Ultrastructural localisation of calcium in peripheral nerves of the rat.

An ultrastructural method which is specific for calcium was applied in a study of calcium distribution in the axoplasm of myelinated nerve fibres of rat sciatic nerves. Electron-dense deposits of calcium oxalate were seen in smooth-membraned vesicles within the axoplasm, and between the two external membranes of axoplasmic mitochondria. The significance of calcium localisation at these sites is discussed, with special reference to the role of calcium in fast axoplasmic transport.