The Neuropeptide Nocistatin Is Not a Direct Agonist of Acid-Sensing Ion Channel 1a (ASIC1a)

Acid-sensing ion channels (ASICs) are ionotropic receptors that are directly activated by protons. Although protons have been shown to act as a neurotransmitter and to activate ASICs during synaptic transmission, it remains a possibility that other ligands directly activate ASICs as well. Neuropeptides are attractive candidates for alternative agonists of ASICs, because related ionotropic receptors are directly activated by neuropeptides and because diverse neuropeptides modulate ASICs. Recently, it has been reported that the neuropeptide nocistatin directly activates ASICs, including ASIC1a. Here we show that nocistatin does not directly activate ASIC1a expressed in Xenopus oocytes or CHO cells. Moreover, we show that nocistatin acidifies the bath solution to an extent that can fully explain the previously reported activation by this highly acidic peptide. In summary, we conclude that nocistatin only indirectly activates ASIC1a via acidification of the bath solution.

Ca2+ Dependence of Volume-Regulated VRAC/LRRC8 and TMEM16A Cl– Channels

All vertebrate cells activate Cl– currents (ICl,swell) when swollen by hypotonic bath solution. The volume-regulated anion channel VRAC has now been identified as LRRC8/SWELL1. However, apart from VRAC, the Ca2+-activated Cl– channel (CaCC) TMEM16A and the phospholipid scramblase and ion channel TMEM16F were suggested to contribute to cell swelling-activated whole-cell currents. Cell swelling was shown to induce Ca2+ release from the endoplasmic reticulum and to cause subsequent Ca2+ influx. It is suggested that TMEM16A/F support intracellular Ca2+ signaling and thus Ca2+-dependent activation of VRAC. In the present study, we tried to clarify the contribution of TMEM16A to ICl,swell. In HEK293 cells coexpressing LRRC8A and LRRC8C, we found that activation of ICl,swell by hypotonic bath solution (Hypo; 200 mosm/l) was Ca2+ dependent. TMEM16A augmented the activation of LRRC8A/C by enhancing swelling-induced local intracellular Ca2+ concentrations. In HT29 cells, knockdown of endogenous TMEM16A attenuated ICl,swell and changed time-independent swelling-activated currents to VRAC-typical time-dependent currents. Activation of ICl,swell by Hypo was attenuated by blocking receptors for inositol trisphosphate and ryanodine (IP3R; RyR), as well as by inhibiting Ca2+ influx. The data suggest that TMEM16A contributes directly to ICl,swell as it is activated through swelling-induced Ca2+ increase. As activation of VRAC is shown to be Ca2+-dependent, TMEM16A augments VRAC currents by facilitating Hypo-induced Ca2+ increase in submembraneous signaling compartments by means of ER tethering.

Effect of Auxin (IAA) on the Fast Vacuolar (FV) Channels in Red Beet (Beta vulgaris L.) Taproot Vacuoles

In contrast to the well-studied effect of auxin on the plasma membrane K+ channel activity, little is known about the role of this hormone in regulating the vacuolar K+ channels. Here, the patch-clamp technique was used to investigate the effect of auxin (IAA) on the fast-activating vacuolar (FV) channels. It was found that the macroscopic currents displayed instantaneous currents, which at the positive potentials were about three-fold greater compared to the one at the negative potentials. When auxin was added to the bath solution at a final concentration of 1 µM, it increased the outward currents by about 60%, but did not change the inward currents. The imposition of a ten-fold vacuole-to-cytosol KCl gradient stimulated the efflux of K+ from the vacuole into the cytosol and reduced the K+ current in the opposite direction. The addition of IAA to the bath solution with the 10/100 KCl gradient decreased the outward current and increased the inward current. Luminal auxin reduced both the outward and inward current by approximately 25% compared to the control. The single channel recordings demonstrated that cytosolic auxin changed the open probability of the FV channels at the positive voltages to a moderate extent, while it significantly increased the amplitudes of the single channel outward currents and the number of open channels. At the positive voltages, auxin did not change the unitary conductance of the single channels. We suggest that auxin regulates the activity of the fast-activating vacuolar (FV) channels, thereby causing changes of the K+ fluxes across the vacuolar membrane. This mechanism might serve to tightly adjust the volume of the vacuole during plant cell expansion.

Influence of temperature and potential range on Zn-Ni deposition properties formed by cyclic voltammetry electrodeposition in chloride bath solution

This paper describes the study of electrodeposition process by cyclic voltammetry for Zn-Ni bimetallic coating on the X52 carbon steel substrate. Prior to the deposition at the bath temperatures of 25°C, 40°C, and 60°C, investigations were carried out to find the optimum potential range for zinc-nickel coatings with respect to the Ag/AgCl reference electrode. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) was used for surface morphology and elemental composition studies. The corrosion rate of the deposits was studied using the linear polarization resistance (LPR) method by immersing the samples (with and without coating) into 3.5% NaCl solution for 24 h. SEM and EDX results showed that the bath temperature has affected the formation of the microstructures and composition of coating. In addition, micro-cracks, nickel content, mobility of ions and compactness of microstructure increased by raising the bath temperature used for electrodeposition. The corrosion rate obtained from the LPR method can be correlated with the SEM/EDX analysis. The coating deposited at the temperature of 60°C including more content of nickel and micro-cracks led to lower corrosion resistance compared to the coating deposited at the bath solution temperatures of 25°C, 40°C, and non-coated X52 steel. Based on the results, the Zn-Ni coating deposited on the X52 steel substrate in the bath solution at 40°C presented the best performance due to more suitable achievements of microstructure compaction, composition, microcracks, and corrosion resistance observations.

Design of Composite I-Beam Section to Prevent Web-Flange Junction Failure and Improving Its Axial Load Carrying Capacity

Most of the chemical industries are used with Polyurethane (PU) coated steel sample which is found that some chemical reaction and rusted in acidic bath solution becomes a problem in industry. For such problems composite materials can be of good solution which does not possess any reaction with working fluids (acids in our case). With composites there is complexity of manufacturing and high cost involvement, so as to avoid those simplified approach is used to get Flat plates made of Glass fiber reinforced in epoxy which is best solution for any acidic bath as it possesses high resistance to any reaction with itself. Glass fiber plates are cut into the size of dimension and with the help of adhesives joint the WFJ of I-Beam, there are two different types of adhesives used, araldite 2015 and Hundsman araldite are used. The hundsman araldite is found to get better performance of Web-Flange junction (WFJ) joint. Finite element analysis (FEA) is used to get initial validation and further it’s observed that Hundsman araldite failure strength on the web-flange junction is better. Also, additional cleat used with 4 mm, 12 mm for increasing the Web-Flange junction (WFJ) area to improve the Load carrying capacity of the Beam. The experimental analysis results clearly indicate that the emersion of the reinforced epoxy glass-fiber in the acidic bath solution for a certain period, there is no any reaction formed in the acidic bath and improved the behavior of the specimen. Results from FEA and experimental test have shown good correlations are obtained with improvement of failure strength on WFJ

Microstructure and corrosion resistance of Ni/Cr3C2-NiCr composite coating

Purpose In this study, electrochemical deposition method which have cheaper equipment than thermal spraying methods and is available for the production of composite coatings were used. Design/methodology/approach Composite coatings were electrodeposited from a Watts's bath solution in which the suspended Cr3C2-NiCr particles were dispersed in the bath solution during deposition. Potentiodynamic polarization and electrochemical impedance spectroscopy techniques have been used to evaluate the corrosion resistance of the composite coating in the 3.5 Wt.% NaCl solution. Findings It was found that the submicron Cr3C2-NiCr particles distributed uniformly in the coating and depend on the current density of deposition, different amount of particles can be incorporated in the coating. The results showed that the corrosion resistance of the Ni/ Cr3C2-NiCr composite coatings is more comparable to the pure nickel coating. Originality/value Production of Ni-base composite coating from an electrolytic bath containing Cr3C2-NiCr particles is possible via electrodeposition.