TEM.

NMJ cultures were prefixed in 2% paraformaldehyde and 2% glutaraldehyde in 0.1 M phosphate buffer (pH 7.4) at 4°C overnight. Postfixation was done in 1% osmium tetroxide solution for 1 hour at room temperature. The samples were dehydrated in graded concentrations of ethanol (30%, 50%, 70%, 90%, 95%, and 100%) and embedded in Epon resin. Ultrathin sections (80 nm) were cut and stained with uranyl acetate and alkaline lead citrate (46). The specimens were examined with a transmission electron microscope (H-7650, Hitachi).