抄録
Recently, ultrasound has been a lot of attention in medical field because of its widely usage in diagnosis and therapeutic treatment. However, the information about the therapeutic treatment mechanism and its safety of MHz ultrasound is insufficient. Therefore we have studied the biological effect of MHz ultrasound on human lymphoma U937 cells in order to properly evaluate the therapeutic effect of ultrasound. For an ultrasound apparatus, ceramic resonators of 1.6 MHz and 2.4 MHz were used and placed in the bottom of water tank made of brass. A glass tube containing 2.0 ml cell suspension was set above the transducer on the water. The frequency of ultrasound was 1.6 MHz, 2.4 MHz, 5.4 MHz and 7.9 MHz. The intensity of ultrasound was determined with calorimetric method. The cells were irradiated with ultrasound for 10 seconds. Because the ultrasonic irradiation to the cells leads to excessive cell death of normal cells, we examined the survival rate of cells. The reproductive cell death was measured for three days after irradiation. In addition, we examined the induction of apoptosis one day after irradiation by flow cytometer. As a result, the cell growth of U937 was inhibited and the induction of apoptosis was observed in 1.6 MHz and 2.4 MHz. On the other hand, the effect of ultrasound on the cell growth was not seen in 7.9 MHz.
