FIG. 1.

The first meiotic division in zinc-insufficient oocytes is accelerated and produces a large first polar body. A) Denuded oocytes are shown from COCs matured in vitro in control medium (i) or medium containing 10 μM TPEN (ii). Bar = 100 μm. A, iii) inset shows a Z stack projection of confocal images of the spindle from an oocyte matured in the presence of TPEN; microtubules are shown in green and chromatin in red; bar = 20μm. Arrows (ii) mark oocytes with large polar bodies; arrowheads show examples of symmetric division. B) Timing of first polar body extrusion for oocytes IVM in control (solid line) or TPEN-containing medium (dashed line) based on the percentage of oocytes displaying a polar body. Data are average percentages over five separate experiments ± SEM; a total of 207 control and 240 TPEN-treated oocytes were scored. Asterisks indicate statistical significance according to Student t-test (P < 0.05).