PubMed Health⌕ Search

Biomedical subjects

E F Bell

Publications and source records attributed to E F Bell.

At least 19 recordsLinked to original sources
PubMed1994

Diet and body composition of preterm infants.

There have been few systematic studies of the effects of energy and protein intake on the body composition of preterm infants. Analysis of published studies suggests a roughly inverse relation between energy stored per gram of weight gain (a measure of the fatness of new tissues) and the ratio of protein to energy in the preterm infant's diet. At least within a certain range of energy and protein intakes, a higher protein diet promotes leaner body composition. Studies of the effects of varying the dietary ratio of carbohydrate to fat in preterm infants have shown reduced rates of carbon dioxide production with high-fat diets, fed by either the parenteral or enteral route. The little information available suggests no clear effect of varying the carbohydrate-to-fat ratio on body composition. The mineral content of the body can be influenced by diet. Insufficient intakes of calcium and phosphorus reduce the bone mineral content and thus the whole-body content of these minerals.

Body Composition↗
PubMed1994

A gradient-layer calorimeter for measurement of energy expenditure of infants.

We have developed and validated a gradient-layer calorimeter for direct measurement of energy expenditure of preterm infants. Infant calorimeters must be operated and tested differently from adult calorimeters, because the calorimeter must be warmed during operation to limit heat loss from the infant, the calorimeter wall temperature (which is selected on the basis of the infant's maturity) must be precisely controlled, and energy expenditure (heat output) is typically < 10 W. We calibrated our calorimeter by varying the heat produced by a dry source (manikin or light bulb) with airflow (n = 42) and without airflow (n = 8) at various water jacket temperatures (n = 7) and by a wet source (combustion of ethyl alcohol) with airflow (n = 9). With no air moving, qc = 0.740 Vc + 0.029 Twj-0.697, where qc (W) is the estimated output of the heat source measured by the calorimeter, Vc (mV) is the gradient-layer voltage of the calorimeter, and Twj (degree C) is the temperature of the water jacket surrounding the walls of the device. From this equation and enthalpy calculations, the slope and intercept of the regression line relating the estimated heat production to the actual heat produced from alcohol combustion are 1.029 +/- 0.046 and -0.549 +/- 0.484 (SE), respectively. The slope is not significantly different from unity, and the intercept is not significantly different from zero. Thus we can accurately estimate the energy expenditure of preterm infants from the equations describing our calorimeter, and we can accurately resolve the total heat output into a dry (nonevaporative) component and a wet (evaporative) component.

Calibration↗
PubMed1993

Effect of intravenous amino acids on protein metabolism of preterm infants during the first three days of life.

Twenty-three preterm infants with respiratory distress syndrome (mean birth weight 1.07 kg, SD 0.24 kg) were randomly assigned to receive glucose alone or glucose with amino acids (1.5 g.kg-1.d-1) i.v. beginning on the 1st d of life. Blood ammonia and serum urea, CO2 content, sodium, potassium, chloride, and ionized calcium concentrations were normal and did not differ between treatment groups. Nitrogen balance was significantly greater in the group that received amino acids [88 (SD 54) versus -135 (SD 45) mg.kg-1.d-1]. In 12 infants (seven, glucose-only; five, glucose and amino acids), leucine kinetic studies were also performed on the 3rd d of life. These 12 infants received a 4-h primed constant infusion of L-[1-13C]leucine. Blood and breath were collected and analyzed for [1-13C]ketoisocaproate and 13CO2, respectively. Leucine turnover and oxidation were calculated. Both leucine turnover and oxidation were significantly higher in the group receiving amino acids than in the glucose-only group [241 (SD 38) versus 164 (SD 25) mumol.kg-1.h-1 and 71 (SD 22) versus 40 (SD 17) mumol.kg-1.h-1, respectively]. In addition, the calculated rate of protein synthesis was higher in the group receiving amino acids [6.9 (SD 1.1) versus 5.0 (SD 1.2) g.kg-1.d-1]. These data indicate that the i.v. administration of amino acids (1.5 g.kg-1.d-1) to ill preterm infants beginning on the 1st d of life improves whole-body protein balance as a result of increased protein synthesis.

Amino Acids↗
PubMed1992

Addition of metolazone to overcome tolerance to furosemide in infants with bronchopulmonary dysplasia.

A decreased response to the loop diuretic furosemide develops within a few doses in young infants. We tested the hypothesis that the use of the thiazide-like diuretic metolazone, in combination with furosemide, would inhibit water and electrolyte reabsorption and overcome pharmacologic tolerance to furosemide alone. Infants with bronchopulmonary dysplasia of similar gestational and postnatal ages were randomly assigned to one of three groups. Group 1 (n = 6) received furosemide (1 mg/kg per dose) intravenously every 24 hours for a total of five doses. Group 2 (n = 8) received the same treatment as group 1, but in addition metolazone (0.2 mg/kg per dose) was given enterally with doses 3 and 4 of furosemide. Group 3 (n = 8) received metolazone (0.2 mg/kg per dose) enterally every 24 hours for five doses. Urine was collected before the first diuretic dose and throughout the study for determination of the urine flow rate; urinary excretion of sodium, chloride, and potassium; and creatinine clearance. Urinary flow rate and urinary sodium and chloride excretion increased after the first dose in all groups. In the infants treated with either furosemide or metolazone, urinary flow rate and urinary and chloride excretion returned to baseline values after the last three doses. In contrast, when furosemide was administered with metolazone, urinary flow rate and urinary excretion of sodium, chloride, and potassium were greater than the values for baseline and for the previous dose, as well as for the corresponding doses of furosemide in group 1 and metolazone in group 3. Tolerance to furosemide (group 1) and metolazone (group 3) appeared to be explained by compensatory increased sodium and chloride reabsorption without changes in creatinine clearance. We conclude that the administration of metolazone with furosemide enhances diuresis, natriuresis, and chloruresis and overcomes the rapid development of tolerance to furosemide in infants with bronchopulmonary dysplasia by blocking the compensatory increase in renal sodium and chloride absorption.

Bronchopulmonary Dysplasia↗
PubMed1991

Plasma amino acid concentrations and amino acid ratios in normal adults and adults heterozygous for phenylketonuria ingesting a hamburger and milk shake meal.

Plasma amino acid concentrations were measured and selected amino acid ratios were calculated in 12 normal adults and 12 adults heterozygous for phenylketonuria (PKU) ingesting a hamburger and milk shake meal providing 1 g protein/kg body wt. Plasma concentrations of all amino acids increased significantly over baseline after meal ingestion in both groups, reaching the highest mean values 3-5 h after meal ingestion. Plasma phenylalanine concentrations were significantly higher in heterozygous than in normal subjects both before and at all times after meal ingestion. The absolute increase in plasma phenylalanine concentration over baseline and the area under the plasma phenylalanine concentration-time curve were approximately twice as large in heterozygous as in normal subjects. However, the molar ratio of the plasma phenylalanine concentration to the sum of the plasma concentrations of the other large neutral amino acids did not increase significantly over baseline, but rather decreased.

Amino Acids↗
PubMed1991

Infrared thermometry of newborn infants.

An infrared thermometer, the FirstTemp, was tested among newborn infants by comparing tympanic membrane temperature measurements in three operating modes, "Cal-tympanic," "Cal-surface," and "Cor-tympanic," with nearly simultaneous tympanic membrane, rectal, and axillary temperature measurements using other standard methods. The FirstTemp underestimated other measurements of body temperature in the "Cal-tympanic" mode and overestimated them in the "Cor-tympanic" mode. In the "Cal-surface" mode, the First-Temp readings were significantly lower than tympanic membrane temperatures measured with a thermistor probe and electronic thermometer (mean difference 0.2 degrees C) but not significantly different from rectal or axillary temperatures. According to these results, the FirstTemp can be used reliably in the "Cal-surface" mode but not in the "Cal-tympanic" or "Cor-tympanic" mode. Its speed and ease of operation offer significant advantages over traditional clinical methods of temperature measurement.

Axilla↗
PubMed1990

Variability of abdominal circumference of premature infants.

Serial measurements of abdominal circumference were made in 27 premature infants 1 hour before feeding, immediately before and after feeding, and 1 and 2 hours after feeding. In some infants these measurements were repeated for 2 (n = 18) or 3 (n = 3) consecutive days. All 258 measurements were performed by the same examiner; 124 were also repeated blindly by another examiner to test interobserver reliability. The coefficient of variation of repeated measurements of any one infant by the same examiner on a single day was 2.7%. Ninety percent of repeated measurements agreed within 1.5 cm. The interobserver reliability was 0.99. Abdominal circumference was positively correlated with birth weight (P = .0001) and time from last defecation (P = .0001) and negatively correlated with time from last feeding (P = .04). Increases in abdominal circumference of less than 1.5 cm occur normally and, in the absence of other clinical signs, should not be considered indicative of disease.

Abdomen↗
PubMed1990

Repeated ingestion of aspartame-sweetened beverages: further observations in individuals heterozygous for phenylketonuria.

Six adults heterozygous for phenylketonuria (PKU) ingested eight successive servings of unsweetened and aspartame (APM)-sweetened beverage at 1-hour intervals in a randomized, balanced, crossover design. In one part, the eight beverage servings were not sweetened. In the other, each of the eight beverage servings provided 600 mg of APM, a dose equivalent to the amount provided by 36 oz of an APM-sweetened diet beverage. Plasma aspartate concentration was not significantly increased after ingestion of unsweetened or APM-sweetened beverage. Similarly, ingestion of the unsweetened beverage had no significant effect on plasma phenylalanine concentration. However, ingestion of APM-sweetened beverage significantly increased plasma phenylalanine concentrations 2.35 to 4.03 mumol/dL above baseline 30 minutes after ingestion. Plasma phenylalanine values reached a steady-state after administration of five servings of APM-sweetened beverage and were slightly, but significantly higher than usual postprandial values for adults heterozygous for PKU. Similarly, the ratio of the plasma phenylalanine concentration to the sum of the concentration of the large neutral amino acids was significantly higher than usual postprandial values. Blood methanol and formate concentrations remained within normal limits. These data indicate that a fasting adult heterozygous for PKU could consume the equivalent of 24 12-oz servings of APM-sweetened beverage over an 8-hour period and only increase plasma phenylalanine concentration to a modest degree.

Adult↗
PubMed1990

Aspartame ingestion with and without carbohydrate in phenylketonuric and normal subjects: effect on plasma concentrations of amino acids, glucose, and insulin.

Seven subjects homozygous for phenylketonuria (PKU) and seven normal subjects were administered four beverage regimens after an overnight fast: unsweetened beverage, beverage providing carbohydrate (CHO), beverage providing aspartame (APM), and beverage providing APM plus CHO. The APM dose (200 mg) was the amount provided in 12 oz of diet beverage; the CHO was partially hydrolyzed starch (60 g). Plasma amino acid concentrations were determined after dosing and the molar plasma phenylalanine (Phe) to large neutral amino acid (LNAA) ratio calculated. APM administration without CHO did not increase plasma Phe concentrations over baseline values in either normal or PKU subjects (5.48 +/- 0.85 and 150 +/- 23.0 mumols/dL, respectively). Similarly, the Phe/LNAA did not increase significantly. Ingestion of beverage providing APM and CHO did not significantly increase plasma Phe concentrations over baseline values in either normal or PKU subjects. However, ingestion of beverage providing CHO (with or without APM) significantly decreased plasma levels of valine, isoleucine, and leucine 1.5 to 4 hours after dosing in both normal and PKU subjects, thereby increasing the Phe/LNAA ratio significantly. These data indicate that changes noted in Phe/LNAA values after ingestion of beverage providing APM plus CHO were due to CHO. The plasma insulin response to beverage providing CHO (with or without APM) was significantly higher in PKU subjects than in normals.

Adolescent↗
PubMed1990

Effect of sucrose on the metabolic disposition of aspartame.

Twelve normal adult subjects ingested a beverage providing 0.136 mmol aspartame/kg body wt on 2 different days. On 1 study day the beverage provided only aspartame, on the other the beverage provided both aspartame and 3.51 mmol sucrose/kg body wt. The high mean plasma phenylalanine concentrations were similar after administration of aspartame alone (158 +/- 28.9 mumol/L, mean +/- SD) and administration of aspartame plus sucrose (134 +/- 44.1 mumol/L). Evaluation of the area under the plasma concentration-time curve (AUC) for phenylalanine also showed no significant difference between groups (197 +/- 49.1 vs 182 +/- 28.3 mumol.L-1.h for aspartame alone and aspartame plus sucrose, respectively). Similarly, the high mean ratio of phenylalanine to large neutral amino acids (Phe:LNAA) in plasma did not differ significantly (0.265 +/- 0.046 for aspartame alone, 0.275 +/- 0.107 for aspartame plus sucrose). However, there was a small but significant difference between groups for the 4-h AUC values for plasma Phe:LNAA. The simultaneous ingestion of sucrose with aspartame had only minor effects on aspartame's metabolic disposition.

Adult↗
PubMed1989

Effect of repeated ingestion of aspartame-sweetened beverage on plasma amino acid, blood methanol, and blood formate concentrations in normal adults.

Aspartame (APM) is a widely used dipeptide sweetener (L-aspartyl-L-phenylalanine methyl ester). It has been suggested that excessive use of APM might elevate plasma aspartate, phenylalanine, and/or methanol concentrations to levels that are potentially harmful. Six normal young adults ingested eight successive servings of unsweetened and APM-sweetened beverage at one-hour intervals in a balanced crossover design. In one part, the beverage was not sweetened. In the other, each serving of beverage provided 600 mg APM, a dose equivalent to the amount provided by 36 oz of APM-sweetened diet beverage. Plasma aspartate concentration was not significantly increased after ingestion of unsweetened or APM-sweetened beverage. Similarly, ingestion of the unsweetened beverage had no significant effect on plasma phenylalanine concentration. However, ingestion of APM-sweetened beverage significantly increased plasma phenylalanine levels 1.41 to 2.35 mumol/dL above baseline 30 minutes after ingestion. Plasma phenylalanine values reached a steady state after administration of four to five servings and did not exceed normal postprandial values at any time. Blood methanol and formate concentrations remained within normal limits. The data indicate ready metabolism of APM when administered at levels that may be ingested by normal individuals who are heavy users of diet beverages.

Adult↗
PubMed1989

Repeated ingestion of aspartame-sweetened beverage: effect on plasma amino acid concentrations in individuals heterozygous for phenylketonuria.

It has been suggested that excessive use of aspartame (APM) (N-L-alpha-aspartyl-L-phenylalanine methyl ester) might grossly elevate plasma aspartate and phenylalanine concentrations in individuals heterozygous for phenylketonuria (PKUH). In study 1 six adult PKUH (three males; three females) ingested three successive 12-oz servings of beverage at 2-h intervals. The study was carried out in two parts in a randomized crossover design. In one arm the beverage was not sweetened. In the other the beverage provided 10 mg APM/kg body weight per serving. The addition of APM to the beverage did not significantly increase plasma aspartate concentration but did increase plasma phenylalanine levels 2.3 to 4.1 mumol/dL above baseline values 30 to 45 min after each dose. The high mean plasma phenylalanine level after repeated APM dosing (13.9 +/- 2.15 mumol/dL) was slightly, but not significantly, above the normal postprandial range for PKUH (12.6 +/- 2.11 mumol/dL). In study 2 six different adult PKUH ingested beverage providing 30 mg APM/kg body weight as a single bolus. The high mean plasma phenylalanine concentration and the phenylalanine to large neutral amino acid ratio were significantly higher when APM was ingested as a single bolus than when ingested as a divided dose.

Adult↗
PubMed1989

Upper limit of vitamin E in infant formulas.

Reports of toxicity to enterally administered vitamin E are rare in infants. However, increased risks of sepsis and necrotizing enterocolitis have been reported after both enteral and parenteral vitamin E, primarily when plasma (or serum) vitamin E levels exceed 3.5 mg/dl. Levels this high are seldom seen with enteral vitamin E when intake is 25 mg d-alpha-tocopherol equivalent/(kg.d) or less. Intakes below this threshold will be provided by infant formulas with vitamin E to energy ratios of up to 20 mg/100 kcal (30 IU/100 kcal) so long as energy intake does not exceed 125 kcal/(kg.d). To allow a margin of safety, it would be reasonable to limit the amount of vitamin E added to the formula during its manufacture to half this amount, or 10 mg/100 kcal (15 IU/100 kcal). This level coincides with the highest levels of vitamin E found in human colostrum and is 20 times the recommended lower limit for vitamin E in infant formula of 0.5 mg/100 kcal.

Adult↗
PubMed1989

Effects of furosemide on body water compartments in infants with bronchopulmonary dysplasia.

We studied the effects of a single dose of intravenous furosemide on the body water compartments of nine infants with bronchopulmonary dysplasia. We measured total body water, extracellular water, and plasma volume using deuterium oxide, sodium bromide, and Evans blue dye, respectively. From the results of these measurements, we calculated cell water, interstitial water, red cell volume, and total blood volume. We performed these measurements on the first day of the study and again 28 h later, 4 h after an intravenous dose of furosemide (1 mg/kg). All infants had a brisk diuresis in the first hour after the dose, but urine output was no greater during the 24-h period after the dose than during the preceding 24-h period. Total body water, extracellular water, and interstitial water were significantly decreased 4 h after furosemide. There was no change in plasma volume, red cell volume, or total blood volume.

Body Fluid Compartments↗
PubMed1989

Antipyrine interferes with chemical determination of bromide in simultaneous estimation of total body water and extracellular water.

Antipyrine and bromide dilution are frequently used to estimate total body water and extracellular water volumes, respectively. We assessed a potential error with the simultaneous use of these methods. In vitro the bromide concentration of solutions measured by the gold chloride or rosaniline methods decreased linearly with increasing concentrations of antipyrine. With the gold chloride method, the "inhibitory" effect of antipyrine was more pronounced for solutions in plasma than in those in water. With the rosaniline method, the "inhibitory" effect was similar for water and plasma. Antipyrine had no effect on bromide concentration measured by fluorescein or fluorescence excitation methods. We conclude that antipyrine potentially affects the measurement of bromide space by certain colorimetric methods. The mean values of previously published data do not appear to have been affected by the technical problems described in this study, although these problems may account, at least in part, for the large variability of the results.

Antipyrine↗
PubMed1987

Plasma amino acid concentrations in normal adults administered aspartame in capsules or solution: lack of bioequivalence.

Some clinical studies require administration of test compounds in capsules to assure that the compound cannot be distinguished from a placebo. This raises the question of whether the pharmacokinetic responses produced by capsule administration are similar to values obtained when test compounds are ingested in solution. To test this, plasma phenylalanine and aspartate concentrations were compared in ten normal subjects ingesting 3 g aspartame in solution and in capsules in a balanced Latin square design. Peak plasma phenylalanine levels were significantly higher (191 +/- 65.4 v 117 +/- 39.5 mumol/L, mean +/- SD) and were reached significantly earlier (32 +/- 15 v 123 +/- 74 minutes) when aspartame was administered in solution than when it was administered in capsules. The area under the four-hour plasma phenylalanine concentration-time curve was significantly higher (15,340 +/- 4,820 v 8,465 +/- 3,356 mumol/L X min) when aspartame was ingested in solution. Administration in solution also produced a significantly higher ratio of plasma phenylalanine concentration to the sum of the plasma concentrations of the other large neutral amino acids (0.36 +/- 0.12 v 0.23 +/- 0.06). Similarly, peak plasma aspartate concentrations were significantly higher 26.2 +/- 16.3 v 10.4 +/- 5.0 mumol/L) and were reached significantly earlier (30 +/- 14 v 106 +/- 61.3 min) when aspartame was administered in solution. The data indicate different plasma phenylalanine and aspartate pharmacokinetics between solution and capsule administration of aspartame.

Adult↗