The mesenchymal intermediate filament protein vimentin and the 70K component of neurofilament were detected by two-dimensional gel electrophoresis in cultures of pure sensory and sympathetic neurones derived from chick embryos. The identities of these neuronal intermediate filament proteins were confirmed by comparison of their molecular weights, isoelectric points, and peptide patterns from limited papain digestions with those of the corresponding proteins from fibroblasts and brain, respectively. A specific antibody to vimentin stained filamentous structures and colcemid-induced coils in both neurones and associated satellite cells. In contrast, a specific antibody to the 70K neurofilament protein stained these structures solely in neurones. This neurone-specific staining, as well as its molecular weight and isoelectric point, distinguishes the 70K neurofilament protein from the 68K neurofilament associated protein described by others, which has been claimed to resemble the tubulin assembly protein.

Cultures of neurons essentially free of non-neuronal cells were prepared from chick sympathetic neurons and from sensory neurons that had been enriched on a simple density gradient. The proteins of these cultures were examined by two-dimensional gel electrophoresis and two species found in each type of nerve cell that ran close to, but not precisely with, muscle actin. They comigrated with the fi and 7 actins previously seen in developing myoblasts (WHALEN et al., 1976).