| Abstrakt: |
To determine morphological changes of the Golgi apparatus during rat amelogenesis, the incisors fixed with glutaraldehyde or glutaraldehyde-formaldehyde mixture were block stained by the Ur-Pb-Cu technique and/or were examined by freeze-fracture replication. The Golgi apparatus of differentiating ameloblasts were not yet well developed and consisted of only from four to five cisterns and the Golgi vesicles. Morphological evidence of condensing-vacuole formation and the occurrence of GERL was already detected at this stage. The Golgi apparatus of secretory ameloblast had reached its maximum expansion and consisted of from four to seven flattened cisterns, numerous Golgi vesicles, and many condensing vacuoles presumably arising from the dilated margins of trans-side cisterns. The morphological polarity of the apparatus was now clear, and the elongated Golgi cisterns formed a continuous, intracellular membranous system. The evident Golgi region formed by several Golgi apparatus in the supranuclear cytoplasm included GERL, multivesicular bodies (MVBs), and many secretion granules. The Golgi apparatus of both ruffle-ended and smooth-ended maturation ameloblasts decreased in extent, and consisted of four to five cisterns and small and large spherical vesicles. Small spherical vesicles were budding from the whole Golgi cisterns, whereas large ones were produced from both the trans-side Golgi cisterns and GERL. GERL was well developed in maturation ameloblasts. Condensing vacuoles and secretion granules were no longer observed. Throughout amelogenesis, MVBs were localized in the Golgi region; and MVB inner vesicles were similar to the Golgi vesicles. From these results, it is strongly suggested that, throughout amelogenesis the Golgi apparatus is concerned with the formation of secretion granules and lysosomes and is closely associated with ameloblast cellular functioning. [ABSTRACT FROM PUBLISHER] |
