Frequency Dependent Alterations of S. Cerevisiae Proliferation Due to LF EMF Exposure

BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE Frequency Dependent Alterations of S. Cerevisiae Proliferation Due to LF EMF Exposure Roman RADIL1, Jan BARABAS 1, Ladislav JANOUSEK 1, Martin BERETA2,3 1Department of Electromagnetic and Biomedical Engineering, Faculty of Electrical Engineering and Information Technology, University of Zilina, Univerzitna 1, 010 26 Zilina, Slovak Republic 2Institute of Measurement Science, Slovak Academy of Sciences, Dubravska cesta 9, 841 04 Bratislava, Slovak Republic 3Department of Radiologic Technology, Faculty of Health, Catholic University in Ruzomberok, Namestie Andreja Hlinku 1159, 034 01 Ruzomberok, Slovak Republic [email protected], [email protected], ladisla[email protected], [email protected] DOI: 10.15598/aeee.v18i2.3461 Abstract. The presented paper deals with low frequency electromagnetic field application on Saccharomyces cerevisiae cells. Experiments performed through wide frequency range have shown selective frequency dependent biological response, which could be successfully predicted by ion parametric resonance theory proposed by V. V. Lednev. Although observed results give satisfying answer to questions whether or not electromagnetic fields could affect cell cultures even at non-thermal levels, the research presented herein opens a multitude of questions about the exact physical mechanisms underlying the observed microorganism behavior, as the theory discussed within the scope of this article is still not completely unambiguous. Keywords Electromagnetism, low frequency electromagnetic fields, proliferation, cell membrane, ion parametric resonance. 1. Introduction It is well known that the electromagnetic conditions in which we live nowadays are different from those in which people used to live in the past. The majority of living beings are confronted with artificial ElectroMagnetic Fields (EMFs), which complement the naturally occurring EMF of the Earth, and questions pertaining to influence thereof on biological systems are more frequent than ever. The number of experimental studies investigating EMF effects on living cells, tissues or on human health in general, has grown rapidly over the last few decades. Much attention is currently being paid to research regarding potential connection between EMF exposure and cancer or other diseases, which has been discussed in various studies [1], [2], [3], [4], [5], [6] and [7]. Numerous works focusing on experiments with living cells have shown differences in the proliferation process between cells exposed to EMF and control (nonexposed) cells [8], [9], [10], [11], [12], [13] and [14]. Other works investigate animal behaviour when exposed to EMF [15] and [16] or possible genomic instabilities due to EMF exposure [17], [18], [19] and [20]. The results of these works are often inconsistent and, as stated in Buchachenko [21], the biological electromagnetic effects sometimes seem to be irreproducible and contradictory. As pointed out in Markov [22], the problem is often discussed within the scope of thermal effects with minor interest on possible non-thermal mechanisms, even when considering currently accepted standards and recommendations (e.g. from International Committee of Nonionizing Radiation Protection - ICNIRP, 1998). Actually, the evaluation of EMF effects on biological objects is much more complicated due to principal differences in each approach, and no part of the problem should be neglected, especially when Low Frequency EMF (LF EMF) and weak signals, that are far below the ICNIRP recommendations, are considered. The complexity of this problem is documented by many authors [23], [24], [25] and [26], who tried to propose physical mechanism of biological LF EMF impact, but there is still lack of general acceptance of any proposed theory across the scientific community. This fact is at c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 99 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE the same time a strong motivational factor for further investigation in this field of research. The Ion Parametric Resonance (IPR) theory, proposed by Lednev [25], [26] and [27], is one of the most discussed models of LF EMF interaction with biological objects. The assumptions of this theory are based on the Ion Cyclotron Resonance theory (ICR), first described by Liboff [24], speculating that the physiological activity of certain important ions can be altered when the frequency of applied timevarying magnetic field is equal to the frequency of ion motion in a static magnetic field. Ions in IPR model are represented by a harmonic oscillator, bound to a specific location at the surface of the cell membrane, and application of combined magnetic field should alter its oscillations. The mentioned physical model included several imperfections, particularly due to the problem of thermal noise, and was criticized by Adair [28] and [29]. The theory was defended by Engstrom [30] and mentioned imperfections were addressed by Lednev [26] and [31]. Despite criticism, there remains an impressive body of experimental evidence that can be taken as an empirical basis for ICR and IPR hypotheses [8], [9], [10], [11], [12] and [13]. In general, as Halgamuge et al. concluded [33]: “. . . models based on electric interactions have difficulties to obtain a high enough signal-to-noise ratio at low field strengths. The fields that are needed to explain the opening of a membrane channel protein are unrealistically high. On the other hand, models based on magnetic interactions can easily obtain a large enough signal-to-noise ratio, because the level of magnetic thermal noise in tissue is low. The reason that these models work, is the same reason that makes the MRI technique possible.” Another attempt to shed more light into this research area is presented within this article. The authors opted to experimentally investigate non-thermal effects of LF EMF on Saccharomyces Cerevisiae cells, at various uncommon frequencies, often neglected in other research works. To gain better reproducibility of conducted experiments, authors used their innovative exposition system described in [33], proposed with the aim of achieving the highest possible homogeneity of magnetic flux density within the exposed volume, taking into account sample dimensions and incubator proportions. This system enables experiments with 3 petri dishes (diameter of 9 cm, height of 2 cm - each), each irradiated by a homogeneous magnetic field. Obtained results and observed biological reactions are then discussed within the scope of the IPR theory. 2. Materials and Methods Saccharomyces cerevisiae cells (brand VIVO – commercially available from Lesaffre Slovakia, Inc.) were selected as the target biological object for irradiation by LF EMF. The reason for this choice is the growth analogy with cancer cells [34], as well as previously published works regarding LF EMF effects on yeast cells [35] and [36]. 2.1. Experimental Protocol Chemical laboratory testing protocol for the mentioned VIVO strand of S. Cerevisiae is publicly available from company Mikrolab, LLC. This means that the microbiological, physical and chemical properties and parameters of investigated microorganisms were known prior to the experiments. Cells were cultivated on GKCH agar, in accordance with STN EN ISO 7218 (560104) and STN ISO 7954 (560087) standards and specifications. Cultivation was performed under identical ambient conditions for 72 hours, with temperature of both exposed and control samples set slightly above room temperature, specifically to 27 ◦C. Continuous temperature monitoring was performed using three Negative Temperature Coefficient (NTC) thermistors and processed and logged in real-time. Two of the NTC thermistors were placed within the incubator chambers to monitor the temperature of both exposed and control samples, and the third thermistor was placed outside the incubator as a reference sensor. To avoid any effects from airflow, humidity, or changes of light conditions, the exposed samples were held in a solid plastic holder, matching the diameter of the coil cavity. 2.2. Experimental Setup and Evaluation Methods The experimental setup, used for all of the presented experiments and detailed in [37], is schematically shown in Fig. 1. The setup was specifically designed for paired sample experiments, conducted on two sets of three Petri dishes inoculated by S. Cerevisiae. One set was placed within one chamber of incubator, housing the mu-metal magnetic shielding box. This set was the control, or reference sample - being shielded from the generated LF EMF. The second set of samples, representing the exposed cells, was placed at specific position within the already mentioned developed coil system, depicted within the real scheme of experimental setup on Fig. 2. The coil system was driven by harmonic current (generated by the Agilent 33220A signal generator, manufacturer Agilent Techc 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 100 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE nologies, Inc.), and amplified using a linear amplifier (Hubert A1110-05, manufacturer Dr. Hubert GmbH) - the resulting amplitude Imbeing in the 0.96–1.09 A range. The exact value of excitation current depended on the impedance matching and frequency used, so as to achieve the required magnitude of magnetic flux density. The experiment was repeated for 5 times at said frequency. PC NI Elvis AmG MS CS ES Incubator A Fig. 1: Experimental setup: G - signal generator Agilent 33220A; Am - amplifier; A - ampere meter; Incubator with two chambers: ES - exposed samples placed within the excitation coil, CS - control samples placed within the MS - magnetic shielding box; NI Elvis II - development board for temperature data acquisition; PC - temperature monitoring and visualization. Fig. 2: Propopsed and constructed experimental setup showing the applicator used in preliminary experiments and the newly designed applicator. From the afore mentioned it is evident that samples were irradiated by LF EMF with magnetic flux density ~ B, which varies spatially within the exposed volume. The exact value of ~ B-field produced by the coil system was validated by measurements, using sensitive fluxgate sensors. Since this method is described in more detail in [33] and [38], for the purpose of this article, it is sufficient to mention the conclusion that real-life measurements re-confirmed values obtained from numerical simulations, documenting minimum magnetic flux variations (max. 5 %) within the irradiated volume, when using the proposed excitation coil system. The value of magnetic flux density varied between ~ B=2.33–2.45 mT, and was frequency independent. After continuous irradiation, the growth dynamics parameter of both control and exposed samples was quantified. Specifically, growth dynamics were computed via semi-automated software called PetriCounter, which was developed as a replacement for commercially available counters. Algorithm thereof is detailed in [39]. Principally, it allows detection and counting of yeast growth areas, using methods of image processing, analysis, and feature extraction, to enable experimental results quantification and comparison of observed effects. Statistical significance of observed results was finally evaluated using Student’s T-test for paired samples, with significance level α= 0.05. 3. Results and Discussion As was mentioned in previous section of this article, experiments were focused on the behaviour of Saccharomyces cerevisiae cells influenced by exogenous LF EMF of different frequencies produced by the designed coil system. Our work follows previously conducted experiments published in [40], [41] and [42], but the frequency range differs, and is wider in comparison with preliminary experiments. At first, we reevaluated the base frequency of 1.6 kHz, which was experimentally proven as statistically relevant for the inhibitory effect on S. Cerevisiae proliferation. The first set of experiments was then conducted with frequencies of 1.6, 0.8, and 0.4 kHz to verify hypothesis regarding effects of subharmonic frequencies and correlation thereof with IPR theory, presented in [30]. Results of these experiments are shown in Tab. 1. Tab. 1: Comparison between experimental results observed at irradiation signal frequencies and IPR predicted frequencies at specified magnetic flux density targeting Ca2+ ion. Magnetic flux 2.39 2.39 2.39 2.39 density (mT) Frequency 1.600 0.800 0.400 0.200 generated (kHz) Frequency 1.596 0.798 0.398 0.204 predicted (kHz) Growth area ratio 0.59 0.54 0.64 0.80 (exposed/control) From the experimental results it is clear that all subharmonic frequencies have shown inhibitory effects and statistically significant biological responses are present at frequencies 0.8 and 0.4 kHz, as well as the base frequency. These frequencies correspond to the ion parametric resonance frequency of Ca2+ ions, and harmonic components thereof in accordance with Lednev’s IPR theory from [25], [26] and [31] and the Eq. (1): f=fc n=1 n · q 2πm ·Bgen,(1) where fcrepresents the cyclotron resonance frequency of the ion, qis the elementary charge of the ion, mis c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 101 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE 0.850 0.800 0.890 0.640 0.899 0.690 0.540 0.750 0.864 0.590 0.720 0.650 0.100 0.200 0.300 0.400 0.700 0.750 0.800 0.850 0.900 1.600 1.800 2.000 Frequency (kHz) 0 0.2 0.4 0.6 0.8 1 1.2 Growth area ratio (exposed/control) Fig. 3: Graphical interpretation of proliferation response of irradiated samples within the investigated frequency range of applied time-varying LF EMF. mass of the ion and ndenotes the corresponding harmonic component. Bgen is the mean value of generated magnetic flux density, which in our case was 2.39 mT. Predicted frequencies for the biological response based on this model are also shown in Tab. 1. It is evident that experimental frequencies at which statistically significant biological effects were observed are closely related to their theoretically predicted counterparts. Also apparent from the presented set of experiments is that the biological effect tends to disappear at lower frequencies, as was the case in experiments using 0.4 kHz. To verify this observation, we opted to investigate a wider frequency range, with focus on low frequencies and also on frequencies around the experimentally proven biologically active frequency of 0.8 kHz. This set of experiments is presented graphically in Fig. 3, for better illustration and interpretation thereof. Observed results once again show inhibitory effects. More interestingly, there are signs of periodicity within the experimental data, with strong peaks at previously described resonance frequencies of Ca2+ that could be predicted by IPR model. Furthermore, the previous assumption, regarding the biological effect extinction at lower frequencies, seemed to occur at frequencies below 0.4 kHz. Another interesting observation concerns the neighbourhood of the frequency 0.8 kHz, where the proliferative response is weak in comparison with the resonance (base) frequency, albeit still present. This observation points to the window theory, mentioned by Markov in [22], but could be also explained as a cumulative effect of other ions, which play an important part in cell proliferation processes. Since frequency dependent biological response is evident from the presented results, we opted to also investigate the influence of magnetic flux density ~ B of the generated LF EMF. For this purpose, we chose the frequency of 0.8 kHz, where the biological response seemed to be most significant, and altered the value of ~ Bto 50 %, 25 % and 10 % of its original value. These alterations were technically performed by amplitude changes of effective value of driving current, which directly influences the amplitude of ~ Bin the coil cavity and thus the exposed volume. Results presented in Fig. 4 show that significantly strong proliferative response is present only with original magnetic flux density of 2.39 mT. The biological response is weak or no longer observed at given frequency due to modified magnetic flux density of the applied LF EMF. Frequency 800 Hz 2.39 1.195 0.5975 0.239 Bgen (mT) 0 0.2 0.4 0.6 0.8 1 1.2 Growth area ratio (exposed/control) 0.56 0.79 0.94 0.90 Fig. 4: Graph of proliferation dependence of S. Cerevisiae on Bgen, at the frequency of 800 Hz. c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 102 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE 4. Conclusion The presented article discusses chosen theories related to LF EMF mechanisms of interaction with biological objects, represented herein by Saccharomyces cerevisiae cells. Repetition of previously conducted experiments published in [8], [38], [40], [41] and [42] confirmed inhibitory effect on the proliferation response at the frequency of 1.6 kHz. Furthermore, the experimental results clearly demonstrated non-thermal effects of externally applied time-varying LF EMF on the proliferation process of cultivated cells. Our findings regarding the Ca2+ are also in correlation with research presented in [43]. The observed biological responses could be referred to as frequency selective because statistically significant effects occur only at specific frequencies, which points to the resonance character of the observed bio-effects. The mechanism of action influencing the behaviour of the irradiated biological samples could be theoretically explained by the IPR theory. This model successfully predicts observed biologically active frequencies, considered resonance frequencies of Ca2+ ions and harmonic components thereof. From this point of view, we can draw the conclusion that Ca2+ ions play an important role in cellular proliferation processes, and could be exploited as targets for irradiation by external LF EMF tuned to parametric resonance frequency thereof, which corresponds with findings presented by Belova [27]. The relevance of V. V. Lednev’s theory can be also confirmed by results of our investigation of magnetic flux density changes with respect to proliferation response at unchanged frequency. This means that when expecting biological response in accordance with the IPR theory and Eq. (1), any change of ~ Bnecessarily leads to change of the ion parametric resonance frequency, but not every change of frequency must lead to change of magnetic flux density. Despite the findings presented within this article, an unambiguous explanation of EMF influence on living structures is still lacking. Thus, many questions are still open in this field of research and can only be answered by great amount of successful and repetitively obtained experimental results from which conclusions and theories can be drawn. Acknowledgment This work was supported by project ITMS: 26210120021, co-funded from EU sources and European Regional Development Fund and by the Slovak Research and Development Agency under the contract no. APVV-16-0190. References [1] ROOSLI, M., M. LORTSCHER, M EGGER, D. PFLUGER, N. SCHREIER, E. LORTSCHER, P. LOCHER, A. SPOERRI and C. MINDER. Leukaemia, Brain Tumours and Exposure to Extremely Low Frequency Magnetic Fields: Cohort Study of Swiss Railway Employees. Occupational and Environmental Medicine. 2007, vol. 64, iss. 8, pp. 553–559. ISSN 1470-7926. DOI: 10.1136/oem.2006.030270. [2] DAVANIPOUR, Z. and E. SOBEL. Long-Term Exposure to Magnetic Fields and the Risks of Alzheimer’s Disease and Breast Cancer: Further Biological Research. Pathophysiology. 2009, vol. 16, iss. 2, pp. 149–156. ISSN 0928-4680. DOI: 10.1016/j.pathophys.2009.01.005. [3] KHEIFETS, L., A. AHLBOM, C. M. CRESPI, M. FEYCHTING, C. JOHANSEN, J. MONROE, M. F. G. MURPHY, S. OKSUZYAN, S. PRESTON-MARTIN, E. ROMAN, T. SAITO, D. SAVITZ, J. SCHUZ, J. SIMPSON, J. SWANSON, T. TYNES, P. VERKASALO and G. MEZEI. A Pooled Analysis of Extremely Low-Frequency Magnetic Fields and Childhood Brain Tumors. American Journal of Epidemiology. 2010, vol. 172, iss. 7, pp. 752–761. ISSN 1476-6256. DOI: 10.1093/aje/kwq181. [4] KOEMAN, T., P. A. VAN DEN BRANDT, P. SLOTTJE, L. J. SCHOUTEN, R. A. GOLDBOHM, H. KROMHOUT and R. VERMEULEN. Occupational Extremely Low-Frequency Magnetic Field Exposure and Selected Cancer Outcomes in a Prospective Dutch Cohort. Cancer Causes &Control. 2014, vol. 25, iss. 2, pp. 203–214. ISSN 1573-7225. DOI: 10.1007/s10552-013-0322x. [5] ZHAO, L., X. LIU, C. WANG, K. YAN, X. LIN, S. LI, H. BAO and X. LIU. Magnetic Fields Exposure and Childhood Leukemia Risk: A Meta-Analysis Based on 11,699 Cases and 13,194 Controls. Leukemia Research. 2014, vol. 38, iss. 3, pp. 269–274. ISSN 0145-2126. DOI: 10.1016/j.leukres.2013.12.008. [6] MATTSSON, M.-O. and M. SIMKO. Is There a Relation Between Extremely Low Frequency Magnetic Field Exposure, Inflammation and Neurodegenerative Diseases? A Review of in Vivo and in Vitro Experimental Evidence. Toxicology. 2012, vol. 301, iss. 1, pp. 1–12. ISSN 0300-483X. DOI: 10.1016/j.tox.2012.06.011. [7] WOLF, F. I., A. TORSELLO, B. TEDESCO, S FASANELLA, A BONINSEGNA, c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 103 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE M. D’ASCENZO, C. GRASSI, G. B. AZZENA and A. CITTADINI. 50-hz Extremely Low Frequency Electromagnetic Fields Enhance Cell Proliferation and Dna Damage: Possible Involvement of a Redox Mechanism. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 2005, vol. 1743, iss. 1, pp. 120–129. ISSN 0167-4889. DOI: 10.1016/j.bbamcr.2004.09.005. [8] BARABAS, J., R. RADIL and I. MALIKOVA. Modification of S. Cerevisiae Growth Dynamics Using Low Frequency Electromagnetic Fields in the 1-2 Khz Range. BioMed Research International. 2015, vol. 2015, iss. 1, pp. 1–5. ISSN 23146141. DOI: 10.1155/2015/694713. [9] LIBOFF, A. R. Bioengineering and Biophysical Aspects of Electromagnetic Fields. 3rd. ed. Cleveland: CRC Press, 2006. ISBN 978-084-9395-390. [10] ROCHEV, Y. A., A. A. NARIMANOV, E. A. SOSUNOV, A. N. KOZLOV and V. V. LEDNEV. Effects of Weak Magnetic-field on the Rate of CellProliferation in Culture. Studia Biophysica. 1990, vol. 135, iss. 2, pp. 93–98. ISSN 0081-6337. [11] LIBOFF, A. R., R. J. ROZEK, M. L. SHERMAN, B. R. MCLEOD and S. D. SMITH. 45Ca2+ Resonance in Human Lymphocytes. Journal of Bioelectricity. 1987, vol. 6, iss. 1, pp. 99–102. ISSN 0730823X. [12] YOST, M. G. and R. P. LIBURDY. Time-Varying and Static Magnetic Fields Act in Combination to Alter Calcium Signal Transduction in the Lymphocyte. FEBS Letters. 1992, vol. 296, iss. 2, pp. 117–122. ISSN 0014-5793. DOI: 10.1016/00145793(92)80361-J. [13] COULTON, L. A. and A. T. BARKER. Magnetic Fields and Intracellular Calcium: Effects on Lymphocytes Exposed to Conditions for’Cyclotron Resonance’. Physics in Medicine &Biology. 1993, vol. 38, iss. 3, pp. 347–360. ISSN 1361-6560. DOI: 10.1088/0031-9155/38/3/002. [14] LEE, H. C., M.-N. HONG, S. H. JUNG, B. C. KIM, Y. J. SUH, Y.-G. KO, Y.-S. LEE, B.-Y. LEE, Y.-G. CHO, S.-H. MYUNG and J.-S. LEE. Effect of Extremely Low Frequency Magnetic Fields on Cell Proliferation and Gene Expression. Bioelectromagnetics, 2015, vol. 36, iss. 7, pp. 506–516. ISSN 0197-8462. DOI: 10.1002/bem.21932. [15] PRATO, F. S. Non-Thermal Extremely Low Frequency Magnetic Field Effects on Opioid Related Behaviors: Snails to Humans, Mechanisms to Therapy. Bioelectromagnetics. 2015, vol. 36, iss. 5, pp. 333–348. ISSN 0197-8462. DOI: 10.1002/bem.21918. [16] MISEK, J., J. VOJTEK, M. VETERNIK, M. KOHAN, V. JAKUSOVA, G. SPANIKOVA, I. BELYAEV and J. JAKUS. New Radiofrequency Exposure System with Real Telecommunication Signals. Advances in Electrical and Electronic Engineering. 2018, vol. 16, iss. 1, pp. 101–107. ISSN 1336-1376. DOI: 10.15598/aeee.v16i1.2768. [17] CRUMPTON, M. J. and A. R. COLLINS. Are Environmental Electromagnetic Fields Genotoxic? DNA Repair. 2004, vol. 3, iss. 10, pp. 1385–1387. ISSN 1568-7864. DOI: 10.1016/j.dnarep.2004.05.006. [18] ROMANENKO, S., R. BEGLEY, A. R. HARVEY, L. HOOL and V. P. WALLACE. The Interaction Between Electromagnetic Fields at Megahertz, Gigahertz and Terahertz Frequencies With Cells, Tissues and Organisms: Risks and Potential. Journal of The Royal Society Interface. 2017, vol. 14, iss. 137, pp. 1–22. ISSN 1742-5662. DOI: 10.1098/rsif.2017.0585. [19] LIN, K.-W., C.-J. YANG, H.-Y. LIAN and P. CAI. Exposure of ELF-EMF and RF-EMF Increase the Rate of Glucose Transport and TCA Cycle in Budding Yeast. Frontiers in Microbiology. 2016, vol. 7, iss. 1, 1378. ISSN 1664-302X. DOI: 10.3389/fmicb.2016.01378. [20] NIKOLOVA, T., J. CZYZ, A. ROLLETSCHEK, P. BLYSZCZUK, J. FUCHS, G. JOVTCHEV, J. SCHUDERER, N. KUSTER and A. M. WOBUS. Electromagnetic Fields Affect Transcript Levels of Apoptosis-Related Genes in Embryonic Stem Cell-Derived Neural Progenitor Cells. The FASEB Journal. 2005, vol. 19, iss. 12, pp. 1686–1688. ISSN 1530-6860. DOI: 10.1096/fj.04-3549fje. [21] BUCHACHENKO, A. Why Magnetic and Electromagnetic Effectsin Biology Are Irreproducible and Contradictory?. Bioelectromagnetics. 2016, vol. 37, iss. 1, pp. 1–13. ISSN 0197-8462. DOI: 10.1002/bem.21947. [22] MARKOV, M. Nonthermal Mechanism of Interactions Between Electromagnetic Fields and Biological Systems: A Calmodulin Example. The Environmentalist. 2011, vol. 31, iss. 2, pp. 114–120. ISSN 1573-2991. DOI: 10.1007/s10669-011-9321-1. [23] FROHLICH, H. Conditions for Coherent Excitations in Biological Systems. Physics Letters A. 1982, vol. 93, iss. 2, pp. 105–106. ISSN 0375-9601. DOI: 10.1016/0375-9601(82)90228-6. [24] LIBOFF, A. R. Geomagnetic Cyclotron Resonancein Living Cells. Journal of Biological Physics. 1985, vol. 13, iss. 4, pp. 99–102. ISSN 1573-0689. DOI: 10.1007/BF01878387. c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 104 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE [25] LEDNEV, V. V. Possible Mechanism for the Influence of Weak Magnetic Fields on Biological Systems. Bioelectromagnetics. 1991, vol. 12, iss. 2, pp. 71–75. ISSN 1521-186X. DOI: 10.1002/bem.2250120202. [26] LEDNEV, V. V. Bioeffects of Weak Combined, Constant and Variable Magnetic Fields. Biophysics. 1996, vol. 1, iss. 41, pp. 241–252. ISSN 0006-3509. DOI: 10.1155/2015/423838. [27] BELOVA, N. A. and V. A. PANCHELYUGA. Lednev’s Model: Theory and Experiment. Biophysics. 2010, vol. 55, iss. 4, pp. 661–674. ISSN 1555-6654. DOI: 10.1134/S0006350910040263. [28] ADAIR, R. K. Criticism of Lednev’s Mechanism for the Influence of Weak Magnetic Fields on Biological Systems. Bioelectromagnetics. 1992, vol. 13, iss. 3, pp. 231–235. ISSN 1521-186X. DOI: 10.1002/bem.2250130307. [29] ADAIR, R. K. A Physical Analysis of the Ion Parametric Resonance Model. Bioelectromagnetics. 1998, vol. 19, iss. 3, pp. 181–191. ISSN 1521-186x. DOI: 10.1002/(SICI)1521186X(1998)19:3<181::AID-BEM6>3.0.CO;2-Y. [30] ENGSTROM, S. Dynamic Properties of Lednev’s Parametric Resonance Mechanism. Bioelectromagnetics. 1996, vol. 17, iss. 1, pp. 58– 70. ISSN 1521-186x. DOI: 10.1002/(SICI)1521186X(1996)17:1<58::AID-BEM8>3.0.CO;2-5. [31] LEDNEV, V. V. Biological Effects of the Extremely Weak Alternating Magnetic Fields: the Identification of Primary Targets. Modelling of Geophysical Processes. 2003, pp. 130–136. [32] HALGAMUGE, M. N., B. R. R. PERSSONT, L. G. SALFORD, P. MENDIS and J. EBERHARDT. Comparison Between Two Models for Interactions Between Electric and Magnetic Fields and Proteins in Cell Membranes. Environmental Engineering Science. 2009, vol. 26, iss. 10, pp. 1473–1480. ISSN 1092-8758, 1557-9018. DOI: 10.1089/ees.2009.0014. [33] RADIL, R. and J. BARABAS. Coil System Proposal for Homogeneous LF-EMF Application. In: CPEE – AMTEE 2015: Joint Conference Computational Problems of Electrical Engineering and Advanced Methods of the Theory of Electrical Engineering. Trebic: 2015, pp. 1–1. ISBN 978-80261-0527-5. [34] NITISS, J. L. and J. HEITMAN. Yeast as a Tool in Cancer Research. 1st. ed. Dordrecht: Springer, 2007. ISBN 978-140-2059-629. [35] POKORNY, J. Measurement of Yeast Cell Electrical Oscillations Around 1khz. In: Proceedings of the Progress in Electromagnetics Research Symposium (PIERS’08). Cambridge: 2008, pp. 780– 784. ISBN: 978-1-934142-06-6. [36] JELINEK, F., M. CIFRA, J. POKORNY, J. VANIS, J. SIMSA, J. HASEK and I. FRYDLOVA. Measurement of Electrical Oscillations and Mechanical Vibrations of Yeast Cells Membrane Around 1 kHz. Electromagnetic Biology and Medicine. 2009, vol. 28, iss. 2, pp. 223–232. ISSN 1536-8386. DOI: 10.1080/15368370802710807. [37] BARABAS, J. Electromagnetic Fields and Biological Structures. Zilina, 2011. Dissertation. University of Zilina. Supervisor prof. Ing. Ivo Cap, CSc. [38] RADIL, R. and L. JANOUSEK. Yeast Growth Influenced by Parallel Combination of Time-Varying and Static LF EMF. Communications-Scientific Letters of the University of Zilina. 2013, vol. 15, iss. 2, pp. 28–32. ISSN 1335-4205. [39] BARABAS, J., R. RADIL and D. GOMBARSKA. Image Processing and Feature Extraction of Circular Objects From Biological Images. In: 2013 36th International Conference on Telecommunications and Signal Processing (TSP). Rome: IEEE, pp. 612–615. ISBN 978-1-4799-0404-4. DOI: 10.1109/TSP.2013.6614008. [40] BARABAS, J. Proliferative Response of Two Different Saccharomyces Cerevisiae Strands to Extremely Low Frequency Electromagnetic Fields. In: Proceedings of POSTER 2011: 15th International Student Conference on Electrical Engineering. Praha: 2011. ISBN 978-80-01-04806-1. [41] BARABAS, J. and I. CAP. Influence of Extremely Low Frequency Electromagnetic Fields on Saccharomyces Cerevisiae Growth. In: TRANSCOM 2011: 9th European Conference of Young Research and Scientific Workers. Zilina: 2011, pp. 15–20. ISBN 978-80-554-0373-1. [42] BARABAS, J. and I. CAP. S. Cerevisiae Growth Regulation via Exogenous Low Frequency Electromagnetic Fields. In: Trends in Biomedical Engineering 2011. Ostrava: 2011, pp. 141–145, ISBN 978-80-248-2475-8. [43] CHOE, M., W. CHOE, S. CHA and I. LEE. Changes of Cationic Transport in AtCAX5 Transformant Yeast by Electromagnetic Field Environments. Journal of Biological Physics. 2018, vol. 44, iss. 3, pp. 433–448. ISSN 1573-0689. DOI: 10.1007/s10867-018-9500-0. c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 105 BIOMEDICAL ENGINEERING VOLUME: 18 |NUMBER: 2 |2020 |JUNE About Authors Roman RADIL was born in Trencin, Slovak Republic, in 1984. Graduated from the Faculty of Electrical Engineering, University of Zilina, in 2008 from Biomedical Engineering and received the Ph.D. degree in Theoretical Electromagnetics at the same university, in 2012. At present he works as assistant professor at the Dept. of Electromagnetic and Biomedical Engineering, Faculty of Electrical Engineering and Information Technology, University of Zilina. His research activities are focused on investigation of LF EMF effects on biological samples and biomedical image processing. Results of his research have been published in several journals and presented in national and international conferences. Jan BARABAS was born in Bardejov, Slovak Republic, in 1982. Graduated from the Faculty of Electrical Engineering, University of Zilina, in 2008 from Biomedical Engineering and received the Ph.D. degree in Theoretical Electromagnetics at the same university, in 2011. At present he works as researcher at the Department of Electromagnetic and Biomedical Engineering, Faculty of Electrical Engineering and Information Technology, University of Zilina. His current research endeavours include ongoing investigation of electromagnetic fields and interaction thereof with biological objects, the findings of which have been published in several journals and international conferences. Other activities include biomedical image processing, signal processing and programming. Ladislav JANOUSEK was born in Michalovce, Slovak Republic, in 1974. Graduated from the Faculty of Electrical Engineering, University of Zilina, in 1997 from Electric Power Systems and received the Ph.D. degree in Electric Machines and Apparatuses at the same university, in 2002. At present he is head of the Department of Electromagnetic and Biomedical Engineering, Faculty of Electrical Engineering and Information Technology, University of Zilina. The main fields of his research activities are electromagnetic methods of materials’ non-destructive evaluation and non-thermal effects of EMF on living organisms. His achievements have been acknowledged by several prestigious awards. Martin BERETA was born in Ruzomberok, Slovak Republic, in 1990. Graduated from the Faculty of Electrical Engineering, University of Zilina, in 2014 from Biomedical Engineering and received the Ph.D. degree in Theoretical Electromagnetics at the same university, in 2017. At present he works as researcher at the Institute of Measurement Science, Slovak Academy of Sciences in Bratislava. His research activities are focused on LF EMF biological effects and monitoring of ultra-weak photon emission from biological samples. Results of his research have been published in several journals and presented in national and international conferences. c 2020 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 106