Distribution of filipin-sterol complexes in the bloodstream form of Trypanosoma brucei gambiense.

The polyene antibiotic, filipin, was used as a probe for demonstrating sterols in the plasma membrane of Trypanosoma brucei gambiense. Three different regions of the continuous plasma membrane over the cell body proper, flagellar pocket, and flagellum, were compared as to density and distribution of the filipin-sterol complexes by freeze-fracture method. The density of the complexes was highest in the cell body membrane and lowest over the flagellar pocket. The filipin-sterol complexes in the cell body membrane were distributed homogeneously on both the protoplasmic and exoplasmic faces except in the zone of flagellar attachment. This junctional zone showed a linear, complex-poor region. In the flagellar membranes, a line of complex-poor regions was observed along the juncture of the flagellum to the cell body. At the neck of the flagellar pocket, the membranes of the flagellar pocket and flagellum were closely opposed, with few filipin-sterol complexes on either membrane. At the base of the flagellar shaft, the complexes were completely lacking on both faces. Based on these observations, the zones of juncture observed in T.b. gambiense seems to be similar in ultrastructure to mammalian cell junctions, such as tight, gap, septate junctions and desmosomes, which show a nearly complete absence of the filipin-sterol complexes.

Freeze-fracture study of the bloodstream form of Trypanosoma brucei gambiense.

The ultrastructure of Trypanosoma brucei gambiense was investigated by the freeze-fracture method. Three different regions of the continuous plasma membrane; cell body proper, flagellar pocket, and flagellum were compared in density and distribution of the intramembranous particles (IMP's). The IMP-density was highest in the flagellar pocket membrane and lowest in flagellum. Intra membranous particles of the cell body membrane were distributed uniformly on both the protoplasmic (P) and exoplasmic (E) faces. On the P face of the flagellar membrane, a single row of IMP-clusters was seen along the juncture of the flagellum to the cell body. Since the spacing of the IMP-clusters was almost equal to the spacing of the paired rivet structures observed in thin section, these clusters likely are related to the junction of flagellum and cell body. At the neck of the flagellar pocket, several linear arrays of IMP's were found on the P face of the flagellar membrane, while on the E face rows of depressions were seen. At the flagellar base, the clusters of IMP's were only seen on the P face. On the flagellar pocket membrane, particle-rich depressions and linear particle arrays were also found on the P face, while on the E face such special particle arrangements were not recognized. These particle-rich depressions may correspond to the sites of pinocytosis of the bloodstream forms which have been demonstrated in thin sections.

The morphology of Trichinella spiralis: ultrastructural study of the mid- and hindgut of the muscle larvae.

The ultrastructure of the gut of Trichinella spiralis muscle larvae is comprehensively described, based on extensive observations. The mid-gut was composed of a single cell layer of epithelium over the basal lamina, the brush border, the septate junction, prominent glycogen aggregates, and other common cell organelles. The epithelial cells of the midgut were basically uniform, but the lumen presented a remarkably diversified appearance. In the ampullar portion, the midgut accommodated an amorphous substance of medium electron density, the middle portion was collapsed, and the terminal portion again dilated, but without any particular contents. The mid- and hindgut were devoid of muscle cells that could be responsible for the peristaltic movement of the gut.