Biomedical subjects

J Eagles

Publications and source records attributed to J Eagles.

At least 19 recordsLinked to original sources

PubMed2001

Structure and conformation of a novel genetically engineered polysaccharide P2.

A new exocellular polysaccharide (P2) has been produced by the manipulation of a glycosyl transferase gene (aceP) involved in the biosynthesis of the polysaccharide acetan by the bacterium Acetobacter xylinum strain CKE5. The P2 polysaccharide has been studied by methylation analysis, reductive cleavage, and 1H and 13C NMR spectroscopy. The data are consistent with the structure predicted when the aceP gene is deactivated: [Molecular structure: see text]. The effect of cooling on proton NMR line width indicates a coil-helix transition in P2 at about 70 degrees C.

Azotobacter↗

PubMed2001

A distinctive flavonoid chemistry for the anomalous genus Biebersteinia.

Leaf surface extracts of Biebersteinia orphanidis have yielded a complex mixture of five flavones with the unusual 5,7-dihydroxy-6,8-dimethoxy A ring substitution pattern. They are acerosin, hymenoxin, nevadensin, sudachitin and 5,7,4'-trihydroxy-6,8-dimethoxyflavone. Also present at the leaf surface are gardenin B, luteolin, apigenin, acacetin and the coumarin umbelliferone. The internal leaf flavonoids include the 7-glucosides of apigenin, luteolin and tricetin, together with the 7-rutinosides of apigenin and luteolin. This profile differs from those of B. heterostemon and B. odora. It appears that B. orphanidis is as highly distinctive in its flavonoid pattern as it is phytogeographically. The data also confirm the conclusion of other studies, including rbcL and atpB gene sequence analysis, that Biebersteinia is completely unrelated to the Geraniaceae, where it was once placed.

Flavonoids↗

PubMed1998

Bioavailability of iron glycine as a fortificant in infant foods.

The bioavailability of iron glycine added to a vegetable infant weaning food was compared with ferrous sulfate. Stable, isotopically labeled compounds (57Fe or 58Fe) were mixed into the midday meal (1.4 mg added Fe/serving) and fed to 9-mo-old infants on alternate days for 8 d. Bioavailability, expressed as a percentage of the dose consumed, was measured from isotopic enrichment of hemoglobin 14 d after the last test meal. There was no difference between iron glycine and ferrous sulfate (x+/-SEM): 9.0+/-0.7% and 9.9+/-0.8%, respectively. The effect of chelation was examined by measuring iron bioavailability of iron glycine and ferrous sulfate added to a high-phytate (310 mg/100 g) whole-grain cereal weaning food and comparing it with a lower-phytate (147 mg/100 g) vegetable food, as used in the first study. Both iron compounds had lower bioavailability from the high-phytate food, 5.2+/-0.5% for iron glycine and 3.8+/-0.9% for ferrous sulfate, than the lower-phytate food, 9.8+/-1.5% for iron glycine and 9.1+/-1.3% for ferrous sulfate. The results showed no significant difference in bioavailability between the two forms of iron when added to infant weaning foods, suggesting that the glycine complex was fully or partially dissociated in the gastrointestinal tract. It is concluded that chelation does not improve the bioavailability of iron in the presence of dietary inhibitors.

Biological Availability↗

PubMed1998

Evaluation of iron bioavailability in infant weaning foods fortified with haem concentrate.

BACKGROUND: Nutritional iron deficiency in infants over 4 months of age is one of the most common deficiency disorders. Dietary iron is comprised of non-haem and haem iron, the latter being absorbed by a separate pathway and more efficiently than non-haem iron. Fortification of infant weaning foods is one of the strategies adopted for preventing iron deficiency and the aim of this project was to examine the potential use of haem iron concentrate as a fortificant. METHODS: Sixteen non-anaemic 6-month old infants were recruited and allocated to two groups of 8. Each infant consumed 2 meals/day of a commercial weaning food (100 g) for 7 consecutive days containing 40 mg ascorbic acid and 2.5 mg haem iron/100 g (Group 1) or the same quantity of iron as ferrous sulphate plus 40 mg ascorbic acid (Group 2). Bioavailability was assessed by chemical balance using carmine to mark the beginning and end of the faecal collection. The effect of haem iron concentrate (as a candidate for the factor in meat that enhances iron absorption) was examined by measuring its effect on 57Fe-labelled non-haem iron absorption. RESULTS: There was no difference in iron balance between the two groups. Mean iron retention was 3.5 (SD 2.1) mg/day in Group 1 (haem iron) and 3.0 (SD 2.4) mg/day in Group 2 (ferrous sulphate). Haem concentrate did not enhance the absorption of 57Fe-labelled non-haem iron, Group 1: 1710 (SD 11.1)%, Group 2: 28.4 (SD 17.7)%. CONCLUSIONS: Haem iron concentrate appears to be a highly bioavailable form of iron when added to infant weaning foods. This protein is not, however, responsible for the enhancing effect of animal protein on non-haem iron absorption.

Absorption↗

PubMed1998

Splanchnic retention of intraduodenal and intrajejunal glucose in healthy adults.

Estimates of the spanchnic retention and appearance in the systemic circulation of orally administered glucose vary among laboratories even after recently identified sources of error have been accounted for [Livesey, G., P. D. G. Wilson, J. R. Dainty, J. C. Brown, R. M. Faulks, M. A. Roe, T. A. Newman, J. Eagles, F. A. Mellon, and R. Greenwood. Am. J. Physiol. 275 (Endocrinol. Metab. 38): E717-E728, 1998]. We questioned whether, in healthy humans, D-glucose delivered intraluminally to the midjejunum appeared systemically as extensively as that delivered intraduodenally. Subjects were infused over a period of 90 min with 50 g of glucose in 1 liter of isotonic saline (incorporating 0.5 g D-[13C6]glucose) per 70 kg of body weight. Infusions were via enteral tubes terminating approximately 15 and 100 cm postpylorus. The systemic appearance of glucose was monitored by means of a primed-continuous intravenous infusion of D-[6,6-2H2]glucose. Whereas 98 +/- 2% (n = 7) of the duodenally infused glucose appeared in the systemic circulation, only 35 +/- 9% (n = 7) of midjejunally infused glucose did so, implying that 65 +/- 9% was retained in the splanchnic bed. Either glucose was less efficiently absorbed at the midintestinal site or hepatic glucose sequestration was increased 10-fold, or both. The proximal intestine plays a key role in the delivery of glucose to the systemic circulation, and the distal intestine potentially delivers more glucose to the liver.

Adult↗

PubMed1998

Simultaneous time-varying systemic appearance of oral and hepatic glucose in adults monitored with stable isotopes.

The rates (and extent) of appearance of glucose in arterialized plasma from an oral glucose load and from liver (RaO, RaH) can be estimated in humans using radioisotopes, but estimates vary among laboratories. We investigated the use of stable isotopes and undertook 22 primed intravenous infusions of D-[6,6-2H2]glucose with an oral load including D-[13C6]glucose in healthy humans. The effective glucose pool volume (VS) had a lower limit of 230 ml/kg body weight (cf. 130 ml/kg commonly assumed). This VS in Steele's one-compartment model of glucose kinetics gave a systemic appearance from a 50-g oral glucose load per 70 kg body weight of 96 +/- 3% of that ingested, which compared with a theoretical value of approximately 95%. Mari's two-compartment model gave 100 +/- 3%. The two models gave practically identical RaO and RaH at each point in time and a plateau in the cumulative RaO when absorption was complete. Less than 3% of 13C was recycled to [13C3]glucose, suggesting that recycling errors were practically negligible in this study. Causes of variation among laboratories are identified. We conclude that stable isotopes provide a reliable and safe alternative to radioactive isotopes in these studies.

Administration, Oral↗

PubMed1997

Chrysin and other leaf exudate flavonoids in the genus Pelargonium.

In a chemotaxonomic survey of 57 Pelargonium species, leaf exudate flavonoids were detected in 35% of the sample, mostly in trace amounts. However, chrysin and a related C-methylflavanone were identified as major leaf surface constituents of P. crispum, and a mixture of quercetin and kaempferol mono-, and di- and trimethyl ethers of P. quercifolium. In two other species, P. fulgidum and P. exstipulatum, methylated flavones were the only lipophilic flavonoids present. This is the first report of leaf surface flavonoids from the genus Pelargonium.

Chromatography, High Pressure Liquid↗

PubMed1997

Rare earth elements as nonabsorbable fecal markers in studies of iron absorption.

The use of rare earth elements as nonabsorbable fecal markers for studies of iron absorption from sources labeled extrinsically with stable isotopes was evaluated. On 3 successive days 13 healthy fasting adults were given different stable isotopes of iron with samarium, ytterbium, or dysprosium. On day 1, three meals were given with 57Fe (1 mg per meal) plus samarium (0.33 mg per meal); on day 2, identical meals (taken with a calcium supplement to reduce iron bioavailability) were given with equivalent amounts of 58Fe-labeled iron and ytterbium; on day 3, a well-absorbed reference dose of 54Fe (3 mg) was given with 1 mg Dy. A complete fecal collection was carried out for 5-9 d and each stool was analyzed for rare earth elements by inductively coupled plasma-mass spectrometry and iron isotopes by thermal ionization quadrupole mass spectrometry. Mean recovery of rare earth elements was 101%, indicating that they are totally unabsorbed. The excretory pattern of the iron isotopes and the rare earth elements was very similar; the correlation coefficients between samarium and 57Fe, ytterbium and 58Fe, and dysprosium and 54Fe were 0.992, 0.989, and 0.988, respectively (P < 0.001). Iron absorption was calculated as the difference between isotope dose and fecal excretion. Mean (+/-SEM) iron absorption was 16.7 +/- 2.4%, 4.3 +/- 1.6%, and 40.3 +/- 3.1% on days 1-3, respectively. Predicted values estimated from the first 4 d of pooled feces, using the rare earth element recovery data to produce corrected figures for unabsorbed isotope, were in close agreement: 19.1 +/- 2.1%, 4.6 +/- 1.7%, and 40.8 +/- 3.1%, respectively (P < 0.001). With the diet of medium iron bioavailability and with the highly bioavailable reference dose it was possible to predict iron absorption accurately from only one or two stools, provided that they were sufficiently enriched with isotope and a rare earth element.

Absorption↗

PubMed1995

A biologically active lipophilic flavonol from Tanacetum parthenium.

A new lipophilic flavonol, 6-hydroxykaempferol 3,7,4'-trimethyl ether, called tanetin, has been characterized in the leaf, flower and seed of feverfew, Tanacetum parthenium. It co-occurs with the known 6-hydroxykaempferol 3,7-dimethyl ether, quercetagetin 3,7-dimethyl ether and quercetagetin 3,7,3'-trimethyl ether. Pharmacological tests indicate that tanetin could contribute to the anti-inflammatory properties of feverfew by inhibiting the generation of pro-inflammatory eicosanoids, although it is unlikely to be the only biologically active compound within the plant. Water soluble flavone glycosides were detected in the leaves and identified as apigenin 7-glucuronide, luteolin 7-glucuronide, luteolin 7-glucoside and chrysoeriol 7-glucuronide.

Chromatography, High Pressure Liquid↗

PubMed1995

The validity of extrinsic stable isotopic labeling for mineral absorption studies in rats.

The use of extrinsic stable and radioisotopic labels (Fe, Zn, Cu and Se) was compared with the use of intrinsic labels by measuring label retention in rats. Saccharomyces cerevisiae (Hansen strain CBS 1171) was prepared intrinsically enriched with a stable isotope of iron, zinc, copper or selenium, and unenriched freeze-dried yeast was extrinsically labeled with the appropriate stable and/or radioisotope. Male Wistar rats, weighing 80-100 g and fed a purified diet, were given a test meal of one of the above labeled yeasts. Isotopic retention was determined by fecal monitoring. Retention of the stable isotopes was determined by thermal ionization quadruple mass spectrometry (TIQMS) and retention of the radioisotopes by counting feces in a whole-body counter. The results indicated that the behavior of the labels differed among the minerals, with copper as the only one in which the intrinsic and extrinsic stable isotopes were comparably retained. With zinc, retention of the extrinsic radiolabel and intrinsic label was similar, but retention of the extrinsic stable isotope label was higher. With iron, the intrinsic label had a significantly lower retention than the two extrinsic labels; with selenium, retention of all three labels was different, but these differences were not of a sufficient magnitude to conclude that extrinsic stable isotopic labelling is not valid. These results demonstrate that an extrinsic stable isotope label can be used for copper, selenium and inorganic iron, but that such a label is not valid for studies on zinc.

Absorption↗

PubMed1995

The bioavailability of iron in different weaning foods and the enhancing effect of a fruit drink containing ascorbic acid.

There is limited information on the bioavailability of Fe in infant weaning foods, mainly because of the difficulties of measuring Fe utilization directly in infants. The aim of this study was to develop a safe and relatively noninvasive method for studying Fe bioavailability (measured as percent Fe incorporation into red blood cells) in infants using 54Fe, 57Fe, and 58Fe stable isotopes. Four commonly used weaning foods were selected for study, labeled extrinsically with 57Fe- or 58Fe-enriched ferrous sulfate, and fed to five female and five male 9-mo-old fasting infants, using a multiple-dosing technique. Each food was given three times, labeled with one isotope, with a fruit juice drink containing 50 mg of ascorbic acid, and three times, labeled with a different isotope, with an ascorbic acid-free drink. Fourteen days after the last test meal, a blood sample was obtained from a heel-prick, spiked with a known amount of 54Fe, digested, and purified by ion exchange; isotopic enrichment and total Fe content were measured by quadrupole thermal ionization mass spectrometry. The proportion of administered dose of isotope circulating in the blood was calculated from an estimate of blood volume. The geometric mean bioavailability (range) was 3.0% (1.2-9.5%) in a proprietary dehydrated vegetable product, 3.0% (1.1-21.2%) in Weetabix whole-wheat breakfast cereal, 3.1% (1.2-15.4%) in wholemeal bread, and 4.3% (1.7-10.3%) in baked beans. When taken with the drink containing ascorbic acid, there was a 2-fold increase in bioavailability in all foods except the vegetable meal, presumably because this was already fortified with ascorbic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1994

Methylated C-glycosylflavones as taxonomic markers in orchids of the subtribe Ornithocephalinae.

In a leaf flavonoid survey of 15 Brazilian orchid species from the subtribe Ornithocephalinae, flavone C-glycosides were found to be the major constituents in all except two Ornithocephalus taxa. In Zygostates cornuta a rare glycoside, apigenin 7,4'-dimethyl ether 6-C-glucoside-2"-O-rhamnoside, was identified. This also occurred in Z. alleniana, Z. lunata, Z. pellucida and Z. pustulata. Two further similar apigenin 7,4'-dimethyl ether C-glycoside-O-rhamnosides, possibly with different C-linked sugars, were detected in Z. multiflora and Z. grandiflora. In Z. cornuta, apigenin 4'-methyl ether 6-C-glucoside-2"-O-rhamnoside was found to co-occur with the apigenin 7,4'-dimethyl ether derivative. Ornithocephalus myrticola was distinguished by the presence of an apigenin 8-C-methylpentoside and three apigenin 7-methyl ether 8-C-glycoside derivatives. In O. bicornis and O. kruegeri, another apigenin 7,4'-dimethyl ether C-glycoside was found, while from Phymatidum falcifolium, apigenin 7,4'-dimethyl ether and apigenin 7-methyl ether C-glycosides and their O-arabinosides were isolated. Chytroglossa marileoniae also contained an apigenin 7,4'-dimethyl ether C-glycoside, which appeared to be the same as that in P. falcifolium. Rauhiella silvana, on the other hand, could be distinguished from all the other taxa studied by the absence of methylated C-glycosylflavones and presence of isovitexin. 6-Hydroxyflavone O-glycosides, which are characteristic leaf constituents of some Oncidium species in the related subtribe Oncidinae were not detected in the present sample.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Sequence↗

PubMed1994

Mass spectrometric methods for studying nutrient mineral and trace element absorption and metabolism in humans using stable isotopes. A review.

Mass spectrometric methods for determining stable isotopes of nutrient minerals and trace elements in human metabolic studies are described and discussed. The advantages and disadvantages of the techniques of electron ionization, fast atom bombardment, thermal ionization, and inductively coupled plasma and gas chromatography mass spectrometry are evaluated with reference to their accuracy, precision, sensitivity, and convenience, and the demands of human nutrition research. Examples of specific applications are described and the significance of current developments in mass spectrometry are discussed with reference to present and probable future research needs.

Absorption↗

PubMed1994

True fractional calcium absorption in Chinese children measured with stable isotopes (42Ca and 44Ca).

True fractional Ca absorption (TFCA) was compared in children with different habitual Ca intakes using a double-label stable-isotope technique. Chinese children aged 7 years from Hongkong (n22) and Jiangmen (n12) participated in the study. An oral administration of 8 mg 44Ca in 100 g chocolate milk was given shortly after an intravenous injection of 0.75 mg 42Ca. Ca isotopic ratios were determined in urine samples collected 24 h later using thermal-ionization mass spectrometry. There was no significant difference in TFCA between Jiangmen and Hongkong children (P = 0.16). TFCA of a lower-Ca-intake group (Ca < or = 500 mg/d, n19) with mean Ca intake 359 mg/d was 63.1 (SD 10.7)% and that of a higher-Ca-intake group (Ca > 500 mg/d, n15) with mean Ca intake 862 mg/d was 54.8 (SD 7.3)%; the difference in TFCA was significant (P = 0.016). Serum levels of 25-hydroxycholecalciferol of the children were adequate (33.7 (SD 7.7) ng/ml). The present study indicates that growing children accustomed to a low-Ca diet appear to be able to enhance their absorptive capacity. If it is assumed that dietary Ca absorption by Chinese children resembles their TFCA from a single meal of chocolate milk, then the recommended dietary allowance (RDA) for Ca for Chinese children would be lower than the US RDA (800 mg/d), which is based on an estimated 40% Ca absorption as reported for Caucasian children. A comparative absorption study is necessary to determine whether there is any difference in TFCA between Caucasian and Chinese children.

Body Height↗

PubMed1994

Assessment of zinc bioavailability: studies in rats on zinc absorption from wheat using radio- and stable isotopes.

Absorption from wheat intrinsically and extrinsically labelled with 67Zn and extrinsically labelled with 65Zn was measured from 67Zn faecal excretion and 65Zn whole-body retention in rats. There were significant differences between the extrinsically- and intrinsically-labelled 67Zn (P < 0.001), but not between the extrinsically-labelled 65Zn and intrinsically-labelled 67Zn. The effect of chicken meat on the absorption of Zn from intrinsically-labelled wheat was also studied in the rat. Mean Zn absorption from wheat and chicken meat fed separately was 18.5 and 68.2% respectively, and from a mixture of the two containing the same level of Zn was 50.1%. The apparent absorption of Zn from the composite meal was significantly higher than predicted from the results of the foods on their own (P < 0.001).

Absorption↗

PubMed1993

The measurement of exchangeable pools of zinc using the stable isotope 70Zn.

The present study was designed to assess the feasibility of using small doses of a stable isotope of Zn to follow plasma kinetics over a 10 d period and, hence, make deductions about Zn turnover and body pool sizes. At the beginning of the 10 d metabolic balance, two adults, consuming their habitual diet, were given an intravenous injection of 70Zn. There was a fourfold difference in the administered dose between the two subjects (0.445 and 2.078 mg). Blood samples were taken at regular intervals and plasma enrichment with 70Zn measured by thermal ionization mass spectrometry. Urine and faeces were collected and analysed for Zn and 70Zn. Kinetic analysis of the plasma 70Zn decay by several different methods was undertaken. It was apparent from both deconvolution analysis of the short-term (0-90 min) decay data and four-compartment modelling of the longer-term (0-24 h) data that isotopic Zn very rapidly equilibrates with the plasma Zn and with a rapidly exchanging non-plasma pool, probably located within the liver. This latter pool appears to contain less than 10 mg Zn and the peak of isotope enrichment occurs at about 20 min post injection. The later decay of plasma Zn enrichment appears to be dictated by exchange with a much larger pool of approximate size 350 mg.

Adult↗

PubMed1992

Zinc absorption in adult men from a chicken sandwich made with white or wholemeal bread, measured by a double-label stable-isotope technique.

Eleven fasted adult men consumed a chicken meat sandwich made with white or wholemeal bread, extrinsically labelled with 2 mg 67Zn, on two different occasions. Immediately after eating the sandwich they were given an intravenous injection of 1.5 mg 70Zn. True Zn absorption (which was approximately 7% higher than apparent absorption) was determined by the faecal balance technique by making an allowance for endogenous excretion from measurements of faecal excretion of 70Zn. There was no significant difference in mean true Zn absorption from the white or wholemeal bread sandwich, 33.6 and 25.4% respectively. It was concluded that the substitution of wholemeal for white bread does not reduce Zn absorption from meat-based sandwiches.

Adult↗

PubMed1991

Intrinsic labelling of different foods with stable isotope of zinc (67Zn) for use in bioavailability studies.

Intrinsically-labelled foods are required to validate extrinsic-labelling techniques used to study the bioavailability of trace elements. Wheat (Triticum aestivum), peas (Pisum sativum), goat's milk, human milk, eggs and chicken meat were selected for intrinsic-labelling studies with 67Zn. Peas were grown hydroponically in enriched nutrient solution and wheat was grown in sand and watered with enriched nutrient solution. Some of the wheat plants were also given stem injections of 67Zn solution. Eggs and chicken meat were prepared by administering 67Zn intravenously to chickens, and human milk was collected after an oral dose of 67Zn in a cola drink. All the foods investigated were sufficiently enriched with 67Zn for Zn absorption studies except wheat prepared by the sand and water-culture method.

Animals↗