この実験研究は、野生型キイロショウジョウバエの幼虫期における電離放射線一回照射に対する生存率が、バックグラウンド磁界（BMF）の低下した環境の影響を受けるか否かを調べた。この実験ではBMFとして60Hzを主成分とする低周波磁界成分と地磁気の静磁界成分を同定している。BMF遮蔽度の異なるμメタル、二重ステンレス、プラスティックで作成した容器（内部磁界レベルは約2、18、43μT）内で、ショウジョウバエを1年間（10世代以上）育てた後の幼虫を各容器から取り出して通常のBMF下で0-100GyのX線照射を行った。3つの容器で育てた幼虫における照射量と生存率の関係の違いを調べた結果、BMFの低下が大きな容器で生育した幼虫の方が、高照射量における生存率の低下が有意に大きくなったことを報告している。著者は、傷害修復におけるBMFの基礎的役割が示唆されたものと解釈している。
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To study the effects of an exposure to an environment, where the background magnetic field has been reduced, on wild-type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation during its larval stage.
Drosophila melanogaster was cultured for several generations in three distinct background magnetic field environments. After one year (more than 10 generations) of continuous exposure to each different background magnetic field, Drosophila melanogaster was exposed to increasing doses of ionizing radiation (0, 20, 40, 60, 80, and 100 Gy) while insects were at the larval stage.
Three cylindrical containers were built to modify the different background magnetic field environments.
| ばく露 | パラメータ |
|---|---|
|
ばく露1:
0–500 Hz
ばく露時間:
12 -18 months before ionizing radiation, 7 days after ionizing radiation
|
|
|
ばく露2:
0–500 Hz
ばく露時間:
12 -18 months before ionizing radiation, 7 days after ionizing radiation
|
|
|
ばく露3:
0–500 Hz
ばく露時間:
12 -18 months before ionizing radiation, 7 days after ionizing radiation
|
Three cylindrical containers were built to isolate the different background magnetic field (BMF) environments studied. Ionizing radiation exposure with different rates (0 - 100 Gy). The separation of the larvae into the vials to be exposed to ionizing radiation took 20 min, during which time flies occupied the laboratory bench's background magnetic field environment. Ionizing radiation treatment corresponded to 14 min exposures for 20 Gy and 70 min exposures for 100 Gy.
| ばく露の発生源／構造 |
|
|---|---|
| ばく露装置の詳細 | 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperature of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside 177 ml polypropylene bottles that were inside the cylinders for several generations |
| Sham exposure | A sham exposure was conducted. |
| ばく露の発生源／構造 |
|
|---|---|
| ばく露装置の詳細 | 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperatrue of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside the cylinder for several generations |
| Sham exposure | A sham exposure was conducted. |
| ばく露の発生源／構造 |
|
|---|---|
| ばく露装置の詳細 | 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperatrue of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside the cylinder for several generations |
| Sham exposure | A sham exposure was conducted. |
The data showed that Drosophila melanogaster of the µ-metal container (field 1) have reduced ability to survive an ionizing radiation exposure of 80 Gy or more compared to an otherwise identical population exposed to the background magnetic field environment of the cardboard-plastic container (control, field 3).
The stainless steel container-generated background magnetic field environment (field 2) failed to elicit a decrease in survivability. Both background magnetic field components were significantly reduced in the µ-metal container, but only partially in the stainless steel container. This suggests that the threshold in magnetic field magnitude required for obtaining the observed biological effects is below that measured in the stainless steel container.
The experimental design shows a timeframe, ionizing radiation dose, and background magnetic field parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that background magnetic fields may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of ionizing radiation.
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