The long-term objective of this study is to contribute to the better understanding of the mechanisms involved in mammalian fertilization. In this study, the major emphasis will be placed on the biology and physiology of mammalian sperm nucleus. Syrian hamsters, mice and rabbits will be used as model animals. Specific questions we intend to answer are: 1) Is the nucleus the only sperm component contributing to the zygote development? 2) If the zygote requires more than the sperm nucleus for its development, what is/are the sperm's component(s) contributing to it? 3) Will it be possible to distinguish genetically abnormal sperm nuclei from normal ones prior to incorporation (injection) into oocytes? 4) Will it be possible to store isolated sperm nuclei without destroying their genetic integrity? 5) When does the sperm nucleus become genetically functional? Seeking answers to such fundamental and teleological questions is not only of academic curiosity, but also may contribute to the advancement of medical and agricultural technology.

National Institute of Health (NIH)
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
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Reproductive Biology Study Section (REB)
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University of Hawaii
Anatomy/Cell Biology
Schools of Medicine
United States
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Yanagimachi, Ryuzo (2005) Intracytoplasmic injection of spermatozoa and spermatogenic cells: its biology and applications in humans and animals. Reprod Biomed Online 10:247-88
Yanagimachi, Ryuzo; Wakayama, Teruhiko; Kishikawa, Hidefumi et al. (2004) Production of fertile offspring from genetically infertile male mice. Proc Natl Acad Sci U S A 101:1691-5
Kishikawa, H; Tateno, H; Yanagimachi, R (1999) Fertility of mouse spermatozoa retrieved from cadavers and maintained at 4 degrees C. J Reprod Fertil 116:217-22
Perry, A C; Wakayama, T; Yanagimachi, R (1999) A novel trans-complementation assay suggests full mammalian oocyte activation is coordinately initiated by multiple, submembrane sperm components. Biol Reprod 60:747-55
Cummins, J M; Kishikawa, H; Mehmet, D et al. (1999) Fate of genetically marked mitochondrial DNA from spermatocytes microinjected into mouse zygotes. Zygote 7:151-6
Maleszewski, M; Kuretake, S; Evenson, D et al. (1998) Behavior of transgenic mouse spermatozoa with galline protamine. Biol Reprod 58:8-14
Wakayama, T; Yanagimachi, R (1998) The first polar body can be used for the production of normal offspring in mice. Biol Reprod 59:100-4
Wakayama, T; Yanagimachi, R (1998) Development of normal mice from oocytes injected with freeze-dried spermatozoa. Nat Biotechnol 16:639-41
Cummins, J M; Wakayama, T; Yanagimachi, R (1998) Fate of microinjected spermatid mitochondria in the mouse oocyte and embryo. Zygote 6:213-22
Dozortsev, D; Wakaiama, T; Ermilov, A et al. (1998) Intracytoplasmic sperm injection in the rat. Zygote 6:143-7

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