Ultracytochemistry of the surface coat/pellicle complex in Trypanosoma brucei

Ultracytochemistry of polysaccharides and specific sugar residues reveals differences in the surface staining pattern between developmental forms of Trypanosoma brucei. The techniques used were the PA (periodic acid)-TCH (thiocarbohydrazide)-silver albumose reaction for the polysaccharides, and the Concanavalin A (Con A)-perioxdase-DAB coupling method for specific sugar residues. Blood and metacyclic forms, both possessing a surface coat, stain distinctly for carbohydrates at the level of the pellicular membrane. The external portion of the bloodform coat lacks any positive staining. Pellicles of non-coated culture and vector forms react only faintly for polysaccharides, whereas heavy staining of oxidized peroxidase/DAB reaction product, indicative of sugar bound Con A, occurs. It is suggested that the sugar moieties of the coat glycoproteins are located close to the membrane-coat junction.