IMAGING CYTOSKELETON MITOCHONDRIAL-MEMBRANE ATTACHMENTS BY EMBEDMENT-FREE ELECTRON-MICROSCOPY OF SAPONIN-EXTRACTED CELLS

Embedment-free electron microscopy images the cytoskeleton and nuclear matrix, which are very difficult to visualize in conventional electron micrographs. However, to be effective, cell structures must be depleted of soluble proteins, which otherwise shroud cell architecture. Nonionic detergents effect this extraction, releasing soluble proteins but also destroying all membranes. Saponin can permeabilize plasma membranes, releasing soluble proteins while preserving many cytoplasmic membranes. Stereoscopic electron microscopy of resinless sections shows the many connections of the cytoskeleton to mitochondrial membranes.