The effects of an acute exposure of Lymantria dispar caterpillars to a static or 50 Hz magnetic field on the morphology of neurosecretory cells and amount of a neurohormone in the insect brain should be investigated.
A1' and L2' neurosecretory cells were investigated. Type A1' is involved in the regulation of digestive processes, whereas type L2' synthesizes the large form of the prothoracicotropic hormone (PTTH), which regulates growth and metamorphosis.
90 caterpillars were randomly divided into the following groups (n=30 each): 1) exposure to the static magnetic field, 2) exposure to the 50 Hz magnetic field, 3) control group. 15 individuals of each group were used for histological analysis and the same amount was used for protein quantification.
| Exposure | Parameters |
|---|---|
| Exposure 1: |
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| Exposure 2: 50 Hz |
|
The control group was kept 5 m away from the magnets in petri dishes (V = 80 ml) exposed only to the natural magnetic field
| Frequency | |
|---|---|
| Type |
| Exposure source |
|
|---|---|
| Chamber | plastic containers (V = 80 ml) |
| Setup | caterpillars were placed between the poles of the permanent magnet (dimension was 26 cm2); the upper half of the magnet had 2 North (N) poles at the terminal ends and a centrally positioned South (S) pole, the lower half of the magnet had the reverse pole configuration; S poles were facing N poles and between them a relatively homogenous magnetic field was created |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 235 mT | maximum | estimated | - | at the poles |
| Frequency | 50 Hz |
|---|---|
| Type |
| Exposure source |
|
|---|---|
| Chamber | plastic vials (V = 80 ml) |
| Setup | caterpillars were placed in magnetic field from three pairs of coils placed around a regular laminated transformer core; dimensions of the poles were 44.6 cm2 and the space between them was 3.2 cm; input current was 1 A; force lines of the magnetic field were parallel to the vertical component of the geomagnetic field |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 2 mT | mean | measured | - | - |
The size of the cell nuclei in A1' neurons was significantly increased in samples from animals exposed to the static magnetic field (group 1) compared to the control group. Moreover, A1' neurons of group 1 had clearly visible axons and showed fine-grained neurosecretory materials in their cytoplasm indicating secretory activity.
The size of the cell bodies of L2' neurons was significantly decreased in samples from animals exposed to the 50 Hz magnetic field (group 2) compared to the control group. L2' neurons of group 2 showed agglomerations of neurosecretory material in their cytoplasm indicating its retention and reduced secretory activity.
The amount of proteins with a weight of 14-16 kD was slightly reduced in samples from group 1 and crucially reduced in group 2 compared to the control group, indicating an overall reduction of the amount of PTTH in the insect brain.
The authors conclude that both an acute exposure of Lymantria dispar caterpillars to both, a static or 50 Hz magnetic field, could influence the neurosecretory activity in the insect brain.
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