Rabbit eggs from the 1-cell to the expanding blastocyst stage were examined for a study of the distribution of supplementary sperm and polar bodies. A total of 252 eggs was recovered from 37 does from 18 to 160 hours following mating; 237 of them were fertilized. Supplementary sperm persisted in 221 of the fertilized eggs (93.2%). Mean number of supplementary sperm in all fertilized eggs was 6.5-15.8, and of those recovered at 160 hrs post coitum was 3.2. Though the proportion of eggs with agglutinated supplementary sperm was over 50% in the 1-cell to the 16-cell eggs, the proportion significantly decreased after the 32-cell stage. Three polar bodies were observed in 27 eggs (19%) out of 142 during the 2-cell to the morula stage. Although the polar body was always located peripherally in the perivitelline space in the 2-cell stage, some eggs with one or two polar bodies located centrally among the blastomeres were found in both the 4-cell and the 8-cell stages in the present study. The same phenomenon was observed during in vitro culture of the 2-or the 4-cell stage eggs, also. It was noted that one to five sperm appeared in some blastocoelic cavities.

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The present study was examine the viavility of separated mouse embryos at 2-cell stage, including production of monozygotic twins.
Two-cell embryos were collected from superovulated donor of three types: CF i1 females which were mated with CF # males (#1 embryo), CF #1 females which were mated with C57BL/6 males (F1 embryo) and F1 (CF#1 -C57BL/6) females which were mated with C57BL/6 males (BC embryo). Zona pellucida were removed in Hanks solution containing 0.2-0.5 % pronase. After removal of zona pellucida, the embryos were separated into two halves by pipetting in Ca++ and Mg++ free Hanks solution containing 0.02 EDTA. Separated blastomers were cultured in drops of cultur medium (M16) covered with paraffin oil at 37 °C in an atmosphere of 5% CO2, 95% air for 72 hours. Then a monozygotic pair of half embryos developed into blastocysts were transferred to CF #1 recipient on Day 4 or 5 of pseudpregnancy. The results were as follow: 1) The proportion of single blastomeres developd into blastocysts, for the #1 embryo, Fl embryo and BC embryo were 72.8, 74.2 and 78.5, and the proportion of a monozygotic pair of embryos developed into blastocysts were 61.1, 61.5 and 70.1%, respectively. 2) The cell numbers of half embryos after 72 hours culture, for the #1 embryo, Fl embryo and BC embryo were 51.6± 2.0, 59.0±3.7 and 63.8±2.1, while the cell numbers of normal embryos were 108. 6±5.5, 128.8±3.7 and 136.6 ±4.6, respectively. 3) By transfer of a monozygotic pair of half embryos into recipients, number of pups were obtained 3 (16.7%), including one pair of twins for the Fl embryo and 1 (5.6 %) for the BC embryo. By transfer of a pair of embryo plus eight of normal embryos into recipient, number of pups were obtaind 5 (25.5 %), including 2 pair of twins for the Fl embryo and 1 (3.6%) for the BC embryo. Three sets of monozygot twins were produced.

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精巣上体尾部精子を用いて人工授精を行い、その後のスナネズミ卵管内における精子の分布と先体反応について調べた。成熟雌スナネズミにPMSGとhCGを用いて過排卵処理を行い、hCG注射後2時間目に麻酔下で開腹し、子宮内に精子懸濁液を注入して人工授精を行った。精子注入後30分に運動精子の多くは卵管狭部下部 (lower isthmus) に認められた。そして、1時間後には大多数のものが上部狭部に移動していた。しかし、卵管膨大部に初めて精子が認めれたのは授精後7時間目であった、授精3時間後にlower isthmusから回収した精子においては先体反応は観察されず、11時間後の卵管膨大部の精子では、ほとんどのものが先体反応を開始していたか誘起していた。この時期には、排卵した卵子ではずでに受精が観察された。

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