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Biomedical subjects

W Lehnert

Publications and source records attributed to W Lehnert.

At least 19 recordsLinked to original sources
PubMed2004

Effects of secretin on extracellular amino acid concentrations in rat hippocampus.

In 1998, Horvath et al. (1998) observed a marked improvement in speech, eye contact, and attention in autistic children five weeks after treatment with secretin, which ocurred in the course of an endoscopic investigation. Since autism is hypothesized to be a hypoglutamatergic disorder we investigated the in vivo effects of secretin on extracellular amino acids in the rat brain. Studies were carried out on freely moving rats with microdialysis probes in the hippocampus. Amino acids were examined using tandem mass spectroscopy and HPLC/fluorometric detection. Following secretin injection (8.7 microg/kg i.p.), considerable increases in microdialysate glutamate and gamma-aminobutyric acid (GABA) levels were observed; other amino acids were not affected. The observed increased microdialysate concentrations of glutamate and GABA following secretin application may explain the results of the Horvath study.

Amino Acids↗
PubMed2004

Guanidinoacetate methyltransferase deficiency: differences of creatine uptake in human brain and muscle.

Deficiency of guanidinoacetate methyltransferase (GAMT), the first described creatine biosynthesis defect, leads to depletion of creatine and phosphocreatine, and accumulation of guanidinoacetate in brain. This results in epilepsy, mental retardation, and extrapyramidal movement disorders. Investigation of skeletal muscle by proton and phosphorus magnetic resonance spectroscopy before therapy demonstrated the presence of considerable amounts of creatine and phosphocreatine, and accumulation of phosphorylated guanidinoacetate in a 7-year-old boy diagnosed with GAMT deficiency, suggesting separate mechanisms for creatine uptake and synthesis in brain and skeletal muscle. The combination of creatine supplementation and a guanidinoacetate-lowering therapeutic approach resulted in improvement of clinical symptoms and metabolite concentrations in brain, muscle, and body fluids.

Arginine↗
PubMed2003

Expression and location of taurine transporters and channels in the epididymis of infertile c-ros receptor tyrosine kinase-deficient and fertile heterozygous mice.

Defective sperm volume regulation causes infertility in c-ros knockout (KO) mice lacking the initial segment of the epididymis (IS). As taurine is in high concentration in the male tract and acts as an organic osmolyte in somatic cells, the taurine transporter (TauT), taurine content and taurine channel phospholemman (PLM) were examined in the epididymides of these and fertile heterozygous (+/-) mice. TauT and PLM genes were demonstrated by RT-PCR in the caput of +/- and c-ros knockout males. Northern blots revealed one transcript of TauT (8 kb) in all regions with different expression between segments (cauda > corpus > IS > caput) and no differences in expression between genotypes. Western blotting revealed three translation products of TauT in all epididymal regions (107, 69, 49 kDa) with higher expression of the 69 kDa and 49 isoforms in the -/- than +/- caput. Immunohistochemical staining revealed staining of principal cells and stronger staining of apical and clear cells in all epididymal regions. The expression of the PLM transcript (0.75 kb: cauda = corpus > caput > IS) was upregulated in the proximal caput and cauda of KO mice. Tissue taurine was higher in the cauda >corpus>IS congruent with caput in fertile males and significantly higher in the proximal caput of the KO male. By contrast, taurine concentrations in cauda epididymidal fluid and content per 10(6) sperm did not differ between genotypes. TauT and PLM may be involved in taurine regulation in the normal epididymis and the proximal accumulation of taurine in the infertile males.

Animals↗
PubMed2003

Recurrent vomiting and ethylmalonic aciduria associated with rare mutations of the short-chain acyl-CoA dehydrogenase gene.

We report identification of short-chain acyl-CoA dehydrogenase (SCAD) deficiency in a 12-year-old boy who suffered from recurrent attacks of vomiting once or twice a year from infancy. Growth and development were normal and there were no muscular symptoms. Metabolic screening was performed during a hospitalization at 8 years of age and revealed an increased excretion of ethylmalonic acid (EMA; 45-80 mmol/mol creatinine, normal 0.2-6.6), suggesting a degradation defect of short-chain fatty acids. An increased n-butyrylcarnitine was found in freshly collected serum (0.9 micromol/L; normal <0.4) but not in dry blood spots. Neither of the frequent SCAD gene variants 625G>A and 511C>T was present, but direct sequencing of the promoter and coding regions of the SCAD gene revealed that the patient had mutations on both alleles: 417G>C (Trpl15Cys) and 1095G>T (Gln341His). Neither mutation has been described before in compound heterozygosity or homozygosity. Enzymatic investigations subsequently confirmed a defect of SCAD in both fibroblasts and muscle extracts. Furthermore, expression studies of both mutations demonstrated impaired enzyme function or structure. To our knowledge, this case is the first description of a patient with proven SCAD deficiency presenting with recurrent emesis but without other symptoms, and emphasizes the wide clinical phenotype of this disorder.

Alleles↗
PubMed2001

"Adult" form of muscular carnitine palmitoyltransferase II deficiency: manifestation in a 2-year-old child.

UNLABELLED: We describe a 6-year-old girl admitted with acute muscular weakness and pain which made her unable to walk. Her parents reported a 4-year history of similar episodes which occurred once or twice a year and always resolved spontaneously. Laboratory investigations showed elevated serum creatine kinase which peaked at day 2 of the attack with 18,600 U/l. Carnitine palmitoyltransferase-II deficiency was suspected based on the determination of serum acylcarnitines by tandem mass spectrometry which showed a characteristic elevation of long-chain C16 and C18:1 acylcarnitines. The diagnosis was confirmed by impaired in-vitro palmitate oxidation in blood and the detection of a homozygous substitution S113L in the carnitine palmitoyltransferase-II gene. CONCLUSION: Carnitine palmitoyltransferase-II deficiency should be included in the differential diagnosis of isolated muscular weakness even when manifesting in early childhood.

Age of Onset↗
PubMed2001

Metabolic cause of Reye-like syndrome.

The most frequent metabolic cause of Reye-like syndrome is medium chain acyl-CoA dehydrogenase (MCAD) deficiency. The authors describe a gypsy boy who was repeatedly hospitalised due to symptoms of Reye-like syndrome (serious hypoglycemia, loss of consciousness, seizures, increased values of aminotransferases, decreased values of free carnitine). The diagnosis of MCAD deficiency was established by analysis of plasmatic acylcarnitines by use of tandem mass spectrometry. DNA analysis proved the most common K329E (G985) mutation in gene for MCAD deficiency in homozygous state. The authors have emphasised the advantage of tandem mass spectrometry in the diagnosis of disorders of fatty acid beta-oxidation. This highly sophisticated method can detect most of these disorders from dry blood spots disregarding the symptoms and type of mutation.

Acyl-CoA Dehydrogenase↗
PubMed2000

Enantioselective analysis of ketone bodies in patients with beta-ketothiolase deficiency, medium-chain acyl coenzyme A dehydrogenase deficiency and ketonemic vomiting.

Enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) is a valuable tool for the differentiation of enantiomers from complex matrices when present in trace amounts. The separation of chiral compounds provides further information on the diagnosis of diseases, and on normal and abnormal biochemical pathways. The formation of the normal urinary metabolite 3-hydroxy-2-methylbutanoic acid (HMBA), excreted in abnormally high amounts in beta-ketothiolase deficiency, is not absolutely clarified. Metabolic pathways involving this metabolite are isoleucine catabolism, as well as presumably beta-oxidation of fatty acids and ketogenesis. The latter two pathways are distinguishable in their enantioselectivity. Enantioselective analysis gives further information on interfering metabolic pathways and the selectivity of the enzyme(s) forming HMBA. Different ratios of the stereoisomers of HMBA in control urine samples and patients with beta-ketothiolase deficiency were detected. Analogous to HMBA urinary 3-hydroxybutanoic acid (HBA) was investigated in several diseases. The formation of HBA and HMBA is expected to result from the same or similar metabolic pathways. Differences in the enantiomeric ratio of HMBA may originate from the enantioselectivity of different enzyme systems.

Acetyl-CoA C-Acyltransferase↗
PubMed1999

Long-term follow up of a new case of hawkinsinuria.

UNLABELLED: Hawkinsinuria is a rarely diagnosed autosomal dominantly transmitted inborn error of tyrosine metabolism with impaired conversion of 4-hydroxyphenylpyruvate to homogentisate. As a consequence of the defective 4-hydroxyphenylpyruvate dioxigenase activity, large amounts of the unusual, ninhydrin-positive amino acid hawkinsin and later on in life 4-hydroxycyclohexylacetic acid are formed and excreted. Clinically the disease is characterised mainly by chronic metabolic acidosis and severe growth retardation as a result of protein overload. As the ability to form 4-hydroxycyclohexylacetic acid and thereby to cope with the still not very well defined reactive and toxic intermediates increases, clinical symptoms vanish. We report here a new patient with hawkinsinuria having experienced a series of admissions because of unclear hepatopathy, growth retardation, and renal tubular acidosis. CONCLUSION: Prolonged tyrosyluria in the newborn and young baby should cause the clinical chemist not only to exclude tyrosinaemia, galactosaemia, and fructose intolerance but also to look carefully for hawkinsin in the aminoacid chromatogram.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed1999

Metabolic stroke in isolated 3-methylcrotonyl-CoA carboxylase deficiency.

A mildly retarded infant with failure to thrive developed hypoglycaemia, focal seizures, respiratory failure and hemiparesis during a febrile episode at the age of 16 months. A brain scan was initially normal and showed hemilateral focal edema and gliosis at later stages. 3-Methylcrotonyl-CoA carboxylase deficiency was suggested by elevated urinary excretion of 3-hydroxyisovaleric acid and 3-methylcrotonylglycine, and confirmed by enzyme assays. The patient was treated with protein restriction and carnitine and remained stable during the following 5 years. Hemiparesis and some developmental delay persisted. In acute focal brain disease, metabolic disorders must be considered. 3-Methylcrotonyl-CoA carboxylase deficiency adds to the list of possible causes of "metabolic stroke".

Amino Acid Metabolism, Inborn Errors↗
PubMed1999

Protection of baculovirus-vectors against complement-mediated inactivation by recombinant soluble complement receptor type 1.

Baculovirus-based vectors are efficient means for gene transfer into hepatocytes in vitro. However, gene transfer in vivo is hampered by inactivation of baculovirus by the complement system. In this study, we demonstrate protection of baculovirus vectors against complement-mediated inactivation through recombinant soluble complement receptor type 1 (sCR1). Blocking of only the alternative complement pathway by a mutant of sCR1 did not result in baculovirus survival in human serum. The data suggest the use of sCR1 as a potent drug to facilitate baculovirus-mediated gene transfer into hepatocytes in vivo.

Animals↗
PubMed1998

Late-onset holocarboxylase synthetase-deficiency: pre- and post-natal diagnosis and evaluation of effectiveness of antenatal biotin therapy.

UNLABELLED: The clinical and biochemical findings in a family with late-onset holocarboxylase synthetase (HCS) deficiency are described. The index patient had two life-threatening episodes of metabolic decompensation at the age of 13 and 18 months with ketotic hypoglycaemia, vomiting and progressive loss of consciousness. The child recovered without biotin therapy. Organic aciduria characteristic of multiple carboxylase deficiency (MCD) was found, however, the key metabolites were only slightly elevated in some samples. Biotinidase deficiency was considered but excluded by the finding of normal plasma biotinidase activity. The correct diagnosis was made only at the age of 19 months when severe MCD was found in lymphocytes in the presence of normal plasma biotin concentration. HCS deficiency was confirmed by fibroblast studies. Biotin therapy (20 or 40 mg/day) prevented further episodes and normalized biochemical parameters with so far normal development. During two subsequent pregnancies, 10 mg biotin/day was administered to the mother from the 20th week of gestation. At delivery plasma biotin in cord blood samples was 3 4 times higher than in maternal plasma. The 2nd child was unaffected. In the 3rd pregnancy prenatal diagnosis was performed at 16 weeks of gestation. The concentration of methylcitrate in amniotic fluid was within the normal range and that of 3-hydroxyisovalerate only slightly elevated. However, enzyme assays in cultured amniotic fluid cells were consistent with an affected fetus. At birth, carboxylase activities in lymphocytes of this newborn were only moderately decreased to 37% of mean normal. HCS deficiency was confirmed postnatally in fibroblasts. Development remains normal on biotin therapy (20 mg/day). CONCLUSION: Prenatal diagnosis in families with milder forms of HCS deficiency has to be performed by enzyme assays in cultured amniotic cells since organic acid analysis of amniotic fluid may be inconclusive in affected fetuses. Biotin administered prenatally is effectively taken up by the fetus and prevents functional deficiency of the carboxylases in an affected newborn.

Biotin↗
PubMed1998

Identification of four new mutations in the short-chain acyl-CoA dehydrogenase (SCAD) gene in two patients: one of the variant alleles, 511C-->T, is present at an unexpectedly high frequency in the general population, as was the case for 625G-->A, together conferring susceptibility to ethylmalonic aciduria.

We have shown previously that a variant allele of the short-chain acyl-CoA dehydrogenase ( SCAD ) gene, 625G-->A, is present in homozygous form in 7% of control individuals and in 60% of 135 patients with elevated urinary excretion of ethylmalonic acid (EMA). We have now characterized three disease-causing mutations (confirmed by lack of enzyme activity after expression in COS-7 cells) and a new susceptibility variant in the SCAD gene of two patients with SCAD deficiency, and investigated their frequency in patients with elevated EMA excretion. The first SCAD-deficient patient was a compound heterozygote for two mutations, 274G-->T and 529T-->C. These mutations were not present in 98 normal control alleles, but the 529T-->C mutation was found in one allele among 133 patients with elevated EMA excretion. The second patient carried a 1147C-->T mutation and the 625G-->A polymorphism in one allele, and a single point mutation, 511C-->T, in the other. The 1147C-->T mutation was not present in 98 normal alleles, but was detected in three alleles of 133 patients with elevated EMA excretion, consistently as a 625A-1147T allele. On the other hand, the 511C-->T mutation was present in 13 of 130 and 15 of 67 625G alleles, respectively, of normal controls and patients with elevated EMA excretion, and was never associated with the 625A variant allele. This over-representation of the haplotype 511T-625G among the common 625G alleles in patients compared with controls was significant ( P < 0.02), suggesting that the allele 511T-625G-like 511C-625A-confers susceptibility to ethylmalonic aciduria. Expression of the variant R147W SCAD protein, encoded by the 511T-625G allele, in COS-7 cells showed 45% activity at 37 degrees C in comparison with the wild-type protein, comparable levels of activity at 26 degrees C, and 13% activity when incubated at 41 degrees C. This temperature profile is different from that observed for the variant G185S SCAD protein, encoded by the 511C-625A allele, where higher than normal activity was found at 26 and 37 degrees C, and 58% activity was present at 41 degrees C. These results corroborate the notion that the 511C-625A variant allele is one of the possible underlying causes of ethylmalonic aciduria, and suggest that the 511C-->T mutation represents a second susceptibility variation in the SCAD gene. We conclude that ethylmalonic aciduria, a commonly detected biochemical phenotype, is a complex multifactorial/polygenic condition where, in addition to the emerging role of SCAD susceptibility alleles, other genetic and environmental factors are involved.

Acyl-CoA Dehydrogenase↗
PubMed1998

Cotinine excretion as a predictor of peak flow variability.

Environmental tobacco smoke (ETS) is suspected to be an important risk factor for bronchial hyperresponsiveness. In order to test the effect of ETS, we measured expiratory flow rates and urine cotinine excretion (UCE) within a narrow time window in two consecutive years. Maternal smoking habits and medical history were ascertained by standardized questionnaires. The percentage ratio of the amplitude over the mean (AVAM) of the diurnal peak flow rates of children (complete values from at least five consecutive days) was calculated as an indicator of bronchial responsiveness. The association of UCE and log10AVAM was analyzed by multiple linear regression. Complete data were available for a sample of 417 children. The median of UCE in children of parents who smoked (3.2 ng/mg and 2.9 ng/mg creatinine, Surveys 1 and 2, respectively) was higher than the median in children of nonsmoking parents (0 ng/mg in both surveys). With increasing UCE the log10AVAM rose in the first and second surveys, as well as in the longitudinal analysis (p = 0.003). This association, however, showed up only in boys (p = 0.0001) and not in girls (p = 0.31). Our data suggest that there is a need both for further analysis of the gender difference and for more support of strategies against passive smoking as far as children are concerned, since airway hyperresponsiveness is a risk factor for chronic airway impairment.

Asthma↗
PubMed1997

The internal dose of passive smoking at home depends on the size of the dwelling.

As part of a longitudinal study two urine samples (survey 1 in 1991 and survey 2 in 1992) were collected from 602 elementary school children to investigate the relationship between urinary cotinine excretion (UCE) and the daily consumption of cigarettes at home (exposure). Size of the dwelling, educational level, and maternal smoking were taken into consideration as additional predictors. The history regarding parental smoking habits and confounding variables was ascertained by standardized questionnaires completed by the parents. Cotinine was measured using gas chromatography selected ion monitoring. UCE was expressed as cotinine/creatinine (ng/mg). In children with detectable UCE in survey 1 (35%) and in survey 2 (44%) the excretion ranged between 1.5 and 24.7 ng/mg (5-95%) and between 1.2 and 25.2 ng/mg, respectively. UCE measurements in both surveys were highly correlated (r = 0.65, P = 0.0001), and 59.6% of the UCE in survey 2 can be explained in linear regression by the UCE in survey 1. Using multiple linear regression, the categorized number of cigarettes reported to be consumed at home (20 cigarettes and more: 1991, P = 0.0001; 1992, P = 0.0003) and low educational level of the parents (P = 0.011 in 1991, P = 0.04 in 1992) were positively associated with UCE, whereas the size of the dwelling turned out to be negatively associated with UCE (P = 0.12 in 1991, P = 0.001 in 1992). In small dwellings (< or = 80 m2) the effect of exposure on UCE was much more pronounced. In conclusion, a single UCE measurement provides information which is widely stable within a yearly interval and is related to passive smoke history as well as to socio-economic status and the size of the dwelling. The latter variable should be considered as an effect modifier of exposure on internal dose and should be taken into account in future studies on passive smoke exposure.

Analysis of Variance↗
PubMed1997

Stridor as the major presenting symptom in riboflavin-responsive multiple acyl-CoA dehydrogenation deficiency.

UNLABELLED: Inspiratory stridor of unknown origin was the leading clinical symptom in an 11-month-old boy. The stridor increased over a period of 4 weeks, and assisted ventilation became necessary. Selective urinary screening by gas chromatography/mass spectrometry analysis revealed excretion of ethylmalonic and 3-OH-isovaleric acid and of N-isobutyryl-, N-2-methylbutyryl-, N-isovaleryl-, N-hexanoyl- and N-suberylglycine. Neither hypoglycaemia nor metabolic acidosis were noticed. Treatment with 200 mg of riboflavin per day led to a dramatic clinical improvement with restoration of normal respiration and an increase in muscular tone within 2 months. During this period, metabolite excretion in urine completely normalized. Riboflavin-sensitive multiple acyl-CoA dehydrogenation deficiency was confirmed in cultured fibroblasts. With riboflavin supplementation, the development of the child has been favourable, with normal school attendance now at an age of 9 years. CONCLUSION: As respiratory symptoms might precede other symptoms in disorders of mitochondrial oxidation, we propose determination of urinary organic acids in all cases of unexplained laryngeal stridor.

Adipates↗