Search results for "Membrane Potential"

Biocompatibility and internalization assessment of bare and functionalised mesoporous silica nanoparticles

2021

[EN] We report herein an evaluation of the effect of several mesoporous silica nanoparticles (MSNs) on the cellular uptake and in vitro cytotoxicity in human cells. Bare MSNs and MSNs functionalized with polyethylene glycol or hyaluronic acid are employed to evaluate uptake efficiency and mechanisms of endocytosis in cancer (MDA-MB-231) and non-cancer (MCF10A) cells. Moreover, changes in viability, cell cycle, oxidative stress, and mitochondrial membrane potential are evaluated. Our results confirm that MSNs are internalized efficiently by human cells and that uptake mechanisms differ for cell types and particles. We also confirm that MSNs are biocompatible materials that do not induce ROS/…

Two Structurally Distinct Pathways for the Voltage-Sensing S4 Helices

2010

In voltage-dependent ion channels, the movement of the voltage-sensing S4 helices produces gating currents. The charge displaced as a function of the membrane potential (Q-V) is well described by a sequential two-state Boltzmann relation, indicating that there are at least two steps of gating charge movement from their Resting state to the Active state. In addition, it has been shown that at a maintained positive potential, the S4 helices of voltage-gated Na, Ca and K channels and the voltage sensitive phosphatase Ci-VSP, undergo a slower secondary conformational transition stabilizing the sensor in a Relaxed (inactivated) state. From the Relaxed state, the Q-V relation exhibits a strong sh…

Cell Systems Bioelectricity: How Different Intercellular Gap Junctions Could Regionalize a Multicellular Aggregate

2021

Simple Summary Electric potential patterns across tissues are instructive for development, regeneration, and tumorigenesis because they can influence transcription, migration, and differentiation through biochemical and biomechanical downstream processes. Determining the origins of the spatial domains of distinct potential, which in turn decide anatomical features such as limbs, eyes, brain, and heart, is critical to a mature understanding of how bioelectric signaling drives morphogenesis. We studied theoretically how connexin proteins with different voltage-gated gap junction conductances can maintain multicellular regions at distinct membrane potentials. We analyzed a minimal model that i…

Fluorescent styrylpyrylium probes for the imaging of mitochondria in live cells

2021

Eight styrylpyrylium tetrafluoroborate salts have been synthesized and fully optically characterized by UV-vis absorption and fluorescence steady-state/time-resolved spectroscopies. The new dyes exhibit strong emission bands with yellow–orange colours, depending on the substituents present in the structure. Notably, the Stokes shift recorded for some of them exceeds 100 nm, a very valuable feature for biological imaging. Four of them have been assayed as biological imaging agents by confocal laser scanning microscopy (CLSM) in the human hepatoma cell line Hep3B. It has been found that all the compounds efficiently stain intracellular structures which have been identified as mitochondria thr…

Electrical Coupling in Ensembles of Nonexcitable Cells: Modeling the Spatial Map of Single Cell Potentials

2015

We analyze the coupling of model nonexcitable (non-neural) cells assuming that the cell membrane potential is the basic individual property. We obtain this potential on the basis of the inward and outward rectifying voltage-gated channels characteristic of cell membranes. We concentrate on the electrical coupling of a cell ensemble rather than on the biochemical and mechanical characteristics of the individual cells, obtain the map of single cell potentials using simple assumptions, and suggest procedures to collectively modify this spatial map. The response of the cell ensemble to an external perturbation and the consequences of cell isolation, heterogeneity, and ensemble size are also ana…

Corrigendum to “Zinc oxide nanoparticles mediated cytotoxicity, mitochondrial membrane potential and level of antioxidants in presence of melatonin” …

2021

Protective effect of bioaccessible fractions of citrus fruit pulps against H2O2-induced oxidative stress in Caco-2 cells

2017

Fruit pulps from Navel (N) and Cara Cara (CC) oranges, and Clementine mandarin freshly harvested (M) and refrigerated stored (M12) were used to evaluate the cytoprotective effect of their bioaccessible fractions (BF) against H2O2-induced oxidative stress in Caco-2 cells. BF of samples preserved viability vs. H2O2 treated cells, reaching values similar to controls. Lipid peroxidation was reduced to levels of control cells, but M did not reach control values. ROS and mitochondrial membrane potential changes (Δψm) values were reduced compared with H2O2 treated cells, but without achieving control levels. A significant reduction in cell proportions in G1 phase and a significant increase in sub-…

Effects of pH on ion transport in weak amphoteric membranes

1997

Abstract We have studied theoretically the effect of pH on the ion transport through amphoteric polymer membranes composed of weak polyelectrolytes where the charged groups are randomly distributed along the axial direction of the membrane. This system serves as a simplified model for the pH controlled ion transport and drug delivery through membranes of biological interest. The theoretical approach employed is based on the Nernst-Planck equations. The complete system of electrical charges formed by: (i) the pH dependent, amphoretic membrane fixed charge, and (ii) the four mobile charges (the salt ions and the hydrogen and hydroxide ions) have been taken into account without any additional …

Integration of different cardiac electrophysiological models into a single simulation pipeline

2012

Clinical translation of computational models of the heart has been hampered by the absence of complete and rigorous technical and clinical validation, as well as benchmarking of the developed tools. To address this issue, a dataset containing the cardiac anatomy and fibre orientations from magnetic resonance images (MRI), as well as epicardial transmembrane potentials from optical mapping acquired on ex-vivo porcine hearts, have previously been made available to the community. Image processing techniques were developed to integrate MRI images with electrical information. Different models were tested and compared with the integrated data1, including: i) a new methodology to customize and reg…

2015

The explosive pollination mechanism of the prayer plants (Marantaceae) is unique among plants. After a tactile stimulus by a pollinator, the style curls up rapidly and mediates pollen exchange. It is still under discussion whether this explosive movement is released electrophysiologically, i.e. by a change in the membrane potential (as in Venus flytrap), or purely mechanically. In the present study, electrophysiological experiments are conducted to clarify the mechanism. Artificial release experiments (chemical and electrical) and electrophysiological measurements were conducted with two phylogenetically distant species, Goeppertia bachemiana (E. Morren) Borchs. & S. Suarez and Donax cannif…