Effects of cold and of isopropyl-N-phenylcarbamate on the second meiotic spindle of mouse oocytes.

The meiotic spindle of ovulated mouse oocytes are cold sensitive similar to the mitotic spindles of somatic cells and unicellular organisms. On crushed ice, the spindle microtubules were disorganized between 15 and 60 min of treatment: continuous microtubules depolymerized at first, then kinetochore fibers followed. MTOCs also dispersed during the cold treatment while kinetochores remained intact. The effects of isopropyl-N-phenylcarbamate (IPC) on the reorganization of the meiotic spindle of mouse oocytes were studied after cold disorganization. This drug is an antimitotic agent which appears to act on cells lacking centrioles (higher plants, amoeba, alga) as oocytes do. In ovulated mouse oocytes, IPC disturbed microtubule orientation and the relative distance between MTOCs and chromosomes. However this herbicide did not seem to act on polymerized microtubules and its action was apparently reversible. The disturbances in microtubule orientation are probably due to the displacement of chromosomes and MTOCs, which are loci of microtubule polymerization.