Anti‐mitotic effects of colchicine and hydrostatic pressure; synergistic action on the cleaving eggs of Lytechinus variegatus

Low concentrations (below 0.00005 m) of colchicine and low intensities (below 2,800 psi) of pressure, applied separately to early prophase eggs ( lytechinus variegatus ) produced no measurable inhibition of the first cleavage division (at 20°c). in combination, however, these subliminal treatments produced marked inhibition. complete blockage, in fact, was observed: at 2,300 psi for eggs in 0.00004 m colchicine; at 2,500 psi for eggs in 0.00003 m; and at 2,800 psi for eggs in 0.00002 m solutions. The curves obtained by plotting percentage inhibition as a function of pressure for each of the colchicine concentrations specified above were approximately parallel to one another; but each decrement in the colchicine concentration shifted the curve about 300 psi higher along the (pressure) abscissa. In short, a distinct synergism was found in reference to the anti‐mitotic effects of colchicine and pressure. This result is quite opposite to that reported previously in regard to the actions of heavy water and high pressure. As to basic mechanism, the evidence indicates that both colchicine and pressure exert their effects by inhibiting polymerization of the subunits of a fibrous protein which constitutes an important structural component of the mitotic apparatus or by depolymerizing the mitotic protein, if it already has been formed at the time of treatment.