Navegando por Palavras-chave "Phosphate"
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- ItemAcesso aberto (Open Access)Estratégias para o desenvolvimento de célula eletroquímica em papel visando à determinação de fosfato(Universidade Federal de São Paulo (UNIFESP), 2021) Nascimento, Hadassa Vaz [UNIFESP]; Ferreira, Tiago Luiz [UNIFESP]; Universidade Federal de São PauloPhosphorus is a chemical element of fundamental importance for life on Earth, as it is part of the biological cycles of several living beings. The excess of phosphate compounds in aquatic environments caused by human actions, cause eutrophication of rivers and lakes. In this context, this work studied the electrochemical behavior of the phosphate using the cyclic voltammetry technique and used an electrochemical cell on paper to identify phosphate. The strategy employed used graphite mines to build the working electrode and the auxiliary electrode. For this, a study carried out from a selection of graphites showed that H graphite is the best option for a working electrode, because its balanced composition of carbon and clay allows the current peaks to be formed with an excellent definition and without adsorption of material. After modifying this electrode with a dispersion of Vulcan® XC 72, there was an increase in signal amplitude, which was lost after successive analysis tests with the same modifier layer. The reference electrode, also built in this work and used in conventional analyzes, made with calomel or silver, was removed from the system and the potential shifted to a more negative region as expected, but the voltammetric profile remained stable, despite the small loss in current amplitude, with tests with hexacyanoferrate (III). This loss of amplitude did not occur for phosphomolybdenum. For the development of the cell on paper, strategies based on the stamping process, construction with modeling of the wax, cutouts of sulfite paper and filter paper and the technique of printing with wax based on microfluidic devices on paper (µPADs) were tested, the last being the one that presented reliable results to make the paper electrochemical cell selective to the phosphate ion.
- ItemSomente MetadadadosFibroblast Growth Factor 23 in Hemodialysis Patients: Effects of Phosphate Binder, Calcitriol and Calcium Concentration in the Dialysate(Karger, 2011-01-01) Cancela, Ana L. E.; Oliveira, Rodrigo B.; Graciolli, Fabiana G.; Reis, Luciene M. dos; Barreto, Fellype [UNIFESP]; Barreto, Daniela V. [UNIFESP]; Cuppari, Lilian [UNIFESP]; Jorgetti, Vanda; Carvalho, Aluizio B. [UNIFESP]; Canziani, Maria Eugenia [UNIFESP]; Moyses, Rosa M. A.; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)Background: Fibroblast growth factor 23 (FGF23) concentrations increase early in chronic kidney disease (CKD), and the influence of current CKD-mineral and bone disorder (MBD) therapies on serum FGF23 levels is still under investigation. Methods: in this post-hoc analysis of a randomized clinical trial, phosphate binders and calcitriol were washed out of 72 hemodialysis patients who were then submitted to bone biopsy, coronary tomography and biochemical measures, including FGF23. They were randomized to receive sevelamer or calcium acetate for 1 year and the prescription of calcitriol and the calcium concentration in the dialysate were adjusted according to serum calcium, phosphate and PTH and bone biopsy diagnosis. Results: At baseline, bone biopsy showed that 58.3% had low-turnover bone disease, whereas 38.9% had high-turnover bone disease, with no significant differences between them with regard to FGF23. Median baseline FGF23 serum levels were elevated and correlated positively with serum phosphate. After 1 year, serum FGF23 decreased significantly. Repeated measures ANOVA analysis showed that the use of a 3.5-mEq/l calcium concentration in the dialysate, as well as the administration of calcitriol and a calcium-based phosphate binder were associated with higher final serum FGF23 levels. Conclusions: Taken together, our results confirm that the current CKD-MBD therapies have an effect on serum levels of FGF23. Since FGF23 is emerging as a potential treatment target, our findings should be taken into account in the decision on how to manage CKD-MBD therapy. Copyright (C) 2010 S. Karger AG, Basel
- ItemSomente MetadadadosSimplified estimates of ion-activity products of calcium oxalate and calcium phosphate in mouse urine(Springer, 2012-08-01) Tiselius, Hans-Goran; Nogueira Ferraz, Renato Ribeiro [UNIFESP]; Heilberg, Ita Pfeferman [UNIFESP]; Karolinska Inst; Universidade Federal de São Paulo (UNIFESP)This study aimed at formulating simplified estimates of ion-activity products of calcium oxalate (AP(CaOx)) and calcium phosphate (AP(CaP)) in mouse urineto find the most important determinants in order to limit the analytical work-up. Literature data on mouse urine composition was used to determine the relative effect of each urine variable on the two ion-activity products. AP(CaOx) and AP(CaP) were calculated by iterative approximation with the EQUIL2 computerized program. the most important determinants for AP(CaOx) were calcium, oxalate and citrate and for AP(CaP) calcium, phosphate, citrate, magnesium and pH. Urine concentrations of the variables were used. A simplified estimate of AP(CaOx) (AP(CaOx)-index(MOUSE)) that numerically approximately corresponded to 10(8) x AP(CaOx) was given the following expression:AP(CaOx)-index(MOUSE) = 0.70 x Calcium(1.05) x Oxalate(0.95)(0.90-0.0225 x Citrate) + (6.6 x 10(-8) x Citrate(3.98))For a series of urine samples with various composition the coefficient of correlation between AP(CaOx)-index(MOUSE) and 10(8) x AP(CaOx) was 0.99 (p = 0.00000). A similar estimate of AP(CaP) (AP(CaP)-index(MOUSE)) was formulated so that it approximately would correspond numerically to 10(14) x AP(CaP) taking the following form:Ap(CaP)-index(MOUSE) = 0.05 x Calcium(1.17) x Phosphate(0.85) x Magnesium(0.18) x (pH - 4.5)(6.8) / Citrate(0.76)For a series of variations in urine composition the coefficient of correlation was 0.95 (p = 0.00000). the two approximate estimates shown in this article are simplified expressions of AP(CaOx) and AP(CaP). the intention of these theoretical calculations was not to get methods for accurate information on the saturation levels in urine, but to have mathematical tools useful for rough conclusions on the outcome of different experimental situations in mice. It needs to be emphasized that the accuracy will be negatively influenced if urine variables not included in the formulas differ very much from basic concentrations.