Hasty D L
Anat Rec. 1983 Apr;205(4):405-20. doi: 10.1002/ar.1092050406.
Differentiation of preodontoblasts to odontoblasts and preameloblasts to ameloblasts during development of the mouse mandibular incisor proceeds in a gradient from the area of the odontogenic organ, where undifferentiated ectomesenchymal and epithelial cells proliferate, toward the incisal tip where mature tooth tissues, dentin and enamel, are present. The freeze-fracture technique has been used in the work presented here to study cell membrane ultrastructure of preodontoblasts and preameloblasts at several stages of differentiation. At early stages of differentiation, cuboidal preameloblasts are joined together distally by numerous gap junctions. Relatively fewer junctions occur elsewhere on the lateral plasma membranes, but gap junctions frequently occur proximally between preameloblasts and stratum intermedium cells. As differentiation proceeds and the cells become columnar, distal and proximal junctions persist. Tight junctions, however, were not observed at any of the stages studied. Intramembrane particle concentration of the lateral preameloblast plasmalemma appears to increase as differentiation proceeds. Odontoblasts are also joined distally by numerous gap junctions which persists through later stages of differentiation. Although odontoblast cell processes were observed to project toward the preameloblast layer, no clear points of cell to cell contact or defined intercellular junctions between the two cell types were observed.
在小鼠下颌切牙发育过程中，前成牙本质细胞向成牙本质细胞的分化以及前成釉细胞向成釉细胞的分化，以一种梯度方式进行，从牙源性器官区域（未分化的外胚间充质细胞和上皮细胞在此增殖）向切端（存在成熟牙组织牙本质和釉质的部位）发展。本文所展示的研究工作运用了冷冻蚀刻技术，来研究前成牙本质细胞和成釉细胞在几个分化阶段的细胞膜超微结构。在分化早期，立方形的前成釉细胞在远端通过大量缝隙连接相连。在外侧质膜的其他部位连接相对较少，但在前成釉细胞与中间层细胞之间的近端经常出现缝隙连接。随着分化进行，细胞变为柱状，远端和近端连接依然存在。然而，在所研究的任何阶段均未观察到紧密连接。随着分化进行，前成釉细胞外侧质膜的膜内颗粒浓度似乎增加。成牙本质细胞在远端也通过大量缝隙连接相连，这些连接在分化后期依然存在。尽管观察到成牙本质细胞的细胞突起伸向成釉细胞层，但未观察到两种细胞类型之间明确的细胞间接触点或特定的细胞间连接。
