The Relation between Cilia and Mitoses in the Mouse Adenohypophysis

In 1961, Barnes (1) reported the presence of cilia in secretory cells of the mouse adenohypophysis . She noted that these cilia differ in several respects from "normal" cilia and flagella with an apparent motile function, but are similar to most cilia to which no motile function can be attributed . Generally speaking, "normal" cilia are located on free cell surfaces and possess a "9 + 2" fibrillar pattern and one basal body, whereas cilia of the second type are not necessarily located on free surfaces and possess a "9 + 0" (or "8 + I," see reference 2) fibrillar pattern and a basal structure consisting of the pair of centrioles of the cell . Since the paper by Barnes, the presence of 9 + 0 cilia has been reported in pituitary glands and in pituitary adenomas of a number of mammalian species (3-8) and in cells from many other mammalian organs (e .g ., references 9, 10) . Although a number of functions has been attributed to the 9 + 0 cilia (e .g ., references 2, 9, 11, 12), their physiological role-if existing-is still unknown . The present work reports on the frequency and distribution of 9 + 0 cilia in the adenohypophyses of mice in a number of physiological conditions, determined by means of large-scale electron microscopic counts . It appears that the distribution of the cilia in the different cell types can provide data concerning cell multiplication in the gland .