Intracristal Rods

Workers in many laboratories (1, 4, 5, 11, 1315) have isolated outer membrane, inner membrane, and matrix fractions from beef heart and rat liver mitochondria and have assayed the enzymes associated with each fraction . Little attention has been directed towards the contents of the intracristal space, that space within the infoldings of the cristae and continuous with the space between the outer and inner membranes of the mitochondrion . Adenylate kinase, creatine kinase, and perhaps nucleosidediphosphate kinase are reportedly localized in this space (3, 6, 14), as these enzymes are eluted from mitochondria which have a broken, but attached, outer membrane . However. no structural element has been reported in the intracristal space . A new structure which has been observed in the intracristal space of isolated heavy beef heart mitochondria by means of thin sectioning will be described here .