研究のタイプ: 医学/生物学の研究 (experimental study)

[地磁気の活動の突然の変化の大きさと強度を模擬した夜間磁界にばく露された癲癇ラットの突然死] med./bio.

Sudden death in epileptic rats exposed to nocturnal magnetic fields that simulate the shape and the intensity of sudden changes in geomagnetic activity: an experiment in response to Schnabel, Beblo and May.

掲載誌: Int J Biometeorol 2005; 49 (4): 256-261

この研究は、てんかん患者の突然死が部分的に地磁気活動に関連するという仮説を前提に、磁気嵐急始(SSCs)をシミュレートして実験的に生成された磁界に辺縁てんかん誘発ラットばく露させる実験を行なった。ラットを用いた先行研究では、てんかん誘発ラット群での突然死に、前夜のSSCsの発生および地磁気活動増加が関連することが示されたが、シュナベルら[(2000)Neurology 54:903–908]は、ヒト患者での突然死と地磁気活動の間に関連がないことを示した。今回の実験では、合計96匹のラットが、3夜連続して深夜から朝8時までの間、1時間に6分間、500、50、10〜40 nTまたは擬似(10 nT未満)の磁界ばく露を受けた。複雑に振幅変調された磁界波形平均的なSSCの波形と構成をシミュレートした。次に、ラットにリチウムおよびピロカルピンを用いててんかん発作を起こさせ、死亡率を測定した。その結果、擬似ばく露群での24時間以内の死亡率は10 %であったのに対し、SSCsシミュレート磁界ばく露群では60 %で、有意差があった(P <.001)、と報告している。

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研究目的(著者による)

To test the hypothesis that sudden unexplained death in some epileptic patients is related to geomagnetic field activity the authors exposed rats in which limbic epilepsy had been induced to experimentally produced magnetic fields designed to simulate sudden storm commencements (SSCs).

詳細情報

Rats were seized with lithium and pilocarpine and the mortality was monitored.
Previous studies with rats had shown that sudden death in groups of rats in which epilepsy had been induced months earlier was associated with the occurrence of SSCs and increased geomagnetic activity during the previous night. Schnabel et al. (see publication 12465) found no relationship between sudden unexplained death in human patients and geomagnetic activity.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 7 Hz
Modulation type: AM
ばく露時間: intermittent, 6 min/hour for 8 hours/night on three consecutive nights
ばく露2: 300 µHz
Modulation type: AM
ばく露時間: intermittent, 6 min/hour for 8 hours/night on three consecutive nights

ばく露1

主たる特性
周波数 7 Hz
タイプ
  • magnetic field
ばく露時間 intermittent, 6 min/hour for 8 hours/night on three consecutive nights
Modulation
Modulation type AM
Additional information

Square waves were amplitude modulated in 14 sequential steps with the duration of each plateau being 14 s and 7 s during the first 3 min and 20 s and the last 1 min and 42 s, respectively.

ばく露装置
ばく露の発生源/構造
チャンバの詳細 4 plastic cages (3 rats/cage) 32 cm x 32 cm x 45 cm with two of them completely surrounded with Helmholtz coils. The long axis of the cages were oriented in a north-south direction.
Sham exposure A sham exposure was conducted.
パラメータ
測定量 種別 Method Mass 備考
磁束密度 50 nT peak 測定値 - -
磁束密度 10 nT peak 測定値 - in control cages

ばく露2

主たる特性
周波数 300 µHz
タイプ
  • magnetic field
ばく露時間 intermittent, 6 min/hour for 8 hours/night on three consecutive nights
Modulation
Modulation type AM
Additional information

Square waves of 7 Hz were amplitude modulated in 14 sequential steps with the duration of each plateau being 14 s and 7 s during the first 3 min and 20 s and the last 1 min and 42 s, respectively.

ばく露装置
ばく露の発生源/構造
  • E1と同じ装置
パラメータ
測定量 種別 Method Mass 備考
磁束密度 500 nT peak 測定値 - -
磁束密度 10 nT peak 測定値 - to 40 nT; in the lower cages

Reference articles

  • Cook LL et al. (2000): [低周波数低強度(6 mG未満)の夜間磁界がLewisラット脳内の単核細胞の浸潤および肥満細胞の数に与える差動効果]

ばく露を受けた生物:

方法 影響評価項目/測定パラメータ/方法

研究対象とした生物試料:
調査の時期:
  • ばく露中

研究の主なアウトカム(著者による)

Whereas 10% of the animals that had been sham-exposed died within 24 h, 60% of the rats that had been exposed to the experimental magnetic fields simulating natural geomagnetic activity died during this period. These data indicate that correlational analyses between sudden unexplained death in epileptic patients and increased geomagnetic activity can be simulated experimentally in epileptic rats and that potential mechanisms might be testable directly.

研究の種別:

研究助成