title: Freeze-etch characterization of the teguments of three metacestodes: Echinococcus granulosus, Taenia crassiceps, and Taenia taeniaeformis.
abstract: The objective of this study was to characterize the teguments of metacestodes of Echinococcus granulosus, Taenia crassiceps, and Taenia taeniaeformis using the freeze-etch technique. Metacestodes of E. granulosus (19 mo old), T. crassiceps (28 days old), and T. taeniaeformis (34 days old) from gerbils, mice and rats, respectively, were fixed for 2 hr in 3% glutaraldehyde and then prepared for freeze-etching and thin sectioning by standard techniques. Freeze-etch replicas of the teguments of all three species displayed morphologic characteristics that were generally in agreement with previous ultrastructural work, although some new features and interpretations arose from use of this technique. For each species there was a concentric ring structure within the microthrix base, and cytoplasmic extensions of the perikarya into the distal tegument were membrane-bound rather than confluent bridges; these extensions frequently branched within the tegument. In addition, channels running from the proximal tegumental membrane to, and opening at the distal surface of, the tegument were seen in thin sections.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D003599:Cytoskeleton / Q000648:ultrastructure; D004446:Echinococcus / Q000648:ultrastructure*; D005613:Freeze Etching; D007425:Intracellular Membranes / Q000648:ultrastructure; D008854:Microscopy, Electron; D009940:Organoids / Q000648:ultrastructure; D013621:Taenia / Q000648:ultrastructure*