Microtubules in Squid Giant Axon

Abstract

Cytoskeletal networks composed of microtubules (MT), neurofilaments (NF) and cross-bridges were well preserved in giant axons of the squid by adding dimethylsulfoxide (DMSO) to the glutaraldehyde solution for fixation. DMSO remarkably supported preservation of the otherwise labile MT in the giant axon. Bundles of MT, frequently associated with NF, were observed in the axoplasm running parallel to the longitudinal axis of the axon. The distribution of MT in the axon was more prominent in the peripheral axoplasm (60-80 MT/.mu.m2) than in the interior (20-25 MT/.mu.m2). At the edge of the periphery of the axoplasm, some MT seemed to end in the axolemma, but others appeared to be cross-bridged to the axolemma by filamentous structures. In axons treated with cold or injured, winding tubules thinner than the MT appeared in the peripheral axoplasm.