Cellular and nuclear volumetric alterations during differentiation of normal hamster cheek pouch epithelium

The aim of this investigation was to determine whether volumetric changes occurred in differentiating layers of stratified squamous epithelium. Samples of cheek pouch mucosa from 5 hamsters were obtained, prepared for electron microscopy using carefully controlled methods, and electron micrographs obtained from defined basal, spinous and granular layers of the epithelium. Stereological point counting procedures were used to determine the ratio of nucleus to cytoplasm for each of the defined cell layers. From direct measurement of nuclear profiles, major and minor axes were transformed to diameters of circles of equivalent area and it was thus possible to obtain an estimate of nuclear volume. Using the previously determined nuclear-cytoplasmic ratio, the volume of cytoplasm and hence cell volume, could be estimated for the cell layers. Between basal and granular layers, nuclear-cytoplasmic ratios decreased from 0.42 to 0.08, whereas cytoplasmic and cellular volumes increased progressively from 248 to 1052 microns 3 and from 352 to 1144 microns 3, respectively. Nuclear axial ratios were highest in the granular layers. These methods can be used in a variety of comparative ultrastructural studies of epithelia, and will also prove valuable in generating additional biological information from more conventionally presented stereological data.