Cathepsin L proteinase secreted by Fasciola hepatica in vitro prevents antibody-mediated eosinophil attachment to newly excysted juveniles.

The ultrastructure of the reproductive system of mature (54-day-old), immature (32-day-old) and females from unisexual infections of Schistosoma mansoni is described in detail. The uterus is tegumentary in structure but the vitelline duct and oviduct are complex and possess cilia as well as lamellae on their luminal surfaces. The characteristics of the cells forming the walls of the ducts suggests that they may have a digestive function. The posterior portion of the oviduct of the adult worm contains sperm which become enveloped by lamellae. The vitelline cells of the adult contain vitelline droplets, much lipid and little glycogen. A second type of body derived from endoplasmic whorls is also present. Mehlis's gland contains only one type of gland cell and these cells pass through the ootype wall and open into its lumen. The female from unisexual infections has an incompletely developed Mehlis's gland, an ovary in which the Golgi complexes do not produce typical cortical granules and has vitelline cells which remain immature. The oviduct, ootype and uterus are well developed in contrast to the vitelline duct.
 A comparison with young, but not inseminated worms, suggests that the presence of sperm in the oviduct is not the major stimulus which induces maturation of the female worm.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182000046394

A comparative study of the reproductive system of mature, immature and ‘unisexual’ female Schistosoma mansoni

Publisher Summary This chapter discusses ultrastructure of the tegument of Schistosoma mansoni at all stages of the life cycle. The chapter has four main sections dealing respectively with the cercaria, the schistosomulum, the adult trematode, and miracidium and sporocyst. The cercaria section concerns the development of the tegument, the cercarial surface coat, and associated structures of the tegument in developed cercariae. A syncytial tegument connected to subtegmental cells occurs in all adult digenetic trematodes that have been examined and this unusual structure involves unusual cytoplasmic inclusions that are also related to the host-parasite interface. Specialized regions of tegument occur in the oesophagus and the uterus that are regarded as tegumental structures but differ in structure. The oesophagus is primarily concerned with digestion and the function of the intestinal caecum is absorption and egestion. Destruction of the tegument is specially considered in respect of the effects of hypo- and hypertonic media and drugs and host immunity. Finally, the epithelium and associated structures of the miracidium are considered and the contrasting tegument of the daughter sporocyst, which has the syncytial tegument and nucleated subtegumental cells of the typical digenetic trematode. All these and other matters are considered in such intricate detail as is necessary at this time, when ultrastructural detail can improve the understanding of the host-parasite relationship in established schistosomiasis.

Ultrastructure of the Tegument of Schistosoma

Purification of a cathepsin L-like proteinase secreted by adult Fasciola hepatica

The fine structure of the miracidium of Schistosoma mansoni.

Mehlis' gland of F. hepatica is composed of two secretory cell types supported by parenchymal cells. The products of the secretory cells are carried by means of cytoplasmic extensions into the ootype. The most prevalent type of secretory cell is termed S1 type. It possesses many narrow granular endoplasmic cisternae and numerous Golgi complexes. The secretory bodies of this cell resemble slightly curved sausages and have a filamentous content radiating from a central core. The other secretory cell type is termed S2 type. It is characterized by distended granular endoplasmic cisternae and numerous Golgi complexes which give rise to round dense secretory bodies with a crystalline or packed fibrous appearance.

Electron microscope studies of Fasciola hepatica. I. The ultrastructure and interrelationship of the parenchymal cells.

The structural relationship between cells of the parenchyma and those of the alimentary and excretory systems, and tegument are described.Junctional complexes are formed in areas of close cell apposition. They occur laterally on invaginations of parenchymal processes which are embedded in the epithelial cells of the alimentary and excretory systems, and on flat plaques between parenchymal cells and the tegument.The ultrastructure of the complexes has been resolved and a three-dimensional interpretation is put forward. It is suggested that the complex is a type of desmosome.The findings reported here add support to the suggestion made in a previous paper that the parenchyma may function as a transport system in this fluke.We wish to acknowledge grants from the Wellcome Trust and the S.R.C. for the purchase of an Akashi TRS 50 and an A.E.I. EM 6B electron-microscope respectively. This research and that reported in a previous paper were carried out while one of us (S.S.E.G.) was in receipt of a Training Studentship Grant from the Wellcome Trust.We also wish to thank Mr W. Ferguson and Mr A. Lyness for photographic and technical assistance.

S. S. E. Gallagher

Papers

Electron microscope studies of Fasciola hepatica. I. The ultrastructure and interrelationship of the parenchymal cells.

Electron-microscope studies of Fasciola hepatica II. The interrelationship of the parenchyma with other organ systems