SEGMENTAL DIFFERENTIATION IN THE NERVOUS SYSTEM

一个基本的，但在很大程度上没有答案的问题， 神经系统的发展是一个区域如何在形态上变得 并且在神经发生过程中与另一个在功能上不同。 的 这个项目的长期目标是发现 在水蛭神经系统中形成了这种区域性的特化。 区域 特化可能源于神经元的内在因素， 每个区域的前体，或由相互作用引入的因素， 其他神经或非神经组织。 我们选择执行我们的 对水蛭节段神经节的观察和实验， 相对简单和易于实验操作。 我们 先前已经确定身体第五和第六节的神经节， 支配性器官的神经元， 邻近的神经节 该项目的第一个目标是描述 这些额外的神经元，无论是在发育中还是在成人中。 这 将需要描述这些神经元何时出现，它们的诞生日期， 哪些细胞是它们的前体，当它们支配性器官时， 器官，以及它们的功能。 我们将使用各种 技术，包括计算机辅助技术进行细胞计数， 细胞重建，[3 H]-胸苷标记，以获得出生日期， 识别前体，细胞记录，染料注射和组织学， 确定其功能。 此外，我们将使用单克隆抗体 以识别发育过程中的特定细胞。 的基础上 我们获得的详细信息，我们将完善我们的假设， 水蛭的节段特化机制。 第二 本项目的目标是开始检验这些假设 实验上，通过对显影剂进行各种操作， 神经节，例如通过切割连接 神经，将神经节与或不与其他组织一起培养， 将神经节移植到不同年龄的宿主体内， 神经节 这些操作的影响将与 上述技术。 详细研究了 水蛭的神经系统相对简单， 适用于研究这一基本问题的更复杂的见解 有机体

One of the fundamental yet largely unanswered questions about the development of the nervous system is how one region becomes morphologically and functionally different from another during neurogenesis. The long-range goal of this project is to discover the mechanisms that give rise to this regional specialization in the leech nervous system. Regional specialization could derive from factors intrinsic to the neuronal precursors for each region, or from factors introduced by interactions with other neural or non-neural tissues. We have chosen to carry out our observations and experiments on leech segmental ganglia because of their relative simplicity and accessibility to experimental manipulation. We have previously determined that the ganglia in body segments five and six, which innervate the sexual organs, contain a few hundred more neurons than adjacent ganglia. The first objective of this project is to characterize in detail these extra neurons, both in development and in the adult. This will entail describing when these neurons arise, what their birthdates, are, which cells are their precursors, when they innervate the sexual organs, and what their functions are. We will do this by using a variety of techniques, including computer-aided techniques to do cell counts and cell reconstructions, [3H]-thymidine labeling to obtain birthdates and to identify precursors, and cell recording, dye injection and histology to determine their functions. In addition we will use monoclonal antibodies to identify particular cells during development. On the basis of the detailed information we obtain, we will refine our hypotheses about the mechanisms that underlie segmental specialization in the leech. The second objective of this project is to begin testing these hypotheses experimentally by performing various manipulations on the developing ganlia, such as isolating the ganglia in the animal by cutting connecting nerves, placing ganglia in culture with or without other tissues, transplanting ganglia into hosts of different ages, and removing individual ganglia. The effects of these manipulations will be studied with the techniques mentioned above. Detailed study of segmental specialization in the leech, with its relatively simple nervous system, can yield valuable insights applicable to studies of this fundamental problem in more complex organisms.