Fig. 5. Distribution of the fusion density and time in stationary and migrating NRK fibroblasts. For each cell, the long axis was defined as the furthest distance from edge to edge through the centre. The total region of the cell was then divided into three orthogonal parts with equal width along the long axis (A). To compare migrating and stationary cells, we chose region 1 to be at the end of each cell that was closest to the nucleus. The number of fusion sites were counted in each region and normalized by the total number of fusions per cell. The fusion density was determined by dividing the normalized number of fusions per region by the normalized area of each region. To account for the higher fusion rate in migrating cells (22 fusions per minute) compared with stationary cells (about eight fusions per minute), the values for the migrating cells were multiplied by 2.75. These fusion-density/time values of each cell [five stationary cells (176 fusions) and four migrating cells (375 fusions)] were averaged and plotted with the SEM as error bar (B).