Various Concentrations Of KCl Research Articles

Sodium Replacement with KCl and MSG: Attitudes, Perception and Acceptance in Reduced Salt Soups.

Sodium intake is linked to multiple negative health outcomes, particularly hypertension, the leading cause of premature death globally. Sodium intake levels in human populations are high, due in part to our desire for palatable salty-tasting foods. Two leading salt replacement strategies are the use of potassium chloride (KCl) and monosodium glutamate (MSG), the latter of which still contains some sodium, but both of which can replace some salty taste in foods while reducing net sodium levels. In this report, we employed a trained descriptive sensory panel to optimize saltiness in sodium-reduced aqueous samples using various concentrations of KCl and MSG. Following this, we assessed consumer attitudes to sodium-reduction strategies in a model food, canned soup, known to typically be high in sodium. Finally, in a large consumer test, we verified that these optimized levels of KCl and MSG did not lead to a drop in liking for the reduced-sodium soups with saltiness subsidized in this manner. Our results showed that sodium can be readily reduced in soups by 18% while actually scoring higher in liking, and in some cases being perceived as even more salty tasting, but that consumers are more open to sodium reduction in this manner when sodium replacements are not specifically highlighted, and when percentage sodium reduction is stated over absolute levels.

Development of a new simple mitochondria-targeted fluorescent K+ sensor and the application in high-throughput monitoring K+ fluxes

A new simple mitochondria-targeted fluorescent potassium ion (K+) sensor (NK1) was synthesized and investigated. The synthetic route of this sensor was much more concise than the previously reported mitochondrial-targeting KS6, enabling the potential broad applications of this sensor NK1. NK1 displays good responses to K+ with broad detection range from 10 to 500 mM, short response time (0.2 s), high sensitivity with 160 folds’ fluorescence enhancement at 1000 mM K+, a large dissociation constant (Kd about 200 mM), and minimum responses to physiological pH (5.0–9.0) as well as other biologically relevant metal ions. K+ fluxes (efflux and influx) in the mitochondria of living cells were observed upon manipulation with ionophores (nigericin or ionomycin) and various concentrations of KCl both under confocal microscope and especially microplate reader for first time high-throughput in-situ monitoring of mitochondrial K+ fluxes. The development of easily synthesized NK1 with excellent performance will be greatly beneficial for ion channel relative drug screening and the investigation of mitochondrial potassium channels as well as mitochondrial metabolism.

Thermal stability of myosin and protective effect of F-actin on myosin affect the thermal inactivation of calcium-ATPase in unstable kuruma prawn myofibrils

The thermal stability of myosin and the protective effect of F-actin on myosin in kuruma prawn myofibrils were investigated from the thermal inactivation rates at 25 °C of Ca-ATPase in myosin and myofibrils at various concentrations of KCl. The thermal inactivation rate constant (kD) of myofibrillar Ca-ATPase increased with increasing KCl concentration; however, the thermal inactivation followed a biphasic first-order reaction regardless of the KCl concentration: a relatively fast inactivation rate in the earlier phase (kDe) followed by a slower inactivation rate in the later phase (kDl) of the heat treatment. The thermal inactivation of myosin at various concentrations of KCl or sorbitol also followed a biphasic first-order reaction, and the differences between the kDe and kDl of myosin were always about twofold. kDe and kDl of myosin at 0.1 M KCl were decreased to 1/6 and 1/13, respectively, by the binding action of F-actin. These results suggest that the thermal stability of myosin and the protective effect of F-actin affect the stability and thermal inactivation of kuruma prawn myofibrils at physiological ionic strength.

ZxSKOR is important for salinity and drought tolerance of Zygophyllum xanthoxylum by maintaining K+ homeostasis

As an important nutrient element, K+ plays a crucial role in plant stress resistance. It was reported that the stelar K+ outward rectifying channel (SKOR) is involved in loading K+ into xylem for its transport from roots to shoots. Zygophyllum xanthoxylum, a succulent woody xerophyte, could maintain stable K+ concentration in leaves to adapt to salt and arid environments. Here we characterized ZxSKOR from Z. xanthoxylum, ZxSKOR expression patterns and Na+ and K+ accumulation in Z. xanthoxylum treated with various concentrations of KCl and NaCl and −0.5 MPa osmotic stress were investigated in order to assess the contribution of ZxSKOR to K+ homeostasis. The results showed that ZxSKOR was predominantly expressed in roots and stems rather than in leaves. Its expression levels in roots and stems increased significantly accompanied by an increase in K+ concentration in leaves when plants were exposed to 5–10 mM KCl. Moreover, a positive correlation was identified not only between ZxSKOR expression in roots and K+ accumulation in shoots, but also between ZxSKOR expression in stems and K+ accumulation in leaves. Transcription levels of ZxSKOR in roots and stems under high salinity (100–150 mM NaCl) and osmotic stress (−0.5 MPa) were 2.0–2.8 times those in plants grown in the absence of NaCl or osmotic stress. Concomitantly, the expression level of ZxSKOR in roots under osmotic stress plus salt (−0.5 MPa +50 mM NaCl) was significantly higher than that under osmotic stress (−0.5 MPa) alone during 12–48 h of treatment. We propose that ZxSKOR in roots and stems is well-coordinated to mediate long-distance K+ transport and perhaps plays an important role in K+ accumulation and homeostasis in Z. xanthoxylum under salt as well as drought stress.

Effect of various Na/K ratios in low-salinity well water on growth performance and physiological response of Pacific white shrimp Litopenaeus vannamei

To investigate the influence of sodium to potassium (Na/K) ratios on the growth performance and physiological response of the Pacific white shrimp (Litopenaeus vananmei), various concentrations of KCl were added to low-salinity well water (salinity 4) in an 8-week culture trial. Six treatments with Na/K ratios of 60:1, 42:1, 33:1, 23:1, 17:1, and 14:1 were replicated in triplicate. The highest weight-gain rate (3 506±48)% and survival rate (89.38±0.88)% was observed in well water with Na/K ratios of 23:1 and 42:1, respectively, while the feed conversion ratio (1.02±0.01), oxygen consumption, and ammonia-N excretion rate was the lowest in the medium with a Na/K ratio of 23:1. Gill Na+-K+-ATPase activity, as an indicator of osmoregulation, peaked in the treatment where the Na/K ratio was 17:1. The total hemocyte count, respiratory burst, and immune-related enzyme activities (ALP, LSZ, PO, and SOD) of L. vananmei were affected significantly by Na/K ratios (P<0.05). After challenged with Vibrio harveyi, the cumulative mortality of shrimp reared in a Na/K ratio of 23:1 (30±14.14)% was significantly lower than the control (75±7.07)%. In conclusion, the addition of K+ to low-salinity well water in L. vannamei cultures is feasible. Na/K ratios ranging from 23:1 to 33:1 might improve survival and growth. Immunity and disease resistance are also closely related to the Na/K ratio of the low-salinity well water. The findings may contribute to the development of more efficient K + remediation strategies for L. vananmei culture in low-salinity well water.

Optimization of Activated Carbon Sulfurization to Reach Adsorbent with the Highest Capacity for Mercury Adsorption

This work deals with the use of elemental sulfur immobilized on the activated carbon surface, as an active phase to enhance the sorbent's mercury adsorption capacity. The sulfurization procedure was optimized, and the influence of two factors (temperature and initial ratio of sulfur to carbon), on the final properties and mercury adsorption capacities of the adsorbents was investigated. The sulfurized adsorbents were characterized using CHNS/O elemental analysis, surface area and porosimetry, FT-IR spectroscopy, SEM-EDS, and pHpzc measurement. A series of batch studies were also conducted to delineate the effect of contact time, initial pH, solution temperature, and initial mercury concentration on the adsorption capacity of the adsorbents. Furthermore, attempts were made to desorb mercury from the metal loaded adsorbents using various concentrations of KCl, KBr and KI solutions.

High-efficiency particulate air filter test stand and aerosol generator for particle loading studies

This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30 x 30 x 29 cm(3) nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5 to 12 standard m(3)/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150 degrees C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7 standard m(3)/min, high mass concentrations (approximately 25 mg/m(3)) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160 nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions.

Potassium as an Intrinsic Uncoupler of the Plasma Membrane H+-ATPase

The plant plasma membrane proton pump (H(+)-ATPase) is stimulated by potassium, but it has remained unclear whether potassium is actually transported by the pump or whether it serves other roles. We now show that K(+) is bound to the proton pump at a site involving Asp(617) in the cytoplasmic phosphorylation domain, from where it is unlikely to be transported. Binding of K(+) to this site can induce dephosphorylation of the phosphorylated E(1)P reaction cycle intermediate by a mechanism involving Glu(184) in the conserved TGES motif of the pump actuator domain. Our data identify K(+) as an intrinsic uncoupler of the proton pump and suggest a mechanism for control of the H(+)/ATP coupling ratio. K(+)-induced dephosphorylation of E(1)P may serve regulatory purposes and play a role in negative regulation of the transmembrane electrochemical gradient under cellular conditions where E(1)P is accumulating.

Dissociation/association properties of a dodecameric cyclomaltodextrinase

As an effort to elucidate the quaternary structure of cyclomaltodextrinase I-5 (CDase I-5) as a function of pH and salt concentration, the dissociation/association processes of the enzyme were investigated under various pH and salt conditions. Previous crystallographic analysis of CDase I-5 indicated that it existed exclusively as a dodecamer at pH 7.0, forming an assembly of six 3D domain-swapped dimeric subunits. In the present study, analytical ultracentrifugation analysis suggested that CDase I-5 was present as a dimer in the pH range of 5.0-6.0, while the dodecameric form was predominant at pH values above 6.5. No dissociation of the dodecamer was observed at pH 7.0 and the above. Gel filtration chromatography showed that CDase I-5 dissociated into dimers at a rate of 8.58 x 10(-2) h(-1) at pH 6.0. A mutant enzyme with three histidine residues (H49, H89, and H539) substituted with valines dissociated into dimers faster than the wild-type enzyme at both pH 6.0 and 7.0. The tertiary structure indicated that the effect of pH on dissociation of the oligomer was mainly due to the protonation of H539. Unlike the pH-dependent process, the dissociation of wild-type CDase I-5 proceeded very fast at pH 7.0 in the presence of 0.2-1.0 M of KCl. Stopped-flow spectrophotometric analysis at various concentrations of KCl showed that the rate constants of dissociation (kd) from dodecamers into dimers were 5.96 s(-1) and 7.99 s(-1) in the presence of 0.2 M and 1.0 M of KCl, respectively.

Interaction between the Catalytic Site and the A-M3 Linker Stabilizes E2/E2P Conformational States of Na+,K+-ATPase

The consequences of mutations Ile(265) --> Ala, Thr(267) --> Ala, Gly(271) --> Ala, and Gly(274) --> Ala for the partial reaction steps of the Na(+),K(+)-ATPase transport cycle were analyzed. The mutated residues are part of the long loop ("A-M3 linker") connecting the cytoplasmic A-domain with transmembrane segment M3. It was found that mutation Ile(265) --> Ala displaces the E(1)-E(2) and E(1)P-E(2)P equilibria in favor of E(1)/E(1)P, whereas mutations Thr(267) --> Ala, Gly(271) --> Ala, and Gly(274) --> Ala displace these conformational equilibria in favor of E(2)/E(2)P. The mutations affect both the rearrangement of the cytoplasmic domains (seen by changes in phosphoenzyme properties and apparent ATP/vanadate affinities) and the membrane sector (indicated by change in K(+)/Rb(+) deocclusion rate). Destabilization of E(2)/E(2)P in Ile(265) --> Ala, as well as a direct effect on the intrinsic affinity of the E(2) form for vanadate, may be explained on the basis of the E(2) crystal structures of the Ca(2+)-ATPase, showing interaction of the equivalent isoleucine with conserved residues near the catalytic region of the P-domain. The rate of phosphorylation from ATP was unaffected in Ile(265) --> Ala, indicating a lack of interference with the catalytic function in E(1)/E(1)P. The effects of mutations Thr(267) --> Ala, Gly(271) --> Ala, and Gly(274) --> Ala provide the first evidence in the literature of a relative stabilization of E(2)/E(2)P resulting from perturbation of the A-M3 linker region. These mutations may lead to increased strain of the A-M3 linker in E(1)/E(1)P, increased stability of the A3 helix of the A-M3 linker in E(2)/E(2)P, and/or a change of the orientation of the A3 helix, facilitating its interaction with the P-domain.

Thermodynamic characterization of the interaction of mutant UvrB protein with damaged DNA.

During the DNA damage recognition of nucleotide excision repair in Escherichia coli the interaction of UvrB protein with damaged DNA ensures the recognition of differences in the intrinsic chemical structures of a variety of adduct molecules in DNA double helix. Our earlier study indicated that a single tyrosine-to-tryptophan mutation at residue 95 converted the UvrB to a protein [UvrB(Y95W)] that is able to bind to a structure-specific bubble DNA substrate, even in the absence of UvrA. Fluorescence spectroscopy therefore was adopted to investigate the biochemical properties and thermodynamics of DNA damage recognition by the mutant protein. We examined the binding of the UvrB(Y95W) mutant protein to a structure-specific 30 bp DNA substrate containing a single fluorescein which serves as both an adduct and a fluorophore. Binding of the protein to the substrate results in a significant reduction in fluorescence. By monitoring the fluorescence changes, binding isotherms were generated from a series of titration experiments at various physiological temperatures, and dissociation constants were determined. Analysis of our data indicate that interaction of UvrB(Y95W) protein with the adduct incurred a large negative change in heat capacity DeltaC(p)(o)(obs) (-1.1 kcal mol(-1) K(-1)), while the DeltaG(o)(obs) was relatively unchanged with temperature. Further study of the binding at various concentrations of KCl showed that on average only about 1.5 ion pairs were involved in formation of the UvrB-DNA complex. Together, these results suggested that hydrophobic interactions are the main driving forces for the recognition of DNA damage by UvrB protein.

Fabrication of Mono- and Multi-Layers of Submicron-Sized Spheres by a Dip-Coating Technique and Their Transmittance Property

This paper describes fabrication of well-ordered mono- and multi-layers of submicron-sized silica or polystyrene (PSt) spheres. The mono-layers of spheres were fabricated on glass plates by a dip-coating technique at various concentrations of KCl, HCl and KOH in colloidal suspension. The mono-layer of spheres in a close-packed hexagonal structure showed an extinction peak in the visible wavelength attributed to a secondary Bragg diffraction. Full width at half maximum (FWHM) of the extinction peak was the lowest at low ionic strength and at neutral pH. Different types of multi-layers of spheres were fabricated by repeating the dip-coating processes. Silica spheres with a size of 589 nm could be mono-layered in the close-packed hexagonal structure on the mono-layer of the 404-nm-PSt spheres. PSt spheres with a size of 404 nm could be layered on the mono-layer of 500-nm-PSt spheres in such a way that the 404-nm-PSt spheres occupied void spaces among three 500-nm-PSt spheres. Silica spheres with a size of 233 nm could be assembled in a two-dimensional network structure on mono-layered 589-nm-silica spheres.

Multiple mechanisms of transmitter release evoked by ‘pathologically’ elevated extracellular [K+]: involvement of transporter reversal and mitochondrial calcium

The release of [3H]GABA evoked by depolarization with various concentrations of KCl was studied using superfused rat cerebrocortex synaptosomes. Elevating [K+] produced release of [3H]GABA over basal which was increasingly less dependent on external Ca2+ but more sensitive to the GABA transporter blocker SKF 100330 A. Accordingly, the sensitivity to clostridial toxins of the depolarization-evoked amino acid release was inversely correlated to the concentration of KCl used. However, at 50 mM K+, one-third of the stimulated release remained which was external Ca2+-independent but insensitive to SKF 100330 A. This release was prevented by BAPTA, thapsigargin or dantrolene; it also was inhibited by blocking in mitochondria the ATP production with oligomycin, the H+-dependent Ca2+ uniporter with RU 360, the Na+/Ca2+ exchanger with CGP 37157 or by lowering extraterminal [Na+]. In fluorescence experiments with fura-2/AM, 50 mM K+ (in Ca2+ free medium) caused elevation of cytosolic [Ca2+] that was sensitive to thapsigargin or CGP 37157; these compounds produced partially additive effects. When exocytosis was monitored with the fluorescent dye acridine orange, the fluorescence elicited by 50 mM K+ was sensitive to thapsigargin or CGP 37157, which produced additive effects, and to low-Na+ media. To conclude, extracellular K+ concentrations occurring in the CNS in certain pathological conditions provoke GABA release by mechanisms different from classical exocytosis. These include carrier-mediated release and internal Ca2+-dependent exocytosis; in the latter, mitochondrial Ca2+ seems to play a primary role.

Preparation of Phosphopeptides Derived from αs-Casein and β-Casein Using Immobilized Glutamic Acid-Specific Endopeptidase and Characterization of Their Calcium Binding

Phosphopeptides that were derived from αs-CN or β-CN were prepared with immobilized glutamic acid-specific endopeptidase, and their Ca2+ binding was characterized. αs-Casein or β-CN was hydrolyzed in a fluidized bed bioreactor containing 2ml of immobilized glutamic acid-specific endopeptidase by recirculating 20ml of αs-CN or β-CN solution (10 mg/ml in 50mM Tris·HCl and 0.02% NaN3, pH 8.0) for 3h at 20°C. The molecular masses of casein peptides were monitored by SDS-PAGE. Each hydrolysate was applied to an anion-exchange column using stepwise elution with various concentrations of KCl to separate peptides. The casein phosphopeptide content of the elution profile was monitored by analysis of protein and P concentrations. Calcium binding in phosphopeptide-enriched fractions was determined by CaCl2 titration and measurement of free Ca2+ with a Ca-selective electrode. The electrophoresis patterns showed four major peptides having molecular masses of 10.8, 9.0, 6.6, and 3.6 kDa in the αs-CN hydrolysate and 9.3, 8.2, and 6.2 kDa in the β-CN hydrolysate. The highest concentrations of P were detected in the fractions that eluted with 0.4 and 0.5M KCl for the αs-CN hydrolysate and with 0.4 M KCl for the β-CN hydrolysate. The calcium-binding ability was found only in the fraction that was eluted with 0.4 M KCl; the maximum Ca2+ binding and the apparent binding constant were 0.24 mmol/mg of protein and 75 M–1, and 0.14 mmol/mg of protein and 148 M–1, respectively. αs-Casein phosphopeptides had different patterns for Ca2+ binding than did β-CN phosphopeptides as the total Ca concentration was increased. Calcium binding to these casein phosphopeptides differed from that previously characterized for the tryptic peptides.

Protective roles of bacterioruberin and intracellular KCl in the resistance of Halobacterium salinarium against DNA-damaging agents.

Halobacterium salinarium, a member of the extremely halophilic archaebacteria, contains a C50-carotenoid namely bacterioruberin. We have previously reported the high resistance of this organism against the lethal actions of DNA-damaging agents including ionizing radiation and ultraviolet light (UV). In this study, we have examined whether bacterioruberin and the highly concentrated salts in this bacterium play protective roles against the lethal actions of ionizing radiation, UV, hydrogen peroxide, and mitomycin-C (MMC). The colourless mutant of H. salinarium deficient in bacterioruberin was more sensitive than the red-pigmented wild-type to all tested DNA-damaging agents except MMC. Circular dichroism (CD) spectra of H. salinarium chromosomal DNA at various concentrations of KCl (0-3.5 M) were similar to that of B-DNA, indicating that no conformational changes occurred as a result of high salt concentrations. However, DNA strand-breaks induced by ionizing radiation were significantly reduced by the presence of either bacterioruberin or concentrated KCl, presumably due to scavenging of free radicals. These results suggest that bacterioruberin and intracellular KCl of H. salinarium protect this organism against the lethal effects of oxidative DNA-damaging agents.

The bundling of actin with polyethylene glycol 8000 in the presence and absence of gelsolin

Actin filament and bundle formation occur in the cytosol under conditions of very high total macromolecular concentration. In this study we have utilized the inert molecule polyethylene glycol 8000 (PEG) as a means of simulating crowded conditions in vitro. Column-purified Ca-actin was polymerized in the absence and presence of gelsolin (to regulate mean filament lengths between 50 and 5000 mers) and PEG (2-8%) using various concentrations of KCl and/or 2 mM divalent cations. Bundling was characterized by the scattered light intensity and mean diffusion coefficients obtained from dynamic light scattering, as well as by fluorescence and phase-contrast microscopy. The minimum concentration of KCl required for bundling decreases both with increasing concentration of PEG at a fixed mean filament length, and with decreasing filament length at a fixed concentration of PEG. In the absence of divalent cation, bundling is reversible on dilution, as determined by intensity levels, diffusion coefficients, and microscopy. However, with either 2 mM Mg2+ or Ca2+ added, bundling is irreversible under conditions of higher PEG concentrations or longer filaments, indicating that osmotic pressure effects cannot fully explain actin bundling with PEG. Weaker divalent cation-binding sites on actin as well as disulfide bonds appear to be involved in the irreversible bundling.

Profiles of conjugation induction by potassium ions in four different Ca2+ channel mutants of Paramecium caudatum.

Conjugation of Paramecium caudatum among cells of a single mating type can be induced parthenogenetically by exposing them to certain chemical solutions, a process called chemical induction of conjugation. The ionic conditions for chemical induction of conjugation are also the conditions that are required for the induction of the activation of voltage dependent Ca2+ channels in Paramecium. Four mutants controlled by independent gene loci with defects in Ca2+ channels, were subjected to an induction solution containing various concentrations of KCl and 0.01, 0.06 and 0.6 mmol/L CaCl2 . Conjugation was able to be induced chemically in all four mutants. However, some locus-dependent differences were observed in the profiles of induction. Mutants controlled by different alleles but with the same locus were similar in their profile of induction, even when they exhibited opposite phenotypes on the activation of Ca2+ channels. These results suggest that the function of Ca2+ channels is not directly involved in the mechanism of chemical induction of conjugation. The locus dependency observed reflects the different role of each gene controlling Ca2+ channel functions.

Equilibrium association constants for oligonucleotide-directed triple helix formation at single DNA sites: linkage to cation valence and concentration.

The linkage between the energetics of oligonucleotide-directed triple helix formation and the cationic solution environment has been investigated in mixed-valence salt solutions. Equilibrium constants for formation of the local pyrimidine.purine.pyrimidine structure afforded by binding of the oligonucleotide 5'-d(T*TTTTCTCTCTCTCT)-3' to a single site within a 339-bp plasmid fragment were measured using quantitative affinity cleavage titrations at pH 7.0 and 22 degrees C in the presence of various concentrations of KCl, MgCl2, and spermine tetrahydrochloride (SpmCl4). In a solution containing 10 mM NaCl, 140 mM KCl, 1.0 mM MgCl2, and 1.0 mM SpmCl4, the measured binding constant was 3.3 (+/- 1.4) x 10(5) M-1. The equilibrium constant previously reported for the same association reaction in 100 mM NaCl and 1 mM SpmCl4 at the same temperature and pH was 10-fold higher [Singleton, S. F., & Dervan, P. B. (1992) J. Am. Chem. Soc. 114, 6957-6965]. Further study demonstrated that varying the potassium ion concentration between 5.0 and 140 mM (in the presence of 10 mM NaCl, 1.0 mM MgCl2, and 1.0 mM SpmCl4) resulted in an overall 100-fold decrease in the binding affinity from the lowest to the highest concentration. In contrast, measured binding constants increased 500-fold as the spermine concentration was increased from 0.40 to 4.0 mM (in the presence of 10 mM NaCl, 140 mM KCl, and 1.0 mM MgCl2). There was a modest effect on the binding constant (a 3-fold decrease) upon varying the magnesium ion concentration from 0.10 to 10 mM (in the presence of 10 mM NaCl, 140 mM KCl, and 1.0 mM SpmCl4).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of nitrate (13NO3) influx and nitrogen (13N) translocation by tomato and melon varieties after short exposure to calcium and potassium chloride salts

Abstract The effect of KC1 or CaCl2 pretreatments on 13NO3 influx into melon or tomato roots was investigated. Plants, previously grown in 1/10 strength Johnson's solution, were exposed for 10 min to 1/10 strength Johnson's solution supplemented with various concentrations of KCl or CaCl2. These solutions were than replaced by identical solutions labeled with 13NO3. After 10 minutes, plants were washed, roots were separated from the tops, introduced into counting vials and radioactivities counted for 30 seconds and corrected for decay. The influx of 13NO3 to the roots of melon (Cucurbita pepo L.), cultivars Rochet and Eshcolit Amakim, and tomato (Lycopersicon esculentum L.), cultivars M‐82 and VF‐785 was depressed at moderate concentrations (10–60 mol/m3) of CaCl2. By contrast, KC1 did not inhibit 13NO3 influx. Tomato plants translocated about 30% of their total 13N label to the shoot at low salt concentration. This proportion was significantly reduced by increased concentrations of KCl or CaCl2 in the ex...

Effects of midaglizole, a new hypoglycaemic drug on the electrophysiological properties of guinea-pig papillary muscle

1. The electrophysiological effects of midaglizole, a new oral hypoglycaemic agent which is an alpha 2-adrenoceptor antagonist, were assessed in the reserpinized ventricular myocardium of the guinea-pig. 2. Midaglizole suppressed the maximal rate of rise (Vmax) and the amplitude of action potentials (APA) of the fast and the slow responses in a concentration-dependent manner without influencing the resting potentials. 3. Voltage-dependency of the Vmax block of the action potentials by midaglizole (10 microM) did not appear in solutions containing various concentrations of KCl. 4. It is concluded that midaglizole has inhibitory effects on the fast Na+ and slow Ca2+ currents of the membrane independent of the blockade of myocardial alpha-adrenoceptors, and that these effects may be significant in some clinical uses of the drug.