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During the breeding seasons 1957-58 and 1958-59, a total of 280 fertilized eggs collected from Suffolk and Welsh Mountain ewes, mated to rams of their own breeds, was transferred at rates of either two or five eggs per animal to the Fallopian tubes or uterine horns of eighty Suffolk recipient ewes. Half of the recipients had been pretreated with injections of 1500 i.u. PMS in order to induce superovulation. The survival and development of transferred eggs, however, was found to be unaffected either by superovulation or by the breed of eggs transferred.

Overall prenatal mortality was divided into two periods (I) up to 17 or 18 days and referred to throughout as embryonic mortality or loss, and (2) 17 or 18 days to term, referred to as foetal mortality or loss.

Two peaks of embryonic mortality were observed, one occurring before and the other after attachment of embryos to the endometrium. Embryonic death accounted for almost all the prenatal mortality and the majority of the loss occurred before attachment. Foetal mortality occurring later than the 17th or 18th day of pregnancy was negligible.

The proportion of recipients becoming pregnant was the same in the groups which received two eggs and the group which received five eggs, but the ovum-survival rate following the transfer of five eggs was significantly lower than that following the transfer of two eggs. However, those ewes which received five eggs and subsequently became pregnant had significantly more lambs at term and normal embryos at autopsy than those which received only two eggs.

Of all the eggs transferred to the uteri and tubes, 49% and 29%, respectively, developed into normal embryos or lambs. The smaller survival rate following tubal transfers was due to a higher rate of embryonic mortality.

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Kwanyee Leung, Vasantha Padmanabhan, E. M. Convey, R. E. Short, and R. B. Staigmiller

Summary. Changes in the ability of Gn-RH to induce gonadotrophin release with time after synchronization of oestrus was determined in 4 groups of 6 cows each. Cows were given Gn-RH at 40-min intervals for 6 h beginning at − 24,0,18 or 36 h (time 0 = removal of progestagen implant). Changes in concentration (ng/ml) of serum LH after Gn-RH averaged 2·9, 6·2, 6·4 and 33·4, whereas serum FSH averaged 25·7, 35·8, 35·8 and 97·3. Thus the responsiveness of the pituitary to Gn-RH had increased by 36 h after implant removal. Other groups of cows subjected to the same synchronization scheme were slaughtered at 0 h, 24 h or at various times after onset of oestrous behaviour. Gn-RH binding to crude pituitary membrane preparations was assessed. There was no apparent change in the affinity constant of Gn-RH-binding sites with time after synchronization. The number of Gn-RH-binding sites remained unchanged until the period of oestrus when a significant decline with time was detected. We conclude that the increase in pituitary responsiveness to Gn-RH that occurs before the preovulatory gonadotrophin surge was not directly associated with changes in number or affinity of pituitary Gn-RH-binding sites in crude pituitary membrane preparations.

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R. E. Short, A. N. Brooks, A. R. Peters, and G. E. Lamming

Summary. Injections of an opioid agonist (bremazocine) and/or an antagonist (quadazocine) were given to heifers during the luteal or follicular phase of the oestrous cycle. Quadazocine was injected (210 mg/injection) three times at 2-h intervals, and bremazocine was injected (0·45 mg/injection) every 15 min for 6 h. Blood samples were taken every 15 min beginning 6 h before treatments started and continued for 18 h.

LH secretion patterns were not affected by quadazocine in the luteal-phase heifers, but quadazocine and bremazocine had marked effects during the follicular phase. Quadazocine increased LH secretion by increasing peak height but not peak frequency. Bremazocine decreased LH secretion through both peak height and frequency. This decrease was of greater magnitude than the increase due to quadazocine. When quadazocine and bremazocine were given together, these effects were cancelled and none of the effects carried over into the bleeding period after treatments stopped. No apparent interruption of follicular maturation was detected since all follicular-phase heifers were detected in oestrus at normal intervals. We conclude that heifers in this experiment did not have an opioid-mediated mechanism for progesterone suppression of LH but that an opioid mechanism for modulating LH does exist during the follicular phase.

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K. Leung, V. Padmanabhan, L. J. Spicer, H. A. Tucker, R. E. Short, and E. M. Convey

Summary. Thirty primiparous suckling beef cows were slaughtered on Day 7, 14, 28,42 or 56 after parturition. Some had resumed oestrous cyclicity by the time they were slaughtered on Days 42 and 56. Amongst acyclic cows between Days 7 and 42, pituitary LH concentrations and basal and GnRH-induced release of LH from pituitary explants doubled. Pituitary FSH concentration and basal release in FSH increased only by 15–20%, while GnRH-induced release of FSH in vitro was unchanged. During post-partum anoestrus, overall mean concentrations of serum FSH did not change, whereas overall mean concentrations and pulse amplitudes of serum LH increased. Numbers and affinity constants of GnRH-binding sites in pituitary glands remained constant during the post-partum period studied. We conclude that, under these experimental conditions, numbers and affinity constants of GnRH-binding sites in the pituitary gland of post-partum beef cows do not limit the ability of the anterior pituitary gland to release gonadotrophins.

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The degree to which the corpus luteum is influenced by the uterus during the period of luteal regression has been investigated in two series of experiments. Ovarian vein blood was collected for progesterone analysis and the uterus was removed from forty normal sheep (Experiment 1) and eleven superovulated animals (Experiment 2) on the 15th day after oestrus. In addition, one ovary was removed from each sheep in Exp. 2 and the corpora lutea were studied histologically. At autopsy, on either Day 18, 25, 50 or 100, further samples of ovarian venous blood and luteal tissue were obtained from those animals whose corpora lutea had been maintained.

Luteal involution was arrested by hysterectomy on Day 15 even when the concentration of progesterone in the ovarian venous blood had declined to values as low as 40 μg/100 ml plasma and karyorrhexis had become widespread. It is suggested that the uterus is essential both for the initiation and for the continuation of the degenerative processes that occur during regression of the corpus luteum.

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M. A. Mirando, E. C. Short Jr, R. D. Geisert, J. L. Vallet, and F. W. Bazer

Summary. In Expt 1, activity of 2′,5′-oligoadenylate (2′,5′-A) synthetase in endometrium collected on Day 16 (oestrus is Day 0) from the uterine horn ipsilateral to the corpus luteum was greater (P < 0·001) for pregnant (135·5 ± 1·72 nmol/mg protein/h) than for cyclic ewes (58·5 ± 0·99 nmol/mg protein/h). In pregnant ewes, activity of 2′,5′-A synthetase in endometrium collected from the contralateral uterine horn(119·5 ± 1·72nmol/mg protein/h) did not differ from that of the ipsilateral horn. In Expt 2, three ovariectomized ewes were treated with progesterone for 10 days and then with oestrogen for 2 days. Activity of 2′,5′-A synthetase on Day 13 was 18% greater (P < 0·10) in endometrium collected from the uterine horn receiving infusions of 30 μg ovine trophoblast protein-1 (oTP-1) twice a day on Days 10,11 and 12(57·7 ± 0·22 nmol/mg protein/h) than from the uterine horn receiving control infusions of serum protein (SP; 48·8 ± 0·22 nmol/mg protein/h). In Expt 3, activity of 2′,5′-A synthetase on Day 15 was not significantly greater in endometrium collected from the uterine horn of cyclic ewes receiving infusions of 30 μg oTP-1 twice a day on Days 12, 13 and 14 (46·5 ± 0·37 nmol/mg protein/h) than in endometrium from the uterine horn receiving infusions of SP (38·2 ± 0·37 nmol/mg protein/h). When results of Expt 2 and Expt 3 were combined, intrauterine infusion of oTP-1 increased (P < 0·05) activity of 2′,5′-A synthetase in endometrium by 20%. In Expt 4, activity of 2′,5′-A synthetase in endometrium collected from cyclic ewes on Day 16 was increased (P < 0·001)by i.m.injection of 1 mg recombinant bovine interferon-αI1 twice a day on Days 12, 13, 14 and 15 (993·8 ± 85·9 nmol/mg protein/h) compared with endometrium from ewes similarly treated with placebo (162·1 ± 85·9 nmol/mg protein/h).

These results indicate that activity of 2′,5′-A synthetase in endometrium of ewes was increased during early pregnancy, probably by the action of the antiluteolytic conceptus interferon oTP-1. Ewes treated with recombinant bovine interferon-αI1 also had increased endometrial2′,5′-A synthetase activity, indicating that systemic administration of this interferon may directly affect the uterus and enhance fertility rate in ewes.

Keywords: pregnancy; endometrium; 2′,5′-oligoadenylate synthetase; ovine trophoblast protein-1; interferon; sheep

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L. K. Christenson, R. E. Short, D. B. Farley, and S. P. Ford

Cows were fed either a control (n = 6) or pine needle (n = 12) diet beginning on day 249 of pregnancy. On day 3 and day 5 of feeding, control-fed and pine needle-fed cows were slaughtered and placentomes were collected for in vitro perfusion of the caruncular artery. Potential sensitive Ca2+ channel (PSC) activity as well as the responsiveness to phenylephrine (α1-adrenergic agonist) and adrenaline (α1- and α2-adrenergic agonist) were determined. Selected gravid uterine tissues (endometrium and myometrium, as well as caruncular and cotyledonary tissues) and associated arteries (caruncular, intercaruncular and umbilical) were isolated, minced and portions either extracted immediately for measurement of PSC or frozen at −90°C until assayed for peroxidase activity or number of α2-adrenergic receptors and affinities or for both. In vitro perfused placentomes from day 5 pine needle-fed cows had greater (P < 0.05) PSC activity, as measured by the increase in perfusion pressure in response to a depolarizing dose of KC1, than day 3 pine needle-fed or control-fed cows (10.3 ± 2.5 versus 6.1 ± 1.2, and 4.3 ± 0.7 kPa, respectively). Furthermore, day 5 pine needle-fed cows also exhibited greater (P < 0.05) contractile responses to adrenaline than day 3 pine needle-fed or control-fed cows. Contractile responses to phenylephrine were similar (P > 0.1) for all three treatment groups. The observed increase in PSC activity and responsiveness to adrenaline, however, was not reflected by increasing numbers or affinities of PSC or α2-adrenergic receptors on caruncular arteries. Peroxidase activity (pg mg−1 tissue) was higher (P < 0.05) in caruncular tissue of pine needle-fed cows (299 ± 39) than in control-fed (186 ± 40) cows. The observed increase in peroxidase activity in caruncular tissue of pine needle-fed cows may function to increase local catechol oestrogen synthesis, in an attempt to inhibit the vasoconstrictor effects of the substance(s) in pine needles.

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Results are presented of a detailed anatomical, histological, steroid and cytogenetic study of a genetically female intersex goat with testes but with no ovarian tissue, and with a bilaterally asymmetrical reproductive tract anterior to the ampullae of the vas deferens. The gonads consisted of a well-developed testis on the right side and a smaller intra-abdominal gonad on the left. On the right side there was a well-developed epididymis and vas deferens and absence of development of the Müllerian duct. On the left side there was a well-developed and fluid-filled uterine horn, a vas deferens, but no epididymis. Both gonads showed the histological appearance of testes, although there was complete absence of spermatogenesis and the left gonad was necrotic.

Chromosome studies showed this animal to be a genetic female with 60 acrocentric chromosomes and no evidence for the presence of a Y chromosome (60, XX). Steroid concentrations in the right gonad were comparable to those in the testis of a normal male; in the left gonad, however, both testosterone and androstenedione were undetectable.

These results are discussed in relation to evidence that the testis is able to exert a local action on its adjacent genital ducts as well as a systemic action on the external genitalia.