The obscuration by dust of most of the growth of supermassive black holes

Supermassive black holes underwent periods of exponential growth during which we see them as quasars in the distant Universe. The summed emission from these quasars generates the cosmic X-ray background, the spectrum of which has been used to argue that most black-hole growth is obscured. There are clear examples of obscured black-hole growth in the form of 'type-2' quasars, but their numbers are fewer than expected from modelling of the X-ray background. Here we report the direct detection of a population of distant type-2 quasars, which is at least comparable in size to the well-known unobscured type-1 population. We selected objects that have mid-infrared and radio emissions characteristic of quasars, but which are faint at near-infrared and optical wavelengths. We conclude that this population is responsible for most of the black-hole growth in the young Universe and that, throughout cosmic history, black-hole growth occurs in the dusty, gas-rich centres of active galaxies.     

Pancreatic polypeptide: A possible role in the regulation of food intake in the mouse. Hypothesis

Summary Pancreatic polypeptide (PP) is a recently identified hormone produced by pancreatic endocrine cells. The islets of genetically obese mice (ob/ob, C57 BL/6J), which are suspected to lack a circulating satiety factor, contain relatively few of the PP-producing cells. Administration of bovine pancreatic polypeptide (bPP) reduces food intake and suppresses body weight gain in the hyperphagic obese mice. It is postulated that PP participates in the regulation of food intake in a manner as yet undefined.This work was supported by grant No. 3.553.75 from Swiss National Science Foundation. We thank Mrs M. Eissler and Mr R. Cuche for their valuable help.     

Exploiting Spillovers to Forecast Crashes

We develop Hawkes models in which events are triggered through self‐excitation as well as cross‐excitation. We examine whether incorporating cross‐excitation improves the forecasts of extremes in asset returns compared to only self‐excitation. The models are applied to US stocks, bonds and dollar exchange rates. We predict the probability of crashes in the series and the value at risk (VaR) over a period that includes the financial crisis of 2008 using a moving window. A Lagrange multiplier test suggests the presence of cross‐excitation for these series. Out‐of‐sample, we find that the models that include spillover effects forecast crashes and the VaR significantly more accurately than the models without these effects. Copyright © 2016 John Wiley & Sons, Ltd.     

Filamentous actin accumulates during plant cell penetration and cell wall plug formation in <Emphasis Type="Italic">Phytophthora infestans</Emphasis>

The oomycete Phytophthora infestans is the cause of late blight in potato and tomato. It is a devastating pathogen and there is an urgent need to design alternative strategies to control the disease. To find novel potential drug targets, we used Lifeact-eGFP expressing P. infestans for high resolution live cell imaging of the actin cytoskeleton in various developmental stages. Previously, we identified actin plaques as structures that are unique for oomycetes. Here we describe two additional novel actin configurations; one associated with plug deposition in germ tubes and the other with appressoria, infection structures formed prior to host cell penetration. Plugs are composed of cell wall material that is deposited in hyphae emerging from cysts to seal off the cytoplasm-depleted base after cytoplasm retraction towards the growing tip. Preceding plug formation there was a typical local actin accumulation and during plug deposition actin remained associated with the leading edge. In appressoria, formed either on an artificial surface or upon contact with plant cells, we observed a novel aster-like actin configuration that was localized at the contact point with the surface. Our findings strongly suggest a role for the actin cytoskeleton in plug formation and plant cell penetration.     

Trans-synaptic shift in anion gradient in spinal lamina I neurons as a mechanism of neuropathic pain

Modern pain-control theory predicts that a loss of inhibition (disinhibition) in the dorsal horn of the spinal cord is a crucial substrate for chronic pain syndromes. However, the nature of the mechanisms that underlie such disinhibition has remained controversial. Here we present evidence for a novel mechanism of disinhibition following peripheral nerve injury. It involves a trans-synaptic reduction in the expression of the potassium-chloride exporter KCC2, and the consequent disruption of anion homeostasis in neurons of lamina I of the superficial dorsal horn, one of the main spinal nociceptive output pathways. In our experiments, the resulting shift in the transmembrane anion gradient caused normally inhibitory anionic synaptic currents to be excitatory, substantially driving up the net excitability of lamina I neurons. Local blockade or knock-down of the spinal KCC2 exporter in intact rats markedly reduced the nociceptive threshold, confirming that the reported disruption of anion homeostasis in lamina I neurons was sufficient to cause neuropathic pain.     

Changes in density of organelles fromNeurospora

Résumé Des mitochondries et des particules possédant certaines caractéristiques des peroxysomes ont été isolées duNeurospora crassa par centrifugation isopycnique. Lorsqu'elles sont extraites d'une culture réprimée, les mitochondries ont une densité apparente de 1,182 g×cm^–3, les particules peroxysomales, de 1,205 g×cm^–3. Isolées d'une culture complètement déréprimée, les densités respectives sont de 1,205 g×cm^–3 et de 1,219 g×cm^–3. La densité apparente des particules peroxysomales, mais non celle du stroma mitochondrial, est fortement affectée par des chocs hypotoniques ménagés.

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Supported by SNSF grant No. 3.575.71.