Studies on the morphologic alterations of axonal membraneous organelles in neurofilamentous neuropathies

Alterations in the membraneous organelles were studied in two experimental neuropathies: 2,5-hexanedione (2,5-HD) and beta,beta'-iminodiproprionitrile (IDPN), both of which exhibit massive neurofilamentous accumulation. The membranous organelles were stained using the diaminobenzidine potassium ferrocyanide (DPF) method. In 2,5-HD, where there is a progressive impairment of fast axoplasmic transport, studies of the smooth endoplasmic reticulum (SER) revealed a fragmentation and disruption of the continuity of the longitudinally oriented interconnecting tubules and a significant increase in the number of free vesicles. In IDPN, where studies of fast transport have been normal, the longitudinal orientation of the smooth SER tubules was not disturbed although channels of longitudinally oriented tubules of SER were clustered with microtubules and mitochondria. This study suggests that in 2,5-HD the accumulation of vesicles in association with fragmentation and disorganization of the SER is one of the morphologic correlates of the impaired fast anterograde transport system.