A scanning electron microscope study of the human glomerulus.

The three-dimensional fine structure of human glomeruli taken at autopsy and by biopsy was studied under the scanning electron microscope. The podocytes and their cytoplasmic processes in their elaborate ramification on the capillary wall were clearly demonstrated in the glomerulus of the autopsy specimens fixed by perfusion of glutaraldehyde as late as 3 hours after death, and in the glomerulus of the biopsy specimen fixed by immersion in the same fixative. The human podocytes were characterized by marked irregularity in the ramification pattern of their cytoplasmic processes, as compared with those of the rat and the rabbit. The interdigitation of the terminal processes was always noticed between those of different cells. The extended loss of the terminal processes was seen in the glomerulus of a case with severe proteinuria. The presence of intercellular spaces between the sheet-like cell peripheries of the podocytes supports the author's hypothesis in his studies on experimental nephrosis of rats that the disappearance of the terminal processes is not due to syncytial fusion of neighboring podocytes, but to retraction of swollen processes toward the central portion.