Rise In Na Research Articles

Water and nutrient availability modulate the salinity stress response in Olea europaea cv. Arbequina

Salinity stress represents a key factor for global agriculture. Plants can respond to salinity stress by adapting their physiology in different ways with the aim of limiting reductions in growth and development. Importantly, moisture retention capacity, permeability and nutrient availability of substrates represent critical variables for plants as they may further influence the effect of osmotic stress. Here, a multidisciplinary approach was applied to evaluate the role of two different substrates, peat and perlite, on 2-year-old potted cuttings of Olea europaea (cultivar Arbequina) under different salinity stress conditions (0, 100 and 200 mM NaCl). Biometric and physiological data indicate that plants potted in perlite (AP) generally present lower growth and photosynthetic rates when compared with peat (AS) in combination with salinity stress. Ion measurements indicate a rise in Na+ accumulation with increasing stress severity, which alters the ion ratio in both substrates. In addition, differences occurred in polyphenol contents, with a general increase in quinic acid and rutin contents in AS and AP samples, respectively. Metabolomic and biometric data were also coupled with metabarcoding analysis, which indicates that the moderate salinity treatment (100 mM NaCl, T100) reshaped the endophytic community of plants grown on both substrates. Taken together, the data suggest that the strategy used by a glycophytic species such as the olive tree to cope with salinity stress seems to be highly related to availability of water and nutrients. The lack of both may be simulated by perlite, enhancing the effect of salinity stress response in woody plants. Lastly, applying the beneficial endophytic bacterial taxa identified here could represent a step forward in increasing plant defence and nutrient uptake and reducing inputs for modern and more sustainable agriculture.

Salicylic acid attenuates salinity-induced growth inhibition in in vitro raised ginger (Zingiber officinale Roscoe) plantlets by regulating ionic balance and antioxidative system

Ginger (Zingiber officinalis Roscoe) is valued as a spice and herbal plant with high economic importance, but its productivity is affected by soil salinity. In the present study, potential of salicylic acid (SA) to reduce salt stress was tested in ginger plantlets grown under in vitro conditions. NaCl stress at 150 mM concentration caused a significant decline in growth parameters and photosynthetic pigment contents and a rise in Na+, Cl−, H2O2, superoxide radical contents, activities of chlorophyllase, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) enzymes. A foliar spray of 0.5 mM salicylic acid showed a remarkable improvement in the growth parameters (around 3-fold increase in shoot number and fresh weight) of stressed plantlets. SA treatment enhanced the contents of chlorophyll a (41%), chlorophyll b (51%), total chlorophyll (48.56%), carotenoids (36%) and reduced chlorophyllase activity (18%) under salt stress conditions. NaCl - induced activities of antioxidative enzymes were further increased by SA treatment. An increase of 71.22, 50.84 and 50.45 percent was recorded for SOD, CAT and POD, respectively. A reduction in H2O2 content (31.24%) and superoxide production rate (43%) in stressed plantlets was noted after SA application. This treatment also reversed the sodium ion toxicity as revealed by a decline in Na+and Cl− contents (90%) with a concomitant rise in K+ ion concentration (25.65%) in stressed plantlets. These results indicated that SA-mediated improvement in ionic balance and antioxidative defense system contributed to the acclimatization of plantlets under salinity. In conclusion, foliar application of 0.5 mM salicylic acid could help recover the reduced growth of stressed plantlets. Therefore, SA treatment could be suggested as a feasible approach to produce salt adapted ginger plantlets in vitro. Such plants can perform well on saline soils and could serve as a continuous source of raw material for ginger industry.

<strong>Nephroprotective activity of <em>Pisonia aculeata</em> L. leaf extract against cisplatin induced nephrotoxicity and renal dysfunction in experimental rodents</strong>

Pisonia aculeata L. (Nyctaginaceae), commonly called Devil's Claws or Pullback, is a folk medicinal plant of India. Herbal medicines due to lesser/no side effect, are being accepted by the society increasingly. Here, we investigated the protective effects of ethanol extract of P. aculeata leaves on cisplatin induced nephrotoxicity. Cisplatin (3 mg/kg, i.p.) co-administered to vehicle and extract (200, 400, 600 mg/kg)-fed rats every 5th day for 25 days. Serum level of urea, uric acid, creatinine, blood urea nitrogen, phospholipid and cholesterol increased, whereas urine urea, uric acid, creatinine, creatinine clearance rate was reduced in cisplatin control group. Cisplatin also negatively alters electrolyte balance, Na+/K+-ATPase activity and redox balance significantly. Treatment with extract for 21 days exerted beneficial effect and ameliorated urine and serum biochemical parameter to normal. Extracts induced a rise in Na+/K+-ATPase activity, and ameliorated level of different enzymatic and non-enzymatic antioxidants positively, whereas lipid peroxidation decreased significantly. Ethanol extract (400 and 600 mg/kg) ameliorated cisplatin-induced nephrotoxicity and other damaging effects caused by cisplatin evidenced by the change in its intrinsic biochemical/antioxidant properties. Taking into account these results, it can be assumed that P. aculeata leaves could be a future key candidate which may maximize the clinical use of cisplatin in the treatment of different cancer without nephrotoxicity.

The Relationship between Dietary Sodium-to-Potassium Ratio and Metabolic Syndrome in Korean Adults: Using Data from the Korean National Health and Nutrition Examination Survey 2013-2015

Background: The dietary sodium-to-potassium ratio (Na:K) is known to have a stronger association with cardiovascular disease compared with a single intake of sodium or potassium. Accordingly, this study sought to examine the relationship between sodium-potassium intake balance and metabolic syndrome, which increases the occurrence of cardiovascular disease.Methods: Data from the Korea National Health and Nutrition Examination Survey 2013-2015 were used, and the subjects were 13,164 adults aged 19 years and over. This study examined sodium and potassium intake and Na:K based on Korean adults' age and sex, and analyzed food groups that contribute to adequate sodium and potassium intake based on an Na:K of 1. Correlations between Na:K, metabolic syndrome, and risk factors were examined through a multiple logistic regression analysis.Results: Korean adults' average daily intake of sodium was 3,976 mg, while that of potassium was 3,076 mg.Meanwhile, the Na:K was identified to be 2.33. The food group that contributed the most to potassium intake was fruits in subjects whose Na:K was below 1, and vegetables in those whose Na:K was over 1. Compared with the lowest quartile, the highest quartile in Na:K was up 19% in the probability that one would suffer from metabolic syndrome (<i>P</i> for trend=0.001). Also, more Na:K led to a significant increase in the risk of elevated blood pressure and elevated blood sugar (<i>P</i> for trend=0.015 and 0.012).Conclusions: A rise in Na:K is related to a risk of hypertension and high blood sugar, and such a rise raises the prevalence rate of metabolic syndrome.

1106 Impact of Splanchnic Vasoconstrictors on Sodium Level in Inpatient Cirrhotics With Hyponatremia: A Retrospective Cohort Study

INTRODUCTION: Hyponatremia (hypoNa) in cirrhosis represents another consequence of splanchnic vasodilation. Splanchnic vasoconstrictors are currently used in hepatorenal syndrome (HRS) which has similar pathogenesis, however their role in hypoNa has not been fully investigated. Aim of the study is to evaluate the effect of octreotide ± midodrine on hypoNa in cirrhotics. METHODS: We retrospectively included adult cirrhotics admitted to the Cleveland Clinic hospitals between 10/1/2011 and 10/1/2015, who had Na < 133 at or during admission. We excluded subjects with less than 5 days of follow up, those who received potent vasoconstrictors as norepinephrine or received hypertonic saline, tolvaptan or renal replacement therapy during admission. Population was divided into those who received octreotide versus those who did not. Outcomes were Na level at days 5, 7 and 10 after starting octreotide. Secondary outcome was determination of predictors of change of Na at day 5 using a multivariate model that included variables with P < 0.1 on univariate analysis. We then performed a subgroup analysis for only those with baseline Na < 125 (as this is the correction threshold for many transplant centers). RESULTS: Patients in the octreotide group were younger, had higher Model for End-Stage Liver Disease score, more patients had ascites and varices compared to controls [Table 1]. The octreotide group had lower baseline Na, but the Na levels at 5,7 and 10 days after octreotide were significantly higher [Figure 1]. The two predictors of higher Na at 5 days were having a lower baseline Na and receiving both octreotide and midodrine Table 2]. When analysis was restricted to the subgroup with baseline Na < 125, 97% of those who received octreotide had Na ≥125 by day 5 (compared to 77% of controls, P = 0.03). In this subgroup, the only predictor of reaching Na ≥125 by day 5 (multivariate logistic regression model) was receiving octreotide; OR 11.2 (1.16- 109), P = 0.04. CONCLUSION: Cirrhotics with hypoNa that received octreotide had a significantly higher rise in Na. On a multivariate analysis accounting for the potential confounders, octreotide remained a significant predictor only when combined with midodrine, suggesting a synergistic effect (similar to HRS). To our knowledge, this is the largest study evaluating the effect of splanchnic vasoconstrictors on sodium level in cirrhotics with hypoNa compared to controls. Prospective studies are needed with matched controls and longer follow up.

Seed Pre-treatment with Polyhydroxy Fullerene Nanoparticles Confer Salt Tolerance in Wheat Through Upregulation of H2O2 Neutralizing Enzymes and Phosphorus Uptake

Polyhydroxy fullerenes nanoparticles (PHF) are regarded as free radical sponges. Can they mitigate oxidative stress and induce tolerance in plants exposed to salinity? The influence of PHF seed pre-treatment on growth and biochemical attributes of NaCl-stressed wheat is studied. Wheat seeds (cv. Ujala) were pre-treated with control, hydro-priming, 10, 40, 80, and 120 nM PHF doses for 10 h and grown in sand-filled pots under control (0 mM NaCl) and salinity (150 mM NaCl) provided through nutrient solution. Salinity markedly decreased root and shoot growth attributes consistent with the reduction in the chlorophyll contents, whereas it increased the antioxidant activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) enzymes. Plants exposed to salinity exhibited increase in malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents which indicated oxidative stress. Further, salinity triggered rise in Na+ uptake while decreased in K+ and Ca2+ contents both in the root and shoot. By contrast, wheat seedlings grown from PHF-treated seeds exhibited recovery in root and shoot growth under salinity. This recovery was linked with lower levels of MDA and H2O2 contents and higher antioxidant activities of CAT, POD, and APX enzymes under salinity stress. The PHF-treated plants had higher chlorophyll, free amino acids, ascorbic acid, and soluble sugars. Moreover, PHF seed pre-treatment resulted in higher K+ and P contents in the root while higher P contents in the shoot. Above all, PHF application mitigated adverse effects of salinity and promoted early seedling growth and establishment in wheat.

The inner mantle of the giant clam, Tridacna squamosa, expresses a basolateral Na+/K+-ATPase α-subunit, which displays light-dependent gene and protein expression along the shell-facing epithelium.

Na+/K+-ATPase (NKA) is essential for maintaining the Na+ and K+ gradients, and supporting the secondary active transport of certain ions/molecules, across the plasma membrane of animal cells. This study aimed to clone the NKA α-subunit (NKAα) from the inner mantle adjacent to the extrapallial fluid of Tridacna squamosa, to determine its subcellular localization, and to examine the effects of light exposure on its transcript level and protein abundance. The cDNA coding sequence of NKAα from T. squamosa comprised 3105 bp, encoding 1034 amino acids with an estimated molecular mass of 114 kDa. NKAα had a basolateral localization along the shell-facing epithelium of the inner mantle. Exposure to 12 h of light led to a significantly stronger basolateral NKAα-immunofluorescence at the shell-facing epithelium, indicating that NKA might play a role in light-enhanced calcification in T. squamosa. After 3 h of light exposure, the transcript level of NKAα decreased transiently in the inner mantle, but returned to the control level thereafter. In comparison, the protein abundance of NKAα remained unchanged at hour 3, but became significantly higher than the control after 12 h of light exposure. Hence, the expression of NKAα in the inner mantle of T. squamosa was light-dependent. It is probable that a higher expression level of NKA was needed in the shell-facing epithelial cells of the inner mantle to cope with a rise in Na+ influx, possibly caused by increases in activities of some Na+-dependent ion transporters/channels involved in light-enhanced calcification.

Influence of Na on grain boundary and properties of Cu(In,Ga)Se2 solar cells

AbstractWhether added from external sources or supplied via substrate, incorporation of Na has always improved the conversion efficiency of polycrystalline thin‐film Cu(In,Ga)Se2 (CIGS) solar cells. Segregation of Na along grain boundary (GB) is thought to be one of the main reasons for better efficiency, and changing its concentration levels may tune the device properties accordingly. Our previous works have shown that changes in GB chemistry over various Ga/In concentrations are the main reason for poor performance of Ga‐rich (18%) CIGS, besides its optimum band gap (1.4 eV) for energy conversion. It was suspected that changes in GB chemistry or device performance or both could be driven by variation in Na concentration at GB. In this research, atomic level fluctuations of Na atoms at GB for various CuIn1−xGaxSe2 thin films were measured accurately with atom probe tomography technique. Fluctuations observed in Na concentration at GB are restricted to the range 0.5–6.5 atoms per nm2 and is irrespective of x value (GGI) and GB surface density. Results also show that changes in GB chemistry for similar CIGS compositions are not necessary due to changes in Na concentration levels at GB. However, an increased density of GBs per unit volume with GGI may indicate an overall rise in Na in thin films and could explain the drop in CIGS performance. Copyright © 2017 John Wiley & Sons, Ltd.

Assessing the national trends in colon cancer among Native Americans: A 12 year SEER database study

IntroductionNative Americans (NA) form a unique cohort of colon cancer (CC) patients among whom the variability in demographics and cancer characteristics remains unclear. MethodsWe abstracted the national estimates for NA with CC using the Surveillance, Epidemiology, and End Result (SEER) database. Trend analysis of incidence, variation in location and patient demographic analysis were performed. ResultsA total number of 26,674 NA with CC were reported during the 12-year study period. While the overall incidence of CC decreased by 12% during the study period, incidence increased by 38% in NA. Incidence of CC was more prevalent and higher increase (42%) seen in NA females than males (p = 0.02; 34%). Stage III tumors represented 29% of all CC, sigmoid colon the most common site location (38%) with 72% of all tumors being moderately differentiated. 55% tumors were localized in left, 36% in right and 9% in transverse colon. 92% of the NA were insured. ConclusionIncidence of CC continues to rise in NA with majority of CC presented at higher stage and moderate differentiation.

Combination of DFP and Taurine Counteracts the Aluminum-Induced Alterations in Oxidative Stress and ATPase in Cortex and Blood of Rats.

The study investigated the combined effect of 1,2-dimethyl-3-hydroxypyrid-4-one (DFP) and taurine on aluminum (Al) toxicity in cortex and blood of rats. The control group received 1ml/kg/day saline solution for 8weeks. Other animals were exposed to Al at a dose of 281.40mg/kg/day orally for 4weeks. Then, they were administered with 1ml/kg/day saline solution, 400mg/(kg·day) taurine, 13.82mg/(kg·day) DFP, 27.44mg/(kg·day) DFP, 400mg/(kg·day) taurine +13.82mg/(kg·day) DFP, and 400mg/(kg·day) taurine +27.44mg/(kg·day) DFP for 4weeks. The changes in markers of oxidative stress, activities of antioxidant enzymes, and triphosphatase (ATPase) in the cortex and blood were determined. Administration of Al led to significant increase in the malondialdehyde (MDA) level and decrease in the activities of antioxidant enzymes, Na+K+-ATPase, Mg2+-ATPase, and Ca2+-ATPase in the cortex and blood, compared with the control group. DFP was observed to reverse alteration of these parameters except for Ca2+-ATPase activity. Treatment with taurine caused significant increase of GSH-Px activity and decrease of the MDA level in the cortex and serum and rise of Na+K+-ATPase in the blood. Effects of DFP combined with taurine were investigated and found to provide a more significant benefit than either drug alone. Combined intake of taurine and DFP could achieve an optimum effect of therapy for Al exposure.

A crosstalk between Na+ channels, Na+/K+ pump and mitochondrial Na+ transporters controls glucose-dependent cytosolic and mitochondrial Na+ signals

Glucose-dependent cytosolic Na+ influx in pancreatic islet β cells is mediated by TTX-sensitive Na+ channels and is propagated into the mitochondria through the mitochondrial Na+/Ca2+ exchanger, NCLX. Mitochondrial Na+ transients are also controlled by the mitochondrial Na+/H+ exchanger, NHE, while cytosolic Na+ changes are governed by Na+/K+ ATPase pump. The functional interaction between the Na+ channels, Na+/K+ ATPase pump and mitochondrial Na+ transporters, NCLX and NHE, in mediating Na+ signaling is poorly understood. Here, we combine fluorescent Na+ imaging, pharmacological inhibition by TTX, ouabain and EIPA, with molecular control of NCLX expression, so as to investigate the crosstalk between Na+ transporters on both the plasma membrane and the mitochondria. According to our results, glucose-dependent cytosolic Na+ response was enhanced by ouabain and was followed by a rise in mitochondrial Na+ signal. Silencing of NCLX expression using siNCLX, did not affect the glucose- or ouabain-dependent cytosolic rise in Na+. In contrast, the ouabain-dependent rise in mitochondrial Na+ was strongly suppressed by siNCLX. Furthermore, mitochondrial Na+ influx rates were accelerated in cells treated with the Na+/H+ exchanger inhibitor, EIPA or by combination of EIPA and ouabain. Similarly, TTX blocked the cytosolic and mitochondrial Na+ responses, which were enhanced by ouabain or EIPA, respectively. Our results suggest that Na+/K+ ATPase pump controls cytosolic glucose-dependent Na+ rise, in a manner that is mediated by TTX-sensitive Na+ channels and subsequent mitochondrial Na+ uptake via NCLX. Furthermore, these results indicate that mitochondrial Na+ influx via NCLX is antagonized by Na+ efflux, which is mediated by the mitochondrial NHE; thus, the duration of mitochondrial Na+ transients is set by the interplay between these pivotal transporters.

The Autocrine/Paracrine Loop After Myocardial Stretch: Mineralocorticoid Receptor Activation

The stretch of cardiac muscle increases developed force in two phases. The first phase, which occurs rapidly, constitutes the well-known Frank-Starling mechanism and it is generally attributed to enhanced myofilament responsiveness to Ca2+. The second phase or slow force response (SFR) occurs gradually and is due to an increase in the calcium transient amplitude as a result of a stretch-triggered autocrine/paracrine mechanism. We previously showed that Ca2+ entry through reverse Na+/Ca2+ exchange underlies the SFR, as the final step of an autocrine/paracrine cascade involving release of angiotensin II/endothelin, and a Na+/H+ exchanger (NHE-1) activation-mediated rise in Na+. In the present review we mainly focus on our three latest contributions to the understanding of this signalling pathway triggered by myocardial stretch: 1) The finding that an increased production of reactive oxygen species (ROS) from mitochondrial origin is critical in the activation of the NHE-1 and therefore in the genesis of the SFR; 2) the demonstration of a key role played by the transactivation of the epidermal growth factor receptor; and 3) the involvement of mineralocorticoid receptors (MR) activation in the stretch-triggered cascade leading to the SFR. Among these novel contributions, the critical role played by the MR is perhaps the most important one. This finding may conceivably provide a mechanistic explanation to the recently discovered strikingly beneficial effects of MR antagonism in humans with cardiac hypertrophy and failure.

Apoplastic Na+ in Vicia faba Leaves Rises After Short‐Term Salt Stress and Is Remedied by Silicon

AbstractSalinity primarily affects plants by inhibiting shoot growth. Salt‐sensitive plants have been suggested to accumulate Na+ within their leaf apoplast under salinity, leading to a reduced water status. Evidence related to apoplastic Na+ accumulation is still enigmatic. We have focused on the effect of a short‐term salt treatment by using the salt‐sensitive Vicia faba. Moreover, we have examined the role of silicon in alleviating sodium accumulation in the apoplast. Salt‐sensitive field beans have been subjected to increasing levels of salinity, with and without the addition of silicon under hydroponic conditions. We have demonstrated that the dicot Vicia faba exhibits a rise in Na+ concentration in the leaf apoplast at higher salinity levels; this is significantly ameliorated by the addition of silicon. Further, enhanced shoot growth under high salt treatment in the presence of added silicon is correlated with a significant decrease in Na+ concentration in the leaves. The novelty of the current study is the detection of a high Na+ concentration in the leaf apoplast of the salt‐sensitive dicot field bean. Our results support Oertli's hypothesis that extracellular salt accumulation can lead to wilting leaves, plant growth reduction and cell death.

Postexercise cooling interventions and the effects on exercise-induced heat stress in a temperate environment

The aim of this study was to examine the effects of cool water immersion (20 °C; CWI) while wearing a cooling jacket (Cryovest;V) and a passive control (PAS) as recovery methods on physiological and thermoregulatory responses between 2 exercise bouts in temperate conditions. Nine well-trained male cyclists performed 2 successive bouts of 45 min of endurance cycling exercise in a temperate environment (20 °C) separated by 25 min of the respective recovery interventions. Capillary blood samples were obtained to measure lactate (La⁻), sodium (Na⁺), bicarbonate (HCO₃⁻) concentrations and pH, whilst body mass loss (BML), core temperature (T(core)), skin temperature (T(skin)), heart rate (HR), oxygen uptake , and minute ventilation were measured before (Pre), immediately after the first exercise bout (Ex1), the recovery (R), and after the second exercise bout (Ex2). V and CWI both resulted in a reduction of T(skin) at R (-2.1 ± 0.01 °C and -11.6 ± 0.01 °C, respectively, p < 0.01). Despite no difference in final values post-Ex2 (p > 0.05), V attenuated the rise in HR, minute ventilation, and oxygen uptake from Ex1 to Ex2, while T(core) and T(skin) were significantly lower following the second session (p < 0.05). Further, CWI was also beneficial in lowering T(core), T(skin), and BML, while a rise in Na⁺ was observed following Ex2 (p < 0.05). Overall results indicate that cooling interventions (V and CWI) following exercise in a temperate environment provide a reduction in thermal strain during ensuing exercise bouts.

Sertraline inhibits pre‐synaptic Na+ channel‐mediated responses in hippocampus‐isolated nerve endings

In the present study, a possible sertraline action on cerebral pre-synaptic Na(+) channels was investigated. For this purpose, the effect of sertraline on responses induced by the Na(+) channel opener, veratridine, namely the increase in Na(+) and in neurotransmitter release in hippocampus-isolated nerve endings was investigated. Results show that sertraline in the low μM range (1.5-25 μM) progressively inhibits the rise in Na(+) and the release of pre-loaded [(3) H]Glu as well as the release of endogenous 5-HT, Glu and GABA (detected by HPLC) induced by veratridine depolarization either under external Ca(2+) -free conditions or in the presence of external Ca(2+) . In addition, under non-depolarized conditions, sertraline (25 μM) increased the external concentration of 5-HT at expense of its internal concentration, and unchanged the external and internal concentrations of the amino acid neurotransmitters and of the 5-HT main metabolite, 5-HIAA. This result is consistent with the sertraline inhibitory action of the serotonin transporter. However, sertraline is unlikely to inhibit pre-synaptic Na(+) channels permeability by increasing external 5-HT. Because 5-HT in a wide concentration range (1-1000 μM) did not change the veratridine-induced increase in Na(+) . In summary, present findings demonstrate that besides the inhibition of 5-HT reuptake, sertraline is an effective inhibitor of pre-synaptic Na(+) channels controlling neurotransmitter release.

A micro-analytical approach to partition coeffi cients in plagioclase and clinopyroxene of basaltic sills in Serra Geral Formation, Paraná Basin, Brazil

In the present study, detailed micro-analytical data (major and trace elements) in minerals from sills of Serra Geral Formation represents the fi rst attempt to evaluate the partition coeffi cient of Sc, Ti, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Mo, Cs, Ba, REE, Hf, Ta, Pb, Th and U among coexisting plagioclase, augite and pigeonite from 12 tholeiitic basaltic sills along the eastern border of the Parana Basin, Brazil. These 12 samples come from Rio Grande do Sul, Parana, Sao Paulo and Goias states. Plagioclase/melt partition coeffi cients K D were determined in core, intermediate and rim zones using LA-ICP-MS and the results were compared with the variations of the elements Ca, Al, Na and Si in those areas. Partition coeffi cients of Sr and Eu decrease with the increase of Ca concentration in plagioclase. A reduction in temperature and consequently a rise in Na and Si levels increase the partition coeffi cients of Sr and Eu at the rim of mineral The K D of Ni and V in clinopyroxene has positive correlations with Mg 2+ , Ca 2+ and Al 3+ due to higher concentrations of those elements at the core and lower concentration towards the rim and negative correlations of K D of Sc, Cr, Co, Pb and Lu, due to preferential substitutions by Fe 2+ in sixfold coordination. The use of LA-ICP-MS and EPMA made possible the chemical quantifi cation of major and trace elements and the determination of partition coeffi cients in coexisting plagioclase and clinopyroxene in basaltic melts.

Experimental investigation of the solubility of albite and jadeite in H 2O, with paragonite + quartz at 500 and 600 °C, and 1–2.25 GPa

The solubilities of the assemblages albite + paragonite + quartz and jadeite + paragonite + quartz in H 2O were determined at 500 and 600 °C, 1.0–2.25 GPa, using hydrothermal piston-cylinder methods. The three minerals are isobarically and isothermally invariant in the presence of H 2O, so fluid composition is uniquely determined at each pressure and temperature. A phase-bracketing approach was used to achieve accurate solubility determinations. Albite + quartz and jadeite + quartz dissolve incongruently in H 2O, yielding residual paragonite which could not be retrieved and weighed. Solution composition fixed by the three-mineral assemblage at a given pressure and temperature was therefore bracketed by adding NaSi 3O 6.5 glass in successive experiments, until no paragonite was observed in run products. Solubilities derived from experiments bounding the appearance of paragonite thus constrain the equilibrium fluid composition. Results indicate that, at a given pressure, Na, Al, and Si concentrations are higher at 600 °C than at 500 °C. At both 500 and 600 °C, solubilities of all three elements increase with pressure in the albite stability field, to a maximum at the jadeite–albite–quartz equilibrium. In the jadeite stability field, element concentrations decline with continued pressure increase. At the solubility maximum, Na, Al, and Si concentrations are, respectively, 0.16, 0.05, and 0.48 molal at 500 °C, and 0.45, 0.27, and 1.56 molal at 600 °C. Bulk solubilities are 3.3 and 10.3 wt% oxides, respectively. Observed element concentrations are everywhere greater than those predicted from extrapolated thermodynamic data for simple ions, monomers, ion pairs, and the silica dimer. The measurements therefore require the presence of additional, polymerized Na–Al–Si-bearing species in the solutions. The excess solubility is >50% at all conditions, indicating that polymeric structures are the predominant solutes in the P– T region studied. The solubility patterns likely arise from combination of the large solid volume change associated with the albite–jadeite–quartz equilibrium and the rise in Na–Al–Si polymerization with approach to the hydrothermal melting curves of albite + quartz and jadeite + quartz. Our results indicate that polymerization of Na–Al–Si solutes is a fundamental aspect of fluid–rock interaction at high pressure. In addition, the data suggest that high-pressure metamorphic isograds can impose unexpected controls on metasomatic mass transfer, that significant metasomatic mass transfer prior to melting should be considered in migmatitic terranes, and that polymeric complexes may be an important transport agent in subduction zones.

Insights into the salt tolerance mechanism in barley (Hordeum vulgare) from comparisons of cultivars that differ in salt sensitivity

Although barley (Hordeum vulgare L.) is a salt-tolerant crop, the underlying physiological and molecular mechanisms of salt tolerance remain to be elucidated. Therefore, we investigated the response of salt-tolerant (K305) and salt-sensitive (I743) cultivars to salt stress at both physiological and molecular levels. Salt treatment increased xylem sap osmolarity, which was attributed primarily to a rise in Na(+) and Cl(-) concentration; enhanced accumulation of the ions in shoots; and reduced plant growth more severely in I743 than K305. The concentration of K(+) in roots and shoots decreased during 8 h of salt treatment in both cultivars but with no marked difference between cultivars. Hence, the severe growth reduction in I743 is attributed to the elevated levels of (mainly) Na(+) in shoots. Analysis of gene expression using quantitative RT-PCR showed that transcripts of K(+)-transporters (HvHAK1 and HvAKT1), vacuolar H(+)-ATPase and inorganic pyrophosphatase (HvHVA/68 and HvHVP1) were more abundant in shoots of K305 than in shoots of I743. Expression of HvHAK1 and Na(+)/H(+) antiporters (HvNHX1, HvNHX3 and HvNHX4) was higher in roots of K305 than in I743 with prolonged exposure to salt. Taken together, these results suggest that the better performance of K305 compared to I743 during salt stress may be related to its greater ability to sequester Na(+) into sub-cellular compartments and/or maintain K(+) homeostasis.

Analysis of exercise‐induced Na+–K+ exchange in rat skeletal muscle in vivo

We aimed to quantify the Na(+)-K(+) exchange occurring during exercise in rat skeletal muscle in vivo. Intracellular Na(+) and K(+) content, Na(+) permeability ((22)Na(+) influx), Na(+)-K(+) pump activity (ouabain-sensitive (86)Rb(+) uptake) and Na(+)-K(+) pump alpha(2) subunit content ([(3)H]ouabain binding) were measured. Six-week-old rats rested (control animals) or performed intermittent running for 10-60 min and were then killed or were killed at 15 or 90 min following 60 min exercise. In the soleus muscle, intracellular Na(+) was 80% higher than in control rats after 60 min exercise, was still elevated (38%) after 15 min rest and returned to control levels after 90 min rest. Intracellular K(+) showed corresponding decreases after 15-60 min exercise, returning to control levels 90 min postexercise. Exercise induced little change in Na(+) and K(+) in the extensor digitorum longus muscle (EDL). In soleus, the exercise-induced rise in Na(+) and reduction in K(+) were augmented by pretreatment with ouabain or by reducing the content of muscular Na(+)-K(+) pumps by prior K(+) depletion of the animals. Fifteen minutes after 60 min exercise, ouabain-sensitive (86)Rb(+) uptake in the soleus was increased by 30% but was unchanged in EDL, and there was no effect of exercise on [(3)H]ouabain binding measured in vitro or in vivo in either muscle. In conclusion, in the soleus, in vivo exercise induces a rise in intracellular Na(+), which reflects the excitation-induced increase in Na(+) influx and leads to augmented Na(+)-K(+) pump activity without apparent change in Na(+)-K(+) pump capacity.

Local Sodium, Global Reach

See related article, pages 1030–1038 The plasma membrane (PM) Na+/Ca2+ exchanger (NCX) in vascular smooth muscle is an unique link between the trans-PM Na+ electrochemical gradient and intracellular Ca2+ and, therefore, between Na+ ions and Ca2+ signaling, vascular tone and blood pressure.1 The mechanisms by which Na+ normally enters the myocytes and influences the Na+ gradient and NCX activity are, however, incompletely understood. Our view of how Na+ ions help regulate sarco-/endoplasmic reticulum (S/ER) Ca2+ stores and contractility in arteries has now been signally enhanced by Poburko and colleagues.2 Using CoroNa green, a Na+-sensitive fluorochrome, they observed local Na+ concentration transient increases (“LNats”) in cultured arterial myocytes. The LNats were generated by Na+ entry through cation-selective TRPC6 channels, a member of the TRP (transient receptor potential) channel family.2 This is direct, dynamic evidence for a predicted sub-PM compartment with greatly restricted Na+ diffusion3,4 in which the local rise in Na+ concentration should drive Ca2+ into the myocytes via NCX. The present study has broad implications for Ca2+ homeostasis and signaling. Earlier vascular smooth muscle studies indicated that other members of the TRP channel family might also admit Na+ to sub-PM domains.3,5 Indirect evidence,6 as well as an electron microprobe study, indicate that cardiomyocytes, too, can exhibit elevated local sub-PM Na+ concentrations ([Na+]SPM).7 Moreover, comparable diffusion-restricted, sub-PM cytosolic compartments may also be present in other types of cells (e.g., astrocytes8). To explain how S/ER Ca2+ stores in smooth muscles could refill from the extracellular fluid without inducing contractions,9,10 van Breeman and colleagues postulated a “privileged pathway” (the Ca2+ “buffer …