Streaming Transparency of Erythrocyte Suspension

Abstract

When one makes erythrocyte counts in blood, one may observe irregular darkbright stripes like a gossamer-“Schlieren-effect”-in a mixer. This peculiar phenomenon led us to make experiments to ascertain whether light transparency will change or not according to the state of the erythrocyte suspensions being resting or flowing when light is projected on them. We have found that the transmitted light is more intensive in the flowing state than in the resting state, and one of us (Kuroda) has called this phenomenon“streaming transparency.”The apparatus for measuring the streaming transparency consists of a Beckman photoelectric spectrophotometer of direct reading type and a chamber with a rotating vessel attached to it, as shown in Fig. 1. The rotating vessel is made of glass and is cylindrical, 8cm in diameter and 1cm in height, as shown in Fig. 2. In the center of the vessel is a glass rod with a small propeller, which is connected with an electric motor with a belt. The erythrocyte suspension is placed in the rotating vessel, and the attenuance (optical density) of the suspension is read at rest and in flow.The term“degree of streaming transparency”, which is introduced to express the streaming transparency quantitatively, is given by the difference between the attenuance of the resting erythrocyte suspension (A) and that of the flowing erythrocyte suspension (A').Degree of streaming transparency=A-A'.The degree of the streaming transparency of the erythrocyte suspension approaches zero when this erythrocyte is completely spherical, while the degree of the streaming transparency becomes larger when the shape of the erythrocyte deviates from the sphere (Tab. 1).As shown in Fig. 5, the degree of the streaming transparency is remarkably increased with the increasing concentration of erythrocytes. However, at higher concentrations of erythrocytes, the degree of the streaming transparency decreases and becomes negative. This phenomenon, which shows that the light intensity transmitted through the erythrocyte suspensions is smaller in flow than at rest, is termed the“negative streaming transparency.”, As shown in Fig. 4, at long wave-lengths the degree of the streaming transparency is positive and high and it drops with decreasing wave-length. At 430mμ it is equal to zero, it is negative in the region of Soret band and at shorter wave-lengths it becomes positive again. Fig. 3 shows the light absorption curve obtained with bovine erythrocyte suspension, in which case the absorption band of hemoglobin appears more remarkable in flow than at rest.In order to explain the cause of the streaming transparency of the erythrocyte suspension, the orientation of erythrocytes in the suspension is first to be considered. Essentially, mammalian erythrocytes are biconcave disc-shaped, and they are distributed in random directions at rests, but when the suspension is allowed to flow in a certain direction, the erythrocytes are arranged in such a direction of to offer the least resistance against flow (Fig.6).The cause of the streaming transparency may be attributed to the orientation of erythrocytes in flow in such a direction as to take the least resistance against flow, and this streaming transparency is regarded to be in a close relation with the shape of the suspended erythrocytes, the degree of the streaming transparency being zero in the case of spherical erythrocytes. The negative streaming transparency observed is also explained from the light absorption effect and the light scattering effect due to the special orientation of erythrocytes in flow.The phenomenon of dark and bright stripes of the flowing erythrocyte suspension is considered to be similar to the Schlieren-effect of colloidal solutions. However, streaming transparency is observed, not only in the erythrocyte suspension, but also in suspensions of non-spherical cells