Nucleoli of human odontoblasts

Abstract

Nucleoli of human odontoblasts were studied in smears stained with buffered toluidine blue at pH 5, for the demonstration of RNP-containing structures, including nucleoli. The odontoblasts were obtained from 5 premolars removed for orthodontic reasons. Three teeth were fully developed, in the two others the apical foramen was still widely open. One hundred odontoblasts were examined in each case. The results show that human odontoblasts possess 1–4 nucleoli, the mean nucleolar coefficient being 2.12. Out of all odontoblasts from fully developed teeth, 97–99 per cent contained ring-shaped nucleoli typical for the reversibly inhibited synthesis of the RNA. In two less developed teeth, 12–14 per cent out of all the odontoblasts contained nucleoli with nucleolonemas and/or compact nucleoli, which represent active nucleolar types in the production of RNA. The nuclear diameter of odontoblasts was 11.6 μm, the nucleolar diameter of ring-shaped nucleoli was 0.72 μm and that of active nucleoli 1.50 μm. The presence of ring-shaped nucleoli in differentiated odontoblasts suggests that these cells are in a reversible state which can be stimulated for production of new ribonucleoprotein structures and thus for the synthesis of proteins engaged in the formation of reparative dentine.