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  • Articles: DFG German National Licenses  (24)
  • 1995-1999  (14)
  • 1970-1974  (10)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2186-2187 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple method is described for forming reliable spot welded cruciform hot junctions with thermocouple wires of diameter 12 μm for use in ac calorimeters. By following this method the mounting of small, thin samples onto thermocouples for measurements of thermal conductivity, diffusivity, and specific heat is facilitated, producing a low thermal contact resistance between sample and thermocouple junction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A monoenergetic slow positron beam has been used for the first time to profile porous silicon films. High values of the Doppler-broadened line shape parameters are observed, which correspond to positron annihilation within the porous layers and these are attributed to the decay of para-positronium. After allowing for the reduced density of the porous film, fitted values of thickness were deduced which were in reasonable agreement with values obtained from ellipsometry measurements. Low values of the Doppler parameters observed for the two samples with the thinnest films are attributed to oxide residing at the interface of the porous and bulk silicon regions. Etching the samples in a solution of 48% hydrogen fluoride reduced the porous film thickness significantly, suggesting that a considerable amount of the film consists of SiO2. A four-component convolution analysis routine is used to analyze the individual 511 keV annihilation peaks, the result of which confirms the formation of positronium within the porous layer. Positron annihilation is shown to be a promising method for the nondestructive investigation of thin porous films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The activities of a number of mitochondrial enzymes involved in the metabolism of pyruvate during development of the rat brain were investigated. The rates of decarboxylation of [1-14C]pyruvate to 14CO2 via pyruvate dehydrogenase and the fixation of H14CO3− in the presence of pyruvate via pyruvate carboxylase by brain homogenates were very low in newborn rats. These rates increased markedly by about four-fold and 15-fold respectively during 10–35 postnatal days. The rates of the fixation of H14CO3− by cerebral homogenates were supported by the development of the activity of pyruvate carboxylase in rat brain. The activities of citrate synthase, aconitase, NAD-malate dehydrogenase, aspartate aminotransferase, alanine aminotransferase and phosphoenol-pyruvate carboxykinase were very low in the particulate fraction of the newborn rat brain. The activities of all these enzymes increased makedly by about three- to 10-fold during 10–35 days after birth. The activity of mitochondrial phosphoenolpyruvate carboxykinase from rat brain was not precipitated by an antibody prepared against rat liver cytosolic phosphoenolpyruvate carboxykinase suggesting that cerebral mitochondrial enzyme is immunologically different from that of the cytosolic form in hepatocytes. The significance of the development of the cerebral mitochondrial metabolism is discussed in relation to biochemical maturation of the brain.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To evaluate the relative significance of CO2-fixing enzymes in the metabolism of rat brain, the subcellular distribution of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase, as well as the fixation of H14CO3− by the cytosol and the mitochondria was investigated. Pyruvate carboxylase and phosphoenol-pyruvate carboxykinase are mainly localized in the mitochondria whereas NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase are present in both the cytosol and the mitochondria. In the presence of pyruvate rat brain mitochondria fixed H14CO3− at a rate of about 170 nmol/g of tissue/min whereas these organelles fixed negligible amounts of H14CO3− in the presence of α-ketoglutarate or phosphoenolpyruvate. Rat brain cortex slices fixed H14CO3− at a rate of about 7 nmol/g of tissue/min and it was increased by two-fold when pyruvate was added to the incubation medium. The carboxylation of α-ketoglutarate and pyruvate by the reversal of the cytosolic NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase respectively was very low as compared to that by pyruvate carboxylase. The rate of carboxylation reaction of both NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase was only about 1/10th of that of decarboxylation reaction of the same enzyme. It is suggested that under physiological conditions these two enzymes do not play a significant role in CO2-fixation in the brain. In rat brain cytosol, citrate is largely metabolized to α-ketoglutarate by a sequential action of aconitate hydratase and NADP-isocitrate dehydrogenase. The operation of the citrate-cleavage pathway in rat brain cytosol is demonstrated. The data show that among four CO2-fixing enzymes, pyruvate carboxylase, an anaplerotic enzyme, plays the major role in CO2-fixation in the brain.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The effect of phenylalanine and phenylpyruvate on the metabolism of pyruvate by homogenates of human brain was investigated. In the presence of 5 mM pyruvate as substrate homogenates of human cerebral cortex fixed about 1 μmol of H14CO3-- per g of tissue in 30 min. Phenylpyruvate at a concentration of 5 raw inhibited the fixation of H14 CO3-- by homogenates of human brain by approximately 50 per cent, whereas 5 mM phenylalanine had no effect. The inhibition of pyruvate carboxylation by phenylpyruvate was dependent upon the concentration of the inhibitor. The activity of pyruvate carboxylase (EC 6.4.1.1) in human cerebral cortex was 02–0.4 units, with a Km for pyruvate of about 0.2 mM. Homogenates of human cerebral cortex decarboxylated [1-14C]pyruvate to 14CO2 at a rate of about 5 μmol per g of tissue per 15 min, with a 20–50 per cent reduction in the presence of 5 mM phenylpyruvate; phenylalanine at the same concentration had no effect. The possible toxic effect of phenylpyruvate on the metabolism of pyruvate in the brains of untreated phenylketonuric patients is discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The oxidation to CO2 and the incorporation of [U-14C]glucose and [U-14C]acetate into lipids by cortex slices from rat brain during the postnatal period were investigated. The oxidation of [U-14C]glucose was low in 2-day-old rat brain, and increased by about two-fold during the 2nd and 3rd postnatal weeks. The oxidation of [U-14C]acetate was increased markedly in the second postnatal week, but decreased to rates observed in 2-day-old rat brain at the time of weaning. Both labeled substrates were readily incorporated into non-saponifiable lipids and fatty acids by brain slices from 2-day-old rat. Their rates of incorporation and the days on which maximum rates occurred were different, however, maximum incorporation of [U-14C]glucose and [U-14]acetate into lipid fractions being observed on about the 7th and 12th postanatal days, respectively. The metabolic compartmentation in the utilization of these substrates for lipogenesis is suggested. The activities of glucose-6-phosphate dehydrogenase, cytosolic NADP-malate dehydrogenase, cytosolic NADP-isocitrate dehydrogenase, ATP-citrate lyase and acetyl CoA carboxylase were measured in rat brain during the postnatal period. All enzymes followed somewhat different courses of development; the activity of acetyl CoA carboxylase was, however, the lowest among other key enzymes in the biosynthetic pathway, and its developmental pattern paralleled closely the fatty acid synthesis from [U-14C]glucose. It is suggested that acetyl CoA carboxylase is a rate-limiting step in the synthesis de novo of fatty acids in developing rat brain.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    USA/Oxford, UK : Blackwell Science Ltd
    Cephalalgia 16 (1996), S. 0 
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We compared data from 243 patients with episodic migraine (EM) and 132 patients with chronic daily headache (CDH). We divided the matter group into those with tension-type headache only (CDH Type 1) and those with headaches having migrainous features (CDH Types 2+3) and compared each with the EM group and all three groups with one another. CDH Type l patients differed from those in the other groups by virtue of gender (more often male) and mean age at headache onset (older). The CDH Types 2+3 and EM groups differed only in that the former were more likely to have undergone a brain-imaging study. These data suggest that CDH Type 1 may represent a distinct headache syndrome, while CDH Types 2+3 closely resemble episodic migraine.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 51 (1996), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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