R Steinfeld

University of Hamburg, Hamburg, Hamburg, Germany

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Publications (5)17.16 Total impact

  • Source
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    ABSTRACT: Phenylketonuria, an inborn error of phenylalanine metabolism, occurs with a frequency of about 1 in 10,000 births and is treated with a strict dietary regimen. Recently, some patients with PKU have been found to show increased tolerance towards phenylalanine intake while receiving tetrahydrobiopterin (BH(4)) supplementation. We have treated two infants with BH(4)-responsive PKU with BH(4) for more than 2 years. No additional dietary control was required to maintain blood phenylalanine concentrations in the desired range. Both children have shown normal development. Generally, our results suggest that BH(4) treatment might be an option for some patients with mild PKU, as it frees them from dietary restrictions and thus improves their quality of life.
    Journal of Inherited Metabolic Disease 02/2004; 27(4):449-53. · 4.07 Impact Factor
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    ABSTRACT: We describe six children with tetrahydrobiopterin (BH(4)) responsive phenylalanine hydroxylase (PAH) deficiency. All patients carry two mutant alleles in the PAH gene. Cofactor deficiency was excluded. The effect of BH(4) administration was studied by correlating different oral BH(4) doses with plasma phenylalanine levels under defined protein intake. Our results indicate that oral BH(4) supplementation may be used as long-term treatment for individuals with BH(4)-responsive PAH deficiency, either without or in combination with a less restrictive diet. Previous in vitro studies have demonstrated that BH(4) inhibits PAH tetramers but activates PAH dimers. This may indicate, that BH(4)-responsiveness results from BH(4) induced stabilization of mutant PAH dimers. In addition, interindividual differences in the cellular folding apparatus may determine the tertiary structure and the amount of mutant PAH dimers and hence may account for divergent BH(4)-responsiveness reported for the same PAH genotype.
    Amino Acids 08/2003; 25(1):63-8. · 3.91 Impact Factor
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    ABSTRACT: A remarkable, intermittent sudden-onset vigilance and movement disorder in an exclusively breast-fed infant is reported, which was caused by cobalamin depletion due to maternal vitamin B12 malabsorption. The lack of cobalamin caused a severe encephalopathy in the infant, whose brain displayed a striking loss of volume and a delay of myelination. Proton magnetic resonance spectroscopy revealed an accumulation of lactate in the gray and white matter of the brain and a sustained depletion of choline-containing compounds in the white matter, reflecting a reversible disturbance of oxidative energy metabolism in brain cells and a long-lasting hypomyelination disorder. The clinical picture in conjunction with MRI and spectroscopic data of this case study yields more insight into the functions of cobalamin in the cerebral metabolism.
    Neuropediatrics 07/2003; 34(5):261-4. · 1.19 Impact Factor
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    ABSTRACT: Summary. We describe six children with tetrahydrobiopterin (BH4) responsive phenylalanine hydroxylase (PAH) deficiency. All patients carry two mutant alleles in the PAH gene. Cofactor deficiency was excluded. The effect of BH4 administration was studied by correlating different oral BH4 doses with plasma phenylalanine levels under defined protein intake. Our results indicate that oral BH4 supplementation may be used as long-term treatment for individuals with BH4-responsive PAH deficiency, either without or in combination with a less restrictive diet. Previous in vitro studies have demonstrated that BH4 inhibits PAH tetramers but activates PAH dimers. This may indicate, that BH4-responsiveness results from BH4 induced stabilization of mutant PAH dimers. In addition, interindividual differences in the cellular folding apparatus may determine the tertiary structure and the amount of mutant PAH dimers and hence may account for divergent BH4-responsiveness reported for the same PAH genotype.
    Amino Acids 06/2003; 25(1):63-68. · 3.91 Impact Factor
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    ABSTRACT: In organotypic corticostriatal and hippocampal slice cultures from rat brain, 3-hydroxyglutaric acid but not glutaric and glutaconic acids induced neurodegeneration by activation of NMDA receptors. Electrophysiological investigations (Xenopus laevis oocytes expressing glutamate receptors; rat mixed cortex culture) revealed no direct interaction of 3-hydroxyglutaric acid with glutamate receptors. We speculate that 3-hydroxyglutaric acid induces a mild energy deprivation that interferes with the voltage-dependent Mg(2+)-block of NMDA receptors.
    Journal of Inherited Metabolic Disease 07/1999; 22(4):392-403. · 4.07 Impact Factor

Publication Stats

109 Citations
15 Downloads
290 Views
17.16 Total Impact Points

Institutions

  • 2004
    • University of Hamburg
      • Department of Paediatrics
      Hamburg, Hamburg, Germany
    • University Medical Center Hamburg - Eppendorf
      • Department of Paediatrics
      Hamburg, Hamburg, Germany