Fine structural and cytochemical observations on the dental epithelial cells during cap enameloid formation stages in Polypterus senegalus, a bony fish (Actinopterygii).
Tooth germs during cap enameloid formation stages in Polypterus senegalus were investigated by transmission electron microscopy and enzyme histo- and cytochemistry. Enameloid formation was divided into three stages: matrix formation, mineralization, and maturation. The enamel organ consisted of the inner dental epithelial cells, stellate reticulum, and outer dental epithelial cells during cap enameloid formation stages, but no stratum intermedium was found. During the matrix formation stage, the tall inner dental epithelial cells contained well-developed Golgi apparatus, abundant cisternae of rough endoplasmic reticulum and mitochondria. Spindle-shaped vesicles containing a filamentous structure were seen in the distal cytoplasm. During mineralization and maturation stages, many ACPase positive lysosomes were present in the cytoplasm, whereas the organelles were decreased in number. The infoldings of the distal plasma membrane of the inner dental epithelial cells were visible in the mineralization stage but were not marked in the maturation stage. The activity of nonspecific ALPase, Ca-ATPase, and K-NPPase was detected at the plasma membrane of the inner dental epithelial cells during the stages of mineralization and maturation. The results of fine structure and enzyme cytochemistry suggested that the dental epithelial cells were mainly involved in the degeneration and removal of enameloid matrix and in material transportation during the enameloid mineralization and maturation stages, rather than in the enameloid matrix formation. The results also showed that the structure of the dental epithelial cells in Polypterus was different from that in teleosts and gars, but that the function of the dental epithelial cells was similar to that in teleosts possessing well-mineralized cap enameloid.
Sasagawa
Ichiro
I
Department of Anatomy, School of Dentistry at Niigata, Nippon Dental University, Niigata, Japan. ichsasgw@ngt.ndu.ac.jp
Ishiyama
Mikio
M
D000818:Animals; D002113:Calcification, Physiologic; D002454:Cell Differentiation; D003743:Dental Enamel / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure*; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure*; D005399:Fishes; D046529:Microscopy, Electron, Transmission; D014070:Tooth / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure*