Relationship between growth, stage development and pLDH optical density of synchronized cultures of P. berghei. Parasites were cultured under drug in vitro assay conditions without drug. Samples were collected and frozen at the different time points. Asterisks represent the mean and standard error of two different experiments. A picture of a mature schizont (usually containing 8–16 nuclei) collected at the end of the assay (hour 22) is also shown.