File:Cytoskeletal-Components-of-an-Invasion-Machine—The-Apical-Complex-of-Toxoplasma-gondii-ppat.0020013.sv001.ogv

English: EGFP-DLC in T. gondii after Treatment with Calcium Ionophore A monolayer culture of human fibroblast cells was infected with a transgenic line of the obligate intracellular parasite T. gondii. The parasites express EGFP-TgDLC, which was imaged by epifluorescence microscopy. Bright fluorescence is seen in the middle of the cell at the centriole/spindle pole, in an apical bright spot at the conoid, and as diffuse fluorescence with a brighter cap at the apical end of the cell. In the video, several parasitophorous vacuoles are seen, each containing two parasites. The nonfluorescent host fibroblasts are not visible. The video sequence commences with addition of Ca2+ ionophore A23187 to the culture medium. After a short delay, the parasites begin egressing from the host cells by vigorous gliding movements, coupled with protrusion of the conoid. An image of one cell, indicated by the orange arrow, has been digitally cut out, rotated into constant orientation, and shown as an enlargement within the box at the upper right. Sudden protrusion of the conoid is particularly clear in this parasite, just after it begins to glide. Note that in this parasite and several others, a waist-like constriction is observed to pass down the cell as it squeezes through the host cell membrane. Some parasites display this twice, once as they exit the host cell and then again as they reinvade a second host. The images were collected at 2-s intervals, at room temperature. The total elapsed time for the video sequence is 288 seconds.