畑中 恒夫

地上には地磁気以外に,さまざまな電気器具から人工的に作られた強い磁場や極低周波の電磁場(変動磁場として作用)があふれている。これらは生体にさまざまな悪影響を及ぼすと考えられているが,その働きについては意見が一致していない。ミツバチは地磁気を受容し,定位に利用していることが知られている。そこで,ミツバチを用いて,悪影響を及ぼす可能性のある強い磁場を避けるかどうか,さらに強磁場に長期にわたって曝露されることで生理的変化が起こり行動に変化が出るか調べた。その結果,今回調べた方法では,強い磁場を避ける傾向は見られず,また,長期の強磁場暴露でもその傾向に変化は見られなかった。しかし強磁界曝露では,普通は加齢とともに活動性が増すのに,活動性が低下することが見られ,また,寿命が短くなるなど老化が早まるような悪影響が見られた。A number of electromagnetic devices have increased and have added intense magnetic fields and extremely low frequency electromagnetic fields (alternating magnetic fields) to the electronic pollution in our atmosphere. They may have potent damaging effects on living organisms, but the evidence remains inconclusive. Honeybees are known to have magnetoreceptors and use them for magnetic compass orientation. So, we investigated whether the bees avoid strong magnetic fields which may be harmful to them and whether continuous exposure to magnetic fields affects to bees'behavior. As a result, no systematic tendency of bee's preferences was shown and the exposure did not effect on preference. But, the continuous exposure to the intense magnetic fields shortened worker bees' lives and depressed bees' behavioral activity. Present study suggests that the chronic exposure to intense magnetic fields may have toxic influences on bee life.

The importance of taste and smell in discrimination of tastes was examined in normal and anosmic mice. We studied the influence of olfaction on taste sensation using behavioral and electrophysiological methods in both normal animals and animals made anosmic mice by destroying their olfactory receptor cells with zinc sulfate (ZnSO4) solution. Electrophysiological responses from chorda tympani nerves showed that peripheral taste receptor cells transmitted taste signals normally to the central nervous system, even when the olfactory senses were abnormal. Behavioral observations showed that mice with abnormal olfaction could not differentiate tastes. (C) 2001 Elsevier Science Inc. All rights reserved.