Abstract
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.
Full Text
The Full Text of this article is available as a PDF (2.6 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- GARNHAM P. C., BAKER J. R., BIRD R. G. Fine structure of cystic form of Toxoplasma gondii. Br Med J. 1962 Jan 13;1(5271):83–84. doi: 10.1136/bmj.1.5271.83. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GARNHAM P. C., BIRD R. G., BAKER J. R. Electron microscope studies of motile stages of malaria parasites. IV. The fine structure of the sporozoites of four species of Plasmodium. Trans R Soc Trop Med Hyg. 1963 Jan;57:27–31. doi: 10.1016/0035-9203(63)90007-5. [DOI] [PubMed] [Google Scholar]
- HUFF C. G., PIPKIN A. C., WEATHERSBY A. B., JENSEN D. V. The morphology and behavior of living exoerythrocytic stages of Plasmodium gallinaceum and P. fallax and their host cells. J Biophys Biochem Cytol. 1960 Feb;7:93–102. doi: 10.1083/jcb.7.1.93. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LUFT J. H. Improvements in epoxy resin embedding methods. J Biophys Biochem Cytol. 1961 Feb;9:409–414. doi: 10.1083/jcb.9.2.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PITELKA D. R. Observations on the kinetoplast-mitochondrion and the cytostome of Bodo. Exp Cell Res. 1961 Oct;25:87–93. doi: 10.1016/0014-4827(61)90309-3. [DOI] [PubMed] [Google Scholar]
- REYNOLDS E. S. The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J Cell Biol. 1963 Apr;17:208–212. doi: 10.1083/jcb.17.1.208. [DOI] [PMC free article] [PubMed] [Google Scholar]
- RISTIC M., KREIER J. P. THE FINE STRUCTURE OF THE ERYTHROCYTIC FORMS OF PLASMODIUM GALLINACEUM AS REVEALED BY ELECTRON MICROSCOPY. Am J Trop Med Hyg. 1964 Jul;13:509–514. doi: 10.4269/ajtmh.1964.13.509. [DOI] [PubMed] [Google Scholar]
- SABATINI D. D., BENSCH K., BARRNETT R. J. Cytochemistry and electron microscopy. The preservation of cellular ultrastructure and enzymatic activity by aldehyde fixation. J Cell Biol. 1963 Apr;17:19–58. doi: 10.1083/jcb.17.1.19. [DOI] [PMC free article] [PubMed] [Google Scholar]