فصلنامه مهندسی پزشکی زیستی
سال ششم شماره 2 (تابستان 1391)

The Mesenchymal Stem cells derived from human newborn cords were cultured and exposed to a 24mT Static magnetic field for 24 hours. The viability percentage and the cell cycle progression was then investigated in exposed samples and the obtained results was compared with the control samples. The results clearly demonstrated a significant reduction of cell viability due to the exposure of 24 hours of SMF and post-exposure cultures within the time frames of 36,48,60 hours. The cell development through the cell-cycle, also verified this finding, however, 72 hours of post-exposure culture, significantly leveled off the drop in viable stem cell rates.

Exposure to magnetic fields can effect on the learning and memory. The protective effect of saffron extract on memory consolidation disorders in rats exposed to magnetic fields was investigated. 120 male Wistar rats in 12 groups exposed to magnetic field For 5 days with intensity 2.5 tesla for 1, 3 and 5 hour and protective effects of saffron extract with doses of 125 mg, 200 mg and 300 mg (P ≤0.05) compared to the control group by passive avoidance learning method in shuttle box. One hour exposure with magnetic field had no effect on the rats’ memory consolidation (P ≤0.05). Increase exposure time to 3 and 5 hours had a memory consolidation Impairment compared to the control group (P ≤0.05). Administered rats with 300 mg Inter peritoneal saffron extract improved memory consolidation (P ≤0.05) compared to the control group. Exposure to magnetic fields 2.5 mT, 50 Hz impair memory consolidation. Saffron aqueous extract at a dose of 300 mg per kg may have a protective effect and be improvement consolidation impairments.

There is a growing public concern that the extremely low frequency (ELF) range of the environmental electromagnetic fields may have adverse biological effects. In this frequency range, 217Hz is the modulating signal being used in Global System of Mobile. This study investigated the possible effects of 217 Hz pulsed electromagnetic field on the anxiety and the cortisol level in rats. Twenty four male Wistar rat (200 - 250 g) were randomly grouped into test, sham and control. Using a pair of Helmholtz coil system, the test group was exposed to a uniform   pulsed EMF of 200µT intensity for 4 h/day for 21 days. A similar procedure with no field was repeated for the sham group. All groups were tested in an `Elevated- plus` maze system. Then via the heart puncture scheme, the blood samples were collected. The serum cortisol levels were evaluated using ELISA method.The ANOVA test revealed no significant differences for the Elevated- plus maze test. Serum cortisol level was significantly higher in test group compared to the control group.These findings were in consistent with the work of others indicating that low frequency band of EMF might not have any effect on the anxiety but it increases the cortisol levels as a stress marker.

In this study cell growth, some physiological parameters, production of Taxol and gene expression in cell culture of hazel under effect of the magnetic field were investigated. Cells in suspension culture were treated by a 30 mT static magnetic field on days 8-11 after subculture and 4 hours each day. The results showed that while the growth rate and viability of cells weren’t affected by the magnetic field but membrane lipid peroxidation rate and H2O2 production increased. Activity of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase enzymes was increased by the magnetic field compared with control. Production of phenolic compounds and Taxolin treated cells showed an increase compared to those of control cells. Magnetic field increased intracellular Taxol more than extracellurTaxol, and in treated cultures total taxol production was 2.9-fold compared to control culture. Gene expression of 1- deoxy -D- xylulose -5 - phosphate reductoisomerase involved in producing Taxol precursors and in its biosynthesis was also increased in treated cells compared to control. It appears that magnetic field by stimulating cell defense responses and inducing gene expression involved in Taxol biosynthesis has resulted in improved its production.

During recent years, the environment has been enormously changed by the wide range of magnetic fields. Therefore, comprehensive studies are being done for investigating their biological effects. The effects such as inhibition of bioelectric activity of neurons which is shown by evidence, like decreasing in the firing frequency or decreasing in the amplitude of action potential, have been shown. To notify and investigate these effects, the theory of “biological windows” have been proposed and considered. The effects of amplitude and/or frequency of magnetic field have been pointed in some research. In this study, regarding the behavior of nervous system, which has non-linear dynamic behavior, we study the behavior of nervous system under exposure to magnetic field. We investigate whether the low frequency field is able to affect the dynamic of nerve cells and to have influence on non-linear features of signal. We used 6 environmental intensities and 6 cells have been used in each intensity, and by calculating some of non-linear features of action potential such as Higuchi Dimension and Return map of signal, during the time and in some different intensities of magnetic fields, It was observed that all intensities magnetic fields lead to increasing in Higuchi Dimension and increasing in the scattering of the Return map of signal. Of course these effects has been more observed in the middle band of frequency which has been confirmed by the theory of ‘frequency window’ effect of magnetic fields, which it has been noticed and discussed in last two decades.

We introduce a new computational approach which is capable of providing estimations of the electric field strength induced in biological bodies at large to ultra-fine scales. The method is theoretically based on multi-scale analysis and excitation of the smaller-scale models by the computed fields at the larger-scale model. The method and its implementation are shown, and as a practical example, the electric field induced inside the plasma membrane has been successfully computed for cells residing at different locations in the human body-model. Also discussed are the origins of the frequency-dependent behavior of the induced field strength and the significance of its practical consequences for bioelectromagnetics.

Self-paced BCI systems are more natural for real-life applications since these systems allow the user to control the system when desired. Detection of event periods in continuous EEG signal is one of the most important challenges in designing self-paced BCIs. In this paper, the Event related synchronization (ERS) is extracted from idle EEG signal using fractal dimensions in frequency range from 6 to 36 Hz and sparse representation based classifier. Our proposed method applied on EEG signal recorded during executing foot movement in 7 subjects. The average true positive rate and false positive rate equal to 90% and 5% were achieved.