Gregory W A, Bennett M V
Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461.
Brain Res. 1988 Aug 1;470(2):205-16. doi: 10.1016/0165-3806(88)90239-8.
Ependyma adjacent to the goldfish preoptic neurosecretory nucleus was examined with transmission electron microscopy. Ependymal cells adjoining the rostroventral end of the nucleus were spindle-shaped with their long axes perpendicular to the ventricular surface. Gap junctions and desmosomes were common near the apical (ventricular) ends of these cells, and less frequent laterally in the ependymal layer. Ependymal cells in more caudodorsal preoptic regions (adjacent to large neurosecretory cells) were progressively more pleomorphic. The frequent occurrence of apparently internalized gap junctions and of gap junction fragments enclosed within lysosome-like organelles indicated extensive turnover of these junctions, or uncoupling. Ependymal cells in the caudodorsal region formed gap junctions on their lateral and basal (abluminal) surfaces with glial processes containing bundles of intermediate filaments. Subependymally, these processes (presumptive radial glia) were parallel to one another and coupled together by gap junctions. Neurites containing dense core vesicles occasionally invaginated into ependymal cells in the caudal region, but did not appear to form gap junctions. Previous observations indicate continuing maturation and growth of the goldfish preoptic area with neurosecretory cell formation rostroventrally and a rostroventral to caudodorsal gradient of maturation. The present findings suggest a parallel and related gradient in preoptic ependyma. Ependymal cell differentiation possibly involves loss of gap junctions, and radial migration or differentiation into underlying neurons and glia.
用透射电子显微镜检查金鱼视前神经分泌核附近的室管膜。毗邻该核吻腹端的室管膜细胞呈纺锤形，其长轴垂直于脑室表面。缝隙连接和桥粒在这些细胞的顶端（脑室）末端附近常见，而在室管膜层的侧面则较少见。视前区更靠尾背侧区域（毗邻大型神经分泌细胞）的室管膜细胞逐渐变得更加多形。明显内化的缝隙连接以及被类似溶酶体的细胞器包裹的缝隙连接片段频繁出现，表明这些连接广泛更新或解偶联。尾背侧区域的室管膜细胞在其侧面和基底（无腔）表面与含有中间丝束的神经胶质突起形成缝隙连接。在室管膜下，这些突起（推测为放射状胶质细胞）相互平行并通过缝隙连接耦合在一起。含有致密核心囊泡的神经突偶尔会内陷到尾侧区域的室管膜细胞中，但似乎并未形成缝隙连接。先前的观察表明金鱼视前区持续成熟和生长，神经分泌细胞在吻腹侧形成，并且存在从吻腹侧向尾背侧的成熟梯度。目前的研究结果表明视前室管膜存在平行且相关的梯度。室管膜细胞分化可能涉及缝隙连接的丧失，以及向下方神经元和神经胶质细胞的放射状迁移或分化。
