Showing papers by "Shigehiko Uni published in 1985"

Structural alteration of the membrane of erythrocytes infected with Babesia bovis.

Abstract: Babesia bovis, causative agent of cattle babesiosis, induces characteristic alterations on the membrane of infected erythrocytes. Elliptical protrusions measuring about 320 nm in long axis and about 160 nm in short axis appear on the membrane of infected erythrocytes, both in vitro and in vivo. Freeze-fracture demonstrated alignment of intramembrane particles (IMP) along the long axis of both the P and E faces of the protrusions. The number of IMP on the endoplasmic face increases, but the number of IMP on the protoplasmic face of the protrusions is not statistically altered from that of uninfected erythrocytes. In vitro, there are more protrusions per erythrocyte infected with the virulent form (low passage form) of B. bovis than with the avirulent form (high passage form). This suggests that the number of protrusions which appear on the membrane of infected erythrocytes may have a direct relationship to the virulence of the parasites. These protrusions may be attached to the capillary endothelial cells, which causes fatal cerebral babesiosis.

Effector mechanism of host resistance in murine giardiasis: specific IgG and IgA cell-mediated toxicity.

Abstract: The role of specific serum and milk anti-Giardia muris antibodies in mediation of host-effector responses to this enteric pathogen is unknown. We have investigated antibody-dependent cell-parasite interactions, potentially important as mediators of protection against infection at the mucosal surface. Elicited mouse peritoneal neutrophils and macrophages were incubated with G. muris trophozoites in the presence of either serum or milk antibodies, and their adherence and phagocytosis of the parasites were assessed. The percentage of trophozoites with adherent neutrophils increased significantly in the presence of heat-inactivated immune rabbit serum (93.5% +/- 6.5) and immune mouse milk (54.4% +/- 11.3) and their purified IgG (35.2% +/- 9.7) and secretory IgA fractions (48.0% +/- 12.3) when compared with incubation in RPMI-10% FCS (21.7% +/- 13.9). Similarly, macrophage adherence to trophozoites increased from 49.7% +/- 14.3 in medium alone to respective values of 92.8% +/- 7.1 in immune rabbit serum and 77.3% +/- 11.0 in immune milk. Phagocytosis of parasites by macrophages also was enhanced after incubation in immune rabbit serum (48.0% +/- 4.0) and immune mouse milk (35.0% +/- 5.0) when compared with the percentage of trophozoites ingested when cells and parasites were incubated in RPMI-10% FCS (3.3% +/- 3.0). Transmission electron microscopy showed ingestion of parasites by neutrophils or macrophages after 15 min of incubation. Morphologic evidence of intracellular parasite injury was observed at 6 hr. A decrease in parasite infectivity also resulted when trophozoites were incubated with neutrophils or macrophages and a source of antibodies, and intragastrically fed to weanling mice. These observations show that both antitrophozoite IgG, secretory IgA, and mouse phagocytic cells interact in vitro to promote parasite clearance. Because both the humoral and cellular components of this system are found intraluminally in the small intestine and in milk, they may represent a biologically relevant protective response against giardiasis.

Electron microscopy of Plasmodium vivax exoerythrocytic schizonts grown in vitro in a hepatoma cell line.

Abstract: Human hepatoma cells (HepG2-A16) have been shown to be useful for the growth of the exoerythrocytic stages of P. vivax. In order to determine whether the parasites grown in these cells are morphologically similar to those grown in vivo, we performed electron microscopy on the exoerythrocytic (EE) schizonts of P. vivax developed from sporozoites. This study showed for the first time that P. vivax EE schizonts within these cells closely resemble other plasmodial EE schizonts both in vivo and in vitro.