Effects of D2O on the movement of chromosomes and the shortening of kinetochore spindle fibers in anaphase in dividing spermatocytes of the grasshopper, Mongolotettix japonicus.

Spindles in anaphase of dividing primary spermatocytes of the grasshopper, Mongolotettix japonicus, were examined with a sensitive polarizing microscope combined with a time-lapse video recorder and a cinematographic apparatus. The pole-to-pole distance of the meiotic spindles was increased and the kinetochore fibers were more birefringent in the presence of 40% D2O. However, the rate of shortening of the kinetochore fibers in anaphase was not affected by D2O. This indicates that D2O did not inhibit microtubule disassembly in anaphase, supporting the earlier observations (3, 18) that D2O did not "stabilize" the spindle microtubules at concentrations below 45%. We confirmed that D2O, at the concentration mentioned above, neither promotes nor inhibits the anaphase A. However, the overall sequence of anaphase was considerably extended in the presence of D2O, presumably due to the increased pole-to-pole distance.