The flowing behavior of individual erythrocytes in blood vessels is usually determined by their deformability, which is controlled mainly by the nature of their interior constituents and the flexibility of their surface membrane. Moreover, the physical behavior of erythrocytes passing through capillaries has been examined in vivo by light microscopy. However, little has been known about ultrastructural changes of such erythrocyte shapes flowing in blood vessels in vivo. Recently, a new technique was developed for freezing cells and tissues in vivo without stopping the blood supply, which was referred to as “in vivo cryotechnique”.This method has been also suitable for obtaining informations about dynamic morphological changes.

Seven female Balb/c mice were anesthetized peritoneally with sodium pentobarbital (100μg/g body weight), and their abdomen was opened through a pararectus incision. For artificial cardiac arrest, some mice were anesthetized with an excessive dose of the anesthetic (500μg/g body weight), their respiration and heart-beat were completely stopped, and the following procedures were done within one minute. A liver was put on a plastic plate without disturbance of blood circulation, and the “in vivo cryotechnique” was performed. Briefly, a cryoknife was pushed into the liver as fast as possible and the tissue was immediately poured with liquid isopentane-propane mixture (-193°C) (Fig.la,b).