Biomedical subjects
Publications and source records attributed to R Wagner.
A massive tumor embolism was observed in a 35-year-old patient suffering from a tumor of the urinary bladder. Pulmonary embolism was suspected after echocardiographic demonstration of an acute cor pulmonale. Postmortem examination demonstrated multiple small tumor emboli within the small pulmonary arteries.
The structures of the two stable conformers of Escherichia coli 5 S RNA, the and B form, were compared. Information about the structures were obtained using the methods of limited enzymatic hydrolysis and chemical modification of accessible nucleotides. Base-specific modifications were performed for adenosines and cytidines using diethylpyrocarbonate and dimethylsulfate in combination with a strand-scission reaction at the modified site. Base-specific (RNase T1) as well as conformation-specific (nuclease S1, cobra venom nuclease) enzymes were employed for the limited enzymatic hydrolysis. Clear differences in the accessibility of the two 5 S RNA conformers to the enzymes and the chemical reagents were established and the regions with altered reactivities were localized in the 5 S RNA structure. The results are consistent with the disruption of the secondary structural interactions in helix II and partly in helices III and IV during the transition from the A to the B form. (The numbering of the helices is according to the generally accepted Fox and Woese model.) In addition some regions presumably involved in the tertiary structure are distorted. There is evidence, however, for the new formation of structural regions between two distant sites in the 5 S RNA B form. The results enable us to refine the existing 5 S RNA A-form model and provide insight into the structural dynamics that lead to the formation of the 5 S RNA B form.
The ribosomal 5S RNA gene from the rrnB operon of E. coli was mutagenised in vitro using a synthetic oligonucleotide hybridised to M13 ssDNA containing that gene. The oligonucleotide corresponded to the 5S RNA sequence positions 34 to 51 and changed the guanosine at position 41 to a cytidine. The DNA containing the desired mutation was identified by dot blot hybridisation and introduced back into the plasmid pKK 3535 which contains the total rrnB operon in pBR 322. Plasmid coded 5S rRNA was selectively labeled with 32p using a modified maxi-cell system, and the replacement of guanosine G41 by cytidine was confirmed by RNA sequencing. The growth of cells containing mutant 5S rRNA was not altered by the base change, and the 5S rRNA was processed and incorporated into 50S ribosomal subunits and 70S ribosomes. The structure of wildtype and mutant 5S rRNA was compared by chemical modification of accessible guanosines with kethoxal and limited enzymatic digestion using RNase T1 and nuclease S1. These results showed that the wildtype and mutant 5S rRNA do not differ significantly in their structure. Furthermore, the formation, interconversion and stability of the two 5S rRNA A- and B-conformers are unchanged.
Pharmacologically relevant concentrations of benzodiazepines have previously been reported to increase 45Ca2+ uptake into synaptosomes. This observation, coupled with the recent report that nifedipine may block the hypnotic effect of flurazepam, led us to study the effects of nifedipine and nitrendipine on 45Ca2+ uptake into synaptosomes. Diazepam (1 microM) significantly increased the uptake of 45Ca2+ to a crude synaptosomal fraction (P2) prepared from rat cerebral cortex and depolarized with 55 mM K+. Nifedipine (1 microM) did not alter the uptake of Ca2+, while nitrendipine (1 microM) reduced uptake by 37%. Both nifedipine and nitrendipine completely antagonized the ability of diazepam to increase 45Ca2+ uptake following K+ depolarization. These observations support the notion that the pharmacologic actions of benzodiazepines may be mediated through effects on a calcium channel.
Glucose transport differs in red cells of various species. The following sequence of transport velocities was found: man greater than newborn pig greater than rat, dog greater than cattle greater than pig. No correlation was found between the amount of protein in band 3 and glucose transport activity. By contrast, a very clear peak in the band 4.5 region was found for newborn pigs, whereas adult pigs did not exhibit a corresponding peak in the electrophoresis. Thus further evidence is provided by our investigations in favour of band 4.5 region for glucose transport activity in red cells.
Functionally active 70S ribosomes were chemically modified with dimethylsulfate (DMS) in the presence and absence of bound tRNA. The ribosomal 16S RNA and 23S RNA were extracted, separated and labeled radioactively at their 3'-ends. DMS modification sites within the last 200 nucleotides from the 3'-ends were investigated on sequencing gels, after borohydride reduction and aniline catalyzed strand scission of the isolated RNA's. tRNA binding caused enhanced reactivity at 9 nucleotide positions while three sites showed decreased reactivity in the 16S RNA. The effects of bound tRNA on the modification of 23S RNA were limited. Only one enhancement was observed in the presence of bound tRNA. mRNA binding alone showed two more sites with enhanced reactivity, however. The results are consistent with the view that the sequence 1400-1500 of the 16S RNA plays an important functional role in the translating ribosome and possibly constitutes part of the tRNA binding site.
The structure of 5 S RNA within the 70 S ribosome from Escherichia coli was studied using the chemical reagent kethoxal (alpha-keto-beta-ethoxybutyraldehyde) to modify accessible guanosines. The modification pattern of 5 S RNA from free 70 S ribosomes was compared with that of poly(U) programmed ribosomes where tRNA had been bound to both the A- and P-sites. Binding to the ribosomal A-site was achieved enzymatically using the elongation factor Tu and GTP in the presence of deacylated tRNA which blocks the ribosomal P-site. Modified guanosines were identified after partial RNase T1 hydrolysis and separation of the hydrolysis products on sequencing gels. Binding of tRNA to the ribosome leads to a strong protection of 5 S RNA guanosine G-41 and to some degree G-44 from kethoxal modification. The limited RNase T1 hydrolysis pattern provides evidence for the existence of a 5 S RNA conformation different from the known 5 S RNA A- and B-forms which are characterized by their gel electrophoretic mobility. The importance of 5 S RNA for the binding of tRNA to the ribosome is discussed.
The serum kinetics of amiodarone and its major metabolite the deethyl analogue were studied in rabbits after intravenous administration. The elimination of the drug and the metabolite from serum occurred as a biexponential function. Both compounds exhibited a rapid distribution phase (6.5 and 4.4 min, respectively) and had elimination half-lives of 136 and 235 min, respectively. There was a rapid uptake of both drugs by the myocardium, with maximal concentrations at 5 and 15 min. The myocardial concentrations were higher than the respective serum concentrations and declined with time. There was a wide scatter in myocardium-serum ratios, which ranged from 1 to 11 for amiodarone and 12 to 29 for the metabolite. Neither the drug nor the metabolite produced significant changes in the surface electrocardiogram after intravenous administration. These data suggest that accumulation of the metabolite does not account for the slow onset of action of amiodarone.
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Eleven strains of obligately purinolytic clostridia have been studied with respect to their assignment to the three type strains of Clostridium acidiurici, C. cylindrosporum, and C. purinolyticum. DNA/DNA-hybridization proved to be the method of choice for differentiation whereas phenotypic characteristics such as spore morphology, substrate spectra, nutritional requirements, product formation, and sensitivity against various antibiotics did not allow unequivocal identification. All strains depended on selenite for growth.
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Using dynamic [18F]fluorodeoxyglucose (FDG) positron emission tomography with a high-resolution, seven-slice positron camera, the kinetic constants of the original three-compartment model of Sokoloff and co-workers (1977) were determined in 43 distinct topographic brain regions of seven healthy male volunteers aged 28-38 years. Regional averages of the cerebral metabolic rate for glucose ( CMRglu ) were calculated both from individually fitted rate constants ( CMRglukinetic ) and from activity maps recorded 30-40 min after FDG injection, employing a four-parameter operational equation with standard rate constants from the literature ( CMRgluautoradiographic ). Metabolic rates and kinetic constants varied significantly among regions and subjects, but not between hemispheres. k1 ranged between 0.0485 +/- 0.00778 min-1 in the oval center and 0.0990 +/- 0.01347 min-1 in the primary visual cortex. k2 ranged from 0.1198 +/- 0.01533 min-1 in the temporal white matter to 0.1472 +/- 0.01817 min-1 in the cerebellar dentate nucleus. k3 was lowest (0.0386 +/- 0.01482 min-1) in temporal white matter and highest (0.0823 +/- 0.02552 min-1) in the caudate nucleus. Maximum likelihood cluster analysis revealed four homogeneous groups of brain regions according to their respective kinetic constants: (1) white matter and mixed brainstem structures; (2) cerebellar gray matter and hippocampal formations; (3) basal ganglia and frontolateral and primary visual cortex; and (4) other cerebral cortex and thalamus. Across the entire brain, k1 and k2 were positively correlated (r = 0.79); k1 and k3 showed some correlation (r = 0.59); but no significant linear association was found between k2 and k3. A strong correlation with CMRglu could be demonstrated for k1 (r = 0.88) and k3 (r = 0.90), but k2 was loosely correlated (r = 0.56). CMRglu kinetic ranged from 17.0 +/- 2.45 mumol/100 g/min in the occipital white matter to 41.1 +/- 5.62 mumol/100 g/min in the frontolateral cortex. In most regions the mean values of CMRglu kinetic did not differ significantly from CMRglu autoradiographic. With few exceptions, however, within-region variance was significantly less for CMRglu kinetic than for CMRglu autoradiographic, suggesting greater individual reliability of results obtained by the kinetic approach.
Previous studies have implicated the benzodiazepine receptor in the sleep-inducing effects of these widely used hypnotics, but the effector mechanism of this process is poorly understood. There is also in vitro evidence that benzodiazepines enhance calcium entry into synaptosomal preparations, leaving open the possibility that altered calcium flux may be involved in their actions. In order to explore this hypothesis, we administered intraventricular nifedipine, a calcium blocking agent. It was found that pretreatment with a dose of nifedipine which by itself does not affect sleep will prevent sleep induction by flurazepam in rats. Effects on anticonvulsant properties of flurazepam or anxiolytic effects of diazepam were not apparent. This suggests that changes in calcium channel function may be involved in the hypnotic action of benzodiazepines.
Our experimental investigation in six mongrel dogs with free revascularized jejunal loop for intraoral lining shows functional adaptation of the small bowel mucosa clinically and histologically. Although 1 year after transplantation 70 percent or more of the graft's surface remains small bowel mucosa, the flattening and widening of the villi produces an epithelial layer that satisfies the conditions of the oropharynx. In 30 clinical cases with a follow-up period of over 4 years our experimental experience is confirmed. After extensive ablative surgery in the oropharynx, primary reconstruction with free revascularized jejunal loop in combination with mandibular replacement has some significant advantages: There is no cicatricial induration of the graft. Mucus production occurs. Flexibility of the grafts and almost unlimited transplant supply lead to satisfying reconstruction even in difficult anatomic sites. Mesenteric fat tissue serves as good transplant material for extended soft-tissue loss. There is good wound healing, owing to abundant blood supply and prompt agglutination of the serosa. The long vascular pedicle provides revascularization apart from the resection area, which is important in irradiated cases. Decreased mucus production after 2 hours of normothermic ischemia and the anatomic reconstruction of mandibular replacement make tracheostomy not necessary.
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The bovine J blood group substance exists as a glycosphingolipid (ceramide decahexoside as well as ceramide dodecahexoside) and as a glycoprotein. The lipidic form occurs in erythrocyte membranes, both forms are found in serum. The lipidic J substances were isolated from erythrocytes and from serum, and identified by thin-layer chromatography with lipidic J substances isolated from spleen. The glycoprotein nature of the non-lipidic J of serum was evident by pronase-catalysed hydrolysis yielding J-active glycopeptides of lower molecular weights. The lipidic J was completely extracted from lyophilized stroma with chloroform/methanol. From lyophilized serum, however, it was completely extracted only in the presence of water, indicating different binding partners in serum and in erythrocyte membranes. The J lipid was incorporated as intact molecule into the erythrocyte membrane by a simple incubation technique. The incorporation was inhibited by various glycerophospholipids (called blockers). The J glycoprotein could not be transferred to the erythrocyte membrane. Three methods are described which are suitable for the preparation of a blocker-free fraction enriched with J lipids from J-positive serum.
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