Viscoelasticity, Conformational Transition and Ultrastructure of Kappa-Carrageenan in the Presence of Potassium Ion around the Critical Total Ion Concentration

2008 ◽  
Author(s):  
María C. Núñez-Santiago ◽  
Alberto Tecante ◽  
Sylvie Durand ◽  
Catherine Garnier ◽  
Jean L. Doublier ◽  
...  
Keyword(s):  
Conformational Transition ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Kappa Carrageenan

scholarly journals DNA Aptamer Functionalized Hydrogels for Interferometric Fiber-Optic Based Continuous Monitoring of Potassium Ions

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 266
Author(s):  
Nataša Žuržul ◽  
Bjørn Torger Stokke
Keyword(s):  
Conformational Transition ◽  
Polymer Network ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Dna Aptamer ◽  
Blood Levels ◽  
Label Free ◽  
Practical Applications ◽  
Hydrogel Matrix ◽  
K Concentration

In the present paper, we describe a potassium sensor based on DNA-aptamer functionalized hydrogel, that is capable of continuous label-free potassium ion (K+) monitoring with potential for in situ application. A hydrogel attached to the end of an optical fiber is designed with di-oligonucleotides grafted to the polymer network that may serve as network junctions in addition to the covalent crosslinks. Specific affinity toward K+ is based on exploiting a particular aptamer that exhibits conformational transition from single-stranded DNA to G-quadruplex formed by the di-oligonucleotide in the presence of K+. Integration of this aptamer into the hydrogel transforms the K+ specific conformational transition to a K+ concentration dependent deswelling of the hydrogel. High-resolution interferometry monitors changes in extent of swelling at 1 Hz and 2 nm resolution for the hydrogel matrix of 50 µm. The developed hydrogel-based biosensor displayed high selectivity for K+ ions in the concentration range up to 10 mM, in the presence of physiological concentrations of Na+. Additionally, the concentration dependent and selective K+ detection demonstrated in the artificial blood buffer environment, both at room and physiological temperatures, suggests substantial potential for practical applications such as monitoring of potassium ion concentration in blood levels in intensive care medicine.

scholarly journals In Vivo Neocortical [K]o Modulation by Targeted Stimulation of Astrocytes

2021 ◽  
Vol 22 (16) ◽  
pp. 8658
Author(s):  
Azin EbrahimAmini ◽  
Shanthini Mylvaganam ◽  
Paolo Bazzigaluppi ◽  
Mohamad Khazaei ◽  
Alexander Velumian ◽  
...  
Keyword(s):  
Nervous System ◽  
Membrane Potential ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Spreading Depolarization ◽  
Potential Tool ◽  
Stimulation Of

A normally functioning nervous system requires normal extracellular potassium ion concentration ([K]o). Throughout the nervous system, several processes, including those of an astrocytic nature, are involved in [K]o regulation. In this study we investigated the effect of astrocytic photostimulation on [K]o. We hypothesized that in vivo photostimulation of eNpHR-expressing astrocytes leads to a decreased [K]o. Using optogenetic and electrophysiological techniques we showed that stimulation of eNpHR-expressing astrocytes resulted in a significantly decreased resting [K]o and evoked K responses. The amplitude of the concomitant spreading depolarization-like events also decreased. Our results imply that astrocytic membrane potential modification could be a potential tool for adjusting the [K]o.

THE INFLUENCE OF POTASSIUM ION UPON GLUCOSE UPTAKE AND GLYCOGEN SYNTHESIS IN THE ISOLATED RAT DIAPHRAGM

1955 ◽  
Vol 33 (1) ◽  
pp. 687-694 ◽  
Author(s):  
D. W. Clarke
Keyword(s):  
Glucose Uptake ◽  
Glycogen Synthesis ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Rat Diaphragm ◽  
High Potassium ◽  
High Concentrations ◽  
Glycogen Breakdown ◽  
Isolated Rat

The amounts of glucose taken from a medium, and the amounts of glycogen synthesized, by rat hemidiaphragms were studied under various conditions. High concentrations of potassium ion inhibited the glucose uptake and there was also a reduced net glycogen synthesis. Glycogen breakdown was probably not increased by high potassium ion concentration. The effect of potassium was most marked when conditions were such that one would ordinarily expect a considerable glucose uptake or glycogen synthesis. The action of insulin was not peculiarly susceptible to potassium ion inhibition.

scholarly journals Anomalous Rectification in the Squid Giant Axon Injected with Tetraethylammonium Chloride

1965 ◽  
Vol 48 (5) ◽  
pp. 859-872 ◽  
Author(s):  
Clay M. Armstrong ◽  
Leonard Binstock
Keyword(s):  
Action Potential ◽  
Outward Current ◽  
Giant Axon ◽  
Potassium Ion ◽  
Ion Concentration ◽  
High Potassium ◽  
Tetraethylammonium Chloride ◽  
Voltage Curve ◽  
Instantaneous Current ◽  
Current Voltage Curve

The injection of tetraethylammonium chloride into the giant axon of the squid prolongs the action potential and eliminates most of the late current under voltage-clamp. Experiments on fibers in an external medium of high potassium ion concentration demonstrate that injected tetraethylammonium chloride causes rectification of the instantaneous current-voltage curve for potassium by excluding outward current. This interference with the flow of outward potassium ion current underlies the prolongation of the action potential seen in tetraethylammonium-injected fibers.

Larval metamorphosis of the opisthobranch molluscAdalaria proxima(Gastropoda: Nudibranchia): the effects of choline and elevated potassium ion concentration

1991 ◽  
Vol 71 (1) ◽  
pp. 53-72 ◽  
Author(s):  
Christopher D. Todd ◽  
Matthew G. Bentley ◽  
Jonathan N. Havenhand
Keyword(s):  
Sea Water ◽  
Choline Chloride ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Dependent Manner ◽  
Larval Metamorphosis ◽  
Artificial Induction ◽  
Ion Substitution ◽  
Veliger Larvae ◽  
Dose Dependent

Veliger larvae of the nudibranch molluscAdalaria proximaare triggered to metamorphose to the benthic form by the adult prey bryozoan,Electro pilosa.Ion substitution and supplementation experiments with artificial sea water (ASW) have, however, shown that metamorphosis can be induced by elevation of the potassium ion concentration alone. Approximately 19 mM K+ASW (10 mM ‘excess’) was found to elicit maximal metamorphic responses: 29 and 39 mM K+ASW had no inductive effect. Choline chloride was also found to induce metamorphosis in a dose-dependent manner, with lO M ineffective, 10 M approximately threshold, and 5×10 M to 10 M optimal. Concentrations of choline >10 M were sub-lethally toxic. That the absence of larval metamorphosis on exposure to 29 and 39 mM K ASW was due to inhibition is inferred from interaction experiments with choline: at these concentrations of K, metamorphosis in response to choline could be abolished. Timed-exposure experiments indicated that artificial induction elicited by elevated K and choline involve either separate mechanisms, or different parts of the same pathway. Thus, whilst larvae required to be continuously exposed to 19 mM K ASW in order to complete metamorphosis, those exposed to 10 M choline would subsequently complete development in normal ASW following only 1–2 h exposure to the inducer. Preliminary experiments failed to specify further the nature of the natural inducer, beyond the confirmation that live intact colonies of the bryozoanElectro pilosawill trigger larvae to metamorphose.

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