A cinematographic study of the penetration of cultured cells by Toxoplasma gondii.

INTRODUCTIO~The cell penetration of Toxoplasma gondii, which has not been fully clarified, will only be solved conclusively by applying cinematography, In 3 preceeding cinematographic works, PULVERTAFT et aL (1954) and LUND et aL (1961) observed the propagation of toxoplasma inside cells.SCHMIDT-HoENSDORF & HOLZ (1953) reported on toxoplasmic penetration, in which penetration was complete within 30-60 minutes. Active penetration of toxoplasma into cells was firstly reported by GULMARAES& MEYER (1942).PULVERTAFT et a1.(195.1)suggested two different ways in which the parasites gain entrance into host cells, active invasion or passive ingestion.Actively penetrating parasites did not multiply but were lethal to the cell; whereas the ingested ones were the proliferating forms.In order to clarify the mode of the penetration of toxoplasma into cultured cells, a cinematographic work was done by the authors by applying phase contrast microscopy.Detail of the penetration which was particularly characterized by the perforating form of toxoplama is described in this paper. MATERIALS AND METHODSTo.:mplasma gOlldii strain RH, originally isolated from a child by SABIN, was provided by Y. TSUNEMATSU, Institute for Infectious Diseases, University of Tokyo, and has been maintained in this department by mouse passage.In this study, 1770th to 1885th passages were used.The parasites were inoculated into mice and the peritoneal fluid of the infected mice were harvested on the 3rd day after inoculation.The fluid, containing numerous toxoplasma, was washed four times with the tissue culture medium described below, which was previously cooled.The number of toxoplasms was counted and adjusted by using hemocytometer to determine the multiplicity of infection.