(A–D Fluorescence images of actin stress fibers and inset illustrations of groups of BPAECs without (A) and with (B–D) cell-cell contact. (E) Western blots for dual-phosphorylated myosin light chain (P-MLC) and total myosin light chain (MLC) in control cells (left) or cells expressing RhoN19 (right). Both blots are without (left) and with (right) RhoN19. (F–I) Fluorescence images of actin stress fibers and inset illustrations of control cells (F,G) or cells expressing RhoN19 (H,I). These cells are either single (F,H) and paired (G,I). (J) Graph of BrdU incorporation in untransfected cells, and cells transfected with dominant negative RhoN19. Arrowheads in (B–D,G) indicate representative stress fibers, with two arrowheads pointing to one fiber. In inset illustrations of cell geometry, “X” indicates transfection with RhoN19. Error bars are standard error with (**) p<0.001 versus corresponding case of zero neighbors by t-test. Scale bars are 10 µm.