Global-scale magnetosphere convection driven by dayside magnetic reconnection.

Plasma convection on a global scale is a fundamental feature of planetary magnetosphere. The Dungey cycle explains that steady-state convection within the closed part of the magnetosphere relies on magnetic reconnection in the nightside magnetospheric tail. Nevertheless, time-dependent models of the Dungey cycle suggest an alternative scenario where magnetospheric convection can be solely driven by dayside magnetic reconnection. In this study, we provide direct evidence supporting the scenario of dayside-driven magnetosphere convection. The driving process is closely connected to the evolution of Region 1 and Region 2 field-aligned currents. Our global simulations demonstrate that intensified magnetospheric convection and field-aligned currents progress from the dayside to the nightside within 10-20 minutes, following a southward turning of the interplanetary magnetic field. Observational data within this short timescale also reveal enhancements in both magnetosphere convection and the ionosphere's two-cell convection. These findings provide insights into the mechanisms driving planetary magnetosphere convection, with implications for the upcoming Solar-Wind-Magnetosphere-Ionosphere Link Explorer (SMILE) mission.

Solving the Power Flow Problem in Bipolar DC Asymmetric Distribution Networks Using Broyden's Method.

This research addresses the power flow analysis in bipolar asymmetric direct current (DC) networks by applying Broyden's numerical method. This general successive approximations method allows for a simple Newton-based recursive formula to reach the roots of multiple nonlinear equations. The main advantage of Broyden's approach is its simple but efficient structure which can be applied to real complex nonlinear equations.The power flow problem in bipolar DC networks is still challenging, as multiple operating options must be considered, e.g., the possibility of having a solidly grounded or floating neutral wire. The main goal of this research is to contribute with a generalization of Broyden's method for the power flow solution in bipolar DC networks, with the main advantage that, under well-defined conditions, this is a numerical method equivalent to the matricial backward/forward power flow, which is equivalent to the successive approximations power flow method. Numerical results in the 21-, 33-, and 85-bus grids while considering two connections for the neutral wire (i.e., solidly grounded at any node or floating) show the effectiveness of Broyden's method in the power flow solution for bipolar asymmetric DC networks. All numerical simulations were carried out in the MATLAB programming environment.

Recovery of a learned behavior despite partial restoration of neuronal dynamics after chronic inactivation of inhibitory neurons.

Maintaining motor skills is crucial for an animal's survival, enabling it to endure diverse perturbations throughout its lifespan, such as trauma, disease, and aging. What mechanisms orchestrate brain circuit reorganization and recovery to preserve the stability of behavior despite the continued presence of a disturbance? To investigate this question, we chronically silenced a fraction of inhibitory neurons in a brain circuit necessary for singing in zebra finches. Song in zebra finches is a complex, learned motor behavior and central to reproduction. This manipulation altered brain activity and severely perturbed song for around two months, after which time it was precisely restored. Electrophysiology recordings revealed abnormal offline dynamics, resulting from chronic inhibition loss, some aspects of which returned to normal as the song recovered. However, even after the song had fully recovered, the levels of neuronal firing in the premotor and motor areas did not return to a control-like state. Single-cell RNA sequencing revealed that chronic silencing of interneurons led to elevated levels of microglia and MHC I, which were also observed in normal juveniles during song learning. These experiments demonstrate that the adult brain can overcome extended periods of abnormal activity, and precisely restore a complex behavior, without recovering normal neuronal dynamics. These findings suggest that the successful functional recovery of a brain circuit after a perturbation can involve more than mere restoration to its initial configuration. Instead, the circuit seems to adapt and reorganize into a new state capable of producing the original behavior despite the persistence of some abnormal neuronal dynamics.

The impact of a two-year long COVID-19 public health restriction program on mechanical thrombectomy outcomes in a stroke network.

OBJECTIVE: The purpose of this study was to evaluate the impact of COVID-19 pandemic public health restrictions on our drip and ship mechanical thrombectomy program in Santiago Chile. MATERIALS AND METHODS: This was a retrospective analysis of a prospectively collected database comparing two cohorts, one during a two-year period before COVID-19 and the second during the two years of the pandemic at our metropolitan stroke program. RESULTS: A total of 100 patients were included in the pre COVID-19 cohort (cohort 1) and 121 in the COVID-19 cohort (cohort 2). There was a significant difference between cohorts, with older patients, different occlusion sites and higher door to arterial puncture time during the COVID-19 period. A non-significant trend for worse 90-day outcomes and higher mortality was present in cohort 2. There were no statistical differences in safety treatment parameters. CONCLUSIONS: COVID-19 pandemic has had a measurable impact on our mechanical thrombectomy program. Results showed similarities to other reported Latin American series, where less robust health systems could adapt less efficiently compared to developed countries. After two years of public health restrictions, there were changes in the treatment population characteristics, delay in some internal management metrics and a non-significant trend to worse 90-day outcomes and higher mortality.

Predictive models for starting antiseizure medication withdrawal following epilepsy surgery in adults.

More than half of adults with epilepsy undergoing resective epilepsy surgery achieve long-term seizure freedom and might consider withdrawing antiseizure medications. We aimed to identify predictors of seizure recurrence after starting postoperative antiseizure medication withdrawal and develop and validate predictive models. We performed an international multicentre observational cohort study in nine tertiary epilepsy referral centres. We included 850 adults who started antiseizure medication withdrawal following resective epilepsy surgery and were free of seizures other than focal non-motor aware seizures before starting antiseizure medication withdrawal. We developed a model predicting recurrent seizures, other than focal non-motor aware seizures, using Cox proportional hazards regression in a derivation cohort (n = 231). Independent predictors of seizure recurrence, other than focal non-motor aware seizures, following the start of antiseizure medication withdrawal were focal non-motor aware seizures after surgery and before withdrawal [adjusted hazard ratio (aHR) 5.5, 95% confidence interval (CI) 2.7-11.1], history of focal to bilateral tonic-clonic seizures before surgery (aHR 1.6, 95% CI 0.9-2.8), time from surgery to the start of antiseizure medication withdrawal (aHR 0.9, 95% CI 0.8-0.9) and number of antiseizure medications at time of surgery (aHR 1.2, 95% CI 0.9-1.6). Model discrimination showed a concordance statistic of 0.67 (95% CI 0.63-0.71) in the external validation cohorts (n = 500). A secondary model predicting recurrence of any seizures (including focal non-motor aware seizures) was developed and validated in a subgroup that did not have focal non-motor aware seizures before withdrawal (n = 639), showing a concordance statistic of 0.68 (95% CI 0.64-0.72). Calibration plots indicated high agreement of predicted and observed outcomes for both models. We show that simple algorithms, available as graphical nomograms and online tools (predictepilepsy.github.io), can provide probabilities of seizure outcomes after starting postoperative antiseizure medication withdrawal. These multicentre-validated models may assist clinicians when discussing antiseizure medication withdrawal after surgery with their patients.

Características de la infección por SARS-CoV-2 en niños y adolescentes asistidos durante el primer año de la pandemia en un prestador privado de salud de Montevideo / Characteristics of the SARS-CoV-2 infection during the first year of the pandemic in children and adolescents assisted at a private health provider in Montevideo / Características da infecção por SARS-CoV-2 em crianças e adolescentes durante o primeiro ano da pandemia atendidas por uma assistência de saúde privada em Montevidéu

Introducción: las infecciones respiratorias agudas virales suelen ser más frecuentes en niños que en adultos. Sin embargo, en el caso de la COVID-19 la mayoría de los casos pediátricos son leves o asintomáticos. Objetivo: describir las características clínicas y epidemiológicas de los niños con COVID-19 asistidos en un prestador de salud de Montevideo durante el primer año de la pandemia. Material y métodos: estudio descriptivo retrospectivo. Inclusión: pacientes menores de 15 años con reacción en cadena de la polimerasa en tiempo real (RT-PCR) positiva para SARS-CoV-2 entre el 13/3/2020 y el 31/03/2021. Principales variables: sintomatología, comorbilidades, nexo epidemiológico y generación de casos secundarios. Resultados: se realizaron 6.642 RT-PCR para SARS-CoV-2, 486 fueron positivas (7%). El 94% se diagnosticaron entre 12/2020 y 3/2021. Los síntomas respiratorios fueron los más frecuentes en el 98% de los casos sintomáticos. Un 60% presentaron fiebre. El 94% habían tenido contacto con un caso confirmado de COVID-19, 57% intradomiciliario, 31% en centro educativo, y 10% en actividades sociales. El 86% de los contactos eran adultos. Doscientos quince niños fueron el caso índice en el hogar y 73 (34%) generaron casos secundarios intradomiciliarios. Conclusiones: los resultados describen la situación clínica y epidemiológica de una población pediátrica de Montevideo durante el primer año de la pandemia. Dado los cambios constantes en la dinámica de transmisión y de casos es necesario continuar con la vigilancia y realización de este tipo de estudios para ajustar las definiciones de caso sospechoso y racionalizar la indicación de testeo.

Introduction: viral acute respiratory infections are usually more frequent and severe in children than in adults. However, in the case of COVID-19, most pediatric cases are mild or asymptomatic. Objective: describe the clinical and epidemiological characteristics of children with COVID-19 assisted by a health provider in Montevideo, during the first year of the pandemic. Materials and methods: retrospective descriptive study. Sample: patients under 15 years of age with positive RT-PCR for SARS-CoV-2 between 3/13/2020-03/31/2021. Main variables: symptomatology, comorbidities, epidemiological link and generation of secondary cases. Results: 6,642 RT-PCR tests were performed for SARS-CoV-2, 486 positive (7%). 94% were diagnosed between 12/2020 and 3/2021. Respiratory symptoms were the most frequent in 98% of symptomatic cases. 60% had fever. 94% had had contact with a confirmed case of COVID-19, 57% intra-domiciliary, 31% at educational centers, and 10% got infected during social activities. 86% of the contacts were adults. Two hundred and fifteen children were the initial case at the household and 73 (34%) generated secondary intra-domiciliary cases. Conclusions: the results describe the clinical and epidemiological situation of a pediatric population in Montevideo during the first year of the pandemic. Given the constant changes in the transmission dynamics and cases, it is necessary to continue to monitor and perform this type of study to adjust the definitions of suspected cases and rationalize testing prescriptions.

Introdução: as infecções respiratórias virais agudas são, geralmente, mais frequentes e graves em crianças do que em adultos. No entanto, no caso da COVID-19, a maioria dos casos pediátricos é leve ou assintomática. Objetivo: descrever as características clínicas e epidemiológicas de crianças com COVID-19 atendidas por uma Assistência de Saúde em Montevidéu, durante o primeiro ano da pandemia. Materiais e métodos: estudo descritivo retrospectivo. Amostra: pacientes menores de 15 anos de idade com RT-PCR positivo para SARS- CoV-2 entre 13/03/2020-31/03/2021. Variáveis principais: sintomatologia, comorbidades, vínculo epidemiológico e geração de casos secundários. Resultados: 6.642 RT-PCR foram realizados para SARS- CoV-2, 486 positivos (7%). 94% foram diagnosticados entre 12/2020 e 3/2021. Os sintomas respiratórios foram os mais frequentes em 98% dos casos sintomáticos. 60% tiveram febre. 94% tiveram contato com caso confirmado de COVID-19, 57% intradomiciliar, 31% em centros educacionais e 10% durante atividades sociais. 86% dos contatos foram adultos. Duzentas e quinze crianças foram o caso inicial do lar e 73 (34%) geraram casos secundários intradomiciliares. Conclusões: os resultados descrevem a situação clínica e epidemiológica de uma população pediátrica em Montevidéu durante o primeiro ano da pandemia. Dadas as constantes mudanças na dinâmica de transmissão e de casos, é necessário continuar monitorando e realizando esse tipo de estudo para ajustar as definições de casos suspeitos e racionalizar a indicação de testagem.

Síndrome inflamatorio multisistémico post-COVID en niños: reporte de casos en Montevideo, Uruguay, 2020-2021 / Multsystemic inflammatory syndrome in post-Covid children: clinical case studies in Montevideo, Uruguay, 2020-2021 / Sindrome inflamatório multisistêmico pós-COVID em crianças: relato de casos em Montevdéu, Uruguai, 2020-2021

El síndrome inflamatorio multisistémico asociado a COVID-19 es una presentación postinfecciosa, que puede ser particularmente grave, pudiendo producir una severa disfunción multiorgánica. Se presenta una serie de 6 casos clínicos, asistidos en Servicio Médico Integral, Montevideo-Uruguay, con el fin de exponer las características clínicas y paraclínicas de este nuevo síndrome, y la evolución clínica de los mismos. Se realiza un estudio observacional descriptivo. La edad media fue de 6 años, con predominio en sexo femenino. Estos pacientes tuvieron una presentación clínica leve a moderada, con buena evolución Las manifestaciones clínicas principales fueron: fiebre, compromiso gastrointestinal, mucocutáneo y afectación ocular; dos de estos pacientes presentaron compromiso cardiovascular. Todos tuvieron alteraciones en la paraclínica, destacándose reactantes de fase aguda elevados. Todos los pacientes recibieron inmunoglobulina intravenosa y corticoides, tres de ellos recibieron heparina de bajo peso molecular por valor de D-dímeros 5 veces por encima del valor de referencia. No descartamos el impacto del diagnóstico y tratamiento precoz en la buena evolución de estos niños.

The Multisystem Inflammatory Syndrome associated with COVID-19 is a postinfectious presentation, which can be particularly serious, and can produce severe multiorgan dysfunction. A report of 6 clinical cases, assisted in the Comprehensive Medical Service, Montevideo-Uruguay, is presented in order to expose the clinical and paraclinical characteristics of this new syndrome, and their clinical evolution. A descriptive observational study was carried out. The mean age was 6 years, with a predominance of females. These patients had a mild to moderate clinical presentation, with good evolution. The main clinical manifestations were: fever, gastrointestinal and mucocutaneous involvement, and ocular involvement; two of these patients had cardiovascular compromise. All had alterations in the paraclinical, standing out elevated acute phase reactants. All patients received intravenous immunoglobulin and corticosteroids, three of them received low molecular weight heparin with a value of D-dimers 5 times higher than the reference value. We do not rule out the impact of early diagnosis and treatment on the positive evolution of these children.

A Síndrome Inflamatória Multissistêmica associada à COVID-19 é uma apresentação pósinfecciosa, que pode ser particularmente grave e produzir disfunção grave de múltiplos órgãos. Apresentamos um relato de 6 casos clínicos, atendidos no Serviço Médico Integral, Montevidéu-Uruguai, com o objetivo de expor as características clínicas e para clínicas desta nova síndrome, e sua evolução clínica. Tratase de um estudo observacional descritivo. A média de idade foi de 6 anos, com predomínio do sexo feminino. Esses pacientes tinham apresentação clínica leve a moderada, com boa evolução. As principais manifestações clínicas foram: febre, envolvimento gastrointestinal, muco cutâneo e ocular; dois desses pacientes apresentaram comprometimento cardiovascular. Todos apresentavam alterações para clínicas, destacandose elevados reagentes na fase aguda. Todos os pacientes receberam imunoglobulina e corticosteroides endovenosos, três deles receberam heparina de baixo peso molecular com valor do dímero D 5 vezes acima do valor de referência. Não descartamos o impacto do diagnóstico e tratamento precoces na evolução positiva dessas crianças.

Sensorless Adaptive Voltage Control for Classical DC-DC Converters Feeding Unknown Loads: A Generalized PI Passivity-Based Approach.

The problem of voltage regulation in unknown constant resistive loads is addressed in this paper from the nonlinear control point of view for second-order DC-DC converters. The converters' topologies analyzed are: (i) buck converter, (ii) boost converter, (iii) buck-boost converter, and (iv) non-inverting buck-boost converter. The averaging modeling method is used to model these converters, representing all these converter topologies with a generalized port-Controlled Hamiltonian (PCH) representation. The PCH representation shows that the second-order DC-DC converters exhibit a general bilinear structure which permits to design of a passivity-based controller with PI actions that ensures the asymptotic stability in the sense of Lyapunov. A linear estimator based on an integral estimator that allows reducing the number of current sensors required in the control implementation stage is used to determine the value of the unknown resistive load. The main advantage of this load estimator is that it ensures exponential convergence to the estimated variable. Numerical simulations and experimental validations show that the PI passivity-based control allows voltage regulation with first-order behavior, while the classical PI controller produces oscillations in the controlled variable, significantly when the load varies.

Breaking the breach in Latin America: A pilot study of mechanical thrombectomy in the public healthcare system in Chile.

BACKGROUND: Mechanical Thrombectomy (MT) is the standard of care for treatment of large vessel occlusion stroke. Until the beginning of 2020 MT was not funded nor widely implemented at the public healthcare level in Chile. OBJECTIVE: To describe the results of a pilot program created to provide access to public MT in Santiago - Chile. METHODS: Analysis from a prospectively collected database of MT cases performed between September 2017 and September 2019 in one center. A stroke network was developed with a single MT capable stroke center and five primary stroke centers. The primary efficacy endpoint was the rate of functional independence (mRS 0-2) at 90 days. Successful reperfusion was defined as 2 b-3 according to the thrombolysis in cerebral infarction scale. Safety outcomes include the rates of symptomatic intracranial hemorrhage and 90-day mortality. RESULTS: A total of 100 patients were treated over the study period. Their mean age was 62.8 ± 11.8 years and median baseline National Institute of Health Stroke Scale (NIHSS) measurement was 17. Seventy-seven percent of the patients received intra venous thrombolysis. Successful reperfusion was achieved in 95% of the cases. NIHSS at 24 hours showed a median drop of 7 points from baseline (p < 0.00001) and 50% of the follow-up patients were functionally independent at 90 days. Symptomatic Intracerebral hemorrhage occurred in 5% of the patients and 90-day all case mortality was 11%. CONCLUSIONS: We demonstrated the feasibility of a publicly funded MT program in Chile, with similar results as other international randomized control trials.

Macropinocytosis-mediated membrane recycling drives neural crest migration by delivering F-actin to the lamellipodium.

Individual cell migration requires front-to-back polarity manifested by lamellipodial extension. At present, it remains debated whether and how membrane motility mediates this cell morphological change. To gain insights into these processes, we perform live imaging and molecular perturbation of migrating chick neural crest cells in vivo. Our results reveal an endocytic loop formed by circular membrane flow and anterograde movement of lipid vesicles, resulting in cell polarization and locomotion. Rather than clathrin-mediated endocytosis, macropinosomes encapsulate F-actin in the cell body, forming vesicles that translocate via microtubules to deliver actin to the anterior. In addition to previously proposed local conversion of actin monomers to polymers, we demonstrate a surprising role for shuttling of F-actin across cells for lamellipodial expansion. Thus, the membrane and cytoskeleton act in concert in distinct subcellular compartments to drive forward cell migration.

Persistence of neuronal representations through time and damage in the hippocampus.

How do neurons encode long-term memories? Bilateral imaging of neuronal activity in the mouse hippocampus reveals that, from one day to the next, ~40% of neurons change their responsiveness to cues, but thereafter only 1% of cells change per day. Despite these changes, neuronal responses are resilient to a lack of exposure to a previously completed task or to hippocampus lesions. Unlike individual neurons, the responses of which change after a few days, groups of neurons with inter- and intrahemispheric synchronous activity show stable responses for several weeks. The likelihood that a neuron maintains its responsiveness across days is proportional to the number of neurons with which its activity is synchronous. Information stored in individual neurons is relatively labile, but it can be reliably stored in networks of synchronously active neurons.

In Vivo Quantitative Imaging Provides Insights into Trunk Neural Crest Migration.

Neural crest (NC) cells undergo extensive migrations during development. Here, we couple in vivo live imaging at high resolution with custom software tools to reveal dynamic migratory behavior in chick embryos. Trunk NC cells migrate as individuals with both stochastic and biased features as they move dorsoventrally to form peripheral ganglia. Their leading edge displays a prominent fan-shaped lamellipodium that reorients upon cell-cell contact. Computational analysis reveals that when the lamellipodium of one cell touches the body of another, the two cells undergo "contact attraction," often moving together and then separating via a pulling force exerted by lamellipodium. Targeted optical manipulation shows that cell interactions coupled with cell density generate a long-range biased random walk behavior, such that cells move from high to low density. In contrast to chain migration noted at other axial levels, the results show that individual trunk NC cells navigate the complex environment without tight coordination between neighbors.

Infecciones respiratorias agudas bajas en niños menores de 2 años: hospitalizaciones durante el invierno del año 2014 / Low acute respiratory infections in children under 2 years: 2014 winter hospitalizations / Infecções agudas das vias respiratórias inferiores em crianças menores de 2 anos: hospitalizações em 2014

Durante el invierno las infecciones respiratorias agudas bajas (IRAB) determinan un incremento en la demanda asistencial, afectando sobre todo a los niños más pequeños. El objetivo de la investigación fue describir las características clínicas, modalidades de tratamiento y evolución de los menores de 2 años hospitalizados en el Hospital Pediátrico-Centro Hospitalario Pereira Rossell por IRAB de etiología viral durante el invierno de 2014. Se realizó un estudio descriptivo, retrospectivo, describiendo las características de los menores de 2 años hospitalizados del 9/6 al 21/9/2014 por IRAB de probable etiología viral. Se describieron las características epidemiológicas y clínicas, el tratamiento realizado y la evolución de los pacientes. En el período evaluado egresaron 742 niños (34% de los egresos de la institución). Tenían una mediana de edad de 4 meses; 18% presentaba al menos un factor de riesgo de IRAB grave. Se identificó al virus respiratorio sincicial en 59,6%. La estadía hospitalaria tuvo una mediana de 4 días. En las salas de cuidados moderados se aplicó ventilación no invasiva a 46 niños, y oxigenación de alto flujo a 129 niños, logrando una mejoría clínica en el 87,0% y el 87,6% respectivamente. Ingresaron a unidades de cuidados intensivos 217 niños, 54% requirió asistencia ventilatoria mecánica. Dos pacientes fallecieron. En el período evaluado los niños pequeños con IRAB representaron una importante proporción de los egresos, con importante carga asistencial. La mayoría eran niños sin factores de riesgo. La aplicación de las técnicas de tratamiento en cuidados moderados fue efectiva, permitiendo disminuir la demanda de camas de cuidados intensivos.

During the winter, low acute respiratory infections (LARI) determine an increase in care demand, especially affecting younger children. The objective of the research was to describe the clinical characteristics, treatment modalities and evolution of children under 2 years of age hospitalized at the Hospital Pediátrico-Centro Hospitalario Pereira Rossell for viral etiology LARI during the 2014 winter. A descriptive, retrospective study was conducted, describing the characteristics of children under 2 years hospitalized between 9/6 and 9/21/2014 for LARI of probable viral etiology. The following features were described: epidemiological and clinical characteristics, treatment performed and patient's evolution. During the period evaluated, 742 children were discharged (34% of the institution's admissions). They had a median age of 4 months; 18% had at least one risk factor for severe LARI. Respiratory syncytial virus was identified in 59.6%. The hospital stay had a median of 4 days. In moderate care rooms noninvasive ventilation was applied to 46 children, and high flow oxygenation to 129 children, achieving clinical improvement in 87.0% and 87.6%, respectively. Two hundred and seventeen children were admitted 54% required mechanical ventilation. Two patients died. In the evaluated period small children with LARI represented a significant proportion of the discharges, with an important burden of care. The majority were children without risk factors. The application of treatment techniques in moderate care was effective, allowed a decrease in the demand for intensive care beds.

Durante o inverno, as infecções respiratórias agudas baixas (IRAB) determinam o aumento da demanda de cuidados, afetando especialmente as crianças menores. O objetivo da pesquisa foi descrever as características clínicas, as modalidades de tratamento e a evolução de crianças menores de dois anos hospitalizados no Hospital Pediátrico-Centro Hospitalario Pereira Rossell devido a IRAB de etiologia viral, durante o inverno de 2014. Foi realizado um estudo descritivo e retrospectivo, descrevendo as características das crianças menores de 2 anos hospitalizadas entre 9/6 e 21/9/2014 devido a IRAB de provável etiologia viral. Descreveram-se: características epidemiológicas e clínicas, tratamento realizado e evolução dos pacientes. Durante o período avaliado, 742 crianças foram hospitalizadas (34% dos ingressos da instituição). Tinham uma idade média de 4 meses; 18% tinham pelo menos um fator de risco para IRAB severa. O vírus sincicial respiratório foi identificado em 59,6%. A estadia hospitalaria teve uma mediana de 4 dias. Em salas de cuidados moderados, a ventilação não invasiva foi aplicada a 46 crianças e a oxigenação de alto fluxo a 129 crianças, atingindo melhora clínica em 87,0% e 87,6%, respectivamente. Foram internadas em unidades de terapia intensiva 217 crianças, 54% necessitaram de ventilação mecânica. Dois pacientes faleceram. No período avaliado, as crianças pequenas com IRAB representaram uma proporção significativa das despesas, com um carga importante de atendimento. A maioria carecia de fatores de risco. A aplicação de técnicas de tratamento em cuidados moderados foi eficaz, permitindo uma diminuição da demanda por leitos de terapia intensiva.

Insights from ion mobility-mass spectrometry, infrared spectroscopy, and molecular dynamics simulations on nicotinamide adenine dinucleotide structural dynamics: NAD+vs. NADH.

Nicotinamide adenine dinucleotide (NAD) is found in all living cells where the oxidized (NAD+) and reduced (NADH) forms play important roles in many enzymatic reactions. However, little is known about NAD+ and NADH conformational changes and kinetics as a function of the cell environment. In the present work, an analytical workflow is utilized to study NAD+ and NADH dynamics as a function of the organic content in solution using fluorescence lifetime spectroscopy and in the gas-phase using trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) and infrared multiple photon dissociation (IRMPD) spectroscopy. NAD solution time decay studies showed a two-component distribution, assigned to changes from a "close" to "open" conformation with the increase of the organic content. NAD gas-phase studies using nESI-TIMS-MS displayed two ion mobility bands for NAD+ protonated and sodiated species, while four and two ion mobility bands were observed for NADH protonated and sodiated species, respectively. Changes in the mobility profiles were observed for NADH as a function of the starting solution conditions and the time after desolvation, while NAD+ profiles showed no dependence. IRMPD spectroscopy of NAD+ and NADH protonated species in the 800-1800 and 3200-3700 cm-1 spectral regions showed common and signature bands between the NAD forms. Candidate structures were proposed for NAD+ and NADH kinetically trapped intermediates of the protonated and sodiated species, based on their collision cross sections and IR profiles. Results showed that NAD+ and NADH species exist in open, stack, and closed conformations and that the driving force for conformational dynamics is hydrogen bonding of the N-H-O and O-H-O forms with ribose rings.

Electron-Scale Quadrants of the Hall Magnetic Field Observed by the Magnetospheric Multiscale spacecraft during Asymmetric Reconnection.

An in situ measurement at the magnetopause shows that the quadrupole pattern of the Hall magnetic field, which is commonly observed in a symmetric reconnection, is still evident in an asymmetric component reconnection, but the two quadrants adjacent to the magnetosphere are strongly compressed into the electron scale and the widths of the remaining two quadrants are still ion scale. The bipolar Hall electric field pattern generally created in a symmetric reconnection is replaced by a unipolar electric field within the electron-scale quadrants. Furthermore, it is concluded that the spacecraft directly passed through the inner electron diffusion region based on the violation of the electron frozen-in condition, the energy dissipation, and the slippage between the electron flow and the magnetic field. Within the inner electron diffusion region, magnetic energy was released and accumulated simultaneously, and it was accumulated in the perpendicular directions while dissipated in the parallel direction. The localized thinning of the current sheet accounts for the energy accumulation in a reconnection.

Synthesis, gallium labelling and characterization of P04087, a functionalized phosphatidylserine-binding peptide.

BACKGROUND: Radiolabeled phosphatidylserine (PS)-binding peptides represent an innovative strategy for molecular imaging of apoptosis and thrombus. The hexapeptide PGDLSR was described as a selective and high affinity ligand for PS. In this work, we synthesized and evaluated a gallium labelled-PGDLSR peptide as a potential and selective radiopharmaceutical for nuclear imaging. PGDLSR-ß-alanine-NODAGA (P04087) was prepared using Fmoc-based synthesis and then chelated with cold gallium, 68Ga and 67Ga. The affinity of Ga-P04087 for PS was evaluated by a competitive binding assay using biotinylated AnnexinV. The in vitro stability of the radiotracer was checked at room temperature and after incubation in human serum at 37 °C with and without a metalloprotease inhibitor. The in vivo binding of 67Ga-P04087 to phosphatidylserine was evaluated in a rat model of infective endocarditis. RESULTS: PGDLSR was successfully prepared with a yield of 31%. P04087 was obtained with a yield of 28% and in high chemical purity (>95%). The radiochemical purities of 67Ga-P04087 and 68Ga-P04087 exceeded 98% in all cases. IC50 of P04087 and Ga-P04087 were in the same order of magnitude (10-7M). The radiolabelled product was stable for 24 h at room temperature, but was very rapidly degraded in human serum in the absence of a protease inhibitor, which had a stabilizing effect. No focal uptake could be detected visually in the cardiac area on SPECT images. On autoradiography however, a focal uptake of 67Ga-P04087 in the valve area was present and histological slices demonstrated localization of peptide binding at the peripheral layer of vegetations. CONCLUSION: In spite of the preservation of the peptide affinity to the PS after its conjugation to the NODAGA chelator, and of the presence of 67Ga-P04087 uptake on autoradiography, the absence of detectable foci in vivo in the valve area may be attributed to both the low intensity of the signal and the presence of background activity originating from blood pool and surrounding tissues in the living animals. Further modifications are necessary to design a radiolabeled peptide with higher binding potencies to PS while possessing enhanced metabolic stability in vivo.

Fluorescently labeled circular DNA molecules for DNA topology and topoisomerases.

DNA topology plays essential roles in several fundamental biological processes, such as DNA replication, recombination, and transcription. Typically agarose gel electrophoresis is employed to study DNA topology. Since gel electrophoresis is time-consuming and labor intensive, it is desirable to develop other methods, such as fluorescence-based methods, for such studies. In this paper we report the synthesis of a type of unique fluorescence-labeled DNA molecules that can be used to study DNA topology and topoisomerases by fluorescence resonance energy transfer (FRET). Specifically, we inserted an 82 nt. synthetic DNA oligomer FL905 carrying a 42 nt. AT sequence with fluorescein and dabcyl labels into a gapped DNA molecule to generate relaxed and supercoiled pAB1_FL905. Since the fluorescence intensity of pAB1_FL905 is dependent on its supercoiling status, pAB1_FL905 is a powerful tool to study DNA topology and topoisomerases by FRET. pAB1_FL905 can also be developed into rapid and efficient high-throughput screening assays to identify inhibitors that target various DNA topoisomerases.

Characterization of the Photophysical, Thermodynamic, and Structural Properties of the Terbium(III)-DREAM Complex.

DREAM (also known as K(+) channel interacting protein 3 and calsenilin) is a calcium binding protein and an active modulator of KV4 channels in neuronal cells as well as a novel Ca(2+)-regulated transcriptional modulator. DREAM has also been associated with the regulation of Alzheimer's disease through the prevention of presenilin-2 fragmentation. Many interactions of DREAM with its binding partners (Kv4, calmodulin, DNA, and drugs) have been shown to be dependent on calcium. Therefore, understanding the structural changes induced by binding of metals to DREAM is essential for elucidating the mechanism of signal transduction and biological activity of this protein. Here, we show that the fluorescence emission and excitation spectra of the calcium luminescent analogue, Tb(3+), are enhanced upon binding to the EF-hands of DREAM due to a mechanism of energy transfer between Trp and Tb(3+). We also observe that unlike Tb(3+)-bound calmodulin, the luminescence lifetime of terbium bound to DREAM decays as a complex multiexponential (τaverage ∼ 1.8 ms) that is sensitive to perturbation of the protein structure and drug (NS5806) binding. Using isothermal calorimetry, we have determined that Tb(3+) binds to at least three sites with high affinity (Kd = 1.8 µM in the presence of Ca(2+)) and displaces bound Ca(2+) through an entropically driven mechanism (ΔH ∼ 12 kcal mol(-1), and TΔS ∼ 22 kcal mol(-1)). Furthermore, the hydrophobic probe 1,8-ANS shows that Tb(3+), like Ca(2+), triggers the exposure of a hydrophobic surface on DREAM, which modulates ligand binding. Analogous to Ca(2+) binding, Tb(3+) binding also induces the dimerization of DREAM. Secondary structural analyses using far-UV circular dichroism and trapped ion mobility spectrometry-mass spectrometry reveal that replacement of Ca(2+) with Tb(3+) preserves the folding state with minimal changes to the overall structure of DREAM. These findings pave the way for further investigation of the metal binding properties of DREAM using lanthanides as well as the study of DREAM-protein complexes by lanthanide resonance energy transfer or nuclear magnetic resonance.