Confocal images of rat oocytes at different stages of IA (left column) or SA (right column).

<p>The DNA and α-tubulin in oocytes were pseudo-colored blue and green, respectively. A is an oocyte at the metaphase II (MII) stage showing a regular spindle with chromosomes aligned on the metaphase plate. B is an IA oocyte in anaphase II (AnII) showing a spindle with chromosomes tidily aligned on either pole. C is an IA oocyte in early telophase II (e-TelII) with a condensed chromosome mass on either pole of the spindle and the initiation of PB2 extrusion. D is an IA oocyte in late telophase II (l-TelII) with extruded PB2 and the initiation of chromosome decondensation. E is an IA oocyte in interphase (Int) with pronuclear formation. F is a SA oocyte in AnII with chromosomes dispersed over the surface of the spindle. G is a SA oocyte in e-TelII with chromosomes arranged toward the spindle poles. H and I are SA oocytes in l-TelII showing disintegrated spindles with chromosomes surrounded by microtubules scattered in the ooplasm. J is a SA oocyte at the MIII stage with microtubules reorganized into several small spindles around the scattered chromosomes. PB2 (arrow) was often observed in IA oocytes but not in SA oocytes. Scale bar is 20 µm.