Ca 2+ oscillations passed among platelets promote clotting.

Calcium fluctuations in the bottom layer of a platelet mass are propagated upwards to determine the size of a blood clot, or thrombus, according to results from Nesbitt et al. presented on page 1151.Platelets adhere to substrates in the vessel wall through receptors such as GPIb and certain integrins. Initial receptor engagement stimulates Ca2+ spikes in the platelets that lead to firm, permanent adhesion between the vessel wall and the primary layer of platelets. Now, Nesbitt et al. show that Ca2+ signals in this bottom layer are propagated among cells to promote platelet aggregation.

The group visualized cytosolic Ca2+ concentrations in platelets and found that cells with strong Ca2+ oscillations efficiently nucleated platelet aggregates. Flowing platelets that contacted an anchored platelet at the peak of its Ca2+ fluctuation adhered and initiated...

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