Immunofluorescent visualization of PARP-1, pADPR synthesis and H2AX phosphorylation in PARP-1+/+ and PARP-1-/- 3T3s exposed to various treatments including H2O2 (1 mM, 10-min) without or with 30 μM ANI, γ-rays (20 Gy, 10-min) or NCS (2 or 30 nM, 10-min). PARP-1-/- 3T3s complemented with the PARP-1 cDNA (pBabePARP-1) are shown for comparison. Cells were grown on coverslips, treated, fixed, incubated with antibodies and counterstained with DAPI. For each preparation the gain of the camera was adjusted relative to DAPI emission. The top part of the figure shows isolated views. The bottom panels show DAPI and immunofluorescence views in coincidence. The bar (top right view) represents 20 μm.