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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 30 (1987), S. 409-413 
    ISSN: 1432-0428
    Keywords: Experimental streptozotocin-diabetes ; blood-brain barrier permeability ; cations ; arterial integral uptake technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Decreased sodium permeability across the blood-brain barrier occurs in streptozotocin-treated rats after 2 weeks of diabetes. To establish whether this is a phenomenon specific for cations, the blood-brain barrier permeability for sodium, potassium and calcium was studied with an arterial integral uptake technique. Experiments were performed in control rats and, after two weeks after diabetes induction, in untreated streptozotocin-diabetic rats and in insulin-treated streptozotocin rats. In untreated diabetes, the neocortical blood-brain barrier permeability for sodium decreased by 35% (5.2±1.7 vs 3.4±1.1 10−5cm3·s−1·g−1) and potassium permeability by 39% (19.8±5.7 vs 12.1±3.9 10−5·cm3·s−1· g−1), whereas no differences in calcium permeability occurred. Insulin treatment was associated with an increase in the blood-brain barrier permeability to sodium (4.8±1.0 10−5·cm3·s−1·g−1) as compared to untreated diabetes (3.4±1.1 10−5·cm3·s−1·g−1). It is concluded that the observed changes in sodium and potassium permeability cannot be caused by electrostatic membrane changes. More specific abnormalities of the transport of sodium and potassium across the blood-brain barrier are likely to occur; disturbances in the sodium-potassium-pump activity could account for such alterations.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2665
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Blood-brain barrier permeability to phenylalanine and leucine in four patients with phenylketonuria and in four volunteers was measured five times by the double-indicator method at increasing plasma concentrations of phenylalanine. Based on the permeability-surface area product (PS) from blood to brain (PS1) and on plasma phenylalanine levels, Vmax and the apparentK m for phenylalanine were determined. Statistically significant relationships between plasma phenylalanine and PS1 were established in three out of four volunteers, the averageV max value being 46.7 nmol/g per min and the apparentK m 0.328 mmol/L. Owing to saturation of the carrier, such a relationship could not be established in the patients. In phenylketonuria, PS1 for phenylalanine and leucine decreased significantly by 55% and 46%, respectively. Transport from brain back to blood, PS2, decreased significantly and cerebral large neutral amino acid net uptake was generally decreased in patients with phenylketonuria. In conclusion, the transport ofl-phenylalanine across the human blood-brain barrier follows Michaelis-Menten kinetics. In phenylketonuria, brain permeability to large neutral amino acids is reduced by about 50% and net uptake appears decreased.
    Type of Medium: Electronic Resource
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