The effects of colchicine and dinitrophenol on the in vivo rates of anaphase A and B in the diatom Surirella.

The rates of chromosome-to-pole movement (anaphase A) and pole-pole separation (anaphase B) in vivo were measured in the pennate diatom Surirella, using differential interference contrast (DIC) light microscopy. In control cells, the rate of anaphase A is 1.6 +/- 0.6 micron/min, the rate of anaphase B is 2.3 +/- 0.3 micron/min, and the extent of anaphase B is 26.7 +/- 9.7% of metaphase spindle length. Colchicine was added to metaphase cells in order to inhibit any further addition of microtubule (MT) subunits onto the spindle. Colchicine, which does not break down the well-ordered Surirella central spindle, caused no significant change in the rate of anaphase A (1.3 +/- 0.3 micron/min) while it significantly decreased both the rate of anaphase B (1.2 +/- 0.4 micron/min) and the extent of anaphase B (14.8 +/- 8.3% of metaphase spindle length). Surirella cells were also treated with the metabolic inhibitor 2-4-dinitrophenol (DNP) in order to test the effects of energy depletion on anaphase. When DNP was added early in anaphase A, prior to the completion of sister chromosome separation, anaphase A was inhibited. When DNP was added after initiation of sister chromosome separation, anaphase A continued to completion, although at a lower rate than control cells (0.5 +/- 0.2 micron/min). Anaphase B was completely inhibited by DNP, but upon recovery from DNP resumed at a normal rate (2.2 +/- 0.5 micron/min) and progressed to a slightly larger than normal extent (44.0 +/- 13.0% of metaphase length).(ABSTRACT TRUNCATED AT 250 WORDS)