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J Eagles

Publications and source records attributed to J Eagles.

34 records · Page 2Linked to original sources
PubMed1991

Apparent zinc absorption by rats from foods labelled intrinsically and extrinsically with 67Zn.

A variety of foods (peas (Pisum sativum), chicken meat, eggs, goat's milk, human milk) enriched with the stable isotope 67Zn were prepared by means of intrinsic- and extrinsic-labelling procedures. They were fed to rats and apparent absorption of 67Zn determined from faecal excretion measurements using thermal ionization mass spectrometry. There were significant differences in the absorption of the extrinsic and intrinsic label which differed in magnitude between the foods tested. The extrinsic 67Zn was less well absorbed in peas, chicken meat, eggs, and human milk than intrinsic 67Zn, but in goat's milk the extrinsic 67Zn was better absorbed than the intrinsic label. These results demonstrate that extrinsically-added stable Zn isotopes do not fully exchange with endogenous Zn in many foods, and illustrate the need for caution when using extrinsic labels for Zn bioavailability studies.

Animals↗
PubMed1990

The effect of moderately increased intakes of complex carbohydrates (cereals, vegetables and fruit) for 12 weeks on iron and zinc metabolism.

Fifteen adult women were given diets in which the intake of complex carbohydrates was increased from 20 to 30 g over a 12 week period. Metabolic balances were carried out, iron and zinc absorption tests performed using stable isotopes, and Fe and Zn status monitored. Although effects on bowel function were observed, the changed diet had no influence on any of the previously described variables. It was concluded that a moderate increase in cereals, fruit and vegetables did not have an adverse effect on Fe or Zn nutrition.

Absorption↗
PubMed1989

Comparison of fast atom bombardment mass spectrometry and thermal ionization quadrupole mass spectrometry for the measurement of zinc absorption in human nutrition studies.

A method is described for the measurement of apparent zinc absorption in human nutrition studies. An enriched source of the stable isotope 67Zn was given to adult subjects together with a wheat cereal and the unabsorbed 67Zn measured in the feces. After drying, subsamples of the homogenized fecal material were ashed at 480 degrees C, purified for analysis by ion exchange chromatography, and the 64Zn/67Zn ratios determined by both fast atom bombardment mass spectrometry and thermal ionization quadrupole mass spectrometry. Good agreement was found between the two sets of results with mean precisions of approximately 0.5% for both techniques.

Biological Availability↗
PubMed1989

Comparison of fast-atom bombardment, thermal ionization and inductively coupled plasma mass spectrometry for the measurement of 64Zn/67Zn stable isotopes in human nutrition studies.

Fast-atom bombardment, thermal ionization and inductively coupled plasma mass spectrometry are contrasted in comparative measurements of 64Zn/67Zn isotope ratios on samples isolated in the course of a human mineral-nutrition experiment. The data are evaluated with reference to the precision normally required in enriched stable-isotope mineral-nutrition studies, and the convenience of the mass spectrometric techniques is also compared.

Adult↗
PubMed1989

Studies on calcium absorption from milk using a double-label stable isotope technique.

Calcium absorption was measured in ten male volunteers from skimmed milk, Ca-enriched skimmed milk or watercress (Nasturtium officinale) soup. The foods were labelled extrinsically with 30 mg 44Ca. Shortly after consuming the labelled meal, each subject was given an intravenous injection of 3 mg 42Ca. Fractional absorption from the oral dose was determined from plasma and urine samples collected 24-72 h later, using fast atom bombardment mass spectrometry to measure isotope ratios. The values for urine and plasma were in good agreement. Mean percentage absorption was 45.5 (SEM 1.9)% from the skimmed milk, 35.7 (SEM 4.7)% from the Ca-enriched milk and 27.4 (SEM 1.9)% from the watercress soup. The effect of consuming 568 ml (1 pint) Ca-enriched milk each day for 4 weeks on the efficiency of absorption of Ca was studied. Although there was no statistically significant difference between Ca absorption before and after the supplementation period, the results were considered to be somewhat inconclusive due to the small number of subjects and wide individual variation in Ca absorption.

Absorption↗
PubMed1989

Iron and zinc absorption in human subjects from a mixed meal of extruded and nonextruded wheat bran and flour.

The effect of extrusion cooking of a bran-flour mixture on iron and zinc retention was measured in normal adults. The stable isotopes 58Fe (1.253 mg) and 67Zn (5.13 mg) were administered with 40 g nonextruded or extruded cereal with milk and isotopic retention was measured from fecal excretion over the next 4-7 d by neutron-activation analysis (Fe) and fast-atom-bombardment mass spectrometry (Zn). 58Fe retention was 15.1 +/- 2.4% (means +/- SEM) with the nonextruded meal and 16.5 +/- 2.7% with the extruded meal. 67Zn retention was 18.9 +/- 1.7% with the nonextruded meal and 18.3 +/- 1.5% with the extruded meal. Extrusion cooking had no effect on 58Fe or 67Zn retention.

Adult↗
PubMed1985

Determination of total iron in foods by isotope dilution fast atom bombardment mass spectrometry.

A method employing isotope dilution fast atom bombardment mass spectrometry has been developed for the quantitative determination of iron in foods. Samples were spiked with an enriched source of 54Fe, digested with concentrated HNO3/H2SO4 and the iron extracted from 6 M HCl into diethyl ether. Bracketing procedures gave precisions ranging from 1.30-4.49% relative standard deviation (RSD) for isotope ratio measurements and 1.26-6.44% RSD for iron measurements.

Food Analysis↗
PubMed1980

The amino acid sequences of the tryptic peptides of cowpea chlorotic mottle virus protein.

The amino acid sequences of the major tryptic peptides from the coat protein of wild type cowpea chlorotic mottle virus are presented. The sequences have been determined by a combination of enzyme hydrolysis, mass spectrometry and Edman degradation, and the relative usefulness of mass spectrometry in this peptide sequence determination is discussed.

Amino Acid Sequence↗
PubMed1979

Remote group derivatives: limitations on the effectiveness of pyrrolidide derivatives of oxygen-containing fatty acids.

The pyrrolidides of a number of fatty acids containing oxygen functions (ether linkage, epoxide ring and hydroxyl group) have been prepared and their mass spectra recorded. Detailed analyses of these, supported by accurate mass measurement, indicate that the presence of the oxygen atom has a profound effect on the normal, sequential, mode of pyrrolidide fragmentation. Cleavage adjacent to the oxygen is enhanced, this being most marked in the spectra of those compounds containing an ether linkage. However, further fragmentation of the carbon chain distal to the pyrrolidide group is minimal and prevents any structural information being obtained. These findings indicate that the usefulness of the pyrrolidide derivative for structural elucidation purposes is severely limited in some cases when an oxygen atom is present in the chain. However, for both the epoxy- and hydroxy-fatty acids, complementary derivatization methods are available.

Chemical Phenomena↗
PubMed1971

N-carbamoyl-2-(p-hydroxyphenyl)glycine from leaves of broad bean (Vicia faba L.).

1. dl-2-(p-Hydroxyphenyl)glycine was resolved through the bromocamphorsulphonate to give its d-isomer. The N-carbamoyl derivatives of these amino acids were synthesized. Circular-dichroism studies on these and related compounds, reported in a deposited Annex, helped to establish the optical configuration. 2. N-Carbamoyl-dl-2-(p-hydroxyphenyl)glycine was isolated from broad-bean leaves. It amounted to about 0.1% of the leaf dry matter. Racemization may or may not have occurred during the isolation. There were indications of the same compound in chicory and in savoy cabbage. Under weakly acidic conditions it was converted gradually into 5-(p-hydroxyphenyl)hydantoin. Both these compounds yielded 2-(p-hydroxyphenyl)glycine on acid hydrolysis. 3. The occurrence is discussed of 2-phenylglycine derivatives in Nature and of N-carbamoyl-amino acids and hydantoins in plants. 4. Gradient elution from anion-exchange resin with acetic acid, besides proving useful for the present work, gave useful separations of pyrrolidonecarboxylic acid and of some N-acetyl-amino acids. 5. Supplementary material (Annex 1: details of experimental work other than ultraviolet and circular-dichroism spectra; Annex 2: ultraviolet absorption and circular dichroism of d-2-phenylglycine and some related compounds) has been deposited as Supplementary Publication SUP 50003 at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1971), 121, 7.

Carbamates↗