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Search Results: 1 - 10 of 3891 matches for " Lisa Foa "
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Presenilins and the γ-secretase: still a complex problem
David H Small, David W Klaver, Lisa Foa
Molecular Brain , 2010, DOI: 10.1186/1756-6606-3-7
Abstract: Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Typically 5-10% of the population over the age of 65 have dementia, and of these cases, a large percentage have AD [1]. AD is characterised by the presence of proteinaceous deposits in the brain [2]. The extracellular amyloid deposits, which are found in the neuropil (amyloid plaques) and in association with small-medium size cerebral blood vessels (cerebral amyloid angiopathy), are composed of a 4 kDa polypeptide known as the amyloid-β protein (Aβ) which is derived by proteolytic cleavage from a much larger amyloid-β precursor protein (APP) [3]. Aβ displays a spontaneous ability to aggregate into oligomers and larger fibrillar structures, and it is generally thought that the accumulation of oligomeric Aβ is chiefly responsible for the neurodegeneration that occurs in AD [4].For the generation of Aβ, APP is first cleaved on the N-terminal side of the Aβ sequence by the β-site APP cleaving enzyme-1 (BACE1), a transmembrane aspartyl protease [3]. The resulting 99-amino acid residue C-terminal fragment (C99) is then cleaved by the γ-secretase to yield Aβ and a C-terminal APP intracellular domain (AICD) fragment (Fig. 1). The function of the AICD fragment is unclear, although it is thought to have a role in intracellular signalling. For example, AICD may be involved in the regulation of gene transcription, synaptic plasticity and cytoskeletal dynamics [5].The major form of Aβ possesses 40 amino-acid residues (Aβ1-40). However, other minor species are also produced which vary in the C-terminal sequence. Production of a longer 42-residue species (Aβ1-42) is thought to be intimately associated with AD pathogenesis [6]. Aβ1-42 aggregates more readily than Aβ1-40, and increased production of Aβ1-42 may seed aggregation of Aβ1-40 or other Aβ species [4].Approximately 5% of all AD cases are autosomal dominant [7]. Soon after the complete APP sequence was cloned in 1987 [8], it became clear that at le
Homer regulates calcium signalling in growth cone turning
Robert Gasperini, Derek Choi-Lundberg, Michael JW Thompson, Camilla B Mitchell, Lisa Foa
Neural Development , 2009, DOI: 10.1186/1749-8104-4-29
Abstract: Homer1 knockdown reversed growth cone turning from attraction to repulsion in response to the calcium-dependent guidance cues brain derived neurotrophic factor and netrin-1. Conversely, Homer1 knockdown had no effect on repulsion to the calcium-independent guidance cue Semaphorin-3A. This reversal of attractive turning suggested a requirement for Homer1 in a molecular switch. Pharmacological experiments confirmed that the operational state of a calcium-calmodulin dependent protein kinase II/calcineurin phosphatase molecular switch was dependent on Homer1 expression. Calcium imaging of motile growth cones revealed that Homer1 is required for guidance-cue-induced rise of cytosolic calcium and the attenuation of spontaneous cytosolic calcium transients. Homer1 knockdown-induced calcium transients and turning were inhibited by antagonists of store-operated channels. In addition, immunocytochemistry revealed the close association of Homer1 with the store-operated proteins TRPC1 and STIM1 within dorsal root ganglia growth cones.These experiments provide evidence that Homer1 is an essential component of the calcium signalling repertoire within motile growth cones, regulating guidance-cue-induced calcium release and maintaining basal cytosolic calcium.Deciphering the cell signalling events that control growth cone navigation and, hence, axon guidance is crucial to our understanding of the development of functional neural circuitry. Cytosolic calcium ([Ca++]i) is a key signalling molecule that regulates growth cone motility [1,2]. The release of calcium from intracellular stores or influx via receptor-mediated or voltage-gated channels leads to discrete localised transients and/or global changes in [Ca++]i [3]. The frequency and magnitude of these [Ca++]i changes correlates with overall axon growth and extension as well as responses to soluble and contact-mediated guidance cues [2,4-6]. These changes in [Ca++]i can be of the order of milliseconds or quite persistent, lasting
(Anti-)Biography and Neo-Impressionism
Foa, Michelle
RIHA Journal , 2012,
Abstract: This article analyzes neo-impressionism in relation to the biographical model of art criticism and art history that became increasingly prevalent in France over the course of the 19th century. Examining the critical response to the neo-impressionists, as well as some of their pictures and writings, I argue for the centrality of questions of authorship, individuality, and subjectivity to the group and its reception. I identify a distinctly anti-biographical tendency in the movement, one that disquieted the critics and led them to try and re-inscribe biographical meaning back into the work of Georges Seurat. Indeed, though Seurat instituted a divide between his work and his life in a variety of ways, he also insisted throughout his career on his paternity over the neo-impressionist method. In all of these ways, the relationship between the self and art was a significant and problematic issue for the neo-impressionists and the critics around them.
TRPM8 and Nav1.8 sodium channels are required for transthyretin-induced calcium influx in growth cones of small-diameter TrkA-positive sensory neurons
Robert J Gasperini, Xu Hou, Helena Parkington, Harry Coleman, David W Klaver, Adele J Vincent, Lisa C Foa, David H Small
Molecular Neurodegeneration , 2011, DOI: 10.1186/1750-1326-6-19
Abstract: Levels of intracellular cytosolic calcium were monitored in dorsal root ganglion (DRG) neurons isolated from embryonic rats using the calcium-sensitive fluorescent indicator Fluo4. An amyloidogenic mutant form of TTR, L55P, induced calcium influx into the growth cones of DRG neurons, whereas wild-type TTR had no significant effect. Atomic force microscopy and dynamic light scattering studies confirmed that the L55P TTR contained oligomeric species of TTR. The effect of L55P TTR was decreased by blockers of voltage-gated calcium channels (VGCC), as well as by blockers of Nav1.8 voltage-gated sodium channels and transient receptor potential M8 (TRPM8) channels. siRNA knockdown of TRPM8 channels using three different TRPM8 siRNAs strongly inhibited calcium influx in DRG growth cones.These data suggest that activation of TRPM8 channels triggers the activation of Nav1.8 channels which leads to calcium influx through VGCC. We suggest that TTR-induced calcium influx into DRG neurons may contribute to the pathophysiology of FAP. Furthermore, we speculate that similar mechanisms may mediate the toxic effects of other amyloidogenic proteins such as the β-amyloid protein of Alzheimer's disease.Protein misfolding is a common feature of many neurodegenerative diseases. In some of these diseases, such as the synucleinopathies and the tauopathies, cytoplasmic proteins aggregate to form intracellular deposits. However, in the amyloidoses, which include Alzheimer's disease (AD), prion diseases and the British and Danish familial dementias, proteinaceous aggregates are observed extracellularly [1-4]. There is increasing evidence that the mechanism of neurotoxicity in these amyloidoses is similar and that it is the conformation of the aggregated protein, rather than its specific amino acid sequence which results in altered membrane permeability to calcium [5]. Therefore, studies on the mechanism of neurotoxicity in one disease may provide insights into the mechanisms involved in other
Forma jurídica burguesa y crisis ecológica: una aproximación marxista al derecho ambiental
Foa Torres,Jorge;
Revista SAAP , 2012,
Abstract: this paper seeks to develop a particular view of the legal phenomenon likely to include a social structural analysis in relation with the "environmental crisis" of global reach, understood as the expression of the breakthrough expropriation of the capitalist mode of production, the development of a particular view of the legal phenomenon likely to include a social structural analysis. in this context, presents a perspective capable of accounting for the place of law in the social whole, in order to avoid approaches that tend to consider social as ultimately determined by their normative propositions. in this sense, against the conception that is the legal regulation of the relationship between owner-thing as the key to limiting the economic development towards environmental protection, the structural relationship between private property rights and property type is proposed as a central issue when addressing the reproduction of the production media.
Mono-parametric quantum charge pumping: interplay between spatial interference and photon-assisted tunneling
Luis E. F. Foa Torres
Physics , 2005, DOI: 10.1103/PhysRevB.72.245339
Abstract: We analyze quantum charge pumping in an open ring with a dot embedded in one of its arms. We show that cyclic driving of the dot levels by a \textit{single} parameter leads to a pumped current when a static magnetic flux is simultaneously applied to the ring. Based on the computation of the Floquet-Green's functions, we show that for low driving frequencies $\omega_0$, the interplay between the spatial interference through the ring plus photon-assisted tunneling gives an average direct current (dc) which is proportional to $\omega_0^{2}$. The direction of the pumped current can be reversed by changing the applied magnetic field.
“Community” as a Reference for American Minority Groups: A Theory of Unintended Negative Consequences  [PDF]
Lisa Fisher
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.56020
Abstract: The phrase “the _____ community” is commonly used in naming minority groups in the US, for example, the African American community or the Muslim community. The phrase carries some benefits in terms of voice, sentiment, solidarity and empowerment, and it is widely accepted as a respectful reference. However, I argue that its use and meaning also carry unintended negative social psychological implications for how some minority group members may view themselves within the larger society and how some non-minority group members may view persons who identify as members of minority groups. In this paper, I examine the meaning and entailments of the word “community” as a convention of naming. I argue that negative implications stem from ubiquitous discursive emphasis on in-group sameness and groupness, which are rooted in historical practices of distillation and homogenization of diverse groups and demonstrate and invite perpetuation of stereotypes and prejudices, reinforce insider/outsider divides, and detract from personhood and social integration.
AC transport in carbon-based devices: challenges and perspectives
L. E. F. Foa Torres,G. Cuniberti
Physics , 2009, DOI: 10.1016/j.crhy.2009.05.003
Abstract: Time-dependent fields are a valuable tool to control fundamental quantum phenomena in highly coherent low dimensional electron systems. Carbon nanotubes and graphene are a promising ground for these studies. Here we offer a brief overview of driven electronic transport in carbon-based materials with the main focus on carbon nanotubes. Recent results predicting control of the current and noise in nanotube based Fabry-P\'{e}rot devices are highlighted.
Controlling the conductance and noise of driven carbon-based Fabry-Perot devices
L. E. F. Foa Torres,G. Cuniberti
Physics , 2008, DOI: 10.1063/1.3147865
Abstract: We report on ac transport through carbon nanotube Fabry-Perot devices. We show that tuning the intensity of the ac gating induces an alternation of suppression and partial revival of the conductance interference pattern. For frequencies matching integer multiples of the level spacing of the system $\Delta$ the conductance remains irresponsive to the external field. In contrast, the noise in the low bias voltage limit behaves as in the static case only when the frequency matches an even multiple of the level spacing, thereby highlighting its phase sensitivity in a manifestation of the wagon-wheel effect in the quantum domain.
Inelastic Quantum Transport and Peierls-like Mechanism in Carbon Nanotubes
L. E. F. Foa Torres,S. Roche
Physics , 2006, DOI: 10.1103/PhysRevLett.97.076804
Abstract: We report on a theoretical study of inelastic quantum transport in $(3m,0)$ carbon nanotubes. By using a many-body description of the electron-phonon interaction in Fock space, a novel mechanism involving optical phonon emission (absorption) is shown to induce an unprecedented energy gap opening at half the phonon energy, $\hbar\omega_{0}/2$, above (below) the charge neutrality point. This mechanism, which is prevented by Pauli blocking at low bias voltages, is activated at bias voltages in the order of $\hbar\omega_{0}$.
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