Schistosoma mekongi: the in vitro effect of praziquantel and artesunate on the adult fluke.

The efficacy and tolerance of 80 microg/ml praziquantel (PZQ) and 40 microg/ml artesunate (ATS) against adult stage Schistosoma mekongi in vitro were investigated after 3, 6, 12, and 24h incubation by monitoring worm motility and compared tegumental changes using scanning electron microscopy (SEM). Thirty mice were infected with S. mekongi cercaria for 49 days. Adult worms were collected by perfusion method and prepared for in vitro study. Contraction and decreased motor activity were observed after as little as 3h incubation with PZQ and ATS. Some of the worms were immobile 12h after exposure, and died within 24h. The tegument of S. mekongi showed severe swelling, vacuolization and disruption, fusion of the tegumental ridges, collapse and peeling. After 12-24h incubation, PZQ induced similar but they less severe, tegumental changes to those observed after exposure to ATS. The direct observation of the fluke motility and SEM study suggest that ATS is more effective than PZQ in causing tegumental damage in adult S. mekongi, and provides a basis for subsequent clinical trials.

Eurytrema pancreaticum: the in vitro effect of praziquantel and triclabendazole on the adult fluke.

The efficacy and tolerance of the 80 microg/ml praziquantel (PZQ) and 40 microg/ml triclabendazole (TCZ) against adult stage Eurytrema pancreaticum in vitro were investigated at 3, 12, and 15 h incubation. Motility of the flukes and histopathological changes were studied. Sudden paralysis and death were observed after exposed to PZQ as early as 3h incubation. In contrast, the TCZ treated flukes showed active mobility at all intervals. By light microscopic examination, severe damages in various organs such as tegument, muscle, and testes were observed early at 12h incubation of these drugs. PZQ caused more severe damage to flukes than TCZ. There were vigorous contraction of musculature, progressive shrinkage of circular and longitudinal muscles, vacuolization and disintegration of the tegument disrupting the worms' outer surface including detachment of spines in the PZQ treatment. The cells in testes were slightly increased in size and followed by degeneration leaving several hollow spaces. The uterus and vitelline glands remained unaffected. The direct observation of the fluke motility and light microscopic study highly suggested that PZQ was more effective than TCZ treatment for the eurytremiasis infection.

Effects of praziquantel and artesunate on the tegument of adult Schistosoma mekongi harboured in mice.

The effects of praziquantel and artesunate on the tegument of adult Schistosoma mekongi harboured in mice were compared using scanning electron microscopy (SEM). Forty-two mice infected with S. mekongi for 49 days were treated intragastrically with either 300 mg/kg praziquantel or 300 mg/kg artesunate. Mice were sacrificed 1 or 3 days post-treatment. Worms were collected by perfusion and examined by SEM. One to 3 days after administration of artesunate, the tegument of S. mekongi showed severe swelling, vacuolization, fusion of the tegumental ridges and loss or shortening of the spines on the trabeculae, collapse and peeling. Praziquantel induced similar tegumental alterations as those observed after administration of artesunate, but they were less severe. Three days post-treatment, there was evidence of recovery only in the case of praziquantel. The results of our study suggest that artesunate is more effective than praziquantel in causing tegumental damage in adult S. mekongi, and provides a basis for subsequent clinical trials.

Ultrastructural alterations in the liver and kidney of white sea bass, Lates calcarifer, in acute and subchronic cadmium exposure.

Ultrastructural alterations in the liver and kidney of 3-month-old white sea bass, Latescalcarifer, after cadmium exposure were studied by transmission electron microscopy (TEM). One group of fish was exposed to a cadmium concentration of 10 mg/L (acute) for 96 h in a static system, and another group was exposed to cadmium concentrations of 0.8 and 3 mg/L cadmium (subchronic) for 3 months in a recirculation closed system. Ultrastructural alterations observed in the hepatocytes included mitochondrial condensation, swelling, and lysis. The rough endoplasmic reticulum (RER) showed dilation, fragmentation, and vesiculation. After subchronic exposure there were numerous large lipid droplets and abundant stored glycogen. Ultrastructural alterations observed in the proximal tubules of the kidney included nuclear degeneration, condensation, and massive swelling of the mitochondria; RER fragmentation and vesiculation. Disorganized brush borders and increased numbers of large hydropic vacuoles and lysosomes were also observed.