Fig. 4. Effect of PD98059 on ureteric bud cell biology. (A) The pattern of cell proliferation (BrdU incorporation) in normal kidneys; the inset shows both ureteric bud and mesenchyme, and the main image shows only the ureteric bud for clarity (the mesenchyme being masked out electronically). Most BrdU incorporation (green) takes place in the ureteric bud tips. The laminin basement membrane of those tips (red) shows numerous short processes reaching out into the mesenchyme (arrowheads). (B) In kidneys cultures in the presence of 25 µM PD98059, there is less proliferation in the ureteric bud, though it is again localised mainly in the tips. There are also fewer processes and typically, as in this image, the only process points directly forward from the tip (arrowhead). (C,D) Propidium iodide staining of nuclei reveals very little apoptosis in the ureteric buds of either PD98059-treated (C) or control (D) kidneys, although in both cases there is mesenchymal apoptosis away from the immediate vicinity of the ureteric bud (arrowheads). (E,F) Filamentous actin is concentrated strongly at the apices of cells of control kidneys (E) (arrowheads), but much less so in kidneys growing in PD98059 (F). (G,H) Ureteric buds of both PD98059-treated kidneys (G) and controls (H) express Ret. (I,J) Ureteric buds of both PD98059-treated (I) and control (J) kidneys express Ros; many tips of control kidneys show reduced immunoreactivity in the few cells right at the ends of the tips (arrowhead), though PD98059-treated kidneys do not show this effect. Scale bars: 50 µm.
