12th Ljudevit Jurak International Symposium on
Comparative Pathology
Zagreb
June 1-2, 2001
 

POSTER PRESENTATION
EFFECT OF THYROXIN ON THE ENAMEL ORGAN OF THE RAT MOLAR
O. Koroleva
Medical Academy of Latvia/Riga Stradins University, Departament of Histology, Riga, Latvia
The enamel organ performs different functions during tooth morphogenesis:
Acts as a paracrine organ producing epithelium growth factor, nerve growth factor, and interleukins (Hormia et al., 1998), influences crown and root development, is responsible for the production of enamel, influences the formation of the junctional epithelium connecting the gingiva to the tooth surface (Sawada and Inoue, 1996).
This study aims to elucidate the role of thyroxin in the morphological changes of the rat molar enamel organ during its morphogenesis.
The hyperthyroid model in this experiment was made according to M. Kunegava et al. (1980).
The lower first molars were dissected from rat embryos (12 to 18 days old) and fixed in 10% paraformaldehyde in a 0.1M phosphate buffer (pH 7.4). Teeth germs were embedded in paraffin. Sections were cut at 8-10 km and stained by hematoxyllin-eosin, methilen blue, and PAS.
Immersing the material in the same fixative for 3-4 hours, then post-fixing them in 0.1% osmium tetroxide for 1h performed the fixation for electron microscopy. Tooth germs were embedded in Epon. Ultrathin sections were examined using the IEM 7A transmission electron microscope.
We observed that tooth germ dental epithelium and ectomesenchyme in the control and experimental groups differ in storage of glycogen and secretion of glycosaminoglycans.
The epithelial cells of the enamel organ, while developing from bud to bell stages, exhibit differences in proliferation, migration, and apoptosis. We found differences in the sequences of the formation of different types of cellular junctions between epithelial cells of the enamel organ. Changes in the structural and chemical composition of the basal lamina were detected. We suggest that the epithelial-mesenchymal interactions might be changed. It will play a crucial role in the events of early tooth morphogenesis.

References:

  1. Hormia M. et al. J. Dent. Res. 1998, 77 (7) :1479
  2. Kunegava M. et al. J. Endocrinology. 1980, 87:431
  3. Sawada T. et al. J. Periodont Res., 1990, 25: 372
Poster Presentation