scholarly journals THE FEEDING MECHANISM OF AVIAN MALARIAL PARASITES

1966 ◽  
Vol 28 (2) ◽  
pp. 355-373 ◽  
Author(s):  
Masamichi Aikawa ◽  
Peter K. Hepler ◽  
Clay G. Huff ◽  
Helmuth Sprinz
Keyword(s):  
Host Cell ◽  
Cross Section ◽  
Single Unit ◽  
Red Cell ◽  
Cell Cytoplasm ◽  
Feeding Mechanism ◽  
Host Cell Cytoplasm ◽  
Food Vacuoles ◽  
Face View ◽  
To Come

Electron microscope studies of the erythrocytic forms, including gametocytes and asexual schizonts, of the protozoa Plasmodium fallax, P. lophurae, and P. cathemerium, have revealed a "cytostome," a specialized organelle of the pellicular membrane which is active in the ingestion of host cell cytoplasm. In material fixed in glutaraldehyde and postfixed in OsO4, the cytostome appears in face view as a pore limited by two dense circular membranes and having an inside diameter of approximately 190 mµ. In cross-section, the cytostome is a cavity bounded on each side by two dense segments corresponding to the two dense circles observed in face view; its base consists of a single unit membrane. In the process of feeding, the cytostome cavity enlarges by expansion of its membrane, permitting a large quantity of red cell cytoplasm to come into contact with the cytostome wall. Subsequent digestion of erythrocyte cytoplasm occurs exclusively in food vacuoles which emanate from the cytostome invagination. As digestion progresses, the food vacuoles initially stain more densely and there is a marked build-up of hemozoin granules. In the final stage of digestion, a single membrane surrounds a cluster of residual pigment particles and very little of the original host cell cytoplasm remains. The cytostome in exoerythrocytic stages of P. fallax has been observed only in merozoites and does not seem to play the same role in the feeding mechanism.

scholarly journals FINE STRUCTURE OF THE ASEXUAL STAGES OF PLASMODIUM ELONGATUM

1967 ◽  
Vol 34 (1) ◽  
pp. 229-249 ◽  
Author(s):  
Masamichi Aikawa ◽  
Clay G. Huff ◽  
Helmuth Sprinz
Keyword(s):  
Fine Structure ◽  
Host Cell ◽  
Malarial Parasite ◽  
Red Cell ◽  
Digestive Vacuole ◽  
Cell Cytoplasm ◽  
Erythrocytic Stage ◽  
New Host ◽  
Feeding Mechanism ◽  
Host Cell Cytoplasm

Plasmodium elongatum, an avian malarial parasite, differs from other such parasites by infecting both the circulating red blood cells and the hematopoietic cells. The exoerythrocytic development of P. elongatum occurs mainly in these red cell precursors. The fine structure of the asexual stages of P. elongatum has been studied in the bone marrow and peripheral blood of canaries and compared with that of the asexual stages of other avian malarial parasites. With minor differences, the merozoites of P. elongatum possess the same organelles as those in the exoerythrocytic merozoites of P. fallax and the erythrocytic stages of P. cathemerium, P. lophurae, P. fallax, and P. gallinaceum. The developmental sequence is also essentially similar to that of other avian malarial parasites, in that upon entry into a new host cell, the dedifferentiation, growth, and redifferentiation phases take place. However, we have found some important differences in the feeding mechanism of P. elongatum. The cytostome is involved in the ingestion of host cell cytoplasm in both exoerythrocytic and erythrocytic stages, in contrast to P. fallax, in which the cytostome is inactive in the exoerythrocytic stages. In P. elongatum, host cell cytoplasm is ingested through the cytostome, and "boluses" are formed and incorporated into a large digestive vacuole. Subsequently, the digestion of the boluses takes place in this digestive vacuole. Thus, in regard to the function of the cytostome, the exoerythrocytic stages of P. elongatum appear to be closely related to the erythrocytic stage which has a feeding mechanism similar to that of the erythrocytic stage of other avian malarial parasites.

The RhopH complex is transferred to the host cell cytoplasm following red blood cell invasion by Plasmodium falciparum

2008 ◽  
Vol 160 (2) ◽  
pp. 81-89 ◽  
Author(s):  
Laetitia Vincensini ◽  
Gamou Fall ◽  
Laurence Berry ◽  
Thierry Blisnick ◽  
Catherine Braun Breton
Keyword(s):  
Plasmodium Falciparum ◽  
Blood Cell ◽  
Host Cell ◽  
Cell Invasion ◽  
Red Blood Cell ◽  
Cell Cytoplasm ◽  
Host Cell Cytoplasm

scholarly journals Brefeldin A inhibits transport of the glycophorin-binding protein from Plasmodium falciparum into the host erythrocyte

1994 ◽  
Vol 300 (3) ◽  
pp. 821-826 ◽  
Author(s):  
J Benting ◽  
D Mattei ◽  
K Lingelbach
Keyword(s):  
Plasmodium Falciparum ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Protein Secretion ◽  
Secretory Pathway ◽  
Binding Protein ◽  
Brefeldin A ◽  
Cell Cytoplasm ◽  
Parasite Cell ◽  
Host Cell Cytoplasm

Plasmodium falciparum, a protozoan parasite of the human erythrocyte, causes the most severe form of malaria. During its intraerythrocytic development, the parasite synthesizes proteins which are exported into the host cell. The compartments involved in the secretory pathway of P. falciparum are still poorly characterized. A Golgi apparatus has not been identified, owing to the lack of specific protein markers and Golgi-specific post-translational modifications in the parasite. The fungal metabolite brefeldin A (BFA) is known to inhibit protein secretion in higher eukaryotes by disrupting the integrity of the Golgi apparatus. We have used the parasite-encoded glycophorin-binding protein (GBP), a soluble protein found in the host cell cytoplasm, as a marker to investigate the effects of BFA on protein secretion in the intracellular parasite. In the presence of BFA, GBP was not transported into the erythrocyte, but remained inside the parasite cell. The effect caused by BFA was reversible, and the protein could be chased into the host cell cytoplasm within 30 min. Transport of GBP from the BFA-sensitive site into the host cell did not require protein synthesis. Similar observations were made when infected erythrocytes were incubated at 15 degrees C. Incubation at 20 degrees C resulted in a reduction rather than a complete block of protein export. The relevance of our findings to the identification of compartments involved in protein secretion from the parasite cell is discussed.

scholarly journals Localization of Chlamydia trachomatis hypothetical protein CT311 in host cell cytoplasm

2011 ◽  
Vol 51 (3) ◽  
pp. 101-109 ◽  
Author(s):  
Lei Lei ◽  
Manli Qi ◽  
Nicole Budrys ◽  
Robert Schenken ◽  
Guangming Zhong
Keyword(s):  
Chlamydia Trachomatis ◽  
Host Cell ◽  
Hypothetical Protein ◽  
Cell Cytoplasm ◽  
Host Cell Cytoplasm

Eimeria canadensis (Protozoa, Sporozoea): ultrastructure of the host–parasite interface during development of first-generation schizonts in vitro

1980 ◽  
Vol 58 (11) ◽  
pp. 2018-2025 ◽  
Author(s):  
Bodo E. G. Mueller
Keyword(s):  
Host Cell ◽  
Parasitophorous Vacuole ◽  
Eimeria Species ◽  
Outer Zone ◽  
Ultrastructural Observation ◽  
Cell Cytoplasm ◽  
Cell Organelles ◽  
Host Cell Cytoplasm ◽  
Host Parasite

Eimeria canadensis sporozoites were inoculated into monolayer cultures of Madin–Darby bovine kidney and primary bovine embryonic kidney cells. Sporozoites retained their shape for at least 9 days. At that time, the nucleus was enlarged and contained a prominent nucleolus, and amylopectin granules were no longer apparent. The width of the parasitophorous vacuole (pv) between host cell cytoplasm and parasite pellicle widened during transformation of sporozoites into multinucleate schizonts. Areas of altered host cell cytoplasm immediately adjacent to the pv membrane increased in size and became confluent, resulting in the formation of two distinct layers of cytoplasm. The outer zone contained the host cell nucleus, mitochondria, Golgi stacks, and ER, whereas the inner layer appeared granular and was void of all cell organelles except structures resembling ribosomes. Microfilaments were abundant at the border between inner and outer zone. In the most advanced stages observed, host cell organelles persisted only in the perinuclear region. The remaining, attenuated cytoplasm resembled the former inner zone.The novel ultrastructural observation of a bilayered cytoplasm of cells harbouring E. canadensis schizonts is compared with light microscope reports of similar effects caused by other Eimeria species of ruminants and with electron microscope findings of altered intestinal and abomasal cells of sheep harbouring "globidial" schizonts.

scholarly journals Chlamydia trachomatis GlgA Is Secreted into Host Cell Cytoplasm

PLoS ONE ◽  
2013 ◽  
Vol 8 (7) ◽  
pp. e68764 ◽  
Author(s):  
Chunxue Lu ◽  
Lei Lei ◽  
Bo Peng ◽  
Lingli Tang ◽  
Honglei Ding ◽  
...  
Keyword(s):  
Chlamydia Trachomatis ◽  
Host Cell ◽  
Cell Cytoplasm ◽  
Host Cell Cytoplasm

scholarly journals Characterization of CPAF Critical Residues and Secretion during Chlamydia trachomatis Infection

2015 ◽  
Vol 83 (6) ◽  
pp. 2234-2241 ◽  
Author(s):  
Zhangsheng Yang ◽  
Lingli Tang ◽  
Xin Sun ◽  
Jijie Chai ◽  
Guangming Zhong
Keyword(s):  
Host Cell ◽  
Sample Treatment ◽  
Cell Cytoplasm ◽  
Inhibitory Peptide ◽  
Lower Efficiency ◽  
Content Type ◽  
Chlamydia Trachomatis Infection ◽  
Host Cell Cytoplasm ◽  
Treatment Conditions ◽  
Critical Residues

CPAF (chlamydial protease-like activity factor), aChlamydiaserine protease, is activated via proximity-induced intermolecular dimerization that triggers processing and removal of an inhibitory peptide occupying the CPAF substrate-binding groove. An active CPAF is a homodimer of two identical intramolecular heterodimers, each consisting of 29-kDa N-terminal and 35-kDa C-terminal fragments. However, critical residues for CPAF intermolecular dimerization, catalytic activity, and processing were defined in cell-free systems. Complementation of a CPAF-deficient chlamydial organism with a plasmid-encoded CPAF has enabled us to characterize CPAF during infection. The transformants expressing CPAF mutated at intermolecular dimerization, catalytic, or cleavage residues still produced active CPAF, although at a lower efficiency, indicating that CPAF can tolerate more mutations insideChlamydia-infected cells than in cell-free systems. Only by simultaneously mutating both intermolecular dimerization and catalytic residues was CPAF activation completely blocked during infection, both indicating the importance of the critical residues identified in the cell-free systems and exploring the limit of CPAF's tolerance for mutations in the intracellular environment. We further found that active CPAF was always detected in the host cell cytoplasm while nonactive CPAF was restricted to within the chlamydial inclusions, regardless of how the infected cell samples were treated. Thus, CPAF translocation into the host cell cytoplasm correlates with CPAF enzymatic activity and is not altered by sample treatment conditions. These observations have provided new evidence for CPAF activation and translocation, which should encourage continued investigation of CPAF in chlamydial pathogenesis.

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