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A. van TIENHOVEN and R. T. DUBY

According to a number of reports, the administration of o,p′-DDT produces effects which mimic those of oestrogens in causing increases in chicken, Gallus domesticus, and quail, Coturnix coturnix japonica, oviduct weight and the uterine weight of immature and ovariectomized rats (Bitman, Cecil, Harris & Fries, 1968; Levin, Welch & Conney, 1968; Duby, Travis & Terrill, 1971). The glycogen content of these organs is also increased as the result of o,p′-DDT injections (Bitman et al., 1968), while the age of vaginal opening in rats is decreased (Wrenn, Wood, Fries & Bitman, 1970). These results might be explained on the basis of an interference of o,p′-DDT with endogenous oestrogen metabolism (Kupfer, 1967, 1969). However, in ovariectomized rats, o,p′-DDT increased the uterine weight and

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D. L. BLACK and R. T. DUBY

Summary.

Oxytocin (100 U.S.P. Units) injected into heifers on Days 1 to 6 or Days 3 to 6 post-oestrum caused precocious oestrus. When 8 mg epinephrine hydrochloride or 50 mg atropine sulphate were superimposed on the oxytocin treatment, there was very little shortening of the oestrous cycle. Epinephrine or atropine administered on Days 3 to 6 post-oestrum did not materially alter the length of the oestrous cycle nor did administration of atropine during the latter part of the oestrous cycle.

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D. L. BLACK, R. T. DUBY and J. RIESEN

Summary.

An apparatus has been constructed for the collection of oviduct fluids from sheep. The use of this equipment makes possible the collection of relatively large amounts of oviduct fluid for biochemical analysis.

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J. D. Godkin, C. Coté and R. T. Duby

Summary. Preimplantation embryos, recovered from sheep on Days 13–15 of pregnancy, were incubated with luteal tissue from cyclic ewes. Extracts of ovine embryos were incubated with luteal tissue from cyclic Holstein cows. Embryos and embryo extracts significantly increased progesterone production by ovine and bovine luteal tissue in vitro. The embryos themselves did not produce measurable amounts of progesterone. We suggest that the ovine preimplantation embryo produces a substance with luteotrophic properties which contributes to the maintenance of early pregnancy.

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R. M. Bigsby, J. C. N. Lungu, R. T. Duby and D. L. Black

Summary. The ability of anti-oestradiol immunoglobulin to withhold oestradiol-17β from its target tissue was examined. The total oestradiol-17β binding capacity present in in-vitro incubations or injected into mice intravenously was related to the amount of [3H]oestradiol present in the media or intravenously injected into the animals respectively. When the ratio of binding capacity to [3H]oestradiol was above 74:1, [3H]oestradiol was successfully withheld from uterine tissue in vitro and in vivo.

Injecting anti-oestradiol immunoglobulin into mice before administration of a tubelocking dose of oestradiol-17β ensured normal passage of ova through the oviduct. Daily administration of anti-oestradiol immunoglobulin to PMSG–hCG stimulated mice (starting 72 h before hCG injection) induced retention of ova for at least 2 days beyond the time when all ova had left the oviducts of control animals. The binding capacity: oestradiol-17β concentration ratios of sera from these animals were >250:1 throughout the experimental period. Non-specific immunoglobulin had no such effects, indicating the specificity of the anti-oestradiol immunoglobulin response.

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D. L. BLACK, LEO V. CROWLEY, R. T. DUBY and C. H. SPILMAN

In recent years, interest in the role played by oviduct fluids in reproduction has increased. With the development of a method for the continuous collection of oviduct fluid from the rabbit (Clewe & Mastroianni, 1960) it became possible to measure the rate of oviduct secretion in the unanaesthetized animal. By slightly modifying their collection apparatus, oviduct fluid was collected from the ewe by Black, Duby & Reisen (1963) and more recently by Perkins, Goode, Wilder & Henson (1965), Restall & Wales (1966) and Wales & Restall (1966).

The oviduct provides a liquid medium for gametes during transport and fertilization. Whether this fluid does more than provide a protective environment is unknown. Spermatozoan respiration is stimulated by oviduct fluid from the cow (Olds & VanDemark, 1957),

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F. J. Auletta, Deborah K. Paradis, Mary Wesley and R. T. Duby

Summary. Oxytocin (10 mi.u./μ1/h) or vehicle (0·5% chlorobutanol in saline, 1 μ1/h) was chronically infused directly into the corpus luteum of normally cyclic rhesus monkeys, by means of an Alzet pump—ovarian cannula system. Infusion of oxytocin (N = 6) or vehicle (N = 5) began 6 days after the preovulatory oestradiol surge, and daily peripheral blood samples were taken. Oxytocin caused a significant (P < 0·05) decrease in progesterone, beginning 1 day after treatment, and oestradiol after 4 days; progesterone and oestradiol remained significantly depressed until menstruation. However, peripheral LH concentrations remained unchanged. The duration of the luteal phase, menstrual cycle and the onset of menses from the initiation of oxytocin infusion were significantly (P < 0·01) shorter when compared to those of vehicle-treated controls. These results show that oxytocin can induce functional luteolysis in the primate and supports the hypothesis that oxytocin of luteal origin may play a role in spontaneous luteolysis.

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D. L. BLACK, A. KUMAR, L. V. CROWLEY, R. T. DUBY and C. H. SPILMAN

It has never been established that fluid collected from the oviducts of rabbits (Clewe & Mastroianni, 1960), ewes (Black, Duby & Riesen, 1963; Restall, 1966; Perkins, Goode, Wilder & Hensen, 1965; Iritani, Gomes & VanDemark, 1969), cows (Carlson, Black & Howe, unpublished data) and monkeys (Mastroianni, Shah & Abdul-Karim, 1961) is comparable with the fluid normally present in the oviduct. The results of Holmdahl & Mastroianni (1965) suggest that it may not be comparable since they found that fluid held at low temperatures during collection from rabbits contained more glucose and less calcium than fluid collected at room temperature. A similar experiment was therefore carried out in sheep. Fourteen ewes of the Dorset and Shropshire breeds were used in the experiment. They were placed in individual stalls, given 1 lb of grain, hay or silage, and unrestricted water. Oestrus was detected with the aid of a ram. Animals to be cannulated for the collection of oviduct fluid were anaesthetized with Equithesin (Jen-Sal Labs) and the reproductive tract was exposed through a ventral incision anterior to the mammary glands. A silicone rubber (Silastic-Dow Corning) cannula (0·217 cm outer diameter, 0·102 cm inner diameter, 61 cm long) was inserted through the infundibulum of one oviduct and into the ampulla for about 1 cm. The cannula was retained within the oviduct
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C. R. Long, P. Damiani, C. Pinto-Correia, R. A. MacLean, R. T. Duby and J. M. Robl

The objective of these experiments was to evaluate factors affecting in vitro fertilization of bovine oocytes matured in vitro, and their subsequent development to blastocysts. In Expts 1 and 2, sperm concentration, spermatozoa and oocyte incubation time, motility enhancers and semen source were manipulated. Fluorescent microscopy of microtubules and chromatin was used to observe sperm penetration rate, sperm aster formation and chromatin decondensation. Oocyte penetration rates were affected by sperm concentration but not by spermatozoa and oocyte incubation time. The effect of sperm concentration was due primarily to changes in polyspermy and not monospermy. Motility enhancers had no effect on any parameter measured. In Expt 3, oocytes were matured for 17, 22, 28 and 34 h before fertilization and evaluated for fertilization rates, morphology of cortical granules and exocytosis and blastocyst development. A domain free of cortical granules that was associated with the metaphase chromatin was not observed in mature bovine oocytes. As oocytes matured from 17 to 34 h, the distribution of cortical granules progressed from clustered to diffuse. Although monospermic fertilization rates were similar and cortical granule exocytosis occurred in all groups, polyspermy increased with maturation time. Development to blastocysts increased from 17 to 22 h of maturation but decreased thereafter with increasing maturation time. These results suggest that polyspermy can be reduced by adjusting sperm concentration and spermatozoa and oocyte incubation time with little effect on monospermic fertilization. Increased polyspermy with increased maturation time was not due to a lack of cortical granule exocytosis.

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R. A. Milvae, R. T. Duby, J. P. Tritschler II, R. F. Pekala, G. G. Gnatek, S. L. Bushmich and D. T. Schreiber Jr

Summary. Oxytocin was administered to Dorset and Shropshire ewes in one experiment and to Dorset ewes in a further 4 experiments. In Exp. 1, concentrations of plasma progesterone and lengths of the oestrous cycle in ewes given oxytocin subcutaneously twice a day on Days 0–3, 2–5, 4–7, 6–9, 8–11, 10–13, 12–15 or 14–17 were similar to those of control ewes. In Exp. 2, intraluteal infusions of oxytocin from Day 2 to Day 9 after oestrus had no effect on concentration of progesterone, weight of CL collected on Day 9 or length of the oestrous cycle. In Exp. 3, intraluteal infusions of oxytocin on Days 10–15 after oestrus had no effect on weight of CL collected on Day 15. In Exp. 4, s.c. injections of oxytocin on Days 3–6 after oestrus had no effect on weight of CL collected on Day 9, concentrations of progesterone or length of the oestrous cycle. In Exp. 5, s.c. injections of oxytocin twice a day did not affect the maintenance and outcome of pregnancy in lactating and nonlactating ewes. Exogenous oxytocin, therefore, does not appear to affect luteal function at any stage of the ovine oestrous cycle although oxytocin has been reported by others to alter ovine CL function.

Keywords: ewe; corpus luteum; oxytocin