Enhancement of DNA synthesis in neonatal mouse tibial epiphyses after exposure to therapeutic ultrasound

In vitro growth response of tibiae removed from newborn mice was monitored after treatment with ultrasound. Bones, in an acoustically uniform medium, were insonated with continuous‐wave ultrasound at a frequency of 1.0 MHz with an intensity of 1.8 W/cm2. Contralateral isolates were used as controls. Purely thermal effects were held to a minimum. A statistically insignificant increase in elongation was observed after three five‐minute exposures 24 hours apart. A similar response was also found for protein accumulation and radioactive proline incorporation into protein in the cartilaginous epiphyses. However, after three exposures of ultrasound the incorporation of radioactive thymidine into DNA was significantly stimulated.