Pressure-induced regression of oral apparatus microtubules in synchronized Tetrahymena

Abstract

The effect of pressure treatment on the later stages of oral morphogenesis was studied in synchronized Tetrahymena pyriformis GL-C. Prior to the end of the treatment, there were alterations in the oral cilia and basal bodies, as well as other microtubular structures. Microtubules in the nondeveloping oral regions were insensitive to the pressure treatment. Cells examined after the release of pressure contained basal bodies and denuded cilia within their cytoplasm. The ciliary doublet microtubules regressed in a definite sequence: (1) the outer wall of the B tubule, (2) the remainder of the B tubule, and (3) the A tubule. This regression was asynchronous among doublets and occurred independently of the state of regression of the central microtubules. The regression of basal body microtubules occurred initially with the loss of the circular arrangement of the triplet microtubules, and then these microtubules disintegrated along all parts of the triplet. Regressing oral structures were never observed to be contained within autophagic vacuoles. The possible significance for the lack of autophagy associated with oral resorption is discussed.