Fetal metabolism and fetal growth

Jones, C. T.

doi:10.1530/jrf.0.0470189

Cited by 31 publications

(7 citation statements)

References 86 publications

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“…The magnitude in the rise of glucose is similar to that previously reported in the fetal lamb during hypoxia or epinephrine infusion (21). The rise in IRG of approximately 3-fold approximates closely the spontaneous surge observed in the newborn of several species including lamb and human neonates (15,17,35).…”

Section: Discussionsupporting

confidence: 85%

Adrenergic Modulation of Pancreatic Hormone Secretion in Utero: Studies in Fetal Sheep

et al. 1980

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SummaryT o assess the functional maturity of adrenergic modulation of plasma concentration of glucose, a s well a s immunoreactive glucagon (IRC) and immunoreactive insulin (IRI) secretion in utero, adrenergic agonists with or without / 3 (propranolol) or a (phentolamine) antagonists were infused to the chronically catheterized sheep fetus (n = 35) late in the third trimester. Mean f S.E. days at study was 129.5 f 1.5; term is 150 days. In 9 separate studies at gestational age 129 f 1 days, the infusion of saline for 3 hr was not associated with significant changes in the basal levels of glucose, IRC, or IRI.With epinephrine, 6 pg/min (n = 6) glucose rose from 16.7 f 3.6 to 41.9 f 9.7 mg/dl, IRC rose from 75 f 8 to 219 f 45 pg/ml, and IRI fell from 22.6 + 1.7 t o 12.7 + 3.5 microunits/ml ( P < 0.05 for each). Propranolol alone (n = 4) did not alter basal glucose or IRC but significantly suppressed IRI. Propranolol did, however, markedly attentuate the rise in glucose and IRC while exaggerating the fall in IRI during epinephrine infusion. Qualitatively similar but smaller responses were obtained with epinephrine. 0.4 pg/min (n = 10). Similarly, elevation of glucose and suppression of IRI was obtained with norepinephrine, 2 gg/min (n = 5), but IRC levels did not rise significantly. a-Adrenergic blockade alone augmented IRI from 18 + 3 to 38 + 5 microunits/ml without affecting glucose or IRC concentrations; during a blockade, norepinephrine infusion failed to induce the rise in glucose, IRG remained unchanged, and IRI remained elevated (n = 5). 2-Deoxy-D-glucose, 200 mg IV over 30 min, did not affect glucose, IRG, or IRI (n = 5). Thus, appropriate adrenergic modulation of plasma concentrations of glucose, and of IRG and IR1 secretion is established in the third trimester.following placental separation and abrupt cessation of the transfer of nutrients from mother to fetus, thereby suggesting that hypoglycemia acts as the stimulus for the observed changes (15,-17). We have recently reported that in newborn lambs there is a similar 5-fold surge of IRG within minutes of delivery, whereas plasma IRI remains low and unchanged (17). In newborn lambs, however, there was no fall in plasma glucose concentration following delivery, so that unless curtailment of a different major nutrient for the lamb acts as the trigger for IRG secretion, hypoglycemia is not the stimulus for the observed surge in IRG. An abrupt increase in catecholamine secretion at birth could adequately explain the . .observed changes because catecholamines are-known to stimulate glucagon secretion, inhibit insulin secretion, and mobilize free fatty acids (9,12,19,23,26,29,32,38). A rise in circulating free fatty acid levels does occur shortly after delivery (1, 17). Moreover, catecholamines increase markedly and abruptly in the arterial plasma of newborns at delivery (10. 24), and urinary excretion of epinephrine increases in the initial hours of life (27). If this hypothesis regarding the role of catecholamines as the trigger for the observed neonatal cha...

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Section: Discussionsupporting

confidence: 85%

Adrenergic Modulation of Pancreatic Hormone Secretion in Utero: Studies in Fetal Sheep

et al. 1980

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“…In addition, the relative size of the placenta accounts for 41% of variation in fetal survival in the tenrec, with smaller mean placental size being associated with lower survival (Nicoli, 1985). The placenta can influence the quality and ratio of nutrients through its ability to synthesize amino acids, lipids and other compounds, including hormones which may influence maternal metabolism (Szabo & Grimaldi, 1970;Burd et ai, 1975;Jones, 1976). Whatever reasons are invoked, the observed variation in fetal weight of up to 273% is unusually high.…”

Section: Discussionmentioning

confidence: 99%

Follicular development, ovulation, fertilization and fetal development in tenrecs (Tenrec ecaudatus)

Nicoll¹,

Racey²

1985

Reproduction

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Reproduction in female tenrecs was studied on Praslin Island (4 degrees 20'S, 55 degrees 45'E) in the Seychelles from November 1977 to September 1980. Dissection and histological examination of reproductive tracts revealed that each ovary is encapsulated in a bursa. Polyovular follicles were abundant and contained up to 5 oocytes. The occurrence of more implanted fetuses than corpora lutea (CL) indicated successful polyovuly in 25% of pregnancies. No antrum was observed during follicular growth at oestrus, and follicles were relatively small at maturation, reaching a maximum diameter of 570 microns. Ovulation involves a gentle extrusion of the granulosa and ovum into the periovarian space. Spermatozoa were abundant in the female reproductive tract including the periovarian space at oestrus. Spermatozoa penetrated the loosely-packed theca of mature follicles and were present in CL, indicating that intrafollicular fertilization may occur. The relatively small CL formed by eversion, reaching a maximum size after implantation. Fusion of up to four CL occurred in the ovaries of 41% of pregnant females. Polyovulation in the tenrec was confirmed by the occurrence of 10.4 +/- 0.5 (mean +/- s.e.m.) CL and 9.7 +/- 0.5 (mean +/- s.e.m.) implantations. Resorption occurred in 74% of 19 dissectable pregnancies, occurring in both uterine horns in 26% of pregnancies. Coefficients of variation in weights of fetuses in each litter were 10.0-26.8%, with the largest value corresponding to 273% variation in fetus weights. Litter size in the Seychelles tenrecs was smaller than in the same species in Madagascar (17.1 +/- 1.9 implantations) where the tenrec is native.

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“…Hormones that antagonize the effects of insulin modulate insulin receptor characteristics in both the adult (2,12,16,25) and fetus (1 1,34). Insulin influences the growth and metabolism of fetal organs (18,30). T4 and glucocorticoids may modify this effect of insulin, since both these hormones have been demonstrated to alter the insulin receptors (10,11,34).…”

mentioning

confidence: 99%

A Differential Effect of Thyroxine and Glucocorticoids on Fetal Brain and Heart Insulin Receptor

1985

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Fetal metabolism and fetal growth

Cited by 31 publications

References 86 publications

Adrenergic Modulation of Pancreatic Hormone Secretion in Utero: Studies in Fetal Sheep

Adrenergic Modulation of Pancreatic Hormone Secretion in Utero: Studies in Fetal Sheep

Follicular development, ovulation, fertilization and fetal development in tenrecs (Tenrec ecaudatus)

A Differential Effect of Thyroxine and Glucocorticoids on Fetal Brain and Heart Insulin Receptor

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