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Summary.

Spirals were inserted by surgery into one or both uterine horns. Ovulation occurred normally at subsequent oestrous periods, but ova were uncleaved at 3 days after oestrus. Spermatozoa were not found at 4 to 24 hr after mating in either oviduct of ewes with a spiral in only one uterine horn. Fertilized ova and spermatozoa were recovered from oviducts of control ewes.

Summary.

Ovum fertilization after natural mating was inhibited in both oviducts after the insertion of a plastic spiral into one uterine horn. Spermatozoa were found in oviducts of control ewes between 4 and 24 hr after mating, but were almost totally absent from both oviducts of ewes with a spiral in one horn. Sperm numbers in the uterus were relatively low in `spiral' ewes. Spirals had these effects both 2 to 4 weeks and 8 to 10 months after insertion.

Ova were fertilized in `spiral' as well as control ewes after injection of semen into the uterus, but there were fewer accessory spermatozoa in ova from `spiral' ewes. After injection of semen into one uterine horn, spermatozoa were found throughout reproductive tracts of `spiral' and control ewes, but most spermatozoa in horns containing a spiral were broken into heads and tails. Similarly, when semen was injected into ligated uterine compartments, most spermatozoa recovered 5 hr later from spiral compartments were tailless; most spermatozoa recovered from non-spiral compartments of the same ewes were intact. Spirals inhibited sperm transport following natural mating, and they also promoted spermicidal conditions in the uterine lumen.

Summary.

A plastic spiral IUD was inserted at laparotomy into one uterine horn of ewes in oestrus; in control ewes in oestrus, an IUD was inserted and removed immediately. In ewes mated 1 to 2 hr and again 5 hr after insertion of the IUD, sperm transport into the uterine horns and oviducts on both sides of the reproductive tract was inhibited and ovum fertilization prevented. The majority of uterine contractions were seen to be moving towards the oviduct in control ewes but towards the cervix in ewes with the IUD 5 hr after its insertion. This may account for the inhibition of sperm transport.

Summary.

Sponges impregnated with medroxyprogesterone acetate (MAP) were left in the vaginae of parous ewes from 8 to 25 days after oestrus. The ewes were inseminated with 0·25 ml of fresh ram semen 45 hr after removal of the sponges. Ewes in natural oestrus were inseminated as controls. In half of the ewes of each group, the reproductive tract was ligated at the vulvovaginal junction at the time of insemination to prevent the loss of sperm cells by drainage. Ewes were killed 24 hr after insemination and the number of spermatozoa in each segment of the reproductive tract was estimated.

While 62% of the spermatozoa were recovered from ewes in which the vulvovaginal junction was ligated, less than 1% were recovered from the ewes with unligated tracts, indicating the loss of large numbers of sperm cells by drainage. Fewer spermatozoa and a higher proportion of tailless sperm heads were recovered from ewes treated with MAP than from control ewes.

Summary.

Motility in vitro was greatest in strips of myometrium from oestrous ewes, intermediate in strips from ovariectomized ewes and least in strips from luteal phase ewes. The presence of a spiral in the uterine lumen in vivo increased the amplitude of contractions for ewes of each endocrine state; the increase was greatest for ovariectomized ewes. Frequency of contractions was not changed significantly. The increased amplitude was localized for the most part to the uterine horn containing the spiral.

Summary.

The direction of uterine contractions in vivo was studied in oestrous ewes by recording the motility of exteriorized uteri on cine film. In eight control ewes, 58% of 1156 contractions moved towards the oviduct, while 16% moved towards the cervix. In eight ewes with a plastic spiral in the lumen of one horn, only 17% of 927 contractions moved towards the oviduct; 70% of the contractions moved towards the cervix. The effect of the IUD on the direction of uterine contractions may explain inhibition of sperm transport and ovum fertilization in `IUD' ewes.

Summary.

Parous ewes were treated orally or intravaginally with synthetic progestagen, or subcutaneously with progesterone. Treatment was begun on Day 8 or 10 of an oestrous cycle and continued for 13 to 17 days. At the oestrus following progestagen withdrawal, the uterus was exposed and uterine contractions observed. Each treatment reduced the number of uterine contractions moving towards the oviducts and increased the number moving towards the cervix. The altered motility pattern probably helps to account for decreased sperm transport to the oviducts at the progestagen-regulated oestrus.

Summary. Zygotes from superovulated cows were centrifuged and pronuclei were detected by differential interference-contrast microscopy in 73% of 106 zygotes. Zygotes were then transferred to ligated oviducts of follicular-phase, 1-day pseudopregnant or 7-day pseudopregnant rabbits and recovered 5 days later. Their development did not differ from that of uncentrifuged zygotes transferred to the opposite oviduct: 41% of the embryos recovered from rabbit oviducts contained 17–32 nuclei and an additional 5% contained >32 nuclei. In another experiment, 399 ova from unmated cows were transferred to rabbit oviducts to determine whether centrifugation induced parthenogenetic development. After 7 days, 257 ova were recovered; 16% of the recovered ova had developed parthenogenetically and contained 2–30 nuclei. Neither centrifugation of the ova nor reproductive status of the rabbits influenced the proportion of parthenogenotes found. Parthenogenetic development was also observed in 14 of 71 ova (20%) recovered on Day 7 from uninseminated superovulated cows. In an attempt to increase the probability of detecting treatment differences, centrifuged and control cow zygotes were incubated for 7 (rather than 5) days in opposite oviducts of fourteen 1-day pseudopregnant rabbits. Development was unaffected by centrifugation: 61% of the zygotes recovered had developed beyond the 16-cell stage, with 23, 24 and 15% containing 17–32, 33–64, and >64 nuclei, respectively. Taking into account the percentage of zygotes in which pronuclei can be seen, the recovery rate from rabbit oviducts, and the proportion of embryos that develop to the morula stage or beyond, 26% of the original group of zygotes would be candidates for transfer into recipient cows.

Keywords: cattle; pronuclei; centrifugation; parthenogenesis; embryo

Summary.

Nine parous ewes were used in each of seven ovarian states or hormone treatment groups : oestrus, the luteal phase of the oestrous cycle, an ovariectomized untreated group, and four groups of ovariectomized ewes treated with oestradiol or combinations of oestradiol and progesterone. Each uterine horn was ligated at either end and 0·07 ml of fresh ram semen, containing an average of 199 × 10⁶ sperm cells, was deposited in the uterine lumen. The horns were flushed 5 hr later and intact sperm cells and tailless sperm heads were counted in the flushings.

As compared with the results from ovariectomized control ewes, either oestradiol administered to ovariectomized ewes or the ovarian hormones of ewes in natural oestrus increased both the breakage and the disappearance of sperm cells. Exogenous progesterone or the ovarian hormones of luteal phase ewes both decreased the breakage and disappearance of sperm cells, and the administration of progesterone before or at the same time as oestradiol tended to decrease sperm cell breakage.

Summary.

The presence of an IUD in the oestrous ewe inhibited sperm transport into the uterine horns and oviducts and caused reversal of the direction of uterine contractions for as long as 2 years after the insertion of the IUD. In rabbits, an IUD did not prevent sperm transport and ovum fertilization and did not alter the pattern of uterine contractions. The results support the hypothesis that the inhibition of sperm transport in IUD-bearing sheep is caused by reversed uterine contractions.