Evidence of trapped red cells in the brain of rhesus monkey infected with Plasmodium knowlesi.

59Fe-labelled normal red cells and 51Cr-labelled P. knowlesi infected red cells were used as tracers for a study on the trapped red cells in the brain of rhesus monkeys infected with P. knowlesi. After instantaneous injection into a common carotid artery, blood was sampled from both of the internal jugular veins at various intervals. Results in 6 experiments on 3 infected monkeys showed that about 17% of infected red cells given was trapped in the capillaries of the brain of the infected monkeys. The remainder of the infected red cells travelled on the same flow rate as the normal red cells. As the volume for the flow of the former was less than that of the latter, the mean transit time of the infected red cells (-ty) was therefore shorter than that of the normal red cells (-th). The mean difference in volume was estimated to be 3.4% in the present study. These findings indicated that some of the P. knowlesi infected red cells were trapped in capillaries of the brains of monkeys infected with P. knowlesi.