Biomedical Reviews 2004; 15: 1-19. ”IN VIVO CRYOTECHNIQUE · FOR PARADIGM SHIFT TO ”LIVING MORPHOLOGY · OF ANIMAL ORGANS

The morphological study has been one of the major approaches in medical and biological fields. For the last century, the con-ventional chemical fixation and alcohol dehydration were commonly used as an easy preparation method, but it was frequently pointed out that they usually yield many structural artifacts during their preparation processes. Although both conventional quick-freezing and high-pressure freezing methods, by which animal tissues are resected and frozen for physical fixation, can reduce such structural artifacts, the tissues have to be removed from living animal organs for the freezing. Therefore, such specimens are inevitably exposed to noxious stresses of anoxia and ischemia, exhibiting only dead morphological states of animal tissues without blood circulation. To the contrary, our “in vivo cryotechnique”, by which all cells and tissues in animal bodies are cryofixed in vivo, can prevent such artifacts of resected specimens. By means of the cryotechnique, it is now possible to reveal the in vivo morphology of cells and tissues in living animal organs. Actually, it has been already applied to several animal organs, such as kidney, liver, intestine, cerebellum, eye ball, blood vessel, and joint cartilage, and brought new morphological findings, reflecting their physiological significance, which had been difficult to demonstrate by the conventional preparation methods. Moreover, its application to immunohistochemistry has also revealed more precise immunolocalizations of dynamically changing molecules in living animal organs, easily translocated by ischemic stresses and anoxia caused during the tissue resection. The “in vivo cryotechnique ” allows us to perform novel morphological investigations of “living ” morphological states, and develops ne