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

[超低周波電磁界はマウス海馬の新生ニューロンの生存率を高める] med./bio.

Extremely low-frequency electromagnetic fields enhance the survival of newborn neurons in the mouse hippocampus.

掲載誌: Eur J Neurosci 2014; 39 (6): 893-903

この研究は、超低周波磁界ばく露(ELFEF;1 mT、50 Hz、3.5 時間/日、ばく露期間6日間)がマウス海馬の新生ニューロン生存率に与える影響を調べた。54匹の幼若C57bl/6雄マウス(4-5週齢)を同数のばく露群と擬似ばく露群に分け、新生ニューロンをラベルするために5-ブロモ-2’-デオキシウリジンBrdU)を3日連続で腹腔内投与した後、9日間おいてからソレノイドコイルによるELFEFばく露(または擬似ばく露)を6日間行った。ばく露終了後、両群の一部は海馬組織学的検査に、残りは、空間学習および短期記憶のテストに供した。その結果、ばく露群では、新生ニューロン生存率が上昇した;このような効果は、空間学習および記憶テストの成績と関連した、と報告している。

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研究目的(著者による)

To investigate the influence of exposure to extremely low frequency magnetic fields on the survival of hippocampal newly developed cells of mice.

詳細情報

In a previous study, the authors demonstrated that exposure to extremely low frequency magnetic fields stimulates the hippocampal neurogenesis in adult mice (Cuccurazzu et al., 2010). To extend the previous study, 2 further experiments were performed: An in vivo and an in vitro experiment.
For the in vivo experiment, 54 juvenile mice were divided into an exposure and a sham exposure group. Different examinations were performed.
1.) For immunohistochemical analysis, 10 mice from each group received daily injections of 100 mg/kg bromodeoxyuridine (BrdU) for 3 consecutive days. 9 days after the last injection, mice were exposed or sham exposed on six days. Half of the mice were killed 3 days after the last exposure or sham exposure session and the other half after 9 days (each group n=5).
2.) For the Western blot analysis, animals were killed 3 days after the last exposure (n=4) or sham exposure (n=4) session.
3.) Apoptosis in the dentate gyrus was examined 3 days after the last exposure (n=3) or sham exposure (n=3) session.
4.) A set of 20 mice (exposure group n=10; sham exposure group n=10) was used for cognitive and memory test. The novel recognition test was performed during the 4th, 5th and 6th day, while the Morris water maze was performed from the 9th to the 13th day after the exposure or sham exposure session.
For the in vitro experiment, cultured hippocampal neural stem cells were cultivated in an incubator while exposed or sham exposed. Apoptosis and protein expression of microtubule-associated protein 2 (MAP2; protein which is involved in microtubule assembly, an essential step in neurogenesis) was tested in the presence or absence of the pro-apoptotic beta-amyloid protein.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 50 Hz
ばく露時間: 3.5 hours/per day for 6 days
in vivo experiment
ばく露2: 50 Hz
ばく露時間: continuous for 3 days
in vitro experiment

ばく露1

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
ばく露時間 3.5 hours/per day for 6 days
Additional information in vivo experiment
ばく露装置
ばく露の発生源/構造
ばく露装置の詳細 solenoid was positioned around a Plexiglas cylinder (diameter 20 cm, length 42 cm), in which the plastic cage (33 x 15 x 13 cm) was placed, 3 to 4 freely moving mice per cage
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 1 mT - - - -

ばく露2

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
ばく露時間 continuous for 3 days
Additional information in vitro experiment
ばく露装置
ばく露の発生源/構造
ばく露装置の詳細 solenoid was positioned inside a CO2 incubator, surfaces of culture plates were parallel to the force lines of the magnetic field, temperature was (due to used incubator) 37.0°C or 37.4°C, maximum temperature increase in the cultures during exposure was 0.4 ± 0.1°C
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 1 mT - - - -

Reference articles

  • Cuccurazzu B et al. (2010): [超低周波(50Hz)電磁界へのばく露は成獣のC57BL/6マウスの海馬における神経新生を強める]

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:
研究対象とした臓器系:
調査の時期:
  • ばく露後

研究の主なアウトカム(著者による)

In exposed mice, the cell proliferation was significantly increased in comparison to the sham exposed group (increased number of BrdU and doublecortin-positive cells). This enhanced cell proliferation in the exposure group was accompanied by an increased mature stage of the cells (significantly increased protein expression of the neural marker NeuN) and a significantly decreased apoptosis rate in comparison to the sham exposure group. Also in the cell cultures, the cell survival was significantly increased and the apoptosis was significantly decreased after exposure in comparison to the sham exposure. Both in the exposed cell cultures and in the hippocampus of exposed mice, the protein expression of the pro-apoptotic protein Bax was significantly decreased while the anti-apoptotic protein Bcl-2 was significantly increased compared to the sham exposed groups. In exposed cell cultures treated with beta-amyloid protein, the protein expression of microtubule-associated protein 2 was significantly higher than in sham exposed ones treated with beta-amyloid protein.
Exposed mice showed significantly improved memory and learning abilities compared to sham exposed mice.
The authors conclude that exposure to extremely low frequency magnetic fields promotes the survival of hippocampal newly developed cells in mice.

研究の種別:

研究助成

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