DEVELOPMENT OF NEURONAL SPECIFICITY

当前项目中的实验有助于理解如何 神经元和它们的目标之间发展出精确的联系。 简单脊椎动物系统的实验和描述性研究 鸡胚胎后肢的运动神经支配，已显示出选择性 通过单个神经突起(“生长锥体”)的生长尖端寻找路径 在精确有序连接的起源中起着很大的作用。这个 生长锥体在生长过程中使用两类导航信号。 第一种是Growth Cone用来选择的高度特定的线索 正确的路径在路径分叉的地方。第二套 线索本身就勾勒出了路径。这个项目中的实验是 旨在描述空间范围、来源和发展 这些轴突引导信号，使用神经追踪技术，简单地消融 手术以及在鹌鹑和小鸡胚胎之间进行移植，在这些胚胎中 供体组织可以从组织学上进行鉴定。这是一个重要的组成部分 计划的研究是分析嵌合体手术的适用性 对雏鸡和鹌鹑之间的研究是为了分析其适用性 小鸡和鹌鹑之间的嵌合手术对神经的研究 系统。初步结果表明，嵌合体技术将是 在研究胚胎组织之间的关系方面具有不可估量的价值 环境和生长锥体的导航。 明年的具体目标是： (1)总结实验以确定是否进行了鹌鹑/雏鸡嵌合手术 可以在该系统中使用技术来研究生长锥与 他们的环境。 (2)总结鹌鹑运动神经元池的定位，以确定 必须考虑到鹌鹑轴突投射模式的差异 在分析嵌合体时进行了解释。 (3)总结评估是否提供导航提示的实验 通过脊髓和肢体之间的组织。 (4)开始胚胎手术，以确定远端病变的范围 允许轴突在背侧和腹侧之间选择的特定提示 四肢底部的小路。 对特定神经元有效的导航提示的分析 在雏鸡后肢系统中寻找路径应该能让我们深入了解 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.