title: Leishmania mexicana: distribution of intramembranous particles and filipin sterol complexes in amastigotes and promastigotes.
abstract: The density and distribution of intramembranous particles was analyzed in freeze fracture replicas of the plasma membrane of amastigotes, and infective as well as noninfective promastigotes of Leishmania mexicana amazonensis. The density of intramembranous particles on both protoplasmic and extracellular faces was higher in infective than in noninfective promastigotes and it was lower in amastigotes than in promastigotes. Amastigotes purified immediately after tissue homogenization were surrounded by a membrane which corresponded to the membrane which lined the endocytic vacuoles where the parasites were located within the tissue macrophages. Aggregation of the particles was seen in the flagellar membrane at the point of emergence of the flagellum from the flagellar pocket. Differences in the organization of the particles were seen in the membrane which lined the flagellar pocket of amastigotes and promastigotes. The polyene antibiotic, filipin, was used as a probe for the detection of sterols in the plasma membrane of L. m. amazonensis. The effect of filipin in the parasite's structure was analyzed by scanning electron microscopy and by transmission electron microscopy of thin sections and freeze fracture replicas. Filipin sterol complexes were distributed throughout the membrane which lined the cell body, the flagellar pocket, and the flagellum. No filipin sterol complexes were seen in the cell body-flagellar adhesion zone. The density of filipin sterol complexes was lower in the membrane lining the flagellum than in that lining the cell body of promastigotes.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D005372:Filipin; D005614:Freeze Fracturing; D007894:Leishmania mexicana / Q000032:analysis / Q000254:growth & development / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D013261:Sterols / Q000032:analysis*
chemical_list: D013261:Sterols; D005372:Filipin