Ultrathin sections about 70 nm were observed at 80 kV with a JEOL 1230 electron microscope (Japan). As a control, sections were immersed in a solution of 100 mmol L1 EGTA (pH 8.0 adjusted with 0.2 mol L1 KOH) for 2 h at room temperature.
Ultrathin sectionsabout 70 nm were observed at 80 kV with a JEOL 1230 electronmicroscope (Japan). As a control, sections were immersed in a solutionof 100 mmol L1 EGTA (pH 8.0 adjusted with 0.2 mol L1 KOH)for 2 h at room temperature.