Ultrastructure of the Non-granulated Hypophysial Cells in the Teleost Pseudocrenilabrus philander (Hemihaplochromis philander), with Particular Reference to Cytological Changes in Culture

Abstract In the intact gland, non-granulated cells are most numerous in the rostral pars distalis; they are characterized by a lack of typical secretory granules, a ribosome-rich cytoplasm and long cytoplasmic processes. The latter extend between the granulated cells and often form a layer beneath the capsule and at the zone of contact between adenohypophysis and neurohypophysis. Study of cultured hypophysial tissue provides unequivocal evidence for the phagocytosis of cytoplasm of granulated cells by non-granulated cells. In short-term cultures (1.5 h), non-granulated cells envelop small portions of granulated cell cytoplasm and their processes extend into intercellular spaces and contact tissue fragments located there. In longer term cultures (6—120 h), large areas of cytoplasm belonging to presumptive prolactin and somatotropic cells are engulfed by non-granulated cells; these phagosomes undergo progressive breakdown to form residual bodies. It is suggested that an accumulation of cellular debris and/or stale secretory material may be important factors promoting phagocytic activity in cultured non-granulated cells.