Electron microscope pictures of β cells in isolated islets from +hIAPP−mIAPP transgenic mice cultured for 2 days. (A, B) Parts of β cells of islets cultured in the presence of 150 µM albumin. No aggregate is seen in the halo region of the granules. (C) Part of β cell of islet incubated in the presence of 300 µM myristic acid and 150 µM albumin. A fibrillar aggregate is present in the halo region of the β cell. (D) β cell granules from an islet cultured in the presence of 300 µM oleic acid and 150 µM albumin reveal fibrillar aggregates in the halo region of the secretory granules. In B, C, and D immunolabeling was performed with an IAPP-specific antiserum. Bar = 300 nm.