May 14, 2021 · After washes and fixation in 1% osmic acid for 1 hr, samples were washed in PBS, dehydrated in a series of gradient ethanol (50, 70, 80, 90, 95, and 100%), embedded in Epon Resin, and then cut into 60 nm ultrathin sections. After uranyl acetate and lead citrate staining, samples were observed with a Hitachi HT7700 electron microscope.