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  • Chemistry  (41)
  • Selenium  (7)
  • Glutathione peroxidase  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Selenium content of human milk, cow's milk and cow's milk infant formulas (1978)
    Springer
    European journal of pediatrics 129 (1978), S. 139-145 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Human milk ; Cow's milk ; Cow's milk infant formula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The selenium content of human milk, cow's milk and cow's milk infant formula were estimated by instrumental neutron activation analysis. The highest values were found in 3 samples of human colostrum (524–865×10-9 g/g dry weight). There was a significant decrease with increasing time post partum. Mature human milk exhibited a selenium content of 230±79×10-9 g/g dry weight. The selenium content of 45 samples of cow's milk from the north-western area of Germany was 200±39×10-9 g/g dry weight. While there was no significant difference between the values of mature human milk and of cow's milk, cow's milk infant formula exhibited significantly (P〈0.01) lower values than human milk. The average selenium content of 107 samples of 10 different commercially available fluid and powdered cow's milk infant formulas (range: 18–171×10-9 g/g dry weight) amounted to about only one third of that in mature human milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442157
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  • 2
    Electronic Resource
    Electronic Resource
    Selenium requirements in patients with inborn errors of amino acid metabolism and selenium deficiency (1980)
    Springer
    European journal of pediatrics 134 (1980), S. 65-68 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Glutathione peroxidase ; Selenium deficiency ; Selenium supplementation ; Nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The diets of 5 patients with phenylketonuria or maple-syrup-urine disease were supplemented with yeast which was rich in selenium. For 120 days the patients received 45 μg Se/day to increase the Se content of their diets to 10–12ng Se/Kjoule. Before supplementation the selenium content of serum (5–15 ng/ml) and whole blood (10–27 ng/ml), and the activity of the erythrocyte glutathione peroxidase (0.19–2.69 U37/g Hb), amounted to only 10–20% of normal. The serum selenium content reached normal values within 4 weeks of supplementation, followed by normalisation of the selenium content of whole blood within 4–8 weeks. Restoration of the activity of erythrocyte glutathione peroxidase took 9 to 15 weeks —the red cell life span. There was a significant positive correlation between the selenium content of the erythrocytes and the activity of erythrocyte glutathione peroxidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442405
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  • 3
    Electronic Resource
    Electronic Resource
    Plasma glutathione peroxidase after selenium supplementation in patients with reduced selenium state (1982)
    Springer
    European journal of pediatrics 138 (1982), S. 138-140 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Supplementation ; Plasma ; Glutathione peroxidase ; Glutathione S-transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The plasma glutathione peroxidase (GSHPx) activity was measured in normal adults and children and in patients with reduced selenium state because of dietary treatment of metabolic diseases (phenylketonuria or maple-syrup-urine disease) before and after selenium supplementation. Besides GSHPx (measured with t-butyl hydroperoxide, cumene hydroperoxide and hydrogen peroxide as acceptor substrates) the activity of glutathione S-transferase was estimated in plasma. Plasma GSHPx activity in healthy children was significantly lower than in healthy adults. In 11 dietetically treated patients with phenylketonuria or maple-syrup-urine disease the plasma GSHPx was reduced to about 17% of the values of healthy children of the same age. No glutathione S-transferase activity could be found in plasma of children in normal or reduced Se state. During administration of yeast rich in Se (200μg Se/d) for 90 days 2 healthy adults showed no significant change of plasma GSHPx activity. During Se supplementation (75–100μg Se/d) for 120–163 days 5 dietetically treated patients with PKU or MSUD exhibited a significant increase of plasma GSHPx activity within 2 days. The values reached a plateau after 1 to 3 weeks of supplementation and remained at this level within the following 4 to 5 months. Therefore, the activity of plasma glutathione peroxidase can be used as an indicator of short-term changes of selenium intake in selenium deficient individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00441140
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  • 4
    Electronic Resource
    Electronic Resource
    The selenium state of healthy children (1977)
    Springer
    European journal of pediatrics 125 (1977), S. 81-88 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Glutathione peroxidase ; Normal values ; Blood ; Infants ; Children ; Milk ; Nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The selenium concentration of serum is age-dependent. The median value at birth ( $$\tilde x$$ =50×10−9g/ml) amounts to half of the median value of adults ( $$\tilde x$$ =102×10−9g/ml). After a decrease in early infancy to $$\tilde x$$ =34×10−9g/ml it steadily increases to $$\tilde x$$ =58×10−9g/ml in the second half of the first year, to $$\tilde x$$ =82×10−9g/ml in 1–5 year old children, and to $$\tilde x$$ =92×10−9g/ml in school children. The activities of the selenium containing enzyme glutathione peroxidase of erythrocytes are also reduced in early infancy (x=7.2±0.36 U37/g Hb), whereas the enzyme activities of cord blood erythrocytes (x=8.72±0.76 U37/g Hb) are in the same range as those of older children or adults. The selenium content of some commercially available milk formulas for infants are lower than those of human and cow's milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00470608
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  • 5
    Electronic Resource
    Electronic Resource
    Selenium intake of infants and young children, healthy children and dietetically treated patients with phenylketonuria (1984)
    Springer
    European journal of pediatrics 143 (1984), S. 99-102 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Intake ; Children ; Phenylketonuria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 20 healthy infants and children, 5–20 months old, the Se intake was estimated by analysing food samples by instrumental neutron activation analysis. The intake was calculated by weighing the portions offered and actually consumed. The median Se content of the food amounted to 27 ng/g wet weight (gww) and median daily Se intake to 33.5 μg. The Se intake was not equally distributed over the day. About 50% of the daily Se intake was derived from the supper. The main Se sources (41%) for young children were cereal paps. Commercially, available meals (30 ng/g) contained less Se than home-made ones (50 ng/g). In nine dietetically treated patients with phenylketonuria the median Se intake amounted only to 6.9 μg/day corresponding to a mean Se content of the diet of 7.9 ng/g. The main Se source in the diet was vegetables (36.3%) and 20% derived from their protein supplements. The Se intake of young children, healthy or dietetically treated, cannot be calculated accurately from tables but must be estimated by measuring the Se content of the local food because cereals and vegetables-the main Se sources-exhibit great regional variations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00445794
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  • 6
    Electronic Resource
    Electronic Resource
    The selenium state of children (1978)
    Springer
    European journal of pediatrics 128 (1978), S. 213-223 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Gluthathione peroxidase ; Dietotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The selenium content of serum, whole blood and hair was measured by neutron activation analysis in dietetically treated patients with phenylketonuria (PKU) and maple-syrup-urine disease (MSUD). Follow-up studies showed a decrease of the serum selenium content and the glutathione peroxidase activity of erythrocytes—a selenoenzyme—from normal values at the beginning of the diet to 20% (selenium) and 50% (gluthione peroxidase) of normal within 10–12 weeks of dietary treatment. In 36 patients the serum selenium content was lower at 6.7–28×10-9 g/ml, independent of the age of the patients (0.5 to 10 years). The selenium content of whole blood was reduced: median=98×10-9 g/g dry weight; range 75 to 165×10-9 g/g dry weight (healthy children: median=381×10-9 g/g dry weight; range 245 to 588×10-9 g/g dry weight). The selenium content of hair was markedly lower in the patients (median=62×10-9 g/g; range 13–140×10-9 g/g) than in healthy children (median=429; range 213 to 720×10-9 g/g). The mean glutathione peroxidase activity of erythrocytes was reduced to 4.6±0.64 U37/g Hb, in comparison to normal values (mean=8.8±0.88 U37/gHb).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00445606
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  • 7
    Electronic Resource
    Electronic Resource
    Hair selenium content during infancy and childhood (1982)
    Springer
    European journal of pediatrics 139 (1982), S. 295-296 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Hair ; Infants ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hair selenium content was estimated by instrumental neutron activation analysis in Libyan infants and children. There was no significant difference between the values of young infants from North and South Libya. The hair selenium content rapidly decreased from 1071 ±75 ng/g in newborns to 301±99 ng/g in 7–10 months old infants in North Libya and to 557±204 ng/g in South Libya. In North Libya the values of preschool children were 409±117 ng/g and those of school children 464±124 ng/g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442184
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  • 8
    Electronic Resource
    Electronic Resource
    Beeinflussung der katalytischen Eigenschaften von Al2O3—SiO2-Katalysatoren durch Alkalivergiftung (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 403 (1974), S. 72-80 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Effect of Alkali Contamination on the Catalytic Properties of Al2O3—Si2Catalytic properties of amorphous Al2O3—SiO2 catalysts containing different amounts of Al2O3 in dehydration of isopropanol and cracking of cumene were examined after a defined contamination of the acid centers by sodium ethylate from alcoholic solution. In both reactions, the catalytic activity is decreased by treatment with sodium ethylate, the cracking of cumene being suppressed at a lower alkali concentration than the dehydration of isopropanol. In dehydration of isopropanol, the dependence of the catalytic activity on the alkali content is influenced strongly by the Al2O3 content of the catalysts. In the cracking of cumene, strongly acid Brönsted centers are active, whereas the dehydration of isopropanol proceeds by joint action of acid Lewis or Brönsted centers, respectively, with basic centers at the surface of the catalyst (hydroxide groups or oxygen anions).
    Notes: An amorphen Al2O3—SiO2-Katalysatoren unterschiedlichen Al2O3-Gehaltes wurden nach definierter Vergiftung der sauren Zentren mit Natriumäthylat aus alkoholischer Lösung die katalytischen Eigenschaften bei der Isopropanoldehydratisierung und bei der Cumolspaltung untersucht. Die Natriumbehandlung vermindert für beide Reaktionen die katalytische Aktivität, wobei die Cumolspaltung bereits bei niedrigeren Alkalikonzentrationen unterdrückt wird als die Isopropanoldehydratisierung. Der Charakter der Abhängigkeit der katalytischen Aktivität bei der Isopropanoldehydratisierung vom Alkaligehalt wird stark vom Al2O3-Gehalt der Katalysatoren beeinflußt. Für die Cumolspaltung sind stark saure BRÖNSTED-Zentren aktiv, während die Isopropanoldehydratisierung unter gemeinsamer Beteiligung von sauren Lewis- bzw. BrÖnsted-Zentren mit basischen Zentren der Katalysatoroberfläche (Hydroxidgruppen oder Sauerstoffionen) abläuft.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744030109
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  • 9
    Electronic Resource
    Electronic Resource
    Hydroxidgruppen an Zeolithen. II. Zahl und Eigenschaften von Hydroxidgruppen an CeNaY- und HNaY-Zeolithen unterschiedlichen Austauschgrades (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 404 (1974), S. 142-160 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hydroxide Groups on Zeolites. II. Number and Properties of Hydroxide Groups on CeNaY and HNaY Zeolites of Different Exchange DegreeThe number of hydroxide groups on CeNaY and HNaY zeolites was examined by D2 exchange, and their properties in dependence of the cation exchange degrees were studied by IR spectroscopy. On CeNaY zeolites there exist six kinds and on HNaY zeolites at least seven kinds of hydroxide groups.On the CeNaY zeolites, the hydroxide groups are produced by dissociative chemisorption of water on Ce3+ ions. Their total number increases continuously with increasing exchange degree. Some of the hydroxide groups are acid BRÖNSTED centers whose number increases with increasing exchange degree and decreases with the temperature of preheating increasing to about 600°C.On the HNaY zeolites, the hydroxide groups are produced by thermal decomposition of the NH+4 ions, by dealumination and interaction of the Al3+ ions produced in this way in the place of cations with water. Above the threshold value of 35% the total number of the hydroxide groups increases very rapidly with increasing exchange degree. One part of the hydroxide groups decreasing with increasing exchange degree acts as acid BRÖNSTED centers. The number of these centers does not decrease until at preheating temperatures above 450°C.
    Notes: An CeNaY- und HNaY-Zeolithen wurden durch D2-Austausch die Zahl und infrarotspektroskopisch die Eigenschaften der Hydroxidgruppen in Abhängigkeit vom Kationenaustauschgrad untersucht. Es existieren an CeNaY-sechs Arten und an HNaY-Zeolithen mindestens sieben Arten von Hydroxidgruppen.An den CeNaY-Zeolithen entstehen die Hydroxidgruppen durch dissoziative Chemisorption von Wasser an Ce3+-Ionen. Ihre Gesamtzahl wächst kontinuierlich mit steigendem Austauschgrad. Einige der Hydroxidgruppen sind saure BRÖNSTED-Zentren, deren Zahl mit steigendem Austauschgrad wächst und mit steigender Vorerhitzungstemperatur bis etwa 600°C sinkt.An den HNaY-Zeolithen entstehen die Hydroxidgruppen durch thermische Zersetzung der eingetauschten NH+4-Ionen und mit wachsendem Austauschgrad zunehmend durch das Herauslösen von Gitteraluminium und Wechselwirkung der so entstehenden Al3+-Ionen auf Kationenplätzen mit Wasser. Die Gesamtzahl der Hydroxidgruppen wächst oberhalb des Schwellenwertes von 35% sehr stark mit steigendem Austauschgrad an. Ein mit steigendem Austauschgrad abnehmender Anteil der Hydroxidgruppen wirkt als saure BRÖNSTED-Zentren, deren Zahl erst bei Vorerhitzungstemperaturen oberhalb von 450°C abnimmt.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744040206
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  • 10
    Electronic Resource
    Electronic Resource
    Untersuchungen an oxidischen Katalysatoren. XXIX. Spektroskopische und katalytische Untersuchungen an Ni2+-, Co2+-, Cr3+- und Cu2+-ausgetauschten MordenitenProfessor Günther Rienäcker gewidmet (1979)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 452 (1979), S. 6-16 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Oxide Catalysts. XXIX. Spectroscopic and Catalytic Investigations on Ni2+-, Co2+-, Cr3+-, and Cu2+-exchanged MordenitesNiNaM, CoNaM, CrNaM und CuNaM (M = Mordenite) have been characterized by UV-VIS, EPR and i.r. spectroscopy and the results were compared with the catalytic activity and the activity-time-dependence in the cracking of n-octane and with the shape selectivity in the cracking of a n-octane and isooctane mixture. Water molecules acting as ligands of the exchanged cations are able to dissociate yielding Brönsted acidity. Brönsted sites may be regarded as catalytic active centers in the cracking reaction. Unreduced transition metal cations facilitate the “coking” of the mordenite.The unreduced chromium and cobalt cations for which a position within the main channel is expected, affect the diffusion of the branched paraffin molecule thus increasing shape selectivity.
    Notes: NiNaM, CoNaM, CrNaM und CuNaM (M = Mordenit) wurden durch UV-VIS-Spektroskopie, EPR- und IR-Untersuchungen charakterisiert und die erhaltenen Ergebnisse mit der katalytischen Aktivität und dem Aktivitäts-Zeit-Verhalten dieser Proben bei der Spaltung von n-Octan und der Formselektivität in der Spaltung eines Gemisches von n/iso-Octan verglichen. Wassermolekeln als Liganden der eingetauschten Kationen können dissoziieren und so einen Beitrag zur Brönsted-Acidität liefern. Die Brönsted-Zentren können als katalytisch aktive Zentren in der Spaltreaktion angesehen werden. Nichtreduzierte Übergangsmetallkationen vergrößern die Neigung des Mordenits zum „Verkoken“ wesentlich. Die nichtreduzierten Co2+- und Cr3+-Kationen, für die eine Position im Hauptkanal angenommen werden kann, wirken als zusätzliche Diffusionsbremse auf die verzweigte Paraffinmolekel und erhöhen die Formselektivität des Mordenits.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19794520103
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