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 flagllum 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.     

DNA Polymorphism Revealed by Arbitrary Primers Polymerase Chain Reaction Among Blastocystis Strains Isolated from Humans, a Chicken, and a Reptile

DNA polymorphisms of different strains of Blastocystis isolated from humans, a chicken, and a reptile were examined by an arbitrary primer PCR method. Two strains of Blastocystis hominis isolated from humans in the USA and Japan yielded nearly identical PCR products. However, one strain of B. hominis (isolated from a human in Singapore) yielded quite different PCR products. Blastocystis sp. isolated from a chicken yielded PCR products similar to those of the former two strains, while Blastocystis lapemi, isolated from a reptile, shared no bands with any of the other isolates. These results indicate the possibility that our isolate from the chicken is a zoonotic strain, and that there is intraspecific variation of Blastocystis hominis.     

Inhibition of Photosystem II in the Green Alga Ankistrodesmus falcatus by Copper

Copper strongly inhibited 2,6-dichloroindophenol (DCIP) photoreduction in the broken cells of the green alga Ankistrodesmus falcatus (C303), and the activity lost could not be restored by adding 1,5-diphenylearbazide (DPC). Inactivation of the DCIP Hill reaction reached 45% after incubation with 10 μM cupric sulfate for 20 min. In the same time, copper (13 μg/mg chlorophyll) was bound to the broken cells. Addition of 10 mM KCl reduced copper binding by about 53%. Fluorescence intensity at room temperature decreased upon addition of cupric sulfate and was partially restored by adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), These results suggest that copper inactivates electron transport between the oxidizing side of the reaction center of photosystem II and the electron-donating site of DPC. Further, the effect of light intensity shows that copper mostly affected the reaction rate of the dark step and had less inhibitory effect on the quantum efficiency of the primary reaction of electron transport in photosystem II.