Periodic units in the intracristal and envelope spaces of neuronal mitochondria. An artifact due to delayed fixation.

Ultrastructural study of the cerebral cortex and spinal anterior horns disclosed periodically repeating processes located in the envelope space or in the intracristal space of neuronal mitochondria. The alteration was observed in postmortem cases in which fixation was delayed either voluntarily or involuntarily, but was not present in postmortem or surgical specimens in which fixation was prompt. The change is interpreted as an artifact due to delayed fixation.