Distribution of type IV collagen and laminin in the gingival capillary basement membrane from streptozotocin-induced diabetic rats was investigated using immunoelectron microscopy. Both type IV collagen and laminin were found throughout the basement membrane. Quantitative analysis revealed that the immunoreactive area for laminin did not change with age, and the width of laminin deposition remained constant, even when diabetes was induced in the animals. However, the immunoreactive area for type IV collagen thickened with age. Further, the width of type IV collagen in the basement membrane increased markedly 36 weeks after diabetes was induced. It was concluded that the thickening of the gingival capillary basement membrane in experimentally induced diabetic rats was due an increase of type IV collagen deposition.
Glycosaminoglycans (GAGs) in monkey palatal lamina propria plus both fatty and glandular zones of palatal submucosa were compared. Chemical analysis revealed that GAG contents of the lamina propria and glandular zone were higher than that of the fatty zone. The four GAGs identified by electrophoretic analysis were hyaluronic acid, dermatan sulfate, chondroitin sulfate and heparan sulfate. Each mucosal layer contained all four GAG components. The predominant GAG in both the lamina propria and glandular zone was dermatan sulfate followed by hyaluronic acid. The reverse situation (predominant hyaluronic acid, less prominent dermatan sulfate) was noted in the fatty zone of the submucosa. The three tissue regions showed different molar ratios of unsaturated chondroitin sulfate disaccharides. The ratio of ΔDi-4S to ΔDi-6S was lower in the lamina propria than in either the fatty or glandular submucosal zones.
In order to elucidate the relationship of tumor invasion with the expression of E-cadherin and type IV collagen, I carried out immunohistochemical studies on a human gingival carcinoma xenograft line, GK-1, in nude mice. The transplanted tumors were divided into four stages of progression for examination at 5, 7, 10 and l5 weeks after transplantation based on the value of the labeling index for BrdU. The labeling index for BrdU showed its greatest value at seven weeks after transplantation. There was a marked decrease of E-cadherin expression in the tumors at seven weeks after transplantation, and the amount of expression negatively correlated with the labeling index. In addition, the expression of type IV collagen decreased, having a positive correlation with the expression of E-cadherin, and it became discontinuous and unstable. From the above findings, both the decreased expression of E-cadherin and the discontinuous expression of type IV collagen suggest that the tumor cells maintain high invasiveness.
In order to investigate the developmental conditions of third molars in Japanese, we studied the panoramic radiographs taken during dental treatment at the Pediatric Outpatient Section of Osaka Dental University Hospital of 9,111 children (4,646 boys and 4,465 girls) between the ages of 7 years 0 months and 16 years 11 months, in addition to 2,769 panoramic radiographs of students of this university (2,312 men 457 women) kept by the Department of Oral Radiology. The following results were obtained. 1. Calcification of the third molars in both boys and girls began as early as 7 years 6 months in the maxilla and 7 years 0 months in the mandible. The average age for initiation of calcification in the maxilla was 9 years 4 months for boys, and 9 years 2 months for girls, while the ages in the mandible were 9 years 1 month and 8 years 9 months, respectively. 2. The average age for completion of the third molar crowns in the maxilla was 11 years 8 months for boys and 11 years 5 months for girls, while in the mandible it was 12 years 4 months and 12 years 3 months, respectively. 3. At greater than 13 years of age, the tooth germ could be found in boys about 70% of the time in the maxilla and 75% of the time in the mandible, while these figures for girls were 65 and 80%, respectively. 4. All four third molars were present in 52.3% of the males and 45.5% of the females, while 9.5% of the males and 12.0% of the females had no third molars at all. 5. The direction of eruption was classified as either vertical, mesial, horizontal, distal, or buccal/lingual type. The rate for the vertical type in males was 70% in the maxilla and 45% in the mandible, while these figures for females were 50 and 40%, respectively. 6. Microdontia of the third molars appeared only in the maxilla. 7. Congenital absence of the third molars was more common in females than males, and occurred more frequently in the maxilla than in the mandible. The results of this study allow a better understanding of the third molars of Japanese and provide an aid to planning in such areas of clinical pediatric practice as guiding occlusal development.