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Biomedical subjects

L J Filer

Publications and source records attributed to L J Filer.

At least 73 records · Page 4Linked to original sources
PubMed1980

Effect of an abuse dose of aspartame upon plasma and erythrocyte levels of amino acids in phenylketonuric heterozygous and normal adults.

Plasma and erythrocyte levels of free amino acids were measured in five female subjects known to be heterozygous for phenylketonuria and six subjects assumed to be normal (three male, three female) who were administered an abuse dose of aspartame (100 mg/kg) in orange juice. Small increases in plasma aspartate levels were noted 30 minutes after aspartame loading in both groups, with mean (+/- SD) levels increasing from 0.15 +/- 0.05 mumoles/100 ml to 0.43 +/- 0.23 mumoles/100 ml in normal subjects (P = 0.02), and from 0.49 +/- 0.23 mumoles/100 ml to 0.80 +/- 0.56 mumoles/100 ml in heterozygous subjects (P > 0.05). However, plasma aspartate levels remained within normal postprandial levels in each case. Erythrocyte aspartate levels were unchanged in both groups. In normal subjects, plasma phenylalanine levels (mean +/- SD) increased from fasting levels (5.40 +/- 1.05 mumoles/100 ml) to mean peak values of 20.2 +/- 6.77 mumoles/100 ml. In heterozygous subjects, mean peak plasma phenylalanine levels were approximately twice as high (41.7 +/- 2.33 mumoles/100 ml), and the area under the plasma concentration-time curve twice as large. Peak plasma phenylalanine levels, however, were below those associated with toxic effects. The data indicate slower, but adequate metabolism and clearance of an abuse dose of aspartame by the phenylketonuric heterozygote.

Amino Acids↗
PubMed1979

Methionine fortification of a soy protein formula fed to infants.

Data from study of nine normal full-term infants fed a soy isolate-based formula unsupplemented with methionine were compared with similar data from study of 10 similar infants fed the same formula supplemented with L-methionine and with data from previous studies of larger groups of infants receiving various other feedings. Food intake, growth, and serum chemical values were studied from 8 through 111 days of age. In addition, nitrogen balance studies were carried out. Statistically significant differences were as follows: lesser weight gain per 100 kcal by infants fed the unsupplemented soy isolate-based formula than by infants fed milk-based or other soy isolate-based formulas; lesser serum concentrations of albumin at age 28 days by infants fed the unsupplemented soy isolate-based formula than by breast-fed infants; greater serum concentrations of urea nitrogen by infants receiving the unsupplemented soy isolate-based formula than by those receiving the same formula supplemented with L-methionine. A number of other differences was noted but were not statistically significant. The results suggest that normal infants fed a formula providing 2.25 /100 kcal of a soy protein isolate not fortified with methionine performed less well during the first 6 weeks of life than did breast-fed infants and infants fed milk-based formulas or other soy isolate-based formulas fortified with methionine. The limiting nutrient appears to have been methionine.

Aging↗
PubMed1978

Early nutrition: its long-term role.

The widespread belief that problems such as lifelong obesity originate in infancy sometimes leads to overzealous attempts to regulate energy intake too soon and may compromise linear growth. Treatment of obesity should wait unitl after age one.

Age Factors↗
PubMed1977

Effect of diet on plasma aminograms of low birth weight infants.

The composition of nutrient mixtures for the low birth weight infant is a matter of considerable concern, and questions have been raised about the adequacy of the cystine and tyrosine contents of available preparations. Low birth weight infants were fed isonitrogenous isocaloric formulas whose content of tyrosine and cystine varied 3- and 7-fold, respectively, for 3-day periods in a Latin Square design. Two-hour postprandial plasma aminograms indicate a statistically significant difference (P = 0.05) between plasma cystine levels noted in infants fed the formula containing cystine at 6 mg/100 ml and those fed the formula containing cystine at 28 mg/100 ml. No significant differences were noted between other formula groupings. Plasma tyrosine concentrations were rapidly reduced whenever tyrosine intake was less then 50 mg/kg of body weight. Such a dietary approach may be of value in reduction of the elevated plasma tyrosine levels seen in infants with transient tyrosinemia of prematurity. Postprandial concentrations of plasma amino acids for the low birth weight infant are a useful reference standard for evaluation of the response of the low birth weight infant to new therapeutic feeding mixtures, particularly parental or jejunal feedings.

Amino Acids↗
PubMed1977

Effect of aspartame and aspartate loading upon plasma and erythrocyte free amino acid levels in normal adult volunteers.

Aspartame is a dipeptide (L-aspartyl-L-phenylalanyl-methyl ester) with a sweeting potential 180 to 200 times that of sucrose. Questions have been raised about potential toxic effects of its constituent amino acids, aspartate and phenylalanine when the compound is ingested in large amounts. Plasma and erythrocyte amino acid levels were measured in 12 normal subjects after administration of either Aspartame (34 mg/kg) or equimolar quantities of aspartate (13 mg/kg) in a crossover design. No changes in either plasma or erythrocyte aspartate levels were noted at any time after either Aspartame or aspartate ingestion. Plasma phenylalanine levels decrease slightly after aspartate loading, and increased from fasting levels (4.9 +/- 1 mumoles/100 ml) to 10.7 +/- 1.9 mumoles/100 ml about 45 to 60 minutes after Aspartame loading. Phenylalanine levels returned to baseline by 4 hours. Erythrocyte phenylalanine levels showed similar changes.

Adult↗
PubMed1977

Skim milk in infant feeding.

Skim milk in infant feeding. Acta Paediatr Scand, 66:17, 1977. --Ninety-four infants were enrolled at 112 days of age in a study of food intake and growth and 88 were considered to have completed satisfactorily the planned 56 days of observation. The infants lived at home. Feedings consisted of a commercially available formula (Similac, 67 kcl/100 ml) or a slightly modified skim milk (Formula 305, 36 kcal/100 ml) and commercially prepared strained foods. Energy intake and gain in weight were significantly greater by infants fed Similac than by those fed Formula 305. Gain in length was nearly identical in the two feeding groups. During the 56 days of observation, triceps and subscapular skinfold thicknesses changed little in infants fed Similac but decreased approximately 25% in infants fed Formula 305. It is suggested that body fat stores of infants fed Formula 305 were mobilized to permit growth of fat-free tissue.

Adipose Tissue↗
PubMed1976

Blood pressure, salt preference, salt threshold, and relative weight.

This study was performed to observe the relationships of salt preference, salt threshold, the relative weight to blood pressure. Three groups were selected from 4,800 school children on the basis of mean blood pressure: less than or equal to fifth percentile, in the area of the 50th percentile, and greater than or equal to 95th percentile. Salt threshold was determined by titrating, on each subject's tongue, solutions ranging from 1 to 60 millimols/liter of sodium chloride. Salt preference was tested by the addition of salt by each subject to unsalted tomato juice and beef broth according to individual taste. The samples were then analyzed for sodium concentration. The coefficient of correlation for the amount of salt added to juice and broth was significant (r=0.63). There was no relationship of salt threshold to preference, nor did threshold or preference relate to blood pressure. Relative weight was related to blood pressure range being the most obese.

Adolescent↗
PubMed1976

Influence of fat and carbohydrate content of diet on food intake and growth of male infants.

Two groups of normal fullterm infants were studied from 8 to 112 days of age while receiving formulas of the same caloric density and prepared from the same ingredients. A limited selection of strained foods were permitted. From the combination of formula and strained foods, one group received 29% of calories from fat and 62% from carbohydrate whereas the other received 57% from fat and 34% from carbohydrate. Fifteen infants in each group completed the study as planned. Energy intakes per kilogram and rates of gain in length and weight were similar in the two feeding groups.

Body Weight↗
PubMed1976

Mercury in human maternal and cord blood, placenta, and milk.

Total mercury concentration was measured by atomic absorption spectrophotometry in 100 maternal-umbilical cord blood pairs, 39 placentae, and 32 breast milk samples, all from patients at the University of Iowa Hospitals. The mean maternal and cord blood levels were 1.01 and 1.24 parts per billion (ppb), respectively. Though the difference between maternal and cord values was not statistically significant, the two were significantly correlated with each other, and maternal blood level increased significantly with maternal age. Mean placental and milk concentrations were 2.28 and 0.93 ppb, respectively. The mercury levels in this study were lower than those reported from elsewhere, probably reflecting a combination of methodological refinement and relatively low mercury exposure in a rural population whose diet is low in fish consumption. These low levels suggest that the risk of perinatal mercury damage is small in such a population.

Age Factors↗
PubMed1975

Placental transfer of glutamate and its metabolites in the primate.

When radioactive glutamate was infused into pregnant rhesus monkeys, 69 to 88 per cent of radioactivity in the maternal plasma remained in association with glutamate while 10 to 22 per cent was converted to glucose. In the fetal plasma, glucose and lactate accounted for more than 80 per cent of radioactivity, with less than 2 per cent of the label found in glutamate. Maternal glutamate infusions resulting in a ten- to twenty-fold increase in maternal plasma glutamate levels (60 to 100 mumoles per 100 ml.) had no effect upon fetal glutamate levels. Infusions producing maternal glutamate levels 70 times normal (280 mumoles per 100 ml.) did result in some transfer of glutamate to the fetal circulation. Labeled glutamate administered to the fetus at 1.5 to 2.4 Gm. per kilogram of fetal weight did not result in glutamate transfer to the maternal circulation. Infusion of glutamate to the fetus at 5 Gm. per kilogram of fetal weight increased fetal plasma glutamate levels to 2, 000 mumoles per 100 ml. and resulted in some transfer of glutamate to maternal circulation. Glutamate metabolites (lactate and glucose) were readily transferred across the placenta in either direction. These studies indicate that the primate placenta is virtually impermeable to glutamate unless extreme elevations of plasma glutamate are induced.

Amino Acids↗
PubMed1975

Monosodium glutamate metabolism in the neonatal monkey.

Monosodium glutamate (MSG) administered by gastric tube to 10 infant monkeys at doses of 1-4 g/kg produced rapid increases in plasma glutamate (17- to 33-fold) and aspartate (50- to 90-fold) levels. The degree of elevation was proportional to the dose administered. Levels of other amino acids were unaffected. Two of the monkeys exhibited high fasting glutamate levels and abnormal glutamate tolerance curves. Despite this apparent decreased ability to metabolize glutamate, neither these animals nor any of the others for whom morphologic studies have been previously reported demonstrated neurotoxicity. Studies using 14-C-labeled glutamated indicated conversion of administered glutamate to two ninhydrin-negative compounds identified as glucose and lactate, as well as to asparate.

Amino Acids↗