Effects of inhibitions by sodium ion and ammonia and different inocula on acetate-utilizing methanogenesis: Methanogenic activity and succession of methanogens

Acetate-fed anaerobic sequential batch experiments with four different inhibitory conditions (non-inhibitory (Lo), sodium-ion inhibitory (Na), ammonia inhibitory (Am), combined inhibitory (Hi)) were conducted using thirteen different inocula to investigate the inhibition effects by sodium-ion and ammonia and different inocula on acetate-utilizing methanogenesis and succession of methanogens. Sodium-ion and ammonia significantly extended lag-time λ and reduced specific-methanogenic-activity RCH4, and caused synergistic inhibition. The inhibition differed according to the initial methanogen community structures: the inhibition effects on λ and RCH4 were strongest ininocula with Methanosaeta concilii dominant and weakest in inocula with Methanoculleus bourgensis dominant. These inhibitory conditions determined the succession of methanogens: the most competitive methanogens were Methanosaeta concilii in Lo, Methanosarcina sp. in Na, Methanosarcina sp. and Methanoculleus bourgensis in Am, Methanoculleus bourgensis in Hi. This study provides valuable information for microbial management and optimization for AD processes treating wastewater that is rich in protein and/or salt.

Auxin alters sodium ion accumulation and nutrient accumulation by playing protective role in salinity challenged strawberry

High salinity in soil affects the strawberry production and fruit quality. Auxin-primed plants have enhanced responses to soil salinization. In this study, we report that exogenous application of IAA can partially relieve stress responses of strawberry seedlings. Cytological analysis showed that the ultrastructure of root tip and leaf cells in strawberry seedlings were altered under high salinity condition, which was partially recovered after the application of IAA. The study showed that the ultrastructure of root tip and leaf cells in strawberry seedlings were altered under salt stress condition, which was partially recovered after the application of IAA. Exogenous IAA ameliorated deleterious effects on seedling growth under salinity were attributed to accelerated Na⁺ fluxes, decreased the contents of Na⁺ to maintain the ion homeostasis, protect root growth, and promote the absorption of nutrients for improved photosynthetic efficiency in strawberry.

Expression level of Na+ homeostasis-related genes and salt-tolerant abilities in backcross introgression lines of rice crop under salt stress at reproductive stage

Salt stress in the rice field is one of the most common abiotic stresses, reducing crop productivity, especially at reproductive stage, which is very sensitive to salt stress. The aim of this investigation was to study mRNA-related Na⁺ uptake/translocation and Na⁺ enrichment in the cellular level, leading to physiological changes, growth characteristics, and yield attributes in FL530 [salt-tolerant genotype; carrying SKC1 (in relation to high-affinity potassium transporters controlling Na⁺ and K⁺ translocation) and qSt1b (linking to salt injury score) QTLs] and KDML105 (salt-sensitive cultivar; lacking both QTLs) parental lines and 221-48 (carrying SKC1 and qSt1b QTLs) derived from BILs (backcross introgression lines) at 50% flowering of rice, under 150-mM NaCl until harvesting process. The upregulation of OsHKT1;5 (mediating Na⁺ exclusion into xylem parenchyma cells) and OsNHX1 (Na⁺/H⁺ exchanger to secrete Na⁺ into vacuole) and downregulation of OsHKT2;1 and OsHKT2;2 (mediating Na⁺ restriction in the roots, leaf sheath and older leaves) in cvs. FL530 and 221-48 (+ SKC1; + qSt1b) under salt stress were observed. It restricted Na⁺ level in flag leaf, thereby preventing salt toxicity, as indicated by maintenance of photon yield of PSII (Φ_PSII), net photosynthetic rate (P_n), transpiration rate (E) and overall growth performances. In contrast, Na⁺ enrichment in flag leaf of cv. KDML105 (-SKC1;-qSt1b) caused the reduction in Φ_PSII by 30.5% over the control, leading to the reduction in P_n by 62.3%, in seed sterility by 88.2%, and yield loss by 85.1%. Moreover, the negative relationships between Na⁺ enrichment in flag leaf, physiological changes, and yield traits in rice crop grown under salt stress were demonstrated. Based on this investigation, rice genotype 221-48 was found to possess salt-tolerant traits at reproductive stage and thus could prove to be a potential candidate for future breeding programs.

Amiodarone exacerbates brain injuries after hypoxic-ischemic insult in mice

Background

Sodium ion transportation plays a crucial role in the pathogenesis of hypoxic–ischemic brain injury. Amiodarone, a Vaughan-Williams class III antiarrhythmic drug, has been widely used to treat life-threatening arrhythmia and cardiac arrest worldwide. In addition to its inhibitory effects on the potassium channel, amiodarone also blocks various sodium ion transporters, including the voltage-gated sodium channel, sodium pump, and Na⁺/Ca⁺ exchanger. Considering these pharmacological profile, amiodarone may affect the influx–efflux balance of sodium ion in the hypoxic–ischemic brain. Previous studies suggest that the blockade of the voltage-gated sodium channel during hypoxic–ischemic brain injury exerts neuroprotection. On the contrary, the blockade of sodium pump or Na⁺/Ca⁺ exchanger during hypoxia–ischemia may cause further intracellular sodium accumulation and consequent osmotic cell death. From these perspectives, the effects of amiodarone on sodium ion balance on the hypoxic–ischemic brain can be both protective and detrimental depending on the clinical and pathophysiological conditions. In this study, we therefore investigated the effect of amiodarone on hypoxic–ischemic brain injury using a murine experimental model.

Results

Compared with the control group mice, mice that received amiodarone after induction of 40-min hypoxic–ischemic brain injury exhibited lower survival rates over 7 days and worse neurological function. After 25-min hypoxic–ischemic brain injury, amiodarone treated mice exhibited larger infarct volumes (16.0 ± 6.9 vs. 24.2 ± 6.8 mm³, P < 0.05) and worse neurological function. In addition, the brains harvested from the amiodarone-treated mice contained larger amounts of sodium (194.7 ± 45.1 vs. 253.5 ± 50.9 mEq/kg dry weight, P < 0.01) and water (259.3 ± 8.9 vs. 277.2 ± 12.5 mg, P < 0.01). There were no significant differences in hemodynamic parameters between groups.

Conclusions

Amiodarone exacerbated brain injuries and neurological outcomes after hypoxic–ischemic insults. Severe brain sodium accumulation and brain edema were associated with the detrimental effects of amiodarone. Amiodarone at the clinical dose can exacerbate brain injury after hypoxic–ischemic insult by affecting sodium ion transportation and facilitate intracellular sodium accumulation in the brain.

Engineered silica nanoparticles alleviate the detrimental effects of Na+ stress on germination and growth of common bean (Phaseolus vulgaris)

During the past 10 years, exploiting engineered nanoparticles in agricultural sector has been rapidly increased. Nanoparticles are used to increase the productivity of different crops particularly under biotic and abiotic stresses. This study aims to test the ability of nanosilica (NS) to ameliorate the detrimental impact of Na⁺ with different concentrations on the seed germination and the growth of common bean seedlings. Five doses of Na⁺ have been prepared from NaCl, i.e., 1000, 2000, 3000, 4000, and 5000 mg L^-1, and distilled water was applied as a control. Seeds and seedlings were treated with three different NS concentrations (100, 200, and 300 mg L^-1). The results proved that Na⁺ concentrations had detrimental effects on all measured parameters. However, treating seeds and seedlings with NS improved their growth and resulted in higher values for all measurements. For instance, the addition of 300 mg L^-1 NS leads to an increase of the final germination percentage, vigor index, and germination speed for seeds irrigated with 5000 mg Na⁺ L^-1 by 19.7, 80.7, and 22.6%, respectively. Although common bean seedlings could not grow at the highest level of Na⁺, fortification seedlings with NS helped them to grow well under 5000 mg L^-1 of Na⁺. An increase of 11.1 and 23.1% has been measured for shoot and root lengths after treating seedlings with 300 mg L^-1 NS under irrigation with 5000 mg Na⁺ L^-1 solutions, and also at the same treatment, shoot and root dry masses are enhanced by 110.9 and 328.0%, respectively. These results proved the importance of using NS to relieve the detrimental effects of Na⁺-derived salinity. This finding could be reinforced by low Na content which was measured in plant tissues after treating seedlings with 300 mg L^-1 of NS.

Transparent exopolymer particles (TEP)-associated membrane fouling at different Na+ concentrations

Membrane filtration has been widely applied for water treatment, wastewater reclamation and seawater desalination. Although extensive research work has been conducted to better understand the fouling mechanism under various conditions, little has been known about the transparent exopolymer particles (TEP)-associated membrane fouling at different Na⁺ concentrations. In this study, the influence of Na⁺ concentration on the TEP formation as well as the filtration behaviors of alginate blocks was investigated. Results showed that increasing Na⁺ concentration substantially reduced the TEP formation from all types of alginate blocks, thus preventing the cake layer development on the membrane surface. As a result, the TEP-associated membrane fouling was found to be kinetically slower and much less at higher Na⁺ level. Furthermore, filtration tests of alginate blocks at freshwater and seawater conditions were also conducted, showing that TEP-associated fouling in freshwater is much server than that in seawater at the defined conditions. This study reveals that the TEP formation is significantly influenced by the chemistry condition of bulk solution and membrane fouling is profoundly affected by the TEP levels in feed water.

Asp73-dependent and -independent regulation of the affinity of ligands for human histamine H1 receptors by Na. Biochem Pharmacol 2016;128:46-54. [PMID: 28040476 DOI: 10.1016/j.bcp.2016.12.021]

The affinity of ligands for G-protein-coupled receptors (GPCRs) is allosterically regulated by Na⁺ via a highly conserved aspartate residue (Asp^2.50) in the second transmembrane domain of GPCRs. In the present study, we examined the Na⁺-mediated regulation of the affinity of ligands for G_q/11-protein-coupled human histamine H₁ receptors in Chinese hamster ovary cells. The affinities of 3 agonists and 20 antihistamines were evaluated by their displacement curves against the binding of [³H]-mepyramine to membrane preparations in the presence or absence of 100mM NaCl. The affinities of most drugs including histamine, an agonist, and d-chlorpheniramine, a first-generation antihistamine, were reduced by NaCl, with the extent of NaCl-mediated changes varying widely between drugs. In contrast, the affinities of some second-generation antihistamines such as fexofenadine were increased by NaCl. These changes were retained in intact cells. The mutation of Asp^2.50 (Asp73) to asparagine abrogated NaCl-induced reductions in affinities for histamine and d-chlorpheniramine, but not NaCl-induced increases in the affinity for fexofenadine. Quantitative structure-activity relationship (QSAR) analyses showed that these Na⁺-mediated changes were explained and predicted by a combination of the molecular energies and implicit solvation energies of the compounds. These results suggest that Na⁺ diversely regulates the affinity of ligands for H₁ receptors from the extracellular sites of receptors via Asp73-dependent and -independent mechanisms in a manner that depends on the physicochemical properties of ligands. These results may contribute to a deeper understanding of the fundamental mechanisms by which the affinity of ligands for their receptors is allosterically regulated by Na⁺.

Connexin hemichannels explain the ionic imbalance and lead to atrophy in denervated skeletal muscles

Denervated fast skeletal muscles undergo atrophy, which is associated with an increase in sarcolemma permeability and protein imbalance. However, the mechanisms responsible for these alterations remain largely unknown. Recently, a close association between de novo expression of hemichannels formed by connexins 43 and 45 and increase in sarcolemma permeability of denervated fast skeletal myofibers was demonstrated. However, it remains unknown whether these connexins cause the ionic imbalance of denervates fast myofibers. To elucidate the latter and the role of hemichannels formed by connexins (Cx HCs) in denervation-induced atrophy, skeletal myofibers deficient in Cx43 and Cx45 expression (Cx43^fl/flCx45^fl/fl:Myo-Cre mice) and control (Cx43^fl/flCx45^fl/fl mice) were denervated and several muscle features were systematically analyzed at different post-denervation (PD) times (1, 3, 5, 7 and 14days). The following sequence of events was found in denervated myofibers of Cx43^fl/flCx45^fl/fl mice: 1) from day 3 PD, increase in sarcolemmal permeability, 2) from day 5 PD, increases of intracellular Ca²⁺ and Na⁺ signals as well as a significant increase in protein synthesis and degradation, yielding a negative protein balance and 3) from day 7 PD, a fall in myofibers cross-section area. All the above alterations were either absent or drastically reduced in denervated myofibers of Cx43^fl/flCx45^fl/fl:Myo-Cre mice. Thus, the denervation-induced Cx HCs expression is an early event that precedes the electrochemical gradient dysregulation across the sarcolemma and critically contributes to the progression of skeletal muscle atrophy. Consequently, Cx HCs could be a therapeutic target to drastically prevent the denervation-induced atrophy of fast skeletal muscles.

Sodium-Ion Intercalated Transparent Conductors with Printed Reduced Graphene Oxide Networks

In this work, we report for the first time that Na-ion intercalation of reduced graphene oxide (RGO) can significantly improve its printed network's performance as a transparent conductor. Unlike pristine graphene that inhibits Na-ion intercalation, the larger layer-layer distance of RGO allows Na-ion intercalation, leading to simultaneously much higher DC conductivity and higher optical transmittance. The typical increase of transmittance from 36% to 79% and decrease of sheet resistance from 83k to 311 Ohms/sq in the printed network was observed after Na-ion intercalation. Compared with Li-intercalated graphene, Na-ion intercalated RGO shows much better environmental stability, which is likely due to the self-terminating oxidation of Na ions on the RGO edges. This study demonstrated the great potential of metal-ion intercalation to improve the performance of printed RGO network for transparent conductor applications.