Intrauterine Growth Retardation Animals Research Articles

MiR-29a Family as a Key Regulator of Skeletal Muscle Dysplasia in a Porcine Model of Intrauterine Growth Retardation

MicroRNAs (miRNAs) play an essential role in many biological processes. In this study, miRNAs in the skeletal muscle of normal and intrauterine growth retardation (IUGR) neonatal piglets were identified by sequencing, and canonical miRNAs were functionally validated in vitro. A total of 403 miRNAs were identified in neonatal piglet skeletal muscle, among them 30 and 46 miRNAs were upregulated and downregulated in IUGR pigs, respectively. Upregulated miRNAs were mainly enriched in propanoate metabolism, endocytosis, beta-Alanine metabolism, gap junction, and tumor necrosis factor signaling pathway. Down-regulated miRNAs were mainly enriched in chemical carcinogenesis—receptor activation, endocytosis, MAPK signaling pathway, insulin resistance, and EGFR tyrosine kinase inhibitor resistance. Co-expression network analysis of umbilical cord blood and skeletal muscle miRNAs showed that the miR-29 family is an essential regulator of IUGR pigs. The dual-luciferase reporter system showed that IGF1 and CCND1 were target genes of the miR-29 family. Transfection of IUGR pig umbilical cord blood exosomes and miR-29a mimic significantly inhibited cell proliferation and promoted the expression of cellular protein degradation marker genes Fbxo32 and Trim63. In summary, these results enrich the regulatory network of miRNAs involved in skeletal muscle development in IUGR animals.

N-Carbamylglutamate and l-arginine supplementation improve hepatic antioxidant status in intrauterine growth-retarded suckling lambs.

The influence of dietary supplementation of l-arginine (Arg) or N-carbamylglutamate (NCG) on the hepatic antioxidant status in intrauterine-growth-retarded (IUGR) suckling lambs remains unclear. The current work aimed to investigate the regulatory mechanisms whereby dietary Arg or NCG alter hepatic antioxidant status in suckling lambs suffering from IUGR. Forty-eight newborn Hu lambs of normal birth weight (CON) and IUGR were allocated randomly into four groups of 12 animals each: CON (4.25 ± 0.14 kg), IUGR (3.01 ± 0.12 kg), IUGR + 1% Arg (2.99 ± 0.13 kg), or IUGR + 0.1% NCG (3.03 ± 0.11 kg). All lambs were raised for a period of 21 days from 7 to 28 days after birth. Compared with the IUGR suckling animals, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and reduced glutathione (GSH) content were greater (P < 0.05), and protein carbonyl and malondialdehyde (MDA) levels were reduced (P < 0.05) in the livers of both IUGR + 1% Arg and 0.1% NCG suckling animals. Relative to IUGR suckling lambs, supplementing with Arg or NCG markedly reduced (P < 0.05) reactive oxygen species (ROS) levels, apoptosis, and necrosis in liver. Relative to IUGR suckling lambs, protein and mRNA expression of GSH-Px1, SOD2, catalase (CAT), heme oxygenase-1 (HO-1), inducible nitric oxide (NO) synthase (iNOS), and epithelial NO synthase (eNOS) increased in IUGR animals receiving Arg or NCG (P < 0.05). Both Arg and NCG can protect neonates from IUGR-induced hepatic oxidative damage through promoting the expression of antioxidative enzymes (including SOD, CAT, and GSH-Px), phase II metabolizing enzymes, and activation of the NO pathway.

Intrauterine Growth Retardation Induced Long-Term Gene Dysregulation Is Associated with Altered Histone Modifications in Rat Islets

Intrauterine growth retardation (IUGR) is associated with the development of type 2 diabetes in adulthood. Although the underlying mechanisms remain unclear, permanent alterations in gene expression implicate epigenetics. Using a rat model of IUGR induced by bilateral uterine artery ligation at e18, we sought to determine if histone modifications are a potential mechanism for permanent IUGR-induced gene dysregulation. We assessed genome-wide histone modifications in islets from 2 and 10 week control and IUGR rats using ChIP-Seq. IUGR induced significant changes in enrichment of H3K4me3, H3K27me3, and H3K27Ac marks in 2 week islets at 2181, 1482, and 4572 annotated genes, respectively. At 10 week there were far more changes in enrichment of these marks (9988, 3489, and 4355 genes, respectively). We then integrated our RNA-Seq transcriptome data obtained at the same ages and found that the expression levels of multiple genes in IUGR islets were correlated with changes in histone marks. In 10 week islets, the expression of 639, 355, and 400 genes correlated with changes in enrichment of H3K4me3, H3K27me3, and H3K27Ac, respectively; whereas in 2 week islets, only 43, 64, and 149 genes were correlated with enrichment of these marks. Interestingly, 6 genes in 10 week islets correlated with changes in all 3 histone marks, strongly suggesting that changes in gene expression were induced by histone modifications. Ingenuity pathway analysis of differential expressed genes that correlated with histone modifications revealed significant enrichment in pathways critical for normal islet function, such as cAMP-mediated signaling, immune function, axonal guidance, and VEGF family ligand-receptor interaction. Collectively, the present findings identify histone modification as a potential epigenetic mechanism that may contribute to long-term gene dysregulation and abnormal islet phenotype in IUGR animals. Disclosure Y. Lien: None. P. Wang: None. R.A. Simmons: None.

Early life protein restriction alters dopamine circuitry

Adverse prenatal environment, such as intrauterine growth retardation (IUGR), increases the risk for negative neurobehavioral outcomes. IUGR, affecting approximately 10% of all US infants, is a known risk factor for attention deficit hyperactivity disorder (ADHD), schizophrenia spectrum disorders and addiction. Mouse dams were fed a protein deficient (8.5% protein) or isocaloric control (18% protein) diet through pregnancy and lactation (a well validated rodent model of IUGR). Dopamine-related gene expression, dopamine content and behavior were examined in adult offspring. IUGR offspring have six to eightfold over-expression of dopamine (DA)-related genes (tyrosine hydroxylase (TH) and dopamine transporter) in brain regions related to reward processing (ventral tegmental area (VTA), nucleus accumbens, prefrontal cortex (PFC)) and homeostatic control (hypothalamus), as well as increased number of TH-ir neurons in the VTA and increased dopamine in the PFC. Cyclin-dependent kinase inhibitor 1C (Cdkn1c) is critical for dopaminergic neuron development. Methylation of the promoter region of Cdkn1c was decreased by half and there was a resultant two to sevenfold increase in Cdkn1c mRNA expression across brain regions. IUGR animals demonstrated alterations in dopamine-dependent behaviors, including altered reward-processing, hyperactivity and exaggerated locomotor response to cocaine. These data describe significant dopamine-related molecular and behavioral abnormalities in a mouse model of IUGR. This animal model, with both face validity (behavior) and construct validity (link to IUGR and dopamine dysfunction) may prove useful in identifying underlying mechanisms linking IUGR and adverse neurobehavioral outcomes such as ADHD.

Intrauterine Growth Retardation Leads to the Functional Change of Insulin Secretion in the Newborn Rats

To investigate the observed variation in glucose tolerance and insulin secretion in intrauterine growth retarded newborn rats and to explore the mechanism of the variations, Sprague-Dawley pregnant rats were allocated into two groups: a control group and an intrauterine energy restricted group. The intrauterine growth retardation (IUGR) in the rats was induced by 50% calorie restriction in pregnant rats from gestational day 15 until term as compared to the control group. The pancreata of control and IUGR newborn rats were dissected respectively. RT-PCR was used to study the mRNA level related to insulin synthesis and exocytosis. Intraperitoneal glucose tolerance tests were done to study the function of the pancreatic islet. We found that birth weight and pancreas mass of IUGR newborn rats were significantly lower than those of controls. Although no significant differences were observed in mRNA level of insulin and PDX-1, the expression of genes related to insulin exocytosis such as munc13-1, vamp-2, syntaxin1a, rab3a were reduced significantly in IUGR newborn rats. IUGR animals were glucose-intolerant. The observed blood insulin level and insulin secretion response to glucose challenge were both found to be at reduced level in IUGR newborn rats as compared with the normal control group rats. With these findings, we hypothesize that IUGR can induce changes in glucose homeostasis due to, at least in part, a reduced function of insulin exocytosis in newborn rats.

Neonatal exendin-4 treatment reduces oxidative stress and prevents hepatic insulin resistance in intrauterine growth-retarded rats

Intrauterine growth retardation (IUGR) has been linked to the development of type 2 diabetes in adulthood. We have developed an IUGR model in the rat whereby the animals develop diabetes later in life. Previous studies demonstrate that administration of the long-acting glucagon-like-peptide-1 agonist, exendin-4, during the neonatal period prevents the development of diabetes in IUGR rats. IUGR animals exhibit hepatic insulin resistance early in life (prior to the onset of hyperglycemia), characterized by blunted suppression of hepatic glucose production (HGP) in response to insulin. Basal HGP is also significantly higher in IUGR rats. We hypothesized that neonatal administration of exendin-4 would prevent the development of hepatic insulin resistance. IUGR and control rats were given exendin-4 on days 1-6 of life. Hyperinsulinemic-euglycemic clamp studies showed that Ex-4 significantly reduced basal HGP by 20% and normalized insulin suppression of HGP in IUGR rats. While Ex-4 decreased body weight and fat content in both Control and IUGR animals, these differences were only statistically significant in Controls. Exendin-4 prevented development of oxidative stress in liver and reversed insulin-signaling defects in vivo, thereby preventing the development of hepatic insulin resistance. Defects in glucose disposal and suppression of hepatic glucose production in response to insulin were reversed. Similar results were obtained in isolated Ex-4-treated neonatal hepatocytes. These results indicate that exposure to exendin-4 in the newborn period reverses the adverse consequences of fetal programming and prevents the development of hepatic insulin resistance.

062. DEVELOPMENTAL ORIGINS OF TYPE 2 DIABETES: EPIGENETIC MECHANISMS IN BETA CELL FAILURE

The abnormal intrauterine milieu of intrauterine growth retardation (IUGR) permanently alters gene expression and function of pancreatic b -cells leading to the development of diabetes in adulthood. Expression of the pancreatic homeobox transcription factor Pdx1 is permanently reduced in IUGR and epigenetic modifications are responsible for this decrease. Exendin-4 (Ex-4), a long-acting glucagon-like peptide 1 (GLP-1) analog, given on days 1-6 of life increases Pdx1 expression and prevents the development of diabetes in the IUGR rat. Here we show that Ex-4 increases USF-1 and PCAF association at the proximal promoter of Pdx1, thereby increasing histone acetyl transferase (HAT) activity leading to a permanent increase in histone H3 acetylation and H3K4 methylation. Normalization of these histone modifications precludes DNA methylation thereby preventing silencing of Pdx1 in islets of IUGR animals. These studies demonstrate a novel mechanism whereby a short treatment course of Ex-4 in the newborn period prevents diabetes in adulthood by restoring Pdx1 promoter chromatin structure thus preserving Pdx1 transcription.

UTEROPLACENTAL INSUFFICIENCY AFFECTS HIPPOCAMPAL INSULIN-LIKE GROWTH FACTOR 1 MESSENGER RIBONUCLEIC ACID LEVELS IN JUVENILE RATS.

Background Intrauterine growth retardation (IUGR) predisposes affected human and rat newborns toward persistent hippocampal dysfunction. This often occurs in association with low circulating insulin-like growth factor 1 (IGF-1) levels. Both circulating IGF-1 and locally produced IGF-1 are required for normal hippocampal development and adult cognitive function. However, the effects of IUGR upon hippocampal IGF-1 expression are not known. Objective We hypothesized that uteroplacental insufficiency (UPI) and subsequent IUGR would decrease postnatal hippocampal IGF-1 mRNA levels. IGF-1 expression involves multiple promoters (P1, P2) and multiple exon variants (IGF-1A, IGF-1B). Each exon variant produces a different E peptide. Design/Methods We used a well-characterized rat model of UPI-induced IUGR: briefly, bilateral uterine artery ligation was performed on day 19 of gestation (term-21.5 d). Litters were culled to six after birth, and brain was harvested and dissected at day 21 of postnatal life (D21). In this model, we have shown that IUGR animals perform poorly on tests of hippocampal function at adulthood. They also have abnormal anatomic and functional hippocampal markers, as well as low serum IGF-1 levels. IGF-1 mRNA variants and total IGF-1 mRNA were quantified by real-time RT-PCR (n = 6-8 litters). Results Data are expressed as % of control. IUGR significantly decreased D21 hippocampal P1 IGF-1 mRNA levels in both male and female rats to 87% of control values (p = .02). As expected, male rats were more severely affected than the female rats. Expression of the IGF-1B mRNA was also significantly decreased in D21 IUGR hippocampal samples to 77.3% of control values (p = .01). Surprisingly, the IGF-1B mRNA levels were more severely in the female IUGR rats versus the male rats. Conclusion Despite low serum levels of IGF-1, hippocampal IGF-1 expression is not up-regulated in P21 IUGR rats. In addition, P1, an IGF-1 mRNA that predominates in the brain and is believed to be the paracrine form of IGF-1, is decreased by IUGR. Finally, IGF-1B, an mRNA variant thought to encode the EB peptide, a peptide that may be important in neuronal differentiation, is also decreased by IUGR. These findings are interesting in the up-regulation of cerebral IGF-1 normally occurs in response to acute hypoxia-ischemia. We speculate that the failure of the IUGR hippocampus to increase IGF-1 mRNA levels contributes to the neurocognitive dysfunction observed in both the IUGR human and rat. (CHRC)

Experimental Intrauterine Growth Retardation in the Rat Causes a Reduction of Pancreatic B-Cell Mass, Which Persists into Adulthood

Background and Objectives: The aim of this study was to investigate the possibility that intrauterine growth retardation (IUGR) causes alterations of glucose tolerance, insulin secretory response to glucose, and pancreatic B-cell growth, and if such changes may persist into adulthood. Methods: Pregnant rats were operated on day 16 of pregnancy ad modum Wigglesworth to induce IUGR. Operated rats gave birth to viable offspring but litter size was reduced. The mothers nursed their pups, which were subsequently weaned and reared to an age of 3 months in apparent good health. Results: At 1 day of age, IUGR pups were 10% lighter than control newborns whose mothers had been subjected to a sham operation. Pancreatic B-cell mass and insulin content were reduced by 35–40% in newborn IUGR offspring. Postnatal growth did not differ between IUGR and control animals of either sex and the difference in body weight at birth was not apparent from 1 week of age and onwards. Tests performed at 3 months of age could not demonstrate differences in glucose tolerance between IUGR and control animals. In females, but not in males, the peak insulin secretory response to glucose was lower in IUGR animals compared to controls. In the 3-month-old rats, B-cell mass was reduced by 40% in male and by 45% in female IUGR rats compared to controls, a reduction corresponding to a similar decrease in pancreatic insulin content (male reduction 48%, female reduction 45%). Conclusions: In the rat, IUGR causes a diminution of pancreatic B-cell mass which persists into adulthood. Normal glucose tolerance could be maintained but it is conceivable that increasing demands on insulin secretion may not be met by the reduced B-cell mass and that impaired glucose tolerance and even diabetes would hence develop.

Uteroplacental insufficiency induces site-specific changes in histone H3 covalent modifications and affects DNA-histone H3 positioning in day 0 IUGR rat liver

Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) increase the risk of adult onset insulin resistance and dyslipidemia in humans and rats. IUGR rats are further characterized by postnatal alterations in hepatic PPAR-gamma coactivator (PGC-1) and carnitine-palmitoyl-transferase I (CPTI) expression, as well as overall hyperacetylation of histone H3. However, it is unknown whether the histone H3 hyperacetylation is site specific or relates to the changes in gene expression previously described in IUGR rats. We therefore hypothesized that uteroplacental insufficiency causes site-specific modifications in hepatic H3 acetylation and affects the association of acetylated histone H3 with PGC-1 and CPTI promoter sequences. Uteroplacental insufficiency was used to produce asymmetrical IUGR rats. IUGR significantly increased acetylation of H3 lysine-9 (H3/K9), lysine-14 (H3/K14), and lysine-18 (H3/K18) at day 0 of life, and these changes occurred in association with decreased nuclear protein levels of histone deacetylase 1 (HDAC1) and HDAC activity. Chromatin immunoprecipitation using acetyl-H3/K9 antibody and day 0 chromatin revealed that uteroplacental insufficiency affected the association between acetylated H3/K9 and the promoters of PGC-1 and CPTI, respectively, in IUGR liver. At day 21 of life, the neonatal pattern of H3 hyperacetylation persisted only in the IUGR males. We conclude that uteroplacental insufficiency increases H3 acetylation in a site-specific manner in IUGR liver and that these changes persist in male IUGR animals. The altered association of the PGC-1 and CPTI promoters with acetylated H3/K9 correlates with previous reports of IUGR altering the expression of these genes. We speculate that in utero alterations of chromatin structure contribute to fetal programming.

Lack of evidence for intergenerational reproductive effects due to prenatal and postnatal undernutrition in the female CD-1 mouse

The impacts of adverse environments during the prenatal and/or early postnatal periods may be manifested as functional deficits that occur later in life. Epidemiological studies have shown an association of sub-optimal pregnancy outcomes in one generation with similar events in the following one, a phenomenon termed the “intergenerational effect”. Data indicate that the incidence of adverse pregnancy outcomes and/or low birth weight infants is more closely correlated with the mother’s perinatal environment than with that during her pregnancy. However, epidemiological studies are inherently limited given the variability of lifestyles, ethnicity, nutritional status, and exposures to environmental factors. An appropriate animal model would permit control of parameters that may be impossible to evaluate in human populations. The current studies investigated the mouse as a possible animal model. Pregnant CD-1 mice were placed on an ad libitum or food-restricted diet (50% normal) throughout gestation to generate control (CON) and intrauterine growth retarded (IUGR) litters. At birth (postnatal day (PD) 1) pups (F1) were cross-fostered to control dams in litters of either 8 (CON) or 16 (postnatal food restriction (FR)). The experimental groups thus generated represented adequate nutrition (CON-CON) and undernutrition during the prenatal (IUGR-CON), or postnatal periods (CON-FR), or both (IUGR-FR). Pups of dams on a restricted diet during gestation had significant IUGR ( P<0.001) as compared to controls (birth weights of 1.32 g versus 1.63 g). At weaning, the average weight of the pups was dependent on postnatal litter size and the difference in birth weights between IUGR and CON animals was not a significant factor. CON-CON pup weight was 24.1 g and IUGR-CON was 22.2 g as compared to the CON-FR (17.0 g) and IUGR-FR (17.3 g) groups. The difference in weaning pup weights between the FR and CON groups was significant ( P<0.01). The F1 FR females did not reach CON female weights at any time point through 11 months after weaning. At PD60, a single breeding period for all groups of females with CON males began and continued for 75 days with 17 opportunities for breeding. Animals that became pregnant during this time were removed and allowed to litter. No significant differences were noted in average F2 litter size or average pup weight at birth: (CON-CON 12.2/1.62 g; IUGR-CON 11.9/1.62 g; CON-FR 10.9/1.70 g; IUGR-FR 11.3/1.61 g). We conclude that body weight at birth in the CD-1 mouse is not correlated with growth through the period of weaning (PD28). We did not find any evidence for an intergenerational reproductive effect after developmental undernutrition.

Intrauterine growth retardation leads to the development of type 2 diabetes in the rat.

Intrauterine growth retardation has been linked to the development of type 2 diabetes in later life. The mechanisms underlying this phenomenon are unknown. We have developed a model of uteroplacental insufficiency, a common cause of intrauterine growth retardation, in the rat. Bilateral uterine artery ligation was performed on day 19 of gestation (term is 22 days) in the pregnant rat; sham-operated pregnant rats served as controls. Birth weights of intrauterine growth-retarded (IUGR) animals were significantly lower than those of controls until approximately 7 weeks of age, when IUGR rats caught up to controls. Between 7 and 10 weeks of age, the growth of IUGR rats accelerated and surpassed that of controls, and by 26 weeks of age, IUGR rats were obese (P < 0.05 vs. controls). No significant differences were observed in blood glucose and plasma insulin levels at 1 week of age. However, between 7 and 10 weeks of age, IUGR rats developed mild fasting hyperglycemia and hyperinsulinemia (P < 0.05 vs. controls). At age 26 weeks, IUGR animals had markedly elevated levels of glucose (P < 0.05 vs. controls). IUGR animals were glucose-intolerant and insulin-resistant at an early age. First-phase insulin secretion in response to glucose was also impaired early in life in IUGR rats, before the onset of hyperglycemia. There were no significant differences in beta-cell mass, islet size, or pancreatic weight between IUGR and control animals at 1 and 7 weeks of age. However, in 15-week-old IUGR rats, the relative beta-cell mass was 50% that of controls, and by 26 weeks of age, beta-cell mass was less than one-third that of controls (P < 0.05). The data presented here support the hypothesis that an abnormal intrauterine milieu can induce permanent changes in glucose homeostasis after birth and lead to type 2 diabetes in adulthood.

Lack of effect of protein deprivation-induced intrauterine growth retardation on behavior and corticosterone and growth hormone secretion in adult male rats: a long-term follow-up study.

To further define the neuroendocrine consequences of intrauterine growth retardation (IUGR), we have used a rat model of maternal protein restriction throughout pregnancy to examine the pattern of corticosterone and GH secretion under basal conditions and in response to psychological stress in male offspring at 4, 9, and 18 months of age. The findings were correlated with studies of behavioral activity. Despite a consistent reduction in birth weight and failure of catch-up growth, there were no significant differences in GH secretory profiles between IUGR and control rats at any age. We were unable to demonstrate a difference in the number, amplitude, length, or area of corticosterone secretory pulses between control and IUGR animals; although again, there was a significant decrease with age. The mean peak plasma concentration of corticosterone in response to a noise stress also declined with age but was unaffected by IUGR. There were no consistent, statistically significant differences in behavioral responses between normal control and IUGR animals or between groups of animals at different ages. These results do not, therefore, support the presence of major functional abnormalities in either GH or corticosterone secretory responses in adult male rats subjected to IUGR.

Abnormal cerebral neuronal migration in a rat model of intrauterine growth retardation induced by synthetic thromboxane A(2).

Many reports have associated intrauterine growth retardation (IUGR) with adverse neurological outcome, but the underlying pathology is imperfectly understood. We have developed a new rat model of IUGR using maternal administration of synthetic thromboxane A(2) (STA(2)). In the present study, the effect of this insult on neuronal migration in the rat cerebral cortex was examined. Bromodeoxyuridine (BrdU), a time-specific cell marker was administered intraperitoneally to the mothers on embryonic day (E) 19. At postnatal day (P) 3, P4, P5, and P6, pups were terminally anesthetized and brains were removed. BrdU-labeled cells were detected immunohistochemically and counted in cerebrum, which was divided into the cortical plate (CP), the intermediate zone, and the subventricular/ventricular zone (SVZ+VZ). Numbers of labeled cells in the three areas over time were compared between IUGR and control animals. Numbers of labeled cells in SVZ+VZ were significantly greater in IUGR than in controls at P3, 5, and 6 (P<0.05). In contrast, labeled cells in the CP were significantly less abundant in IUGR animals than in controls at P3, 4, and 6 (P<0.05). We concluded that neuronal migration was delayed in IUGR rats.

CELL POPULATIONS IN THE BONE MARROW OF GUINEA PIG FETUSES WITH INTRAUTERINE GROWTH RETARDATION

Bone marrow smears and blood samples were examined in guinea pig fetuses in which intrauterine growth retardation (IUGR) had been induced by uterine artery ligation and compared with those of control (well-grown) fetuses from uterine horns with intact circulation. Differential bone marrow cell counts were obtained from a count of 300 cells per smear and blood samples were assayed for hemoglobin concentration and 2,3-diphosphoglycerate (DPG). Results of blood assays showed no difference in hemoglobin concentration. DPG levels were reduced in the IUGR guinea pigs (P < .05), which could be a consequence of decreased glucose availability or represent an adaptation to reduced oxygen availability. Comparisons of bone marrow counts revealed an increase in total erythrocyte precursors (P < .05) and a decrease in total granulocytic precursors (P < .05) in IUGR fetuses. Within the erythroid lineage there was a significant increase in late (orthochromatic) erythroblasts (P < .005) in the IUGR animals compared with control animals. The granulocytic lineage of the IUGR fetuses showed a significant decrease in mature neutrophils (P < .05) and eosinophilic precursors (P < .05) compared with controls. These data suggest that the hypoxic stress of uterine artery ligation leads to an increase in medullary erythropoiesis. In concert with a previous study that showed a reduction in hepatic erythropoiesis, these data suggest a precocious shift of the anatomic site of erythropoiesis from the liver to the bone marrow under conditions of hypoxia.

Cell Populations in the Bone Marrow of Guinea Pig Fetuses with Intrauterine Growth Retardation

Bone marrow smears and blood samples were examined in guinea pig fetuses in which intrauterine growth retardation (IUGR) had been induced by uterine artery ligation and compared with those of control (well-grown) fetuses from uterine horns with intact circulation. Differential bone marrow cell counts were obtained from a count of 300 cells per smear and blood samples were assayed for hemoglobin concentration and 2,3-diphosphoglycerate (DPG). Results of blood assays showed no difference in hemoglobin concentration. DPG levels were reduced in the IUGR guinea pigs (P < .05), which could be a consequence of decreased glucose availability or represent an adaptation to reduced oxygen availability. Comparisons of bone marrow counts revealed an increase in total erythrocyte precursors (P < .05) and a decrease in total granulocytic precursors (P < .05) in IUGRfetuses. Within the erythroid lineage there was a significant increase in late (orthochromatic) erythroblasts (P < .005) in the IUGR animals compared with control animals. The granulocytic lineage of the IUGR fetuses showed a significant decrease in mature neutrophils (P < .05) and eosinophilic precursors (P < .05) compared with controls. These data suggest that the hypoxic stress of uterine artery ligation leads to an increase in medullary erythropoiesis. In concert with a previous study that showed a reduction in hepatic erythropoiesis, these data suggest a precocious shift of the anatomic site of erythropoiesis from the liver to the bone marrow under conditions of hypoxia.

Developmental Effects of Intrauterine Growth Retardation on Cerebral Amino Acid Transport

Early restriction of nutrients during the perinatal period of life can modify the development of the mammalian fetus and have marked repercussions on the ontogeny of the CNS. The brain is vulnerable to undernutrition, with delayed morphologic and biochemical maturation leading to impaired functions. The aim of the present investigation was to assess whether modified brain neurotransmitter and amino acid concentrations found in an animal model of intrauterine growth retardation were related to modified blood-brain amino acid transport properties. Four amino acids were tested: alanine and taurine, plus two neurotransmitter precursors, tryptophan and tyrosine. Intrauterine growth retardation was induced by restriction of maternal-fetal blood flow from the 17th d of gestation. Blood-brain transport of these amino acids was measured by i.v. injection of radiolabeled amino acids in 7-d-old, 21-d-old, and 60-d-old intrauterine growth-retarded or control rats. No major statistical differences were revealed either for brain regional transport or between intrauterine growth-retarded animals and controls at any age studied. Transfer coefficients and influxes remained statistically similar for almost all brain regions in both groups. A significant decrease and different time course for amino acid transport with age related to the blood-brain barrier maturation are confirmed in this model. Our results are related to a major role of the blood-brain barrier as a part of mechanisms leading to "brain growth sparing."

Hepatic histology in intrauterine growth retardation following uterine artery ligation in the guinea pig.

Hepatic histology was examined in guinea pig fetuses in which intrauterine growth retardation (IUGR) was induced by unilateral uterine artery ligation and compared with that of control (well-grown) fetuses from uterine horns with intact circulations. From all animals, sections taken from the six lobes of the liver were prepared using hematoxylin and eosin stains. Periodic acid-Schiff and Prussian blue stains (both on fixed samples) and Oil Red O stains on frozen tissues were performed on a subset of samples. Comparisons revealed greater fat content in hepatocytes (P < .05) and decreased total hepatic hematopoiesis (P < .01) in IUGR animals than in controls. No differences in hepatocyte histology among lobes were observed in control animals. IUGR animals had increased fat content and decreased extramedullary hematopoiesis in the lobes receiving the portal circulation (P < .05). These data indicate significant abnormalities of hepatic lipid metabolism in IUGR animals following uterine artery ligation. An unexpected and counterintuitive finding was the decrease in hepatic hematopoiesis in the right side of the liver.

New Evidence that the Intra-Uterine Growth-Retarded Piglet Is a Member of a Discrete Subpopulation

The statistical distribution of birth weights in 54 litters of piglets was examined in an attempt to identify intra-uterine growth-retarded animals. Although birthweight distribution was normal in some litters, in others there appeared to be a discrete subpopulation of 1 or more growth-retarded animals. Inspection of published data from the rat and mouse suggests that a similar phenomenon occurs in other polytocous species. These findings imply that growth-retarded neonates of these and possibly other species should not be regarded as the tail-end of a normal distribution, but that they are the result of some distinct process occurring during gestation.

Total body-glucose turnover in normal and intra-uterine growth-retarded neonatal piglets.

1. Because studies of the metabolic problems of the human intra-uterine growth-retarded neonate are limited by ethical considerations we have used the intra-uterine growth-retarded piglet as an animal model. Total body-glucose kinetics were measured in 16 intra-uterine growth-retarded and 11 normal piglets from the same litters with [3H]glucose as a tracer. 2. The intra-uterine growth-retarded animals had marginally smaller brains than their normal littermates, but substantially smaller livers. Liver weight was reduced in proportion to body weight. 3. Total body-glucose turnover rate was significantly lower (P less than 0.001) in the intra-uterine growth-retarded animals in comparison with their normal littermates, but was appropriate for their smaller body and liver weights. Brain weight was only slightly reduced in the intra-uterine growth-retarded group so that glucose turnover adjusted to a common brain weight was significantly lower (P less than 0.001) in these animals. 4. Total body-glucose pool size was lower in the intra-uterine growth-retarded animals (P less than 0.01), but was appropriate for their body and liver weights. It was significantly reduced in relation to brain weight (P less than 0.001). 5. Resting plasma glucose concentration was lower in the intra-uterine growth-retarded animals (P less than 0.001). There was no relationship between concentration and turnover in either group. 6. It is suggested that the observed differences in total body-glucose turnover may be associated with profound differences in cerebral metabolism in the intra-uterine growth-retarded animals.