Echinococcus granulosus equinus: the histochemistry of the laminated layer of the hydatid cyst.

The laminated layer of the hydatid cyst of E. granulosus equinus grown in mice has a polysaccharide substrate, which is not glycogen, but which possesses 1,2 glycols. This periodate-reactive component is demonstrated at the ultrastructural level using the thiosemicarbazide-silver proteinate technique which is also positive in Golgi-derived vesicles in the cytons and within the superficial cytoplasm at the parasite tissue/laminated layer interface. A carboxyl-acid mucopolysaccharide, lacking uronic and sialic acid residues, is present and weak reactions for sulphated acid mucopolysaccharide are recorded. The equivocal evidence for the presence of a chitin-like substrate is discussed. The predominantly basic protein component of the laminated layer has histochemically identifiable SS groups which are only very weakly demonstrated at the cytochemical level. Arginine and tryptophan are recorded. Lipid levels are low, and divalent cations, possibly calcium, are present.