Fig. 8. Bielschowsky's silver impregnation of axons was used to measure axonal density in neurons of the spinal cord, brain motor cortex and hippocampus. SC: spinal cord; BC: brain cortex; H: hippocampus; scale bar = 100 μm. (A–C) Bielschowsky's silver staining method non-specifically stains normal neurons including pyramidal cells in the brain motor cortex and hippocampus, showing a typical regular and triangular shape (arrows in A and C); and large motor neurons (MNs) in the anterior horn of the spinal cord (B). Density of neurofilaments began to become sparse from the second week after l-BMAA injections (D–F), and significant loss of axons was detected at four weeks post l-BMAA treatment (G–I). Loss of neurites in neurons at six weeks post l-BMAA injections (J–L) displayed deformed ovoid-shaped forms with a swelling nucleus (arrows in J and K); and finally, at eight weeks post injection (M–O), the normal structure of neurons especially in the anterior horn of the spinal cord completely disappeared, and neurons presented a dissolving necrotic appearance with only a few remaining neurofilaments (arrow in N).