Effects Of Electrical Field Stimulation Research Articles

Effects of electrical field stimulation on the physicochemical and sensory attributes of aged chicken meat

AbstractVarious physical, chemical, and biological practices have been adopted in the meat industry to enhance the tenderness of aged chicken meat. Among these, electrical field stimulation is used as an innovative tool in enhancing meat quality. Purposely, the present study was designed to evaluate the effectiveness of electrical stimulation (ES) on different quality attributes (chemical, physical, & sensory) of laying aged chicken (Gallus domesticus) carcasses. To assess the effect of ES on meat quality of aged chicken (1.5 years), a total of 54 birds were slaughtered and their respective carcasses were subjected to electric field strengths (EFSs) of 3.67 and 7.33 V/cm. Physicochemical and sensorial characteristics of the ES‐treated groups (3.67 and 7.33 V/cm) and control group (without ES) meat were compared during the storage periods 0, 30, and 60 days. The results revealed that the electrical conductivity and specific energy consumption increased significantly with an increase in the EFS. ES significantly (p < .05) decreased peroxide number (by 12.62%), free fatty acids (FFA; by 13.46%), drip loss (by 4.25%), and cooking loss (by 50.85%), and increased pH (by 5.90%). Besides, ES‐treated samples showed significant superiorities in terms of sensory characteristics in comparison with control samples. An artificial neural network (ANN) gave a good fitting to predict the development of peroxide value and FFA during storage.Practical applicationsElectrical stimulation (ES) has been studied as a means to reduce the time required for aging to prevent meat hardness. ES improves the tenderness of meat by reducing cut values, increasing the sarcomere length, and reducing the diameter of muscle fibers. The application of ES helps in reducing the storage time, storage cost, de‐feathering force, and microbial load on a chicken carcass. Aged chicken meat carcass can be treated by ES before storage to help meat processing industries for storing meat safely. This study aimed to investigate the use of ES to improve the qualitative and sensory characteristics of aged chicken meat carcass during storage periods.

Expression and function of vasoactive intestinal peptide receptors in human lower esophageal sphincter.

Vasoactive intestinal peptide (VIP) is an important neurotransmitter involved in the modulation of gastrointestinal function through the stimulation of VIP receptors. However, the expression of VPAC1R, VPAC2R and PAC1R in the human Lower esophageal sphincter (LES) has not been fully clarified. Therefore, the purpose of this study is to explore the expression of these receptors in the human Lower esophageal sphincter, the responses of the Lower esophageal sphincter to Vasoactive intestinal peptide, and the role of Vasoactive intestinal peptide receptors in the responses. Sling and clasp fiber samples of LES were acquired from patients undergoing subtotal esophagectomy, while circular muscle bundles from the esophagus and gastric fundus were used as control groups. Western blotting and RT-PCR technology were performed to determine the expression of the three VIP receptor subtypes. The isometric tension responses of the muscle sample strips to Ro25-1553 and PG99-465, and the effect of electrical field stimulation (EFS) on the sling and clasp fibers were studied. We found that VPAC2R messenger RNA (mRNA) and protein were expressed in the sling and clasp fibers of human LES. However, no VPAC1R or PAC1R mRNA and protein expressions were found in the LES samples. The sling and clasp fibers of the LES produced significant concentration-dependent relaxation following exposure to Ro25-1553 and EFS could induce them to produce frequency-dependent relaxation. Furthermore, the relaxation responses of the LES were inhibited by PG99-465 and induced by EFS and Ro25-1553. VPAC2R, but not VPAC1R or PAC1R, is expressed by the human LES. The relaxation responses of the LES generated by the VIP receptor agonist Ro25-1553 and EFS could be inhibited by the selective VPAC2 receptor antagonist PG99-465. VPAC2R may be important for the generation of relaxation and functional regulation of the LES.

Bioelectronics-on-a-chip for cardio myoblast proliferation enhancement using electric field stimulation

BackgroundCardio myoblast generation from conventional approaches is laborious and time-consuming. We present a bioelectronics on-a-chip for stimulating cells cardio myoblast proliferation during culture.MethodThe bioelectronics chip fabrication methodology involves two different process. In the first step, an aluminum layer of 200 nm is deposited over a soda-lime glass substrate using physical vapor deposition and selectively removed using a Q-switched Nd:YVO4 laser to create the electric tracks. To perform the experiments, we developed a biochip composed of a cell culture chamber fabricated with polydimethylsiloxane (PDMS) with a glass coverslip or a cell culture dish placed over the electric circuit tracks. By using such a glass cover slip or cell culture dish we avoid any toxic reactions caused by electrodes in the culture or may be degraded by electrochemical reactions with the cell medium, which is crucial to determine the effective cell-device coupling.ResultsThe chip was used to study the effect of electric field stimulation of Rat ventricular cardiomyoblasts cells (H9c2). Results shows a remarkable increase in the number of H9c2 cells for the stimulated samples, where after 72 h the cell density double the cell density of control samples.ConclusionsCell proliferation of Rat ventricular cardiomyoblasts cells (H9c2) using the bioelectronics-on-a-chip was enhanced upon the electrical stimulation. The dependence on the geometrical characteristics of the electric circuit on the peak value and homogeneity of the electric field generated are analyzed and proper parameters to ensure a homogeneous electric field at the cell culture chamber are obtained. It can also be observed a high dependence of the electric field on the geometry of the electrostimulator circuit tracks and envisage the potential applications on electrophysiology studies, monitoring and modulate cellular behavior through the application of electric fields.

Rat mesenteric small artery neurogenic dilatation is predominantly mediated by β1 -adrenoceptors in vivo.

The prevailing dogma about neurogenic regulation of vascular tone consists of major vasodilatation caused by CGRP (and possibly substance P) released from sensory-motor nerves and vasoconstriction caused by noradrenaline, ATP and neuropeptode Y release from sympathetic nerves. Most studies on perivascular nerve-mediated vasodilatation are made in vitro. In the present study, we provide evidence indicating that in vivo electrical perivascular nerve stimulation in rat mesenteric small arteries causes a large β1-adrenoceptor-mediated vasodilatation, which contrasts with a smaller vasodilatation caused by endogenous CGRP that is only visible after inhibition of Y1 NPY receptors. Mesenteric arteries are densely innervated and the nerves are important regulators of vascular tone and hence blood pressure and blood flow. Perivascular sensory-motor nerves have been shown to cause vasodilatation in vitro. However, less is known about their function in vivo. Male Wistar rats (10-12 weeks old; n=72) were anaesthetized with ketamine (3mg kg-1 ) and xylazine (0.75mg kg-1 ) or pentobarbital (60mg kg-1 ). After a laparotomy, a section of second-order mesenteric artery was visualized in an organ bath after minimal removal of perivascular adipose tissue. The effects of electrical field stimulation (EFS) and drugs on artery diameter and blood flow were recorded with intravital microscopy and laser speckle imaging. EFS caused vasodilatation in arteries constricted with 1μm U46619 in the presence of 140μm suramin and 1μm prazosin. The vasodilatation was inhibited by 1μm tetrodotoxin and 5μm guanethidine, although not by the 1μm of the CGRP receptor antagonist BIBN4096bs. In the presence of 0.3μm Y1 receptor antagonist BIBP3226, BIBN4096bs partly inhibited the vasodilatation. Atenolol at a concentration 1μm inhibited the vasodilatation, whereas 0.1μm of the β2 -adrenoceptor selective antagonist ICI-118,551 had no effect. Increasing the extracellular [K+ ] to 20mm caused vasodilatation but was converted to vasoconstriction in the presence of 1μm BIBN4096bs, and constriction to 30mm potassium was potentiated by BIBN4096bs. Atenolol but not BIBN4096bs increased contraction to EFS in the absence of suramin and prazosin. In mesenteric small arteries of anaesthetized rats, EFS failed to stimulate major dilatation via sensory-motor nerves but induced sympathetic β1 -adrenoceptor-mediated dilatation.

Effect of electrical field stimulation on intracellular sodium concentration in human iPS cardiomyocytes

Effect of electrical field stimulation on intracellular sodium concentration in human iPS cardiomyocytes

Preoperative administration of the 5-HT4 receptor agonist prucalopride reduces intestinal inflammation and shortens postoperative ileus via cholinergic enteric neurons.

ObjectivesVagus nerve stimulation (VNS), most likely via enteric neurons, prevents postoperative ileus (POI) by reducing activation of alpha7 nicotinic receptor (α7nAChR) positive muscularis macrophages (mMφ) and dampening surgery-induced intestinal inflammation. Here, we evaluated if 5-HT4 receptor (5-HT4R) agonist prucalopride can mimic this effect in mice and human.DesignUsing Ca2+ imaging, the effect of electrical field stimulation (EFS) and prucalopride was evaluated in situ on mMφ activation evoked by ATP in jejunal muscularis tissue. Next, preoperative and postoperative administration of prucalopride (1–5 mg/kg) was compared with that of preoperative VNS in a model of POI in wild-type and α7nAChR knockout mice. Finally, in a pilot study, patients undergoing a Whipple procedure were preoperatively treated with prucalopride (n=10), abdominal VNS (n=10) or sham/placebo (n=10) to evaluate the effect on intestinal inflammation and clinical recovery of POI.ResultsEFS reduced the ATP-induced Ca2+ response of mMφ, an effect that was dampened by neurotoxins tetrodotoxin and ω-conotoxin and mimicked by prucalopride. In vivo, prucalopride administered before, but not after abdominal surgery reduced intestinal inflammation and prevented POI in wild-type, but not in α7nAChR knockout mice. In humans, preoperative administration of prucalopride, but not of VNS, decreased Il6 and Il8 expression in the muscularis externa and improved clinical recovery.ConclusionEnteric neurons dampen mMφ activation, an effect mimicked by prucalopride. Preoperative, but not postoperative treatment with prucalopride prevents intestinal inflammation and shortens POI in both mice and human, indicating that preoperative administration of 5-HT4R agonists should be further evaluated as a treatment of POI.Trial registration number NCT02425774.

The effect of pulsed electric field on expression of ECM proteins: Collagen, elastin, and MMP1 in human dermal fibroblasts

Electrical stimulation of tissues has many uses in pain management, antibacterial treatment, and wound healing. The electric field stimulates epidermal migration and increases fibroblast cell proliferation. Here we show the effects of electrical field (EF) stimulation of human dermal fibroblasts (HDF) on the expression of collagen, elastin, and collagenase (MMP1; matrix metalloproteinase 1). The effects of EF stimulation are evaluated in terms of changes in cell morphology and extracellular matrix (ECM) protein expression, defined as intracellular concentration of collagen, elastin, and MMP1. HDF are stimulated in a bioreactor using square wave voltage pulses for up to 24 h. The pulse voltage (0-10 V), pulse bias (0, +), pulse time (10–1000 ms), and rest time (0.1–10 s) were varied. We show that expression of collagen, elastin, and MMP1 increases in response to applied EF. The intracellular concentration of ECM proteins more than doubles depending on stimulation conditions with a threshold of effective stimulation above 3 V/cm. The short time voltage pulses used for EF stimulation are more effective, while the rest time between pulses has a small effect on intracellular concentration of collagen, MMP1 and elastin. The previously studied HDF stimulation with chemical factors (i.e. TNF-α, TGF-β) shows negative correlation between concentration of collagen and MMP1. Contrary to that observation, we show that EF stimulation causes increase in the intracellular concentration of both collagen and MMP1. We also demonstrate that the transdermal stimulation of HDF in subcutaneous tissue is possible, thus it might be utilized in the future to improve the wound healing and tissue regeneration process.

Ih interacts with somato-dendritic structure to determine frequency response to weak alternating electric field stimulation.

Transcranial current stimulation (tCS) modulates brain dynamics using weak electric fields. Given the pathological changes in brain network oscillations in neurological and psychiatric illnesses, using alternating electric field waveforms that engage rhythmic activity has been proposed as a targeted, network-level treatment approach. Previous studies have investigated the effects of electric fields at the neuronal level. However, the biophysical basis of the cellular response to electric fields has remained limited. Here, we characterized the frequency-dependent response of different compartments in a layer V pyramidal neuron to exogenous electric fields to dissect the relative contributions of voltage-gated ion channels and neuronal morphology. Hyperpolarization-activated cation current (Ih) in the distal dendrites was the primary ionic mechanism shaping the model's response to electric field stimulation and caused subthreshold resonance in the tuft at 20 ± 4 Hz. In contrast, subthreshold Ih-mediated resonance in response to local sinusoidal current injection was present in all model compartments at 11 ± 2 Hz. The frequencies of both resonance responses were modulated by Ih conductance density. We found that the difference in resonance frequency between the two stimulation types can be explained by the fact that exogenous electric fields simultaneously polarize the membrane potentials at the distal ends of the neuron (relative to field direction) in opposite directions. Our results highlight the role of Ih in shaping the cellular response to electric field stimulation and suggest that the common model of tCS as a weak somatic current injection fails to capture the cellular effects of electric field stimulation. NEW & NOTEWORTHY Modulation of cortical oscillation by brain stimulation serves as a tool to understand the causal role of network oscillations in behavior and is a potential treatment modality that engages impaired network oscillations in disorders of the central nervous system. To develop targeted stimulation paradigms, cellular-level effects must be understood. We demonstrate that hyperpolarization-activated cation current (Ih) and cell morphology cooperatively shape the response to applied alternating electric fields.

The expression, localization and function of α7 nicotinic acetylcholine receptor in rat corpus cavernosum.

Alpha7 nicotinic acetylcholine receptor (α7-nAChR), an emerging pharmacological target for a variety of medical conditions, is expressed in the most mammalian tissues with different effects. So, this study was designed to investigate the expression, localization and effect of α7-nAChR in rat corpus cavernosum (CC). Reverse transcription polymerase chain reaction (RT-PCR) revealed that α7-nAChR was expressed in rat CC and double immunofluorescence studies demonstrated the presence of α7-nAChR in corporal neurons. The rat CC segments were mounted in organ bath chambers and contracted with phenylephrine (0.1μm -300μm) to investigate the relaxation effect of electrical field stimulation (EFS,10Hz) assessed in the presence of guanethidine (adrenergic blocker, 5μm) and atropine (muscarinic cholinergic blocker, 1μm) to obtain non-adrenergic non-cholinergic (NANC) response. Cumulative administration of nicotine significantly potentiated the EFS-induced NANC relaxation (-log EC50=7.5±0.057). Whereas, the potentiated NANC relaxation of nicotine was significantly inhibited with different concentrations of methyllycaconitine citrate (α7-nAChR antagonist, P<0.05) in preincubated strips. L-NAME (non-specific nitric oxide synthase inhibitor, 1μm) completely blocked the neurogenic relaxation induced by EFS plus nicotine. To conclude α7-nAChR is expressed in rat CC and modulates the neurogenic relaxation response to nicotine.

Electric field stimulation protects injured spinal cord from secondary inflammatory response in rats.

To investigate acute beneficial effects of electrical field stimulation (EFS) on secondary inflammatory response in spinal cord injury (SCI) rats. Sprague-Dawley (SD) rats were divided into three groups,sham group rats received laminectomy only, control group rats were subjected to SCI only, and EFS group rats received EFS immediately after the injury. During the 30-min-stimulation, the injury potential modulated to 0 ± 0.5 mV by EFS. At 12h, 24h and 48h after the surgery, the rats in each group were sacrificed. Immunofluorescence staining for macrophage marker (ED-1), the tautomerase activity of macrophage inhibitory factor (MIF) assay and real-time PCR analysis for interleukin-1β (IL-1β) and matrix metalloproteinase-9 (MMP-9) were performed. Compared to the rats in control group, the rats treated with EFS presented less ED-1 positive cells 12h (P <; 0.05), 24h (P <; 0.01) and 48h (P <; 0.05) after the surgery and showed a lower MIF tautomerase activity 12h (P <; 0.01), 24h (P <; 0.01) and 48h (P <; 0.01) after the surgery. Moreover, EFS significantly decreased the mRNA levels of IL-β (P <; 0.05) and MMP-9 at 48h (P <; 0.01) after the injury. EFS could attenuate secondary inflammatory response of injured spinal cord shortly after SCI, and EFS treatment could be a candidate for SCI therapy.

Dual Excitatory and Smooth Muscle-relaxing Effect of Sideritis montana Extract on Guinea-pig Ileum

The neuronal and smooth muscle effects of a methanol extract prepared from the air-dried flowering aerial parts of Sideritis montana L. (SME) was tested in vitro on Guinea-pig ileum. The chemical composition of the investigated extract was analysed by HPLC-MS, and chrysoeriol, chlorogenic acid and caffeic acid were detected as main constituents. The isolated organ assay showed that S. montana extract caused an immediate contraction and a more slowly developing inhibitory response in the ileum. The SME-induced contractions were strongly inhibited by the acetylcholine muscarinic receptor antagonist atropine (0.5 μM), but not by either the Na+ channel blocker tetrodotoxin (TTX; 0.5 μM) or the histamine H1 receptor antagonist chloropyramine (0.5 μM). Selective desensitization of capsaicin-sensitive neurons by the sensory neuron stimulant and blocker capsaicin did not influence the contractile effect of SME. As to the spasmolytic effect, SME inhibited the effects of electrical field stimulation, exogenous acetylcholine, and histamine. These smooth muscle-relaxing effects were reversible in 40 min by repeated renewals of the bathing solution.

Endogenous cortical oscillations constrain neuromodulation by weak electric fields.

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation modality that may modulate cognition by enhancing endogenous neocortical oscillations by application of sine-wave electric fields. Yet, the role of endogenous network activity in enabling and shaping the effects of tACS has remained unclear. We combined optogenetic stimulation and multichannel slice electrophysiology to elucidate how the effect of a weak sine-wave electric field depends on the ongoing cortical oscillatory activity. We hypothesized that endogenous cortical oscillations constrain neuromodulation by tACS. We studied the effect of weak sine-wave electric fields on oscillatory activity in mouse neocortical slices. Optogenetic control of the network activity enabled the generation of in vivo-like cortical oscillations for studying the temporal relationship between network activity and sine-wave electric field stimulation. Weak electric fields enhanced endogenous oscillations but failed to induce a frequency shift of the ongoing oscillation for stimulation frequencies that were not matched to the endogenous oscillation. This constraint on the effect of electric field stimulation imposed by endogenous network dynamics was limited to the case of weak electric fields targeting in vivo-like network dynamics. Together, these results suggest that the key mechanism of tACS may be enhancing, but not overriding, intrinsic network dynamics. Our results contribute to understanding the inconsistent tACS results from human studies and propose that stimulation precisely adjusted in frequency to the endogenous oscillations is key to rational design of non-invasive brain stimulation paradigms.

194 Sympathetic Activity in Perivascular Adipose Tissue

IntroductionPerivascular adipose tissue (PVAT) and the sympathetic nervous system (SNS) both regulate vascular tone. Healthy PVAT is a potent paracrine tissue that exerts an anti-contractile effect in response to agonist-induced...

Effect of electrical field stimulation on spontaneous Ca2+ transients in rat pulmonary vein cardiomyocytes (864.4)

The pulmonary veins (PVs) are widely recognised as an important source of ectopic electrical activity that can lead to atrial fibrillation. While the ectopic activity most likely originates in the cardiomyocytes that form an external sleeve around the PVs, the underlying mechanism remains to be elucidated. Recently, changes in the intracellular Ca2+ concentration have been proposed to play a role. Studies were carried out on intact PVs isolated from the rat, using fluo‐4 to monitor intracellular Ca2+ within individual cardiomyocytes. Under basal unstimulated conditions, spontaneous Ca2+ transients were observed that were asynchronous in neighbouring cells. The frequency of spontaneous Ca2+ transients increased from 0.45 ± 0.06 Hz to 0.59 ± 0.05 Hz (P&lt;0.001) immediately following electrical field stimulation at 5 Hz. Increasing the external Ca2+ concentration to 4.5 mM enhanced this effect, with the frequency of spontaneous Ca2+ transients increasing from 0.45 ± 0.05 Hz under basal conditions to 0.91 ± 0.07 Hz after electrical stimulation (P&lt;0.001). Thus, although electrical field stimulation significantly increased the frequency of the spontaneous Ca2+ transients, their asynchronous nature would mean that they are unlikely to be capable of triggering an action potential. Other interventions that could lead to entrainment of the Ca2+ transients are currently being investigated.

Neurohumoral regulation of spontaneous constrictions in suburothelial venules of the rat urinary bladder

Venules of the bladder suburothelium develop spontaneous phasic constrictions that may play a critical role in maintaining venular drainage of tissue metabolites. We aimed to investigate neurohumoral regulation of the spontaneous venular constrictions (SVCs). Changes in venular diameter of the rat bladder suburothelium were monitored using a video tracking system, whilst the effects of electrical field stimulation (EFS) and bath-applied bioactive substances were investigated. The innervation of the suburothelial microvasculature was examined by immunohistochemistry. EFS (10Hz for 30s) induced an increase in the frequency of SVCs that was prevented by phentolamine (1μM). In phentolamine-pretreated venules, EFS suppressed SVCs with a venular dilatation in a manner attenuated by propranolol (1μM) or l-nitro arginine (LNA, 10μM). BRL37344 (1μM), a β3 adrenoceptor agonist, dilated venules and reduced the frequency of SVCs in an LNA-sensitive manner. ACh (1–10μM) increased the frequency of SVCs. ATP (1μM) transiently constricted venules and then caused LNA-sensitive cessation of SVCs associated with a dilatation. Substance P (100nM) caused a venular constriction, whilst calcitonin gene related peptide (CGRP, 100nM) caused a dilatation of venules and suppression of SVCs that were not inhibited by LNA. Immunohistochemical staining demonstrated sympathetic as well as substance P- and CGRP-containing nerves running along the venules. Spontaneous constrictions of suburothelial venules are accelerated by sympathetic α-adrenergic stimulation, but suppressed upon β-adrenergic stimulation. In addition, suburothelial venular constrictions appear to be modulated by several bioactive substances that could be released from urothelium or suburothelial sensory nerves.

Neural circuit modulation during deep brain stimulation at the subthalamic nucleus for Parkinson's disease: what have we learned from neuroimaging studies?

Deep brain stimulation (DBS) targeting the subthalamic nucleus (STN) represents a powerful clinical tool for the alleviation of many motor symptoms that are associated with Parkinson's disease. Despite its extensive use, the underlying therapeutic mechanisms of STN-DBS remain poorly understood. In the present review, we integrate and discuss recent literature examining the network effects of STN-DBS for Parkinson's disease, placing emphasis on neuroimaging findings, including functional magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. These techniques enable the noninvasive detection of brain regions that are modulated by DBS on a whole-brain scale, representing a key experimental strength given the diffuse and far-reaching effects of electrical field stimulation. By examining these data in the context of multiple hypotheses of DBS action, generally developed through clinical and physiological observations, we define a multitude of consistencies and inconsistencies in the developing literature of this rapidly moving field.

Irregular Rhythm Adversely Influences Calcium Handling in Ventricular Myocardium

Background— Despite adequate rate control, the combination of atrial fibrillation with heart failure (HF) has been shown, in a number of studies, to hasten HF progression. In this context, we aimed to test the hypothesis that an irregular ventricular rhythm causes an alteration in ventricular cardiomyocyte excitation–contraction coupling which contributes to the progression of HF. Methods and Results— We investigated the effects of electrical field stimulation (average frequency 2 Hz) in an irregular versus regular drive train pattern on the expression of calcium-handling genes and proteins in rat ventricular myocytes. The effect of rhythm on intracellular calcium transients was examined using Fura-2AM fluorescence spectroscopy. In conjunction, calcium-handling protein expression was examined in left ventricular samples obtained from end-stage HF patients, in patients with either persistent atrial fibrillation or sinus rhythm. Compared with regularly paced ventricular cardiomyocytes, in cells paced irregularly for 24 hours, there was a significant reduction in the expression of sarcoplasmic reticulum calcium (Ca 2+ ) ATPase together with reduced serine-16 phosphorylation of phospholamban. These findings were accompanied by a 59% reduction ( P &lt;0.01) in the peak Ca2+ transient in irregulary paced myocytes compared with those with regular pacing. Consistent with these observations, we observed a 54% ( P &lt;0.05) decrease in sarcoplasmic reticulum Ca 2+ ATPase protein expression and an 85% ( P &lt;0.01) reduction in the extent of phosphorylation of phospholamban in the left ventricular myocardium of HF patients in atrial fibrillation compared with those in sinus rhythm. Conclusions— Together, these data demonstrate that ventricular rhythmicity contributes significantly to excitation–contraction coupling by altering the expression and activity of key calcium-handling proteins. These data suggest that control of rhythm may be of benefit in patients with HF.

Effects of aging on cholinergic neuromuscular transmission in isolated small intestine of ad libitum fed and calorically‐restricted rats

Age-associated losses of enteric neurons have been described. In rat ileum, myenteric neurons lost during aging have been reported to be predominantly cholinergic, and caloric restriction (CR) has been shown to protect against these losses. Cholinergic myenteric neurons include excitatory motor neurons, so the aim of this work was to determine whether neuronal loss in ad libitum (AL)-fed animals is reflected in dysfunctional cholinergic neuromuscular transmission, and if CR reduces any such dysfunction. Effects of electrical field stimulation (EFS) and applied acetylcholine (ACh) were examined in the longitudinal muscle of isolated ileal segments from 6-month-old rats and from 13- and 24-month-old rats fed either AL or CR diets. Contractile responses to EFS were abolished by atropine and potentiated by the acetylcholinesterase inhibitor, eserine. Frequency-response relationships were not significantly different amongst the three age-groups. Sensitivity to applied ACh, however, was three-fold lower in the oldest animals (P < 0.05). Eserine potentiated responses to ACh; there were no statistically significant differences amongst the sensitivities to ACh in its presence. No significant differences between AL- and CR-fed animals were measured, although variability was less in CR-fed than in AL-fed groups. The cholinergic system supplying the rat ileum longitudinal muscle did not appear to be impaired in old age. Decreased sensitivity to applied ACh in old tissues may have been due to increased acetylcholinesterase activity. Caloric restriction had no significant effect on responses to EFS or applied ACh. The implications of these results are discussed.

Comparison of the Effects of Electrical Field Stimulation and Low-Level Laser Therapy on Bone Loss in Spinal Cord–Injured Rats

This study investigated the effects of low-level laser therapy (LLLT) and electrical stimulation (ES) on bone loss in spinal cord-injured rats. Thirty-seven male Wistar rats were divided into four groups: standard control group (CG); spinal cord-injured control (SC); spinal cord-injured treated with laser (SCL; GaAlAs, 830 nm, CW, 30 mW/cm, 250 J/cm(2)); and spinal cord-injured treated with electrical field stimulation (SCE; 1.5 MHz, 1:4 duty cycles, 30 mW, 20 min). Biomechanical, densitometric, and morphometric analyses were performed. SC rats showed a significant decrease in bone mass, biomechanical properties, and morphometric parameters (versus CG). SCE rats showed significantly higher values of inner diameter and internal and external areas of tibia diaphyses; and the SCL group showed a trend toward the same result (versus SC). No increase was found in either mechanical or densitometric parameters. We conclude that the mentioned treatments were able to initiate a positive bone-tissue response, maybe through stimulation of osteoblasts, which was able to determine the observed morphometric modifications. However, the evoked tissue response could not determine either biomechanical or densitometric modifications.

Electrical stimulation of human embryonic stem cells: Cardiac differentiation and the generation of reactive oxygen species

Exogenous electric fields have been implied in cardiac differentiation of mouse embryonic stem cells and the generation of reactive oxygen species (ROS). In this work, we explored the effects of electrical field stimulation on ROS generation and cardiogenesis in embryoid bodies (EBs) derived from human embryonic stem cells (hESC, line H13), using a custom-built electrical stimulation bioreactor. Electrical properties of the bioreactor system were characterized by electrochemical impedance spectroscopy (EIS) and analysis of electrical currents. The effects of the electrode material (stainless steel, titanium-nitride-coated titanium, titanium), length of stimulus (1 and 90 s) and age of EBs at the onset of electrical stimulation (4 and 8 days) were investigated with respect to ROS generation. The amplitude of the applied electrical field was 1 V/mm. The highest rate of ROS generation was observed for stainless steel electrodes, for signal duration of 90 s and for 4-day-old EBs. Notably, comparable ROS generation was achieved by incubation of EBs with 1 nM H 2O 2. Cardiac differentiation in these EBs was evidenced by spontaneous contractions, expression of troponin T and its sarcomeric organization. These results imply that electrical stimulation plays a role in cardiac differentiation of hESCs, through mechanisms associated with the intracellular generation of ROS.