THE ACTIVITY OF SUCCINIC DEHYDROGENASE IN THE EXPERIMENTAL EPENDYMOMA OF C3H MICE

1. The activity of succinic dehydrogenase in the transplantable ependymoma induced with methylcholanthrene in C 3 H mice was studied by both biochemical (Q O 2 ) and histochemical (using nitroneotetrazolium chloride) methods under aerobic conditions. The mitochondria were identified by Mallory's method in fixed tissue. 2. Succinic dehydrogenase activity in the ependymoma was much lower than in normal cerebrum. 3. In the normal cerebrum as well as in ependymoma there was close parallelism between the number, distribution and localization of mitochondria and succinic dehydrogenase activity. 4. In the normal cerebrum, neurons revealed the highest succinic dehydrogenase activity, followed by choroidal epithelium and ependymal cells. Formazan granules were scattered throughout the neuropil. Oligodendrocytes, particularly satellites, showed moderate activity. Occasionally very low activity was present in astroglia. 5. Ependymoma cells contained a smaller number of formazan granules than average normal cerebrum, and the mitochondrial dots, rods and filaments in the ependymoma cells were smaller, finer and fewer. In addition, ependymoma cells in mitosis appeared to have lower succinic dehydrogenase activity and to be poorer in mitochondria than cells in the interphase. 6. It is postulated that the low enzymatic activity observed in ependymoma homogenates is related mainly to the scarcity of mitochondria and in part to the high incidence of mitotic cells.