Brightman M W
J Cell Biol. 1965 Jul;26(1):99-123. doi: 10.1083/jcb.26.1.99.
From 10 minutes to 3(1/2) hours after the intraventricular injection into rats of 15 to 100 mg of ferritin, an appreciable fraction of the protein, visualized electron microscopically, traverses the ependymal epithelium by diffusing along the dense intercellular substance of the luminal open junction and thence, by circumventing discrete intercellular fusions which partition rather than seal the interspace. These partitions shunt additional protein into the cell, where ferritin is transported within pinocytotic vesicles to the lateral and basal plasma-lemma and, presumably, back into the interspace again. The basal interspace is irregularly distended by pools of moderately dense "filler" within which ferritin accumulates. The larger fraction of protein enters the ependyma by pinocytosis and is eventually segregated within membrane-enclosed organelles such as vacuoles, multivesicular bodies, and dense bodies, where the molecules may assume a crystalline packing. As a result of the accumulation of ferritin within these inclusions and within filler substance, only a small amount of protein remains to enter the underlying parenchyma. Presentation of ferritin to prefixed cells leads to a random dispersion of free cytoplasmic ferritin. This artifactual distribution in both prefixed and postfixed cells is concurrent with disruption of cell membranes.
给大鼠脑室内注射15至100毫克铁蛋白后10分钟至3.5小时内，通过电子显微镜观察可见，相当一部分蛋白质沿着管腔开放连接的致密细胞间物质扩散，穿过室管膜上皮，然后绕过将细胞间隙分隔而非封闭的离散细胞间融合处。这些分隔将额外的蛋白质分流到细胞内，在细胞内铁蛋白通过胞饮小泡运输到外侧和基底质膜，大概又回到细胞间隙。基底细胞间隙被中等密度的“填充物”池不规则地扩张，铁蛋白在其中积累。大部分蛋白质通过胞饮作用进入室管膜，最终被隔离在膜包裹的细胞器内，如液泡、多囊体和致密体，分子可能在其中呈晶体排列。由于铁蛋白在这些内含物和填充物质中积累，只有少量蛋白质进入下层实质。将铁蛋白呈现给固定前的细胞会导致游离细胞质铁蛋白随机分散。在固定前和固定后的细胞中这种人为分布与细胞膜的破坏同时发生。
