Alterations of the surface tegument of Opisthorchis viverrini exposed to praziquantel in vitro and in vivo.

The in vitro and in vivo effects of praziquantel on the ultrastructural surface of Opisthorchis viverrini were investigated using scanning electronmicroscopy. For the in vitro study, adult flukes were collected from experimentally infected hamsters, and were incubated for various time intervals at 37 degrees C in Earle's basal medium containing praziquantel at final concentrations of 0.01-100 micrograms/ml. For the in vivo study, flukes were collected from the biliary system of experimentally infected hamsters that had been treated 4 hours previously with 350 mg of praziquantel per kg body weight (mg/kg). Flukes were also obtained from the feces of a patient with opisthorchiasis who had been given praziquantel once at a dose of 40 mg/kg 4-6 hours previously and from the bile of a patient at the time of operation 24 hours after praziquantel treatment. Scanning electronmicroscopic analyses of the surface teguments of flukes exposed to praziquantel either in vitro or in vivo showed similar changes. Tegumental bubbles of different sizes appeared on the surface; they later ruptured and resulted in the formation of crater-like lesions. These lesions might be so extensive as to result in the peeling of the entire areas. On occasions, "micronodules" appeared later in these areas and those at the periphery of the lesions; these micronodules may represent an attempt by the worm to regenerate new tegument. The possibility that these ultrastructural changes may represent a generalized response of the tegumental surface to an obnoxious agent was discussed.

Microtopography of the surface of adult Schistosoma japonicum-like (Malaysian) as observed by scanning electron microscopy.

The surface of adult Schistosoma japonicum-like (Malaysian) was studied by scanning electron microscopy. The basic pattern of surface microtopography is similar to other strains of S. japonicum as previously reported. However, among male member there are some unique differences in the types, number and distribution of surface papillae and morphology of ridges. Three kinds of papillae were observed: (1) the large fungiform papillae (3.5-4 micron in diameter, most without cilia) are more numerous than in other strains of S. japonicum, they concentrate on the lateral aspect of the anterior and middle parts close to the edge of the gynecophoral canal, and on the dorso-lateral aspect of the posterior part towards the tail tip; (2) the small hemispherical papillae (1.5-2 micron in diameter, all bearing cilia) are especially numerous in the suckers, the gynecophoral canal and parts of the tegument around the suckers and close to the tail tip; on the rest of the surface they are evenly distributed; (3) the cratered papillae (3-4 micron in diameter, about half having cilia) are more numerous than on other strains, they concentrate on the lateral aspect of the middle part and on the edges of the gynecophoral canal. The surface ridges (about 0.2-0.3 micron in width) are tall, highly branching and perforated; they are most developed in the middle part. Spines were observed only in the suckers and the gynecophoral canals. In contrast to the male, the female has numerous spines on all parts of the surface except the most anterior, where a large number of long cilia were observed. All three kinds of papillae were present; fungiform papillae are more numerous than in females of other strains; they concentrate on the latero-dorsal aspect of middle and posterior parts, and around the excretory pore. Ridges are much less developed than in the male and are prominent only in the middle part.