The application of cryo-ultramicrotomy in the study of the fine structure of myofilaments

The possibility of using sections obtained by cryo-ultramicrotomy in the study of the fine structure of myofilaments was explored. Heart and skeletal muscles were stabilized for 5–15 min in 2.5% glutaraldehyde. Neither cryo-protection, encapsulation nor any other chemical treatment preceded the freezing in Freon-12 cooled by liquid nitrogen. ‘Wet’ sectioning was performed using dimethyl sulphoxide (50% in water) in the knife trough. The sections were stained using either positive or negative contrasting techniques. The results showed that sections prepared by cryo-ultramicrotomy permit high resolution studies, especially if negatively stained. By eliminating several steps of specimen preparation that destroy the native configuration of biopolymers, the method promises to make it possible to study well-preserved myofilaments and their fine structure, both in longitudinal and cross-section, in situ. It is not yet certain, however, that new sources of artefacts are not introduced.