MORPHOLOGICAL-STUDY BY AN IN-VIVO CRYOTECHNIQUE OF THE SHAPE OF ERYTHROCYTES CIRCULATING IN LARGE BLOOD-VESSELS

Changes in the shape of erythrocytes circulating in large blood vessel s of mice were examined by our 'in vivo cryotechnique'. The abdominal aorta and inferior vena cava (IVC) were cut vertically with a precoole d knife and simultaneously an isopentane-propane mixture (-193 degrees C) was poured over them for freezing. They were freeze-substituted in acetone containing 2% osmium tetroxide. Some specimens were embedded in Quetol-812, and thick or ultrathin sections were examined by light or transmission electron microscopy. Serial ultrathin sections were us ed to reconstruct 3-dimensional images of native erythrocytes. Others were transferred into t-butyl alcohol and freeze-dried for scanning el ectron microscopy. The tissue surfaces were sufficiently frozen to pre vent large ice crystal formation, and erythrocyte shapes were also pre served. The shapes of circulating erythrocytes appeared to be varied i n the abdominal aorta but typical biconcave discoid shapes were rarely observed. Conversely, erythrocytes were approximately biconcave disco id in shape in the IVC. Our in vivo cryotechnique was useful for clari fying the in vivo morphology of erythrocytes circulating in large bloo d vessels.