medium. The culture volume in 75 cm2 culture flasks, was increased to 25 ml from 12 ml. The flasks were kept at 37°C and the medium was prewarmed before use. The flasks were gassed with a mixture of 5% C02, 3% 02 and 92% N2 for a i minimum of 20 seconds at a pressure of around 5 Ib/in2. The culture medium was changed daily without the addition of RBCs. Blood smears were prepared once or twice a week to check the ~tate of the cultures and the presence of gametocytes. Typically, mature gametocytes were observed after 14-17 days

Fresh stock of parasites was thawed for culture as described above. Thin blood smears were made on the fourth day after setting up the culture. When high , parasitemia with "stressed" parasites was observed, culture volume was increased by the addition of medium. At this stage, fresh RBCs were not added to the culture

32p -dCTP specific activity 400 or 800 Ci 1 mmole was from Amersham, UK or from New England Nuclear division of DuPont, USA. 125I was from Amersham.

Oligonucleotides used in this study were chemically synthesized by Sigma-Genosys (The Woodlands, TX, U.S.A.).

The antibiotics were used at the below concentrations (μg/ml) unless otherwise stated