A new method for preparing embeddment-free sections for transmission electron microscopy: Applications to the cytoskeletal framework and other three-dimensional networks

Diethylene glycol distearate is used as a removable embedding medium to produce embeddment-free sections for transmission electron microscopy. The easily cut sections of this material float and form ribbons in a water-filled knife trough and exhibit interference colors that aid in the selection of sections of equal thickness. The images obtained with embeddment-free sections are compared with those from the more conventional epoxy-embedded sections, and illustrate that embedding medium can obscure important biological structures, especially protein filament networks. The embeddment-free section methodology is well suited for morphological studies of cytoskeletal preparations obtained by extraction of cells with nonionic detergent in cytoskeletal stabilizing medium. The embeddment-free section also serves to bridge the very different images afforded by embedded sections and unembedded whole mounts.