Isolation of 10-nm filaments from astrocytes in the mouse optic nerve.

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Abstract
Astroglial filaments .apprx. 10 nm in diameter were isolated from degenerated mouse optic nerves by Triton X-100 and DNase I treatments followed by sucrose density gradient centrifugation. Optic nerves contained virtually a single population fo 10 nm filaments (astroglial filaments), free from neurofilaments 2-4 wk after bilateral enucleation. In negative-staining and thin-section EM, the isolated filaments were seen as nonbranching linear structures with smooth contour, and were morphologically identical to those in situ. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the isolated filaments to be composed of 2 major polypeptides with MW of 45,000 and 55,000, present in an approximate molar ratio of 1:1. These findings, together with the results of 1-dimensional peptide mapping and solubility study, indicate that the astroglial filaments in the mouse optic nerve are primarily composed of these 2 polypeptides.