817 resultados para landscape modulation


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The prefrontal (PFC) and orbitofrontal cortex (OFC) appear to be associated with both executive functions and olfaction. However, there is little data relating olfactory processing and executive functions in humans. The present study aimed at exploring the role of olfaction on executive functioning, making a distinction between primary and more cognitive aspects of olfaction. Three executive tasks of similar difficulty were used. One was used to assess hot executive functions (Iowa Gambling Task-IGT), and two as a measure of cold executive functioning (Stroop Colour and Word Test-SCWT and Wisconsin Card Sorting Test-WCST). Sixty two healthy participants were included: 31 with normosmia and 31 with hyposmia. Olfactory abilities were assessed using the ''Sniffin' Sticks'' test and the olfactory threshold, odour discrimination and odour identification measures were obtained. All participants were female, aged between 18 and 60. Results showed that participants with hyposmia displayed worse performance in decision making (IGT; Cohen's-d = 0.91) and cognitive flexibility (WCST; Cohen's-d between 0.54 and 0.68) compared to those with normosmia. Multiple regression adjusted by the covariates participants' age and education level showed a positive association between odour identification and the cognitive inhibition response (SCWT-interference; Beta = 0.29; p = .034). The odour discrimination capacity was not a predictor of the cognitive executive performance. Our results suggest that both hot and cold executive functions seem to be associated with higher-order olfactory functioning in humans. These results robustly support the hypothesis that olfaction and executive measures have a common neural substrate in PFC and OFC, and suggest that olfaction might be a reliable cognitive marker in psychiatric and neurologic disorders.

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Background: CD8 T-cells play a critical role in antiviral immunity. However, mechanisms of virus control and immune correlates of protection are still not fully understood. Among other factors, TCR avidity (antigen sensitivity) is thought to play a critical role. Whereas there is a large consensus that high TCR avidity T-cell responses are correlated to higher efficacy against cancer and acute viral infections, it may be not the case in chronic persistent viral infections. Methods: TCR avidity (measured by the effect concentration 50% [EC50]) of HIV-1-specific CD8 T-cell responses directed against optimal epitopes was investigated in different cohorts of HIV-1- infected subjects (n¼114) including early acute and chronic (progressive and non-progressive) HIV-1-infection. Overall, TCR avidity was investigated in 245 HIV-1-specific CD8 T-cell responses. The relationships between TCR avidity, T-cell differentiation and functional profile including cytokine secretion, proliferation and cytotoxic potential (determined by polychromatic flow cytometry) were analyzed. Results: HIV-1-specific CD8 T-cell responses from patients with acute infection had significantly lower TCR avidity as compared to patients with chronic (progressive or non-progressive) HIVinfection (P¼0.03 and 0.003, respectively). These differences remained significant when the analyses were restricted to common epitopes (same epitopes restricted by the same class I HLA). Interestingly, some patients treated during acute infection underwent spontaneous treatment interruption. Re-exposure to high viral load induced two major effects: a) the increase in TCR avidity of pre-existing high avidity (EC50<0.01) T-cell responses (P<0.02) and b) the generation of new T-cell responses with higher TCR avidity as compared to the average pre-existing T-cell responses. Conclusion: These results suggest that high TCR avidity T-cell responses are selected during the course of HIV-1 infection and that one of the potential driving mechanisms is continuous exposure to HIV-1 antigens. These results advance our understanding of the relationship between TCR avidity and Ag exposure of antiviral memory CD8 T-cells.

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It is currently suspected that sugar overconsumption, and more specifically fructose, may promote the development of obesity and of several cardio-metabolic disorders. However, environmental factors, such as fish oil and dietary proteins, may prevent some deleterious effects of fructose. The aim of this thesis was to identify potential environmental factors that may modulate the metabolic effects of fructose. The first study was designed to evaluate the impact of endurance exercise in healthy young men fed a high-fructose, isocaloric diet. Fructose-induced effects on lipid profile were totally prevented by endurance exercise and may be explained by an enhanced clearance of TRL-TG and the inhibition of de novo lipogenesis. As energy intake was adjusted to energy requirement, we can conclude that exercise acts on fructose metabolism independently of energy imbalance. The second study aimed at determining whether coffee and more specifically chlorogenic acid consumption may prevent fructose-induced intrahepatic lipids accumulation, hypertriglyceridemia and hepatic insulin resistance, through a stimulation of lipid oxidation. Coffee did not prevent the fructose-induced increase in IHCL or plasma TG. Interestingly, the three coffees tested prevented the decrease in hepatic insulin sensitivity, independently of their content in caffeine or chlorogenic acid. Finally, in the third study, we evaluated the effect of essential amino acid supplementation on the increase of hepatic lipids induced by a high-fructose diet. This intervention slightly decreased IHCL concentration. The exact mechanisms remain unidentified but may involve an increased secretion of VLDL-TG. In conclusion, the environmental factors evaluated allow to prevent some of the deleterious effects of fructose and suggest that recommendations on fructose consumption should also take into account environmental factors.

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Extensive theoretical and experimental work on the neuronal correlates of visual attention raises two hypotheses about the underlying mechanisms. The first hypothesis, named biased competition, originates from experimental single-cell recordings that have shown that attention upmodulates the firing rates of the neurons encoding the attended features and downregulates the firing rates of the neurons encoding the unattended features. Furthermore, attentional modulation of firing rates increases along the visual pathway. The other, newer hypothesis assigns synchronization a crucial role in the attentional process. It stems from experiments that have shown that attention modulates gamma-frequency synchronization. In this paper, we study the coexistence of the two phenomena using a theoretical framework. We find that the two effects can vary independently of each other and across layers. Therefore, the two phenomena are not concomitant. However, we show that there is an advantage in the processing of information if rate modulation is accompanied by gamma modulation, namely that reaction times are shorter, implying behavioral relevance for gamma synchronization.

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Cell-to-cell communication mediated by gap junctions made of Connexin36 (Cx36) contributes to pancreatic β-cell function. We have recently demonstrated that Cx36 also supports β-cell survival by a still unclear mechanism. Using specific Cx36 siRNAs or adenoviral vectors, we now show that Cx36 downregulation promotes apoptosis in INS-1E cells exposed to the pro-inflammatory cytokines (IL-1β, TNF-α and IFN-γ) involved at the onset of type 1 diabetes, whereas Cx36 overexpression protects against this effect. Cx36 overexpression also protects INS-1E cells against endoplasmic reticulum (ER) stress-mediated apoptosis, and alleviates the cytokine-induced production of reactive oxygen species, the depletion of the ER Ca(2+) stores, the CHOP overexpression and the degradation of the anti-apoptotic protein Bcl-2 and Mcl-1. We further show that cytokines activate the AMP-dependent protein kinase (AMPK) in a NO-dependent and ER-stress-dependent manner and that AMPK inhibits Cx36 expression. Altogether, the data suggest that Cx36 is involved in Ca(2+) homeostasis within the ER and that Cx36 expression is downregulated following ER stress and subsequent AMPK activation. As a result, cytokine-induced Cx36 downregulation elicits a positive feedback loop that amplifies ER stress and AMPK activation, leading to further Cx36 downregulation. The data reveal that Cx36 plays a central role in the oxidative stress and ER stress induced by cytokines and the subsequent regulation of AMPK activity, which in turn controls Cx36 expression and mitochondria-dependent apoptosis of insulin-producing cells.

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Silver Code (SilC) was originally discovered in [1–4] for 2×2 multiple-input multiple-output (MIMO) transmission. It has non-vanishing minimum determinant 1/7, slightly lower than Golden code, but is fast-decodable, i.e., it allows reduced-complexity maximum likelihood decoding [5–7]. In this paper, we present a multidimensional trellis-coded modulation scheme for MIMO systems [11] based on set partitioning of the Silver Code, named Silver Space-Time Trellis Coded Modulation (SST-TCM). This lattice set partitioning is designed specifically to increase the minimum determinant. The branches of the outer trellis code are labeled with these partitions. Viterbi algorithm is applied for trellis decoding, while the branch metrics are computed by using a sphere-decoding algorithm. It is shown that the proposed SST-TCM performs very closely to the Golden Space-Time Trellis Coded Modulation (GST-TCM) scheme, yetwith a much reduced decoding complexity thanks to its fast-decoding property.

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Acid-sensing ion channels (ASICs) are neuronal Na(+)-selective channels that are transiently activated by extracellular acidification. ASICs are involved in fear and anxiety, learning, neurodegeneration after ischemic stroke, and pain sensation. The small molecule 2-guanidine-4-methylquinazoline (GMQ) was recently shown to open ASIC3 at physiological pH. We have investigated the mechanisms underlying this effect and the possibility that GMQ may alter the function of other ASICs besides ASIC3. GMQ shifts the pH dependence of activation to more acidic pH in ASIC1a and ASIC1b, whereas in ASIC3 this shift goes in the opposite direction and is accompanied by a decrease in its steepness. GMQ also induces an acidic shift of the pH dependence of inactivation of ASIC1a, -1b, -2a, and -3. As a consequence, the activation and inactivation curves of ASIC3 but not other ASICs overlap in the presence of GMQ at pH 7.4, thereby creating a window current. At concentrations >1 mm, GMQ decreases maximal peak currents by reducing the unitary current amplitude. Mutation of residue Glu-79 in the palm domain of ASIC3, previously shown to be critical for channel opening by GMQ, disrupted the GMQ effects on inactivation but not activation. This suggests that this residue is involved in the consequences of GMQ binding rather than in the binding interaction itself. This study describes the mechanisms underlying the effects of a novel class of ligands that modulate the function of all ASICs as well as activate ASIC3 at physiological pH.

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Coherent regulation of landscape as a resource is a major challenge. How can the development interests of some actors (eg cable car operators and property developers) be reconciled with those of others (agriculture, forestry) and with conservation of biodiversity and scenic value? To help understand how the newly introduced Regional Nature Parks (RNPs) can improve the coherence of the regulation regime in Switzerland, we highlight current direct mechanisms for regulation of landscape as a resource (bans, inventories, subsidies) as well as indirect mechanisms (taking place through the regulation of the physical basis of landscapes, eg forest, land, and water planning policies). We show that RNPs are fundamentally innovative because they make it possible to manage and coordinate indirect strategies for appropriate regulation of resources at a landscape scale. In other words, RNPs enable organization of governance of landscape as a resource in a perimeter that is not necessarily restricted to administrative boundaries.