tonofibrils present in defined epithelial strata undergoing differentiation. Hamster cheek pouch epithelium was processed for electron microscopy and, following strict sampling procedures, micrographs were obtained from basal, spinous and granular layers. Using stereological point counting techniques, the volume density of tonofibrils present in unit volume of epithelial cytoplasm was determined for each layer. From previously determined estimates of cytoplasmic volume in this tissue, it was possible to calculate the absolute volume of tonofibrils present in the 'average' epithelial cell of each layer. The results describe essentially similar volume density data for each of the layers investigated. However, estimates of tonofibril volume in the 'average' cell increase more than threefold between basal and granular layers. It is concluded that as the epithelial cell differentiates through spinous and granular strata, synthesis of tonofilaments may occur.