T-NET, a dynamic model for simulating daily stream temperature at the regional scale based on a network topology.

International audienceCurrently, the distribution areas of aquatic species are studied by using air temperature as a proxy of water temperature, which is not available at a regional scale. To simulate water temperature at a regional scale, a physically based model using the equilibrium temperature concept and including upstream-downstream propagation of the thermal signal is proposed. This model, called Temperature-NETwork (T-NET), is based on a hydrographical network topology and was tested at the Loire basin scale (105 km2). The T-NET model obtained a mean root mean square error of 1.6 °C at a daily time step on the basis of 128 water temperature stations (2008–2012). The model obtained excellent performance at stations located on small and medium rivers (distance from headwater<100 km) that are strongly influenced by headwater conditions (median root mean square error of 1.8 °C).The shading factor and the headwater temperature were the most important variables on the mean simulated temperature, while the river discharge influenced the daily temperature variation and diurnal amplitude. The T-NET model simulates specific events, such as temperature of the Loire during the floods of June 1992 and the thermal regime response of streams during the heatwave of August 2003, much more efficiently than a simple point-scale heat balance model. The T-NET model is very consistent at a regional scale and could easily be transposed to changing forcing conditions and to other catchments

BDNF-induced local protein synthesis and synaptic plasticity

Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptic transmission and longterm potentiation (LTP) in the hippocampus and in other brain regions, playing a role in the formation of certain forms of memory. The effects of BDNF in LTP are mediated by TrkB (tropomyosin-related kinase B) receptors, which are known to be coupled to the activation of the Ras/ERK, phosphatidylinositol 3-kinase/Akt and phospholipase C-g (PLC-g) pathways. The role of BDNF in LTP is best studied in the hippocampus, where the neurotrophin acts at pre- and post-synaptic levels. Recent studies have shown that BDNF regulates the transport of mRNAs along dendrites and their translation at the synapse, by modulating the initiation and elongation phases of protein synthesis, and by acting on specific miRNAs. Furthermore, the effect of BDNF on transcription regulation may further contribute to long-term changes in the synaptic proteome. In this review we discuss the recent progress in understanding the mechanisms contributing to the short- and long-term regulation of the synaptic proteome by BDNF, and the role in synaptic plasticity, which is likely to influence learning and memory formation. This article is part of the Special Issue entitled ‘BDNF Regulation of Synaptic Structure, Function, and Plasticity’.The work in the authors laboratory is funded by Fundação para a Ciência e Tecnologia, COMPETE (Programa Operacional Factores de Competitividade), QREN and FEDER (Fundo Europeu de Desenvolvimento Regional) (PTDC/SAU-NEU/104297/2008, PTDC/SAU-NMC/ 120144/2010 and PEst-C/SAU/LA0001/2011)