Effect of VEGF gradients on the mean overtake rate per sprout. The mean overtake rate per sprout was calculated from ten simulations with the contact inhibition model in which only tip cells have a chemotactic sensitivity (λ c,VEGF  = 0.1) to an external VEGF field. The different lines represent different shapes of the gradients of the external VEGF field ranging from concentration 0 to 1, which was uniformly spread over the grid, or increased from left to right over the grid in a linear, exponential or sigmoidal fashion. The mean overtake rate per sprout is plotted against the percentage of Vegfr2 haploid cells in a mixed spheroid of WT cells and Vegfr2 haploids. The grey regions represent the 95 % confidence intervals. The mean overtake rate per sprout is not significantly different for distinct gradients of VEGF. (TIF 8044 kb)