Prenatal maturation, the timing of birth and how it may be regulated in domestic animals

Silver, M.

doi:10.1113/expphysiol.1990.sp003405

Cited by 115 publications

(125 citation statements)

References 67 publications

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“…However, the present data show that IVM-IVF procedures alone alter the duration of gestation, and as the birth is triggered by the fetus (Silver, 1990), the prolongation of gestation alone is likely to be a result of physiological changes in the fetus.…”

Section: Discussionmentioning

confidence: 53%

Embryo viability, duration of gestation and birth weight in sheep after transfer of in vitro matured and in vitro fertilized zygotes cultured in vitro or in vivo

Holm¹,

Walker²,

Seamark³

1996

Reproduction

130

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The influence of various in vitro procedures on embryo survival and the production of normal offspring was investigated in sheep. Zygotes with both in vivo cultured IVM\p=n-\IVF zygotes and control zygotes 25\p=n-\35% versus 51\p=n-\60%, respectively, P < 0.05). Day 6.5 IVM\p=n-\IVFmorulae had a lower survival rate than did control morulae regardless of culture treatment (P < 0.05), while survival rates of day 6.5 IVM\p=n-\IVF blastocysts cultured in vivo did not differ from those of control blastocysts (P > 0.1). Both the gestation period and birth weight of IVM\p=n-\IVFlambs were increased when compared with controls, the former significantly in all groups (154.0\p=n-\154.9days versus 150.6 days; P < 0.01), while the latter increase was on the borderline of significance (4\ m=. \ 5\ p=n-\ 4\ m=. \ 8 kg versus 4.0 kg; 0.01 \m=le\P \m=le\0.1, respectively) and dependent on the prolongation of the gestation period. It is concluded that in vitro maturation and fertilization compromise subsequent embryonic and fetal development in sheep irrespective of the subsequent in vivo or in vitro culture treatment. Subjecting IVM\p=n-\IVF zygotes to in vivo culture for 6.5 days minimizes only some of these effects, thus leading to the aberrant production of some offspring.

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Section: Discussionmentioning

confidence: 53%

Embryo viability, duration of gestation and birth weight in sheep after transfer of in vitro matured and in vitro fertilized zygotes cultured in vitro or in vivo

Holm¹,

Walker²,

Seamark³

1996

Reproduction

130

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“…In a sense, all fetal growth is metabolically constrained (Vatnick et al 1991, Gluckman et al 1992 and increasing fetal size in late gestation places greater demands on maternal metabolism and transplacental transfer of nutrients (Schneider 1996). Poor maternal weight gain, fetal growth restriction and maternal fasting have all been identified as factors associated with premature delivery in humans and domestic species (Silver 1990, Ott 1993, Hediger et al 1995, McMillen et al 1995. Cord blood concentrations of leptin correlate with birthweight and fat mass (Jaquet et al 1998, Geary et al 1999, suggesting that leptin might signal information to the fetal HPA axis about fetal metabolic status.…”

Section: Introductionmentioning

confidence: 99%

The late gestation increase in circulating ACTH and cortisol in the fetal sheep is suppressed by intracerebroventricular infusion of recombinant ovine leptin

Howe¹,

Gertler²,

Challis³

2002

Journal of Endocrinology

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The obese gene product leptin, originally characterised as an adipocyte hormone coordinating the behavioural and neuroendocrine responses to starvation, is expressed in fetal adipocytes and placental trophoblast cells and is present in the fetal circulation. Concentrations of leptin in fetal blood correlate with fetal bodyweight and fat mass. In post-natal life, leptin conveys information about calorie intake and the state of adipose tissue energy stores, and plasma leptin levels are generally inversely correlated with hypothalamo-pituitary adrenal (HPA) activity. Late fetal life is characterised by increasing HPA activity that prepares the fetus for extrauterine life and initiates the endocrine cascade leading to parturition. We have investigated the hypothesis that leptin in the fetal circulation can inhibit the fetal HPA axis, thereby providing a mechanism by which the fetus can determine the fine timing of parturition as long as it is adequately nourished and growing appropriately. Here we show that a 5-day intracerebroventricular infusion of leptin to the sheep fetus in late gestation inhibits the pre-parturient rise in ACTH and cortisol concentrations, and that this seems to be a centrally mediated effect.

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“…During late pregnancy, fetal cortisol plays a major part in maturation of several fetal organ systems, including the lung, liver, kidneys and gut (Fowden et al 1998). In the fetal liver, glucocorticoids regulate hepatic functions, including lipid and carbohydrate metabolism (Silver 1990, Jamieson et al 1999. Cortisol reaches the liver from the systemic circulation, or may be produced locally under the influence of the enzyme 11 -hydroxysteroid dehydrogenase (11 -HSD).…”

Section: Introductionmentioning

confidence: 99%

Effects of cortisol and oestradiol on hepatic 11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor proteins in late-gestation sheep fetus

Gupta¹,

Alfaidy²,

Holloway³

et al. 2003

Journal of Endocrinology

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In the late-gestation sheep, increased fetal plasma cortisol concentration and placental oestradiol (E 2 ) output contribute to fetal organ maturation, in addition to the onset of parturition. Both cortisol and E 2 are believed to regulate the enzyme 11 -hydroxysteroid dehydrogenase type 1 (11 -HSD1), which interconverts bioactive 11-hydroxy glucocorticoids and their inactive 11-keto metabolites. 11 -HSD1, abundantly expressed in fetal liver, operates primarily as a reductase enzyme to produce bioactive cortisol and thus regulates local hepatic glucocorticoid concentrations. Cortisol acts through the glucocorticoid receptor (GR) present in the liver. In this study, we examined the effects of cortisol and E 2 on hepatic 11 -HSD1 and GR in the liver of chronically catheterized sheep fetuses treated with saline (n=5), cortisol (1·35 mg/ h; n=5), saline+4-hydroxyandrostendione, a P450 aromatase inhibitor (4-OHA; 1·44 mg/h; n=5), or cortisol+4-OHA (n=5). Cortisol infusion resulted in increased plasma concentrations of fetal cortisol and E 2 ; concurrent administration of 4-OHA attenuated the increase in plasma E 2 concentrations. Using immunohistochemistry, we showed that fetal hepatocytes expressed both 11 -HSD1 and GR proteins. Cortisol treatment increased GR in both cytosol and nuclei of hepatocytes; concurrent administration of 4-OHA was associated with distinct nuclear GR staining. Western blot revealed that cortisol, in the absence of increased E 2 concentrations, significantly increased concentrations of 11 -HSD1 (34 kDa) and GR (95 kDa) proteins. 11 -HSD1 enzyme activity was measured in the liver microsomal fraction in the presence of [ + (dehydrogenase activity) respectively. 11 -HSD1 reductase activity was significantly greater in the presence of cortisol. In summary, we found that, in sheep during late gestation, cortisol increased both 11 -HSD1 and GR in the fetal liver, and these effects were accentuated in the absence of increased E 2 .

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Prenatal maturation, the timing of birth and how it may be regulated in domestic animals

Cited by 115 publications

References 67 publications

Embryo viability, duration of gestation and birth weight in sheep after transfer of in vitro matured and in vitro fertilized zygotes cultured in vitro or in vivo

Embryo viability, duration of gestation and birth weight in sheep after transfer of in vitro matured and in vitro fertilized zygotes cultured in vitro or in vivo

The late gestation increase in circulating ACTH and cortisol in the fetal sheep is suppressed by intracerebroventricular infusion of recombinant ovine leptin

Effects of cortisol and oestradiol on hepatic 11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor proteins in late-gestation sheep fetus

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