The purpose of this study was to examine the changes of the proliferating zone of articular cartilage in the mandibular condyle from aged rat by light and electron microscopy. For this study, twenty rats of the 1, 2 weeks and 1, 3, 12 months of age were used.
Animal were perfused through the left venticle with 2.5% glutaraldehyde under anesthesia with sodium pentobarbital.
For light microscopy, condyle processes were removed and decalcified in 0.1M EDTA with glutar aldehyde solution for 2 weeks. Each specimen was processed for paraffin embedding, sectioned at 6um, stained with hematoxylin and eosin, and viewed the proliferating zone of articular cartilage in the mandibular condyle.
For transmisssion electron microscopy, the specimen was removed, decalcified in O.IM EDTA with 2:5% glutaraldehyde solution for two weeks. The specimens-were rinsed with phosphate buffer solution (pH 7..2-7.4) and post fixed with 2% osmium tetroxide at 4°C for two weeks. Thereafter the specimens were dehydrated within alcohol series, infiltrated with propylene oxide and embedded within Epon 812 resin. The ultrathin sections were made and viewed the proliferating zone of articular cartilage in mandibular condyie.
The results were as follows:
1. In the 2 weeks age group, the proliferating zone in the cartilage of mandibular condyle was formed, and the chondrocyte in the proliferating zone had a poorly developed organelles in the cytoplasm and the cytoplasmic processes were appeared.
2. In the 1 month age group, the thickness of the proliferating zone in the cartilage of mandi-bular condyle was greatly increased.and the chondrocyte in the proliferating zone contained a well developed nucleus and a organelles in the cytoplasm such as rER, Golgi appratus and mitochondria.
3. In the 3 months age group, the thickness of the proliferating zone in the cartilage of the mandibular condyle was somewhat decreased and the chondrocyte in the proliferating zone became indistinct to boundary of the nucleus and a organelles in the cytoplasm, and was more or less atrophied and the cytoplasmic processes were also atrophied.
4. In the12 months age: group, the distinction of the proliferating zone in the cartilage of the mandibular condyle was difficult and the chondrocyte in the proliferating zone was characterized with a irregularly condensed chromatin, a large number of lipid droplets and lipofuscin granules, formation of vacuoles, disappearance and -destruction of cellular organelles, loss of cytoplasmic processes.
|