Inkyo-Hayasaka K, Sakai T, Kobayashi N, Shirato I, Tomino Y
Department of Medicine, Juntendo University, School of Medicine, Tokyo, Japan.
Kidney Int. 1996 Aug;50(2):672-83. doi: 10.1038/ki.1996.364.
The three-dimensional structure of the mesangium was analyzed by means of reconstruction from serial semithin and ultrathin sections of the rat glomerulus. The mesangial domains traced on light micrographs of semithin sections were transferred to styrene models, which were stacked up to reconstruct the whole mesangium. The reconstructed mesangium was tree-like in shape and was divided into three lobes that were connected to the vascular pole by a slender neck. The glomerulus contained no islets of mesangium which were not connected to the vascular pole. The mesangium contained 64 mesangial loops that were penetrated by capillaries. Reliability of the findings on the mesangial loops was ascertained by various methods including reconstruction of part of the mesangium from ultrathin sections. Electron microscopic observations revealed that the arms of the mesangial loops were frequently very slender and consisted of mesangial cell processes containing prominent bundles of actin filaments. The mesangial loops were distributed evenly within the mesangium. Considering previous reports showing about 400 capillary branches in the rat glomerulus as well as the present findings, we concluded that the mesangial loops may change the distribution of intraglomerular blood flow by dynamic contraction of the mesangial cells, or serve as an additional safety device to prevent the expansion of glomerular capillaries.
通过对大鼠肾小球连续半薄切片和超薄切片进行重建分析系膜的三维结构。在半薄切片的光学显微镜照片上描绘的系膜区域被转移到苯乙烯模型上，这些模型堆叠起来以重建整个系膜。重建后的系膜呈树状，分为三个叶，通过细长的颈部与血管极相连。肾小球中不存在不与血管极相连的系膜小岛。系膜包含64个被毛细血管穿透的系膜袢。通过包括从超薄切片重建部分系膜在内的各种方法确定了关于系膜袢发现的可靠性。电子显微镜观察显示，系膜袢的臂通常非常细长，由含有突出肌动蛋白丝束的系膜细胞突起组成。系膜袢在系膜内均匀分布。考虑到先前报道显示大鼠肾小球中有约400个毛细血管分支以及目前的发现，我们得出结论，系膜袢可能通过系膜细胞的动态收缩改变肾小球内血流分布，或作为防止肾小球毛细血管扩张的额外安全装置。
