928 resultados para Glandular complexity
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We present an abstract model of the leader election protocol used in the IEEE 1394 High Performance Serial Bus standard. The model is expressed in the probabilistic Guarded Command Language. By formal reasoning based on this description, we establish the probability of the root contention part of the protocol successfully terminating in terms of the number of attempts to do so. Some simple calculations then allow us to establish an upper bound on the time taken for those attempts.
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The Wilms' tumour suppressor gene (WT1) encodes a zinc finger-containing nuclear protein essential for kidney and urogenital development. Initially considered a transcription factor, there is mounting evidence that WT1 has a role in post-transcriptional processing. Using the interspecies heterokaryon assay, we have demonstrated that WT1 can undergo nucleocytoplasmic shuttling. We have also mapped the region responsible for nuclear export to residues 182-324. Our data add further complexity to the role of WT1 in trancriptional and post-transcriptional regulation. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.
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We analyzed the mouse Representative Transcript and Protein Set for molecules involved in brain function. We found full-length cDNAs of many known brain genes and discovered new members of known brain gene families, including Family 3 G-protein coupled receptors, voltage-gated channels, and connexins. We also identified previously unknown candidates for secreted neuroactive molecules. The existence of a large number of unique brain ESTs suggests an additional molecular complexity that remains to be explored. A list of genes containing CAG stretches in the coding region represents a first step in the potential identification of candidates for hereditary neurological disorders.
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The standard mathematical models in population ecology assume that a population's growth rate is a function of its environment. In this paper we investigate an alternative proposal according to which the rate of change of the growth rate is a function of the environment and of environmental change. We focus on the philosophical issues involved in such a fundamental shift in theoretical assumptions, as well as on the explanations the two theories offer for some of the key data such as cyclic populations. We also discuss the relationship between this move in population ecology and a similar move from first-order to second-order differential equations championed by Galileo and Newton in celestial mechanics.
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The work of Michel Foucault sees modern penal technology its ann expression of power that operates through and is motivated by a dry instrumental reason. This article draws upon Durkheim and Bakhtin to advance a radically alternative approach. It is suggested that such technology is invested with sacred and profane symbolism and is understood via emotionally charged, dramatically compelling narrative frames. Tensions between official and unauthorized discourses can be understood through a center/periphery model of culture. In an extended case study of the guillotine, it is shown dial the apparatus was initially legitimated as an expression of a sacred revolutionary code. Such a discourse was subsequently destabilized by popular medical debates that raised the specter of pain after decapitation. While inconclusive, these new motifs mobilized Gothic and grotesque themes that confronted the rationalist aesthetics of the guillotine. A situation of Bakhtinian hetoroglossia eventuated. Uncertainty, the uncanny and fable entered a discursive field of increasing complexity.
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The tribe Hilarini (Diptera: Empididae), commonly known as dance flies, can be recognised by their swollen silk-producing prothoracic basitarsus, a male secondary sexual characteristic. The ultrastructure and function of the silk-producing basitarsus from one undescribed morphospecies of Hilarini, 'Hilarempis 20', is presented. Male H. 20 collect small parcels of diatomaceous algae from the surface of freshwater creeks that they bind with silk produced by the gland in the basitarsus. The gift is then presented to females in a nearby swarm, composed predominately of females. The basitarsus houses approximately 12 pairs of class III dermal glandular units that congregate on the ventral side of the cavity. Each gland cell has a large extracellular lumen where secretion accumulates. The lumen drains to the outside via a conducting canal encompassed by a canal cell and a duct extending through the shaft of a specialised secretory spine. The secretory spines lie in pairs in a ventral groove that runs the length of the basitarsus. A comparison of the basitarsal secretory spines with sensilla on the basitarsi of non gland-bearing legs of males, and with non gland-bearing prothoracic. basitarsi of females, suggests that the glandular units are derived from contact chemosensory sensilla. (C) 2003 Elsevier Ltd. All rights reserved.
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Functional genomics is the systematic study of genome-wide effects of gene expression on organism growth and development with the ultimate aim of understanding how networks of genes influence traits. Here, we use a dynamic biophysical cropping systems model (APSIM-Sorg) to generate a state space of genotype performance based on 15 genes controlling four adaptive traits and then search this spice using a quantitative genetics model of a plant breeding program (QU-GENE) to simulate recurrent selection. Complex epistatic and gene X environment effects were generated for yield even though gene action at the trait level had been defined as simple additive effects. Given alternative breeding strategies that restricted either the cultivar maturity type or the drought environment type, the positive (+) alleles for 15 genes associated with the four adaptive traits were accumulated at different rates over cycles of selection. While early maturing genotypes were favored in the Severe-Terminal drought environment type, late genotypes were favored in the Mild-Terminal and Midseason drought environment types. In the Severe-Terminal environment, there was an interaction of the stay-green (SG) trait with other traits: Selection for + alleles of the SG genes was delayed until + alleles for genes associated with the transpiration efficiency and osmotic adjustment traits had been fixed. Given limitations in our current understanding of trait interaction and genetic control, the results are not conclusive. However, they demonstrate how the per se complexity of gene X gene X environment interactions will challenge the application of genomics and marker-assisted selection in crop improvement for dryland adaptation.
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Mental retardation in individuals with Down syndrome (DS) is thought to result from anomalous development and function of the brain; however, the underlying neuropathological processes have yet to be determined. Early implementation of special care programs result in limited, and temporary, cognitive improvements in DS individuals. In the present study, we investigated the possible neural correlates of these limited improvements. More specifically, we studied cortical pyramidal cells in the frontal cortex of Ts65Dn mice, a partial trisomy of murine chromosome 16 (MMU16) model characterized by cognitive deficits, hyperactivity, behavioral disruption and reduced attention levels similar to those observed in DS, and their control littermates. Animals were raised either in a standard or in an enriched environment. Environmental enrichment had a marked effect on pyramidal cell structure in control animals. Pyramidal cells in environmentally enriched control animals were significantly more branched and more spinous than non-enriched controls. However, environmental enrichment had little effect on pyramidal cell structure in Ts65Dn mice. As each dendritic spine receives at least one excitatory input, differences in the number of spines found in the dendritic arbors of pyramidal cells in the two groups reflect differences in the number of excitatory inputs they receive and, consequently, complexity in cortical circuitry. The present results suggest that behavioral deficits demonstrated in the Ts65Dn model could be attributed to abnormal circuit development.
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Arguably the most complex conical functions are seated in human cognition, the how and why of which have been debated for centuries by theologians, philosophers and scientists alike. In his best-selling book, An Astonishing Hypothesis: A Scientific Search for the Soul, Francis Crick refined the view that these qualities are determined solely by cortical cells and circuitry. Put simply, cognition is nothing more, or less, than a biological function. Accepting this to be the case, it should be possible to identify the mechanisms that subserve cognitive processing. Since the pioneering studies of Lorent de No and Hebb, and the more recent studies of Fuster, Miller and Goldman-Rakic, to mention but a few, much attention has been focused on the role of persistent neural activity in cognitive processes. Application of modern technologies and modelling techniques has led to new hypotheses about the mechanisms of persistent activity. Here I focus on how regional variations in the pyramidal cell phenotype may determine the complexity of cortical circuitry and, in turn, influence neural activity. Data obtained from thousands of individually injected pyramidal cells in sensory, motor, association and executive cortex reveal marked differences in the numbers of putative excitatory inputs received by these cells. Pyramidal cells in prefrontal cortex have, on average, up to 23 times more dendritic spines than those in the primary visual area. I propose that without these specializations in the structure of pyramidal cells, and the circuits they form, human cognitive processing would not have evolved to its present state. I also present data from both New World and Old World monkeys that show varying degrees of complexity in the pyramidal cell phenotype in their prefrontal cortices, suggesting that cortical circuitry and, thus, cognitive styles are evolving independently in different species.
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The branching structure of neurones is thought to influence patterns of connectivity and how inputs are integrated within the arbor. Recent studies have revealed a remarkable degree of variation in the branching structure of pyramidal cells in the cerebral cortex of diurnal primates, suggesting regional specialization in neuronal function. Such specialization in pyramidal cell structure may be important for various aspects of visual function, such as object recognition and color processing. To better understand the functional role of regional variation in the pyramidal cell phenotype in visual processing, we determined the complexity of the dendritic branching pattern of pyramidal cells in visual cortex of the nocturnal New World owl monkey. We used the fractal dilation method to quantify the branching structure of pyramidal cells in the primary visual area (V1), the second visual area (V2) and the caudal and rostral subdivisions of inferotemporal cortex (ITc and ITr, respectively), which are often associated with color processing. We found that, as in diurnal monkeys, there was a trend for cells of increasing fractal dimension with progression through these cortical areas. The increasing complexity paralleled a trend for increasing symmetry. That we found a similar trend in both diurnal and nocturnal monkeys suggests that it was a feature of a common anthropoid ancestor.
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O tamanho e a complexidade do desafio de combater a pobreza t??m criado a necessidade de se identificar novas maneiras de atacar o problema. Um importante elemento da atual discuss??o ?? o envolvimento dos stakeholders prim??rios nas atividades da interven????o de desenvolvimento. O presente trabalho revisa e sintetiza a literatura especializada para analisar as contribui????es da participa????o para a redu????o da pobreza. Ele identificou que participa????o aumenta o impacto das estrat??gias de redu????o da pobreza, por meio do empoderamento dos stakeholders prim??rios e de melhorias na efetividade, na efici??ncia e na sustentabilidade das interven????es. Os estudos de caso indicam, tamb??m, que altos n??veis de participa????o tendem a contribuir mais para o sucesso da estrat??gia. Contudo, garantir uma ???real??? participa????o dos benefici??rios n??o ?? f??cil. Como resultado desse estudo, s??o dadas algumas recomenda????es para futuras pol??ticas de combate ?? pobreza. Se adotadas, elas podem ajudar a vencer as dificuldades e desafios apontados e a maximizar as contribui????es da participa????o.
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Se nos estados federais os mecanismos de coopera????o e coordena????o intergovernamental j?? s??o relevantes, no caso brasileiro eles ganham centralidade ainda maior. A Constitui????o Federal de 1988 agregou complexidade ao desenho federativo brasileiro, reconhecendo o munic??pio como ente federado. Esse processo foi acompanhado por intensa descentraliza????o de pol??ticas p??blicas, pelo fortalecimento do poder local e por mecanismos pouco coordenados de rela????o vertical e horizontal entre os entes federativos. Ao mesmo tempo, a aus??ncia de pol??ticas de desenvolvimento regional acentuou as desigualdades locais e regionais observadas historicamente no pa??s. Diferentes experi??ncias de consorciamento foram levadas a cabo por munic??pios no pa??s e ainda hoje esse ?? um instrumento de larga utiliza????o. De forma diversa, as iniciativas de coopera????o entre estados s??o ainda incipientes. As limita????es institucionais e jur??dicas dos desenhos utilizados pelos munic??pios, no entanto, levaram ?? aprova????o da Emenda Constitucional n?? 19/98, que instituiu os cons??rcios p??blicos e a gest??o associada de servi??os p??blicos.
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O artigo analisa o curso de forma????o inicial para a carreira de Especialista em Pol??ticas P??blicas e Gest??o Governamental (EPPGG), recentemente reformulado. Conclui-se que as mudan??as realizadas no curso, tendo em vista os problemas enfrentados em edi????es anteriores, os desafios contempor??neos da administra????o p??blica, a crescente complexidade dos problemas e as demandas da sociedade, proporcionaram respostas bastante adequadas. No entanto, persistem in??meros desafios, dentre os quais se destacam o aprimoramento do ensino de aplica????o e novas tecnologias. Ao longo das nove edi????es do curso, percebe-se que os principais objetivos do projeto inicial da carreira permaneceram, mesmo com todas as descontinuidades administrativas. Preservaram-se o perfil generalista e as policompet??ncias na forma????o do EPPGG, a fim de permitir ao profissional uma vis??o abrangente e integrada dos complexos problemas da administra????o p??blica e desenvolver a capacidade de analisar, decidir e buscar os melhores resultados em prol do cidad??o, conduzindo as rela????es e as atividades profissionais de acordo com os princ??pios da ??tica p??blica.
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O artigo rev??, com base na bibliografia especializada, as reformas e tentativas de reformas administrativas realizadas no pa??s, desde o Estado Novo, passando pelas tentativas dos governos militares e pelas propostas mais recentes da Nova Rep??blica, e chegando at?? a reforma Bresser Pereira. O balan??o cr??tico ?? bastante negativo, sobretudo, porque as grandes reformas, precisamente pela sua abrang??ncia, nunca foram efetivamente implementadas. O sistema do m??rito no servi??o p??blico federal ?? um bom exemplo. As dificuldades de implementa????o das grandes reformas, advindas principalmente de sua grande complexidade, resultam tamb??m de sua intera????o negativa com o contexto pol??tico mais geral, pela carga ret??rica de que se fazem acompanhar, e pelo fato de subestimarem os aspectos t??cnicos necess??rios ?? sua implementa????o.
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Desde a d??cada de 1980, as reformas t??m dominado as agendas governamentais em todo o mundo; os governos embarcaram em uma not??vel jornada de inova????o. O ritmo dessas reformas provavelmente n??o ir?? diminuir. O n??mero crescente de desafios na pol??tica p??blica demanda a participa????o ativa de in??meros atores dentro e fora do governo e requer que o governo trabalhe para al??m dos limites convencionais. Esses desafios for??am o governo a utilizar sua autoridade e recursos para habilitar e empoderar outros. O aumento da complexidade e da incerteza nas quest??es de pol??tica e nos contextos de governan??a levam os governos a aprimorar sua capacidade de antecipar, intervir, inovar, aprender e adaptar-se. Futuras reformas ir??o requerer uma vis??o mais ampla dos pap??is do governo e dos cidad??os.