| Abstract: | The degeneration process of Pick's bodies (PB) was investigated using methenamine‐silver (MS) staining and immunohistochemistry. Methenamine‐silver staining sensitively detected extracellular PB as well as intracellular PB in the granular cell layer of the dentate gyrus. Extracellular PB appeared as granular masses with ill‐defined boundaries in the neuropil. For MS electron microscopy, the extracellular PB were composed of randomly oriented fibrillary components measuring 9–12 nm in diameter with astroglial processes and degenerated organelles. Tau immunoreactivity of extracellular PB was reduced or abolished. These findings indicate that MS staining is a convenient method for detecting extracellular PB. In addition, it was shown that microglial involvement was associated with PB‐bearing neurons at the late stage of the degeneration process and that extracellular PB remained in the neuropil with astroglial reaction. |
