30日齢、60～90日齢および180～210日齢のマウスから採取した排卵直後の卵母細胞について、Δ5-3β-ヒドロキシステロイド脱水素酵素 (Δ5-3β-HSD, 基質にdehydroepiandrosteroneを使用) 活性を組織化学的に比較した。その結果.どの日齢においても、この酵素活性は観察したすべての卵母細胞に認められたが、強い活性を示す卵母細胞の割合は180～210日齢の動物のもので他の日齢の動物のものより有意に低かった。また、180～210日齢のマウスの卵母細胞については、hCGを含む液に浸漬後、Δ5-3β-HSD活性を観察したが、強い活性を示す卵母細胞の割合に増加はみられず、hCGを含まない液に浸漬した卵母細胞のものと差がなかった。したがって、高齢動物の卵母細胞のステロイド合成能は低下しており、この原因として卵母細炮のゴナドトロピンに対する感受性の低下が考えられた。

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30日齢、60～90日齢および180～210日齢のマウスから採取した排卵直後の卵母細胞について、スダン好性脂質 (脂質一般)、類脂質および中性脂肪の検出を組織化学的に行い、これらの量が動物の加齢に伴って変化するか否かを調べた。
各日齢のマウスにおいて、ほとんどすべての卵母細胞は一般脂質と類脂質を少量ないし多量含んでおり、これらの脂質の含量は各日齢の動物の間で差がなかった。一方、中性脂肪は30日齢のマウスの卵母細胞には検出されなかったが、60～90日齢および180～210日齢の動物の卵母細胞の1.0%と6.3%に、それぞれ少量観察され、180～210日齢の動物における割合は60～90日齢の動物のものに比べて有意に高かった.これらのことから、動物の加齢に伴って、卵母細胞のスダン好性脂質と類脂質の含量には変化がみられないが、卵母細胞に中性脂肪が出現し、これを含有する卵母細胞の割合は増加することがうかがわれた。

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The study was conducted to elucidate the interrelationship between the blastocyst and endometrium at early stage of implantation. Japanese White does were autopsied at 7 and 8 days post coitum. The samples were prepared with the method described by us eleswhere, and observed by use of Scanning electron microscopy. The results were as follows. 1. The inner part of the trophoblast was smoothly at 7 days post coitum, and the cellular bolders of the trophoblast was covered yet an abundance of microvilli. The endometrium richly provided round shaped cells with short microvilli. A small number of ciliated cells could be found at the antimesometrial surface of the uterus. 2. The blastocyst at 8 days post coitum contacted loosely with the endometrium antimesometrial portion. The surface of endometrium at this stage contained the characteristic microvilli which formed like a flower structure by the bundle of microvilli.

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Rat 2-cell embryos were preserved successfully in liquid nitrogen by vitrification. Embryos needed to be equilibrated in 90%VS1 in a stepwise manner, while protective agents could be removed directly from the vitrified embryos. The vitrified embryos developed to live youngs at high rates (59-67%) by transferring to pseudopregnant recipients.

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The development of mouse embryos formed by the aggregation of two 8-cell embryos was analysed in comparison with control single (normal) embryos. The analysis revealedthat:(1) No significant diffrence was observed in the weights of fetuse and placenta from postimplantation embryo at 18 days post coitum of recipient mice between aggregated and control embryos.(2) Postimplantation aggregated embryo was at about the same developmental stage as control embryo of the same chronological age, both before and after size regulation.(3) Size regulation of the aggregated embryos was brought about by 6 days and 5 hours post coitum of recipient mice.

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The copulation rate and the average number of normal embryos were examined after superovulatory treatment with 5iu PMSG and 5iu hCG given 48h apart in the adult femeals of 23 inbred and 3 mutant strains. Singnificant strain differences were observed in the copulation rate (15.8-84.2%) as well as in the rate of normal embryos among those recoverd (10.1-79.7%). Average number of normal embryos at the 8-16 cell stage, recoverd on Day 2 of pregnancy. varied from 3.5 to 31.3 among the strains.

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