Most of the microtubules close to the anterior margins of these osteoblasts are
aligned with, and run alongside, the steep posterior flanks of adjacent circuli (Fig. 3).
In immunofluorescent preparations the decorated micro tubules contribute to
fluorescent bands and strands that spatially coincide with the positions and
alignments of circuli (Figs 5, 6). However, in the remaining more posteriorly
situated portions of these cells most of the microtubules are oriented approximately
at right angles to circuli and some of them span inter-circulus spacings (Figs 5,6).
Examination of thin sections revealed microtubules concentrated along the anterior
margins of these osteoblasts (Fig. 3, short arrows). However, profiles of microtubules
were rarely encountered in the more posterior lamelliform portions of the