Demonstration of Taenia crassiceps cysteine proteinase activity in tegumentary lysosome-like vesicles.

Larval stages of Taenia species survive for prolonged periods in the tissues of their intermediate hosts. Other groups have demonstrated that host immunoglobulins are taken up by the cysticerci by adsorptive endocytosis, degraded, and the amino acids incorporated into parasite proteins. We have shown that a 43-kDa cysteine proteinase is the major parasite enzyme that degrades immunoglobulin in vitro. To localize this enzyme in situ, Taenia crassiceps cysticerci were incubated with the peptide substrate Z-Phe-Arg-methoxynaphthylamide. Free methoxynaphthylamide was coupled to p-rosanilin and osmium and visualized by transmission electron microscopy. Initial studies of cysticerci incubated without substrate confirmed the normal microanatomy and absence of significant host inflammation. In comparison to controls with no substrate, sections of cysticerci incubated with substrate revealed electron-dense deposits in round vesicles. The vesicles were found primarily within the tegumentary cytons and internuncial processes, a location similar to that described for vesicles associated with adsorptive endocytosis. There were proportionately more endocytotic vesicles and electron-dense vesicles in smaller cysticerci than larger ones. Formation of electron-dense deposits was inhibited by heat and partially inhibited by the cysteine proteinase inhibitor E-64. These data are consistent with localization of the cysteine proteinase activity to lysosome-like vesicles.

Ultrastructural features of the tegument of adult Cynodiplostomum azimi (Trematoda:Digenea) in experimentally infected albino rats.

The ultrastructure of the tegument of adult Cynodiplostomum azimi and the lesions caused by the worm at this host parasite interface in albino rats are described. The tegument consists of a syncytial distal cytoplasm (approx. 2.01-3.1 microns in thickness), bounded by an outer apical plasma membrane and an inner basal trilaminated lamina. The subtegumental cells (approx. 10.34 microns in length) are connected with the distal cytoplasm by means of cytoplasmic trabeculae. The morphology of the tegument appeared very variable. Large areas were formed of irregular folds, while other areas carried finger-like or papilla-form structures. Tegumental spines appear to have a crystalline lattice structure. Three morphologically distinct types of membrane-bound inclusion bodies were described in the tegumental/perikaryal complex. The electron-lucent elongate bodies (approx. 0.23 micron in length) were the predominant first type. The second was round-ovoid bodies (average length 0.12 micron) with a central core of electron-dense material. The third was electron-dense, rod-like in shape (0.28 micron in length) and occurred occasionally. The majority of these inclusion bodies were oriented parallel to the tegumental surface. The host's mucosa at the parasite interface showed marked flattening and partial to complete loss of mucosal microvilli. Inflammatory cells, particularly eosinophils were observed at the host-parasite interface.

Scanning electron microscopy of the small intestine of rats experimentally infected with Cynodiplostomum azimi.

Scanning electron micrographs of the proximal intestine of rats infected with C. azimi showed mild villous changes and excessive mucus secretion as early as the first day after infection. On the second day the regular leaf-like pattern of the villi was not seen, the epithelial lining of the mucosa was damaged with large amounts of mucus. Goblet cell openings appeared either empty or filled with secretions. The mucosal damage persisted for three months. Four months after infection, villi regained part of their normal pattern. Their epithelial lining although less damaged, appeared delicate. Villi away from the worm were less affected. Pathological changes at different intervals of infection were discussed in relation to the surface structure of the parasite.

Some ultrastructural studies on the excretory bladder of the adult Cynodiplostomum azimi (Trematoda: Digenea) in infected rats.

Transmission electron microscope was used to reveal the reserve bladder system of the adult Cynodiplostomum azimi in experimentally infected rats. It was shown that this system consisted of a number of lacunae. The lacunar lining appeared as syncytial epithelium containing many nuclei, mitochondria, dense secretory bodies, Golgi complex and bundles of smooth muscles. The outer surface of the excretory epithelium was highly folded and lamellated. These lamellae were continuous with the excretory epithelium. Small lipid droplets were observed within the excretory epithelium, while larger ones were associated with the lamellae. The large lipid droplets were released in the lacunal lumen after the rupture of the lamellae surrounding them.

Scanning electron microscopy of normal and praziquantel treated S. haematobium worms (Egyptian strain).

The ultrastructure of the tegument of S. haematobium was examined before and after treatment with Praziquantel using scanning electron microscopy. The surface of the adult male worms prior to treatment showed numerous tubercles with apically directed spines and the lateral border showed highly pitted folds. The oral and ventral suckers showed well developed spines. Praziquantel administration caused various structural changes in the various groups studied. Blebs and spine deformities appeared as early as half an hr. after administration. Changes were also observed when the drug was administered prior to worm maturation resulting in generalized deformities in the worms which survived treatment, loss of spines and tegumental swellings.