Microtubules were labeled in red with mouse anti-alpha tubulin antibody (with
alexa594 donkey anti-mouse antibody as secondary antibody) and nuclei were labeled in blue with Hoechst. (A, A') the negative control without low pH application. (B–D and B'–D')
Images were taken at t=5 min (B, B'); 10 min (C, C'); and 125 min (D, D') after the beginning of low pH application. For each pair of images, the second image (images A'–D') includes
the superimposition of the nuclei, which helps in distinguishing single and multinucleated cells, and clarifying the position of the nuclei in the syncytia, but can hide the MTOC. Scale
bar, 25 μm.