Absence of a 45 or 60 Hz Electric Field-Induced Respiratory Effect in Physarum polycephalum

Microplasmodia of Physarum polycephalum strain ${\rm M}_{3}{\rm C}$ were exposed to 60 Hz continuous wave electric fields of 0.7 and 70 V/m for more than 13 weeks and to 45 Hz CW fields of the same strengths for nearly 7 weeks. At a particular field strength, duplicate subcultures of sham-exposed and field-exposed microplasmodia were independently maintained and measured to allow comparison of variation between subcultures within an exposure treatment group. Microplasmodial oxygen uptake rates were measured using a Clark-type oxygen electrode system, and respiratory rates were expressed on a unit protein basis. Few consistent respiratory rate differences between sham- and field-exposed subcultures were detected at either 0.7 or 70 V/m. These findings are in contrast to earlier reports of significant microplasmodial respiratory rate depression in response to 45 or 75 Hz, combined 0.7 V/m, 2.0 G electric and magnetic fields and in response to 75 Hz, 0.7 V/m electric field exposure [Greenebaum et al., DHEW Report FDA-77-8010, Vol. I, pp. 449-459 (1977); Goodman et al., Radiat. Res. 78, 485-501 (1979)]. Growth rate data are also presented and similarly fail to show an exposure treatment effect.