Protein synthesis in vivo by Schistosoma mansoni cercariae

Cercariae of Schistosoma mansoni were labeled with [14C]leucine in vivo and their protein studied by one- and two-dimensional electrophoretic fluorography. With molecular weight (Mr) and isoelectric point (pI) as parameters, polypeptides from different stages of cercarial embryogenesis were compared with each other and with those of adult worms. Up to six polypeptides with different isoelectric points were found in a single electrophoretic band of the same Mr. Three polypeptides of high molecular weight were synthesized by cercariae 3 days before escape, and were similar to polypeptides synthesized by adults. The most prominent cercarial polypeptides synthesized three days before emergence (during tail elongation) are two which comigrate electrophoretically with actin and heavy chain of myosin. The rate of actin synthesis decreased at 48 and 24 h, with little or no synthesis in the 4 h preceding emergence. Many polypeptides found in cercariae labeled 4 h before emergence differ in pI and Mr from those synthesized in earlier stages of embryogenesis. From the water in which the cercariae emerge, labeled polypeptides were precipitated which are identical to several found both in shed, washed cercariae and the infected hepatopancreas. Polypeptides of high Mr are not synthesized by cercariae in the period shortly before escape; this stage is represented by polypeptide products with Mr values of 35 000, 53 000 and 58 000.