Effect of Manetic Field at Low Frequency on Cells Arrangement
Chiaki Miyamoto, Shigehiro Hashimoto, Yusuke Morita, Hidekazu Tsuji,
Atsushi Yamanaka, Takayuki Sekiyama, Tomohiro Sahara, Kenichi Yamasaki,
Teruyuki Yamanari, Yuuta Morioka, Yue Wu
Biomedical Systems, Dept. of Electronics, Information, and Communication Engineering,Osaka Institute of Technology, Osaka, 535-8585, Japan
hasimoto@elc.oit.ac.jp
andHajime Otani, Hiroji Imamura
Dept. of Thoracic and Cardiovascular Surgery, Kansai Medical University
Moriguchi, JapanABSTRUCTThe effect of the magnetic field at extremely low frequency oncells was investigated in vitro. An experimental system of a
uniform alternating magnetic field was designed with theHelmholtz coil. Rat’s fibroblasts or endothelial cells wereexposed to a magnetic field for six days. The results showthat there are minor effects of the magnetic field in the intensity
level of 0.05 mT on cells at frequency of 50 Hz, and that there
are possible effects on the culture medium and on thealignment of the fibroblasts.

of two circular coils of which both radius and turns are equal toeach other. In the Helmholtz coil, two coils are located in theparallel position with the common axis (X). The distance
between two coils (L) is equal to the radius (a) of the coil (Fig.
1). The magnetic field generated between two coils is
quasi-uniform (Fig. 2), and the magnetic flux density between
them is approximately constant (Fig. 3).

Keywords: Bioelectronics, Magnetic field, Cell culture, Low
frequency

1. INTRODUCTION

L2aX

The effects of the magnetic field on a living body werediscussed in many previous studies. Some epidemiologicalresearches show possible effects of the magnetic field on
human health [1, 2]. Some animal tests were also performedin the previous studies [3]. Another experiments show thatthe molecules of collagen orient along the static magnetic field[4].

B
Coil ofradius aI
2. METHODS
Fig. 1: Principle of coil.
An experimental equipment was manufactured to generateuniform alternating magnetic field at extremely low frequency.
Helmholtz coil
An alternating magnetic field is generated around a coil withalternating electric current (I). To generate uniform magnetic
field, Helmholtz coil was used. The Helmholtz coil consists

ICoilFig. 2: Magnetic field between two coils.

Bo=0.716(N・I/a)koMagnetic flux density BFig. 5: Circuit diagram of converter from voltage to electric
current.
2a0aX

A uniform alternating magnetic field (50 Hz, 0.05 mT) wasgenerated with the Helmholtz coil manufactured with radius of
70 mm (Fig. 4(a)). Four dishes (radius, 30 mm) were placedin the magnetic field so that the culture plane of the dish iseither parallel to or perpendicular to the field.
Magnetic shieldThe Helmholtz coil was enclosed with the flexible sheet ofmetal to shield the experimental space from the surrounding
magnetic field (Fig. 4 (b)).

Fig. 3: Magnetic flux of Helmholtz coil.

Converter from voltage to electric current
Through the converter, the output electric current is controlledwith the input voltage (Figs. 5 & 6). The current in the coil isable to be kept independent of load resistance of the coil. The
output current varies 0.5 mA with the variation of 1 V in theinput voltage. The maximum output voltage of operationalamplifier is 10 V, which makes the maximum output current of5 mA. The offset circuit was added to the converter.

Fig. 4: (a) Helmholtz coil (dishes parallel to the magneticfield), (b) Magnetic shield.

Fig. 6: Converter from voltage to electric current.

222

H=[I a / {2(a +L /4)22(a +L /4)}

x2]

3/ 222}] [2−3{(a −L )/(3)When the radius (a) is equal to the distance (L), the magneticfield (H) becomesaaIIPO

H＝0.716(I/a)(4)

B=k0 H(5)IX
L/ 2When each coil consists of N turns, the magnetic flux density(B) is calculated with

L/ 2

Bo=0.716(N I/a)koFig. 7: Two circular coils.

Oscillator

Incubator

Helmholtz coil

Voltage-electric
current converter Magnetic shieldFig. 8: Experimental system.

Magnetic field between two coils
Two circular coils of radius (a) are located in the parallel
position with distance of L at the common axis (Fig. 7). An
electric current (I) flows in the clockwise direction at each coil.
The magnetic field (H) at the point P, which is away from thecenter of the axis (O) with distance of X, is calculated by thefollowing equations.
2222x) }3/ 2222]+ I a / [2{a +(L/2−CellTwo types of cells were alternatively used in the experiment:
rat’s fibroblasts L929, or endothelial cells. The endothelial
cells were exfoliated from the descending aorta of a rat. Thecells were cultured in each magnetic condition for 6 days.
The results were evaluated about four points of view:
multiplication rate of cells, destruction of cells, thearrangement of cells, and the condition of the medium.
Multiplication rate of cells
The population of cells in the certain area in the dish wascounted every twelve hours with a phase contrast microscope.
To trace the same area, the plate which has twenty-one holes of
1 mm diameter was attached on the bottom of the dish.

]22= [I a / {2(a +L / 4) }2[{1+ (L x+ x2

3/ 2Measurement system
The input voltage generated with the oscillator (Kenwood,AG-D) is converted into the electric current, which flows in theHelmholtz coil. In the experiment, both the magnetic flux
density and frequency were controlled with the oscillator.
The wave-forms of input voltage and output current aremeasured with an oscilloscope (Kenwood, CS-5170). The
generated magnetic flux density is measured with thegaussmeter (Wandel & Goltermann, EFA-2).
Three sets of the instruments were manufactured and placed
simultaneously in an incubator for comparison about threekinds of magnetic conditions: exposed to the parallel magnetic
field, exposed to the perpendicular magnetic field, and shieldedfrom the magnetic field.

DishH=I a / [2{a +(L/2+x) }(6)2(a +L /4)}

23/ 2]

2)/(a +L /4)}
−3 / 2−3 / 2

2+ {1−(L x−x )/](1)

The magnetic field (H) can be approximated with Eq. (2), whenx is small.
2

22

2

2

21＞＞（L x+ x ）/ a +(L /4) , (L x−x )/ a +(L /4)(2)

Destruction of cells
LDH (lactate dehydrogenase) is released from a destructed cell.
Concentration of LDH was measured with P-L method(Wroblewski method) in the culture medium collected every
twenty-four hours from each dish during the test.
Arrangement of cells
The acute angle between the direction of magnetic field and thelongitudinal axis of each L929 cell was measured after
cultivation for 72 hours. The distribution was compared withthat of the direction of longitudinal axes of L929 cells, whichwere not exposed to the magnetic field.

L929 cell

Direction of magnetic field

Fig. 9：The arrows show a direction of magnetic field andlongitudinal axis of L929 cell.

× Non-exposed △ Parallel □ Perpendicular

The number of the cell1000

Fig. 12: Distribution of the angles.

1001013040506070Time, h8090100

Condition of the medium
The color of the medium solution in which cells are culturedchanges with its pH. The change shows variation of contents
in the medium. The change of the color was measured withintensity of transmitted light through the solution. The
intensity was measured every twenty-four hours with thespectrophotometer (Shimadzu, UV-1200) relative to that of
distilled water as 100 percent. The deference between
intensity of medium exposed to magnetic field and that ofmedium shielded from the magnetic field was calculated.

Fig. 10: The rates of multiplication of the three kinds ofmagnetic conditions (endothelial cells).
3. RESULT

Table 1: Concentration of LDH (IU/L at 37 degree C).
Time (hour)TimeparallelperpendicularNon-exposure

The intensity of surrounding magnetic fields sufficiently
decreased with the flexible sheet of metal.
Multiplication rate of cells
Each point in Fig. 10 shows mean value of population in sixareas.
The population of endothelial cells increases
exponentially with time. The slopes of three lines are similar,
which shows the similar multiplication rate in three kinds ofmagnetic conditions: exposed to the parallel magnetic field,
exposed to the perpendicular magnetic field, and shielded fromthe magnetic field.
Destruction of cells
Concentration of LDH does not significantly vary with thethree magnetic conditions (Table 1).

(a)

(b)

Fig. 11: L929 cells after 72 hours of cultivation: (a)Exposure to the parallel magnetic field, (b)Non-exposure. The direction of the magnetic field isfrom right to left.

Arrangement of cells
Figure 11 shows L929 cells after 72 hours cultivation. The
distribution of angle between the direction of magnetic field
and the longitudinal axis of each L929 cell is shown withdivision of every 15 degrees in Fig. 12. The angles of 315
and 321 cells were measured for two magnetic conditions:shielded from the magnetic field and exposed to the parallel
magnetic field, respectively. The angles distribute randomly
in the cells shielded from magnetic field, where they distributeat smaller division in the cells exposed to the parallel magneticfield.

were in the same level in the present experiments.
Table 2: The average angle.

Non-exposure
Exposure to paralell

Theresults show constant low destruction of cells regardless of themagnetic field conditions.

The number of the cells

Mean angle

315
321

45.4
37.1

The present experiments show only minor effects of themagnetic field of 0.05 mT at extremely low frequency on
multiplication of cells. The difference of transmittanceintensity indicates the difference of solutes in the medium,
which have not been identified.

Intensity of transmission (%)

To study the effect of the alternating magnetic field on cells,
three magnetic conditions were designed with cell culture.
The study shows that there are minor effects of the alternating
magnetic field in the intensity level of 0.05 mT on cells at
extremely low frequency of 50 Hz, and that there are possible
effects of the alternating magnetic field both on the cellalignment and on the culture medium.

5. ACKNOWLEDGMENT
This work was supported in part by a Grant-in-Aid for
Scientific Research from the Japanese Ministry of Education,
Culture, Sports, Science and Technology.
Wavelength (nm)

6. REFERENCES
Fig. 13: Difference of transmittance of the medium. L929
cells after 120 hours of cultivation.
×: exposure to perpendicular ◆: exposure to parallel.

The mean angle of cells exposed to the parallel magnetic fieldis smaller than that of cells shielded from magnetic field (Table2). The result shows that the cells tend to align with thedirection of the magnetic field.
Condition of the medium
Deference of transmitted light intensity between the medium
solution exposed to the magnetic field and the medium
shielded from the magnetic field is shown as a function of the
wavelength between 300 and 900 nm in Fig. 13. Only small
deviations are shown around 350 nm, 500 nm and 650 nm.

4. DISCSSION AND CONCLUSION

The Helmholtz coil is effective to generate the parallel
magnetic field. The uniform alternating magnetic field
was controlled in the present experimental device withthe Helmholtz coil and with the flexible sheet of
micro-grain metal. The intensity level of 0.05 mT
occurs in the atmosphere of daily urban life.
The lactate dehydrogenase is released from cells during
their destruction process, and used as an index fordestruction of cells. The concentrations of lactate
dehydrogenase in the medium replaced every 24 hours[1] UK Childhood Cancer Study Investigators, “Exposure topower-frequency magnetic fields and the risk of childrencancer”, Lancet, vol. 354, 1999, pp. 1925-1931.
[2] M. Feychting, et al, “Fields and breast cancer in Swedish
adults residing near high-voltage power lines",
Epidemiology, 1998.
[3] A. A. Mario, Different outcomes biological experiments
involving weak EMFs: is chaos possible explanation?,
The American physiological Society, 1995, pp.
R1013-R1018.
[4] H. Kotani, M. Iwasaka, S. Ueno, and A. Curtis, “Magneticorientation of collagen and bone mixture”, Journal ofApplied Physics, vol. 87, No. 9, 2000, pp. 6191-6193.