Changes in the pericardial cells of Periplaneta americana induced by exposure to homogenates of the corpus cardiacum

Abstract

ABSTRACT The pericardial cells of the cockroach, Periplaneta americana, undergo change associated with secretion when they are exposed to homogenates of the corpus cardiacum. The cells become markedly larger, and the nuclei send out branches as far as the cell border. Large secretory droplets appear as vacuoles first near the nucleus and later throughout the cytoplasm. Smaller vacuoles come to occupy the area near the periphery of the cell: these are considered to be the remains of the larger vacuoles after they have discharged their contents. Prolonged exposure of the cells to the homogenates in vitro leads to the cessation of these secretory activities, presumably as a result of the exhaustion of metabolites concerned in the secretory process. The cells also become more pronouncedly argentaffin as a result of exposure to the corpus cardiacum. These changes are considered in the light of the discovery that the pericardial cells produce a pharmacologically active material from an inert precursor in response to a secretion from the corpus cardiacum.