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

Gametocyte cultures

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.

Radioactive chemicals.

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

Oligonucleotides

In this method, tannase activity was estimated through spectrophotometric method by determining the concentration of the end product i.e., gallic acid, by estimating the absorbance at 260 nm. Reagents: •Tannic acid (1.0%): The solution was prepared by dissolving 1.0 g of tannic acid in 100 ml of citrate-phosphate buffer of the desired pH.•Bovine serum albumin (BSA): BSA (2.0%) was prepared in citrate phosphate buffer (pH 5.0)

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

Antibiotics