Sprayer tank agitation check: A proposal for a simple instrumental evaluation

The performance of the sprayer agitation system has an important effect on both pesticide distribution quality and environmental contamination. The visual inspection of sprayer tank agitation systems during inspections of sprayers in use could not give enough precise and repeatable information also due to the human factor. With the aim to provide more reliable and objective results for the equipment already in use, experiments were carried out for individuating instruments and methods enabling to make a simple and quick evaluation of sprayer tank agitation systems efficiency. Use of a solid inert tracer (glass microspheres) characterized by high sedimentation velocity, to be inserted with the water in the main tank, was found suitable to provide useful information about the efficiency of tank agitation systems in a quick and reproducible way. Further tests are in course in order to confirm the reliability of results obtained using this tracer and to define the details of a test methodology to propose for inspections of sprayers in use

p190 Rho-GTPase activating protein associates with plexins and it is required for semaphorin signalling

Plexins are transmembrane receptors for semaphorins, guiding cell migration and axon extension. Plexin activation leads to the disassembly of integrin-based focal adhesive structures and to actin cytoskeleton remodelling and inhibition of cell migration; however, the underlying molecular mechanisms are unclear. We consistently observe a transient decrease of cellular RhoA-GTP levels upon plexin activation in adherent cells. One of the main effectors of RhoA downregulation is p190, a ubiquitously expressed GTPase activating protein (GAP). We show that, in p190-deficient fibroblasts, the typical functional activities mediated by plexins (such as cell collapse and inhibition of integrin-based adhesion) are blocked or greatly impaired. Notably, the functional response can be rescued in these cells by re-expressing exogenous p190, but not a mutant form specifically lacking RhoGAP activity. We furthermore demonstrate that semaphorin function is blocked in epithelial cells, primary endothelial cells and neuroblasts upon treatment with small interfering RNAs that knockdown p190 expression. Finally, we show that p190 transiently associates with plexins, and its RhoGAP activity is increased in response to semaphorin stimulation. We conclude that p190-RhoGAP is crucially involved in semaphorin signalling to the actin cytoskeleton, via interaction with plexins