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Biomedical subjects

R Wagner

Publications and source records attributed to R Wagner.

At least 397 records · Page 22Linked to original sources
PubMed1986

The importance of individual nucleotides for the structure and function of rRNA molecules in E. coli. A mutagenesis study.

Methods of in vitro mutagenesis were employed to determine the importance of individual nucleotides within the ribosomal RNAs for the structure and function of E. coli ribosomes. A series of defined nucleotides in the genes for the 5 S and 16 S RNA were altered by transition and transversion mutations using either oligonucleotide-directed or bisulfite-catalyzed mutation procedures. Plasmids harbouring the mutated rRNA genes were expressed and the ribosomes containing such altered RNAs were investigated for impairments in RNA-protein interaction assembly and mRNA-coded tRNA binding.

Base Sequence↗
PubMed1986

Identification of neighbouring proteins by cross-linking of intact 70 S ribosomes from Escherichia coli.

70 S ribosomes from Escherichia coli have been reacted with the bifunctional reagent 1,4-phenyldiglyoxal under near physiological conditions. As a result of the cross-linking reaction a number of high-molecular-weight protein fractions with altered electrophoretic mobility could be isolated. A new chemical procedure has been introduced to reverse the cross-links between proteins at least partially. The cleavage reaction did not affect the gel electrophoretic mobility of the proteins. Thus a direct identification of cross-linked proteins using one- or two-dimensional gels was made possible. Two protein trimers, S3-S4-S5 and L1-S4-S5, as well as five protein dimers, S3-S4, L6-L7/12, L10-L7/12, S9-L19 and L18-L19 could be identified as close neighbours in the E. coli 70 S ribosome. The protein pairs S9-L19 and L18-L19 had previously not been identified as near neighbours using cross-linking studies.

Cross-Linking Reagents↗
PubMed1986

Characterization of a collection of deletion mutants at the 3'-end of 16S ribosomal RNA of Escherichia coli.

Deletions were constructed in plasmid pKK3535 in the coding region for the 3'-end of E. coli 16S rRNA. The plasmid was cleaved with restriction endonuclease Hae2 under conditions favoring the production of single cut linear plasmid DNA and deletions were produced by digestion with exonuclease Bal31. Seven different deletions were isolated ranging in size from 90 to about 200 base pairs. Transcription of ribosomal DNA, processing of ribosomal RNA and incorporation of mutant rRNA into mutant particles was studied in UV-sensitive cells using a modified maxicell labeling procedure. The different mutants were missing defined features in the secondary structure of 16S rRNA and were characterized according to their stability, ability to be processed, sensitivity to colicin E3, and ability to bind ribosomal protein S1 and to interact with 50S subunits. These analyses show that the small stem and loop structure at positions 1350 to 1372 is necessary for the stability of rRNA. The deletion of the long terminal stem structure (1409-1491) in all mutant rRNAs does not block processing of the mutant rRNAs or S1 binding, although processing of the mutant rRNAs or S1 binding, although it does prevent the association of particles containing the mutant rRNA with 50S subunits.

Base Sequence↗
PubMed1986

The innervation of the pyloric region of the crab, Cancer borealis: homologous muscles in decapod species are differently innervated.

The muscles of the pyloric region of the stomach of the crab, Cancer borealis, are innervated by motorneurons found in the stomatogastric ganglion (STG). Electrophysiological recording and stimulating techniques were used to study the detailed pattern of innervation of the pyloric region muscles. Although there are two Pyloric Dilator (PD) motorneurons in lobsters, previous work reported four PD motorneurons in the crab STG (Dando et al. 1974; Hermann 1979a, b). We now find that only two of the crab PD neurons innervate muscles homologous to those innervated by the PD neurons in the lobster, Panulirus interruptus. The remaining two PD neurons innervate muscles that are innervated by pyloric (PY) neurons in P. interruptus. The innervation patterns of the Lateral Pyloric (LP), Ventricular Dilator (VD), Inferior Cardiac (IC), and PY neurons were also determined and compared with those previously reported in lobsters. Responses of the muscles of the pyloric region to the neurotransmitters, acetylcholine (ACh) and glutamate, were determined by application of exogenous cholinergic agonists and glutamate. The effect of the cholinergic antagonist, curare, on the amplitude of the excitatory junctional potentials (EJPs) evoked by stimulation of the pyloric motor nerves was measured. These experiments suggest that the differences in innervation pattern of the pyloric muscles seen in crab and lobsters are also associated with a change in the neurotransmitter active on these muscles. Possible implications of these findings for phylogenetic relations of decapod crustaceans and for the evolution of neural circuits are discussed.

Acetylcholine↗
PubMed1986

Positron emission tomography in neuropsychology.

By positron emission tomography (PET) of 18F-2-fluoro-2-deoxy-D-glucose (FDG) local cerebral metabolic rate for glucose (LCMRGl) can be measured in man. Normal values in cerebral cortex and basal ganglia range from 35 to 50 mumol/100 g/min, the values in gray matter structures of the posterior fossa were 25-30 mumol/100 g/min, the lowest LCMRGl was found in the white matter (15-20 mumol/100 g/min). During sensory stimulation by various modalities functional activation increases LCMRGl in the respective special areas, while sleep decreases metabolic rate in all cortical and basal gray matter structures. In many neurological disorders CMRGl is altered in a disease-specific pattern. In dementia of the Alzheimer type CMRGl is impaired even in early stages with accentuation in the parieto-temporal cortex, while in multi-infarct dementia glucose uptake is mainly reduced in the multifocal small infarcts. In Huntington's chorea the most conspicuous changes are found in the caudate nucleus and putamen. In cases of focal lesions (e.g. ischemic infarcts) metabolic disturbances extend far beyond the site of the primary lesion and inactivation of metabolism is found in intact brain structures far away from the anatomical lesion. Additional applications of PET include determination of the metabolism of various substrates, of protein synthesis, of function and distribution of receptors, of tumor growth and of the distribution of drugs as well as the measurement of oxygen consumption, blood flow and blood volume.

Brain↗
PubMed1986

Accumulation of hydroxyethyl starch (HES) in the liver of patients with renal failure and portal hypertension.

Hydroxyethyl starch (HES) has gained wide clinical acceptance as a colloidal plasma substitute. We were able to study the liver biopsies of two patients with renal failure who developed ascites after repeated infusions of HES. All types of liver cells displayed massive accumulation of HES with the morphologic resemblance to a storage disease. These changes could be distinguished clearly from the lesions of a hereditary disorder by light and electron microscopy. Although it is difficult to establish a causative role for HES in the development of ascites on the bases of morphological changes alone, one should be cautious about giving HES to patients with renal failure until exact data from further experimental studies are available.

Female↗
PubMed1986

Methyl-directed repair of frameshift mutations in heteroduplex DNA.

DNA heteroduplexes with single unpaired bases of the four different kinds were prepared by annealing separated strands of bacteriophage lambda DNA and used to transfect Escherichia coli. Genetic analysis of the progeny phages obtained from transfected bacteria indicates that the E. coli mismatch repair system can recognize and repair heteroduplexes with single unpaired bases--i.e., frameshift/wild-type heteroduplexes. The repair of a particular strand of the heteroduplex is inhibited by full methylation of the adenines in the GATC sequences of that strand. Thus, it appears that the E. coli mismatch repair system can act on newly synthesized DNA strands to remove replication errors involving the insertion or deletion of a single base.

Bacteriophage lambda↗
PubMed1986

Mismatch-stimulated killing.

DNA duplexes with or without mismatches and with or without adenine-methylated GATC sequences were prepared from separated strands of bacteriophage lambda DNA and used to transfect Escherichia coli. Unmethylated heteroduplexes containing one or more repairable mismatches transfect cells with a functioning mismatch repair system less efficiently than they transfect cells deficient in mismatch repair. No difference is observed when the duplexes contain no mismatch or a poorly repaired mismatch or when the heteroduplexes are fully or hemimethylated. These results and the phenotypes of E. coli dam mutants suggest that the E. coli mismatch repair system may introduce double-strand breaks in unmethylated DNA at or near repairable mismatches.

Adenine↗
PubMed1986

The reactions of the hydroxymethyl radical with 1,3-dimethyluracil and 1,3-dimethylthymine.

Hydroxymethyl radicals .CH2OH, generated by the radiolysis of methanol (0.5 mol dm-3) in N2O-saturated aqueous solutions, were reacted with 1,3-dimethyluracil or 1,3-dimethylthymine (10(-3) mol dm-3). The products were identified and their G values determined. It has been concluded that in 1,3-dimethyluracil .CH2OH attack occurs only at C(6) while in 1,3-dimethylthymine there is partitioning between addition (two-thirds) and H-abstraction from the C(5)-methyl group (one-third). A rate constant for CH2OH addition to 1,3-dimethyluracil of about 10(4) dm3 mol-1 s-1 is estimated. Complexities that may arise in the radiolysis of pyrimidines such as 1,3-dimethylthymine, apparently as a consequence of the formation of 5-alkylidenepyrimidines, are discussed. A value of 0.15 has been estimated for the disproportionation/combination ratio for the hydroxymethyl radical self-termination reaction.

Chromatography, Gas↗
PubMed1986

Ambulatory pacemaker surgery--medical and economical advantages.

The first pacemaker implantation on an ambulatory basis was done in our hospital in 1980. Since then, approximately 1,000 pacemaker patients have been operated on as outpatients. In 1984, we performed 781 pacemaker operations including 624 ambulatory operations. 583 patients received ambulatory new implantations. 54 persons were supplied as outpatients with a dual chamber system, 31 with a rate responsive system. In order to avoid complications, we use a standardized procedure, especially because the operators change daily following a plan of rotation. Patients are observed for 3-4 h postoperatively before discharge. Complications due to ambulatory operating have not been noticed. The ambulatory implantation of single or dual chamber pacemakers has been proving true as a safe treatment in our clinic. The economical advantage is obvious. In 1984, 5,000 days of hospitalization could be avoided; complications attributable to hospital cross-infection, immobilization, etc. could be reduced.

Ambulatory Surgical Procedures↗
PubMed1986

Toxic shock syndrome following septoplasty using plastic septal splints.

Toxic Shock Syndrome (TSS) is an acute multisystem disease that has been recognized to occur in a variety of clinical settings. Postoperative TSS has been described following nasal surgery associated with the use of postoperative nasal packing. We report a case of classic TSS following septoplasty where intranasal splints without nasal packing were used. Recommendations for prevention of TSS associated with nasal surgery are presented.

Adult↗
PubMed1986

Construction and functional analysis of ribosomal 5S RNA from Escherichia coli with single base changes in the ribosomal protein binding sites.

The ribosomal 5S RNA gene from E. coli was altered by oligonucleotide-directed mutagenesis at positions A66 and U103. The mutant genes were cloned into an expression vector and selectively transcribed in an UV-sensitive E. coli strain using a modified maxicell system. The mutant 5S RNA genes were found to be transcribed and processed normally. The 5S RNA molecules were assembled into 50S ribosomal subunits. Under in vitro conditions the stability of the mutant 70S ribosomes seemed, however, to be reduced, since they dissociated into their subunits more easily than those of the wild type. The isolated mutated 5S RNAs with base changes in the ribosomal protein binding sites for L18 and L25, together with a point mutant at G41 (G to C), constructed earlier, were tested for their capacity to bind the 5S RNA binding proteins L5, L18 and L25. The following effects were observed: The base change A66 to C within the L18 binding site did not affect the binding of the ribosomal protein L18 but enhanced the stability of the L25-5S RNA complex considerably. The base changes U103 to G and G41 to C slightly reduced the binding of L5 and L25 whereas the binding of L18 to the mutant 5S RNAs was not altered. In addition 70S ribosomes with the single point mutations in their 5S RNAs were tested in their tRNA binding capacity. Mutants containing a C41 in their 5S RNA showed a reduction in the poly(U)-dependent Phe-tRNA binding, whereas the mutations to C66 and G 103 lead to completely inactive ribosomes in the same assay. Based on previous results a spatial model of the 5S RNA molecule is presented which is consistent with the findings reported in this paper.

Cloning, Molecular↗
PubMed1985

Nosocomial legionellosis in surgical patients with head-and-neck cancer: implications for epidemiological reservoir and mode of transmission.

A prospective pneumonia study was conducted simultaneously on head-and-neck surgery wards at two hospitals over 2 years; one hospital had a water supply contaminated with Legionella pneumophila but no record of having had a case of legionella pneumonia, and the other had just decontaminated its water supply because of known endemic nosocomial legionellosis. Special laboratory tests for legionella were done on all cases of nosocomial pneumonia irrespective of clinical impression. Over the first 18 months, the rate of nosocomial legionellosis was 30% at the first hospital and 0% at the second. Patients who underwent laryngectomy did not acquire the disease. Hyperchlorination at the first hospital was followed by a fall (p less than 0.01) in legionella pneumonias. Thus legionella pneumonias can be overlooked if special laboratory tests are not applied routinely, and surgical patients with head-and-neck cancer may be at high risk of nosocomial legionellosis because of the potential for pulmonary aspiration of contaminated water or orophyaryngeal microflora and/or frequent manipulation of the respiratory tract. This study demonstrates the benefits of examining the environment for legionella despite the absence of documented disease.

Chlorine↗
PubMed1985

Analysis of a sequence region of 5S RNA from E. coli cross-linked in situ to the ribosomal protein L25.

70S ribosomes from E. coli were chemically cross-linked under conditions of in vitro protein biosynthesis. The ribosomal RNAs were extracted from reacted ribosomes and separated on sucrose gradients. The 5S RNA was shown to contain the ribosomal protein L25 covalently bound. After total RNase T1 hydrolysis of the covalent RNA-protein complex several high molecular weight RNA fragments were obtained and identified by sequencing. One fragment, sequence region U103 to U120, was shown to be directly linked to the protein first by protein specific staining of the particular fragment and second by phosphor cellulose chromatography of the covalent RNA-protein complex. The other two fragments, U89 to G106 and A34 to G51, could not be shown to be directly linked to L25 but were only formed under cross-linking conditions. While the fragment U89 to G106 may be protected from RNase T1 digestion because of a strong interaction with the covalent RNA-protein complex, the formation of the fragment A34 to G51 is very likely the result of a double monovalent modification of two neighbouring guanosines in the 5S RNA. The RNA sequences U103 to U120 established to be in direct contact to the protein L25 within the ribosome falls into the sequence region previously proposed as L25 binding site from studies with isolated 5S RNA-protein complexes.

Electrophoresis, Polyacrylamide Gel↗