(1/180) Ovarian follicular responses in dairy cows treated with GnRH and cloprostenol.

Lactating, nonpregnant (with a corpus luteum) Holsteins were given 100 ug GnRH (n = 12) or saline (n = 12) and 500 ug cloprostenol 6 d later. Following luteolysis, ovulation occurred 10.1 +/- 0.2 d (range, 9-12 d) after GnRH and 8.6 +/- 1.0 d (range, 3-12 d) after saline (differences between groups: means, P > 0.05; variability, P < 0.001). Treatment with GnRH and cloprostenol resulted in a relatively synchronous ovulation.  (+info)

(2/180) Synchronization of estrus in beef cattle with norgestomet and estradiol valerate.

Fifty-six cows received a norgestomet implant and an injection of norgestomet and estradiol valerate; half (n = 28) received 500 IU equine chorionic gonadotrophin (eCG) at implant removal, 9 d later. A third group (n = 25) received 2 doses of cloprostenol (500 micrograms) 11 d apart. Estrous rate was higher (P < 0.05) for cows given norgestomet and estradiol plus 500 IU eCG (75.0%) than for those receiving cloprostenol (44.0%); for those receiving norgestomet and estradiol alone, it was intermediate (67.8%). Pregnancy rates to artificial insemination (after estrus or timed) were higher (P < 0.05) for cows given norgestomet and estradiol than for those given cloprostenol (23 of 28, 82.1% vs 13 of 25, 52.0%), and intermediate (67.8%) for those given norgestomet and estradiol plus eCG. In a second experiment, for heifers treated with norgestomet and estradiol plus eCG (n = 15) or with 2 doses of cloprostenol (n = 16), estrous rates were 66.7% vs 56.2% (P > 0.5), ovulation rates were 100.0% vs 81.2% (P = 0.08), intervals from implant removal or cloprostenol treatment to estrus were 48.0 +/- 4.4 hours vs 61.3 +/- 7.0 hours (P = 0.12) and to ovulation were 70.4 +/- 4.4 hours vs 93.2 +/- 7.5 hours (P < 0.01), respectively; pregnancy rates were 41.7 and 35.7%, respectively (P > 0.5). Norgestomet and estradiol were as good as (heifers) or superior to (cows) a 2-dose cloprostenol regimen. In cows given norgestomet and estradiol, injecting eCG at implant removal did not significantly improve estrous or pregnancy rates.  (+info)

(3/180) Functional evidence for divergent receptor activation mechanisms of luteotrophic and luteolytic events in the human corpus luteum.

Using a dispersed human luteal cell culture model, progesterone synthesis following treatment by incremental doses of human chorionic gonadotrophin (HCG) and the stable prostaglandin F2alpha (PGF2alpha) analogue cloprostenol, alone or in combination, was related to corpora lutea (CL) mRNA transcript abundance coding for the luteinizing hormone (LH)/HCG receptor (LH-R) and PGF2alpha-receptor (FP) by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) in 33 otherwise healthy women, scheduled for surgery due to benign conditions. CL were grouped according to age, based on the occurrence of a preovulatory LH surge where post-LH days 2-5 were designated as early luteal phase, days 6-10 as mid-luteal phase and days 11-14 as late luteal phase. When exposed to HCG, maximal progesterone output was raised 2.2-fold (P = 0.08, n = 5) compared with untreated controls in the early CL, while it increased 5.7- and 4.6-fold in the mid- and late groups respectively (P<0.05, n = 4 mid-luteal phase, n = 3 late luteal phase). This stimulation pattern was found to be concordant with the value of mRNA coding for LH-R in all groups (n = 6 early luteal phase, n = 5 mid-luteal phase, n = 6 late luteal phase). The integrated response to HCG and cloprostenol showed a dose-dependent 60% inhibition of progesterone production; but only in late luteal phase luteal cells (P<0.01, n = 3). FP mRNA values were lowest in early luteal phase, and increased with the age of the CL. Interestingly, lowest CL tissue concentrations of the natural FP agonist PGF2alpha were found during mid-luteal phase while it increased again 1.6-fold during late luteal phase (P<0.05, n = 8 versus mid-luteal phase, n = 6). Collectively, these data demonstrate that (i) the extrinsic functional control (or rescue of CL in the event of pregnancy) occurs when the sensitivity towards LH/HCG is maximal; and (ii) the demise of CL function is mediated via an acquisition of sensitivity towards the intrinsic luteolytic signal, PGF2alpha in the ageing CL.  (+info)

(4/180) Effect of sodium cloprostenol and flunixin meglumine on luteolysis and the timing of birth in bitches.

At birth, the physiological role of prostaglandins in bitches is unclear. Bitches were treated before parturition with either saline, the prostaglandin analogue, sodium cloprostenol, or the prostaglandin synthetase inhibitor, flunixin meglumine. The animals were examined regularly to determine the onset of parturition and a series of blood samples were taken to define the hormonal profiles before, during and after birth. Animals treated with cloprostenol whelped earlier than did controls. In addition, the prostaglandin F2 alpha metabolite surge and decrease in plasma progesterone concentration and rectal temperature were earlier than in controls. Flunixin meglumine disrupted the normal 13,14-dihydro-15-keto prostaglandin F2 alpha profile but did not abolish prostaglandin synthesis completely or delay the onset of labour in treated animals. This study confirms that prostaglandins induce luteolysis and the onset of labour in the bitch. However, the partial inhibition of prostaglandin synthesis does not prevent parturition.  (+info)

(5/180) Source and site of action of anti-luteolytic interferon in red deer (Cervus elaphus): possible involvement of extra-ovarian oxytocin secretion in maternal recognition of pregnancy.

Six conceptuses were collected from red deer hinds on day 22 after synchronization of oestrus with intravaginal progesterone-releasing devices (removal of device = day 0). Within 24 h of culture in vitro, the supernatant from five of six conceptuses showed detectable antiviral activity. Interferon alpha (IFN-alpha) receptors were identified by immunohistochemistry on the luminal surface of the endometrium, in the neurohypophysis and paraventricular hypothalamus, but not in the ovaries of the hinds from which the conceptuses were collected. Another 16 intact hinds were synchronized as above. Injection of 4 mg IFN i.m. twice a day on days 13-15 had no effect on cloprostenol-induced oxytocin secretion on day 15 and did not prevent cloprostenol-induced luteal regression. Sixteen ovariectomized hinds received a protocol of steroid treatment to mimic ovarian hormone secretion during the normal oestrous cycle. On day 16, hinds showed undulant oxytocin secretion that showed a degree of temporal association with uterine PGF2 alpha release. Treatment with 4 mg IFN-alpha I 1 twice a day on days 13-16 had no effect on this spontaneous oxytocin secretion, but reduced the magnitude of cloprostenol-induced oxytocin secretion on day 17 (P < 0.05). These results indicate that red deer conceptuses secrete an anti-luteolytic IFN to which the endometrium expresses a receptor during early pregnancy. The presence of IFN receptors in the hypothalamus and posterior pituitary and the IFN-induced suppression of extra-ovarian oxytocin secretion provides tentative evidence of an involvement of the central nervous system in maternal recognition of pregnancy in deer.  (+info)

(6/180) Direct effects of ovine follicular fluid on ovarian steroid secretion and expression of markers of cellular differentiation in sheep.

The objective of this study was to assess the effect of ovine follicular fluid (FF) treatment (with or without FSH replacement) during the late follicular phase on plasma concentrations of gonadotrophins and the development of the ovulatory follicle. Ovarian steroid secretion and expression of mRNA encoding inhibin alpha and beta A, beta B subunits, P450 aromatase and P450 17 alpha-hydroxylase were used as endpoints. After induction of luteolysis by injection of 100 micrograms cloprostenol on days 10-12, Scottish Blackface ewes were allocated to one of three groups: (1) control (n = 7): no further treatment; (2) FF (n = 9): subcutaneous injections of 3 ml steroid-free ovine follicular fluid at 9 h intervals, 18 and 27 h after cloprostenol injection; (3) FF + FSH (n = 8): injections of follicular fluid as above plus subcutaneous injections of 0.36 iu ovine FSH at 6 h intervals, 18, 24, and 30 h after cloprostenol injection. Jugular venous blood samples were obtained via indwelling cannulae at 6 h intervals from 0 to 36 h after cloprostenol injection, and at 10 min intervals from 12 to 18 h (control phase) and from 30 to 36 h after cloprostenol injection (treatment phase). At laparotomy, 36 h after cloprostenol injection, ovarian venous blood was collected and ovaries were removed and processed for in situ hybridization. Plasma concentrations of FSH, luteinizing hormone (LH) and oestradiol were determined by radioimmunoassay. Follicular fluid treatment resulted in a decrease (P < 0.001) in FSH concentrations associated with an acute decrease in ovarian steroid secretion (P < 0.01) and a specific depression in P450 aromatase, (P < 0.001), inhibin-activin beta B subunit (P < 0.05) and thecal LH receptor (P < 0.001) expression. Follicular fluid treatment had no effect on inhibin-activin alpha and beta A, subunit or P450 17 alpha-hydroxylase expression. FSH co-treatment with follicular fluid restored circulating FSH concentrations to normal values and reversed some of the effects of follicular fluid (androstenedione, testosterone and progesterone secretion, and inhibin beta B and thecal LH receptor expression) but not oestradiol secretion or P450 aromatase expression. It was concluded that the actions of follicular fluid are mediated via both central effects on pituitary FSH secretion and by direct ovarian effects on granulosa cell aromatase activity. The results indicate that follicular fluid contains a factor that inhibits aromatase activity of granulosa cells directly and may play a role in the selection of the dominant follicle.  (+info)

(7/180) Relationship between the responsiveness to multiple-ovulation treatment and the number of bovine oocytes collected by transvaginal follicle aspiration.

To characterize factors affecting the number of bovine oocytes recovered transvaginally, a regression analysis was performed between the responsiveness to multiple-ovulation treatment and the number of oocytes recovered transvaginally. The number of embryos recovered following multiple-ovulation treatment and the number of oocytes recovered transvaginally increased when the number of follicles to be aspirated transvaginally increased (P<0.05. P<0.01). The number of cumulus-oocyte complexes recovered transvaginally also increased when the number of oocytes to be aspirated transvaginally increased (P<0.001). However, the number of viable embryos that recovered following multiple-ovulation treatment had no relation to the number of cumulus-oocyte complexes recovered transvaginally. These results suggested that more oocytes can be recovered from donors that have a high responsiveness to multiple-ovulation treatment.  (+info)

(8/180) Prostaglandin f(2alpha) induces distinct physiological responses in porcine corpora lutea after acquisition of luteolytic capacity.

This study examines differences in intracellular responses to cloprostenol, a prostaglandin (PG)F(2alpha) analog, in porcine corpora lutea (CL) before (Day 9 of estrous cycle) and after (Day 17 of pseudopregnancy) acquisition of luteolytic capacity. Pigs on Day 9 or Day 17 were treated with saline or 500 microgram cloprostenol, and CL were collected 10 h (experiment I) or 0.5 h (experiment III) after treatment. Some CL were cut into small pieces and cultured to measure progesterone and PGF(2alpha) secretion. In experiment I, progesterone remained high and PGF(2alpha) low in luteal incubations from either Day 9 or Day 17 saline-treated pigs. Cloprostenol increased PGF(2alpha) production 465% and decreased progesterone production 87% only from Day 17 luteal tissue. Cloprostenol induced prostaglandin G/H synthase (PGHS)-2 mRNA (0.5 h) and protein (10 h) in both groups. In cell culture, cloprostenol or phorbol 12, 13-didecanoate (PDD) (protein kinase C activator), induced PGHS-2 mRNA in luteal cells from both groups. However, acute cloprostenol treatment (10 min) decreased progesterone production and increased PGF(2alpha) production only from Day 17 luteal cells. Thus, PGF(2alpha) production is induced by cloprostenol in porcine CL with luteolytic capacity (Day 17) but not in CL without luteolytic capacity (Day 9). However, this change in PGF(2alpha) production is not explained by a difference in induction of PGHS-2 mRNA or protein.  (+info)