We investigated the expression of Ca++ pump epitopes during enamel and dentin mineralization in the rat incisor. Secretory and maturation ameloblasts were studied as well as odontoblasts, using a monoclonal antibody (5F10) against human erythrocyte plasma membrane Ca++, Mg(++)-ATPase. A progressive increase in staining intensity in ameloblasts and the odontoblasts was observed beginning with the onset of mineralization. The mainly membrane-related labeling of ameloblasts showed variable intensity depending on the stage of enamel formation, whereas that of the odontoblasts showed even intensity during continued dentinogenesis. Staining of papillary cells was evident only during enamel maturation. Western blot analysis of freeze-dried ameloblasts was also used to determine the molecular weight of the Ca++ pump epitopes as well as the distribution and relative concentration of epitopes at each stage. An immunoreactive band of MW 140 KD and lower molecular weight bands that are more intense in late than in early maturation were demonstrated. Our studies suggest that the expression of plasma membrane Ca++ pump parallels the progression of mineralization in rat incisor enamel and dentin.
Osteocytes communicate through a canalicular system that maintains
the vitality and mineral metabolism of bone. Casting the vascular
canals and canaliculi of compact bone with methacrylate and
viewing them with scanning electron microscopy shows their extent
and relationships. Confocal laser scanning microscopy of the
same specimen before corrosion establishes the degree of
calcification of the different tissue components. These methods
were used to compare basal with alveolar compact bone in the
rat mandible at different ages. Sections of the mandibular molar
region were placed in a methacrylate resin. After polymerization
and study with confocal microscopy, the organic matrix was removed.
Juvenile rats had large irregular central vascular canals and
lacunae that were more concentric in the basal than the alveolar
bone. Cast lacunae were round, and the canaliculi from these
lacunae were short and thick in both bones. Adult rats had regular
concentrically arranged lacunae in the basal bone. Cast lacunae
were ellipsoid and flatter in the basal bone than in the alveolar
bone. The intercommunicating canaliculi were increased and
canaliculi had more branching than the juvenile rats. The aged
rats had fewer vascular canals, lacunae, and canaliculi and
had osteoporotic changes. The cast lacunae were slender and
flat especially in the basal bone. The porosity of the mandible
became more pronounced in the alveolar than in the basal bone
with aging. The canaliculi of mandibular compact bone thinned
and developed extensive branching with adulthood but decreased
in size and number with advanced age. Lacunae proceed from the
large circular structures of youth to the flat forms of the
aged. These studies show that the internal structure of compact
bone changes with age and mirrors its functional state.
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