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Biomedical subjects

G Wagner

Publications and source records attributed to G Wagner.

At least 307 records · Page 17Linked to original sources
PubMed1992

Application of a microbial sensor for determination of short-chain fatty acids in raw milk samples.

A microbial sensor system, based on the use of immobilized Arthrobacter nicotiana and an oxygen electrode, was applied to determine free short-chain fatty acids in raw milk samples and the result was compared with gas chromatography (GC) and a titrimetric method. The sensor response was linearly related to the concentration of short-chain fatty acids obtained by GC (n = 10, r = 0.92) and to the total concentration of free fatty acids obtained by titrimetric measurement (n = 10, r = 0.78). This result suggests that the present microbial sensor can selectively determine free short-chain fatty acids in raw milk samples and may be useful as a very fast detection method of rancidity in milk.

Animals↗
PubMed1992

A triple-resonance pulse scheme for selectively correlating amide 1HN and 15N nuclei with the 1H alpha proton of the preceding residue.

A 3D 1H-15N-13C triple resonance experiment is presented that contains exclusively cross peaks between the 1HN and 15N nuclei of one residue with the H alpha of the preceding residue. The pulse sequence, designed to minimize the time coherence, is transverse on nuclei with short T2 values. The experiment consists of coherence transfers via one-bond couplings from the HN via N, CO, C alpha to the H alpha and back to the HN for detection; it is called HN(COCA)HA. The experiment was tested on uniformly 15N- and 13C-enriched T4 lysozyme.

Amides↗
PubMed1992

A new 3D HN(CA)HA experiment for obtaining fingerprint HN-Halpha peaks in 15N- and 13C-labeled proteins.

A new 3D 1H-15N-13C triple resonance experiment is presented that provides in-phase absorptive cross peaks between amide protons and alpha-protons of the same and the sequentially preceding residue. The experiment yields similar connectivities as those described previously by Montelione and Wagner (1990a) (J. Magn. Reson., 87, 183-188) and Kay et al. (1991) (J. Magn. Reson., 91, 84-92). However, the pulse sequence was designed to minimize the time that transverse coherence of the 13Calpha nucleus is present, since this nucleus has the shortest transverse relaxation time of all the nuclei involved in these experiments. This is achieved by using a coherence transfer pathway from 1HN to 15N, 13Calpha, 1Halpha and back to the 1HN. In the sequence described, transverse 13Calpha coherence is present only for a length of ca. 1/1J(Calpha-Halpha). This reduces loss of signal due to transverse relaxation. We tested the technique on uniformly 15N- and 13C-enriched T4 lysozyme.

Carbon Isotopes↗
PubMed1992

Glutathione S-transferases in human testicular germ cell tumors: changes of expression and activity.

Glutathione S-transferases are involved in the detoxification of carcinogens and xenobiotics and are potentially associated with the development of drug-resistance. Forty-six testicular germ cell tumors and 33 adjacent normal testicular tissue specimens were analyzed at the RNA level for the expression of glutathione S-transferase alpha and pi. Glutathione S-transferase alpha was expressed in 31 of the 33 normal testicular tissues (94%) but in only three of the 46 germ cell tumors (7%). Glutathione S-transferase pi mRNA was detected in all normal and malignant testicular tissue samples. Thirteen testicular germ cell tumors and eight normal testicular tissue samples were analyzed at the protein level. The mean specific activity of total cytosolic glutathione S-transferase in tumor tissue was decreased by about 80% as compared to normal testicular tissue. Protein analysis of the glutathione S-transferase subunits of normal testicular tissue demonstrated the presence of the glutathione S-transferase classes alpha, mu and pi, with a predominance of the mu class. In testicular germ cell tumors the glutathione S-transferase subunit pattern showed a predominance of glutathione S-transferase pi representing 88% +/- 3% of total glutathione S-transferase. Since all three glutathione S-transferase isoenzyme classes contribute to the resistance to antineoplastic drugs, the altered glutathione S-transferase isoenzyme pattern and the decrease of glutathione S-transferase activity may play a role in the high inherent drug sensitivity of human testicular germ cell tumors.

Glutathione Transferase↗
PubMed1992

Partial nucleotide sequence of phytochrome from the zygnematophycean green alga Mougeotia.

Following polymerase chain reaction, a fragment of about 800 bp was amplified from genomic Mougeotia DNA using oligonucleotides directed to conserved regions of known phytochrome genes. The nucleotide sequence points to a different exon/intron structure in the neighborhood of the chromophore attachment site of this Mougeotia phytochrome gene, as compared to other phytochromes. Alignment of the derived amino acid sequence to phytochromes of higher and lower plants shows highest homology (> 60%) to type II (green type) phytochrome, while Northern blot analysis of total Mougeotia RNA indicates down-regulation of the phytochrome transcription in light. Signal pattern of hybridized genomic DNA after digestion reveals the presence of probably only one phytochrome gene in Mougeotia.

Amino Acid Sequence↗
PubMed1992

Non-immunologic methods of diagnosis of babesiosis.

The diagnosis of tick-borne diseases such as babesiosis still depends on observing the parasite in the infected erythrocyte. Microscopic observation is tedious and often problematic in both early and carrier infections. Better diagnostic methods are needed to prevent clinical disease, especially when susceptible cattle are being moved into disease enzootic areas. This study evaluates two techniques for early diagnosis of Babesia bovis infections in cattle, DNA probes specific for the organism and fluorescent probes specific for nucleic acid. The radioisotopically labeled DNA probes are used in slot blot hybridizations with lysed blood samples, not purified DNA. Thusfar, the probe is specific for B. bovis and can detect as few as 1000 B. bovis parasites in 10 microliters of blood. The specificity of the fluorescent probe depends on the characteristic morphology of the babesia in whole blood samples, as determined microscopically. The fluorescent probe detects as few as 10,000 B. bovis parasites in 10 microliters os blood. The application of each method for laboratory and field use is discussed.

Animals↗
PubMed1992

Selected issues from an overview on nicorandil: tolerance, duration of action, and long-term efficacy.

Nicorandil exerts its pharmacodynamic effects through two different modes of action: increase of cyclic GMP and activation of K+ channels of smooth muscle cells. The latter mechanism could explain the lack of development of tolerance that had been demonstrated clearly in various animal experiments. Therefore, it was attempted to elucidate this mechanism in humans. In 16 healthy subjects, the acute hemodynamic effects of a single oral dose of 40 mg nicorandil were compared with those of a single sublingual dose of 0.8 mg nitroglycerin. Thereafter, the subjects were treated with 30 mg isosorbide-5-mononitrate (IS-5-MN) slow release t.i.d. for 7 days to induce nitrate tolerance. Two hours after the last dose of IS-5-MN, hemodynamic measurements were repeated before and after administration of nicorandil and nitroglycerin, respectively. Recordings obtained from impedance cardiography and finger plethysmography as well as measurements of systolic time intervals provided evidence that nicorandil in the state of IS-5-MN tolerance continued to exert hemodynamic effects similar to those exerted after the first dose. The hemodynamic actions of nitroglycerin were no longer observed after chronic treatment with IS-5-MN. The duration of action of nicorandil was investigated in 22 patients with coronary artery disease (CAD). After a 2-week run-in period on placebo, patients had to perform a symptom-limited bicycle exercise tolerance test (ETT) on two separate days in which the reproducible anginal threshold had to be proven. After qualification, patients were allocated randomly to receive double-blind 10 or 20 mg nicorandil b.i.d. for 4 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

[Reactions of 4-oxo-4H-pyrido(3',2':4,5)thieno(3,2-d)-1,3-oxazines with amines].

The reaction of the title compounds with amines gave in dependence of the reaction conditions and the structure of the title compounds and the amine 3-acylamino-thieno[2,3-b]pyridine-2-carbonamides (B), 4-oxo-4 H-pyrido[3',2':4,5]thieno[3,2-d]pyrimidines (D),N-(2-carboxy-thieno[2,3-b]pyridine-3-yl)amidines (C) and N-(thieno[2,3-b]pyridin-3-yl)amidines (E). Substances of structure C and E seem to be of biological interest, especially for their antianaphylactic reactions.

Amines↗
PubMed1992

[Synthesis of N-(2-carboxy-thieno(2,3-b)pyridin-3-yl)-amidines by the reaction with 4-oxo-4H-pyrido(3',2':4,5)-thieno(3,2-d)-1,3-oxazines with secondary cycloaliphatic amines].

4-Oxo-4H-pyrido[3',2':4,5]thieno[3,2-d]1,3-oxazines react with secondary cycloaliphatic amines to give besides the expected bisamides the amine salts of N-(2-carboxy-thieno[2,3-b]pyridine-3-yl)amidines. These compounds showed inhibitory activity against different lipoxygenases, but a small chemical stability.

Amidines↗
PubMed1991

Solution structure of Fe(II) cytochrome c551 from Pseudomonas aeruginosa as determined by two-dimensional 1H NMR.

The solution structure of Fe(II) cytochrome c551 from Pseudomonas aeruginosa based on 2D 1H NMR data is reported. Two sets of structure calculations were completed with a combination of simulated annealing and distance geometry calculations: one set of 20 structures included the heme-peptide covalent linkages, and one set of 10 structures excluded them. The main-chain atoms were well constrained within the two structural ensembles (1.30 and 1.35 A average RMSD, respectively) except for two regions spanning residues 30-40 and 60-70. The results were essentially the same when global fold comparisons were made between the ensembles with an average RMSD of 1.33 A. In total, 556 constraints were used, including 479 NOEs, 53 volume constraints, and 24 other distances. This report represents the first solution structure determination of a heme protein by 2D 1H NMR and should provide a basis for the application of these techniques to other proteins containing large prosthetic groups or cofactors.

Bacterial Proteins↗
PubMed1991

1H and 15N resonance assignments of oxidized flavodoxin from Anacystis nidulans with 3D NMR.

Proton and nitrogen-15 sequence-specific nuclear magnetic resonance assignments have been determined for recombinant oxidized flavodoxin from Anacystis nidulans (169 residues, Mr 19,048). Assignments were obtained by using 15N-1H heteronuclear three-dimensional (3D) NMR spectroscopy on a uniformly nitrogen-15 enriched sample of the protein, pH 6.6, at 30 degrees C. For 165 residues, the backbone and a large fraction of the side-chain proton resonances have been assigned. Medium- and long-range NOE's have been used to characterize the secondary structure. In solution, flavodoxin consists of a five-stranded parallel beta sheet involving residues 3-9, 31-37, 49-56, 81-89, 114-117, and 141-144. Medium-range NOE's indicate the presence of several helices. Several 15N and 1H resonances of the flavin mononucleotide (FMN) prosthetic group have been assigned. The FMN-binding site has been investigated by using polypeptide-FMN NOE's.

Amino Acid Sequence↗
PubMed1991

Solution structure of kistrin, a potent platelet aggregation inhibitor and GP IIb-IIIa antagonist.

The structure of kistrin, which is a member of a homologous family of glycoprotein IIb-IIIa (GP IIb-IIIa) antagonists and potent protein inhibitors of platelet aggregation, has been determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The 68-residue protein consists of a series of tightly packed loops held together by six disulfide bonds and has almost no regular secondary structure. Kistrin has an Arg-Gly-Asp (RGD) adhesion site recognition sequence important for binding to GP IIb-IIIa that is located at the apex of a long loop across the surface of the protein.

Amino Acid Sequence↗
PubMed1991

Methotrexate binds in a non-productive orientation to human dihydrofolate reductase in solution, based on NMR spectroscopy.

Dihydrofolate reductase (DHFR) is an intracellular target enzyme for folate antagonist drugs, including methotrexate. In order to compare the binding of methotrexate to human DHFR in solution with that observed in the crystalline state, NMR spectroscopy has been used to determine the conformation of the drug bound to human DHFR in solution. In agreement with what has been observed in the crystalline state, NOE's identified protein and methotrexate protons indicate that methotrexate binds in a non-productive orientation. In contrast to what has been reported for E. coli DHFR in solution, only one bound conformation of methotrexate is observed.

Binding Sites↗