Fig. 5. Electron energy-loss imaging (ESI) and electron energy-loss spectral (EELS) analysis of 20 nm thick sections of cryofixed, freeze-substituted anterior sternal epithelium after loading the smooth endoplasmic reticulum with calcium oxalate. Some of the calcium oxalate precipitates are indicated by arrows. cl, cuticular layer. Scale bars, 0.5 µm. (A) ESI image at E=320±5 eV. (B) ESI image at E=360±5 eV; the calcium oxalate precipitates transmit a bright signal. (C) EELS of the precipitate within smooth membrane cisterns; Ca_L2,3 indicates the absorption edges for calcium.