DEVELOPMENT OF NEURONAL SPECIFICITY

本项目中的实验有助于理解 神经元和它们的目标之间形成了精确的连接。 一个简单的脊椎动物系统的实验和描述研究， 鸡胚后肢的运动神经支配，已经表明，选择性 通过单个神经突的生长尖端（“生长锥”）来寻路 在精确有序的连接的起源中起着重要作用。 的 生长锥在其生长期间使用两类导航线索。 第一种是高度特异性的线索，生长锥用来选择 在路径分叉的地方找到正确的路径。 第二组 线索描绘了路径本身。 在这个项目中的实验是 旨在描述空间范围，来源和发展 这些轴突引导线索，使用神经追踪技术，简单的消融 手术，以及鹌鹑和鸡胚胎之间的移植， 供体组织可以在组织学上鉴定。 的重要组成部分 本研究的目的是分析嵌合运算的适用性 鸡与鹌鹑的关系进行研究，分析 鸡与鹌鹑嵌合手术对神经系统的影响 系统 初步结果表明，嵌合体技术将是 在研究胚胎中组织之间的关系方面非常有价值， 环境和生长锥的导航。 明年的具体目标是： (1)结束实验，以确定鹌鹑/鸡嵌合体手术是否 技术可用于该系统中，以研究生长锥与 他们的环境。 (2)总结鹌鹑运动神经元池的映射，以确定 鹌鹑轴突投射模式的差异必须考虑到 在分析嵌合体的帐户。 (3)总结评估是否提供导航线索的实验 脊髓和肢根之间的组织。 (4)开始胚胎手术，旨在表征远端范围的 让轴突在背侧和腹侧之间做出选择的特定线索 四肢根部的通路 在特定神经元中有效的导航线索的分析 小鸡后肢系统中的寻路应该可以让我们深入了解 人类神经系统的正常和异常发育。

Experiments in the current project contribute to an understanding of how precise connections develop between neurons and their targets. Experimental and descriptive studies of a simple vertebrate system, the motor innervation of the chick embryo hindlimb, have shown that selective pathfinding by the growing tips of individual neurites (the "growth cones") plays a large role in the genesis of precise and orderly connections. The growth cones use navigational cues of two classes during their outgrowth. The first of these are highly specific cues that growth cone use to select the correct pathways at points where pathways diverge. The second set of cues delineate the pathways themselves. Experiments in this project are designed to characterize the spatial extent, source, and development of these axonal guidance cues, using nerve tracing techniques, simple ablation surgeries, and transplants between quail and chick embryos in which the donor tissues can be identified histologically. An important part of the projected study is to analyze the applicability of chimaeric operations between chick and quail to studies is to analyze the aplicability of chimaeric operations between chick and quail to studies of the nervous system. Preliminary results suggest that the chimaeric technique will be invaluable in studying the relationship between tissues in the embryonic environment and the navigation of growth cones. The specific objectives for the next year are to: (1) conclude experiments to determine if the quail/chick chimaeric surgical technique can be used in this system to study growth cone interactions with their environment. (2) conclude the mapping of quail motoneuron pools to determine what differences in axonal projection patterns in quail must be taken into account in analyzing chimaeras. (3) conclude experiments that assess whether navigational cues are provided by tissues between the spinal cord and the limb base. (4) begin embryonic surgeries designed to characterize the distal extent of specific cues that allow axons to choose between dorsal and ventral pathways at the limb base. Analysis of the navigational cues that are effective in specific neuronal pathfinding in the chick hindlimb system should give insights into the normal and abnormal development of the human nervous system.