The study tests the capacity of 50-Hz magnetic and electric fields to stimulate neurite outgrowth in PC-12D cells. The cells were plated on collagen-coated plastic petri dishes and exposed to sinusoidal 50-Hz magnetic fields for 22 hours in a 5% CO2 incubator at 37 C. Two 1,000-turn coils, 20 cm in diameter, were assembled in a Helmholtz configuration to generate a magnetic field in a vertical orientation, thereby including a companion electric field in the dish with intensity proportional to radius. A co-netic metal magnetic-field shield housed the control samples in the same incubator. Total cells and number of cells with neurites at least as long as one cell diameter or having a growth cone were counted within a radius of 0.3 cm of the dish center and within an annulus of 1.7 to 1.8 cm radii in 60-mm dishes, at 3.6 mm radius in 100-mm dishes, and between 1.9 and 2.1 cm radii in the outer well of organ culture dishes, which are physically separated into two concentric wells. Sham exposure demonstrated no difference in percentage of cells with neurites between the exposed and control locations in the incubator. Exposures were done at 4.0, 8.9, 22, 29, 40, 120, 236 and 400 milliGauss (mG). At dish radii of 1.7 - 1.8 cm in the 60-mm dishes these magnetic flux densities induced electric fields of 1.1, 2.5, 5.9, 8.1, 11, 33, 65 and 110 microV/m, respectively, while within a radius of 0.3 cm, the induced electric fields were less than 0.2, 0.4, 1.0, 1.5, 1.9, 6.0, 11 and 19 microV/m, respectively. For other dishes, the larger radii produced proportionally larger induced electric fields. At each field strength, there were two control dishes and four to nine exposed dishes; 100 or more cells were counted at each dish location. (Copyright (c) 1993 Wiley-Liss, Inc.)