The establishment of a new type of long-term culture system in which the whole embryo cultu lowed by a mandibular organ culture.

1.牙齿是由第一咽中的上皮细胞和间充质细胞之间的相互作用形成的。尽管在啮齿动物胚胎中已经发现了中脑和后脑嵴细胞对第一咽弓的作用，但没有直接证据表明这些细胞实际上参与了牙间充质的形成。为了阐明颅神经嵴细胞在牙齿形成中的作用，我们首先确定了提供嵴的位置和阶段，迁移到假定的牙齿形成区域的牙齿。用DiI标记大鼠胚胎中脑和前脑嵴，标记胚胎培养30或60小时，所得的迁移模式表明，4体节期结束时迁移的后中脑细胞主要迁移到牙芽发育的区域。第二，建立了一种新型的长周期培养体系， ...更多信息 一种文化利用该系统，大鼠胚胎从早期的体节雄鹿磨牙在外植体保持能够在8天内达到芽期。最后，为了确定在4-体节期结束时迁移的后中胚层细胞是否参与牙间充质，这些细胞被培养并进行长期培养。标记的嵴细胞在间充质中清晰可见。这些结果表明早期迁移的中脑后嵴细胞对大鼠胚胎磨牙的发育有一定的促进作用.经典的两栖动物组织移植实验表明，牙齿的发育不仅依赖于口腔外胚层和神经嵴，也依赖于前肠内胚层。此外，口腔组织学观察表明，牙胚起源于前肠附近的一些外胚层细胞和神经嵴细胞。这些研究表明，牙齿的发生需要这三种细胞的存在和合作。然而，没有直接证据表明牙齿的形成涉及口腔外胚层和前肠内胚层区域。为了阐明前肠内胚层在牙齿形成中的作用，我们用重组腺病毒Adex-lacZ建立了一种内胚层细胞示踪系统，并在长期培养体系中进行了细胞示踪。Adex-lacZ标记的细胞与未标记的th上皮（假定的切牙上皮）相邻。这些研究结果表明，在哺乳动物中的第一个直接的证据，也采取的地方在指定的部分口腔外胚层相邻的前肠内胚层，表明前肠在牙齿的启动中发挥作用。少

1. Teeth are formed by reciprocal interactions between the epithelium and mesenchyme in the first pharyng. Although the contribution of midbrain and hindbrain crest cells to the first pharyngeal arch has been previouined in rodent embryos no direct evidence exists that these cells are actually involved in the dental mesenc order to elucidate the contribution of the cranial neural crest cells in the tooth formation, we first identified th tion sites and stages poviding the crest, cells that, migrate to the presumed tooth-forming region of the m.prominence. Focal labeling with DiI was performed at the midbrain and anterior hindbrain crests in rat embryo labeled embryos were cultured for 30 or 60 hr. The resultant migration pattern indicated that posterior midb cells emigrating by the end of the 4-somite stage predominantly migrated to the region where tooth buds develop. Second, we established a new type of long-term culture system in which the whole embryo culture is by a mandibular org … More an culture. Using this system, rat embryos were maintained from the early somite stag molars in the explants were able to reach the bud stage within 8 days. Finally, to ascertain if posterior midb cells emigrating by the end of the 4-somite stage were involved in the dental mesenchyme, these cells were lat DiI and processed the long-term culture. Labeled crest cells were found to be clearly detectable in t mesenchyme. These findings indicate that the early-emigrating posterior midbrain crest cells ontribute to m molar tooth development in rat embryos.2. Classical transplantation experiments with various amphibian tissues have shown that tooth development re* only oral ectoderm and neural crest but also foregut endoderm. In addition, histological observation of oral n showed that the tooth germs are initiated in some ectodermal cells and neural, crest cells adjacent to foregut e These studies suggest that tooth initiation requires the presence and cooperation of these three components. mals, however, there is no direct evidence that tooth formation is involved in the region of oral ectoderm a* foregut endoderm. In order to elucidate the contribution of foregut endoderm to tooth formation, we establist type of endodermal cell tracing system with a recombinant adenovirus called Adex-lacZ, and performed en cell tracing in a long term culture system. Cells labelled with Adex-lacZ were seen next to non-labelled th epithelium, presumptive incisor epithelium. These findings show the first direct evidence in mammals that too taks place in the specified part of oral ectoderm adjacent to foregut endoderm, suggesting that foregut plays a role in tooth initiation. Less