Abstract
The topography and structure of the follicular cells and the follicular cavity of the hypophyseal pars tuberalis (PT) were studied in adult hibernating bats (Pipistrellus pipistrellus and Rhinolophus ferrumequinum) of both sexes, during the annual seasonal cycle and the reproductive cycle. The follicular cells were found to be organized around a central cavity. They showed a polyhedral shape and apical microvilli protruding into central cavities. During hibernation, the follicular cells showed active cytoplasmic organelles, clusters of glycogen particles, and lipid droplets. In the supranuclear cytoplasm, 9+2 type cilia, some dense bodies, microvesicular vacuoles, and thin actinโlike filaments (rather scarce during autumn) were detected. The contents of the follicular cavity showed wellโdefined ultrastructural seasonal characteristics, with a colloidโlike aspect during awakening and a strongly granular aspect during autumn oestrus and mating. Positive staining for PAS and paraldehyde fuchsin, and a marked reaction to lectins PHAโL4, MAM, and RCA 60 suggested the presence of sialoโglycoproteins in the follicular cavities. Both follicular and endocrine PTโspecific cells appeared to mark the boundary of follicular cavities. This finding suggests that the follicular cavity contents are comprised of both types of cells, rather than by cell fragmentation or degeneration products. Anat Rec Part A 273A:763โ771, 2003. ยฉ 2003 WileyโLiss, Inc.