Effect of Ovariectomy on Pregnancy Maintenance and Parturition in Dairy Cows

Estergreen, V.L.; Frost, O; Gomes, W. R.; Erb, R.E.; Bullard, J.F.

doi:10.3168/jds.s0022-0302(67)87615-x

Cited by 116 publications

(49 citation statements)

References 2 publications

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“…Moreover, the collapse of bovine placental progesterone production and an enhanced production of estrogens as a result of an increase in placental CYP17 activity was shown in in vitro studies (Schuler et al 1994). However, the signal cascade controlling the initiation of parturition in the cow must clearly be more complex than in the late pregnant sheep where the placenta is the sole significant source of progesterone (Denamur & Martinet 1955, Bassett et al 1969, Al-Gubory et al 1999, while in the cow it is the corpus luteum (Estergreen et al 1967, Day et al 1977a, 1977b, Chew et al 1979 with the prepartal decline in maternal progesterone levels clearly resulting from luteolysis (Hoffmann et al 1979). The bovine placenta contributes -if at all -only insignificantly to systemic maternal progesterone levels during late gestation (Comline et al 1974, Conley & Ford 1987 but is still capable of producing high local progesterone concentrations at the feto-maternal interface (Tsumagari et al 1994).…”

Section: Introductionmentioning

confidence: 99%

Investigations into the mechanisms controlling parturition in cattle

Shenavai

Preissing²,

Hoffmann³

et al. 2012

Reproduction

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A pronounced increase in fetal cortisol concentrations stimulating an increase in estrogen production at the expense of progesterone precursors in the placenta, luteolysis, and progesterone withdrawal is considered as a key event during the complex signal cascade leading to the initiation of parturition in cattle. However, there are many questions concerning the exact functional and/or temporal relationships between these individual processes which finally result in the expulsion of the calf and the timely release of the placenta. Thus, parturition was induced in 270-day pregnant cows using the progesterone receptor blocker aglepristone (group AG, nZ3), the prostaglandin F 2a analog cloprostenol (group PG, nZ4), and the glucocorticoid dexamethasone (group GC, nZ4) to characterize the effect on maternal steroid and prostaglandin levels and to identify immediate subsequent changes in placental morphology and gene expression as compared with untreated controls sampled on day 272 (group D272, nZ3) and cows during normal parturition (group NT, nZ4). All calves of the treatment groups were born on days 271-272, whereas gestational length in NT cows was 280.5G1.3 days. However, none of the treatments significantly induced the prepartal remodeling of placentomes characterized by a decline in trophoblast giant cells and reduction of the caruncular epithelium. Data on placental CYP17 and COX2 expression confirm that these key enzymes are upregulated by GC, whereas placental aromatase expression was not affected by any treatment. Maternal progesterone and prostaglandin profiles suggest differential effects of the treatments on luteal function and placental or uterine prostaglandin production. The results provide new information on the initiation of parturition in cattle but raise many new questions.

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Section: Introductionmentioning

confidence: 99%

Investigations into the mechanisms controlling parturition in cattle

Shenavai

Preissing²,

Hoffmann³

et al. 2012

Reproduction

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“…Data on the mRNA levels of StAR, P450scc, and 3b-HSD during the first 4 months of gestation in cows (Veduzco et al, 2008), on the other hand, suggest that the maternal caruncles exhibit greater steroidogenic capacity than the foetal cotyledons in the first half of gestation. Regardless of whether the maternal caruncles or the foetal cotyledons produce more progesterone in the first half of gestation, there is insufficient progesterone produced from the placenta to sustain the pregnancy if the CL is lost during the first 5-6 months of pregnancy (Estergreen et al, 1967;Erb et al, 1968;Chew et al, 1979).…”

Section: Compartmentalization Of Progesterone Synthesismentioning

confidence: 99%

“…Unlike humans and sheep, wherein the placenta replaces the CL as the major site of progesterone production relatively early in gestation (Moore et al, 1972;Simpson and MacDonald, 1981), the CL in the pregnant cow continues to produce progesterone and remains an important source of progesterone until near term (Estergreen et al, 1967;Chew et al, 1979), even though evidence suggests that luteal function and secretory capacity decline in late gestation (Shemesh et al, 1983). Although the bovine placenta is steroidogenically active at an early stage of gestation, its capacity to fully replace the CL in producing enough progesterone to maintain the pregnancy is restricted to the later stages of gestation, from about days 180 to 200 onwards (Erb et al, 1968;Chew et al, 1979); in experiments where the CL was removed and the pregnancy survived, the animals gave birth prematurely (Estergreen et al, 1967). Generally, the bovine placenta contributes less progesterone to the maternal circulation than does the placenta of ewes or women (Geisert and Conley, 1998).…”

Section: Progesterone Productionmentioning

confidence: 99%

Multilevel regulation of steroid synthesis and metabolism in the bovine placenta

Nguyen

Conley

Soboleva

et al. 2012

Molecular Reproduction Devel

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SUMMARYSteroid hormones play critical roles in almost all physiological processes in male and female reproduction. In a normal pregnancy, the concentrations of steroid hormones in maternal and foetal blood vary with gestation in response to changing needs. The placenta plays a central role in producing the appropriate steroids to support the pregnancy by coordinating its own steroidogenic activity with that of the corpus luteum and responding to foetal signals. Although much is known about the steroidogenic potential of the bovine placenta, far less is known about how the placenta integrates the synthesis of steroids with their subsequent metabolism and clearance to achieve appropriate local and peripheral concentrations of steroids in maternal and foetal blood at each stage of gestation. This review focuses on the current knowledge of the temporal and spatial regulation and compartmentalization of the biochemical pathways by which potent steroid hormones are synthesized and metabolized in the bovine placenta. The aim is to increase our understanding of how the balance of synthesis and metabolism determines placental steroid output as it changes with development and differentiation, and how this is regulated in response to the variations in the foetal signals and luteal secretory activity. The review highlights knowledge gaps and suggests that mathematical modelling can help understand the effect of different levels of regulation on the steroidogenic output of an organ, such as the bovine placenta.

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“…The ovary is the main secretory source of progestin and estrogen and is indispensable to maintenance of pregnancy throughout gestation in many mammals, including cows (Estergreen et al 1967), goats (Meites et al 1951), dogs (Verstegen-Onclin & Verstegen 2008), and/or rabbits (Pickworth & Lamming 1967). On the other hand, an ovariectomy at mid-pregnancy or the later trimester of pregnancy does not disrupt the process of pregnancy in several mammals, including humans (Csapo et al 1972), monkeys (Albrecht et al 2000), guinea pigs (Bland & Donovan 1969), and/or mares (Hinrichs et al 1987), whose progestin and estrogen are supplied by other tissues such as the placenta.…”

Section: Introductionmentioning

confidence: 99%

The complete control of murine pregnancy from embryo implantation to parturition

Terakawa¹,

Watanabe²,

Obara³

et al. 2012

Reproduction

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The ovary is the main secretory source of progestin and estrogen and is indispensable to the maintenance of all events of pregnancy in mice. The purpose of this study was to control all processes of pregnancy in mice, from embryo implantation to parturition, without ovaries. The ovaries were removed before embryo implantation, and a single injection of medroxyprogesterone acetate (MPA) was given. Embryo implantation was induced by leukemia inhibitory factor, which can substitute 17b-estradiol (E 2 ). Continuous exposure to E 2 was necessary at mid-pregnancy, when placentation was completed. All mice sustained pregnancy without ovaries before parturition, which was initiated by the removal of E 2 and MPA. Murine pregnancy is a complicated process involving embryo implantation, placentation, and parturition. Complete control of pregnancy was achieved with the simple treatment of MPA and E 2 after induction of embryo implantation. Here, time-dependent events in the uterus during pregnancy could be realized without the ovaries, because the initiation of each event could be stringently controlled by hormonal treatments.

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Effect of Ovariectomy on Pregnancy Maintenance and Parturition in Dairy Cows

Cited by 116 publications

References 2 publications

Investigations into the mechanisms controlling parturition in cattle

Investigations into the mechanisms controlling parturition in cattle

Multilevel regulation of steroid synthesis and metabolism in the bovine placenta

The complete control of murine pregnancy from embryo implantation to parturition

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