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pH Indicators (ph + indicator)
Selected AbstractsEvidence of placental haemorrhage and preterm deliveryBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 4 2010JW Gargano Please cite this paper as: Gargano J, Holzman C, Senagore P, Reuss M, Pathak D, Williams M, Fisher R. Evidence of placental haemorrhage and preterm delivery. BJOG 2010;117:445,455. Objective, To evaluate evidence of placental haemorrhage (PH) obtained through maternal interviews, patient charts and placental pathology examinations as potential indicators of a ,bleeding pathway' to preterm delivery (PTD). Design, Prospective cohort. Setting, Fifty-two clinics in five communities in Michigan, USA (1998,2004). Population, A subset (n = 996) of cohort participants with complete placental pathology data. Methods, First-trimester bleeding and placental abruption were ascertained by mid-trimester interviews and chart review, respectively. Disc-impacting blood clot was defined as a gross placental examination finding of a blood clot impacting adjacent tissue. Microscopic haemorrhage was defined as ,high' (top quintile) scores on an aggregate measure of placental pathology findings suggestive of atypical maternal vessel haemorrhage. These four PH indicators were compared with one another and with risk of PTD assessed by logistic regression analyses. Main outcome measures, Preterm delivery and PTD subtypes (i.e. <35 weeks, 35,36 weeks; spontaneous, medically indicated) compared with term deliveries. Results, Placental abruption cases had 2.3-fold to 5.5-fold increased odds of the other three PH indicators. Disc-impacting blood clots and microscopic haemorrhage were associated with one another (odds ratio [OR] = 4.6), but not with first-trimester bleeding. In a multivariable model that included all four PH indicators and confounders, risk of PTD < 35 weeks was elevated with first-trimester bleeding (OR = 1.9 [1.0, 3.4]), placental abruption (OR = 5.2 [1.7, 16.2]), disc-impacting blood clots (OR = 2.3 [1.0, 5.0]) and microscopic haemorrhage (OR = 2.4 [1.4, 4.2]). Conclusions, Multiple clinical and subclinical PH indicators are associated with PTD, particularly early PTD. [source] Regulatory Mechanisms and Physiological Relevance of a Voltage-Gated H+ Channel in Murine Osteoclasts: Phorbol Myristate Acetate Induces Cell Acidosis and the Channel Activation,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 11 2003Hiroyuki Mori Abstract The voltage-gated H+ channel is a powerful H+ extruding mechanism of osteoclasts, but its functional roles and regulatory mechanisms remain unclear. Electrophysiological recordings revealed that the H+ channel operated on activation of protein kinase C together with cell acidosis. Introduction: H+ is a key signaling ion in bone resorption. In addition to H+ pumps and exchangers, osteoclasts are equipped with H+ conductive pathways to compensate rapidly for pH imbalance. The H+ channel is distinct in its strong H+ extrusion ability and voltage-dependent gatings. Methods: To investigate how and when the H+ channel is available in functional osteoclasts, the effects of phorbol 12-myristate 13-acetate (PMA), an activator for protein kinase C, on the H+ channel were examined in murine osteoclasts generated in the presence of soluble RANKL (sRANKL) and macrophage-colony stimulating factor (M-CSF). Results and Conclusions: Whole cell recordings clearly showed that the H+ current was enhanced by increasing the pH gradient across the plasma membrane (,pH), indicating that the H+ channel changed its activity by sensing ,pH. The reversal potential (Vrev) was a valuable tool for the real-time monitoring of ,pH in clamped cells. In the permeabilized patch, PMA (10 nM-1.6 ,M) increased the current density and the activation rate, slowed decay of tail currents, and shifted the threshold toward more negative voltages. In addition, PMA caused a negative shift of Vrev, suggesting that intracellular acidification occurred. The PMA-induced cell acidosis was confirmed using a fluorescent pH indicator (BCECF), which recovered quickly in a K+ -rich alkaline solution, probably through the activated H+ channel. Both cell acidosis and activation of the H+ channel by PMA were inhibited by staurosporine. In ,80% of cells, the PMA-induced augmentation in the current activity remained after compensating for the ,pH changes, implying that both ,pH-dependent and -independent mechanisms mediated the channel activation. Activation of the H+ channel shifted the membrane potential toward Vrev. These data suggest that the H+ channel may contribute to regulation of the pH environments and the membrane potential in osteoclasts activated by protein kinase C. [source] The effect of bulking agents on the chemical stability of acid-sensitive compounds in freeze-dried formulations: Sucrose inversion studyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2009Enxian Lu Abstract The goal of the study was to evaluate the impact of amorphous bulking agents on the chemical stability of freeze-dried materials. Polyvinylpyrrolidone and dextran of different molecular weights and lactose were used as bulking agents, and sucrose was used as an example of an acid-sensitive compound. Lyophiles containing bulking agent and sucrose at 10:1 (w/w) ratio, citrate buffer, and optionally bromophenol blue (pH indicator) were tested by X-ray powder diffractometry, differential scanning calorimetry, and Karl Fischer titrimetry. Diffuse reflectance UV,vis spectroscopy was used to obtain the concentration ratio of the deprotonated (In2,) to the protonated (HIn,) indicator species, from which the Hammett acidity function (H2,) was calculated. The extent of sucrose inversion in lyophiles stored at 60°C was quantified by HPLC. The bulking agent had a major impact on both the apparent solid-state acidity (H2,) and the degradation rate, with the degradation rate constants value highest for dextran lyophiles (most "acidic", lower H2,) followed by lactose and polyvinylpyrrolidone lyophile (least "acidic", higher H2,). The Hammett acidity function can be used as an empirical solid-state acidity scale, to predict the rank-order stability of acid-sensitive compounds in lyophiles prepared with different bulking agents. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3387,3396, 2009 [source] Determination of Transverse Dispersion Coefficients from Reactive Plume LengthsGROUND WATER, Issue 2 2006Olaf A. Cirpka With most existing methods, transverse dispersion coefficients are difficult to determine. We present a new, simple, and robust approach based on steady-state transport of a reacting agent, introduced over a certain height into the porous medium of interest. The agent reacts with compounds in the ambient water. In our application, we use an alkaline solution injected into acidic ambient water. Threshold values of pH are visualized by adding standard pH indicators. Since aqueous-phase acid-base reactions can be considered practically instantaneous and the only process leading to mixing of the reactants is transverse dispersion, the length of the plume is controlled by the ratio of transverse dispersion to advection. We use existing closed-form expressions for multidimensional steady-state transport of conservative compounds in order to evaluate the concentration distributions of the reacting compounds. Based on these results, we derive an easy-to-use expression for the length of the reactive plume; it is proportional to the injection height squared, times the velocity, and inversely proportional to the transverse dispersion coefficient. Solving this expression for the transverse dispersion coefficient, we can estimate its value from the length of the alkaline plume. We apply the method to two experimental setups of different dimension. The computed transverse dispersion coefficients are rather small. We conclude that at slow but realistic ground water velocities, the contribution of effective molecular diffusion to transverse dispersion cannot be neglected. This results in plume lengths that increase with increasing velocity. [source] Facile synthesis, characterization, and potential applications of two kinds of polymeric pH indicators: Phenolphthalein formaldehyde and o -cresolphthalein formaldehydeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005Zhihong Liu Abstract Two kinds of applicable polymeric pH indicators were synthesized by the reaction of phenolphthalein and o -cresolphthalein with formaldehyde under alkaline conditions by a one-pot method. The synthesized products were fully characterized with Fourier transform infrared, 1H NMR, ultraviolet,visible spectroscopy, and gel permeation chromatography. The results indicated that the reaction was a typical phenol formaldehyde reaction. The dosage of formaldehyde and the reaction time were well controlled to obtain soluble polymers, instead of crosslinked products. The polymeric-pH-indicator-immobilized poly(vinyl alcohol) (PVA) membranes were easily fabricated and had good long-term stability under highly basic conditions and a fast equilibrium response. Moreover, the phenolphthalein formaldehyde immobilized PVA membrane had a linear response from pH 10.0 to 14.0, and so it has promise as a optical transducer for high pH value determinations. The o -cresolphthalein formaldehyde immobilized PVA membrane had a nonlinear response from pH 9.0 to 13.0. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1019,1027, 2005 [source] | ||||||||||