The fine morphology of the basal cell in the frog's taste organ

We investigated the fine morphology of basal cell in the frog's taste organ by means of transmission electron microscopy. Results show that basal cells are placed at the base of the disc and are highly polarized; the cell body is peripherally located and a long cell process reaches the central region of the taste disc without branching. The cell body contains the nucleus, the Golgi apparatus and large lysosomes; junctions between more peripherally located 'marginal' cells prevent passage of macromolecules from oral ambient to basal cells as shown by horse-radish peroxidase experiments. The cell process, running just over the basement membrane in the taste disc epithelium, is rich in microtubules, filaments and clustered secretory granules arranged near the plasmalemma. Nerves interrupting the basement membrane make synaptic-like junctions with basal cells. The cell process ends in the central region of the taste disc; here, the basal cell is expanded to contain filaments, secretory granules and mitochondria in characteristic arrangement and contacts intraepithelial nerve endings as well as basal processes of sensory and supporting cells. Marginated granules are found where basal cell contacts nerve ending and also where nerve and sensory cells contact basal cell. Our findings are consistent with the hypothesis that basal cells are under nerve control and that they may have a diffuse (paracrine) influence on neighbouring cells in the frog's taste organ.