title: Further studies on the organization of the hydrogenosome in Tritrichomonas foetus.
abstract: The fine structure of the hydrogenosome of Tritrichomonas foetus was analysed using different approaches: routine transmission electron microscopy, quick-freezing techniques followed by freeze-fracture, deep-etching and freeze-substitution, cryo-ultramicrotomy, serial sectioning followed by three-dimensional (3D) reconstruction and cytochemical detection of carbohydrates, Ca++ and phosphates. The presence of two closely apposed unit membranes surrounding the hydrogenosome, as well as its internal vesicle, was shown both in thin sections of well-preserved cells and in freeze-fracture replicas. Analysis of light micrographs, thin serial sections used to 3-D reconstruction and freeze-fracture replicas, show that the hydrogenosome of T. foetus resembles a sphere, but presents a protusion towards the cytoplasm. The vesicle varies in size from organelle to organelle and represent about 8.5% of the volume of the organelle. Based on the fact that the vesicle (a) presents a distinct morphological appearance from the hydrogenosome matrix, (b) was the main site of Ca++-accumulation, (c) presents phosphatase activity and (d) its membrane presents N-acetyl-glucosamine-containing glycoconjugates, as revealed by incubation of cryosections in the presence of gold-labeled WGA, we conclude that it represents a specialized sub-compartment of the hydrogenosome. Freeze-fracture followed by deep etching showed the presence of large number of particles, probably correspondent to macromolecules, within the hydrogenosomal matrix. These structures were not randomly distributed.
authors.affiliation: Laboratório de Biologia Cellular e Tecidual, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Rio de Janeiro, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Benchimol
authors.forename: J C
authors.initials: JC
authors.lastname: Almeida
authors.forename: W
authors.initials: W
authors.lastname: de Souza
mesh_terms: D000818:Animals; D005615:Freezing; D006651:Histocytochemistry; D007091:Image Processing, Computer-Assisted; D008081:Liposomes; D008854:Microscopy, Electron; D015388:Organelles / Q000648:ultrastructure*; D016835:Tritrichomonas foetus / Q000648:ultrastructure*
chemical_list: D008081:Liposomes