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PubMed2002

Steroidogenic acute regulatory protein expression is decreased in the adrenal gland of the growth-restricted sheep fetus during late gestation.

Functional development of the adrenal cortex is critical for fetal maturation and postnatal survival. In the present study, we have determined the developmental profile of expression of the mRNA and protein of an essential cholesterol-transporting protein, steroidogenic acute regulatory protein (StAR), in the adrenal of the sheep fetus. We have also investigated the effect of placental restriction (PR) on the expression of StAR mRNA and protein in the growth-restricted fetus. Adrenal glands were collected from fetal sheep at 82-91 days (n = 10), 125-133 days (n = 10), and 140-144 days (n = 9) and from PR fetuses at 141-145 days gestation (n = 9) (term = 147 +/- 3 days gestation). The adrenal StAR mRNA:18S rRNA increased (P < 0.05) between 125 days (7.44 +/- 1.61) and 141-144 days gestation (13.76 +/- 1.88). There was also a 13-fold increase (P < 0.05) in the amount of adrenal StAR protein between 133 and 144 days gestation in these fetuses. However, the amount of StAR protein (6.9 +/- 1.7 arbitrary densitometric units [AU]/microg adrenal protein) in the adrenal of the growth-restricted fetal sheep was significantly reduced, when compared with the expression of StAR protein (17.1 +/- 1.9 AU/microg adrenal protein) in adrenals from the age-matched control group. In summary, there is a developmental increase in the expression of StAR mRNA and protein in the fetal sheep adrenal during the prepartum period when adrenal growth and steroidogenesis is dependent on ACTH stimulation. We have found that, while the level of expression of StAR protein is decreased in the adrenal gland of the growth-restricted fetus during late gestation, this does not impair adrenal steroidogenesis. Our data also suggest that the stimulation of adrenal growth and steroidogenesis in the growth-restricted fetus may not be ACTH dependent.

Adrenal Glands↗
PubMed2003

Genomic and transcriptional alterations in mouse fetus liver after transplacental exposure to cigarette smoke.

The transplacental exposure of fetuses to maternal cigarette smoke may increase the risk of developmental impairments, congenital diseases, and childhood cancer. The whole-body exposure of Swiss mice to environmental cigarette smoke (ECS) during pregnancy decreased the number of fetuses per dam, placenta weight, and fetus weight. ECS increased DNA adducts, oxidative nucleotide alterations, and cytogenetic damage in fetus liver. Evaluation by cDNA array of 746 genes showed that 61 of them were expressed in fetus liver under basal conditions. The oral administration of N-acetylcysteine (NAC) during pregnancy enhanced the expression of three genes only, including two glutathione S-transferases and alpha1-antitrypsin precursor, whose deficiency plays a pathogenetic role in congenital emphysema. Transplacental ECS upregulated the expression of 116 genes involved in metabolism, response to oxidative stress, DNA and protein repair, and signal transduction. NAC inhibited the ECS-related genetic damage and upregulation of most genes. ECS stimulated pro-apoptotic genes and genes downregulating the cell cycle, which may justify growth impairments in the developing fetus. Thus, both genetic and epigenetic mechanisms were modulated by ECS. Moreover, hypoxia-related genes and several oncogenes and receptors involved in proliferation and differentiation of leukocytes were induced in the fetal liver, which also bears hematopoietic functions.

Acetylcysteine↗
PubMed2004

Mathematical models of the embryo and fetus for use in radiological protection.

This development of new mathematical models arose from our current work in external neutron dosimetry for the embryo and fetus when pregnant women travel at commercial aircraft altitudes. A problem of concern in radiation protection is exposure of pregnant women to ionizing radiation because of the high radiosensitivity of the embryo and fetus. Special regulations and dosimetric considerations are necessary for pregnant women at the work place and in the public. To perform dosimetry, mathematical models for the embryo and the fetus, together with the modified adult female model for pregnant woman, are required. There are no models available for embryo. Models developed for the fetus need to be updated with the new reference values such as those in ICRP Publication 89. This article presents mathematical models for the embryo and fetus at different stages: the embryo at 8 wk and the fetus at the end of each trimester. In addition to fetal skeleton, the fetal brain is explicitly modeled because of its high radiosensitivity. All model parameters are determined from the most recent reference values available. The models are designed so that an interpolation can be easily performed to generate a model of embryo/fetus at any given stage of development. This feature also allows convenient adaptation of the models to different reference values representing various ethnic populations. The new mathematical models presented here were developed for external dosimetry. They can also be used for internal dosimetry purposes, if other organs inside the female phantom are adjusted accordingly.

Adult↗
PubMedDate not supplied

Cardiopulmonary bypass in ewe's fetus: advances and setbacks in our learning curve.

Fetal cardiac surgery represents a surgical challenge and several centers are attempting to establish a suitable methodology in animals. We present our experience with extra-corporeal bypass procedures in preterm and term sheep fetuses. Twenty-two fetuses (103-139 days gestation, mean 115 days gestation) underwent a 1-hour period of right heart-to-pulmonary artery extracorporeal circulation followed by 1 hour of observation. Animals were divided into group 1 and group 2, according to gestational age (above and below 0.85). Three pumps were used: centrifugal without (group 1) reservoir, centrifugal with (group 2) reservoir, and roller with reservoir (group 2). Experiments were completed in 75% of fetuses in group 1 and in 37% of fetuses in group 2. Bleeding was the main cause of failure, especially for group 2. A slow deterioration of blood gas status was noted in group 1, while this trend could be partially reversed in group 2 with corrective measures. Complete heart bypass could not be achieved in either group, and residual fluctuations in arterial pressure were observed. During bypass, body temperature decreased more in group 2 than in group 1. We conclude that cardiac bypass is feasible over a short period in near-term fetuses. A successful outcome may also be obtained in younger fetuses, but better measures need to be implemented for the prevention of surgical bleeding.

Animals↗
PubMed2006

Intrauterine proximity to male fetuses affects the morphology of the sexually dimorphic nucleus of the preoptic area in the adult rat brain.

Previous studies on polytocous rodents have revealed that the fetal intrauterine position influences its later anatomy, physiology, reproductive performance and behavior. To investigate whether the position of a fetus in the uterus modifies the development of the brain, we examined whether the structure of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of rat brains accorded to their intrauterine positions. Brain sections of adult rats gestated between two male fetuses (2M) and between two female fetuses (2F) in the uterus were analysed for their immunoreactivity to calbindin-D28k, which is a marker of the SDN-POA. The SDN-POA volume of the 2M adult males was greater than that of the 2F adult males, whereas the SDN-POA volume of the 2M and 2F adult females showed no significant difference. This result indicated that contiguous male fetuses have a masculinizing effect on the SDN-POA volume of the male. To further examine whether the increment of SDN-POA volume in adulthood was due to exposure to elevated steroid hormones during fetal life, concentrations of testosterone and 17beta-estradiol in the brain were measured with 2M and 2F fetuses during gestation, respectively. On gestation day 21, the concentrations of testosterone and 17beta-estradiol in the brain were significantly higher in the 2M male rats as compared with the 2F male rats. The results suggested that there was a relationship between the fetal intrauterine position, hormone transfer from adjacent fetuses and the SDN-POA volume in adult rat brains.

Animals↗
PubMed1998

Developmental regulation of glucogenesis in the sheep fetus during late gestation.

1. Using tracer methodology, endogenous glucose production was measured in twenty-six chronically catheterized sheep fetuses during normal fed conditions and in response to a 48 h period of maternal fasting at different gestational ages during the last 10-15 days of gestation (term, 145 +/- 2 days). 2. In normal fed conditions, the rate of fetal glucose production was negligible until 143-145 days when it rose significantly to account for 50 % of the glucose used by the fetus. The rise in fetal glucogenesis towards term closely parallelled the normal prepartum rise in fetal plasma cortisol and catecholamines. 3. Maternal fasting for 48 h induced endogenous glucose production in fetuses at 139-141 days but not at 133-135 days of gestation. Maternal fasting also induced increases in the plasma cortisol and noradrenaline levels in all the fetuses studied. Fetal plasma cortisol levels at the end of the fast and the increment in fetal plasma cortisol during maternal fasting were significantly greater in the older groups of fasted animals. 4. When the data from all the fetuses were combined, partial correlation analysis of fetal glucose production and the log plasma concentrations of cortisol and total catecholamines showed that plasma cortisol was the predominant regulator of fetal glucogenesis during late gestation. However, once plasma cortisol levels exceeded 17.5 ng ml-1, plasma catecholamines were a major influence on fetal glucogenesis. 5. The results show that glucogenesis occurs in fetal sheep during late gestation in conditions in which the fetal plasma concentrations of cortisol and catecholamines are elevated. They also suggest that cortisol enhances the capacity for glucogenesis in utero, while catecholamines actually activate glucose production in sheep fetuses close to term.

Animals↗
PubMed1999

Adrenergic and vasopressinergic contributions to the cardiovascular response to acute hypoxaemia in the llama fetus.

1. The effects of fetal intravenous treatment with phentolamine or a vasopressinergic V1-receptor antagonist on the fetal cardiovascular responses to acute hypoxaemia in the llama were investigated. 2. Six llama fetuses were surgically prepared between 60 and 70 % of gestation under general halothane anaesthesia with vascular catheters and transit-time ultrasonic flow probes around a carotid artery and a femoral artery. At least 4 days after surgery all fetuses were subjected to a 3 h experiment: 1 h of normoxia, 1 h of hypoxaemia and 1 h of recovery while on slow i.v. infusion with saline. On separate days this experiment was repeated with fetal i.v. treatment with either phentolamine or a V1-receptor antagonist dissolved in saline. 3. During saline infusion all llama fetuses responded to acute hypoxaemia with intense femoral vasoconstriction. Phentolamine during normoxia produced hypotension, tachycardia and vasodilatation in both the carotid and the femoral circulations. During hypoxaemia, fetuses treated with phentolamine did not elicit the pronounced femoral vasoconstriction and all died within 20 min of the onset of hypoxaemia. A V1-receptor antagonist produced a femoral vasodilatation during normoxia but did not affect the fetal cardiovascular responses to acute hypoxaemia. 4. In conclusion, alpha-adrenergic and V1-vasopressinergic mechanisms contribute to a basal vasoconstrictor tone in the femoral circulation in the llama fetus. The enhanced femoral vasoconstriction during acute hypoxaemia in the llama fetus is not mediated by stimulation of V1-vasopressin receptors, but is dependent on alpha-adrenergic receptor stimulation. Such alpha-adrenergic efferent mechanisms are indispensable to fetal survival during hypoxaemia in the llama since their abolition leads to cardiovascular collapse and death.

Adrenergic alpha-Antagonists↗
PubMed1994

Doppler colour flow imaging of fetal intracerebral arteries and umbilical artery in the small for gestational age fetus.

OBJECTIVE: To assess with Doppler colour flow imaging whether a brain-sparing effect is present in all cerebral arteries of the circle of Willis in the small for gestational age fetus, to determine which cerebral flow velocity parameter is most discriminating in this pathological condition, and to relate this parameter to the umbilical artery pulsatility index. DESIGN: Prospective, cross-sectional, matched case-control study. SETTING: Academic department of obstetrics and gynaecology. SUBJECTS: Twenty-eight small for gestational age fetuses and 28 normal controls at 24 to 38 weeks of gestation. INTERVENTIONS: Blood flow velocity waveforms from the umbilical and fetal intracerebral arteries were studied with Doppler colour flow imaging for measurement of peak systolic, end-diastolic and time averaged velocities, and calculation of the pulsatility index. MAIN OUTCOME MEASURES: Comparison of intracerebral and umbilical artery waveform parameters between small for gestational age fetuses and controls. RESULTS: Acceptable flow velocity waveforms were obtained in the intracerebral circulation in more than 85%. In small for gestational age fetuses, all intracerebral arteries displayed reduced downstream impedance. The end-diastolic velocities of the middle and anterior cerebral artery are the most discriminative factors between small for gestational age fetuses and controls. The highest sensitivity was reached for the umbilical artery pulsatility index. CONCLUSIONS: Doppler colour flow imaging allows easy identification of fetal intracerebral arterial vasculature. Whereas for the intracranial vasculature, the end-diastolic blood flow velocities in the anterior and middle cerebral artery are the most sensitive parameters discriminating between small for gestational age and controls, umbilical artery pulsatility index remains the best indicator for the small for gestational age fetus.

Adolescent↗
PubMed2006

Cerebral blood flow and oxygenation in ovine fetus: responses to superimposed hypoxia at both low and high altitude.

For the fetus, although the roles of arterial blood gases are recognized to be critical in the regulation of cerebral blood flow (CBF) and cerebral oxygenation, the relation of CBF, cortical tissue P(O2) (tP(O2)), sagittal sinus P(O2), and related indices of cerebral oxygenation to arterial blood gases are not well defined. This is particularly true for that fetus subjected to long-term hypoxia (LTH). In an effort to elucidate these interrelations, we tested the hypothesis that in the fetus acclimatized to high altitude, cerebral oxygenation is not compromised relative to that at low altitude. By use of a laser Doppler flowmeter with a fluorescent O2 probe, in near-term fetal sheep at low altitude (n = 8) and those acclimatized to high altitude hypoxia (3801 m for 90 +/- 5 days; n = 6), we measured laser Doppler CBF (LD-CBF), tP(O2), and related variables in response to 40 min superimposed hypoxia. At both altitudes, fetal LD-CBF, cerebral O2 delivery, tP(O2), and several other variables including sagittal sinus P(O2), correlated highly with arterial P(O2) (P(a,O2)). In response to superimposed hypoxia (P(a,O2) = 11 +/- 1 Torr), LD-CBF was significantly blunted at high altitude, as compared with that at low altitude. In the two altitude groups fetal cerebral oxygenation was similar under both control conditions and with superimposed hypoxia, cortical tP(O2) decreasing from 8 +/- 1 and 6 +/- 1 Torr, respectively, to 2 +/- 1 Torr. Also, for these conditions sagittal sinus P(O2) and [HbO2] values were similar. In response to superimposed hypoxia, cerebral metabolic rate for O(2) decreased approximately 50% in each group (P < 0.05). For both the fetus at low altitude and that acclimatized to high altitude LTH, we present the first dose-response data on the relation of LD-CBF, cortical tP(O2), and sagittal sinus blood gas values to P(a,O2). In addition, despite differences in several variables, the fetus at high altitude showed evidence of successful acclimatization, supporting the hypothesis that such fetuses demonstrate no compromise in cerebral oxygenation.

Altitude↗
PubMed2000

Chronic atrophic gastritis in SCID mice experimentally infected with Campylobacter fetus.

Campylobacter fetus is a cause of enteritis and invasive extraintestinal disease in humans. In order to develop an animal model of C. fetus infection, outbred ICR SCID mice were orally challenged with a clinical isolate of C. fetus. The stomachs of SCID mice were heavily colonized with C. fetus, and colonization was associated with the development of chronic atrophic gastritis. This lesion was characterized by an inflammatory infiltrate of granulocytes and macrophages that over time resulted in a loss of specialized parietal and chief cells in the corpus and the appearance of a metaplastic mucous epithelium. This lesion bears similarity to that encountered during experimental murine infection with Helicobacter pylori or Helicobacter felis. Despite colonization of the cecum and colon tissues by C. fetus in SCID mice, no lesions were noted in these tissues. A follow-up study confirmed these findings for SCID mice and also demonstrated that C. fetus could also infect the gastric mucosa of wild-type, outbred ICR mice. However, in ICR mice, the anatomic extent of colonization was more limited and the severity of inflammation and epithelial alterations was significantly less than that observed in infected SCID mice. The stomach may represent an unrecognized environmental niche for Campylobacter species.

Animals↗
PubMed1981

Evaluation of transport and storage techniques for isolation of Campylobacter fetus subsp. jejuni from turkey cecal specimens.

Immediate culturing of fecal specimens is not always possible, and appropriate methods for transport and storage of Campylobacter fetus subsp. jejuni specimens have not been fully evaluated. Using nine techniques, we studied the survival of C. fetus subsp. jejuni in cecal specimens from infected turkeys. The organisms survived in specimens held without transport medium for 3 to 15 days (median, 9 days) at 4 degrees C, and 2 to 9 days (median, 4 days) at 25 degrees C. Only 20% of specimens frozen for 24 h at either -20 or -70 degrees C yielded C. fetus subsp. jejuni. Specimens dried on filter paper strips were negative for C. fetus subsp. jejuni within 1.5 h. Cary-Blair medium with decreased agar was the best of the six transport media tested, it enabled recovery of the organism from 100% (3 days) and 71% (7 days) of cecal samples held at 4 degrees C and 94% (3 days) and 85% (7 days) of cecal specimens held at 25 degrees C. In contrast, more than half of all cecal specimens held at 4 or 25 degrees C in Culturettes or buffered glycerol saline were negative by 3 days, and all were negative at 7 days. Results with the other three media studied (Campy-thio, thioglycolate medium, and alkaline peptone water) were intermediate. Overnight incubation of specimens in alkaline peptone water at 37 or 42 degrees C did not enhance recovery of C. fetus subsp. jejuni. Therefore, refrigeration without a transport medium is satisfactory for up to 3 days for recovery of C. fetus subsp. jejuni from specimens, however, we recommend the use of Cary-Blair medium with decreased agar for specimens that must be transported or stored for longer than 3 days and for rectal swabs, to prevent drying.

Animals↗
PubMed1982

Hippurate hydrolysis by and triphenyltetrazolium tolerance of Campylobacter fetus.

A rapid test of hippurate hydrolysis and a test of tolerance to triphenyltetrazolium chloride (TTC) were studied in 315 strains of Campylobacter fetus subsp. jejuni to determine their usefulness for biotyping this organism and for distinguishing it from C. fetus subsp. intestinalis. Of the 315 strains tested, 84% hydrolyzed hippurate and 97% were resistant to TTC. Ability to hydrolyze hippurate was seen in 99% of 155 human isolates, 75% of 60 avian isolates, 100% of 41 cattle and dog isolates, 84% of 31 zoo mammal isolates, and none of 28 hog isolates. Resistance to 400 micrograms of TTC per ml was seen in 97% of the human isolates, 95% of the avian isolates, and 100% of the mammalian isolates (other than human). In no case did any of the 315 isolates of C. fetus subsp. jejuni show both lack of ability to hydrolyze hippurate and sensitivity to TTC. In contrast, all 18 strains of C. fetus subsp. intestinalis failed to hydrolyze hippurate and were sensitive to TTC. These two tests may be useful to distinguish between C. fetus subsp. jejuni and subsp. intestinalis and also to biotype strains of C. fetus subsp. jejuni.

Animals↗
PubMed1994

Persistence of Campylobacter fetus bacteremia associated with absence of opsonizing antibodies.

Campylobacter fetus causes systemic infections in immunocompromised hosts. We describe a case in which C. fetus bacteremia apparently relapsed after 7 years in a patient with hypogammaglobulinemia and characterize the serum resistance of the patient's C. fetus strain and the inability of the patient's serum, with and without commercial intravenous immunoglobulin, to opsonize this and another C. fetus strain effectively. The probable presence of a sequestered site of infection in bone, the intrinsic serum resistance of the C. fetus strain, and the absence of specific antibody may account for the persistent infection in this patient. These studies suggest that intravenous immunoglobulin treatment is not useful in eradicating C. fetus bacteremia.

Agammaglobulinemia↗
PubMed1993

The disposal of the aborted fetus--new guidelines: ethical considerations in the debate in Sweden.

During the 70s and 80s ethical debate concerning the fetus became intensive. The great advances made in medical technology and research and improvements in prenatal diagnosis as well as in embryological research have led us to believe that the fetus is an individual with recognised claims to protection. In Sweden the aborted fetus has previously been considered merely as a risk-disposal problem, equivalent to dangerous and infected material and there have been no specific guidelines for the treatment of the fetus after abortion. In July 1990 treatment of aborted fetuses was changed with the general guidelines from the National Board of Health and Welfare. The present paper sets out the main contents of the guidelines and discusses the gradually changing views concerning the status of the human fetus in Sweden, as well as the public debate which has been a contributing factor to these changes.

Aborted Fetus↗
PubMed1980

Parathyroid hormone responsiveness in the sheep fetus and newborn lamb.

Responsiveness of the sheep fetus to parathyroid hormone (PTH) infusion was studied in the unanesthetized fetus in situ and the results were compared with those obtained in the newborn lamb, PTH, 0.5 USP U/min per kilogram body weight was infused intravenously to four sheep fetuses in utero (gestational age 127-141 days) and 10 newborn lambs (1-20 days of age). PTH infusion increased plasma Ca in the fetus and the PTH-induced hypercalcemia increased plasma calcitonin although the maternal levels of Ca and calcitonin did not change. In the fetus, as well as in the newborn lamb, PTH decreased the percentage tubular reabsorption of phosphate (TRP) and increased urinary excretion of cAMP. These results indicate that the sheep fetus has developed the target organ responsiveness to PTH and a normal calcitonin secretory mechanism by the last trimester of gestation.

Animals↗
PubMed1989

Can sonographers reliably identify anatomic features associated with Down syndrome in fetuses?

To standardize femur measurement for the identification of fetuses at risk for Down syndrome, sonographers of varying professional experience and background measured the femurs of 20 Down syndrome fetuses and 709 normal control fetuses. A regression analysis performed to compare biparietal diameter to femur length on the 709 control fetuses yielded the following formula: expected femur length = -9.3105 + 0.9028.biparietal diameter. A ratio of measured-to-expected femur length of 0.91 or lower indicated Down syndrome with a sensitivity of 40%, a specificity of 95%, and a positive predictive value of 3.1%. Eight of the 20 fetuses with Down syndrome (40%) also had a thickened nuchal fold (6 mm or larger). If the nuchal fold findings had been considered with the femur length findings, two more of the fetuses with Down syndrome would have been identified, yielding a sensitivity of 45% and a positive predictive value of 4.3%. Because these measurements were made by eight sonographers rather than a single experienced sonologist, these results could be achieved in most ultrasound laboratories where measurements are done primarily by sonographers.

Down Syndrome↗
PubMed1993

Effects of thyroparathyroidectomy, parathyroid hormone, and PTHrP on kidneys of ovine fetuses.

The fetal parathyroid glands and parathyroid hormone-related protein (PTHrP) have been shown to be important regulators of fetal calcium metabolism through their actions on the placenta and bone. This study examined the effects of fetal thyroparathyroidectomy (with thyroxine replacement) and exogenous infusion of human parathyroid hormone [PTH-(1-34)], PTHrP-(1-34), and PTHrP-(1-141) on the urinary excretion of calcium in chronically cannulated ovine fetuses during the last one-fifth of gestation. Fetal plasma total and ionized calcium concentrations were significantly lower in thyroparathyroidectomized (TxPTx) fetuses when compared with intact fetuses, but there were no significant differences in urinary excretion rates of total calcium. However, TxPTx produced a significant increase in the fractional excretion rate of total calcium and a significant decrease in the excretion of adenosine 3',5'-cyclic monophosphate (cAMP) compared with intact fetuses. Infusions of PTH-(1-34), PTHrP-(1-34), and PTHrP-(1-141) into the jugular vein of TxPTx fetuses (n = 5) at the rate of 1 nmol/h for 2 h, after a 1-nmol loading dose, significantly decreased the excretion rate of total calcium and increased the excretion rate of cAMP in fetal urine. Infusions of all three peptides resulted in significant increases in the concentration of total calcium in fetal plasma but had no effect on the plasma concentrations or urinary excretion rates of phosphate. Infusion of either PTH-(1-34), PTHrP-(1-34), or PTHrP-(1-141) also resulted in an increase in fetal urine osmolality and pH and a decrease in free water clearance in TxPTx fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1997

Placental transport of threonine and its utilization in the normal and growth-restricted fetus.

Placental transport and fetoplacental utilization of threonine (Thr) were compared at 130 +/- 1 days gestational age between seven control ewes (C) and six ewes in which intrauterine growth restriction (IUGR) had been induced by exposure to high ambient temperature from 33 +/- 1 to 112 +/- 2 days of gestation. The fluxes were measured using simultaneous intravenous infusions of L-[1-13C]Thr into the mother and L-[U-14C]Thr into the fetus. The IUGR group had less fetal weight (1.27 +/- 0.14 vs. 3.10 +/- 0.10 kg, P < 0.01) and placental weight (120 +/- 17 vs. 295 +/- 14 g, P < 0.01) than the C group. The direct flux of maternal Thr into the fetal systemic circulation was less in the IUGR fetuses, both relative to fetal weight (1.40 +/- 0.19 vs. 2.19 +/- 0.18 mumol.min-1.kg fetus-1, P = 0.0107) and placental weight (1.5 +/- 0.2 vs. 2.3 +/- 0.2 mumol.min-1.100 g placenta-1, P = 0.0187). In both groups, there was excretion of CO2 produced from fetal Thr. The rate of CO2 production from fetal plasma Thr carbon by fetus plus placenta was reduced in the IUGR group (1.50 +/- 0.23 vs. 2.86 +/- 0.32 mumol.min-1.kg fetus-1, P = 0.0065). We conclude that the flux of maternal Thr into the IUGR fetus is markedly reduced because of a reduction in placental mass and because of a weight-specific reduction in Thr placental transport. The reduced flux is routed into fetal Thr accretion via a decrease in fetal Thr oxidation.

Animals↗