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Alloying transition metals, such as Mo, into BiVO4 has emerged as the primary mechanism for improving carrier transport in this photoanode for solar fuels production. The present work establishes the generality of improving photoelectrochemical performance through co-alloying with a transition metal electron donor and a structure-modulating rare earth. Further improvement for all such alloys is obtained by annealing the oxide materials in H2, ultimately producing photoanodes with above 3 mA cm-2 photocurrent density under AM 1.5G illumination, in the top tier of compact BiVO4 films.
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The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.
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Cristalografía por Rayos X , Electrones , Rayos Láser , Catálisis , Rayos XRESUMEN
BACKGROUND AND OBJECTIVES: Evaluation of variant Creutzfeldt-Jakob disease (vCJD) diagnostic/donor screening tests is made complicated by the very limited supply of blood samples from clinically confirmed cases of vCJD. To determine appropriate access for test developers to rare Creutzfeldt-Jakob disease (CJD) blood samples, the oversight committee of the NIBSC CJD Resource Centre has developed a process and protocols detailing minimum requirements for both test sensitivity and specificity. This protocol is broadly similar to that outlined in the common technical specification (European Directive 98/79/EC). MATERIALS AND METHODS: Tests are subjected to a stepwise evaluation (step 1). vCJD tissue homogenates spiked into pooled human plasma (step 2). Blood samples from animals known to be incubating (Transmissible spongiform encephalopathy) TSE disease (scrapie/Bovine Spongiform encephalopathy (BSE)-infected sheep, BSE-infected primates) and appropriate controls (step 3). Fresh or frozen plasma from normal UK blood donors and (step 4). Plasma samples from individuals with confirmed clinical stage variant CJD (transfusion transmission) or sporadic CJD (no evidence of blood transmission). RESULTS: The assay evaluated performed with good sensitivity with vCJD-spiked tissue homogenates, poor sensitivity for ovine TSE-infected blood samples and failed with plasma from BSE-infected non-human primates and with true vCJD clinical samples. CONCLUSIONS: The test evaluated here is currently unsuitable for use in blood donor screening or diagnosis using blood.
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Donantes de Sangre , Síndrome de Creutzfeldt-Jakob/sangre , Síndrome de Creutzfeldt-Jakob/diagnóstico , Selección de Donante/métodos , Pruebas Hematológicas/métodos , Reacción a la Transfusión , Animales , Bovinos , Síndrome de Creutzfeldt-Jakob/transmisión , Encefalopatía Espongiforme Bovina/sangre , Encefalopatía Espongiforme Bovina/diagnóstico , Encefalopatía Espongiforme Bovina/transmisión , Femenino , Humanos , Plasma/química , Primates , Scrapie/sangre , Scrapie/diagnóstico , Scrapie/transmisión , Sensibilidad y Especificidad , OvinosRESUMEN
BACKGROUND AND OBJECTIVES: With four transfusion related transmissions of variant Creutzfeldt-Jakob Disease (vCJD), three of which developed clinical disease and the other died of other causes but was positive for markers of infection, there is an increased urgency to identify and implement a test for blood donor screening. With limited amounts of blood samples from vCJD cases available test evaluation is challenging. Alternative approaches are therefore needed. Control and vCJD tissues homogenates, where levels of markers of infectivity are known, were sequentially diluted in pooled human plasma. Identical sets of samples were provided blind to research groups developing diagnostic tests for vCJD; identical sample sets allows for direct comparisons of sensitivity to be made. MATERIALS AND METHODS: Control and vCJD tissue homogenates were sequentially diluted in pooled human plasma (detergent solvent treated or cryo-depleted) supplied by commercial fractionators. Dilutions of vCJD tissues were within and beyond the limits of detection previously determined by the conformation-dependent immunoassay (Cooper et al.: Vox Sang 2007;92:302-310; Bellon et al.: J Gen Virol 2003;84: 1921-1925). A number of methods were used for the analysis of the blinded panels; with background signal from the normal prion protein (PrP) being removed by digestion with proteinase, epitope protection or selective capture of PrP(tse). RESULTS: Assay sensitivities were directly compared using identical sample sets. This approach identified several transmissible spongiform encephalopathies (TSE) diagnostic tests, based on different principles, high in analytical sensitivity that reproducibly detected markers of vCJD infectivity in tissue homogenates. CONCLUSION: The approach outlined has successfully compared in vitro diagnostics assays for their sensitivity and reproducibility and is a first step toward the evaluation of an assay suitable for blood donor screening/diagnosis of vCJD.
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Síndrome de Creutzfeldt-Jakob/diagnóstico , Plasma/química , Priones/análisis , Biomarcadores/análisis , Donantes de Sangre , Química Encefálica , Estudios de Casos y Controles , Síndrome de Creutzfeldt-Jakob/sangre , Síndrome de Creutzfeldt-Jakob/etiología , Detergentes/farmacología , Humanos , Plasma/efectos de los fármacos , Bazo/químicaRESUMEN
OBJECTIVE: The purpose of this study was to establish normal fetal cardiac axis values during the first and early second trimesters of pregnancy. METHODS: This was a prospective observational cohort study in which the fetal cardiac axis was assessed during ultrasound examinations in 100 consecutive fetuses between 11 + 0 and 14 + 6 weeks of gestation. Transabdominal, and, when indicated, transvaginal, approaches were used. Intraobserver and interobserver reproducibility were calculated. RESULTS: The cardiac axis ranged from 34.5 to 56.8° (mean (SD) 47.6 ± 5.6°) in 94 fetuses with normal cardiac anatomy. The fetal cardiac axis tended to be significantly higher in fetuses at 11 + 0 to 11 + 6 weeks of gestation than in fetuses at 12 + 0 to 14 + 6 weeks of gestation. Congenital heart defects were found in six out of 100 fetuses, four of which had abnormal cardiac axis values at 11 + 0 to 14 + 6 weeks of gestation. CONCLUSION: Cardiac axis measurement is possible in the first and early second trimesters of pregnancy. The assessment of cardiac axis at an early gestational age may help to identify pregnancies at high risk for congenital heart defects. Copyright
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Arritmias Cardíacas/diagnóstico por imagen , Corazón Fetal/diagnóstico por imagen , Cardiopatías Congénitas/diagnóstico por imagen , Adulto , Arritmias Cardíacas/embriología , Ecocardiografía Doppler en Color , Femenino , Corazón Fetal/anomalías , Corazón Fetal/fisiopatología , Edad Gestacional , Cardiopatías Congénitas/embriología , Humanos , Variaciones Dependientes del Observador , Embarazo , Primer Trimestre del Embarazo , Segundo Trimestre del Embarazo , Estudios Prospectivos , Ultrasonografía Prenatal/métodosRESUMEN
BACKGROUND AND OBJECTIVES: A standard panel of materials is needed for the evaluation of assays being developed for the diagnosis of variant Creutzfeldt-Jakob disease. MATERIALS AND METHODS: Tissues from human and animals incubating transmissible spongiform encephalopathy disease have been prepared, aliquoted and where possible characterized by in vitro methods. RESULTS: A standardized preparation of materials has been generated. CONCLUSIONS: Large-scale preparations of tissues and blood fractions can be used to directly compare the sensitivities of assays using different formats.
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Síndrome de Creutzfeldt-Jakob/diagnóstico , Priones/aislamiento & purificación , Animales , Secuencia de Bases , Western Blotting/métodos , Western Blotting/normas , Química Encefálica , Síndrome de Creutzfeldt-Jakob/sangre , Síndrome de Creutzfeldt-Jakob/genética , ADN/genética , Femenino , Humanos , Inmunoensayo/métodos , Inmunoensayo/normas , Proteínas PrPSc/sangre , Proteínas PrPSc/genética , Proteínas PrPSc/aislamiento & purificación , Proteínas PrPSc/normas , Priones/sangre , Priones/genética , Priones/normas , Conformación Proteica , Estándares de Referencia , Scrapie/sangre , Scrapie/diagnóstico , Scrapie/genética , Ovinos , Bazo/química , Distribución TisularRESUMEN
BACKGROUND: health status is increasingly used as a measure of healthcare effectiveness. How diseases and symptoms are associated with health status is not completely understood. OBJECTIVES: to find diseases, symptoms and demographic factors associated with physical and mental health status in older Americans. METHODS: we analysed data from a survey of over 100 000 Medicare beneficiaries aged 65 and older. We used the short-form 36 physical and mental summary scores as measures of health status. Other data collected included demographic details, symptoms and diagnoses. RESULTS: age as a single variable explained 4% of variation in physical health status. Adding other demographic information and increased disease burden explained variation to 8% and 27% respectively. Together, shortness of breath, back pain, difficulty getting in and out of chairs, arthritis of hip or knee, a recent change in health and age explained 54% of variation. All available variables explained 59%. The role of age as an independent factor decreased markedly after disease and symptoms were considered. Similar factors were associated with lower mental health status, but age was not. CONCLUSION: these data suggest that heart and lung disease and back pain are the most important factors affecting the average physical health status of older people. Sex, marital status and race have very little independent effect. Efforts to improve average physical health status scores might best be targeted at these conditions rather than demographic characteristics. Mental health status does not decline with age, and similar factors affect it but to a lesser degree.
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Evaluación Geriátrica/estadística & datos numéricos , Psiquiatría Geriátrica , Aptitud Física/fisiología , Anciano , Anciano de 80 o más Años , Dolor de Espalda , Femenino , Cardiopatías , Humanos , Enfermedades Pulmonares , Masculino , Vigilancia de la Población/métodos , Encuestas y Cuestionarios , Estados UnidosRESUMEN
Physicians have a unique role in supporting patients and families throughout their lives; their expertise is called on not only in life, but also at its end. This study was designed to determine the effect of an individual's age, gender, and attachment to the decision maker with regard to life support choices. A total of 151 subjects completed the researcher-developed instrument. Results suggest that the age of patients is significantly related to the life support options chosen. Specifically, the greater the age of the patient, the more likely a less vigorous life support alternative was chosen. Gender and attachment had no effect on the level of care chosen. Study participants also identified reasons for selecting a particular life support choice for each case. The most common reasons given for a close relative centered around quality-of-life issues. In situations involving a nonrelative, life support decisions were likely to be made using the principle of best interest. The primary care physician has a unique opportunity to initiate discussions about life support issues with patients and families. These decisions must be framed in the context of individual patient expectations and desires throughout the life span.
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Directivas Anticipadas , Cuidados para Prolongación de la Vida/estadística & datos numéricos , Rol del Médico , Derecho a Morir , Adulto , Anciano , Actitud del Personal de Salud , Ética Médica , Femenino , Humanos , Masculino , Inutilidad Médica , Persona de Mediana Edad , Probabilidad , Muestreo , Encuestas y CuestionariosRESUMEN
OBJECTIVE: A new measurement of health care quality for Medicare beneficiaries has been implemented by the Health Care Financing Administration (HCFA). This paper describes the program, presents baseline data and highlights associated issues. DESIGN: The Health Outcomes Survey (HOS) is a longitudinal cohort mail survey. Changes in population health status after 2 years will be evaluated on an individual plan level. SETTING: Two-hundred and eighty-seven US Medicare managed care plans. MAIN OUTCOMES MEASURES: Physical component and mental component summary scales derived from the SF-36. FINDINGS: Baseline data documented lower health status in older populations, while functional limitations and disease prevalence were higher. Among different plans, mean functional levels were found to be similar, although a few plans contained populations with exceptionally low levels. These data do not support the assertion that enrolees in for-profit plans are healthier than non-profit plans. CONCLUSIONS/IMPLICATIONS: The HOS is the first large-scale program to evaluate health outcomes among older Americans. HCFA recognizes several technical and policy issues. Technical issues include possible biased reporting for subpopulations, the validity of proxy responses and respondent burden. Policy issues concern the appropriateness of using a generic measure such as the SF-36 and how much change in health status can be attributed to quality of health care. HCFA plans to extend the HOS to beneficiaries in traditional Medicare. The HOS project is expected to encourage more efforts to maintain or improve the health status of the Medicare managed care population.
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Indicadores de Salud , Programas Controlados de Atención en Salud/normas , Medicare/normas , Evaluación de Resultado en la Atención de Salud/métodos , Garantía de la Calidad de Atención de Salud/métodos , Calidad de Vida , Anciano , Centers for Medicare and Medicaid Services, U.S. , Encuestas de Atención de la Salud , Humanos , Estudios Longitudinales , Propiedad , Prevalencia , Indicadores de Calidad de la Atención de Salud , Estados Unidos/epidemiologíaRESUMEN
Expanded polyglutamine repeats have been proposed to cause neuronal degeneration in Huntington's disease (HD) and related disorders, through abnormal interactions with other proteins containing short polyglutamine tracts such as the transcriptional coactivator CREB binding protein, CBP. We found that CBP was depleted from its normal nuclear location and was present in polyglutamine aggregates in HD cell culture models, HD transgenic mice, and human HD postmortem brain. Expanded polyglutamine repeats specifically interfere with CBP-activated gene transcription, and overexpression of CBP rescued polyglutamine-induced neuronal toxicity. Thus, polyglutamine-mediated interference with CBP-regulated gene transcription may constitute a genetic gain of function, underlying the pathogenesis of polyglutamine disorders.
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Enfermedad de Huntington/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Proteínas Nucleares/metabolismo , Péptidos/metabolismo , Transactivadores/metabolismo , Transcripción Genética , Animales , Encéfalo/metabolismo , Proteína de Unión a CREB , Núcleo Celular/metabolismo , Supervivencia Celular , Células Cultivadas , Humanos , Proteína Huntingtina , Enfermedad de Huntington/genética , Ratones , Ratones Transgénicos , Mutación , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Neuronas/citología , Proteínas Nucleares/química , Proteínas Nucleares/genética , Péptidos/química , Secuencias Repetitivas de Aminoácido , Transactivadores/química , Transfección , Células Tumorales CultivadasRESUMEN
Expansion of a polyglutamine sequence in the N terminus of huntingtin is the gain-of-function event that causes Huntington's disease. This mutation affects primarily the medium-size spiny neurons of the striatum. Huntingtin is expressed in many neuronal and non-neuronal cell types, implying a more general function for the wild-type protein. Here we report that wild-type huntingtin acts by protecting CNS cells from a variety of apoptotic stimuli, including serum withdrawal, death receptors, and pro-apoptotic Bcl-2 homologs. This protection may take place at the level of caspase-9 activation. The full-length protein also modulates the toxicity of the poly-Q expansion. Cells expressing full-length mutant protein are susceptible to fewer death stimuli than cells expressing truncated mutant huntingtin.
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Apoptosis/fisiología , Caspasas/metabolismo , Proteínas del Tejido Nervioso/genética , Neuronas/citología , Neuronas/enzimología , Proteínas Nucleares/genética , Animales , Caspasa 3 , Caspasa 9 , Línea Celular Transformada , Supervivencia Celular/fisiología , Corteza Cerebral/citología , Cuerpo Estriado/citología , Regulación Enzimológica de la Expresión Génica , Etiquetado Corte-Fin in Situ , Mutagénesis/fisiología , Neuronas/química , Regiones Promotoras Genéticas/fisiología , Proteínas Proto-Oncogénicas c-bcl-2/genética , Transfección , Proteína bcl-XRESUMEN
The spatial arrangement of resources in patchy habitats influences the distribution of individuals and their ability to acquire resources. We used Chironomus riparius, a ubiquitous aquatic insect that uses leaf particles as an important resource, to ask how the dispersion of resource patches influences the distribution and resource acquisition of mobile individuals in patchy landscapes. Two experiments were conducted in replicated laboratory landscapes (38×38 cm) created by arranging sand and leaf patches in a 5×5 grid so that the leaf patches were either aggregated or uniformly dispersed in the grid. One-day-old C. riparius larvae were introduced into the landscapes in one of three densities (low, medium, high). In experiment 1, we sampled larvae and pupae by coring each patch in each landscape 3, 6, 12, or 24 days after adding larvae. In experiment 2, emerging adults were collected daily for 42 days from each patch in each landscape. In aggregated landscapes, individuals were aggregated in one patch type or the other during a particular developmental stage, but the "preferred" type changed depending on developmental stage and initial density. Adult emergence was lower by about 30% in all aggregated landscapes. In dispersed landscapes, individuals used both types of patch throughout their life cycles at all initial densities. Thus, patch arrangement influences the distribution of mobile individuals in landscapes, and it influences resource acquisition even when average resource abundance is identical among landscapes. Regardless of patch arrangement, high initial density caused accumulation of early instars in edge patches, 75% mortality of early instars, a 25% increase in development time, and a 60% reduction in adult emergence. Because mortality was extremely high among early-instar larvae in high-density treatments, we do not have direct evidence that the mechanism by which patch arrangement operates is density dependent. However, the results of our experiments strongly suggest that dispersion of resource patches across a landscape reduces local densities by making non-resource patches available for use, thereby reducing intraspecific competition.
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Huntington's disease is a neurodegenerative disorder resulting from expansion of the polyglutamine region in huntingtin. Although huntingtin is normally cytoplasmic, in affected brain regions proteolytic fragments of mutant huntingtin containing the polyglutamine repeat form intranuclear inclusions. Here, we examine the contribution of nuclear localization to toxicity by transiently transfecting neuro-2a cells with an N-terminal huntingtin fragment similar in size to that believed to be present in patients. The huntingtin fragment, HD-N63, was targeted either to the cytoplasm with a nuclear export signal (NES) or to the nucleus with a nuclear localization signal (NLS). The NES decreased the number of cells with aggregates in the nucleus while an NLS had the opposite effect. By cotransfecting HD-N63 with GFP as a marker, we observed direct cell loss with constructs containing expanded polyglutamine repeats. Compared to unmodified HD-N63-75Q, adding an NES reduced cell loss by 57% while an NLS increased cell loss by 111%. These results indicate that nuclear localization of mutant huntingtin fragments plays an important role in cell toxicity.
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Núcleo Celular/patología , Supervivencia Celular , Proteínas del Tejido Nervioso/genética , Neurotoxinas , Proteínas Nucleares/genética , Animales , Núcleo Celular/fisiología , Humanos , Proteína Huntingtina , Enfermedad de Huntington/genética , Ratones , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/fisiología , Neuroblastoma , Proteínas Nucleares/química , Proteínas Nucleares/fisiología , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Transfección , Células Tumorales CultivadasRESUMEN
An increasing number of neurodegenerative disorders have been found to be caused by expanding CAG triplet repeats that code for polyglutamine. Huntington's disease (HD) is the most common of these disorders and dentatorubral-pallidoluysian atrophy (DRPLA) is very similar to HD, but is caused by mutation in a different gene, making them good models to study. In this review, we will concentrate on the roles of protein aggregation, nuclear localization and proteolytic processing in disease pathogenesis. In cell model studies of HD, we have found that truncated N-terminal portions of huntingtin (the HD gene product) with expanded repeats form more aggregates than longer or full length huntingtin polypeptides. These shorter fragments are also more prone to aggregate in the nucleus and cause more cell toxicity. Further experiments with huntingtin constructs harbouring exogenous nuclear import and nuclear export signals have implicated the nucleus in direct cell toxicity. We have made mouse models of HD and DRPLA using an N-terminal truncation of huntingtin (N171) and full-length atrophin-1 (the DRPLA gene product), respectively. In both models, diffuse neuronal nuclear staining and nuclear inclusion bodies are observed in animals expressing the expanded glutamine repeat protein, further implicating the nucleus as a primary site of neuronal dysfunction. Neuritic pathology is also observed in the HD mice. In the DRPLA mouse model, we have found that truncated fragments of atrophin-1 containing the glutamine repeat accumulate in the nucleus, suggesting that proteolysis may be critical for disease progression. Taken together, these data lead towards a model whereby proteolytic processing, nuclear localization and protein aggregation all contribute to pathogenesis.
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Encéfalo/patología , Enfermedad de Huntington/genética , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/química , Proteínas Nucleares/genética , Péptidos/genética , Expansión de Repetición de Trinucleótido , Animales , Atrofia , Giro Dentado/patología , Globo Pálido/patología , Humanos , Proteína Huntingtina , Enfermedad de Huntington/patología , Cuerpos de Inclusión/patología , Ratones , Proteínas del Tejido Nervioso/metabolismo , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/patología , Proteínas Nucleares/metabolismoRESUMEN
Huntington's disease (HD) is an inherited, neurodegenerative disorder caused by the expansion of a glutamine repeat in the N-terminus of the huntingtin protein. To gain insight into the pathogenesis of HD, we generated transgenic mice that express a cDNA encoding an N-terminal fragment (171 amino acids) of huntingtin with 82, 44 or 18 glutamines. Mice expressing relatively low steady-state levels of N171 huntingtin with 82 glutamine repeats (N171-82Q) develop behavioral abnormalities, including loss of coordination, tremors, hypokinesis and abnormal gait, before dying prematurely. In mice exhibiting these abnormalities, diffuse nuclear labeling, intranuclear inclusions and neuritic aggregates, all immunoreactive with an antibody to the N-terminus (amino acids 1-17) of huntingtin (AP194), were found in multiple populations of neurons. None of these behavioral or pathological phenotypes were seen in mice expressing N171-18Q. These findings are consistent with the idea that N-terminal fragments of huntingtin with a repeat expansion are toxic to neurons, and that N-terminal fragments are prone to form both intranuclear inclusions and neuritic aggregates.
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Enfermedad de Huntington/genética , Enfermedad de Huntington/patología , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/genética , Fragmentos de Péptidos/genética , Animales , Secuencia de Bases , Núcleo Celular/patología , Cartilla de ADN/genética , Modelos Animales de Enfermedad , Humanos , Proteína Huntingtina , Enfermedad de Huntington/fisiopatología , Cuerpos de Inclusión/patología , Ratones , Ratones Transgénicos , Neuritas/patología , FenotipoRESUMEN
Dentatorubral and pallidoluysian atrophy (DRPLA) is a member of a family of progressive neurodegenerative diseases caused by polyglutamine repeat expansion. Transgenic mice expressing full-length human atrophin-1 with 65 consecutive glutamines exhibit ataxia, tremors, abnormal movements, seizures, and premature death. These mice accumulate atrophin-1 immunoreactivity and inclusion bodies in the nuclei of multiple populations of neurons. Subcellular fractionation revealed 120 kDa nuclear fragments of mutant atrophin-1, whose abundance increased with age and phenotypic severity. Brains of DRPLA patients contained apparently identical 120 kDa nuclear fragments. By contrast, mice overexpressing atrophin-1 with 26 glutamines were phenotypically normal and did not accumulate the 120 kDa fragments. We conclude that the evolution of neuropathology in DRPLA involves proteolytic processing of mutant atrophin-1 and nuclear accumulation of truncated fragments.
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Núcleo Celular/metabolismo , Modelos Animales de Enfermedad , Atrofia de Múltiples Sistemas/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Fragmentos de Péptidos/metabolismo , Adolescente , Animales , Ataxia , Encéfalo/patología , Niño , Corea , Femenino , Humanos , Masculino , Ratones , Ratones Transgénicos , Atrofia de Múltiples Sistemas/genética , Atrofia de Múltiples Sistemas/patología , Enfermedades Neurodegenerativas/genética , Secuencias Repetitivas de Ácidos Nucleicos , TemblorRESUMEN
Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expanding CAG repeat coding for polyglutamine in the huntingtin protein. Recent data have suggested the possibility that an N-terminal fragment of huntingtin may aggregate in neurons of patients with HD, both in the cytoplasm, forming dystrophic neurites, and in the nucleus, forming intranuclear neuronal inclusion bodies. An animal model of HD using the short N-terminal fragment of huntingtin has also been found to have intranuclear inclusions and this same fragment can aggregate in vitro . We have now developed a cell culture model demonstrating that N-terminal fragments of huntingtin with expanded glutamine repeats aggregate both in the cytoplasm and in the nucleus. Neuroblastoma cells transiently transfected with full-length huntingtin constructs with either a normal or expanded repeat had diffuse cytoplasmic localization of the protein. In contrast, cells transfected with truncated N-terminal fragments showed aggregation only if the glutamine repeat was expanded. The aggregates were often ubiquitinated. The shorter truncated product appeared to form more aggregates in the nucleus. Cells transfected with the expanded repeat construct but not the normal repeat construct showed enhanced toxicity to the apoptosis-inducing agent staurosporine. These data indicate that N-terminal truncated fragments of huntingtin with expanded glutamine repeats can aggregate in cells in culture and that this aggregation can be toxic to cells. This model will be useful for future experiments to test mechanisms of aggregation and toxicity and potentially for testing experimental therapeutic interventions.