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

[2450MHｚマイクロ波の胎仔ばく露後のマウスにおける腫瘍成長遅滞および寿命延長] med./bio.

Retarded tumor growth and greater longevity in mice after fetal irradiation by 2450-MHz microwaves

著者: Preskorn SH, Edwards WD, Justesen DR
掲載誌: J Surg Oncol 1978; 10 (6): 483-492
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この研究は、CFWマウスを用いた、2,450MHzマイクロ波の子宮内ばく露に関する２つの実験で構成されている。第１の実験では、CFWマウス48匹は、子宮内の胎仔の時（妊娠11〜14日目）に、１日20分間のマイクロ波ばく露（または擬似ばく露）を受け、その後、出生16日目に、リンパ網内系組織細胞肉腫のホモジネートを移植され、19日目からはまた、１日１回のマイクロ波のばく露または擬似ばく露を36日間受けた。その結果、出生後93日目の剖検で組織学的に確認された腫瘍発生率は、子宮内ばく露を受けた群の方が、子宮内擬似ばく露を受けた群より低かった（13 % vs 46 %）；子宮内ばく露時の母マウスの結腸温度は平均2.24℃上昇していた、と報告している。第2の実験では、84匹のCFWマウスに子宮内ばく露、60匹のマウスに子宮内擬似ばく露を与えた。144匹全てに、出生１６日目にホモジネートを移植したが、生後のばく露は行わなかった。触診可能な腫瘍の発生および寿命について約36月間、観察した。その結果、子宮内ばく露を受けた群での腫瘍発生率は初めのうち低く、移植後2.5ヶ月では、子宮内ばく露群および擬似ばく露群での発生率はそれぞれ、第１の実験での実験終了時に観察されたものと同程度であった；その後、子宮内ばく露群での腫瘍発生率はさらに上昇し、4ヵ月後には46 %に達し、対照での40％をわずかに超えた；子宮内ばく露群における担癌動物と無腫瘍動物の両方とも、擬似ばく露群でのそれぞれよりも平均的に長生きした、と報告している。

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研究目的（著者による）

To test the hypothesis that frequent elevation of body temperature in mammal would, if resulting in augmentation of metabolic rate, eventuate in a shorter span of life. The strategy in implanting a rapidly growing sarcoma in mice near time of weaning was not to treat the tumor but to produce a mammalian preparation with a truncated lifespan.

詳細情報

In the first study mice were exposed/sham-exposed in utero (20 minutes daily, 2450 MHz, 0 or 35 mW/g during days of 11-14 of gestation). All mice were implanted with a homogenate of a lymphreticular cell sarcoma on the 16th day postpartum. Commencing on the 19th day, they underwent a series of 36 daily exposures to the microwaves.
In the second study, mice received the four irradiation treatments in utero. Postnatal exposure was not administered. All mice were implanted with the homogenate on the 16th day postpartum and then they were observed for nearly 36 months for development of palpable tumors and for longevity.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 2.45 GHz
ばく露時間: 20 min/day during days 11 to 14 of gestation and 19 th to 54 th day post-partum
  • SAR: 35 mW/g mean (whole body) (33 to 3 mW/g; determined calorimetrically)
ばく露2: 2.45 GHz
ばく露時間: 20 min/day during days 11 to 14 of gestation
  • SAR: 35 mW/g mean (whole body) (33 to 38 mW/g; determined calorimetrically)
ばく露3: 2.45 GHz
ばく露時間: 20 min/day on 11th, 12th, 13th and 14th days of gestation
  • SAR: 35 mW/g mean (whole body) (33 to 38 mW/g; determined calorimetrically)

ばく露1

主たる特性
周波数 2.45 GHz
特性
  • guided field
ばく露時間 20 min/day during days 11 to 14 of gestation and 19 th to 54 th day post-partum
Additional information Experiment 1
Modulation
Modulation type cf. additional information
Additional information

60 Hz sinusoidally modulated signals were applied
ばく露装置
ばく露の発生源／構造
ばく露装置の詳細 Maternal subjects were located in the cavity
Sham exposure A sham exposure was conducted.
Additional information animals were assigned to one of the following groups: i) sham exposure during both periods ii) sham exposure during utero and exposure during postnatal iii) exposure during utero and sham exposure during postnatal iv) exposure during the both periods
パラメータ
測定量 値 種別 Method Mass 備考
SAR 35 mW/g mean 計算値 whole body 33 to 3 mW/g; determined calorimetrically

ばく露2

主たる特性
周波数 2.45 GHz
特性
  • guided field
ばく露時間 20 min/day during days 11 to 14 of gestation
Additional information Experiment 1
Modulation
Modulation type cf. additional information
Additional information

60 Hz sinusoidally modulated signals were applied
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.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 35 mW/g mean 計算値 whole body 33 to 38 mW/g; determined calorimetrically

ばく露3

主たる特性
周波数 2.45 GHz
特性
  • guided field
ばく露時間 20 min/day on 11th, 12th, 13th and 14th days of gestation
Additional information Experiment 2
Modulation
Modulation type cf. additional information
Additional information

60 Hz sinusoidally modulated signals were applied
ばく露装置
ばく露の発生源／構造
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
SAR 35 mW/g mean 計算値 whole body 33 to 38 mW/g; determined calorimetrically

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）

Fetal irradiation, which elevated dams colonic temperature by an average of 2.24°C, was associated with a lower incidence of tumors as verified histologically at necropsy on the 93rd day postpartum (first study).
In the second study tumors initially developed at a lower rate in fetally exposed mice and 2.5 months after implantation the respective percentages of "takes" in sham- and microwave exposed mice were comparable to those observed at termination of the first study. Subsequently the rate of tumor induction in exposed mice accelerated, and after the fourth month the final percentage of exposed animals with tumors slightly exceeded that of controls.
Both tumor-bearing and tumor-free mice that had been irradiated as fetuses lived longer on the average than respective controls. Long-term augmentation of immunocompetency by in utero hyperthermia is believed to be responsible for the enhancement in survival and delayed induction of tumors.

研究の種別:

研究助成