The kidney carcinoma of the leopard frog has served for various studies on catalase activity, as a first step in gaining information on enzymatic properties of neoplasms in cold blooded animals.

It was found that the activity level of this tumor is reduced to approximately 13 per cent of that of the normal frog's kidney.

Systemic effects of the tumor on catalase activity of liver and kidney are evident. Liver catalase in tumor-bearing frogs is diminished to about 50 per cent of the normal, and kidney catalase to an even greater degree; i.e., to about 34 per cent. A positive correlation exists between levels of catalase in tumor and in liver.

Frogs kept at 3 different temperatures, 8, 18, and 26.5°C., for upward of 29 days exhibited no significant change in activity levels either of tumor or of livers from normal or from tumor-bearing animals. It is suggested that a seasonal variation may occur in catalase activity of the frog. During the winter months catalase activity of the tumors was found to be higher than during the summer, whereas liver catalase was below the level of normal frogs examined during the summer.

Intracoelomic injections of homogenates of tumors promptly lead to diminution of liver catalase lasting for several days. Injection of normal kidney has no such effect.

These results with a spontaneous tumor of a cold blooded animal are in essential agreement with the many observations made with transplanted tumors of warm blooded animals. They lend support to the view that neoplasia is a ubiquitous biological process with similar characteristics in all species or classes of vertebrates.

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