The Effect of Thiouracil and Thyroid Extract on the Natural Resistance of Mice to Hymenolepis Infection

Abstract

White mice about 2.5 months old appear to be the most susceptible to an initial experimental infection with Hymenolepis nana var. fraterna, whereas those past 5 months of age demonstrate the greatest resistance (Shorb, 1933; Hunninen, 1935; Larsh, 1944.) When Holtman (1946) showed that an altered metabolic rate in mice affected their natural resistance to a certain virus, it suggested a possible explanation for the above difference in response to Hymenolepis as the metabolic rate differs greatly for mice of these separate age groups. The present experiments were designed, therefore, to test the effect on natural resistance to Hymenolepis of depressing the normal high metabolic rate of young mice with thiouracil injections, and elevating the normal low rate of old mice with thyroid extract injections; these results were reported earlier in abstract form (Larsh, 1947a). As far as known, this approach differs from that used in related studies, as in these cases the normal rate of young animals alone was depressed or elevated to determine the effect on natural resistance (Todd, 1948, 1949; Wheeler et al, 1948; Whitlock, 1949).