Schistosoma japonicum: changes in lipase activity in adults maintained in vitro

Schistosoma japonicum (Chinese strain) adult worm pairs (10-12 weeks old) were fixed in 4 degrees C absolute acetone or neutral buffered formalin either immediately after recovery from mice, or following incubation for 0.5 or 1.0 h. Males and females were incubated individually in Earle's balanced salt solution at 37 degrees C. Lipase activity was determined in frozen sections by Gomori's method using Tween 80 as substrate. In unincubated males, lipase activity was localized only in the parenchyma; in females it was present in the vitellaria and parenchyma subjacent to the tegument. After 0.5 h incubation, males showed less lipase activity in the parenchyma than unincubated males, and females showed increased activity in the parenchyma subjacent to the tegument, but not in the vitellaria. Following 1.0 h incubation, males showed less lipase activity than previously, and females showed a marked increase in activity, particularly in the parenchyma subjacent to the tegument.