Opisthorchis viverrini: effect of praziquantel on the adult tegument
Apinhasmit, W.; Sobhon, P.
Southeast Asian Journal of Tropical Medicine and Public Health 27(2): 304-311
1996
ISSN/ISBN: 0125-1562 PMID: 9279994 Document Number: 461938
Ultrastructural changes to the tegument of adult Opisthorchis viverrini were studied (by scanning (SEM) and transmission (TEM) electron microscopy) after incubation in Minimal Essential Medium containing 0.0, 0.1, 1.0 or 10.0 micro g/ml of praziquantel for 5, 15, 30, 45 and 60 minutes. SEM observations showed that the surface damage was composed of blebbing due to the swelling of microvilli, followed later by the disruption of these structures to form lesions that caused the erosion and desquamation of the surface. Sensory papillae, by contrast, appeared relatively unaffected. The surface changes were observed at all doses but the extent of damage increased with increasing duration of incubation and concentration of the drug. The ventral and dorsal surfaces exhibited similar changes, whereas the anterior body tended to be damaged less than the posterior body. Under TEM, the earliest sign of changes was the depolymerization of the microtrabecular network in scattered foci, which resulted in the formation of non-membrane-bound vacuoles under microvilli. The basal infoldings also became dilated, and some turned into membrane-bound vacuoles in the basal zone. Subsequently, microvilli became enlarged, and eventually formed blebs that later ruptured to form lesion spots as observed in the SEM. Finally, the microtrabecular network in all regions broke down, creating vacuoles of various sizes throughout the tegument, leading to its total disintegration and detachment. The sequence of morphological changes was generally similar at all doses; however, the changes occurred faster at the higher doses. With the longer durations of exposure, myofilaments in most muscle cells also became depolymerized, whereas microtubules were unchanged by the drug. It is suggested that praziquantel, through its induction of Ca2+ influx, causes depolymerization of the microtrabecular network that leads to the vacuolization, swelling, blebbing, and eventually the disruption and detachment of the tegument, and the breakdown of myofilaments in the muscle cells.