AT of early-prometaphase RPE1 cell. (A) Maximum-intensity projection (MIP) of the entire cell volume and selected 70-nm sections depicting kinetochores (CenpF), microtubules (α-tubulin), and DNA (Hoechst 33343). Microtubules radially emanate from the centrosomes (arrows in sect.05, sect.42, and MIP) and extend toward the chromosome ring near the spindle equator (sect.15–sect.33). The density of microtubules is relatively low near the center of the spindle but higher in the area adjacent to the centromeres (sect.23). See Video 1 for full volume of this cell. (B) Full series of 70-nm sections through a centromere (box in A, sect.23) at higher magnification. α-Tubulin is highly concentrated near kinetochores. Sister kinetochores (k1 and k2) form a crescent that partially encircles the centromere. Microtubules appear to emanate from the kinetochores but not toward the spindle poles. α-Tubulin concentration is the highest near the kinetochores (sect.21–sect.23).