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Biomedical subjects

G F Hoffmann

Publications and source records attributed to G F Hoffmann.

At least 73 records · Page 4Linked to original sources
PubMed2001

Contribution of reactive oxygen species to 3-hydroxyglutarate neurotoxicity in primary neuronal cultures from chick embryo telencephalons.

Glutaryl-CoA dehydrogenase deficiency is an autosomal recessively inherited neurometabolic disorder with a distinct neuropathology characterized by acute encephalopathic crises during a vulnerable period of brain development. 3-Hydroxyglutarate (3-OH-GA), which accumulates in affected patients, has been identified as an endogenous neurotoxin mediating excitotoxicity via N-methyl-D-aspartate receptors. As increased generation of reactive oxygen species (ROS) and nitric oxide (NO) plays an important role in excitotoxic neuronal damage, we investigated whether ROS and NO contribute to 3-OH-GA neurotoxicity. 3-OH-GA increased mitochondrial ROS generation in primary neuronal cultures from chick embryo telencephalons, which could be prevented by MK-801, confirming the central role of N-methyl-D-aspartate receptor stimulation in 3-OH-GA toxicity. ROS increase was reduced by alpha-tocopherol and--less effectively-by melatonin. alpha-Tocopherol revealed a wider time frame for neuroprotection than melatonin. Creatine also reduced neuronal damage and ROS formation but only if it was administered >or=6 h before 3-OH-GA. NO production revealed only a slight increase after 3-OH-GA incubation. NO synthase inhibitor N(omega)-nitro-L-arginine prevented NO increase but did not protect neurons against 3-OH-GA. The NO donor S-nitroso-N-acetylpenicillamine revealed no effect on 3-OH-GA toxicity at low concentrations (0.5-5 microM), whereas it potentiated neuronal damage at high concentrations (50-500 microM), suggesting that weak endogenous NO production elicited by 3-OH-GA did not affect neuronal viability. We conclude from our results that ROS generation contributes to 3-OH-GA neurotoxicity in vitro and that radical scavenging and stabilization of brain energy metabolism by creatine are hopeful new strategies in glutaryl-CoA dehydrogenase deficiency.

Animals↗
PubMed2001

Spectrophotometric microassay for delta-aminolevulinate dehydratase in dried-blood spots as confirmation for hereditary tyrosinemia type I.

BACKGROUND: Hereditary tyrosinemia type I (HT) fulfills the criteria for inclusion in neonatal screening programs, but measurement of tyrosine lacks clinical specificity and quantitative assay of succinylacetone is laborious. We developed a semiquantitative assay based on inhibition of delta-aminolevulinate dehydratase (ALA-D) by succinylacetone. METHODS: Preincubation of 3-mm discs from dried-blood spots and reaction of the enzyme with delta-aminolevulinic acid as substrate were performed in microtiter plates. After separation of the supernatant and 10 min of color reaction with modified Ehrlich reagent, the formation of porphobilinogen was measured at 550 nm in a plate reader. RESULTS: The detection limit for succinylacetone was 0.3 micromol/L; imprecision (CV) was <5.5% within-run and 10-16% between-run. Storage of blood spots at ambient temperature for several days led to a significant decrease of ALA-D activity. Enzyme activity was lost in filter cards at 45 degrees C, but remained stable at 2-37 degrees C. Enzyme activity was decreased in EDTA blood. The absorbance at 550 nm was 0.221 (+/- 0.073) in healthy neonates and 0.043-0.100 in 11 patients with HT. All neonates with increased tyrosine (above the 99.5th centile) in neonatal screening (97 of 47 000) had normal results by the new assay. CONCLUSIONS: The spectrophotometric microassay for ALA-D is a simple and sensitive test for HT. This represents a basis for further examination of its general reliability as a confirmatory test if tyrosine is found to be increased.

Blood Specimen Collection↗
PubMed2001

Inborn errors of metabolism at the turn of the millennium.

Great progress has been made in the field of hereditary metabolic diseases since the beginning of the past century, when metabolic disorders were not really understood and could only be clinically described. Due to the development of basic sciences and advances in technology, we gained insight in the biochemical and molecular basis of hereditary metabolic diseases. It opened possibilities for their treatment, and also led to the discovery of more metabolic diseases, so today, there are more than 500 inborn errors of metabolism known. Although each of these diseases is quite rare, as a group, however, they affect about 1-2% of newborns and therefore pose a significant health problem. The realization about 50 years ago that some hereditary diseases are curable if timely diagnosed led to the introduction of newborn screening in most countries. Modern technologies in this field allow early diagnosis of more than 30 inborn errors of metabolism. Nevertheless, to diagnose most patients correctly, both selective screening involving teamwork and proper use of current technology are required. In addition to considerable development of diagnostic possibilities, the past decade was marked by advances in the therapy of inborn errors of metabolism. A number of clinical trials are currently underway, promising new and more effective approaches in the treatment of these patients. Thus, the field of inborn errors of metabolism at the beginning of the new millennium continues to be a scientific challenge to modern medicine.

Human Genome Project↗
PubMed2000

Analysis of leukotrienes in cerebrospinal fluid of a reference population and patients with inborn errors of metabolism: further evidence for a pathognomonic profile in LTC(4)-synthesis deficiency.

Cysteinyl leukotrienes (LTC(4), LTD(4), LTE(4)) are potent lipid mediators derived from arachidonate in the 5-lipoxygenase pathway. Recently, the first inborn error of leukotriene synthesis, LTC(4)-synthesis deficiency, has been identified in association with a fatal developmental syndrome. The absence of leukotrienes in cerebrospinal fluid was one of the most striking biochemical findings in this disorder. We analysed leukotrienes in cerebrospinal fluid of patients with a broad spectrum of other well-defined inborn errors of metabolism, including glutathione synthetase deficiency (n=2), Zellweger syndrome (n=3), mitochondrial disorders (n=8), fatty acid oxidation defects (n=7), organic acidurias (n=7), neurotransmitter defects (n=5) and patients with non-specific neurological symptoms, as a reference population (n=120). The concentrations of leukotrienes were not related to age. Representative percentiles were calculated as reference intervals of each leukotriene. In all patients with an inborn error of metabolism concentration of cysteinyl leukotrienes and LTB(4) did not differ from the reference group. Our results indicate that absence of cysteinyl leukotrienes (<5 pg/ml) in association with normal or increased LTB(4) (50.0-67.3 pg/ml) is pathognomonic for LTC(4)-synthesis deficiency. The unique profile of leukotrienes in cerebrospinal fluid in this new disorder is primarily related to the defect and represents a new diagnostic approach.

Adolescent↗
PubMed2000

Mutation analysis in glycogen storage disease type 1 non-a.

We report molecular and clinical findings in 13 patients with rare types of glycogen storage disease 1 (GSD1 non-a). Analysis of G6PT encoding a microsomal transporter protein has revealed mutations on both chromosomes in each case, four of which are novel. Diagnosis has been confirmed in three patients suspected of having GSD1 non-a without enzymatic studies involving liver biopsy, thus emphasising the advantage of G6PT mutation analysis for all GSD1 non-a patients.

Adolescent↗
PubMed2000

Cerebral organic acid disorders induce neuronal damage via excitotoxic organic acids in vitro.

Glutaryl-CoA dehydrogenase deficiency (GDD), which is one of the most frequent organic acid disorders, is characterized by a specific age- and regional-dependent neuropathology. We hypothesized that the distinct brain damage in GDD could be caused by the main pathologic metabolites, the organic acids glutaric (GA) and 3-hydroxyglutaric (3-OH-GA) acids, through an excitotoxic sequence. Therefore, we investigated the effects of 3-OH-GA and GA on primary neuronal cultures from chick embryonic telencephalons. Here we report that 3-OH-GA and GA decreased cell viability concentration- and time-dependently, which could be only totally prevented by preincubation with MK-801, ifenprodil and NR2B antibodies. Furthermore, cell viability decreased in parallel with the increasing expression of NR2B subunit on cultured neurons from 2nd to 6th DIV. We conclude that GA and 3-OH-GA act as excitotoxic organic acids (EOA) specifically through NR1/NR2B and that the extent of induced neurotoxicity is dependent on NR1/NR2B expression during maturation.

Age Factors↗
PubMed2000

Tyrosine hydroxylase deficiency with severe clinical course: clinical and biochemical investigations and optimization of therapy.

Tyrosine hydroxylase deficiency was diagnosed after determination of cerebrospinal fluid neurotransmitters and DNA analysis in a child with severe axial hypotonia and hypokinesia associated with dystonic and ballistic movements. L-dopa therapy was unsuccessful, whereas a combination with selegiline, a selective monoamine oxidase-beta inhibitor, with low-dose L-dopa markedly improved the severe clinical picture.

Child, Preschool↗
PubMed2000

Erythropoietic and hepatic porphyrias.

Porphyrias are divided into erythropoietic and hepatic manifestations. Erythropoietic porphyrias are characterized by cutaneous symptoms and appear in early childhood. Erythropoietic protoporphyria is complicated by cholestatic liver cirrhosis and progressive hepatic failure in 10%, of patients. Acute hepatic porphyrias (delta-aminolaevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria, hereditary coproporphyria and variegate porphyria) are characterized by variable extrahepatic gastrointestinal, neurological-psychiatric and cardiovascular manifestations requiring early diagnosis to avoid life-threatening complications. Acute hepatic porphyrias are pharmacogenetic and molecular regulatory diseases (without porphyrin accumulation) mainly induced by drugs, sex hormones, fasting or alcohol. The disease process depends on the derepression of hepatic delta-aminolaevulinic acid synthase following haem depletion. In contrast to the acute porphyrias, nonacute, chronic hepatic porphyrias such as porphyria cutanea tarda are porphyrin accumulation disorders leading to cutaneous symptoms associated with liver disease, especially caused by alcohol or viral hepatitis. Alcohol, oestrogens, haemodialysis, hepatitis C and AIDS are triggering factors. Porphyria cutanea tarda is the most common porphyria, followed by acute intermittent porphyria and erythropoietic protoporphyria. The molecular genetics of the porphyrias is very heterogenous. Nearly every family has its own mutation. The mutations identified account for the corresponding enzymatic deficiencies, which may remain clinically silent throughout life. Thus, the recognition of the overt disorder with extrahepatic manifestations depends on the demonstration of biochemical abnormalities due to these primary defects and compensatory hepatic overexpression of hepatic delta-aminolaevulinic acid synthase in the acute porphyrias. Consequently, haem precursors are synthesized in excess. The increased metabolites upstream of the enzymatic defect are excreted into urine and faeces. The diagnosis is based on their evaluation. Primary enzymatic or molecular analyses are noncontributary and may be misleading. Acute polysymptomatic exacerbations accompany a high excretory constellation of porphyrin precursors delta-aminolaevulinic acid and porphobilinogen. Homozygous or compound heterozygous variants of acute hepatic porphyrias may already manifest in childhood.

Animals↗
PubMed2000

A branch site mutation leading to aberrant splicing of the human tyrosine hydroxylase gene in a child with a severe extrapyramidal movement disorder.

We report a branch site mutation in the gene of the enzyme tyrosine hydroxylase (TH): a -24t > a substitution two bases upstream of the adenosine in the branchpoint sequence (BPS) of intron 11. As normal lariat formation is therefore prevented, alternative splicing takes place; use of the BPS of intron 12 results in skipping of exon 12, whereas the use of a cryptic branch site in intron 11 leads to partial retention of this intron in the mRNA. This leads in both cases to an aberrant protein product. In the one case, skipping of exon 12 results in the absence of 32 amino acids. In the other, retention of 36 nucleotides of intron 11 in the mRNA results in the incorporation of twelve additional amino acids. The functional consequences of this mutation for the patient, who is also heterozygous for another previously identified mutation, become apparent in a severe clinical phenotype.

Basal Ganglia Diseases↗