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Reynolds RM, Thureen PJ. 277 PRETERM INTRAUTERINE GROWTH RESTRICTED INFANTS AND PROTEIN (NITROGEN) METABOLISM:. J Investig Med 2005. [DOI: 10.2310/6650.2005.00005.276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
Increasingly, neonatologists are realizing that current feeding practices for preterm infants are insufficient to produce reasonable rates of growth, and earlier and larger quantities of both parenteral and enteral feeding should be provided to these infants. Unfortunately, there is very little outcome data to recommend any particular nutritional strategy to achieve better growth. Instead, the rationale for feeding regimens in many nurseries has been quite variably extrapolated from animal data and human studies conducted in gestationally more mature and/or stable neonates. Additionally, there are no well-controlled, prospective studies that validate any nutritional regimen for the very preterm and or sick, unstable neonate. The goal of this review is to present available data to help define the risks and benefits of early parenteral and enteral nutrition, particularly in very preterm neonates, concluding with a more aggressive approach to feeding these infants than has been customary practice.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
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Stephens E, Thureen PJ, Goalstone ML, Anderson MS, Leitner JW, Hay WW, Draznin B. Fetal hyperinsulinemia increases farnesylation of p21 Ras in fetal tissues. Am J Physiol Endocrinol Metab 2001; 281:E217-23. [PMID: 11440896 DOI: 10.1152/ajpendo.2001.281.2.e217] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Even though the role of fetal hyperinsulinemia in the pathogenesis of fetal macrosomia in patients with overt diabetes and gestational diabetes mellitus seems plausible, the molecular mechanisms of action of hyperinsulinemia remain largely enigmatic. Recent indications that hyperinsulinemia "primes" various tissues to the mitogenic influence of growth factors by increasing the pool of prenylated Ras proteins prompted us to investigate the effect of fetal hyperinsulinemia on the activitiy of farnesyltransferase (FTase) and the amounts of farnesylated p21 Ras in fetal tissues in the ovine experimental model. Induction of fetal hyperinsulinemia by direct infusion of insulin into the fetus and by either fetal or maternal infusions of glucose resulted in significant increases in the activity of FTase and the amounts of farnesylated p21 Ras in fetal liver, skeletal muscle, fat, and white blood cells. An additional infusion of somatostatin into hyperglycemic fetuses blocked fetal hyperinsulinemia and completely prevented these increases, specifying insulin as the causative factor. We conclude that the ability of fetal hyperinsulinemia to increase the size of the pool of farnesylated p21 Ras may prime fetal tissues to the action of other growth factors and thereby constitute one mechanism by which fetal hyperinsulinemia could induce macrosomia in diabetic pregnancies.
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Affiliation(s)
- E Stephens
- Veterans Affairs Research Service, Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80220, USA
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4
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Abstract
We developed a model of maternal hyperglycaemia with secondary hyperinsulinaemia and hypoaminoacidaemia in pregnant sheep (H) to determine the effect of these conditions on uterine, uteroplacental and fetal amino-acid uptake rates and fetal amino-acid concentrations [AA]. Results were compared with normal pregnant ewes (C). Plasma glucose concentrations were greater in H versus C animals: 7.7+/-0.3 versus 3.9+/-0.1 mmol/l maternal, P< 0.005; 2.6+/-0.1 versus 1.1+/-0.1 mmol/l fetal, P< 0.005. Maternal insulin concentrations [I] were greater in the H group (132+/-30 H versus 31+/-5 C microU/ml, P< 0.005); fetal [I] were not different (15+/-2 H versus 16+/-2 C microU/mL). Maternal [AA] were lower in H than C groups except for SER (P=ns) and GLY (approx twofold higher, P< 0.01). Uterine, uteroplacental and fetal uptake rates of several AA, particularly the branch chain AA, were lower in H than C animals, producing lower total fetal nitrogen uptake rates (270+/-64 mg N/kg fetus/day H, 696+/-75 mg N/kg fetus/day C, P=0.001) and lower fetal plasma concentrations for the branch chain AA. Most fetal [AA], however, remained at control values, which could occur by relative increase in fetal amino-acid production and/or decrease in utilization, but not by increased uteroplacental transport rates.
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Affiliation(s)
- P J Thureen
- The Perinatal Research Center, Department of Pediatrics, University of Colorado Health Sciences Center, 4200 East 9th Avenue, Denver, CO 80262, USA.
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Abstract
We studied the effect of an acute 4-h period of hyperinsulinemia (H) on net utilization rates (AAUR(net)) of 21 amino acids (AA) in 17 studies performed in 13 late-gestation fetal sheep by use of a novel fetal hyperinsulinemic-euglycemic-euaminoacidemic clamp. During H [84 +/- 12 (SE) microU/ml H, 15 +/- 2 microU/ml control (C), P < 0. 00001], euglycemia was maintained by glucose clamp (19 +/- 0.05 micromol/ml H, 1.19 +/- 0.04 micromol/ml C), and euaminoacidemia (mean 4.1 +/- 3.3% increase for all amino acid concentrations [AA], nonsignificantly different from zero) was maintained with a mixed amino acid solution adjusted to keep lysine concentration constant and other [AA] near C values. H produced a 63.7% increase in AAUR(net) (3.29 +/- 0.66 micromol. min(-1). kg(-1) H, 2.01 +/- 0.55 micromol. min(-1). kg(-1) C, P < 0.001), accounting for a 60.1% increase in fetal nitrogen uptake rate (2,064 +/- 108 mg. day(-1). kg(-1) H, 1,289 +/- 73 mg. day(-1). kg(-1) C, P < 0.001). Mean AA clearance rate (AAUR(net)/[AA]) increased by 64.5 +/- 18.9% (P < 0. 001). Thus acute physiological H increases net amino acid and nitrogen utilization rates in the ovine fetus independent of plasma glucose and [AA].
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Affiliation(s)
- P J Thureen
- Perinatal Research Center and Departments of Pediatrics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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Abstract
We tested the hypothesis that decreased fetal amino acid (AA) supply, produced by maternal hypoaminoacidemia (low AA) during hyperglycemia (HG), is reversible with maternal AA infusion and regulates fetal insulin concentration ([I]). We measured net uterine and umbilical AA uptakes during maternal HG/low AA concentration ([AA]) and after maternal intravenous infusion of a mixed AA solution. After 5 days HG, all maternal [AA] except glycine were decreased >50%, particularly essential [AA] (P < 0.00005). Most fetal [AA] also were decreased, especially branched-chain AA (P < 0.001). Maternal AA infusion increased net uterine uptakes of Val, Leu, Ile, Met, and Ser and net umbilical uptakes of Val, Leu, Ile, Met, Phe, and Arg but did not change net uteroplacental uptake of any AA. Fetal [I] increased 55 +/- 14%, P < 0.001, with correction of fetal [AA], despite the lack of change in fetal glucose concentration. Thus generalized maternal hypoaminoacidemia decreases uterine and umbilical uptakes of primarily the essential AA and decreases fetal branched-chain [AA]. These changes are reversed with correction of maternal [AA], which also increases fetal [I].
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, Perinatal Research Center, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. patti.thureen.uchsc.edu
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7
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Abstract
The purpose of this study was to determine oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure (EE) in a group of preterm ventilated infants during the first 3 weeks of life, and to determine the major factors that influence EE. Thirty-eight indirect calorimetry studies were performed in 18 ventilated infants with mean gestational age of 27.9 +/- 0.6 (SEM) weeks. The relationship of demographic factors, nutrient intake, and severity of illness assessments of EE were determined by regression analysis. Repeated measure analysis was performed for the effect of multiple studies in the same patient. Although VO2, VCO2, and EE all tended to increase over the first 3 weeks of life, there was a wide range of values. EE was best predicted by nonprotein calorie intake and postnatal age, while there was no correlation with birthweight, weight at the time of study, gestational age, protein intake, or severity of illness. Multiple regression analyses demonstrated a strong interaction between PNA and EI. In this population EE is best predicted by PNA and EI. The interactive effect between PNA and EI on EE is probably explained by the clinical practice of daily increments in substrate intake in these patients.
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Affiliation(s)
- M P DeMarie
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver, USA
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Abstract
There is a growing body of evidence that early nutritional practices may affect short-term growth and developmental outcome. In addition, they may play a role in determining adult health and disease. There is much that needs to be learned about safe and efficacious nutrient administration in the ELBW population; about techniques to assess the effect of different nutritional strategies; and about the long-term effects of these regimen or development outcome, growth, and disease.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado School of Medicine, Denver, USA.
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9
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Abstract
Bivariate regression is used to estimate energy expenditure from doubly labeled water data. Two straight lines are fitted to the logarithms of the enrichments of oxygen-18 and deuterium simultaneously as a bivariate regression, so that the correlations between the oxygen and deuterium regression coefficients can be estimated. Maximum likelihood methods are used to extend bivariate regression to unbalanced situations caused by missing observations and to include replicate laboratory determination from the same urine samples, even if one of the replicates is missing. Use of maximum likelihood allows the determination of a confidence interval for the energy expenditure based on the log likelihood surface rather than use of the propagation of variance methods for nonlinear transformations. The model is extended to include the subject's deviations from the two lines as a bivariate continuous-time first-order autoregression to allow for serial correlation in the observations. The analysis of data from two subjects, one without apparent serial correlation and one with serial correlation, is presented.
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Affiliation(s)
- R H Jones
- Departments of Preventive Medicine and Biometrics and of Pediatrics, School of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. rhj2times.uchsc.edu
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Affiliation(s)
- P J Thureen
- Associate Professor, Department of Pediatrics, University of Colorado Health Sciences Center, Denver, CO, USA
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Thureen PJ, Reiter PD, Gresores A, Stolpman NM, Kawato K, Hall DM. Once- versus twice-daily gentamicin dosing in neonates >/=34 Weeks' gestation: cost-effectiveness analyses. Pediatrics 1999; 103:594-8. [PMID: 10049962 DOI: 10.1542/peds.103.3.594] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVES To compare performance and cost analysis of two gentamicin regimens in infants >/=34 weeks' gestation requiring antibiotics for a 72-hour rule-out sepsis evaluation. A once-daily dosing (ODD) regimen of 4 mg/kg was compared with a standard twice-daily dosing (TDD) regimen of 2.5 mg/kg every 12 hours. SETTING AND DESIGN Infants at two university-affiliated Level III nurseries were prospectively temporally allocated to receive ODD (n = 27) or TDD (n = 28) as part of their 72-hour empirical antibiotic regimen. Performance of dosing regimens was based on target serum gentamicin concentrations (SGC) established prospectively as a peak of 5 to 10 microgram/mL and a trough of </=2 microgram/mL. SGC were determined by fluorescence polarization immunoassay on day 3 of therapy. Cost data were obtained by distributing a questionnaire to 15 pediatric pharmacy practice sites. Inquiries were made regarding hospital cost of drug acquisition, drug supplies, drug preparation and administration, and serum concentration analysis. Performance and cost data were then used to do a cost-effectiveness analysis. RESULTS Mean peak concentrations were higher with ODD (7.9 +/- 0.2 microgram/mL) than TDD (6.7 +/- 0.3 microgram/mL). Half of the patients in the TDD group had trough concentrations >2 microgram/mL, compared with none in the ODD group. Overall, 57% of the SGCs in the TDD group were outside the target concentration range versus 7% in the ODD group. Based on questionnaire results, a total 72-hour process cost of ODD versus TDD was compared for regimens with and without use of SGC analysis. If SGCs are obtained, more than 75% of the cost associated with gentamicin therapy is attributable to SGC analysis. Based on a cost-effectiveness analysis, ODD was the dominant dosing strategy in all categories analyzed. CONCLUSIONS ODD of gentamicin at 4 mg/kg in neonates >/=34 weeks' gestation is the preferable treatment strategy based on: 1) significantly improved SGC performance compared with TDD; 2) elimination of the need for routine SGC collection in infants on short courses of therapy; and 3) significant antibiotic-associated hospital cost savings when compared with conventional therapy of TDD and SGC analysis.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, Section of Neonatology, University of Colorado Health Sciences Center and Children's Hospital, Denver, Colorado, USA
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Thureen PJ, Anderson AH, Baron KA, Melara DL, Hay WW, Fennessey PV. Protein balance in the first week of life in ventilated neonates receiving parenteral nutrition. Am J Clin Nutr 1998; 68:1128-35. [PMID: 9808233 DOI: 10.1093/ajcn/68.5.1128] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Protein intake is frequently delayed in ill neonates because of concerns about their ability to metabolize substrates. OBJECTIVE We aimed to determine the factors affecting protein balance in ventilated, parenterally fed newborns during the first week of life. DESIGN Leucine kinetic studies were performed in 19 neonates by using the [1-(13)C]leucine tracer technique after 24 h of a stable total parenteral nutrition (TPN) regimen. TPN intakes were prescribed by rotating attending physicians, enabling assessment of protein metabolism over a range of clinically used nutrient intakes. RESULTS Mean (+/-SD) birth weight was 1.497 +/- 0.779 kg, gestational age at birth was 30.3 +/- 4.0 wk, and age at study was 3.9 +/- 1.4 d. Amino acid intakes (AAIs) ranged from 0.0 to 2.9 g x kg(-1) x d(-1). Based on leucine kinetic data, protein balance was calculated as the difference between protein synthesis and catabolism. By multiple regression analysis, AAI was the only predictor associated independently with protein balance (P < 0.01); energy intake, lipid intake, glucose intake, birth weight, and gestational age were not. Both leucine oxidation and nonoxidative leucine disposal rates were significantly correlated with leucine intake (P < 0.0005 and P < 0.01, respectively). Of the 12 infants with AAIs > 1 g x kg(-1) x d(-1), only 1 infant was significantly catabolic (protein balance <-1 g x kg(-1) x d(-1)). There was no evidence of protein intolerance as determined by elevated creatinine (69 +/- 31 micromol/L), plasma urea nitrogen (6.7 +/- 2.53 mmol/L), or metabolic acidosis (pH: 7.36 +/- 0.05). CONCLUSIONS Ill neonates can achieve a positive protein balance in the first days of life without laboratory evidence of protein toxicity.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA.
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Battaglia FC, Thureen PJ. Nutrition of the fetus and the premature infant. Diabetes Care 1998; 21 Suppl 2:B70-4. [PMID: 9704230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Developments in fetal and placental nutrition have highlighted the interaction of the placenta and fetal liver for the exchange and metabolism of nutrients. Of particular importance is the exchange of serine and glycine and their interconversion within these two organs and the exchange of glutamine and glutamate. Placental metabolism of nutrients and the placenta's role in the production and utilization of certain amino acids alters significantly the delivery rate of nutrients into the fetal circulation. Postnatal nutrition has focused on the role of early nutritional intervention in the extremely low birth weight infants and the recognition of the category of semi-essential amino acids in these infants. The role of minimal enteral feedings in small babies and the changes in nutritional requirements induced by medical complications has also received increasing attention.
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Affiliation(s)
- F C Battaglia
- University of Colorado School of Medicine, Denver 80262, USA
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Thureen PJ, Phillips RE, Baron KA, DeMarie MP, Hay WW. Direct measurement of the energy expenditure of physical activity in preterm infants. J Appl Physiol (1985) 1998; 85:223-30. [PMID: 9655779 DOI: 10.1152/jappl.1998.85.1.223] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The energy cost of physical activity (EEA) has been estimated to account for 5-17% of total energy expenditure (TEE) in neonates. To directly measure EEA, a force plate was developed and validated to measure work outputs ranging from 0.3 to 40 kcal . kg-1 . day-1. By use of this force plate plus indirect calorimetry, TEE and EEA were measured and correlated with five activity states in 24 infants with gestational age of 31.6 +/- 0.5 (SE) wk and postnatal age of 24.8 +/- 3.7 days. TEE and EEA were 69.2 +/- 1.5 and 2.4 +/- 0.2 kcal . kg-1 . day-1, respectively. EEA per state was 0.5 +/- 0.0 (quiet sleep), 2.4 +/- 0.2 (active sleep), 2.8 +/- 0.4 (quiet awake), 7.5 +/- 0.8 (active awake), and 15.1 +/- 2.3 (crying) kcal . kg-1 . day-1. This provides the first direct measurement of the contribution of physical activity to TEE in preterm infants and will enable measurement of caloric expenditure from muscle activity in various disease conditions and development of nursing strategies to minimize unnecessary energy losses.
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Affiliation(s)
- P J Thureen
- Section of Neonatology, Department of Pediatrics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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Abstract
Nutrition in the fetus and the premature infant is a rapidly changing field, not solely due to the acquisition of new knowledge but also because there have been major conceptual advances that have altered our approach to nutrition during early stages of development. This special report will highlight some of these conceptual advances in this area.
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Affiliation(s)
- F C Battaglia
- University of Colorado School of Medicine, Denver, USA
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Thureen PJ, Hall DM, Hoffenberg A, Tyson RW. Fatal meconium aspiration in spite of appropriate perinatal airway management: pulmonary and placental evidence of prenatal disease. Am J Obstet Gynecol 1997; 176:967-75. [PMID: 9166153 DOI: 10.1016/s0002-9378(97)70387-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Our purpose was to summarize eight cases of fatal meconium aspiration syndrome where pathologic review showed evidence of chronic prenatal disease and to compare these findings with those of a group of control infants and fetuses who died of other causes. STUDY DESIGN A 15-year retrospective chart review identified the infants who died of meconium aspiration within 48 hours of life and who also had autopsies performed. Neonatal pulmonary and available placental pathologic findings are described from these study infants and are compared with published norms and with autopsy results from a group of control infants and fetuses. RESULTS Seven of the eight study infants underwent suctioning of the trachea immediately after birth. In all eight cases the neonatal lungs demonstrated histologic evidence of significant hypoxic changes of a chronic nature with onset before birth. The available placentas showed variable but significant abnormalities that support a case for subacute or chronic in utero compromise. CONCLUSIONS As in other reports, there is evidence that meconium aspiration may be a prenatal rather than a postnatal disease. However, this is the first study that presents evidence on the basis of both pulmonary and placental pathologic findings and reinforces the importance of placental examinations in complicated pregnancies.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver, USA
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Thureen PJ, Phillips RE, DeMarie MP, Hoffenberg A, Bronstein MN, Spedale SB, Hay WW. Technical and methodologic considerations for performance of indirect calorimetry in ventilated and nonventilated preterm infants. Crit Care Med 1997; 25:171-80. [PMID: 8989195 DOI: 10.1097/00003246-199701000-00031] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE To evaluate and refine indirect calorimetry measurement techniques so that accurate metabolic measurements can be performed in mechanically ventilated and convalescing preterm infants who require supplemental oxygen. DESIGN Laboratory validation of an indirect calorimeter; clinical and laboratory assessments of technical problems in performing metabolic measurements; and clinical indirect calorimetry studies in mechanically ventilated and nonventilated preterm infants. SETTING Neonatal intensive care unit (ICU) in a tertiary care university hospital. PATIENTS Level II and level III mechanically ventilated (n = 10) and nonventilated (n = 14) neonatal ICU patients who required FIO2 levels ranging from 0.21 to 0.42. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS System calibration was assessed by combustion of 100% ethanol; the mean respiratory quotient was 0.667 +/- 0.001 (SEM). In addition, oxygen consumption (Vo2) and CO2 production (Vco2) were simulated by CO2/nitrogen infusions within the range expected for 0.5- to 7-kg infants. Mean relative errors were 0.6 +/- 0.3% and 1.8 +/- 0.3% for expected Vo2 and Vco2 values, respectively. In 27 mechanically ventilated patients with no audible endotracheal tube leak, measured endotracheal tube leak ranged from 0.0% to 7.5%. Fluctuations in FIO2 during mechanical ventilation were monitored in 30-min studies, using wall-source (n = 27) or tank-source (n = 11) supplemental oxygen. Mean FIO2 variation was 0.00075 +/- 0.00013 vs. 0.00011 +/- 0.00001 using wall-source and tank-source oxygen, respectively. Some of the difficulties of obtaining accurate measurements in supplemental hood oxygen studies were overcome by using tank-source vs. wall-source oxygen and a unique hood design. CONCLUSIONS Accurate indirect calorimetry studies can be performed in both ventilated and nonventilated infants weighing as little as 500 g, providing that sufficient attention is paid to technical and methodologic measurement details.
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MESH Headings
- Calorimetry, Indirect/methods
- Calorimetry, Indirect/standards
- Critical Care/methods
- Evaluation Studies as Topic
- Humans
- Infant, Newborn
- Infant, Premature/metabolism
- Infant, Premature/physiology
- Infant, Very Low Birth Weight/metabolism
- Infant, Very Low Birth Weight/physiology
- Intensive Care Units, Neonatal
- Oxygen Inhalation Therapy
- Reproducibility of Results
- Respiration, Artificial
- Respiratory Function Tests
- Ventilators, Mechanical
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver, USA
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Thureen PJ, Hay WW. Advice for selected breast-feeding issues. Compr Ther 1996; 22:802-5. [PMID: 9030460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado, Health Sciences Center, Denver 80262, USA
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Abstract
Using stable isotopes of serine, glycine, and glutamine, the metabolism of serine and glycine was investigated in primary hepatocytes from six mid-gestation fetal lambs (mean gestational age = 81 +/- 6 d, normal gestation = 145 d). Serine production was 6.84 +/- 1.22 mumol/24 h/mg of DNA and exceeded serine utilization (3.76 +/- 1.44 mumol/24 h/mg of DNA) with a resultant net increase in medium serine of 2.58 +/- 1.70 mumol/24 h/mg of DNA. In contrast, glycine production (6.84 +/- 1.16 mumol/24 h/mg of DNA) was less than glycine utilization (12.10 +/- 1.78 mumol/24 h/mg of DNA) with a net decline in medium glycine of -5.44 +/- 2.03 mumol/24 h/mg of DNA. Of the serine produced, 50.4 +/- 4.3% was derived from glycine via the action of serine hydroxymethyltransferase (SHMT) and the glycine cleavage enzyme complex (GCS). Increasing the medium serine concentration resulted in an increase in serine utilization and sparing of the utilization of other amino acids. Biosynthesis of glycine from serine accounts for only 18.1 +/- 5.6% of glycine production, and this percentage is not affected by changes in medium serine concentration. Using 2.5-[15N2]glutamine as the tracer, an estimated 18 +/- 7% of serine production was derived from transamination reactions. The specific activity of both cytosolic and mitochondrial SHMT was constant for the duration of the cultures. We conclude that, in mid-gestation fetal ovine hepatocytes, there is net production of serine (with glycine as the primary metabolic source of this serine biosynthesis) and net glycine utilization. These data suggest that flux through SHMT and GCS accounts for 50% of serine biosynthesis in mid-gestation fetal ovine hepatocytes. The sparing of the utilization of other amino acids by serine suggests that serine a conditionally essential amino acid for the mid-gestation fetal liver.
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Affiliation(s)
- M R Narkewicz
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA
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20
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Abstract
Previous in vivo studies in the ovine fetus have demonstrated net serine production by the fetal liver, a pattern not seen in the adult sheep. The goal of this study was to determine the major metabolic pathways responsible for fetal hepatic serine production by using stable isotope methodology in primary culture of late gestation ovine fetal hepatocytes. Specifically selected tracers of glycine were added to individual cultures, with production of labeled serine determined after 24 h of incubation. When [1-13C1]glycine or [2-13C1]glycine was used as the initial tracer, serine enrichment at 24 h indicated that approximately 30% of serine production comes from glycine. Quantitative comparison of serine enrichment from these two tracers suggests that serine synthesis from glycine occurs via the combined action of the glycine cleavage enzyme system (GCE) and serine hydroxymethyltransferase (SHMT). Using [1,2-13C2(15)N1]glycine as the tracer, there was no significant increase in M + 2 glycine in the medium over 24 h, suggesting no reversible transamination of glycine, and therefore no significant movement of glycine through the glyoxalate pathway. These data demonstrate that in primary culture of fetal ovine hepatocytes, approximately 30% of serine biosynthesis is derived from glycine, primarily via the combined action of GCE and SHMT.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA
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21
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Thureen PJ, Briggs K, Fennessey PV, Battaglia FC. Plasma disposal rate and hepatic alanine metabolism in pregnant and nonpregnant rabbits. Pediatr Res 1995; 37:764-70. [PMID: 7651761 DOI: 10.1203/00006450-199506000-00015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To better define the glucose-alanine relationship and hepatic alanine metabolism during pregnancy, glucose and alanine turnover rates (TR) and simultaneous hepatic alanine uptake were determined in nine term pregnant (P) and 12 nonpregnant (NP) rabbits who had undergone chronic catheterization of both the systemic and hepatic circulations. [U-14C3]Alanine and [3-3H1]glucose were used as tracers. Whole animal [U-14C3]alanine TR was significantly greater in P than in NP animals (42.7 +/- 1.7 versus 31.9 +/- 1.8 mumol.min-1, respectively, p < 0.001). However, there was no difference when the alanine TR was compared on a weight-specific basis (11.3 +/- 0.6 versus 9.6 +/- 0.6 mumol.min-1.kg-1). The glucose TR was higher in P compared with NP rabbits on both an absolute (122.3 +/- 6.2 versus 79.8 +/- 5.8 mumol.min-1, p < 0.001) and a weight-specific basis (32.9 +/- 1.4 versus 24.0 +/- 1.9 mumol.min-1.kg-1, p < 0.005). Although the fraction of plasma glucose derived from plasma alanine in the whole animal was similar in P and NP animals (16.7% +/- 1.4 versus 13.9 +/- 0.7%, respectively), the absolute amount of plasma glucose derived from plasma alanine was greater in P rabbits (20.8 +/- 1.8 versus 11.2 +/- 1.2 mumol.min-1, p < 0.0005). In addition, the percentage of plasma alanine being converted to plasma glucose was greater in P than in NP animals (48.1 +/- 2.6 versus 34.6 +/- 2.0%, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA
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Thureen PJ, Moreland S, Rodden DJ, Merenstein GB, Levin M, Rosenberg AA. Failure of tracheal aspirate cultures to define the cause of respiratory deteriorations in neonates. Pediatr Infect Dis J 1993; 12:560-4. [PMID: 8345996 DOI: 10.1097/00006454-199307000-00002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The spectrum of organisms responsible for lower respiratory tract infection in chronically ventilated neonates is poorly defined. During an 18-month period 63 infants with a respiratory deterioration defined as an increase in fractional inspired O2 concentration > or = 20% and/or mean airway pressure > or = 3 cm H2O were evaluated for pulmonary infection. These infants were compared with 58 stable control ventilated infants. Tracheal aspirates for culture and Gram stain were taken from both groups and were cultured for bacteria, viruses, Chlamydia trachomatis, Ureaplasma urealyticum and Mycoplasma hominis. In addition each infant had complete blood counts with differential and chest roentgenograms evaluated. Positive tracheal aspirates defined as a heavy growth of a single or two bacterial organisms, and/or any growth of virus, Chlamydia and U. urealyticum were found in 23 of 63 study patients and 20 of 58 controls (P > 0.05). The most frequent isolate in both groups was U. urealyticum. Chest radiographs were positive (new changes, particularly atelectasis and infiltrates) more frequently in the study group than in controls, but complete blood count and tracheal aspirate Gram-stained smears were not helpful in discerning colonization from infection. We conclude that positive tracheal aspirates occur with equal frequency among infants with a clinical suspicion of lower respiratory tract infection and in "well" controls. Chest roentgenogram may be a useful adjunctive test to discriminate between colonization and lower respiratory tract infection.
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Affiliation(s)
- P J Thureen
- Neonatology, University of Colorado Health Sciences Center, Denver 80262
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Townsend SF, Thureen PJ, Hay WW, Narkewicz MR. Development of primary culture of ovine fetal hepatocytes for studies of amino acid metabolism and insulinlike growth factors. In Vitro Cell Dev Biol Anim 1993; 29A:592-6. [PMID: 8354668 DOI: 10.1007/bf02634153] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We report the development and characterization of a system of primary culture of ovine fetal hepatocytes to aid in the understanding of the cellular regulation of fetal growth and metabolism with emphasis on amino acid metabolism and insulinlike growth factor gene expression and to allow comparison to in vivo studies. Hepatocytes were isolated from late gestation fetal lambs by in situ perfusion and collagenase digestion utilizing occlusion of the ductus venosus to limit intrahepatic shunting. Hepatocytes were cultured in media modified to mimic fetal concentrations of glucose, lactate, and amino acids. Ovine fetal hepatocytes in primary culture maintain the pattern of fetal amino acid production and utilization seen across the fetal liver in vivo. Specifically, there is a net production of serine and a net utilization of glycine. Cultured ovine fetal hepatocytes specifically increase tritiated thymidine incorporation in response to insulin and insulinlike growth factor II (IGF-II). IGF-II mRNA abundance is high and IGF-I mRNA is low in cultured ovine fetal hepatocytes as in the fetal sheep liver in vivo. These data demonstrate the successful isolation of ovine fetal hepatocytes that retain some of the characteristics of the ovine fetal liver while maintained in short-term culture.
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Affiliation(s)
- S F Townsend
- Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262
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Abstract
In six ewes heat stressed from 39 to 125 days gestation and studied in a normothermic environment at 135 days, fetal and placental masses were less than in control sheep (1,645 vs. 3,112 and 149 vs. 356 g, respectively, P less than 0.01). Umbilical glucose uptakes (Rf,UP) were measured keeping maternal arterial plasma glucose at 70 mg/dl at spontaneously occurring fetal plasma glucose values (state A) and at two additional fetal glucose levels, to determine the transplacental glucose difference (delta) vs. Rf,UP relation. At normal delta of 49.2 mg/dl, Rf,UP was less in the experimental group (3.2 vs. 5.6 mg.min-1.kg fetus-1, P less than 0.05). Differences in placental perfusion and glucose consumption could not account for this result, thus indicating a reduced placental glucose transport capacity. In state A, fetal hypoglycemia enlarged significantly (P less than 0.01) the delta to 56.7 mg/dl and increased Rf,UP approximately 50% over the Rf,UP at a normal delta. In heat-induced fetal growth retardation, fetal hypoglycemia increases the flux of maternal glucose across a placenta with reduced glucose transport capacity.
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Affiliation(s)
- P J Thureen
- Department of Pediatrics, University of Colorado School of Medicine, Denver 80262
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