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Journal of Visualized Experiments : JoVE Jul 2022Ex vivo preparations enable the study of many neurophysiological processes in isolation from the rest of the body while preserving local tissue structure. This work...
Ex vivo preparations enable the study of many neurophysiological processes in isolation from the rest of the body while preserving local tissue structure. This work describes the preparation of rat sciatic nerves for ex vivo neurophysiology, including buffer preparation, animal procedures, equipment setup and neurophysiological recording. This work provides an overview of the different types of experiments possible with this method. The outlined method aims to provide 6 h of stimulation and recording on extracted peripheral nerve tissue in tightly controlled conditions for optimal consistency in results. Results obtained using this method are A-fibre compound action potentials (CAP) with peak-to-peak amplitudes in the millivolt range over the entire duration of the experiment. CAP amplitudes and shapes are consistent and reliable, making them useful to test and compare new electrodes to existing models, or the effects of interventions on the tissue, such as the use of chemicals, surgical alterations, or neuromodulatory stimulation techniques. Both conventional commercially available cuff electrodes with platinum-iridium contacts and custom-made conductive elastomer electrodes were tested and gave similar results in terms of nerve stimulus strength-duration response.
Topics: Action Potentials; Animals; Electric Conductivity; Electric Stimulation; Electrodes; Neurophysiology; Rats; Sciatic Nerve
PubMed: 35913135
DOI: 10.3791/63838 -
Methods in Molecular Biology (Clifton,... 2022The mitochondrial membrane potential (ΔψM) is the major component of the bioenergetic driving force responsible for most cellular ATP produced, and it controls a host...
The mitochondrial membrane potential (ΔψM) is the major component of the bioenergetic driving force responsible for most cellular ATP produced, and it controls a host of biological processes. In intact cells, assay readouts with commonly used fluorescence ΔψM probes are distorted by factors other than ΔψM. Here, we describe a protocol to calculate both ΔψM and plasma membrane potential (ΔψP) in absolute millivolts in intact single cells, or in populations of adherent, cultured cells. Our approach generates unbiased data that allows comparison of ΔψM between cell types with different geometry and ΔψP, and to follow ΔψM in time when ΔψP fluctuates. The experimental paradigm results in fluorescence microscopy time courses using a pair of cationic and anionic probes with internal calibration points that are subsequently computationally converted to millivolts on an absolute scale. The assay is compatible with wide field, confocal or two-photon microscopy. The method given here is optimized for a multiplexed, partial 96-well microplate format to record ΔψP and ΔψM responses for three consecutive treatment additions.
Topics: Cells, Cultured; Fluorescent Dyes; Membrane Potential, Mitochondrial; Microscopy, Fluorescence; Mitochondria
PubMed: 35771433
DOI: 10.1007/978-1-0716-2309-1_2 -
Proceedings of the National Academy of... Aug 2019Current approaches for electric power generation from nanoscale conducting or semiconducting layers in contact with moving aqueous droplets are promising as they show...
Current approaches for electric power generation from nanoscale conducting or semiconducting layers in contact with moving aqueous droplets are promising as they show efficiencies of around 30%, yet even the most successful ones pose challenges regarding fabrication and scaling. Here, we report stable, all-inorganic single-element structures synthesized in a single step that generate electrical current when alternating salinity gradients flow along its surface in a liquid flow cell. Nanolayers of iron, vanadium, or nickel, 10 to 30 nm thin, produce open-circuit potentials of several tens of millivolt and current densities of several microA cm at aqueous flow velocities of just a few cm s The principle of operation is strongly sensitive to charge-carrier motion in the thermal oxide nanooverlayer that forms spontaneously in air and then self-terminates. Indeed, experiments suggest a role for intraoxide electron transfer for Fe, V, and Ni nanolayers, as their thermal oxides contain several metal-oxidation states, whereas controls using Al or Cr nanolayers, which self-terminate with oxides that are redox inactive under the experimental conditions, exhibit dramatically diminished performance. The nanolayers are shown to generate electrical current in various modes of application with moving liquids, including sliding liquid droplets, salinity gradients in a flowing liquid, and in the oscillatory motion of a liquid without a salinity gradient.
PubMed: 31358629
DOI: 10.1073/pnas.1906601116 -
Hearing Research Nov 2013This review is concerned with how communication calls are processed and represented by populations of neurons in both the inferior colliculus (IC), the auditory midbrain... (Review)
Review
This review is concerned with how communication calls are processed and represented by populations of neurons in both the inferior colliculus (IC), the auditory midbrain nucleus, and the dorsal nucleus of the lateral lemniscus (DNLL), the nucleus just caudal to the IC. The review has five sections where focus in each section is on inhibition and its role in shaping response selectivity for communication calls. In the first section, the lack of response selectivity for calls in DNLL neurons is presented and discusses why inhibition plays virtually no role in shaping selectivity. In the second section, the lack of selectivity in the DNLL is contrasted with the high degree of response selectivity in the IC. The third section then reviews how inhibition in the IC shapes response selectivities for calls, and how those selectivities can create a population response with a distinctive response profile to a particular call, which differs from the population profile evoked by any other call. The fourth section is concerned with the specifics of inhibition in the IC, and how the interaction of excitation and inhibition creates directional selectivities for frequency modulations, one of the principal acoustic features of communication signals. The two major hypotheses for directional selectivity are presented. One is the timing hypothesis, which holds that the precise timing of excitation relative to inhibition is the feature that shapes directionality. The other hypothesis is that the relative magnitudes of excitation and inhibition are the dominant features that shape directionality, where timing is relatively unimportant. The final section then turns to the role of serotonin, a neuromodulator that can markedly change responses to calls in the IC. Serotonin provides a linkage between behavioral states and processing. This linkage is discussed in the final section together with the hypothesis that serotonin acts to enhances the contrast in the population responses to various calls over and above the distinctive population responses that were created by inhibition. This article is part of a Special Issue entitled "Communication Sounds and the Brain: New Directions and Perspectives".
Topics: Acoustic Stimulation; Animals; Auditory Pathways; Brain Stem; Evoked Potentials, Auditory, Brain Stem; Inferior Colliculi; Neural Inhibition; Pattern Recognition, Physiological; Reaction Time; Serotonin; Species Specificity; Synaptic Transmission; Time Factors; Vocalization, Animal
PubMed: 23545427
DOI: 10.1016/j.heares.2013.03.001 -
Journal of Electrocardiology 2014In a patient with chest pain and suspected acute coronary syndrome, the electrocardiogram (ECG) is the only readily available diagnostic tool. It is important to... (Review)
Review
In a patient with chest pain and suspected acute coronary syndrome, the electrocardiogram (ECG) is the only readily available diagnostic tool. It is important to maximize its usefulness to detect acute myocardial ischemia that may evolve to myocardial infarction unless the patient is treated expediently with reperfusion therapy. Since diagnostic guidelines have usually included only ST-elevation myocardial infarction (STEMI) as the entity that should be diagnosed and treated urgently, a patient with coronary occlusion represented on ECG as ST depression is likely not to be considered a candidate for receiving immediate coronary angiography and coronary intervention. ECG criteria for STEMI detection require that ST elevation meet predetermined millivolt thresholds and appear in at least two spatially contiguous ECG leads. The typical ECG reader recognizes only three contiguous pairs: aVL and I; II and aVF; aVF and III. However, viewing the "orderly sequenced" 12-lead ECG display, two more contiguous pairs become obvious in the frontal plane: +I and -aVR; -aVR and +II. The 24-lead ECG is a display of the standard 12-lead ECG as both the classical positive leads and their negative (inverted) counterparts. Leads +V1, +V2, +V3, +V4, +V5, and +V6 and their inverted counterparts are used to generate a "clock-face display" for the transverse plane. Similarly, +aVL, +I, -aVR, +II, +aVF, +III in the frontal plane and their inverted counterparts are used to generate a clock-face display for the frontal plane. Optimum results, 78% sensitivity and 93% specificity, were obtained using the following 19 ECG leads: frontal plane: +aVR, -III, +aVL, +I, -aVR, +II, +aVF, +III, -aVL; transverse plane: +V1, +V2, +V3, +V4, +V5, +V6, -V1, -V2, -V3.
Topics: Cardiology; Diagnosis, Computer-Assisted; Electrocardiography; Humans; Internationality; Myocardial Infarction; Pattern Recognition, Automated; Practice Guidelines as Topic; Reproducibility of Results; Sensitivity and Specificity
PubMed: 24880763
DOI: 10.1016/j.jelectrocard.2014.04.007 -
Nature Communications Oct 2021Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and...
Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and desirable stability for catalytic applications requires smart design of materials' structures. Herein, we report iridium metallene oxide: 1 T phase-iridium dioxide (IrO) by a synthetic strategy combining mechanochemistry and thermal treatment in a strong alkaline medium. This material demonstrates high activity for oxygen evolution reaction with a low overpotential of 197 millivolt in acidic electrolyte at 10 milliamperes per geometric square centimeter (mA cm). Together, it achieves high turnover frequencies of 4.2 s (3.0 s) at 1.50 V vs. reversible hydrogen electrode. Furthermore, 1T-IrO also shows little degradation after 126 hours chronopotentiometry measurement under the high current density of 250 mA cm in proton exchange membrane device. Theoretical calculations reveal that the active site of Ir in 1T-IrO provides an optimal free energy uphill in *OH formation, leading to the enhanced performance. The discovery of this 1T-metallene oxide material will provide new opportunities for catalysis and other applications.
PubMed: 34650084
DOI: 10.1038/s41467-021-26336-2 -
Science (New York, N.Y.) Jul 2018An efficient way to reduce the power consumption of electronic devices is to lower the supply voltage, but this voltage is restricted by the thermionic limit of...
An efficient way to reduce the power consumption of electronic devices is to lower the supply voltage, but this voltage is restricted by the thermionic limit of subthreshold swing (SS), 60 millivolts per decade, in field-effect transistors (FETs). We show that a graphene Dirac source (DS) with a much narrower electron density distribution around the Fermi level than that of conventional FETs can lower SS. A DS-FET with a carbon nanotube channel provided an average SS of 40 millivolts per decade over four decades of current at room temperature and high device current of up to 40 microamperes per micrometer at 60 millivolts per decade. When compared with state-of-the-art silicon 14-nanometer node FETs, a similar on-state current is realized but at a much lower supply voltage of 0.5 volts (versus 0.7 volts for silicon) and a much steeper SS below 35 millivolts per decade in the off-state.
PubMed: 29903885
DOI: 10.1126/science.aap9195 -
Science (New York, N.Y.) Jun 1967There is a maintained electrical potential of 15 to 40 millivolts across the two epithelial layers forming the body wall of Hydra, the inside of the animal being...
There is a maintained electrical potential of 15 to 40 millivolts across the two epithelial layers forming the body wall of Hydra, the inside of the animal being positive. Negativegoing (depolarizing) spikes are recorded spontaneously and sometimes in response to depolarizing current pulses. These spikes usually overshoot the zero potential level. The large size of the spikes and the orientation of the potential difference across the body wall indicate that this electrical activity is epithelial rather than nervous in origin.
Topics: Animals; Cnidaria; Electrophysiology; Epithelium; Membrane Potentials
PubMed: 4381624
DOI: 10.1126/science.156.3782.1629 -
Physiological Reviews Oct 1995Nonsynaptic interactions between neurons have been eclipsed by our increasingly detailed understanding of chemical synapses, but they do play significant roles in the... (Review)
Review
Nonsynaptic interactions between neurons have been eclipsed by our increasingly detailed understanding of chemical synapses, but they do play significant roles in the nervous system. This review considers four classes of nonsynaptic interaction, mainly in mammalian brain. 1) Electrotonic (and chemical) coupling through gap junctions has effects during development and under some, often pathological, conditions in the mature brain. 2) Ephaptic transmission is mediated by electrical coupling between specific neuronal elements in the absence of specialized contacts, notably in the cerebellum, and in axon tracts affected by demyelination. 3) Field effect interactions are mediated by large extracellular currents and potential fields generated by the hippocampus and other cortical structures. Both endogenous and applied electric fields alter neuronal excitability at field strengths over a few millivolts per millimeter. Weaker fields have more subtle effects, for instance, on axonal growth during development and repair and, more controversially, in behavioral responses to environmental fields. 4) There are fluctuations in extracellular ions such as K+, which are released during neuronal activity and which alter neuronal excitability. Field effects and ion fluctuations probably have modest effects during physiological activity but have a significant impact on epileptic seizures, and can sustain them in the absence of synaptic transmission.
Topics: Animals; Brain; Calcium; Electric Stimulation; Epilepsy; Evoked Potentials; Gap Junctions; Humans; Ions; Mammals; Neurons; Synapses; Synaptic Transmission; Vertebrates
PubMed: 7480159
DOI: 10.1152/physrev.1995.75.4.689 -
Frontiers in Bioscience (Landmark... Jan 2009A molecular film of pulmonary surfactant covers the hydrated lung epithelium to the air. We recently showed that the film exhibits a locally strongly variable electrical... (Review)
Review
A molecular film of pulmonary surfactant covers the hydrated lung epithelium to the air. We recently showed that the film exhibits a locally strongly variable electrical surface potential of up to several hundred millivolts. The potential arises from aligned molecular dipoles of the molecules. In the case of the complex structural organization of the phase-separated film of pulmonary surfactant, a map of the local surface potentials allows insight into the local distribution and order of its molecular constituents. Here, we summarize our recent findings and discuss how the electrical surface potential influences the architecture of the film but also changes the way how the lung interacts with the environment.
Topics: Electricity; Pulmonary Surfactants; Surface Properties
PubMed: 19273353
DOI: 10.2741/3531