4,031 research outputs found
A Cholinergic Synaptically Triggered Event Participates in the Generation of Persistent Activity Necessary for Eye Fixation
An exciting topic regarding integrative properties of the nervous system is how transient motor commands or brief sensory stimuli are able to evoke persistent neuronal changes, mainly as a sustained, tonic action potential firing. A persisting firing seems to be necessary for postural maintenance after a previous movement. We have studied in vitro and in vivo the generation of the persistent neuronal activity responsible for eye fixation after spontaneous eye movements. Rat sagittal brainstem slices were used for the intracellular recording of prepositus hypoglossi (PH) neurons and their synaptic activation from nearby paramedian pontine reticular formation (PPRF) neurons. Single electrical pulses applied to the PPRF showed a monosynaptic glutamatergic projection on PH neurons, acting on AMPA-kainate receptors. Train stimulation of the PPRF area evoked a sustained depolarization of PH neurons exceeding (by hundreds of milliseconds) stimulus duration. Both duration and amplitude of this sustained depolarization were linearly related to train frequency. The train-evoked sustained depolarization was the result of interaction between glutamatergic excitatory burst neurons and cholinergic mesopontine reticular fibers projecting onto PH neurons, because it was prevented by slice superfusion with cholinergic antagonists and mimicked by cholinergic agonists. As expected, microinjections of cholinergic antagonists in the PH nucleus of alert behaving cats evoked a gaze-holding deficit consisting of a re-centering drift of the eye after each saccade. These findings suggest that a slow, cholinergic, synaptically triggered event participates in the generation of persistent activity characteristic of PH neurons carrying eye position signals
Applying the Random Variable Transformation method to solve a class of random linear differential equation with discrete delay
[EN] We randomize the following class of linear differential equations with delay, x(tau)' (t) = ax(tau) (t) bx(tau) (t -tau), t> 0, and initial condition, x(tau )(t) = g(t), -tau 0(+), to the first probability density function, say f(x, t), of the corresponding associated random linear problem without delay (tau = 0). The paper concludes with several numerical experiments illustrating our theoretical findings.This work has been partially supported by the Ministerio de Economia y Competitividad grant MTM2017-89664-P and MTM2015-63723-P and Junta de Andalucia under Proyecto de Excelencia P12-FQM-1492. Ana Navarro Quiles acknowledges the Fundacio Ferran Sunyer i Balaguer and the Instituto de Estudios Catalanes for its contribution through the Borsa Ferran Sunyer i Balaguer. Ana Navarro Quiles acknowledges the postdoctoral contract financed by DyCon project funding from the European Research Council(ERC) under the European Unions Horizon 2020 research and innovation programme (grant agreement No 694126-DYCON). The authors express their deepest thanks and respect to the editors and reviewers for their valuable comments.Caraballo, T.; Cortés, J.; Navarro-Quiles, A. (2019). Applying the Random Variable Transformation method to solve a class of random linear differential equation with discrete delay. Applied Mathematics and Computation. 356:198-218. https://doi.org/10.1016/j.amc.2019.03.048S19821835
Terahertz imaging of sub-wavelength particles with Zenneck surface waves
Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations
The Imprint of Galaxy Formation on X-ray Clusters
It is widely believed that structure in the Universe evolves hierarchically,
as primordial density fluctuations, amplified by gravity, collapse and merge to
form progressively larger systems. The structure and evolution of X-ray
clusters, however, seems at odds with this hierarchical scenario for structure
formation. Poor clusters and groups, as well as most distant clusters detected
to date, are substantially fainter than expected from the tight relations
between luminosity, temperature and redshift predicted by these models. Here we
show that these discrepancies arise because, near the centre, the entropy of
the hot, diffuse intracluster medium (ICM) is higher tha possible if the ICM
is heated at modest redshift (z \ltsim 2) but prior to cluster collapse,
indicating that the formation of galaxies precedes that of clusters and that
most clusters have been assembled very recently.Comment: 5 pages, plus 2 postscript figures (one in colour), accepted for
publication in Natur
On the use of surfaces of section in the N‐body ring problem
In the N‐body ring problem, we investigate the motion of a massless body interacting with N bodies of equal masses at the vertices of a regular polygon that rotates around a central mass. In this paper, we analyze the use of different surfaces of section in the numerical exploration of the escape in the N‐body ring problem in order to get some conclusions about the geometry of the basins of escape in the corresponding configuration spaces
Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation
Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of > 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of > 0.5 W m−2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m−2 and the global mean cloud-albedo aerosol indirect effect of between −0.008 and −0.056 W m−2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates
Brain activity changes with emotional words in different stages of psychosis
BackgroundTo date, a large number of functional magnetic resonance imaging (fMRI) studies have been conducted on psychosis. However, little is known about changes in brain functioning in psychotic patients using an emotional auditory paradigm at different stages of the disease. Such knowledge is important for advancing our understanding of the disorder and thus creating more targeted interventions. This study aimed to investigate whether individuals with first-episode psychosis (FEP) and chronic schizophrenia show abnormal brain responses to emotional auditory processing and to compare the responses between FEP and chronic schizophrenia. MethodsPatients with FEP (n = 31) or chronic schizophrenia (n = 23) and healthy controls (HCs, n = 31) underwent an fMRI scan while presented with both emotional and nonemotional words. ResultsUsing HC as a reference, patients with FEP showed decreased right temporal activation, while patients with chronic schizophrenia showed increased bilateral temporal activation. When comparing the patient groups, individuals with FEP showed lower frontal lobe activation. ConclusionTo the best of our knowledge, this is the first study with an emotional auditory paradigm used in psychotic patients at different stages of the disease. Our results suggested that the temporal lobe might be a key issue in the physiopathology of psychosis, although abnormal activation could also be derived from a connectivity problem. There is lower activation in the early stage and evolution to greater activation when patients become chronic. This study highlights the relevance of using emotional paradigms to better understand brain activation at different stages of psychosis
Proteomics and gene expression analyses of squalene-supplemented mice identify microsomal thioredoxin domain-containing protein 5 changes associated with hepatic steatosis
Squalene is an abundant hydrocarbon present in virgin olive oil. Previous studies showed that its administration decreased atherosclerosis and steatosis in male apoE-knock-out mice. To study its effects on microsomal proteins, 1 g/kg/day of squalene was administered to those mice. After 10 weeks, hepatic fat content was assessed and protein extracts of microsomal enriched fractions from control and squalene-treated animals were analyzed by 2D-DIGE. Spots exhibiting significant differences were identified by peptide fingerprinting and MSMS analysis. Squalene administration modified the expression of thirty-one proteins involved in different metabolic functions and increased the levels of those involved in vesicle transport, protein folding and redox status. Only mRNA levels of 9 genes (Arg1, Atp5b, Cat, Hyou1, Nipsnap1, Pcca, Pcx, Pyroxd2, and Txndc5) paralleled these findings. No such mRNA changes were observed in wild-type mice receiving squalene. Thioredoxin domain-containing protein 5 (TXNDC5) protein and mRNA levels were significantly associated with hepatic fat content in apoE-ko mice. These results suggest that squalene action may be executed through a complex regulation of microsomal proteins, both at the mRNA and post-transcriptional levels and the presence of apoE may change the outcome. Txndc5 reflects the anti-steatotic properties of squalene and the sensitivity to lipid accumulation
Measuring Outcome after Wrist Injury: Translation and Validation of the Swedish Version of the Patient-Rated Wrist Evaluation (PRWE-Swe)
<p>Abstract</p> <p>Background</p> <p>There is a need for outcome measurement instruments for evaluation of disability after trauma. The Patient-Rated Wrist Evaluation (PRWE) is a self-administered region-specific outcome measuring instrument developed for use in evaluating disability and pain of the wrist. The aim of this study is to translate and to cross-culturally adapt the PRWE for use in a Swedish patient population. Moreover, we aim at investigating the PRWE in terms of validity, reliability and responsiveness.</p> <p>Methods</p> <p>We performed a translation and cross-cultural adaptation of the PRWE to Swedish (PRWE-Swe), utilising the process recommended by the American Association of Orthopedic Surgeons. A total of 124 patients with an injury to the wrist were included in the study. They filled in the PRWE and the DASH questionnaires at two separate occasions.</p> <p>Results</p> <p>Reliability of the PRWE in terms of internal consistency (Cronbach's alpha 0.97) and test-retest stability (intraclass correlation coefficient 0.93) were excellent. Face validity and content validity were judged as good. Criterion validity assessed as the correlation between the PRWE and the DASH was also good (Spearman's rho = 0.9). Responsiveness measured by the standardized response mean (SRM) was good with an SRM<sub>PRWE </sub>of 1.29.</p> <p>Conclusion</p> <p>This Swedish version of the PRWE is a short and easily understood self-administered questionnaire with good validity, reliability, and responsiveness. Our results confirm that the PRWE is a valuable tool in evaluating the results after treatment of a wrist injury.</p
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