Massive cell death, which accompanies the freeing of the digits, occurs in the interdigits of the developing chick foot during stages 30-35. The possibility was reexamined that mitochondrial succinic dehydrogenase activity disappears in the interdigital cells of the chick foot 24 h before cell mortality. Using standard histochemical means it was found that succinic dehydrogenase activity was demonstrable in the interdigital cell population up to and including the time when cell death begins. This was confirmed quantitatively employing biochemical methods which indicated that succinic-cytochrome c reductase specific activity was approximately the same in homogenates of digital and interdigital tissues harvested just prior to the death of interdigital cells. Further, NADH-cytochrome c reductase specific activity was comparable in digital and interdigital tissue homogenates. These data make it unlikely that ‘biochemical degeneration’ associated with alterations in aerobic energy metabolism occurs in the interdigital cells before death as has been suggested by other workers previously. The methods used by these authors to demonstrate succinic dehydrogenase were repeated on chick feet in our laboratories and an alternative interpretation of the results is offered.

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