PARTIAL CHARACTERIZATION OF CYTOPLASMIC COMPARTMENTS INVOLVED IN THE ENDOCYTIC PROCESS OF TRITRICHOMONAS-FETUS

The endocytic pathway of Tritrichomonas foetus, a parasitic protozoan of cattle, was studied using (a) vital dyes, such as Lucifer yellow, n eutral red and acridine orange, (b) cationized ferritin, (c) gold-labe led lactoferrin and lectins: HPA, UEA, PNA and LPA, and (d) DAMP (3-(2 ,4-dinitroanilino) 3' amino-N-methyldipropylamine). Light and confocal laser microscopy as well as transmission electron microscopy were use d in this study. Assays were monitored by fluorescence and electron mi croscopy after exposing the parasites to different conditions, Cells t hat were incubated at 15 degrees C or 20 degrees C with gold-labeled l actoferrin and processed for electron microscopy show that at 15 degre es C this ligand is found only in an early endosomal compartment and a t 20 degrees C it is found in late endosomes but not in lysosomes. Imm unocytochemical data from cryosections using DAMP as a pH probe show t hat T. foetus has acidic compartments, with a pH range of 5.2 to 6.6, with variable morphology, localization and size. Lectin-binding sites and anionic sites were also internalized and appear to be associated w ith membranes lining the vacuoles. Images of patching and shedding of these sites were also observed when HPA and UEA were used.