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Hydropower production and other human activities change the natural flow regime of rivers (e.g., hydropeaking effects), in turn, impacting the riparian environment. Here we present an experiment conceived to investigate the response of forced offsets in water table dynamics on the temperate floodplain riparian vegetation species of Salix viminalis . Three specific water level regimes, simulating daily hydropeaking effects in terms of daily water table variations and offsets, were applied to three batteries of Salix cuttings growing outdoors in plastic pots. All pots initially were provided the same unlimited water supply. Then the dynamics were changed to include 90-cm daily oscillations of water table. The transitory responses of the cuttings were quantified with measurements of continuous sap flow and water potential. We regularly monitored growth parameters, leaf water potential, and gas exchange measurements, and took pictures of each plant. At the end of the experiment, all cuttings were removed and the biomass, from both above and below ground, analyzed. The 3D root structure was investigated using high-resolution computed tomography. Our results showed a clear link between root distribution and water regime. The strong offset of water table dynamics was followed by root system adjustment and plant adaptation to the new conditions. Macroscopic effects in terms of growth parameters corresponded with water pressure and transpiration measurements, strengthening our interpretation of the results. Daily hydropeaking offset appeared to have only a minor impact on the development and photosynthesis of S. viminalis cuttings, and can probably be neglected in real cases of dam regulation. On the other hand, weekly periodicity (e.g., weekend periods of dryness) could have harsher impacts, and should be evaluated in future studies. [ABSTRACT FROM AUTHOR]

Abstract: We report the identification of proteins induced in response to RET/PTC2, an oncogene implicated in thyroid cancers. Anti-phosphotyrosine antibody affinity resin was used to purify Tyr(P)-containing and interacting proteins from 293T and NIH3T3 cells which were transfected with kinase active or inactive RET/PTC and RETMEN2 oncogenes. Proteins were separated by one-dimensional SDS-PAGE, extracted by in-gel digestion, and identified by MALDI-TOF peptide mass fingerprinting. The expression and tyrosine phosphorylation of Sam68, a protein implicated in mRNA nucleocytoplasmic translocation and splicing, were further examined in RET-transfected cells and thyroid tumors. Of relevance, cells transfected with RETMEN2B examined for anti-phosphotyrosine bound proteins, showed other proteins implicated in splicing: DEAD-box p68 RNA helicase, SYNCRIP, and hnRNP K. Western blotting analysis suggested that these proteins are singularly tyrosine phosphorylated in RETMEN2B-transfected cells, and that they constitutively bind with Sam68. The study concludes that regulation of splicing factors is likely to be important in RET-mediated thyroid carcinogenesis. [Copyright &y& Elsevier]

The RET gene encodes two main isoforms of a receptor tyrosine kinase (RTK) implicated in various human diseases. Activating germ-line point mutations are responsible for multiple endocrine neoplasia type 2-associated medullary thyroid carcinomas, inactivating germ-line mutations for Hirschsprung's disease, while somatic rearrangements (RET/PTCs) are specific to papillary thyroid carcinomas. SH2B1β, a member of the SH2B adaptors family, and binding partner for several RTKs, has been recently described to interact with proto-RET. Here, we show that both RET isoforms and its oncogenic derivatives bind to SH2B1β through the SRC homology 2 (SH2) domain and a kinase activity-dependent mechanism. As a result, RET phosphorylates SH2B1β, which in turn enhances its autophosphorylation, kinase activity, and downstream signaling. RET tyrosine residues 905 and 981 are important determinants for functional binding of the adaptor, as removal of both autophosphorylation sites displaces its recruitment. Binding of SH2B1β appears to protect RET from dephosphorylation by protein tyrosine phosphatases, and might represent a likely mechanism contributing to its upregulation. Thus, overexpression of SH2B1β, by enhancing phosphorylation/activation of RET transducers, potentiates the cellular differentiation and the neoplastic transformation thereby induced, and counteracts the action of RET inhibitors. Overall, our results identify SH2B1β as a key enhancer of RET physiologic and pathologic activities.Oncogene (2007) 26, 6546–6559; doi:10.1038/sj.onc.1210480; published online 30 April 2007 [ABSTRACT FROM AUTHOR]