on the basis of our observations in untreated cells and our experiments with microtubule perturbation , we conclude that microtubules and the er are highly interdependent in two ways : ( a ) polymerization of individual microtubules and extension of individual er tubules occur together at the level of resolution of the fluorescence microscope , and ( b ) depolymerization of microtubules does not disrupt the er network in the short term ( 15 min ) , but prolonged absence of microtubules ( 2 h ) leads to a slow retraction of the er network towards the cell center , indicating that over longer periods of time , the extended state of the entire er network requires the microtubule system .
C0007634
cell
C0014239
er