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Biomedical subjects

R R Eitenmiller

Publications and source records attributed to R R Eitenmiller.

At least 19 recordsLinked to original sources
PubMed2001

Comparison of the column performance of narrow-bore and standard-bore columns for the chromatographic determination of alpha-, beta-, gamma-, and delta-tocopherol.

A comparison of the performance of narrow-bore (2.1-mm i.d.) and standard-bore (4.6-mm i.d.) analytical silica columns having the same length is completed for the resolution of alpha-, beta-, gamma-, and delta-tocopherol. The studies are performed on high-performance liquid chromatographic equipment with minimum extracolumn contribution. Column permeabilities are 1.16 x 10(-9) and 2.48 x 10(-9) cm2 for narrow and standard bore, respectively. The narrow-bore column gives up to a 7 times increase in sensitivity compared with a standard-bore column at equivalent running times for the analytes. Approximately one-third solvent savings can be achieved with the narrow-bore column. Theoretical plates of the standard-bore column are higher than that of the narrow-bore column.

Chromatography, High Pressure Liquid↗
PubMed2000

Liquid chromatographic analysis of all-trans-retinyl palmitate, beta-carotene, and vitamin E in fortified foods and the extraction of encapsulated and nonencapsulated retinyl palmitate.

A liquid chromatographic method is described for the analysis of natural vitamin E homologues, all-rac-alpha-tocopheryl acetate, retinyl palmitate (encapsulated and nonencapsulated), and beta-carotene in various fortified foods. The vitamins are extracted in 2-propanol and hexane without saponification and quantitated by normal phase chromatography with fluorescence and visible detection. The sample components were identified using an on-line three-dimensional photodiode array detector, which permitted profiling of the 190-800 nm absorption spectrum of any chromatographic peak. The method showed linearity for the analytes in their respective calibration ranges. The percent recoveries for retinyl palmitate using starch- and gelatin-encapsulated standards were 101.0 +/- 1.0 and 100.1 +/- 0.9, respectively. The method measures six or more analytes in a single injection and differentiates between natural and synthetic forms of vitamin E.

Chromatography, Liquid↗
PubMed1999

High dietary iron enhances oxidative stress in liver but does not increase aberrant crypt foci development in rats with low vitamin E status.

The purpose of this study was to examine the effects of high-iron and low-vitamin E diets on lipid peroxidation and aberrant crypt foci (ACF) development in rats. In a 2 x 2 x 2 factorial design, male Sprague-Dawley rats were fed 45 or 450 mg Fe/kg diet (adequate and high iron, respectively) and 15 or 100 IU vitamin E/kg diet (low and adequate vitamin E, respectively) for three weeks, when they received saline or azoxymethane (15 mg/kg for 2 wk). Diets were continued for an additional six weeks. Serum alpha-tocopherol concentrations in rats fed low-vitamin E diets were decreased to 30% of concentrations observed in rats fed adequate-vitamin E diets (p < 0.0001). Also, serum alpha-tocopherol concentrations tended to be lower in rats supplemented with iron (p < 0.08). Lipid peroxidation in liver was significantly elevated by high-iron diets after 3 and 10 weeks of treatment, but lipid peroxidation in colonic mucosa was not altered by dietary iron or vitamin E. The total number of ACF and number of large ACF (> or = 4 aberrant crypts/focus) were not significantly altered by iron or vitamin E intakes. However, the size distribution of ACF was slightly altered, such that iron-supplemented rats had 12% more ACF with two crypts per focus (p < 0.02) than rats fed adequate-iron diets. Our data suggest that high-iron diets enhanced oxidative stress in liver, but not colon, of rats fed low-vitamin E diets. Furthermore, a high-iron diet does not increase the total number of ACF, even when vitamin E status is low.

Animals↗
PubMed1995

The folic acid requirements of starting broiler chicks fed diets based on practical ingredients. 1. Interrelationships with dietary choline.

Five experiments were conducted to evaluate the effect of dietary supplemental folic acid in starting broiler chick diets. In the first two experiments, basal diets based on corn and soybean meal contained 10 micrograms/kg vitamin B12 but no supplemental methionine or choline. Chicks showed curvilinear responses to folic acid supplementation with maximum growth and feed efficiencies from 1.45 mg/kg diet. The liver folic acid response was also curvilinear but reached a plateau at 1.70 mg folic acid/kg diet. The basal diet for three additional experiments contained soybean meal that had been washed with methanol to remove most of the choline. The basal diet contained only 750 mg/kg choline. Chicks exhibited a larger growth response to folic acid at low choline levels as evidenced by a significant folic acid by choline interaction. Choline and folic acid both increased tibia length and width. Folic acid supplementation increased but then decreased valgus deformity. Choline chloride supplementation also decreased the incidences of valgus and varus deformities and decreased bone ash, but increased the incidence of tibial dyschondroplasia. It is concluded that chicks fed practical ingredient-based diets require 1.3 mg folic acid/kg diet with low levels of choline, but only 1.2 mg folic acid/kg when choline is offered near the NRC recommended level of 1,300 mg/kg of choline.

Animals↗
PubMed1995

The folic acid requirements of starting broiler chicks fed diets based on practical ingredients. 2. Interrelationships with dietary methionine.

Two experiments were conducted to determine the effects of dietary supplemental folic acid and methionine on the performance of starting broiler chicks for 18 d. Four levels of dietary folic acid (.24, .54, 1.14, and 2.34 mg/kg) and four levels of dietary methionine (.45, .53, .61, and .69%) were fed in a factorial design. There were three replicates of eight chicks each per each treatment. The basal diet was based on corn, isolated soybean protein, meat and bone meal, and fish meal. It contained adequate amounts of all nutrients except methionine and folic acid. Increased growth was observed in chicks fed the basal diet supplemented with either folic acid or methionine. Total dietary folic acid and methionine plus cysteine requirements for maximum growth were estimated to be 1.80 mg/kg and .85% in Experiment 1 and 1.47 mg/kg and .87% in Experiment 2, respectively. There were interactions between dietary folic acid and methionine on weight gain in both experiments. Chicks fed the diet containing 2.34 mg folic acid/kg tended to have depressed growth, as in previous experiments. There was a significant linear feed conversion response to folic acid in Experiment 1 and to methionine in Experiment 2. There were both linear and quadratic liver folic acid responses to dietary folic acid in both experiments. There was no indication that dietary methionine had any effect on liver folic acid content. No differences in bone ash, hemoglobin, hematocrit, or incidence of tibial dyschondroplasia were detected due to methionine or folic acid supplementation.

Animals↗
PubMed1983

Copper, iron, and zinc contents of human milk at early stages of lactation.

The Cu, Fe, and Zn contents of early milk from 102 American mothers were examined in relation to stage of lactation, intake of prenatal mineral supplements, maternal age, parity, and previous history of lactation. A total of 412 samples was collected at three stages of lactation: early transitional (4 to 7 days postpartum); transitional (10 to 14 days postpartum); and mature (30 to 45 days postpartum). For the transitional and mature stages, representative samples of late evening (PM) and early morning (AM) feedings were collected. Diurnal variation in concentration was observed only for Fe. Concentrations of all elements decreased significantly at successive stages of lactation with Zn showing the greatest decline. Cu, Fe, and Zn contents (means +/- SEM) were 104.1 +/- 5.4, 96.5 +/- 6.5, and 520 +/- 20 micrograms/100 g in early transitional milk; 93.9 +/- 3.6, 85.4 +/- 4.5, and 410 +/- 10 micrograms/100 g in transitional milk, and 84.7 +/- 3.8, 76.1 +/- 3.8, and 290 +/- 10 micrograms/100 g in mature milk, respectively. No significant relationship was found between levels of Cu and Zn in milk and whether mothers had taken dietary supplements containing these elements. In addition, no significant correlations were found between maternal age, parity, or previous history of lactation and the elemental content of milk. Based on these data, it was estimated that fully breast-fed infants would receive approximately 0.11, 0.10, and 0.50 mg/kg per day of Cu, Fe, and Zn, respectively, during the neonatal period.

Circadian Rhythm↗
PubMed1983

Calcium, phosphorus, and magnesium contents of human milk during early lactation.

Early milk samples from 102 American mothers were examined for Ca, P, and Mg contents in relation to stage of lactation, intake of prenatal mineral supplements, maternal age, parity, and previous history of lactation. A total of 415 samples were collected at three stages of lactation: early transitional (4-7 days postpartum); transitional (10-14 days postpartum); and mature (30-45 days postpartum). No diurnal variations in element concentrations were observed in representative samples of late evening (PM) and early morning (AM) feedings collected during the transitional and mature stages. The mean concentrations for the major elements were highest in early transitional milk and in some cases decreased significantly (p less than 0.05) as lactation progressed. Ca, P, and Mg contents (means +/- SEM) were 26.3 +/- 0.6, 14.6 +/- 0.4, 5.3 +/- 0.1 mg/100 g in early transitional milk and 26.2 +/- 0.5, 13.3 +/- 0.3, and 5.0 +/- 0.1 in mature milk, respectively. Increasing uniformity in the elemental content of milk was noted among the mothers as lactation became established. No significant relationship was found between intake of dietary supplements containing Ca and Mg and levels of these elements in milk. Also, no significant correlations were found between maternal age, parity, or previous history of lactation and the elemental content of milk. From these data, it was estimated that fully breast-fed infants would receive approximately 33, 18, and 6.5 mg/kg/day of Ca, P, and Mg, respectively, during the neonatal period.

Calcium↗
PubMed1980

Human milk ribonuclease.

Two components having ribonuclease (EC 3.1.27.5) activity were isolated from human milk. Each component of human milk ribonuclease (RNAase) moved at a slightly different rate when electrophoresed on polyacrylamide gel but at the same rate when ultracentrifuged. The major component had a molecular weight of approx. 14 000, an isoelectric point of pH 7.9, and exhibited a broad absorbance maximum between 277 and 281 nm. Human milk RNAase hydrolyzed yeast RNA, poly(cytidylic acid) and poly(uridylic acid) but not DNA, poly(adenylic acid) or poly(guanylic acid). Maximum activity occurred at pH 7.7 and 60 degrees C. Amino acid analysis of the major component revealed a large number of alanine, valine, glycine and aspartic acids but no tryptophan or free sulfhydryl groups. Lysine was the N-terminal amino acid. Tryptic hydrolysis yielded 18 peptides, some of which are similar to those from bovine pancreatic RNAase. Human milk RNAase activity was increased in the presence of NaCl, KCl and sodium citrate and decreased by CaCl(2), MgCl(2), FeSO(4), ZnSO(4) and CuSO(4).

Amino Acid Sequence↗
PubMed1979

Application of gel permeation chromatography and nonaqueous reverse phase chromatography to high pressure liquid chromatographic determination of retinyl palmitate and beta-carotene in oil and margarine.

A high pressure liquid chromatographic method was developed using high pressure gel permeation chromatography (HP-GPC) and high pressure reverse phase chromatography (RP-HPLC) for quantitation of retinyl palmitate and beta-carotene. HP-GPC was used for fractionation of vitamin A active compounds from oil preliminary to quantitation on nonaqueous RP-HPLC. HP-GPC fractionation was completed on oil and margarine dissolved in methylene chloride by 2 elution passes through 2 muStyragel (100 angstrom) columns connected in series with methylene chloride as the mobile phase. RP-HPLC separation of retinyl palmitate and beta-carotene was achieved on muBondapak C18 (10 micrometers), using methylene chloride-acetonitrile (30+70). Based on 10 repetitive analyses, recoveries of added beta-carotene and retinyl palmitate from vegetable oils were 98.6+/-2.9 and 95.2+/-2.6%, respectively. The coefficients of variation were 2.9% for beta-carotene and 2.7% for retinyl palmitate. The determination of vitamin A activity in 7 margarine brands with label claims of 10% U.S.RDA/serving revealed that all but one of the margarines contained at least 94% of the label claim. Vitamin A activity in the margarines ranged from 90.6 to 110.8% of the label declaration.

Carotenoids↗
PubMed1976

Relationship between composition and stability of bovine milk lysozyme.

The amino acid analysis, peptide mapping, and heat stability of bovine milk lysozyme are presented. The bovine milk lysozyme molecule contains approximately 154 amino acids and is strikingly different in amino acid content from human milk lysozyme and egg white lysozyme. Tryptic hydrolysis yielded 26 peptides, all of which are unique from tryptic peptides of human milk lysozyme and egg white lysozyme. In addition, bovine milk lysozyme was more heat stable than human milk lysozyme at pH 4.0 but more labile at pH 7.0 and 9.0. Possible explanations for the differences in heat stability are discussed.

Amino Acids↗
PubMed1975

Arylamidase activity of Salmonella species.

Arylamidase activity in cell extracts of sonically cell treated suspensions of 23 Salmonella strains, including 12 strains of S. typhimurium, was investigated. All cultures hydrolyzed five of nine different neutral and basic substrates. Activity against aspartyl-, cystyl- histidinyl-, and isoleucyl-beta-naphylamide was negligible. Alanyl-beta-naphthylamide was the preferred substrate for the Salmonella species; however, specific activities ranged widely. Of several gram-negative organisms surveyed, all except Proteus vulgaris hydrolyzed alanyl-beta-naphthylamide at the fastest rate. The most preferred substrate for the Proteus culture was glycyl-beta-naphthylamide. No relationship could be shown between virulence and arylamidase activity for the Salmonella strains.

Amides↗
PubMedDate not supplied

A liquid chromatographic method for analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical food using matrix solid-phase dispersion in conjunction with a zero reference material as a method development tool.

A liquid chromatographic method is described for analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted from medical food without saponification by matrix solid-phase dispersion and chromatographed by normal-phase chromatography with fluorescence detection. Retinyl palmitate and all-rac-alpha-tocopheryl acetate are quantitated isocratically with a mobile phase of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results compared favorably with label declarations on retail medical foods. Recoveries determined on an analyte-fortified zero reference material for a milk-based medical food averaged 98.3% (n = 25) for retinyl palmitate spikes and 95.7% (n = 25) for all-rac-alpha-tocopheryl acetate spikes. Five concentrations were examined for each analyte, and results were linear (r2 = 0.995 for retinyl palmitate and 0.9998 for all-rac-alpha-tocopheryl acetate) over the concentration range examined, with coefficients of variation in the range 0.81-4.22%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and all-rac-alpha-tocopheryl acetate in fortified medical foods.

Chromatography, Liquid↗
PubMedDate not supplied

Analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical foods using a zero control reference material (ZRM) as a method development tool.

A liquid chromatographic method is described for analysis of all- rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted in isopropyl alcohol and hexane-ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All rac-alpha-tocopheryl acetate and retinyl palmitate are chromatographed isocratically with a mobile phase of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recovery studies performed on a medical food zero control reference material (ZRM) fortified with the analytes averaged 99.7% (n = 25) for retinyl palmitate and 101% (n = 25) for all- rac-alpha-tocopheryl acetate. Coefficients of variation were 0.87-2.63% for retinyl palmitate and 1.42-3.20% for all-rac-alpha-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in medical foods. Use of chlorinated solvents is avoided.

Chromatography↗
PubMedDate not supplied

Analysis of beta-carotene in medical food by liquid chromatography with matrix solid-phase dispersion.

A liquid chromatographic method is described for analysis of beta-carotene in medical food. The nutrient is extracted from medical food without saponification by matrix solid-phase dispersion and quantitated by isocratic normal-phase chromatography with a Si 60 column and a mobile phase of hexane containing 0.125% (v/v) isopropyl alcohol. The limit of quantitation is 0.02 microgram/mL at 436 nm. Standard response was linear over the concentration range of 0.02-1.0 microgram/mL (r2 = 0.99998). Recoveries were determined on a zero control reference material containing added beta-carotene at various levels. Recoveries averaged 91.2% (n = 25) with coefficients of variation from 0.50 to 3.10%. The method provides a rapid, specific, sensitive, and easily controlled assay for analysis of beta-carotene in fortified medical food. In addition, retinyl palmitate can be assayed simultaneously with an in-line fluorescence detector.

Chromatography, Liquid↗