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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 60 (1982), S. 1165-1172 
    ISSN: 1432-1440
    Keywords: Epithelial transport ; Kidney ; Lactate transport ; Electrolyte transport ; Epithelialer Transport ; Niere ; Laktattransport ; Elektrolyttransport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Resorption bzw. Sekretion im proximalen Nierentubulus läuft einmal passiv auf dem parazellulären Weg, d.i. zwischen den Zellen hindurch, ab, zum anderen aktiv, transzellulär, durch die Zellen hindurch. Der transzelluläre aktive Transport ist in der Regel sekundär aktiv. Er verläuft gekoppelt an den Fluß von Na+-Ionen, wobei ein transzellulärer Gradient von Na+-Ionen, der seinerseits durch die kontraluminal gelegene (Na+-K+)-ATPase geschaffen wird, die Triebkraft liefert. Einmal in der Zelle, verlassen die Substanzen die kontraluminale Zellseite vermittels Karrier, die Na+-unabhängig sind. Mit Hilfe von Mikroperfusions- und elektrophysiologischen Techniken sowie mit Hilfe von Bürstensaumvesikeln wurde der Na+-Kotransport von Aminosäuren, Phosphat, Sulfat, Thiosulfat, Gallensäuren, aliphatischen und aromatischen Monokarboxylsäuren (Laktat) sowie der von Dikarboxylsäuren untersucht. Besonderes Augenmerk wurde dem bidirektionalen Transport von Thiosulfat sowie der Spezifität des Mono- und Dikarboxylsäure-Transportsystems gewidmet.
    Notes: Summary The transport through the epithelial cell layer of the renal proximal tubule proceeds in principle by passive paracellular and active transcellular transport. The active transcellular transport is mostly secondary active. This means it proceeds coupled with the flux of Na+ ions, where-by the transcellular gradient of sodium, created by the (Na++K+)-ATPase, located at the contraluminal cell side, provides the main driving force. Once in the cell the substances leave the other cell side by a Na+-independent, but carrier-mediated transport system. Using microperfusion and electrophysiological techniques as well as brush border membrane vesicle preparation the Na+-H+ countertransport and the Na+-cotransport of amino acids, phosphate, sulfate, thiosulfate, bile acids, aliphatic-aromatic monocarboxylic acids (lactate) and dicarboxylic acids was studied. Special emphasis will be given to the bidirectional transport of thiosulfate as well as to the specificity of the monocarboxylic acid and dicarboxylic acid transport system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 61 (1983), S. 307-309 
    ISSN: 1432-1440
    Keywords: Alpha1-Antitrypsin deficiency ; β-Hexosaminidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Secretion of lysosomal β-hexosaminidase by cultivated skin fibroblasts and receptor-mediated endocytosis of leucocyte β-hexosaminidase from a patient by cultivated non-parenchymal rat liver cells and skin fibroblasts were similar to that of a control proband. The results suggest normal oligosaccharide side chains of high mannose type on lysosomal enzymes in alpha1-antitrypsin (AAT) deficiency.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 57 (1979), S. 977-991 
    ISSN: 1432-1440
    Keywords: Epithelial transport ; Kidney ; Small intestine ; Electrolyte ; Epithelialer Transport ; Niere-Darm-Elektrolyt ; Elektrochemisches Gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das Epithel von Niere und Darm besteht aus einer einzigen Lage von Zellen, die an ihrer luminalen Seite durch Schlußleisten zusammengekittet sind. Der Stofftransport geht entweder transzellulär durch die Zellen hindurch und ist dann in der Regel aktiv, oder er geht parazellulär an den Zellen vorbei durch die Schlußleisten und interzellulären Spalten und ist dann passiv. Die Triebkraft für den aktiven Transport kommt entweder direkt aus dem Stoffwechsel und wirkt mittels ATPasen auf die zu transportierenden Stoffe. Wir haben dann einen primär aktiven Transport vor uns. Oder sie kommt aus Gradienten von Substanzen, in erster Linie Natriumionen, die ihrerseits primär aktiv transportiert wurden. Man spricht dann von sekundär aktivem Transport. Die Triebkräfte für den passiven Transport sind Konzentrations- bzw. elektrochemische Potentialdifferenzen sowie der durch Reibung bedingte Mitreißeffekt des resorbierten Wassers. Sowohl in Niere als auch im Darm haben die proximalen Abschnitte, wo eine große Flüssigkeitsmenge isoton resorbiert wird, undichte Schlußleisten, so daß eine beträchtliche Substanzmenge passiv resorbiert werden kann. In den distalen Abschnitten hingegen, wo der Transport geregelt wird, sind die Schlußleisten dicht, so daß entsprechende Konzentrationsunterschiede erzeugt und aufrecht erhalten werden können. Aktiver Transport durch die Epithelzellen hindurch ist indessen nur möglich, wenn der Stofftransport polar ist, d.h. an der luminalen Zellseite anders als an der kontraluminalen Zellseite. Durch elektrophysiologische Messungen an den einzelnen Zellseiten als auch durch Transportmessungen an geschlossenen Vesikeln, die von den beiden Zellseiten gewonnen wurden, konnten die treibenden Kräfte für die einzelnen Substanzen weitgehend festgelegt werden. An Schemata, in die die Transportmechanismen der einzelnen Zellseiten eingezeichnet sind, wird eine weitgehende Identität der Transportmechanismen im proximalen Tubulus und Dünndarm deutlich.
    Notes: Summary Epithelia of kidney and small intestine consist of one layer of cells which, at their luminal edge, are linked together by terminal bars. Solute transport proceeds either across the cells, which is true of all active transports, or it proceeds paracellularly through the basolateral spaces and terminal bars and is then passive. The driving force for the active transport of a substance is derived either directly from metabolism (primary active transport), or from the gradient of another solute, usually Na+, which in turn is created by primary active transport. In the latter case the transport is referred to as secondary active. The driving forces of passive transport are the electrochemical gradient of the respective substance and solvent drag. The proximal parts of the kidney as well as of the intestine are leaky so that a considerable part of net reabsorption proceeds passively. Their distal parts, however, where the transport is regulated, are tight so that large concentration differences can be created and maintained. Transcellular active transport is only possible if the cells are polar, i.e., the transport characteristics of the luminal cell membrane differ from those of the contraluminal cell membrane. By measuring the cellular electrical potential difference or by measuring transport into isolated plasma membrane vesicles from either cell side the driving forces for the two transport steps, the luminal and contraluminal, have been elucidated. Schemes for the transport steps in the proximal tubule and in the small intestine are given. They show the principal similarity of the transport of many substances in both epithelia.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The transport theory of Kedem and Katchalsky which was derived for passive transport in a two-compartment system is generalized for a multicomponent system with active transport, so that it can be applied to more complicated biological membranes. Equations have been derived to describe the transport of urea through the proximal convolution of the rat kidney and the permeability and the reflection coefficient have been determined. The permeability coefficient $$(\tilde P_u )$$ measured with the microperfusion and stop flow microperfusion methods, was found to be 6.0 and 5.2×10−5 mm2/sec, respectively. The reflection coefficient (σ) was determined in a stationary state situation and found to be 0.68. Earlier free flow micropuncture results together with theP u andσ u of this study indicate that 50% of the filtered urea is reabsorbed proximally and that approximately half of this amount is reabsorbed by solvent drag and the rest by diffusion. In the Appendix, a theoretical treatment of nonelectrolyte transport in a multicomponent system with active transport is given.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A new mutation (CGA to TGA) in codon 261 of exon 7 of the phenylalanine hydroxylase gene transforms Arg261 to a stop codon in two unrelated patients of German and Turkish origin. The different ethnic backgrounds and the different polymorphic characteristics of the two mutant alleles suggest an independent origin of the mutation. This is the second defect detected in codon 261 of the phenylalanine hydroxylase gene, a codon that thus appears to be a mutation hot spot.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1076
    Keywords: Glycogen storage disease type I ; Hypoglycemia ; Hypertriglyceridemia ; Growth rate ; α-Glucosidase inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Seven patients with glycogen disease type I have been treated with nocturnal intragastric feeding combined with frequent daytime feeding. Follow-up shows a striking improvement in their clinical condition including growth rate. Determination of biochemical parameters reveals a significant increase of lactate, pyruvate, alanine, uric acid, triglycerides, and SGOT in blood. Additional administration of an α-glucosidase inhibitor in four patients caused a significant increase in blood lactate despite unchanged blood glucose levels.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 153 (1994), S. S38 
    ISSN: 1432-1076
    Keywords: Lysosomal disorders ; Screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients at any age who develop regression of learned skills, onset of dementia, loss of motor control and organ enlargement should be considered for lysosomal screening. Morphological and biochemical screening methods may reinforce the clinical suspicion, but they are not diagnostic. A widespread use of enzyme assays that appear to be related to the clinical problems is recommented.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1076
    Keywords: Phenylketonuria ; Selective ; sustained attention ; Impaired frontal lobe functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twenty normally intelligent children with early treated phenylketonuria (PKU) (IQ: mean=101.4, SD=10.0; age: mean=10 years 11 months, SD=1.3 years) and 20 healthy controls, matched for age, sex and IQ, were assessed for their selective (Stroop Task) and sustained attention (Test-d-2). Using positron emission tomography an activation of the frontal lobe during the Stroop task had previously been demonstrated. In addition to the Stroop Task and the Test-d-2, a short-term memory test as a “non-frontal-lobe-function-task” was administered to all subjects. Group comparisons demonstrated that PKU children had specific deficits in selective and sustained attention, which were significantly correlated with the concurrent serum phenylalanine concentration. Conclusion The results give evidence that even dietary treated children with PKU were suffering from impaired attentional control mechanisms in spite of a normal IQ. The deficits might be the result of impaired frontal lobe functions.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; l-dopa therapy ; Neuropsychological tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight adult, untreated patients with classical phenylketonuria received L-dopa and a decarboxylase inhibitor for 2 weeks. No effect of l-dopa therapy on choice reaction time tasks, sustained attention, frontal lobal function as well as latencies of visual evoked potentials was found. The results raise the question if adult patients with phenylketonuria really suffer from functional dopamine deficiency.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Positron emission tomography ; Dopamine D2-receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients with phenylketonuria (PKU) may suffer from cognitive and neurological deficits which are related to reduced intracerebral concentrations of catecholamines. The function of phenylalanine (Phe) as an inhibitor of the uptake of the precursor amino acid tyrosine (Tyr) through the blood-brain barrier as well as an inhibitor of the expression of dopamine receptors in the brain is under investigation. Positron emission tomography (PET) is a method for quantitatively determining biochemical and physiological processes in vivo. In the current pilot study, l-[1-11C]-Tyr and 18F-fluoro-ethyl-spiperone (FESP) have been used. The metabolic pathway of carboxylic labelled Tyr is mainly incorporation into protein. From the measured tissue and plasma activity as a function of time in combination with a compartimental model the Protein Synthesis Rate (PSR) for Tyr can be calculated. FESP is a ligand which binds irreversibly to the dopamine D2-receptor and has also a low non specific binding, although affinity to the serotonin receptor has been described. The ratio of FESP concentration in striatum and in cerebellum is a measure of the receptor status in vivo. In patients with plasma Phe levels above the maximum therapeutic concentration (〉 700 μmol/l) the PSR for Tyr was decreased as compared to controls and patients with plasma Phe concentrations within the therapeutic range, indicating a decreased availability of Tyr for neurotransmitter synthesis, and hence explaining the reduced cerebral concentration of catecholamines.
    Type of Medium: Electronic Resource
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