Ultrastructural Localization of Enzymes Involved in the Feeding Process in Plasmodium chabaudi and Babesia hylomysci1

Publisher Website
Google Scholar
Abstract
In P. chabaudi, Hb digestion occurs in 2 ways: micropinocytosis and cytostomal phagocytosis. Both mechanisms lead to the formation of digestive vesicles which evolve to pigment vesicles containing hemozoin crystals. Ultrastructural enzyme cytochemistry was used to detect and localize endoarylamidase and aminopeptidase activity. In P. chabaudi, these 2 enzymes are at first detected at the level of cytoplasmic ribosomes. When pinocytic vesicles appear, enzyme activity is localized at the membrane of the newly formed vesicles. The labeling then extends to the vesicle contents where it becomes very prominent. In the late trophozoite, enzymatic activity decreases and is no longer detected. In B. hylomysci, no endoarylamidase activity can be detected. Aminopeptidase is noted in the cytoplasm, the labeling being heavier in the growing trophozoites than in the younger stages. No vesicles or pigment can be observed. Aminopeptidase or endoarylamidase are synthesized in the cytoplasm of P. chabaudi and migrate to the digestive vesicles where Hb digestion occurs. Whether Babesia degrades Hb is not known since residual pigment is not produced. Babesia could feed from small peptides or amino acids coming from or through the stroma of the red blood cell.