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M KCl (m + kcl)
Selected AbstractsElectrochemical Evaluation of Nucleoside Analogue Lamivudine in Pharmaceutical Dosage Forms and Human SerumELECTROANALYSIS, Issue 20 2005Burcu Dogan Abstract Lamivudine (LAM) is a synthetic nucleoside analogue with activity against human immunodeficiency virus-type 1 (HIV-1) and Hepatitis B virus (HBV). The aim of this study was to determine LAM levels in serum and pharmaceutical formulations, by means of electrochemical methods using hanging mercury drop electrode (HMDE). On this electrode, LAM undergoes irreversible reduction at the peak potential near Ep,1.26,V (vs. Ag/AgCl/3,M KCl). Reduction LAM signals were measured by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square-wave voltammetry (OSW). DPV and OSW techniques for the determination of LAM in acetate buffer at pH,4.5, which allows quantitation over the 4×10,6 to 1×10,4,M range in supporting electrolyte for both methods, were proposed. The linear response was obtained in acetate buffer in the ranges of 2×10,6 to 2×10,4,M for spiked serum samples at pH,4.5 for both techniques. The repeatability and reproducibility of the methods for all media were determined. The standard addition method was used in serum. Precision and accuracy were also checked in all media. No electroactive interferences from the endogenous substances were found in serum. With respect to side effects of high doses and short half-life of LAM, a fast and simple detection method is described in this study. [source] Growth response of the bacterial community to pH in soils differing in pHFEMS MICROBIOLOGY ECOLOGY, Issue 1 2010David Fernández-Calviño Abstract The effect of pH on the instantaneous growth of soil bacterial communities was studied in five soils with different pH (4.5,7.8) using leucine (Leu) and thymidine (TdR) incorporation. The pH dependency of bacterial growth was modelled using three different unimodal functions, and the pHopt for growth and the pH range in which growth was >50% of the optimal growth were compared. Leu and TdR incorporation yielded very similar results. The best fits were obtained using a third-degree polynomial function and the cardinal pH model. However, a simple second-degree function was adequate in most cases, yielding very similar pHopt values to the other two models. Bacterial growth was highly influenced by pH, showing optimum growth at a pH related to the soil pH. The lowest pHopt was found in the most acidic soil and the highest pHopt in the soil with the highest pH. The pHopt for bacterial growth was close to the soil pH measured in water, but higher (0.7,2.1 units) than the pH measured with 0.1 M KCl. The pH range in which bacterial growth was >50% of that at optimum was, on average, 1.7 units below and above the optimum pH. [source] Acid decomposition of omeprazole in the absence of thiol: A differential pulse polarographic study at the static mercury drop electrode (SMDE)JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2006Ali M. Qaisi Abstract The reactions of omeprazole, a potent proton pump inhibitor (PPI), were investigated in the absence of a nucleophile. Reactions were monitored, using differential pulse polarography (DPP) at the static mercury drop electrode (SMDE), in solutions buffered to pH values ranging from 2.0 to 8.0. The fast, sensitive, and selective electrochemical technique facilitated to repeat recordings of successive voltammograms [peak current (nA) vs. peak potential (volts vs. Ag/AgCl saturated with 3.0 M KCl)]. The DPP signals of omeprazole and its degradation products, believed to be due to sulfur functional group (the principal site of electrode reaction), gave advantages over the previously employed UV detection technique. The latter primarily relied on pyridine and benzimidazole analytical signals, which are common reaction products of PPI in aqueous acidic solutions. After peak identification, the resulting current (nA)-time (s) profiles, demonstrated that omeprazole undergoes degradation to form two main stable compounds, the first is the cyclic sulfenamide (D+), previously believed to be the active inhibitor of the H+, K+ -ATPase, the second is omeprazole dimer. This degradation is highly dependant on pH. Unlike previous studies which reported that the lifetime of D+ is few seconds, the cyclic sulfenamide (D+) was found to be stable for up to 5,20 min. The results further indicated that omeprazole converts into the cyclic sulfenamide in an irreversible reaction, consequently, D+ and sulfenic acid (an intermediate which rapidly converts into D+) were not interconvertable. The present work suggested that the sulfenic acid is the active inhibitor in vivo. In addition, the omeprazole reactions, in the absence of the thiol, were not as complicated as were previously reported. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:384,391, 2006 [source] A double-blind, randomized controlled trial of cystometry using saline versus 0.3 M potassium chloride infusion in women with overactive bladder syndrome,,NEUROUROLOGY AND URODYNAMICS, Issue 1 2007Joe Philip Abstract Aim To evaluate the effect of 0.3 M potassium chloride on cystometric parameters by comparing it with normal saline as a filling solution in women with overactive bladder (OAB). Patients and Methods Twenty-three women with significant OAB symptoms underwent consecutive cystometrograms (CMGs) using 0.9% normal saline (NS) and 0.3 M potassium chloride (KCl), the order of which was randomized for each patient. Individual CMGs were performed by separate investigators and both patients and investigators were blinded to the order in which each solution was given and to the results of the other CMG. Results Regardless of the nature of the filling solution, the order in which the CMGs were performed had little influence on either first desire to void (FDV, mean 83.5 ml vs. 117.8 ml for first and second CMGs respectively, P,=,0.10) or on maximum cystometric capacity (Cmax, mean 265.0 ml vs. 264.4 ml, P,=,0.98). KCl produced a significant (24%) reduction in mean Cmax compared to NS (mean 228.6 ml vs. 300.8 ml, P,=,0.001), irrespective of the order of infusion. Conclusion This comparative study using 0.3 M KCl versus NS as filling solutions suggests that intravesical potassium may not simply act on urothelial sensory nerve endings; it may also stimulate detrusor muscle contraction. These findings may influence the interpretation of the potassium sensitivity test in patients with OAB symptoms, particularly in those suspected of having interstitial cystitis. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source] Influence of the supporting salt concentration on the electrodeposition of ZnO/eosin Y hybrid filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2008C. Boeckler Abstract ZnO/eosin Y hybrid films were electrodeposited from O2 -saturated ZnCl2 -solution under variation of the concentration of the supporting salt KCl. The supporting salt concentration was found to have a significant influence on the amount of dye loading and the morphology of the ZnO/eosin Y films. By decreasing the supporting salt concentration to 0.01 M KCl, porous films with a high dye loading can be obtained at potentials of ,0.8 V vs. SCE at low eosin Y concentrations in the electrodeposition bath, which usually only lead to porous films at potentials where eosin Y is reduced (< ,0.9 V vs. SCE). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Distance dependence and salt sensitivity of pairwise, coulombic interactions in a proteinPROTEIN SCIENCE, Issue 5 2002Kelly K. Lee Abstract Histidine pKa values were measured in charge-reversal (K78E, K97E, K127E, and K97E/K127E) and charge-neutralization (E10A, E101A, and R35A) mutants of staphylococcal nuclease (SNase) by 1H-NMR spectroscopy. Energies of interaction between pairs of charges (,Gij) were obtained from the shifts in pKa values relative to wild-type values. The data describe the distance dependence and salt sensitivity of pairwise coulombic interactions. Calculations with a continuum electrostatics method captured the experimental ,Gij when static structures were used and when the protein interior was treated empirically with a dielectric constant of 20. The ,Gij when rij , 10 Å were exaggerated slightly in the calculations. Coulomb's law with a dielectric constant near 80 and a Debye-Hückel term to account for screening by the ionic strength reproduced the salt sensitivity and distance dependence of ,Gij as well as the structure-based method. In their interactions with each other, surface charges behave as if immersed in water; the Debye length describes realistically the distance where interactions become negligible at a given ionic strength. On average, charges separated by distances (rij) ,5 Å interacted with ,Gij , 0.6 kcal/mole in 0.01 M KCl, but ,Gij decayed to ,0.10 kcal/mole when rij = 20 Å. In 0.10 M KCl, ,Gij , 0.10 kcal/mole when rij = 10 Å. In 1.5 M KCl, only short-range interactions with rij , 5 Å persisted. Although at physiological ionic strengths the interactions between charges separated by more than 10 Å are extremely weak, in situations where charge imbalance exists many weak interactions can cumulatively produce substantial effects. [source] High-resolution structure of the native histone octamerACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2005Christopher M. Wood Crystals of native histone octamers (H2A,H2B),(H4,H3),(H3,,H4,),(H2B,,H2A,) from chick erythrocytes in 2,M KCl, 1.35,M potassium phosphate pH 6.9 diffract X-rays to 1.90,Å resolution, yielding a structure with an Rwork value of 18.7% and an Rfree of 22.2%. The crystal space group is P65, the asymmetric unit of which contains one complete octamer. This high-resolution model of the histone-core octamer allows further insight into intermolecular interactions, including water molecules, that dock the histone dimers to the tetramer in the nucleosome-core particle and have relevance to nucleosome remodelling. The three key areas analysed are the H2A,,H3,H4 molecular cluster (also H2A,H3,,H4,), the H4,H2B, interaction (also H4,,H2B) and the H2A,,H4 ,-sheet interaction (also H2A,H4,). The latter of these three regions is important to nucleosome remodelling by RNA polymerase II, as it is shown to be a likely core-histone binding site, and its disruption creates an instability in the nucleosome-core particle. A majority of the water molecules in the high-resolution octamer have positions that correlate to similar positions in the high-resolution nucleosome-core particle structure, suggesting that the high-resolution octamer model can be used for comparative studies with the high-resolution nucleosome-core particle. [source] Total and soluble fluorine concentrations in relation to properties of soils in New ZealandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2006P. Loganathan Summary Soil fluorine (F) concentrations continue to increase in agricultural soils receiving regular applications of phosphatic fertilizer. Continued accumulation of soil F poses a risk to grazing ruminants and may pose a future risk to groundwater quality. This paper examines the range of total F (Ft) concentrations and forms of soluble F species and their relationship to selected soil properties in New Zealand agricultural soils. The Ft and soluble F (soil F extracted with water (Fwater) and 0.01 m KCl (FKCl)) concentrations in 27 soil samples (0,75 mm depth) taken from predominantly pasture sites in the North and South Islands of New Zealand were much less than those reported in the literature for sites contaminated with F from industry. The Ft concentrations ranged from 212 to 617 µg F g,1 soil. The F-toxicity risk to grazing animals in farms at these sites through soil ingestion is small at present, but farms with very large Ft concentrations (i.e. > 500 µg F g,1) need to adopt suitable grazing and fertilizer management practices to avoid future F-toxicity risk. The Ft concentration had very strong positive correlations with both total soil P and total soil Cd concentrations, reflecting the link between P fertilizer use and F accumulation in the soils. It also had significant positive correlations with organic matter and amorphous Al oxides contents, indicating that F is strongly bound to Al polymers adsorbed to organic matter and amorphous Al oxides. The Fwater and FKCl concentrations and free F, ion concentrations in water (F,water) and 0.01 m KCl (F,KCl) extracts were generally two and three orders of magnitude, respectively, less than the Ft concentrations and were much less than the concentrations considered phytotoxic. The Fwater and FKCl concentrations were positively related to soil organic matter content and negatively related to soil pH. Regression models relating Fwater and FKCl concentrations to soil organic matter content and soil pH suggest that F can be very soluble in extremely acidic soils (pH(water) < 4.9) with large organic matter contents and therefore F potentially may contaminate groundwater if these soils are also coarse-textured and the water table is shallow. [source] ISC1-encoded inositol phosphosphingolipid phospholipase C is involved in Na+/Li+ halotolerance of Saccharomyces cerevisiaeFEBS JOURNAL, Issue 16 2002Christian Betz In Saccharomyces cerevisiae, toxic concentrations of Na+ orLi+ ions induce the expression of the cation-extrusion ATPase gene, ENA1. Several well-studied signal transduction pathways are known correlating high salinity to the transcriptional activation of ENA1. Nevertheless, information on the actual sensing mechanism initiating these pathways is limited. Here, we report that the ISC1 -encoded phosphosphingolipid-specific phospholipase C appears to be involved in stimulation of ENA1 expression and, consequently, in mediating Na+ and Li+ tolerance in yeast. Deletion of ISC1 distinctly decreased cellular Na+ and Li+ tolerance as growth of the ,isc1::HIS5 mutant, DZY1, was severely impaired by 0.5 m NaCl or 0.01 m LiCl. In contrast,K+ tolerance and general osmostress regulation wereunaffected. Isc1, mutant growth with 0.9 m KCl and glycerol accumulation in the presence of 0.9 m NaCl or 1.5 m sorbitol were comparable to that of the wild-type. ENA1 -lacZ reporter studies suggested that the increased salt sensitivity of the isc1, mutant is related to a significant reduction of Na+/Li+ -stimulated ENA1 expression. Correspondingly, Ena1p-dependent extrusion of Na+/Li+ ions was less efficient in the isc1, mutant than in wild-type cells. Itis suggested that ISC1 -dependent hydrolysis of an unidentified yeast inositol phosphosphingolipid represents an early event in one of the salt-induced signalling pathways of ENA1 transcriptional activation. [source] ,-blockers improve chronic ischaemia of the lower urinary tract in patients with lower urinary tract symptomsBJU INTERNATIONAL, Issue 3 2008Germar-M. OBJECTIVE To investigate whether a mechanism of action of ,-blockers on lower urinary tract symptoms (LUTS) involves improved perfusion of the LUT. PATIENTS, SUBJECTS AND METHODS The accuracy of perfusion measurements using transrectal colour Doppler ultrasound (TRCDUS) and colour pixel density (CPD) was initially confirmed in a porcine model. Following this confirmation, measurements were taken from four healthy male volunteers and 19 patients with LUTS. The urinary bladder was filled slowly (50 mL/min) with 0.2 m KCl, which resembles the osmolarity of concentrated urine, and evaluated by cystometry. In parallel, TRCDUS and measurement of the CPD of the LUT were performed. The patients with LUTS were then treated with daily ,-blocker (0.4 mg tamsulosin) for 5 weeks and urodynamic variables as well as perfusion were evaluated again. RESULTS In the healthy men, perfusion of the LUT increased considerably (157%) during filling of the bladder to a mean (sd) maximum cystometric capacity (Cmax) of 481 (28.9) mL. All the patients with LUTS had a reduced mean Cmax during filling with KCl at 322.4 (58.5) mL. The mean CPD in the urinary bladder and the prostate were only increased by 58.4% during filling with KCl. After ,-blocker therapy the mean Cmax during filling with KCl rose to 382.5 (42.9) mL; furthermore, perfusion of the LUT measured by CPD was significantly increased (132.8%). CONCLUSIONS The present data strongly suggest that LUTS are associated with chronic ischaemia of the prostate and urinary bladder. ,-blockers increase perfusion in the LUT and Cmax. These results might explain the therapeutic effects of ,-blockers on LUTS. [source] | |||||||||||||