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.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
900 MHz
Modulation type:
CW
Exposure duration:
continuous for 1 h/day for 14 days
survival experiment
|
|
|
Exposure 2:
900 MHz
Modulation type:
CW
Exposure duration:
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
| Frequency | 900 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 1 h/day for 14 days |
| Additional info | survival experiment |
| Additional info | horizontally polarized |
| Modulation type | CW |
|---|
| Exposure source | |
|---|---|
| Chamber | 5.67 m long, 2.83 m wide and 2.07 m high GTEM cell as exposure chamber |
| Setup | 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 |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 12 µW/cm² | - | measured | - | - |
| power density | 120 µW/cm² | - | measured | - | - |
| power density | 1,200 µW/cm² | - | measured | - | - |
| SAR | 5.48 mW/kg | - | calculated | whole body | for 12 µW/cm² |
| SAR | 54.8 mW/kg | - | calculated | whole body | for 120 µW/cm² |
| SAR | 548 mW/kg | - | calculated | whole body | for 1200 µW/cm² |
| Frequency | 900 MHz |
|---|---|
| Type | |
| Exposure duration | continuous for 1 h/day for 14 days |
| Additional info | all other experiments |
| Additional info | horizontally polarized |
| Modulation type | CW |
|---|
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| power density | 120 µW/cm² | - | measured | - | - |
| SAR | 54.8 mW/kg | - | calculated | whole body | - |
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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