AN ALTERNATIVE EXPLANATION FOR A POSTULATED NONTHERMAL, NONCAVITATIONAL ULTRASOUND MECHANISM OF ACTION ON INVITRO-CELLS AT HYPERTHERMIC TEMPERATURE

V-79 cells were suspended in medium with 10 or 20% serum, and exposed to a continuous wave of 1 or 3.4 MHz ultrasound (0.7-1 W/cm2) for 0-90 min in polystyrene test tubes at 37 or 43°C, and subsequently assessed for cell lysis, plating efficiency and surviving fraction. The effectiveness of the ultrasound regimens was enhanced at 43°C. Thermocouple measurements of temperatures in the cell culture medium in the test-tube revealed an increase of about 0.5°C under insonation conditions, using the 1 MHz; 10% serum; 37°C regimen. The results were broadly consistent with an ultrasound-induced incremental theraml burden causing an increased effectiveness of the ultrasound exposures at hyperthermic temperatures. © 1990.