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

[線虫Caenorhabditis Elegansにおける熱ショック遺伝子発現のマイクロ波による見かけ上の誘導に僅かな温度上昇が寄与する可能性がある] med./bio.

A small temperature rise may contribute towards the apparent induction by microwaves of heat-shock gene expression in the nematode Caenorhabditis Elegans.

掲載誌: Bioelectromagnetics 2006; 27 (2): 88-97

この研究は、著者らの先行研究(低強度マイクロ波ばく露がhsp16-1レポータ遺伝子を持つ線虫に、見かけ上非熱的な熱ショック応答を誘発したと報告)でばく露に用いたTEMセルに問題が発見されたため、問題点を改善したTEMセルで再実験した。先行研究では、銅製TEMセルを用いた低強度マイクロ波ばく露(0.5 W、0.75-1.0 GHz CW、SAR 4-40 mW / kg)により、擬似ばく露群ではみられなかったが、ばく露群においてのみ、わずかなレポーター遺伝子誘導がみられた、と報告した。その後、この銅製TEMセルのNational Physical Laboratory(NPL)によるトレーサビリティ付き校正により、セルでの電力損失(1.0 GHzで8.5 %)およびばく露試料でのわずかな加熱(1.0 Wで約0.3℃)が明らかになった。そこで改良を行い、新たに製作された銀メッキセルでは、電力損失は1.0 GHzで1.5 %、試料の加温は1.0 Wで約0.15℃に減少した(つまり、0.5 Wで0.1℃以下)。 実験の結果、sham:sham条件において、銀メッキセルと銅セルの間でレポーター遺伝子発現に違いはなかった;しかし、銅セルを用いた擬似ばく露対照群を比較の対象とすると、銀メッキセルでのマイクロ波(1.0 GHzおよび0.5 W)ばく露群での検出可能なレポーター遺伝子発現誘導は示されなかった;したがって、先行研究で2つの銅セルで観察された「マイクロ波による誘導の差」は、擬似およびばく露条件の間の小さな温度差によって引き起こされた可能性がある、と報告している。

The detailed summary of this article is not available in your language or incomplete. Would you like to see a complete translation of the summary? Then please contact us →

研究目的(acc. to editor)

To study the effects of microwave exposure on heat shock (HSP) responses in transgenic nematodes (Caenorhabditis elegans). The aim of the investigation was to replicate data of previous studies (see publication 4466, publication 4467, and publication 6611).

詳細情報

Worms were incubated at 15, 26, 26.2, and 27°C.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 1 GHz
Modulation type: CW
ばく露時間: continuous for 2.5 hours
ばく露2: 1 GHz
Modulation type: CW
ばく露時間: nearly continuous for up to 20 hours (see add. information)

ばく露1

主たる特性
周波数 1 GHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 continuous for 2.5 hours
Modulation
Modulation type CW
ばく露装置
ばく露の発生源/構造
チャンバの詳細 The TEM cell used here was identical to that described in [Daniells et al., 1998], except that it was constructed of copper rather than aluminium. It was 34 cm long and of a square cross-section, tapering from a maximum of 24 x 24 cm at the center to 1.5 x 1.5 cm at the ends. The inner septum (waveguide) was central and 27/32 of the total width, giving a 50 Ω impedance, which matched the load and cables. Power was limited by the matched load to 500 mW (27 dBm).
ばく露装置の詳細 Identical loaded 24-well multiwell plates (containing 1.0 ml of K medium per well) were placed in two copper TEM cells located on the same shelf of a large incubator set at 26.0 ± 0.1 °C, one for RF and the other one for sham exposure.
Sham exposure A sham exposure was conducted.
Additional information In later experiments, an unmodified copper TEM cell was used for shams, while the TEM cell used for exposures was modified with the aim of reducing both power loss and consequent heating, including removal of internal polystyrene foam from beneath the septum, replacement of BNC by APC 3.5 connectors, and silver plating the copper surfaces of the cell.
パラメータ
測定量 種別 Method Mass 備考
電力 0.5 W - - - -

ばく露2

主たる特性
周波数 1 GHz
タイプ
  • electromagnetic field
特性
  • guided field
ばく露時間 nearly continuous for up to 20 hours (see add. information)
Modulation
Modulation type CW
ばく露装置
ばく露の発生源/構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
Additional information Sham and microwave-exposed PC161 worms (as for Part A) were kept for 20 h in black non-fluorescent multiwell plates, which were removed at 2 or 4 h intervals (for <5 min per plate) to allow determination of GFP fluorescence levels.
パラメータ
測定量 種別 Method Mass 備考
電力 0.5 W - - - -

Reference articles

  • Daniells C et al. (1998): [マイクロ波によって誘起されるストレスのバイオモニターとしてのトランスジェニック線虫]

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:
  • ばく露後

研究の主なアウトカム(著者による)

Using copper TEM cells for both exposed and sham exposed groups, only modest reporter gene induction in the exposed group was detected (15-20% after 2.5 h at 26°C, rising to approximately 50% after 20 h). Calibration of the copper TEM cell by the National Physical Laboratory (Teddington, UK) revealed significant power loss (8.5% at 1.0 GHz) within the cell, accompanied by slight heating of exposed samples (approximately 0.3°C at 1 W). Thus, exposed samples were slightly warmer (by less/equal 0.2°C at 0.5 W) than sham-exposed controls.
The TEM cell design was modified with the aim of reducing both power loss and consequent heating. In the modified silver-plated TEM cell, power loss was only 1.5 % at 1.0 GHz, and sample warming was reduced to approximately 0.15°C at 1.0 W (i.e., less/equal 0.1°C at 0.5 W).
Under sham exposure/sham exposure conditions, there was no difference in reporter gene expression between the modified silver TEM cell and an unmodified copper TEM cell. However, worms exposed to microwaves (1.0 GHz, 0.5 W) in the silver TEM cell also showed no detectable induction of reporter gene expression relative to sham exposed controls in the copper TEM cell. Thus, the 20 % "microwave induction" revealed using two copper TEM cells may be caused by a small temperature difference between sham exposure and exposure conditions.
The authors conclude that previous interpretation of a non-thermal effect of microwaves cannot be sustained.

研究の種別:

研究助成

Replicated studies

関連論文