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M. YAMAUCHI, T. NAKAHARA, Y. KANEDA and S. INUI

Summary.

The effects on the oestrous cycle of the cow of uterine distension caused by injecting a viscous gel-like substance into the uterus were investigated. Intra-uterine injection in the early luteal phase shortened the cycle length in thirteen of fourteen cases, giving a mean of 12·5 days (P <0·01). Treatments during the late luteal phase lengthened the cycle in five animals, giving a mean of 25·8 days (P <0·01). Cycles were of normal length in ten of twelve cases treated at post-oestrus, functional luteal phase or pro-oestrus. In twenty-three of twenty-five cycles in which the treatments were performed between early luteal phase and late luteal phase, the mean length from the treatment to ovulation was 9·3 ± 1·6 days, suggesting that intra-uterine treatment is effective in synchronizing the oestrous cycle and ovulation in cows except during pro-oestrus, oestrus and post-oestrus. Gel treatment produced a temporary endometritis associated with cloudy mucus and numerous leucocytes and epithelial cells in the vagina. The retention of gel in the uterus was longer in animals treated at late luteal phase than in those treated at early luteal phase. Of six animals which received the intra-uterine treatment during early luteal phase three became pregnant after artificial insemination.

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Y. Shiina, M. Kaneda, K. Matsuyama, K. Tanaka, M. Hiroi and K. Doi

Changes in intracellular calcium concentration ([Ca2+]i) in fertilized mouse oocytes were measured using the calcium-sensitive dye, fura-2. After fertilization, an initial long-lasting [Ca2+]i increase was followed by a periodic [Ca2+]i increase. The periodic increase in [Ca2+]i persisted for 1 to 3 h and all fertilized oocytes extruded the second polar body within 4 h. The mean interval of periodic [Ca2+]i increase was 470 ± 180 s (mean ± sd). The frequency of the periodic [Ca2+]i increase depended on the extracellular calcium concentration. Verapamil and nifedipine inhibited the periodic [Ca2+]i increase. Sixty-five per cent of tested cells extruded the second polar body within 90 min of exposure to 7% ethanol. In these activated oocytes, the long-lasting [Ca2+]i increase was observed. However, no cells showed a repetitive increase in [Ca2+]i Both release of calcium from intracellular stores and influx of extracellular calcium contribute to the increase in [Ca2+]i induced by ethanol. We conclude that the extrusion of the second polar body requires an increase in [Ca2+]i above a certain threshold level and the mobilization of calcium of both the intracellular and extracellular space in mouse oocytes.