Abstract
INTRODUCTION: The functions and mechanisms of prion proteins (PrP(C)) are currently unknown, but most experts believe that deformed or pathogenic prion proteins (PrP(Sc)) originate from PrP(C), and that there may be plural main sites for the conversion of normal PrP(C) into PrP(Sc). In order to better understand the mechanism of PrP(C) transformation to PrP(Sc), the most important step is to determine the replacement or substitution site. MATERIAL AND METHODS: BALB/c mice were challenged with prion RML strain and from 90 days post-challenge (dpc) mice were sacrificed weekly until all of them had been at 160 dpc. The ultra-structure and pathological changes of the brain of experimental mice were observed and recorded by transmission electron microscopy. RESULTS: There were a large number of pathogen-like particles aggregated in the myelin sheath of the brain nerves, followed by delamination, hyperplasia, swelling, disintegration, phagocytic vacuolation, and other pathological lesions in the myelin sheath. The aggregated particles did not overflow from the myelin in unstained samples. The phenomenon of particle aggregation persisted all through the disease course, and was the earliest observed pathological change. CONCLUSION: It was deduced that the myelin sheath and lipid rafts in brain nerves, including axons and dendrites, were the main sites for the conversion of PrP(C) to PrP(Sc), and the PrP(Sc) should be formed directly by the conversion of protein conformation without the involvement of nucleic acids.