Potential Mechanism For Generation Research Articles

GHK eq. and HH eq. for a real system is mathematically associable to each other but their physiological interpretation needs a reconsideration

Despite the long and broad acceptance of the Goldman - Hodgkin - Katz equation (GHK eq.) and the Hodgkin - Huxley equation (HH eq.) as strong tools for the quantitative analysis of the membrane potential behavior, for a long time they have been utilized as separate concepts. That is the GHK eq. and the HH eq. have not been associated with each other mathematically. In this paper, an attempt to associate these equations to each other mathematically was demonstrated and was successful by viewing the system in question as a thermodynamically real system rather than an ideal system. For achieving that, two fundamental physical chemistry concepts, the mass action law, and the Boltzmann distribution were employed. Hence, this paper’s achievement is completely within the framework of common thermodynamics. Through this work, the origin of the membrane potential generation attributed to the ion adsorption-desorption process and governed by the mass action law and the Boltzmann distribution is expressed to be plausible, whereas the existing membrane potential generation mechanism states that membrane potential is generated by transmembrane ion transport. As at this moment, this work does not intend to deny the transmembrane ion transport as a membrane potential generation mechanism but urges the readers to reconsider its validity, since this work suggests that the ion adsorption-desorption mechanism is as plausible as the transmembrane ion transport mechanism as a cause of membrane potential generation.

Interpretation of Action Potential Generation Mechanism in Cardiomyocytes by Potassium Channel "Origami Windmill" Model

Interpretation of Action Potential Generation Mechanism in Cardiomyocytes by Potassium Channel "Origami Windmill" Model

Spontaneous random potential spike induction across a nonliving separator intervening two aqueous solutions and the implication of its physiological meaning

Membrane theory attributes the cause of action potential generation to the ion transport across the plasma membrane. It even states that the action potential generation is a unique phenomenon in the living cell. There have been some reports that the action potential-like potential spike is induced even in the nonliving system. Ling’s adsorption theory (LA theory) is a typical opposing concept to the membrane theory. The LA theory attributes the action potential generation mechanism to the ion adsorption-desorption process. The authors examined the LA theory and found that the membrane theory has a limitation. By contrast, the LA theory is in line with the experimental results. Therefore, it might be necessary to take into consideration the ion adsorption-desorption effect at least as a part of the action potential generation mechanism.

The biosensing with NV centers in diamond: Related challenges

Here, we discussed the current challenges related with the application of Nitrogen-vacancy (NV)-based magnetometers for biological systems. Major constraints for diamond sensor type as optical illumination, microwave field, bias magnetic field, optics, method of photoluminescence detection and sample preparation have been analyzed. Special attention was paid to the estimation of electromagnetic fields in the nervous system. The mechanism of action potential generation and resultant local current flows was discussed, corresponding magnetic field outside an axon was estimated. It was shown that sensitivity of upcoming generation of NV magnetic field sensors may not be enough for the measurement of single neuron action potential, while monitoring electromagnetic signals in brain slices or cardiac tissues seems very promising.

A compartmentalized mathematical model of mouse atrial myocytes.

Various experimental mouse models are extensively used to research human diseases, including atrial fibrillation, the most common cardiac rhythm disorder. Despite this, there are no comprehensive mathematical models that describe the complex behavior of the action potential and [Ca2+]i transients in mouse atrial myocytes. Here, we develop a novel compartmentalized mathematical model of mouse atrial myocytes that combines the action potential, [Ca2+]i dynamics, and β-adrenergic signaling cascade for a subpopulation of right atrial myocytes with developed transverse-axial tubule system. The model consists of three compartments related to β-adrenergic signaling (caveolae, extracaveolae, and cytosol) and employs local control of Ca2+ release. It also simulates ionic mechanisms of action potential generation and describes atrial-specific Ca2+ handling as well as frequency dependences of the action potential and [Ca2+]i transients. The model showed that the T-type Ca2+ current significantly affects the later stage of the action potential, with little effect on [Ca2+]i transients. The block of the small-conductance Ca2+-activated K+ current leads to a prolongation of the action potential at high intracellular Ca2+. Simulation results obtained from the atrial model cells were compared with those from ventricular myocytes. The developed model represents a useful tool to study complex electrical properties in the mouse atria and could be applied to enhance the understanding of atrial physiology and arrhythmogenesis.NEW & NOTEWORTHY A new compartmentalized mathematical model of mouse right atrial myocytes was developed. The model simulated action potential and Ca2+ dynamics at baseline and after stimulation of the β-adrenergic signaling system. Simulations showed that the T-type Ca2+ current markedly prolonged the later stage of atrial action potential repolarization, with a minor effect on [Ca2+]i transients. The small-conductance Ca2+-activated K+ current block resulted in prolongation of the action potential only at the relatively high intracellular Ca2+.

High ice concentration observed in tropical maritime stratiform mixed-phase clouds with top temperatures warmer than −8 °C

Abstract In this study, airborne in situ measurements of ice concentrations in mixed-phase clouds over the tropical ocean sampled during the Ice in Clouds Experiment (ICE-T) project are analyzed. High concentrations of ice larger than 250 μm in diameter (0.05–10 L−1) were observed in three shallow stratiform clouds whose top temperatures were warmer than −8 °C. The observed ice particles were mostly needles and columns, which are preferred ice crystal shapes between −3 °C and − 8 °C. Drizzle size drops (>100 μm in diameter) were also observed. Biological particles are a potential source of ice nucleating particles (INPs), however, any direct connection to the high ice concentrations observed in the stratiform clouds at temperatures warmer than −8 °C could not be shown, because the observed INP concentrations were 3 orders of magnitude lower than the ice concentrations. Simulations using a parcel model suggest that secondary ice mechanisms, such as the Hallett-Mossop process and fragmentation of freezing drops, which were often assumed previously to be the explanation for observed high ice concentration, cannot fully explain the observed high ice concentration in these shallow stratiform clouds either. The Hallett-Mossop process and fragmentation of freezing drops are important to the strong ice production only in clouds with relatively high concentration of large drops and rimed graupel observed, such as convective clouds. Therefore, other potential ice generation mechanisms, such as droplet collisional freezing and pre-activated INPs, which are still poorly understood, could play significant roles in tropical stratiform and convective mixed-phase clouds.

Preparation of dissociated mouse primary neuronal cultures from long-term cryopreserved brain tissue

BackgroundDissociated primary neuronal cultures are widely used as a model system to investigate the cellular and molecular properties of diverse neuronal populations and mechanisms of action potential generation and synaptic transmission. Typically, rodent primary neuronal cultures are obtained from freshly-dissociated embryonic or postnatal brain tissue, which often requires intense animal husbandry. This can strain resources when working with genetically modified mice. New methodHere we describe an experimental protocol for frozen storage of mouse hippocampi, which allows fully functional dissociated primary neuronal cultures to be prepared from cryopreserved tissue. ResultsWe show that thawed hippocampal neurons have functional properties similar to those of freshly dissociated neurons, including neuronal morphology, excitability, action potential waveform and synaptic neurotransmitter release, even after cryopreservation for several years. Comparison to the existing methodsIn contrast to the existing methods, the protocol described here allows for efficient long-term storage of samples, allowing researchers to perform functional experiments on neuronal cultures from brain tissue collected in other laboratories. ConclusionsWe anticipate that this method will facilitate collaborations among laboratories based at distant locations and will thus optimise the use of genetically modified mouse models, in line with the 3Rs (Replacement, Reduction and Refinement) recommended for scientific use of animals in research.

P2559The mechanisms of spontaneous action potential generation in sinoauricular valve of the chick embryos

Abstract Background The changes in the density of ion channels and/or damage of ion channel proteins violates the homeostasis of the potential forming ions in myocardium cells and may contribute to arrhythmogenesis. The study of ion channel function in embryos is important in order to understand the mechanisms of arrhythmia. The purpose of the present study was to identify the key ion channels that form action potentials (APs) in pacemaker cells in the area of the sinoauricular (SA) chicken embryo valve. Material and methods The embryos were removed from fertilized White Leghorn breed chicken eggs on the 10±1 day of incubation (ED10). The experiments were performed on freshly prepared strips (3 mm × 2 mm) of the right atrium, which included the left SA valve itself as well as the surrounding tissue. After that the APs were recorded from the area of left SA valve using the microelectrode technique. The functional analysis of ion channels was performed using the specific ion channel blockers. Results The strips generated APs with slow diastolic depolarization (SDD) and frequency from 132 to 251 impulses per min (ipm) (average - 177±22 ipm). The APs amplitude and dV/dtmax were 102±9 mV and 98±25 V/s (nstrips=49). At the third minute of exposure to E-4031 (1 μmol), a blocker of rapid outward K-current channels, IKr, the increase in the duration of the AP repolarization phase by 30% and the shortening of SDD by 20–25% (p<0.05; n=6) were registered. The APs generation frequency increased by 10%. Subsequently we observed the monotonic decrease in the AP amplitude due to the reduced overshoot and depolarized Emax. The electrical activity of all strips was blocked on the 20±2 min (Fig.1.a-c). Lidocaine (500 μmol), a blocker of Nav1.5 channels, increased a duration of SDD and APD90 twice, but decreased dV/dtmax by 2.5 times. The APs generation frequency decreased by 30% in comparison to the control. After 8±2 min exposure to lidocaine, the APs generation was blocked in 56% of samples. It is important to mention that in these strips right before the APs generation was blocked dV/dtmax was 30±15 V/s. In the samples, where the APs were not blocked after the exposure to lidocaine this parameter was 14±10 V/s (Fig. 1d-e). Nifedipine (10 μmol), a blocker of L-type Ca2+-channels, decreased APD90 by 56% and SDD by 25%. The APs generation frequency increased twice in comparison to the control samples (fig.1f-h). The chronotropic effects of nifedipine were dose-dependent. Nifedipine did not induce the blocking of APs generation. Figure 1. Effects of E-4031 (a-c), lidocaine (d-e) and nifedipine (e-g) on APs. Conclusions The received data demonstrate that the key role in the APs formation in ED10 embryos belong to the outward IKr and inward INa, but not to ICa,L. Thus, the mechanisms of spontaneous action potential generation in ED10 chick embryos have more in common with that in human iPSC-derived cardiomyocytes rather than in SA area cells of the ED11 mice embryos. Acknowledgement/Funding Rus fund Basic Research No. 18-34-00654; Project RAS No. 0415-2019-0006 and No. AAAA-A17-117012310152-2

Interpretation of Action Potential Generation Mechanism in Cells by Potassium Channel "Origami Windmill" Model

Interpretation of Action Potential Generation Mechanism in Cells by Potassium Channel "Origami Windmill" Model

Chlorophyll Rings around Ocean Eddies in the North Pacific

Chlorophyll rings (CRs) are defined as elevated chlorophyll along eddy peripheries and have been observed in anticyclonic oceanic eddies occasionally. This study presents observations of CRs around both anticyclonic and cyclonic eddies from a large observational data set. An innovative algorithm is developed to identify CRs from satellite observations of sea level anomalies and near-surface chlorophyll concentration in the North Pacific Ocean between 2003 and 2010. The results show that only 1% of mesoscale eddies are associated with CRs, which implies the CRs are not ubiquitous. We propose two potential generation mechanisms for CRs: horizontal advection and wind-current interaction. The former dominates the formation of about two-thirds of the CRs. The CRs associated with both cyclones and anticyclones represents an important contribution to better understanding of mesoscale physical/biological coupled phenomena.

Mathematical expression of membrane potential based on Ling's adsorption theory is approximately the same as the Goldman-Hodgkin-Katz equation.

The Goldman-Hodgkin-Katz equation (GHK equation), one of the most successful achievements of membrane theory in electrophysiology, can precisely predict the membrane potential. Its conceptual foundation lies in the idea that the transmembrane ion transport across the plasma membrane is responsible for the membrane potential generation. However, the potential virtually equivalent to the membrane potential is generated even across the impermeable membrane. In this work, I discus the membrane potential generation mechanism and find that the potential formula based on the long-dismissed Ling's adsorption theory, which attributes the membrane potential generation to the mobile ion adsorption rather than the transmembrane ion transport, is the same as the GHK equation. Based on this finding, I derive a conclusion that the membrane potential is generated by the ion adsorption against the existing electrophysiological concept.

Another interpretation of the Goldman-Hodgkin-Katz equation based on Ling's adsorption theory.

According to standard membrane theory, the generation of membrane potential is attributed to transmembrane ion transport. However, there have been a number of reports of membrane behavior in conflict with the membrane theory of cellular potential. Putting aside the membrane theory, we scrutinized the generation mechanism of membrane potential from the view of the long-dismissed adsorption theory of Ling. Ling's adsorption theory attributes the membrane potential generation to mobile ion adsorption. Although Ling's adsorption theory conflicts with the broadly accepted membrane theory, we found that it well reproduces experimentally observed membrane potential behavior. Our theoretical analysis finds that the potential formula based on the GHK eq., which is a fundamental concept of membrane theory, coincides with the potential formula based on Ling's adsorption theory. Reinterpreting the permeability coefficient in the GHK eq. as the association constant between the mobile ion and adsorption site, the GHK eq. turns into the potential formula from Ling's adsorption theory. We conclude that the membrane potential is generated by ion adsorption as Ling's adsorption theory states and that the membrane theory of cellular potential should be amended even if not discarded.

Generation of Lower Harmonic Magnetosonic Waves Through Nonlinear Wave‐Wave Interactions

AbstractAlthough magnetosonic waves in the Earth's magnetosphere have been well understood by the linear theory, low harmonic magnetosonic waves, which often lack of free energy, can be unusually present. By employing a 1‐D particle‐in‐cell simulation model, we have investigated the generation of those unusual lower harmonic magnetosonic waves in a plasma containing a proton ring distribution. In our simulation, the higher harmonic magnetosonic waves (from~9Ωh to ~12Ωh) are firstly excited due to the unstable proton ring, which can be well explained by the linear theory. Several lower harmonic magnetosonic waves (below 5Ωh), which well separates away from the higher harmonics, soon appear in the system. Those lower harmonics, which do not have any positive linear growth rates, can be generated by a nonlinear mechanism. The bicoherence analysis demonstrates that there is a strong phase coupling among the unusual lower harmonic magnetosonic waves and the magnetosonic waves generated due to the proton ring, supporting the idea that the lower harmonic waves could be driven by the wave‐wave couplings of the generated magnetosonic waves. This wave‐wave coupling generation mechanism is further confirmed by another two simulations, where two or three pump magnetosonic waves are initially injected. The lower‐frequency waves, that is, the fundamental wave and its second harmonic, are also successfully reproduced due to the nonlinear coupling of pump magnetosonic waves. Our simulations not only propose a potential generation mechanism of unusual lower harmonic magnetosonic waves in the Earth's magnetosphere, but also give some new insights on the evolution of magnetosonic spectra.

Lévy foraging patterns of rural humans.

Movement patterns resembling Lévy walks, often attributed to the execution of an advantageous probabilistic searching strategy, are found in a wide variety of organisms, from cells to human hunter-gatherers. It has been suggested that such movement patterns may be fundamental to how humans interact and experience the world and that they may have arisen early in our genus with the evolution of a hunting and gathering lifestyle. Here we show that Lévy walks are evident in the Me’Phaa of Mexico, in Brazilian Cariri farmers and in Amazonian farmers when gathering firewood, wild fruit and nuts. Around 50% of the search patterns resemble Lévy walks and these are characterized by Lévy exponents close to 1.7. The other search patterns more closely resemble bi-phasic walks. We suggest potential generative mechanisms for the occurrence of these ubiquitous Lévy walks which can be used to guide future studies on human mobility. We show that frequent excursions and meanderings from pre-existing trails can account for our observations.

Migration of Interneuron Precursors in the Nascent Cerebellar Cortex.

The cerebellum arguably constitutes one of the best characterized central nervous circuits, and its structure, cellular function, and histogenesis have been described in exceptional quantitative detail. A notable exception to this is the development of its inhibitory interneurons, and in particular the extensive migrations of future basket and stellate cells. Here, we used acute slices from 8-day-old mice to assess the migration of Pax2-EGFP-tagged precursors of these cells en route to the molecular layer during their transit through the nascent cerebellar cortex. We document that movement of these cells is highly directed. Their speed and directional persistence are larger in the nascent granule cell layer than in the molecular layer. And they migrate periodically, with periods of effective, directed translocation separated by bouts of rather local movement. Finally, we document that the arrangement of these cells in the adult molecular layer is characterized by clustering. These data are discussed with a focus on potential generative mechanisms for the developmental pattern observed.

Wind farm noises: Mechanisms and evidence for their dependency on wind direction

The mechanisms responsible for swishing and thumping noises generated by wind turbines are unclear and the existence of which have significantly affected the perception of wind energy by the community. To better understand the nature of this noise source, this study, for the first time, investigates the correlation between the potential noise generation mechanisms in wind farms and the characteristics of the perceived noise reported by residents in the vicinity of the farms in survey data. Published reports and measurements show that in addition to the perceived noise near the turbines, the thumping noise, in general, is perceived far downstream of the turbines. Normal swish perceived in a short distance from a wind turbine, especially in the cross-wind directions, can be explained by the convective amplification and directivity of the trailing edge noise. As will be discussed in this article, there exists strong evidence that the dominant mechanism of wind farm noise is associated with amplitude modulation of the aerodynamic noise by the eddies generated when the turbine blade partially stalls or due to an interaction with the turbine wake. This hypothesis is primarily based on the low frequency characteristics of the stall and also the distance and direction of the noise propagation. Moreover, it is hypothesised that the wake supplements this effect as it results in refraction and modulation of the emitted noise.

Pharmacological analysis of the transmembrane action potential configuration in myoepithelial cells of the spontaneously beating heart of the ascidian Styela rustica in vitro.

The mechanisms of action potential (AP) generation in the myoepithelial cells of the tunicate heart are not yet well understood. Here, an attempt was made to elucidate these mechanisms by analyzing the effects of specific blockers of K+, Na+ and Ca2+ currents on the configuration of transmembrane APs and their frequency in the spontaneously beating ascidian heart. In addition, an immunocytochemical analysis of heart myoepithelial cells was performed. Staining with anti-FMRF-amide and anti-tubulin antibodies did not reveal any nerve elements within the heart tube. Treatment with 1 mmol l-1 TEA (IK blocker) resulted in depolarization of heart cell sarcolemma by 10 mV, and inhibition of APs generation was recorded after 3 min of exposure. Prior to this moment, the frequency of AP generation in a burst decreased from 16-18 to 2beatsmin-1 owing to prolongation of the diastole. After application of ivabradine (3 or 10 µmoll-1), the spontaneous APs generation frequency decreased by 24%. Based on these results and published data, it is concluded that the key role in the automaticity of the ascidian heart is played by the outward K+ currents, Na+ currents, activated hyperpolarization current If and a current of unknown nature IX.

Excitation-induced Delayed Onset of Epileptic Poly-spike and Wave Discharges

In this paper we employ an improved thalamo-cortical model to uncover the potential generation mechanisms of pS-WD patterns by means of bursting oscillation's analysis approaches in the process of seizures generation at both fast and slow timescales. Interestingly, it is found that the onset of epileptic discharges can be delayed as an increase of excitatory regulating function of the thalamic relay neuronal population on cortical PY. The obtained numerical results show that the initiation of absence seizures arises from the thalamus and the termination of them in the cortex.

Observational evidence of generation mechanisms for very oblique lower band chorus using THEMIS waveform data

AbstractChorus waves are intense coherent whistler mode waves with frequency chirping which play a dual role in both loss and acceleration of radiation belt electrons in the Earth's magnetosphere. Although the generation of parallel chorus waves has been extensively studied by means of theory, simulations, and observations, the generation mechanism of very oblique chorus waves still remains a mystery. In this study, we have analyzed hundreds of very oblique discrete (rising or falling tone) lower band chorus events collected from 7 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) waveform data to investigate their potential generation mechanisms. Comparisons between wave normal angles directly measured onboard THEMIS in the dawn‐day sector at L = 5–9 and inferred from theoretical models on the basis of measured wave characteristics (frequency sweep rate, mean frequency, and amplitude) show that these very oblique waves are more commonly generated through cyclotron resonance with anisotropic electron streams. However, a second generation mechanism via Landau resonance with low‐energy electron beams seems to be also operating on the nightside at L < 6.7 and at all local times at L > 8.5. Moreover, very oblique lower band chorus waves with large frequency chirping rates or small magnetic field amplitudes are more likely excited via cyclotron resonance, while waves with small frequency chirping rates or large magnetic field amplitudes are preferentially generated through Landau resonance. This comprehensive statistical study provides interesting insight into the possible generation mechanisms of very oblique lower band chorus waves in the Earth's magnetosphere.

3D inversion of irregular gridded 2D electrical resistivity tomography lines: Application to sinkhole mapping at the Island of Corfu (West Greece)

ABSTRACTWe study the case of the combined interpretation of irregularly gridded 2D electrical resistivity tomography lines. A 3D inversion algorithm was specially modified to accommodate the full 3D processing of such lines. The chosen approach uses a dense structured mesh and a flexible parameter design scheme. Tests with synthetic data show that full 3D inversion results are significantly improved when compared with the equivalent quasi‐3D imaging of the 2D inversion results. It is also shown that 3D inversion results can provide correct location and shape information about targets that are not directly located under the measured lines. The scheme was tested with real data from a site in the northern part of the Corfu Island (West Greece) where a large number of irregular gridded 2D electrical resistivity tomography lines were collected in order to map sinkholes related to gypsum. The 3D inverted images provide important information about the structure of the existing sinkholes and the potential sinkhole generation mechanism. Overall, the possibility of 3D interpretation of irregularly gridded lines is not only important for obtaining better subsurface images but also allows a more flexible and practical design of electrical resistivity tomography field surveys.