Ultrastructure of secretory ameloblasts in a monkey Macaca mulatta.

A 13-month-old animal was fixed by perfusion; the tooth buds of the permanent dentition were removed and prepared for transmission electron microscopy. Secretory ameloblasts were about 35 micrometers long and Tomes processes varied from 6 to 16 micrometers in length. The organelles included a basal nucleus, a Golgi apparatus concentrated in a spherical region about 4 micrometers in diameter in the supranuclear region, rough endoplasmic reticulum situated between the basal and apical terminal webs, and mitochondria dispersed throughout the cytoplasm, including Tomes processes. Many ameloblasts also contained a variety of granules, rosettes of small vesicles, and multivesicular bodies interpreted as parts of a lysosomal or GERL system. Stippled material was observed only at the distal end of the Tomes process of some ameloblasts. The results demonstrate that the Tomes process in the macaque was longer than reported in cats or man, otherwise the secretory ameloblast ultrastructure is similar among the three species.