The possibility of using surface charge to separate and concentrate Plasmodium sporo-zoites from mosquitoes was suggested by pre-vious work which indicated that P. berghei sporozoites were less negatively charged than any other component observed after homogenization of infected Anopheles stephensi mos-quitoes (Miller et al., 1973, J Parasitol 59: 925-927). We now report a relatively simple DEAE-cellulose column procedure for the separation of P. berghei sporozoites from infected mosquitoes. This technique permits the preparation of cleaner suspensions of sporo-zoites than have been obtainable with any previously described procedure. The buffer used contained 8.8 g Tris (Hydroxymethyl) aminomethane (Trizma Base, Sigma), 5 g NaH2PO4 H20, 5 g NaCl, and 18 g glucose/liter H20, and had a pH of 8.2 _ 0.05, and an ionic strength of 0.121 (calculated as in Lanham and Godfrey 1970, Exp Parasitol 28: 521-534). After equilibration of pre-swollen microgranular Diethylaminoethyl Cellulose (DE 52, Whatman) with buffer, columns were prepared using 12-ml disposable plastic syringes (inside diameter 16 mm). A 16-mm disc of fine nylon mesh was cut with a cork borer to fit the outlet end of the syringe, and a slurry of equilibrated DE 52 was pi-petted in to form a 25-mm column. Following further washing with at least 100 ml buffer from a reservoir-60 cm above the column, the DE 52 packed to a total height of-20 mm. Prior to application of the sporozoite preparation to the column, the buffer was drained until the top of the column was barely covered. Buffer was freshly prepared for each experiment, since its effectiveness decreased after several days of storage at 4 C. However, columns packed with equilibrated DE 52

The possibility of using surface charge to separate and concentrate Plasmodium sporo-zoites from mosquitoes was suggested by pre-vious work which indicated that P. berghei sporozoites were less negatively charged than any other component observed after homogenization of infected Anopheles stephensi mos-quitoes (Miller et al., 1973, J Parasitol 59: 925-927). We now report a relatively simple DEAE-cellulose column procedure for the separation of P. berghei sporozoites from infected mosquitoes. This technique permits the preparation of cleaner suspensions of sporo-zoites than have been obtainable with any previously described procedure. The buffer used contained 8.8 g Tris (Hydroxymethyl) aminomethane (Trizma Base, Sigma), 5 g NaH2PO4 H20, 5 g NaCl, and 18 g glucose/liter H20, and had a pH of 8.2 _ 0.05, and an ionic strength of 0.121 (calculated as in Lanham and Godfrey 1970, Exp Parasitol 28: 521-534). After equilibration of pre-swollen microgranular Diethylaminoethyl Cellulose (DE 52, Whatman) with buffer, columns were prepared using 12-ml disposable plastic syringes (inside diameter 16 mm). A 16-mm disc of fine nylon mesh was cut with a cork borer to fit the outlet end of the syringe, and a slurry of equilibrated DE 52 was pi-petted in to form a 25-mm column. Following further washing with at least 100 ml buffer from a reservoir-60 cm above the column, the DE 52 packed to a total height of-20 mm. Prior to application of the sporozoite preparation to the column, the buffer was drained until the top of the column was barely covered. Buffer was freshly prepared for each experiment, since its effectiveness decreased after several days of storage at 4 C. However, columns packed with equilibrated DE 52