Study type: Medical/biological study (experimental study)

Reduction of the background magnetic field inhibits ability of Drosophila melanogaster to survive ionizing radiation. med./bio.

Published in: Bioelectromagnetics 2012; 33 (8): 706-709

Aim of study (acc. to author)

To study the effects of an exposure to an environment, where the background magnetic field has been reduced, on wild-type Drosophila melanogaster by measuring its ability to survive a single exposure to ionizing radiation during its larval stage.

Background/further details

Drosophila melanogaster was cultured for several generations in three distinct background magnetic field environments. After one year (more than 10 generations) of continuous exposure to each different background magnetic field, Drosophila melanogaster was exposed to increasing doses of ionizing radiation (0, 20, 40, 60, 80, and 100 Gy) while insects were at the larval stage.
Three cylindrical containers were built to modify the different background magnetic field environments.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 0–500 Hz
Exposure duration: 12 -18 months before ionizing radiation, 7 days after ionizing radiation
Exposure 2: 0–500 Hz
Exposure duration: 12 -18 months before ionizing radiation, 7 days after ionizing radiation
Exposure 3: 0–500 Hz
Exposure duration: 12 -18 months before ionizing radiation, 7 days after ionizing radiation

General information

Three cylindrical containers were built to isolate the different background magnetic field (BMF) environments studied. Ionizing radiation exposure with different rates (0 - 100 Gy). The separation of the larvae into the vials to be exposed to ionizing radiation took 20 min, during which time flies occupied the laboratory bench's background magnetic field environment. Ionizing radiation treatment corresponded to 14 min exposures for 20 Gy and 70 min exposures for 100 Gy.

Exposure 1

Main characteristics
Frequency 0–500 Hz
Type
Exposure duration 12 -18 months before ionizing radiation, 7 days after ionizing radiation
Additional info maximum of AC field at 60 Hz
Exposure setup
Exposure source
  • double-walled µ-metal cylinder (to attenuate the static and time-varying component of the BMF)
Setup 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperature of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside 177 ml polypropylene bottles that were inside the cylinders for several generations
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.201 µT effective value measured - AC
magnetic flux density 1.7 µT - measured - DC

Exposure 2

Main characteristics
Frequency 0–500 Hz
Type
Exposure duration 12 -18 months before ionizing radiation, 7 days after ionizing radiation
Additional info maximum of AC field at 60 Hz
Exposure setup
Exposure source
  • stainless steel cylinder (attenuates the static and time-varying component to a lesser degree)
Setup 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperatrue of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside the cylinder for several generations
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.951 µT effective value measured - AC
magnetic flux density 18.2 µT - measured - DC

Exposure 3

Main characteristics
Frequency 0–500 Hz
Type
Exposure duration 12 -18 months before ionizing radiation, 7 days after ionizing radiation
Additional info maximum of AC field at 60 Hz
Exposure setup
Exposure source
  • cadboard-plastic cylinder (control; no BMF attenuation)
Setup 15.5 cm high outer cylinder with a diameter of 24 cm; 14 cm high inner cylinder with a diameter of 21.7 cm; treated with plastic coating, placed inside an incubator with a constant temperatrue of 27 ± 0.5 °C and 60 % relative humidity; insects stayed inside the cylinder for several generations
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1.06 µT effective value measured - AC
magnetic flux density 42.5 µT - measured - DC

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The data showed that Drosophila melanogaster of the µ-metal container (field 1) have reduced ability to survive an ionizing radiation exposure of 80 Gy or more compared to an otherwise identical population exposed to the background magnetic field environment of the cardboard-plastic container (control, field 3).
The stainless steel container-generated background magnetic field environment (field 2) failed to elicit a decrease in survivability. Both background magnetic field components were significantly reduced in the µ-metal container, but only partially in the stainless steel container. This suggests that the threshold in magnetic field magnitude required for obtaining the observed biological effects is below that measured in the stainless steel container.
The experimental design shows a timeframe, ionizing radiation dose, and background magnetic field parameters that will cause a significant and reproducible reduction of survival on this insect model. These results suggest that background magnetic fields may play a fundamental role in the recovery or harm of a biological system that is exposed to single doses of ionizing radiation.

Study character:

Study funded by

Related articles