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Credit: C. J. Weijer, Science 300, 96 (2003)
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Propagating nerve impulses, contracting muscles, chemotaxis (the directed, regulated movement of cells in response to chemical cues): these phenomena and others require cells to sense signals from their environment and transmit information within or between cells. Improved microscopic imaging techniques and the development of fluorescent sensors for intracellular signaling molecules have made it possible to visualize, with high resolution in space and time, the intricacies of these dynamic communications. This movie [2.0 MB] shows an aggregate of cells moving from left to right in response to waves of cAMP, a second messenger crucial for countless cell functions. The result is an image not only of movement but of signaling at the cell-membrane level: The bright regions at the leading edges of the cells indicate localization of specific signal molecules and membrane proteins required for cell movement. C. J. Weijer reviews methods for visualizing signals in moving cells in Science's 4 April 2003 special issue.
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