Biopsies of the gastric fundal mucosa were obtained from 25 dogs and processed for light and electron microscopy. A cell distinguishable from superficial mucous, mucous neck, chief, parietal, or argentaffin cells was observed.
By light microscopy in resin-embedded, methylene-blue-stained sections, this cell was noted to have a prominent apical region which protruded into the gland lumen, a conspicuous terminal web traversed by parallel fibrils, and a crescent-shaped nucleus; secretory granules were absent.
By electron microscopy this cell had the following features: (1) short, stubby microvilli with well developed terminal web, (2) fibril-bundles constituting the cores of microvilli and extending through the apical cytoplasm to the paranuclear region, (3) characteristic vesicles and tubular structures in the apical cytoplasm, (4) spiral structures, and (5) oval dense bodies.
Morphological evidence supported the hypothesis that this is a distinct cell type; it is referred to as a fibrillovesicular (FV) cell.