International Journal of Radiation Biology, May 2014; 90(5): 337–343 © 2014 Informa UK, Ltd. ISSN 0955-3002 print / ISSN 1362-3095 online DOI: 10.3109/09553002.2014.888105

Extremely low frequency magnetic field (50 Hz, 0.5 mT) modifies fitness components and locomotor activity of Drosophila subobscura Danica Dimitrijević1, Tatjana Savić2, Marko Anđelković2,3,4, Zlatko Prolić2 & Branka Janać2 1University of Belgrade, Vinča Institute of Nuclear Sciences, Belgrade, Serbia, 2University of Belgrade, Institute for Biological

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Research “Siniša Stanković”, Belgrade, Serbia, 3University of Belgrade, Faculty of Biology, Belgrade, Serbia, and 4Serbian Academy of Sciences and Arts, Belgrade, Serbia

Abstract Purpose: Extremely low frequency (ELF) magnetic fields are essential ecological factors which may induce changes in many organisms. The aim of this study was to examine the effects in Drosophila subobscura exposed for 48 h to ELF magnetic field (50 Hz, 0.5 mT) at different developmental stages. Materials and methods: Egg-first instar larvae developmental stage of D. subobscura isofemale lines was exposed to ELF magnetic field, and fitness components (developmental time, developmental dynamics, viability and sex ratio) and locomotor activity of three-day-old males and females were monitored. Also, just eclosed D. subobscura isofemale adults were exposed to ELF magnetic field and their locomotor activity was monitored just after. Results: ELF magnetic field shortens developmental time, increases viability and does not affect sex ratio of D. subobscura. No matter which developmental stage is exposed, ELF magnetic field significantly decreases locomotor activity of adult flies, but after exposure of just eclosed adults observed change lasts longer. Conclusions: Applied ELF magnetic field modifies fitness components and locomotor activity of D. subobscura. Observed effects can be attributed to the influence of magnetic field on different stages of development where the hormonal and nervous systems play important role in the control of examined parameters.

are among the most important. They derive from power lines and nearly all household electrical appliances: Computers, television sets, hair dryers, kitchen appliances, etc. (Gauger 1985, Gandhi et al. 2001). There are many reports showing changes in biological systems caused by ELF magnetic fields (Balcavage et al. 1996, Santini et al. 2009) and suggesting possible cause of damage in cells (Li and Chow 2001, Ivancsits et al. 2003). The only established action of ELF magnetic fields on biological systems is inducing electric fields and current in them (Mathie et al. 2003). The ionic, bipolar macromolecules and magnetic materials in biological systems respond to ELF magnetic fields by producing changes in cell membrane potential and further affecting molecular and biochemical levels (Berg 1993, Neumann 2000). Moreover, ELF magnetic fields can affect chemical bounds between adjacent atoms with consequent production of free radicals (Rollwitz et al. 2004). It has been demonstrated that the effects of ELF magnetic field on the cell membrane (Lednev 1993, Blanchard and Blackman 1994) are primarily mediated through the modification of Ca2⫹ flux (Liburdy 1992, Lindstrom et al. 1993, 1995, Zhang et al. 2010) and consequently many Ca2⫹-dependent processes (Kataev et al. 1993, Jenrow et al. 1995, Lindstrom et al. 1995). Furthermore, ELF magnetic field can have an effect on receptor clustering, binding of ligand to the receptor and receptor capping (Adey and Lawrence 1984, Chiabrera et al. 1991, Sun et al. 2008), as well as the activity of membraneassociated enzymes (Kataev et al. 1993). All these changes affect the function of various cells and are dependent on the cell cycle state and magnetic field intensity (Walleczek and Budinger 1992). The influence of ELF magnetic fields on nervous system is still undetermined. Studies on motor behavior give opportunity to indirectly provide more information of ELF magnetic fields effects on nervous system integrity (Thomas et al. 2001). Some studies have already shown changes in motor behavior of insects exposed to ELF magnetic fields (Prolic´ et al. 2003). These behavioral alternations may involve modulation of

Keywords: 50 Hz magnetic field, developmental time, viability, distance travelled, mobility, Drosophila

Introduction Humans and other biological systems are constantly exposed to natural electromagnetic fields. In times of intense industrial and technological progress, additional sources of electromagnetic fields are everyday electrical appliances in homes and workplaces. Electromagnetic fields of different characteristics are considered to be an important ecological factor and those of extremely low frequency (ELF, ⬍ 300 Hz)

Correspondence: Danica Dimitrijevic´, Department of Materials Science, Vinc˘a Institute of Nuclear Sciences, University of Belgrade, Mihaila Petrovic´a Alasa 12-14, 11001 Belgrade, Serbia. Tel: ⫹ 381 11 6447 335. Fax: ⫹ 381 11 3408 224. E-mail: [email protected]; [email protected] (Received 18 November 2013; revised 6 January 2014; accepted 22 January 2014)

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central neurotransmitter systems which play important role in motor behavior expression (Osborne 1996). Studies dealing with ELF magnetic fields exposure mainly consider their influence on the cellular level, development, viability and reproductive behavior of Drosophila melanogaster. Goodman et al. (1992) showed altered transcriptional activity and translational patterns in D. melanogaster salivary gland cells after exposure to ELF electromagnetic field. Statistically significant enhancement in somatic recombination spot frequency was also revealed in D. melanogaster third instar larvae exposed to ELF magnetic field (50 Hz, 20 mT) for 24 h (Koana et al. 2001). Panagopoulos et al. (2013) demonstrated decreased reproduction in D. melanogaster, probably due to DNA damage induction, after exposure to three different intensities of 50 Hz alternating magnetic field (0.1, 1.1 and 2.1 mT). Ramírez et al. (1983) showed decreased oviposition after exposure to pulsated ELF (100 Hz, 1.76 mT) and sinusoidal fields (50 Hz, 1 mT). In addition, exposure of Drosophila eggs to the same fields for 48 h increases eggs mortality and diminishes adults’ viability. Recently, Gonet et al. (2009) exposed D. melanogaster females and progeny to ELF magnetic field and monitored their oviposition and development: ELF magnetic field weakens the oviposition of these insects in their subsequent generations. Mirabolghasemi and Azarnia (2002) used magnetic field produced by pair of Helmholtz coils (50 Hz, 11 mT) and observed significant increase in the number of abnormal adult flies from the exposed larvae at different stages of development, contrary to groups raised from the exposed eggs. The aim of this study was to examine if fitness components and locomotor activity of D. subobscura change after 48 h exposure to ELF magnetic field (50 Hz, 0.5 mT) at different developmental stages (egg-first instar larvae and just eclosed adult).

Materials and methods Drosophila stock Flies D. subobscura were collected from beech forest on Serbian mountain Gocˇ (Abieto-fagetum, N 43°33′28.43″ and E 20°45′10.96″). Single pair of flies were used to form isofemale (IF) lines which were maintained in five full-sib inbreeding generations at 19°C, humidity 60%, on standard cornmeal medium: 9% sugar (Notadolce, Senta, Serbia), 10% cornmeal (Stari mlinar-Žitko, Bacˇka Topola, Serbia), 2% agar (Torlak, Belgrade, Serbia), 2% yeast (Alltech Serbia Senta, Serbia), nipagin (Alpha Aesar Gmbh & Co, Karlsruhe, Germany) dissolved in 96% ethanol (MOSS and HEMOSS, Belgrade, Serbia), in a 12 h:12 h light:dark cycle (lights turned on at 06:00 h) and at 300 lux illumination. D. subobscura was chosen because there is lack of studies dealing with the effects of ELF magnetic fields on this model organism, otherwise well-known for chromosomal polymorphism associated with changeable environmental factors.

Magnetic field apparatus The ELF magnetic field was generated by an electromagnet consisting of three circular coils of insulated copper wire (0.75 mm in diameter). The coils were 37 cm in diameter

and set at 23 cm distance from each other, which produced homogeneous magnetic field in a horizontal direction. The 50 Hz current was taken from our local 220 V power network via an adjustable transformer. The electromagnet was supplied by a current of 2.8 A, producing uniform 50 Hz magnetic field without any observable temperature fluctuation or vibrations. The induction of the magnetic field, within the coils where the samples were placed, was 0.5 ⫾ 0.01 mT, measured using a Hirst GM05 Gaussmeter (probe PT 2837, Hirst Magnetic Instruments Ltd, Cornwall, UK). Chosen value of the magnetic induction is within the safety limit recommended by ICNIRP for occupational exposure (1000 μT) and often used in our studies concerning the effects of ELF magnetic field on evolutionary distant species (Janac´ et al. 2005, 2009, Nikolic´ et al. 2010, Rauš et al. 2012, 2013).

Experimental procedure Different developmental stages (egg-first instar larvae and just eclosed adult) of D. subobscura were exposed for 48 h to ELF magnetic field (50 Hz, 0.5 mT). Control groups were intact individuals (egg-first instar larvae and adults were outside the ELF magnetic field apparatus) and sham-exposed ones (egg-first instar larvae and adults were placed in turned off ELF magnetic field apparatus). Differences between intact and sham-exposed flies were not significant, thus these were cumulated and used as one control group. All groups were kept in an isolated room throughout the experimental period under the same optimal laboratory conditions (see above, Drosophila stock). In the first series of experiments, randomly collected 30 non-virgin 3–8 day-old females were maintained for 24 h to lay eggs on standard medium for Drosophila. Collected eggs (75 per vial) were transferred to thin film of standard medium in Petri dishes and exposed or not to the ELF magnetic field. After 48 h these mediums were replaced in 60 cm3 vials for completing egg-adult development (20, 15 and 35 replicas of intact, sham-exposed and ELF magnetic field exposed, respectively), on standard cornmeal substrate at optimal laboratory conditions. In order to measure fitness components such as developmental time, developmental dynamics (number of eclosed flies in every successive day), viability and sex ratio, in each replica was counted eclosed males and females at the same time each day. Also, locomotor activity of these eclosed and three-day-old flies was monitored. In the second series of experiments, flies were maintained on standard medium in 60 cm3 vials during the whole time of egg-adult development. Just eclosed males and females were exposed or not to ELF magnetic field for 48 h and locomotor activity of three-day-old flies was monitored.

Locomotor activity monitoring Locomotor activity was measured for both sexes. Just after eclosion males and females were separated under CO2 anesthesia. Single three-day-old D. subobscura naive males and virgin females were separately released to move in the empty plastic Petri dish (35 mm diameter, 10 mm high to maximally limit vertical and fly movement) immediately before monitoring. Locomotor activity of Drosophila flies was monitored for 30 min in a circular open field arena from 08:00–09:00 h

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Effects of alternating magnetic field in Drosophila 339

Figure 1. Developmental time of D. subobscura males and females in control conditions and after exposure of egg-first instar larvae stage to ELF magnetic field (50 Hz, 0.5 mT).

(Dimitrijevic´ et al. 2013), in an isolated room at optimal laboratory conditions. Locomotor activity of seven flies was simultaneously videotaped by camera (Microsoft LifeCam VX600) positioned above the dishes. ANY-maze software (v.4.73, Stoelting Co., Wood Dale, IL, USA) was used to analyze distance travelled (the total distance in meters that the animal travelled during the test) and mobility (the amount of time in seconds the animal was mobile during the test).

Statistical analysis Kolmogorov-Smirnov test was used to confirm data normality. All analyses were performed using Statistica for Windows 5.0 (StatSoft Inc., Aurora, CO, USA). The mean values of developmental time (28 replicas per group) and viability (24 replicas per group) were analyzed by two-way analysis of variance (ANOVA), while sex ratio values expressed in percentage were compared by Z-test (Zar 1999). Embryonic and post-embryonic developmental time (Dt) was measured in days once all the adults had emerged. Egg-to-adult viability (Vi) was calculated as the ratio of the emerged adults to the number of collected eggs. The normality of data was found in all treatments. Developmental time and viability in groups were compared using post hoc Fisher’s Least Significant Difference (LSD) test. The results of locomotor activity were presented as mean ⫾ standard error of the mean (SEM) of distance travelled and mobility for 30 min (total and in 10-min intervals). The number of samples used in statistical analysis was 45 and 75 for experiments performed on egg-first instar larvae developmental stage and just eclosed adult developmental stage, respectively. Since data did not show normal distribution, Kruskal-Wallis ANOVA followed by post hoc Mann-Whitney U-test was used to evaluate the differences between ELF magnetic field exposed and control groups (Zar 1999).

Results An egg-first instar larvae stage exposed to ELF magnetic field Eclosing of adults from control and ELF magnetic field exposed groups started on the 18th day (Figure 1). Peak of eclosing in ELF magnetic field exposed groups was on the

19th day (males 36.7%, females 43.0%), while in control groups it was on the 20th day (males 47.2%, females 44.1%). Likewise, adults from ELF magnetic field exposed groups finished eclosing one day earlier (the 25th day) comparing to control groups. Two-way ANOVA showed significantly shorter developmental time for flies from ELF magnetic field exposed groups (Table I) and LSD post hoc test detected that significance only in females (p ⬍ 0.01). Viability of D. subobscura flies (Figure 2) was higher after the ELF magnetic field exposure (57.2%) comparing to control ones (51.2%). Viability of control and ELF magnetic field exposed males was 23.7% and 28.2%, respectively, while viability of control and ELF magnetic field exposed females was 27.4% and 29.0%, respectively. Females in both groups showed higher viability than males, but these differences were not significant (Table I). Two-way ANOVA showed significantly higher viability of flies from ELF magnetic field exposed groups (Table I). LSD post hoc test revealed that significance only in males (p ⬍ 0.05). The Z-test did not show significant differences in a number of eclosed females and males in control and ELF magnetic field-exposed groups. After exposure to ELF magnetic field at egg-first instar larvae developmental stage, three-day-old flies’ locomotor activity was significantly lower comparing to control groups (Figure 3A, Table II), particularly in the first 10-min interval of monitoring (Figure 3B, Table II). There were no significant differences shown in locomotor activity between sexes.

Just eclosed adult stage exposed to ELF magnetic field Locomotor activity of three-day-old flies previously exposed to ELF magnetic field for 48 h was significantly lower Table I. Results of two-way ANOVA for developmental time and viability of D. subobscura after exposure of egg-first instar larvae developmental stage to ELF magnetic field (50 Hz, 0.5 mT). Developmental time Viability Treatment Sex Treatment ⫻ Sex Error

Df

MS

1 1 1 78

4.836 0.000 0.239 0.430

F 11.249** 0.001 0.557

MS

F

207.406 88.089 49.158 48.766

4.253* 1.806 1.008

*p ⬍ 0.05, **p ⬍ 0.01. df, degree of freedom; MS, mean square; F, the ratio of the variance.

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Figure 2. Total viability (both sexes) and viability of D. subobscura males and females in control conditions and after exposure of egg-first instar larvae stage to ELF magnetic field (50 Hz, 0.5 mT). Each bar represents mean ⫾ SEM (24 replicas per group). *p ⬍ 0.05 (two-way ANOVA, LSD test).

comparing to that of control groups (Figure 4A, Table II). The distance travelled of ELF magnetic field-exposed flies was significantly decreased during the whole time of monitoring, while in the case of mobility it was only in the first 10-min interval of monitoring (Figure 4B, Table II). No significant differences in locomotor activity were detected between sexes.

Discussion Results in this study revealed that exposure to ELF magnetic field (50 Hz, 0.5 mT) at egg-larvae developmental stage shortens developmental time, increases viability and does not affect sex ratio of D. subobscura. Furthermore, it was shown that exposure to this magnetic field decreases locomotor activity of flies no matter which developmental stage is exposed (egg-larvae or just eclosed adult). It may be possible that there is a common cause for the different effects

observed. The nervous system, the hormonal system and some physiological functions may be affected, and this may be the cause of the different effects revealed here. Using sensory systems, organisms appropriately respond to environmental factors and may develop mechanisms for adapting to the changing environment (Seligman 1970, Mayr 1974, Domjan 2005). Sensory systems are coupled with many downstream machinery which might affect fitness components and motor behavior (Niven et al. 2003, She˘ı man and Kreshchenko 2009, 2010, Todorovic´ et al. 2013). Moreover, at cellular level it is well known that proliferating and less differentiated cells are more sensitive and vulnerable to electromagnetic radiation than non-proliferating and more differentiated ones (Prasad 1995). In this study was detected that exposure of D. subobscura to ELF magnetic field (50 Hz, 0.5 mT) at egg-larvae developmental stage modifies fitness components. Literature data considering fitness components showed that the duration of ELF magnetic field (50 Hz, 11 mT) exposure is positively correlated with the number of abnormal flies, without significant differences in mortality rate and sex distribution of abnormal flies between exposed and control groups (Mirabolghasemi and Azarnia 2002). Graham et al. (2000) used ELF magnetic field (60 Hz, from 1.5–80 μT) and found significant reduction in weight of D. melanogaster and greater developmental stability compared to control flies. Development of Drosophila in the first 48 h implies developing of fertilized eggs and the first instar larvae. Among many processes which are subject to the development of eggs (Poulson 1950), the most important ones for this study are central and peripheral nervous system differentiation, head involution and serotonin biosynthesis (Foe 1998, Colas et al. 1999). Small-molecule neurotransmitters such as serotonin are important modulatory signals in neuronal development (Gaspar et al. 2003). In the first instar

Figure 3. Locomotor activity of 3 days old D. subobscura males and females in control conditions and after exposure of egg-first instar larvae stage to ELF magnetic field (50 Hz, 0.5 mT) monitored for 30 min. Each bar represents mean ⫾ SEM (n ⫽ 45) of distance travelled and mobility during the total time of monitoring (A), as well as in 10-min intervals (B). *p ⬍ 0.05, **p ⬍ 0.01 and ***p ⬍ 0.001 (Kruskal-Wallis ANOVA, Mann-Whitney U-test).

Effects of alternating magnetic field in Drosophila 341 Table II. Results of Kruskal-Wallis ANOVA for distance travelled and mobility of D. subobscura adults after exposure of egg-first instar larvae developmental stage and just eclosed adult developmental stage for 48 h to ELF magnetic field (50 Hz, 0.5 mT). Egg-first instar Just eclosed larvae stage adult stage Distance travelled

Mobility

Total

H(3, 180) 16.859***

H(3, 300) 78.494***

1st 10-min interval 2nd 10-min interval 3rd 10-min interval Total 1st 10-min interval 2nd 10-min interval 3rd 10-min interval

23.857*** 3.881 3.451 22.692*** 30.158*** 6.506 6.374

94.572*** 23.369*** 15.015** 14.995** 21.066*** 2.870 3.216

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**p ⬍ 0.01, ***p ⬍ 0.001. H

(number of groups of values, number of flies).

larvae stage, developing of nervous system is continuous and brain is in capacity to proliferate, differentiate and reorganize. In this study we also showed that ELF magnetic field exposure at this developmental stage decreases locomotor activity of three-day-old flies. Due to the ELF magnetic field exposure at the time of brain development, when the activation of serotonin receptors begins, later reduced locomotor activity may be linked with a possible impact of magnetic field on serotonergic transmission in the brain (Leonardo and Hen 2006). It is well known that serotonin has a role in response to stimuli from environment (Heym et al. 1982, Waterhouse et al. 2004) and that serotonergic neurons are sensitive to changes in behavioral activation (Grahn et al. 1999, Jacobs and Fornal 1999, Portas et al. 2000, Abrams et al. 2004). All those changes can last for minutes or less and intensity is specific to brain region which is affected (Inoue et al. 1994, Pum et al. 2008). Thus, we can propose that altered locomotor activity in adult flies might be the effect

of the applied magnetic field on serotonergic transmission. Moreover, obtained results suggest that egg and the first instar larvae developmental stage are very sensitive to ELF magnetic field, since changes are maintained and expressed at adult stage. In the first 5 min of spontaneous activity in the open field arena, flies show intensive exploration of a novel environment, with crucial role of Kurtz nonvisual arrestin in the nervous system (Liu et al. 2007). The krz gene encodes the only nonvisual arrestin in Drosophila (Roman et al. 2000) which is important scaffolding proteins regulating the activity of several families of cell-surface receptors (Lefkowitz and Whalen 2004). In later phase of flies’ activity in the open field arena dopamine takes place (Bainton et al. 2000, Friggi-Grelin et al. 2003). Regarding time profile of behavioral changes, applied ELF magnetic field showed a short (in the first 10 min) or a prolonged (during 30 min) effect on adults’ locomotor activity, depending on which developmental stage was exposed. We can propose that ELF magnetic field exposure at egglarvae developmental stage predominantly affects processes underlying exploration, while at the just eclosed adult developmental stage, it affects both exploration and dopaminemediated activity. Earlier studies have already shown that different biological effects of environmental factors depend on developmental stage in which they are applied (Mayer and Baker 1984, Tsutsayeva and Sevryukova 2001, Jensen et al. 2007), and thus the adaptation to a particular environmental factor may be specific to a particular life stage (Krebs and Loeschcke 1994, 1996). Observed changes induced by ELF magnetic field allow us to consider them as a stress factor in relation to monitored parameters. Goodman et al. (1989) showed that exposure of human cultured cells increased the level of selected RNA transcripts. It has been found that 50 Hz magnetic field causes

Figure 4. Locomotor activity of 3 days old D. subobscura males and females in control conditions and after exposure of just eclosed adult stage to ELF magnetic field (50 Hz, 0.5 mT) monitored for 30 min. Each bar represents mean ⫾ SEM (n ⫽ 75) of distance travelled and mobility during the total time of monitoring (A), as well as in 10-min intervals (B). *p ⬍ 0.05, **p ⬍ 0.01 and ***p ⬍ 0.001 (Kruskal-Wallis ANOVA, Mann-Whitney U-test).

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changes in humans’ cell cycle and the levels of the proteins responsible for that process (Lange et al. 2002). Heat-shock proteins are a group of proteins which affect cell cycle progression and have function being chaperons for newly synthesized proteins. Their expression is increased when cells are exposed to elevated temperatures or other stress (De Maio 1999). It has already been shown that stimulation of their transcription and generation is induced after ELF magnetic field exposure (Goodman and Blank 1998, Mannerling et al. 2010, Mariucci et al. 2010). It is known that short-term exposure to ELF magnetic field causes mild oxidative stress by modest reactive oxygen species increases and changes in antioxidant level, and possibly activates anti-inflammatory processes by decreasing in pro-inflammatory and increasing in anti-inflammatory cytokines (Frahm et al. 2010, Garip and Akan 2010, Mattsson and Simkó 2012). Based on our results, we can conclude that the durability of effects depends on the developmental stage exposed to ELF magnetic field. When comparing the vulnerability of insects and mammals to different types of electromagnetic radiation in many studies, it has been found that insects are more resistant (Koval et al. 1977, 1979, Koval and Kazmar 1988). Therefore, it is reasonable to expect in humans the effects of electromagnetic fields revealed in Drosophila.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This work was supported by the Ministry of Education, Science and Technological Development, Republic of Serbia (Grant nos. 173012 and 173027).

References Abrams JK, Johnson PL, Hollis JH, Lowry CA . 2004. Anatomic and functional topography of the dorsal raphe nucleus. Ann NY Acad Sci 1018:46–57. Adey WR, Lawrence AF. 1984. Nonlinear electrodynamics in biological systems. New York: Plenum Press. pp 3–22. Bainton RJ, Tsai LT, Singh CM, Moore MS, Neckameyer WS. 2000. Dopamine modulates acute responses to cocaine, nicotine and ethanol in Drosophila. Curr Biol 10:187–194. Balcavage WX, Alvager T, Swez J, Goff CW, Fox MT, Abdullyava S, King MW. 1996. A mechanism for action of extremely low frequency electromagnetic fields on biological systems. Biochem Biophys Res Commun 222:374–378. Berg H. 1993. Electrostimulation of cell metabolism by low frequency electric and electromagnetic fields. Bioelectrochem Bioenerget 31:1–25. Blanchard JP, Blackman CF. 1994. Clarification and application of an ion parametric resonance model for magnetic field interactions with biological systems. Bioelectromagnetics 15:217–238. Chiabrera A , Bianco B, Kaufman JJ, Pilla AA . 1991. Quantum dynamics of ions in molecular creviers under electromagnetic exposure. In: Brighton CT, Pollack SR, editors. Electromagnetics in medicine and biology. San Francisco, CA: San Francisco Press. pp 21–26. Colas J, Launay J, Maroteaux L. 1999. Maternal and zygotic control of serotonin biosynthesis are both necessary for Drosophila germband extension. Mechan Develop 87:67–76. De Maio A . 1999. Heat shock proteins: Facts, thoughts, and dreams. Shock (Augusta, Ga.) 11:1–12. Dimitrijevic´ D, Janac´ B, And¯elkovic´ M, Savic´ T. 2013. Spontaneous locomotor activity of Drosophila subobscura under controlled laboratory conditions. Arch Biologic Sci Belgrade 65:977–987.

Domjan M. 2005. Pavlovian conditioning: A functional perspective. Ann Rev Psychol 56:179–206. Foe VE. 1998. Mitotic domains reveal early commitment of cells in Drosophila embryos. Development 107:1–22. Frahm J, Mattsson MO, Simkó M. 2010. Exposure to ELF magnetic fields modulate redox related protein expression in mouse macrophages. Toxicol Lett 192:330–336. Friggi-Grelin F, Coulom H, Meller M, Gomez D, Hirsh J. 2003. Targeted gene expression in Drosophila dopaminergic cells using regulatory sequences from tyrosine hydroxylase. J Neurobiol 54:618–627. Gandhi OP, Kang G, Wu D, Lazzi G. 2001. Currents induced in anatomic models of the human for uniform and nonuniform power frequency magnetic fields. Bioelectromagnetics 22:112–121. Garip AI, Akan Z. 2010. Effect of ELF-EMF on number of apoptotic cells; correlation with reactive oxygen species and HSP. Acta Biologica Hungarica 61:158–167. Gaspar P, Cases O, Maroteaux L. 2003. The developmental role of serotonin: News from mouse molecular genetics. Nature Rev Neurosci 4:1002–1012. Gauger JR. 1985. Household Appliance Magnetic Field Survey. IEEE Transactions on Power Apparatus and Systems Vol. PAS104: 2436–2444. Gonet B, Kosik-Bogacka DI, Kuz´na-Grygiel W. 2009. Effects of extremely low-frequency magnetic fields on the oviposition of Drosophila melanogaster over three generations. Bioelectromagnetics 30:687–689. Goodman R, Blank M. 1998. Magnetic field stress induces expression of hsp70. Cell Stress Chap 3:79–88. Goodman R, Wei L-X, Xu J-C , Henderson A . 1989. Exposure of human cells to low-frequency electromagnetic fields results in quantitative changes in transcripts. Biochim Biophys Acta 1009:216–220. Goodman R, Weisbrot D, Uluc A , Henderson A . 1992. Transcription in Drosophila melanogaster salivary gland cells is altered following exposure to low-frequency electromagnetic fields: Analysis of chromosome 3R. Bioelectromagnetics 13:111–118. Graham JH, Fletcher D, Tigue J, McDonald M. 2000. Growth and developmental stability of Drosophila melanogaster in low frequency magnetic fields. Bioelectromagnetics 21:465–472. Grahn RE, Will MJ, Hammack SE, Maswood S, McQueen MB, Watkins LR, Maier SF. 1999. Activation of serotonin-immunoreactive cells in the dorsal raphe nucleus in rats exposed to an uncontrollable stressor. Brain Res 826:35–43. Heym J, Trulson ME, Jacobs BL. 1982. Raphe unit activity in freely moving cats: Effects of phasic auditory and visual stimuli. Brain Res 232:29–39. Inoue T, Tsuchiya K , Koyama T. 1994. Regional changes in dopamine and serotonin activation with various intensity of physical and psychological stress in the rat brain. Pharmacol Biochem Behav 49:911–920. Ivancsits S, Diem E, Jahn O, Rüdiger HW. 2003. Intermittent extremely low frequency electromagnetic fields cause DNA damage in a dose-dependent way. Int Arch Occupat Environ Health 76:431–436. Jacobs BL, Fornal CA . 1999. Activity of serotonergic neurons in behaving animals. Neuropsychopharmacology 21: S9–15. Janac´ B, Pešic´ V, Jelenkovic´ A , Vorobyov V, Prolic´ Z. 2005. Different effects of chronic exposure to ELF magnetic field on spontaneous and amphetamine-induced locomotor and stereotypic activities in rats. Brain Res Bull 67:498–503. Janac´ B, Tovilovic´ G, Tomic´ M, Prolic´ Z, Radenovic´ L. 2009. Effect of continuous exposure to alternating magnetic field (50 Hz, 0.5 mT) on serotonin and dopamine receptors activity in rat brain. Gen Physiol Biophys 28:41–46. Jenrow KA , Smith CH, Liboff AR. 1995. Weak extremely-low-frequency magnetic fields and regeneration in the planarian Dugesia tigrina. Bioelectromagnetics 16:106–112. Jensen D, Overgaard J, Sørensen JG. 2007. The influence of developmental stage on cold shock resistance and ability to cold-harden in Drosophila melanogaster. J Insect Physiol 53:179–186. Kataev AA , Alexandrov AA , Tikhonova LI, Berestovsky GN. 1993. Frequency-dependent electromagnetic millimeter-wave effects on ionic currents in the cell membrane of Nitellopsis: Non-thermal action. Biophysics 38:445–460. Koana T, Okada MO, Takashima Y, Ikehata M, Miyakoshi J. 2001. Involvement of eddy currents in the mutagenicity of ELF magnetic fields. Mutat Res 476:55–62. Koval TM, Hart RW, Myser WC, Hink WF. 1977. A comparison of survival and repair of UV-induces DNA damage in cultured insect versus mammalian cells. Genetics 87:513–518.

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Effects of alternating magnetic field in Drosophila 343 Koval TM, Hart RW, Myser WC, Hink WF. 1979. DNA single-strand break repair in cultured insects and mammalian cells after x-irradiation. Int J Radiat Biol Rel Stud Phys Chem Med 35:183–188. Koval TM, Kazmar ER. 1988. DNA double-strand break repair in eukaryotic cell lines having radically different radio sensitivities. Radiat Res 113:268–277. Krebs RA , Loeschcke V. 1994. Response to environmental change: Genetic variation and fitness in Drosophila buzzatii following temperature stress. EXS 68:309–321. Krebs RA , Loeschcke V. 1996. Acclimation and selection for increased resistance to thermal stress in Drosophila buzzatii. Genetics 142: 471–479. Lange S, Richard D, Viergutz T, Kriehuber R, Weiss DG, Simkó M. 2002. Alterations in the cell cycle and in the protein level of cyclin D1, p21CIP1, and p16INK4a after exposure to 50 Hz MF in human cells. Radiat Environ Biophys 41:131–137. Lednev VV. 1993. Possible mechanism for the effect of weak magnetic fields on biological systems: Correction of the basic expression and its consequences. In: Blank M, editor. Electricity and magnetism in biology and medicine. San Francisco, CA: San Francisco Press, Inc. pp 550–552. Lefkowitz RJ, Whalen EJ. 2004. Beta-arrestins: Traffic cops of cell signaling. Cur Opin Cell Biol 16:162–168. Leonardo ED, Hen R. 2006. Genetics of affective and anxiety disorders. Ann Rev Psychol 57:117–137. Li SH, Chow KC. 2001. Magnetic field exposure induces DNA degradation. Biochem Biophys Res Communic 280:1385–1388. Liburdy RP. 1992. Calcium signaling in lymphocytes and ELF fields; Evidence for an electric field metric and a site of interaction involving the calcium ion channel. FEBS Lett 301:53–59. Lindstrom E, Lindstrom P, Berglund A , Lundgren E, Mild KH. 1995. Intracellular calcium oscillations in a T-cell line after exposure to extremely low-frequency magnetic fields with variable frequencies and flux densities. Bioelectromagnetics 16:41–47. Lindstrom E, Lindstrom P, Berglund A , Mild KH, Lundgren E. 1993. Intracellular calcium oscillations induced in a T-cell line by a weak 50 Hz magnetic field. J Cell Physiol 156:395–398. Liu L, Davis RL, Roman G. 2007. Exploratory activity in Drosophila requires the kurtz nonvisual arrestin. Genetics 175: 1197–1212. Mannerling AC, Simkó M, Mild KH, Mattsson MO. 2010. Effects of 50-Hz magnetic field exposure on superoxide radical anion formation and HSP70 induction in human K562 cells. Radiat Environ Biophys 49:731–741. Mariucci G, Villarini M, Moretti M, Taha E, Conte C , Minelli A , Aristei C , Ambrosini MV. 2010. Brain DNA damage and 70-kDa heat shock protein expression in CD1 mice exposed to extremely low frequency magnetic fields. Int J Radiat Biol 86: 701–710. Mathie A , Kennard LE, Veale EL. 2003. Neuronal ion channels and their sensitivity to extremely low frequency weak electric field effects. Radiat Protect Dosim 106:311–316. Mattsson MO, Simkó M. 2012. 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 301:1–12. Mayer PJ, Baker GT. 1984. Developmental time and adult longevity in two strains of Drosophila melanogaster in a constant low-stress environment. Mechan Ageing Develop 26:283–298. Mayr E. 1974. Behavior programs and evolutionary strategies. Am Scientist 62:650–659. Mirabolghasemi G, Azarnia M. 2002. Developmental changes in Drosophila melanogaster following exposure to alternating electromagnetic fields. Bioelectromagnetics 23:416–420. Neumann E. 2000. Digression on chemical electromagnetic field effects in membrane signal transduction – cooperativity paradigm of the acetylcholine receptor. Bioelectrochemistry 52:43–49. Nikolic´ LM, Rokic´ MB, Todorovic´ NV, Kartelija GS, Nedeljkovic´ MS, Zakrzewska JS. 2010. Effect of alternating magnetic field on phosphate metabolism in the nervous system of Helix pomatia. Biolog Res 43:243–250. Niven JE, Vähäsöyrinki M, Juusola M. 2003. Shaker K(⫹)-channels are predicted to reduce the metabolic cost of neural information in Drosophila photoreceptors. Proc Royal Soc B: Biologic Sci 270(Suppl. 1): S58–61.

Osborne RH. 1996. Insect neurotransmission: Neurotransmitters and their receptors. Pharmacol Therapeut 69:117–142. Panagopoulos DJ, Karabarbounis A , Lioliousis C. 2013. ELF alternating magnetic field decreases reproduction by DNA damage induction. Cell Biochem Biophys 67:703–716. Portas CM, Bjorvatn B, Ursin R. 2000. Serotonin and the sleep/wake cycle: Special emphasis on microdialysis studies. Progress Neurobiol 60:13–35. Poulson DF. 1950. Histogenesis, organogenesis and differentiation in the embryo of Drosophila melanogaster. In: Demerec M, editor. Biology of Drosophila. New York: Wiley and Son. pp 168–270. Prasad KN. 1995. Handbook of Radiobiology, 2nd ed. Boca Raton, FL: CRC Press. Prolic´ Z, Jovanovic´ R, Konjevic´ G, Janac´ B. 2003. Behavioral differences of the insect Morimus funereus (Coleoptera, Cerambycidae) exposed to an extremely low frequency magnetic field. Electromag Biol Med 22:63–73. Pum M, Huston JP, De Souza Silva MA , Muller CP. 2008. Visual sensory-motor gating by serotonin activation in the medial prefrontal and occipital, but not in the rhinal, cortices in rats. Neuroscience 153:361–372. Ramírez E, Monteagudo JL, García-Gracia M, Delgado JM. 1983. Oviposition and development of Drosophila modified by magnetic fields. Bioelectromagnetics 4:315–326. Rauš S, Selakovic´ V, Manojlovic´-Stojanoski M, Radenovic´ L, Prolic´ Z, Janac´ B. 2013. Response of hippocampal neurons and glial cells to alternating magnetic field in gerbils submitted to global cerebral ischemia. Neurotox Res 23:79–91. Rauš S, Selakovic´ V, Radenovic´ L, Prolic´ Z, Janac´ B. 2012. Extremely low frequency magnetic field induced changes in motor behaviour of gerbils submitted to global cerebral ischemia. Behav Brain Res 228:241–246. Rollwitz J, Lupke M, Simkó M. 2004. Fifty-hertz magnetic fields induce free radical formation in mouse bone marrow-derived promonocytes and macrophages. Biochimic Biophys Acta 1674:231–238. Roman G, He J, Davis RL. 2000. kurtz, a novel nonvisual arrestin, is an essential neural gene in Drosophila. Genetics 155:1281–1295. Santini MT, Rainaldi G, Indovina PL. 2009. Cellular effects of extremely low frequency (ELF) electromagnetic fields. Int J Radiat Biol 85: 294–313. Seligman SA . 1970. Dangers of decimals. Lancet 1(7641):306. She˘l man IM, Kreshchenko ND. 2009. Influence of weak electromagnetic field on different forms of behavior in grain beetle Tenebrio molitor. Zhurnal vysshei nervnoi deiatelnosti imeni I P Pavlova 59:488–494. She˘l man IM, Kreshchenko ND. 2010. Effects of weak electromagnetic irradiation on various types of behavior in the mealworm Tenebrio molitor. Neurosci Behav Physiol 40:863–868. Sun W, Gan Y, Fu Y, Lu D, Chiang H. 2008. An incoherent magnetic field inhibited EGF receptor clustering and phosphorylation induced by a 50-Hz magnetic field in cultured FL cells. Cellular Physiol Biochem 22:507–514. Thomas AW, Drosta DJ, Prato FS. 2001. Human subjects exposed to a specific pulsed (200 μT) magnetic field: Effects on normal standing balance. Neurosci Lett 297:121–124. Todorovic´ D, Markovic´ T, Prolic´ Z, Mihajlovic´ S, Rauš S, Nikolic´ L, Janac´ B. 2013. The influence of static magnetic field (50 mT) on development and motor behaviour of Tenebrio (Insecta, Coleoptera). Int J Radiat Biol 89:44–50. Tsutsayeva AA , Sevryukova LG. 2001. Effect of cold exposure on survival and stress protein expression of Drosophila melanogaster at different development stages. Cryo Lett 22:145–150. Walleczek J, Budinger TF. 1992. Pulsed magnetic field effects on calcium signaling in lymphocytes: Dependence on cell status and field intensity. FEBS Lett 314:351–355. Waterhouse B, Devilbliss D, Seiple S, Markowitz R. 2004. Sensorimotorrelated discharge of simultaneously recorded, single neurons in the dorsal raphe nucleus of the awake, unrestrained rat. Brain Res 1000:183–191. Zar JH. 1999. Biostatistical analysis, 4th ed. Upper Saddle River, NJ: Prentice Hall, 662 pp., plus appendices. Zhang X, Liu X, Pan L, Lee I. 2010. Magnetic fields at extremely lowfrequency (50 Hz, 0.8 mT) can induce the uptake of intracellular calcium levels in osteoblasts. Biochem Biophys Res Communic 396:662–666.