Title: TIME LAPSE VIDEO MICROSCOPY AND ULTRASTRUCTURE OF PENETRATING SPOROZOITES, TYPES 1 AND 2 PARASITOPHOROUS VACUOLES, AND THE TRANSFORMATION OF SPOROZOITES TO TACHYZOITES OF THE VEG STRAIN OF TOXOPLASMA GONDII
Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 1997
Publication Date: N/A
Interpretive Summary: Infections by the protozoan parasite, Toxoplasma gondii are widely prevalent in man and animals. It causes abortion in livestock and birth defects in children. Toxoplasma gondii can grow in virtually all cells of the body, including immune cells. The mechanisms of growth and protection are not fully known. Scientists at the Beltsville Agricultural Research Center and the Montana State University have followed penetration and escape of T. gondii in host cells by videomicroscopy. The results will be helpful in understanding the biology of this organism and will be of interest to scientists that study control of toxoplasmosis.
Videomicroscropy and transmission electron microscopy were used to study the interaction of T. gondii sporozoites with cultured cardiopulmonary artery endothelial (CPA) and Madin-Darby bovine kidney (MDBK) cells. No moving junction nor exocytosis of rhoptries, micronemes and dense granules were detected during the initial penetration of sporozoites into cultured cells, whereas a moving junction and partial exocytosis of rhoptries occurred during movement of the sporozoite from the first parasitophorous vacuole (PV1) into the second vacuole (PV2). The PV1 was unusually large, lacked a tubulovesicular membrane network (TMN), and had an indistinct parasitophorous vacuolar membrane (PVM). Comparatively, the PV2 was small, had a distinct PVM, contained a well- developed TMN and was surrounded by numerous host cell mitochondria. Sporozoites that passed completely through cells carried with them an envelope of host cell membranes and cytoplasm and yet some were still capable of penetrating into other cells. After formation of the PV2, sporozoites replicated by endodyogeny to form tachyzoites.