To investigate the in vivo effects of short-term and long-term exposure to extremely low frequency magnetic fields on the male fruit fly (Drosophila melanogaster).
Two experiments were performed: In the first experiment, a transcriptome analysis was performed. Three groups were examined (n=20 per group): 1 a) control group, 1 b) short-term exposure (72 hours in the adult form) and 1 c) long-term exposure (312 hours as egg, larvae and in the adult form). As a further verification quantitative real-time RT-PCR was used. The same groups as for the transcriptome analysis were formed, but with 60 individuals per group. RNA for gene expression analysis was extracted from three day-old flies in all groups.
In the second experiment, fertility was analyzed. Four groups were analyzed (n=20 for every examined group or exposure duration, respectively): 2 a) short-term control group, 2 b) short-term exposure (8, 16, 24, 48, 72 hours in the adult form), 2 c) long-term control group and 2 d) long-term exposure (312 hours as egg, larvae and in the adult form). Directly after the exposure, male flies were mated with unexposed virgin females. The number of F1 pupae was used to represent the fertility of the male flies.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for up to 72 hours
short-term exposure
|
|
|
Exposure 2:
50 Hz
Exposure duration:
continuous for 312 hours
long-term exposure
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for up to 72 hours |
| Additional info | short-term exposure |
| Exposure source | |
|---|---|
| Setup | Helmholtz coil (length 15 cm, diameter 40 cm) was wrapped with 260 turns of a single strand of copper wire; fruit flies were placed in a 19 cm space between the two coils; system was put in an incubator (25 ± 0.5°C, 60% relative humidity, 12 hours dark/light cycle); incubator, including the exposure system was put in room at 25°C |
| Additional info | control group was placed in another incubator in a location with an equal background magnetic field |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 3.03 mT | - | measured | - | ± 0.04 mT |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 312 hours |
| Additional info | long-term exposure |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 3.03 mT | - | measured | - | ± 0.04 mT |
The transcriptome analysis showed that under short-term exposure conditions 439 genes were up-regulated and 874 genes were down-regulated in comparison to the control group, while under long-term conditions 514 genes were up-regulated and 1206 were down-regulated. Taken together both exposure groups (short-term and longt-term exposure), the expression of 836 genes was modified. Out of those, 6 genes related to apoptosis, aging, immunological stress and reproduction were verified via PCR: The genes Jra, ark, decay and cat were down-regulated compared to the control while hsp22 and totA were up-regulated.
In the exposed males, the number of F1 pupae was decreased compared to the corresponding control group, but that was only significant for the short-term exposure group.
The authors conclude that the study showed the in vivo effects of short-term and long-term exposure to extremely low frequency magnetic field on the male fruit fly.
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