Journal of Cell Science, Vol 7, 793-821, Copyright © 1970 by Company of Biologists

Submitted on March 18, 1970

Initiation and Differentiation of Microtubule Patterns in the Ciliate Nassula

¹ Department of Zoology, University of Cambridge, England, and Department of Zoology, The University, St. Andrews, Fife, Scotland.

The mechanisms specifying microtubule arrangement and controlling the dimensions and shaping of microtubular components during cytopharyngeal development have been investigated. Heat shocks interfere with, or prevent, the operation of some of the processes involved, while others continue in a fairly normal fashion. For certain microtubular components the patterns of microtubule packing and the shapes of the components are very largely specified by the arrangement of the sites where tubule growth is initiated. Here the development of cross-connexions between tubules serves only to stablize pre-existing tubule arrangements. However, there are indications that other intertubular materials are involved in the rearrangement of certain tubules. At several points in development the shapes and positions of extant microtubular components influence the patterns of tubules and other components subsequently developing in contact with them.

Heat shocks inhibit initiation of the development of certain tubules but longitudinal growth of existing tubules continues. When the number of developing tubules is reduced they attain greater than normal lengths, indicating that the extent of longitudinal tubule growth is largely determined by the size of the tubule precursor pool.

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