Electron Microscopy Examination of Monkey Brain

The procedure of EM examination has been described in our previous studies.^{50 (link)} In brief, freshly isolated monkey brain tissue blocks were fixed with 4% paraformaldehyde and 0.2% glutaraldehyde for 48 h and sectioned using a vibratome. All sections used for electron microscopy were dehydrated in ascending concentrations of ethanol and propylene oxide/Eponate 12 (1:1) and embedded in Eponate 12 (Ted Pella, Redding, CA). Ultrathin sections (60 nm) were cut using a Leica Ultracut S ultramicrotome. Thin sections were counterstained with 5% aqueous uranyl acetate for 5 min followed by Reynolds lead citrate for 5 min and examined using a Hitachi (Tokyo, Japan) H-7500 electron microscope.