Biomedical subjects
Publications and source records attributed to H Deelstra.
Atomic absorption spectrometric determination of zinc, copper and selenium in milk from cow and goat from Burundi provide values, which agree quite well with literature data. Muscle from both animals is a rich source of zinc, but not for copper and selenium. Liver accumulates the highest amount of copper, while for selenium the kidney is the target organ.
The selenium (Se) distribution in sheep's milk is reported. Skim milk was found to contain the major part (98%) of total milk Se. The Se distribution over casein and whey protein fractions depends on the separation method used, but irrespective of these methods, skim milk Se is mainly associated with the casein fraction (> 68%). Approximately 11%, 4% and 17% Se is removed by dialysis (molecular mass cut-off 10-12 kDa) from skim milk, casein and whey respectively, indicating a major association of Se with milk proteins. This observation is confirmed through Se analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Se concentrations of the different isolated milk proteins show considerable variations (caseins, 304-750 ng Se/g; whey proteins, 241-806 ng Se/g).
The present studies were undertaken to characterize selenium distribution in egg white. Ion-exchange chromatography fast protein liquid chromatography (FPLC) and flow injection atomic (absorption) spectrometry (FIAS) were used to separate egg white proteins and to determine the selenium content of different fractions. After purification, nine different proteins were identified with sodium dodecyl sulphate-polyacrylamide gel electrophoresis and 56% of the total selenium content was found to be associated with ovalbumin-1 and -2 (+/- 500 ng/g), which is the main protein in egg white. Flavoprotein was determined to be the richest selenium-containing protein (1800 ng/g). The selenium content of the other proteins (lysozyme, conalbumin, globulins and ovomucoid) ranged from 359 to 1094 ng/g.
The present study evaluates the application of an in vitro digestion procedure for estimating the selenium (Se) availability from cow's milk. The results obtained by this in vitro method indicate that only a small portion (< 10%) of milk Se can be estimated as available. The available fraction of whole milk (4.7%) was significantly lower compared to the Se availability of skim milk (7.3%). Investigations on the methodology of the in vitro method indicate that the portion of total potentially available Se, determined as total dialysable Se, increases simultaneously with protein digestibility along with the digestion process. Therefore it is concluded that protein digestibility might largely influence the Se availability from milk.
Atomic absorption spectrometry is used to determine copper and zinc content of several duplicate meals consumed by different population groups in the Antwerp region (Belgium). Daily elemental intake, beverages not included, is calculated and proven to be below the recommended daily allowances (National Academy of Sciences, USA), except for copper intake by macrobiotics. Values obtained in this study are compared with scarce data on intake by similar groups in other countries.
This study reports on selenium distribution in goat milk. Skim milk was found to contain the major part (94%) of total milk selenium. The selenium distribution over casein and whey protein fractions depends on the separation method used, but irrespective of these methods, skim milk selenium is mainly associated with the casein fraction (greater than 69%). Approximately 9%, 7% and 24% of selenium is removed by dialysis (molecular cutoff 10-12 kDa) from skim milk, casein and whey respectively, indicating a major association of selenium with milk proteins. This observation is confirmed by selenium analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Selenium concentrations of the different isolated milk proteins show considerable variation (caseins: 294-550 ng Se/g; whey proteins: 217-457 ng Se/g).
Manganese has been proven to be an essential trace element in animals since 1931. Today, it is known that manganese deficiency results in a wide variety of structural and physiological defects in animals. For humans, the safe and adequate range of intakes for manganese by enteral nutrition is 2.0 to 5 mg per day; for parenteral nutrition a range of 0.15 to 0.8 mg per day is proposed. The manganese content of components of enteral nutrition (EN) and total parenteral nutrition (TPN) solutions is determined using electrothermal atomic absorption spectrometry. Comparison is made between calculated and measured values. The manganese present in supplementary nutrition and flavor stuffs is also measured. The intake of manganese by EN is calculated based on the daily administration, and is found to vary from 192 to 7373 micrograms per day. In prepared TPN-solutions, the manganese contribution of all components before adding the Oligo Complex is found to be less than 0.2% of the total manganese content. After addition of the Oligo Complex mixture, a mean daily intake of 5.02 +/- 0.16 mg per day is found.
Atomic absorption spectrometric determination of zinc, copper and selenium in fish from Lake Tanganyika (Burundi) shows that, although this lake is not polluted, trace element intake by fish contributes an important part of the elemental intake by man. No correlations were found between trace element levels in the fish and fish lipid and protein content. Copper and zinc were positively and highly correlated (P less than 0.005). Interspecies comparison for trace element content of fish samples is discussed. Unless the level of water pollution is taken into account, intraspecies variation cannot be evaluated.
Sampling, storing, sample pretreatment, and experimental conditions for selenium (Se) determination in human serum, plasma, and whole blood by X-ray emission spectrometric (XRS) methods are described. Concentration levels in these biological fluids, found by this technique, are discussed and compared to values found by other techniques for the same healthy population group in the same area. XRS analysis of blood from patients with various pathological conditions is reviewed, with special attention to the relation of Se with the concentration level of other essential or nonessential trace elements.
A mixture of palladium/magnesium nitrate was used as matrix modifier in graphite furnace atomic absorption spectrometry for the direct determination of selenium in human whole blood Addition of HCl up to 0.2 M, a twenty-five fold diluted sample and an appropriate furnace program are necessary to eliminate the interference of iron. Reproducibility of less than 3% at the 95 micrograms/L level, a detection limit of 10 micrograms/L and good accuracy, as determined by intercomparison runs and recovery of spiked samples, are obtained. The proposed method can be used for analysing 4 blood samples per hour.
Direct graphite furnace atomic absorption spectrometry after appropriate sample dilution is applied to whole blood of Belgian blood bank donors from different geographical areas. Highest values were obtained for the northern part of the country (Flanders). Different consumption habits may explain the significant difference in selenium level found for the two cultural communities (Flemish and Walloon). No sex difference was obtained in both parts of the country and no influence of age was observed for the two communities. Values obtained are compared with literature data on whole blood selenium content for other European countries.
The chromium content of human breast milk, infant formulae, cow's milk and beikost was measured by graphite furnace atomic absorption spectrometry following different digestion steps. No significant variation in chromium concentration during lactation was found. The mean concentration was 0.18 ng/ml. The daily chromium intake for Belgian infants of 3 months of age using different types of food was estimated. Exclusively breast fed infants consumed 0.1 microgram/day, while for infants fed cow's milk the intake was five times higher. The exclusive use of commercial infant formulas resulted in an intake of 2 up to 10 micrograms chromium a day.
Cow's milk of different lactation stages and of different seasons was analysed for its vitamin E and selenium contents. The concentrations of these nutrients vary with the lactation stage as well as with the sampling period. The results are compared with corresponding values for human milk. Cow's milk has appreciatly lower concentrations of vitamin E; the selenium content of cow's and human milk are the same. The lack of vitamin E when cow's milk is used for infant formulae is compensated for the addition of alpha-tocopheryl acetate. The selenium concentration of different protein fractions of cow's milk was determined. It was found that the whey proteins contain more selenium than the caseins.
Longitudinal changes of the trace element (Fe, Cu, Zn, Mn, Mo, Cr, Co, As, Se) composition of human milk are discussed. The mean daily intake of breast fed infants is compared with the intake of infants fed cow's milk and with recommended dietary allowances. Parameters which can be used to check the selenium status are discussed. Clinical consequences of selenium deficiency are discussed.
The selenium content of commercial infant formulae, processed milk and beikost was measured by hydride generation atomic absorption spectrometry after previous wet acid digestion. The median daily intake by infants (1-6 months) fed milk, soya or cereal-based infant formulae was 3.0-7.8 micrograms/day; lower than the mean daily intake by Belgian breast-fed infants (6.1-8.6 micrograms/day) and cow's milk bottle-fed infants (7.6-10.8 micrograms/day).
The selenium content of expressed human milk obtained at different stages of lactation from 32 lactating mothers was measured by hydride generation atomic absorption spectrometry after previous wet acid digestion. The highest selenium level was found in colostrum (14.8 ng/g; wet weight), subsequently the content declined and plateaued off after one month (9.4 ng/g; wet weight). The daily selenium intake for Belgian infants of 3 months of age was found to be 7.1 micrograms (girls) and 8.1 micrograms (boys), which is lower than the values obtained in most other countries and lower than the recommended safe and adequate daily intake of 10 to 40 micrograms/day for the same age group.
The tetravalent and hexavalent selenium content of water samples can be determined by conventional energy-dispersive X-ray fluorescence after different preconcentration steps. Selenium values of nearly three-hundred different environmental and drinking water samples in Belgium are reported. The results are quite low, ranging from the detection limits up to 1 microgram 1-1. The concentration levels are compared to literature data and the speciation is discussed. The contribution of drinking water to the daily intake of selenium in Belgium ranges from less than 0.2 to 5%.