Biomedical subjects
Publications and source records attributed to H Köster.
Open surgery is still used to treat massive combined paraesophageal and hiatal hernias. The operative principles include repositioning of the stomach in the abdomen, resection of the hernia sac, narrowing of the hiatus, and gastropexy. We report on a case in which a life-threatening, gastro-pericardial fistula was an early complication after open surgical treatment.
Sets of RNA ladders can be synthesized by transcription of a bacteriophage-encoded RNA polymerase using 3'-deoxynucleotides as chain terminators. These ladders can be used for sequencing of DNA. Using a nicked form of phage SP6 RNA polymerase in this study substantially enhanced yields of transcriptional sequencing ladders. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of chain-terminated RNA ladders allowed DNA sequence determination of up to 56 nt. It is also demonstrated that A-->G and C-->T variations in heterozygous and homozygous samples can be unambiguously identified by the mass spectrometric analysis. As a step towards single-tube sequencing reactions, alpha-thiotriphosphate nucleotide analogs were used to overcome problems caused by chain terminator-independent, premature termination and by the small mass difference between natural pyrimidine nucleotides.
OBJECTIVES: The practice of homeopathy rests on symptoms, which have been produced by medicinal substances in healthy volunteers, often applied at ultramolecular dilutions. It is unknown whether these symptom patterns are due to specific effects or chance fluctuation. METHODS: We tested the hypothesis that a homeopathic substance can bring about symptoms different from observation and placebo in a double-blind, placebo-controlled crossover design with baseline observation. RESULTS: 87 out of 118 healthy volunteers took both placebo and homeopathic belladonna 30CH in random sequence, after a 2-week observation period, and finished the 8-week trial. Apart from an insignificant tendency for subjects to report more symptoms with belladonna (mean number: 27.34), as compared to observation (24.26) or placebo (24.17), there was no indication that subjects reacted differently to homeopathy than to placebo or during baseline. CONCLUSION: There is no indication that belladonna 30CH produces symptoms different from placebo or from no intervention. Symptoms of a homeopathic pathogenetic trial (HPT) are most likely chance fluctuations.
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Genomic imprinting is the result of a gamete-specific modification leading to parental origin-specific gene expression in somatic cells of the offspring. Several embryonal tumors show loss of imprinting of genes clustered in human chromosome 11p15.5, an important tumor suppressor gene region, harboring several normally imprinted genes. TSSC3, a gene homologous to mouse TDAG51, implicated in Fas-mediated apoptosis, is also located in this region between hNAP2 and p57 (KIP2). TSSC3 is the first apoptosis-related gene found to be imprinted in placenta, liver and fetal tissues where it is expressed from the maternal allele in normal human development. This study investigated the imprinting status of TSSC3 in human normal, adult brain and in human neuroblastomas, medulloblastomas and glioblastomas. A polymorphism in exon 1 at position 54 was used to analyze the allelic expression of the TSSC3 gene by a primer oligo base extension (PROBE) assay using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). We found that the TSSC3 gene is not imprinted in human normal, adult brain and blood. In contrast, strong allelic bias resembling imprinting could be detected in most examined tumor specimens. The results demonstrate for the first time that the tumors under investigation are associated with a retention of imprinting of a potential growth inhibitory gene.
Silicon chips with immobilized target DNAs were used for accurate genotyping by mass spectrometry. Genomic DNAs were amplified with PCR, and the amplified products were covalently attached to chip wells via N-succinimidyl (4-iodoacetyl)aminobenzoate (SIAB) chemistry. Primer annealing, extension, and termination were performed on a 1-microl scale directly in the chip wells in parallel. Diagnostic products thus generated were detected in situ by using matrix-assisted laser desorption ionization mass spectrometry. This miniaturized method has the potential for accurate, high-throughput, low-cost identification of genetic variations.
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DNA preparations from three different groups of serum samples were examined for HBV-DNA via a nested polymerase chain reaction assay (lower detection limit: 10 viral genomes in 100 microliters serum): Group I consisted of 11 uninfected control sera, group II consisted of sera obtained from 11 HBV infected patients and group III consisted of 21 isolated anti-HBc positive samples. The 21 samples from group III were HBV-DNA negative according to a conventional non-nested PCR assay and hybridization with a 32P-labelled probe. Using nested PCR and mass spectrometry, HBV-DNA was detected in none of group I and in all of group II samples. In 11 out of 21 (52%) of the isolated anti-HBc positive sera from group III, HBV-DNA was detected. No correlation was observed between HBV-DNA positivity and anti-HBc titers. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry provided a fast, sensitive and non-radioactive assay for the detection of PCR products without the need for gel electrophoresis or hybridization with labelled probes.
Matrix-assisted laser desorption ionization time of flight mass spectrometry was used to sequence exons 5 to 8 of the human p53 gene. A single tube procedure was established for target amplification and mass spectrometric (MS) sequencing. The MS sequencing scheme is designed for high throughput and parallel sample processing, and is amenable to full automation. Reliable sequencing data were obtained using fmol sample amounts. The high resolution and accuracy of MS sequencing was demonstrated by direct sequencing of a heterozygous template.
The primer oligo base extension reaction combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, recently introduced by our group for detection of single-point mutations and small insertions/deletions, has been applied to the reliable quantification of nucleotide repeat units in microsatellites. The AluVpA DNA marker within intron 5 of the interferon-alpha receptor gene was chosen as the model system. By varying the dNTP/ddNTP mixtures used, the assay could also be directed to detect the location of second-site mutations within the repeats, resulting in identification of alleles not detectable by electrophoretic sizing methods and thus an increase of the polymorphism information content for a sampling of 28 unrelated individuals. The method results in highly informative mass signals and has the potential to increase the polymorphism information content for systems containing second-site mutations; thus it is a very attractive alternative technique in statistics-based gene mapping, cancer diagnostics, and forensic applications.
We describe an approach, which combines the process of DNA amplification and sequence determination by using a pair of primers and two DNA polymerases with different incorporation rates for dideoxynucleotides. The process of target sequence amplification is carried out by the DNA polymerase with a low dideoxynucleotide incorporation rate while its polymerase counterpart with a high incorporation rate generates a sequence ladder. The needs for separate amplification via polymerase chain reaction (PCR) or cloning into plasmids including the respective purification steps therefore can be avoided. In addition, the use of dye terminator chemistry enables the simultaneous generation of forward and reverse sequence ladders, which can be separated based on the streptavidin-biotin system when one amplification primer is biotinylated.
The effects of ammonium hydroxide treatment of complexes consisting of biotinylated nucleic acids and immobilized streptavidin were investigated. It was found that incubation of such complexes with ammonium hydroxide at room temperature leads to denaturation of double-stranded DNA molecules, liberating only the complementary nonbiotinylated strand, whereas incubation at elevated temperatures leads to an efficient dissociation of biotin-streptavidin complexes. The introduced procedure is especially suitable as a purification and conditioning format prior to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometric analysis of DNA from complex enzymatic reactions. This is demonstrated by analysis of polymerase chain reaction (PCR) and sequencing products.
Duplex probes with five base single-stranded overhangs can capture dsDNA targets from type IIS restriction nuclease digests. Ligation generates a predesigned nick site, where DNA polymerase can generate sequencing ladders by strand displacement or nick translation in the presence of trace amounts of dideoxynucleotides. This allows dsDNA targets to be captured from mixtures and directly sequenced without subcloning, purification or denaturation.
Mutations located in the RET proto-oncogene at codon 634 associated with multiple endocrine neoplasia type 2A and medullary thyroid carcinoma are detected by low-resolution and high-resolution mass spectrometry schemes not requiring labeling or electrophoretic separation of diagnostic products. The former requires measurement by matrix-assisted laser desorption ionization time-of-flight mass spectrometry of 21- to 27-mer oligonucleotides generated by a primer oligo base extension reaction. The latter is based upon direct measurement of artificial products which include the mutation site using matrix-assisted laser desorption ionization Fourier transform mass spectrometry. In this feasibility study a synthetic 25-mer representing the wildtype allele (7660.3 Da) was easily distinguished from G to A (7644.3 Da) and G to T (7635.3 Da) mutant alleles; the mutant alleles, which differed in mass by only 9.0 Da, were easily resolved when analyzed as a mixture. The results of both detection schemes were highly accurate and reliable, indicating mass spectrometry to be a high-quality alternative for future DNA diagnostics performed in clinical laboratories and genetic profiling studies.
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A rapid, robust and widely applicable mutation detection scheme not requiring radioactivity or gel-based detection is introduced. It is a single-tube, competitive oligonucleotide single-base extension (COSBE) reaction using a pair of primers with the 3'-terminal base complementary to either the normal or mutant allele. Upon hybridization and addition of a polymerase and the nucleotide triphosphate corresponding to the next base after the primer, only those primers properly annealed (i.e., no 3'-terminal mismatch) are extended; products are resolved by molecular weight shifts as determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (single-scan spectrum acquisition < < 1 s). For the cystic fibrosis delta F508 polymorphism, 28-mer "normal" (N) and 30-mer "mutant" (M) primers generate 29-mer (N + I) or 31-mer (M + 1) products for homozygotes and both for heterozygotes. Since primer and product molecular weights are relatively low (< 10 kDa) and the mass difference between these are at least that of a single approximately 300-Da nucleotide unit, a low-resolution mass spectrometer is suitable for such measurements.
A new method for the reliable identification of localized variations in DNA by detection of associated diagnostic products with matrix-assisted laser desorption ionization time-of-flight mass spectrometry is described. The diagnostic products are generated by the primer oligo base extension (PROBE) reaction, which requires a single detection primer complementary to a region down-stream of a target strand's variable site. On addition of a polymerase, three dNTPs, and the fourth nucleotide in dideoxy form, the primer is extended through the mutation region until the first ddNTP is incorporated; the mass of the extension products determines the composition of the variable site. Tests for five cystic fibrosis mutations, including two exon 11 sites measured in a biplex reaction, and for differentiating between three common alleles of the poly(T) tract at the intron 8 splice acceptor site of the CFTR gene are presented. All experimental steps required for PROBE are amenable to the high degree of automation desirable for a high-through-put diagnostic setting. Furthermore, it requires no fluorescent, chemiluminescent, or radioactive labeling; the mass signals measured offer a far more analytically definitive signal, leading in all cases to high-quality unambiguous and easily interpreted results.