الفهرس 
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Abstract
The present work is devoted to study the effect of exposing experimental male albino rats to a combined static and ELF alternating magnetic fields of average intensity 3 mT, to evaluate the risk on human workers who occupationally exposed to similar fields, and to overcome the controversial suggestions and researches of the possible effect of such fields.
The exposure system has been designed locally in Bio-Medical Physics Department, Medical Research Institute, Alexandria University. The system consists of two Helmholtz coils. Coil “A” with a diameter 23.7 cm and 2174 turns and coil “B” with a diameter 32.2 cm and 2082 turns. The diameter and the resistance of the wire were 1mm and 25 ohm respectively. The coils were separated by a distance of 11.5 cm in which rats were placed. The magnetic flux density of alternating magnetic field was measured using search coil (1.10 cm in diameter and 100 turns), while the flux density of static magnetic field was measured using teslameter (CTM 2010 Chauvin Arnoux, Japan).
A total of thirty male albino rats of average weight 70 ± 2.5 gm were used. The animals were divided into three groups, each on of ten rats. Group A served as control group, placed in the same conditions of exposed groups but without connection between electric current and the coils. Group B was exposed to the magnetic fields, 8 hours/day for two successive weeks. Group C was exposed to the magnetic fields, 8 hours/day for four successive weeks. During the 8 hours of the exposure period, coil A was arranged to produce 50 Hz alternating magnetic field, while coil B was arranged to produce static magnetic field.
At the end of the exposure periods, cervical decapitation of the rats was done. The blood was collected from each rat, the plasma was separated, and the hemoglobin was extracted from RBCs. Some biophysical, and biochemical parameters were studied as follows:
a- Biophysical parameters
Hemoglobin dielectric properties.
Hemoglobin absorption spectra.
Cellulose acetate hemoglobin electrophoresis.
Red blood cell’s osmotic fragility.
b- Biochemical parameters
Plasma glucose level.
Plasma cholesterol level.
Plasma ALT level.
Plasma AST level.
Plasma urea level.
RBC’s catalase activity.
Plasma malondialdehyde level.
The results revealed that
The dielectric properties of hemoglobin of exposed rats showed a dose-response increase in the dielectric constant and the conductivity which may indicate a change in the partial charges of the hemoglobin of the exposed rats.
No observed change in the hemoglobin absorption band position (but there was an increase in the absorption bands at 280, 340 and 578 which are aromatic amino acids, globin-heme interaction and heme-heme interactions respectively) or electrophoretic pattern of exposed group compared with control. This may be due to the unability of the used magnetic field intensity to alter or cause change in the hemoglobin molecule to a degree where it can be considered as an abnormal, but can affect the molecule stability only.
An increase in the osmotic fragility of RBCs of the exposed group was observed compared to the control, i.e. a decrease of RBCs membrane elasticity of the exposed groups which support the suggestion that the main point of interaction between the magnetic fields and the biological systems is the cell membrane.
An increase in glucose level in group B than control by 32.92%. While more or less the percentage change did not be altered in group C. The same result occurred in cholesterol level which increased in group B than control by 31.72%, while this percents is approximately the same in group C. This may indicate a hormonal disturbance and the hormonal system is acted upon to decrease the disturbance to reach homeostasis.
An increase in ALT and AST levels in group B by 24.94%, and 13.48% respectively than control was observed. While further increase in group C than control by 110.26% for ALT, and 37.10% for AST. This may indicate some damage in the liver cell membranes after 2 weeks of exposure, and higher degree of damage after 4 weeks exposure.
No change in urea levels of exposed groups compared with control indicating no effect of such field intensity on kidney.
A small increase in malondialdehyde level in group B compared with control (5.14%), and significant increase in group C (23.40 %) than control was occurred, i.e. after two weeks exposure the amount of the produced free radicals is not too high to be handled by the body systems while after 4 weeks of exposure this amount was highly increased. This result was supported by catalase increase from 8.42% in group B to 11.83% in group C than control, i.e the body systems increased the antioxidant activity (catalase) to face the increase in free radicals amount.