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Wageningen, Netherlands

Fritz R.D.,University of Basel | Letzelter M.,University of Basel | Letzelter M.,Perkin Elmer Corporation | Reimann A.,University of Basel | And 9 more authors.
Science Signaling | Year: 2013

Genetically encoded, ratiometric biosensors based on fluorescence resonance energy transfer (FRET) are powerful tools to study the spatiotemporal dynamics of cell signaling. However, many biosensors lack sensitivity. We present a biosensor library that contains circularly permutated mutants for both the donor and acceptor fluorophores, which alter the orientation of the dipoles and thus better accommodate structural constraints imposed by different signaling molecules while maintaining FRET efficiency. Our strategy improved the brightness and dynamic range of preexisting RhoA and extracellular signal-regulated protein kinase (ERK) biosensors. Using the improved RhoA biosensor, we found micrometer-sized zones of RhoA activity at the tip of F-actin bundles in growth cone filopodia during neurite extension, whereas RhoA was globally activated throughout collapsing growth cones. RhoA was also activated in filopodia and protruding membranes atthe leading edge of motile fibroblasts. Using the improved ERK biosensor, we simultaneously measured ERK activation dynamics in multiple cells using low-magnification microscopy and performed in vivo FRET imaging in zebrafish. Thus, we provide a construction toolkit consisting of a vector set, which enables facile generation of sensitive biosensors. Copyright 2008 American Association for the Advancement of Science. All Rights Reserved. Source

Versteegh C.P.C.,Experimental Zoology Group | Versteegh C.P.C.,Rockefeller University | Muller M.,Experimental Zoology Group | Muller M.,Physical Biology Institute Momchilovtsi Bulgaria PBIMB
Animal Biology | Year: 2014

Aquatic organisms have to deal with different hydrodynamic regimes, depending on their size and speed during locomotion. The pea crab swims by beating the third and fourth pereiopod on opposite sides as pairs. Using particle tracking velocimetry and high-speed video recording, we quantify the kinematics and vortices in the wake of the pea crab. Where the proximal parts of the pereiopods beat in antiphase, their distal parts show an overlapping beat period. By using four instead of two limbs for propulsion, an uninterrupted forward movement is established, reducing the influence of the acceleration reaction. Before body speed is maximal, force generation of the pereiopods seems most active when passing an orthogonal position with the body. © Copyright 2014 by Koninklijke Brill NV, Leiden, The Netherlands. Source

Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 1982

How do behaviour and growth optimalize the chance to catch a prey in growing fish larvae. How is an optimal relation reached between energy expenditure and energy gain during feeding.

Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 1984

sense organs, mucus, muscle-bone, kinematics head parts, feeding habits

Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 2000

The discrimination between direct genomic control and the influence of environmental factors on gene expression and differentiation of cells is an important issue in biology and medicine. Environmental factors influencing cells may be of chemical (i.e. induction) or physical nature. In our group, this problem is tackled in a study of the formation, during development, of the serially arranged myomeres and myosepts in fish. Previously, we developed a biochemical model ( Van Leeuwen, 1999) that predicts several aspects of the complex shape of fish myomers from mechanical principles and functional demands. Recently, the self-organization of the internal architecture of the myoseptum was included in this model. The location and orientation of intra-muscular bones and main ligaments in the myoseptum were successfully predicted by assuming that the production or deletion of extra-ceullular substances by the cells depends on the experienced mechanical load. Strikingly, the model predicts that a complex adaptive and functional system can be built by defining simple rules for the response of the cellular elements. In vivo and in vitro studies on mammalian tissues shows that a number of mesodermal cell types may change gene expression patterns after mechanical stimulation. As a result, the cells (trans)differentiate to a particular type. (e.g. fibroblast, osteoblast or muscle cell), change shape, reorientate, and produce particular extra-cellular substances such as bone and collagen. We hypothesise that from the moment that mechanical strain is produced within cells of somitic origin these cells and their neighbours are influenced by these forces and may change gene expression patterns, leading to specific differentiation processes. Bones for example will be formed at those locations where pressure forces are produced. In combination with gene expression studies, the above model is a unique tool to tackle basic morphogenetic questions of complexes of muscle, collagenous tissue and bone.

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