Thin and semi-thick sections of approximately 70 and 250 nm, respectively, were cut using a diamond knife and a model EM UC6 microtome (Leica Microsystems). Thin sections were collected on uncoated 200 mesh copper grids. Once thoroughly dried, the sections were stained with fresh 1% lead citrate using 1 minute of microwave irradiation at 167 watts, followed by a 1 minute water wash at 167 watts and standard drop-wise washing.