Microfibrillar paracrystalline inclusion (MPI) within dorsal root ganglia (DRG) of humans and ferrets in cisplatinum toxicity

Abstract

MPI consist of large aggregates of regularly arranged microfilaments (MF) occuring in the soma and proximal processes of neurons of humans and various animal species. These inclusions have been described in the sympathetic ganglia, the caudate, the thalamus and the substantia nigra but their occurence in the DRG has not yet been reported. In the present study, they were found in DRG of humans and ferrets treated with cisplatinum as well as in the controls.On one micron epon sections stained with methylene blue, MPI appeared as bright blue inclusions of variable size, with an average diameter of 5 μm. At the ultrastructural level, their tendency to be located at the periphery of the cytons with a predilection for the axon hillocks (Fig. 1) and the proximal unmyelinated axons (PUMA) was confirmed (Fig. 2). They formed compact bundles of straight filaments measuring 5-6 nm in diameter. Within each individual bundle, the MF were organized in a highly parallel fashion with periodic intervals of 5-6 nm and regular transverse striations 5-7 nm apart (Fig. 3).