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This paper presents the integrated modelling study of an experimental hydrogeological site recently developed near Poitiers city. The objective assigned to this site is the design of reliable methodologies to simulate flow and transport in highly-heterogeneous reservoirs. Around 30 wells have been drilled on this low-depth captive aquifer, according to a square and centred pattern, with an average well spacing of 70 meters. All the observations and measurements acquired on this Site lead to a characterization of the spatial distribution of the aquifer heterogeneities, and to the recognition of their probable origin. Firstly, pumping tests and production logs revealed the heterogeneous flow behaviour at the Site scale. A static characterization of the reservoir was then undertaken from geophysical surveys and especially from the joint geological analysis of cores and logs, while taking into account flow measurements. Most information were found to be consistent with a paleo-karstic origin of this aquifer, an assumption that was recently corroborated by wellbore images. The first step of this project ends up with the construction of a geostatistical model that illustrates the spatial organization of the main drains and their link with the background facies. This model, once enriched by recent data, will constitute the support model for simulating and interpreting the pumping and interference tests. This second step, i.e. the dynamic simulation of the Site, will be indispensable to constrain the location and size of the drains that ensure the productivity of each well and their hydraulic connections.

We developed a new methodology for 3D restoration by coupling a geometric modelling software and a mechanical finite-element code. This method allows the geologist to impose the displacement on the main faults in order to get an adequate restored geometry and to compute the 3D strain and stress fields within the main blocks based on the unfolding with the mechanical approach. Complex meshing of the solid take into account heterogeneities due to the layering and facies variation. Results are discussed on compressive and extensional contexts, as well as in backward and forward approaches. The compressive case is illustrated by the restoration of a faulted anticline with massive sand and shaly beds. This case has been also restored with 2D surface unfolding processes and we will compare the information that geologists may get from the various methods. The second case concerns the deformation, in a gravity gliding context, of a sandy channel embedded into a shaly matrix. The mixed approach allows to quantify the reorientation of the stress field on the sand/shale boundary.

Neurotrophin-3 binds to the receptor tyrosine kinase, TrkC. Several naturally occurring splice variants of TrkC exist including those with 14- and 39-amino acid inserts within the tyrosine kinase homology region. When expressed in fibroblasts, full-length TrkC, but not the kinase insert variants, mediated neurotrophin-3-stimulated cell proliferation. We investigated the molecular basis of this signaling defect. The kinase inserts blocked the ability of TrkC to mediate neurotrophin-3 stimulated c-myc and c-fos transcription and activation of the AP-1 transcriptional complex. In cells expressing full-length TrkC, neurotrophin-3 promoted a sustained activation of mitogen-activated protein kinase; TrkC containing kinase inserts only mediated transient activation of mitogen-activated protein kinase. The kinase inserts specifically blocked neurotrophin-3-stimulated autophosphorylation of the phospholipase C gamma binding site on TrkC (tyrosine 789) resulting in a severe reduction in phospholipase C gamma association with TrkC and its tyrosine phosphorylation. Neurotrophin-3-stimulated phosphorylation of the Shc binding site (tyrosine 485) on TrkC, and tyrosine phosphorylation of Shc itself, was unaffected by the kinase inserts; however, the kinase inserts blocked high affinity Shc association with TrkC. It is proposed that the lack of high affinity binding of Shc and/or phospholipase C gamma to the TrkC kinase insert variants may be responsible for the inability of these variants to bring about a full biological response in fibroblasts.

Brain-derived neurotrophic factor (BDNF) interacts with the TrkB receptor tyrosine kinase, the tyrosine kinase domain of which has homology with the insulin receptor subfamily of protein kinases. This includes the conservation of three regulatory tyrosines (residues 670, 674, and 675) known to play a crucial role in signal transmission by the insulin receptor (tyrosines 1158, 1162, and 1163). Wild-type TrkB and TrkB mutants with Y670F, Y674F/Y675F, Y751F (the tyrosine reported to be important in phosphatidylinositol 3-kinase binding (Obermeier, A., Lammers, R., Wiesmuller, K. H., June, G., Schlessinger, J., and Ullrich, A. (1993) J. Biol. Chem. 268, 22963-22966)), and K540R (consensus ATP binding lysine) substitutions were transiently expressed in COS cells for analysis of phosphorylation sites by two-dimensional phosphopeptide mapping. TrkB phosphorylation sites were also studied in MG86 cells stably expressing wild-type TrkB. In addition, the mutants were expressed in Chinese hamster ovary cells for analysis of the ability of the receptor to mediate BDNF-stimulated transcription from a 12-O-tetradecanoylphorbol-13-acetate response element (TRE). BDNF stimulated the phosphorylation of wild-type TrkB on multiple tyrosine and serine residues. This phosphorylation occurred on tyrosines 670, 674, and 675 plus two other tyrosines and at least two serines that were not unequivocally identified. Wild-type TrkB mediated a pronounced stimulation of TRE-dependent transcription. A Y674F/Y675F, but not Y670F, substitution dramatically inhibited this response. Surprisingly, in COS cells, a Y751F substitution induced dramatically lower tyrosine and serine phosphorylation at all sites but mediated a normal BDNF-stimulated activation of a TRE. Our results demonstrate a critical role for the phosphorylation of tyrosines 674 and 675 in BDNF-dependent signaling by wild-type TrkB.