Effect of Temperature Decline on the Cytoskeletal Organization of the Porcine Oocyte

The purpose of this study was to evaluate effect of cooling on the cytoskeletal organization affecting the distribution and structure of the meiotic spindle in the porcine metaphase II (MII) oocyte. Fluorescence staining was done for visualization of microtubules, microfilaments and chromosomes. In vitro-matured oocytes were either maintained at 37 °C (for controls) or cooled abruptly to 5 or 18°C. Microtubules were preferentially labeled at the meiotic spindle and microfilaments were mainly detected at the cortex of the MII oocyte. The majority of controls (87%, n=97) had a barrel-shaped spindle, whereas the remaining 13% showed a broad, box-shaped spindle. After exposure to 18 °C for 30 min, 94% of oocytes (n=48) possessed either a box-shaped spindle (63%) with a shortened interpolar distance (7.4 ± 0.4 μm vs. 9.8 ± 0.2 μm for controls P