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Figure 1. Schematic for MagShield apparatus enclosure.Schematic diagrams for constructing the 16 × 16 × 16 in enclosure out of 0.125 in thickness mu-metal. See Supplemental File S2 for complete details.
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Figure 2. Mu-metal enclosure.As unpacked directly from the supplier, before the addition of the partition. (A) Inside. (B) Front outside. Note the door latches (asterisks), access ports at the top (arrows), and the access ports at the bottom (arrowheads).
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Figure 3. Constructing the mu-metal partition.(A) Mu-metal foil showing a corner where the adhesive packing is peeled off (arrow). (B) Plexiglass sheet. (C) View of Plexiglass sheet thickness 1/8 in (3.175 mm). (D) Cutting the mu-metal foil with adhesive backing into 16 in lengths. (E) First 16 in strip of foil attached to half of the Plexiglass sheet.
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Figure 4. Installing the mu-metal partition.(A) Correct placement (arrow) of the foil-covered Plexiglass sheet, bisecting the mu-metal enclosure. (B) Taping the partition to the enclosure for extra stability. (C) Final installation of the mu-metal partition, showing the tape (arrowheads) connecting the partition to the enclosure.
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Figure 5. Helmholtz coil anatomy.(A) 3D model of the base frame. (B) Actual 3D printed base frame, with breakaway supports (arrowheads) still attached. (C) Close-up of the 3D printed base frame with breakaway supports removed. Note the raised zip-tie anchors (arrows) for correct positioning of coil rows and wire management. (D) Diagram of 3-axial Helmholtz coil showing the three coil pairs for the three axes (x in blue, y in red, and z in grey).
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Figure 6. Winding the coils.(A) Free end of the copper wire (arrow) for one coil, where 4 in (~10 cm) of wire is left unwound at each end for attaching to the power supply. (B) View of one face of a completed coil, showing the crossing of the copper wire (asterisk) between the left and right coil pairs. (C) Free end of one coil, showing the stripped insulation (arrowhead) required for a strong connection to the power supply lead. (D) Completed Helmholtz coil with three coil pairs (x, y, and z) that have been zip-tied (white clasps) to the base frame via the anchors and had the zip-tie “tails” cut off.
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Figure 7. Placement of the coils, samples, and leads.(A) The alligator clip end of a red lead is attached to the exposed end of one coil pair (arrow). The alligator clip of a black lead is attached to the other end of that same wire (middle of image). To ensure a good connection, secure the clip to the wire with electrical tape (arrowhead). (B) A taped stack of used pipette tip boxes is used to position the Helmholtz coil in the center of each partition. (C) A complete Helmholtz coil with a stack of used plasticware (welled plates) to position the samples (Petri dish) in the center of the coil base frame. (D) Final positioning of both Helmholtz coils, one in each partition. Note in the lower-right corner where a pair of red and black leads clipped to each end of a single coil pair have been taped together (green tape).
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Figure 8. Connecting to the power source.(A) Leads from a Helmholtz coil fed through an upper access port (arrowhead). (B–C) Views of a set of leads fed through a lower access port (yellow arrows), shown from the outside (B) and the inside (C) of the enclosure. (D) Power supplies with attached leads. Red arrow shows axis labeling of each lead. (E) Alligator clip end of ground lead (asterisk) attached to an upper port on the enclosure. (F) Probe end of a milli/Gaussmeter, taped to the stage in the correct orientation for that make of probe, during a test of field strength.
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Figure 9. Completed MagShield apparatus.Shown with enclosure safety latches securing the door shut and power supplies positioned next to the mu-metal enclosure so that the leads can reach the coils inside.
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Figure 10. Modified MagShield setup for cell culture.View of MagShield apparatus inside a carbon dioxide (CO2) incubator used for cell culture, as previously reported [17]. This modification is required to maintain specific temperature, humidity, and gas composition needed to support the growth of cells in culture. Modifications include additional environmental sensors and considerations to prevent gas leaks while accommodating lead access to the power supplies.
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Figure 11. Hypomagnetic field exposure setup.(A) Interior of MagShield apparatus showing a Helmholtz coil in the left partition for Earth-normal controls, and an additional mu-metal-covered container for “near-zero” (< ~10 μT) hypomagnetic fields in the right partition (red arrow). (B) Mu-metal covered near-zero containers shown with tape covering sharp edges. (C) Photo of the hypomagnetic field exposure setup, with a single power supply and Helmholtz coil for controls, and additional mu-metal container for near-zero experiments.
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Figure 12. Effects of static magnetic fields on planarian regeneration.Regenerating fragments analyzed for blastema size (new tissue growth, visualized as the white region at the wound site) after three days of exposure to 500 µT (activating), 200 µT (inhibiting), or 45 µT (control) field strengths, using the MagShield apparatus as described in this protocol at 20 °C (room temperature). (A) Diagram of cuts. Adult planarians were transected by scalpel at one of two different amputation planes (dotted red lines), one above and the other below the pharynx (feeding tube), producing three different fragment types. (B) Head fragments, regenerating their pharynx and tail. (C) Posterior fragments, regenerating their head. (D) Tail fragments, regenerating their pharynx and head. (E) Quantification of B–D. Anterior is up. Single solid arrows: control blastema size. Double solid arrows: increased tissue growth. Empty arrows: inhibited tissue growth. Scale bars = 100 µm. n ≥ 5. Error bars = SEM. * p < 0.05, *** p < 0.001, **** p < 0.0001.
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Figure 13. Effects of static magnetic field intensity on fibrosarcoma cells.HT-1080 cell line exposed to a range of 0.5–600 µT static MFs, with 45 µT as controls (“C” bar on graphs), using the modified MagShield apparatus for cell culture in a 37 °C CO2 incubator. (A) Effects on cell growth. Cell growth rates expressed as a function of static MF exposure (mean ± SD) with the fields perpendicular to the flask bottom; n = 12, N = 3 for each group. (B) Effects on hydrogen peroxide (H2O2) levels. H2O2 concentrations as a function of static MF exposure (mean ± SD); n = 63, N = 3 for each group. (C) Effects on mitochondrial calcium (Ca2+) levels. Mitochondrial Ca2+ concentrations as a function of static MF exposure (mean ± SD) for fields oriented at 90° with respect to the plane of the cell flask bottom; n = 63, N = 3 for each group. * p < 0.05, ** p < 0.01, and *** p < 0.001. Error bars = standard deviation (SD).
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Figure 14. Preliminary developmental phenotypes from hypomagnetic field exposure of Xenopus larvae.Embryos exposed to either 45 µT (controls) or near-zero static MFs using the modified MagShield apparatus for hypomagnetic fields at 20 °C (room temperature). (A) Trial run 1: phenotypes at 3 days of development. (A1) Controls, phenotype n = 28/28. (A2-3) Near-zero affected phenotypes at 11–12 μT: Stunted growth with defects in anterior structures and anterior-posterior (AP) axis formation; n = 2/29. (A4) Representative phenotype of 11–12 μT animals with normal appearance. (B) Trial run 2: phenotypes at 5 days of development. (B1) Controls, phenotype n = 30/30. (B2-3) Near-zero affected phenotypes at 2–5 μT: Continued stunted growth with defects in anterior structures and AP axis formation; n = 3/30. (B4) Representative phenotype of 2–5 μT animals with normal appearance. Anterior is to the right and dorsal is up.
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