Ryuzo Yanagimachi - Other Major Work Before and After 1960

Other 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 cirripeds). 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 studies after 1960 were the analyses of the process and mechanisms of natural fertilization in mammals and development of assisted fertilization technologies. He was recognized on the citation for the 2010 Nobel Prize in medicine awarded to Robert G. Edwards. 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. It was announced in March 2004 that the Yanagimachi laboratory had helped to produce a live birth of a mammal other than a mouse from freeze-dried sperm. The rabbit kit was born at the Dr. Jerry Yang's laboratory

at University of Connecticut, but soon died because the mother did not care for it. The lab supplied the freeze-dried sperm.