Changes in the excitability of primary hippocampal neurons following exposure to 3.0 GHz radiofrequency electromagnetic fields.

Exposures to radiofrequency electromagnetic fields (RF-EMFs, 100 kHz to 6 GHz) have been associated with both positive and negative effects on cognitive behavior. To elucidate the mechanism of RF-EMF interaction, a few studies have examined its impact on neuronal activity and synaptic plasticity. However, there is still a need for additional basic research that further our understanding of the underlying mechanisms of RF-EMFs on the neuronal system.

Intrinsic properties of primary hippocampal neurons contribute to PIP depletion during nsEP-induced physiological response.

High-energy, short-duration electric pulses (EPs) are known to be effective in neuromodulation, but the biological mechanisms underlying this effect remain unclear. Recently, we discovered that nanosecond electric pulses (nsEPs) could initiate the phosphatidylinositol-bisphosphate (PIP) depletion in non-excitable cells identical to agonist-induced activation of the G coupled receptors. PIP is the precursor for multiple intracellular second messengers critically involved in the regulation of intracellular Ca homeostasis and plasma membrane (PM) ion channels responsible for the control of neuronal excitability.

Caveolin-1 is Involved in Regulating the Biological Response of Cells to Nanosecond Pulsed Electric Fields.

Nanosecond pulsed electric fields (nsPEFs) induce changes in the plasma membrane (PM), including PM permeabilization (termed nanoporation), allowing free passage of ions into the cell and, in certain cases, cell death. Recent studies from our laboratory show that the composition of the PM is a critical determinant of PM nanoporation. Thus, we hypothesized that the biological response to nsPEF exposure could be influenced by lipid microdomains, including caveolae, which are specialized invaginations of the PM that are enriched in cholesterol and contain aggregates of important cell signaling proteins, such as caveolin-1 (Cav1).

Receptor- and store-operated mechanisms of calcium entry during the nanosecond electric pulse-induced cellular response.

Nanosecond electric pulses have been shown to open nanopores in the cell plasma membrane by fluorescent imaging of calcium uptake and fluorescent dyes, including propidium (Pr) iodide and YO-PRO-1 (YP). Recently, we demonstrated that nsEPs also induce the phosphoinositide intracellular signaling cascade by phosphatidylinositol-4,5-bisphosphate (PIP) depletion resulting in physiological responses similar to those observed following stimulation of G-coupled receptors. In this paper, we explore the role of receptor- and store-operated calcium entry (ROCE/SOCE) mechanisms in the observed response of cells to nsEP.

nsPEF-induced PIP depletion, PLC activity and actin cytoskeletal cortex remodeling are responsible for post-exposure cellular swelling and blebbing.

Cell swelling and blebbing has been commonly observed following nanosecond pulsed electric field (nsPEF) exposure. The hypothesized origin of these effects is nanoporation of the plasma membrane (PM) followed by transmembrane diffusion of extracellular fluid and disassembly of cortical actin structures. This investigation will provide evidence that shows passive movement of fluid into the cell through nanopores and increase of intracellular osmotic pressure are not solely responsible for this observed phenomena.

Ryanodine and IP receptor-mediated calcium signaling play a pivotal role in neurological infrared laser modulation.

Pulsed infrared (IR) laser energy has been shown to modulate neurological activity through both stimulation and inhibition of action potentials. While the mechanism(s) behind this phenomenon is (are) not completely understood, certain hypotheses suggest that the rise in temperature from IR exposure could activate temperature- or pressure-sensitive ion channels or create pores in the cellular outer membrane, allowing an influx of typically plasma-membrane-impermeant ions. Studies using fluorescent intensity-based calcium ion ([Formula: see text]) sensitive dyes show changes in [Formula: see text] levels after various IR stimulation parameters, which suggests that [Formula: see text] may originate from the external solution.

Nanosecond pulsed electric field induced dose dependent phosphatidylinositol--bisphosphate signaling and intracellular electro-sensitization.

Previously, it was demonstrated that nanometer-sized pores (nanopores) are formed in outer cellular membranes after exposure to nanosecond electric pulses (nsEPs). We reported that plasma membrane nanoporation affects phospholipids of the cell membrane, culminating in cascading phosphoinositide phosphatidylinositol--bisphosphate (PIP) intracellular signaling. In the current study, we show that nsEPs initiated electric field (EF) dose-dependent PIP hydrolysis and/or depletion from the plasma membrane.

Action potential block in neurons by infrared light.

Short infrared laser pulses (SILP) have many physiological effects on cells, including the ability to stimulate action potentials (APs) in neurons. Here, we show that SILPs can also reversibly block APs. Reversible AP block in hippocampal neurons was observed following SILP (0.

Cellular response to high pulse repetition rate nanosecond pulses varies with fluorescent marker identity.

Nanosecond electric pulses (nsEP's) are a well-studied phenomena in biophysics that cause substantial alterations to cellular membrane dynamics, internal biochemistry, and cytoskeletal structure, and induce apoptotic and necrotic cell death. While several studies have attempted to measure the effects of multiple nanosecond pulses, the effect of pulse repetition rate (PRR) has received little attention, especially at frequencies greater than 100 Hz. In this study, uptake of Propidium Iodide, FM 1-43, and YO-PRO-1 fluorescent dyes in CHO-K1 cells was monitored across a wide range of PRRs (5 Hz-500 KHz) using a laser-scanning confocal microscope in order to better understand how high frequency repetition rates impact induced biophysical changes.

Evaluation of the Genetic Response of U937 and Jurkat Cells to 10-Nanosecond Electrical Pulses (nsEP).

Nanosecond electrical pulse (nsEP) exposure activates signaling pathways, produces oxidative stress, stimulates hormone secretion, causes cell swelling and induces apoptotic and necrotic death. The underlying biophysical connection(s) between these diverse cellular reactions and nsEP has yet to be elucidated. Using global genetic analysis, we evaluated how two commonly studied cell types, U937 and Jurkat, respond to nsEP exposure.

Permeabilization of the nuclear envelope following nanosecond pulsed electric field exposure.

Permeabilization of cell membranes occurs upon exposure to a threshold absorbed dose (AD) of nanosecond pulsed electric fields (nsPEF). The ultimate, physiological bioeffect of this exposure depends on the type of cultured cell and environment, indicating that cell-specific pathways and structures are stimulated. Here we investigate 10 and 600 ns duration PEF effects on Chinese hamster ovary (CHO) cell nuclei, where our hypothesis is that pulse disruption of the nuclear envelope membrane leads to observed cell death and decreased viability 24 h post-exposure.

Plasma membrane nanoporation as a possible mechanism behind infrared excitation of cells.

Objective: Short infrared (IR) laser pulses have been used to stimulate action potentials in neurons both in vivo and in vitro. However, the mechanism(s) underlying this phenomenon has remained elusive. In vitro studies have found that pulsed IR exposure generates a nearly instant change in capacitance in the plasma membrane, characterized by inward rectification, a common feature in pore-forming exposures, such as electrical pulses and acoustic shock waves.

Disruption of the actin cortex contributes to susceptibility of mammalian cells to nanosecond pulsed electric fields.

Nanosecond pulsed electric fields (nsPEFs) perturb membranes of cultured mammalian cells in a dose-dependent manner with different types of cells exhibiting characteristic survivability. Adherent cells appear more robust than non-adherent cells during whole-cell exposure. We hypothesize that cellular elasticity based upon the actin cytoskeleton is a contributing parameter, and the alteration of a cell's actin cortex will significantly affect viability upon nsPEF exposure.

600 ns pulse electric field-induced phosphatidylinositol4,5-bisphosphate depletion.

The interaction between nsPEF-induced Ca(2+) release and nsPEF-induced phosphatidylinositol4,5-bisphosphate (PIP2) hydrolysis is not well understood. To better understand this interrelation we monitored intracellular calcium changes, in cells loaded with Calcium Green-1 AM, and generation of PIP2 hydrolysis byproducts (inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG)) in cells transfected with one of two fluorescent reporter genes: PLCδ-PH-EGFP or GFP-C1-PKCγ-C1a. The percentage fluorescence differences (ΔF %) after exposures were determined.

Oxygen consumption during oxygenated hypothermic perfusion as a measure of donor organ viability.

Hypothermic machine perfusion (HMP) for the preservation of kidneys, recovered from extended criteria organ donors (ECDs), presents the opportunity for assessing ex vivo parameters that may have value in predicting postimplantation organ viability. Organ perfusion and vascular resistance are the parameters most frequently cited as the basis for the decision to use or discard a donor kidney. The limitation of these measures is emphasized by the observation that a significant percentage of ECD kidneys with poor perfusion parameters can provide life-sustaining function after transplantation.

Activation of intracellular phosphoinositide signaling after a single 600 nanosecond electric pulse.

Exposure to nanosecond pulsed electrical fields (nsPEFs) results in a myriad of observable effects in mammalian cells. While these effects are often attributed to the direct permeabilization of both the plasma and organelle membranes, the underlying mechanism(s) are not well understood. We hypothesize that nsPEF-induced membrane disturbance will initiate complex intracellular lipid signaling pathways, which ultimately lead to the observed multifarious effects.

Nanosecond pulsed electric field thresholds for nanopore formation in neural cells.

The persistent influx of ions through nanopores created upon cellular exposure to nanosecond pulse electric fields (nsPEF) could be used to modulate neuronal function. One ion, calcium (Ca(2+)), is important to action potential firing and regulates many ion channels. However, uncontrolled hyper-excitability of neurons leads to Ca(2+) overload and neurodegeneration.

Potential mechanisms of sudden unexpected death in epilepsy.

Sudden unexpected death in epilepsy (SUDEP) accounts for 15% of all deaths in people with epilepsy and 50% in refractory epilepsy. The underlying mechanisms are not well understood, but seizure-induced cardiac and respiratory arrests are involved. The cardiovascular and respiratory systems are subject to precise reflex regulation to ensure appropriate oxygen supply under a wide range of circumstances.

Resolving the spatial kinetics of electric pulse-induced ion release.

Exposure of cells to nanosecond pulsed electric fields (nsPEF) causes a rapid increase in intracellular calcium. The mechanism(s) responsible for this calcium burst remains unknown, but is hypothesized to be from direct influx through nanopores, the activation of specific ion channels, or direct disruption of organelles. It is likely, however, that several mechanisms are involved/activated, thereby resulting in a complex chain of events that are difficult to separate by slow imaging methods.

Chronic Cellular Hyperexcitability in Elderly Epileptic Rats with Spontaneous Seizures Induced by Kainic Acid Status Epilepticus while Young Adults.

Emerging data indicate that age-related brain changes alter seizure susceptibility, seizure-associated neurodegeneration, and responsiveness to AEDs. The present study assessed long-term animal survival in the Kainic Acid (KA) model along with in-vivo spontaneous seizure frequency, cellular hyperexcitability in CA1 in-vitro and in-vivo in subiculum, and responsiveness of in-vitro CA1 hyperexcitability to topiramate. Sprague-Dawley male rats were given KA to induce convulsive status epilepticus (KA-SE) at 2-3 months of age.

Novel portable hypothermic pulsatile perfusion preservation technology: Improved viability and function of rodent and canine kidneys.

Background: A reliable, portable, cost effective device for perfusion preservation of donor organs remains elusive. A portable, organ perfusion device design for hypothermic, machine perfusion (HMP) that successfully supported rodent kidneys for 24 hours was evaluated in canine kidneys.

Material/methods: Freshly recovered rodent and canine kidneys were subjected to 24 hours of HMP or static storage (SS).

Determinants within the turret and pore-loop domains of KCNQ3 K+ channels governing functional activity.

KCNQ1-5 (Kv7.1-7.5) subunits assemble to form a variety of functional K(+) channels in the nervous system, heart, and epithelia.

Regulation of neural KCNQ channels: signalling pathways, structural motifs and functional implications.

Neural M-type (KCNQ/Kv7) K(+) channels control somatic excitability, bursting and neurotransmitter release throughout the nervous system. Their activity is regulated by multiple signalling pathways. In superior cervical ganglion sympathetic neurons, muscarinic M(1), angiotensin II AT(1), bradykinin B(2) and purinergic P2Y agonists suppress M current (I(M)).

Inositol triphosphate-mediated Ca2+ signals direct purinergic P2Y receptor regulation of neuronal ion channels.

Purinergic P2Y receptors are one of four types of G(q/11)-coupled receptors in rat superior cervical ganglia (SCG) sympathetic neurons. In cultured SCG neurons, purinergic and bradykinin suppression of I(M) were similar in magnitude and somewhat less than that by muscarinic agonists. The effects of the P2Y receptor agonist UTP on neuronal excitability and discharge properties were studied.

Voltage-dependent calcium currents are enhanced in nucleus of the solitary tract neurons isolated from renal wrap hypertensive rats.

The nucleus of the solitary tract (NTS) is the central site of termination of baroreceptor afferents. We hypothesize that changes occur in voltage-gated calcium channels (VGCCs) within NTS neurons as a consequence of hypertension. Whole-cell patch-clamp recordings were obtained from adult normotensive (109+/-2 mm Hg; n=6 from 6 sham-operated and 31 nonsurgically treated) and hypertensive (158+/-6 mm Hg; n=24) rats.