Primary cilia associated with striated rootlets in granulated and folliculo-stellate cells of the avian adenohypophysis

Summary

During observation of the ultrastructure of adenohypophyses of normal and experimentally-manipulated quails, primary cilia were found in secretory cells as well as in non-granulated, folliculo-stellate cells of both cephalic and caudal lobes of the gland. These solitary cilia shared morphological characteristics with those observed in other cell types and species, i.e. they arose from a basal body, which basically had a centriolar structure and 9 doublets of microtubules and no central tubules in their axoneme. A 8+1 arrangement of microtubules was exceptionally observed. A 9+2 pattern, which is commonly described in motile cilia, was never found. The cilia extended in extracellular spaces between secretory cells, but not in the follicular cavities nor in the blood vessels. In addition to the basal body, a single centriole was frequently present in its vicinity. The basal body was often associated with a basal foot or satelllite from which microtubules radiated, and with ladderlike structures corresponding to the classical description of striated rootlets. The presumptive roles of primary cilia in general, and of their morphological features in particular, are discussed in view of our results and compared to the several observations reported in mammalian adenohypophyses. As the evidence gained in favour of a given function of primary cilia has, so far, always been circumstantial, extreme caution in interpretation must be exercised.