Effects of Heavy Water (D2O) on the Length of the Mitotic Period in Developing Sea Urchin Eggs

Abstract

The sequence of mitosis in sea urchin eggs was investigated in the presence and absence of D₂O. Direct observations of living cells under a polarizing microscope and observations with fixation-staining procedures were used. The duration of mitosis was extended by the presence of D₂O. The slight extension of anaphase was due to elongation of the spindle in D₂O, but the period from prophase to metaphase was clearly prolonged in the deuterated condition. These results indicate that D₂O does not suppress anaphase chromosome movement, but does affect prometaphase and delays the alignment of chromosomes on the equatorial plane of the mitotic spindle at metaphase.
The stability of the isolated mitotic apparatus against Ca ions and low temperature also was investigated. There was no difference in the deterioration of isolated spindle birefringence under normal and deuterated conditions. The implications of these results are discussed in relation to the enhancement effect of D₂O on the volume and birefringence of the living mitotic spindle.