3-DIMENSIONAL ULTRASTRUCTURE OF HUMAN GLOMERULAR-BASEMENT-MEMBRANE BYA QUICK-FREEZING AND DEEP-ETCHING METHOD

The three-dimensional ultrastructure of glomerular basement membrane ( GEM) in surgically resected human kidneys was observed by the quick-fr eezing and deep-etching method. In three layers of human GEM, the midd le layer exhibited polygonal meshwork structures, which were composed of fine fibrils. In addition, the outer and inner layers were formed b y lines of perpendicular fibrils, which connected the epithelial or en dothelial cell surfaces with the meshwork structures of the middle lay er. These ultrastructures might correspond to the three layers, such a s lamina densa and laminae rara externa and interna, which were also o bserved on conventional ultrathin sections. It is concluded that the h uman GEM has the same meshwork structures and perpendicular fibrils as those previously observed in animals and that these structures may ac t functionally as size and/or charge barriers.