The studies of the tooth germ differentiation and the transformation of chondrocytes in vitro.

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(1)The studies on the transformation of Meckel's chondrocytes : Chick serum(CKS) contains factors that stimulate adipocyte induction in Mekel's chondrocytes in vitro. We examined whether sex horomones as shown by the analysis of hormone level in CKS have the capacity to induce lipogenesis in Meckel's chondrocytes in vitro. At pharmacological concentrations, these hormones induced dose-dependent lipogenesis in Merkel's chondrocytes. Further analysis of the fatty acid level in CKS revealed significant contains to fatty acids such as oleic acid and docosatetraenoic acid. We were to establish a mimed fatty acid-containing that had the potential to induced adipogenesis in Meckel's chondrocytes in vitro. In conclusion, it may be suggested that fatty acid elements in CKS can induce Meckel's chondrocytes to differentiate into adipocytes simply and at high frequency.(2)The differentiation of the tooth germ : Hertiwig's epithelial root sheath(HERS) plays an important role in tooth formation. To elucidate the mechanism of root formation in tooth development, we examined the role of insulin-like growth factor(IGF-I) in organ culture. The presence of IGF-I resulted in elongation of HERS and increased cell proliferation in it's outer layer. These effects were negated by the addition of antibodies specific for IGF-I. From these finding, it may be suggested that IGF-I related in the root formation.