elf exposure systems for in vitro and in vivo experiments
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ELF exposure systems for in vitro and in vivo experimentsInternational School of Biolelectromagnetics “Alessandro Chiabrera”1st COURSE “Methodology in bioelectromagnetic experimental investigations”
21 – 28 April 2004, Erice
ELF exposure systemsfor in vitro and in vivo experiments
Section of Toxycology and Biomedical SciencesCR ENEA Casaccia, Roma
G.A. Lovisolo, L. Ardoino
ELF exposure systems for in vitro and in vivo experiments
Summary
General requirements of ELF exposure systems
How to generate a uniform magnetic field?
Systems of coils
Basic concepts and definitions
How to determine optimal values for the electric parameters
First steps of improvements: most widely used “reference” systems
Experimental and technical improvements
Two examples of ELF exposure systems for in vivo and in vitro studies
ELF exposure systems for in vitro and in vivo experiments
Before listing the requirements, a simple consideration about ELF fieldcharacteristic must be done…
At ELF the electric and magnetic part of EM field can be consideredacting in a separate manner.
An external electric field is greatly attenuated inside the body andperpendicularly oriented to the surface. This is due to the dielectricproperties (conductivity and permittivity) of the body tissues.
On the contrary, the magnetic field penetrate the body virtuallyunperturbed and induced electric fields and currents inside the tissues.
“the main objective of the bioeffects studies of ELF fields isto investigate the effects related to the exposure to the
magnetic field, thus the exposure system has to be essentiallya system for generating magnetic fields”
ELF exposure systems for in vitro and in vivo experiments
Basic requirements - all exposure systems -
(Real time) Measurements of the generated fields and of the backgroundlevels
Shielding from external disturbances
Allow sham exposure
Dosimetry: assessment of induced electric fields and currents inside thetarget (especially for in vitro experiments)
Assessment and monitoring of environmental parameters and otherchanges introduced by the system (electrical heating effects, noise and/orvibrations produced by the coils, ...)
ELF exposure systems for in vitro and in vivo experiments
Modify intensity and frequency values of magnetic field generated in awide range (0 – 100 Hz).
Large volumes of uniform magnetic field, related to the size of thebiological model.
Simultaneous generation of static and dynamic magnetic fields.
Opportunity of varying magnetic field direction and generating linearlyand circularly polarized fields.
Basic requirements - ELF exposure systems -
ELF exposure systems for in vitro and in vivo experiments
• How to generate a uniform magnetic field?
ELF exposure systems for in vitro and in vivo experiments
*(Spiegel et al. 1987; Paul et al. 1995)
**(Gundersen 1986; Miller 1989)
Generation of static and ELF magnetic field
Permanent magnets and ferromagnetic materials
Ferromagnetic structures with loop of wires
Other special arrangements: Crawford cell*, flat plates**
Current loops
onlystaticfield
Static and ELF magnetic field can be generated by:
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: ferromagneticmaterial with loops
Reference:Mullins RD, Sisken JE, Hejase HAN and Sisken BF: ’Design and Characterization of a System for Exposure of CulturedCells to Extremely Low Frequency Electric and Magnetic Fields Over a Wide Range of Fields Strengths’Bioelectromagnetics 14: 173-186, 1993.
“Air-gap reactor constructed from lamination of aferromagnetic material with a multiturn winding ofwire on one arm and an air gap in the opposite one.A rectangular medium filled chamber containing livingcells is placed in the air gap.”
lengthgap !=
NIB
0µ
N=1000; lgap= 0.015 m
B = 8.316 10-2 T for one Ampereof current applied to the coil
! B > 80 mT with 1 A
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: MF produced by“sheets of currents”
Three parallel plates used in vertical stacked configuration and appropriately energized:the sheet of current in the central plate divides equally between the upper and the lower onesproducing a magnetic field, parallel to the plates, that is in opposite direction in the two zones
V+V-
E
EB
I
I/2
I/2
BI
I/2
I/2
Magnetic field lines
Reference:Miller DL, Miller MC and Kaune WT, “Addition of Magnetic Field Capability to Existing Extremely Low Frequency Electric FieldExposure System”, Bioelectromagnetics 10: 85-98, 1998.
These kind of systems result inadequate to the present research needs in thebioelectromagnetic area that requests high homogeneous field volumes!
ELF exposure systems for in vitro and in vivo experiments
These kind of systems result inadequate to the present research needs in thebioelectromagnetic area that requests high homogeneous field volumes!
An equivalent systems consist of tworectangular solenoid…
I
I/2
I/2
Magnetic field lines
I/2
I/2 B
B
This arrangements eliminatessignificant skin effects andrequires less current than‘plates’ to produce the samefield
Generation of magnetic field at ELF: MF produced by“sheets of currents”
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: system of loops
Because of symmetry consideration, Bx and By vanish along the z-axis and the total flux density B is equal to the z-component Bz
P(x,y,z)
xy
r’1
r’2
r1
r2
r3
r4
s
z2b
2a
!="
""#
µ )(4
0 rfBz
NIi
!=i
zzrBB )()(Pi
P
z-component of flux density B (due to one coil) at thelocation of P is the sum of the contribution of each side (α)
By the principle of superposition, the flux density at P dueto the current in both loops (assuming the same N andcurrent direction), is:
square loops
ELF exposure systems for in vitro and in vivo experiments
square loops:
Graphs show
• the uniformity of Bz in awide area (with respect tothe overall volume),
• Bx and By components arenegligible in the samearea.
Generation of magnetic field at ELF: system of loops
Bz along z-axis
Bz along vertical lineat points (x, y ≠ 0)
Bx and By along verticalline at points (x, y ≠ 0)
1.0
0.9
1.1
1.2
Bz(x,y,z) / Bz(0,0,0.1)
Bz(0,0,z) / Bz(0,0,0.1)
0 1.00.75z / s
0.25 0.5
Bx(x,y,z) / Bz(0,0,0.1)By(x,y,z) / Bz(0,0,0.1)
0
-0.1
0.1
0.2
0 1.00.75z / s
0.25 0.5
Nor
mal
ized
flux
den
sity
ELF exposure systems for in vitro and in vivo experiments
circular loops
[ ]...)(cos)(cos2)
),( 4
44
2
225.12
2
0 ++++
= rPArPAdb
brB
z!!µ!
22(
NI
where: ),('2 dbfA = ),(''4 dbfA =[m-2] [m-4]and
z-of flux density B at the location of P is given by thefollowing formula.
d
d
I
I
P(r,θ)
xy
z
b
Generation of magnetic field at ELF: system of loops
As for square loops, for symmetry consideration, Bxand By vanish along the z-axis and the total fluxdensity B is equal to the z-component Bz
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: solenoids
Pθ1
L
az
θ2
z
2
NIL
NI
La
B
LzB
z
z
+=
+=
20
210
4)2/(
)cos(cos2
)(
µ
!!µ
For a long cylinder (L>>a) the field within the solenoid is nearly uniformexcept close to the ends and to the turns of wire …
[In a solenoid N turns of wire wound on a cylindrical form of length L and radius a]
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: ferromagneticmaterials or coils?
are able of producing UNIFORM magnetic flux density across a wide range ofvalues (up to some Teslas), higher than those generated with systems of coils ofsimilar dimension
Systems using ferromagnetic core
cannot vary the magnetic vector direction or generate circularly polarized field
Systems realized by coils and loops
can vary the magnetic vector direction and generate circularly polarized field
can generate and control simultaneously both the static and dynamic fieldcomponents
are restricted in generating high magnetic field by the currents that flow through the wires …
ELF exposure systems for in vitro and in vivo experiments
Most suitable arrangements for the generation ofuniform magnetic fields and for satisfying otherfundamental requirements are
systems of coils
ELF exposure systems for in vitro and in vivo experiments
Steps and improvements in the generation of the uniformmagnetic fields with coils
I. Two axial coils (Helmholtz)
II. Set of more than two coils:• Rubens (1945)• Lee-Whiting (1957)• Alldred & Scollar (1967)• Merritt (1983)
III. Double wrapped coil
IV. Multiple orthogonal sets
Increasing the level of generated field
Increasing the level of generated fieldand improving the high uniformityvolume
Generation of null field
Generation of circularly polarized fieldsand anyway oriented field
ELF exposure systems for in vitro and in vivo experiments
LOOP: single circular or square wire
COIL: several turns of wire
SET: several axial coils (usually from 2 to 5)
SYSTEM: One, two or three orthogonal sets
set
Coils (circular)
B
Scheme of two orthogonal sets of twocoils (multiwire) each, for the
generation of circularly polarizedmagnetic field
Basic concepts and definitions I
B
loop
B
coil
wires
coil section
ELF exposure systems for in vitro and in vivo experiments
Basic concepts and definitions IGeneration of low intensity magnetic field at ELF: one single coil
N: number of turns of the coil;I: current which flows through it (A)r: coil radius (m)
r200
NIHB µµ == (T)
loop B
B
y
x
zcoil
r200
IHB µµ == (T)
ELF exposure systems for in vitro and in vivo experiments
Generation of magnetic field at ELF: two coils (Helmholtz)
a
x
Px
C1 C2
a = r/2
r
C
Using two axial coils the field in the center of the system canbe increased …It is the sum of the contributions of the two coils
[ ]21
0)0(|0
C
z
C
zyz HHHBBz
+=== = µµ
( )[ ] ( )[ ] !"!#
$
!%
!&
'
++
+
(+
==322
322
211
20
xarxar
r)(yzNI
H
x = 0a = r/2
rr)(yz
243,17155,00NINI
H ===
Basic concepts and definitions I
ELF exposure systems for in vitro and in vivo experiments
Basic concepts and definitions I - Helmholtz system
• Most common commercial generators have R=50 Ω and Vmax<40V …
One coil (radius r, N turns, …)
B
y
x
z
Two coils (radius r, N turns, …)
a
x
C1 C2
a = r/2
rB
N is increased by a factor 2I is divided by a factor 2R required for each coil is 100Ω(the 2 coils are set in parallel)
r200
NIHB µµ == (T)
r243,1 0
NIB µ=
Using the same generators (R=50 Ω; Vmax<40V)we can increase the intensity field and theuniformity area
ELF exposure systems for in vitro and in vivo experiments
How design a system of coils?
Which factors should be considered?
ELF exposure systems for in vitro and in vivo experiments
• uniformity flux density volume (as a function of D)
• field exposure level (required B)
are defined by the experiment design
ELF exposure systems for in vitro and in vivo experiments
Definitions of technical parameters
Designing ELF exposure systems several geometrical and physicalconstrains should be considered.
These constrains concern, mainly, the following physical factors:
a) Small-diameter coils do not allow large spatial region of uniformity
b) Large-diameter coils cause weight and cost problems
c) High value of current cause high power dissipation and temperatureincrease
ELF exposure systems for in vitro and in vivo experiments
Geometrical and physical constrains
If we want to keep R=100 Ω …N is only a function of D and d
224
4
dd
l NDDN
SR !
"
"!! ===
D
RN
22
4
d
d
t
!="
#
$%&
'=
Physical constrain:
2/DN <d
d
wire
dNt =
Coil cross-section
Elements definition:d - is the wire diametert - is the coil thicknessD – is the coil diameter (2r)
Geometrical constrain: Maximal distance between coils is D/2 Minimal distance … is t=√N d
D/2
t/2 t/2
Definitions of technical parameters
ELF exposure systems for in vitro and in vivo experiments
How determine optimal values for the
coil diameters (D),
wire diameter (d),
number of turns (N),
current (I) ?
ELF exposure systems for in vitro and in vivo experiments
Geometrical and physical constraints: number of turns N and B level
Reference:De Seze R., Lahitte A., Moreau J.M., Veyret B.:’ Generation of extremely-low frequency magnetic fields with standardavailable commercial equipment: implications for experimental bioelectromagnetics work’. Bioelectrochemistry andBioenergetics 35: 127-131, 1994.
Definitions of technical parameters
2/1
22/1
4 D
dRt !!
"
#$$%
&=
'
a: unreasonable value;b: acceptable value4.77 a2.381.651.060.590.410.26200
5.89 a2.94 b2.041.310.730.510.33180
8.49 a4.23 a2.94 b1.881.060.730.47150
19.1 a9.52 a6.61 a4.23 b2.381.651.06100
76.4 a38.1 a26.4 a16.9 a9.52 a6.61 a4.2350
212 a106 a73.4 a47.0 a26.4 a18.4 a11.8 a30
0.850.60.50.40.30.250.2Field intensity B (mT) as a function of coil diameter D and wire diameter d with 10 V
D (mm)
61.930.921.413.77.75.43.4200
65.332.522.614.58.15.63.6180
71.535.624.715.88.96.24.6150
87.6 a43.630.319.410.97.64.8100
123.8 a61.7 a42.9 a27.4 b15.410.76.950
159.9 a79.7 a55.3 a35.4 a19.9 a13.88.930
0.850.60.50.40.30.250.2
Coil thickness t (mm) as a function of coil diameter D and wire diameter d for 100 ΩD (mm)
880N !""#
$%%&
'=
2
2
d
t
1180N !""#
$%%&
'=
2
2
d
t
Example:RequiredD ≥ 15 cmandB = 1 mT
ELF exposure systems for in vitro and in vivo experiments
Definitions of technical parameters
Coil section, length and mass as a function of wire diameter (copper, R=100 Ω)MassM (g)
Lengthl (m)
SectionS (mm2)
Wire diameterd (mm)
1684133360.570.85
32261a46180.791
516179b184713.142
418116620.280.6
201611540.200.5
8267390.130.4
2614160.070.3
521850.030.2
DN!=lengthcoil _
kLength
lengthcoil=
_
System Mass = 2 · k · Mass
Feasibility: current density
Reference:De Seze R., Lahitte A., Moreau J.M., Veyret B.:’ Generation of extremely-low frequency magnetic fields with standardavailable commercial equipment: implications for experimental bioelectromagnetics work’. Bioelectrochemistry andBioenergetics 35: 127-131, 1994.
ELF exposure systems for in vitro and in vivo experiments
28.3-------50.00
11.325.535.3-----20.00
5.712.717.635.4----10.00
2.86.48.817.725.540--5.00
1.12.53.57.110.21628-2.00
0.61.31.83.55.18.014321.00
0.280.640.881.82.54.07.1160.50
0.110.250.350.711.01.62.86.40.20
0.060.130.180.350.510.801.43.20.10
1.55 mm1.77 mm2
1 mm0.79 mm2
0.85 mm0.57 mm2
0.6 mm0.28 mm2
0.5 mm0.20 mm2
0.4 mm0.13 mm2
0.3 mm0.07 mm2
0.2 mm0.03 mm2
Current density J (A/mm2) as a function of wire diameter and sectionI (A)
Definitions of technical parameters
Reference:De Seze R., Lahitte A., Moreau J.M., Veyret B.:’ Generation of extremely-low frequency magnetic fields with standardavailable commercial equipment: implications for experimental bioelectromagnetics work’. Bioelectrochemistry andBioenergetics 35: 127-131, 1994.
Feasibility: current density
Unreasonable valuesAcceptable values
N
B1I
043.1
2µ
r=
ELF exposure systems for in vitro and in vivo experiments
Improvements in the generation ofuniform magnetic fields with coils
ELF exposure systems for in vitro and in vivo experiments
• Helmholtz configuration consists of a pair of parallel coils separated at adistance obtained with the condition that the first and second spatialderivatives of the applied field are equal to zero at the center of volumebetween the two coils.
• Subsequent work showed that several higher-order derivatives can bezeroed using assemblies of three, four or five coils, yielding much largervolumes of uniform field space.
• From this concept several systems of different size, coils shape, numbersof coils and wires have been studied and performed by severalresearchers.
ELF exposure systems for in vitro and in vivo experiments
A. - Helmholtz
B. - Rubens
C. - Lee-Whiting
D. - Merritt et al.
E. - Merritt et al.
F. - Alldred & Scollar
Basic “reference” systems
ELF exposure systems for in vitro and in vivo experiments
46.65/D26 / 11 / 11 / 26-0.51 D, -0.13 D,+0.13 D, +0.51 D
D, D ,D ,D4squareMerritt et al.(2)
35.69/D19 / 4 / 10 / 4 / 19-0.5 D, -0.25 D, 0,
+0.25 D, +0.5 DD, D ,D ,D, D5squareRubens
40.29/D21 / 11 / 11 / 21-0.52 D, -0.14 D,+0.14 D, +0.52 D
0.95 D, D,D, 0.95 D
4squareAlldred andScollar
68.21/D39 / 20 / 39-0.41 D, 0,
+0.41 DD, D, D3squareMerritt et al.
(1)
17.96/D9 / 4 / 4 / 9-0.47 D, -0,12 D,+0.12 D, +0.47 D
D, D ,D ,D4circularLee-Whiting
1.629/D1 / 1-0.27 D, +0.27 DD, D2square
1.798/D1 / 1-0.25 D, +0.25 DD, D2circularHelmholtz
Centralfield
(µT/A)
Ampere-turnRatios
Coil spacing w.r.t.center of system
Coil diameteror side length
N° ofcoils
CoilShape
Design specifications for basic “reference” systems
Reference: Kirschvink JL, ‘Uniform Magnetic Field and Double Wrapped Coil Systems: Improved techniques for the design of bioelectromagneticsexperiments’, Bioelectromagnetics 13: 401-411 (1992)
ELF exposure systems for in vitro and in vivo experiments
Uniformity levels of basic coil configurations
HelmoltzHigh uniformity area:
20 cm x 20 cmArea within 20% contour:
1 m x 1 m
Merritt et al. (4 coil) –Alldred & ScollarHigh uniformity area:
40 cm x 40 cmArea within 20% contour:
1,4 m x 1,4 m
ELF exposure systems for in vitro and in vivo experiments
Overall dimensions and uniformity of basic “reference” systems
Reference:* Gottardi G, Mesirca P, Agostini C, Remondini D and Bersani F, ‘A Four Coil Exposure System (Tetracoil) Producing a Highly UniformMagnetic Field’, Bioelectromagnetics 24: 125-133 (2003)
0. 086 D20.163 D20.132 D21.01 D3Merritt et al. (2)
0.012 D20.115 D20.269 D2D3Rubens
0.04 D20.147 D20.228 D20.984 D3Alldred andScollar
0.046 D20.096 D20.169 D20.821 D3Merritt et al. (1)
0.067 D20.212 D20.371 D20.739 D3Lee-Whiting
0.006 D20.016 D20.049 D20.393 D3Helmholtz
Uniformity region0.01%
Uniformity region0.1%
Uniformity region1%
OverallDimension
ELF exposure systems for in vitro and in vivo experiments
Last steps for the realization of the “ideal” system:
• Generation of null field: “double-wrapped coil”
• Generation of circular polarization: orthogonal sets
ELF exposure systems for in vitro and in vivo experiments
Why a null field should be generated
“Control experiments should be designed such that the only difference betweentreated and untreated groups is the magnetic field …”
In addition to the magnetic field, the coils introduce other undesired changeswhich might have some influence:
Electrical (ohmic) heating effects (temperature increase)
Variable-frequency noise and / or vibration
Small electric fields produced by the voltage drop between loops withinthe coils
The proposed solution consist in the realization of coils “wrapped in parallelwith two separate strands of wire” … where currents can flow in parallel andin antiparallel direction …
Double-wrapped coils also facilitate the use of truly double-blind procedure.
ELF exposure systems for in vitro and in vivo experiments
Generation of null field: basic technique
B’=2BPhase shifter(0°)
in out out
Double wrapped coil
B’= + B - B = 0Phase shifter(180°)
in out out
Double wrapped coil
r20
NIB µ=
I1= I2 :
( ) 0IIB2
N
=+=210
2rµ
I1= -I2 :
Double-wrapped coils( )210
2IIB
2N
+=r
µ
ELF exposure systems for in vitro and in vivo experiments
Each set of coils generates a field components along its axis; the magnetic field vector is the sum of these components: it rotates and traces an ellipse in the plane perpendicular to both sets; the period of rotation coincides with the period of the ac voltage applied to the loops.
Phase shifter90°
in out 0°
amplifiers
Magnetic field coils
Set 2
Set 1
B1
B2
Generation of circularly polarized field
ELF exposure systems for in vitro and in vivo experiments
Each set of coils generates a field components along its axis; the magnetic field vector is the sum of these components: resulting B vector have thedesired direction
Generation of oriented field
in out out
amplifiers
Magnetic field coils
Set 2
Set 1
B1
B2
B
ELF exposure systems for in vitro and in vivo experiments
-73 / 107 / 107 / 731 (linear)0.67 D / D / D / 0.67 D4CircularGottardi et al.(2003)
Alldred andScollar21 / 11 / 11 / 213 (linear and
circular)
X: int 1.099, ext 1.15Y: int 0.908, ext 0.95Z: int 0.745, ext 0.78
4SquareRaganella etal. (1994)
Harvey (*)4 / 2 / 2 / 41 (linear)3.15 x 1.164Doublerectangular
Yasui &Otaka (1993)
Rubens11 / 2 / 5 / 2 /112 (circular)Hor: 1.7Ver: 1.85SquareShigemitsu et
al. (1993)
Merrit at al. (1)68 / 34 / 6864 / 32 / 642 (circular)Hor: 2.14
Ver: 1.963SquareBaum et al.(1991)
Basicconfiguration
Ampere-turnRatios
Number of sets(polarization)
coil diameter or lenght(m)
n° ofcoils /setCoil Shape
Design specifications for other systems
ELF exposure systems for in vitro and in vivo experiments
Some recent systems for in vivo and in vitro experiments
ELF exposure systems for in vitro and in vivo experiments
An In vivo triaxial exposure system*
* Raganella L, Guelfi M and d’Inzeo G, ‘Triaxial Exposure System Providing Static And Low-frequency Magnetic Fields For In Vivo And In Vitro Biological Studies’, Bioelectrochemistry andBioenergetics 35 (1994)
This tri-axial exposure systemprovides static and low-frequencymagnetic fields with differentpolarization.
ELF exposure systems for in vitro and in vivo experiments
• The apparatus consists of three sets of four square coils (Alldred &Scollar) to provide greater uniformity.
A magnetic field linearly polarized along the coil axis is allowed. Therefore, we needthree nested systems, each fed independently, to control the component directed alongits axis.Such a configuration also generates elliptically polarized fields.
• Each coil is made by wrapping together two copper wires (Φ=2.5 mm) on a fibreglass frame;
• If the current flows in the same direction in both wires the induced magnetic fields add together producing the desired exposure conditions, while equal and opposite currents produce a null field in the direction of each system;
• The untreated group can be placed in the same experimental conditions as the treated group except for the presence of the magnetic field.
• The number of turns is 44 for the inner coils and 84 for the outer coils. The carrying structure of the system is made entirely of plastic material;
In vivo triaxial exposure system
ELF exposure systems for in vitro and in vivo experiments
In vivo triaxial exposure systemIsofield regions for the xz plane of this system (side D<1.2 m)
Uniformity levels are, from the inner to the outer region,0.01%, 0.1% and 1% with respect to the central value.
x (m)
z (m
)
> (50 x 70) cm2
0.01!"
00
00
B
BBxz
Uniformity of 1%with respect to thecentral value:
DEFINITION
ELF exposure systems for in vitro and in vivo experiments
In vivo triaxial exposure system
Supply and control system:1= triaxial system;2=PC and Labview (NI);3= analog output board*;4=data acquisition board;5=amplifiers;6=digital teslameter;7=triaxial magnetic field sensor and Hall effect probe;8=thermometer;9=GPIB-PCIIA interface board (NI)
*The waveforms, one for each axis component, are generated in digital form (2) bya D/A converter (3); the amplifiers (5) connect the board to the exposure system (1).
5 55
3
8 7
4
6
9
1
2
ELF exposure systems for in vitro and in vivo experiments
In vivo triaxial exposure system
• Field values generated by each system in thecenter of the exposure area as a function ofthe current
The control program compares the measured and thedesired values, and adjusts the waveform in order toobtain a stable static component of the field along eachaxis.The dynamic components can be superimposed on thestatic component.The values of static and dynamic fields and thetemperature are shown on the panel.
Bx/I= 140.129 µT/A
By/I= 169.629 µT/A
Bz/I= 206.600 µT/A5 55
3
8 7
4
6
9
1
2
ELF exposure systems for in vitro and in vivo experiments
Measurements of:• background values (magnetic field) and• residual values when nullifying the field
are necessary for planning the experiments
ELF exposure systems for in vitro and in vivo experiments
Electric and magnetic fields measurements: In vivo ELF exposure systems
A B CDE
Bx
By
Bz
General requirements: background measurements I
Background Magnetic field
Background Electric field
The electric field is measured by Holaday HI3638 (directional sensor), while flux magnetic density by Holaday 3627 (isotropic sensor).The static geomagnetic field is about 40 ±1 µT and has been measured by Group3-Danfysik-Hall sensor (directional) and Bartingtonfluxgate magnetometer-MAG-01H (directional).
3020163,5E (V/m)
B = 1.5 mTB = 1.0 mTB = 0
¦I¦ = 11 AB = 0I = 0
0,20-E
0,40-D
0,40-C
0,250,02B
0,30-A
Null magnetic fieldB=0, ¦I¦ = 11 A (µT)
Backgroundmagnetic fieldB=0, I=0 (µT)
ELF exposure systems for in vitro and in vivo experiments
A similar exposure system has been realized for in vitro experiments, scaling theprevious one.
In vitro triaxial exposure system
ELF exposure systems for in vitro and in vivo experiments
General requirements: background measurements II
1,81,4B max
1,41,0B min
Null magneticfield
B=0, ¦I¦ = 5 A (µT)
Backgroundmagnetic fieldB=0, I=0 (µT)
Electric and magnetic fields measures: In vitro ELF exposure systems
A B CDE
Bx
By
Bz
Square coils system (side 40 cm) is placed in a water jacket incubator.
Background Magnetic field
Background Electric field
31273,5E (V/m)
B = 1,0 mTB = 0¦I¦ = 5 A
B = 0I = 0
ELF exposure systems for in vitro and in vivo experiments
An In vitro (Tetracoil) exposure system**
** Gottardi G, Mesirca P, Agostini C, Remondini D and Bersani F, ‘A Four Coil Exposure System(Tetracoil) Producing a Highly Uniform Magnetic Field’, Bioelectromagnetics 24: 125-133 (2003)
A particular four coils system in which thecoils are geometrically constrained on asphere, producing a very uniform magneticfield over a wide volume.
ELF exposure systems for in vitro and in vivo experiments
In vitro “Tetracoil” exposure system
R
-b1 b1 b2-b2
a1 a1 a2 a2
1
23
4
1%
0.1%
Uniformity level within 1% (a) and 0.1% (b) with respect to the central value.
ELF exposure systems for in vitro and in vivo experiments
If the background values are significantly high compared to the plannedexposure level (B required by experiment design) orexposed and sham-exposed groups need to be placed in the sameincubatorthe system should be surrounded by µ-shieldthusit should also be provided by forced ventilation.
Use of shielding materials (µ-metal)
ELF exposure systems for in vitro and in vivo experiments
EF: two horizontal electrodes;MF: five pairs of vertically arrangedrectangular coils
Vertical EFHorizontal MF
EF: 1, 5, 25, 100kV/m,MF: 5, 100 mT; 50 Hz
Various morphologic andchemical parameters
Sprague-Dawleymale rats
Margonato et al.(1993/98)
Three orthogonally systems of four squarecoils each one; basic configuration:Alldred & Scollar
Linear andcircular
2 mT, sham;50 HzImmune system functionC57BL/6 female
miceFrasca et al(1997)
Three pairs of Helmoltz coilsLinear1 mT, sham;50 Hz
Lymphoma/leukemiainduction on DMBAtreated animals
Swiss WebstermiceShen et al (1997)
EF: two horizontal electrodes;MF: two sets of uniformly spacedconductors, around the EF system
Vertical EFHorizontal MF
EF: 65 kV/m,MF: up to 100 mT; 60Hz
Behavioral andneuroendocrine effectsBaboonsRogers et al
(1995)
Three orthogonally systems of four squarecoils each one; basic configuration:Alldred & Scollar
Linear andcircular
2 mT,sham; 50 Hz
Incidence and growth ofimplanted mammarytumor; comparison with X-rays treatment
C3HxDBAfemale mice
Marino et al.(1995/98)
Four coils Merrit system(coil length= 1 m)Linear100 mT,
sham; 50 Hz
Incidence and growth ofmammary tumor with andwithout DMBA treatment
Sprague-Dawleyfemale rats
Baum, Mevissenet al. (1994)
Solenoidal coils(dia= 40 cm; length= 66 cm)Linear0.3-1 mT, 30 mT,
sham; 50 Hz
Incidence and growth ofmammary tumor aftertreatment with DMBA
Sprague-Dawleyfemale rats
Mevissen,Loscher et al.(1993)
Two systems of four rectangular Helmoltzcoils each one, assembled coaxially
Linear(horizontal)
1, 100, 1000 mT,sham; 50 HZLymphoma inductionEm-PIM1
transgenic miceRepacholi et al.(1998)
Exposure systemPolarizationFlux density ;frequencyEnd-pointsAnimals
In vivo experiments with their relative exposure systems
ELF exposure systems for in vitro and in vivo experiments
Two pairs of Helmholtz coilsperpendicular to each other housed in an
incubatorCircular0.22 mT;
60 HzCythogenetic and cell kinetic
studiesHuman lymphocytesand CHO fibroblasts
Livingston at al.(1991)
Two pairs of Helmholtz coilsperpendicular to each other placed in a
mu-metal box inside an incubatorVertical0.05 mT;
60 HzNorepinephrine-inducedproduction of Melatonin
Primary pinealocytesof Sprague-Dawley
rats
Rosen at al.(1998)
A pair of Helmholtz coils mounted onthe objective stage of an inverted
microscopeVertical0.04-0.15 mT
5-100 HzIntracellular calcium
oscillations
Jurkat cells(human leukemic
T-cell line)
Lindstrom et al.(1995)
Two pairs of Helmholtz coilsperpendicular to each other and four
small solenoid coils housed in a woodenincubator
Horizontal andVertical
20.9 mT; 16 Hz65.3 mT; 50 Hz
Ca++ intracellularconcentration
T-Lymphocytes fromthymus of BALB-c
mice
Coulton &Barker(1993)
A rotating four coils Merrit system witha mu-metal chamber is placed in a
commercial incubator
Horizontal orVertical
0.2, 1.2 mT;60 HZ
Inhibition of antiproliferativeaction of Tamoxifen and
Melatonin
MCF-7 human breastcancer cells
Harland &Liburdy(1997)
Exposure systemPolarizationFlux density ;frequencyEnd-pointsCells line
In vitro experiments with relative exposure systems
ELF exposure systems for in vitro and in vivo experiments
Exposure systems for in vivo experiments require large uniform magneticfield volumes since is fundamental to allow the simultaneous treatment of asmany animals as possible, thus configurations with square coils are generallyemployed,
for animal studies, it is suitable to generate circularly polarized magneticfields thus exposure apparatus with two orthogonal oriented systems of coilsare generally employed.
In vivo experiments
ELF exposure systems for in vitro and in vivo experiments
The simple Helmholtz design provide an adequate field uniformity just for invitro experiments, and it’s widely employed for these ones, because is easier tomake for experiments that require relatively small volumes,
apparatus with orthogonal oriented systems of coils would be employed alsofor in vitro experiments, in order to allow the control of all the static and ELFcomponents.
In vitro experiments
ELF exposure systems for in vitro and in vivo experiments
Barnes, F. S. (1992). Some engineering models for interactions of electric and magnetic fields with biological systems.Bioelectromagnetics, Suppl. 1.Barnes, F.S. (1996). Interaction of DC and ELF electric fields with biological materials and systems. Handbook of Biological Effects ofElectromagnetic Fields. Second Edition. C. Polk, E. Postow, eds., Boca Raton: CRC Press, 103-147.Bassen, H., Litovitz, T., Penafiel, M. & Meister, R. (1992). ELF in vitro exposure systems for inducing uniform electric and magneticfields in cell culture media. Bioelectromagnetics, 13, 183-198.Baum, J.W., Kuehner, A.V., Benz, R.D., & Carsten, A.L. (1991). A system for simultaneous exposure of small animals to 60-Hzelectric and magnetic fields. Bioelectromagnetics, 12, 85-99.DeSeze, R., Lahitte, A., Moreau, J.M., Veyret, B. (1994) Generation of extremely-low frequency magnetic fields with standardavailable commercial equipment: implications for experimental bioelectromagnetics work. Bioelectrochemistry and Bioenergetics 35,127-131.Kirschvink, J.L. (1992b). Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design ofbioelectromagnetic experiments. Bioelectromagnetics, 13, 401-411.Merritt, R., Purcell, C. & Stroink, G. (1983). Uniform magnetic field produced by three, four, and five square coils. Review ofScientific Instruments, 54, 879-882.Raganella, L., Guelfi, M. & D’Inzeo, G. (1994) Triaxial exposure system providing static and low-frequency magnetic fields for invivo and in vitro biological studies. Bioelectrochemistry and Bioenergetics, 35, 121-126.Rogers, W.R., Lucas, J.H., Cory, W.E., Orr, J.L. & Smith, H.D. (1995a). A 60 Hz electric and magnetic field exposure facility fornonhuman primates: design and operational data during experiments. Bioelectromagnetics, 3, 2-22.Shigemitsu, T., Takeshita, K., Shiga, Y. & Kato, M. (1993). 50 Hz magnetic field exposure system for small animals.Bioelectromagnetics, 14, 107-116.Wang, P.K.C. (1997). ELF magnetic field exposure system with feedback-controlled disturbance rejection. Bioelectromagnetics, 18:299.306.Yasui, M., Kikuchi, T., Ogawa, M., Otaka, Y., Tsuchitani, M. & Iwata, H. (1997). Carcinogenicity test of 50 Hz sinusoidalmagnetic fields in rats. Bioelectromagnetics, 18, 531-540.Yasui, M., Otaka, Y. (1993). Facility for chronic exposure of rats to ELF magnetic fields. Bioelectromagnetics, 14, 535-544.
References
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