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The effects of an in vivo exposure of cockroaches and an in vitro exposure of cockroach nerves to a 50 Hz magnetic field on the effects of the scorpion alpha toxin should be investigated.
The scorpion alpha toxin LqhαIT is a polypeptide highly active on insects. It binds to the sodium ion channels of nerves and inactivates them, causing hyper-excitation and paralysis. Magnetic fields might alter the effects of the toxin by modulating the nerve membrane potential and changing the binding properties or by influencing the neural transmission. The authors propose that in vitro and in vivo tests with the toxin could be a useful tool for distinguishing between primary and secondary effects of the magnetic field. For the in vitro experiments, the abdominal nerve cord was isolated from the body of a cockroach together with the cercal nerve linked to the cerci (paired appendages of insects) and placed in culture medium. The following groups were observed (n=15 measurements each): 1) exposure to a 0.7 mT magnetic field only, 2) LqhαIT (5 Œ 10-8 M) administration only, 3) co-exposure to a 0.7 mT magnetic field and LqhαIT administration and 4) control group without exposure and with a sham administration (saline). For the in vivo experiments cockroaches were divided into 3 groups (n=15 each): 5) exposure to a 0.7 mT magnetic field, 6) exposure to a 7 mT magnetic field and 7) sham exposure. Immediately before the beginning of the exposure, each insect was injected with 5 µl of LqhαIT (10-8 M; sublethal dose) and the animals were investigated after 1 h, 2 h and 24 hours of exposure.
神経系への影響: bioelectrical activity of central and peripheral nerves and whole body paralysis
coil wound around a plastic cylinder of 19 cm (inner diameter) and 21 cm in length; coil was able to ensure the maximum homogeneity (within 8%) in a central cylindrical area (radius and height of 7.5 cm) where glass chamber with free moving insects was placed; coil was located in an isolated room (temperature: 23 ± 1°C)
A sham exposure was conducted.
sham apparatus with the same size and temperature but lacking a coil was constructed
神経系への影響: bioelectrical activity of abdominal nerve (central nervous system) and cercal nerve (peripheral nervous system) (cercus stimulation with loudspeaker membrane; extracellular electrodes, oscilloscope, PC); whole body paralysis (ability of cockroach to turn from dorsal to ventral side, observation and scaled evaluation from 0 (no movement) to 4 (no impairment of movement))
認知的／行動学的影響評価項目: see "effects on the neurological system"
In the in vitro experiments, administration of LqhαIT (group 2) led to a significantly increased bioelectrical activity in the cercal nerve compared to the control. Co-exposure to the toxin and to the magnetic field (group 3) attenuated the effect of the toxin. In the abdominal nerve, the administration of LqhαIT (group 2) led to a significantly increased bioelectrical activity similar to the cercal nerve, but co-exposure to the toxin and to the magnetic field (group 3) significantly increased the effect of the toxin in comparison to the control. In both nerves, the activity was decreased (remark EMF-Portal: significance unclear) compared to the control when the nerves were exposed to the magnetic field alone (group 1). In the in vivo tests, exposure to the 0.7 mT (group 5) led to significantly reduced paralysis effects after 1 hours and 24 hours compared to sham exposed group (group 7). Exposure to the 7 mT (group 6) had a stronger effect and led to significantly reduced paralysis effects after 1 h, 2 h and 24 hours. The authors conclude that exposure to a 50 Hz magnetic field could modify the effects of the scorpion alpha toxin in cockroaches. They suggest a primary effect of the magnetic field on the nerves and a secondary effect on the metabolism.