Correlative scanning and transmission electron microscopy of glomeruli.

Scanning electron microscopy was performed on 125 human renal specimens and control rat kidneys in conjunction with light microscopy and transmission electron microscopy. Specimens were prepared by glomerular isolation, free hand slicing, alcohol cryofracture, and polyethylene glycol embedding and ultraplaning. Heavy metal secondary electron sources on the tissues were produced by osmic acid, thiocarbohydrazide, osmic acid treatment (O-T-O) followed by gold-palladium coating, or by staining with uranyl acetate and lead citrate. Critical point drying was used uniformly. Useful observations of normal rat glomeruli were made. In the study of diseased human glomeruli, podocyte changes were classed as cytoplasmic projection, foot process changes, and changes of necrosis or basement membrane denudation. Artificial lesions of compression and contamination were defined. Cryofractured and ultraplaned stained specimens were very useful for studying diseased tissues. These methods offer the opportunity to increase our conceptual and diagnostic understanding of glomerular disease.