HISTOCHEMICAL AND ULTRASTRUCTURAL STUDIES OF PRIMARY SENSORY NEURONS IN MICE WITH DYSTONIA MUSCULORUM .1. ACETYLCHOLINESTERASE AND LYSOSOMAL HYDROLASES

Enzyme histochemical and fine structural studies were performed on mice with a hereditary sensory neuropathy (dystonia musculorum). The dystonic mice were compared with normal litter mates. Acetylcholinesterase activity was studied in trigeminal and spinal ganglia, sensory receptors and sympathetic ganglia. Lysosomal hydrolases and ultrastructural features were studied in the trigeminal and spinal ganglia. Striking changes in the amount and distribution of enzymic activity were observed in the perikarya of sensory ganglion neurons in dystonic mice. Perikaryal involvement was indicated by displacement of the nucleus, enlargement of the perikaryon, peripheral location of Nissl substance, loss of enzymic activity and an increase in the number of neurofilaments, features similar to those that follow physical interruption of the axon. The focal axonal swellings that occurred along sensory nerve fibers contained concentrations of lysosomal hydrolases and sometimes acetylcholinesterase activity. They were generally more numerous in the nerve fibers located distal to the ganglion rather than proximal to it. At the ultrastructural level these swellings contained lysosomal bodies and remnants of organelles. Some abnormalities in the myelin and the size of paranodal gaps were also observed. Interruptions in axoplasmic flow and experimental neuropathies including those of the dying-back type were discussed.