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Ryuzo Yanagimachi (柳町 隆造 Yanagimachi Ryūzō?, born August 27, 1928) is a Japan-born US based scientist. He has made contributions toward understanding the process and mechanism of mammalian fertilization. He is a pioneer of assisted fertilization technologies such as in vitro fertilization and direct sperm injection into egg (commonly called intracytoplasmic sperm injection or ICSI) which are widely used today in human infertility clinics throughout the world. He was also a pioneer in the cloning field. In 1997 his laboratory at the University of Hawaiʻi at Mānoa successfully cloned mice using the Honolulu technique. The first one was a female named Cumulina from the cells that surround the developing ovarian follicle in mice.
Early and later years
Yanagimachi was born in Japan. He received a BS in zoology in 1952 and a DSc in animal embryology in 1960 from Hokkaido University. He then taught high school for two years because he could not find a research position.
Yanagimachi applied for a post-doctoral position with Dr. M. C. Chang of the Worcester Foundation for Experimental Biology in Shrewsbury, Massachusetts. He got this position and there discovered how to fertilize hamster eggs "in vitro." This work led to in vitro fertilization of eggs of human and other mammalian species.
In 1964 he returned to Hokkaido University as a temporary lecturer with the possibility of later being appointed to an assistant professorship. However, another person eventually got the position.
In 1966 Yanagimachi ended up at the University of Hawaii as an assistant professor and has become a full professor of anatomy, biochemistry, physiology and reproductive biology at the John A. Burns School of Medicine. After working for 38 years at the university of Hawaii, he retired the end of 2004 to become a professor emeritus, but keeps working with junior fellows. He is married to Hiroko, a former child psychologist. She could not find work in her field when they came to the U.S. due to a language barrier, so she went to work with researchers in his lab as an electron microscopist.
In July 1998 the Yanagimachi laboratory published work in Nature on cloning mice from adult cells. Yanagimachi named the new cloning technique they had created to do this work the "Honolulu technique". The first mouse born was named Cumulina, after the cumulus cells whose nuclei were used to clone her. At the time of the publication of this work over fifty mice spanning three generations had been produced through this technique. 
This work was done by an international team of scientists dubbed "Team Yanagimachi" or "Team Yana" for short. This team included co-authors Teruhiko "Teru" Wakayama (also a native of Japan), Anthony "Tony" Perry (United Kingdom), Maurizio Zuccotti (Italy), and K. R. Johnson (United States).
The Yanagimachi laboratory moved from the warehouse which had housed it for over thirty years into the newly created Institute for Biogenesis Research in the biomedical tower of the John A. Burns School of Medicine. Money and renown from the opportunities opened up by the Nature article made the institute possible.
The Yanagimachi laboratory and his former associates continue to make advances in cloning. The first male animal cloned from adult cells was announced in 1999. In 2004 the laboratory participated in the cloning of an infertile male mouse. This advance may be used to produce many infertile animals for use in research in human infertility.
Major work before and after 1960
Before beginning his study of mammalian fertilization in 1960, Yanagimachi studied fish (herring) fertilization and the sexual organization of rhizocephalans (parasitic barnacles). In fish, he discovered calcium-dependent, chemotactic movement of spermatozoa into the micropyle through which the fertilizing spermatoon enters the egg. In rhizocephala, he found that adults are not hermaphroditic as generally thought, but bisexual. So-called "testis" in an adult animal is a receptacle of cells from larval males. This discovery revolutionized biological studies of rhizocephalans and related animals.
His major work since 1960 was the analysis of the process and mechanism of natural fertilization in mammals and the development of assisted fertilization technologies. While he was at the Worcester Foundation, he witnessed and recorded the entire process of sperm penetration through the zona pellucida and fusion with the egg proper in living (hamster) egg, which was for the first in mammals. Yanagimachi's comprehehsive review of Mammalian Fertilization published in 1994 (In: Physiology of Reproduction, Knobil & Neill eds, Raven Press) is classic. His group pioneered intracytoplasmic sperm injection which overcomes many forms of male infertility. They were the first to produce normal (mouse) offspring using pre-spermatozoal cells such as round spermatids and spermatocytes as well as freeze-dried spermatozoa.
He retired in 2005, but continues working on mammalian fertilization and reproduction and has resumed working on fish (and insect) fertilization.
Awards and honors
- Zoological Society Prize, Japan, 1977
- Research Award, Society for Study of Reproduction, USA, 1982
- University of Hawaii Regents' Medal for Excellence in Research, USA, 1988
- Recognition Award, Serono Symposia, USA, 1989
- Marshall Medal, Society for the Study of Fertility, UK,1994
- International Prize for Biology, Japan, 1996
- Honorable Degree of Philosophy from the University of Rome, Italy, 1997
- Distinguished Andrologist Award, American Society of Andrology, USA, 1998
- Induction to the Polish Academy of Scicnes, Poland, 1998
- Carl G. Hartman Award, Society for the Study of Reproduction, USA, 1999
- Honorable Degree of Philosophy, University of Pavia, Italy, 1999
- Honorary Member, European Society of Human Reproduction and Embryology, 1999
- Pioneer Award, International Embryo Transfer Society, 2000
- Induction to the National Academy of Sciences, USA, 2001
- Honrable Degree of Philosophy, Hokkaido University, Japan, 2002
- Induction to Hall of Honor, National Institute of Child Health and Human Development, USA, 2003
- Donald Henry Barron Lecture, University of Florida, 2003
- Pioneer Award in Reproduction Research, 2012