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Biomedical subjects

R Bauer

Publications and source records attributed to R Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1991

Interaction between systemic circulation and brain injuries in newborns.

In several studies different pathogenetic mechanisms of metabolic and/or cardiovascular origin were shown depending on the type of hypoxic or hypoxic/hypercapnic stress and conditions of animals (normal developed or intrauterine growth retarded newborn piglets). Thus, in normal-weight piglets the prevention of compensatory hyperventilation owing to severe hypoxia (artificially ventilated animals) leads to critical, i.e. lethal acidosis. In intrauterine growth retarded piglets, a severe hypoxia cannot be vitally compensated because of the restricted circulatory centralization. Moreover, a limited cerebrovascular dilatation during moderate hypoxia/hypercapnia produces a critical state of the metabolic supply in those animals.

Adaptation, Physiological↗
PubMed1991

Investigations of cerebral glucose utilization into the newborn brain: a [18F]-FDG positron emission tomography study using a high resolution multiwire proportional chamber detector device.

An experimental approach is presented, where for the first time positron emission tomography (PET, the most important method for in vivo measuring the key functions of brain physiology and metabolism) was applied together with other techniques for quantitative-topological estimation of key parameters such as rCMRGlu in normal and disturbed brain function states in the newborn period.

Animals↗
PubMed1991

Analysis of alkamides and caffeic acid derivatives from Echinacea simulata and E. paradoxa roots.

The constituents of the roots of Echinacea simulata and E. paradoxa were examined by HPLC. The major lipophilic and hydrophilic compounds could be identified. E. paradoxa contained several ketoalkenynes and proved to have almost identical constituents as E. pallida. E. simulata contained alkamides as found in E. angustifolia and in addition ketoalkenynes as in E. pallida. Echinacoside was found in both species.

Amides↗
PubMed1991

The Zn-site in bovine copper, zinc superoxide dismutase studied by 111Cd PAC.

The active site in bovine copper, zinc superoxide dismutase (Cu2, Zn2SOD) has been studied by 111Cd time differential Perturbed Angular Correlation (PAC) on enzyme with Zn2+ replaced by excited 111Cd2+. The PAC spectra obtained for both the oxidized and the reduced form of Cu2Cd2SOD show no asymmetry between the two Zn-sites in the dimeric enzyme. The spectra further reveal that a significant change has taken place at the Zn-site in the reduced form compared to the oxidized form. Semi-empirical calculations based on the Angular Overlap Model (AOM) and coordinates from the crystal structure of the native enzyme are in agreement with the experimental PAC data of the oxidized enzyme. The results indicate that Cd2+ coordinates in the same manner as Zn2+ and that the crystal structure of SOD is valid for the enzyme in solution. The PAC spectrum of the reduced enzyme can be explained by extending the AOM calculations to the enzyme in the reduced form and assuming that the imidazol ring of His61 is no longer bridging the copper and cadmium ions in the reduced state.

Animals↗
PubMed1991

Coordination geometry of cadmium at the zinc and copper sites of superoxide dismutases: a study using perturbed angular correlation of gamma-rays from excited 111Cd.

111Cd time-differential perturbed gamma-gamma angular correlation (PAC) has been used to investigate the Zn site in yeast and bovine copper and zinc-containing superoxide dismutases by substitution of the zinc ions with excited 111Cd(2+) ions. The PAC spectra obtained from the enzymes in aqueous solution reveal a single coordination geometry of 111Cd(2+) showing that the coordination of 111Cd(2+) to the Zn site in the two subunits is identical. Furthermore, the PAC spectra of the yeast and bovine enzymes show that the Zn sites are very similar in the two enzymes. The PAC experiments show a clear difference depending on whether the copper ion is in the oxidized or the reduced state. In the latter case the results resemble those obtained for derivatives with no metal ion at the Cu site. Hence the coordination geometry of the Zn site in these two situations must be similar, and it is very unlikely that the imidazole ring of His61 bridges the two metal ions in the reduced enzyme. The PAC spectrum of 111Cd(2+) ions at the Zn site with copper(II) ions at the Cu site is in agreement with that predicted by applying the angular overlap model (AOM) to the known crystal structure of the bovine enzyme, with known nuclear quadrupole interactions for the ligands involved. Furthermore results from experiments with copper in the reduced state show that reduction of the copper ion causes a significant change at the Zn site. An explanation for this conformational change has been proposed by computer modelling. The PAC experiments also show that it is possible to incorporate cadmium ions into the Cu site in the absence of copper ions, and the result has also been interpreted in terms of the AOM.

Binding Sites↗
PubMed1990

Postnatal development of [3H]flunitrazepam and [3H]strychnine binding sites in rat spinal cord localized by quantitative autoradiography.

The development of inhibitory receptors in rat spinal cord was investigated by autoradiography using [3H]flunitrazepam as a ligand for benzodiazepine receptors and [3H]strychnine as a ligand for glycine receptors. The development of benzodiazepine receptors follows a similar pattern at all levels of the spinal cord. The density of [3H]flunitrazepam binding sites is already high at birth, increases 2-fold by days 3-7 and thereafter declines to levels already present at birth. In contrast, [3H]strychnine binding sites are weakly expressed at birth and increase up to 7-fold between days 4 and 21. A craniocaudal gradient in the development of glycine receptors is not apparent. However, maturation of [3H]strychnine binding in the ventral horn precedes that in the dorsal horn for 3-4 days. In summary, the developmental expression of these two inhibitory receptors in the spinal cord appears to be regulated differently.

Aging↗
PubMed1990

A quantitative assay for neomycin phosphotransferase activity in plants.

A sensitive, simple, and quantitative assay for determining neomycin phosphotransferase (NPT) activity in plant cell extracts is described. The procedure retains the simplicity of previously published methods, yet offers up to a 140-fold increase in sensitivity. This increase is due to (1) the addition of bovine serum albumin (BSA) to the assay mixture, (2) desalting of crude maize extracts to remove a low-molecular-weight inhibitor of the enzyme, and (3) use of a different extraction buffer and an improved extraction procedure to liberate more enzyme from the cells. This method has been used successfully to detect and quantitate both stable and transient expression of NPT in transgenic tobacco and maize tissue.

Animals↗
PubMed1990

Determination of regional blood flow in abdominal organs and other structures in normal female rats and in rats with TAA-induced chronic liver injury using 99mTc labelled HSA-microsphere technique.

A method for simultaneous determination of cardiac output and regional blood flow distribution in a chronically instrumented, unrestrained rat preparation for different experimental conditions (i.e. conscious, free movement; general anesthesia) and in an experimental chronic liver injury model is described. The use of a modified radioactive microsphere reference sample method using 99mTc labelled HSA-microspheres provides valid measurements of cardiac output [255 +/- 21.6 ml/(min.kg b.wt.)] and of the determined blood flow rates of abdominal organs (with separate determination of arterial and portal-venous hepatic blood flow rates; the latter by means of arterial blood flow measurement of the gastrointestinal tract and the spleen), the myocard, the adrenals, the kidneys, and various brain regions. Furthermore, it is demonstrated that this measuring approach with chronical preparation can also advantageously be used in pharmacological or pathogenetical studies, especially because of the simple measuring equipment and the comparatively low costs that offer a broader application.

Abdomen↗
PubMed1990

[The weighting of SE, IE and GE sequences in tumors of the head and neck].

In a review of 82 patients having different benign and malignant head and neck tumours we studied the value of spin echo (SE), inversion echo (IE) and gradient echo (GE) sequences. The strong T1 weighted IE mode is highly sensitive to demonstrate pathological tissue. Tumour diagnosis was in 20% and lymph node diagnosis in 29% better than T2 weighted SE sequences. According to this experience we choose the IE mode as the first one for all patients examined for tumour staging. All other sequences and orientations are planned on this tomograms knowing the location of the tumour and lymph nodes. T1 weighted SE mode is indispensable and should be recorded in transversal orientation, covering the whole head and neck region. This mode has the best imaging of anatomical structures as the known fatty limitations. The best differentiation of the tumour is usually obtained after contrast enhancement by i.v. Gd-DTPA. The highest contrast enhancement is seen on T1 weighted GE tomograms, which we prefer. T2 weighted SE sequences are less sensitive than IE sequences and T1 weighted tomograms after Gd-DTPA to show the tumour. The T2 weighted SE mode cannot be replaced by the T2 weighted GE mode having a better signal to noise ratio. To minimise the scan-time of T2 weighted SE mode, only one measurement is performed; the quality of the tomograms is satisfactory.

Adult↗
PubMed1990

[Initial experiences with transpopliteal, laser-assisted balloon angioplasty of femoral artery occlusions].

For many years great efforts are being made to recanalise totally occluded vessels and averting a bypass operation as long as possible. In two years 190 patients were treated successfully by the Lastac System. Encouraged by very good results, we started to recanalise the totally occluded superficial femoral artery via a transpopliteal approach. Meanwhile, 29 patients were treated. Primary successful were 22 patients with an average length of a total occlusion of 27.5 cm.

Adult↗
PubMed1990

Phenotypic and functional characterization of tumor infiltrating lymphocytes in mycosis fungoides: continuous growth of CD4+ CD45R+ T-cell clones with suppressor-inducer activity.

Tumor-infiltrating lymphocytes (TIL) were obtained by mechanical release from a solitary rapidly grown tumor of a patient with mycosis fungoides. The preparations separated by density gradient centrifugation contained a major portion of CD3+ CD8+ WT31+ CD5- large T-cell blasts and a minor portion of non-blastic TIL predominantly of the CD3+ CD4+ phenotype. Using cDNA-probes for the constant region of the T-cell receptor beta-genes, the large cell fraction was identified as tumor by its distinct monoclonal rearrangement. TIL were expanded by culture in recombinant interleukin 2 and cloned by limiting dilution. Phenotypic analysis of expanded TIL and two clones further analyzed in more detail showed CD3+, CD4+, CD8-, and 2H4+ (CD45R+) expression. Cloned and uncloned TIL showed no NK and LAK activity, no proliferative response, and no cytotoxic activity against autologous tumor cells. These cells were unable to suppress the proliferative response of alloreactive T-cell clones stimulated by B-lymphoblastoid cell lines (i.e., they had no suppressor-effector activity), but strongly suppressed proliferation responses in allogeneic mixed lymphocyte culture (i.e., they most likely had suppressor-inducer activity). This was not the case when irradiated tumor cells were added. The present results demonstrate continuous in vitro growth of CD4+ and 2H4+ T-cell clones with suppressor-inducer activity obtained from TIL, and indicate that a subpopulation of TIL may down-regulate immune responses which may lead to suppression of antitumor immunity.

Antigens, CD↗
PubMed1990

[Acrosyringium and follicular infundibulum: immunomorphologic aspects].

Acrosyringium and infundibulum are epidermal structures with different morphology, but functional similarities regarding re-epithelialization, transport of antigens, and attraction of infiltrates. Immunomorphologically, the infundibula revealed an immunoreactivity of Langerhans cells and keratinocytes comparable with that of the interfollicular epidermis, whereas the acrosyringia reacted differently because of the permanent expression of MHC class II antigens and reduced Langerhans cells in the perisyringial region. Our findings suggest that these epidermal compartments differ with regard to their individual immunologic situations. While the mechanisms of epidermal immunity known from the interfollicular epidermis are possibly the same in the infundibula, we have to expect a basically different immunologic situation in the acrosyringia.

Antigens, CD1↗
PubMed1990

[Percutaneous radio-frequency sympathetic block in peripheral circulatory disorders].

Thirty patients with inoperable diabetic angiopathies (degree III and IV concerning to Fontaine) were treated by means of percutanous radiofrequency thermolesion of the lumbar sympathetic chain (PRFS). All patients reported immediately after this procedure a distinct feeling of warmth in the treated leg. After a period of 6 month to two years 22 patients were re-examined clinically: Fifteen patients changed to Fontaine IIa and ten patients were free of further complaints. Also an improved wound healing and ulcer demarcation following amputation or skin transplantation was observed. The advantage of PRFS in comparison to the surgical sympathectomy is the fact that there is no general anesthesia necessary, which too minimizes the risk especially for the aged vascular patient. Moreover the patient can be mobilised immediately after the procedure. There were no complications like lesion of the ureter or the genitofemoral nerve as well as bleading into the psoas muscle as reported in percutanous chemical lesion of the sympathetic chain.

Adult↗
PubMed1990

[Differential behavior of skin temperature in vascular patients vs. pain patients in lumbar radicular stimulation and nerve block].

Plantar skin temperature monitoring during the procedure of percutaneous radiofrequency-thermolesion of the sympathetic chain (PRFS) in patients with vascular diseases and patients with lumbar radicular pain and signs of sympathetic irritation showed a distinct difference. A significant decrease of skin temperature was observed during stimulation of the sympathetic chain by means of canula placement and contrast medium instillation only in the group of "vascular" patients, while "radicular pain" patients showed a significant increase of skin temperature after PRFS. This observation leads to the conclusion that the effect of sympathectomy more or less is to prevent physiological hyperactivity of the sympathetic system.

Adult↗