Metabolic changes associated with the migration of the schistosomulum ofSchistosoma mansoniin the mammal host

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Abstract
SUMMARY: A variety of measurements was made on small samples of schistosomula recovered from the skin, lungs and hepatic portal system of percutaneously infected mice, on the basis of which development could be divided into a migration and a growth phase. The density of schistosomula, estimated using a Ficoll gradient, was found not to vary significantly between Day 0 and Day 24 post-infection, having a mean value of 1·077. The reduced weight was measured by means of a Cartesian diver balance and used in conjunction with density to estimate the change in wet weight of schistosomula. Wet weight was found to decline slightly during the migration phase and to increase exponentially following arrival of schistosomula in the hepatic portal system. No change in nitrogen content was detected during migration but there was a rapid increase after arrival in the hepatic portal system. The rate of oxygen consumption, measured by Cartesian diver respirometer, declined significantly during migration and then increased exponentially after arrival of worms in the hepatic portal system. No change was detected in the lactic dehydrogenase activity of migrating worms but again, an exponential increase occurred after entry into the hepatic portal system. It was concluded that the migrating schistosomulum is in a semi-quiescent metabolic state, although it possesses the ability to take up nutrients and undergoes morphological changes. Growth is triggered by an unknown mechanism after arrival in the hepatic portal system. Examination of the various sets of data suggests that it is initiated between 10 and 11 days post-infection in the most advanced schistosomula.