Search Results

You are looking at 1 - 8 of 8 items for

  • Author: D. H. Keisler x
Clear All Modify Search
Free access

D. H. Keisler and L. W. Keisler

Summary. Of 19 dioestrous ewes given 50 μg GnRH on Day 10 of the oestrous cycle, 15 (79%) formed corpora haemorrhagica within 2 days after injection of GnRH. After excision of the Day 10 spontaneous CL, the GnRH-induced CL were short lived when compared to spontaneous CL in saline-treated ewes (3·1 ± 0·4 vs 17·3 ± 0·3 days, respectively). Hysterectomy of ewes bearing the GnRH-induced CL prevented regression of the short-lived CL, thus extending functional lifespan ≥ 38 days. Serum concentrations of progesterone produced by the GnRH-induced CL in hysterectomized ewes were less than those observed during a comparable interval (Days 7–14) in saline-treated, non-hysterectomized ewes (2·24 ± 0·1 vs 3·67 ± 0·15 ng/ml, respectively; P ⩽ 0·001).

When GnRH was given before (5 h before) or during (5 h after) PGF-2α-induced regression of the Day 10 spontaneous CL, the GnRH-induced CL which formed were also short-lived. In contrast, when GnRH was given following (36 h after) PGF-2α-induced regression of the Day 10 spontaneous CL, the CL which formed were not different in lifespan or production of progesterone from spontaneous CL. Efforts to enhance function of the GnRH-induced subnormal CL by treating ewes with the synthetic progestagen, norgestomet, to suppress follicular development after CL formation, were unsuccessful.

We suggest that these results provide new evidence to support the hypothesis that subnormal luteal function may be the result of inadequate follicle development (i.e. the follicle needs exposure to some sequence of events characteristic of luteal regression and/or a normal follicular phase) which impairs uterine luteolytic mechanisms. These results also support the hypothesis that periovulatory determinants of normal luteal function are established between 5 and 36 h after PGF-2α-induced luteal regression.

Keywords: corpus luteum; ewes; hysterectomy; GnRH

Free access

T. G. Rozell and D. H. Keisler

Summary. This study was conducted to test the hypothesis that the rate (dose/time) at which oestradiol-17β (oestradiol) is presented to the hypothalamo–pituitary axis influences secretion of LH, FSH and prolactin. A computer-controlled infusion system was used to produce linearly increasing serum concentrations of oestradiol in ovariectomized ewes over a period of 60 h. Serum samples were collected from ewes every 2 h from 8 h before to 92 h after start of infusion, and assayed for oestradiol, LH, FSH and prolactin. Rates of oestradiol increase were categorized into high (0·61–1·78 pg/h), medium (0·13–0·60 pg/h) and low (0·01–0·12 pg/h). Ewes receiving high rates of oestradiol (N = 11) responded with a surge of LH 12·7 ± 2·0 h after oestradiol began to increase, whereas ewes receiving medium (N = 15) and low (N = 11) rates of oestradiol responded with a surge of LH at 19·4 ± 1·7 and 30·9 ± 2·0 h, respectively. None of the surges of LH was accompanied by a surge of FSH. Serum concentrations of FSH decreased and prolactin increased in ewes receiving high and medium rates of oestradiol, when compared to saline-infused ewes (N = 8; P < 0·05). We conclude that rate of increase in serum concentrations of oestradiol controls the time of the surge of LH and secretion of prolactin and FSH in ovariectomized ewes. We also suggest that the mechanism by which oestradiol induces a surge of LH may be different from the mechanism by which oestradiol induces a surge of FSH.

Keywords: oestradiol; LH; FSH; prolactin; ovariectomized ewes

Free access

H. Francis, D. H. Keisler and R. M. Roberts

Summary. We examined the effect of recombinant bovine interferon-αI 1 (rboIFN-αI1) or recombinant bovine trophoblast protein-1 (rbTP-1) on protein synthesis by endometrial explants from Day-13 cyclic ewes and studied the ability of rboIFN-αI1 injected i.m. to influence subsequent protein scretion by endometrial tissue explants.

In Expt 1, ewes were injected with either 2 mg rboIFN-αI1 or vehicle alone at 12-h intervals beginning on Day 11 of the oestrous cycle and ending on the morning of Day 13; 8 h after the last injection, ewes were hysterectomized and endometrial explant cultures were prepared. Explants were cultured for 24 h in leucine-deficient medium supplemented with 250 μCi l-[3H]leucine per culture. For Expt 2, additional explants were prepared from Expt 1 controls. Explants were cultured in the presence of 0, 20 or 200 ng/ml of either rboIFN-αI1 or rbTP-1 for 24 h in leucine-deficient medium supplemented with 250 μCi l-[3H]leucine per culture. Secreted proteins were analysed by two-dimensional electrophoresis and fluorography. There was a marked enhancement of a 70 kDa acidic protein, p70, in explants cultured in the presence of rboIFN-αI1 or rbTP-1. This polypeptide is a product of the gravid uterine horn from Day 14 to Day 20 of pregnancy and is a useful marker of the action of interferon-α (IFN-α) on endometrium. Enhanced production of p70 also occurred in ewes injected i.m. with rboIFN-αI1. These results are consistent with the hypothesis that injected rboIFN-αI1 exerts its effects on such variables as interoestrus interval and maternal recognition of pregnancy by actions on the uterus.

Keywords: cattle; interferon-α; pregnancy; protein; sheep; trophoblast

Free access

C. M. V. Bettencourt, R. J. Moffatt and D. H. Keisler

The hypothesis that pregnancy success could be improved in early postpartum ewes by prolonging the lifespan of the corpus luteum via active immunization against prostaglandin F (PGF) was tested. Further experiments in ewes immunized against PGF investigated the effects of exogenous PGF on the preovulatory follicle and the effects of PGF and oestradiol benzoate on corpus luteum function. Four weeks prepartum, 39 ewes bred to lamb during seasonal anoestrus received either 5 mg PGF–ovalbumin conjugate (n = 20; immunized) or ovalbumin (n = 19; control) in Freund's complete adjuvant. Treatments were repeated on day 5 post partum with reagents emulsified in Freund's incomplete adjuvant. On day 17 post partum, ewes received 500 iu pregnant mares' serum gonadotrophin (PMSG) and 48 h later 50 μg gonadotrophin-releasing hormone (GnRH). Laparoscopy was performed 36 h after GnRH to assess ovarian activity and ewes with recent ovulations were inseminated into the uterus. No immunized ewes had ovulated, but ten had follicles that luteinized and secreted progesterone during the 8 weeks studied. Eighteen of 19 control ewes ovulated and 15 of 18 had increased progesterone concentration for at least 21 days. By day 70 post partum, progesterone had returned to basal values in all control ewes. In a second study, 24 immunized ewes bearing persistent corpora lutea, and for which the interval from the previous parturition was greater than 90 days, received 15 mg PGF and 500 iu PMSG followed 48 h later by 50 μg GnRH. PGF induced corpus luteum regression in all ewes. PMSG and GnRH treatments resulted in oestrus in 21 of 24 ewes. Sixteen hours after GnRH, 10 ewes received a second injection of 15 mg PGF. PGF induced follicular rupture in eight of ten immunized ewes, whereas only two of 14 ewes not receiving PGF ovulated (P < 0.01). All anovular ewes had large cystic follicles that luteinized. In a third study, 22 ewes immunized against PGF, and having persistent corpora lutea, received, on two consecutive days, either oestradiol benzoate (750 μg; n = 11) in oil or oil (n = 11). Laparoscopy was performed on all ewes immediately before injections and four of the 11 ewes in each group possessed uterine horns that were filled with fluid. No fluid was judged to be in the horns of the remaining seven ewes in each group. On the basis of serum concentrations of progesterone and laparoscopies, oestradiol benzoate induced luteal regression in those ewes with uterine fluid and failed to induce luteal regression in those ewes lacking uterine fluid. Luteal function was unaffected in ewes that received the oil vehicle. These data suggest that premature luteal regression was not the reason for failure of occurrence of pregnancy. Immunization against PGF was effective in blocking ovulation, but not in inhibiting oestrous behaviour or the formation of persistent luteal tissue. Treatment of immunized ewes with exogenous PGF restored the ability of ewes to ovulate, providing further evidence for the involvement of PGF in ovulation. The ability of oestradiol to induce luteolysis in immunized ewes was associated with the presence of uterine fluid.

Free access

S. F. Sharif, H. Francis, D. H. Keisler and R. M. Roberts

Summary. We studied the biosynthesis of two proteins, p70 (M r 70 000; pI 4·0) and p15 (M r 15 000; pI 5·7), by endometrial tissues from ewes between Days 12 and 24 of pregnancy and between Days 12 and 16 of the oestrous cycle to determine whether production of the two was correlated with the period of biosynthesis of ovine trophoblast protein-1 (oTP-1) by the conceptus. We also compared the protein synthetic activities of endometrium from gravid and non-gravid horns of pregnant ewes at Days 14, 16 and 18 in which the conceptus had been confined to one uterine horn. Proteins p70 and p15 were produced maximally between Days 14 and 20 of pregnancy, but synthesis by endometrial cultures from cyclic ewes was low or absent. Furthermore, synthesis of Protein p70 in particular was much greater by the gravid than non-gravid horn of unilaterally pregnant ewes. We conclude that synthesis of Proteins p70 and p15 by the uterus of sheep coincides with the time of oTP-1 production by the conceptus.

Keywords: ovine trophoblast protein-1; endometrium; sheep; pregnancy; interferon

Free access

J. P. Copelin, M. F. Smith, D. H. Keisler and H. A. Garverick

Summary. Mature beef cows were actively immunized pre partum (N = 5) or post partum (N = 10) against a PGF-2α–ovalbumin conjugate or against ovalbumin alone (control; N = 5). All cows in the control group exhibited first oestrous cycles which were of short duration (⩽ 12 days). Mean specific serum binding to [3H]PGF-2α in the control group was consistently < 1%. In the pre-partum PGF-2α-immunized cows, lifespan and progesterone secretion of the first corpus luteum formed post partum was maintained for > 39 days. Specific serum binding to [3H]PGF-2α in pre-partum and post-partum PGF-2α-immunized cows was elevated. Lifespan of the first corpus luteum formed in post-partum PGF-2α-immunized cows was short (<10 days; N = 1), normal (mean = 22 days; N = 4) or maintained (>31 days; N = 5). Luteal lifespan was dependent upon serum PGF-2α antibody titres, with cows exhibiting higher titres frequently having prolonged luteal lifespans after first ovulation. We conclude that active immunization of beef cows against PGF-2α extends the lifespan and progesterone secretion of corpora lutea anticipated to be short-lived. These results support the concept that the shorter lifespan of some corpora lutea in post-partum cows is due to a premature release of PGF-2α from the uterus.

Keywords: active immunization; PGF-2α; corpus luteum; cattle

Free access

C. A. Pinkert, D. L. Kooyman, A. Baumgartner and D. H. Keisler

Summary. Ten prepubertal and 8 mature gilts were superovulated with PMSG and hCG, and inseminated with fresh boar semen. Zygotes were surgically recovered from oviducts 54–60 h after hCG. One and 2-cell zygotes were randomly allotted to Medium PL (modified BMOC-3 supplemented with 0·1 mm-EDTA and 1·5% BSA) or Medium G (Medium PL without pyruvate or lactate). Eggs were washed twice in medium, and placed in microdrops of medium overlaid with silicon oil for culture in an humidified 5% CO2, 5% O2, 90% N2 environment, then observed daily for 6 days. Development of eggs was dependent (P < 0·001) on the interactive effects of age of gilt (prepubertal versus mature) and medium type (PL versus G) used in culture. A greater proportion of eggs cultured in Medium G developed further than did eggs in Medium PL (P < 0·001). Additionally, a greater proportion of eggs from mature gilts developed further than did eggs from prepubertal gilts (P < 0·02). We suggest that these results provide evidence that zygotes resulting from superovulation regimens of prepubertal gilts do not possess the same capacity for in-vitro development as do zygotes from pubertal gilts.

Keywords: zygote; blastocyst; prepubertal; pigs

Free access

H. A. Garverick, M. T. Moser, D. H. Keisler, S. A. Hamilton, R. M. Roberts and M. F. Smith

Summary. This study was conducted to determine whether intrauterine infusion of recombinant bovine interferon-αI1 (rboIFN-αI1), which has 70% sequence identity to bovine trophoblast protein-1, will prevent regression of corpora lutea anticipated to have a short lifespan.

Twenty-six beef cows in good body condition were allotted to four treatment groups at parturition in a 2 × 2 factorial design. Treatments were: group 1, saline; group 2, rboIFN-αI1; group 3, norgestomet–saline; and group 4, norgestomet–rboIFN-αI1. Norgestomet implants were inserted on days 21–24 postpartum and removed 9 days later (before injection of human chorionic gonadotrophin (hCG)). Ovulation was induced 30 to 33 days postpartum with 5000 or 10 000 iu hCG. Groups 1 (n = 7) and 3 (n = 5) were given intrauterine infusions (rectocervical approach) twice daily with saline on days 1–12 or 13–24 after hCG injection, respectively. Cows allotted to groups 2 (n = 8) and 4 (n = 6) were given intrauterine infusions (rectocervical approach) of 2 mg rboIFN-αI1 twice daily on days 1–12 or 13–24 after hCG injection, respectively.

Treatment with both norgestomet and rboIFN-αI1 delayed (P < 0·01) luteolysis. Lengths of luteal phases (days; mean ± sem) were 8·4 ± 0·7 (group 1, saline), 12·1 ± 1·0 (group 2, rboIFN-αI1), 18·6 ± 1·3 (group 3, norgestomet–saline and 20·8 ± 1·2 (group 4, norgestomet–rboIFN-αI1). Concentration of progesterone in serum was similar among all groups the first 6 days following hCG-induced ovulation, but differed (P < 0·01) thereafter. Mean concentration of progesterone was lower (P < 0·01) in saline-treated cows (group 1) from days 8 to 13 than in cows infused with rboIFN-αI1 or pretreated with norgestomet. In summary, intrauterine infusion of rboIFN-αI1 delayed luteolysis of corpora lutea anticipated to have a short lifespan.

Keywords: corpus luteum; progesterone; norgestomet; recombinant bovine interferon-αI1; cow