Effect of ultrasound on axonal outgrowth in the sympathetic nervous system of the chick.

The effects of ultrasound exposure on the rate and specificity of sympathetic preganglionic axonal outgrowth were examined in the chick embryo. Using a technique which allows for exact quantitation of exposure for exact quantiation of exposure conditions, embryos were irradiated in ovo for 5 min daily on 3 consecutive days at an intensity of 1 W/cm2 Spatial Average, Temporal Average (SATA), with a frequency of 1.1 MHz pulsed at 1 kHz and a pulse width of 75 microsecond(s). Our results show no significant difference between irradiated and sham-irradiated embryos. In addition, we have examined the distributions of several major extracellular matrix molecules (fibronectin, laminin and collagen IV) in irradiated and sham-irradiated embryos using immunofluorescent staining. No difference in the staining pattern was found. Finally, we found no increase in the incidence of gross abnormalities and no evidence of lesions and malformations in irradiated embryos.