Biomedical subjects
Publications and source records attributed to K Bartholomé.
We present methods for detecting phase synchronization of two unidirectionally coupled, self-sustained noisy oscillators from a signal of the driven oscillator alone. One method detects soft phase locking; another hard phase locking. Both are applied to the problem of detecting phase synchronization in von Kármán vortex flow meters.
A method for measuring the phase of oscillations from noisy time series is proposed. To obtain the phase, the signal is filtered in such a way that the filter output has minimal relative variation in the amplitude over all filters with complex-valued impulse response. The argument of the filter output yields the phase. Implementation of the algorithm and interpretation of the result are discussed. We argue that the phase obtained by the proposed method has a low susceptibility to measurement noise and a low rate of artificial phase slips. The method is applied for the detection and classification of mode locking in vortex flow meters. A measure for the strength of mode locking is proposed.
Four different mutations in the GTP cyclohydrolase I gene were found (P199L, M211V, IVS5+1G>A, G203R) in 6 out of 33 families with dopa-responsive dystonia. A splice mutation (IVS5+1G>A) located at the border of exon 5 to intron 5 was found in one of these families. Three members of the family carry the IVS5+1G>A mutation on one allele, inherited from the father to the daughter and son. Examination of the mRNA showed an exon 5 skipping that results in a reduction of enzyme activity in cultured fibroblasts to 4-17% compared to controls. The father and daughter never had clinical symptoms of dopa-responsive dystonia. The son was symptomatic at the age of 3 years and was treated successfully with L-dopa/carbidopa. After 20 years this therapy was terminated and for the next 6 years he was free of symptoms. With increased motoric activity, symptoms reappeared and the therapy was reintroduced.
Explore the source record for details and available documents.
Tyrosine hydroxylase (TH) catalyzes the conversion of L-tyrosine to L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of dopamine. This report describes a missense point mutation in the human TH (hTH) gene in a girl presenting parkinsonian symptoms in early infancy and a very low level of the dopamine metabolite homovanillic acid in the CSF. DNA sequencing revealed a T614-to-C transition in exon 5 (L205P). Both parents and the patient's brother are heterozygous for the mutation. Site-directed mutagenesis and expression in different systems revealed that the recombinant mutant enzyme had a low homospecific activity, i.e. approximately 1.5% of wt-hTH in E. coli and approximately 16% in a cell-free in vitro transcription-translation system. When transiently expressed in human embryonic kidney (A293) cells a very low specific activity (approximately 0.3% of wt-hTH) and immunoreactive hTH (< 2%) was obtained. The expression studies are compatible with the severe clinical phenotype of the L205P homozygous patient carrying this recessively inherited mutation. Treatment with L-DOPA resulted in normalisation of the CSF homovanillic acid concentration and a sustained improvement in parkinsonian symptoms.
A polymorphism of human tyrosine hydroxylase changing the amino acid 81Val to 81Met is located in exon 2 of the human tyrosine hydroxylase gene.
We have examined the molecular basis of Segawa's syndrome in six families with seven affected children. In one family two siblings with this disease carried a point mutation in exon 11 of the tyrosine hydroxylase gene, resulting in an amino acid exchange of Gln381 to Lys381. These results suggest that a change in tyrosine hydroxylase causes this form of Segawa's syndrome.
Tyrosine hydroxylase (TH) catalyzes the conversion of L-tyrosine to L-dihydroxyphenylalanine (L-DOPA), the rate-limiting step in the biosynthesis of dopamine. Recently, we described a point mutation in hTH (Q381K) in a family of two siblings suffering from progressive L-DOPA-responsive dystonia (DRD), representing the first reported mutation in this gene. We here describe the cloning, expression and steady-state kinetic properties of the recombinant mutant enzyme. When expressed by a coupled in vitro transcription-translation system and in E. coli, the mutant enzyme represents a kinetic variant form, with a reduced affinity for L-tyrosine. The 'residual activity' of about 15% of the corresponding wild-type hTH (isoform hTH1), at substrate concentrations prevailing in vivo, is compatible with the clinical phenotype of the two Q381K homozygote patients carrying this recessively inherited mutation.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
We report a mutation within the phenylalanine hydroxylase (PAH) gene that causes aberrant splicing of the mRNA and that is in tight association with chromosomal haplotypes 6, 10, and 36. Because of the high frequency of these particular haplotypes in Bulgaria, Italy, and Turkey, it appears to be one of the more frequent defects in the PAH gene causing classical phenylketonuria in this part of Europe. The mutation is a G to A transition at position 546 in intron 10 of the PAH gene, 11 bp upstream from the intron 10/exon 11 boundary. It activates a cryptic splice site and results in an in-frame insertion of 9 nucleotides between exon 10 and exon 11 of the processed mRNA. Normal amounts of liver PAH protein are present in homozygous patients, but no catalytic activity can be detected. This loss of enzyme activity is probably caused by conformational changes resulting from the insertion of three additional amino acids (Gly-Leu-Gln) between the normal sequences encoded by exon 10 and exon 11.
By direct sequence analysis of 94 mutant phenylalanine hydroxylase alleles using polymerase chain reaction-based techniques, we identified a C to T transition in exon 7 of the human phenylalanine hydroxylase gene that is associated with RFLP haplotypes 1 and 4. A leucine for proline substitution at position 281 can be predicted from the nucleotide sequence of the mutant codon. Expression analysis in cultured mammalian cells after site-directed mutagenesis proved that the base substitution is a disease causing gene lesion. Dot-blot hybridization analysis using allele-specific oligonucleotides revealed that 25% of all mutant haplotype 1 alleles in the German population bear this mutation. In addition, this mutation could be detected on one mutant haplotype 4 allele. The fact that this mutation is associated with only 25% of all mutant haplotype 1 alleles suggests that multiple mutations may be associated with this haplotype. The occurrence of several different mutations would be in agreement with the clinical heterogeneity observed in the group of patients whose PKU alleles belong to haplotype 1.
In two 14-year-old children with the typical clinical picture of Segawa's syndrome the metabolism of L-DOPA was examined and compared to an age matched control. The very different responses to DOPA- and benser-acid-medication underline the hypothesis, that Segawa's disease may result from at least two different pathological conditions. Since this disease mimics hereditary degenerative nervous tissue disorders, evoked potentials of both patients are demonstrated, showing that those pathways of the CNS, who can be examined by these methods, are unaffected.
Cystic fibrosis is the most common autosomal recessive genetic disorder in the Caucasian population (1:2000-1:4000) (Warwick, W. J. (1978) Helv. Paediatr. Acta 33, 117-125). This defect is characterized by chronic obstructive pulmonary disease, pancreatic exocrine insufficiency and abnormally high perspiration electrolytes in most patients (Talamo et al. (1985) In: The metabolic basis of inherited diseases, pp. 1887-1917). The elevated electrolyte level provides the most reliable diagnostic test for cystic fibrosis homozygotes. Although prospects for cystic fibrosis patients have improved, genetically homozygous cystic fibrosis is effectively a lethal disease. Because of the seriousness of the disease, many families with one affected child desire a prenatal diagnosis when a second pregnancy occurs. Despite extensive research, the biochemical basis of cystic fibrosis remains unknown. Secondary effects on microvillar enzymes allow second trimester diagnosis (17-18 weeks of gestation (Brock, D. H. J. (1983) Lancet II, 941-943). First trimester prenatal diagnosis for cystic fibrosis became possible with DNA technology. Application of polymorphic marker loci to problems of prenatal diagnosis and carrier-testing is discussed.
Two hundred and thirty five subjects from 48 German cystic fibrosis (CF) families were typed for restriction fragment length polymorphisms (RFLPs) detected by the probes pmet H, pmet D, and pJ 3.11, known to be tightly linked to the CF gene. Gene and haplotype frequencies suggest a linkage disequilibrium with the CF locus. The analysis of the predictive value of this typing in individual CF families indicates that the combined use of these probes provides a powerful diagnostic system both for carrier detection and prenatal diagnosis. In 33 out of 48 families carriers and non-carriers could be identified, and in 26 of these 33 families prenatal diagnosis could discriminate between affected and unaffected offspring.
Cat allergen 1, the major allergen from cats, has been demonstrated to be present in surface washing and in saliva. With the use of an immunohistologic technique with monospecific anti-CA 1, we demonstrated two different sources of the protein, mucous salivary glands and hair roots, where it originates from sebaceous glands.
Three children with hyperphenylalaninaemia and hyperphenylalaninaemic mothers are presented. At least one of the affected children was a compound heterozygote for hyperphenylalaninaemia and phenylketonuria. The families were examined by an L-phenylalanine loading test, by direct determination of phenylalanine hydroxylase and/or a loading test with hepta-deuterophenylalanine. We conclude that most of the patients with moderately elevated serum phenylalanine should have the genotype hyperphenylalaninaemia/phenylketonuria, i.e. they are compound heterozygotes.
A 9 10/12 year year old girl developed severe hyperosmolar diabetic coma, and 5 days later acute renal failure. Extremely elevated levels of myoglobin were measured in serum and urine with a radioimmunoassay kit leading to the diagnosis of atraumatic rhabdomyolysis. Intermittent hemodialysis was performed for 2 weeks. Subsequently myoglobin and creatinine values in serum returned to normal. Psychological disturbances and paresis of the lower extremities subsided 4 resp. 12 weeks after the onset of acute illness.