Ion Pump Activity Research Articles

Sinomenine: A Protential Biomaterial for Its Antitumor Effect in H22 Hepatoma-Bearing Mice and Its Mechanisms

Sinomenine (SIN) is a natural isoquinoline alkaloid extracted from the Chinese medicinal plant Sinomenium acutum with promising antitumor properties. Although its antitumor effect and mechanism have been studied, its effects on the structure and function of tumor cell membranes remain unclear. This study aimed to evaluate the antitumor effect of SIN on H22 hepatoma-bearing mice and its mechanism of action on tumor cell membranes, and the tumor inhibition rate and life extension rate were examined. Flow cytometry was used to evaluate the dose-dependent induction of apoptosis in H22 cells. The main components of tumor cell membrane, including total protein, cholesterol and sialic acid (SA) were characterized. The ultrastructure of cell membrane was observed using transmission electron microscopy (TEM). Furthermore, SIN’s effect on the function of cell membranes was studied by analyzing fluidity, sealing, and ion pump activity. The results demonstrated that SIN effectively inhibited the growth of liver cancer cells in vivo and prolonged the lifespan of H22 hepatoma-bearing mice. SIN induced apoptosis of H22 cells in a dose-dependent manner, significantly reduced total protein, cholesterol, and SA contents in H22 cell membranes, and significantly decreased the fluidity, sealing, Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities of H22 cell membranes with increasing doses. Overall, these findings suggested that SIN reduced the main component contents of H22 cell membranes, leading to changes in structure and function of cell membrane, ultimately resulting in tumor cell apoptosis and inhibition of tumor growth. The findings indicated that SIN has great potential as a biomaterial for anti-liver cancer drugs, and provides new ideas and methods for developing antitumor drugs through membrane pharmacology.

Model Analysis of Post-Stimulation Block of a Myelinated Axon by Direct Current.

To determine the role of ion concentrations and ion pump activity in conduction block of myelinated axon induced by a long-duration direct current (DC). A new axonal conduction model for myelinated axons based on the classical Frankenhaeuser-Huxley (FH) equations is developed that includes ion pump activity and allows the intracellular and extracellular Na+ and K+ concentrations to change with axonal activity. Action potential generation, propagation, and acute DC block occurring within a short period (milliseconds) that do not significantly change the ion concentrations or trigger ion pump activity are successfully simulated by the new model in a similar way as the classical FH model. Different from the classical model, the new model also successfully simulates the post-stimulation block phenomenon, i.e., the axonal conduction block occurring after terminating a long-duration (30 seconds) DC stimulation as observed recently in animal studies. The model reveals a significant K+ accumulation outside the axonal node as the possible mechanism underlying the post-DC block that is slowly reversed by ion pump activity during the post-stimulation period. Changes in ion concentrations and ion pump activity play an important role in post-stimulation block induced by long-duration DC stimulation. Long-duration stimulation is used clinically for many neuromodulation therapies, but the effects on axonal conduction/block are poorly understood. This new model will be useful for better understanding of the mechanisms underlying long-duration stimulation that changes ion concentrations and triggers ion pump activity.

Coevolutionary escalation led to differentially adapted paralogs of an insect's Na,K-ATPase optimizing resistance to host plant toxins.

Cardiac glycosides are chemical defence toxins known to fatally inhibit the Na,K-ATPase (NKA) throughout the animal kingdom. Several animals, however, have evolved target-site insensitivity through substitutions in the otherwise highly conserved cardiac glycoside binding pocket of the NKA. The large milkweed bug, Oncopeltus fasciatus, shares a long evolutionary history with cardiac glycoside containing plants that led to intricate adaptations. Most strikingly, several duplications of the bugs' NKA1α gene provided the opportunity for differential resistance-conferring substitutions and subsequent sub-functionalization of the enzymes. Here, we analysed cardiac glycoside resistance and ion pumping activity of nine functional NKA α/β-combinations of O. fasciatus expressed in cell culture. We tested the enzymes with two structurally distinct cardiac glycosides, calotropin, a host plant compound, and ouabain, a standard cardiac glycoside. The identity and number of known resistance-conferring substitutions in the cardiac glycoside binding site significantly impacted activity and toxin resistance in the three α-subunits. The β-subunits also influenced the enzymes' characteristics, yet to a lesser extent. Enzymes containing the more ancient αC-subunit were inhibited by both compounds but much more strongly by the host plant toxin calotropin than by ouabain. The sensitivity to calotropin was diminished in enzymes containing the more derived αB and αA, which were only marginally inhibited by both cardiac glycosides. This trend culminated in αAβ1 having higher resistance against calotropin than against ouabain. These results support the coevolutionary escalation of plant defences and herbivore tolerance mechanisms. The possession of multiple paralogs additionally mitigates pleiotropic effects by compromising between ion pumping activity and resistance.

Overexpression of RtSYP121 confers cadmium colerance by promoting vesicle trafficking, maintaining ion homeostasis, and alleviating photosynthetic inhibition in Arabidopsis

Cadmium (Cd) is a toxic heavy metal in soil that seriously threatens crop production, food security, and human health. Syntaxins, a prototype family of Soluble N-ethyl-maleimide-associated protein receptors (SNAREs) involved in vesicle trafficking, are implicated in resistance to abiotic stresses, including Cd stress, but the molecular mechanisms underlying the involvement of syntaxins in Cd tolerance in plants are unclear. In this study, we isolated and functionally characterized the syntaxin gene RtSYP121 from Reaumuria trigyna to evaluate its potential for phytoremediation. RtSYP121 resides in the plasma membrane. The transcriptional level of RtSYP121 was strongly increased by salt, drought, and Cd stress. Overexpression of RtSYP121 significantly enhanced the Cd tolerance of transgenic Arabidopsis. The Cd tolerance of transgenic plants mainly depended on elevated vesicle trafficking, which increased the content of K+ and Ca2+ and thus decreased the accumulation of Cd2+ by regulating the delivery or activity of ion transporters, channels, and pumps. Moreover, overexpression of RtSYP121 in Arabidopsis ameliorated Cd stress–induced phytotoxic effects, including growth inhibition, ROS burst, photosynthetic impairment, and cell death. Therefore, we suggest that RtSYP121 plays multiple roles in the plant response to Cd stress by promoting vesicle trafficking, maintaining ion homeostasis, and alleviating photosynthetic inhibition.

Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography

Dungeness crab (Metacarcinus magister) have significant socioeconomic value, but are threatened by ocean acidification (OA) and other environmental stressors that are driven by climate change. Despite evidence that adult harvests are sensitive to the abundance of larval populations, relatively little is known about how Dungeness megalopae will respond to these stressors. Here we evaluate the ability to use micro-computed tomography (μCT) to detect variations in megalope exoskeleton density and how these measurements reflect environmental variables and calcification mechanisms. We use a combination of field data, culture experiments, and model simulations to suggest resolvable differences in density are best explained by minimum pH at the time zoeae molt into megalopae. We suggest that this occurs because more energy must be expended on active ion pumping to reach a given degree of calcite supersaturation at lower pH. Energy availability may also be reduced due to its diversion to other coping mechanisms. Alternate models based on minimum temperature at the time of the zoea-megalope molt are nearly as strong and complicate the ability to conclusively disentangle pH and temperature influences. Despite this, our results suggest that carryover effects between life stages and short-lived extreme events may be particularly important controls on exoskeleton integrity. μCT-based estimates of exoskeleton density are a promising tool for evaluating the health of Dungeness crab populations that will likely provide more nuanced information than presence-absence observations, but future in situ field sampling and culture experiments are needed to refine and validate our results.

Involvement of alpha-subunit N-termini in the mechanism and regulation of the Na+,K+- and H+,K+-ATPases.

The cytoplasmic lysine-rich N-termini of the Na+,K+- and H+,K+-ATPases have been designated as R domains because of their possible role in regulation of ion pumping activity. Prior to the publication of any crystal structures of either protein, it was suggested, based on mutagenesis studies, that regulation of the Na+,K+-ATPase could involve the formation and breakage of a salt bridge between Lys30 of the N-terminus and Glu233 in the first M2-M3 cytoplasmic loop of the alpha subunit. In structural studies of the Na+,K+-ATPase, the N-terminus has never been able to be resolved, probably because it is intrinsically disordered. Nevertheless, after theoretically predicting the N-terminus conformation, and adding it to the structure, the distance between residues Lys30 and Glu233 makes it doubtful that a direct long-lived interaction between them is involved in pump regulation. As an alternative hypothesis, we propose that regulation could occur via an interaction of the positively charged lysine residues of the N-terminus with negatively charged lipid headgroups (notably phosphatidylserine) on the cytoplasmic surface of the surrounding membrane, and that such an interaction could potentially be regulated by an electrostatic switch mechanism, whereby serine and tyrosine residues of the N-terminus are phosphorylated by protein kinases. Phosphorylation of these residues would decrease the positive charge of the N-terminus, allowing its release from the membrane. Experimental and theoretical data will be presented which support this hypothesis.

Ion-pumping microbial rhodopsin protein classification by machine learning approach

BackgroundRhodopsin is a seven-transmembrane protein covalently linked with retinal chromophore that absorbs photons for energy conversion and intracellular signaling in eukaryotes, bacteria, and archaea. Haloarchaeal rhodopsins are Type-I microbial rhodopsin that elicits various light-driven functions like proton pumping, chloride pumping and Phototaxis behaviour. The industrial application of Ion-pumping Haloarchaeal rhodopsins is limited by the lack of full-length rhodopsin sequence-based classifications, which play an important role in Ion-pumping activity. The well-studied Haloarchaeal rhodopsin is a proton-pumping bacteriorhodopsin that shows promising applications in optogenetics, biosensitized solar cells, security ink, data storage, artificial retinal implant and biohydrogen generation. As a result, a low-cost computational approach is required to identify Ion-pumping Haloarchaeal rhodopsin sequences and its subtype.ResultsThis study uses a support vector machine (SVM) technique to identify these ion-pumping Haloarchaeal rhodopsin proteins. The haloarchaeal ion pumping rhodopsins viz., bacteriorhodopsin, halorhodopsin, xanthorhodopsin, sensoryrhodopsin and marine prokaryotic Ion-pumping rhodopsins like actinorhodopsin, proteorhodopsin have been utilized to develop the methods that accurately identified the ion pumping haloarchaeal and other type I microbial rhodopsins. We achieved overall maximum accuracy of 97.78%, 97.84% and 97.60%, respectively, for amino acid composition, dipeptide composition and hybrid approach on tenfold cross validation using SVM. Predictive models for each class of rhodopsin performed equally well on an independent data set. In addition to this, similar results were achieved using another machine learning technique namely random forest. Simultaneously predictive models performed equally well during five-fold cross validation. Apart from this study, we also tested the own, blank, BLAST dataset and annotated whole-genome rhodopsin sequences of PWS haloarchaeal isolates in the developed methods. The developed web server (https://bioinfo.imtech.res.in/servers/rhodopred) can identify the Ion Pumping Haloarchaeal rhodopsin proteins and their subtypes. We expect this web tool would be useful for rhodopsin researchers.ConclusionThe overall performance of the developed method results show that it accurately identifies the Ionpumping Haloarchaeal rhodopsin and their subtypes using known and unknown microbial rhodopsin sequences. We expect that this study would be useful for optogenetics, molecular biologists and rhodopsin researchers.

How dynamic prestress governs the shape of living systems, from the subcellular to tissue scale.

Cells and tissues change shape both to carry out their function and during pathology. In most cases, these deformations are driven from within the systems themselves. This is permitted by a range of molecular actors, such as active crosslinkers and ion pumps, whose activity is biologically controlled in space and time. The resulting stresses are propagated within complex and dynamical architectures like networks or cell aggregates. From a mechanical point of view, these effects can be seen as the generation of prestress or prestrain, resulting from either a contractile or growth activity. In this review, we present this concept of prestress and the theoretical tools available to conceptualize the statics and dynamics of living systems. We then describe a range of phenomena where prestress controls shape changes in biopolymer networks (especially the actomyosin cytoskeleton and fibrous tissues) and cellularized tissues. Despite the diversity of scale and organization, we demonstrate that these phenomena stem from a limited number of spatial distributions of prestress, which can be categorized as heterogeneous, anisotropic or differential. We suggest that in addition to growth and contraction, a third type of prestress-topological prestress-can result from active processes altering the microstructure of tissue.

Electromechanical model for object roughness perception during finger sliding

Touch allows us to gather abundant information in the world around us. However, how sensory cells embedded in the fingers convey texture information into their firing patterns is still poorly understood. Here, we develop an electromechanical model for roughness perception by incorporating main ingredients such as voltage-gated ion channels, active ion pumps, mechanosensitive channels, and cell deformation. The model reveals that sensory cells can convey texture wavelengths into the period of their firing patterns as the finger slides across object surfaces, but they can only convey a limited range of texture wavelengths. We also show that an increase in sliding speed broadens the decoding wavelength range at the cost of reduction of lower perception limits. Thus, a smaller sliding speed and a bigger contact force may be needed to successfully discern a smooth surface, consistent with previous psychophysical observations. Moreover, we show that cells with slowly adapting mechanosensitive channels can still fire action potentials under static loadings, indicating that slowly adapting mechanosensitive channels may contribute to the perception of coarse textures under static touch. Our work thus provides a new theoretical framework to study roughness perception and may have important implications for the design of electronic skin, artificial touch, and haptic interfaces.

Fluorometric setup and method for studying the functional activity of corneal endotheliocytes

Subject of study. Experimental methods for investigating the state of preservation and functionality of the corneal endothelium, which is determined by the water permeability of the cells and activity of ion pumps, mainly by sodium–potassium adenosine triphosphatase, were considered. Aim of study. The aim of this study was to identify significant measurable parameters such as the fluorescence intensity integrated over the entire cornea preparation and the temporal dynamic of this fluorescence. Additionally, a specialized experimental fluorometric setup was designed based on fiber optics. Method. Modifications were introduced to the composition and design of a universal experimental setup for the measurement of cell functions that enabled implementation of a fluorescence-based method for determination of the intracellular sodium concentration without processing the digital image of the cornea preparation. Main results. The specialized experimental setup and method were developed for investigating functions of the corneal endothelial cells and the intracellular signaling mechanisms whose activation or disfunction under conditions of a traumatic inflammation and after a hypothermic preservation can be related to the development of a corneal edema and a corneal graft disease. Practical significance. The specialized experimental setup and methods for functional testing of the corneal endothelial cells developed in this study can be applied to determine the degree of suitability of the cornea as a transplantation material. They can also be used as a system of tests for determining the effectiveness of the cornea preservation methods.

Na+/HCO3- cotransporter 1 (nbce1) isoform gene expression during smoltification and seawater acclimation of Atlantic salmon.

The life history of Atlantic salmon (Salmo salar) includes an initial freshwater phase (parr) that precedes a springtime migration to marine environments as smolts. The development of osmoregulatory systems that will ultimately support the survival of juveniles upon entry into marine habitats is a key aspect of smoltification. While the acquisition of seawater tolerance in all euryhaline species demands the concerted activity of specific ion pumps, transporters, and channels, the contributions of Na+/HCO3- cotransporter 1 (Nbce1) to salinity acclimation remain unresolved. Here, we investigated the branchial and intestinal expression of three Na+/HCO3- cotransporter 1 isoforms, denoted nbce1.1, -1.2a, and -1.2b. Given the proposed role of Nbce1 in supporting the absorption of environmental Na+ by ionocytes, we first hypothesized that expression of a branchial nbce1 transcript (nbce1.2a) would be attenuated in salmon undergoing smoltification and following seawater exposure. In two separate years, we observed spring increases in branchial Na+/K+-ATPase activity, Na+/K+/2Cl- cotransporter 1, and cystic fibrosis transmembrane regulator 1 expression characteristic of smoltification, whereas there were no attendant changes in nbce1.2a expression. Nonetheless, branchial nbce1.2a levels were reduced in parr and smolts within 2days of seawater exposure. In the intestine, gene transcript abundance for nbce1.1 increased from spring to summer in the anterior intestine, but not in the posterior intestine or pyloric caeca, and nbce1.1 and -1.2b expression in the intestine showed season-dependent transcriptional regulation by seawater exposure. Collectively, our data indicate that tissue-specific modulation of all three nbce1 isoforms underlies adaptive responses to seawater.

Ca2+ signals in plant immunity.

Calcium ions function as a key second messenger ion in eukaryotes. Spatially and temporally defined cytoplasmic Ca2+ signals are shaped through the concerted activity of ion channels, exchangers, and pumps in response to diverse stimuli; these signals are then decoded through the activity of Ca2+‐binding sensor proteins. In plants, Ca2+ signaling is central to both pattern‐ and effector‐triggered immunity, with the generation of characteristic cytoplasmic Ca2+ elevations in response to potential pathogens being common to both. However, despite their importance, and a long history of scientific interest, the transport proteins that shape Ca2+ signals and their integration remain poorly characterized. Here, we discuss recent work that has both shed light on and deepened the mysteries of Ca2+ signaling in plant immunity.

ACYP1 Is a Pancancer Prognostic Indicator and Affects the Immune Microenvironment in LIHC.

BackgroundACYP1 plays important physiological and metabolic roles in glycolysis and membrane ion pump activity by catalyzing acyl phosphate hydrolysis. ACYP1 is related to tumorigenesis and progression and poor prognosis in gastrointestinal cancer. However, its pancancer roles and mechanisms are unclear. Our study aimed to understand the ACYP1 expression signature and prognostic value across cancers and investigate immune infiltration patterns in liver hepatocellular carcinoma (LIHC) and verify them in LIHC samples.MethodsTranscriptional expression profiles of ACYP1 across cancers were analyzed using Oncomine and TIMER. The prognostic value of ACYP1 was assessed across PrognoScan, Kaplan—Meier Plotter, and GEPIA. Significant pathways associated with ACYP1 in LIHC were obtained via Gene Set Enrichment Analysis. The correlation between ACYP1 expression and immune infiltration in LIHC was investigated using TIMER. We validated ACYP1 expression, prognostic value, and association with immune cells in tumor tissues by immunohistochemistry and flow cytometry.ResultsACYP1 was overexpressed across cancers. High expression of ACYP1 correlated with a poor prognosis in most tumor types, especially in LIHC. ACYP1 was significantly implicated in immune and metabolic related pathways. High ACYP1 expression showed significant correlations with the abundances of Th2 cells, Tregs, macrophages, dendritic cells, and myeloid-derived suppressor cells in LIHC. LIHC patients with high ACYP1 expression showed significantly shorter overall survival and relapse-free survival rates concomitant with increased infiltration of CD4+ T cells. Mouse subcutaneous tumors with ACYP1 overexpression exhibited significantly accelerated tumor progression with increased aggregation of CD4+ T cells.ConclusionOverall, ACYP1 may serve as a vital prognostic biomarker and play an immunoregulatory role in LIHC.

Bioelectricity Buzz

BioelectricityVol. 4, No. 2 Bioelectricity BuzzFree AccessBioelectricity BuzzAnn M. RajnicekAnn M. RajnicekAnn M. Rajnicek, BS, PhD, FRSB, Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, AB25 2ZD Aberdeen, Scotland, United Kingdom. E-mail Address: a.m.rajnicek@abdn.ac.ukSearch for more papers by this authorPublished Online:26 May 2022https://doi.org/10.1089/bioe.2022.0018AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Recent Bioelectricity-Related Articles Selected by Ann M. Rajnicek, Media Editor of BioelectricityThe Buzz for this Special Issue on the Bioelectricity of the Tumor Microenvironment includes reviews and primary articles to whet your appetite on topics related to tumor cells (of course!) but also encompasses topics on the nanoscale (ions, small molecules, membranes, and nanoparticles), microscale (electroactive microorganisms), electrode–tissue interfaces (in spinal cord, brain, and tumor microenvironments [TMEs]) and ion transporting tissues (organoids). Enjoy!Cells Versus Tissues: The Potential for CancerThere is growing interest in controlling tumors by changing the bioelectrical traits of cancer cells. This article describes a bioelectric model underpinning cancer progression and treatment that reflects the dynamic interaction of the bioelectrical properties of cells and tissues.Joao Carvalho. A bioelectric model of carcinogenesis, including propagation of cell membrane depolarization and reversal therapies. Sci Rep 2021;11:13607. https://www.nature.com/articles/s41598-021-92951-0The long-standing idea that cancer arises from a succession of genetic mutations, known as the “somatic mutation theory,” fails to explain carcinogenic consequences of exposure to nongenomic toxins. An alternative, the tissue organization field theory (TOFT) considers the origin of cancer as a tissue-scale event, with the bioelectrical state of cells and tissues central to its progression.Carvalho presents a computational model consistent with TOFT principles, incorporating membrane potential, ionic conduction, cellular gap junctions, and cell–cell communication at tissue level. The model builds on one proposed by Cervera et al. in 2020 (doi.org/10.1103/PhysRevE.102.052412), revising it to simplify cell automata and to incorporate the stochastic nature of tissues, while permitting consideration in three dimensions, taking tissue domains into account.The simulations confirm that the cellular neighborhood, not just the state of the individual cell, is key to controlling fate. A polarized tissue with cells in a quiescent state will be stable until perturbed sufficiently by a carcinogenic event that propagates a depolarization wave through the tissue, driving it toward a cancer state. By this model, the depolarized state can be reversed, repolarizing the tissues if cell conductivity or ion pump activities change appropriately.Carvahlo concludes that this observation, which should be framed in conjunction with other (e.g., genetic and biomechanical) considerations, contributes to cancer progression and that it can be targeted pharmacologically (or otherwise) to prevent or treat cancer. Indeed, cancer therapies based on manipulation of the bioelectric state of cells are being developed in several laboratories. This model adds to the resources that may aid identification of new electrical/ion transport-based therapies.Ironing Out Cancer: Targeted Antitumor Properties of Zero-Valent Iron NanoparticlesMoving from ions to iron. Zero-valent iron (ZVI) nanoparticles were initially developed for magnetic resonance imaging to improve the magnetic properties of iron-based nanoparticles used as contrast agents. Here Wu et al. review ZVI properties and propose mechanisms by which ZVI nanoparticles can selectively and lethally target cancer cells, perhaps exploiting the acidic extracellular TME to aid efficiency.Ya-Na Wu, Li-Xing Yang, Pei-Wen Wang, Filip Braet, Dar-Bin Shieh. From microenvironment remediation to novel anticancer strategy: The emergence of zero valent iron nanoparticles. Sci Pharm 2022;14:99. https://doi.org/10.3390/pharmaceutics14010099Compared with iron oxide nanoparticles, when inside cells, ZVI nanoparticles generate stronger reactive oxygen species by the Fenton reaction, and in cancer cells they alter mitochondrial membrane potential, mitochondrial structure, and energy metabolism. Consequently, they can kill cancer cells selectively, while sparing nearby noncancer cells. There is in vitro and in vivo evidence to support this idea (e.g., lung/oral carcinoma, leukemia, and breast cancer).Several mechanisms for inducing antitumor activity have been proposed for ZVI nanoparticles. (1) In vivo, ZVI nanoparticles within the TME are thought to modulate tumor-associated macrophages, inhibiting tumor growth and metastasis by polarizing protumoral M2 macrophages to antitumoral M1 macrophages. (2) In vitro studies suggest a role for modulation of membrane potential. Although ZVI nanoparticle uptake was the same for control and oral or colorectal cancer cells, only cancer cells showed an irreversible loss of membrane potential in mitochondria. (3) The Fenton reaction is triggered in cancer cells by ZVI nanoparticles. In the acidic microenvironment of cancer, rapid ionization of iron nanoparticles enables release of ferrous ions, which react further with hydrogen peroxides. The resulting hydroxyl radicals are toxic to cancer cells.These mechanisms are likely to coexist. For example, attenuated immune responses are associated with acidic TME, where the ZVI nanoparticles degrade into “iron ion bombs” that modulate tumor-associated immunity. Since blood vessels in TME are often more permeable, ZVI nanoparticles may enter tumor tissues more readily through leaky blood vessels. The ability to target “iron ion bombs” that activate specifically in the TME (and inside cancer cells) offers an advantage over conventional small molecule compounds (e.g., doxorubicin).A caveat to ZVI nanoparticle therapies is that some cells demonstrate ZVI resistance, attenuating ZVI-induced oxidative stress, and displaying different genetic and metabolic profiles for mitochondrial function compared with nontumor cells. However, profiling tumors may allow personalized therapy to optimize ZVI-based outcomes.ZVI nanoparticles offer further possibilities to exploit their magnetic properties combined with therapies such as thermodynamic therapy and computational tomography, meaning tumor localization and treatment efficacy can be monitored.Molecular Multitasking: An Organic Molecule to Sense and Modulate Electric FieldsThe ability to both detect and modulate electric fields using a single molecule has far-reaching utility for bioelectricity research. Excitingly, Zhang et al. have designed and tested an organic molecule that can perform both functions.Yingmu Zhang, Jinghan He, Patrick J.G. Saris, Hyun Uk Chae, Subrata Das, Rehan Kapadiac, Andrea M. Armani. Multifunctional photoresponsive organic molecule for electric field sensing and modulation. J Mater Chem C 2022;10:1204–1211. DOI: 10.1039/d1tc05065fMolecules or particles with fluorescence properties are familiar tools for biological research. They provide information about cell structure and function and have emerging roles as indicators in optoelectronic devices to detect specific molecules. Designing a molecule that has dual functions (e.g., sensing and controlling an electric field) presents many challenges. For example, there is a need to isolate different excitation mechanisms to reduce crosstalk between domains within the single molecular entity.Zhang et al. have designed the first dual-purpose molecule that has an electric field sensor module and an electric field modulator module. They call it “NAI–TPE-PyS” because the sensor module is derived from the photo-induced electron transfer dye tetraphenylethylene (TPE) modified with 3-(4-methylpyridin-1-ium-1-yl)propane-1-sulfonate (PyS), and the modulator module is the organic photoconductor naphthalimide (NAI). A long noninteracting alkyl chain separates the modules, and further prevention of crosstalk is provided because TPE and NAI have little overlap in their absorption and emission spectra.The reporter module was modeled and tested in silico to optimize molecule design. It was found to have appropriate properties to facilitate voltage dependence. Importantly, the authors predict that the molecule will retain voltage-sensitive luminescence even if its motion is restricted by biological constraints, such as insertion in a cell membrane in an aligned form.The two modules can be controlled separately. Stimulating with 350 nm light activates the NAI-based module, emitting light at 400 nm wavelength, but stimulating with 390 nm light emits light at 585 nm, the emission spectrum for the TPE-based dye without emission from the NAI module. Therefore, 390 nm light is used for voltage imaging and 350 nm light is used for voltage modulation. This was demonstrated directly. When photoconductivity of a film of NAI–TPE-PyS deposited onto electrodes was assessed experimentally, current versus voltage measurements with 19 mW of 350 nm illumination revealed a stable, real-time, increase in voltage upon illumination, which decreased sharply when the light was switched off.The elegance and potential utility of this system will be clear to Bioelectricity readers. The technology builds on fluorescence microscopy technologies already found in most laboratories. If the molecules can be shown to be safe in biological systems, the mind boggles with possible experiments. I just wish it had a snappier name!Striking the Right (Spinal) Cord: Improved Electrical Stimulation Parameters in Spinal Cord InjurySpinal cord injury with functional deficits is often accompanied by significant physical, psychological, and economic challenges. Unfortunately, few effective treatments are available. Rowald et al. report rapid improvement of functional outcomes in three patients as part of a clinical trial using an improved modality for electrical stimulation of the damaged cord.Andreas Rowald, Salif Komi, Robin Demesmaeker, Edeny Baaklini … + 64 others …, and Grégoire Courtine. Activity-dependent spinal cord neuromodulation rapidly restores trunk and leg motor functions after complete paralysis. Nat Med 2022;28:260–271. https://doi.org/10.1038/s41591-021-01663-5Injury to the spinal cord can cause devastating loss of sensory and motor function, and the human spinal cord is notoriously poor at spontaneous repair. However, electrical stimulation therapies aiming to improve function of spared neuronal circuitry have been gaining prominence. Epidural electrical stimulation (EES) of the lumbosacral spinal cord, coupled with intense physical training, has shown promise, with restoration of supported walking in some individuals. Existing protocols are based on the idea that targeted stimulation of specific dorsal root nerve fibers using defined stimulation patterns can recapitulate the natural spatiotemporal activation patterns used for walking.The paddle type electrodes used for previous studies were designed for epidural positioning on the dorsal column, which would not target motor functions optimally. Rowald et al. reasoned that targeting the dorsal roots involved specifically in leg and trunk movements would be more likely to restore motor control.The team designed a 16-electrode EES array using a computational model to optimize precise electrode arrangements. The modeling data were coupled with anatomical scans of each participant and intraoperative single EES pulse stimulation and accompanying electromyograms to guide electrode placement for each patient. A wireless biomimetic EES implant pulse generator was configured that could deliver up to 10 stimulation waveforms. The impulse generator was implanted in the abdomen and controlled by a touchscreen interface using custom software that provided real-time EES waveforms, kinematics, and muscle recordings.Optimized EES stimulation protocols for each patient were then delivered with pulse frequencies of 20 Hz for extensor muscles and 100 Hz for flexor muscles, to reflect differences in natural neuron activation frequencies.Before the EES implant procedure, each of the three participants had complete sensorimotor paralysis and all were unable to take any steps. Impressively, on the first day, all participants could step independently on a treadmill, but with poor gait and extension. By the third day, gait patterns improved, and participants could walk on level ground with a weight supporting aid, as well as cycle on a recumbent bike, swim, and control trunk movements.Importantly, the improvement, with continued training, permitted independence in real-world settings, with the ability to fully support standing weight by 5 months. This is crucial to quality of life, permitting one participant to climb stairs and walk over uneven terrain. Previous studies have demonstrated that electrostimulation for spinal cord injury is generally effective only during episodes of stimulation. Importantly, Rowald et al. found that two participants recovered the ability to activate proximal muscles without needing EES. This represents an exciting step forward for spinal cord repair using bioelectricity. I look forward to the next chapter.Boning up on Biomaterials: An Electroactive Material for Bone Repair in Diabetic ConditionsThe report by Wu et al. (2022) elsewhere in this edition of Buzz describes modulation of macrophage activity by iron nanoparticles to target cancer. Here, Dai et al. drive macrophage function using a ferroelectric composite material in the context of diabetic bone repair.Xiaohan Dai, Boon Chin Heng, Yunyang Bai, Fuping You, Xiaowen Sun, Yiping Li, Zhangui Tang, Mingming Xu, Xuehui Zhang, Xuliang Deng. Restoration of electrical microenvironment enhances bone regeneration. Bioact Mater 2021;6:2029–2038. https://doi.org/10.1016/j.bioactmat.2020.12.020Diabetic individuals have increased incidence of bone fracture, delayed fracture resolution, and higher risk of bone graft failure. This is attributable in part to diabetes being a chronic inflammatory condition. Macrophages are key regulators of the immune response that can display a proinflammatory M1 phenotype or a prohealing M2 phenotype. Since bone has inherent electrical properties and electric fields drive tissue (including bone) repair, it follows that electroactive materials may stimulate bone repair. However, how electrically active materials impact diabetic osteogenesis has been underexplored.Dai et al. prepared a ferroelectric BaTiO3/poly (vinylidene fluoridetrifluoroethylene) [BTO/P(VDF-TrFE)] nanocomposite membrane to recapitulate the electrically active microenvironment within bone. Corona poling treatment creates a dipole, polarizing the material, which can be implanted in a bone defect with the negatively charged side facing the defect to create an enclosed electrical microenvironment. Under physiological conditions, the material approximated the electrical properties of bone, with a stable piezoelectric coefficient of ∼8.19 pC/N.The ability of the polarized material to influence macrophage function was tested in vitro using a human monocytic THP-1 cell line cultured for 2 days under normal glucose (NG; 5.5 mM) or high glucose (HG; 25 mM) conditions (19.5 mM mannitol was used in an osmotic control group). THP-1 cells grown under NG or mannitol control conditions displayed hallmarks of a nonactivated M0 state, whereas under HG conditions, they resembled the M1 proinflammatory phenotype, including elevation of inducible nitric oxide synthase (iNOS) and an array of proinflammatory cytokine genes.When grown in NG medium in vitro on the unpolarized electrically inert membrane (UP-NG), macrophages displayed an M0 phenotype, but in HG medium on a polarized electrically active membrane (P-HG), they had an M1 phenotype. Flow cytometry revealed a predominantly M2 macrophage phenotype in the P-HG group. Collectively, the data suggest that the electrically active membrane attenuated the HG-induced shift to M1 phenotype and promoted the M2 phenotype.To determine whether altering macrophage phenotype induced bone formation, human bone marrow mesenchymal stem cells (BM-MSCs) were grown for 7 days in vitro using macrophage-conditioned medium and osteogenic differentiation markers were quantified. Osteogenic gene and protein expression were downregulated for BM-MSCs in medium from UP-HG conditions, but conditioned medium collected from macrophages under P-HG conditions induced osteogenic markers in BM-MSCs.The ability of the material to induce bone formation was tested in a rat model of type 2 diabetes. Bilateral skull bone defects (5 mm) were made in male adult mice. Polarized electrically active membrane was implanted over the defect on one side with unpolarized material over the contralateral injury site. Micro-CT scans at 4 and 8 weeks postsurgery revealed more bone formation on the polarized electrically active material side, which was confirmed by histological analysis.The ability of an electrically active material to stimulate bone growth is a welcome addition to therapies to treat healing disorders in diabetes. What would be valuable in conjunction with this study is evidence for how diabetes impacts the natural electrical properties of bone.Spelling It Out: A Brain Computer Interface for Communication by a Completely “Locked in” PersonProgressive neurodegeneration and loss of muscle control in conditions such as amyotrophic lateral sclerosis (ALS) may eventually remove all possible modes of communication, leaving the individual in a “locked in” state (LIS), particularly after external ventilation becomes necessary. Chaudhary et al. demonstrate for the first time that a person with chronic LIS can communicate solely using a brain-based communication interface.Ujwal Chaudhary, Ioannis Vlachos, Jonas B. Zimmermann, Arnau Espinosa, Alessandro Tonin, Andres Jaramillo-Gonzalez, Majid Khalili-Ardali, Helge Topka, Jens Lehmberg, Gerhard M. Friehs, Alain Woodtli, John P. Donoghue, Niels Birbaumer. Spelling interface using intracortical signals in a completely locked-in patient enabled via auditory neurofeedback training. Nat Commun 2022;13:1236. https://doi.org/10.1038/s41467-022-28859-8This field has attracted some controversy! Although there has been success using cursor control and sentence formation for patients in LIS, those modes have not been successful at the level of volitional sentence communication for chronic LIS patients. One idea was that communication was prevented by frontotemporal brain degeneration in combination with chronic lack of sensory input, motor output, and cognitive dysfunction. This study set out to determine whether volitional brain-based communication was retained in LIS individuals.Two intracortical 64 microelectrode arrays were implanted in the brain precentral gyrus and superior frontal gyrus of a male patient with ALS leading to chronic LIS, who had lost all purposeful eye movement, his last remaining communication mode. On the 86th day after electrode implantation, a neurofeedback paradigm was used to provide the patient with an auditory feedback tone relating to his neural activity. He could modulate the neural firing rate (by a mechanism that remains mysterious) to change the pitch of the tone. From day 106, he could select letter groups or individual letters presented by a synthesized voice to free spell by modulating the tone up or down to indicate “yes” or “no.” He produced intelligible output on 44 of the 107 days when the speller was used.Although this study demonstrates proof of concept that a person with chronic LIS can communicate through a brain interface, significant improvements are required. The system is invasive and slow; the rate of character production in intelligible spelling episodes averaged only 1.08 characters per minute over the study period, and even then, only on some (41%) days. It is also possible that as neurodegeneration progresses further, even this mode of communication would prove ineffective.However, this patient was able to communicate with carers, family, and the study team using the device to provide personal messages, statements regarding needs, guidance for his physical care, and to suggest improvements to the system. For someone in chronic LIS, their carers, and loved ones, this has the potential, with refinement, to offer valued improvement of quality of life.Extremely Small: Growth and Enrichment of Extreme Electroactive MicroorganismsIn addition to basic bioelectricity research interest, electroactive microbes are gaining attention for their potential utility in microbial fuel cells and other emerging technologies. Most studies have used microbes from nonextreme environments due to their relative ease of culture, but Singh et al. offer a way to extend this work, describing detailed methods for growing and characterizing electroactive microorganisms from extreme environments.Ramandeep Singh, Srishti Chaudhary, Sukrampal Yadav, Sunil A. Patil. Protocol for bioelectrochemical enrichment, cultivation, and characterization of extreme electroactive microorganisms. STAR Protoc 2022;3:101114. https://doi.org/10.1016/j.xpro.2021.101114Electromicrobiology is the study of microorganisms that undergo extracellular electron transfer (EET) processes to or from a solid-state electron acceptor or donor. The microbes are categorized based on their EET traits as exoelectrogens (if they transfer electrons to a solid-state electron acceptor) or as electrotrophs (if they oxidize a solid-state electron donor). Singh et al. present a detailed protocol for a process to enrich, cultivate, and analyze the electrical properties of nitrate-enriching electrotrophs from a lake with extremely high salinity and pH.The procedure is broken down into six steps: (1) Preparation of media, reactor equipment, and inoculation with microbes (1–2 days). (2) Electrochemical enrichment of target microbes on electrodes and monitoring of bioelectrocatalytic current production (2–8 weeks). (3) Cyclic voltammetry to check for presence of redox compounds (4–6 h). (4) Analysis of redox metabolites and soluble redox mediators (5–6 h). (5) Microscopic confirmation of microbial growth at the electrode surface and bulk phase (2–3 days). (6) Identification of the enriched microbial communities (40–60 days).The ability to culture and characterize electroactive microbes from extreme environments may reveal populations with properties superior to those already targeted for bioelectrochemical reactors. This methodology has the potential to be modified for requirements of other extreme microbes.Easy to Swallow: An In Vitro Model for Study of Esophageal Ion Transport MechanismsEsophageal inflammation and cancer may arise from altered ion transport across esophageal tissues, but preclinical studies have been hampered by lack of an appropriate in vitro model. Korsós et al. have developed a three-dimensional mouse organoid model to overcome that barrier and identify ion transport activity in the organoids for the first time.Marietta Margaréta Korsós, Tamás Bellák, Eszter Becskeházi, Eleonóra Gál, Zoltán Veréb, Peter Hégyi, Viktória Venglovecz. Mouse organoid culture is a suitable model to study esophageal ion transport mechanisms. Am J Physiol Cell Physiol 2021;321:C798–C811. https://journals.physiology.org/doi/full/10.1152/ajpcell.00295.2021Although normal and esophageal adenocarcinoma cell lines can be used in classical Ussing chamber studies for ion transport, technical issues and cell line instability hamper reproducibility. A better solution is an organoid model in three dimensions (3D) that more faithfully recapitulates the esophageal tissues using noncancerous native cells. Esophageal organoid models exist in which undifferentiated stem cells at the basal layer proliferate and migrate to the lumen, differentiating as they move to replace the suprabasal cells. However, ion transporter activities have not been reported for such organoids.Korsós et al. used two different mouse strains to create 3D organoids. Esophageal tissues were dissociated and plated in a Matrigel matrix. Cell-filled organoid structures 250–300 μm in diameter formed 3–4 days after plating that continued to grow, with peak diameter between 7 and 9 days after plating. Organoids were characterized by immunomicroscopic and flow cytometric methods, confirming epithelial stem cell origin by expression of the stem cell marker leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) and the cytoplasmic keratin (CK) marker CK14, which is expressed in basal epithelial cells.Further analysis using polymerase chain reaction and immunochemistry demonstrated the presence of the most common ion transporters in esophageal organoids, including the Slc26a6 Cl−/HCO3− anion exchanger (AE), the Na+/H+ exchanger (NHE), the Na+/HCO3+ cotransporter (NBC), the cystic fibrosis transmembrane conductance regulator (CFTR), and anoctamin 1 Cl− channels. Functionally, although microfluorimetric studies showed low CFTR activity, NHE, AE, and NBC activities were relatively high.The ability to freeze and passage such organoids offers experimental flexibility and consistency. Consequently, this model will find use in pre-clinical studies of the causative roles for ion transport in esophageal immunoinflammatory conditions and cancer. It could thus aid development of therapies that target ion transport in these conditions.From Both Sides Now: Bipolar Electrodes for Sensing and Actuating Electrical Activities in CellsThis article emphasizes the underappreciated potential of bipolar electrochemistry as a tool for controlling and detecting redox reactions at the nanoscale inside cells.Andie J. Robinson, Akhil Jain, Ruman Rahman, Sidahmed Abayzeed, Richard J. M. Hague, Frankie J. Rawson. Impedimetric characterization of bipolar nanoelectrodes with cancer cells. ACS Omega 2021;6:29495–29505. https://doi.org/10.1021/acsomega.1c03547Stimulation and recording electrodes used in vivo are usually connected (hardwired) to an external power source. However, an alternative approach uses an external electric field (EF) and redox reactions in a conductive material to produce an EF wirelessly in the material by bipolar electrochemistry. Robinson et al. are working to harness such systems that operate remotely and noninvasively to report electrical input on a nanoscale.The basic principles of bipolar electrochemistry are intuitive, but often underappreciated. Consider any conductive material (electrode or particle) of any shape (sphere, flat plane) immersed in an electrolyte (cell cytoplasm, saline solution, culture medium, body fluid). When the electrolyte is subjected to an EF from external (feeder) electrodes, redox reactions at the edges of the electroconductive material poles induce an EF (potential difference) within it. The EF induced in the material bestows properties of a bipolar electrode (BPE), with an opposite polarity to the EF within the electrolyte itself. BPE properties arise spontaneously in the material with no direct connection to the external electrodes needed.The example describes a direct current BPE, but Robinson et al. propose that alternating BPEs offer advantages due to the ability to tune them by altering frequency. The authors further propose that electrochemical impedance spectroscopy could allow assessment of BPE systems on the nanoscale. To demonstrate this, they modeled the behavior of 125 nm gold nanoparticles (AuNPs) bathed in electrolytes (saline and deionized water) positioned between feeder electrodes. Thus, it could be shown theoretically that current could be driven through AuNPs in a high impedance electrolyte, making them act as nano-BPEs.The ability of AuNPs as BPEs to impact cell function was tested experimentally by incubating malignant brain cancer cells (U251 cell line) with AuNPs BPEs. Excitingly, the particles (500 μg/mL) were successfully internalized by the cells. In addition, the AuNPs were proven to act as BPEs within the cells. Electrochemical impedance spectroscopy measurements identified changes in cells loaded with AuNP BPEs compared with cells alone (in both water and saline) that suggested that current was being driven through them.Loading cells with nanoparticle BPEs offers many exciting experimental opportunities. For example, controlling cell behaviors by applying current with BPE nanoparticles (NPs) or obtaining electrical readout from discrete cell populations loaded with them. It is tempting to imagine that multiple populations of BPE NPs could be tuned for specific purposes in cells or tissues controlled remotely and noninvasively.It was a challenge to pare down the number of featured articles for this issue since so much interesting and important work is being published across a variety of topics. Thank you to everyone who is working so hard to advance this work. I am confident that you will continue to make my task of selecting articles even more difficult for the next issue. I look forward to it.FiguresReferencesRelatedDetails Volume 4Issue 2May 2022 InformationCopyright 2022, Mary Ann Liebert, Inc., publishersTo cite this article:Ann M. Rajnicek.Bioelectricity Buzz.Bioelectricity.May 2022.126-132.http://doi.org/10.1089/bioe.2022.0018Published in Volume: 4 Issue 2: May 26, 2022PDF download

Na,K-ATPase α1 and β-subunits show distinct localizations in the nervous tissue of the large milkweed bug

The Na,K-ATPase (NKA) is an essential ion transporter and signaling molecule in all animal tissues and believed to consist at least one α and one ß-subunit to form a functional enzyme. In the large milkweed bug, Oncopeltus fasciatus, adaptation to dietary cardiac glycosides (CGs), which can fatally block the NKA, has resulted in gene duplications leading to four α1-subunits. These differ in sensitivity to CGs, but resistance trades off against ion pumping activity, thus influencing the α1-subunits’ suitability for specific tissues. Besides, O. fasciatus possesses four different ß-subunits that can alter the NKA's kinetics and should play an essential role in the formation of cellular junctions.Proteomic analyses revealed the distribution and composition of α1/ß-complexes in the nervous tissue of O. fasciatus. The highly CG-resistant, but less active α1B and the highly active, but less resistant α1C predominated in the nervous tissue and co-occurred with ß2 and ß3, partly forming larger complexes than just heterodimers. Immunohistochemical analyses provided a fine scale resolution of the subunits’ distribution in different morphological structures of the nervous tissue. This may suggest that α1 as well as ß-subunits occur in isolation without the other subunit, which contradicts the present understanding that the two types of subunits have to associate to form functional complexes. An isolated occurrence was especially prominent for ß3 and βx, the enigmatic fourth and N-terminally largely truncated ß-subunit. We hypothesize that dimerization of these ß-subunits plays a role in cell–cell contacts.

Generation and Export of Red Blood Cell ATP in Health and Disease.

Metabolic homeostasis in animals depends critically on evolved mechanisms by which red blood cell (RBC) hemoglobin (Hb) senses oxygen (O2) need and responds accordingly. The entwined regulation of ATP production and antioxidant systems within the RBC also exploits Hb-based O2-sensitivity to respond to various physiologic and pathophysiologic stresses. O2 offloading, for example, promotes glycolysis in order to generate both 2,3-DPG (a negative allosteric effector of Hb O2 binding) and ATP. Alternatively, generation of the nicotinamide adenine dinucleotide phosphate (NADPH) critical for reducing systems is favored under the oxidizing conditions of O2 abundance. Dynamic control of ATP not only ensures the functional activity of ion pumps and cellular flexibility, but also contributes to the availability of vasoregulatory ATP that can be exported when necessary, for example in hypoxia or upon RBC deformation in microvessels. RBC ATP export in response to hypoxia or deformation dilates blood vessels in order to promote efficient O2 delivery. The ability of RBCs to adapt to the metabolic environment via differential control of these metabolites is impaired in the face of enzymopathies [pyruvate kinase deficiency; glucose-6-phosphate dehydrogenase (G6PD) deficiency], blood banking, diabetes mellitus, COVID-19 or sepsis, and sickle cell disease. The emerging availability of therapies capable of augmenting RBC ATP, including newly established uses of allosteric effectors and metabolite-specific additive solutions for RBC transfusates, raises the prospect of clinical interventions to optimize or correct RBC function via these metabolite delivery mechanisms.

A missense mutation converts the Na+,K+-ATPase into an ion channel and causes therapy-resistant epilepsy

The ion pump Na+,K+-ATPase is a critical determinant of neuronal excitability; however, its role in the etiology of diseases of the central nervous system (CNS) is largely unknown. We describe here the molecular phenotype of a Trp931Arg mutation of the Na+,K+-ATPase catalytic α1 subunit in an infant diagnosed with therapy-resistant lethal epilepsy. In addition to the pathological CNS phenotype, we also detected renal wasting of Mg2+. We found that membrane expression of the mutant α1 protein was low, and ion pumping activity was lost. Arginine insertion into membrane proteins can generate water-filled pores in the plasma membrane, and our molecular dynamic (MD) simulations of the principle states of Na+,K+-ATPase transport demonstrated massive water inflow into mutant α1 and destabilization of the ion-binding sites. MD simulations also indicated that a water pathway was created between the mutant arginine residue and the cytoplasm, and analysis of oocytes expressing mutant α1 detected a nonspecific cation current. Finally, neurons expressing mutant α1 were observed to be depolarized compared with neurons expressing wild-type protein, compatible with a lowered threshold for epileptic seizures. The results imply that Na+,K+-ATPase should be considered a neuronal locus minoris resistentia in diseases associated with epilepsy and with loss of plasma membrane integrity.

Protective Effects of Inosine on Memory Consolidation in a Rat Model of Scopolamine-Induced Cognitive Impairment: Involvement of Cholinergic Signaling, Redox Status, and Ion Pump Activities.

This study investigated the effects of inosine on memory acquisition and consolidation, cholinesterases activities, redox status and Na+, K+-ATPase activity in a rat model of scopolamine-induced cognitive impairment. Adult male rats were divided into four groups: control (saline), scopolamine (1mg/kg), scopolamine plus inosine (50mg/kg), and scopolamine plus inosine (100mg/kg). Inosine was pre-administered for 7days, intraperitoneally. On day 8, scopolamine was administered pre (memory acquisition protocol) or post training (memory consolidation protocol) on inhibitory avoidance tasks. The animals were subjected to the step-down inhibitory avoidance task 24hours after the training. Scopolamine induced impairment in the acquisition and consolidation phases; however, inosine was able to prevent only the impairment in memory consolidation. Also, scopolamine increased the activity of acetylcholinesterase and reduced the activity of Na+, K+-ATPase and the treatment with inosine protected against these alterations in consolidation protocol. In the animals treated with scopolamine, inosine improved the redox status by reducing the levels of reactive oxygen species and thiobarbituric acid reactive substances and restoring the activity of the antioxidant enzymes, superoxide dismutase and catalase. Our findings suggest that inosine may offer protection against scopolamine-induced memory consolidation impairment by modulating brain redox status, cholinergic signaling and ion pump activity. This compound may provide an interesting approach in pharmacotherapy and as a prophylactic against neurodegenerative mechanisms involved in Alzheimer's disease.

A hydro-osmotic coarsening theory of biological cavity formation.

Fluid-filled biological cavities are ubiquitous, but their collective dynamics has remained largely unexplored from a physical perspective. Based on experimental observations in early embryos, we propose a model where a cavity forms through the coarsening of myriad of pressurized micrometric lumens, that interact by ion and fluid exchanges through the intercellular space. Performing extensive numerical simulations, we find that hydraulic fluxes lead to a self-similar coarsening of lumens in time, characterized by a robust dynamic scaling exponent. The collective dynamics is primarily controlled by hydraulic fluxes, which stem from lumen pressures differences and are dampened by water permeation through the membrane. Passive osmotic heterogeneities play, on the contrary, a minor role on cavity formation but active ion pumping can largely modify the coarsening dynamics: it prevents the lumen network from a collective collapse and gives rise to a novel coalescence-dominated regime exhibiting a distinct scaling law. Interestingly, we prove numerically that spatially biasing ion pumping may be sufficient to position the cavity, suggesting a novel mode of symmetry breaking to control tissue patterning. Providing generic testable predictions, our model forms a comprehensive theoretical basis for hydro-osmotic interaction between biological cavities, that shall find wide applications in embryo and tissue morphogenesis.

An equivalent electrical circuit for the Hindmarsh‐Rose model

SummaryHardware realizations of neural networks can pave the way towards a new generation of processors due to the biological role model being superior in terms of speed and energy‐efficiency compared to today's processors. This can be achieved by deriving novel design principles for circuits being obtainable when replicating and investigating real biological neural networks in depth. This has, for example, been done by utilizing the Hindmarsh‐Rose model, offering a rich repertoire of neuronal firing patterns. Our aim is to synthesize a theoretical, equivalent electrical circuit of the Hindmarsh‐Rose model being well interpretable in terms of biology, since this supports the derivation of design principles from biology and can serve as a basis for a systematic circuit simplification. We do this by starting from a linearized model because this allows for a systematic approach and then first derive a linear and afterwards a nonlinear equivalent electrical circuit. The resulting circuit has a structure similar to conductance‐based models, where a deployed negative impedance converter can be seen as a deeper modeling of ion pump activity. Simulation results of the proposed circuits show the functionality of the equivalent circuits.