A functional mitotic spindle prepared from mammalian cells in culture.

MITOTIC CELLS LYSED INTO SOLUTIONS OF POLYMERIZABLE MICROTUBULE PROTEIN CONTAIN A SPINDLE WHICH IS SIMILAR TO THE LIVING SPINDLE IN TWO RESPECTS

it will lose and gain birefringence when cooled and warmed, and it will move anaphase chromosomes to the opposite ends of the cell. Early anaphase cells lysed into buffers containing high molecular weight polyethylene glycol and nucleotide triphosphates will continue chromosome motion and spindle elongation in the absence of exogenous spindle subunits. These results suggest that while spindle growth requires microtubule polymerization, anaphase motions do not.