Tsuyoshi Uehara
The Modern Laboratory · People
The Modern Laboratory
Tsuyoshi Uehara
Working at a microscope in Hawaii that showed everything upside down, he placed the first sperm inside a mammalian egg.
Tsuyoshi Uehara came from Okinawa, in southern Japan, and worked in Ryuzo Yanagimachi’s laboratory at the University of Hawaii in the 1970s. Little else about his life has been published. But his name stands first on one of the founding papers of ICSI.
The 1976 experiment. In November 1976, Uehara and Yanagimachi reported in Biology of Reproduction that they had injected hamster sperm directly into hamster eggs. Inside the egg the sperm heads swelled and became male pronuclei, the first visible step of fertilisation. They showed that human sperm, including frozen and thawed sperm and freeze-dried sperm, could do the same inside hamster eggs. A 2024 history of ICSI notes that the paper was also the first to use a thick solution, PVP, to stop sperm sticking inside the injection pipette.
Working upside down. Colleagues recall that he used an upright microscope rather than the inverted kind used in ICSI today. He had to turn every image round in his head, guiding his needles through a view that was upside down and reversed.
Two more papers. In 1977 the pair published again. One study followed what happened to sperm taken from different parts of the male tract once they were injected. Another showed that simply pricking a hamster egg with a fine glass needle could wake it into activity. Uehara has since died. Yanagimachi’s colleagues remember him as the man who first achieved fertilisation by injection in a mammal.
Also see: Ryuzo Yanagimachi
About the sources
- Thompson JG, McLennan HJ, Heinrich SL, Inge MP, Gardner DK, Harvey AJ. A brief history of technical developments in intracytoplasmic sperm injection (ICSI). Reproduction, Fertility and Development 2024;36(10):RD24047 (published 20 June 2024): human sperm validation, frozen-thawed and freeze-dried sperm, first use of PVP.
- Akutsu H, Ogura A. Commentary on the Achievements of the Laureate: Ryuzo Yanagimachi. The 2023 Kyoto Prize Commemorative Lecture, Inamori Foundation, 30 October 2024 (kyotoprize.org PDF): “It was done by Dr. Tsuyoshi Uehara from Okinawa”; the upright microscope.
- Kyoto Prize interview with Ryuzo Yanagimachi (Japanese, kyotoprize.org PDF, October 2023): refers to the late Dr Uehara (故・上原剛博士) as the first to achieve mammalian microinsemination in 1976.
- Morishita N, Ochi M, Horiuchi T. History and prospects of intracytoplasmic sperm injection (ICSI) and the development of golden hamster ICSI embryos. Reproductive Medicine and Biology 2021;20:410–418 (Table 1: Uehara and Yanagimachi 1976, the first report of fertilisation by ICSI in mammals).
- Uehara T, Yanagimachi R. Activation of hamster eggs by pricking. Journal of Experimental Zoology 1977;199(2):269–274. PubMed 557528.
- Uehara T, Yanagimachi R. Behavior of nuclei of testicular, caput and cauda epididymal spermatozoa injected into hamster eggs. Biology of Reproduction 1977;16(3):315–321. PubMed 843559.
- Uehara T, Yanagimachi R. Microsurgical injection of spermatozoa into hamster eggs with subsequent transformation of sperm nuclei into male pronuclei. Biology of Reproduction 1976;15(4):467–470 (1 November 1976). DOI 10.1095/biolreprod15.4.467. PubMed 974199.
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Compiled with AI-assisted research and checked against the original sources. Not yet peer-reviewed. Corrections are warmly welcomed.
