88.電磁環境特にマイクロ波や磁場のショウジョウバエの生体におよぼす影響

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An article entitled "Microwave can seriously damage your health" in the November, 1988, issue of New Scientist suggested that caution be taken when conducting chemical research using a kitchen microwave oven. However it lacked information about any specific phenomena found by researchers. The July 10, 1989, issue of Newsweek similarly quoted a stern but vaguely supported warning entitled "An Electromagnetic Storm" by Paul Brodeur of "the New Yorker". For three years since 1987 we have conducted studies, using research-aid funds from the Ministry of Education, on the effects of microwaves on Drosophila melanogaster and Drosophila virilis using home-use microwave cookers (output power: 550 W at 2.45 GHz). We found that distinct mutants of the phenotype occurred on the wings of both species. This was reported by Tonomura and Shima in 1986 and by Ohno, Shima, and Tonomura in 1988. In D. melanogaster, the gene locus is on the X-chromosome; we succeeded in system preservation in the laboratory (Fig. 1). In this experiment, we have focused our efforts on: 1) establishing whether microwaves are mutagens of mutants; 2) whether the mutants are caused by microwaves or by the effects of the heat shock the microwaves produce, and 3) a preliminary experiment under a magnetic field. The item 1) was previously investigated by Fujikawa et al. in 1984 using wing-hair-spot tester stocks. Third-instar larvae of the F_1 mwh+/+flr mated with recessive maker genes, 24-hour old pupae, and 72-hour old pupae were used to detect somatic mutations of the mutagen. Table 1 shows the results of the experiment. Wing-hair-spots occurred at a high frequency after 24 hours in younger pupae in the five-second region; this indicates that the mutagen is positive (Table 1). The somatic mutation of a mutagen is known to be induced, since pupae with a shorter exposure to microwaves have a higher chance of growing to adults. This suggests that the mutagen is not observed because the damage due to exposure is greater on pupae with longer exposure. Abnormal wings without a wing vein at the terminal end of 4th and 5th longitudinal veins are observed in adult flies of pupae that have been exposed to microwaves (Fig. 2). 2) In order to establish the relation between the abnormalites of the wings and the effects of the heat shock induced by microwaves, chemical research was conducted using the electrophoresis method and puffing on the third-instar larvae's salivary-gland chromosome. Kishi found that Drosophila has two protein bands labeled in the molecular-weight region of 300,000. Flies with an abnormal phenotype caused by exposure to microwaves have only one band, those with a normal phenotype have two bands, but one of them is less conspicuous than the other (Fig. 3). This is contrary to the report by Yura (1986) which suggested that a temporarily synthesized protein due to a high temperature is induced during an experiment using Escherichia coli and that the synthesis of three types of proteins is accelerated temporarily; this results were confimed by the one-dimensional electrophoresis method. These findings indicate that the abnormal wings are not caused only by the exposure to microwaves. Ritossa (1962) and Ashburner (1970) reported that a total of nine new puffs were induced on each chromosome arm of the salivary glands of third-instar larvae after they had been fed for 40 min. at 37℃ (Fig. 4). Our experiment confirmed the existence of similar puffs on the light arm of the third chromosome at 30-second and 60-second exposures with microwaves of 2.45 GHz and at an output power of 500 W (high). The other puffs, however, were not identical with the earlier findings (Fig. 5). The puffs were analyzed using the Chromosome Image Analyzing System (CHIAS) (Fig. 6); the types of puffs and the chromosome aberrations need to be clarified in the future. Through experiments using electrophoresis and puffing on chromosomes, however, we have come to consider that microwaves exert "heat" and "α" in addition to their characteristic effects. A paper cup filled with 100ml of water is placed in the center of a microwave cooker, and microwaves with output powers of 500 W (high) and 200 W (low) are radiated for 30 and 60 seconds respectively. From the results of the analysis (Fig. 7), Suzuki concluded that the exact effect of microwaves excluding heat may be ascertained by radiating microwaves for a very short period of time (five to 10 seconds). 3) We have conducted a preliminary experiment on the magnetic field using the magnetic-field generator (Fig. 8) in the Physics Department of the University of Osaka with the following method. Pupae one-day old or less of D. melanogaster and D. virilis are placed in a container covered with mesh and subjected to 10,000 gauss for 8 hours and 16 hours using a tesla. The dercease in the ratio of emergence, the occurrence of abnormal wings, and the results of the expermental mating of flies are similar to the results of exposure to microwaves (Tables 2 and 3). However, an interesting phenomenon was found in this experiment. When the subject region was placed in the room where the magnetic-field generator was located, abnormal wings that lacked the terminal end of the 4th and 5th longitudinal veins occurred 22 percent more often than in those placed in the experimental region (Table 4). Other abnormal wings were found outside the experimental region (Fig. 9). This suggests that the magnetic field has a significant effect. We propose to make further research on a static magnetic field based On the above findings in addition to our research involving microwaves.
東京女子大学の論文
1990-03-15

88.電磁環境特にマイクロ波や磁場のショウジョウバエの生体におよぼす影響

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