In vitro hatching and activation ofTaenia taeniaeformis oncospheres

Previously described techniques for hatching eggs ofTaenia taeniaeformis were found to give inconsistent and generally ineffective results, even the degree of disaggregation of the embryophore varying with the strain of parasite. Furthermore, the hatched and activated oncospheres did not survive in the hatching fluid.Following a series of studies on the composition of the hatching fluids, a more reliable procedure was developed.Pretreatment with hypochlorite, at 0.67% w/w available chlorine, caused disaggregation of the embryophoral blocks of virtually all the eggs. When this was followed by exposure to a solution containing 10 mg.ml^–1 trypsin, 10% ox bile and 10% heat-inactivated foetal calf serum in modified RPMI with HEPES buffer and L-glutamine, about 50% of the viable oncospheres were activated and escaped from the oncospheral membrane. Most of the activated oncospheres survived in this hatching fluid for at least three hours.