Impact of High-Dose Irradiation on Human iPSC-Derived Cardiomyocytes Using Multi-Electrode Arrays: Implications for the Antiarrhythmic Effects of Cardiac Radioablation.

Cardiac radioablation is emerging as an alternative option for refractory ventricular arrhythmias. However, the immediate acute effect of high-dose irradiation on human cardiomyocytes remains poorly known. We measured the electrical activities of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) upon irradiation with 0, 20, 25, 30, 40, and 50 Gy using a multi-electrode array, and cardiomyocyte function gene levels were evaluated. iPSC-CMs showed to recover their electrophysiological activities (total active electrode, spike amplitude and slope, and corrected field potential duration) within 3-6 h from the acute effects of high-dose irradiation. The beat rate immediately increased until 3 h after irradiation, but it steadily decreased afterward. Conduction velocity slowed in cells irradiated with ≥25 Gy until 6-12 h and recovered within 24 h; notably, 20 and 25 Gy-treated groups showed subsequent continuous increase. At day 7 post-irradiation, except for cTnT, cardiomyocyte function gene levels increased with increasing irradiation dose, but uniquely peaked at 25-30 Gy. Altogether, high-dose irradiation immediately and reversibly modifies the electrical conduction of cardiomyocytes. Thus, compensatory mechanisms at the cellular level may be activated after the high-dose irradiation acute effects, thereby, contributing to the immediate antiarrhythmic outcome of cardiac radioablation for refractory ventricular arrhythmias.

Electromagnetic field affects the voltage-dependent potassium channel Kv1.3.

PURPOSE: Theoretical and experimental evidences support the hypothesis that Extremely Low-Frequency Electromagnetic Fields (ELF-EMF) can modulate voltage-gated channels. In this work we investigated the effect of ELF-EMF on Kv1.3, a member of the family of the voltage-gated potassium channels that is thought to be involved in key physiological functions, including the regulation of T-cells activation during the immune response. MATERIALS AND METHODS: Kv1.3 expressing CHO-K1 cells were exposed to a 20 Hz electromagnetic field at two different intensities: 268 µT and 902 µT. Kv1.3 potassium currents were recorded by whole-cell patch-clamp before, during and after field exposure. RESULTS: We found that the Kv1.3 current was increased significantly by the ELF-EMF in a subpopulation of CHO-K1 cells. The increase developed after a few seconds from the start of exposure, reached a steady-state and took several minutes to return to the baseline after field removal. CONCLUSIONS: These findings suggest that Kv1.3 may mediate interactions between ELF-EMF and living cells, disclosing new research opportunities on the molecular mechanisms with which electromagnetic fields affect physiological and pathological processes, including immunomodulation, inflammation and cancer.

Single-Cell Bacterial Electrophysiology Reveals Mechanisms of Stress-Induced Damage.

An electrochemical gradient of protons, or proton motive force (PMF), is at the basis of bacterial energetics. It powers vital cellular processes and defines the physiological state of the cell. Here, we use an electric circuit analogy of an Escherichia coli cell to mathematically describe the relationship between bacterial PMF, electric properties of the cell membrane, and catabolism. We combine the analogy with the use of bacterial flagellar motor as a single-cell "voltmeter" to measure cellular PMF in varied and dynamic external environments (for example, under different stresses). We find that butanol acts as an ionophore and functionally characterize membrane damage caused by the light of shorter wavelengths. Our approach coalesces noninvasive and fast single-cell voltmeter with a well-defined mathematical framework to enable quantitative bacterial electrophysiology.

Flexible and precise control of cardiac rhythm with blue light.

Optogenetics is an innovative method for precise control of biological function, which makes light manipulation displays more advantages than electric energy because of contactless spatial flexibility and cell-to-cell synchronous communication. The aim of this study was to perform different illumination modes with blue laser to investigate optical control of the mice hearts. In this study, we transfected the light sensitive protein ChR2(H134R) into mouse hearts, which were illuminated with a 473 nm laser on the Langendorff apparatus. We recorded all the signals of electrograms (EGs), epicardium monophasic action potential (MAPs) and light output signals to analyze myocardial electrical activity. EGs and MAP showed that ChR2 expression in the heart can be flexibly controlled by blue light across different illumination sites with corresponding triggered ectopic rhythm. Illumination intensity, pulse duration, and impulse frequency were associated with the light capture rate. Continuous illumination with the threshold intensity on the left ventricle had little influence on sinus rhythm and ventricular electrophysiology. Our results support that flexible control of the cardiac rhythm with optogenetics provides an innovative approach to cardiac research and therapy.

Simultaneous excitatory and inhibitory dynamics in an excitable laser.

Neocortical systems encode information in electrochemical spike timings, not just mean firing rates. Learning and memory in networks of spiking neurons is achieved by the precise timing of action potentials that induces synaptic strengthening (with excitation) or weakening (with inhibition). Inhibition should be incorporated into brain-inspired spike processing in the optical domain to enhance its information-processing capability. We demonstrate the simultaneous excitatory and inhibitory dynamics in an excitable (i.e., a pulsed) laser neuron, both numerically and experimentally. We investigate the bias strength effect, inhibitory strength effect, and excitatory and inhibitory input timing effect, based on the simulation platform of an integrated graphene excitable laser. We further corroborate these analyses with proof-of-principle experiments utilizing a fiber-based graphene excitable laser, where we introduce inhibition by directly modulating the gain of the laser. This technology may potentially open novel spike-processing functionality for future neuromorphic photonic systems.

Effect of low-level 1800 MHz radiofrequency radiation on the rat sciatic nerve and the protective role of paricalcitol.

The nervous system is an important target of radiofrequency (RF) radiation exposure since it is the excitable component that is potentially able to interact with electromagnetic fields. The present study was designed to investigate the effects of 1,800 MHz RF radiation and the protective role of paricalcitol on the rat sciatic nerve. Rats were divided into four groups as control, paricalcitol, RF, and RF + paricalcitol. In RF groups, the rats were exposed to 1,800 MHz RF for 1 h per day for 4 weeks. Control and paricalcitol rats were kept under the same conditions without RF application. In paricalcitol groups, the rats were given 0.2 µg/kg/day paricalcitol, three times per week for 4 weeks. Amplitude and latency of nerve compound action potentials, catalase activities, malondialdehyde (MDA) levels, and ultrastructural changes of sciatic nerve were evaluated. In the RF group, a significant reduction in amplitude, prolongation in latency, an increase in the MDA level, and an increase in catalase activity and degeneration in the myelinated nerve fibers were observed. The electrophysiological and histological findings were consistent with neuropathy, and the neuropathic changes were partially ameliorated with paricalcitol administration. Bioelectromagnetics. 39:631-643, 2018. © 2018 Wiley Periodicals, Inc.

Trigeminal neurons detect cellphone radiation: Thermal or nonthermal is not the question.

Cellphone electromagnetic radiation produces temperature alterations in facial skin. We hypothesized that the radiation-induced heat was transduced by warmth-sensing trigeminal neurons, as evidenced by changes in cognitive processing of the afferent signals. Ten human volunteers were exposed on the right side of the face to 1 GHz radiation in the absence of acoustic, tactile, and low-frequency electromagnetic stimuli produced by cellphones. Cognitive processing manifested in the electroencephalogram (EEG) was quantitated by analysis of brain recurrence (a nonlinear technique). The theoretical temperature sensitivity of warmth-sensing neurons was estimated by comparing changes in membrane voltage expected as a result of heat transduction with membrane-voltage variance caused by thermal noise. Each participant underwent sixty 12-s trials. The recurrence variable r ("percent recurrence") was computed second by second for the ∆ band of EEGs from two bilaterally symmetric derivations (decussated and nondecussated). Percent recurrence during radiation exposure (first 4 s of each trial) was reduced in the decussated afferent signal compared with the control (last four seconds of each trial); mean difference, r = 1.1 ± 0.5%, p < 0.005. Mean relative ∆ power did not differ between the exposed and control intervals, as expected. Trigeminal neurons were capable of detecting temperature changes far below skin temperature increases caused by cellphone radiation. Simulated cellphone radiation affected brain electrical activity associated with nonlinear cognitive processing of radiation-induced thermal afferent signals. Radiation standards for cellphones based on a thermal/nonthermal binary distinction do not prevent neurophysiological consequences of cellphone radiation.

Effects of UVB Radiation on the Physicochemical Properties of Fibroblasts and Keratinocytes.

The skin is the largest human organ, providing the first line of defense to protect the body from physical and environmental effects. The aim of this study was to determine the influence of short-wave ultraviolet (UVB) radiation on the membrane electrical properties, phospholipid content, and lipid peroxidation levels of fibroblasts and keratinocytes. Changes in cell function may affect the basal electrical surface properties of cell membranes. These changes can be detected using electrokinetic measurements. In this study, the surface charge densities of fibroblasts and keratinocytes were measured as a function of pH. A four-component equilibrium model was used to describe the interaction between the ions in solution and on cell membrane surfaces. Agreement was found between the experimental and theoretical charge variation curves of leukemia cells from pH 2.5 to pH 9. Phospholipid composition was determined qualitatively and quantitatively by HPLC, and lipid peroxidation was estimated by measuring the level of malondialdehyde. The acidic functional group concentrations and average association constants with hydroxyl ions were higher, and the average association constants with hydrogen ions were smaller in UVB-treated skin cell membranes compared to those in untreated cells. Moreover, our results showed that UVB radiation is associated with increased levels of phospholipids and lipid peroxidation products in fibroblasts and keratinocytes.

The effects of Ni(2+) on electrical signaling of Nitellopsis obtusa cells.

The effect of nickel (Ni) on the generation of plant bioelectrical signals was evaluated in Nitellopsis obtusa, a Characean model organism. Conventional glass-microelectrode technique and K(+)-anaesthesia method in current-clamp and voltage-clamp modes were used for the measurement and analysis of electrical parameters. Ni(2+) treatment rapidly influenced the action potential (AP) parameters namely, excitation threshold, AP peak and duration, membrane potential at various voltages and dynamics of ion currents. We conclude that altered electrical signaling pathway in the test organism constituted the early target for Ni toxicity imposition. The observed Ni interference could be ascribed to disturbed [Ca(2+)]cyt content, impaired Cl(-) and K(+) channels activity resulting in decreased excitability and repolarization rate in generated AP.

Thermal effects of 2450 MHz microwave exposure near a titanium alloy plate implanted in rabbit limbs.

This study aimed to examine the safety profile of microwave therapy on limbs with metal implants. New Zealand white rabbits were implanted with titanium alloy internal fixation plates. Femurs were exposed to 20, 40, 60, or 80 W of microwave radiation for 30 min (microwave applicator at 2450 MHz), and temperatures of the implants and muscles adjacent to implants were recorded. To evaluate thermal damage, nerves were electrodiagnostically assessed immediately after radiation, and histologic studies performed on nerve and muscle sections. As expected, implant temperature was highest in the exposure field. Temperatures of limbs with titanium alloy implants increased significantly at 60 and 80 W, with a significant decline in the nerve conduction velocity and acute thermal injuries in nerves and muscles adjacent to implants. However, temperature remained unchanged and no adverse effects were observed in nerves and muscles at 20 and 40 W. These findings are inconsistent with the current notion that surgical metal implants in the treatment field are contraindications for microwave therapy. Hence, we believe that a lower dose of continuous wave microwave irradiation is safe for limbs with titanium alloy implants.

Electrogenic events upon photolysis of CO from fully reduced cytochrome c oxidase.

CO photolysis from fully reduced Paracoccus denitrificans aa(3)-type cytochrome c oxidase in the absence of O(2) was studied by time-resolved potential electrometry. Surprisingly, photo dissociation of the uncharged carbon monoxide results in generation of a small-amplitude electric potential with the same sign as the physiological charge separation during activity. The number of electrogenic events after CO photolysis depends on the state of the enzyme. CO photolysis following immediately after activation by an enzymatic turnover, showed a two-component potential development. A fast (~1.5µs) phase was followed by slower potential generation with a time constant varying from 8µs at pH 7 to 250µs at pH 10. The amplitude of the fast phase was independent of the time of incubation after enzyme activation, whereas the slower phase vanished with a time constant of ~25min. CO photolysis from enzyme that had not undergone a prior single turnover showed the fast phase, but the amplitude of the slow phase was reduced to 10-30%. The amplitude of the fast phase corresponds to charge movement of 0.83Å perpendicular to the membrane dielectric, and is independent of the time after enzyme activation. Thus it can be used as an internal ruler for normalization of the electrogenic responses of CcO. The slow phase was absent in the K354M mutant with a blocked proton-conducting K channel. We propose that CO photolysis increases the pK of the K354 residue, which results in its partial protonation, and generation of electric potential.

Hypothesis on how to measure electromagnetic hypersensitivity.

Electromagnetic hypersensitivity (EHS) is an ill-defined term to describe the fact that people who experience health symptoms in the vicinity of electromagnetic fields (EMFs) regard them as causal for their complaints. Up to now most scientists assume a psychological cause for the suffering of electromagnetic hypersensitive individuals. This paper addresses reasons why most provocation studies could not find any association between EMF exposure and EHS and presents a hypothesis on diagnosis and differentiation of this condition. Simultaneous recordings of heart rate variability, microcirculation and electric skin potentials are used for classification of EHS. Thus, it could be possible to distinguish "genuine" electromagnetic hypersensitive individuals from those who suffer from other conditions.

Effects of electromagnetic fields on neuronal ion channels: a systematic review.

Many aspects of chemistry and biology are mediated by electromagnetic field (EMF) interactions. The central nervous system (CNS) is particularly sensitive to EMF stimuli. Studies have explored the direct effect of different EMFs on the electrical properties of neurons in the last two decades, particularly focusing on the role of voltage-gated ion channels (VGCs). This work aims to systematically review published evidence in the last two decades detailing the effects of EMFs on neuronal ion channels as per the PRISM guidelines. Following a predetermined exclusion and inclusion criteria, 22 papers were included after searches on three online databases. Changes in calcium homeostasis, attributable to the voltage-gated calcium channels, were found to be the most commonly reported result of EMF exposure. EMF effects on the neuronal landscape appear to be diverse and greatly dependent on parameters, such as the field's frequency, exposure time, and intrinsic properties of the irradiated tissue, such as the expression of VGCs. Here, we systematically clarify how neuronal ion channels are particularly affected and differentially modulated by EMFs at multiple levels, such as gating dynamics, ion conductance, concentration in the membrane, and gene and protein expression. Ion channels represent a major transducer for EMF-related effects on the CNS.

Charge Transport by Light-Activated Rhodopsins Determined by Electrophysiological Recordings.

Electrophysiological experiments are required to determine the ion transport properties of light-activated currents from microbial rhodopsin expressing cells. The recordings set the quantitative basis for correlation with spectroscopic data and for understanding of channel gating, ion transport vectoriality, or ion selectivity. This chapter focuses on voltage-clamp recordings of channelrhodopsin-2-expressing cells, and it will describe different illumination protocols that reveal the kinetic properties of gating. While the opening and closing reaction is determined from a single turnover upon a short laser flash, desensitization of the light-gated currents is studied under continuous illumination. Recovery from the desensitized state is probed after prolonged illumination with a subsequent light activation upon different dark intervals. Compiling the experimental data will define a minimum number of states in kinetic schemes used to describe the light-gated currents in channelrhodopsins, and emphasis will be given on how to correlate the results with the different time-resolved spectroscopic experiments.

Electromagnetic field and TGF-ß enhance the compensatory plasticity after sensory nerve injury in cockroach Periplaneta americana.

Recovery of function after sensory nerves injury involves compensatory plasticity, which can be observed in invertebrates. The aim of the study was the evaluation of compensatory plasticity in the cockroach (Periplaneta americana) nervous system after the sensory nerve injury and assessment of the effect of electromagnetic field exposure (EMF, 50 Hz, 7 mT) and TGF-ß on this process. The bioelectrical activities of nerves (pre-and post-synaptic parts of the sensory path) were recorded under wind stimulation of the cerci before and after right cercus ablation and in insects exposed to EMF and treated with TGF-ß. Ablation of the right cercus caused an increase of activity of the left presynaptic part of the sensory path. Exposure to EMF and TGF-ß induced an increase of activity in both parts of the sensory path. This suggests strengthening effects of EMF and TGF-ß on the insect ability to recognize stimuli after one cercus ablation. Data from locomotor tests proved electrophysiological results. The takeover of the function of one cercus by the second one proves the existence of compensatory plasticity in the cockroach escape system, which makes it a good model for studying compensatory plasticity. We recommend further research on EMF as a useful factor in neurorehabilitation.

Direct-Coupled Electroretinogram (DC-ERG) for Recording the Light-Evoked Electrical Responses of the Mouse Retinal Pigment Epithelium.

The retinal pigment epithelium (RPE) is a specialized monolayer of cells strategically located between the retina and the choriocapillaris that maintain the overall health and structural integrity of the photoreceptors. The RPE is polarized, exhibiting apically and basally located receptors or channels, and performs vectoral transport of water, ions, metabolites, and secretes several cytokines. In vivo noninvasive measurements of RPE function can be made using direct-coupled ERGs (DC-ERGs). The methodology behind the DC-ERG was pioneered by Marmorstein, Peachey, and colleagues using a custom-built stimulation recording system and later demonstrated using a commercially available system. The DC-ERG technique uses glass capillaries filled with Hank's buffered salt solution (HBSS) to measure the slower electrical responses of the RPE elicited from light-evoked concentration changes in the subretinal space due to photoreceptor activity. The prolonged light stimulus and length of the DC-ERG recording make it vulnerable to drift and noise resulting in a low yield of useable recordings. Here, we present a fast, reliable method for improving the stability of the recordings while reducing noise by using vacuum pressure to reduce/eliminate bubbles that result from outgassing of the HBSS and electrode holder. Additionally, power line artifacts are attenuated using a voltage regulator/power conditioner. We include the necessary light stimulation protocols for a commercially available ERG system as well as scripts for analysis of the DC-ERG components: c-wave, fast oscillation, light peak, and off response. Due to the improved ease of recordings and rapid analysis workflow, this simplified protocol is particularly useful in measuring age-related changes in RPE function, disease progression, and in the assessment of pharmacological intervention.

Local tissue electrical parameters predict oral mucositis in HNSCC patients: A diagnostic accuracy double-blind, randomized controlled trial.

Oral Mucositis (OM) is a common adverse effect of head and neck squamous cell carcinoma (HNSCC) treatment. The purpose of this study was to investigate the significance of early changes in tissue electrical parameters (TEPs) in predicting the development of OM in HNSCC patients receiving radiation therapy (RT). The current study combined two study designs. The first was a case-control study. The control group comprised of RT patients who did not receive head and neck RT, and patients with HNSCC who received RT comprised the case group. In the second part of the study, the case group was included in a parallel cohort. A total of 320 patients were assessed for eligibility, and 135 patients were enrolled. Double blinding was performed, and neither the patients nor the care providers knew the measured parameters. The primary outcome was the detection of between-group changes in local TEPs over the follow-up period. The secondary outcome was the appearance of OM grades II, III, or IV and the predictive value of local TEPs in determining the incidence of OM after RT. The variables, impedance module, resistance, reactance, phase angle, and capacitance, were analyzed by the receiver operator curves (ROC). The case and control groups did not differ in demographic and clinical characteristics. Radiation therapy increased the local impedance module, resistance, reactance, and phase angle and reduced the local tissue capacitance in both groups. Evaluation of TEPs in the first week of RT correlated with the development of OM lesions during cancer therapy. ROC analysis showed that local impedance module and resistance presented higher specificity than did other parameters in predicting OM. In conclusion, local tissue electrical parameters measured at the first RT week can be useful tools to predict oral mucositis.

Ultrasound Produces Extensive Brain Activation via a Cochlear Pathway.

Ultrasound (US) can noninvasively activate intact brain circuits, making it a promising neuromodulation technique. However, little is known about the underlying mechanism. Here, we apply transcranial US and perform brain mapping studies in guinea pigs using extracellular electrophysiology. We find that US elicits extensive activation across cortical and subcortical brain regions. However, transection of the auditory nerves or removal of cochlear fluids eliminates the US-induced activity, revealing an indirect auditory mechanism for US neural activation. Our findings indicate that US activates the ascending auditory system through a cochlear pathway, which can activate other non-auditory regions through cross-modal projections. This cochlear pathway mechanism challenges the idea that US can directly activate neurons in the intact brain, suggesting that future US stimulation studies will need to control for this effect to reach reliable conclusions.

Effect of acute exposure to radiofrequency electromagnetic fields emitted by a mobile phone (GSM 900 MHz) on electrodermal responsiveness in healthy human.

PURPOSE: The present study aimed to determine the effect of acute exposure to electromagnetic fields (EMF) emitted by a mobile phone on electrodermal activity (EDA) in response to an auditory stimulus. MATERIALS AND METHODS: The EDA of 28 young volunteers was recorded following 26 min of exposure to a GSM mobile phone (900 MHz). Palmar sensors enabled repeat recording of 2 min 45 s in the pre-exposure, exposure and post-exposure phases in response to sound stimuli. RESULTS: The latency, amplitude of skin conductance responses (SCRs), integral of skin conductance response and number of SCRs in response to the auditory stimuli were not modified by exposure. Skin conductance and tonic activity decomposition of the recorded signal were significantly different between the two sessions (p < .0001), but the changes could not be attributed to EMF exposure. There was also a tendency toward a fast reduction in the amplitude and number of electrodermal responses after placement of the mobile phone. In response to successive stimuli, there was a significant difference between the first response and subsequent responses for all variables except latency. CONCLUSIONS: Our results showed a decrease in the number of responses and their amplitude as a result of placement of the mobile device and whether it was turned 'on' or 'off', but there were no changes associated with exposure to GSM radiofrequency waves in this group of volunteers.

Impact of Ionizing Radiation on Electrophysiological Behavior of Human-induced Ipsc-derived Cardiomyocytes on Multielectrode Arrays.

Cardiac arrhythmia presumably induced through cardiac fibrosis is a recurrent long-term consequence of exposure to ionizing radiation. However, there is also evidence that cardiac arrhythmia can occur in patients shortly after irradiation. In this study, the authors employed multielectrode arrays to investigate the short-term effects of x-ray radiation on the electrophysiological behavior of cardiomyocytes derived from human-induced pluripotent stem cells. These cardiomyocytes with spontaneous pacemaker activity were cultured on single-well multielectrode arrays. After exposure to 0, 0.5, 1, 2, 5, 10 Gy x-ray radiation, electrical activity was measured at time points ranging from 10 min to 96 h. RNA sequencing was employed to verify the expression of genes specifically involved in cardiomyocyte differentiation and function. A decrease in beating rate was observed after irradiation with 5 and 10 Gy starting 48 h after exposure. Cells exposed to higher doses of radiation were more prone to show changes in electrophysiological spatial distribution. No radiation-induced effects with respect to the corrected QT interval were detectable. Gene expression analysis showed up regulation of typical cardiac features like ACTC1 or HCN4. In this study, early dose-dependent changes in electrophysiological behavior were determined after x-ray irradiation. Results point towards a dose-dependent effect on pacemaker function of cardiomyocytes and indicate a possible connection between irradiation and short-term changes in electrophysiological cardiac function. Cardiomyocytes derived from human-induced pluripotent stem cells on multielectrode arrays represent a promising in vitro cardiac-modeling system for preclinical studies.