Apoptosis induced by DHA in ASTC-a-1cells. The cells were treated with 20 μg/ml of DHA for 48 h. Nuclear morphology was detected by Hoechst33258 staining and examined by fluorescence microscope. a Control cells with dispersive light blue nuclei and intact structure. c With 20 μg/ml of DHA treated, cell shrinkage, chromatin condensation and margination in the nucleus were visualized as well as STS treatment for 6 h (b: positive control). d The same cells as panel c showing that the plasma membrane remained well defined. e PI didn't penetrate into DHA-treated cells, demonstrating that DHA caused cell apoptosis but not necrosis. f DIC morphology of control cells was determined and photographed by the confocal microscope. (h, i) 10, 20 μg/ml DHA treated respectively: cell shrinkage, ovalisation, membrane frill, blebbing and the boundary between nucleus and cytoplasm became blurred.a-d: Magnification × 400; e-i: Scale Bar: 20 μm.