Initiation of Parturition

Liggins, G. C.

doi:10.1007/978-94-011-1286-4_9

Cited by 78 publications

(26 citation statements)

References 636 publications

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“…These molecules are then aromatized to estrogens, which results in an overall decline in progesterone levels (i.e., cessation of "progesterone block") and increased estrogen levels [44,45]. This alteration in the ratio of progesterone to estrogen occurs a few days prior to parturition [46]. The change in the ratio of estrogen to progesterone stimulates the release of prostaglandin F 2α (PGF 2α ) from the uterus [46].…”

Section: Putative Mechanisms Of Natural Cervi-cal Dilation In Periparmentioning

confidence: 99%

“…This alteration in the ratio of progesterone to estrogen occurs a few days prior to parturition [46]. The change in the ratio of estrogen to progesterone stimulates the release of prostaglandin F 2α (PGF 2α ) from the uterus [46]. Increased placental estrogen production is required for up-regulation of PGHS-2 in maternal, but not fetal, tissues prior to labor [43].…”

Section: Putative Mechanisms Of Natural Cervi-cal Dilation In Periparmentioning

confidence: 99%

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A Review of Advances in Artificial Insemination (AI) and Embryo Transfer (ET) in Sheep, with the Special Reference to Hormonal Induction of Cervical Dilation and its Implications for Controlled Animal Reproduction and Surgical Techniques

Candappa¹,

Bartlewski²

2011

TORSJ

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Artificial insemination (AI) and embryo transfer (ET) play an important role in the genetic improvement of sheep herds. This review primarily describes the methods that have recently been researched and/or adapted to circumvent the problematic anatomy of the ovine cervix, which prevents the widespread application of transcervical AI and ET in this species. A mechanism of cervical ripening at parturition and the endocrine influences on cervical tone are described as a backdrop to understanding the action of various pharmacological agents used to induce cervical dilation. Although several catheters have been designed to penetrate the ovine cervix, and a specific protocol has been developed for TCAI in sheep (Guelph Method), penetration rates and resulting pregnancy/lambing rates are still inconsistent and unpredictable. Hormonal dilation of the cervix may significantly improve the ease with which the ovine cervix can be traversed. Treatment with Cervidil ® , a dinoprostone-containing vaginal insert with a slow release mechanism, currently used to induce labor in women, could significantly improve cervical penetration in ewes without adverse effects on uterine contractility. This mode of drug delivery holds promise to result in the development of a safe method to induce cervical dilation for a broad range of transcervical reproductive manipulations in mammalian species including, but not limited to, AI, ET, embryo and oocyte recovery, treatment of ringwomb and transcervical surgical procedures. However, more studies are needed to evaluate the effects of hormonal methods on cervical morphology/pathomorphology, sperm/embryo transport and viability, and fertility in both cyclic and seasonally anovular ewes.

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Section: Putative Mechanisms Of Natural Cervi-cal Dilation In Periparmentioning

confidence: 99%

Section: Putative Mechanisms Of Natural Cervi-cal Dilation In Periparmentioning

confidence: 99%

A Review of Advances in Artificial Insemination (AI) and Embryo Transfer (ET) in Sheep, with the Special Reference to Hormonal Induction of Cervical Dilation and its Implications for Controlled Animal Reproduction and Surgical Techniques

Candappa¹,

Bartlewski²

2011

TORSJ

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“…In addition, for a number of species including the sheep, the increase in fetal cortisol production is also the critical trigger determining the timing of labour (Liggins & Thorburn 1994).…”

Section: Introductionmentioning

confidence: 99%

“…It is clear that an intact hypothalamopituitary-adrenal (HPA) axis is critical for the normal cortisol surge and parturition, as disruption at any level of the axis results in decreased cortisol concentrations and a failure of parturition (Liggins et al 1967, Drost & Holm 1968, Antolovich et al 1991, Myers et al 1993. Furthermore, the infusion of pituitary adrenocorticotrophin (ACTH 1-24 ) or adrenal (cortisol) hormones of the HPA axis induces premature labour in intact fetuses, and restores cortisol concentrations and parturition in fetuses that have had lesions of these respective organs (Liggins & Thorburn 1994, Poore et al 1998. It is generally believed that increasing ACTH concentrations drive the increase in cortisol concentrations, though many studies have demonstrated only modest, linear increases in ACTH concentrations in the face of a large, exponential increase in cortisol (Norman et al 1985, Deayton et al 1994, Phillips et al 1996, Canny et al 1998, Poore et al 1998).…”

Section: Introductionmentioning

confidence: 99%

The role of the pituitary gland and ACTH in the regulation of mRNAs encoding proteins essential for adrenal steroidogenesis in the late-gestation ovine fetus

Simmonds¹,

Phillips²,

Poore³

et al. 2001

Journal of Endocrinology

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To further understand the relative roles of the pituitary gland and ACTH in the regulation of mRNAs encoding proteins that are essential for adrenal development, we investigated the effects of, first, an ACTH infusion and labour in intact fetuses and, secondly, the effect of an ACTH infusion to fetuses with and without a pituitary gland, on the relative abundance of the mRNA encoding for the ACTH receptor (MC2R), steroidogenic factor 1 (SF-1), cholesterol side-chain cleavage enzyme (P450 scc ), 3 -hydroxysteroid dehydrogenase (3 HSD) and 17 -hydroxylase (P450 C17 ) in the fetal adrenal gland. ACTH 1-24 infusion (14·7 pmol/kg per h) to intact fetuses was without effect on the abundance of mRNA encoding MC2R and SF-1, irrespective of whether the infusion was given for 18 (115-132 days of gestation) or 32 days (115 days to term (147 days of gestation)). Hypophysectomy (HX) did not alter the expression of MC2R mRNA; however, the abundance of SF-1 mRNA fell by approximately 50% following the removal of the pituitary gland. ACTH 1-24 infusion to HX fetuses failed to restore levels of SF-1 mRNA to that seen in intact animals. P450 scc and 3 HSD mRNAs were increased by ACTH 1-24 infusion for 18 days in intact animals, although no effects of the infusion were seen on P450 C17 mRNA levels. For all three of these mRNAs, there was a significant increase in their abundance between 132 days of gestation and term in intact fetuses. By term, ACTH 1-24 infusion was without any additional effect on their abundance. HX decreased the expression of P450 scc , 3 HSD and P450 C17 mRNAs, while ACTH 1-24 infusion to HX fetuses increased the expression of these mRNAs to levels seen in intact animals. There were significant correlations between the abundance of the mRNA for P450 scc , 3 HSD and P450 C17 , but not MC2R and SF-1, and premortem plasma cortisol concentrations. These results emphasise the importance of the pituitary gland and ACTH in the regulation of the enzymes involved in adrenal steroidogenesis. Factors in addition to ACTH may also play some role, as the infusion was not always effective in increasing the abundance of the mRNAs. Surprisingly, the mRNA for MC2R and SF-1 did not appear to be regulated by ACTH in the late-gestation ovine fetus, though a pituitary-dependent factor may be involved in the regulation of SF-1 mRNA abundance.

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“…Estrone sulfate is a sulfo-conjugate of estrogen and is mainly derived from the conceptus during gestation in cattle 13 . Its concentrations in maternal blood…”

Section: Introductionmentioning

confidence: 99%

Changes in Plasma Estrogen Concentrations during the First Trimester of Gestation in Dairy Cows: Comparison with the Origin of Embryos and Fetal Number

Hirako

Takahashi

et al. 2003

JARQ

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The objectives of this study were to determine the profiles of plasma estrogen concentrations during the first trimester of gestation and to correlate them with the origin of the embryos and fetal number. Pregnancies were induced either by artificial insemination (AI) on the day of estrus (day 0) or by transfer of 1 or 2 blastocysts produced in vitro (IVF-ET) on day 7. Five singleton-bearing cows impregnated by AI, and 6 singleton and 6 twin pregnancies induced by IVF-ET were used in the experiment. Blood was collected by jugular venipuncture at 2 to 5-day intervals until day 100. The concentrations of plasma estrone, estradiol-17β and estrone sulfate were measured by using a radioimmunoassay. Concentrations of all the estrogens fluctuated at low levels until day 50 in all the groups. Thereafter, the concentration of estrone sulfate gradually increased, whereas those of estrone and estradiol-17β remained at basal levels until day 80. The concentration of estrone sulfate after day 50 was affected by the day of gestation and the number of fetuses. After day 80, the concentration of estrone sulfate increased drastically, coinciding with the increases in the estrone and estradiol-17β concentrations. The rate of increase in the concentration of estrone sulfate during days 80 to 100 was the highest among all the estrogens. In the singleton pregnancies, the concentrations of estrone and estrone sulfate between days 80 and 100 were higher in the artificially inseminated cows than in the IVF-ET cows. In the pregnancies induced by IVF-ET, estrone sulfate levels were higher in the twin-bearing cows than in the singleton-bearing cows during days 50 to 80 and 80 to 100. These results suggest that the concentrations of estrogens in bovine peripheral blood plasma could be applied for monitoring fetoplacental development in the first trimester of gestation.Discipline: Animal industry Additional key words: estradiol-17β, estrone, estrone sulfate, in vitro fertilization and multiple pregnancies JARQ 37 (3), 195 -200 (2003) http://www.jircas.affrc.go.jp Present address:

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Initiation of Parturition

Cited by 78 publications

References 636 publications

A Review of Advances in Artificial Insemination (AI) and Embryo Transfer (ET) in Sheep, with the Special Reference to Hormonal Induction of Cervical Dilation and its Implications for Controlled Animal Reproduction and Surgical Techniques

A Review of Advances in Artificial Insemination (AI) and Embryo Transfer (ET) in Sheep, with the Special Reference to Hormonal Induction of Cervical Dilation and its Implications for Controlled Animal Reproduction and Surgical Techniques

The role of the pituitary gland and ACTH in the regulation of mRNAs encoding proteins essential for adrenal steroidogenesis in the late-gestation ovine fetus

Changes in Plasma Estrogen Concentrations during the First Trimester of Gestation in Dairy Cows: Comparison with the Origin of Embryos and Fetal Number

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