Quantitative light and electron microscopic studies on the ventral roots of the wobbler mutant mouse.

In wobbler mutant mice and normal litter-mates the numbers of axons have been counted in cervical and lumbar ventral roots and the dimensions of nerve fibres measured in the fifth cervical, C5, and third lumbar, L3, roots. In wobbler cervical ventral roots C5, C7 and C8 and lumbar roots L4 and L5 the number of axons was reduced. Abnormal features were seen in all mutant cervical ventral roots but not in the lumbar roots. The histogram of fibre size was shifted to the left in the wobbler C5 roots where axon loss was considerable, particularly amongst the large diameter axons, and in L3 roots where, although there was no over-all loss of axons, there were fewer ventral root fibres of large diameter. Abnormal features were also observed in a few dorsal root ganglion cells.