Lack of an effect of static magnetic field on calcium efflux from isolated chick brains

Effect of a static magnetic field on ion transport in a cellulose membrane

A cellulose membrane was exposed to the static magnetic field (SMF) in the presence of KCl solution and ion transport through the membrane was measured before and after the SMF exposure. SMF at 0.24 T significantly enhanced the rate of ion transport, especially after the first exposure (p<0.05), while the increased ion transport rate did not return to the initial basal level after exchange of the aqueous medium. These results suggest that an irreversible, temporal conformation change took place on the cellulose membrane or on the water bound to the cellulose surface. The accelerating effect of SMF on the ion transport seems to have occurred as a result of stabilized hydration layer on the cellulose surface.

Magnetic fields (MF) of 50 Hz at 1.2 microT as well as 100 microT cause uncoupling of inhibitory pathways of adenylyl cyclase mediated by melatonin 1a receptor in MF-sensitive MCF-7 cells

Magnetic fields (MF) of 60 Hz at 1.2 microT were previously shown to inhibit the antiproliferative effect of melatonin on MCF-7 cells (Liburdy,R.P., 1993, J. Pimeal Res. 14, 89-97). In addition, three laboratories (Blackman,C.F. and Benane,S.G., 1998; Luben,R.A. and Morgan,A.P., 1998; Morris,J.E., Chrisler,W.B., Miller,D.L., Sasser,L.B. and Anderson,L.E., 1998; 20th Annual Meeting of the Bioelectromagnetics Society, At. Pete Beach, FL) independently reported results consistent with this finding. In this study, we investigated the molecular basis of the biological effects of MF using MCF-7 cells. Only 1a melatonin receptors were identified by the [125I]melatonin binding assay and RT-PCR analysis. Moreover, preceding exposures to MF of 100 microT for 3, 5 and 7 days blocked the melatonin-induced inhibition of cAMP accumulation in a time-dependent manner, while none of the melatonin receptor functions or GTPase and adenylyl cyclase activities were affected. Estrogen-evoked cell proliferation was not altered by MF either. Exposure to 1.2 microT MF exerted the same effects on the melatonin-signaling pathway as that to 100 microT. Thus, this is the first study to provide evidence that MF may cause uncoupling of signal transduction from melatonin receptors to adenylyl cyclase.

Short-term exposure to a 1.5 tesla static magnetic field does not affect somato-sensory-evoked potentials in man

The literature is contradictory regarding the effect of static magnetic fields on the function of the central nervous system of mammals. Since human subjects are exposed to intense static magnetic fields during magnetic resonance imaging, it is important to determine if the static magnetic field adversely affects the nervous system of man. Therefore, somato-sensory evoked potentials (SEPs) elicited from median nerve stimulation were measured in 11 normal subjects before and during short-term exposure to a 1.5 Tesla static magnetic field. Specially modified instrumentation was used to record SEPs that were unperturbed by the static magnetic field. There were no statistically significant differences in the N20 or P25 latencies or in the amplitude from N20 negative peak to P25 positive peak of the SEPs obtained before compared to those recorded during exposure to the static magnetic field. In addition, there were no changes in the waveforms associated with exposure to the static magnetic field. We conclude that short-term exposure to a 1.5 Tesla static magnetic field does not affect SEPs (i.e., nerve conduction and synaptic transmission were within normal limits) in normal human subjects.

Effects of nonionizing radiation on birds

1. With the ability to fly comes a greater probability of direct irradiation by nonionizing radiation. The effect of nonionizing radiation on birds is, therefore, of environmental significance. 2. Most biological effects of exposure to nonionizing radiation in avian species are a result of radiation-induced temperature increases. 3. The incubating avian egg provides a model to study nonthermal effects of microwave exposure since ambient incubation temperature can be adjusted to compensate for absorbed thermal energy. 4. Some studies have shown that exposure to nonthermal levels of nonionizing radiation affect a bird's ability to recover from acute physiological stressors. 5. Although earlier research indicated that modulated radiofrequency radiation increased calcium-ion efflux in chick forebrain tissue, criticism of experimental techniques and contradictory results between related studies have made final conclusions elusive. 6. Birds have been shown to be able to reliably detect magnetic fields in both the field and laboratory. Some researchers have reported malformations in chicken embryos exposed to a sinusoidal bipolar oscillating magnetic field.