Induction of metallothionein and stimulation of calcification by dexamethasone in cultured clonal osteogenic cells, MC3T3-E1.

To clarify the effects of dexamethasone (Dex) on metallothionein (MT) synthesis and calcification in osteoblastic cells, a clonal osteogenic cell line (MC3T3-E1) was used in the present study. Under culture conditions designed not to cause calcification, MT synthesis of cells at 3 days after inoculation increased with increasing concentration of Dex (2.5-50 nM) for a 24-h culture period. Cells at 6 or 9 days after inoculation also synthesized MT by a 24-h exposure to Dex. These show that undifferentiated osteoblasts have the ability to synthesize MT by Dex. Under culture conditions designed to cause calcification, cells at 6 days after inoculation were cultured with 50 nM Dex in the presence of 7 mM beta-glycerophosphate (beta-GP) for 7 days. Ca content of Dex-treated cells was about 7.5 times as high as that of untreated cells. Dex-treated cells showed a high activity of alkaline phosphatase (ALP). The Zn content of the MT fraction in Dex-treated cells was about 8 times as high as that of untreated cells. These results show that Dex has the ability to induce MT synthesis in osteoblastic cells and to cause a high calcification which is due at least partly to an enhanced activity of ALP.

[An epidemiological study on dental caries of children in the town of Fuji].

An epidemiological investigation of dental caries was undertaken during the period of 1987-1989 with all children of nursery school, kindergarten, elementary and junior high school age in the town of Fuji, Saga prefecture which is a mountain villate, experiencing little movement of the population. From this investigation the following results were obtained. 1. Although the number of the children in each age group who had dental caries in deciduous and permanent teeth appeared to have decreased compared with 1987 and 1989, the dental caries prevalence in the children still remained high. 2. It appeared that it was important to give dental health education during the stage of immature young permanent teeth since there was prior to evidence of high dental caries in this stage. 3. The following was suggested for the improvement of caries experienced in immature young permanent teeth in the school in Fuji: (1) no stock of soft drinks in the refrigerator, (2) guardian's strict supervision of their children concerning snacks and, (3) acquiring of the habit of brushing during infancy and preschool years with parental assistance.