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Biomedical subjects

R J Cooke

Publications and source records attributed to R J Cooke.

53 records · Page 3Linked to original sources
PubMed1985

Impairment of lipid emulsion metabolism associated with carnitine insufficiency in premature infants.

Carnitine status and its relation to lipid metabolism were determined in 11 premature infants (less than 34 weeks of gestation) receiving parenteral nutrition. Intravenous administration of lipid emulsion increased serum concentrations of free fatty acids at 2, 4, and 8 h after infusion. Despite this increase, serum levels of ketone bodies remained low, reaching only 40 to 45% of levels in full-term infants receiving enteral feeds. In premature infants, levels of plasma total and free carnitine were about half those in full-term infants and were not altered by lipid infusion. The results indicate limited potential for lipid emulsion as a source of energy in premature infants, possibly because carnitine insufficiency restricts fatty acid oxidation.

Carnitine↗
PubMed1985

Safflower oil emulsion administration during parenteral nutrition in the preterm infant. 1. Effect on essential fatty acid status.

To determine the effect of a safflower oil emulsion on the essential fatty acid (EFA) status of preterm infants during parenteral nutrition, subjects were randomized to receive Liposyn at 0.34 g (group 1), 0.68 g (less than 0.5% of lipid from linolenic acid, group 2), or Modified Liposyn at 0.68 g/kg/day (5.0% of lipid from linolenic acid, group 3). Doses of 0.34 and 0.68 g of Liposyn provided linoleic acid in amounts equivalent to 2 and 4% of the estimated caloric requirement (120 cal/kg/day) and 5 and 10% of the actual caloric intake. No significant differences were detected in plasma phospholipid triene/tetraene ratios and arachidonic acid levels between groups 1 and 2 or between groups 2 and 3, respectively. Plasma phospholipid triene/tetraene ratio and arachidonic acid did not change in the lipid-supplemented group throughout the study period, but the former remained significantly lower (p less than 0.001) and the latter significantly greater (p less than 0.001) than in a reference group of infants who received fat-free parenteral nutrition. We conclude that Liposyn administration providing linoleic acid at 2 or 4% of the estimated caloric requirement or 5 or 10% of the actual caloric intake prevented any significant changes in essential fatty acid status from occurring. Moreover, linolenic acid supplementation at 5% of the total lipid intake did not appear to affect arachidonic acid synthesis in the preterm infant.

Arachidonic Acid↗
PubMed1985

Safflower oil emulsion administration during parenteral nutrition in the preterm infant. 2. Effect on triglyceride and free fatty acid levels.

During a study to evaluate the effect of a safflower oil emulsion on essential fatty acid status during parenteral nutrition, we also measured plasma triglycerides and plasma free fatty acids (FFA) in a group of preterm infants. Subjects received 0.34 g/kg (group 1) or 0.68 g/kg (group 2) of lipid daily for 5 days. Essential fatty acid status remained normal in both groups, but the changes in plasma triglycerides were greater (p less than 0.025), and hypertriglyceridemia was somewhat more common (p = 0.06) in group 2 than in group 1. Plasma FFA did not differ in either treatment group. However, postinfusion FFA were greater (p less than 0.05) and FFA uptake was less (p less than 0.05) in infants at less than 32 than at 32-34 weeks gestation, but in no instance did postinfusion FFA exceed an FFA/albumin ratio of 6:1. In addition, triglyceride and FFA uptake did not improve during the study, but the changes in plasma triglycerides and FFA were greater (p less than 0.05) at the end than at the beginning of the study.

Emulsions↗
PubMed1984

Effect of taurine supplementation on hepatic function during short-term parenteral nutrition in the premature infant.

To evaluate the potential role of taurine deficiency in the pathogenesis of parenteral nutrition-induced cholestasis, 20 premature (less than 34 weeks AGA) infants were randomized to receive parenteral nutrition with and without taurine (10.8 mg/kg/day) during the first 10 days of life. Birth weight, gestational age, and protein and caloric intake were similar in both groups. Plasma taurine levels and hepatic function were assessed before the study began (3 +/- 1 days of age), at 5 +/- 1 days of age, and at 9 +/- 1 days of age. Although plasma taurine levels were significantly greater at 5 +/- 1 and 9 +/- 1 days of age (p = 0.009) in the group receiving supplementation, no differential effect on hepatocellular function could be detected during this short period of time. A decrease in plasma ammonia (p = 0.001), alanine aminotransferase (ALT) (p = 0.036), gamma-glutamyltranspeptidase (GGTP) (p = 0.05), 5'-nucleotidase (5'N) (p = 0.001), and bile salt concentrations was noted in both groups, indicating the rapid maturation of hepatic function even in the presence of parenteral nutrition during the first 10 days of life.

Animals↗
PubMed1984

Essential fatty acid status of the premature infant during short-term fat-free parenteral nutrition.

This study was designed to evaluate the effect of fat-free parenteral nutrition on the essential fatty acid status of a group of stable premature infants during the first 10 days of life. Nine infants had a gestational age of less than 32 weeks (Group 1), and 10 infants, 32-34 weeks (Group 2). Five of nine infants in Group 1 and two of 10 infants in Group 2 developed essential fatty acid deficiency (EFAD) (triene/tetraene ratio greater than 0.4). In three infants, EFAD was present by 5 days of age; and in four, between 5 and 10 days of age. The difference in frequency of EFAD between Groups 1 and 2 is statistically significant (p less than 0.05). The development of EFAD as a function of postnatal age could be predicted using a simple regression, y = -0.14 + 0.07x (r = 0.64, p less than 0.0001), where y represents the triene/tetraene ratio and x the postnatal age in days. We conclude that (a) EFAD may develop rapidly in the premature infant; (b) the more immature the infant, the greater the risk of EFAD; (c) the degree of EFAD increases with the duration of fat-free parenteral nutrition.

Chromatography, Thin Layer↗
PubMed1980

General characteristics of normal and stress-enhanced protein degradation in Lemna minor (duckweed).

The general features of protein degradation in Lemna minor were studied by using a double-isotope technique. In common with several animal systems, there are correlations between the relative rate of protein degradation on the one hand and molecular weight, charge and carbohydrate content on the other. Large proteins, acidic proteins and non-glycosylated proteins are degraded relatively more rapidly than small or basic proteins, or glycoproteins. The correlations with size and carbohydrate content are explicable on the basis of differential susceptibility to Pronase, whereas the charge correlation cannot be explained on the basis. In addition, acidic proteins are not generally of higher molecular weight than neutral or basic proteins. The correlations are found in fronds growing in normal complete medium and in fronds transferred to medium lacking nitrate of made 50% (v/v) with respect to deuterium oxide, both of which are conditions that induce a large increase in protein breakdown in Lemna. Thus basal protein degradation and enhanced degradation do not appear to differ fundamentally in their general characteristics. The results are discussed in relation to the reported features of normal and enhanced proteolysis in animal tissues and to the possible mechanism of protein degradation in Lemna.

Carbohydrate Metabolism↗
PubMed1980

Model for Stress-induced Protein Degradation in Lemna minor.

Transfer of Lemna minor fronds to adverse or stress conditions produces a large increase in the rate of protein degradation. Cycloheximide partially inhibits stress-induced protein degradation and also partially inhibits the protein degradation which occurs in the absence of stress. The increased protein degradation does not appear to be due to an increase in activity of soluble proteolytic enzymes. Biochemical evidence indicates that stress, perhaps acting via hormones, affects the permeability of certain membranes, particularly the tonoplast. A general model for stress-induced protein degradation is presented in which changes in membrane properties allow vacuolar proteolytic enzymes increased access to cytoplasmic proteins.

Journal Article↗
PubMed1979

Stress and Protein Turnover in Lemna minor.

Transfer of fronds of Lemna minor L. to adverse growth conditions or stress situations causes a lowering of the growth rate and a loss of soluble protein per frond, the extent of the loss being dependent on the nature of the stress. The loss or protein is due to two factors: (a) a decrease in the rate constant of protein synthesis (ks); (b) an increase in the rate constant of protein degradation (kd). In plants adapted to the stresses, protein synthesis increases and the initially rapid rate of proteolysis is reduced. Addition of abscisic acid both lowers ks and increases kd, whereas benzyladenine seems to alleviate the effects of stress on protein content by decreasing kd rather than by altering ks. Based on the measurement of enzyme activities, stress-induced protein degradation appears to be a general phenomenon, affecting many soluble proteins. The adaptive significance of stress-induced proteolysis is discussed.

Journal Article↗
PubMed1975

Palmitic acid and lecithin measurements in amniotic fluid.

A method is described for the rapid and quantitative estimation of total amniotic fluid palmitic acid. Palmitic acid and lecithin were measured in 140 samples of amniotic fluid in normal and abnormal pregnancy, and the correlation coefficient between the two parameters was 0.93. It is concluded that amniotic fluid palmitic acid measurements are of value in the prenatal determination of fetal pulmonary maturity.

Amniocentesis↗
PubMedDate not supplied

Methodology of nutrient balance studies in the preterm infant.

Although nutrient balances are used to determine nutrient assimilation, the balance technique is not well described in the preterm infant. Our purpose is to describe the balance technique; discuss factors that may interfere with complete balance collections; and determine the effects of intake, patient characteristics, and formula fed on nutrient assimilation in the preterm infant. Fifty-four 84-h balances were performed in a group of well premature infants receiving either a casein- (Similac with Iron) or whey-predominant (Similac with Whey plus Iron) infant formula. Mean (+/- SD; range) birth weight, gestation, postnatal age, and balance weight were 1,320 g (+/- 200; 820-1,720), 32.0 weeks (+/- 2.0; 27-34), 36 days (+/- 14.8; 15-87), and 1,729 g (+/- 146; 1,435-2,070), respectively. Although absorption and retention varied, results were comparable with previous studies in the preterm infant. Results of linear regression analysis, using the stepwise regression procedure, indicate that variability in nutrient intake (mg/kg/day) accounted for 97 and 84% of the variability in nitrogen absorption and retention (mg/kg/day). Variability in nutrient intake (mg/kg/day) also accounted for 96 and 57% of the variability in phosphorus absorption and retention (mg/kg/day). Effects due to intake, birth weight, gestation, postnatal age, balance weight, and formula fed also accounted for a substantial part of the variability in calcium, zinc, and copper absorption and retention. The results of this study indicate that factors other than birth weight, gestation, and the type of formula fed have a significant effect on absorption and retention of nutrients and should be considered as confounding variables when interpreting effects due to treatment.

Absorption↗
PubMedDate not supplied

Nutrient balance studies in the preterm infant: crossover and parallel studies as methods of experimental design.

Crossover and parallel studies were compared as methods of experimental design during nutritional balance studies in the preterm infant. Twelve formula-fed infants (birth weight, 1,362 +/- 125 g, mean SD; gestational age, 32.3 +/- 1.7 weeks) were studied over 2 continuous weeks, "period" being the only obvious difference between the weeks. During each week, growth was determined, and 84-h nutrient balance was performed. Growth was adequate during both weeks. Increased absorption and retention (mg/kg/day and percent) of calcium and copper were noted during the 2nd week. Increased retention (mg/kg/day and percent) of phosphorus and magnesium was noted also, indicating increased nutrient assimilation due to a period effect. However, the variance due to the period effect (crossover) was less than that associated with "patient characteristics" (parallel study). In addition, sample size requirements were less, indicating that crossover studies are more efficient than parallel studies as a method of experimental design.

Analysis of Variance↗
PubMedDate not supplied

Overestimation of neonatal PO2 by collection of arterial blood gas values with the butterfly infusion set.

The butterfly, or scalp vein infusion set, is a widely used and convenient way to collect arterial blood gas samples in neonates. Analyzing arterial blood gas values by using this technique in a clinical situation, we obtained elevated values of PO2 in blood samples collected and measured from butterfly tubing in comparison with tuberculin syringe controls. Diffusion of gas through the polyvinylchloride tubing was suggested and proved by a study of pairs of butterfly and tuberculin syringes filled with venous blood from the blood bank. In conclusion, the butterfly gives falsely elevated PO2 values as a result of gas diffusion and is not a reliable technique for arterial blood gas sampling in neonates.

Blood Specimen Collection↗