RESUMEN
Employing Western blot analysis, we investigated the effect of maternal uterine artery ligation causing uteroplacental insufficiency with asymmetrical intrauterine growth restriction (IUGR) upon fetal (22d) and postnatal (1d, 7d, 14d and 21d) brain (Glut 1 and Glut 3) and skeletal muscle (Glut 1 and Glut 4) glucose transporter protein concentrations. IUGR was associated with a approximately 42% decline in fetal plasma glucose (p<0.05) and a approximately 25% decrease in fetal body weights (p<0.05) with no change in brain weights when compared to the sham operated controls (SHAM). In addition, IUGR caused a approximately 45% increase in fetal brain Glut 1 (55 kDa) with no change in Glut 3 (50 kDa) protein concentrations. This fetal brain Glut 1 change persisted, though marginal, through postnatal suckling stages of development (1d-21d), with no concomitant change in brain Glut 3 levels at day 1. In contrast, in the absence of a change in fetal skeletal muscle Glut 1 levels (48 kDa), a 70% increase was observed in the 1d IUGR with no concomitant change in either fetal or postnatal Glut 4 levels (45 kDa). The change in skeletal muscle Glut 1 levels normalized by d7 of age. We conclude that IUGR with hypoglycemia led to a compensatory increase in brain and skeletal muscle Glut 1 concentrations with a change in the brain preceding that of the skeletal muscle. Since Glut 1 is the isoform of proliferating cells, fetal brain weight changes were not as pronounced as the decline in somatic weight. The increase in Glut 1 may be protective against glucose deprivation in proliferating fetal brain cells and postnatal skeletal myocytes which exhibit 'catch-up growth', thereby preserving the specialized function mediated by Glut 3 and Glut 4 towards maintaining the intracellular glucose milieu.
Asunto(s)
Animales Recién Nacidos/metabolismo , Encéfalo/metabolismo , Retardo del Crecimiento Fetal/metabolismo , Feto/metabolismo , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas Musculares , Músculo Esquelético/metabolismo , Proteínas del Tejido Nervioso , Envejecimiento/metabolismo , Animales , Animales Recién Nacidos/crecimiento & desarrollo , Desarrollo Embrionario y Fetal/fisiología , Transportador de Glucosa de Tipo 1 , Transportador de Glucosa de Tipo 3 , Transportador de Glucosa de Tipo 4 , Ratas , Ratas Sprague-DawleyRESUMEN
To examine the in vivo and in vitro time-dependent effects of glucose on placental glucose transporter (GLUT-1) protein levels, we employed Western blot analysis using placenta from the short-term streptozotocin-induced diabetic pregnancy (STZ-D), uterine artery ligation-intrauterine growth restriction (IUGR) rat models, pregnant sheep exposed to chronic maternal glucose and insulin infusions, and the HRP.1 rat trophoblastic cell line exposed to differing concentrations of glucose. In the rat, 6 days of STZ-D with maternal and fetal hyperglycemia caused no substantive change, whereas 72 h of IUGR with fetal hypoglycemia and ischemic hypoxia resulted in a 50% decline in placental GLUT-1 levels (P < 0.05). In late-gestation ewes, maternal and fetal hyperglycemia caused an initial threefold increase at 48 h (P < 0.05), with a persistent decline between 10 to 21 days, whereas maternal and fetal hypoglycemia led to a 30-50% decline in placental GLUT-1 levels (P < 0.05). Studies in vitro demonstrated no effect of 0 mM, whereas 100 mM glucose caused a 60% decline (P < 0.05; 48 h) in HRP.1 GLUT-1 levels compared with 5 mM of glucose. The added effect of hypoxia on 0 and 100 mM glucose concentrations appeared to increase GLUT-1 concentrations compared with normoxic cells (P < 0.05; 100 mM at 18 h). We conclude that abnormal glucose concentrations alter rodent and ovine placental GLUT-1 levels in a time- and concentration-dependent manner; hypoxia may upregulate this effect. The changes in placental GLUT-1 concentrations may contribute toward the process of altered maternoplacentofetal transport of glucose, thereby regulating placental and fetal growth.
Asunto(s)
Glucosa/farmacología , Proteínas de Transporte de Monosacáridos/metabolismo , Placenta/metabolismo , Animales , Arterias/cirugía , Western Blotting , Células Cultivadas , Diabetes Mellitus Experimental/metabolismo , Femenino , Retardo del Crecimiento Fetal/metabolismo , Transportador de Glucosa de Tipo 1 , Ligadura , Placenta/efectos de los fármacos , Embarazo , Embarazo en Diabéticas/metabolismo , Ratas , Ratas Sprague-Dawley , Ovinos , Factores de Tiempo , Trofoblastos/metabolismo , Útero/irrigación sanguíneaRESUMEN
Employing immunohistochemical and Western blot analyses, we investigated the cellular localization (22-d fetal and 14-d postnatal animals) and concentrations (22-d fetal to 21-d postnatal animals) of rat hepatic glucose transporters (Glut 1 and Glut 2) and glucokinase in response to development and uteroplacental insufficiency with IUGR. Glut 1, the predominant fetal hematopoietic cellular isoform, persisted in postnatal hematopoietic islands and was noted minimally in fetal hepatic cellular membranes. A approximately 40% extrauterine decline in Glut 1 levels paralleled the decline in hematopoietic cells. IUGR increased the fetal hepatic Glut 1 levels in parallel with an expanded hematopoietic cell mass (p < 0.05). In contrast, IUGR failed to alter the 2-fold increase in extrauterine Glut 2 concentrations (1-7-d postnatal animals), the isoform found in fetal and postnatal hepatocytic cell membranes. Glucokinase, the nuclear enzyme, increased 25% postnatally. IUGR caused a 16% increase in fetal glucokinase levels and a approximately 25% decline at postnatal d 1 (p < 0.05) without a comparable change in the hepatocytic cell number (92 +/- 6 versus 86 +/- 4). We conclude that hepatic Glut 1 concentrations reflect the extramedullary hematopoietic cellular mass, whereas extrauterine Glut 2 changes herald the need for enhanced flexibility in hepatocytic glucose transport with the initiation of food ingestion. The age-related alteration along with the IUGR-induced compensatory changes in the nuclear-mitochondrial glucokinase levels attributes a critical role for this enzyme in perinatal hepatocytic glucose homeostasis.
Asunto(s)
Desarrollo Embrionario y Fetal , Retardo del Crecimiento Fetal , Glucoquinasa/fisiología , Proteínas de Transporte de Monosacáridos/fisiología , Animales , Femenino , Transportador de Glucosa de Tipo 1 , Transportador de Glucosa de Tipo 2 , Inmunohistoquímica , Embarazo , Ratas , Ratas Sprague-DawleyRESUMEN
To examine the effect of development on rabbit brain insulin and insulin-like growth factor (IGF) receptor expression, we characterized and quantitated receptor mRNAs by Northern blot analysis and affinity-labeled ligand bound receptors by SDS-PAGE and autoradiography. At various stages of development ranging from 23 to 30 day gestational (term approximately 31 days), 1 to 10 day postnatal ages and the adult, no change in the whole brain insulin receptor mRNA (7.0, 6.0 and 5.5 kb) and affinity-labeled receptor protein (approximately 125 kDa) levels was observed. The IGF-I receptor mRNA (11.5, 6.5 and 4.5 kb) and affinity-labeled receptor (approximately 125 kDa) protein levels declined during the neonatal stages of development. In the case of the IGF-II receptor, while the mRNA levels (9.0 and 4.5 kb) remained constant, the corresponding affinity-labeled receptor protein (approximately 230 kDa) declined with maturation. We conclude that a differential regulation of brain insulin, IGF-I and IGF-II receptor expression occurs during development.
Asunto(s)
Encéfalo/crecimiento & desarrollo , Receptor IGF Tipo 2/biosíntesis , Receptor de Insulina/biosíntesis , Animales , Autorradiografía , Northern Blotting , Encéfalo/embriología , Química Encefálica/fisiología , Electroforesis en Gel de Poliacrilamida , Femenino , Factor I del Crecimiento Similar a la Insulina/metabolismo , Factor II del Crecimiento Similar a la Insulina/metabolismo , Radioisótopos de Yodo , Proteínas de la Membrana/metabolismo , Embarazo , ARN Mensajero/metabolismo , ConejosRESUMEN
We investigated the effect of a serum-containing medium, exogenous insulin, and insulin-free/serum-free media in the regulation of the rabbit brain insulin-like peptide (ILP) in neuronal cell cultures. The presence of serum or insulin in the medium resulted in approximately 3-5% of neurons that were positive for the peptide by immunohistochemistry and for insulin mRNA by in situ hybridization. The absence of insulin in the medium resulted in a three- to fourfold increase (p less than 0.001) in the insulin-immunoreactive and insulin mRNA-containing neurons. Additionally, in the presence of exogenous insulin or serum, the amount of insulin present in the medium, as measured by ELISA, decreased with time (approximately 80%), the former slower than the latter when compared with their respective zero time point values. However, an increase (approximately 80% from zero time) was noted in the absence of insulin or serum, and this lasted for 24-48 hours alone. The presence of an increased insulin/ILP content in the medium and the increase in the numbers of insulin-immunoreactive neurons suggests an important role of the peptide in the brain. The observation of increased synthesis and secretion of neuronal ILP in the absence of insulin is indicative of an autocrine effect of exogenous insulin on neuronal production of ILP, which in turn may be important in the growth and maintenance of neuronal and possibly glial cells.
Asunto(s)
Insulina/biosíntesis , Neuronas/metabolismo , Neuropéptidos/biosíntesis , ARN Mensajero/análisis , Animales , Células Cultivadas , Medios de Cultivo , Ensayo de Inmunoadsorción Enzimática , Inmunohistoquímica , Insulina/genética , Neuronas/citología , Neuropéptidos/genética , ConejosRESUMEN
We investigated the effect of maternally administered thyrotropin-releasing hormone on functional and morphologic fetal lung maturation. Thyrotropin-releasing hormone (40 micrograms/kg/day) or the vehicle was injected intravenously into the New Zealand White rabbit does on days 25, 26, and 27 of gestation. On day 27 of pregnancy, the does were killed and the fetuses were delivered. The functional pulmonary maturity was assessed by pressure-volume hysteresis while morphologic maturity was assessed by histologic techniques. Enhanced functional and morphologic fetal lung maturation was noted in animals treated with thyrotropin-releasing hormone when compared with controls. An important role of thyrotropin-releasing hormone in fetal lung maturation is proposed.
Asunto(s)
Madurez de los Órganos Fetales/efectos de los fármacos , Pulmón/embriología , Intercambio Materno-Fetal , Hormona Liberadora de Tirotropina/farmacología , Animales , Femenino , Embarazo , ConejosRESUMEN
Fifty-two Broviac catheters were inserted in 40 preterm and eight term infants for 1733 days of catheter use. Thirty-six (69%) catheters were associated with complications of infection and/or thrombosis, a complication rate of 1/48 catheter days. The patients who developed complications were of a significantly lower gestational age and had a lower mean birth weight when compared with those who developed no complications. The incidence of catheter-related sepsis was 69% in the very low birth weight infants and only 20% in the infants with birth weights over 1500 g. Eighteen of the 26 catheter-associated infections were treated with antibiotics without catheter removal. Successful resolution of the infections with retention of the catheter occurred in 14 of the 18 episodes. Infections with Staphylococcus aureus constituted three of four treatment failures. Urokinase infusion was successful in causing thrombolysis in eight of the nine cases. Broviac catheters in neonates, and especially in preterm infants under 1500 g, are associated with a high incidence of complications. Our experience indicates that some complications can be selectively managed without sacrificing the venous access.
Asunto(s)
Catéteres de Permanencia/efectos adversos , Recién Nacido de Bajo Peso , Sepsis/etiología , Infecciones Estafilocócicas/etiología , Trombosis/etiología , Antibacterianos/uso terapéutico , Candidiasis/epidemiología , Candidiasis/etiología , Humanos , Recién Nacido , Venas Yugulares , Sepsis/tratamiento farmacológico , Sepsis/epidemiología , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/epidemiología , Staphylococcus epidermidis , Trombosis/tratamiento farmacológico , Activador de Plasminógeno de Tipo Uroquinasa/uso terapéuticoRESUMEN
Although rabbit has been used as a convenient animal model in understanding the role of thyroid hormones during the perinatal development, ontogenetic changes in plasma-free thyroxine or triiodothyronine concentration has not been studied in this species. We delineated the ontogeny of immunoreactive plasma-free thyroxine and triiodothyronine concentration during the perinatal period. It is generally believed that thyroid hormones do not cross the placenta from the mother to the fetus in sufficient concentrations to exert biological effects in the fetus. We administered 250 micrograms/kg of thyroxine (T4) or 125 micrograms/kg of triiodothyronine (T3) intramuscularly to the rabbit doe on the 25th and 26th day of gestation. Maternal and fetal plasma-free T4, T3 and glucose concentration and fetal liver glycogen content were quantitated on the 27th day of gestation. Maternal and fetal plasma-free T4 and T3 concentration was significantly higher than the control in T4-treated animals. Maternal and fetal plasma T3 concentration was higher and free T4 concentration lower than the control in T3-treated animals. T3 or T4 treatment resulted in fetal hyperglycemia and depletion of fetal hepatic glycogen content. We conclude that T4 or T3 cross the rabbit placenta and exert thyromimetic effects in the fetus. A convenient animal model to investigate in utero effects of T4 or T3 in mammalian fetal development is proposed.
Asunto(s)
Intercambio Materno-Fetal , Tiroxina/sangre , Triyodotironina/sangre , Animales , Animales Recién Nacidos/metabolismo , Glucemia/metabolismo , Femenino , Feto/metabolismo , Glucógeno Hepático/metabolismo , Embarazo , Conejos , Tirotropina/sangreRESUMEN
Although the role of thyroid hormones in enhancing lung and brain maturation during the perinatal period is well established, the cellular mechanisms involved in these processes are incompletely understood. Hypothyroidism retards the development of fetal pulmonary insulin, neonatal pulmonary beta-adrenergic and neonatal brain insulin receptors. In this study, we investigated the effect of hypo- or hyperthyroidism on the development of neonatal brain and lung epidermal growth factor (EGF) receptors. The rabbit pups were rendered hypothyroid by adding 0.05% propylthiouracil to the drinking water starting at 23 days of gestation and thereafter. The neonatal hyperthyroid state was achieved by intramuscular administration of 100 micrograms/kg of synthroid to the rabbit doe on the 29th and 30th day of pregnancy. Neonatal plasma free thyroxine (T4) concentrations were quantitated by a radioimmunoassay. Brain and lung plasma membranes were isolated by differential centrifugation. EGF receptor characteristics were studied using 125I-EGF binding assays and Scatchard analysis. The plasma free T4 concentrations were 0.36 +/- (SEM) 0.02 (n = 6), p less than 0.01 (n = 7) and 1.76 +/- 0.1 (n = 6) ng/dl in the control, hypothyroid and hyperthyroid pups, respectively. The percent specific binding of 125I-EGF to 200 micrograms of brain plasma membrane (BPM) protein was significantly lower in the hypothyroid (0.62 +/- 0.03, n = 7, p less than 0.01), and higher in the thyroxine-treated (1.58 +/- 0.08, n = 6, p less than 0.01) group when compared to control (1.08 +/- 0.06, n = 6) animals. However, the percent specific binding of 125I-EGF to 100 micrograms of lung plasma membrane (LPM) protein was similar in all three groups (2.24 +/- 0.28, control; 2.01 +/- 0.5, hypothyroid, and 2.26 +/- 0.3, hyperthyroid). The number of EGF receptors per milligram of BPM protein (X 10(-10] were lower in the hypothyroid (2.24 +/- 0.03, n = 5) and higher in the hyperthyroid (6.6 +/- 0.02, n = 4) group when compared to control (4.4 +/- 0.05, n = 4) with no apparent difference in Kd. There was no difference in the number of EGF binding sites per milligram of LPM protein (X 10(-10] within the groups (6.6 +/- 0.8, n = 6, control; 7.9 +/- 0.4, n = 4, hypothyroid, and 7.3 +/- 0.3, n = 4, hyperthyroid). Presence of high affinity receptors for EGF in the neonatal brain as well as lung supports the hypothesis that EGF may play an important role in neonatal brain and lung maturation.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Encéfalo/metabolismo , Factor de Crecimiento Epidérmico/metabolismo , Pulmón/metabolismo , Receptores de Superficie Celular/metabolismo , Hormonas Tiroideas/fisiología , 5'-Nucleotidasa , Animales , Sitios de Unión , Peso Corporal , Membrana Celular/metabolismo , Femenino , Nucleotidasas/metabolismo , Embarazo , Unión Proteica , ConejosRESUMEN
Experimental evidence in animals and humans suggest that glucocorticoids enhance fetal pulmonary maturation. Mechanisms of glucocorticoid effects remain unclear; but apparently include up regulation of fetal pulmonary insulin and beta-adrenergic receptors. A role of Epidermal Growth Factor (EGF) in fetal lung maturation through plasma membrane bound receptors has been recently proposed. Betamethasone, 0.085 mg/kg, was administered on 25th and 26th day of gestation to the rabbit doe. Fetal pulmonary EGF receptor characteristics in male or female fetuses were studied on the 27th day of pregnancy. The percent specific binding of 125-I-EGF to lung plasma membranes (LPM) and the number of receptor sites per mg of LPM protein or DNA content were significantly higher in the glucocorticoid treated female as well as male fetuses when compared to the control pups, with no difference in the Kd. Presence of high affinity receptors for EGF and their up regulation by glucocorticoids support the hypothesis that EGF plays an important role in fetal lung maturation and that some of the beneficial effects of glucocorticoids in decreasing the incidence of HMD may be mediated through its interaction with EGF.