Some observations on the fine structure of light and dark cells in the gall bladder epithelium of the mouse

Summary Electron microscopic observations have been made of the two epithelial cell types, light barrel-shaped and dark rod-shaped cells in the gall bladder of the mouse.The light cells have a voluminous cytoplasm of low electron opacity in which cell organelles such as mitochondria, elements of granular endoplasmic reticulum, and free ribosomes undergo more or less degenerative changes. However, there are a relatively abundant Golgi apparatus and numerous lysosomal dense bodies. The ultrastructural features of the light cells suggest that they are an aged, degenerative cell type with declining functional activity and a high degree of hydration.The dark cells are characterized by a high concentration of mitochondria and free ribosomes, more or less distinctive elements of granular endoplasmic reticulum, and well developed components of the Golgi apparatus. Such ultrastructural characteristics indicate that the dark cell type has a high synthetic activity.What has been observed in the present study can well be correlated with the results of previous studies on the same cells by methods of light microscopic histochemistry.