To examine potential biological effects of extremely low frequency magnetic fields on the development of zebrafish embryos.
Fish embryos were divided into seven groups: 1.) no treatment ("cage control"), 2.) sham exposure, 3.) 30 µT magnetic field exposure, 4.) 100 µT magnetic field exposure, 5.) 200 µT magnetic field exposure, 6.) 400 µT magnetic field exposure and 7.) 800 µT µT magnetic field exposure. Directly after fertilization of the eggs, exposure was started.
Per group, three dishes with embryos were used. For every examination, 10 embryos were randomly chosen from each dish.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 96 hours
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 96 hours |
| Exposure source | |
|---|---|
| Chamber | zebrafish embryos were cultured in dishes in the center of the coils |
| Setup | square Helmholtz coils were used to generate the magnetic field, each consisting of 100 turns of 1.5-mm diameter copper wire; 50 Hz AC current was allowed to pass through a variable voltage transformer, producing a relatively homogeneous 50-Hz magnetic field; magnetic field strength was axial and was parallel to the coil axis |
| Sham exposure | A sham exposure was conducted. |
| Additional info | sham group was conducted with coils similar to those in the exposure system, but without electricity passing through the coils |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 30 µT | - | measured | - | less than 1% spatial variation (calculated) |
| magnetic flux density | 100 µT | - | measured | - | less than 1% spatial variation (calculated) |
| magnetic flux density | 200 µT | - | measured | - | less than 1% spatial variation (calculated) |
| magnetic flux density | 400 µT | - | measured | - | less than 1% spatial variation (calculated) |
| magnetic flux density | 800 µT | - | measured | - | less than 1% spatial variation (calculated) |
No significant differences regarding mortality and malformations were found between the groups. However, in the exposed groups 5, 6, and 7 (magnetic flux density of 200 µT and higher) a significantly delayed hatching and a significantly decreased heart rate in the early developmental stages was observed compared to the control groups (group 1 and 2). In the exposed embryos of the groups 5, 6, and 7, considerable signs of apoptosis were found mainly in the ventral fin and spinal column, which were not present in the control embryos. This finding was confirmed by a significant up-regulation of caspase-3 in the exposed groups 5, 6, and 7 and of caspase-9 in group 7 in comparison to the control.
The authors conclude that extremely low frequency magnetic fields have a detrimental effect on the development of zebrafish embryos.
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