In this paper, the variation of surface electricity of two Entamoeba histolytica isolar es was investigated using the cell electrophoretic technique. By testing the electrophoretic iondition of amoeba in gradient pH and the effect of some enzymes, we provided infor-nations for the physiology and pathogenicity of this parasite.Cell electrophoresis for the two isolates of E. histolytica (isolate A and isolate B) n pH 2.05-8.00 Mcllvaine buffer revealed that EPM (electrophoretic mobility) was negative under the pH gradients of 3.00-8.00, which meant the amoeba cell surfacecar- ried negative charge in this condition. Surface charge densities of isolates A and B were found to be ( + ) 148.3-(-) 6035.9 esu/cm2 and (+ )222.4-(-) 6624.0 esu/cm2 respectively. In addition, except in pH 2.05, the EPMs in Mcllvaine buffer were different between the two amoeba isolates, with significant statistical difference.The enzyme test demonstrated there was no neuraminic acid on the surface of these two amoeba isolates. The surface negative groups of the protozoa were sensitive to trypsin and deoxyribonuclease I.

The antischistosomal effects of Levo-praziquantel (L-PZQ) compared with racemic prazi-quantel (dL-PZQ) in vitro on miracidium and cercaria of Schistosoma japonicum were reported in this paper. The results indicated that the schistosomicidal effect on the two larval stages of the parasite induced by L-PZQ (0. 2 ?g/ml) and double amount of dL-PZQ (0. 4?g/ml) had no significant difference. Miracidial stage was more sensitive to the drugs than the cer-carial stage. The schistosomicidal mechanism caused by L-PZQ was discussed briefly.