Role of membrane permeabilities (calcium, chloride, and potassium) in the genesis of the notch observed on simian and prosimian cardiac action potentials

Cardiac action potentials are long because the magnitude of some potassium currents is reduced at depolarized potentials. The slow onset of repolarization is initiated by the opening of delayed rectifier potassium channels. A decrease in function of these channels resulting from gene mutations or pharmacological block increases risk of life-threatening ventricular arrhythmias.

Download Full-text

Basic Cardiac Electrophysiology

Mayo Clinic Electrophysiology Manual ◽

10.1093/med/9780199941193.003.0007 ◽

2013 ◽

pp. 171-190

Author(s):

Hon-Chi Lee ◽

Arshad Jahangir

Keyword(s):

Ion Channels ◽

Cardiac Arrhythmias ◽

Action Potentials ◽

Cardiac Electrophysiology ◽

Structure And Function ◽

Learning Objectives ◽

Cardiac Ion Channels ◽

Cardiac Action ◽

And Function

The learning objectives of this chapter are to review some basic electrophysiologic concepts that are useful for the clinician. These include 1) the structure and function of cardiac ion channels; 2) the role of ion channels in the generation of cardiac action potentials; 3) the mechanisms of cardiac arrhythmias; and 4) inherited and acquired channelopathies.

Download Full-text

New Molecular Scaffolds for Fluorescent Voltage Indicators

10.26434/chemrxiv.7338683.v1 ◽

2018 ◽

Author(s):

Steven Boggess ◽

Shivaani Gandhi ◽

Brian Siemons ◽

Nathaniel Huebsch ◽

Kevin Healy ◽

...

Keyword(s):

Membrane Potential ◽

Action Potentials ◽

Induced Pluripotent Stem Cell ◽

Molecular Wire ◽

Voltage Sensing ◽

Design Synthesis ◽

Cardiac Action ◽

Action Potential Waveform ◽

Induced Pluripotent ◽

Voltage Sensing Domain

<div> <p>The ability to non-invasively monitor membrane potential dynamics in excitable cells like neurons and cardiomyocytes promises to revolutionize our understanding of the physiology and pathology of the brain and heart. Here, we report the design, synthesis, and application of a new class of fluorescent voltage indicator that makes use of a fluorene-based molecular wire as a voltage sensing domain to provide fast and sensitive measurements of membrane potential in both mammalian neurons and human-derived cardiomyocytes. We show that the best of the new probes, fluorene VoltageFluor 2 (fVF 2) readily reports on action potentials in mammalian neurons, detects perturbations to cardiac action potential waveform in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, shows a substantial decrease in phototoxicity compared to existing molecular wire-based indicators, and can monitor cardiac action potentials for extended periods of time. Together, our results demonstrate the generalizability of a molecular wire approach to voltage sensing and highlights the utility of fVF 2 for interrogating membrane potential dynamics.</p> </div>

Download Full-text

Tetrodotoxin: A New Strategy to Treat Visceral Pain?

Toxins ◽

10.3390/toxins13070496 ◽

2021 ◽

Vol 13 (7) ◽

pp. 496

Author(s):

Ana Campos-Ríos ◽

Lola Rueda-Ruzafa ◽

Salvador Herrera-Pérez ◽

Paula Rivas-Ramírez ◽

José Antonio Lamas

Keyword(s):

Action Potentials ◽

Channel Blocker ◽

Visceral Pain ◽

Visceral Hypersensitivity ◽

Afferent Neurons ◽

Sodium Channel Blocker ◽

Voltage Gated Sodium Channels ◽

New Strategy ◽

Specific Receptors

Visceral pain is one of the most common symptoms associated with functional gastrointestinal (GI) disorders. Although the origin of these symptoms has not been clearly defined, the implication of both the central and peripheral nervous systems in visceral hypersensitivity is well established. The role of several pathways in visceral nociception has been explored, as well as the influence of specific receptors on afferent neurons, such as voltage-gated sodium channels (VGSCs). VGSCs initiate action potentials and dysfunction of these channels has recently been associated with painful GI conditions. Current treatments for visceral pain generally involve opioid based drugs, ≠≠which are associated with important side-effects and a loss of effectiveness or tolerance. Hence, efforts have been intensified to find new, more effective and longer-lasting therapies. The implication of VGSCs in visceral hypersensitivity has drawn attention to tetrodotoxin (TTX), a relatively selective sodium channel blocker, as a possible and promising molecule to treat visceral pain and related diseases. As such, here we will review the latest information regarding this toxin that is relevant to the treatment of visceral pain and the possible advantages that it may offer relative to other treatments, alone or in combination.

Download Full-text

The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

Scientific Reports ◽

10.1038/s41598-021-85712-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Charalampos Konstantinou ◽

Yuze Wang ◽

Giovanna Biscontin ◽

Kenichi Soga

Keyword(s):

Calcium Carbonate ◽

Calcium Chloride ◽

Urease Activity ◽

Coarse Sand ◽

Carbonate Precipitation ◽

Population Densities ◽

Carbonate Cements ◽

Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

Download Full-text

Tetrodotoxin-resistant release of ATP from superfused rabbit detrusor muscle during electrical field stimulation in the presence of luciferin–luciferase

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y84-026 ◽

1984 ◽

Vol 62 (1) ◽

pp. 153-156 ◽

Cited By ~ 15

Author(s):

Archana Chaudhry ◽

John W. Downie ◽

Thomas D. White

Keyword(s):

Action Potentials ◽

Electrical Field Stimulation ◽

Detrusor Muscle ◽

Electrical Field ◽

Stimulation Parameters ◽

Rabbit Bladder ◽

Firefly Luciferin ◽

Rabbit Urinary Bladder ◽

Stimulation Of

The present study was carried out to assess the possible role of ATP in the noncholinergic, nonadrenergic transmission in the rabbit urinary bladder. When rabbit detrusor muscle strips were superfused with medium containing firefly luciferin–luciferase and stimulated transmurally at low stimulation parameters, tetrodotoxin-sensitive contractions were obtained but no release of ATP could be detected. However, at somewhat higher stimulation parameters, release of ATP was observed. This release of ATP was not diminished by tetrodotoxin indicating that ATP was not likely released as a result of propagated action potentials in nerves. Because contractions persisted in the presence of tetrodotoxin, it is possible that the ATP might have been released as a result of direct electrical stimulation of the muscle. These results do not support the idea that ATP is released as a neurotransmitter in the rabbit bladder.

Download Full-text