Abstract
Summary
A new method is presented for nonchemical isolation and fractionation of the malaria parasite Plasmodium knowlesi. Since the mechanical fragility of erythrocytes is considerably greater than that of the Plasmodia, it was possible to preferentially fragment the red cell membrane without apparent alteration of the parasites. This was achieved by utilizing the precisely controlled conditions obtained with a French pressure cell operated at 1500-2000 psi. Parasites isolated by this method were subsequently fragmented at higher pressures (20,000 psi) and the solubil-ized substances fractionated by gel filtration. Fractions showing the major complement fixing activity reacted strongly with P. knowlesi antisera, were colorless, exhibited no anticomplementary properties and showed no serologic evidence of red cell contaminants. The findings indicate that the method may provide essential material for further studies on plasmodial composition and be of particular value for isolation of other intra-erythro-cytic parasites.
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