the nerve cell body, where they rapidly assemble into neurofilament polymers within about 30 minutes. These assembled neurofilament polymers are transported along the axon on microtubule tracks powered by microtubule motor proteins. The filaments move bidirectionally, i.e. both towards the axon tip (anterograde) and towards the cell body (retrograde), but the net direction is anterograde. The filaments move at velocities of up to 8 µm/s on short time scales (seconds or minutes), with average velocities of approximately 1 µm/s. However, the average velocity on longer time scales (hours or days) is slow because the movements are very infrequent, consisting of brief sprints interrupted by long pauses. Thus on long time scales neurofilaments move in the slow component of axonal transport. Clinical and research applications Numerous specific antibodies to neurofilament proteins have been developed and are commercially available. These antibodies can be used to detect neurofilament proteins in cells and tissues using immunofluorescence microscopy or immunohistochemistry. Such antibodies are widely used to identify neurons and their processes in histological sections and in tissue culture. The type VI intermediate filament protein Nestin is expressed in developing neurons and glia. Nestin is considered a marker of neuronal stem cells, and the presence of this protein is widely used to define neurogenesis. This protein is lost as development proceeds. Neurofilament antibodies are also commonly used in diagnostic neuropathology. Staining with these antibodies can distinguish neurons (positive for neurofilament proteins) from glia (negative for neurofilament proteins). There is also considerable clinical interest in the use of neurofilament proteins as biomarkers of axonal damage in diseases affecting the central nervous system When neurons or axons degenerate, neurofilament proteins are released into the blood or cerebrospinal fluid. Immunoassays of neurofilament proteins in cerebrospinal fluid and plasma can thus serve as indicators of axonal damage in neurological disorders. NfL is a useful marker for disease monitoring in amyotrophic lateral sclerosis, multiple sclerosis, and more recently Huntington's disease. It has also been evaluated as a prognostic marker for functional outcome following acute ischemic stroke Mutant mice with neurofilament abnormalities have phenotypes resembling amyotrophic lateral sclerosis. See also Bielschowsky stain References Cytoskeleton