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PubMed1982

Purification and properties of a proteolytic enzyme from the cercariae of the human trematode parasite Schistosoma mansoni.

Skin penetration by the cercarial stage of the human trematode parasite Schistosoma mansoni is mediated by the secretion of proteolytic enzymes able to digest components of mammalian connective tissues. In the present study the purification of these proteinases from cercarial homogenates is reported. The major proteinase species has a mol. wt. of approx. 25 000 and exists in monomeric form as determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. This proteinase has an isoelectric point of 6.0. Studies presented here, with a variety of substrates and inhibitors, confirm previous claims that these proteinases belong to the serine class, and, in addition, suggest that they resemble the vertebrate chymotrypsins rather than trypsins or elastases. However, the amino acid composition of the cercarial proteinase differs significantly from bovine chymotrypsin and from the human leucocyte chymotrypsin-like cathepsin G. The amino-acid-composition differences between these proteinases are consistent with their differences in isoelectric point. In order to obtain an insight into the role of the proteinase in skin penetration, its activity on cartilage proteoglycan monomers and on the isolated peptide backbone of proteoglycan was studied. The results of the present study indicate that the cercarial enzyme catalyses a limited specific digestion of the peptide core.

Amino Acids↗
PubMed1982

[Sensillae and protonephridia of cercaria of Centrocestus formosanus and Centrocestus sp. (Centrocestinae, Heterophyidae)].

A description is given of cercarial chaetotaxy of two Centrocestinae (Heterophyidae, Opisthorchioidea) from Malaysia: Centrocestus formosanus and Centrocestus sp.--Comparison with cercarial chaetotaxy of taxonomically related groups indicates that 1. The chaetotaxy of the Centrocestinae agrees with that of other Opisthorchioidea, 2. There is an important difference between chaetotaxy of Centrocestinae and other Heterophyidae which suggest that the family is heterogeneous.

Animals↗
PubMed1986

[Superficial argentophilic structures in the miracidium and cercaria of Paramphistomum microbothrioides Price and Mac Intosh, 1944 (Trematoda, Paramphistomidae)].

Superficial argentophilic structures of the miracidium are identical to those observed in the other species of the genus. On the other hand, on the terebratorium, they are different from those of the miracidium of Calicophoron calicophorum. Cercarial papillae are rarely symmetrical and their number varies according to specimens. However differences between the species are obvious. If Paramphistomum microbothrioides, P. microbothrium and P. daubneyi are related by acetabular papillae, the number of lateral papillae and the caudal chaetotaxy allow to distinguish these three species.

Animals↗