2% 1,6-HD treatment does not irreversibly affect the morphology and vitality of cells. (A) Bright-field micrograph of HeLa cells treated with 1,6-HD as described in Materials and methods. Cells were allowed to recover in alcohol-free medium. Cells returned to a normal morphology within 120 min after 1,6-HD withdrawal. Scale bar: 20 µm. (B) Representative images of HeLa WT cells treated or not with 1,6-HD for 30 min and stained for Cajal bodies (CBs, α-coilin antibody) or nuclear speckles (NSs, α-SC-35 antibody). Scale bar: 20 µm. (C) Quantification of Cajal bodies and nuclear speckles in untreated and 1,6-HD–treated cells. HeLa cells were treated with 2% 1,6-HD for 30 min and then stained with DAPI and either anti-coilin or anti-SC35 antibodies. Quantification was performed as in Materials and methods. Experiments were done in duplicate, and 200 cells were analyzed per experiment. Statistics: Student’s t test (***, P < 0.001).