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OBJECTIVE: This study aimed to estimate amyotrophic lateral sclerosis (ALS) incidence and survival rates in the Metropolitan region of Chile. METHODS: We conducted a cohort study of ALS cases in the Metropolitan Region from 2016 to 2019. A total of 219 ALS patients were recruited from Corporación ELA-Chile registry, in collaboration with neurologists from Sociedad de Neurología, Psiquiatría y Neurocirugía de Chile. We calculated incidence rates by sex and age and determined median survival from onset and diagnosis. Survival analysis used the Kaplan-Meier statistic, estimating hazard ratios for age, sex, time from symptom onset and from diagnosis using a Weibull regression model. All analyses were done using R 4.1.0. RESULTS: Overall, ALS diagnosis incidence was 0.97 cases per 100,000 inhabitants, peaking in the 70-79 age group and declining thereafter. The male-to-female ratio was 1.23. The median time to death from diagnosis was 2.3 years (95% confidence interval [CI]: 1.9-2.5), and from the first symptom, it was 3.1 years (95% CI: 2.8-3.5). CONCLUSIONS: This is the first population-based study reporting ALS incidence and survival rates in Chile's Metropolitan region. Incidence resembled other Latin American studies. Median survival from diagnosis and from the first symptom were in line with previous findings. Our results corroborated lower ALS rates in Latin America, consistent with prior research.

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OBJECTIVE: The Latin American Epidemiologic study of ALS (LAENALS) aims to gather data on ALS epidemiology, phenotype, and risk factors in Cuba, Chile, and Uruguay, to understand the impact of genetic and environmental factors on ALS. METHODS: A harmonized data collection protocol was generated, and a Latin-American Spanish language Register was constructed. Patient data were collected in Uruguay in 2018, in Chile from 2017 to 2019, and in Cuba between 2017 and 2018. Statistical analysis was performed using SPSS 25.0.0 software. Crude cumulative incidence, standardized incidence, and prevalence were calculated in the population aged 15 years and older. RESULTS: During 2017-2019, 90 people with ALS from Uruguay (55.6% men), 219 from Chile (54.6% men), and 49 from Cuba (55.1% men) were included. The cumulative crude incidence in 2018 was 1.73/100,000 persons in Uruguay, 1.08 in Chile and 0.195 in Cuba. Crude prevalence in 2018 was 2.19 per 100,000 persons in Uruguay, 1.39 in Chile and 0.55 in Cuba. Mean age at onset was 61.8 ± 11.96 SD years in Uruguay, 61.9 ± 10.4 SD years in Chile, and 60.21 ± 12.45 SD years in Cuba (p = 0.75). Median survival from onset was 32.43 months (21.93 - 42.36) in Uruguay, 24 months (13.5 - 33.5) in Chile, and 29 months (15 - 42.5) in Cuba (p = 0.006). CONCLUSIONS: These preliminary data from LAENALS confirm the lower incidence and prevalence of ALS in counties with admixed populations. The LAENALS database is now open to other Latin American countries for harmonized prospective data collection.

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Hydride transfer reactions involving 1,4-dihydropyridines play a central role in bioorganic chemistry as they represent an important share of redox metabolism. For this class of reactions, direct hydride transfer is the commonly accepted mechanism; however, an Alder-Ene-like pathway has been proposed as a plausible alternative. The reaction between 1,4-ditrimethylsilyl-1,4-dihydropyridine and α,ß-unsaturated nitriles is a solid candidate for this latter pathway. In this work, we perform high level ab initio and density functional theory computations to characterize the mechanism of this reaction, taking into account diverse reaction paths, and evaluating the effect of solvent polarity and variations in the chemical structure. Our analysis explains the stereochemical aspects of the reaction, characterizing the up to now unresolved spatial configurations of the predominant products, and may contribute to the understanding of enzymatic reactions involving NADP(H). The reactions are found to proceed in an asynchronous fashion, with transition states that display significant aromatic features. With this observation in mind, Alder-Ene and direct hydride transfer pathways can be understood as two extremes of a continuous mechanistic spectrum for this kind of reaction, with the analyzed systems located approximately equidistant from both ends.

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Local reactivity descriptors such as atom-condensed Fukui functions are promising computational tools to study chemical reactivity at specific sites within a molecule. Their applications have been mainly focused on isolated molecules in their most stable conformation without considering the effects of the surroundings. Here we propose to combine quantum mechanics/molecular mechanics Born-Oppenheimer molecular dynamics simulations to obtain the microstates (configurations) of a molecular system using different representations of the molecular environment and calculate Boltzmann-weighted atom-condensed local reactivity descriptors based on conceptual density functional theory. Our approach takes the conformational fluctuations of the molecular system and the polarization of its electron density by the environment into account, allowing us to analyze the effect of the molecular environment on reactivity. In this contribution, we apply the method mentioned above to the catalytic fixation of carbon dioxide by crotonyl-CoA carboxylase/reductase and study if the enzyme alters the reactivity of its substrate compared with an aqueous solution. Our main result is that the protein environment activates the substrate by the elimination of solute-solvent hydrogen bonds from aqueous solution in the two elementary steps of the reaction mechanism: the nucleophilic attack of a hydride anion from NADPH on the α,ß-unsaturated thioester and the electrophilic attack of carbon dioxide on the formed enolate species.

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Carboxylation reactions represent a very special class of chemical reactions that is characterized by the presence of a carbon dioxide (CO2 ) molecule as reactive species within its global chemical equation. These reactions work as fundamental gear to accomplish the CO2 fixation and thus to build up more complex molecules through different technological and biochemical processes. In this context, a correct description of the CO2 electronic structure turns out to be crucial to study the chemical and electronic properties associated with this kind of reactions. Here, a systematic study of CO2 electronic structure and its contribution to different carboxylation reaction electronic energies has been carried out by means of several high-level ab initio post-Hartree Fock (post-HF) and density functional theory (DFT) calculations for a set of biochemistry and inorganic systems. We have found that for a correct description of the CO2 electronic correlation energy it is necessary to include post-CCSD(T) contributions (beyond the gold standard). These high-order excitations are required to properly describe the interactions of the four π-electrons associated with the two degenerated π-molecular orbitals of the CO2 molecule. Likewise, our results show that in some reactions it is possible to obtain accurate reaction electronic energy values with computationally less demanding methods when the error in the electronic correlation energy compensates between reactants and products. Furthermore, the provided post-HF reference values allowed to validating different DFT exchange-correlation functionals combined with different basis sets for chemical reactions that are relevant in biochemical CO2 fixing enzymes. © 2019 Wiley Periodicals, Inc.

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Catechol- O-methyltransferase is an enzyme that catalyzes the methylation reaction of dopamine by S-adenosylmethionine, increasing the reaction rate by almost 16 orders of magnitude compared to the reaction in aqueous solution. Here, we combine the recently introduced adaptive string method and the mean reaction force method, in combination with the structural and electronic descriptors to characterize the reaction mechanism. The catalytic effect of the enzyme is addressed by the comparison of the reaction in the human wild-type enzyme, in the less effective Y68A mutant, and in aqueous solution. The influence of these different environments at different stages of the chemical process and the significance of the key collective variables describing the reaction were quantified. Our results show that the native enzyme limits the access of water molecules to the active site, enhancing the interaction between the reactants and providing a more favorable electrostatic environment to assist the SN2 methyl transfer reaction.

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Methyl transfer reactions play an important role in biology and are catalyzed by various enzymes. Here, the influence of the molecular environment on the reaction mechanism was studied using advanced ab initio methods, implicit solvation models and QM/MM molecular dynamics simulations. Various conceptual DFT and electronic structure descriptors identified different processes along the reaction coordinate e.g. electron transfer. The results show that the polarity of the solvent increases the energy required for the electron transfer and that this spontaneous process is located in the transition state region identified by the (mean) reaction force analysis and takes place through the bonds which are broken and formed. The inclusion of entropic contributions and hydrogen bond interactions in QM/MM molecular dynamics simulations with a validated DFTB3 Hamiltonian yields activation barriers in good agreement with the experimental values in contrast to the values obtained using two implicit solvation models.

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S-Adenosylmethionine (AdoMet) is involved in many biological processes as cofactor in enzymes transferring its sulfonium methyl group to various substrates. Additionally, it is used as drug and nutritional supplement to reduce the pain in osteoarthritis and against depression. Due to the biological relevance of AdoMet it has been part of various computational simulation studies and will also be in the future. However, to our knowledge no rigorous force field parameter development for its simulation in biological systems has been reported. Here, we use electronic structure calculations combined with molecular dynamics simulations in explicit solvent to develop force field parameters compatible with the AMBER99 force field. Additionally, we propose new dynamic Hirshfeld-I atomic charges which are derived from the polarized electron density of AdoMet in aqueous solution to describe its electrostatic interactions in biological systems. The validation of the force field parameters and the atomic charges is performed against experimental interproton NOE distances of AdoMet in aqueous solution and crystal structures of AdoMet in the cavity of three representative proteins.

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Sydenham's chorea is often regarded as a relatively benign and self-limiting condition. Treatment is typically symptomatic, although occasionally immunomodulatory therapies are required in severe forms. Here we report a girl who was affected with the severe variant, chorea paralytica, who responded dramatically and rapidly to plasmapheresis, having failed other therapies.

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The objective of high activity antiretroviral therapy (HAART) in patients with AIDS, is to obtain immune restoration. This means a reduction of the viral load and restitution of the CD4 cell count. A decreased rate of HIV replication improves both the number and function of CD4 cells. Nevertheless, this treatment sometimes results in the reappearance of previous symptoms from treated conditions due to opportunistic infections (ie: tuberculosis, criptococcosis, hepatitis, Pneumocystis jirovesi, toxoplasmosis, etc) or non infectious condition such as sarcoidosis, Graves disease or Kaposi sarcoma. This is known as Inflammatory Reconstitution Immune Syndrome (IRIS). We report a 37 year-old woman in stage C3-AIDS with a previous criptococcal meningitis. She was treated, achieving a marked improvement with treatment and subsequent suppressive therapy with fluconazole 200 mg/day. IRIS appeared after 8 months of ongoing antiretroviral therapy with immune restoration with the development of aseptic meningitis and intracranial hypertension. The opportunistic agent could not be identified by cultures. Additional laboratory tests excluded toxoplasmosis, tuberculosis, bacterial cerebral abscesses, syphilitic cerebral gummas, and lymphoma. Brain CT and magnetic resonance studies were compatible with brain vasculitis and leptomeningitis. The patient condition improved with general measures, such as a repeated lumbar punctures and non steroidal anti-inflammatory drugs. We conclude that this patient had an IRIS due to a Cryptococcus neoformans antigen.

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BACKGROUND: Plasmapheresis can be useful in myasthenia gravis, Guillain Barré syndrome and chronic demyelinating inflammatory polyradiculoneuritis. AIM: To report our experience with plasmapheresis in patients with neurological diseases. MATERIAL AND METHODS: Retrospective review of plasmapheresis procedures done between 1995 and 2001, in a public hospital. Indications criteria, clinical results and technical yield were analyzed. RESULTS: One hundred fifty nine procedures were reviewed. One hundred forty (88%) were indicated for neurological diseases (44% for Guillain Barré syndrome and 29% for myasthenia gravis). Clinical improvement or eventual complications were avoided in 70% of patients with Guillain Barré syndrome and 100% of patients with myasthenia gravis. Hypotension in 10% and paresthesias in 7% were observed. All complications were successfully controlled with crystalloid or fresh plasma infusions or citrate management. In 11 cases, the procedure was interrupted due to obstruction of the venous access, that was peripheral in eight of these. The most common difficulties of the procedure were delay in performing it in 50% of patients and insufficient exchange volumes in 30%. CONCLUSIONS: Plasmapheresis was safe and useful in patients with myasthenia gravis and Guillain Barré syndrome. The drawbacks of the procedure are its costs and requirement of special equipment.

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BACKGROUND: Subacute combined degeneration is a clinical manifestation of vitamin B12 deficiency, that we observe with unusual frequency. AIM: To report a series of eleven patients with subacute combined degeneration. PATIENTS AND METHODS: Retrospective analysis of 11 patients hospitalized in a public hospital in Santiago, between March 2001 and February 2003. All had a myelopathy of more than three weeks of evolution with serum vitamin B12 levels of less than 200 pg/ml. RESULTS: A risk factor was identified in 10 cases and the most common was an age over 60 years old. The main presenting symptom was the presence of paresthesias. On admission, sphincter dysfunction, posterior column and pyramidal syndromes coexisted in nine patients. A level of sensitive deficit was detected in six. Ten patients had macrocytosis and eight were anemic. Serum vitamin B12 was measured in ten and in nine, it was below 200 pg/ml. The mean lapse between onset of symptoms and treatment was eight months. All received intramuscular vitamin B12 in doses on 1,000 to 10,000 IU/day. Sphincter dysfunction and propioception were the first symptoms to improve. CONCLUSIONS: Subacute combined degeneration must be suspected in patients older than 60 years with a subacute myelopathic syndrome and low serum vitamin B12 levels.

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Presentamos un caso de CADASIL (acrónimo inglés de arteriopatía cerebral autosómica dominante con infartos subcorticales y leucoencefalopatía), que corresponde al primero de una serie de 4 casos diagnosticados en nuestro servicio desde 1998, con correlato clínico, imageno-lógico y de ultrapatología muscular (microscopia electrónica). Se trata de una paciente mujer con historia de dos crisis isquémicas cerebrales transitorias a los 29 años, sin factores de riesgo tradicionales para patología cerebrovascular, que luego de 7 años desarrolló síntomas de tipo depresivos, asociados a un cuadro de retraimiento sicomotor y parkinsonismo de carácter progresivo y sin respuesta a terapia farmacológica convencional. En su estudio, la resonancia nuclear magnética de cerebro mostró extensas alteraciones en sustancia blanca a nivel fronto-occipital, bilaterales, hiperintensas en T2 e hipointensas en T1, cuya señal no se reforzó con gadolinio, sin efecto de masa, asociadas a leucoaraiosis, compatibles con el diagnóstico de CADASIL. El estudio de una biopsia muscular mediante microscopia electrónica, confirmó una arteriopatia con depósito de material granular osmiofílico en los vasos sanguíneos, tipo CADASIL. No encontramos antecedentes de cuadros demenciales ni cerebrovasculares sintomáticos en otros parientes de la paciente, madre, padre, tíos, abuelos, por lo que es probable que se trate de un cuadro esporádico. No realizamos estudio genético ni biopsico de los parientes asintomáticos. Las características de la paciente ilustran cuando sospechar el diagnóstico de CADASIL, aún frente a un caso aparentemente esporádico.

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Hereditary hypercoagulability has been identified as risk factor in approximately 30% of cerebral venous thrombosis cases. We report three females with this association. A 38 years old female with a history of deep venous thrombosis of the lower limb, presented with headache, vomiting and a generalized seizure. Magnetic resonance angiography showed a partial thrombosis of the left lateral and superior longitudinal venous sinuses. Coagulation study showed a resistance to activated C protein and factor V Leyden. A 42 years old woman with a history of deep venous thrombosis, presented a right hemiplegia during a hospitalization. Magnetic resonance showed a left lateral hemorrhagic infarction. Magnetic resonance angiography showed an absence of signal in three venous sinuses. Coagulation study showed a protein C deficiency. A 17 years old woman presented a right hemiparesis in the sixth day of puerperium. CAT scan showed a left frontoparietal subcortical venous infarction. Coagulation study showed an antithrombin III deficiency.

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In contrast to the reactions of Sn(NMe(2))(2) with unfunctionalized primary amines (RNH(2)), which yield the simple imido Sn(II) cubanes [SnNR](4), the reactions of 2-pyridyl or 2-pyrimidinyl amines give the mixed-oxidation-state Sn(II)/Sn(IV) double cubanes [Sn(7)(NR)(8)]. In addition to [Sn(7)[2-N(5-Mepy)](8)] x 2thf (1 x 2thf) (py = pyridine) and [Sn(7)[2-N(pm)](8)] x 0.33thf (2 x 0.33thf) (pm = pyrimidine), which were communicated previously, the syntheses and structures of the new complexes [Sn(7)[2-N(4-Mepm)](8)] x 2thf (3 x 2thf), [Sn(7)[2-N(4,6-Me(2)pm)](8)] x 4thf (4 x 4thf), [Sn(7)[2-N(4-Me-6-MeO-pm)](8)] (5), and [Sn(7)[2-N(4-MeO-6-MeO-pm)](8)] (6) are reported. Model DFT calculations on the reactions of Sn(NMe(2))(2) with 2-pmNH(2) or PhNH(2), producing the cubanes [Sn[2-N(pm)]](4) and [SnNPh](4) (respectively), and the corresponding double cubanes [Sn(7)[2-N(pm)](8)] and [Sn(7)(NPh)(8)], show that the presence of intramolecular Sn...N bonding which spans the cubane halves of the complexes is crucial to the formation of the double-cubane structure.

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Se presentan los resultados de la distribución de dosis de los trabajadores vigilados (TV) en röentgendiagnóstico médico en Cuba durante el período comprendido entre 1991 y 1994. El análisis se realizó según las recomendaciones del Comité Científico de las Naciones Unidas para el estudio de los Efectos de la Radiaciones Atómicas (UNSCEAR). Se observó una brusca disminución en el número de trabajadores expuestos a niveles mediables (TENM) a partir de 1991, se establece una gran desproporción de éstos con respecto al número de TV y se discuten sus causas. Los TENM con dosis mayores que los 3/10 del límite permisible de dosis vigente, poseen el peso de la contribución la dosis colectiva recibida por los TV en el período, con cerca del 22 porciento. Se realiza un análisis de la repercusión en los resultados del nuevo límite permisible de dosis para la exposición ocupacional. Se recomienda un mejoramiento del sistema dosimétrico y en general del sistema de protección radiológica que incrementen la calidad en el control de la exposición ocupacional en röentgendiagnóstico médico(AU)

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Se presenta la parametrización de una ecuación semiempírica de tipo exponencial-polinomial para la descripción de la transmisión de las diferentes calidades de la radiación gamma del Co-60 en medios finitos de hormigón (p = 2350 kgm(3)) y plomo. Esta ecuación unida a la expresión obtenida para la relación de dispersión, facilitaron la implementación en computadora de una solución analítica para la estimación de blindajes en locales de teleterapia con Co-60. Se obtuvo una adecuada correlación entre los valores de transmisión calculados y los datos experimentales correspondientes. El error estándar en la estimación de los parámetros para todos los casos es inferior al 1,7 por ciento, excepto para el caso de la atenuación en hormigón de la radiación dispersada según 150º que para uno de los parámetros resultó un error del 6,3 por ciento. Se comparan los espesores de blindaje obtenidos con los valores ofrecidos por el Consejo de protección contra las Radiaciones de los EE.UU. para las condiciones observándose una buena correlación. El programa de cálculo desarrollado adquiere aplicación práctica en el diseño y la comprobación de los blindajes en instalaciones de cobaltoterapia(AU)

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