Potassium Chloride Medium Research Articles

Corrosion Characterization of Aluminium 2024 Metal Matrix Composites Reinforced with Fly Ash in Potassium Chloride Medium

Corrosion Characterization of Aluminium 2024 Metal Matrix Composites Reinforced with Fly Ash in Potassium Chloride Medium

Investigation into the voltammetric behaviour and detection of selenium(IV) at metal electrodes in diverse electrolyte media

The voltammetric behaviour of selenium(IV) was studied at platinum and gold electrodes in sulphuric acid, perchloric acid and potassium chloride media as a basis for its voltammetric detection. The best voltammetric behaviour was recorded at gold electrodes with perchloric acid as the supporting electrolyte. The concomitant presence of metals, such as copper or lead, and of model biomolecules, such as bovine serum albumin, in the solution resulted in a deterioration of the electrochemical response for selenium(IV). Quantitative detection of selenium(IV) by square wave anodic stripping voltammetry at both a millimetre-sized gold disc electrode and a microband electrode array revealed linear responses to selenium concentration in the ranges 5–15 μM and 0.1–10 μM, respectively, with 60 s preconcentration. The sensitivities were 6.4 μA μM −1 cm −2 and 100 μA μM −1 cm −2 at the disc and the microband array, respectively. The detection limit at the microband electrode array was 25 nM, illustrating the potentiality of such microelectrodes for the development of mercury-free analytical methods for the trace detection of selenium(IV).

Effect of selective inhibition of potassium channels on vasorelaxing response to cromakalim, nitroglycerin and nitric oxide of canine coronary arteries.

A comparative study was performed on the sensitivity of in-vitro vasorelaxation by nitroglycerin and cromakalim to block glibenclamide, a blocker of ATP-sensitive potassium channels, and iberiotoxin, a selective inhibitor of large-conductance calcium-activated potassium channels. In isolated canine coronary arteries preconstricted with 25 microM prostaglandin F2 alpha, nitroglycerin (0.005-1.8 microM) and cromakalim (0.15-9.6 microM) produced dose-dependent vasodilations. Glibenclamide (30 microM) had no significant effect on relaxation of the dose-response curve to nitroglycerin and almost completely abolished the relaxation by cromakalim, a known opener of ATP-sensitive potassium channels. Iberiotoxin (90 nM) decreased the maximal response to nitroglycerin and had no effect on the vasodilation induced by cromakalim. The effect of iberiotoxin on the vasorelaxing action of nitric oxide, the active metabolite of nitroglycerin, was also examined. In a low potassium chloride (14.4-20.4 mM) medium, as a contractile stimulus, iberiotoxin inhibited relaxations by exogenous nitric oxide (100-200 nM). Enhancement of potassium concentrations to 35.4-40.4 mM significantly decreased relaxation by nitric oxide and under these conditions the inhibitory action of iberiotoxin disappeared. The present study demonstrated that in canine coronary arteries, the functional role of two potassium channels can be separated by pharmacological means. Nitroglycerin-induced vasorelaxation may be mediated, at least in part, by its enzymatic breakdown product, nitric oxide that activates large-conductance calcium-activated potassium channels.

ORIGINAL RESEARCH—BASIC SCIENCE: Initial Characterization of Hydrogen Sulfide Effects in Female Sexual Function

ABSTRACT Introduction In our male animal models, hydrogen sulfide (H2S) displayed significant vasodilatory and smooth muscle relaxant effects suggestive of an endogenous physiological role in erectile process. Aim In this first exploratory study, we aimed to identify the existence and mechanism of H2S pathway in female sexual physiology. Methods Vaginal and clitoral cavernosal smooth muscle strips from New Zealand white rabbits (N = 12) were exposed to stable H2S donor, sodium hydrosulfide hydrate (NaHS.xH2O, 100 µM–1.6 mM), in isometric tension studies. The NaHS responses were repeated after incubations with (i) Nω-nitro-L-arginine (50 µM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µM) or cis-N-[2-phenylcyclopentyl]-azacyclotridec-1-en-2-amine (MDL 12,330A) (10 µM); and (ii) potassium chloride medium (high K+ 60 mM/low K+ 10 mM), tetraethylammonium (10 mM) or glibenclamide (100 µM). Relaxant effect of NaHS was also compared with those of nitroglycerine (0.18–78.2 µM) and sildenafil (0.084–25.3 µM). Additionally, samples (N = 16) were collected for estimations of plasma and tissue H2S and expression levels of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) proteins. Main Outcome Measures In vitro evidences for H2S formation and its physiopharmacological effects. Results NaHS produced significant concentration-dependent relaxation of vaginal and cavernosal smooth muscles with inhibitions by combination of ODQ and MDL 12,330A (26.4%), Nω-nitro-L-arginine (22.2%), high K+ (15.1%) or glibenclamide (10.1%). Based on molar potency, NaHS was 18.3 and 6.3 times weaker than nitroglycerine and sildenafil, respectively. Quantitative assays indicated that plasma H2S level was 16.5 ± 2.58 µM, and H2S was synthesized in the clitoral and vaginal smooth muscles (1.8 and 3.9 nmol/mg soluble protein compared with 26.5 nmol/mg in the liver: positive control). Similarly, western blotting identified the protein expression bands of CSE (44.5 kDa) and CBS (63 kDa) in these genital tissue samples. Conclusion These pilot studies clearly indicate the smooth muscle relaxant effect of H2S in female genital tract, mediating through cyclic adenosine 3′:5′-monophosphate, nitric oxide-cyclic guanosine monophosphate and K+ATP channels. Taken together with biochemical and molecular evidences for endogenous formation, H2S pathway could be a contributing factor in female sexual responses.

In Situ ESR and UV/Vis Spectroelectrochemical Study of Eosin Y Upon Reduction with and without Zn(II) Ions

The electroreduction of eosin Y on a platinum electrode in deaerated slightly acidic aqueous 0.1 mol L(-1) potassium chloride medium is followed in situ by electron spin resonance (ESR) spectroscopy and UV/Vis spectroscopy. The electrochemical formation of a semiquinone radical is proved by both the appearance of an absorbing band at 408 nm, and a strong ESR signal observed during a negative-going scan. The system is also studied in the presence of Zn(II) ions due to its importance for understanding the growth mechanism of nanostructured ZnO/Eosin Y hybrid films by electrodeposition; under such conditions the ESR and UV/Vis response of the semiquinone radical is not observed. Zinc (II) ions form a complex with the dye, which is reduced by a fast two-electron process.

A Novel Lipolytic Enzyme, YcsK (LipC), Located in the Spore Coat of Bacillus subtilis , Is Involved in Spore Germination

The predicted amino acid sequence of Bacillus subtilis ycsK exhibits similarity to the GDSL family of lipolytic enzymes. Northern blot analysis showed that ycsK mRNA was first detected from 4 h after the onset of sporulation and that transcription of ycsK was dependent on SigK and GerE. The fluorescence of the YcsK-green fluorescent protein fusion protein produced in sporulating cells was detectable in the mother cell but not in the forespore compartment under fluorescence microscopy, and the fusion protein was localized around the developing spores dependent on CotE, SafA, and SpoVID. Inactivation of the ycsK gene by insertion of an erythromycin resistance gene did not affect vegetative growth or spore resistance to heat, lysozyme, or chloroform. The germination of ycsK spores in a mixture of L-asparagine, D-glucose, D-fructose, and potassium chloride and LB medium was also the same as that of wild-type spores, but the mutant spores were defective in L-alanine-stimulated germination. In addition, zymogram analysis demonstrated that the YcsK protein heterologously expressed in Escherichia coli showed lipolytic activity. We therefore propose that ycsK should be renamed lipC. This is the first study of a bacterial spore germination-related lipase.

The effects of nicotine on dopamine and DOPAC output from rat striatal tissue

The effects of varying doses of nicotine infusion upon spontaneous (basal) and subsequent potassium chloride-stimulated dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) output from superfused corpus striatal tissue fragments of male rats were tested. Spontaneous dopamine and DOPAC outputs were increased in response to 1, 5 and 10, but not to 0.1 and 0 (control) μM concentrations of nicotine. Interestingly, the subsequent K +-stimulated (30 mM) dopamine output was completely abolished in preparations infused with the 5 and 10 μM nicotine, but not with the 1 or 0.1 μM nicotine. No overall significant differences in K +-stimulated DOPAC were obtained among the five doses. In experiment 2, the effects of an initial infusion of amphetamine (10 μM), potassium chloride (30 mM), nicotine (10 μM) or normal superfusion medium (control) were compared upon subsequent K +-evoked dopamine release. The amount of dopamine released in response to the second (subsequent) infusion of K + was significantly greater in the potassium chloride and control conditions versus the nicotine and amphetamine stimulated groups. No overall differences in DOPAC output were observed among the four conditions of experiment 2. These results demonstrate that nicotine can exert differential modulatory effects upon striatal dopaminergic activity as a function of the dose. The augmented levels of DOPAC output along with the abolition of the K +-stimulated dopamine release in response to the 5 and 10 μM nicotine doses suggest that these doses may simultaneously produce an activation of intraneuronal metabolism of dopamine to DOPAC along with an activation of release and inhibition of uptake to diminish stores available for subsequent responses to K + stimulation.

Polarographic Determination of In(III) and Cd(II) by pH Adjustment of a Potassium Chloride Medium

Abstract A polarographic determination of In(III) and Cd(II), the reduction potentials of which are very close to each other, was investigated by a pH adjustment of a potassium chloride medium. The reduction wave of In(III) decreased linearly with the pH. At pH 7.0, the reduction wave of In(III) completely disappeared, while that of Cd(II) remained unchanged. This fact enables us to determine In(III) and Cd (II) separately; In(III) can be determined from the merged-wave height of In(III) plus Cd(II) by subtracting that of Cd(II), which can be directly determined.

On the shape of human red blood cells interacting with flat artificial surfaces — the ‘glass effect’

The morphology of the human red blood cell (RBC) contained between two flat artificial surfaces has been investigated. Shape transformation from the discocytic into various crenated (echinocytic) states was not caused soley by glass (‘glass effect’). Various organic polymers, and mica, were effective, provided the distance (0.1 mm) between the two surfaces was carefully controlled. The discocytic state could only be preserved using moderately hydrophobic glass, extensive dimethylsilytion induced stomatocytes. With washed blood samples occured in a potassium chloride medium and in the presence of EDTA. Temperature-dependent transformation in the shape of human erythrocytes occured between two glass surfaces 0.1 mm apart, e.g, in a hemacytometer. With cells in blood diluted directly 200-times with isotonic saline crenation appeared at 32–36°C. A sphero-echinocytic state prevailed at 34°C and outside the temperature range of 32–36°C the RBCs retained the shape of a biconcave disk. Cells responding to the ‘glass effect’ even at temperatures below the transition region did not respond further at elevated temperatures. The ‘glass effect’ was found to be dependent on the RBC concentration (hematocrit). Raising this concentration reversibly decreased the degree of crenation. The amount of endogenous albumin present was estimated to be insufficient to cover the exposed glass surfaces with a protein monolayer. With washed cells over a wide concentration range, approximately the same total amount of albumin (serum) had to be present to avoid crenation, as long as observation was performed at a fixed low cell concentration. The effect of albumin was not abolished by γ-globulin or anti-human albumin IgG. The discocyte-stabilizing influence of albumin is discussed.

Simultaneous determination of In(III) and Cd(III) in the presence of polyethylene glycol monostearate by direct current polarography

In the presence of polyethylene glycol monostearate (PEGMS), the reduction potentials for In(III) and Cd(II) become well separated in 0.1 mol dm −3 potassium chloride medium. The relationships between the currents for the ions and their concentrations are linear in the presence of PEGMS, which makes the simultaneous determination of In(III) and Cd(II) possible.

Vasoconstrictor hormones depolarize renal glomerular mesangial cells by activating chloride channels

Mesangial cells are smooth muscle-like cells of the renal glomerulus which contract and produce prostaglandins in response to vasopressin and angiotensin. These responses serve to regulate the glomerular capillary filtering surface area. We have used the membrane potential-sensitive fluorescent dye bis-oxonol and the intracellular fluorescent calcium-sensitive probe Indo-1 to study the changes in membrane potential (Em) and intracellular free calcium concentration ([Ca2+]i) in cultured rat mesangial cells in response to vasoconstrictor hormones. Basal [Ca2+]i was 227 +/- 4 nM, and stimulation by maximal concentrations of either vasopressin or angiotensin resulted in a transient 4-6-fold rise. Resting membrane potential was 45.8 +/- 0.9 mV and vasoconstrictor hormones caused a depolarization of 14-18 mV. The following extracellular ion substitutions indicated that chloride efflux was the predominant ion flux responsible for depolarization: 1) depolarization persisted when sodium in the medium was substituted with N-methylglucamine; 2) substitution of medium sodium chloride with sodium gluconate, which enhances the gradient for chloride efflux, augmented vasoconstrictor-stimulated depolarization; 3) suspension of cells in potassium chloride medium resulted in depolarization, following which, stimulation by either vasopressin or angiotensin resulted in hyperpolarization; and 4) this hyperpolarization did not occur when potassium gluconate medium was used to depolarize the cells. The calcium ionophore ionomycin also resulted in membrane depolarization. However, prevention of the rise in [Ca2+]i by prior exposure to ionomycin in calcium-free medium or by loading mesangial cells with the intracellular calcium buffer BAPTA did not abrogate the depolarization response to vasoconstrictor hormones. This indicates that a rise in intracellular calcium is not necessary for depolarization. In contrast, prior depolarization of the cells using varying concentrations of KCl in the external medium, which dissipated the electrochemical gradient for chloride efflux, resulted in a corresponding prolongation of the transient calcium response to vasopressin and angiotensin. These findings indicate that angiotensin and vasopressin depolarize mesangial cells by activating chloride channels and that this activation can occur by both calcium-dependent and -independent mechanisms. In addition, activation of chloride channels with resulting depolarization may serve to modulate the calcium signal.

Effect of ouabain and bumetanide on the basal and the osmolality-affected prolactin secretion from human decidual cells in vitro

Human decidual explants were incubated in vitro in media containing 10 −5 mol/l ouabain or 10 −4 mol/l ouabain or 0.5 · 10 −4 mol/l bumetanide to change the intracellular ionic concentrations. In isosmotic incubations (osmolality 315 mmol/kg), no significant effect of either 10 −5 mol/l ouabain or 0.5 · 10 −4 mol/l bumetanide was found on the decidual prolactin secretion (D-PRL-s). 10 −4 mol/l ouabain significantly decreased both decidual prolactin production and D-PRL-s ( P < 0.05) and was therefore not used for the following cross-over experiments. Hyperosmotic media (387 mmol/kg) were produced by changing the concentration of either sodium chloride, potassium chloride, or mannitol. All increased D-PRL-s compared with the isosmotic media (315 mmol/kg). 10 −5 mol/l ouabain significantly diminished the increase otherwise elicited by the sodium chloride and the mannitol hyperosmotic media. However, in the hyperosmotic potassium chloride medium with 10 −5 mol/l ouabain, the D-PRL-s remained increased. The hyperosmotic medium (252 mmol/kg) reduced D-PRL-s compared with the isosmotic media (315 mmol/kg) and no significant effect of ouabain was found. Bumetanide did not change the D-PRL-s into any of the hypo- or hyperosmotic media compared with the secretion at 315 mmol/kg. Based on experience from other cell types, the results further indicate that the intracellular ionic concentrations could be of importance to the secretion of decidual prolactin in vitro.

Analysis of variance in determinations of equivalence volume and of the ionic product of water in potentiometric titrations

Homogeneous sets of data from strong acid—strong base potentiometric titrations in aqueous solution at various constant ionic strengths have been analysed by statistical criteria. The aim is to see whether the error distribution matches that for the equilibrium constants determined by competitive potentiometric methods using the glass electrode. The titration curve can be defined when the estimated equivalence volume VEM, with standard deviation (s.d.) σ (VEM), the standard potential E 0, with s.d. σ( E 0), and the operational ionic product of water K * w (or E * w in mV), with s.d. σ( K * w) [or σ( E * w)] are known. A special computer program, BEATRIX, has been written which optimizes the values of VEM, E 0 and K * w by linearization of the titration curve as a Gran plot. Analysis of variance applied to a set of 11 titrations in 1.0 M sodium chloride medium at 298 K has demonstrated that the values of VEM belong to a normal population of points corresponding to individual potential/volume data-pairs ( E i ; v i ) of any titration, whereas the values of p K * w (or of E * w) belong to a normal population with members corresponding to individual titrations, which is also the case for the equilibrium constants. The intertitration variation is attributable to the electrochemical component of the system and appears as signal noise distributed over the titrations. The correction for junction-potentials, introduced in a further stage of the program by optimization in a Nernst equation, increases the noise, i.e., σ(p K * w). This correction should therefore be avoided whenever it causes an increase of σ(p K * w). The influence of the ionic medium has been examined by processing data from acid—base titrations in 0.1 M potassium chloride and 0.5 M potassium nitrate media. The titrations in potassium chloride medium showed the same behaviour as those in sodium chloride medium, but with an s.d. for p K * w that was smaller and close to the expected instrumental noise, whereas the titrations in nitrate medium had a high noise level and even the determination of VEM was less certain. Procedures are also proposed for obtaining reference sets of data and checking the conformity of the solutions and apparatus to the chosen reference.

Constantes d'acidite de l'acide pyrophosphorique et constantes de stabilite des complexes avec le potassium et le sodium: en|The acidity constants of pyrophosphoric acid and the stability constants of complexes with potassium and sodium ions

( The acidity constants of pyrophosphoric acid and the stability constants of complexes with potassium and sodium ions) The effect of potassium and sodium ions on the acidity constants of pyrophosphoric acid is studied by potentiometry at 25°C and at an ionic strength of 0.5 mol l -1. Comparison of the results obtained in potassium chloride or sodium chloride medium with those found in tetramethylammonium chloride medium provides evidence of the formation of potassium and sodium complexes of the type MHP 2O 2- 7 and MP 2O 3- 7. Stability constants of these complexes are calculated and distribution diagrams of the species as a function of pH are given for the three different media utilized.

Transport of ascorbate into guinea pig liver mitochondria

The amount of ascorbate associated with guinea pig liver mitochondria was estimated by high-performance liquid chromatography. Incubation of mitochondria with ascorbate revealed a time-dependent and temperature-dependent accumulation of the vitamin. A steady-state level of ascorbate was obtained in the mitochondria after about 20 min of incubation at 37°C, whereas no accumulation was observed at 0°C. The matrix concentration of ascorbate was highly correlated to the concentration of ascorbate in the incubation medium. The initial rate of accumulation (about 7 pmol/mg protein per min at 10°C) was three orders of magnitude less than for compounds that are transported across the mitochondrial inner membrane by specific carriers. Experiments with the enzyme ascorbate oxidase demonstrated that the mitochondrial membrane is also permeable to dehydroascorbate, and that the accumulated dehydroascorbate is stable in the mitochondria. There was no effect of the energy state of the mitochondrial membrane on the initial transport rate of ascorbate. Electrostatic binding of ascorbate to the membrane was excluded from experiments performed in isosmotic potassium chloride medium. Diffusion of ascorbate across the mitochondrial inner membrane accounts for the experimental findings.

ChemInform Abstract: LINEAR FREE‐ENERGY RELATIONSHIPS IN THE HYDROLYSIS OF METAL IONS. THE EFFECT OF THE IONIC MEDIUM

AbstractAus potentiometräschen und kalorimetrischen Untersuchungen folgt, daß das Ausmaß der Hydrolyse von Th(IV), die Stabilitätskonstanten seiner hydrolytischen Komplexe und die entsprechenden thermodynamischen Parameter vom Ionenmedium (LiCl, NaCl, KCl) beeinflußt werden.

Polarography of europium(III) in water-dimethylformamide mixtures

The kinetics of the electrochemical reduction of europium(III) in water-N, N dimethyl formamide mixtures in potassium chloride medium has been studied. The formal rate constant for the reduction increases markedly from 10−4 cm sec−1 in low concentrations to 10−2 cm sec−1 at high concentrations of the solvent. The effects of solvent on the formal potential and diffusion current are discussed.

Linear free-energy relationships in the hydrolysis of metal ions. The effect of the ionic medium

The effect of a lithium, sodium, and potassium chloride medium on the hydrolysis of thorium(IV) has been studied by a potentiometric and calorimetric method. The data obtained show that the extent of hydrolysis of thorium, the stability constants of its hydrolytic complexes, and the associated thermodynamic parameters are affected by the ionic medium. Correlations between the free energies of the hydrolytic processes and the properties of the medium are considered by the linear free-energy approach. The uranyl and nickel hydrolysis data imply generality of the proposed relationship.

The kinetics of dissolution of calcium oxalate hydrates

The kinetics of dissolution of the monohydrate and trihydrate of calcium oxalate have been studied at temperatures from 15–50°C using a highly reproducible technique. The dissolution of both salts appears to be diffusion controlled, proceeding with rates which were proportional to the undersaturations. The activation energies were 13.0 and 16.6kJ mol-1 for the monohydrate and trihydrate, respectively. The solubilities of the hydrates in sodium and potassium chloride media were significantly different and the data in potassium chloride solutions have been used to determine a thermodynamic ion-association equilibrium constant for the KC2O4¯ ion-pair of 10 ∓ 1 M-1 at 37°C. Different preparations of calcium oxalate monohydrate were used to investigate the importance of specific surface area in controlling the rate of dissolution. It is interesting to note that seed prepared from human monohydrate kidney stone material dissolved with a markedly lower diffusional rate constant than that calculated from synthetic calcium oxalate monohydrate crystals on the basis of available specific surface area.

The influence of adenine nucleotides and oxidizable substrates on triethyltin-mediated chloride uptake by rat liver mitochondria in potassium chloride media

In a 100 mM-KCl medium, pH 6.8, containing ATP increasing concentrations of triethyltin cause an uptake of Cl- into mitochondria with a maximum at 1 muM. This can be inhibited by atractylate or oligomycin, but is virtually unaffected by the presence of rotenone. When the medium contains substrate (pyruvate, beta-hydroxybutyrate or succinate), both in the presence and absence of adenine nucleotides, Cl- uptake is greater with a maximum at 1-10 muM-triethyltin. If substrate oxidation is blocked by respiratory-chain inhibitors the Cl- uptake mediated by triethyltin is inhibited except in the media containing ATP, when the characteristics of Cl- uptake similar to that found in the medium containing ATP alone are observed. Under all conditions tested Cl- uptake is decreased by the presence of 2,4-dinitrophenol. It is concluded that energy from either the oxidation of substrate or the hydrolysis of ATP is associated with the generation of sufficient OH- to enable the triethyltin-mediated Cl-/OH- exchange to occur under the metabolic conditions relevant to this action of triethyltin.