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C. H. SPILMAN

The mammalian oviduct provides the environment for the embryo during its early development. Since oviducal fluid is composed of secretory products and products of transudation (Hamner, 1971), systemically administered compounds might influence the oviducal environment in two ways: (1) by altering the volume and/or chemical composition, and (2) by entering the oviducal fluid directly. The following experiment was performed to evaluate the influence of prostaglandins on embryo development.

Twenty-two New Zealand does were injected intramuscularly with 150 i.u. PMSG (Ayerst Laboratories, Inc.) 72 hr before being mated naturally or artificially inseminated. Immediately after insemination, all does were injected intravenously with 100 i.u. HCG (Sigma Chemical Co.) and, 6 to 7 hr later, both oviducts were ligated with silk sutures at the uterotubal junction. Because of the reported effects of prostaglandins on egg transport (Ellinger & Kirton, 1972;

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C. H. SPILMAN, G. R. HOWE and D. L. BLACK

Hawk (1967) reported that an intrauterine device (IUD) in one uterine horn blocked sperm transport, and thus fertilization, on both sides of the ovine reproductive tract. Although this effect seemed to be due to a change in uterine motility, attempts to counteract the contraceptive effect of an IUD were unsuccessful (Warren & Hawk, 1968). Furthermore, it was reported that an IUD altered uterine activity in vitro only in ovariectomized animals (Brinsfield & Hawk, 1968). Brinsfield & Hawk (1969) and Mann (1969) have observed that the direction of uterine contractions is reversed in IUD-bearing animals. The present study was undertaken to determine if an IUD caused changes in the amplitude of uterine contractions as well as a change in the direction of contractions. Preliminary data

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L. L. LARSON, C. H. SPILMAN, H. O. DUNN and R. H. FOOTE

Summary.

The reproductive efficiency of twenty-eight aged does, 49 to 72 months old, was compared with that of eighteen young does, 6 to 13 months old. Fertilization rate and development in vitro of fertilized ova from rabbits induced to superovulate were not influenced by the doe's age. Ovulation rates following natural mating were only slightly reduced with age. However, the number of embryos per doe was much greater in young than in old does at 12 and 24 days post coitum. All young does had viable embryos, whereas the percentages of aged does with detectable implantation sites and viable embryos were 80 and 40, respectively, at 12 days post coitum, and 77 and 44 at 24 days post coitum.

Aged female rabbits were given supplemental exogenous progesterone and/or oestradiol benzoate in an effort to increase reproductive efficiency. Progesterone treatment had no effect on the total number of young kindled but did prolong the gestation period, increase the birth weight and result in fewer live young kindled/doe. When administered on Days 3 to 29 of pregnancy, 4 μg/day of oestradiol alone or in combination with 2 and 4 mg progesterone completely blocked pregnancy in all does. Starting on Day 5 of pregnancy, oestradiol levels of 1 μg/day, with or without progesterone, had no effect.

Chromosomal analysis of fourteen embryos revealed eleven normal females (44,XX), one normal male (44,XY), one abnormal embryo (45,XX) with an extra acrocentric chromosome and one embryo with a modal number of forty-two chromosomes in 35% of the metaphases. Since most of the embryonic wastage in aged rabbits occurred during the first 12 days post coitum, chromosome studies of embryos younger than 12 days post coitum are indicated.

Most of the embryonic wastage could not be attributed to ovulation rate, fertilization rate, ovum potential, CL function, circulating levels of progesterone and oestrogen, or to chromosomal anomalies of the fetuses. It was concluded that uterine factors apparently limit reproductive performance in aged rabbits.

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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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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