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

[超広域帯電磁界にばく露したラットの神経、行動、奇形に関する評価] med./bio.

Neural and behavioral teratological evaluation of rats exposed to ultra-wideband electromagnetic fields

著者: Cobb BL, Jauchem JR, Mason PA, Dooley MP, Miller SA, Ziriax JM, Murphy MR
掲載誌: Bioelectromagnetics 2000; 21 (7): 524-537
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この研究は、超広域帯（UWB）電磁界による非熱的影響の可能性を調べた。UWB電磁界は、ピーク電力が高く、ナノ秒のパルス幅のマイクロ波パルスで、ピコ秒のパルス立ち上がり時間で、UWBの周波数帯域という、これまでに生体影響が調べられてきた電磁界にはない特徴がある。ラット胎仔に奇形が生じるか否かを、（i）妊娠3-18日の間、1日2分間のUWBばく露、(ii) 妊娠3-18日の間に加え、生まれた仔ラットに出産後10日間の1日2分間のUWBばく露、という条件で検討した。母ラット36匹は、6匹ずつの6群（iおよびiiの条件でのばく露群、擬似ばく露群、ポジティブコントロール群（鉛ばく露））に分けられた。UWBばく露は、ピーク電界強度55kV/m、立ち上がり時間300ps、パルス幅1.8nsパルス幅、全身平均SARは45mW/kgであった。全ての出生仔について、一腹の子の数、性別比率、体重、毛皮外観、歯の発生、開眼、空中立ち直り反応、超音波ストレスに対する発声を検査し、パフォーマンス試験（運動、水迷路学習、受精能力）を行った。またii条件で出生後USBばく露を受けた仔ラットでは、海馬の形態構造とオペラント行動を調べた。その結果、UWBばく露の行動、機能、形態学への影響は、以下の点を除き、顕著に見られなかった；出生後ばく露を受けた仔ラット群では、擬似ばく露群に比べ、ストレスに対する発声が顕著であった；同じく、海馬の一部の長さが異なった；子宮内UWBばく露された仔ラット群では､擬似ばく露群に比べ、交配回数が少なかったが、交配した場合の生殖能力に違いはなかった；全体的に系統的な変化はなく、多数の統計的な比較により生じる見せかけの結果(spurious results)である可能性も考えられる、と報告している。

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研究目的（著者による）

To study if teratological changes occur in rat pups as a result of (1) daily ultra wideband exposures during gestation days 3-18, or (2) as a result of both prenatal and postnatal (10 days) exposures.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 0.1–1 GHz
Modulation type: pulsed
ばく露時間: repeated daily exposure for 2 min, see add. information
  • 電界強度: 55 kV/m peak
  • SA: 0.45 mWs/kg peak
  • SAR: 45 mW/kg mean (whole body) (dams)

ばく露1

主たる特性
周波数 0.1–1 GHz
タイプ
  • electromagnetic field
波形
  • pulsed
特性
  • guided field
ばく露時間 repeated daily exposure for 2 min, see add. information
Modulation
Modulation type pulsed
Pulse width 1.8 ns
Rise time 300 ps
Repetition frequency 1,000 Hz
ばく露装置
ばく露の発生源／構造
ばく露装置の詳細 Each rat was lightly restrained within a cylindrical Plexiglas™ holder that was placed within a custom-made parallel transmission plate exposure system with the long axis of the body parallel to the K-vector of the propagating field.
Sham exposure A sham exposure was conducted.
Additional information Dams were exposed during gestation days 3 to 18 either to UWB or sham irradiation or, as a positive control, to lead (Pb) acetate solution (2 g/l) continuously available in the drinking water. The second exposure regimen group received the same prenatal exposures, but in addition, the pups were postnatally exposed (UWB, sham, or Pb acetate) from day 1 to 10. The Pb-exposed rats were transported to and from the UWB exposure facility, but were not placed inside the parallel plates.
パラメータ
測定量 値 種別 Method Mass 備考
電界強度 55 kV/m peak 測定値 - -
SA 0.45 mWs/kg peak 計算値 - -
SAR 45 mW/kg mean 推定値 whole body dams
測定および計算の詳細

The electric field generated between the plates was continuously monitored and displayed on an oscilloscope. Extensive characterization of the electromagnetic field and details of the waveform were provided using a multi-GHz-bandpass System Verification Apparatus. A typical waveform of the electric field produced by a similar UWB pulse generator has been published previously [Jauchem et al., 1999]. The average, whole-body SAR of the dams was determined from the UWB field measured with a D-dot sensor and a transient digitizer by Fourier transform calculation using a method previously described by Jauchem et al. [1998]. It was estimated that during these brief UWB exposures there was no more than a 0.02 °C increase in any local body or brain tissue.

Reference articles

  • Jauchem JR et al. (1999): [UWB電磁パルスに短期ばく露されたケタミンで麻酔されたラットの心拍と血圧には影響はない]
  • Jauchem JR et al. (1998): [超広帯域電磁パルス：ラットでの2分間ばく露中に心拍数および血圧への影響見られず]

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
  • ばく露後

研究の主なアウトカム（著者による）

Behavioral, functional, and morphological effects of ultra wideband irradiation were unremarkable with these exceptions: (1) The exposed pups emitted significantly more stress vocalizations than the sham-exposed pups; (2) the medial-to-lateral length of the hippocampus was significantly longer in the exposed animals than in the sham-exposed pups; (3) male offspring exposed in utero mated significantly less frequently than sham-exposed males, but when they did mate there was no difference in fertilization and offspring numbers from the sham-exposed group.
There does not appear to be a unifying physiological or behavioral relationship among the significant differences revealed, and the data could be due to the expected spurious results derived when a large number of statistical comparisons are made.

研究の種別:

研究助成

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