Oxidoreductases were studied histochemically in 162 cases of
neuroectodermal tumors. In order of decreasing activity in the cytoplasma these
enzymes could be arranged as follows:
NADH diaphorase,
lactate dehydrogenase,
NADPH diaphorase,
glutamate dehydrogenase,
glucose-6-phosphate dehydrogenase,
isocitrate dehydrogenase,
succinate dehydrogenase,
malate dehydrogenase. The weak activity of Krebs cycle
enzymes and the relatively strong activity of other
oxidoreductases, particularly of
lactate dehydrogenase, permits to conclude that glycolysis prevails over oxidative processes in
neuroectodermal tumor cells. But this should not be interpreted as a decrease of the Krebs cycle
enzymes in
astrocytoma and
oligodendroglioma cells as compared with their parent cells because the latter themselves display a weak activity of these
enzymes. A real decrease of Krebs cycle
enzyme activity was established only for
tumors, the parent cells of which are characterized by a strong (in choroid-
papillomas) or moderate (in
ependymomas) activity of these
enzymes. Many
neuroectodermal tumors, in particular those of astrocytic origin, demonstrate a certain correlation between the amount of cytoplasm and
oxidoreductase activity. This results in enzymatic polymorphism of the
tumor tissue. A certain similarity was established of the
oxidoreductase activity in
tumor cells and in reactive hypertophic astrocytes. This indicates that both
tumor cells and reactive astrocytes may in certain conditions utilize similar mechanisms of increased metabolism. The
oxidoreductase activity correlates not with the grade of
anaplasia but with different directions of
anaplasia reflected in different variants of
neuroectodermal tumors. The concept "
anaplasia" includes not only certain degrees of dedifferentiation of
tumor cells but, as it has been shown histochemically, also an increase of metabolic processes in the
tumor cell cytoplasma.