Intercellular Forces and Separation Energy of Red Cells Sludged by Contrast Medium. ∗

Knisely and his coworkers showed that sludging of red blood cells occurs in over 100 pathological conditions, or, alternatively, in the presence of excess of a contrast medium such as sodium diatrizoate(1). Bernstein and his coworkers enumerated possible intercellular forces of repulsion and attraction which could be altered with the occurrence of such red cell sludging (2), while Bloch and his coworkers reported that this sludging involves the formation of a sticky coating around the sludged red cells(3). This coating is observable with the electron microscope but usually not with the light microscope. The data given here were obtained by applying Berwick and Coman's method(4) to measurement of the adhesion forces and energy of sludged red cells, and these data are combined with microelectrophoresis findings to show that viscosity and/or surface energy of the sludge are more important than ionic forces.

Methods and results. Both heparinized and citrated dog blood was tested in both micromanipulation and in microelectrophoresis studies. A standard 75% diatrizoate solution was added to produce cell sludges, and both clumped and unclumped cells were studied.

For micromanipulation an Aloe Co. pneumatic micromanipulator (of De Fonbrune type) and a semimicromanipulator, made by W. R. Price and Co., Ltd., were used in conjunction with a binocular microscope. Eyepieces with grids in one and 2 orthogonal directions, respectively, were inserted in the microscope, and its oil immersion lens was removed for convenience. The microneedles were prepared as described by Jones(5), and were calibrated with microweights at several positions on each needle. The microweights were made of high-grade steel wool and human hair (which was sometimes split). The microweights were weighed to less than 0.002 mg on a torque balance, and the calibration was reconfirmed after several days of experimentation.