Influence of Thymectomy and of Thymic-Extract Treatment in the Development and Growth of 3,4-Benzpyrene-Induced Sarcomas in the Rat

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Abstract
Forty-five female and male albino rats, 3 months old, were given 3 subcutaneous injections of 5 mg of 3,4-benzpyrene in almond oil, once every 20 days. Fifteen animals had been thymectomized at 1 month of age; 15 were given daily intravenous injections of an aqueous thymic extract for 10 days prior to each treatment with benzpyrene; 15 were kept as controls. Four of the thymectomized animals developed subcutaneous sarcomas, while sarcomas appeared in all the animals of the other two groups. The latent period for the appearance of tumors in the thymectomized animals was not significantly different from that observed in the controls. The survival time after the appearance of tumors was significantly longer in the thymectomized animals than in those of the other groups. In the thymic-extract-treated group, the latent period and the survival time were significantly shorter than in the other groups. The results are discussed and it is called attention particularly to the partial inhibiting effect of the thymectomy.