[en] Poly (ADP-ribose) polymerase (PARP) is a nuclear enzyme encompassing two zinc finger motifs which specifically binds to radiation induced DNA strand breaks. We develop a new immuno-labelling of poly ADP-ribose which coupled together with the immuno-detection of cells in cycle with MIB₁, permits to detect and quantify the DNA fragmentation induced by γ radiations (Cesium¹³⁷). This method, applied to organo-typical cultures of human oligodendrogliomas, submitted to γ radiation, a dose dependant nuclear signal. This one increased significantly in the presence of a radiosensitizer like iododeoxyuridine (IUDR 5 μg/ml). (authors)