Biomedical subjects
S E Carlson
Publications and source records attributed to S E Carlson.
First year growth of preterm infants fed standard compared to marine oil n-3 supplemented formula.
Very low birth weight (VLBW) infants (748-1390 g, n = 65) were randomly assigned to receive control or marine oil-supplemented formula when they achieved intakes > 454 kJ (110 kcal)/kg/d of a formula designed for VLBW infants. Study formulas with or without marine oil were provided until 79 wk of postconceptional age (PCA), first in a formula designed for preterm infants followed by a formula designed for term infants. Infants were studied at regular intervals through 92 wk PCA. Weight, length, and head circumference were determined by standardized procedures and normalized to the National Center for Health Statistics figures for growth of infants born at term of the same age and gender. Mean normalized weight, weight-to-length, and head circumference were greatest at 48 wk and decreased thereafter. The decline in normalized weight was greater in infants fed the marine oil-supplemented formula. Beginning at 40 wk, marine oil-supplemented infants compared to controls had significantly poorer Z-scores for weight, length and head circumference. In addition, birth order (negatively) and maternal height (positively) influenced weight and length achievement in infancy as shown previously in infants born at term.
Effect of vegetable and marine oils in preterm infant formulas on blood arachidonic and docosahexaenoic acids.
Adding docosahexaenoic acid (DHA) (22:6n-3) to formulas is more effective than increasing formula alpha-linolenic acid (18:3n-3) in maintaining blood phospholipid DHA levels similar to those in breast-fed infants. However, in long-term trials supplementary DHA given as marine oil reduces blood phospholipid arachidonic acid (AA) in preterm infants. This effect is not seen in short-term trials unless the total n-3 intake from marine oil exceeds 0.5% of the total fatty acids. In addition, there is considerable variability among individual preterm infants in blood phospholipid AA and DHA levels that is not dependent on diet. Within dietary treatments, a significant positive correlation between AA and DHA concentrations suggests that factor(s) other than marine oil supplementation affect both AA and DHA status. Docosahexaenoic acid and AA concentrations in plasma phospholipids are significantly correlated with DHA and AA concentrations in red blood cell phospholipids, suggesting that the observed individual differences in DHA and AA within groups represent true differences in fatty acid status. Preterm infants appear to be vulnerable to a poor status of both DHA and AA; further feeding trials are needed to identify the optimal balance of fatty acids for feeding these infants.
Vitamin A status of preterm infants during infancy.
Plasma retinol and retinol-binding protein (RBP) were measured in 67 enterally fed preterm infants (750-1398 g) at 33 +/- 2 wk postconceptional age (PCA), and at regular intervals during infancy. Retinol and RBP declined by 35 +/- 2 wk PCA and remained low at 38 wk after discharge, with the infants fed a term-infant formula. At 38 +/- 2 wk PCA, 48% (32 of 67) of these infants had plasma retinol concentrations less than 0.35 mumol/L. Mean retinol and RBP rose over the next 7 mo, but large numbers of infants (26 of 59 at 48 wk, 10 of 61 at 57 wk) had hyporetinolemia (0.35-0.67 mumol/L). Plasma RBP leveled off at 57 +/- 2 wk PCA and remained low (less than 0.95 mumol/L) in many infants throughout the first year of life. Lower plasma retinol and RBP concentrations at 33 and 38 wk correlated with longer periods of intravenous nutrition. At 57 and 69 wk, lower retinol and RBP correlated with higher birth order. Suboptimal vitamin A status may occur for many months after preterm infants are discharged from the hospital.
Effects of different levels of intravenous alpha-linolenic acid and supplemental breast milk on red blood cell docosahexaenoic acid in very low birth-weight infants.
Preterm infants weighing less than 1,500 g were started on total parenteral nutrition (TPN) if unable to tolerate full enteral feedings. They were randomly assigned to receive intravenous lipids containing either 4.2 or 9.0% alpha-linolenic acid to assess the effect on red blood cell (RBC) phospholipid polyenoic fatty acid composition, particularly docosahexaenoic acid (22:6n3) (DHA). DHA ultimately comes from alpha-linolenic acid (18:3n3), although there is evidence in human preterm infants that they require preformed DHA. After 1 week of TPN, infants were started on gradually increasing amounts of enteral feeding, breast milk, if elected by mothers, or premature milk formula (Preemie Enfamil). RBC phospholipid fatty acids were measured weekly. Results were evaluated comparing samples from week 1 and week 6. Supplying 9% alpha-linolenic acid in intravenous lipids did not prevent a fall in DHA by 6 weeks; however, infants receiving breast-milk feeding did not have a significant decrease in DHA. Studies are needed to evaluate supplying DHA in intravenous lipids.
Plasma cholesterol and lipoprotein levels during fetal development and infancy.
Intrauterine changes in plasma cholesterol and lipoprotein concentrations have been linked to the development of the adrenal gland (utilization of cholesterol) and liver (production of cholesterol by new synthesis). At term birth, racial and gender differences have been observed with white compared to black, and female compared to male, infants having higher cholesterol concentrations. Within hours of the beginning of oral feeding, total and LDL cholesterol rise significantly. Little further increase occurs after 7 days, and the concentration seen after this time is highly dependent upon the cholesterol and polyunsaturated fat content of the diet. By 12 months of age, investigators cease to find any effect of the milk source fed earlier in infancy on cholesterol and lipoproteins. This is not evidence that diet no longer influences cholesterol and lipoprotein concentrations, but only that individual lipid intakes are varied and difficult to quantitate. Cross-cultural comparisons of infants at this age in fact provide strong suggestive evidence that a large environmental component determines the circulating cholesterol and lipoprotein concentrations seen at one year and beyond.
Growth and development in infants.
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Essentiality of omega 3 fatty acids in growth and development of infants.
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Long-term feeding of formulas high in linolenic acid and marine oil to very low birth weight infants: phospholipid fatty acids.
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% alpha-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/100 g) and plasma AA (g/100 g; mg/L plasma) decreased progressively until late infancy and were depressed further by marine oil.(ABSTRACT TRUNCATED AT 250 WORDS)
Physical properties of aerosols produced by dermabrasion.
Medical personnel who perform dermabrasions are exposed to airborne blood and tissue fragments. The safety or hazards of exposure to such aerosols have not been adequately studied. Using scanning electron microscopy, the air density and size distribution of particles produced during dermabrasion were analyzed. Such particles are of sufficient size to allow for access to and retention by mucosal and pulmonary surfaces. Transmission electron microscopy reveals amorphous particles without discernible cell membranes. Commonly used personnel protection standards do not prevent respiration of these particulates. Mathematical estimation of particle size production allows extrapolation of these data to other rotary instrument applications.
Increase in plasma phospholipid docosahexaenoic and eicosapentaenoic acids as a reflection of their intake and mode of administration.
The fatty acid, docosahexaenoic acid (DHA, 22:6n-3), is a major constituent of red blood cell phosphatidylethanolamine and phosphatidylserine at birth but declines in all phospholipid classes following preterm delivery unless the diet contains DHA. A bolus of fish oil prevented declines in DHA of red cell phospholipids (phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine) during 4 to 6 wk of feeding, with red blood cell DHA indistinguishable from that of infants fed human milk. The amount of DHA fed was almost an order of magnitude greater than usually provided by human milk, however, suggesting poor absorption of fish oil by preterm infants. The purpose of these studies was to determine if uptake of fish oil DHA could be improved by dispersion in preterm formula. Since plasma phospholipids rapidly reflect changes in dietary fatty acid composition, DHA uptake was assessed by fatty acid analysis of plasma phosphatidylethanolamine and phosphatidylcholine. All groups receiving fish oil (both bolus and dispersed) demonstrated a rise in plasma phospholipid phosphatidylethanolamine DHA. Infants receiving 11 mg/kg/day DHA from dispersed fish oil, however, appeared to absorb as much or more as those receiving 71 mg/kg/day DHA in a bolus. The lower intake of DHA provided only 0.2% of total dietary fatty acids (human milk typically provides 0.1 to 0.3%). This study, in conjunction with an earlier report, demonstrates the feasibility of 1) long-term maintenance of red cell membrane DHA by its inclusion in infant formula and 2) DHA maintenance by "physiological" intakes of DHA; i.e. the amount provided by human milk.(ABSTRACT TRUNCATED AT 250 WORDS)
High fat diets varying in ratios of polyunsaturated to saturated fatty acid and linoleic to linolenic acid: a comparison of rat neural and red cell membrane phospholipids.
The polyunsaturated-saturated (P/S) fatty acid, and linoleic-linolenic (18:2n6/18:3n3) acid ratios of diets fed to rats were varied independently during pregnancy, lactation and, in the young, for 8 d after premature weaning. The intent was to alter the proportion of membrane phospholipid fatty acids derived from 18:2n6 and 18:3n3 in the developing rat, and to compare changes in very-long-chain polyunsaturated fatty acids in membranes from the central nervous system with those of the red blood cell. All experimental diets contained 40% of energy from fat. Similar relative changes in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) fatty acid pattern occurred in both neural and red blood cell membranes when dietary 18:2n6/18:3n3 was increased from 7 to 240. Docosapentaenoate (22:5n6) from 18:2n6 increased, and docosapentaenoate (22:5n3) and docosahexaenoate (22:6n3) from 18:3n3 decreased in both types of membranes. On the other hand, P/S ratios of 0.3 and 1.6 at a constant ratio of 18:2n6/18:3n3 produced identical membrane phospholipid fatty acid patterns. Both red blood cell and neural membranes show the same relative effects of modification of dietary lipids on the composition of very-long-chain polyunsaturated fatty acids.
Hepatic HMG CoA reductase and cholesterol 7 alpha-hydroxylase activities in normal and hyperlipidemic-restricted ovulator atherosclerosis-prone chickens before and after the commencement of egg laying.
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Sex-related differences in diurnal activities and development of hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol 7alpha-hydroxylase.
The activities of hepatic microsomal 3-hydroxy-3-methylglutaryl CoA reductase and cholesterol 7alpha-hydroxylase were consistently higher (up to 3-fold) in female compared to male rats fed 2% cholestyramine for 8 h daily. In all animals studied, enzymic activities were highest 6 h after feeding began. However, 85% of the rise in cholesterol 7alpha-hydroxylase activity occurred in the 6 h before and 89% of the rise in 3-hydroxy-3-methylglutaryl CoA reductase activity occurred in the 6 h after feeding started. Sex-related differences in both enzymic activities first became apparent at the time of sexual maturity. Enzymic activities before weaning were generally low and a late-suckling (13--20 days) rise in cholesterol 7alpha-hydroxylase was not accompanied by a rise in 3-hydroxy-3-methylglutaryl CoA reductase. For all of these studies we assayed cholesterol 7alpha-hydroxylase at two concentrations of exogenous cholesterol to obviate problems relating to size of the cholesterol pool.
Influence of dietary lipid and meal pattern on body composition and lipogenesis in adult rats.
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Dietary fat and cholesterol metabolism in adult rats undergoing rapid tissue repletion.
An experimental model in which adult rats underwent rapid rates of tissue repletion after dietary restriction served to explore the influence of dietary fat on cholesterol metabolism. Adult rats severely restricted in protein and energy were refed either 8 or 24 hours per day for 10 days. Refeeding diets contained approximately 0% or 20% fat by weight as safflower oil or beef tallow and 4% or 17% protein on an energy basis. Concentration or source of dietary fat did not significantly influence either serum or hepatic cholesterol concentrations. Inclusion of dietary fat increased incorporation of 3H-acetate into digitonin precipitable sterols although type of fat did not influence this parameter. Specific activities of serum and hepatic cholesterol were identical for rats fed with diets containing safflower oil and beef tallow, but an elevation in acidic 14C-steroid excretion per g diet consumed occurred with safflower oil as compared with beef tallow. The data suggest that, in the absence of exogenous cholesterol, high levels of polyunsaturated fat may influence cholesterol metabolism primarily by increasing synthesis and excretion of bile acids.
A sensitive enzymatic method for determination of free and esterified tissue cholesterol.
An enzymatic assay currently in use in clinical laboratories for quantitating total serum cholesterol has been modified for the determination of microgram quantities of tissue cholesterol. Two types of assays were developed. In the first, more generally useful method, lipids extracted with chloroform/methanol were solubilized by the addition of detergent and assayed for free and total cholesterol using laboratory prepared mixtures of reagents. Although different detergents were effective, it appears that Triton X-100 may be most universally applicable. In the second type of assay, commercially available reagent mixtures were employed for the determination of total cholesterol only. Results of both types of assays compare favorably with determination using the colorimetric assay on 3beta-hydroxysterols recovered from digitonides.