ELEMENTAL AND STRUCTURAL ORGANIZATION OF NEURONS AND GLIA

这两个部分的项目研究的组织和职能 神经元和神经胶质细胞中的特化膜。第一部分旨在 平行突触活动中钙调节的特征 纤维~浦肯野细胞突触的小脑皮质和 CA3海马区锥体细胞。新的冷冻切片技术， 结合扫描电子显微镜(STEM)，有 细胞质总钙协调变化的允许研究 它们伴随着对细胞内游离钙的调节，通过 内质网。一种新的基于暗场质量映射的方法 STEM，已被用于原位测定分子质量 神经元突起内的细胞器。这样的测量提供了 关于束流引起的质量损失影响的基本新信息，以及 带来了新的方法来校正浓度测量 这样的影响。化学固定和直接冷冻的结构分析 一种新型海马体器官培养物的制备 已确定的培养条件可提供良好的器官转化 CA3苔藓纤维突触。这些突触距离地表足够近 适用于直接冷冻研究。在第二部分中， 对特殊髓鞘膜的组装进行了研究。共焦光 显微镜先前显示雪旺细胞依赖于微管 用于髓鞘特异性蛋白的细胞内运输和组装。 现在，我们发现雪旺细胞微管的组织 因此，细胞质的细胞器和细丝也是如此 依靠微管组织的通道是 必须依赖于轴突接触。因此，这一特点 雪旺细胞表面膜的极化不发生在 没有轴突，髓鞘蛋白的正确分选和靶向 因此不可能发生。

This two~part project studies the organization and function of specialized membranes in neurons and glia. The first part aims to characterize calcium regulation during synaptic activity in parallel fiber~Purkinje cell synapses of the cerebellar cortex and in synapses of CA3 hippocampal pyramidal cells. New frozen sectioning techniques, combined with scanning transmission electron microscopy (STEM), have permitted studies of coordinated changes in cytoplasmic total calcium which accompany the regulation of free intracellular calcium by endoplasmic reticulum. A new method, based on darkfield mass mapping in the STEM, has been used to determine the in situ molecular mass of organelles within neuronal processes. Such measurements have provided fundamental new information on the effects of beam~induced mass loss, and have led to new approaches to correcting concentration measurements for such effects. Structural analysis of chemically fixed and directly frozen preparations of a new kind of organotypic culture of hippocampus has identified culture conditions which provide excellent organ~ization of CA3 mossy fiber synapses. These synapses are close enough to the surface to be suitable for direct freezing studies. In the second part, the assembly of specialized myelin membranes is studied. Confocal light microscopy had previously shown that Schwann cells depend on microtubules for intracellular transport and assembly of myelin~specific proteins. Now, we have found that the organization of the Schwann cell microtubule network and therefore also of the organelles and filaments of cytoplasmic channels which depend on microtubules for their organization is obligatorily depend on axonal contact. Thus, the characteristic polarization of Schwann cell surface membranes does not occur in the absence of axons, and the proper sorting and targeting of myelin proteins consequently cannot take place.