Experimental modifications of the circadian rythm of Plasmodium vinckei petteri following cryopreservation; probable resistance of the merozoïte to thawing.

Plasmodium vinckei petteri, in white mice, is a particularly useful strain for studies on the circadian rythm of Plasmodium. An experimental model was set up: it showed that the rythm of asexual schizogony in the blood varies with the time and the mode of inoculation (cryopreserved blood or syringe passage). When frozen blood is injected, the time of schizogony depends on the time of injection; on the contrary, when the passage is by syringe from mouse to mouse, the rythm of schizogony is the same in the donor and the receptor mouse, regardless of the time of injection. The only possible explanation is that all intracellular parasites are destroyed by the thawing of blood and the free merozoïte is the only resistant stage.