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S. Reddy and W. B. Watkins

Summary. Immunoreaction to ovine placental lactogen was found in binucleate and uninucleate cells of the fetal trophoblast.

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W. B. Watkins and S. Reddy

Summary. Antibodies raised against purified ovine placental lactogen were used to demonstrate the cellular localization of the hormone in tissues of the ewe placenta and chorionic membranes by immunofluorescence and immunoperoxidase techniques. Although binucleate cells have been shown to appear as early as Day 16 of pregnancy, ovine placental lactogen was not detected in the trophoblast until Day 22, and in substantial numbers of cells until Day 80, of gestation. In the more mature placenta, lactogen-immunoreactive material was demonstrated in (a) binucleate cells of the fetal trophoblast, (b) uninucleate cells associated with the maternal epithelium syncytium and (c) binucleate cells of the chorionic membranes.

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W. B. Watkins and L. G. Moore

Summary. Systemic intravenous infusion of physiological concentrations of PGF-2α and its major metabolite, 13,14-dihydro-15-keto-PGF-2α (PGFM) into non-pregnant ewes possessing a corpus luteum induced the release of oxytocin—neurophysin. These results suggest that, during luteolysis, endogenous release of uterine PGF-2α would be able to stimulate the release of ovarian oxytocin and oxytocin—neurophysin from the ovary.

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J. C. Peek and W. B. Watkins

Summary. Bull seminal plasma administered to male rats at the time of castration inhibited the rise in the levels of FSH and LH otherwise seen in the serum 24 h later. That the gonadotrophin-inhibiting activity was also present in the seminal plasma from vasectomized bulls suggests that it was not of testicular origin. Although the substance with gonadotrophin-inhibiting activity was a protein, it may be chemically distinct from inhibin.

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G. W. Asher, A. J. Peterson, and W. B. Watkins

Summary. Concentrations of progesterone, oxytocin and PGFM (pulmonary metabolite of PGF-2α) were measured in plasma from peripheral blood samples collected from 5 fallow does every hour or 2 h for 12-h periods on Days 15–20 inclusive of the oestrous cycle (i.e. luteolysis). For 3 does that exhibited oestrus on Day 21, plasma progesterone concentrations fluctuated between 3 and 10 ng/ml on Days 15–18 inclusive. Thereafter, values declined progressively to attain minimum concentrations of <0·5 ng/ml on Day 20. Basal concentrations of plasma oxytocin and PGFM fluctuated between 5 and 20 pg/ml and 10 and 100 pg/ml respectively. Episodic pulses of plasma oxytocin (>300 pg/ml) occurred on Days 15 and 16, whereas pulses of plasma PGFM (>400 pg/ml) occurred on Days 19 and 20. There was little apparent correlation between episodic pulses of the two hormones. For 2 does that exhibited oestrus on Day 22, plasma progesterone concentrations declined to minimum values of 1·0–1·5 ng/ml by Day 20. One of these does showed very high levels of oxytocin secretion throughout the sampling period while the other showed an apparent paucity of oxytocin secretory periods. Two does hysterectomized on Day 13 of their second oestrous cycle failed to exhibit further oestrous cycles. Continual elevation of plasma progesterone concentrations (2–6 ng/ml) for an 8-month period indicated persistence of the corpus luteum after hysterectomy. It is concluded that luteolysis in fallow deer involves episodic secretion of both oxytocin and PGF-2α.

Keywords: fallow deer; Dama dama; reproduction; luteolysis; prostaglandin; oxytocin

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L. G. Moore, V. J. Choy, R. L. Elliot, and W. B. Watkins

Summary. Frequent blood samples were removed from a utero-ovarian vein, a jugular vein and a femoral artery of 5 ewes during luteolysis. Analysis of these samples for oxytocin-associated neurophysin revealed a significant venous—arterial difference across the ovary and uterus but not across the head. This occurred during the pulsatile surges as well as when levels were basal and confirms the corpus luteum as a major source of the pulsatile surges of oxytocin-associated neurophysin and oxytocin that occur during CL regression and also of the elevated luteal phase concentrations of both hormones. The pulsatile surges of oxytocin-associated neurophysin measured in the utero-ovarian vein were accompanied by the release of an approximately equimolar amount of oxytocin.

The concentration of PGF-2α in the utero-ovarian vein samples began to increase before the levels of oxytocin and oxytocin-associated neurophysin started to increase. This suggests that uterine PGF-2α initiates the release of ovarian oxytocin and oxytocin-associated neurophysin during luteolysis in the ewe.