Electron microscopic observations on immature chief and parietal cells in the mouse gastric mucosa.

Panoramic and conventional electron microscopic examinations were conducted on the mouse gastric mucosa with special reference to the distribution of immature forms of chief and parietal cells. Immature chief cells were occasionally present as high as the transitional region between the isthmus and neck of the gland, although their main localization was at the uppermost part of the base. Immature parietal cells were found in the lower part of the isthmus and throughout the neck. Cells at the same stage of maturation were often present side by side. Some cells in the neck, showing the characteristic morphology of immature parietal cells, also contained mucous granules resembling those in the mucous neck cells (intermediate cell). These findings suggest that: a chief cell may be formed by direct differentiation from the stem cell in the isthmus as well as by possible maturation of the mucous neck cell and mitotic division of the immature chief cell itself; and a parietal cell can be formed in the lower part of the isthmus and throughout the neck by direct differentiation from the stem cell or by mitotic division of the cell already determined to be a parietal cell as well as maturation of the intermediate cell.