0.1 m cacodylic acid buffer

Mitochondria were obtained either from treated cells or microparticles from SNs of cell cultures. Thin sections were obtained from purified mitochondria fixed with 3% glutaraldehyde in 0.1 M cacodylic acid buffer (pH 7.4) (Ladd Research Industries, Williston, VT). The samples were washed three times with 0.1 M cacodylic acid buffer and poststained with 1% osmium tetroxide in cacodylic buffer for 1 h. Cells were then washed and embedded in 1% agarose. The agarose containing the cell sample was then prestained with 2% uranyl acetate (Polaron Instruments, Hatfield, PA) overnight at 4°C. The samples were washed and carried through acetone dehydration steps. Infiltration was done using the Epon-Embedding Kit (Electron Microscopy Sciences, Hatfield, PA). Samples were ultrathin sectioned (60–70 nm) on a Reichert Ultracut E Ultramicrotome, and sections were stained with 2% uranyl acetate in 50% ethanol for 30 min and SATO lead stain for 1 min. Samples were imaged on a Philips CM12 electron microscope.