The Linear Motor in the Human Neutrophil Migration
Résumé
The kinematics and dynamics of human neutrophils in a narrow glass tube (4.9 μm to 6.3 μm in diameter) have been investigated both experimentally and theoretically. Cells were activated by the tri-peptide (fMLP) to migrate through a tube with a mean speed of $0.15\pm 0.03~\mu$m/s (54 activated cells). When a hydrostatic pressure was applied across the cell, the mean speed of the cell leading front linearly decreases when the pressure is increased. At a pressure difference of 1530±140 Pa (9 activated cells), the cell was forced to stop. The cell migration has been approximated by a tractor-trailer model. The cellular motor (leading front), the tractor, produced a traction force by converting chemical energy into mechanical work. This motor has been characterized as a linear motor with two machine coefficients: (i) the maximum traction $T_0~(37.7$ nN) at V = 0, where V is the cellular speed (ii) the maximum cellular speed $V_{\rm max}~(0.15~\mu$m/s). A characteristic time of approximately 100 s was measured for the action cycle of the linear motor. A phenomenological description of the chemotactic machine has been presented.
Domaines
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