Journal of Dental Research, Vol 63, 622-628, Copyright © 1984 by International & American Associations for Dental Research Online Journals
A freeze-fracture study of ruffle-ended post-secretory ameloblasts
P. R. Garant, A. Nagy and M. I. Cho
The post-secretory portion of the rat incisor enamel organ was prepared for
routine transmission electron microscopy and freeze-fracture replication in
order to define further the structural surface features of the ruffle-ended
ameloblasts. Surface views of the distal plasma membrane of the
ruffle-ended ameloblasts revealed a well-developed zonula occludens
junction with from six to ten rows of tight junctional strands. Gap
junctions were also observed just proximal to the tight junctional strands.
The membranes of the ruffled border contained a rich supply of
intramembrane particles (IMP). The IMPs were approximately 7 to 8 nm in
diameter and preferentially located on the P-face profiles of the membrane.
The density of IMPs on the membranes of the ruffled border was higher than
that on the lateral borders of the cell. It is suggested that the IMPs of
the ruffled border may represent enzymatic proteins in the basal cell
membrane of absorptive ameloblasts. In addition, the large,
highly-developed zonula occludens appeared structurally capable of sealing
the intercellular spaces between the ruffle-ended ameloblasts.
