title: Rheological properties of rosettes formed by red blood cells parasitized by Plasmodium falciparum.
abstract: A proportion of red blood cells parasitized by Plasmodium falciparum form rosettes with non-parasitized red cells. Although these rosettes are thought to impair microcirculatory flow, their rheological characteristics have not been fully described. Using dual-micropipette manipulation to pull apart individual rosettes, we found that the forces binding rosettes together were strong (average force for removal of a cell was 4.4 x 10(-10) N, approximately 5 times that required to detach a parasitized cell adhered to cultured endothelium). If disrupted rosettes were re-formed, cells rosetted immediately on contact, but the strength of attachment increased over minutes, and did not apparently reach its maximal level for hours. All non-parasitized cells tested could adhere to rosette-forming parasitized cells. Rosettes could withstand arterial flow stresses (1.4-1.6 Pa) for minutes without disintegration. To test the effects of rosetting on flow resistance, the time required for entry into a 4.3 microns pipette was measured. Entry times depended strongly on the number of cells in the rosette, and averaged 35 times longer than for non-parasitized cells. Our studies show that the cell-cell attachments within rosettes are strong, and suggest that rosettes might survive both the arterial circulation and passage through microvessels and could contribute to the ischaemic complications of falciparum malaria.
authors: Department of Haematology, Medical School, University of Birmingham, U.K.
authors: G B
authors: GB
authors: Nash
authors: B M
authors: BM
authors: Cooke
authors: J
authors: J
authors: Carlson
authors: M
authors: M
authors: Wahlgren
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D004912:Erythrocytes / Q000469:parasitology*; D006801:Humans; D007700:Kinetics; D016778:Malaria, Falciparum / Q000097:blood; D010963:Plasmodium falciparum; D012212:Rheology; D012397:Rosette Formation