SEGMENTAL DIFFERENTIATION IN THE NERVOUS SYSTEM

一个基本但在很大程度上仍未得到解答的问题是 神经系统的发育是一个区域如何形成形态的过程 在神经发生过程中与另一个在功能上有所不同。这个 这个项目的长期目标是发现 在水蚤神经系统中形成这种地区性的专门化。地区性 专门化可能源于神经元固有的因素。 每个区域的前兆，或来自与 其他神经或非神经组织。我们选择执行我们的 水蚤节段性神经节的观察与实验 相对简单和易于进行实验操作。我们 先前已经确定身体第五节和第六节中的神经节， 它所含的神经细胞比 邻近的神经节。这个项目的第一个目标是描述 详细地说，这些额外的神经元，无论是在发育中还是在成年中。这 将需要描述这些神经元何时出现，它们的出生日期， 是，哪些细胞是它们的前体，当它们支配性行为时 器官，以及它们的功能。我们将通过使用各种 技术，包括计算机辅助技术，以进行细胞计数和 细胞重建，[~3H]-胸腺嘧啶核苷标记以获得出生日期和 识别前体，细胞记录，染料注射和组织学，以 确定它们的功能。此外，我们还将使用单抗 在发育过程中识别特定的细胞。根据 我们得到的详细信息，我们将完善我们的假设 水蚤的节段性特化的基础机制。第二 这个项目的目标是开始检验这些假说 通过在显影上执行各种操作来进行实验 神经节，例如通过切断连接来隔离动物的神经节 神经，在有或没有其他组织的情况下培养神经节， 将神经节移植到不同年龄段的宿主体内，并取出个体 神经节。这些操作的影响将通过 上面提到的技术。分段式专业化的详细研究 水蚤的神经系统相对简单，可以生产出有价值的 适用于更复杂的这一根本问题研究的见解 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.