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

1. 牙齿是由第一次咽部上皮细胞和间质相互作用形成的。虽然中脑和后脑嵴细胞对第一咽弓的贡献已经在啮齿类动物胚胎中得到证实，但没有直接证据表明这些细胞实际上参与了牙系膜的形成，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，这些细胞迁移到下颌突牙形成区域。在大鼠胚胎的中脑和前后脑峰进行DiI标记，标记的胚胎培养30或60小时。由此产生的迁移模式表明，在4体期结束时，后中间细胞主要迁移到牙芽发育的区域。第二，我们建立了一种新型的下颌骨组织全胚培养的长期培养体系。利用该系统，大鼠胚胎在8天内就能从早期牡牙发育到芽期。最后，为了确定在4体期结束时迁移的后中细胞是否参与牙间质，这些细胞是DiI晚期的，并进行了长期培养。在t间质中可明显检测到标记的嵴细胞。这些结果表明，早期迁移的后中脑嵴细胞参与了大鼠胚胎磨牙的发育。对多种两栖动物组织的经典移植实验表明，牙齿发育不仅包括口腔外胚层和神经嵴，还包括前肠内胚层。此外，口腔组织的组织学观察表明，牙齿的细菌是在一些外胚层细胞和邻近前肠的神经嵴细胞中形成的。这些研究表明，牙齿的形成需要这三种成分的存在和合作。然而，在哺乳动物中，没有直接证据表明牙齿的形成与口腔外胚层和前肠内胚层有关。为了阐明前肠内胚层对牙齿形成的作用，我们利用重组腺病毒Adex-lacZ建立了内胚层细胞示踪系统，并在长期培养系统中进行了细胞示踪。标记有Adex-lacZ的细胞与未标记的切牙上皮相邻。这些发现提供了哺乳动物口腔外胚层与前肠内胚层相邻的特定部位发生牙齿形成的第一个直接证据，表明前肠在牙齿形成过程中起作用。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