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1.
J Struct Biol ; 136(3): 181-9, 2001 Dec.
Article in English | MEDLINE | ID: mdl-12051898

ABSTRACT

Treatment of tachyzoites of Toxoplasma gondii with the calcium ionophore A23187 induced dramatic ultrastructural changes that were observed by light and electron microscopy. Light microscopy showed a higher percentage (22%) of tachyzoites with the conoid extruded when compared to control parasites. Electron microscopy confirmed the conoid extrusion by both transmission and scanning electron microscopy. Freeze-fracture replicas showed that the plasma membrane adjacent to cytoplasmic dense granules appeared devoid of intramembranous particles. Membrane-limited vesicles and filopodium-like structures at the cell surface were observed in treated cells. 3-D reconstruction from serial sections confirmed the data and showed a heterogeneity in dense granule shape not reported in control cells.


Subject(s)
Calcimycin/pharmacology , Toxoplasma/ultrastructure , Animals , Cell Membrane/ultrastructure , Freeze Fracturing , Image Processing, Computer-Assisted , Intracellular Membranes/ultrastructure , Ionophores/pharmacology , Microscopy, Electron , Toxoplasma/drug effects , Toxoplasma/physiology
2.
FEMS Microbiol Lett ; 185(1): 79-82, 2000 Apr 01.
Article in English | MEDLINE | ID: mdl-10731610

ABSTRACT

Tachyzoites of Toxoplasma gondii multiply within the parasitophorous vacuole (PV) until the lysis of the host cell. This study was undertaken to evaluate the effect of hydroxyurea (a specific drug that arrests cell division at G1/S phase) on the multiplication of T. gondii tachyzoites in infected Vero cells. Infected host cells were treated with hydroxyurea for periods varying from 5 to 48 h, and the survival and morphology of the parasite were determined. Hydroxyurea arrested intracellular T. gondii multiplication in all periods tested. After 48 h of incubation with hydroxyurea, intracellular parasites were not easily observed in Vero cells. Ultrastructural observations showed that infected host cells treated with hydroxyurea for 24 h or more presented disrupted intracellular parasites within the PV. However, the host cells exhibited a normal morphology. Our observations suggest that hydroxyurea was able to interfere with the cycle of the intracellular parasite, leading to the complete destruction of the T. gondii without affecting the host cells.


Subject(s)
Hydroxyurea/pharmacology , Nucleic Acid Synthesis Inhibitors/pharmacology , Toxoplasma/drug effects , Animals , Chlorocebus aethiops , Host-Parasite Interactions , Mice , Microscopy, Electron , Toxoplasma/growth & development , Vero Cells/parasitology , Vero Cells/ultrastructure
3.
Parasitol Res ; 83(3): 252-6, 1997.
Article in English | MEDLINE | ID: mdl-9089721

ABSTRACT

Confocal laser scanning microscopy and transmission electron microscopy were used to study the inner membrane complex of tachyzoites of Toxoplasma gondii. DiOC6, a lipophilic cationic fluorescent dye used to visualize the endoplasmic reticulum of eukaryotic cells, labeled cytoplasmic structures in a reticulated pattern and the periphery of the nucleus of the host cell. Intracellular and extracellular tachyzoites were stained. Observation of several focal planes showed labeling of the most peripheral region of the protozoan. Reaction product was observed in the outer nuclear membrane, in profiles of the endoplasmic reticulum, and in the inner membrane complex of tachyzoites subjected to the KI-OsO4 technique. Taken together, these observations suggest that the inner membrane complex may represent a specialized region of the endoplasmic reticulum of tachyzoites of T. gondii.


Subject(s)
Toxoplasma/ultrastructure , Animals , Carbocyanines/chemistry , Cell Membrane , Chlorocebus aethiops , Fixatives/chemistry , Fluorescent Dyes/chemistry , Mice , Osmium Tetroxide/chemistry , Potassium Iodide/chemistry , Staining and Labeling , Vero Cells
4.
Cell Struct Funct ; 21(1): 47-52, 1996 Feb.
Article in English | MEDLINE | ID: mdl-8726473

ABSTRACT

Fluorescence microscopy, with dyes analog of ceramide, and transmission electron microscopy, were used to analyze lipid traffic during interaction of Toxoplasma gondii with host cells. It is C6-NBD-Ceramide (C6-NBD-Cer), a fluorescent analog of ceramide, stained the Golgi complex where was metabolized into fluorescent sphingolipid and glucosylceramide, and translocated via the Golgi complex to the plasma membrane of living cells. In uninfected cells, C6-NBD-Cer initially concentrated at the perinuclear region, and after its fluorescent products were present in the cytoplasm and the plasma membrane. In infected cells, the probe initially is stained the Golgi complex. After 4 hours incubation with C6-NBD-Cer, the parasites within the parasitophorous vacuole began to be stained, and at 5 hours incubation, the parasites are completely fluorescent. The Golgi complex, as revealed by fluorescent probe and electron microscopy, maintained its perinuclear position throughout the evolution of intracellular parasitism. These results suggested that the intracellular parasite used the lipid pathway of the host cell.


Subject(s)
4-Chloro-7-nitrobenzofurazan/analogs & derivatives , Ceramides/metabolism , Membrane Lipids/metabolism , Toxoplasma/metabolism , 4-Chloro-7-nitrobenzofurazan/metabolism , Animals , Chlorocebus aethiops , Fluorescent Dyes , Microscopy, Electron , Vero Cells/parasitology
5.
Cell Struct Funct ; 17(5): 311-7, 1992 Oct.
Article in English | MEDLINE | ID: mdl-1473161

ABSTRACT

Fluorescence microscopy, using dyes which specifically label mitochondria, endoplasmic reticulum and the Golgi complex, and transmission electron microscopy, were used to analyze the changes which occur in the organization of these structures during interaction of Toxoplasma gondii with host cells. In uninfected cells the mitochondria are long filamentous structures which radiate from the nuclear region toward the cell periphery. After parasite penetration they become shorter and tend to concentrate around the parasite-containing vacuole (parasitophorous vacuole) located in the cytoplasm of the host cell. The mitochondria of extracellular parasites, but not of those located within the parasitophorous vacuole, were also stained by rhodamine 123. Labeling with DiOC6, which binds to elements of the endoplasmic reticulum, in association with transmission electron microscopy, revealed a concentration of this structure around the parasitophorous vacuole. The membrane lining this vacuole was also stained, suggesting that components of the endoplasmic reticulum are also incorporated into this membrane. The Golgi complex, as revealed by staining with NBD-ceramide and electron microscopy, maintains its perinuclear position throughout the evolution of the intracellular parasitism.


Subject(s)
Endoplasmic Reticulum/ultrastructure , Mitochondria/ultrastructure , Toxoplasma/physiology , 4-Chloro-7-nitrobenzofurazan/analogs & derivatives , Animals , Carbocyanines , Ceramides , Fluorescent Dyes , Microscopy, Electron , Microscopy, Fluorescence , Rhodamine 123 , Rhodamines , Vero Cells
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