Figure 1.

Above a threshold, thrombin concentration has no systematic effect on platelet spreading and force generation. (A) Schematic representation of the experimental setup. A contracting platelet (blue) on top an elastic gel (light green) displaces the fluorescent beads (green). The deformation of the gel due to the contraction is visualized as orange beads. (B) Epifluorescence micrographs of a blood platelet stained for actin and spreading on an elastic gel after stimulation by thrombin. The last image shows a binarized version of the $t=30$ min micrograph. The scale bars correspond to 5 μm and refer to all sub-panels. The example platelet shown here is also shown in Figs. 3, 4A, and 5. (C) The average time-dependent total area covered by actin structures $A_a\left(t\right)$ upon stimulation by different concentrations of thrombin. Each averaged curve contains a minimum of 18 datasets and the SEs are shown as the transparent areas. Averaged exponential fits are shown as solid lines. (D) Maximum areas for each dataset determined from the averaged total $A_a\left(t\right)$ curves shown in (C). (E) Time constants for each dataset determined from the averaged total $A_a\left(t\right)$ curves shown in (C). (F) Average total force curves for blood platelets (n$\ge$ 18) upon stimulation by different concentrations of thrombin are shown as dotted lines, and the SEs are included as the transparent areas. Averaged exponential fits are shown as solid lines. (G) Maximum forces for each dataset comprising the averaged total force curves shown in (F). (H) Time constants for each dataset comprising the averaged total force curves shown in (F). The violin plot outlines illustrate the kernel probability density; the width of the shaded area represents the proportion of the data points located there. In each violin plot, the white circle indicates the median, the thick gray bar indicates interquartile range, and the thin gray line indicates the full range of distribution without outliers. Experimental conditions with a statistical difference below a 5% significance level are marked by asterisks (^∗). To see this figure in color, go online.