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Histologic differentiation and motility of rat stomach.

An ultrastructural and immunohistochemical study was done to investigate the normal developmental process of rat gastric wall. Neuronal processes were observed on the external side of immature muscle cells on gestational day 15, and Auerbach's plexus was found on gestational day 18, after which neuronal elements extended just under the subepithelial area. Myofilaments appeared in undifferentiated mesenchyme cells on gestational day 15. On day 17, stomach was responsive to Ach stimulation. On the day after the initiation of gastric motility, gastric glands started to form on the mucosal surface. At the same developmental stage, some parts of the mucosal epithelium and the submucosal connective tissues were stained with antiserum against tenascin. Endocrine and parietal cells appeared in the mucosal epithelium on gestational day 19. Dense secretory granules on the apical surface of mucosal epithelium were increased between day 20 and 21. The cytoplasmic organelles gradually developed with advancing fetal age. We suggest that tenascin may play a role in gastric gland formation and that there are some relationships between gastric gland formation and gastric motility. We believe that the development of subepithelial tissues may be closely associated with epithelial growth.