Tubules within the cristae of mitochondria can sometimes take on
unusual configurations. Here, in the upper panel, a
mitochondrion from an astrocyte in hamster brain appears to have
prismatic tubules that are triangular in cross section. The
lower panel shows a mitochondrion from rat adrenal cortex with
what appears to be vesicular cristae. Arrows point to evidence
suggesting that instead, these are probalby tubules with
alveolar branches. Description here. Figure 245 (upper) by K.
Blinzinger, J. Cell Biol. 25: 293, 1965; fig. 246 (lower)
courtesy of Daniel Friend, from Chapter 7 (Mitochondria) of 'The
Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the
accompanying chapter is available on the ASCB's BioEDUCATE
website.