Light- and electron-microscopic studies of intracytoplasmic acidophilic granules in the human locus ceruleus and substantia nigra.

Using the brains of 30 patients with mental and neurologic disorders, we studied the intracytoplasmic acidophilic granules in neurons of the substantia nigra and locus ceruleus by light and electron microscopy. The granules were present in all 30 brains, including those with no recognizable pathologic change, there was no correlation between their appearance and the age, sex, disease of, or the medication received by, the patients. In four electron-microscopically examined brains, we noted many small, round electron-dense bodies in the perikarya and neuronal processes of the substantia nigra and locus ceruleus. The bodies were packed tightly within a double membrane; in shape, size, and distribution in the neuronal cytoplasm, they corresponded to acidophilic granules. Some mitochondrial matrices contained one or more similar, but smaller inclusion bodies; large bodies pushed aside the mitochondrial cristae. We conclude that the acidophilic granules represent high developed forms of mitochondrial inclusions.