Pneumococcal septicemiae (Streptococcus pneumoniae) in the calves

Les auteurs décrivent un foyer de septicémie à pneumocoques ( Strepto coccus pneumoniae) chez des veaux en France. L’affection sévit chez des animaux très jeunes de 0 à 8 semaines jusqu’à 3 mois et est d’évolution très rapide (quelques heures) accompagnée d’entérite subaiguë, et de lésions pulmonaires diffuses. Cette maladie peut être confondue avec de la colibacillose ou de la salmonellose ; seuls les examens bactériologiques permettent le diagnostic. C’est une affection bien connue en Allemagne, Danemark, Suisse, présente aussi en Italie et en Angleterre. En France, la maladie existe mais l’évolution est telle que les différentes phases de son diagnostic sont difficiles. Le sérotype de Streptococcus pneumoniae trouvé dans cette étude est un 18, sérotype assez fréquent en médecine humaine.The authors describe an outbreak of pneumococcal septicemiae ( Strep tococcus pneumoniae ) in the calves in France. The disease take its course in very young animals of 0 to 8 weeks old up to 3 months. The evolution is very speedy (a few hours) with clinical signs of sub acute enteritis and diffuse pulmonary lesions ; this disease can be confused with collibacillosis and salmonellosis ; and the diagnosis can be made only by bacteriological examination. This affection is well known in Germany, Denmark and Switzerland, and exists in Italy and Great Britain. In France the disease exists but the evolution is such that the different phases of the different phases of the diagnosis are difficult. The serotye of Streptococcus pneumoniae isolated in this study is serotype 18 wich is rather frequent in human medicine

Neuromodulated synaptic plasticity on the SpiNNaker neuromorphic system

SpiNNaker is a digital neuromorphic architecture, designed specifically for the low power simulation of large-scale spiking neural networks at speeds close to biological real-time. Unlike other neuromorphic systems, SpiNNaker allows users to develop their own neuron and synapse models as well as specify arbitrary connectivity. As a result SpiNNaker has proved to be a powerful tool for studying different neuron models as well as synaptic plasticity—believed to be one of the main mechanisms behind learning and memory in the brain. A number of Spike-Timing-Dependent-Plasticity(STDP) rules have already been implemented on SpiNNaker and have been shown to be capable of solving various learning tasks in real-time. However, while STDP is an important biological theory of learning, it is a form of Hebbian or unsupervised learning and therefore does not explain behaviors that depend on feedback from the environment. Instead, learning rules based on neuromodulated STDP (three-factor learning rules) have been shown to be capable of solving reinforcement learning tasks in a biologically plausible manner. In this paper we demonstrate for the first time how a model of three-factor STDP, with the third-factor representing spikes from dopaminergic neurons, can be implemented on the SpiNNaker neuromorphic system. Using this learning rule we first show how reward and punishment signals can be delivered to a single synapse before going on to demonstrate it in a larger network which solves the credit assignment problem in a Pavlovian conditioning experiment. Because of its extra complexity, we find that our three-factor learning rule requires approximately 2× as much processing time as the existing SpiNNaker STDP learning rules. However, we show that it is still possible to run our Pavlovian conditioning model with up to 1 × 104 neurons in real-time, opening up new research opportunities for modeling behavioral learning on SpiNNaker

Element abundances in the stars of the MILES spectral library: the Mg/Fe ratio

We have obtained [Mg/Fe] measurements for 76.3 per cent of the stars in the Mid-resolution Isaac Newton Telescope Library of Empirical Spectra (MILES) spectral library used for understanding stellar atmospheres and stellar populations in galaxies and star clusters. These abundance ratios were obtained through (1) a compilation of values from the literature using abundances from high-resolution (HR) spectroscopic studies and (2) a robust spectroscopic analysis using the MILES mid-resolution (MR) optical spectra. All the [Mg/Fe] values were carefully calibrated to a single uniform scale, by using an extensive control sample with results from HR spectra. The small average uncertainties in the calibrated [Mg/Fe] values [respectively 0.09 and 0.12 dex with methods (1) and (2)] and the good coverage of the stars with [Mg/Fe] over stellar atmospheric parameter space of the library will permit the building of new simple stellar populations (SSPs) with empirical α-enhancements. These will be available for a range of [Mg/Fe], including both sub-solar and super-solar values, and for several metallicities and ages. These models will open up new prospects for testing and applications of evolutionary stellar population synthesis

Prospects for population synthesis in the H band: NeMo grids of stellar atmospheres compared to observations

For applications in population synthesis, libraries of theoretical stellar spectra are often considered an alternative to template libraries of observed spectra, because they allow a complete sampling of stellar parameters. Most attention in published theoretical spectral libraries has been devoted to the visual wavelength range. We present a detailed comparison of theoretical spectra in the range 1.57-1.67$\mu$m, for spectral types from A to early M and for giants and dwarf stars, with observed stellar spectra at resolutions around 3000, which would be sufficient to disentangle the different groups of late type stars. We have selected the NeMo grids of stellar atmospheres to perform such a comparison. We first demonstrate that after combining atomic and molecular line lists, it is possible to match observed spectral flux distributions with theoretical ones very well for almost the entire parameter range covered by the NeMo grids at moderate resolution in the visual range. In the infrared range, although the overall shape of the observed flux distributions is still matched reasonably well, the individual spectral features are reproduced by the theoretical spectra only for stars earlier than mid F type. For later spectral types the differences increase and theoretical spectra of K type stars have systematically weaker line features than those found in observations. These discrepancies are traced back to stem primarily from incomplete data on neutral atomic lines, although some of them are also related to molecules. Improving atomic data in the near infrared is a key element in making the construction of reliable libraries of stellar spectra in the infrared feasible.Comment: 17 pages, 19 figures, accepted for publication in A&

IL-26 is overexpressed in chronically HCV-infected patients and enhances TRAIL-mediated cytotoxicity and interferon production by human NK cells

Objective Interleukin-26 (IL-26) is a member of the IL-10 cytokine family, first discovered based on its peculiar expression by virus-transformed T cells. IL-26 is overexpressed in chronic inflammation (rheumatoid arthritis and Crohn’s disease) and induces proinflammatory cytokines by myeloid cells and some epithelial cells. We thus investigated the expression and potential role of IL-26 in chronic HCV infection, a pathology associated with chronic inflammation.Design IL-26 was quantified in a cohort of chronically HCV-infected patients, naive of treatment and its expression in the liver biopsies investigated by immunohistochemistry. We also analysed the ability of IL-26 to modulate the activity of natural killer (NK) cells, which control HCV infection. Results The serum levels of IL-26 are enhanced in chronically HCV-infected patients, mainly in those with severe liver inflammation. Immunohistochemistry reveals an intense IL-26 staining in liver lesions, mainly in infiltrating CD3+ cells. We also show that NK cells from healthy subjects and from HCV-infected patients are sensitive to IL-26. IL-26 upregulates membrane tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) expression on CD16− CD56bright NK cells, enabling them to kill HCV-infected hepatoma cells, with the same efficacy as interferon (IFN)-α-treated NK cells. IL-26 also induces the expression of the antiviral cytokines IFN-β and IFN-γ, and of the proinflammatory cytokines IL-1β and TNF-α by NK cells. Conclusions This study highlights IL-26 as a new player in the inflammatory and antiviral immune responses associated with chronic HCV infection

Comprendre les comportements face à un risque modéré d’inondation. Etude de cas dans le périurbain toulousain (Sud-Ouest de la France)

Les espaces urbanisés soumis à des risques modérés d’inondation pour les vies humaines sont souvent peu considérés dans les études sur la vulnérabilité aux risques naturels en dépit des enjeux qu’ils représentent en termes de gestion de crise. Comment les riverains y font-ils face au danger et quelles sont leurs « bonnes raisons » d’agir? A partir de l’étude socio-géographique de deux inondations récentes (2000 et 2003) dans la périphérie toulousaine (Sud-Ouest de la France), nous montrons que les caractéristiques de l’aléa dans les vallées étudiées influencent les représentations du risque et par conséquent les motivations à se protéger. Face au risque majeur, la vulnérabilité sociale se trouve ainsi augmentée. Pour améliorer la résilience des populations, il convient d’adapter la communication sur les risques: personnaliser l’information, améliorer la compréhension de l’événement vécu et mobiliser de nouvelles formes de médiation entre gestionnaires et riverains

IL-34 and macrophage colony-stimulating factor are overexpressed in hepatitis C virus fibrosis and induce profibrotic macrophages that promote collagen synthesis by hepatic stellate cells

Chronic hepatitis C virus (HCV) infection is characterized by progressive hepatic fibrosis, a process dependent on monocyte recruitment and accumulation into the liver. The mediators expressed in chronically injured liver that control the differentiation of human monocytes into profibrotic macrophages (Mφ) remain poorly defined. We report that chronically HCV-infected patients with high fibrosis stages have higher serum levels of macrophage colony-stimulating factor (M-CSF) and interleukin (IL)−34 than HCV-infected patients with lower fibrosis stages and healthy subjects. Immunohistochemistry reveals an intense expression of IL-34 and M-CSF by hepatocytes around liver lesions. In addition, HCV infection and inflammatory cytokines enhance the in vitro production of IL-34 and M-CSF by hepatocytes. We next analyzed the acquisition of profibrotic properties by Mφ generated with M-CSF (M-CSF-Mφ) or IL-34 (IL-34-Mφ). M-CSF and IL-34 up-regulate the expression, by differentiating monocytes, of chemokine (C-C motif) ligand (CCL)2, CCL4, C-C chemokine receptor (CCR)1, and CCR5, which are involved in monocyte recruitment/Mφ accumulation in liver lesions. M-CSF-Mφ and IL-34-Mφ also express the hepatic stellate cell (HSC) activators, platelet-derived growth factor, transforming growth factor beta, and galectin-3. IL-34-Mφ and M-CSF-Mφ induce type I collagen synthesis by HSCs, the main collagen-producing cells in liver fibrosis. IL-13, whose expression correlates with the fibrosis stage in HCV-infected patients, decreases the expression of the collagenase, matrix metalloproteinase 1, by IL-34-Mφ and M-CSF-Mφ, thereby enhancing collagen synthesis. By inhibiting the production of interferon-gamma (IFN-γ) by activated natural killer cells, IL-34-Mφ and M-CSF-Mφ prevent the IFN-γ-induced killing of HSCs. Conclusion: These results identify M-CSF and IL-34 as potent profibrotic factors in HCV liver fibrosis

Spike-Based Reinforcement Learning in Continuous State and Action Space: When Policy Gradient Methods Fail

Changes of synaptic connections between neurons are thought to be the physiological basis of learning. These changes can be gated by neuromodulators that encode the presence of reward. We study a family of reward-modulated synaptic learning rules for spiking neurons on a learning task in continuous space inspired by the Morris Water maze. The synaptic update rule modifies the release probability of synaptic transmission and depends on the timing of presynaptic spike arrival, postsynaptic action potentials, as well as the membrane potential of the postsynaptic neuron. The family of learning rules includes an optimal rule derived from policy gradient methods as well as reward modulated Hebbian learning. The synaptic update rule is implemented in a population of spiking neurons using a network architecture that combines feedforward input with lateral connections. Actions are represented by a population of hypothetical action cells with strong mexican-hat connectivity and are read out at theta frequency. We show that in this architecture, a standard policy gradient rule fails to solve the Morris watermaze task, whereas a variant with a Hebbian bias can learn the task within 20 trials, consistent with experiments. This result does not depend on implementation details such as the size of the neuronal populations. Our theoretical approach shows how learning new behaviors can be linked to reward-modulated plasticity at the level of single synapses and makes predictions about the voltage and spike-timing dependence of synaptic plasticity and the influence of neuromodulators such as dopamine. It is an important step towards connecting formal theories of reinforcement learning with neuronal and synaptic properties

Stellar population synthesis in the presence of diluting components

Aims.Numerous studies of the host galaxy of Seyfert nuclei are being conducted in the optical/visible range. However, in the case of Seyfert 1, the spectra of the inner galactic core can be dominated by broad emission lines coming from the nucleus that totally flood the underlying galactic spectrum, preventing any study of stellar populations. Methods.Because part of the IR H-band is free of the strongest AGN emission lines, we developed a method that allows the stellar population of the very internal regions of the Seyfert 1 galaxies to be studied in the presence of a diluting continuum. Results. A new inverse method using the flux as observables was developed and deeply tested. The specificity of the method is to take the non stellar parameters (reddening, dust emission, and non-stellar continuum) into account directly in the synthetic distance to be minimised. Conclusions. The method is powerful for deriving the stellar content of the very central part of AGN. However, the results for the stellar population are still tentative, as the incompleteness of the stellar base (lack of supermetallic giant stars) could lead to large uncertainties. New observations of stars in the infrared at high spectral resolution, in particular metal-rich stars, are mandatory to build a complete stellar library that can be used to synthesise the host galaxies of AGN with as much accuracy as possible