The multifaceted role of astrocytes in regulating myelination

Astrocytes are the major glial cell of the central nervous system (CNS), providing both metabolic and physical support to other neural cells. After injury, astrocytes become reactive and express a continuum of phenotypes which may be supportive or inhibitory to CNS repair. This review will focus on the ability of astrocytes to influence myelination in the context of specific secreted factors, cytokines and other neural cell targets within the CNS. In particular, we focus on how astrocytes provide energy and cholesterol to neurons, influence synaptogenesis, affect oligodendrocyte biology and instigate cross-talk between the many cellular components of the CNS

Existence of Singularity Bifurcation in an Euler-Equations Model of the United States Economy: Grandmont was Right

Abstract: Grandmont (1985) found that the parameter space of the most classical dynamic general-equilibrium macroeconomic models are stratified into an infinite number of subsets supporting an infinite number of different kinds of dynamics, from monotonic stability at one extreme to chaos at the other extreme, and with all forms of multiperiodic dynamics between. But Grandmont provided his result with a model in which all policies are Ricardian equivalent, no frictions exist, employment is always full, competition is perfect, and all solutions are Pareto optimal. Hence he was not able to reach conclusions about the policy relevance of his dramatic discovery. As a result, Barnett and He (1999, 2001, 2002) investigated a Keynesian structural model, and found results supporting Grandmont’s conclusions within the parameter space of the Bergstrom-Wymer continuous-time dynamic macroeconometric model of the UK economy. That prototypical Keynesian model was produced from a system of second order differential equations. The model contains frictions through adjustment lags, displays reasonable dynamics fitting the UK economy’s data, and is clearly policy relevant. In addition, results by Barnett and Duzhak (2008,2009) demonstrate the existence of Hopf and flip (period doubling) bifurcation within the parameter space of recent New Keynesian models. Lucas-critique criticism of Keynesian structural models has motivated development of Euler equations models having policy-invariant deep parameters, which are invariant to policy rule changes. Hence, we continue the investigation of policy-relevant bifurcation by searching the parameter space of the best known of the Euler equations general-equilibrium macroeconometric models: the path-breaking Leeper and Sims (1994) model. We find the existence of singularity bifurcation boundaries within the parameter space. Although never before found in an economic model, singularity bifurcation may be a common property of Euler equations models, which often do not have closed form solutions. Our results further confirm Grandmont’s views. Beginning with Grandmont’s findings with a classical model, we continue to follow the path from the Bergstrom-Wymer policy-relevant Keynesian model, to New Keynesian models, and now to Euler equations macroeconomic models having deep parameters.Bifurcation; inference; dynamic general equilibrium; Pareto optimality; Hopf bifurcation; Euler equations; Leeper and Sims model; singularity bifurcation; stability

A study of ethnicity as a crucial casework issue in maternal attitudes

Thesis (M.S.)--Boston Universit

Human olfactory mesenchymal stromal cell transplants promote remyelination and earlier improvement in gait co-ordination after spinal cord injury

Autologous cell transplantation is a promising strategy for repair of the injured spinal cord. Here we have studied the repair potential of mesenchymal stromal cells isolated from the human olfactory mucosa after transplantation into a rodent model of incomplete spinal cord injury. Investigation of peripheral type remyelination at the injury site using immunocytochemistry for P0, showed a more extensive distribution in transplanted compared with control animals. In addition to the typical distribution in the dorsal columns (common to all animals), in transplanted animals only, P0 immunolabelling was consistently detected in white matter lateral and ventral to the injury site. Transplanted animals also showed reduced cavitation. Several functional outcome measures including end-point electrophysiological testing of dorsal column conduction and weekly behavioural testing of BBB, weight bearing and pain, showed no difference between transplanted and control animals. However, gait analysis revealed an earlier recovery of co-ordination between forelimb and hindlimb stepping in transplanted animals. This improvement in gait may be associated with the enhanced myelination in ventral and lateral white matter, where fibre tracts important for locomotion reside. Autologous transplantation of mesenchymal stromal cells from the olfactory mucosa may therefore be therapeutically beneficial in the treatment of spinal cord injury

Ideas, implementation and indicators: epistemologies of the post-2015 urban agenda

This is the pre-publication submitted draft of the following paper: Clive Barnett and Susan Parnell, 2016, Ideas, implementation and indicators: epistemologies of the post-2015 urban agenda, Environment and Urbanization, DOI: 10.1177/0956247815621473.Copyright © 2016 International Institute for Environment and Development (IIED).The success of the campaign for a dedicated urban Sustainable Development Goal (SDG) reflected a consensus on the importance of “cities” in sustainable development. The relevance accorded to cities in the SDGs is twofold, reflected both in the specific place- based content of the Urban Goal and the more general concern with the multiple scales at which all indicators will be institutionalized. Divergent views of the city and urban processes, suppressed within the Urban Goal, are, however, likely to become more explicit as attention shifts to implementation. Acknowledging the different theoretical traditions used to legitimize the new urban agenda is an overdue task. As this agenda develops post-2015, the adequacy of these forms of urban theory will become more contested around, among other concerns, the possibilities and limits of place-based policy, advocacy and activism; and practices of monitoring and evaluating ongoing processes of urban transformation along multiple axes of development.Leverhulme TrustEconomic and Social Research Council (ESRC)Department for International Development (DFID

The mediating roles of disgust sensitivity and danger expectancy in relation to hand washing behaviour

Copyright © 2010 British Association for Behavioural and Cognitive PsychotherapiesBackground: Recent interest in the role of vulnerability factors in obsessional washing has suggested that disgust sensitivity, danger expectancy and health anxiety may be of interest. Aims: This study explores the differential impact of these factors on both behavioural and cognitive measures of washing behaviour and is based on a replication of the Jones and Menzies (1997) experiment, during which participants immersed their hands in a noxious compound while rating themselves on a range of measures: the time they subsequently took to wash their hands was measured and danger expectancies were found to be the best predictor of this. Method: The present study added measures of disgust sensitivity and health anxiety to this experimental methodology while removing factors they found to be of little import to compulsive washing. Thirty non-clinical participants took part. Results: Results confirmed that disgust sensitivity was related to the behavioural measure of washing time, but that this relationship was almost entirely mediated by the danger expectancy concerning judgements of severity of consequent disease. However, a different pattern emerged when the outcome measure was questionnaire based: danger expectancy was not at all related to this. Disgust sensitivity mediated the relationship between health anxiety and scores on a questionnaire measure of washing compulsions. Interestingly, these scores were not related to the behavioural measure of washing time. Conclusions: The implications of these relationships to the further development of subtypes of Obsessive Compulsive Disorder (OCD) are discussed

How Effective Is Security Screening of Airline Passengers?

With a simple mathematical model, we explored the antiterrorist effectiveness of airport passenger prescreening systems. Supporters of these systems often emphasize the need to identify the most suspicious passengers, but they ignore the point that such identification does little good unless dangerous items can actually be detected. Critics often focus on terrorists\u27 ability to probe the system and thereby thwart it, but ignore the possibility that the very act of probing can deter attempts at sabotage that would have succeeded. Using the model to make some preliminary assessments about security policy, we find that an improved baseline level of screening for all passengers might lower the likelihood of attack more than would improved profiling of high-risk passengers

Astroglial-axonal interactions during early stages of myelination in mixed cultures using in vitro and ex vivo imaging techniques

<b>Background</b><p></p> Myelination is a very complex process that requires the cross talk between various neural cell types. Previously, using cytosolic or membrane associated GFP tagged neurospheres, we followed the interaction of oligodendrocytes with axons using time-lapse imaging in vitro and ex vivo and demonstrated dynamic changes in cell morphology. In this study we focus on GFP tagged astrocytes differentiated from neurospheres and their interactions with axons.<p></p> <b>Results</b><p></p> We show the close interaction of astrocyte processes with axons and with oligodendrocytes in mixed mouse spinal cord cultures with formation of membrane blebs as previously seen for oligodendrocytes in the same cultures. When GFP-tagged neurospheres were transplanted into the spinal cord of the dysmyelinated shiverer mouse, confirmation of dynamic changes in cell morphology was provided and a prevalence for astrocyte differentiation compared with oligodendroglial differentiation around the injection site. Furthermore, we were able to image GFP tagged neural cells in vivo after transplantation and the cells exhibited similar membrane changes as cells visualised in vitro and ex vivo.<p></p> <b>Conclusion</b><p></p> These data show that astrocytes exhibit dynamic cell process movement and changes in their membrane topography as they interact with axons and oligodendrocytes during the process of myelination, with the first demonstration of bleb formation in astrocytes

Using Libguides to Support Library Instruction

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