いくつかの発生段階のマウス生殖系列細胞の培養が可能になっている。いずれの組織へも運命決定されていない原腸陥入前のエピブラストから始原生殖細胞が分化する初代培養系が確立され、その分化に胚体外外胚葉の働きによって誘導されるエピブラスト内の位置特異的な環境が重要であることが明らかになった。また移動期の始原生殖細胞はフィーダー細胞との共培養で増やすことができ、Steel factorを始めとしたいくつかの増殖因子の共同作用により増殖が促進されていることがわかった。始原生殖細胞から配偶子への分化は、生殖隆起の器官培養によりある程度再現できる。この場合メスでは減数分裂が進行し卵母細胞が分化するが、オスでは精原細胞以降への分化は起こらない。また生後の生殖細胞を培養することで、卵の成熟や精巣生殖細胞の減数分裂が進行することが示されている。こういった培養系により生殖細胞の発生機構の詳細がさらに解明され、また発生工学へ応用されることが期待される。

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Animal transgenesis by transferring genes in male germ cells has achieved little success despite the continuos interest in its practical applications. A dominant reason for drawing such strong attention is the simplicity and ease to handle when compared with manipulations of female germ cells. At the moment, it is fair to consider that the state of the art in male germ cellmediated transgenesis is far from useful because no reliable method is yet available. However, characterization of a variety of gene transfer methods in male germ cells may lead one to recognize that this methodology still has a large potential. Problems inherently involved in each gene transfer method have been briefly discussed.

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This study introduces that newly developed serum-free media (IVD101 and IVMD101) can improve the yield and quality of bovine blastocysts from in vitro matured and fertilized oocytes. The media were particularly designed in the absence (IVD101) or presence (IVMD101) of bovine cumulus/granulosa cell (BCGC) coculture. The proportion of embryos developing to the blastocyst stage and the mean cell number per blastocyst in IVD101 and IVMD101 were greater than in serum-supplemented medium (TCM199+5% calf serum). Furthermore, the post-thaw survival rates of cryopreserved blastocysts derived in IVD101 and IVMD101 were superior to that of blastocysts derived in serum-supplemented medium. The serum-derived blastocysts showed abundant lipid droplets in cytoplasm under transmission electron microscopic observation and contained high levels of unsaturated fatty acids such as palmitoleic and oleic acids. The evidence may partly explain the sensitivity of serum-derived embryos after freezing and thawing. It is known that the embryo transfer of in vitro-derived embryos often results in the production of bovine calves with abnormalities such as heavier than normal birth weight and a high incidence of dystocia. In this study, high pregnancy rate of blastocysts cultured in IVD101 after embryo transfer was obtained and the birth weights of live calves derived in IVD101 were normal range of birth weights produced from in vivo-derived embryos. These new serum-free media are beneficial, not only for the study of the mechanisms of early embryogenesis, but also for mass production of good quality embryos for embryo transfer, cloning and transgenesis.

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理研・細胞開発銀行では、潜在ウイルス検出法開発の一環として、ヒト細胞の染色体に溶原化して潜在している可能性のあるHIV-IのPCRによる検出を試みている。これまでに254株を検査した範囲では検出例はないものの、その方法をここに紹介しておく。

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