Histologic studies and transmission electron microscopy

Formalin fixed kidneys were embedded in paraffin and prepared sections (3 μm thick). For general histologic analysis, sections were processed for Periodic acid-Schiff (PAS) staining. The kidney cortical specimens were cut into small pieces (1 mm³), fixed with 2.5% glutaraldehyde in phosphate buffered saline, pH 7.4, and embedded in Epon 812 (Polysciences, Warrington, PA, USA). Transmission electron micrographs were obtained using a Zeiss EM-10 electron microscope operated at 80 kV with absolute magnifications of 8000 or 20000. For examination of podocyte foot processes, 6 random electron microscopic fields of glomeruli per animal were examined. The morphologic features were assessed by a single observer in a blinded manner.