Mechanical models of pseudopod formation.
The active locomotion of polymorphonuclear leukocytes into a glass pipette has been recently reported using formyl-methionyl-leucyl-phenylalanine (fMLP) as a chemoattractant. The frontal portion of the leukocyte appears clear and free of granules as observed in pseudopod formation. Three possible mechanisms for pseudopod formation are considered: (1) pressure-flow generated by actin-myosin contraction at the rear of the cell or at the base of the pseudopod; (2) osmotic pressure generated at the cell membrane, interior to the cell; and (3) actin polymerization of the cell membrane at the leading edge of the pseudopod. Experimental data on the movement of F-actin toward the rear of the cell, away from the front, favors polymerization of G-actin to F-actin at the leading edge. The active role of osmotic pressure and contraction at the base of the pseudopod are possible but not yet proven.
Skalak
R
R
Institute of Biomedical Engineering, University of California-San Diego, La Jolla 92093-0412.
Skierczynski
B A
BA
Wung
S L
SL
Chien
S
S
Usami
S
S
D000199:Actins / Q000378:metabolism / Q000502:physiology; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D002634:Chemotaxis, Leukocyte; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D009218:Myosins / Q000378:metabolism / Q000502:physiology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000502:physiology*
D000199:Actins; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009218:Myosins