Further studies on the endocytic activity of Tritrichomonas foetus

The endocytic activity of Tritrichomonas foetus was studied at the ultrastructural level using gold-labeled macromolecules (bovine lactoferrin, human and bovine transferrin, bovine albumin, human low-density lipoprotein, horseradish peroxidase, and protein A). All macromolecules were ingested by the...

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Bibliographic Details
Published in:Parasitology research (1987) 1994, Vol.80 (5), p.403-413
Main Authors: AFFONSO, A. L, BENCHIMOL, M, RIBEIRO, K. C, LINS, U, DE SOUZA, W
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
Cattle
Endocytosis
Fundamental and applied biological sciences. Psychology
Gold Colloid
Humans
Immunohistochemistry
Invertebrates
Lactoferrin - metabolism
Life cycle. Host-agent relationship. Pathogenesis
Lipoproteins, LDL - metabolism
Male
Microscopy, Electron
Protozoa
Receptors, Cell Surface - metabolism
Serum Albumin, Bovine - metabolism
Spectrum Analysis
Transferrin - metabolism
Tritrichomonas foetus - physiology
Tritrichomonas foetus - ultrastructure
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Summary:The endocytic activity of Tritrichomonas foetus was studied at the ultrastructural level using gold-labeled macromolecules (bovine lactoferrin, human and bovine transferrin, bovine albumin, human low-density lipoprotein, horseradish peroxidase, and protein A). All macromolecules were ingested by the protozoan. Binding experiments showed that only bovine lactoferrin bound to the parasite surface in a process that could be inhibited by the unlabeled protein, suggesting that it binds and is internalized via receptors. Label-fracture experiments showed that the receptors were distributed in clusters that did not colocalize with intramembranous particles. Kinetics analysis of the internalization of bovine lactoferrin and horseradish peroxidase, associated with the cytochemical detection of acid phosphatase, revealed that proteins were rapidly ingested through small uncoated vesicles and delivered to acid phosphatase-containing compartments. The colocalization of gold-labeled proteins and reaction product indicative of enzyme activity was confirmed by electron spectroscopic imaging. Simultaneous incubation of cells in the presence of two proteins labeled with gold particles of different diameters showed that they were ingested through the same pathway and were concentrated into cytoplasmic vacuoles corresponding to lysosome-like organelles. These data suggest that the endocytic process in T. foetus is very rapid and that the intracellular pathway for receptor-mediated and fluid-phase endocytosis seems to be the same.
ISSN:0932-0113
1432-1955
DOI:10.1007/BF00932378