Wnt Signaling Through Nitric Oxide Synthase Promotes the Formation of Multi-Innervated Spines

Structural plasticity of synapses correlates with changes in synaptic strength. Dynamic modifications in dendritic spine number and size are crucial for long-term potentiation (LTP), the cellular correlate of learning and memory. Recent studies have suggested the generation of multi-innervated spines (MIS), in the form of several excitatory presynaptic inputs onto one spine, are crucial for hippocampal memory storage. However, little is known about the molecular mechanisms underlying MIS formation and their contribution to LTP. Using 3D enhanced resolution confocal images, we examined the contribution of Wnt synaptic modulators in MIS formation in the context of LTP. We show that blockage of endogenous Wnts with specific Wnt antagonists supresses the formation of MIS upon chemical LTP induction in cultured hippocampal neurons. Gain- and loss-of-function studies demonstrate that Wnt7a signaling promotes MIS formation through the postsynaptic Wnt scaffold protein Disheveled 1 (Dvl1) by stimulating neuronal nitric oxide (NO) synthase (nNOS). Subsequently, NO activates soluble guanylyl cyclase (sGC) to increase MIS formation. Consistently, we observed an enhanced frequency and amplitude of excitatory postsynaptic currents. Collectively, our findings identify a unique role for Wnt secreted proteins through nNOS/NO/sGC signaling to modulate MIS formation during LTP

All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration < 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc^3 for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range 5 10^-22 Hz^-1/2 to 1 10^-20 Hz^-1/2. The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.Comment: 15 pages, 7 figures: data for plots and archived public version at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=70814&version=19, see also the public announcement at http://www.ligo.org/science/Publication-S6BurstAllSky

Phylogenetically Distinct Bacteria Involve Extensive Dechlorination of Aroclor 1260 in Sediment-Free Cultures

PLoS ONE83

Sustainable use of termite activity in agro-ecosystems with reference to earthworms. A review

International audienceAbstractSustainable agriculture and agro-ecology justify the need to study and understand the role played by ecological processes, and soil biodiversity in particular, in agro-ecosystem functioning. A large number of studies have focused on earthworms in temperate and humid tropical ecosystems and have demonstrated their importance for improving soil biological, physical, and chemical properties in agro-ecosystems. Their “success” is so essential that earthworms are widely considered key species and relevant indicators of soil health in temperate ecosystems. In arid and sub-arid ecosystems, the role of “soil engineer” is usually attributed to termites, and especially fungus-growing termites in Africa and Asia. However, despite this recognition, significant effort is spent eradicating them in plantations because of their pest status. In this review, we discuss the status of termites (“pests” vs. “soil engineers”) and question whether termites play similar roles to earthworms in arid- and sub-arid agroecosystems, with a focus on their influence on nutrient cycling and water dynamics. We argue that the dream of controlling natural interactions and ridding plantations of termites remains a costly legacy of the green revolution. We review the agricultural practices that have been used to reduce termite damage in plantations by restoring refuges to predators or by reorienting termite foraging activity towards organic amendments. Then, we show that the stimulation of termite activity can be used to improve key ecological functions in agro-ecosystems, such as increasing water availability to plants or producing fertility hot-spots. Finally, we suggest that more research on how termites can be used for improving ecosystem services, as is actually done with earthworms in temperate and humid tropical countries, could lead to a paradigm shift in our understanding of the impact of termites in tropical agro-ecosytems