Stellate cells as phagocytes of the anuran pars distalis.

When the stellate cells (nongranulated cells) from dissociated-cell preparations of the anuran pars distalis were examined, they were seen to contain debris within phagocytic vacuoles (phagosomes). These phagosomes were variable; some contained granules from secretory cells while others were similar to lipid-like bodies and myelin figures. In situ partes distales from frogs were examined at the breeding season. The tissues were divided into lobules that were bounded by processes of stellate cells located between the secretory cells. Processes of stellate cells in the interior of a lobule interdigitate with processes extending inward from the stellate cells forming the border of the lobule. When these processes come together, a small cavity is formed. In many of the intact frogs the spaces between the stellate and secretory cells were greatly enlarged. At this particular time the processes of the stellate cells were attenuated and enclosed secretory granules that were also present as debris in these dilated, intercellular spaces. Within the cytoplasm of these stellate cells were not only phagosomes containing secretory granules but also organelles that appeared to be lipid bodies and lysosomes. Thus, the stellate cells of the pars distalis function in vivo, as well as in vitro, as phagocytes. In addition, macrophage-like cells moving from the blood may form another component of this system of phagocytes.