6,092 research outputs found
Clinical Association of White Matter Hyperintensities Localization in a Mexican Family with Spastic Paraparesis Carrying the PSEN1 A431E Mutation
Presenilin 1 gene (PSEN1) mutations are the most common cause of familial Alzheimer’s disease (FAD). One of the most abundant FAD mutations, PSEN1 A431E, has been reported to be associated with spastic paraparesis in about half of its carriers, but the determining mechanisms of this phenotype are still unknown. In our study we characterized three A431E mutation carriers, one symptomatic and two asymptomatic, from a Mexican family with a history of spastic paraparesis in all of its affected members. At cognitive assessment and MRI, the symptomatic subject showed an atypical non-amnestic mild cognitive impairment with visuospatial deficits, olfactory dysfunction and significant parieto-occipital brain atrophy. Furthermore, we found several periventricular white matter hyperintensities whose progression pattern and localization correlated with their motor impairment, cognitive profile, and non-motor symptoms. Together, our data suggests that in this family the A431E mutation leads to a divergent neurological disorder in which cognitive deterioration was clinically exceeded by motor impairment and that it involves early glial and vascular pathological changes
Quantum interference in the resonance fluorescence of a - atomic system: Quantum beats, nonclassicality, and non-Gaussianity
We study theoretically quantum statistical and spectral properties of the
resonance fluorescence of a single atom or system with angular momentum driven by a monochromatic linearly polarized laser field, due to
quantum interference among its two antiparallel, transitions. A magnetic
field parallel to the laser polarization is applied to break the degeneracy
(Zeeman effect). In the nondegenerate case, the transitions evolve at
different generalized Rabi frequencies, producing quantum beats in the
intensity and the dipole-dipole, intensity-intensity, and quadrature-intensity
correlations. For a strong laser and large Zeeman splitting the beats have mean
and modulation frequencies given by the average and difference, respectively,
of the Rabi frequencies, unlike thebeats studied in many spectroscopic systems,
characterized by a modulated exponential-like decay. Further, the Rabi
frequencies are those of the pairs of sidebands of the Mollow-like spectrum of
the system. In the two-time correlations, the cross contributions, i.e., those
with products of probability amplitudes of the two transitions, have a
lesser role than those from the interference of the probability densities. In
contrast, there are no cross terms in the total intensity. We also consider
nonclassical and non-Gaussian properties of the phase-dependent fluorescence
for the cases of weak to moderate excitation and in the regime of beats. The
fluorescence in the beats regime is nonclassical, mainly from third-order
dipole fluctuations, which reveal them to be also strongly non-Gaussian, and
their quadrature spectra show complex features around the Rabi frequencies. For
small laser and Zeeman detunings, a weak to moderate laser field pumps the
system partially to one of the ground states, showing slow decay in the two
time correlations and a narrow peak in the quadrature spectra.Comment: 19 pages, 14 figure
Overexploitation and water quality in the Crevillente aquifer (Alicante, SE Spain)
The Crevillente aquifer is a karstic aquifer, situated in Alicante province in the SE of Spain. The aquifer basically comprises a series of Jurassic limestones and dolomites, belonging to the Betic Cordillera. Intense exploitation of the aquifer started in the early 1960s. Exploitation was initially concentrated in two sectors of the Sierra de Crevillente and, years later, extended to a third sector. As a consequence of abstractions that were much greater than recharge into the system, a continual drop in the water level persisted for several decades. These abstractions have occasionally caused local dewatering over depths of more than 300 m. From a hydrogeological point of view, the aquifer dewatering in one of the sectors was accompanied by increased mineralization and a fall in quality of the groundwater, and several boreholes had to be abandoned. In recent years, the degree to which the aquifer is overexploited has fallen considerably, and it appears to have entered a new hydrodynamic stage. New hydrogeochemical characterisations have been carried out, which indicate that the aquifer water is relatively strongly mineralised due, fundamentally, to the dissolution of evaporite rocks. On the other hand, deterioration in water quality as a consequence of the degree of overabstraction can also be confirmedDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEGeneralitat ValencianaUNESCOpu
Mesoscopic structure conditions the emergence of cooperation on social networks
We study the evolutionary Prisoner's Dilemma on two social networks obtained
from actual relational data. We find very different cooperation levels on each
of them that can not be easily understood in terms of global statistical
properties of both networks. We claim that the result can be understood at the
mesoscopic scale, by studying the community structure of the networks. We
explain the dependence of the cooperation level on the temptation parameter in
terms of the internal structure of the communities and their interconnections.
We then test our results on community-structured, specifically designed
artificial networks, finding perfect agreement with the observations in the
real networks. Our results support the conclusion that studies of evolutionary
games on model networks and their interpretation in terms of global properties
may not be sufficient to study specific, real social systems. In addition, the
community perspective may be helpful to interpret the origin and behavior of
existing networks as well as to design structures that show resilient
cooperative behavior.Comment: Largely improved version, includes an artificial network model that
fully confirms the explanation of the results in terms of inter- and
intra-community structur
Serendipitous detection of an overdensity of Herschel-SPIRE 250 micron sources south of MRC1138-26
We report the serendipitous detection of a significant overdensity of
Herschel-SPIRE 250 micron sources in the vicinity of MRC1138-26. We use an
adaptive kernel density estimate to quantify the significance, including a
comparison with other fields. The overdensity has a size of ~3.5-4' and stands
out at ~5sigma with respect to the background estimate. No features with
similar significance were found in four extragalactic control fields:
GOODS-North, Lockman, COSMOS and UDS. The chance of having a similar
overdensity in a field with the same number but randomly distributed sources is
less than 2%. The clump is also visible as a low surface brightness feature in
the Planck 857 GHz map. We detect 76 sources at 250 micron (with a
signal-to-noise ratio greater than 3), in a region of 4' radius; 43 of those
are above a flux density limit of 20 mJy. This is a factor of 3.6 in excess
over the average in the four control fields, considering only the sources above
20 mJy. We also find an excess in the number counts of sources with 250 micron
flux densities between 30 and 40 mJy, compared to deep extragalactic
blank-field number counts. Assuming a fixed dust temperature (30 K) and
emissivity (beta=1.5) a crude, blackbody-derived redshift distribution, zBB, of
the detected sources is significantly different from the distributions in the
control fields and exhibits a significant peak at zBB ~ 1.5, although the
actual peak redshift is highly degenerate with the temperature. We tentatively
suggest, based on zBB and the similar S250/S350 colours of the sources within
the peak, that a significant fraction of the sources in the clump may be at a
similar redshift. Since the overdensity lies ~7' south of the z=2.16 Spiderweb
protocluster MRC1138-26, an intriguing possibility (that is presently
unverifiable given the data in hand) is that it lies within the same
large-scale structure.(abridged)Comment: 10 pages, 8 figures, accepted for publication in MNRA
The action of obestatin in skeletal muscle repair: stem cell expansion, muscle growth, and microenvironment remodeling
The development of therapeutic strategies for skeletal muscle diseases, such as physical injuries and myopathies, depends on the knowledge of regulatory signals that control the myogenic process. The obestatin/GPR39 system operates as an autocrine signal in the regulation of skeletal myogenesis. Using a mouse model of skeletal muscle regeneration after injury and several cellular strategies, we explored the potential use of obestatin as a therapeutic agent for the treatment of trauma-induced muscle injuries. Our results evidenced that the overexpression of the preproghrelin, and thus obestatin, and GPR39 in skeletal muscle increased regeneration after muscle injury. More importantly, the intramuscular injection of
obestatin significantly enhanced muscle regeneration by simulating satellite stem cell expansion as well as myofiber hypertrophy through a kinase hierarchy. Added to the myogenic action, the obestatin administration resulted in an increased expression of VEGF/VEGFR2 and the consequent microvascularization, with no effect on collagen deposition in skeletal muscle. Furthermore, the potential inhibition of myostatin during obestatin treatment might contribute to its myogenic action improving muscle growth and regeneration. Taken together, our data demonstrate successful improvement of muscle regeneration, indicating obestatin is a potential therapeutic agent for skeletal muscle injury and would
benefit other myopathies related to muscle regeneration
Phases I–III Clinical Trials Using Adult Stem Cells
First randomized clinical trials have demonstrated that stem cell therapy can improve cardiac recovery after the acute phase of myocardial ischemia and in patients with chronic ischemic heart disease. Nevertheless, some trials have shown that conflicting results and uncertainties remain in the case of mechanisms of action and possible ways to improve clinical impact of stem cells in cardiac repair. In this paper we will examine the evidence available, analyze the main phase I and II randomized clinical trials and their limitations, discuss the key points in the design of future trials, and depict new directions of research in this fascinating field
Automatic pre-alignment of multimodality rat brain images using principal axes transformation
Abstract of: AMI Annual Conference 2006, March 25-29The use of small animal studies of different modalities isnowadays widespread, since functional studies like positron emission tomography (PET) or single photon emission computed tomography (SPECT) are better analyzed when mapped to the underlying anatomical structure coming from magnetic resonance imaging (MRI) or computed tomography (CT). The different positioning of the animals in the scanners results in the need for automated image registration methods. One important drawback of the existing algorithms is their limited capture range: if case of large initial misregistration (large translations and rotations) the optimization may not converge to the right solution, and the images do not become correctly coregistered. To avoid this problem we propose the use of a pre-alignment step based on the principal axes transformation.Publicad
- …