Investigation of several animal tissue cell types has shown that many of their
microtubules grow out from their centrosomes (see Tucker, 1979; McIntosh, 1983;
Bornens & Karsenti, 1984). Presumably this is also the case for microtubules that
project from the vicinities of centrosomes in the cells examined in this study. These
cells seem to provide examples of three types of situations where the distal portions of
microtubules curve into orientations that are markedly different from those of their
proximal portions (Fig. 18). For example, microtubules that are more or less radially
oriented with respect to cell centres curve into alignment with each other and follow
paths around the margins of flattened Hyphessobrycon osteoblasts that are positioned