摘要:

Two approaches have been used to arrive at estimates of the requirement for protein by infants. The factorial approach consists of adding the requirement for growth to the requirement for replacement of inevitable losses in urine and feces and from the skin. Protein requirement estimated in this way was 1.98 g·kg−1·d−1during the 1st mo of life and decreased rapidly to 1.18 g·kg−1·d−1by 4 to 5 mo of age, then remained at about that level to age 1 y. Believing that protein intakes of the breast-fed infant are near the level of the requirement, researchers used the intakes of breast-fed infants as a second estimate of requirement. Although intakes of protein by breast-fed infants during the first 2 mo of life are generally similar to the requirement values estimated by the factorial approach, intakes from 2 to 6 mo of age are less than the requirement values estimated by the factorial approach. Possible explanations for the discrepancy are presented. Recommended dietary intakes of protein somewhat greater than the requirements estimated by the factorial approach are proposed. These recommended intakes are less than those proposed by the FAO/WHO/UNU “safe levels of protein intake” and are less than the Recommended Dietary Allowances of the Food and Nutrition Board.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The purpose of our study was to determine if the ethane content of expired air could be a useful index of vitamin E status in children. Eight children with vitamin E deficiency secondary to chronic severe liver disease were studied: six of these children were treated with parenteral vitamin E (2–5 mg/kg/dose every 4–7 d). Measures of vitamin E status pre- and posttherapy were: serum vitamin E, 2 ± 1versus7 ± 1 μg/mL (p< 0.001); serum vitamin E:total lipids, 0.3 ± 0.1versus1.0 ± 0.1 mg/g (p< 0.001); and erythrocyte peroxide hemolysis test, 80 ± 10versus6 ± 12% (p< 0.001). Fasting breath ethane in the patients pre- and posttherapy was 78 ± 10versus31 ± 11 pmol/kg/min (p< 0.001). Breath ethane correlated negatively with serum vitamin E (p< 0.042) and serum E:total lipids (p< 0.004) and positively with the erythrocyte peroxide hemolysis test (p< 0.003). Values for treated patients did not differ from those for fasted sibling controls (34 ± 12 pmol/kg/min), postprandial sibling controls (31 ± 12 pmol/kg/min), and healthy children sampled randomly, in the nonfasted state (21 ± 14 pmol/kg/min). Breath ethane production in one patient (up to 168 pmol/kg/min) did not normalize after treatment of vitamin E deficiency until her selenium deficiency was corrected as well. We conclude that this noninvasive test can be useful as a screen for vitamin E deficiency in children and for ascertaining response to therapy. The presence of high concentrations of ethane in expired air in vitamin E-sufficient subjects may indicate deficiencies of other antioxidants such as selenium.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Red blood cell (RBC) phospholipids of infants fed human milk compared with formula have more arachidonic acid (AA) and docosahexanoic acid (DHA). The addition of low levels of marine oil to infant formula with 0.6 to 2.0% α-linolenic acid (LLA, 18:3n-3) prevented declines in DHA in formula-fed infants; however, the feeding trials were short (4 to 6 wk), LLA concentrations were low compared with current formulas (3.0 to 5.0% LLA), and the formulas were unstable. Trials with stable formulas were necessary to determine if dietary DHA could maintain phospholipid DHA after discharge from the hospital and, in fact, if it was necessary with higher intakes of LLA. The results of acute (4 wk) and extended (to 79 wk postconception) feeding of such formulas on RBC and plasma phospholipid AA and DHA are reported here. Control formulas were identical to commercially available formulas. Experimental formulas differed only in the addition of small amounts of marine oil. DHA in RBC and plasma phosphatidylethanolamine (PE) declined during four weeks of feeding but not if marine oil provided DHA (0.2% or 0.4%) and plasma phospholipid AA (g/100 g) decreased with time and marine oil feeding. Extended feeding with marine oil accounted for half the DHA in RBC and plasma phosphatidylethanolamine at equilibrium; however, RBC (g/100g) and plasma AA (g/100 g; mg/L plasma) decreased progressively until late infancy and were depressed further by marine oil. We conclude that1) AA and DHA decline in RBC and plasma phospholipids of preterm infants when only their n-6 and n-3 fatty acid precursors are consumed; and 2) marine oil can maintain cord concentrations of RBC phosphatidylethanolamine DHA but further reduces AA.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Intralipid, derived from soybean oil and containing a high percentage of n-6 family polyunsaturated fatty acids (PUFA) and also linolenic acid, an n-3 family PUFA, is commonly the first fat source provided to very low birth weight premature infants. Following up on our previous reports that newborn rats born to dams fed high-PUFA diets demonstrate superior tolerance to hyperoxia, we examined whether the high-PUFA fat source Intralipid might also protect against oxygen toxicity. Adult female rats were fed either regular Rat Chow or fat-free diet containing 20%-Intralipid as the fat source for 3 wk before and then throughout pregnancy and lactation. One- and 5-d-old offspring of Intralipid diet-fed dams demonstrated significant increases in lung lipid n-6 family PUFA plus elevated linolenic acid compared with regular diet-fed offspring. These characteristic fatty acid patterns, apparent in total lung lipids, were even more pronounced in the triglyceride fraction compared with the phospholipid fraction. Associated with these fatty acid changes were significantly improved hyperoxic survival rates (89 out of 95 = 94% survival after 7 d of >95% O2exposure) in Intralipid offspring (versus89 out of 106 = 84%,p< 0.05 in regular diet offspring) and evidence of superior clinical/pathologic status. No differences in pulmonary antioxidant enzyme or surfactant system development, response of antioxidant enzymes to hyperoxic exposure, or lung prostaglandin E2, 6-keto PGF2-α or leukotrienes C4-F4were present. These findings continue to support the hypothesis that increasing lung PUFA content may provide increased O2free radical scavenging capacity, thus protecting against hyperoxic lung damage. The results also suggest a role for Intralipid administration in protecting the lungs of high oxygen-exposed very low birth weight premature infants.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Rates of protein turnover were measured in 19 infants during the first few days of life while they were receiving i.v. glucose. The technique consisted of a continuous i.v. infusion of L-[1-13C]leucine to measure whole body leucine flux and determination of total urinary nitrogen excretion to assess leucine oxidation rates. Subsequent to each of the studies, the decision to start total parenteral nutrition (TPN) was made by the clinician concerned, with the result that seven infants did not start TPN and 12 did. There were significantly greater urinary nitrogen excretion (p< 0.001) and lower rates of whole body protein synthesis (p= 0.024) and breakdown (p= 0.015) in those who did start TPN compared with those who did not. The marked difference in nitrogen excretion between the two groups suggests that this could be a useful determinant for deciding which neonate should start TPN.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

During fasting of the ewe, the rate of amino acid oxidation by the ovine fetus increases substantially. We hypothesized that the increase in amino acid oxidation derived mainly from reduced protein synthesis. We further hypothesized that fetal glucose supplementation would result in diminished amino acid oxidation. To test these hypotheses, nine ovine fetuses were infused with [15N,1-13C]leucine to determine the rates of leucine appearance and disposal. Simultaneously, the fetal uptake of leucine was determined. Animals were studied in the fed and fasted state. After baseline measurements, glucose was infused into the fetal inferior vena cava at a rate estimated to match the fetal glucose uptake. Results of these studies indicate that leucine nitrogen flux, leucine carbon flux and fetal leucine uptake were constant. Leucine oxidation was increased by 50% in the fasted state (6.3versus13.4 μmol/min); glucose infusion resulted in a 25% decline in oxidation (to 10.4 μmol/min) in the fasted state, but had no effect in the fed state. Mean leucine umbilical uptake during fasting was 9.3 μmol/min, 4.1 μmol/min less than leucine oxidation. These data suggest that leucine (and potentially other amino acids) may be in negative balance during maternal fasting, and can be spared by supplementation of the fetus with exogenous glucose.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Total body and renal elimination of L-allo-isoleucine was assessed after oral loads (0.57 mmol/kg body wt) in four healthy subjects and in five patients with maple syrup urine disease (MSUD) of different degrees of severity. As judged from the fictive initial concentration, L-alloisoleucine is distributed evenly in the total body water space. In the controls, estimated half-time of total elimination was 9.2 ± 2.2 h (n= 4). In the MSUD patients, it ranged from 26 h (mild variant) to about 8 d (classical type). Because of its low renal clearance rate, L-alloisoleucine was cleared through ketomethylvalerate to >99% in normals and to at least 73% in the MSUD patients. Assuming small variation in the losses of ketomethylvalerate through L-isoleucine formation and through renal excretion, this test allows ranking of MSUD patients with regard to their residualin vivobranched-chain oxo-acid dehydrogenase activity.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Some cases of primary hyperphenylalaninemia are not caused by the lack of phenylalanine hydroxylase, but by the lack of its cofactor tetrahydrobiopterin. These patients are not clinically responsive to a phenylalanine-restricted diet, but need specific substitution therapy. Thus, it became necessary to examine all newborns screened as positive with the Guthrie test for tetrahydrobiopterin deficiency. Methods based on urinary pterin or on specific enzyme activity measurements are limited in their availability, and the simplest method, based on the lowering of serum phenylalanine after loading with cofactor, was discouraged by the finding that some dihydropteridine reductase-deficient patients were unresponsive. The preliminary observation that this limitation could be overcome by increasing the dose of the administered cofactor prompted us to reevaluate the potential of the tetrahydrobiopterin loading test in hyperphenylalaninemia. Fifteen patients, eight with ultimate diagnosis of phenylketonuria, three with 6-pyruvoyl tetrahydropterin synthase-, and four with dihydropterine reductase-deficiency, have been examined by administering synthetic tetrahydrobiopterin both orally, at doses of 7.5 and 20 mg/kg, and i.v., at a dose of 2 mg/kg. All the tetrahydrobiopterin-deficient patients, unlike those with phenylketonuria, responded to the oral dose of 20 mg/kg cofactor by lowering their serum phenylalanine concentration markedly below baseline to an extent easily detectable by Guthrie cards. This method allows for a simple screening method when enzyme or pterin studies are not available.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The prenatal diagnosis of a male fetus with glutaric aciduria type II and the time course of metabolite urinary excretion, starting immediately after birth, are described. Prenatal diagnosis was undertaken at the 17th wk of gestation by immunoblot analysis and pulse labeling experiments of amniocytes and, retrospectively, by stable isotope dilution analysis of six metabolites in amniotic fluid. The results were as follows:1) The immunochemical analysis on cultured amniocytes showed that the fetus, as the previous index case in this family, was affected with a deficiency of the β-subunit of electron transfer flavoprotein.2) Glutarate concentration was significantly increased in the cell-free supernatant of the amniotic fluid. In the postnatal period, most of the organic acids and acylglycines characteristic of the disorder appeared in urine within a week, although an increased excretion of hexanoylglycine was the only biochemical abnormality detectable in the first urine sample collected at 9 h after birth. Growth and development of this infant were normal during the following 6 mo of life, when he was receiving oral supplementation with L-carnitine and riboflavin. It should be underscored that transient abnormalities in routine blood tests (glutamic oxaloacetic transaminase, lactate dehydrogenase, and creatine phosphokinase) were present soon after birth, despite his asymptomatic clinical course. Early detection and aggressive treatment could be effective in such a form of glutaric aciduria type II.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The fetal and maternal concentration of various plasma proteins alters during pregnancy. Cells in the livers of fetal hamsters accumulate serum amyloid A (SAA) and C-reactive protein (CRP) mRNA, major acute phase reactants, when lipopolysaccharide is administered to the fetal circulation. No fetal SAA or CRP mRNA response is seen when the mother is stimulated at a remote site by endotoxin or a nonspecific inflammatory agent. In addition, cells of the fetal hamster liver do not respond by accumulating SAA mRNA when exposed to the specific cytokines, tumor necrosis factor, IL-1, and IL-6. CRP mRNA levels increased in fetal livers after administration of tumor necrosis factor and IL-1. These data suggest that cells contained in the fetal liver can respond during an acute phase reaction but that the capacity of some acute phase reactant genes to respond to cytokines may be developmentally regulated. Studies of immature hamsters after birth show that the responses of CRP and SAA genes to lipopolysaccharide, tumor necrosis factor, IL-1, and IL-6 are reduced when compared with induction of mRNA accumulation for these acute phase reactants in adult animals.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID