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

1.牙齿是由第一咽上皮和间充质相互作用形成的。虽然在啮齿动物胚胎中已发现中脑和后脑脊细胞对第一咽弓的贡献，但没有直接证据表明这些细胞确实参与了牙齿中膜的形成。为了阐明颅神经脊细胞在牙齿形成中的作用，我们首先确定了提供脊细胞的位置和阶段，即迁移到隆起的假定成牙区域的细胞。在大鼠胚胎的中脑和后脑前部进行DiI焦点标记，标记胚胎培养30或60小时。由此产生的迁移模式表明，在4体节阶段结束时迁出的后中脉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胚胎长期培养体系，在这种体系中，整个胚胎的培养都是通过下颌组织…进行的更像是一种文化。使用该系统，大鼠胚胎从早期的体节雄鹿磨牙中培养出来，在8天内就能达到蕾期。最后，为了确定在4-体节期末迁出的后中胚细胞是否参与了牙齿间充质，对这些细胞进行了后期DII和长期培养。在间质中可清晰地检测到标记的脊细胞。这些结果表明，早期迁出的中脑后顶细胞与大鼠胚胎磨牙的发育有关。经典的两栖动物组织移植实验表明，牙齿的发育不仅包括口腔外胚层和神经脊，还包括前肠内胚层。此外，对口腔n的组织学观察表明，牙胚是在一些外胚层细胞和邻近前牙的神经、脊细胞中启动的。这些研究表明，牙齿的启动需要这三种成分的存在和协同作用。然而，没有直接证据表明牙齿形成涉及口腔外胚层和前肠内胚层。为了阐明前肠内皮细胞在牙齿形成中的作用，我们用重组腺病毒Adex-LacZ建立了一种新型的内皮细胞示踪系统，并在长期培养系统中进行了EN细胞示踪。Adex-LacZ标记的细胞紧邻未标记的TH上皮，推测是门牙上皮。这些发现首次在哺乳动物身上发现了ToTks位于口腔外胚层与前肠内胚层相邻的特定部分的直接证据，表明前肠在牙齿起始过程中发挥了作用。较少

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