Despite arsenite can be reduced to As(0) and deposited at the surface of solid electrodes such as gold, platinum, or copper, it cannot form amalgams with mercury, and so the addition of other metal ...ions is required for its deposition. In this manuscript, mechanistic analysis of the cathodic stripping square-wave voltammetric response of the system copper‑arsenic is presented. For the analysis of experimental responses, a mathematical model is used to consider that a surface-active reagent undergoes a charge transfer step followed by a chemical reaction. The dependences of the differential peak current, and the respective peak potential and half-peak width on the square-wave frequency were used to estimate the apparent stability constant of arsenide formation and that the electrode reaction would involve the direct transfer of 2 electrons, while the simulation and fit of forward and backward voltammetric responses have been useful for inferring other parameters such as the formal charge transfer rate constant of the global electron transfer reaction, a pseudo-first order homogeneous rate constant associated with arsenide formation, and the charge transfer coefficient of the global electron transfer reaction. Besides the values estimated for each of those parameters, all simulations indicate that the reduction of copper instead of arsenic would be taking place during the cathodic stripping scan.
Accordingly, the trace-analysis reaction of arsenic in the presence of copper would be based on the surface accumulation of a metal complex, where Cu2+ would be the metal cation and an arsenide species the ligand. The stability of that complex at the surface of a mercury electrode would depend not only on the applied potential, but also on the ratio between copper, arsenic, and protons.
•Mechanistic analysis of the CS-SWV response of the system copper-arsenic is presented.•This is the first time that a mathematical model of such complexity is used for simulating experimental voltammograms.•The simulation and fit of the experimental curves are step-by-step described.•Simulations indicate that the reduction of Cu(II) instead of As(0) takes place during the cathodic stripping scan.•A surface analysis is required when the scan-rate affect the apparent reversibility of more than one kinetic constant.
A theoretical model about the voltammetric response of electrode processes complicated by adsorption of reactant and a following coupled chemical reaction of soluble species (E(ad)C(sol) mechanism) ...is presented. The results are focused on reactions studied by square-wave voltammetry (SWV) where the electrochemical and the chemical kinetics affect the voltammetric response. The quasi-reversible maximum is a well-known characteristic of systems that involve adsorbed species and that are assessed by SWV. This characteristic usually helps researchers to estimate the value of ks. In this manuscript some warnings about the overuse of the quasi-reversible maximum are presented. Special attention should be paid for those systems where the quasi-reversible maximum does not have the shape of theoretical curves or where the frequency of the maximum shifts when the pH or another experimental variable is modified. All these outcomes are pointing out the presence of a reaction mechanism more complicated than a simple reaction scheme of an adsorbed reagent that releases a soluble product. This type of E(ad)C(sol) reaction mechanism would explain several aspects associated with the reduction of metal cations complexed with organic ligands. To the best of our knowledge, systems of this complexity have been not modeled so far. In this regard, this manuscript presents one step forward for the deconvolution of these not that simple reactions.
•A theoretical model for adsorptive stripping SWV of an E(ad)C(sol) mechanism is presented.•The electrochemical and chemical reactions are assumed to be quasi-reversible processes.•The effect of the equilibrium constant of the chemical reaction on the voltammetric response is analyzed.•Several SW voltammograms are provided for comparison purposes.•The presence and position of the quasi-reversible maximum is conditioned by the coupled chemical reaction.
The boron removal capacity from an aqueous solution using MgAlFe mixed oxides from layered double hydroxides (LDH) was studied. They were synthesized by the coprecipitation method at 70 °C and were ...characterized as potential filter materials. The Fe3+ analyzed by X-ray photoelectron spectroscopy and UV–visible diffuse reflectance showed their tetrahedral and octahedral coordination. Scanning electron microscopy micrographs and thermogravimetric and differential scanning calorimetry analysis evidenced the presence of clusters and particles aggregates and decreased dehydroxylation temperature when the iron content increased. Mixed oxides and boron solution in a ratio of 20:1 Mg/B were put in a batch reactor at different contact times. The borate removal process was due to the memory effect of the mixed oxides and superficial adsorption by electrostatic attraction. This fact is directly related to the specific surface area, Fe content, and surface charge. The maximum boron removals were achieved with the CS25 and CS50 samples with values higher than 85%.
Layered Double Hydroxides of Mg–Al–Fe and their mixed metallic oxides of high specific surface area were synthesized by the coprecipitation method. A natural zeolite from a regional quarry with high ...clinoptilolite content was conditioned and modified. Initially, an acid treatment was applied and subsequently Fe(III) was incorporated by the wet impregnation method. Then the prepared solid materials were characterized by XRD, N
2
adsorption–desorption at 77 K, SEM, DRS UV–Vis, and MP-AES to determine their physicochemical properties. Finally, the solid materials were evaluated as adsorbents for arsenic removal in water. The tracking of As and its species concentration at trace levels was carried out by cathodic stripping Square-wave voltammetry, which has proved to be a highly selective and sensitive electrochemical method. High levels of effectiveness in terms of removal were achieved, particularly with the natural zeolites and mixed oxides of highest iron content.
In this work, the adsorption of As(III) species from aqueous solutions onto mixed oxides (MOs) synthesized from layered double hydroxides (LDHs) has been assessed by cathodic stripping square-wave ...voltammetry (CS-SWV). The optimized electrochemical protocol involves the accumulation of arsenic for 60 s at −0.4 V, in presence of 0.5 mM Cu(II), 0.3 μM pyrrolidine dithiocarbamate (PDTC), and 0.9 M HCl, followed by a reductive scan to −1.0 V. A stable and well-defined peak was observed at −0.780 V, with a linear range that goes from 2 to 110 μg L
−1
of As(III). A value of limit of detection (LOD) = 4 μg L
−1
was calculated as three times the ratio between the standard deviation of the ordinate and slope of the linear regression curve. The presence of Cu(II) increases the signal of current and minimizes the effect of interfering species, while PDTC forms a complex that stabilizes the signal observed during the cathodic scan. Ternary LDHs and their MOs composed by MgAlFe were synthesized and characterized as potential filtering materials. X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance analysis showed that the Fe(III) ions can be found in tetrahedral and octahedral coordination environments, while SEM micrographs evidenced the cluster formation and aggregates of particles when the Fe/(Fe+Al) molar ratio is increased. The capacity of MOs for removing As(III) has been studied at different contact times in a batch reactor, and in all cases, removals of As(III) above 75% were achieved.
Introduction: Mutations in the promoter region of telomerase reverse transcriptase occur frequently in meningiomas.
Objective: To estimate the prognostic importance of telomerase reverse ...transcriptase mutations in Colombian patients with grades II and III meningioma.
Materials and methods: This was a multicenter retrospective cohort study of patients diagnosed with refractory or recurrent WHO grades II and III meningiomas, recruited between 2011 and 2018, and treated with systemic therapy (sunitinib, everolimus ± octreotide, and bevacizumab). Mutation status of the telomerase reverse transcriptase promoter was established by PCR.
Results: Forty patients were included, of which telomerase reverse transcriptase mutations were found in 21 (52.5%), being C228T and C250T the most frequent variants with 87.5 % and 14.3 %, respectively. These were more frequent among patients with anaplastic meningiomas (p=0.18), with more than 2 recurrences (p=0.04); and in patients with parasagittal region and anterior fossa lesions (p=0.05). Subjects characterized as having punctual mutations were more frequently administered with everolimus, sunitinib and bevacizumab drug series (p=0.06). Overall survival was 23.7 months (CI95% 13.1-34.2) and 43.4 months (CI95% 37.5-49.3; p=0.0001) between subjects with and without mutations, respectively. Multivariate analysis showed that the number of recurrences and the presence of telomerase reverse transcriptase mutations were tthe only variables that negatively affected overall survival.
Conclusions: Mutations in telomerase reverse transcriptase allows the identification of high-risk patients and could be useful in the selection of the best medical treatment.
Background
Amplification of
EGFR
and its active mutant
EGFRvIII
are common in glioblastoma (GB). While
EGFR
and
EGFRvIII
play critical roles in pathogenesis, targeted therapy with EGFR-tyrosine ...kinase inhibitors or antibodies has shown limited efficacy. To improve the likelihood of effectiveness, we targeted adult patients with recurrent GB enriched for simultaneous
EGFR
amplification and
EGFRvIII
mutation, with osimertinib/bevacizumab at doses described for non-small cell lung cancer.
Methods
We retrospectively explored whether previously described
EGFRvIII
mutation in association with
EGFR
gene amplification could predict response to osimertinib/bevacizumab combination in a subset of 15 patients treated at recurrence. The resistance pattern in a subgroup of subjects is described using a commercial next-generation sequencing panel in liquid biopsy.
Results
There were ten males (66.7%), and the median patient’s age was 56 years (range 38–70 years). After their initial diagnosis, 12 patients underwent partial (26.7%) or total resection (53.3%). Subsequently, all cases received IMRT and concurrent and adjuvant temozolomide (TMZ; the median number of cycles 9, range 6–12). The median follow-up after recurrence was 17.1 months (95% CI 12.3–22.6). All patients received osimertinib/bevacizumab as a second-line intervention with a median progression-free survival (PFS) of 5.1 months (95% CI 2.8–7.3) and overall survival of 9.0 months (95% CI 3.9–14.0). The PFS6 was 46.7%, and the overall response rate was 13.3%. After exposure to the osimertinib/bevacizumab combination, the main secondary alterations were
MET
amplification,
STAT3
,
IGF1R
,
PTEN
, and
PDGFR
.
Conclusions
While the osimertinib/bevacizumab combination was marginally effective in most GB patients with simultaneous
EGFR
amplification plus
EGFRvIII
mutation, a subgroup experienced a long-lasting meaningful benefit. The findings of this brief cohort justify the continuation of the research in a clinical trial. The pattern of resistance after exposure to osimertinib/bevacizumab includes known mechanisms in the regulation of
EGFR
, findings that contribute to the understanding and targeting in a stepwise rational this pathway.
Introducción. En los meningiomas, ocurren con frecuencia mutaciones en la región promotora de la transcriptasa inversa de la telomerasa.Objetivo. Estimar la importancia pronóstica de las mutaciones ...de la transcriptasa inversa de la telomerasa en pacientes colombianos con meningiomas de grados II y III.Materiales y métodos. Es un estudio de cohorte, retrospectivo y multicéntrico, que incluyó pacientes con diagnóstico de meningioma persistente o recidivante, de grados II y III, según la clasificación de la OMS, reclutados entre el 2011 y el 2018, con tratamiento sistémico (sunitinib, everolimus con octreótido o sin él, y bevacizumab). El estado de la mutación del promotor de la transcriptasa inversa de la telomerasa se determinó por medio de la PCR. Resultados. Se incluyeron 40 pacientes, en 21 (52,5 %) de los cuales se encontraron mutaciones en la transcriptasa inversa de la telomerasa, siendo las variantes más frecuentes la C228T (87,5 %) y la C250T (14,3 %). Estas fueron más frecuentes entre los pacientes con meningiomas anaplásicos (p=0,18), en aquellos con más de dosrecurrencias (p=0,04), y en los que presentaron lesiones en la región parasagital y la fosa anterior (p=0,05). Los sujetos caracterizados por tener alteraciones puntuales fueron tratados con mayor frecuencia con la serie de medicamentos everolimus, sunitinib y bevacizumab (p=0,06). Tras el inicio del tratamiento médico, la supervivencia global fue de 23,7 meses (IC95% 13,1-34,2) en los pacientes con mutaciones y, de 43,4 meses (IC95% 37,5-49,3), entre aquellos sin mutaciones (p=0,0001).Los resultados del análisis multivariado demostraron que, únicamente, el número de recurrencias y la presencia de mutaciones en el gen de la transcriptasa inversa de la telomerasa, fueron factores que afectaron negativamente la supervivencia global. Conclusiones. Las mutaciones en el gen promotor de la transcriptasa inversa de la telomerasa permiten identificar los pacientes con alto riesgo, cuya detección podría ser de utilidad para seleccionar el mejor esquema terapéutico.
La paleo-oncología es el estudio de carcinomas y sarcomas en animales, poblaciones humanas antiguas y sus precursores homínidos. Estas poblaciones resultan informativas sobre las posibles influencias ...en el cáncer de la evolución morfológica y funcional, la dieta, el estilo de vida y otros factores ambientales. La prevalencia del cáncer en poblaciones antiguas podría haber diferido de la de los humanos modernos, debido a diferencias sustanciales en la exposición a agresores externos, por el envejecimiento, y la disponibilidad de las intervenciones terapéuticas contemporáneas. Los datos físicos disponibles sobre el cáncer en la antigüedad incluyen la evidencia de su existencia en fósiles de animales y humanos, y en sus precursores. Las dificultades de la investigación paleo-oncológica incluyen un registro tisular limitado. Al evaluar el cáncer en restos antiguos, también se debe abordar el problema de la pseudopatología, en la que un cambio tisular observado puede representar una lesión tumoral antemortem o un artefacto postmortem. Los descubrimientos arqueológicos futuros y la aplicación de técnicas de diagnóstico mejoradas pueden permitir que la paleo-oncología proporcione contribuciones a nuestra comprensión actual del cáncer.
Las arritmias cardiacas son complicaciones frecuentes durante el embarazo en mujeres consideradas previamente sanas, con o sin cardiopatía orgánica de base, siendo más comunes las triculares. Su ...manejo un desafío por el elevado riesgo de presentar eventos adversos maternos y fetales, tanto por la arritmia en sí misma, como por los medicamentos usados para el tratamiento. Se relata el caso clínico de una paciente obstétrica de 24 años con embarazo de 18.3 semanas, que desarrolla fibrilación auricular con descompensación hemodinámica durante su estancia hospitalaria, a consecuencia de sepsis de origen urinario. Se realiza tratamiento farmacológico, presentando tanto la madre como el feto una evolución favorable. El embarazo puede asociarse con arritmias potencialmente letales y la conducta a adoptar debe ser inmediata buscando salvaguardar el bienestar materno-fetal. La literatura es escasa acerca del manejo de arritmias durante el embarazo, se propone analizar los elementos para el correcto miento de la auricular durante la gestación.
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