Costacurta L, de Carvalho C A, König B, Bilotta J A
Anat Anz. 1976;139(1-2):165-79.
An electronmicroscopical study of the enamel organ of the upper incisors germs of Wistar rats was performed to analyse the ultrastructural features of the cells of the inner epithelium, the intermediate layer and the stellate reticulum, during preimary, young, transitional and mineralized enamel phases of amelogenesis. So, it was observed that the mitochondria in the ameloblasts are ovoid before the beginning of the enamel matrix formation and in the primary and young enamel phases. However, in the transitional and mineralized phases, these organelles are long and tortuous and some are characterized by a compact structure. In the cells of intermediate layer and stellate reticulum, the mitochondria are ovoid until the beginning of the mineralized phase. At the ending of this phase, these organelles are very long and present irregular form; many of them show also a compact structure. The "zonula adhaerens" could be observed only in the ameloblasts of the primary and young enamel phase. The cytoplasm of ameloblasts, during primary and young enamel phases is characterized by an abundance of free ribosomes and a branular endoplasmic reticulum; but during transitional and mineralized enamel phases, the cytoplasm of these cells shows little granular endoplasmic reticulum and free ribosomes, but ehe agranular endoplasmic reticulum is present. The granular endoplasmic reticulum and free ribosomes are abundant in the cells of the intermediate layer and stellate reticulum at the ending of the young enamel phase, in the transitional enamel phase and in the beginning of the minieralized phase. During different phases of amelogenesis, in the three above referred layers of the enamel organ, were also studied the features of the Golgi apparatus the presence and topographic distribution of the pigment granules, as well as the lysosomes, desmosomes and the tonophibriles.
对Wistar大鼠上颌切牙牙胚的釉器进行了电子显微镜研究，以分析成釉细胞、中间层细胞和星网状层细胞在釉质形成的初级、年轻、过渡和矿化阶段的超微结构特征。结果发现，在釉质基质形成开始前以及初级和年轻釉质阶段，成釉细胞中的线粒体呈椭圆形。然而，在过渡和矿化阶段，这些细胞器长而弯曲，有些具有紧密的结构。在中间层和星网状层细胞中，线粒体在矿化阶段开始前呈椭圆形。在这个阶段结束时，这些细胞器非常长，形态不规则；其中许多也显示出紧密的结构。“黏着小带”仅在初级和年轻釉质阶段的成釉细胞中可见。在初级和年轻釉质阶段，成釉细胞的细胞质富含游离核糖体和粗面内质网；但在过渡和矿化釉质阶段，这些细胞的细胞质显示粗面内质网和游离核糖体较少，但存在滑面内质网。在年轻釉质阶段结束时、过渡釉质阶段以及矿化阶段开始时，中间层和星网状层细胞中的粗面内质网和游离核糖体丰富。在釉质形成的不同阶段，还研究了上述釉器三层中高尔基体的特征、色素颗粒的存在和拓扑分布，以及溶酶体、桥粒和张力原纤维。
