EXPERIMENTAL FIGURE 18-10 Fluorescence microscopy reveals growth and shrinkage of individual microtubules in vivo. Fluorescently labeled tubulin was microinjected into cultured human fibroblasts. The cells were chilled to depolymerize preexisting microtubules into tubulin dimers and were then incubated at 37 °C to allow repolymerization, which incorporated the fluorescent tubulin into all the cells’ microtubules. A region of a cell periphery was viewed in the fluorescence microscope at 0 seconds, 27 seconds later, and 3 minutes 51 seconds later (left to right panels). During this period, several microtubules can be seen to have elongated and shortened. The dots labeled A, B, and C mark the positions of the ends of three microtubules.

[Reprinted by permission from Macmillan Publishers Ltd: P.J. Sammak and G. Borisy, “Direct observation of microtubule dynamics in living cells,” Nature, 1998, 332:724-726.]