Taxol affects meiotic spindle function in locust spermatocytes

Abstract

Addition of 0.1 to 10 ΜM taxol to meiotic spindles in locust spermatocytes leads to a concentration dependent promotion of MT assembly at the centrosomes and depletion of MTs at the kinetochores, leading to the formation of prominent asters. In anaphase spindles, the equatorial region of the interzone becomes partly depleted of MTs, too. Microcinematographically, cytostatic effects are highly concentration/time dependent, being most rapid and nearly complete at 10 ΜM taxol, but even in 0.1 ΜM and 1 ΜM taxol anaphase A movement is clearly affected. The drug strongly reduces the rate of chromosome-to-pole movement (anaphase A), leading to an insufficient separation of the chromosomes which indirectly hampers cytokinesis. Obviously, the chromosomal movement seems to be ratelimited by the compactness of the centrosomal “asters” reaching the equatorial plane in meta- and anaphase. Although the interzonal MT-number has become strongly reduced, anaphase B is not seriously affected but appears even slightly accelerated. Together with an occasional broadening of the cell equator (“transverse elongation”) instead of normal elongation, these results could be taken as an indication of the previously suggested active role of the cell's cortex in spindle pole separation during anaphase B (Daub andHauser 1986).