Khaejornbut J, Wilson D J, Owens P D
Department of Oral Biology, Prince of Songkla University, Haadyai, Thailand.
J Anat. 1991 Dec;179:85-96.
The lamina of the first mandibular molar teeth of rats, age range 13 d intrauterine (i.u.) to 16 d postnatal (p.n.), was examined by light and transmission electron microscopy to establish histological baselines of its development and fate. All material was obtained from animals anaesthetised with ether, killed by cervical dislocation and prepared by routine methods for both types of examination. Contrary to earlier reports that the lamina remains intact throughout development, mesenchymal elements disrupt the lamina. These were seen first at 19 d i.u., as collagen-filled bays in the basal epithelial layers, associated with partial loss of related basal lamina. In the early stages, collagen deposition was limited and it was not obviously preceded by epithelial cell death or transformation, even though many bay-related cells showed lipid and glycogen accumulations. Later disruption of the lamina showed more mesenchymal cells as well as collagen in deeper spaces. After the onset of tooth eruption, mesenchymal cells external to and within the lamina contained lysosomal bodies and these plus evidence of related epithelial cell death and capillaries in the laminar spaces became more and more apparent. Similar collagen deposits were observed in a successional tooth primordium, which appeared at term but eventually aborted between days 5 and 10 p.n. Thus disruption of the lamina by connective tissue began earlier than has been reported previously and progressed as the tooth erupted towards the oral cavity. The evidence suggests that this disruption is initiated and sustained by mesenchymal cell activity rather than by programmed cell death or transformation of the epithelium.
对年龄范围为子宫内13天至出生后16天的大鼠第一下颌磨牙牙板进行了光镜和透射电镜检查，以建立其发育和命运的组织学基线。所有材料均取自用乙醚麻醉、经颈椎脱臼处死的动物，并通过常规方法制备用于两种类型的检查。与早期报道称牙板在整个发育过程中保持完整相反，间充质成分会破坏牙板。这些最早在子宫内19天时可见，表现为基底上皮层中充满胶原的凹陷，伴有相关基底膜的部分缺失。在早期阶段，胶原沉积有限，且在其之前并没有明显的上皮细胞死亡或转化，尽管许多与凹陷相关的细胞显示出脂质和糖原积累。牙板后期的破坏显示在更深的间隙中有更多的间充质细胞以及胶原。在牙齿萌出开始后，牙板外部和内部的间充质细胞含有溶酶体，这些以及层状间隙中相关上皮细胞死亡和毛细血管的证据变得越来越明显。在一个相继牙胚中观察到类似的胶原沉积，该牙胚足月出现，但最终在出生后第5天至第10天之间退化。因此，结缔组织对牙板的破坏比以前报道的要早开始，并随着牙齿向口腔萌出而进展。证据表明，这种破坏是由间充质细胞活性引发和维持的，而不是由上皮细胞的程序性死亡或转化引起的。
