Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The apical and basal membranes of the surface syncytium of Schistosoma mansoni were separated and found to exhibit the predictable, polarised ATPase distributions of other transporting epithelial layers. A multilamellar body fraction was prepared from adult worms and the major phospholipid classes determined. Phosphatidylcholine constituted the major phospholipid class. An apparent projection core was described in schistosome multilamellar bodies, which showed structural analogy to multilamellar bodies from lung.;Methods were devised for sequentially stripping the outer (OB) and inner (IB) bilayers from the surface apical membrane complex of adult worm pairs. Tritiated Concanavalin A and {lcub}('125)I{rcub} diazotised iodosulfanilic acid were found to be useful markers for the OB, while alkaline phosphatase and a Mg('2+) dependent, Na('+) ATPase were described from the IB. Removal of the OB did not result in cytosolic leakage from the syncytium, while removal of the IB resulted in the loss of high molecular weight soluble proteins. Differences in phospholipid composition between the OB, IB and multilamellar bodies were found to be quantitative rather than qualitative. Preliminary evidence suggested that major phospholipid classes of the OB and IB exhibited heterogeneous turnover or post-synthetic modulation.;Radiolabelled glycerol was incorporated into the lipids of adult worms and had a turnover half-time (t 1/2) of 13.0 hours. Loss of glycerol from the aqueous phase exhibited biphasic kinetics. Glycerol was found not to be ideal for measurements of turnover rates of OB and IB lipids. ('14)C Palmitate was incorporated into the lipid phase of adult worms and was lost with t 1/2 = 11.5 hours. The IB lipids showed biphasic kinetics with t 1/2 = 11.5 hours. The IB lipids showed biphasic kinetics with t 1/2 = 12 minutes and 17.3 hours. Results of the turnover studies emphasized the ability of S. mansoni to rapidly renew its surface and to modulate surface phospholipids.;A negatively charged, sialic acid - containing glycocalyx was discovered on the schistosome surface and was found to show regional and sexual heterogeneity. The presence of this surface coat on lung stage and adult parasites, combined with the lack of a coat on very young schistosomula, may help to explain the phenomenon of concomitant immunity.



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