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Morphological changes during conoid extrusion in Toxoplasma gondii tachyzoites treated with calcium ionophore
V G Monteiro1, E J de Melo, M Attias
1Laboratório de Biologia Celular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Avenida Alberto Lamego 2000, Campos, RJ, Brazil.
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.