Fig. 2. Ran localization in activated Xenopus eggs. Xenopus oocytes were co-injected with calcium green dextran (15 µM final concentration) and Rh-Ran (1.2 µM) then were matured. (A) The matured eggs were prick activated to initiate a calcium wave that releases the meiosis II arrest. The calcium green image shown was taken a few seconds after the calcium wave had passed through the spindle region. The calcium wave is progressing from right to left. The bright circular region is the location of the meiotic spindle; it is bright because of the lack of volume-excluding yolk platelets. (B) Rh-Ran in the meiotic spindle of the egg in the preceding panel was imaged at high magnification. Since the spindle is oriented perpendicularly to the cell surface, it was necessary to take z series sequences to document anaphase movements. z series with a step of 3.1 µm were taken at approximately 2 minute intervals (each series of 14 images took 35 seconds to obtain) and were made into stereo pairs. Timing of the pairs shown is indicated on the figure. Anaphase movements appear to begin between 13 and 15 minutes. Nuclear envelopes reform around individual chromosomes after they have separated (Lemaitre et al., 1998); these should later fuse to form a single nucleus but this was not imaged. See stereo movie http://terasaki.uchc.edu/ran/anaphase.mov. Bars, 10 µm.