Effects of B16 melanoma transplantation on the respiration of grouped C57Bl female mice.

Two batches of 110 females C57Bl mice were grafted with B 16 melanoma, the first batch at the age of 67 days, the second at 82 days. The animals were divided into groups of 10, and kept under a LD 12 : 12 regimen. The growth of the tumors was more rapid in the second batch. This was accompanied in this batch, by a decrease in body growth, a diminution of heart rate and an increase in QRSII amplitude. Significant decreases in carbon dioxide emission (VCO2) level, mostly during the dark period of time, when the mice had their greatest activity, and decrease in respiratory photic variations at light transitions were obtained when the tumors were well developed. Harmonic analysis of the continuous recording of carbon dioxide shows slight changes in VCO2 ultradian (40 minutes less than tau less than 12 hours) rhythms. The effects on respiration were confirmed by different survival rates and rectal temperatures between tumor grafted and controls submitted to an acute nitrogen normobaric hypoxia.