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Suspension. Overall view. Intermittent Contact Mode.
Cell sedimentation from an erythrocyte suspension is a more equilibrium process than preparation of a blood smear. We use this process when we have to obtain a size and form distribution of blood cells without mechanical deformation. Model experiments are another advantage of cell sedimentation from a suspension. It is possible to study physical, chemical and other actions on the cell membrane, for example, that of viral particles or drugs (see Virus-cell Interaction).
Cell sedimentation from a suspension is a more complex process than blood smear preparation. There is a risk of introducing changes of the shape and the structure of the cell membrane. This occurs when pH or ionic strength of the buffer change (see Artifacts of Preparation). Suspension of blood cells is prepared by adding fresh blood to a buffer containing anticoagulant (EDTA, sodium citrate, heparin) in order to avoid blood coagulation.
Inevitable disbalance between blood proteins and buffer salts results in salt crystallization that occurs in drying and deformation of blood cells in the scan picture. Removal of salts with distilled water causes detachment of adsorbed cells from the support. That’s why, when working with suspensions, cells should be either immobilized on the support with special agents (such as polylisine) or released from the support into distilled water. Cells should be chemically fixed before being released into distilled water to avoid their damage and deformation caused by low ionic force. We used the paraformaldehyde fixation method followed by release into distilled water. Erythrocytes can be also deformed in a suspension when contact of two or more cells occurs. Therefore, single objects should be chosen for deformation studies.
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Fig. 1 (a, b)
a) – erythrocytes of rhesus monkey that deposited from a suspension. IC mode. The shapes of soft red blood cells of mammals are deformed by neighboring cells.
b) - chicken erythrocytes. IC mode. Nucleated avian erythrocytes are more rigid than mammalian erythrocytes and keep the shape during mutual contact.
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contacts
