【目的】900MHzのRF電磁界への事前ばく露を受けたマウスに適応応答が誘導されるか否かを調べること。【対象と方法】雄の成獣のKunmingマウスに900MHz電磁界ばく露を、14日間、1日1時間行い、その電力密度は12、120、1200 μW/cm2とした。その後、全身のガンマ線照射を行った。ばく露群の結果を、非ばく露群およびガンマ線照射単独群（RF電磁界の事前ばく露なし）のものと比較した。生存割合、造血組織の損傷（致死的ばく露を受けたマウスの骨髄有核コロニー形成細胞および脾臓コロニー形成細胞のコロニー形状で評価される）および細胞周期関連遺伝子の発現を調べた。【結果】結果は、ガンマ線照射の前にRFばく露されたマウス群における有意な生存期間増加と造血組織損傷低下（ガンマ線単独ばく露群に比較して）を示した。この結果は、細胞周期関連遺伝子（すなわち、造血細胞のcyclin-D1、 cyclin-E、cyclin-DK4、cyclin-DK2）の発現の有意な上昇を同時に示した。【結論】900MHzのRF電磁界への事前ばく露は、その後の電離放射線ばく露が引き起こす造血組織損傷を有意に低下させる結果をもたらした。この現象は、いわゆる「適応応答」とよく似ているように見える。
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To study whether an adaptive response can be induced in mice which were pre-exposed to 900 MHz radiofrequency fields and to determine the optimal power intensity needed for radiofrequency pre-exposure in order to achieve considerable "protection" from subsequent ionizing radiation-induced damage.
For the survival experiment, a total of 140 mice were divided into the following five groups (each group n=28): 1) 8 Gy gamma radiation alone (lethal dose), 2) radiofrequency exposure at 12 µW/cm² + gamma radiation on day 15 after the last day of exposure, 3) radiofrequency exposure at 120 µW/cm² + gamma radiation on day 15, 4) radiofrequency exposure at 1200 µW/cm² + gamma radiation on day 15, 5) positive control (free radical scavenger treatment (amifostine) + gamma radiation.
For all other experiments 144 animals were divided into the following groups (each group n=12): 1) three groups of unexposed controls, 2) 8 Gy gamma radiation (lethal dose; for organ weight evaluation) or 5 Gy gamma radiation (for all other experiments) on day 15, 3) three groups of 120 µW/cm² radiofrequency exposure (for all experiments), 4) one group at 120 µW/cm² radiofrequency exposure + 8 Gy gamma radiation (lethal dose; for organ weight evaluation) or two groups at at 120 µW/cm² radiofrequency exposure + 5 Gy gamma radiation (for colony forming units in bone marrow cells and gene expression) on day 15.
Additionally, for evaluation of colony forming units in the spleen of lethally irradiated "recipient" mice, 12 donor mice (each group n=3) were divided into 1) an unexposed control group, 2) 5 Gy gamma radiation only group, 3) group of 120 µW/cm² radiofrequency exposure and 4) group of 120 µW/cm² radiofrequency exposure + 5 Gy gamma radiation. Following gamma radiation, the mice were sacrificed, the nucletaed cells of the bone marrow were collected, pooled for each group and injected in the tail vein of recipient mice (each group n=10). Recipient mice were exposed to a lethal dose of 8.5 Gy gamma radiation 4-6 h before injection of bone marrow cells.
| ばく露 | パラメータ |
|---|---|
|
ばく露1:
900 MHz
Modulation type:
CW
ばく露時間:
continuous for 1 h/day for 14 days
survival experiment
|
|
|
ばく露2:
900 MHz
Modulation type:
CW
ばく露時間:
continuous for 1 h/day for 14 days
all other experiments
|
For the survival experiments animals were divided into five groups: i) 8.0 Gy gamma radiation on day 15 ii) 12 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 iii) 120 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 iv) 1200 µW/cm² RF exposure + 8.0 Gy gamma radiation on day 15 v) 500 ng/ml Amifostine + 8.0 Gy gamma radiation on day 15 For all other experiments animals were divided into four groups: i) unexposed control ii) 8.0 Gy gamma radiation (for organ weight) or 5.0 Gy gamma radiation (for all other experiments) on day 15 iii) 120 µW/cm² RF exposure iv) 120 µW/cm² RF exposure + 8.0 Gy gamma radiation (for organ weight) or 5.0 Gy gamma radiation (for all other experiments) on day 15
| 周波数 | 900 MHz |
|---|---|
| タイプ |
|
| ばく露時間 | continuous for 1 h/day for 14 days |
| Additional information | survival experiment |
| Additional information | horizontally polarized |
| Modulation type | CW |
|---|
| ばく露の発生源／構造 |
|
|---|---|
| チャンバの詳細 | 5.67 m long, 2.83 m wide and 2.07 m high GTEM cell as exposure chamber |
| ばく露装置の詳細 | signal fed through an antenna into the GTEM cell; single mouse placed in a plastic box; boxes positioned on a 1 m high table at the location inside the GTEM cell where the desired power density was measured |
| 周波数 | 900 MHz |
|---|---|
| タイプ |
|
| ばく露時間 | continuous for 1 h/day for 14 days |
| Additional information | all other experiments |
| Additional information | horizontally polarized |
| Modulation type | CW |
|---|
| ばく露の発生源／構造 |
|
|---|
The data indicated significant increases in survival time, in the weights of spleen and thymus, number of colony forming units in the bone marrow and spleen of lethally irradiated recipient mice, and a reduction in the hematopoietic tissue damage in radiofrequency pre-exposed mice (120 µW/cm²) which were gamma radiated (as compared with those exposed to gamma radiation alone). This was accompanied by significantly increased expression of cell cycle-related genes (different cyclins) in hematopoietic cells. The findings suggested that the 120 µW/cm² power intensity for 900 MHz radiofrequency pre-exposure was adequate and optimum to lead to the maximum protection of hematopoietic tissue damage induced by subsequent exposure to gamma radiation.
The authors conclude, that pre-exposure of mice to 900 MHz radiofrequency fields has resulted in a significant reduction in hematopoietic damage caused by subsequent exposure to ionizing radiation. This phenomenon appears to be similar to that of the "adaptive response" which is well documented in scientific literature.
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