Samples were processed further in a Biowave model laboratory microwave oven, equipped with a Coldspot water circulator (Ted Pella, Inc.) as follows: washed twice in 0.1 M sodium phosphate buffer, pH 7.2, for 1 minute each; post-fixed in 1% osmium tetroxide in phosphate buffer for two cycles of 2 minutes on, 2 minutes off, and 2 minutes on; washed once in phosphate buffer for 1 minute and twice in water for 1 minute each; contrasted with 1% uranyl acetate in water for two cycles of 2 minutes on, 2 minutes off, and 2 minutes on; dehydrated in three changes of ethanol for 1 minutes each; and embedded in Spurr's resin using steps of 50%, 75%, and two changes of 100% resin in ethanol for two periods of 5 minutes each. The power output of the oven was set at 250 watts for dehydration and embedding. All other steps were performed at a setting of 167 watts. The cover slips were placed cell-side down onto resin block molds, polymerized overnight at 65uC, and removed from hardened blocks after a 5 second immersion in liquid nitrogen.