Confocal microscopy images of the microtubule architecture of SNO cells with the use of anti-α tubulin antibodies and nuclear stain 4′,6-diamidino-2-phenylindole. (A) Cells propogated in medium only, (B) cells exposed to DMSO – vehicle control, (C) cells exposed to actinomycin D – positive control and (D) cells exposed to ESE-16 at a concentration of 0.2 μM. The α-tubulin of the cells were stained green by a FITC-conjugate diluent while the nuclei were stained blue by DAPI to provide contrast to the green fluorescence. Cells propogated in medium and vehicle control cells showed normal microtubule architecture. The positive control showed a decrease in cell density and revealed shrunken cells. ESE-16-treated cells showed a decrease in cell density and abnormal spindle formation when compared to the appropriate controls. The abnormal spindle formation is indicative of metaphase block. Scale bar: 10 μm.