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Electron microscopic autoradiography of Ca45 during dentinogenesis

Summary

Calcium transfer from the capillaries of the dental papilla to predentine and dentine has been studied by quantitative electron microscopic autoradiography in toothgerms of newborn cats following intravenous injection of Ca45. Two transfer pathways of almost identical importance were demonstrated. The direct pathway from the capillaries followed the intercellular spaces of the dental papilla and between the odontoblasts to reach dentine via predentine. The second route involved passage through the intercellular spaces of the dental papilla, and then a transcellular transfer through the odontoblast. Of the odontoblast organelles, the mitochondria and the Golgi apparatus were most heavily and progressively labelled at 5 min, 30 min. and 1 h. after intravenous injection. The calcium diffused throughout the cytoplasm of the odontoblast process without being associated with the dense elongated vesicles. At 6 hours, the maximum radioactivity was observed in the intertubular dentine, especially along the enamel-dentine junction.

Résumé

Le trasfert du Ca45 à travers la papille dentaire et la couche des ondontoblastes, vers la prédentine et la dentine, a été étudié par autoradiographie quantitative en microscopie électronique, au niveau de germes dentaires de chats nouveau-nés, après injection intraveineuse. Deux voies de transfert, d'importance sensiblement égale, ont pu être mises en évidence. La voie directe emprunte, à partir de la lumière des capillaires, les espaces intercellulaires de la papille dentaire et des odontoblastes, pour atteindre la dentine via la prédentine. La seconde voie consiste, après passage par les espaces extracellulaires de la papille dentaire, en un transfert intracellulaire par l'odontoblaste. Parmi les organelles, ce sont les mitochondries, puis l'appareil de Golgi qui sont progressivement les plus marqués à 5 min., 30 min. et 1 h. après injection intraveineuse. Le calcium diffuse dans le cytoplasme des prolongements odontoblastiques sans être associé aux vésicules denses allongés. A 6 heures, le maximum de radioactivité est observé dans la dentine intercanaliculaire et en particulier, au voisinage de la jonction émail-dentine.

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Correspondence to Prof. R. M. Frank.

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Nagai, N., Frank, R.M. Electron microscopic autoradiography of Ca45 during dentinogenesis. Cell Tissue Res. 155, 513–523 (1974). https://doi.org/10.1007/BF00227012

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Key words

  • Dentinogenesis
  • Ca45
  • Autoradiography, Electron microscopy