Yamada M, Ozawa H
Arch Histol Jpn. 1978 Sep;41(4):309-23. doi: 10.1679/aohc1950.41.309.
Tooth germs of killifish were examined by both ultrastructural and cytochemical methods. The ultrastructure of the dentin in the early calcification stage of its development resembled that of mammals. Numerous extracellular membrane-bounded vesicles, matrix vesicles, were seen in the predentinal space, especially abundantly in the basal portion of the tooth germ. They were more numerous and more uniform in appearance than in any other higher vertebrates. Where calcification was going to start, slightly identifiable needles of apatite crystals were found in the vesicular structures. Crystals increase in number filling up the vesicles and then ther surroundings, finally to form many calcified spherules. Where calcification was more extensive, the matrix vesicles were no longer visible having been buried calcified among spherules. Contrary, to popular belief, there was no relationship seen between collagen fibrils and the initial deposits of minerals, that is, collagen fibrils did not seem to work as the initial site of calcification. Instead, matrix vesicles and plasma membranes of odontoblasts likely were involved in calcification as they both showed alkaline phosphatase activity. The ultrastructural and cytochemical findings from this study thus indicated that calcification of the killifish tooth germs was initiated not in the enamel, but in their dentin by the matrix vesicles which were liberated into the dentin matrix from odontoblasts mainly by way of fragmentation of cell processes.
用超微结构和细胞化学方法对鳉鱼的牙胚进行了研究。在其发育的早期钙化阶段，牙本质的超微结构与哺乳动物的相似。在前期牙本质空间可见大量细胞外膜包被的小泡，即基质小泡，在牙胚基部尤为丰富。它们比任何其他高等脊椎动物的数量更多且外观更均匀。在即将开始钙化的部位，在小泡结构中发现了略微可辨认的磷灰石晶体针状物。晶体数量增加，充满小泡及其周围环境，最终形成许多钙化小球。在钙化更广泛的部位，基质小泡不再可见，已被埋在小球之间钙化。与普遍看法相反，未发现胶原纤维与矿物质的初始沉积之间存在关系，即胶原纤维似乎不是钙化的起始部位。相反，成牙本质细胞的基质小泡和质膜可能参与了钙化，因为它们都显示出碱性磷酸酶活性。因此，本研究的超微结构和细胞化学结果表明，鳉鱼牙胚的钙化不是在釉质中开始，而是在牙本质中由基质小泡启动，这些基质小泡主要通过细胞突起的碎片化从成牙本质细胞释放到牙本质基质中。
