| To explore the relationship between aging of Pekingese and degeneration of intervertebral disc, histological changes of thoracolumbar intervertebral discs in Pekingese of different ages were observed in comparison with those in patients and large-sized crossbreed dogs. The timing of the epiphysis fusion of vertebra was observed and the index of intervertebral discs was determined on the lateral roentgenogramoThe results showed : ①Epiphysis fusion in Pekingese began around 8-9 months of age, and the sequence of its development was gradually from thorax to lumbar with the value of T11-12/T12 being the smallest and L6-7/L7 being the largest in terms of index of intervertebral discs. The index of the intervertebral discs before the accomplishment of the epiphysis fusion was higher than that of intervertebral discs after the accomplishment of the epiphysis fusion , and the changes were extremely prominent when compared with that in paitients.②The degeneration of intervertebral disc was observed more clearly in 2-3 year-old than in 1-2 year-old or less than 1 year-old Pekingese. These degenerations included transform or rupture of annulus fibrousus and extrusion of the nucleus pulposus and annulus fibrousus. It was found that the frequency and degree of thoracolumbar disc degeneration was higher than those of lumbar disc degeneration. ③The thickness of calcification layer was up with age in 1-2 year-old and less than 1 year-old Pekingese, while the thickness of noncalcification layer was quite the reverse. The ratio of the thickness of calcification layer to the thickness of cartilaginous end-plate with age was as follows: 32.4%(1-2mos.), 46.7%(3-4mos.), 48.0%(5mos.), 59.8%(10-11mos.) and 64.6%(1-2yrs.). The average thickness of cartilaginous end-plate of Pekingese was 105.50±13.35μm, whereas that of the large-sized crossbreed dogs was 97.61±9.05μm. ④The number of blood vessels and marrow spaces in the cartilaginous end-plate of Pekingese of different ages was 9.7 + 2.8(l-2mos.), 11.5±2.9(3-4mos.) and 12.5±4.4(5mos.), respectively. The largest was found in 10-11 month-old Pekingese(22.3±4.1), and then it dropped to 13.3±2.2 in 1-2 year-old Pekingese and 10.2±2.2 in 2-3 year-old Pekingese, while the smallest(7.4± 3.5) was found in patients. Compared with the results in Pekingese, it was much higher in large-sized crossbreed dogs with the number of 38.5±5.3(1-2mos.), 38.3±3.6(6mos.) and 15.0±4.7(1-2yrs.). ⑤ The type of cell in the nucleus pulpous varied with age. There were no other cells but notochord cells being observed before 1-2 months of age. After 3 month of age, there were some changes around the periphery of the nucleus pulpous. By 5 months old, 8 types of cell were seen in the nucleus pulpous and cartilage cells were abundant. As aging up, the notochord cells were getting far less, and almost not observed by 2-3 years of age, then all disappeared by 5 years old. Those cells were not found at all in the patients aged 4 and 7 years. In contrast, before one and half a year there were chiefly notochord cells in the nucleus pulpous in large-sized crossbreed dogs. |
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