Study type: Medical/biological study (experimental study)

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

Published in: J Surg Oncol 1978; 10 (6): 483-492

Aim of study (acc. to author)

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.

Background/further details

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.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Exposure duration: 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)
Exposure 2: 2.45 GHz
Exposure duration: 20 min/day during days 11 to 14 of gestation
  • SAR: 35 mW/g mean (whole body) (33 to 38 mW/g; determined calorimetrically)
Exposure 3: 2.45 GHz
Exposure duration: 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)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Charakteristic
  • guided field
Exposure duration 20 min/day during days 11 to 14 of gestation and 19 th to 54 th day post-partum
Additional info Experiment 1
Modulation
Modulation type cf. additional info
Additional info

60 Hz sinusoidally modulated signals were applied

Exposure setup
Exposure source
Setup Maternal subjects were located in the cavity
Sham exposure A sham exposure was conducted.
Additional info 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
Parameters
Measurand Value Type Method Mass Remarks
SAR 35 mW/g mean calculated whole body 33 to 3 mW/g; determined calorimetrically

Exposure 2

Main characteristics
Frequency 2.45 GHz
Charakteristic
  • guided field
Exposure duration 20 min/day during days 11 to 14 of gestation
Additional info Experiment 1
Modulation
Modulation type cf. additional info
Additional info

60 Hz sinusoidally modulated signals were applied

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 35 mW/g mean calculated whole body 33 to 38 mW/g; determined calorimetrically

Exposure 3

Main characteristics
Frequency 2.45 GHz
Charakteristic
  • guided field
Exposure duration 20 min/day on 11th, 12th, 13th and 14th days of gestation
Additional info Experiment 2
Modulation
Modulation type cf. additional info
Additional info

60 Hz sinusoidally modulated signals were applied

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 35 mW/g mean calculated whole body 33 to 38 mW/g; determined calorimetrically

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

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.

Study character:

Study funded by