ELECTRON-MICROSCOPIC STUDIES OF NUCLEAR-BODIES IN THE HUMAN PERIODONTAL-LIGAMENT

Nuclear bodies are proteinaceous structures containing ribonucleoprote ins found throughout the cell nucleus. The presence of simple and comp lex nuclear bodies in fragments of periodontal ligament obtained from IO teeth and in fibroblast-like cells cultured from the same specimens was studied. Nuclear bodies were seen in fibroblasts and less commonl y in endothelial cells from all periodontal ligament specimens in vivo and also in periodontal ligament fibroblasts cultured in vitro. The m ajority of the nuclear bodies were of the simple type, viz. spherical, filamentous and surrounded by a clear halo. Complex nuclear bodies we re also identified, mainly in fibroblasts. They were spherical and sur rounded by a filamentous capsule but their core was granular or filame ntous and sometimes exhibited a concentric arrangement. Some of the bo dies resembled, and were close to nucleoli; others were similar to lip id bodies and were free within the nucleoplasm. Although recent studie s have suggested that certain types of nuclear bodies may be involved in active transcription, the function of the nuclear bodies in the per iodontal ligament remains unknown.