Accumulation Of Potassium Ions Research Articles

Simultaneous recordings from vestibular Type I hair cells and their calyceal afferents in mice.

The vestibular hair cell receptors of anamniotes, designated Type II, are presynaptic to bouton endings of vestibular nerve distal neurites. An additional flask-shaped hair cell receptor, Type I, is present in amniotes, and communicates with a chalice-shaped afferent neuritic ending that surrounds the entire hair cell except its apical neck. Since the full repertoire of afferent fiber dynamics and sensitivities observed throughout the vertebrate phyla can be accomplished through Type II hair cell-bouton synapses, the functional contribution(s) of Type I hair cells and their calyces to vestibular performance remains a topic of great interest. The goal of the present study was to investigate electrical coupling between the Type I hair cell and its enveloping calyx in the mouse semicircular canal crista ampullaris. Since there are no gap junctions between these two cells, evidence for electrical communication would necessarily involve other mechanisms. Simultaneous recordings from the two cells of the synaptic pair were used initially to verify the presence of orthodromic quantal synaptic transmission from the hair cell to the calyx, and then to demonstrate bi-directional communication due to the slow accumulation of potassium ions in the synaptic cleft. As a result of this potassium ion accretion, the equilibrium potentials of hair cell conductances facing the synaptic cleft become depolarized to an extent that is adequate for calcium influx into the hair cell, and the calyx inner face becomes depolarized to a level that is near the threshold for spike initiation. Following this, paired recordings were again employed to characterize fast bi-directional electrical coupling between the two cells. In this form of signaling, cleft-facing conductances in both the hair cell and calyx increase, which strengthens their coupling. Because this mechanism relies on the cleft resistance, we refer to it as resistive coupling. We conclude that the same three forms of hair cell-calyceal transmission previously demonstrated in the turtle are present in the mammalian periphery, providing a biophysical basis for the exceptional temporal fidelity of the vestibular system.

Interactions between cathodic- and anodic-pulses during high-frequency stimulations with the monophasic-pulses alternating in polarity at axons—experiment and simulation studies

Background. Electrical neuromodulation therapies commonly utilize high-frequency stimulations (HFS) of biphasic-pulses to treat neurological disorders. The biphasic pulse consists of a leading cathodic-phase to activate neurons and a lagging anodic-phase to balance electrical charges. Because both monophasic cathodic- and anodic-pulses can depolarize neuronal membranes, splitting biphasic-pulses into alternate cathodic- and anodic-pulses could be a feasible strategy to improve stimulation efficiency. Objective. We speculated that neurons in the volume initially activated by both polarity pulses could change to be activated only by anodic-pulses during sustained HFS of alternate monophasic-pulses. To verify the hypothesis, we investigated the interactions of the monophasic pulses during HFS and revealed possible underlying mechanisms. Approach. Different types of pulse stimulations were applied at the alvear fibers (i.e. the axons of CA1 pyramidal neurons) to antidromically activate the neuronal cell bodies in the hippocampal CA1 region of anesthetized rats in-vivo. Sequences of antidromic HFS (A-HFS) were applied with alternate monophasic-pulses or biphasic-pulses. The pulse frequency in the A-HFS sequences was 50 or 100 Hz. The A-HFS duration was 120 s. The amplitude of antidromically-evoked population spike was measured to evaluate the neuronal firing induced by each pulse. A computational model of axon was used to explore the possible mechanisms of neuronal modulations. The changes of model variables during sustained A-HFS were analyzed. Main results. In rat experiments, with a same pulse intensity, the activation volume of a cathodic-pulse was greater than that of an anodic-pulse. In paired-pulse tests, a preceding cathodic-pulse was able to prevent a following anodic-pulse from activating neurons due to refractory period. This indicated that the activation volume of a cathodic-pulse covered that of an anodic-pulse. However, during sustained A-HFS of alternate monophasic-pulses, the anodic-pulses were able to prevail over the cathodic-pulses in activating neurons in the overlapped activation volume. Model simulation results show the mechanisms of the activation failures of cathodic-pulses. They include the excessive membrane depolarization caused by an accumulation of potassium ions, the obstacle of hyperpolarization in the conduction pathway and the interactions from anodic-pulses. Significance. The study firstly showed the domination of anodic-pulses over cathodic-pulses in their competitions to activate neurons during sustained HFS. The finding provides new clues for designing HFS paradigms to improve the efficiency of neuromodulation therapies.

PabCIPK24 plays an important role in the response of hybrid poplar to salt stress

The CBL-Interacting Protein Kinases (CIPK) is an important protein in stress responses. However, the research of CIPK function is limited in poplar. The research objective is to improve the salt tolerance of poplar using CIPK. In the present study, a CIPK24 gene from Populus alba × P. Berolinensis (PabCIPK24) was cloned, which possesses a kinase domain and a regulatory domain and shows the closest homology to CIPK24 of Populus alba (PaCIPK24). Seven PabCIPK24 overexpression transgenic lines were obtained through Agrobacterium-mediated transformation. Under salt stress treatment, transgenic lines accumulated less sodium ions and more potassium ion accumulation than wild type (WT) and had lower degree of cell damage. The transgenic line shows significant differences compared to the WT in terms of root length (The transgenic line is 0.83 cm taller than the WT.), dry weight (The transgenic lines weighs 0.07 g more than the WT), and seedling height (The transgenic line is 1.52 cm taller than the WT) during the tissue culture seedling stage. Additionally, transgenic lines have strong reactive oxygen species (ROS) scavenging ability and increases the gene expression of salt tolerant related genes. The study indicates that PabCIPK24 positively regulates salt stress, and obtained salt tolerant transgenic poplar.

Sett priming with salicylic acid improves salinity tolerance of sugarcane (Saccharum officinarum L.) during early stages of crop development

Sugarcane (Saccharum officinarum L.), a globally cultivated carbohydrate producing crop of industrial importance is being challenged by soil salinity due to its glycophytic nature. Water stress coupled with cellular and metabolic alterations resulting from excess sodium (Na+) ion accumulation is irreversibly damaging during early crop developmental stages that often results in complete crop failure. This study therefore aimed to explore the potential of salicylic acid as a sett priming material to mitigate the negative effects of salt stress on sugarcane during germination and early growth stages. Five doses of salicylic acid (0 [hydropriming] [control], 0.5 mM, 1 mM, 1.5 mM and 2 mM) were tested against three levels of salinity (0.5 dS m−1 [control], 4 dS m−1, and 8 dS m−1) within a polyhouse environment. Results revealed 11.2%, 18.5%, 25.4%, and 38.6%, average increase in final germination, germination energy, seedling length and seedling vigor index respectively with a subsequent reduction of 21% mean germination time. Investigations during early seedling growth revealed 21.6%, 17.5%, 27.0%, 39.9%, 10.7%, 11.5%, 17.5%, 47.9%, 35.3% and 20.5% overall increase in plant height, total leaf area, shoot dry matter, root dry matter, leaf greenness, relative water content, membrane stability index, proline content, total antioxidant activity and potassium (K+) ion accumulation respectively with a subsequent reduction of 24.9% Na+ ion accumulation and 35.8% Na+/K+ ratio due to salicylic acid priming. Germination, seedling growth and recovery of physiochemical traits were highly satisfactory in primed setts than non-primed ones even under 8 dS m−1 salinity level. This study should provide useful information for strategizing salinity management approaches for better productivity of sugarcane.

Plant Growth Promoting Bacteria and Arbuscular Mycorrhizae Improve the Growth of Persea americana var. Zutano under Salt Stress Conditions

In Peru, almost 50% of the national agricultural products come from the coast, highlighting the production of avocado. Much of this area has saline soils. Beneficial microorganisms can favorably contribute to mitigating the effect of salinity on crops. Two trials were carried out with var. Zutano to evaluate the role of native rhizobacteria and two Glomeromycota fungi, one from a fallow (GFI) and the other from a saline soil (GWI), in mitigating salinity in avocado: (i) the effect of plant growth promoting rhizobacteria, and (ii) the effect of inoculation with mycorrhizal fungi on salt stress tolerance. Rhizobacteria P. plecoglissicida, and B. subtilis contributed to decrease the accumulation of chlorine, potassium and sodium in roots, compared to the uninoculated control, while contributing to the accumulation of potassium in the leaves. Mycorrhizae increased the accumulation of sodium, potassium, and chlorine ions in the leaves at a low saline level. GWI decreased the accumulation of sodium in the leaves compared to the control (1.5 g NaCl without mycorrhizae) and was more efficient than GFI in increasing the accumulation of potassium in leaves and reducing chlorine root accumulation. The beneficial microorganisms tested are promising in the mitigation of salt stress in avocado.

Efficient interlayer confined nitrate reduction reaction and oxygen generation enabled by interlayer expansion.

Electrochemically converting nitrate ions back to ammonia can not only eliminate water pollution but also obtain valuable ammonia without a serious carbon footprint, and is thus deemed as an efficient supplement to the traditional Haber-Bosch process. Currently reported catalysts can achieve a single electrode reaction in the electrochemical nitrate reduction reaction. However, the bifunctionality of a single catalyst for both cathodic and anodic reactions has not yet been reported. Herein, we report Fe-doped layered α-Ni(OH)2 with expanded interlayer spacing as an efficient bifunctional catalyst for the nitrate reduction reaction and oxygen evolution reaction. The expanded interlayer spacing facilitates in situ electrochemical potassium ion intercalation between layers. In situ Raman spectroscopy characterization confirms that both the nitrate reduction reaction and oxygen evolution reaction are confined between layers and are triggered by the accumulation of potassium ions. The obtained α-Ni0.881Fe0.119(OH)2 nanosheets deliver an ammonia yield rate of 8.1 mol gcat.-1 h-1 with a NO3--to-NH3 faradaic efficiency of 97.5% at the cathode. The overpotential of oxygen generation at 10 mA cm-2 is reduced to 254 mV at the anode. As a bifunctional catalyst in overall electrolysis, the current density of α-Ni0.881Fe0.119(OH)2 reaches 24.8 mA cm-2 at a voltage of 2.0 V and performs continuously for 50 h with a current retention of 80.2%.

Utilização de bioestimulante no capim-pangolão Digitaria pentzii submetido a estresse salino

ABSTRACT Salinity caused by excess salts in soil solutions is one of the most limiting environmental stresses in agriculture worldwide. In this scenario, among strategies that favor the expression of the genetic potential of plants, the use of biostimulants stands out. The objective of this study was to evaluate the influence of a seaweed-based biostimulant on growth, forage production, gas exchange, and accumulation of sodium and potassium ions in pangolão grass (Digitaria pentzii) under saline stress. The experiment was conducted from March to July 2019 using a randomized block design, in a 2 × 3 factorial scheme with two concentrations of biostimulant (0 and 8 mL L-1) and three electrical conductivities of irrigation water (0.03, 2 and 4 dS m-1), with four replicates. The accumulation of 50 µmol g-1 of sodium in leaves corresponded to a reduction of 0.3 g of dry matter in the leaf blade production per plot. The biostimulant did not influence the structural characteristics, phytomass accumulation, or stomatal conductance of the pangolão grass, regardless of salinity. At the level of 4 dS m-1 in irrigation water, the ionic stress toxicity due to the accumulation of salts in the aerial part of pangolão grass was more severe. This is the first evidence of the “moderate” salinity tolerance of pangolão grass in semi-arid regions.

The Salinity and Irrigation Methods Affect the Content of Macronutrients in Different Organs of Quinoa (Chenopodium quinoa Willd.)

ABSTRACT Salinity causes nutrient imbalances in plants, even in quinoa (Chenopodium quinoa Willd.), a halophyte with high nutritional value. Current investigation is a complementary study, carried out in continuation of the previous research on quinoa which illustrated that the Salinity Threshold Value (STV) of quinoa varies during different stages of its growth; it was performed in three cultivation periods, each period containing two irrigation methods (IM): i) Irrigating by ‎constant levels of ‎water salinity (ECi) (i.e. 0.3, 10, 15, 20, 25dSm−1) regardless of STV(P); and ii) Considering STV ‎at each ‎growth stage(T). Present study investigated the effect of abovementioned IMs (P, T) and ECis (i.e. 0.3, 10, 15, 20, 25dSm−1) on accumulation of nitrogen (N), phosphorus (P), and potassium (K) ions in shoots (end of vegetation) and seeds (end of seed-filling) of quinoa. Results indicated that an increase in ECi ‎from 0.3 to 25dSm−1, especially after STV, caused a 56.6% and 12.8% increase of N while a 44.3% and 27.8% decrease of P, respectively in shoot and seed of quinoa. K only showed 30.2% increase in shoot. The change of all three ions was sharper in shoot than seed due to halophytic properties of quinoa which reduces salinity influence on seed embryo. The seed of quinoa is the main source of N and protein while the shoot is rich in P and K. The T ‎method of irrigation was preferred for providing the plant chance to survive in more saline condition.

Genomic Analysis of Halotolerant Bacterial Strains Martelella soudanensis NC18T and NC20.

Two novel, halotolerant strains of Martelella soudanensis, NC18T and NC20, were isolated from deep subsurface sediment, deeply sequenced, and comparatively analyzed with related strains. Based on a phylogenetic analysis using 16S rRNA gene sequences, the two strains grouped with members of the genus Martelella. Here, we sequenced the complete genomes of NC18T and NC20 to understand the mechanisms of their halotolerance. The genome sizes and G+C content of the strains were 6.1 Mb and 61.8 mol%, respectively. Moreover, NC18T and NC20 were predicted to contain 5,849 and 5,830 genes, and 5,502 and 5,585 protein-coding genes, respectively. Both strains contain the identically predicted 6 rRNAs and 48 tRNAs. The harboring of halotolerant-associated genes revealed that strains NC18T and NC20 might tolerate high salinity through the accumulation of potassium ions in a "salt-in" strategy induced by K+ uptake protein (kup) and the K+ transport system (trkAH and kdpFABC). These two strains also use the ectoine transport system (dctPQM), the glycine betaine transport system (proVWX), and glycine betaine uptake protein (opu) to accumulate "compatible solutes," such as ectoine and glycine betaine, to protect cells from salt stress. This study reveals the halotolerance mechanism of strains NC18T and NC20 in high salt environments and suggests potential applications for these halotolerant and halophilic strains in environmental biotechnology.

Swelling of kappa carrageenan hydrogels in simulated body fluid for hypothetical vessel occlusion applications.

The swelling ability of kappa-carrageenan (KC) hydrogels was investigated in simulated body fluid (SBF). The SBF mimics the ionic concentrations in the vasa deferentia of human males. The study clarifies if these hydrogels can be adjusted to occlude the vasa deferentia by swelling. For this purpose, swelling to twice the initial volume is desirable. In this study, hydrogels of different primary potassium concentrations, biopolymer concentrations and ethanol-exchanged gels, were immersed in SBF either directly or after drying (pre-dried). We measured the absolute and relative swelling degree, and the swelling rates of the gels. Extensive pre-drying leads to irreversible gel densification and absolute swelling magnitudes decrease. We found that immersion into the SBF also leads to potassium ion accumulation, and network restructuring in the hydrogels. This markedly increases the storage moduli of the gel networks. The ion content in the gel structures also directly affects the swelling speed, the fastest swelling occurred in ethanol-exchanged and pre-dried gels. We found that by pre-drying and potassium content adjustment, swelling of the hydrogels is sufficient to render KC hydrogels as a possible candidate for the occlusion of the vasa deferentia.

Denitrifying halophilic archaea derived from salt dominate the degradation of nitrite in salted radish during pickling

Salted radish is a popular high-salinity table food in China, and nitrite is always generated during the associated pickling process. However, this nitrite can be naturally degraded, and the underlying mechanism is unknown. Here, we identified the microbial groups that dominate the natural degradation of nitrite in salted radish and clarified the related metabolic mechanism. Based on dynamic monitoring of pH and the concentrations of nitrogen compounds as well as high-throughput sequencing analysis of the structural succession of microbial communities in the tested salted radish, we determined that the halophilic archaea derived from pickling salt dominate the natural degradation of nitrite via denitrification. Based on isolation, identification, nitrite reduction assays, and genome annotation, we further determined that Haloarcula, Halolamina, and Halobacterium were the key genera. These halophilic archaea might cope with high salt stress through the “salt-in” mechanism with the assistance of the accumulation of potassium ions, obtain electrons necessary for “truncated denitrification” from the metabolism of extracellular glucose absorbed from salted radish, and efficiently reduce nitrite to nitrogen, bypassing nitrite generation from nitrate reduction. The present study provides important information for the prevention and control of nitrite hazards in salted vegetables with high salinity, such as salted radish.

Prevention, diagnosis and treatment of tumor lysis syndrome

Tumor lysis syndrome (TLS) is an acute, life-threatening condition that occurs either spontaneously or as a complication of cytoreductive antitumor therapy, and occurs in both children and adults. As a result of TLS, intracellular components are released into the extracellular space, leading to dysregulation of the body's homeostasis due to the accumulation of uric acid, phosphate and potassium ions, and hypocalcemia, which may lead to cardiac arrhythmias, convulsions, or kidney failure.

Nitrification performance evaluation of activated sludge under high potassium ion stress during high-ammonia nitrogen organic wastewater treatment

The recycling reverse osmosis (RO) membrane concentrate of some high-ammonia nitrogen (NH4+-N) organic wastewater to the biological unit could cause potassium ion (K+) accumulation, thereby affecting the removal of NH4+-N by activated sludge. Thus, the effects of high K+ stress on activated sludge nitrification performance was studied. The results showed that the high K+ stress promoted the floc sludge to produce more extracellular polymers (EPS), which accelerated the sludge sedimentation and enriched the biomass in sequential batch reactors (SBRs). The ammonia oxidation process and nitrite (NO2--N) oxidation process were further analyzed in the nitrification process. High K+ stress enriched ammonia oxidizing bacteria (AOB), which ensured the efficient ammonia oxidation process in SBRs, and ensured the removal rate of NH4+-N was maintained above 93%. However, high K+ stress (15g/L KCl) inhibited the activity of NO2−-N oxidizing bacteria (NOB) and reduced the abundance of NOB, thus leading to the accumulation of NO2−-N, and finally worsened the nitrification performance of activated sludge. In short, the performance of activated sludge will not be inhibited when the K+ in the wastewater does not exceed 5.23 g/L. The results could provide a reference for the optimization of the biological performance in treating high-NH4+-N organic wastewater with activated sludge coupled RO membrane treatment process.

Land Use and Seasonal Effects on the Soil Microbiome of a Brazilian Dry Forest.

Drylands occupy approximately 41% of the Earth’s terrestrial surface. Climate change and land use practices are expected to affect biogeochemical cycling by the soil microbiome in these ecosystems. Understanding how soil microbial community might respond to these drivers is extremely important to mitigate the processes of land degradation and desertification. The Caatinga, an exclusively Brazilian biome composed of an extensive seasonal tropical dry forest, is exposed to variable spatiotemporal rainfall patterns as well as strong human-driven pressures. Herein, an integrated analysis of shotgun metagenomics approach coupled to meteorological data was employed to unravel the impact of seasonality and land use change on soil microbiome from preserved and agriculture-affected experimental fields in Caatinga drylands. Multivariate analysis suggested that microbial communities of preserved soils under seasonal changes were shaped primarily by water deficit, with a strong increase of Actinobacteria and Proteobacteria members in the dry and rainy seasons, respectively. In contrast, nutrient availability notably played a critical role in driving the microbial community in agriculture-affected soils. The strong enrichment of bacterial genera belonging to the poorly-known phylum Acidobacteria (‘Candidatus Solibacter’ and ‘Candidatus Koribacter’) in soils from dry season affected by ferti-irrigation practices presupposes a contrasting copiotrophic lifestyle and ecological role in mitigating the impact of chemical fertilization. Functional analyses identify overrepresented genes related to osmotic stress response (synthesis of osmoprotectant compounds, accumulation of potassium ions) and preferential carbon and nitrogen utilization when comparing the microbiome of preserved soils under seasonal changes, reflecting differences in the genetic potential for nutrient cycling and C acquisition in the environment. However, the prevalence of nitrosative stress and denitrification functions in irrigation/fertilization-affected soils of the dry season clearly suggest that nutrient input and disruption of natural water regime may impact biogeochemical cycles linked to the microbial processes, with potential impacts on the ecosystem functionality. These findings help to better understand how natural seasonality and agricultural management differentially affect soil microbial ecology from dry forests, providing support for the development of more sustainable land management in dryland ecosystems.

Simulation Study of Intermittent Axonal Block and Desynchronization Effect Induced by High-Frequency Stimulation of Electrical Pulses.

Deep brain stimulation (DBS) has been successfully used in treating neural disorders in brain, such as Parkinson’s disease and epilepsy. However, the precise mechanisms of DBS remain unclear. Regular DBS therapy utilizes high-frequency stimulation (HFS) of electrical pulses. Among all of neuronal elements, axons are mostly inclined to be activated by electrical pulses. Therefore, the response of axons may play an important role in DBS treatment. To study the axonal responses during HFS, we developed a computational model of myelinated axon to simulate sequences of action potentials generated in single and multiple axons (an axon bundle) by stimulations. The stimulations are applied extracellularly by a point source of current pulses with a frequency of 50–200 Hz. Additionally, our model takes into account the accumulation of potassium ions in the peri-axonal spaces. Results show that the increase of extracellular potassium generates intermittent depolarization block in the axons during HFS. Under the state of alternate block and recovery, axons fire action potentials at a rate far lower than the frequency of stimulation pulses. In addition, the degree of axonal block is highly related to the distance between the axons and the stimulation point. The differences in the degree of block for individual axons in a bundle result in desynchronized firing among the axons. Stimulations with higher frequency and/or greater intensity can induce axonal block faster and increase the desynchronization effect on axonal firing. Presumably, the desynchronized axonal activity induced by HFS could generate asynchronous activity in the population of target neurons downstream thereby suppressing over-synchronized firing of neurons in pathological conditions. The desynchronization effect generated by intermittent activation of axons may be crucial for DBS therapy. The present study provides new insights into the mechanisms of DBS, which is significant for advancing the application of DBS.

Physiological Mechanisms of Solanum tuberosum L. Plants’ Tolerance to Chloride Salinity

The mechanisms of potato (Solanum tuberosum L.) plants’ tolerance to chloride salinity were investigated in cv. Lugovskoi regionalized in Russia. Regenerated plants were produced in vitro from apical meristem and grown on half-strength Murashige and Skoog medium (0.5 MS) using a hydroponic unit in controlled-climate conditions. At the age of six weeks, the plants were exposed to salt stress (50–150 mM NaCl, 7 days). Plant response to salt stress was estimated by growth parameters (fresh and dry biomass of the aboveground and underground parts of plants, linear dimensions of shoot and root, area of leaf surface, and number of stolons) and physiological characteristics (level of photosynthetic pigments, accumulation of sodium, potassium, and calcium ions in the aboveground and underground parts of plants, content of proline, activity of antioxidant enzymes, plant tissue hydration, osmotic potential, and POL). It was found that, in response to salinity, the plants of potato, cv. Lugovskoi, showed a considerable inhibition of growth processes, reduction in chlorophyll a content, and suppression of stolon formation, which points to a rather low salinity tolerance of the cultivar. At the same time, under weak or moderate salt stress, the plants preserved water homeostasis owing to effective osmoregulation, actively accumulated proline that acted as a stress protector, and showed hardly any signs of oxidative stress. It was assumed that low salt tolerance of this cultivar depends on the inability of its root system to retain sodium ions and ensure selective ion transport to the aboveground part of the plant and on inefficiency of the system of sodium ions’ removal from the cytoplasm of leaf cells and their compartmentalization in the central vacuole with the purpose of reducing their toxic effect. The obtained results may be useful for working out a technique of improving salt tolerance of this cultivar by the methods of molecular genetics.

Temporal and spatial changes in ion homeostasis, antioxidant defense and accumulation of flavonoids and glycolipid in a halophyte Sesuvium portulacastrum (L.) L.

Salinity is an important environmental constraint limiting plant productivity. Understanding adaptive responses of halophytes to high saline environments may offer clues to manage and improve salt stress in crop plants. We have studied physiological, biochemical and metabolic changes in a perennial, fast growing halophyte, Sesuvium portulacastrum under 0 mM (control), 150 mM (low salt, LS) and 500 mM (high salt, HS) NaCl treatments. The changes in growth, relative water content, cation, osmolyte accumulation, H2O2 and antioxidant enzyme activity (SOD, CAT and APX) were observed under different treatment conditions. A positive correlation was revealed for sodium ion accumulation with malondialdehyde (r2 = 0.77), proline (r2 = 0.88) and chlorophyll content (r2 = 0.82) under salt treatment while a negative correlation was observed with relative tissue water content (r2 = -0.73). The roots and leaves showed contrasting accumulation of potassium and sodium ions under LS treatment. Temporal and spatial study of sodium and potassium ion content indicated differential accumulation pattern in roots and leaves, and, high potassium levels in root. Higher H2O2 content was recorded in roots than leaves and the antioxidant enzyme activities also showed significant induction under salt treatment conditions. Gene expression profiling of sodium transporters, Sodium proton exchanger (NHX3), Vacuolar ATPase (vATPase) and Salt overly sensitive1 (SOS1) showed up regulation under salt stress after 6–24 hr of NaCl treatment. Metabolite changes in the salt stressed leaves showed increased accumulation of flavonoids (3,5-dihydroxy-6,4’-dimethoxy-flavone-7-O-[α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside], and3,5-dihydroxy-6,3’,4’-trimethoxy-flavone-7-O-[α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside] in both LS and HS treatments, while a glycolipid, 1-O-linolenyl-2-O-(palmitoyl)-3-O-galactopyranosyl glycerol, accumulated more in LS over HS treatments and control. The results suggest that differential spatial and temporal cation levels in roots and leaves, and accumulation of flavanoid and glycolipid could be responsible for salt adaptation of S. portulacastrum.

Early-onset neonatal hyperkalemia associated with maternal hypermagnesemia: a case report

BackgroundNeonatal nonoliguric hyperkalemia (NOHK) is a metabolic abnormality that occurs in extremely premature neonates at approximately 24 h after birth and is mainly due to the immature functioning of the sodium (Na+)/potassium (K+) pump. Magnesium sulfate is frequently used in obstetrical practice to prevent preterm labor and to treat preeclampsia; this medication can also cause hypermagnesemia and hyperkalemia by a mechanism that is different from that of NOHK. Herein, we report the first case of very early-onset neonatal hyperkalemia induced by maternal hypermagnesemia.Case presentationA neonate born at 32 weeks of gestation developed hyperkalemia (K+ 6.4 mmol/L) 2 h after birth. The neonate’s blood potassium concentration reached 7.0 mmol/L 4 h after birth, despite good urine output. The neonate and his mother had severe hypermagnesemia caused by intravenous infusion of magnesium sulfate given for tocolysis due to pre-term labor.ConclusionThe early-onset hyperkalemia may have been caused by the accumulation of potassium ions transported through the placenta, the shift of potassium ions from the intracellular to the extracellular space in the infant due to the malfunctioning of the Na+/K+ pump and the inhibition of renal distal tube potassium ion secretion, there is a possibility that these mechanisms were induced by maternal and fetal hypermagnesemia after maternal magnesium sulfate administration. Because neonatal hyperkalemia poses a significant risk for the development of life-threatening cardiac arrhythmia, this case highlights the necessity of maternal blood magnesium monitoring during magnesium sulfate administration and neonatal blood potassium monitoring when there is severe maternal hypermagnesemia at delivery.

Study on the mechanisms of seizure-like events suppression effect by electrical stimulation using a microelectrode array.

In this paper, we studied the mechanisms underlying the suppression of seizure-like events (SLEs) by electrical stimulation. We conducted an in-vitro experiment using entorhinal cortex combined hippocampal slices and two convulsant drugs, bicuculline and 4-aminopyridine, to induce spontaneous SLEs. We used a microelectrode array to observe network dynamics over the entire hippocampal area simultaneously, including regions far from the stimulation site. We stimulated the entorhinal cortex region, which has been determined to be a focus of SLEs by Granger causality analysis of multichannel time series data, by an external electrode. In bicuculline application, electrical stimulation showed a marked suppression effect, even though the sizes of the effective region differed. In 4-aminopyridine application, however, stimulation under the same conditions did not suppress the activities in ∼80% of SLEs. The suppression effect was more remarkable in the areas surrounding the stimulation site in both cases. Our experimental results could support the neuronal depolarization blockade mechanism by accumulation of extracellular potassium ions, which is one of the most convincing mechanisms to understand seizure suppression phenomena because of electrical stimulation. Computer simulation using a neuronal network model also confirmed the mechanism.

Mechanisms of regulation of erythrocyte volume in common carp Cyprinus carpio (Cyprinidae) at increase in the osmotic concentration of blood plasma within the zone of critical water salinity

In common carp Cyprinus carpio, acclimated to NaCl content in water of 0–6 g/L, the concentration of sodium in blood plasma was relatively constant (130.8 ± 0.7 mM/L). In the fish acclimated to 6−12 g/L NaCl, which corresponds to critical water salinity, plasma sodium content rose to the maximal value of 205.6 ± 1.3 mM/L. Within the interval of water salinity of 0–6 g/L NaCl, the content of potassium in erythrocytes exhibits a trend to gradual decrease from 104.8 ± 1.6 mM/L to 96 ± 1.5 mM/L. In the zone of critical salinity, potassium content increases exponentially to 130.3 ± 2.9 mM/L. The erythrocytes adapted to the increase in osmotic concentration of plasma by accumulation of potassium ions. According to published data on the studies in vitro, the erythrocytes adapt to hypertonic solutions by means of increase in intracellular sodium concentration. Possible reasons for discrepancy between the results of in vivo and in vitro studies are discussed in the present paper.