The cytoskeleton of cryofixed Purkinje cells of the chicken cerebellum.

Cerebella of 3- to 6-week-old chickens were cryofixed in a nitrogen-cooled propane jet, deep-etched and rotary-shadowed. The use of a brief perfusion of 0.32 M sucrose improved the quality of the cryofixation and allowed the study of the deeper layers of the cerebellar cortex. It is reported that the cytoskeleton of the Purkinje cells (PC) shows distinct domains and composition of filamentous structures in the different regions of the cell cytoplasm, such as the perikaryon, the cytoplasm of dendrites and the axoplasm. The perikaryon is occupied by a meshwork of fine filaments, 4-7 nm in diameter, that extends from the nuclear outer membrane to the cell membrane. In this zone the cell organelles (e.g., endoplasmic reticulum, mitochondria) adopt a circular arrangement around the nucleus. All structures are anchored by microfilaments to the cytoplasmic network. The dendrites show a dense cytoplasmic network including bundles of microtubules, neurofilaments and microfilaments. Numerous aggregated globular components are attached to this cytoskeleton. The cytoskeleton of the dendritic spines shows axially oriented 10-nm bundles of filaments, which are interconnected and anchored also to the cell membrane and the components of the agranular endoplasmic reticulum by cross-linkers. As described in peripheral nerves, the axoplasm of axons in the central nervous system exhibits predominantly neurofilaments and microtubules aligned along the axis of the neurites in a three-dimensional arrangement and interconnected by cross-linker filaments and filamentous structures.