Electron microscope study on endocrine cells and tumor cells in the glandular stomach of Praomys (mastomys) natalensis.

Endocrine cells in the normal glandular stomach and gastric carcinoids of mastomys were observed by electron microscopy and at least five types of endocrine cells, EC, G, D-like, R (round-granule) and ECL cells were identified. Of these, four types excepting G cells were recognized in the fundic mucosa. Characteristic in mastomys was a scarcity of endocrine cells in the fundic mucosa, where ECL and R cells were predominant types. Silver impregnation methods including SEVIER-MUNGER's argyrophil reaction of our own modifications were applied to tissue sections and the endocrine cells were examined by electron microscopy. Only EC cells revealed argentaffin granules under the light and electron microscope. R, ECL and some of the G cells were non-argentaffin and argyrophil in reaction and D-like cells and the rest of the G cells failed to show even an argyrophil reaction. Granules of mastomys carcinoid cells, as noted in the previous reports, were non-argentaffin but faintly argyrophil. Mastomys gastric carcinoids were studied by the same method, with special reference to the parent cells of this particular neoplasia. Noteworthily, mastomys gastric carcinoids arise mostly from the fundus, the area where R and ECL cells mainly occur in normal animals. The neoplasms are composed of cells containing granules resembling partly those of R cells and partly those of ECL cells. ECL cells and neoplastic cells in the present investigation have a similar reactivity to SEVIER-MUNGER's method. Considering the generally accepted fact that neoplastic cells may not fully duplicate their parent cells in cytological features, it seems reasonable to presume that R and/or ECL cells might be the parent cells of the mastomys gastric carcinoids. In connection with this assumption histamine has been demonstrated to be produced both in mastomys carcinoid cells and normal ECL cells.