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Search Results: 1 - 10 of 327804 matches for " Miriam S. Nokia "
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Disrupting neural activity related to awake-state sharp wave-ripple complexes prevents hippocampal learning
Miriam S. Nokia,Jarno E. Mikkonen,Markku Penttonen,Jan Wikgren
Frontiers in Behavioral Neuroscience , 2012, DOI: 10.3389/fnbeh.2012.00084
Abstract: Oscillations in hippocampal local-field potentials (LFPs) reflect the crucial involvement of the hippocampus in memory trace formation: theta (4–8 Hz) oscillations and ripples (~200 Hz) occurring during sharp waves are thought to mediate encoding and consolidation, respectively. During sharp wave-ripple complexes (SPW-Rs), hippocampal cell firing closely follows the pattern that took place during the initial experience, most likely reflecting replay of that event. Disrupting hippocampal ripples using electrical stimulation either during training in awake animals or during sleep after training retards spatial learning. Here, adult rabbits were trained in trace eyeblink conditioning, a hippocampus-dependent associative learning task. A bright light was presented to the animals during the inter-trial interval (ITI), when awake, either during SPW-Rs or irrespective of their neural state. Learning was particularly poor when the light was presented following SPW-Rs. While the light did not disrupt the ripple itself, it elicited a theta-band oscillation, a state that does not usually coincide with SPW-Rs. Thus, it seems that consolidation depends on neuronal activity within and beyond the hippocampus taking place immediately after, but by no means limited to, hippocampal SPW-Rs.
Learning to Learn: Theta Oscillations Predict New Learning, which Enhances Related Learning and Neurogenesis
Miriam S. Nokia, Helene M. Sisti, Monica R. Choksi, Tracey J. Shors
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031375
Abstract: Animals in the natural world continuously encounter learning experiences of varying degrees of novelty. New neurons in the hippocampus are especially responsive to learning associations between novel events and more cells survive if a novel and challenging task is learned. One might wonder whether new neurons would be rescued from death upon each new learning experience or whether there is an internal control system that limits the number of cells that are retained as a function of learning. In this experiment, it was hypothesized that learning a task that was similar in content to one already learned previously would not increase cell survival. We further hypothesized that in situations in which the cells are rescued hippocampal theta oscillations (3–12 Hz) would be involved and perhaps necessary for increasing cell survival. Both hypotheses were disproved. Adult male Sprague-Dawley rats were trained on two similar hippocampus-dependent tasks, trace and very-long delay eyeblink conditioning, while recording hippocampal local-field potentials. Cells that were generated after training on the first task were labeled with bromodeoxyuridine and quantified after training on both tasks had ceased. Spontaneous theta activity predicted performance on the first task and the conditioned stimulus induced a theta-band response early in learning the first task. As expected, performance on the first task correlated with performance on the second task. However, theta activity did not increase during training on the second task, even though more cells were present in animals that had learned. Therefore, as long as learning occurs, relatively small changes in the environment are sufficient to increase the number of surviving neurons in the adult hippocampus and they can do so in the absence of an increase in theta activity. In conclusion, these data argue against an upper limit on the number of neurons that can be rescued from death by learning.
Memory-Based Mismatch Response to Frequency Changes in Rats
Piia Astikainen, Gabor Stefanics, Miriam Nokia, Arto Lipponen, Fengyu Cong, Markku Penttonen, Timo Ruusuvirta
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024208
Abstract: Any occasional changes in the acoustic environment are of potential importance for survival. In humans, the preattentive detection of such changes generates the mismatch negativity (MMN) component of event-related brain potentials. MMN is elicited to rare changes (‘deviants’) in a series of otherwise regularly repeating stimuli (‘standards’). Deviant stimuli are detected on the basis of a neural comparison process between the input from the current stimulus and the sensory memory trace of the standard stimuli. It is, however, unclear to what extent animals show a similar comparison process in response to auditory changes. To resolve this issue, epidural potentials were recorded above the primary auditory cortex of urethane-anesthetized rats. In an oddball condition, tone frequency was used to differentiate deviants interspersed randomly among a standard tone. Mismatch responses were observed at 60–100 ms after stimulus onset for frequency increases of 5% and 12.5% but not for similarly descending deviants. The response diminished when the silent inter-stimulus interval was increased from 375 ms to 600 ms for +5% deviants and from 600 ms to 1000 ms for +12.5% deviants. In comparison to the oddball condition the response also diminished in a control condition in which no repetitive standards were presented (equiprobable condition). These findings suggest that the rat mismatch response is similar to the human MMN and indicate that anesthetized rats provide a valuable model for studies of central auditory processing.
Nove espécies novas do gênero Rineloricaria (Siluriformes, Loricariidae) do rio Uruguai, do sul do Brasil
Ghazzi, Miriam S.;
Iheringia. Série Zoologia , 2008, DOI: 10.1590/S0073-47212008000100014
Abstract: nine new species of rineloricaria are described from upper and middle rio uruguay basin in states of rio grande do sul and santa catarina, brazil. rineloricaria misionera rodriguez & miquelarena, 2005 is the only species currently known from this basin. the new species are diagnosed mainly by abdominal plates arrangement, color pattern, extension of the anterior snout naked area, and fins length. the species described here are endemic to the rio uruguay. rineloricaria anitae and r. tropeira are restricted to the tributaries of the rio canoas and the rio pelotas; r. zaina is widely distributed from the confluence of the rio canoas with the rio pelotas to the rio ibicuí; r. anhanguapitan is restricted to the rio passo fundo; r. capitonia occurs in the upper rio ijuí; r. stellata is known from the rio buricá, rio ijuí, rio piratini and rio ibicuí; r. setepovos and r. reisi are described from the rio piratini; and r. sanga is only known from the vicinity of iraí. comments on the fish diversity of the rio uruguay and on the variation of abdominal plates in rineloricaria are made.
Qualidade de vida e reformas de programas sociais: o Brasil no cenário latino-americano
Draibe, S?nia Miriam;
Lua Nova: Revista de Cultura e Política , 1993, DOI: 10.1590/S0102-64451993000300002
Abstract: given the bad record of brazilian social policies in a latin-american comparative perspective (even if compared with a case of social programs reform under a non-democratic regime, like the chilean one) the author studies the specifity of the brazilian case. the background of the analysis is given by the problems of the reform of the state and of the country's modernization
Coes?o social e integra??o regional: a agenda social do MERCOSUL e os grandes desafios das políticas sociais integradas
Draibe, S?nia Miriam;
Cadernos de Saúde Pública , 2007, DOI: 10.1590/S0102-311X2007001400007
Abstract: in the consolidation of the southern cone common market (mercosur), social policies are still in the embryonic stage. however, since the latter half of the 1990s there has been a speedup in the creation of institutions dedicated to such policies with the common market's framework. this article focuses on health policy and the broader social policy system in order to identify the reasons for the imbalance, through three movements: reconstitution of the history of the institutional construction of social policies in mercosur; identification and comparison of the successive strategies for the formulation and implementation of the social integration agenda; and reflection on the current dilemmas and challenges faced by the process. according to the study, mercosur operates with strategies that are difficult to mutually reconcile. on the institutional level, it follows a minimalist strategy, while on the conceptual/ discursive level it adopts a maximalist strategy for supranational unification of social policies. the fact is that it operates a minimalist social policy strategy, since it fails to bring to the field of social integration the debate and proposals on economic and social development models that could sustain the effective construction of regional social citizenship.
Development and Optimization of a Voltammetry Adsortive Method with Alizarine for Aluminium Determination in Water
Quirós,Miriam Barquero;
Portugaliae Electrochimica Acta , 2005,
Abstract: some of the aluminium complexes are electroactive at positive potentials, being necessary a carbon vitreous electrode to their quantitative determination. nevertheless the aluminium alizarine complex could be measured at negative potential with a mercury hanging electrode, but this complex is not electroactive at negative potential; instead of that, the residual alizarin non complex could be measured. the kinetic complex is very slow, so it is necessary to heat at 80 0c, for five minutes. the study of experimental conditions of complex formation was established at ph 9.25 and is determinant in the complex formation; besides, the buffers employed should be of high regulatory capacity to obtain derivative formation. the optimization of the measurement experimental conditions was done by square wave voltammetry (swv). detection limit got using standard deviation of seven blank solutions was 3 mg /l, the variation coefficient was 8%, and the mean recovery for 16 mg /l was 97%. the calibration curves were done in a linear interval of 8 to 64 mg /l. the method application to water samples is possible after previous evaporation.
Comparación de Metodologías Analíticas para Determinación de Aluminio en Fluidos de Hemodiálisis
Quirós,Miriam B.;
Portugaliae Electrochimica Acta , 2009,
Abstract: in order to quantifying aluminium by analyzing hemodialysis fluids, two methodologies were developed and validated: square wave adsorptive voltammetry (swav) and electrothermic absortion. performance parameters were established for the two methodologies. they were both applied successfully to the analysis of hemodialysis fluids.
Comparación de metodologías voltamperométricas adsortivas para la determinación de aluminio en agua potable
Miriam Barquero Quirós
Tecnología en Marcha , 2005,
Abstract: La determinación cuantitativa de aluminio en diversas técnicas a nivel de μg/L está sujeta a contaminación e interferencias. El aluminio por técnicas voltamperómétricas directas es difícil de reducir debido a su alto potencial. Para superar este problema, se forman complejos solubles de aluminio, que se adsorben en un electrodo de Hg. Luego se reducen siendo la corriente de pico proporcional a la concentración. Se estudiaron dos diferentes complejos de aluminio con alizarina y con cupferrón; en ambos casos se optimizaron las condiciones experimentales de formación de los complejos tales como pH óptimo, concentración de reactivo acomplejante, las condiciones experimentales de medición fueron opimizadas: potencial de acumulación, tiempo de acumulación, frecuencia, amplitud de pulso, tiempo de equilibrio, se determinaron los parámetros de desempe o de ambas determinaciones: veracidad, ámbito lineal, límite de detección, y límite de cuantificación para la técnica de voltamperometría de onda cuadrada (SWV). El complejo de aluminio-alizarina no es electroactivo, y la alternativa es medir la alizarina residual después de la formación del complejo con aluminio, cuya cinética es muy lenta y debe calentarse 5 minutos a 80 °C. Se procedió al estudio de las condiciones experimentales, siendo el pH de 9,25 determinante. Es necesario que el buffer sea de alta capacidad reguladora para obtener la formación del derivado. El límite de detección obtenido a partir de la desviación estándar de 7 blancos fue 3 μg/L, y el coeficiente de variación de los blancos 8 por ciento, la recuperación promedio para 16 μg/L con n=7, fue de 97 por ciento. Las curvas de calibración se realizaron en un ámbito de 8 a 64 μg/L. La aplicación del método a muestras de agua es posible mediante la previa evaporación de estas. Se desarrolló y se validó una metodología apta para cuantificar aluminio en aguas basada en la reacción de Al con cupferrón (sal de amonio de la N- nitroso fenil hidroxil amina) con las siguientes figuras de mérito: límite de detección 2 μg/L, límite de cuantificación 7 μg/ L, ámbito lineal 60 μg/L, veracidad para 20 μg/L con n=4 98 por ciento, veracidad 4 μg/L n=4,150 por ciento. Ambas metodologías son adecuadas para la determinación de aluminio, siendo la determinación con alizarina menos susceptible a la contaminación y los reactivos más estables. La determinación con cupferrón se realiza a niveles de concentración menores y las regresiones son más precisas.
Comparación de Metodologías Analíticas para Determinación de Aluminio en Fluidos de Hemodiálisis Comparison of Analytical Methodologies for Aluminium Determination in Hemodialysis Fluids
Miriam B. Quirós
Portugaliae Electrochimica Acta , 2009,
Abstract: Se desarrolló y validó una metodología para cuantificar aluminio en fluidos utilizados en hemodiálisis renal, basada en la reacción de Al con cupferrón, adsorción del complejo sobre un electrodo de gota de Hg y la posterior desorción y medida de la corriente producida por la reducción del complejo. Se realizó la validación de parámetros para voltamperometría de onda cuadrada (SWV). Se determinaron también los parámetros de desempe o del método, veracidad, ámbito lineal, límite de detección, límite de cuantificación. Se aplicó a la determinación de aluminio en muestras de hemodiálisis. Se desarrolló y validó posteriormente una metodología para la determinación de aluminio en fluidos empleados en hemodiálisis renal por absorción electrotérmica. Se determinaron las mejores condiciones para el tratamiento de la muestra. También se determinaron los parámetros de desempe o del método. Esta metodología se aplicó durante un a o al análisis de los fluidos de la Unidad de Hemodiálisis del Hospital México de la Caja Costarricense del Seguro Social de Costa Rica. El contenido en μg/L de la mayor parte de las muestras analizadas por ambas metodologías se encontraban sobre las recomendaciones internacionales en agua empleada en hemodiálisis. In order to quantifying aluminium by analyzing hemodialysis fluids, two methodologies were developed and validated: square wave adsorptive voltammetry (SWAV) and electrothermic absortion. Performance parameters were established for the two methodologies. They were both applied successfully to the analysis of hemodialysis fluids.
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