Search results for " channels."

Hydraulic jumps at drop and abrupt enlargement in rectangular channel

2002

The different types of hydraulic jumps that occur in a rectangular channel at an abrupt increase in section are experimentally studied. The abrupt section increase is due to both a drop and an increase in the channel width. Experiments were carried out with three different values of the ratio L/l between the channel widths respectively downstream and upstream of the abrupt section increase. For each L/l value five values of Froude number F1, of the supercritical flow upstream of the section increase were considered, and for each of them live values of the depth y1 of the same flow. The experiments showed that, as the depth y2 of the downstream subcritical flow increases, several types of hy…

Ion conduction in the KcsA potassium channel analyzed with a minimal kinetic model.

2004

We use a model by Nelson to study the current-voltage and conductance-concentration curves of bacterial potassium channel KcsA without assuming rapid ion translocation. Ion association to the channel filter is rate controlling at low concentrations, but dissociation and transport in the filter can limit conduction at high concentration for ions other than ${\mathrm{K}}^{+}$. The absolute values of the effective rate constants are tentative but the relative changes in these constants needed to qualitatively explain the experiments should be of significance.

On Equivalent Random Traffic method extension

2011

The key result of the paper is the Equivalent Random Traffic (ERT) method extension for estimation of the throughput for schemes with traffic splitting. The excellent accuracy (relative error is less than 1%) is shown in numerical example. A numerical algorithm is given — how to estimate the throughput for schemes at traffic splitting and merging. The paper also contains new Erlang-B formula algorithm for non-integer number of channels based on parabolic approximation.

TRPA1 channel is a cardiac target of mIGF-1/SIRT1 signaling.

2014

Cardiac overexpression of locally acting muscle-restricted (m)IGF-1 and the consequent downstream activation of NAD+-dependent protein deacetylase sirtuin 1 (SIRT1) trigger potent cardiac antioxidative and antihypertrophic effects. Transient receptor potential (TRP) cation channel A1 (TRPA1) belongs to the TRP ion channel family of molecular detectors of thermal and chemical stimuli that activate sensory neurons to produce pain. Recently, it has been shown that TRPA1 activity influences blood pressure, but the significance of TRPA1 in the cardiovascular system remains elusive. In the present work, using genomic screening in mouse hearts, we found that TRPA1 is a target of mIGF-1/SIRT1 sign…

Regulation of Calcium Channel Activity by Lipid Domain Formation in Planar Lipid Bilayers

2003

The sarcoplasmic reticulum channel (ryanodine receptor) from cardiac myocytes was reconstituted into planar lipid bilayers consisting of 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE) and 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) in varying ratios. The channel activity parameters, i.e., open probability and average open time and its resolved short and long components, were determined as a function of POPE mole fraction (X(PE)) at 22.4 degrees C. Interestingly, all of these parameters exhibited a narrow and pronounced peak at X(PE) approximately 0.80. Differential scanning calorimetric measurements on POPE/POPC liposomes with increasing X(PE) indicated that the lipid bilayer ente…

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…

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…

Membrane potential bistability in nonexcitable cells as described by inward and outward voltage-gated ion channels.

2014

The membrane potential of nonexcitable cells, defined as the electrical potential difference between the cell cytoplasm and the extracellular environment when the current is zero, is controlled by the individual electrical conductance of different ion channels. In particular, inward- and outward-rectifying voltage-gated channels are crucial for cell hyperpolarization/depolarization processes, being amenable to direct physical study. High (in absolute value) negative membrane potentials are characteristic of terminally differentiated cells, while low membrane potentials are found in relatively depolarized, more plastic cells (e.g., stem, embryonic, and cancer cells). We study theoretically t…

An ion channel-gated adenylyl cyclase

1992

G protein-coupled odorant receptors underlie mechanosensitivity in mammalian olfactory sensory neurons

2014

Mechanosensitive cells are essential for organisms to sense the external and internal environments, and a variety of molecules have been implicated as mechanical sensors. Here we report that odorant receptors (ORs), a large family of G protein-coupled receptors, underlie the responses to both chemical and mechanical stimuli in mouse olfactory sensory neurons (OSNs). Genetic ablation of key signaling proteins in odor transduction or disruption of OR–G protein coupling eliminates mechanical responses. Curiously, OSNs expressing different OR types display significantly different responses to mechanical stimuli. Genetic swap of putatively mechanosensitive ORs abolishes or reduces mechanical res…