Papers Published

1. Needham, D. and Hochmuth, R.M., Rapid flow of passive neutrophils into a 4 μm pipet and measurement of cytoplasmic viscosity, Trans. ASME, J. Biomech. Eng. (USA), vol. 112 no. 3 (1990), pp. 269 - 76 .
   (last updated on 2007/04/10)

   Abstract:
   Neutrophils from five different individuals are isolated with a density separation technique. A total of 151 unactivated (passive) cells are rapidly aspirated at constant suction pressure and at room temperature into a pipet with a diameter of 4 μm. The suction pressures in excess of an initial yield threshold are 0.5, 1 and 2 kPa and are comparable to those encountered in the microcirculation. These pressures are well in excess of the small suction pressure of ~20 Pa that is required to form a static hemispherical bump on the cell. At a given aspiration pressure, the leading edge of an individual cell is `tracked' as it flows into the pipet. A theory based on the flow of a Newtonian liquid from either a hemisphere or a spherical segment into a cylinder is used to model the entry process. Both theory and experiment show that during most of the entry process the leading edge of the cell moves at a nearly constant velocity with a rapid acceleration at the end. For cells from five different individuals at the three different excess aspiration pressures, Newtonian theory gives a cytoplasmic viscosity of 135±54 Pa·s and overall entry times of 3.3 s (0.5 kPa), 1.6 s (1 kPa) and 0.82 s (2 kPa)

   Keywords:
   biological techniques and instruments;biorheology;blood;cellular transport and dynamics;viscosity measurement;