Electron micrographs of the PRBC stained with Hansson's stain for carbonic anhydrase. (a) Electron-dense reaction product of CA is seen as small dense granules along the RBC plasma membrane and throughout the cytoplasm of both unparasitized RBC and PRBC. It also is present along the parasite membrane and is present in greater abundance within the cytosol of intraerythrocytic P. falciparum (trophozoite stage) than in erythrocyte cytosole. Magnification: x 40 000. (b) Intraerythrocytic P. falciparum (schizont stage) have electrondense reaction product of CA with their cytosol and nucleoplasm, but not in food vacuole. The CA reaction product is more abundant within the parasite than in erythrocyte. Magnification: x 25 000.Sein KK, Aikawa M. The pivotal role of carbonic anhydrase in malaria infection. Med Hypotheses. 1998 50:19-23.