Cellular visualization of MNPs. Primary cerebellar and Schwann cell/fibroblast cultures are stained with nuclear fast red-aluminium sulphate (visualizing the cells) and Prussian blue (visualizing MNPs). (A) shows control (CO) cerebellar cells and (B) cerebellar cells incubated with MNPs. (C) illustrates Schwann cell/fibroblast cultures of the control and (D) incubated with MNPs. Arrows indicate stained MNPs. Bars represent 50 μm.