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  • 1
    Electronic Resource
    Electronic Resource
    Effect of the cationic polypeptide polylysine on neutral amino acid transport in isolated brain microvessels (1992)
    Springer
    Amino acids 3 (1992), S. 253-260 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cationic polypeptide ; Blood brain barrier ; Neutral amino acids transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The functionality of isolated brain microvessels — used as anin vitro model of the blood-brain barrier — can be influenced by interaction with cationic proteins. The various polylysines (Mr ranging from 0.9 to 180 kDa) tested affected the activity of both the Na+-dependent (“A”) and the Na+-independent (“L”) systems for neutral amino acid transport. Exposure to the 180 kDa polylysine caused a conspicuous inhibition of both transport systems, associated to an increased passive permeability. There was a constant, Mr-dependent, inhibition of the the L-system-mediated uptake of hydrophobic neutral amino acids. The activity of the A-system was enhanced, upon exposure to polymers larger than 22 kDa reaching its peak at 68 kDa and and declining at higher Mr values. The effect which was Na+-ions dependent and abolished by phloretine, could be essentially ascribed to an increased affinity of the MeAIB for its carrier (Km value decreasing from 265 to 169µM in presence of 68 kDa polylysine).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806000
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of oral 5-hydroxytryptophan administration on feeding behavior in obese adult female subjects (1989)
    Springer
    Journal of neural transmission 76 (1989), S. 109-117 
    Details
    ISSN: 1435-1463
    Keywords: 5-Hydroxytryptophan ; feeding behavior ; obesity ; serotoninergic system ; tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nineteen obese female subjects with body mass index ranging between 30 and 40 were included in a double-blind crossover study aimed at evaluating the effects of oral 5-hydroxytryptophan administration on feeding behavior, mood state and weight loss. Either 5-hydroxytryptophan (8 mg/kg/day) or placebo was administered for five weeks during which patients were not prescribed any dietary restrictions. Feeding behavior was investigated by means of a questionnaire designed to establish the onset of anorexia and related symptoms. Food intake was evaluated using a three-day diet diary. BDI, SI, STAI-T, and STAI-S were used to assess mood state. The administration of 5-hydroxytryptophan resulted in no changes in mood state but promoted typical anorexiarelated symptoms, decreased food intake and weight loss during the period of observation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578751
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Synergism between different transport systems stimulates the uptake of neutral amino acids by isolated brain microvessels (1992)
    Springer
    Amino acids 2 (1992), S. 13-23 
    Details
    ISSN: 1438-2199
    Keywords: Amino acid transport ; Blood-brain barrier ; Glutamine ; Methionine ; Methanethiol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The polar long-chain amino acids glutamine and methionine can be transported across the endothelial cells of brain microvessels either by an L-system which operates by a facilitated diffusion, exchanging mechanism, or by a concentrating, energy-dependent A-system. The presence of glutamine and/or of methionine can induce a synergism between the two transport systems which results, by a transstimulation mechanism, in a net increased uptake of neutral hydrophobic aminoacids. The methionine analog S-methylthiocysteine, which is the mixed disulfide resulting from the combination of methanethiol with cysteine, behaves similarly to methionine in stimulating the uptake of neutral hydrophobic amino acids. The same transstimulating effect can even be obtained in collagenase-treated, A-system-deprived microvessels by inducing the direct formation of S-methylthiocysteine within the cytoplasmic compartment of the endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806074
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Plasma and CSF tryptophan in cancer anorexia (1990)
    Springer
    Journal of neural transmission 81 (1990), S. 225-233 
    Details
    ISSN: 1435-1463
    Keywords: Amino acids transport ; anorexia ; blood brain barrier ; cancer ; CSF tryptophan ; plasma tryptophan ; serotoninergic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eighteen untreated cancer patients and ten sex- and age-matched healthy volunteers were studied. In all patients eating behavior was investigated by means of a specific questionnaire from which the presence of anorexia and anorexia-related symptoms was assessed. To investigate the role of tryptophan in cancer anorexia, fasting plasma and CSF levels of tryptophan and other neutral amino acids were assayed in patients and controls. Cancer patients showed abnormally high plasma free tryptophan levels. In case of patients with cancer anorexia a significant rise of the ratio in plasma between free and tryptophan/large neutral amino acids, competing with tryptophan for its brain entry, was observed. This increase was correlated to a consistent rise of CSF tryptophan levels suggesting a specific role of the serotoninergic system in the pathogenesis of cancer anorexia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01245044
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    Paper (German National Licenses)
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