A simple noninvasive technique for measuring specific airway resistance (airway resistance X thoracic gas volume) in unanesthetized guinea pigs is described. Specific airway resistances measured by this technique correlated well (r = 0.81) with the resistances obtained using a pleural catheter pressure measurement over a wide range of airway resistances. This range of resistances was generated by exposing the pigs to an aerosolized histamine bronchial challenge. The average specific airways resistance in unchallenged pigs was 1.24 +/- 3.47 cmH2O/s, somewhat lower than found by others, probably reflecting in part our larger pigs and in part some uncertainty in the absolute value of resistance inherent in our measurement technique. This technique is particularly useful in bronchial challenge experiments because of its sensitivity to acute changes in airway resistance.

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Inbred C3H mice were inoculated subcutaneously with syngeneic, methylcholanthrene-induced sarcomas. During tumor growth, tumors were measured, and a cutaneous paw test carried out with viable tumor cells as antigen. In general, tumor paw tests were more reactive in mice with small tumors than in non-tumor-bearing control mice. When mice developed large tumors, their paw test reactivity decline, approaching that of unsensitized controls as tumors grew. The inverse correlation between tumor paw test reactivity and tumor volume is discussed. Side-to-side comparison of footpad reactivity indicated that the tumor paw test is highly reproducible. This model system in inbred mice appears useful for study of this and similar phenomena observed with some human neoplasms.

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