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Nitellopsis cells grown in fresh water have a relatively low cytoplasmic Na+ (11 mol m-3) and high cytoplasmic K+ (90 mol m-3 content. A 30-min treatment with 100 mol m-3 external NaCl resulted in a high [Na+]c (90 mol m-3) and a low [K+]c (33 mol m-3). Subsequent addition of external Ca2+ (10 mol m-3) prevented Na+ influx and then [Na+]c decreased slowly. Changes in [K+]c were opposite to [Na+]c. During the recovery time vacuolar Na+ increased, while vacuolar K+ decreased. Since all these processes proceeded also under ice-cold conditions, the restoration of original cytoplasmic ion compositions is suggested to be a passive nature. The notion that the passive movement of ions across the tonoplast can act as an effective and economic mechanism of salt tolerance under transient or under mild salt stress conditions is discussed. [ABSTRACT FROM AUTHOR]

The mechanism of salt tolerance was studied using isolated internodal cells of the charophyte Nitellopsis obtusa grown in fresh water. When 100 mM NaCl was added to artificial pond water (0.1 mM each of NaCl, KC1, CaCl), no cell survived for more than one day. Within the first 30 minutes, membrane potential (E) depolarized and membrane resistance (R) decreased markedly. Simultaneously, cytoplasmic Na increased and K decreased greatly. At steady state the increase in Na content was roughly equal to the decrease in K content. The Cl content of the cytoplasm did not change. These results suggest that Na enters the cytoplasm by exchange with cytoplasmic K. Both the entry of Na and the exit of K are assumed to be passive and the latter being caused by membrane depolarization. Vacuolar K, Na, and Cl remained virtually constant, suggesting that rapid influx of Na from the cytoplasm did not occur. In 100 mM NaCl containing 10 mM CaCl, membrane depolarization, membrane resistance decrease and changes in cytoplasmic [Na] and [K] did not occur, and cells survived for many days. When cells treated with 100 mM NaCl were transferred within 1 hour to 100 mM NaCl containing 10 mM CaCl, Em decreased, Rm increased, cytoplasmic Na and K returned to their initial levels, and cells survived. Two possible mechanisms for the role of Ca in salt tolerance in Nitellopsis are discussed; one a reduction in plasmalemma permeability to Na and the other a stimulation of active Na-extrusion. [ABSTRACT FROM AUTHOR]

In Nitellopsis, salt stress causes a depolarization of the membrane potential and a decrease in the membrane resistance, both of which can be prevented by the addition of calcium to the external medium ( Katsuhara and Tazawa 1986). The effect of calcium is also observed in tonoplast-free cells containing ATP. However, in the absence of intracellular ATP, addition of external calcium is ineffective. AMP, AMPPNP, and GTP can replace ATP in supporting the calcium effect. [ABSTRACT FROM AUTHOR]

In the cells of Chara corallina, permeant monohydric alcohols including methanol, ethanol and 1-propanol increased the hydraulic resistance of the membrane (Lp m -1 ). We found that the relative value of the hydraulic resistance ( r Lp m -1 ) was linearly dependent on the concentration (C s ) of the alcohol. The relationship is expressed in the equation: r Lp m -1  = ρ m C s  + 1, where ρ m is the hydraulic resistance modifier coefficient of the membrane. Ye et al. (2004) showed that membrane-permeant glycol ethers also increased Lp -1 . We used their data to estimate Lp m -1 and r values of all the permeant alcohols and glycol ethers against their molecular weights (MW), we obtained a linear curve with a slope of 0.014 M m -1 . The values of r Lp m -1 fit the above relation we found for alcohols. When we plotted the ρ m ) were linearly related to the MW of the permeant solutes with a slope of 0.012 M -1 /MW and with a correlation coefficient of 0.99. We analyzed the influence of the permeant solutes on the relative hydraulic resistance of the membrane ( r Lp m -1 ) as a function of the external (π 0 ) and internal (π i ) osmotic pressures. The analysis showed that the hydraulic resistance modifier coefficients (ρ m ) were linearly related to the MW of the permeant solutes with a slope of 0.012 M -1 /MW and with a correlation coefficient of 0.84. The linear relationship between the effects of permeating solutes on the hydraulic resistance modifier coefficient (ρ m ) and the MW can be explained in terms of the effect of the effective osmotic pressure on the hydraulic conductivity of water channels. The result of the analysis suggests that the osmotic pressure and not the size of the permeant solute as proposed by (Ye et al., J Exp Bot 55:449-461, 2004) is the decisive factor in a solute's influence on hydraulic conductivity. Thus, characean water channels (aquaporins) respond to permeant solutes with essentially the same mechanism as to impermeant solutes., (© 2024. The Author(s).)

High urinary levels of dialkylphosphates (DAPs), which are common structures of organophosphate pesticides (OPs), have been associated with several adverse health outcomes in human biomonitoring studies. Previous studies have indicated that dietary OP exposure and ingestion of environmentally degraded DAP, which is inactive with acetylcholinesterase, can lead to an increase in urinary DAP levels in the general population. However, the specific food sources contributing to the intake of OPs and DAPs have not been identified. In this study, we analyzed the levels of OPs and preformed DAPs in various food items. DAP levels were markedly high in certain fruits, such as persimmon, apple juice, kiwi, and mandarin. In contrast, only moderate levels of OPs were detected in these foods. Furthermore, the levels of OPs and DAPs were positively associated with vegetables, whereas no such association was observed in fruits. Increased consumption of certain fruits presumably leads to a marked increase in urinary DAP levels in individuals despite limited exposure to OPs, resulting in reduced reliability of urinary DAPs as a marker of OP exposure. Therefore, the possible effects of dietary habits and the resulting intake of preformed DAPs should be considered when interpreting biomonitoring data of urinary DAPs. Additionally, DAP levels in most organic foods were much lower than those in conventional foods, suggesting that the reduction in urinary DAPs by organic diet intervention may be mainly attributed to the reduced intake of preformed DAPs rather than reduced exposure to OPs. Therefore, urinary DAP levels may not be suitable indicators for evaluating ingested OP exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We have developed a novel composite filler with Poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonic acid) (PEDOT:PSS), a biocompatible organic conductive polymer, adsorbed on carbon particles for biological electrodes. This composite filler enables to fabricate high-performance biological electrodes simply by adding it to resin in the same way as conventional conductive fillers. The fabricated electrodes achieve ion exchange properties similar to those of PEDOT:PSS polymers and therefore low skin and electrode contact impedance. Electroencephalogram (EEG) measurements show that these electrodes capture various brain activities and exhibit high correlation (≥ 0.9) to commercially available wet and AgCl electrodes. Additionally, each electrode can be molded into various shapes and structures while retaining its electrode characteristics. Therefore, the proposed electrode is promising for EEG measurement, which requires high comfort and signal quality.

HAK family transporters primarily function as K+ transporters and play major roles in K+ uptake and translocation in plants, whereas several HAK transporters exhibit Na+ transport activity. OsHAK2, a rice HAK transporter, was shown to mediate Na+ transport in Escherichia coli in a previous study. In this study, we investigated whether OsHAK2 is involved in Na+ transport in the rice plant. Overexpression of OsHAK2 increased Na+ translocation from the roots to the shoots of transgenic rice. It also increased both root and whole-plant Na+ content, and enhanced shoot length under low Na+ and K+ conditions. Meanwhile, OsHAK2 overexpression increased salt sensitivity under a long-term salt stress condition, indicating that OsHAK2 is not involved in salt tolerance, unlike in the case of ZmHAK4 in maize. These results suggest that OsHAK2 is permeable to Na+ and contributes to shoot growth in rice plants under low Na+ and K+ conditions., (© The Author(s) 2023. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

The hydraulic resistance (the reciprocal of the hydraulic conductivity Lp) Lp -1 was measured in cells of Chara corallina by the method of transcellular osmosis. Treatment of cells with 100 mM KCl decreased Lp -1 significantly. Subsequent treatment of the cells with 70 mM CaCl 2 recovered the decreased Lp -1 to the original value. To know whether K + or Ca 2+ /Mg 2+ acts on the cell wall and/or the membrane, the hydraulic resistances of the cell wall (Lp w -1 ) and that of the membrane (Lp m -1 ) were determined in one and the same cell. For this, a pair of cells (twin cells) were made from an internodal cell, one used for measurement of Lp -1 and the other used for the measurement of Lp w -1 . From Lp -1 and Lp w -1 , Lp m -1 was calculated. Both Lp -1 and Lp w -1 were decreased by K + , while Lp m -1 was not affected by K + . The same result was obtained with 5 mM EGTA. Lp w -1 was decreased more than it was by KCl but Lp m -1 remained constant after EGTA treatment. The recovery of the K + -decreased Lp -1 with Ca 2+ can be explained exclusively by the recovery of Lp w -1 with Ca 2+ . The Ca 2+ recovery of Lp w -1 was observed in the intact cell wall but not in the cell wall tube isolated from an internodal cell. The different response to Ca 2+ between the intact cell wall and the isolated cell wall was discussed in relation to the tension in the cell wall which may be an important factor for the ionic regulation of hydraulic conductivity., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)