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R Takiguchi

Publications and source records attributed to R Takiguchi.

At least 37 records · Page 2Linked to original sources
PubMed1986

Correlated observations and analysis of maturation-ameloblast morphology and enamel mineralization.

A combined HCl-collagenase digestion technique and scanning electron microscopy were used to isolate the enamel organ and to confirm the presence of maturation ameloblasts of both ruffle-ended (RA) and smooth-ended (SA) types on maturing enamel in kitten permanent tooth germs. EDTA perfusion of animals fixed with aldehyde produced two or three belt-like shallow grooves (from 30 to 100 micron wide) running horizontally through the maturing enamel surface, coinciding closely with the SA distribution pattern. In animals that had been perfusion-fixed with unbuffered osmium tetroxide containing 2.5% potassium pyroantimonate, SEM-EDX analysis detected K in a superficial enamel layer overlaid by the SA layer. Potassium concentration decreased gradually toward the deeper layers. Very little K penetrated the enamel under the RA layer. Energy-dispersive x-ray analysis of Ca and P concentrations in the enamel revealed an even distribution of these elements throughout the superficial layer of maturing enamel. These results suggest that the SA layer forms an access route for K and EDTA and that, in spite of the obvious morphological and functional differences between RA and SA, the maturing enamel surfaces overlaid by these two cell types show similar degrees of mineralization.

Ameloblasts↗
PubMed1985

Formation of tight and gap junctions in the inner enamel epithelium and preameloblasts in human fetal tooth germs.

Human fetal primary tooth germs in the cap stage were fixed with a glutaraldehyde-formaldehyde mixture, and formative processes of tight and gap junctions of the inner enamel epithelium and preameloblasts were examined by means of freeze-fracture replication. Chains of small clusters of particles on the plasma membrane P-face of the inner enamel epithelium and preameloblasts were the initial sign of tight junction formation. After arranging themselves in discontinuous, linear arrays in association with preexisting or forming gap junctions, these particles later began revealing smooth, continuous tight junctional strands on the plasma membrane P-face and corresponding shallow grooves of a similar pattern on the E-face. Although they exhibited evident meshwork structures of various extents at both the proximal and distal ends of cell bodies, they formed no zonulae occludentes. Small assemblies of particles resembling gap junctions were noted at points of cross linkage of tight junctional strands; but large, mature gap junctions no longer continued into the tight junction meshwork structure. Gap junctions first appeared as very small particle clusters on the plasma membrane P-face of the inner enamel epithelium. Later two types of gap junctions were recognized: one consisted of quite densely aggregated particles with occasional particle-free areas, and the other consisted of relatively loosely aggregated particles with particle-free areas and aisles. Gap junction maturation seemed to consist in an increase of particle numbers. Fusion of gap junctions in the forming stage too was recognized. The results of this investigation suggest that, from an early stage in their development, human fetal ameloblasts possess highly differentiated cell-to-cell interrelations.

Ameloblasts↗
PubMed1984

Intercellular junctions in the cells of the human enamel organ as revealed by freeze-fracture.

Examined by thin sections and freeze-fracture replication techniques, secretory ameloblasts possessed two sets of the junctional complexes at both proximal and distal ends of the cell bodies, which consisted of tight junctions and occasional gap junctions and desmosomes. The proximal tight junction was fascia occludens, whereas the distal tight junction was zonula occludens. Between adjacent ameloblasts, mature gap junctions were frequent. The stratum-intermedium cells were connected to each other and to the stellate-reticulum cells and ameloblasts by well-developed desmosomes, gap junctions and fascia or macula-type tight junctions. Stellate-reticulum cells were inter-connected by many extensive cytoplasmic processes, in which well-developed desmosomes, small gap junctions and occasional macula-type tight junctions appeared. Thus fascia or macula-type tight junctions as well as many desmosomes seem to serve in mechanical, cell-to-cell adhesion during tooth formation. Frequent and large gap junctions between adjacent stratum-intermedium cells and between the stratum intermedium and the base of the ameloblast suggest that, in relation to enamel formation, these two cell layers form a functional unit.

Ameloblasts↗