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R Bauer

Publications and source records attributed to R Bauer.

At least 19 recordsLinked to original sources
PubMed1992

The mapping by high-pH anion-exchange chromatography with pulsed amperometric detection and capillary electrophoresis of the carbohydrate moieties of human plasma alpha 1-acid glycoprotein.

The reducing oligosaccharides released from alpha 1-acid glycoprotein (AGP) by conventional hydrazinolysis have been analyzed by two different mapping techniques, using high-pH anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) and capillary electrophoresis (CE) with uv detection at 190 nm. The CE measurements proved about 4000 times more sensitive than the measurements by HPAE-PAD. The N-glycan pool was fractionated by Mono Q anion-exchange chromatography, and individual fractions so obtained were desialylated using Vibrio cholerae neuraminidase. The resulting asialo-N-glycans were further analyzed by HPAE-PAD, revealing 2 major, 4 intermediate, and 4 small peaks and at least 3 spikes, which counted for at least 13 different asialo-N-glycans. The carbohydrate structures were tentatively assigned by comparison of the Mono Q-separated N-glycans with the known AGP carbohydrate structures and known structures contained in a mapping database that allows structural assignment of N-glycans by mere comparison of retention times. In addition to the hitherto known AGP carbohydrate structures, we have tentatively identified a number of sulfated N-glycans that are currently being analyzed in more detail. We have also compared the glycan pools recovered from AGP using hydrazinolysis and glycopeptidase F (PNGase F). Approximately 40 distinct peaks could be detected in the hydrazinolysis-derived N-glycan pool by either technique (HPAE-PAD and CE), while about 30 distinct peaks were detected in the N-glycan pool derived by PNGase F digestion of the tryptic AGP digest of the same batch of AGP. These differences were attributed to an increased desialylation (approximately 3 mol%) during hydrazinolysis, based on the detection by HPAE-PAD and CE of free sialic acid and monosialylated oligosaccharides in the glycan pool derived by conventional hydrazinolysis. The integrity of the N-glycans' chitobiose core was examined by 500-MHz 1H NMR spectoscopy. The hydrazinolysis procedure could be optimized such that the hydrazinolysis-derived N-glycan pool was chromatographically essentially identical to the PNGase F-derived N-glycan pool. Hydrazinolysis proved best, with practically no loss of N-acetlylneuraminic acid and the closest resemblance to the PNGase F-derived N-glycan pool, using an automated apparatus. Notably, it was recognized that, in our hands, PNGase F digestion in the presence of sodium dodecyl sulfate resulted in partial desialylation of the liberated N-glycans.

Capillary Action↗
PubMed1992

Monofunctional DNA-platinum(II) adducts block frequently DNA polymerases.

The question of whether monofunctional DNA platinum(II) adducts block synthesis of DNA by purified DNA polymerases of different types and origin has been investigated by comparing the time dependence of synthesis arrest and of DNA adduct formation. Activated salmon testis DNA is used as a suitable substrate for DNA synthesis allowing to probe inhibition by platinum(II) monoadducts for the variety of inherent template-primers. Reaction amplitudes are related to defined mixtures of dichloro and chloroaqua platinum(II) complexes. It is found that (i) all investigated DNA polymerases seem arrested (100% efficiency) at bifunctional DNA adducts. (ii) human DNA polymerase beta bypasses most of the monofunctional lesions of the three platinum(II) complexes investigated. (iii) Klenow fragment is blocked by monoadducts with increasing efficiency in the order cis-diamminechloroaquaplatinum(II) (0%) less than meso-[1,2-bis(2,6- dichloro-4-hydroxyphenyl)ethylenediamine] chloroaquaplatinum(II) (50%) less than trans-diamminechloro-aquaplatinum(II) (75%). (iv) Escherichia coli DNA polymerase I, Thermus aquaticus DNA polymerase, Physarum polycephalum DNA polymerase alpha, and calf thymus DNA polymerase alpha appear to be arrested by monoadducts. According to these examples, blocking efficiencies depend on the cis/trans-stereogeometry of fixation of the carrier ligands at platinum(II) residues, on the size/chemical nature of the platin(II) carrier ligand and on the type/origin of DNA polymerase.

Animals↗
PubMed1992

Comparison of magnetic resonance imaging with cross-sectional echocardiography in the assessment of left ventricular mass in children without heart disease and in aortic isthmic coarctation.

Although left ventricular (LV) mass may be important to judge effects of left-sided cardiac obstruction or hypertension, reproducible noninvasively determined normal data in the pediatric age group are scarce. To validate cross-sectional echocardiographic LV mass determination, our data were compared with LV mass assessed by magnetic resonance imaging (MRI). MRI was considered to be a good reference method because there is usually no problem in defining endo- and epicardial borders with MRI. LV mass was assessed in 14 children aged 5.3 years (10 days to 14.7 years) with a mean body surface area of 0.78 m2 (range 0.25 to 1.61). With cross-sectional echocardiography the epicardial and endocardial volumes were calculated using a Simpsons rule algorithm in the apical 2- and 4-chamber view. The difference between epi- and endocardial volumes was multiplied by 1.05 to yield the mass. Mass was assessed with MRI using a multislice technique; the area of each myocardial slice was calculated and multiplied with the slice thickness, and the resultant slice volumes were added to obtain the myocardial volume. On cross-sectional echocardiography, the mass was 55 g (range 12 to 126) or 64 g/m2 (range 46 to 79); on MRI it was 60 g (range 33 to 87) or 69 g/m2 (range 46 to 89). Regression analysis yielded an r value of 0.98 with a standard error of the estimate of 5.7 g or a 10% difference. In older children, LV mass determined by MRI was bigger than the one derived by echocardiography. It is concluded that cross-sectional echocardiography can reliably assess LV myocardial mass in pediatric patients.

Adolescent↗
PubMed1992

Contrast variation studies of clathrin coated vesicles by small-angle neutron scattering.

Structural information on clathrin coated vesicles has been obtained by small angle neutron scattering using contrast variation. A characteristic peak in the neutron scattering profile, which is apparent in 75% D2O, as well as in H2O, disappears when contrast matching the protein component of the coated vesicles in 42% D2O. Neutron, as well as dynamic, light scattering give a coated vesicle size of about 900 A in H2O and D2O, but for neutron scattering the diameter decreases when matching out the protein coat of the clathrin coated vesicles. From the match point for the clathrin coated vesicles it is demonstrated that the clathrin cages do contain internal membrane. The mass of 34 MD and composition of 75% protein and 25% lipid found from the analysis of the small-angle scattering data are both in good agreement with the values reported in the literature. Electron microscopy gives an average outer diameter of 880 A for the coated vesicles and an average diameter of 460 A for the vesicle itself.

Biophysical Phenomena↗
PubMed1992

Cervical pheochromocytoma: a rare localization and a difficult diagnosis.

A 45-year-old hypertensive female with insulin-treated diabetes mellitus presented to our clinic with elevated urinary norepinephrine (NE) concentrations and a negative 131-metaiodobenzylguanidine (MIBG) scintigraphy, errouneously limited to the abdomen, for evaluation of a pheochromocytoma (Pheo). Despite antihypertensive medications blood pressure remained highly variable and frequently elevated. Further biochemical testing, including a glucagon provocation test and a clonidine-suppression test, revealed autonomous NE secretion. In order to avoid repeat MIBG-scintigraphy, other non invasive imaging techniques were performed, including real time sonography (7.5 MHz) of the neck which revealed a tumor. Fine needle aspiration of this tumor tissue demonstrated cells compatible with Pheo. Histology and immunohistochemistry of the excised tumor confirmed the diagnosis of Pheo. After surgical removal of the tumor, urinary and plasma NE levels normalized. Without any medication the blood pressure of the patient was now only slightly hypertensive. Only half of the daily insulin dose was needed to maintain the patient euglycemic.

Adrenal Gland Neoplasms↗
PubMed1992

Scoliosis correction by Cotrel-Dubousset instrumentation. The effect of derotation and three dimensional correction.

In 30 patients undergoing Cotrel-Dubousset instrumentation, computerized tomography was performed before and after surgery. The RAsag-angle was measured for each vertebral level. Coronal and sagittal translation were evaluated in the same computerized tomographic scans by means of a new method. Based on the hooks used, various sections of the spine were defined. In these sections relative rotation as well as relative sagittal and frontal translation were calculated by an algorithm comparing the most severely rotated or translated vertebra with the mean value of both end vertebrae. Significant correction of rotation did not occur in any of these sections. A significant increase of kyphosis, however, could be demonstrated in all thoracic sections. Above the second intermediate hook combined correction of all three parameters was achieved. Below this hook correction occurred almost independently in the frontal and sagittal planes.

Adolescent↗
PubMed1992

Reduced rate of uptake of zinc ions in a calf affected with the lethal syndrome A46 relative to clinically normal calves using whole body radio-isotope scanning of 62Zn.

Four clinically healthy control calves were scanned and blood clearance was determined from blood samples taken during the first hour after intravenous injection of 62Zn. Furthermore, one clinically healthy control calf and one calf suffering from the lethal hereditary syndrome A46 were scanned and blood samples taken from five min after intravenous and abomasal injection of 62Zn and onwards for a period of up to 26th. The results show a very fast liver uptake of 62Zn. The estimated rate of plasma/blood clearance and liver uptake for the control calves agrees with values derived from studies on other animals. In contrast, the A46 calf had a decreased rate of plasma/blood clearance and liver uptake relative to the control calves.

Animals↗
PubMed1992

[Morphological and immunohistochemical findings on the frequency of intranuclear immunoglobulin inclusions (Dutcher bodies) in malignant B-cell lymphomas].

318 cases of 682 malignant B-cell lymphomas reacted positive for cIg. 66 of them showed Dutcher bodies (DB). DB were found in about 22% of plasmacytomas, 17% of immunocytomas, and in 7.5% of follicular lymphomas and polymorphic centroblastomas, respectively. Regarding only the cIg-positive cases, DB occurred in about 27% of immunocytomas, 20% of follicular lymphomas and 18% of polymorphic centroblastomas. A single case of prolymphocytic leukaemia, centrocytoma, monomorphic centroblastoma, and immunoblastoma each showed also DB. Usually, DB-positive plasmacytomas showed kappa, alpha, and J-chains. The remaining lymphomas mostly expressed kappa, my, and J-chains. In conclusion Dutcher bodies can occur with any cIg-producing B-cell lymphoma. They are not limited to immunocytomas.

Cell Nucleus↗
PubMed1992

[Evoked potentials following cerebral ischemia in the rat: the effect of the stimulus frequency].

EEG and somatosensory evoked potentials were recorded in anesthetized rats before and up to 24 h after 30 min of global forebrain ischemia. Before ischemia, SEP (sweep time 1000 ms) included primary (N25P50) components and late potentials of low amplitude. During ischemia, SEP and EEG were isoelectric. During postischemic recirculation SEP evoked by stimulation at 1.0 Hz remained severely suppressed for 24 h, although long-latency potentials (> 100 ms) recovered. Using a very low stimulation frequency of 0.1 Hz, late components strongly increased in amplitude and the overall evoked activity in the averaged post-stimulus-EEG reached 90% of control. These results demonstrate that the SEP evoked at very low stimulation frequency may serve as an early indicator of functional brain recovery after prolonged cerebro-circulatory arrest.

Animals↗
PubMed1992

[Early detection of morphologic-functional changes in the airways using a simple method of inhalation scintigraphy].

In order to validate a method of inhalation scintigraphy with 99mTc-labeled human serum albumin in the early diagnosis of morphologic-functional changes of the airways 35 volunteers and patients (12 healthy non-smokers and smokers each, 11 patients with bronchitis) were studied. Deposition of the aerosol immediately after inhalation was calculated quantitatively by a ROI technique and qualitatively (scoring of central deposition, homogeneity, and recognizability of lung outline). Additionally, the regional clearance of the inhaled aerosol was determined by continuous lung imaging up to 60 min (mainly regional mucociliary removal rates). Discrimination between healthy volunteers and patients with bronchitis was possible by means of deposition patterns immediately after inhalation. On the other hand, no differences could be recognized in this way between healthy non-smokers and smokers. Regional mucociliary removal was higher in non-smokers than in smokers, but there was no difference between smokers and patients with bronchitis.

Adult↗
PubMed1991

113Cd-NMR investigation of a cadmium-substituted copper, zinc-containing superoxide dismutase from yeast.

113Cd nuclear magnetic resonance spectroscopy has been used to investigate the metal binding sites of cadmium-substituted copper, zinc-containing superoxide dismutase from baker's yeast. NMR signals were obtained for 113Cd(II) at the Cu site as well as for 113Cd(II) at the Zn site. The two subunits in the dimeric enzyme were found to have identical coordination properties towards 113Cd(II) at the Zn site when no copper is coordinated at the Cu site, and when Cu(I) or Cd(II) is coordinated, were found to be very small indicating that 113Cd(II) must be bound to the same number and type of ligands in both cases. Furthermore, the spectra show that the rate of exchange of protein-bound 113Cd(II) and free 113Cd2+ is slow on the NMR time scale also at the Cu site. The present study suggests an explanation for the discrepancy in the literature regarding 113Cd-NMR investigations of bovine superoxide dismutase.

Binding Sites↗
PubMed1991

Complementary global maps for orientation coding in upper and lower layers of the cat striate cortex and their possible functions.

Preferred stimulus orientations of striate cortical cells in the cat were analyzed for possible isotropic or anisotropic distributions. We separated the data twice, into central (0-5 degrees) vs. peripheral subgroups and into upper vs. lower layer cells. In the central group, absolute orientations were counted; in the periphery, a radial test was adopted by normalizing the preferred stimulus orientation of a cell to the line connecting the receptive field center to the retinal center. We found that in the center, vertical and horizontal orientations are overrepresented. In the periphery, the histograms show complementary anisotropies for upper and lower layers, favoring a map for radial orientation detection in upper layers and a more concentric map for orientation detection in lower layers. These results are possibly related to the probabilities of different optic flow fields on the retina under natural conditions of stimulation. They are discussed as possible neuronal structures supporting figure-ground discrimination, the distinction of self motion from object motion, and the location of objects in three-dimensional space.

Animals↗
PubMed1991

Coordination geometry for cadmium in the catalytic zinc site of horse liver alcohol dehydrogenase: studies by PAC spectroscopy.

Active site substituted Cd(II) horse liver alcohol dehydrogenase has been studied by Perturbed Angular Correlation of Gamma rays Spectroscopy during turnover conditions for benzaldehyde and 4-trans-(N,N-dimethylamino)cinnamaldehyde. The ternary complex between alcohol dehydrogenase NAD+ and Cl-, and the binary complex between alcohol dehydrogenase and orthophenanthroline have also been studied. The Nuclear Quadrupole Interaction parameters have been interpreted in terms of different coordination geometries for Cd(II) in the catalytic zinc site of the enzyme. Calculation of the nuclear quadrupole interaction for cadmium in the catalytic site of the enzyme with and without coenzyme, based upon the four coordinated geometries determined from X-ray diffraction, agrees with the experimentally determined values. The ternary complexes between enzyme, NAD+ and either Cl- or trifluoroethanol and the binary complex between enzyme and orthophenanthroline have almost identical spectral parameters which are not consistent with a four coordinated geometry, but are consistent with a five coordinated geometry. The non-protein ligands for the ternary complex with trifluoroethanol are suggested to be an alkoxide group and a water molecule. The Nuclear Quadrupole Interaction parameters for the productive ternary complex between enzyme, NADH and an aldehyde is consistent with the four coordinated geometry predicted from X-ray diffraction data having the carbonyl group of the aldehyde substituting the water molecule as ligand to the metal.

Alcohol Dehydrogenase↗
PubMed1991

Local and global principles of striate cortical organization: an advanced model.

A model of the functional architecture in monkey striate cortex is proposed, based on recent data, in which the global structure is a result of the local structure. The local structure itself is organized around the cytochrome oxidase blobs. It is characterized by different anisotropic distributions of preferred orientations in upper and lower layers. In particular, the upper layers show a bias for "radial" orientations and the lower layers show a bias for "concentric" orientations (Bauer and Dow 1989). This organization may derive from the symmetry of the visual field and visual system which tends to be radial or concentric rather than cartesian. Functionally, the increased sensitivities of the different radial and concentric maps of orientation and movement detectors seem to be an adaptive fit to optic flow fields on the retina during complex movements of the subject in its environment.

Animals↗
PubMed1991

The potential of perturbed angular correlation of gamma rays as a tool for dynamic studies of peptides/proteins.

Four peptides and serum albumin have been derivatized with the bicyclic anydride of diethylenetriamine-pentaacetic acid. Procedures were developed to isolate the labelled species and determine the degree of derivatization. By using perturbed angular correlation of gamma-ray spectroscopy it is possible, through the determination of rotational correlation times, to decide whether labelled peptides interact with other molecules (receptors). In the case of the peptide cholecystokinin it is shown that the interaction between the peptide and its corresponding polyclonal antibody can be determined down to 1 pmol hormone. Experiments on 111In- and 111mCd-labelled Gly-Trp showed that, where the 111Cd PAC spectrum directly reflected the rotational motion of the molecule, the 111In PAC spectrum was affected by the nuclear transitions to 111mCd.

Anisotropy↗
PubMed1991

Experimental and clinical main forms of hypoxic-ischaemic brain damage and their monitoring.

A short review of main pathogenetic forms of hypoxic-ischaemic brain damage and its consequences for causally orientated therapy and monitoring is given. Different pathogenetic components act in several combinations. In these processes disturbances of the cardio-vascular system, of the haemorheology mainly at the level of microvessels, and disturbances of the blood brain barrier are involved. Furthermore, there are relevant disturbances of the neuronal metabolism such as accumulation of cytosolic Ca++ or disturbances caused by the effect of radicals, lipid peroxidation and changes of protein synthesis. Nowadays, chances of a cause-related therapy are increased by improved evaluation of main pathogenetic components especially regarding secondary brain damage. To evaluate these components in detail, animal models must be more clinically related, especially regarding long-term studies. The increasing knowledge about critical thresholds of reversible and irreversible brain changes also favours effective cerebral function monitoring. The main conclusions from previous experimental as well as clinically related studies indicate the necessity of very early therapeutical interventions.

Brain↗