PULSE SHAPE OF MAGNETIC-FIELDS INFLUENCES CHICK EMBRYOGENESIS

Abstract

Chick embryos (295) were exposed during the first 48 h of development to pulsed electromagnetic fields (EMF) of 100 Hz and 0.4-104 microTeslas (.mu.T), and findings were compared with those in 364 control embryos. General morphology was analyzed and supplemented by light microscopy studies. Exposure to EMF with pulse rise time (rt) of 100 .mu.s produced teratogenic changes when 1.0 and 13.9 .mu.T were used but not with lower or higher intensities, demonstrating a window effect and ruling out the possible influence of a rise in internal embryonic temperature. Exposure to 1.0 .mu.T EMF specifically altered organogenesis of the truncal nervous system (TNS) and drastically reduced the alcian blue stained components: with 13.9 .mu.T, there were abnormalities in the circulatory system and foregut, altering cell-to-cell contacts in the walls of developing vessels. When embryos were exposed to intensities of 0.4 and 1.0 .mu.T with 2.0 and 42 .mu.s pulse rise times, teratogenic effects were greater and alterations involved all developing systems. The most powerful effects were obtained with 10 .mu.T and 42 .mu.s rise time. Findings confirm the sensitivity of chick embryos to EMF of extremely low frequency and intensity and indicate that pulse shape may be a decisive parameter determining strong, slight or no modification of embryonic development. Mechanisms of EMF action are still unclear but induced alterations in extracellular mucopolysaccharides could be a causal factor in the observed malformations.