1) To study if reported protection by a 60 Hz magnetic field on UV-induced death in 96 h-old chick embryos (see previous studies publication 2843 and publication 2882) are reproducible.
2) To test possible frequency dependence as well as effects of various flux densities and of different polarizations of the applied fields.
Embryos received 0.4 mW/cm² at 254 nm (UV exposure, 75 min).
60 eggs were used (30 for exposure and 30 for sham exposure).
To test the possible induction of HSP70 as a consequence of magnetic field-induced protection against UV-radiation, immunoblotting was performed on material obtained from human cells (as controls) and from exposed chicken embryos (additionally, positive controls (heat shock) were performed at 42°C).
| Exposure | Parameters |
|---|---|
| Exposure 1: 60 Hz |
|
| Exposure 2: 50 Hz |
|
| Exposure 3: 50 Hz |
|
|
Exposure 4:
50 Hz
Exposure duration:
continuous for 20 min or 1 hour
|
|
During each experiment, 60 eggs were randomly divided into sham or exposure groups (30 eggs each).
| Exposure source |
|
|---|---|
| Chamber | All experiments were performed in a matched pair of cell culture incubators. Both incubators served as "sham" or "exposure" incubator in a random fashion. |
| Setup | The field was created by a double Helmholtz coil arrangement with two horizontal and two vertical coils (diameter 40 and 42 cm, resp.). The coils were wound with 30 turns each of a twisted set of three Litz leads, where the twist was about three turns per meter of length of the thread. Thus each coil had three separate windings, each with 30 turns. Two of the windings were used for the AC current and were coupled through a switch which allowed to control the current in the two windings as either parallel or anti-parallel. The latter case then served as a "sham" exposure, since the AC fields cancelled each other. The ambient DC field within the incubators was found to be 30.5 and 41.8 µT, respectively, with a predominantly vertical inclination. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 10 µT | effective value | measured | - | vertical field |
| power density | 0.4 mW/cm² | - | - | - | UV-C at 254 nm |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 10 µT | effective value | measured | - | vertical field |
| magnetic flux density | 50 µT | effective value | measured | - | vertical field |
| magnetic flux density | 100 µT | effective value | measured | - | vertical field |
| power density | 0.4 mW/cm² | - | - | - | UV-C at 254 nm |
| power density | 0.8 mW/cm² | - | - | - | UV-C at 254 nm for the second flock |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 10 µT | effective value | measured | - | horizontal field |
| magnetic flux density | 50 µT | effective value | measured | - | horizontal field |
| magnetic flux density | 100 µT | effective value | measured | - | horizontal field |
| power density | 0.4 mW/cm² | - | - | - | UV-C at 254 nm |
| power density | 0.8 mW/cm² | - | - | - | UV-C at 254 nm for the second flock |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 20 min or 1 hour |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 10 µT | effective value | measured | - | vertical field |
| magnetic flux density | 200 µT | effective value | measured | - | vertical field |
The UV exposure resulted in a 20% survival rate in sham-exposed embryos 3 h post UV exposure. In contrast, exposure to a 50 Hz (10, 50, or 100 µT) or 60 Hz (10 µT) vertical magnetic field caused a significant increase in survival rate, observed only 30 min after UV exposure (and until the last observation time). No difference in protection levels was found between these exposure intensities.
A horizontal 50 Hz magnetic field (10, 50, or 100 µT) did not result in a general protection against UV-induced death, indicating that the size of the induced electric field (which differs between horizontal and vertical exposure) is important for the magnetic field-induced protection.
Furthermore, application of magnetic field (50 Hz, 200 µT, 1 h) induced HSP70 expression in human K562 cells, but not in chicken embryo material (irrespective of treatment conditions, heat shock or magnetic field exposure).
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