Membrane Capacitance Research Articles

Pyridoxine Synergistically Potentiates Mast Cell-Stabilizing Property of Ascorbic Acid.

Besides their physiological properties, vitamins, such as vitamin C (ascorbic acid) and B6 (pyridoxine), ameliorate the symptoms of allergic disorders. Because exocytosis in mast cells can be detected electrophysiologically by the changes in the membrane capacitance (Cm), its continuous monitoring in the presence of these vitamins would determine their mast cell-stabilizing, anti-allergic properties. Employing the whole-cell patch-clamp technique in rat peritoneal mast cells, we examined the effects of ascorbic acid and pyridoxine on the degranulation of mast cells and the increase in the Cm during exocytosis. Both ascorbic acid and pyridoxine dose-dependently suppressed the GTP-γ-S-induced increase in the Cm and inhibited the degranulation from mast cells. Surprisingly enough, relatively low concentrations of pyridoxine (1, 2 mM) synergistically enhanced the suppressive effect of 2 mM ascorbic acid on mast cell degranulation. These results provided electrophysiological evidence for the first time that ascorbic acid and pyridoxine inhibited the process of exocytosis in a dose-dependent manner. At relatively lower concentrations, these vitamins were not enough to stabilize mast cells. However, such concentrations of pyridoxine synergistically potentiated the mast cell-stabilizing property of ascorbic acid.

Induced neural progenitor cells and iPS-neurons from major depressive disorder patients show altered bioenergetics and electrophysiological properties

The molecular pathomechanisms of major depressive disorder (MDD) are still not completely understood. Here, we follow the hypothesis, that mitochondria dysfunction which is inevitably associated with bioenergetic disbalance is a risk factor that contributes to the susceptibility of an individual to develop MDD. Thus, we investigated molecular mechanisms related to mitochondrial function in induced neuronal progenitor cells (NPCs) which were reprogrammed from fibroblasts of eight MDD patients and eight non-depressed controls. We found significantly lower maximal respiration rates, altered cytosolic basal calcium levels, and smaller soma size in NPCs derived from MDD patients. These findings are partially consistent with our earlier observations in MDD patient-derived fibroblasts. Furthermore, we differentiated MDD and control NPCs into iPS-neurons and analyzed their passive biophysical and active electrophysiological properties to investigate whether neuronal function can be related to altered mitochondrial activity and bioenergetics. Interestingly, MDD patient-derived iPS-neurons showed significantly lower membrane capacitance, a less hyperpolarized membrane potential, increased Na+ current density and increased spontaneous electrical activity. Our findings indicate that functional differences evident in fibroblasts derived from MDD patients are partially present after reprogramming to induced-NPCs, could relate to altered function of iPS-neurons and thus might be associated with the aetiology of major depressive disorder.

Measurement of dielectric properties of cells at single-cell resolution using electrorotation.

Dielectric properties of a cell are biophysical properties of high interest for various applications. However, measuring these properties accurately is not easy, which can be exemplified by the large variations in reported dielectric properties of the same cell types. This paper presents a method for measuring the dielectric properties of cells at high frequency, especially lipid-producing microalgae, at single-cell resolution, by integrating an electrorotation-based dielectric property measurement method with a negative dielectrophoretic (nDEP) force-based single-cell trapping method into a single device. In this method, a four-electrode nDEP structure was used to trap a single cell in an elevated position in the center of another four-electrode structure that can apply electrorotational force. By measuring the speed of cell rotation under different applied electrorotation frequencies and fitting the results into a theoretical core-shell cell model, the dielectric properties of cells, including membrane capacitance and cytoplasm conductivity, could be obtained. This system was applied to measure the dielectric properties of lipid-accumulating microalga Chlamydomonas reinhardtii strain Sta6 by applying an electrorotation signal of up to 100MHz. By utilizing a broad frequency range and expanding the measurement spectra to a high frequency region, increased accuracy in fitting the dielectric parameters to a theoretical model was possible, especially the cytoplasm conductivity. The developed method can be used in various applications, such as screening microalgae based on their lipid production capabilities, separating cells of different dielectric properties, identifying different cell types, as well as conducting basic biophysical analyses of cellular properties.

ECIS-based biosensors for real-time monitor and classification of the intestinal epithelial barrier damages

• Gut epithelial barrier was mimicked and real-time monitored in ECIS-based IECs. • Gut barrier damages by adverse factors can be classified via analysis of ECIS data. • ECIS-based biosensor verified theanine a nutrient alleviates DON-induced damage. Mycotoxin and pathogens-induced intestinal barrier damages are the pathogenesis for inflammatory bowel diseases. Here, we established electric cell-substrate impedance sensing (ECIS) based biosensors to real-time monitor the intestinal barrier, and classify the barrier damage patterns induced by dextran sodium sulfate (DSS) or deoxynivalenol (DON). The developed ECIS-based biosensors monitored a time-dependent decrease of impedance induced by DSS or DON, during which the Rb (resistance between cells), α (resistance between cell and extracellular matrix), and Cm (cell membrane capacitance) were decreased, indicating the disruption of the intestinal barrier. Noteworthy, the cell micromotion in ECIS can be quantified to the Cellular-Energy, Detail-VAR, Detail-SD, Detail-SMA, and Cellular-Power, by which the DSS and DON induced barrier damage patterns can be classified. Besides, results based on ECIS and traditional assays both verified l -theanine as a nutrient that alleviates the DON-induced intestinal barrier damage. In conclusion, the ECIS-based biosensor was demonstrated as a multiparametric tool to characterize the barrier function, shedding light on exploiting real-time platforms for intestinal barrier-targeted drug screening.

FEATURES OF THE PARAMETERS OF RED BLOOD CELLS AND HEMOSTASIS IN PATIENTS WITH STROKES ASSOCIATED WITH CORONAVIRUS INFECTION

Objective: The purpose is to identify the peculiarities of the parameters of red blood cells (RBC) and hemostasis in patients with strokes associated with coronavirus infection. Design and method: A total of 124 patients (48.5 + 1.9 years) with impairments of cerebral circulation due to COVID-19 (confirmed by positive PCR test) had been examined. Among them, 74 patients had ischemic stroke, 25– transient ischaemic attack, 17– intracerebral hemorrhage, 8– subarachnoid hemorrhage. The parameters of hemostasis were measured by standard methods, electrical, viscoelastic parameters of RBC - by dielectrophoresis. Results: 71 patients (the 1st group) showed signs of intravascular coagulation and thrombosis: accelerated platelet-leukocyte aggregation, increased levels of coagulation products, reduced fibrinolysis activity (p = 0.001–0.04). The levels of D-dimer, fibrinogen, ESR, platelet count were higher in this group compared to the second one (p < 0.01). A moderate increase of RBC summarized rigidity, viscosity was noted. The level of RBC hemolysis was associated with platelet count (r = 0.735,p = 0.03), D-dimer (r = 0.482, p < 0.05), fibrinogen level (r = 0.374, p = 0.04). In 2nd group (53 persons), the markers of thrombosis had moderate deviations. Sharply reduced RBC deformability with increased summarized rigidity, viscosity was dominant coupled with the background of high electrical conductivity of cell membranes compared to the indicators in the 1st group (p < 0.01). There was a decrease of membrane capacity, surface charge, cell dipole moment, polarizability than those in the 1st group (p = 0.0001–0.05). A sharp decrease of RBC deformability creates obstacles to overcoming small-diameter capillaries, leading to violations of microcirculatory blood flow. RBC deformability was associated with levels of ferritin (r = 0.451, p = 0.02), HbA1c (r = 0.480, p = 0.03), uric acid (r = -0.371, p < 0.05), LDL cholesterol (r = 0.461, p = 0.02). Incubation of blood samples in vitro for 10 min with riboflavin, nicotinamide, inosine, which ensures RBC energy metabolism, restored the reduced RBC deformability (p < 0.01), altered cell morphology (p = 0.04), decreased RBC aggregation (p < 0.001). Conclusions: The revealed features of parameters of RBC hemostasis in stroke patients with coronavirus infection are associated with two independent pathogenetic mechanisms: thrombotic and hemorheologic. The thrombotic variant is due to procoagulant state and an activity of inflammation. The hemorheologic variant is caused by decrease of RBC energy metabolism, activity of enzymes.

Influence of pollutant concentration on the separation efficiency of chelating membranes for removing simultaneously metal ions and proteins from simulated industrial wastewater

AbstractBACKGROUNDA novel chelating membrane was fabricated for removing simultaneously metal ions (Cd2+, Pb2+ and Cu2+) and proteins (bovine serum albumin and lysozyme) from simulated industrial effluent. The purpose of the study was to investigate the influence of pollutant concentration on the separation efficiency of the chelating membrane for pollutants.RESULTS(i) The removal of metal ions mainly relies on the adsorption capacity of the chelating membrane, and seems to be independent of the concentration of protein. (ii) The retention of proteins depends mainly on their concentration in solution. (iii) When the wastewater contains high concentration of metal ions (C = 100 mg L−1) and low concentration of proteins (C = 10 mg L−1), the chelating membrane exhibits overall poor separation performance, with a low ion removal efficiency (55–70%) and a low protein rejection rate (ca 60%). (iv) When the wastewater contains low concentration of metal ions (C = 10 mg L−1) and high concentration of proteins (C = 100 mg L−1), the chelating membrane exhibits overall excellent separation performance, with ion removal rates of higher than 90% (except for Cd2+) and protein rejection rates of higher than 90%.CONCLUSIONSThe separation efficiency of the chelating membrane for metallic and organic pollutants greatly depends on the pollutant concentration in the wastewater. This study provides a theoretical basis for membrane technology for removing simultaneously heavy metals and organic pollutants in wastewater. © 2022 Society of Chemical Industry (SCI).

Localized nonlinear waves in a myelinated nerve fiber with self-excitable membrane

We systematically study the evolution of modulated nerve impulses in a myelinated nerve fiber, where both the ionic current and membrane capacitance provide the necessary nonlinear feedbacks. This is achieved by using a perturbation technique, in which the Liénard form of the modified discrete Fitzhugh–Nagumo equation is reduced to the complex Ginzburg–Landau amplitude equation. Three distinct values of the capacitive feedback parameter are considered. At the critical value of the capacitive feedback parameter, it is shown that the dynamics of the system is governed by the dissipative nonlinear Schrödinger equation. Linear stability analysis of the system depicts the instability of plane waves, which is manifested as burst of modulated nerve impulses that fulfills the Benjamin–Feir criteria. Variations of the capacitive feedback parameter generally influences the plane wave stability and hence the type of wave profile identified in the neural network. Results of numerical simulations mainly confirm the propagation, collision, and annihilation of nerve impulses in the myelinated axon.

In vitro characterisation of murine pre-adipose nucleated cells reveals electrophysiological cycles associated with biological clocks.

Adipocytes are energy stores of the body which also play a role in physiological regulation and homeostasis through their endocrine activity. Adipocyte circadian clocks drive rhythms in gene expression, and dysregulation of these circadian rhythms associates with pathological conditions such as diabetes. However, although the role of circadian rhythms in adipose cells and related tissues has been studied from phsyiological and molecular perspectives, they have not yet been explored from an electrical perspective. Research into electro‐chronobiology has revealed that electrical properties have important roles in peripheral clock regulation independently of transcription–translation feedback loops. We have used dielectrophoresis to study electrophysiological rhythms in pre‐adipocytes – representing an adipocyte precursor and nucleated cell‐based model, using serum shocking as the cellular method of clock entrainment. The results revealed significant electrophysiological rhythms, culminating in circadian (ca. 24 hourly) cycles in effective membrane capacitance and radius properties, whereas effective membrane conductance was observed to express ultradian (ca. 14 hourly) rhythms. These data shed new light into pre‐adipocyte electrical behaviour and present a potential target for understanding and manipulation of metabolic physiology.

On the frequency response of prestin charge movement in membrane patches

Outer hair cell (OHC) nonlinear membrane capacitance derives from voltage-dependent sensor charge movements within the membrane protein prestin (SLC26a5) that drive OHC electromotility. The ability of the protein to influence hearing depends on its reaction to membrane receptor potentials across auditory frequency. Estimates of prestin’s frequency response have been evaluated by several groups out to tens of kHz in voltage-clamped macro-patches of OHC membrane. The response is a power function of frequency that is down 40 dB at 77 kHz. Despite these observations, concerns remain that the macro-patch approach is flawed due to mechanical constraints of pipette solution column load or patch size itself. In the absence of these influences, prestin’s frequency response is posited by some to be ultrasonic in nature. Here we evaluate the influence of these putative confounding factors on prestin’s frequency response. We show that neither pipette column height nor negative or positive pipette pressure substantially influence total sensor charge frequency response. Additionally, patch surface area has negligible influence. We conclude that the speed of voltage-driven conformational changes in prestin within the plasma membrane is accurately assessed with the macro-patch technique, permitting investigations of membrane characteristics that can substantially alter prestin’s performance bandwidth. We illustrate significant alterations in bandwidth by perturbation of membrane fluidity and chloride anion concentration. Finally, we speculate that OHC membrane characteristics may differ along the tonotopic axis of the cochlea to tune nonlinear membrane capacitance frequency cutoffs.

Inulin-Modified Liposomes as a Novel Delivery System for Cinnamaldehyde.

Cinnamaldehyde as an antioxidant was encapsulated in inulin-modified nanoliposomes in order to improve its physical and antioxidant stability. The microstructure, particle size and volume distribution of cinnamaldehyde liposomes were characterized by atomic force microscopy (AFM) and dynamic light scattering (DLS). The particle size and polydispersion index (PDI) values of the inulin modified liposomes were 72.52 ± 0.71 nm and 0.223 ± 0.031, respectively. The results showed that the liposomes after surface modification with inulin remained spherical. Raman and Fourier transform infrared (FTIR) spectra analysis showed that hydrogen bonds were formed between the inulin and the liposome membrane. Inulin binding also restricted the freedom of movement of lipid molecules and enhanced the order of the hydrophobic core of the membrane and the polar headgroup region in lipid molecules. Therefore, the addition of different concentrations of inulin influenced the permeability of the liposome bilayer membrane. However, when inulin was excessive, the capacity of the bilayer membrane to load the cinnamaldehyde was reduced, and the stability of the system was reduced. Additionally, the encapsulation efficiency (EE) and retention rate (RR) of cinnamaldehyde from inulin-modified liposomes during storage were determined. The EE value of the inulin modified liposomes was 70.71 ± 0.53%. The liposomes with 1.5% inulin concentration had the highest retention rate (RR) and the smallest particle size during storage at 4 °C. The addition of inulin also enhanced the thermal stability of the liposomes. Based on the results, the surface modification improved the oxidation stability of liposomes, especially the DPPH scavenging ability. In conclusion, these results might help to develop inulin as a potential candidate for the effective modification of the surface of liposomes and provide data and conclusions for it.

Hyperexcitability in young iPSC-derived C9ORF72 mutant motor neurons is associated with increased intracellular calcium release.

A large hexanucleotide repeat expansion in the C9ORF72 gene is the most prevalent cause of amyotrophic lateral sclerosis (ALS). To better understand neuronal dysfunction during ALS progression, we studied motor neuron (MN) cultures derived from iPSC lines generated from C9ORF72 (C9) expansion carriers and unaffected controls. C9 and control MN cultures showed comparable mRNA levels for MN markers SMI-32, HB9 and ISL1 and similar MN yields (> 50% TUJ1/SMI-32 double-positive MNs). Using whole-cell patch clamp we showed that C9-MNs have normal membrane capacitance, resistance and resting potential. However, immature (day 40) C9-MNs exhibited a hyperexcitable phenotype concurrent with increased release of calcium (Ca2+) from internal stores, but with no changes to NaV and KV currents. Interestingly, this was a transient phenotype. By day 47, maturing C9-MNs demonstrated normal electrophysiological activity, displaying only subtle alterations on mitochondrial Ca2+ release. Together, these findings suggest the potential importance of a developmental component to C9ORF72-related ALS.

Intermittent Cocaine Self‐Administration Infusions Increases Subthreshold Activity in Putative Dopaminergic Neurons of The Ventral Tegmental Area

Intermittent Access (IntA) cocaine self‐administration is a protocol suggested to better simulate human addictive behavior due to the intermittent pattern of drug administration. IntA is also known to produce incentive salience and psychomotor sensitization. It is documented that IntA produces a neurochemical sensitization of the mesolimbic dopamine (DA) system by increasing both release and uptake of DA. The ventral tegmental area (VTA) DA neurons display a prominent mixed cation current conductance known as the hyperpolarization‐activated cyclic nucleotide current, or Ih. Neural processes such as resting membrane potential, firing frequency modulation, and synaptic integration are influenced by the Ih. Previous results from our laboratory demonstrated that Ih amplitude and membrane capacitance of putative VTA DA neurons are significantly reduced after cocaine sensitization. This Ihand capacitance reduction resulted in an increased temporal summation, mean depolarization and excitatory postsynaptic potential (EPSP) amplitude, all related to an enhanced neuronal excitability state. It is not known how IntA alters the intrinsic properties of VTA DA cells. Since the cocaine sensitization model involves experimenter administered drug injections (non‐contingent) it is important to determine if electrophysiological changes in VTA DA cells are present when drugs are self‐administered (contingent). In the present study we explored if synaptic integration, membrane capacitance and cell activity alterations are present after exposure to cocaine IntA. Our hypothesis is that IntA enhances synaptic integration and neuronal excitability of VTA DA cells. Whole‐cell patch‐clamp technique in rat brain slices was used to inject a 33‐Hz train of 5 αEPSCs (α = 5 ms; Imax = 50) into the soma of putative VTA DA neurons when clamped at ‐70 mV and analyze the effects of cocaine IntA, and passive cocaine infusions (yoked controls) on synaptic integration. Increasing depolarizing current injections were used to evaluate how neurons respond to a depolarizing stimulus. Our results demonstrate that an IntA protocol, but not passive cocaine infusions, produces a significant increase in the number of APs (P<0.05). Temporal summation was increased at depolarized potentials in the IntA group and Yoked controls (P<0.0001). These results suggests that neuronal activity regulation is dependent on associative learning to drug cues. The findings also suggest that enhanced synaptic integration could possibly be a cocaine‐induced pharmacological effect.

A light-induced small G-protein gem limits the circadian clock phase-shift magnitude by inhibiting voltage-dependent calcium channels.

Calcium signaling is pivotal to the circadian clockwork in the suprachiasmatic nucleus (SCN), particularly in rhythm entrainment to environmental light-dark cycles. Here, we show that a small G-protein Gem, an endogenous inhibitor of high-voltage-activated voltage-dependent calcium channels (VDCCs), is rapidly induced by light in SCN neurons via the calcium (Ca2+)-mediated CREB/CRE transcriptional pathway. Gem attenuates light-induced calcium signaling through its interaction with VDCCs. The phase-shift magnitude of locomotor activity rhythms by light, at night, increases in Gem-deficient (Gem-/-) mice. Similarly, in SCN slices from Gem-/- mice, depolarizing stimuli induce larger phase shifts of clock gene transcription rhythms that are normalized by the application of an L-type VDCC blocker, nifedipine. Voltage-clamp recordings from SCN neurons reveal that Ca2+ currents through L-type channels increase in Gem-/- mice. Our findings suggest that transcriptionally activated Gem feeds back to suppress excessive light-evoked L-type VDCC activation, adjusting the light-induced phase-shift magnitude to an appropriate level in mammals.

Thalamocortical Projections Are Significantly Impaired in the R6/2 Mouse Model of Huntington's Disease.

As Huntington’s disease (HD) progresses, there is a significant loss of neurons in the striatum in addition to a distinct thinning of the cerebral cortex. Despite an early presence of sensorimotor deficits in patients with HD, electrophysiological studies designed to assess the integrity of thalamocortical circuits are sparse. Using the R6/2 mouse model of HD, we provide evidence of reduced connectivity between thalamic cells and their targeted cortical regions. Whole-cell patch clamp recordings from ventral anterolateral nucleus (VAL; motor) and ventral posteromedial nucleus (VPM; somatosensory) thalamic neurons in ex vivo brain slices of R6/2 and wild-type (WT) mice revealed that cells in both thalamic nuclei of R6/2 mice exhibited significant differences in passive and active cell membrane properties (smaller cell membrane capacitances, faster decay time constants and increased input resistances) compared with WT cells. Although only cells in the VPM of symptomatic R6/2 mice had more depolarized resting membrane potentials compared with WTs, cells in both nuclei displayed increased excitability in symptomatic, but not presymptomatic, R6/2 mice. Optical activation of VAL and VPM terminals elicited smaller magnitude current responses in cortical pyramidal neurons (CPNs) in both motor cortex (M1CTX) and somatosensory barrel cortex (BCTX) of symptomatic R6/2 mice compared with CPNs in WT mice. Furthermore, we observed a decrease in the frequency of thalamocortical excitatory quantal events in R6/2 BCTX CPNs, with no genotype-dependent differences in AMPA:NMDA response amplitude ratios. These data suggest there is a decrease in the transmission of thalamocortical information that is likely because of impaired neurotransmitter release.

PI3K/AKT1 Signaling Pathway Mediates Sinomenine-Induced Hepatocellular Carcinoma Cells Apoptosis: An in Vitro and in Vivo Study.

Hepatocellular carcinoma (HCC) is one of the most frequent cancers. Sinomenine (SIN) is a compound derived from Sinomenium acutum. Our previous investigations have found that SIN inhibited protein kinase B (AKT) signaling to induce autophagic death of tumor cells. However, whether inhibition of this pathway by SIN could impact the proliferation of HCC cells is unknown. Thus, we applied SIN to SK-Hep-1 cells and used cell counting kit 8 (CCK8), lactate dehydrogenase (LDH), colony formation and 5-ethynyl-20-deoxyuridine (EdU) incorporation experiments to detect cell viability. Then, staining with annexin V/propidium iodide (PI) coupled with terminal deoxynucleotidyl transferase-mediated biotinylated uridine 5'-triphosphate (UTP) nick end labeling (TUNEL) staining were utilized to monitor apoptosis. Changes in cell mitochondrial membrane capacity were explored via 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining, whilst Western blot or immunohistochemistry was applied to evaluate the expression levels of key proteins, consisting of Cleaved Caspase 3, AKT1, B-cell leukemia/lymphoma 2 (BCL-2), phosphatidylinositol 3-kinase (PI3K) p85α, and Cleaved Caspase 9 etc. The Balb/c nude mice were utilized to establish HCC xenograft tumor model, administered by SIN. After treatments, the tumor volume along with weight were measured. The results illustrated that SIN suppressed SK-Hep-1 HCC cells' proliferation, enhanced the collapse of potential of the mitochondrial membrane, triggered cell apoptosis, down-regulated PI3K p85α, AKT1, BCL-2, Pro-Caspase 9, Pro-Caspase 3 expressions, and up-regulated Cleaved Caspase 9 and Cleaved Caspase 3 expressions in vitro and in vivo. Meanwhile, SIN reduced the tumor volume along with weight of mice. In addition, insulin-like growth factor-1 (IGF-1), a powerful activator of the PI3K/AKT pathway, could reverse the high apoptosis of SK-Hep-1 HCC cells induced by SIN. Overall, inhibition of PI3K/AKT1 signaling cascade by SIN induced HCC cells apoptosis.

Characterization of Extra-Cellular Vesicle Dielectrophoresis and Estimation of Its Electric Properties.

Dielectrophoresis (DEP) refers to a type of electrical motion of dielectric particles. Because DEP is caused by particle polarization, it has been utilized to characterize particles. This study investigated the DEP of three types of exosomes, namely bovine milk, human breast milk, and human breast cancer exosomes. Exosomes are kinds of extracellular vesicles. The crossover frequencies of the exosomes were determined by direct observation of their DEPs. Consequently, bovine and human milk exosomes showed similar DEP properties, whereas the cancer exosomes were significantly different from the others. The membrane capacitance and conductivity of the exosomes were estimated using determined values. A significant difference was observed between bovine and human milk exosomes on their membrane capacitance. It was revealed that the membrane capacitances of human breast milk and human breast cancer exosomes were almost identical to those of their host cells and the conductivity of the exosomes were much lower than that of the host cell. Based on these results, DEP separation of the human breast milk and cancer exosomes was demonstrated. These results imply that DEP can be utilized to separate and identify cancer exosomes rapidly. Additionally, our method can be utilized to estimate the electric property of other types of extracellular vesicles.

Inherent single-cell bioelectrical parameters of thousands of neutrophils, eosinophils and basophils derived from impedance flow cytometry.

Single-cell bioelectrical properties are commonly used for blood cell phenotyping in a label-free manner. However, previously reported inherent single-cell bioelectrical parameters (e.g., diameter Dc , specific membrane capacitance Csm and cytoplasmic conductivity σcy ) of neutrophils, eosinophils and basophils were obtained from only tens of individual cells with limited statistical significance. In this study, granulocytes were separated into neutrophils, eosinophils and basophils based on fluorescent flow cytometry, which were further aspirated through a constriction-microchannel impedance flow cytometry for electrical property characterization. Based on this microfluidic impedance flow cytometry, single-cell values of Dc , Csm and σcy were measured as 10.25 ± 0.66 μm, 2.17 ± 0.30 μF/cm2 , and 0.37 ± 0.05 S/m for neutrophils (ncell =9442); 9.73 ± 0.51 μm, 2.07 ± 0.19 μF/cm2 , and 0.30 ± 0.04 S/m for eosinophils (ncell =2982); 9.75 ± 0.49 μm, 2.06 ± 0.17 μF/cm2 , and 0.31 ± 0.04 S/m for basophils (ncell =5377). Based on these inherent single-cell bioelectrical parameters, neural pattern recognition was conducted, producing classification rates of 80.8% (neutrophil vs. eosinophil), 77.7% (neutrophil vs. basophil) and 59.3% (neutrophil vs. basophil). These results indicate that as inherent single-cell bioelectrical parameters, Dc , Csm and σcy can be used to classify neutrophils from eosinophils or basophils to some extent while they cannot be used to effectively distinguish eosinophils from basophils.

Numerical simulations of capsule deformation in a combined shear flow and DC electric field

In this work a numerical method for fully three dimensional simulations of capsules in the electrohydrodynamic regime is proposed. A quasi-steady dual time-stepping scheme allows for iterative computation of the capsule's fluid velocity using the multigrid lattice Boltzmann method at each time step. The capsule's elasticity is computed using a linear finite element method and the membrane's bending resistance is computed from the Helfrich bending energy. The immersed interface method (IIM) is used to compute the electric field arising due to the electrical properties of the interior fluid, exterior fluid, and the membrane. The fluid structure interaction is facilitated through the immersed boundary method (IBM), which is coupled to the IIM through least squares interpolation between the control points of the IIM and the Lagrangian nodes of the IBM. The method is validated by comparing the numerical results to analytical solutions and previously published studies. The method is then used to study the deformation of capsules in a combined shear flow and DC electric field for various membrane conductances, membrane capacitances, and conductivity ratios. For nonconducting membranes the interaction between the distribution of the electric forces and the capsule inclination angle due to the shear flow result in complex equilibrium dynamics not reported for neutral capsules.

Selective neural stimulation by leveraging electrophysiological differentiation and using pre-pulsing and non-rectangular waveforms.

Efforts on selective neural stimulation have concentrated on segregating axons based on their size and geometry. Nonetheless, axons of the white matter or peripheral nerves may also differ in their electrophysiological properties. The primary objective of this study was to investigate the possibility of selective activation of axons by leveraging an assumed level of diversity in passive (Cm & Gleak) and active membrane properties (Ktemp & Gnamax). First, the stimulus waveforms with hyperpolarizing (HPP) and depolarizing pre-pulsing (DPP) were tested on selectivity in a local membrane model. The default value of membrane capacitance (Cm) was found to play a critical role in sensitivity of the chronaxie time (Chr) and rheobase (Rhe) to variations of all the four membrane parameters. Decreasing the default value of Cm, and thus the passive time constant of the membrane, amplified the sensitivity to the active parameters, Ktemp and GNamax, on Chr. The HPP waveform could selectively activate neurons even if they were diversified by membrane leakage (Gleak) only, and produced higher selectivity than DPP when parameters are varied in pairs. Selectivity measures were larger when the passive parameters (Cm & Gleak) were varied together, compared to the active parameters. Second, this novel mechanism of selectivity was investigated with non-rectangular waveforms for the stimulating phase (and HPP) in the same local membrane model. Simulation results suggest that Kt2 is the most selective waveform followed by Linear and Gaussian waveforms. Traditional rectangular pulse was among the least selective of all. Finally, a compartmental axon model confirmed the main findings of the local model that Kt2 is the most selective, but rank ordered the other waveforms differently. These results suggest a potentially novel mechanism of stimulation selectivity, leveraging electrophysiological variations in membrane properties, that can lead to various neural prosthetic applications.

P 16 Effects of pallidal deep brain stimulation on striatal medium spiny neurons in the animal model of the dystonic dtsz mutant hamster

Introduction: Electric stimulation of the deep brain nuclei, such as globus pallidus internus (GPi), indicated the most relevant therapeutic option for patients with severe dystonias. However, the mechanisms of the deep brain stimulation (DBS) of the GPi are far from understood. Dystonia, a hyperkinetic movement disorder, is thought to result from an imbalance in the direct and indirect pathway arises from disturbance in the striatum. In the dt sz mutant hamster, a model of inherited generalized, paroxysmal dystonia, it has been already shown that the number of parvalbumin-positive gabaergic interneurons declined, which leads to uncontrolled projections via the medium spiny neurons (MSN) (see also Paap, et al. (2020), DOI: 10.1016/j.nbd.2020.105163). We hypothesized that DBS via backfiring, or indirectly via thalamic and cortical coupling, modifies striatal network function. Materials & Methods: The dt sz mutant hamsters were bilaterally implanted with stimulation electrodes targeting the entopeduncular nucleus (EPN; equivalent of the human GPi). DBS (130 Hz, rectangular pulse of 50 µA and 60 µs) and sham-DBS was performed in vivo in unanaesthetized animals for three hours. Acute brain slices of stim- and sham-groups were immediately prepared after the DBS has been terminated. Additionally, acute brain slices were obtained from untreated dt sz mutant hamsters (native group) to assess the effects of electrode implantation. With whole-cell patch clamp recordings, we investigated the spontaneous cortico-striatal synaptic activity and the characteristics of the D1- (direct pathway) and D2- (indirect pathway) MSN, which are capable of being differentiated by adding the D2-agonist sumanirole. Additionally, molecular analysis was performed for studying the DBS effect on ion channel gene expression. Results: In view of spontaneous release activity from cortical projections, our study indicated a strong dampening effect on the frequency of spontaneous miniature excitatory postsynaptic currents (mEPSC) of the stim-group in contrast to sham-group. The specific cellular parameters of D1- and D2-MSN, which include resting membrane potential, input resistance, membrane capacity, rheobase, and firing properties of action potentials, did not differ between native-, sham-, and stim- group. Conclusions: To conclude, while short-term EPN-DBS obviously dampens spontaneous presynaptic glutamate release at cortico-striatal synapses, there is no alteration on MSN properties. Future studies will consider the effects of long-term stimulation on synaptic plasticity by a novel implantable stimulation system which enables DBS over weeks (see also Plocksties et al. (2021). DOI: 10.1088/1741-2552/ac23e1). This study is supported by the German Research Foundation (DFG) within the Collaborative Research Centre (SFB 1270/1 ELAINE 299150580)