Cavitational bio-effects of 1.5 MHz

The effects of continuous wave ultrasound on three different classes of biosystems have been investigated at a frequency of 1.5 MHz. The criteria for cavitation are given, and these are applied to experimentally observed growth retardation of plant roots, cell death and DNA degradation in bacteria and pyknosis of human lymphocytes. An attempt is being made to find common physical mechanisms for all these biological responses, and cavitation processes in particular are examined here. A description is given of the techniques used to monitor the presence of cavitation, and indirect evidence, drawn from pulsed field and elevated pressure experiments, is presented to show that other-non-linear processes are also operative.