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An autonomous electrochemical system prototype for ammonia oxidation reaction (AOR) measurements was efficiently done inside a 4'' x 4'' x 8'' 2U Nanoracks module at the International Space Station (ISS). This device, the Ammonia Electrooxidation Lab at the ISS (AELISS), included an autonomous electrochemical system that complied with NASA ISS nondisclosure agreements, power, safety, security, size constrain, and material compatibility established for space missions. The integrated autonomous electrochemical system was tested on-ground and deployed to the International Space Station as a "proof-of-concept" ammonia oxidation reaction testing space device. Here are discussed the results of cyclic voltammetry and chronoamperometry measurements done at the ISS with a commercially available channel flow-cell with eight screen-printed electrodes, including Ag quasi-reference (Ag QRE) and carbon counter electrodes. Pt nanocubes in Carbon Vulcan XC-72R were used as the catalyst for the AOR and 2 µL drop of Pt nanocubes/ Carbon Vulcan XC-72R, 20 wt%, ink was placed on the carbon working electrodes and allowed to dry in air. After the AELISS was prepared for launch to the ISS, a 4 days delayed (2 days in the space vehicle Antares and 2 days space transit to the ISS) cause a slight shift on the Ag QRE potential. Nevertheless, the AOR cyclic voltametric peak was observed in the ISS and showed ca. 70% current density decrease due to the buoyancy effect in agreement with previous microgravity experiments done at the zero-g aircraft.
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Although phosphorus is an essential element for life, it is not found in nature in its native state but rather combined in the form of inorganic phosphates (PO43-), with tightly regulated plasma levels that are associated with deleterious effects and mortality when these are out of bounds. The growing interest in the accumulation of PO43- in human pathophysiology originated in its attributed role in the pathogenesis of secondary hyperparathyroidism (SHPT) in chronic kidney disease. In this article, we review the mechanisms by which this effect was justified and we commemorate the important contribution of a Spanish group led by Dr. M. Rodríguez, just 25 years ago, when they first demonstrated the direct effect of PO43- on the regulation of the synthesis and secretion of parathyroid hormone by maintaining the structural integrity of the parathyroid glands in their original experimental model. In addition to demonstrating the importance of arachidonic acid (AA) and the phospholipase A2-AA pathway as a mediator of parathyroid gland response, these findings were predecessors of the recent description of the important role of PO43- on the activity of the calcium sensor-receptor, and also fueled various lines of research on the importance of PO43- overload not only for the pathophysiology of SHPT but also in its systemic pathogenic role.
Assuntos
Hiperparatireoidismo Secundário , Insuficiência Renal Crônica , Humanos , Glândulas Paratireoides , Fosfatos , Hormônio Paratireóideo , Hiperparatireoidismo Secundário/complicações , Insuficiência Renal Crônica/complicaçõesRESUMO
Studying the oxygen reduction reaction (ORR) in the alkaline electrolyte has proven to promote better catalytic responses and accessibility to commercialization. Ni-nanowires (NWs) were synthesized via the solvothermal method and modified with Pt using the spontaneous galvanic displacement method to obtain PtNi-NWs. Carbon Vulcan XC-72R (V) was used as the catalyst support, and they were doped with NH3 to obtain PtNi-NWs/V and PtNi-NWs/V-NH3. Their electrocatalytic response for the ORR was tested and PtNi-NWs/V provided the highest specific activity with logarithmic values of 0.707 and 1.01 (mA/cm2 Pt) at 0.90 and 0.85 V versus reversible hydrogen electrode (RHE), respectively. PtNi-NWs showed the highest half-wave potential (E 1/2 = 0.89 V) at 1600 rpm and 12 µgPt/cm2 in 0.1 M KOH at 25.00 ± 0.01 °C. Additionally, the catalysts followed a four-electron pathway according to the Koutecký-Levich analysis. Moreover, durability experiments demonstrated that the PtNi-NW/V performance loss was like that of commercial Pt/V along 10,000 cycles. Electrochemical ORR in situ X-ray absorption spectroscopy results showed that the Pt L3 edge white line in the PtNi-NW catalysts changed while the electrochemical potential was lowered to negatives values, from 1.0 to 0.3 V versus RHE. The Pt/O region in the in situ Fourier transforms remained the same as the potentials were applied, suggesting an alloy formation between Pt and Ni, and Pt/Pt contracted in the presence of Ni. These results provide a better understanding of PtNi-NWs in alkaline electrolytes, suggesting that they are active catalysts for ORR and can be tuned for fuel cell studies.
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BACKGROUND AND AIMS: An increasing number of studies have been published concerning meeting targets of clinical guidelines for different aspects of the diagnosis and treatment of patients with end-stage renal disease. Most of these studies have shown that guideline recommendations are not always satisfied, and results outside target limits have been associated with high rates of mortality and morbidity. The objective of this study was to analyze the frequency of reaching mineral and bone metabolism-related guideline targets and its impact on clinical outcomes in Mexican chronic dialysis patients. METHODS: A cohort of prevalent peritoneal dialysis (PD) and hemodialysis (HD) patients were analyzed at baseline and followed for at least 16 months. Patients were on continuous ambulatory peritoneal dialysis (CAPD), automated peritoneal dialysis (APD), and HD and contracted HD modalities where patients received HD sessions outside institution facilities. RESULTS: We studied 753 patients. The percentage of patients within target limits for phosphorus was 35%, for calcium 32%, and for PTH 12%. The most frequent pattern was hyperphosphatamia, hypercalcemia, and low PTH. This was even more frequent in CAPD patients, probably due to the high percentage of diabetic patients. Hypercalcemia was found as an independent risk factor for mortality. CONCLUSIONS: The most important results suggest that guideline recommendations are not usually satisfied and that hypercalcemia, in addition to other traditional risk factors, is associated with high mortality rates. The study also detected some opportunities to improve the quality of treatment by reducing the calcium content of dialysis solutions and reducing the use of calcium carbonate as a phosphate binder.
Assuntos
Cálcio/metabolismo , Falência Renal Crônica/metabolismo , Falência Renal Crônica/terapia , Diálise Peritoneal , Fósforo/metabolismo , Guias de Prática Clínica como Assunto , Diálise Renal , Adulto , Cálcio/sangue , Carbonato de Cálcio/administração & dosagem , Estudos de Coortes , Diabetes Mellitus , Feminino , Humanos , Falência Renal Crônica/complicações , Falência Renal Crônica/mortalidade , Masculino , México , Pessoa de Meia-Idade , Hormônio Paratireóideo/sangue , Hormônio Paratireóideo/metabolismo , Fósforo/sangue , Fatores de Risco , Taxa de Sobrevida , Resultado do TratamentoRESUMO
Mineral and bone disorders (MBD) are both an early and very common complication of chronic kidney disease (CKD). It is now accepted that they represent a significant risk factor, explaining the high cardiovascular morbidity and mortality in CKD patients. During the last decade, we have been witnessing many advances in the nomenclature, classification, pathophysiology, diagnosis, and treatment of CKD and some of its complications, such as CKD-MBD. The identification of the calcium-sensing receptor (CaSR) involvement in the pathogenesis of primary and secondary hyperparathyroidism (SHPT) and the availability of a new class of drugs called calcimimetics are two outstanding examples. Cinacalcet, the only available calcimimetic, has been shown to be a very effective therapeutic tool in CKD-MBD. Many clinical trials with cinacalcet in hemodialysis patients with SHPT have shown a reduction in parathyroid hormone, calcium (Ca), phosphate (P) and Ca x P product levels, allowing far greater success in reaching therapeutic goals as recommended by international guidelines. Additionally, some studies have shown that the use of cinacalcet may improve other aspects of CKD-MBD, reducing the risk of vascular calcification and parathyroidectomy, among others. Prospective studies on dialysis patients, with hard endpoint data, are currently underway. This review summarizes the most significant aspects of calcimimimetics based on both experimental and clinical results, underlining their possibilities not only for the treatment of isolated SHPT but also for other CKD-MBD related conditions.