Mechanism of controlling blood-cell passage between the sinus endothelial cells

用透射电子显微镜和免疫荧光显微镜观察大鼠脾内窦内皮细胞的超微结构。此外，计算机辅助重建还显示了小管的三维排列，经皂苷提取后，应激纤维在细胞的基底部明显电子致密，并呈现出两种特征型和混合型。从统计上看，两种应力纤维的长度有显著差异。磷酸酪氨酸定位于内皮细胞的基底部和细胞间黏附部位。窦内皮细胞内有两种类型的应力纤维，它们形成一个广泛的网络，窦内皮细胞表面连接的小管系统由细小的小管组成，这些小管分叉、吻合，与质膜呈连续性。它们在细胞器之间来回缠绕，特别是与质膜的球形内陷紧密相对，同时也沿着它们运行。通过计算机辅助重建，发现从质膜不同部位凹陷的小管相互连续，穿透窦内皮细胞，同时也在细胞质中分支和吻合，形成复杂的网络。然而，目前尚不清楚脾静脉窦内皮细胞表面连接的小管系统网络是否具有生理意义。

Fine structure of sinus endothelial cells in the rat spleen were examined by transmission electron microscopy and immunofluorescence microscopy. In addition, the three dimensional arrangement of the canaliculi was also demonstrated by computer-aided reconstruction.After extraction with saponin, the stress fibers were found to be conspicuously electron-dense in the basal portion of the cells and demonstrated two characteristic types and the mixed type of these. Statistically, the lengths of two types of stress fibers are significantly different. Phosphotyrosine is localized in the basal part and at the intercellular adhesion site of the endothelial cells. Two types of stress fibers were organized in the sinus endothelial cells and they form a wide-spread network.The surface connected canalicular system of the sinus endothelial cells consisted of slender canaliculi which were branched, anastomosed, and showed continuity with the plasma membrane. They twisted in and out among the organelles and were particularly found in close apposition to the spherical invaginations of the plasma membrane while also running along them. From a computer-aided reconstruction the canaliculi, which were invaginated from various sites of the plasma membrane, were found to be continuous with each other and penetrate the sinus endothelial cell, while also branching and anastomsing to form a complex network in the cytoplasm. However, it is unclear at present as to whether or not the network of the surface connected canalicular system in the splenic sinus endothelial cells has any physiological significance.