title: Taenia crassiceps: regional variations in ultrastructure and evidence of endocytosis in the cysticercus' tegument.
abstract: Regional variations in the thickness of the tegument, in the morphology of microtriches and mitochondria, in the distribution of dense bodies, smooth micropinocytotic vesicles (SMVs), and coated micropinocytotic vesicles (CMVs) have been shown for the cysticercus of Taenia crassiceps. The number of SMVs and CMVs present in the syncytial layer are in inverse proportion to each other, the former being more numerous in the bladder wall and upper part of the invagination canal and the latter in the lower part of the canal and the rostellar region. Tegumental cells contain numerous granular endoplasmic reticulum-Golgi complexes involved in the synthesis of both primary lysosomes and dense bodies. Vesicles characteristic of various stages of heterolysosomes are present and show regional variations in numbers and size. Acid phosphatase activity (EC 3.1.3.2) is present on the tegumental surface, and within the Golgi complex, primary lysosomes, and heterophagosomes of the tegumental cells. CMVs are reported for the first time in the tegument of any helminth and have characteristics similar to CMVs in other tissues. T. crassiceps, therefore, because of the presence of both SMVs and CMVs, is a unique model system for the study of basic mechanisms of endocytosis.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D004705:Endocytosis; D006056:Golgi Apparatus / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D010873:Pinocytosis; D013621:Taenia / Q000502:physiology / Q000648:ultrastructure*