Changes In Ionic Composition Research Articles

Long-term trends in sodium and chloride in the Mohawk River, New York: the effect of fifty years of road-salt application

Ecological studies have demonstrated the adverse effects of road-salt, primarily NaCl, on water quality, flora, and fauna. In this study, we quantified changes in ionic composition and solute flux of water draining the Mohawk River Basin (9103 km 2) in New York State, from 1952 to 1998. Using various statistical, graphical, and modeling techniques, we showed that concentrations of Na + and Cl − have increased by 130 and 243%, respectively, while other constituents have decreased or remained constant. The use of de-icing salt on roads within the watershed, which we estimate at 39 kg km −2 day −1, appears to be the primary mechanism responsible for reported increases, accounting for the increase in NaCl export from 16 to 46 kg km −2 day −1 over the 47-year period. Moreover, despite population decline within this rural upstate watershed, increased environmental stewardship, and The Clean Water Act, concentrations of Na + and Cl − still increased during the 1990s.

Ionic composition and osmolality of paddlefish ( Polyodon spathula , Acipenseriformes) seminal fluid

Changes in ionic composition as Na+,K+, Ca2+ and Mg2+, osmolality inseminal fluid, percentage of motile spermatozoaand velocity were investigated in response toCPP and different dosage of LHRHa. The lowestvelocity of sperm was observed after use CPPtreatment. The velocity of spermatozoa,significant main effect of the treatment(P < 0.0001) and the time of sperm collection(P < 0.0104) were evaluated. The osmolality ofseminal fluid was different betweenexperimental groups of LHRHa (48.0–62.7mOsmol.kg−1) and CPP (33.0–46.3mOsmol.kg−1) treatments. The osmolalitywas significantly higher on the first day andone-half, then declined on day three, rangingfrom 33.0 to 62.7 mOsmol.kg−1. Analysisof variance showed significant main effects ofthe treatment (P < 0.0001) and the time ofsperm collection (P < 0.0002) on the osmolalityof seminal fluid. The level of Na+ andK+ ion was different between experimentalgroups of LHRHa and CPP treatment. The highestconcentration of 11.11 mmol.l−1 wasobserved at Na+ ion. Then theconcentrations declined on the level 1.56, 0.52and 0.36 mmol.l−1 for K+, Ca2+and Mg2+ ions, respectively. There werehighly positive correlations between osmolalityof seminal fluid and dosage of LHRHa treatment(r = 0.84), velocity of spermatozoa andosmolality of seminal fluid (r = 0.57) andosmolality of seminal fluid and Na+concentration at seminal fluid (r = 0.70).Injection with LHRHa increased quality of spermas velocity of sperm, level of Na+,K+ and osmolality at seminal fluidcompared to CPP treatments.

Radiation synthesis and characteristic of the hydrogels based on carboxymethylated chitin derivatives

Carboxymethylchitin (CM-chitin) and its deacetylated product carboxymethylchitosan (CM-chitosan) were irradiated in aqueous solutions at various irradiation dose by high-energy radiation electronic accelerator in vacuum. Carboxymethylated chitin derivatives irradiated at paste-like conditions were found to introduce crosslinking structure. When the dosage of electron beam irradiation was 20 kGy or more, transparent hydrogels could be produced. In the case of CM-chitosan, high degree of deacetylation was found to negatively correlate to crosslinking even if it has a high degree of substitution. The hydrogels created from carboxymethylated chitin derivatives, exhibited excellent mechanical properties and good swelling in water. The further study on the swelling properties at various conditions indicated that CM-chitin and CM-chitosan hydrogels displayed characteristically pH-sensitive character in their swelling behavior. The gel of CM-chitosan with a high DS (0.91) swelled in acid (pH<3.5) and alkaline (pH>6) conditions and deswelled between pH 3.5 and 6.0 due to the ionic composition changes of the gel network. In addition, the antibacterial activity against E. coli was also found in CM-chitosan hydrogel.

Groundwater and surface water contamination in the area of the Hitura nickel mine, Western Finland

Tailings-derived mine drainage water that is neutral in character, has a high electrical conductivity and contains elevated sulphate, chloride and nickel concentrations, has caused deterioration in groundwater and surface water quality in the mining area of Hitura in Western Finland. This deterioration, and thereby the location of the contaminant plume, was recognized in the water chemistry in the form of a gradual change in ion composition from Ca-HCO3-type water towards a Mg-SO4-rich type. It was possible to define the extent of the pollution by using cluster analysis to distinguish between hydrochemically different regimes and performing an electrical sounding survey. The results indicated that contamination is most intense close to the tailings impoundment and is related to an esker complex running across this area. Nevertheless, the water in the eastern and southern parts of the area upgradient of the hydraulic head is uncontaminated and suitable for water supply purposes.

Polarization jet events and excitation of weak SAR arcs

Polarization Jet (PJ), also known as Sub‐Auroral Ion Drift (SAID), events are supersonic westward plasma drifts on the equatorward edge of the diffuse aurora in the evening and nighttime sector. Their optical F‐region signatures are weak 630.0 nm red arcs colocated with regions of fast convection. These weak arcs resemble Stable Auroral Red (SAR) arcs observed during the recovery phase of magnetic storms, but have lower intensities, shorter lifetimes, and occur without a significant heat flux from the magnetosphere. Previous model studies underestimated the brightness of weak SAR arcs. We present calculations showing that ion‐neutral collisional heating and ion composition changes during PJ events may be an additional source of 630.0 nm emission, and propose experimental tests that could verify our modeling results.

Modulation of the two-pore domain acid-sensitive K+ channel TASK-2 (KCNK5) by changes in cell volume.

The molecular identity of K(+) channels involved in Ehrlich cell volume regulation is unknown. A background K(+) conductance is activated by cell swelling and is also modulated by extracellular pH. These characteristics are most similar to those of newly emerging TASK (TWIK-related acid-sensitive K(+) channels)-type of two pore-domain K(+) channels. mTASK-2, but not TASK-1 or -3, is present in Ehrlich cells and mouse kidney tissue from where the full coding sequences were obtained. Heterologous expression of mTASK-2 cDNA in HEK-293 cells generated K(+) currents in the absence intracellular Ca(2+). Exposure to hypotonicity enhanced mTASK-2 currents and osmotic cell shrinkage led to inhibition. This occurred without altering voltage dependence and with only slight decrease in pK(a) in hypotonicity but no change in hypertonicity. Replacement with other cations yields a permselectivity sequence for mTASK-2 of K(+) > Rb(+) Cs(+) > NH(4)(+) > Na(+) congruent with Li(+), similar to that for the native conductance (I(K, vol)). Clofilium, a quaternary ammonium blocker of I(K, vol), blocked the mTASK-2-mediated K(+) current with an IC(50) of 25 microm. The presence of mTASK-2 in Ehrlich cells, its functional similarities with I(K, vol), and its modulation by changes in cell volume suggest that this two-pore domain K(+) channel participates in the regulatory volume decrease phenomenon.

Change of energetic ion composition in the plasma sheet during substorms

It has been reported by previous studies that the energetic particle flux of ions of ionospheric origin like O+ ions is more enhanced than that of H+ ions in the near‐Earth tail (X ∼ −6 to −16 RE) during substorms. To explain this strong O+ flux enhancement, some studies have surmised that thermal O+ ions in the plasma sheet boundary layer or the lobe are strongly accelerated at the magnetic reconnection region (X ∼ −20 to −30 RE), and are subsequently transported into the near‐Earth plasma sheet with earthward plasma flows. However, other studies have supposed that the strong O+ flux enhancement is caused by local magnetic field reconfiguration (local dipolarization). In the present study, we used Geotail/EPIC measurements of energetic (60 keV to 3.6 MeV) ion flux to test the above two scenarios. We investigated ion composition in the plasma sheet while earthward plasma flows and/or dipolarization signatures were observed. In terms of energy density ratio of oxygen ions to protons, the observational results can be summarized as follows: (1) earthward plasma flows without dipolarization signatures did not accompany large increases of the ratio in most cases; (2) when earthward plasma flows appeared with dipolarization signatures, they accompanied increases of the ratio; and (3) most of dipolarization events were associated with large increases of the ratio. These results suggest that the strong increase in the energetic oxygen constituent in the near‐Earth plasma sheet is due to acceleration of ions during dipolarization, consistent with the latter scenario.

Multi-proxy Holocene palaeoclimatic record from a saline lake in the Canadian Subarctic

Multi-proxy palaeolimnological analyses of a postglacial sedimentary sequence at a centennial-scale resolution from an athalassic saline lake in the Yukon were conducted to infer patterns of Holocene climatic change in the Canadian Subarctic, using sediment mineralogy and biostratigraphy (diatoms, pigments). Diatominferred quantitative estimates of palaeosalinity were obtained by use of transfer functions developed from a calibration set of 219 lakes from western North America. The sediment mineralogy and fossil pigments at the base of the core indicated a moderately deep non-stratified lake dominated by clastic influx, probably in a basin fed by glacial meltwater. The early-Holocene history ( c. 11 000–8100 14C yr BP) was characterized by a relatively deep mesosaline lake with diatom-inferred salinities approximating 20 g L-1. The occurrence of both aragonite and dolomite, as well as elevated concentrations of chlorophyll and carotenoid pigments, support the interpretation of deepwater anoxia and possibly strong chemical stratification. High concentrations of the chemically stable b-carotene suggest that total algal abundance was particularly high during the early Holocene, when planktonic Cyclotella cf. choctawhatcheeana and Chaetoceros muelleri were the most common diatom taxa. Relatively fresh (2–15 g L-1) eutrophic conditions prevailed during the mid-Holocene period ( c. 8000– 2000 yr BP), with four periods of alternating fresh and saline conditions. The diatom-inferred salinity profile reveals significant fluctuations within these cycles, but overall they indicate humid climatic conditions compared to today. Algal abundance is inferred to have declined three-fold relative to the early Holocene, particularly in the case of eukaryotic algae (e.g., diatoms, cryptophytes, chlorophytes). The recent history of the lake (about 2000 years BP until the present day) was marked by important changes in ionic composition (e.g., occurrence of gypsum and Mg-carbonates) and hydrologic conditions. The lakewater composition during the last two millennia was characterized by hypersaline Mg-SO4 brines. The palaeolimnological evidence from most proxies indicates a trend towards drier conditions during the past 2000 years. The various indicators reveal a complex history of frequent and rapid shifts in palaeosalinity and lake palaeoproductivity during the Holocene, and the effects of the Younger Dryas and ‘Little Ice Age’ episodes may be recorded in the palaeoclimate proxy data. The palaeoclimatic interpretation emerging from this high-latitude lake corroborates existing broad trends based on palynological studies in this region but provides evidence for more dynamic climatic change during the mid- and late Holocene.

Quantitative in Situ Studies of Ionic Doping of Polypyrrole Employing Rotated Ring−Disk Electrode Voltammetry

Changes in ionic composition (i.e., doping) accompany changes in the redox level of conducting polymers such as polypyrrole. These processes are of paramount interest because they often control the polymer's charge capacity and, more importantly, its rates of oxidation and reduction (i.e., charge and discharge). The most commonly used approaches for studying polymer doping are either ex situ techniques (e.g., elemental analysis, X-ray photoelectron spectroscopy) or nonspecific techniques (e.g., electrochemical quartz crystal microgravimetry). We have developed a paradigm whereby rotated ring−disk electrode (RRDE) voltammetry can be used to quantitatively measure both anion and cation fluxes, in situ, across the conducting polymer−solution interface. This can be accomplished in real time under operational electrochemical conditions. Herein we report studies where we use RRDE voltammetry to investigate the doping behavior of electrochemically grown films of polypyrrole which are in contact with a range of d...

Hemolymph ion composition and volume changes in the supralittoral isopod Ligia pallasii Brandt, during molt.

We analyzed ion composition and volume of the hemolymph of Ligia pallasii in four different stages of the molt cycle using capillary electrophoresis and 3H-inulin. The main ions in the hemolymph were Na+, K+, Mg2+ , Ca2+, and Cl-. The Ca2+ concentration increased significantly during the molt by 47% from intermolt to intramolt and by 37% from intermolt to postmolt, probably due to resorption of Ca2+ from the cuticle and sternal CaCO3 deposits. The K+ concentration increased significantly by 20% during molt. The hemolymph volume normalized to the dry mass of the animals decreased by 36% from intermolt to late premolt. This was due to a reduction in the hemolymph volume and to an increase in dry mass of the animals during premolt. A sudden increase in the hemolymph volume occurring between late premolt and intramolt served to expand the cuticle. Since the Na+, K+, Mg2+, and Cl- concentrations did not change significantly from late premolt to intramolt, the increase in hemolymph volume suggests an uptake of seawater rather than freshwater.

Stability of major ions and sampling variability in daily bulk precipitation samples

Daily (24-h) precipitation samples were collected in four parallel bulk samplers in order to examine differences between parallel samples and the maximum acceptable time delay between sampling and analysis. After an immediate analysis, the samples were stored at +4°C over a seven-week time period to regularly examine the changes in ionic composition. The experiment was carried out in Helsinki, Finland, over the period from June 1997 to June 1998, with six rain events collected. Electrical conductivity, pH and the concentrations of the major ions Na +, NH 4 +, K +, Mg 2+, Ca 2+, Cl −, NO 3 − and SO 4 2− were studied. No significant differences between the parallel samplers were observed showing that dry deposition does not usually result in increased variability for 24-h bulk sampling due to the short dry period exposed. Sodium, potassium, magnesium, calcium, chloride, nitrate and sulphate concentrations remained constant for at least seven weeks. The electrical conductivity decreased by up to 30% and the pH increased by up to 0.3 pH unit, in thunderstorm sample even 1 pH unit, after six days. The ammonium concentration had a slight decreasing trend in all rain events and in some events the concentration decreased by upto 25% during the seven weeks storage. To achieve as precise results as possible for pH, electrical conductivity and ammonium the recommended maximum time delay between sampling and analysis is one week.

Insights into ototoxicity. Analogies to nephrotoxicity.

The most common ototoxic compounds in clinical practice are aminoglycoside antibiotics, cisplatin, and loop diuretics (ethacrynic acid and furosemide). These agents also have substantial renal effects in the form of nephrotoxicity or diuresis. The understanding of these renal effects may provide insight into ototoxic mechanisms. For aminoglycosides, the renal proximal tubule cell is susceptible due to high concentration achieved and slow clearance with direct effects on phosphoinositide binding and mitochondrial bioenergetics. Pathogenesis appears to involve iron-induced free-radical formation, since iron chelators prevent nephrotoxicity. Analogous effects of aminoglycosides on the inner and outer hair cells have been observed. Cisplatin is also highly concentrated in the proximal tubule cell. Less is known about the direct toxic effects of this agent on renal cells. Insights into mechanisms or renal tubule cells could be directly relevant to the inner ear. The loop diuretics are direct inhibitors of the Na(+)-K(+)-2Cl- cotransport system, which also exists in the marginal and dark cells of the stria vascularis, which are responsible for endolymph secretion. The ototoxicity of these agents may be indirect, due to changes in ionic composition and fluid volume within the endolymph.

Salt and Drought Stress Differentially Affect the Accumulation of Extracellular Proteins in Barley

Abstract Barley (Hordeum vulgare) was grown for eight days in the presence of a range of salt concentrations or subjected to repeated cycles of wilting and rehydration. Changes in apoplastic protein content, protein pattern, enzymic activities and ion composition were in­ vestigated under salinity and drought. The protein content of intercellular washing fluid (IWF) increased 2.5-to 3.0-fold when the NaCl concentration in the growth medium was increased from 0 to 100 mᴍ. The elevated protein content was the result of a general increase in most polypeptides and a pronounced increase in the abundance of specific polypeptides of apparent molecular masses of 15, 21, 22, 26, 36, 40 and 62 kDa. Conversely, the IWF protein content decreased during wilting similar as after application of colchicin, cytochalasin B or cycloheximide suggesting that inihibition of protein synthesis or vesicle transport may be the cause for the decrease in apoplastic protein content and enzyme activities in dehydrating plant tissue. The changes in apoplastic protein content were accompanied by stress-specific alterations in activities of apoplastic enzymes. The greater apoplastic protein content was the consequence of stimulated protein synthesis in the presence of NaCl, as evidenced by increased incorporation of [35S]-methionine into IWF protein. The results demonstrate that the leaf apoplast is a compartment which sensitively and differentially responds to drought and salinity with consequences for plant growth.

Renal response of euryhaline toad (Bufo viridis) to acute immersion in tap water, NaCl, or urea solutions.

Green toads (Bufo viridis) were acclimated to either tap water, 230 mOsmol NaCl kg-1 H2O (saline), 500 mOsmol NaCl kg-1 H2O (high saline), or 500 mmol L-1 urea. Renal functions for each acclimation group were studied on conscious animals that had one ureter chronically catheterized. Reciprocal immersion of tap-water- and saline-acclimated toads in the opposite solution did not stress the animals osmotically, and plasma osmolality increased or decreased by no more than 15%. However, urine osmolality and ionic composition changed immediately and profoundly on exposure to the other solution. Exposure of tap-water-acclimated toads to saline decreased urine flow by 30%, whereas the reciprocal immersion led to an increase of 30%. Immersion of tap-water-acclimated toads in high saline led to immediate cessation of urine flow, whereas immersion of 500 NaCl- or urea-acclimated toads in tap water led to a large increase in urine flow, with an overshoot that lasted 10 h (as a result of either salt or urea diuresis). Urine flow then stabilized at a level 5-6 times higher than the value attained at high-salt environment. On immersion of 500 urea-acclimated toads in 500 NaCl, urine flow doubled, accompanied by a change in ion composition, without change in the osmolality. In all experimental conditions, plasma potassium concentration was maintained within a narrow range. The results show that the toad's kidneys contributed efficiently both to osmo- and ionoregulation in a wide range of ambient solutions.

Structure and function of the silk production pathway in the Spider Nephila edulis

Our observations on the major ampullate gland of the spider Nephila edulis indicate that the exceptionally tough and strong core and coat composite structure of the dragline thread is formed by the co-drawing of two feedstocks through a single die. The cuticle that lines the gland’s duct has the structure of an advanced hollow fibre dialysis membrane and is thought to facilitate a rapid removal of water and change in ionic composition involved in the spinning process. A structure previously termed the ‘valve’ is thought to advance the broken thread and act as a pump to restart spinning after the accidental internal rupture of a thread. Together, these observations indicate that the spider silk production pathway is highly optimised for the production of silk threads and shows considerable biomimetic potential.

Influence of pH on Protein Interactions and Microstructure of Process Cheese

During the manufacture of process cheese, biochemical characteristics (casein solubilization, peptization coefficient, and water-holding capacity) were investigated using a combination of microscopic and rheological techniques in order to understand the influence of pH. The contribution of ionic interactions to the stabilization of this structure was also studied.Relationships were observed between pH variation and the characteristics of process cheese that demonstrated the importance of pH control during the manufacturing process. Optimal pH conditions during manufacture ranged from 5.7 to 6.0. Small changes in ionic composition and strength modified the protein interactions substantially and had important repercussions on the final structure and quality of the protein gel that was established during processing of cheese. In addition to ionic interactions, hydrogen and hydrophobic interactions appeared to be important in the structural stabilization of process cheese.

Nightside ion frictional heating: atomic and molecular ion temperature anisotropy and ion composition changes

An ion frictional heating event was observed by the EISCAT facility at 22:00 UT on 5th September (1989). The Sheffield University plasmasphere and ionosphere model has been used to investigate this event. A closed subauroral tube of plasma is considered in the model which has been developed to include temperature anisotropy in the NO+ as well as in the O+ ion populations. During the event the O+ temperature distribution becomes more anisotropic than the NO+. This means that in the F region the temperature of the NO+ ions parallel to the magnetic field is substantially greater than the temperature of the O+ ions parallel to the magnetic field. The model predicts that the ion composition in the F region becomes more molecular during the event. At an altitude of 300 km the composition changes from almost 100% O+ ions to 70% NO+ ions. To account for the change in ion composition which is not considered in the standard EISCAT analysis the EISCAT data were reanalysed using the ion composition predicted by the model. To compare with the measured ion temperature an average ion temperature was calculated from the model O+ and NO+ distributions. An additional heat source was introduced to enhance the model electron temperatures. There was then reasonable agreement between the modelled and measured parameters. Similar observational and model results were obtained for the ion frictional heating event observed at 21:00 UT on 9th May (1982).

Ultramicroelectrodes for membrane research

This article describes the construction, testing, calibration and application of ion-selective double-barrelled microelectrodes based on neutral carrier or ion-exchanger liquid membranes. At present the use of ion-selective microelectrodes is the only method available for the direct and continuous measurement of ion activities in the intra- and extracellular spaces, on membrane surfaces, and even in subcellular organelles of a variety of intact cells. Intracellular ion activities in identified neurones of the central nervous system of the leech ( Hirudo medicinalis L.) have been measured with K +-, Na +-, H +-, Mg 2+- and Ca 2+-selective double-barrelled microelectrodes under various experimental conditions, such as changes in ion composition of the external medium, application of neurotransmitters and exposure to drugs. This approach has provided significant information about electrochemical potentials of ions, properties of receptor-coupled ion channels, and membrane transport related to ion activities in this nervous system.

Inhibition of angiotensin-converting enzyme modulates structural and functional adaptation to loop diuretic-induced diuresis

The roles of elevated cell sodium concentrations and the angiotensin-aldosterone system (AAS) in the structural and functional adaptation of the distal tubule and collecting duct system to a chronic increase of sodium delivery were examined using electron microprobe and quantitative morphologic/stereologic analyses. Studies were performed on rats given the loop diuretic torasemide acutely (20 min) or chronically (12 days), either alone or in combination with the angiotensin-converting enzyme (ACE) inhibitor, enalapril. In the sodium-absorbing cells of the distal tubule and cortical collecting duct-that is, in distal convoluted tubule (DCT), connecting tubule (CNT) and principal cells-an acute increase in sodium delivery caused a significant rise in intracellular sodium concentration and rubidium uptake, the latter an index of in vivo Na,K(Rb)-ATPase activity. The elevated cell sodium concentrations returned to, or close to, control values during chronic torasemide treatment. Intracellular rubidium concentrations, measured after a 30-second rubidium exposure, were not different from controls in DCT and CNT cells but were still higher in principal cells. Since, however, the distribution space for rubidium was significantly increased in chronic torasemide animals, rubidium uptake, and hence Na,K-ATPase activity, must have increased in proportion to cell volume in DCT and CNT cells, but more than proportionately in principal cells. When ACE was inhibited during chronic torasemide, the epithelial volume of DCT and cortical collecting duct (CCD) was increased mainly by lengthening and not, as was the case in rats given torasemide alone, by thickening of the tubule wall. Adaptation of the proximal tubule exclusively by lengthening was not affected by inhibition of the ACE. These data indicate that changes in cell ion composition may participate in initiating cell processes leading to adaptation of distal nephron segments to chronically increased salt delivery. Inhibition of the ACE reverses the torasemide-induced increase in apparent Na pump density in principal cells and seems to shift the relationship between hypertrophy and hyperplasia noted in DCT and CCD after chronic torasemide in favor of hyperplasia.

Plasma characteristics of the boundary layer in the Martian magnetosphere

Plasma and magnetic field data from circular orbits of the Phobos 2 spacecraft near Mars are examined to provide a description of the plasma properties of inner regions of the Mars magnetosheath and the boundary layer/plasma mantle. The data are analyzed in the VB coordinate system, which is reasonable for draping magnetospheres of nonmagnetized planets and comets. It is shown that a boundary almost impermeable for protons is formed. The ion composition changes at this boundary, and a transition layer dominated by planetary ions is observed. The characteristics of the magnetosheath plasma is drastically changed near this ion composition boundary. A strong drop of the proton bulk velocity is accompanied by an increase of the proton temperature and intense fluxes of planetary ions. In dependence of the solar wind dynamic pressure and other factors, radius of the “magnetospheric cavity”, virtually void of solar wind plasma varies from 4500 to 9500 km. During time intervals of very high solar wind dynamic pressure, the cavity, divided up in lobe cells, is almost degenerated. The comparison of positions of different magnetospheric boundaries identified earlier from single‐instrument measurements shows their collocation.