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C Sturm

Publications and source records attributed to C Sturm.

At least 19 recordsLinked to original sources
PubMed2006

Four-loop QCD corrections to the electroweak rho parameter.

The four-loop QCD corrections to the electroweak rho parameter arising from top and bottom quark loops are computed. Specifically we evaluate the missing "nonsinglet" piece. Using algebraic methods the amplitude is reduced to a set of around 50 new master integrals which are calculated with various analytical and numerical methods. The inclusion of the newly completed term halves the final value of the four-loop correction for the minimally renormalized top-quark mass. The predictions for the shift of the weak mixing angle and the W-boson mass are thus stabilized.

Journal Article↗
PubMed2006

In-medium effects on phase space distributions of antikaons measured in proton-nucleus collisions.

Differential production cross sections of K+/- mesons have been measured in p + C and p + Au collisions at 1.6, 2.5, and 3.5 GeV proton beam energy. At beam energies close to the production threshold, the K- multiplicity is strongly enhanced with respect to proton-proton collisions. According to microscopic transport calculations, this enhancement is caused by two effects: the strangeness exchange reaction NY --> K- NN and an attractive in-medium K- N potential at saturation density.

Journal Article↗
PubMed2005

Observation of different azimuthal emission patterns of K+ and of K- mesons in heavy-ion collisions at 1-2 A GeV.

Azimuthal distributions of pi+, K+, and K- mesons have been measured in Au+Au reactions at 1.5A GeV and Ni+Ni reactions at 1.93 A GeV. In semicentral collisions at midrapidity, pi+ and K+ mesons are emitted preferentially perpendicular to the reaction plane in both collision systems. In contrast for K- mesons in Ni+Ni reactions, an in-plane elliptic flow was observed for the first time at these incident energies.

Journal Article↗
PubMed2003

First evidence for different freeze-out conditions for kaons and antikaons observed in heavy-ion collisions.

Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 A GeV. The K(-)/K(+) ratio is found to be nearly constant as a function of the collision centrality and system size. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+ mesons decouple earlier from the fireball than K- mesons.

Journal Article↗
PubMed2003

Coulomb dissociation of 8B and the low-energy cross section of the 7Be(p,gamma)8B solar fusion reaction.

An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254A MeV allowed the study of the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S17(0)=18.6+/-1.2+/-1.0 eV b, where the first error is experimental and the second one reflects the theoretical uncertainty in the extrapolation.

Journal Article↗
PubMed2001

Evidence for a Soft Nuclear Equation-of-State from Kaon Production in Heavy-Ion Collisions.

The production of pions and kaons has been measured in 197Au+197Au collisions at beam energies from 0.6 to 1.5A GeV with the kaon spectrometer at SIS/GSI. The K+ meson multiplicity per nucleon is enhanced in Au+Au collisions by factors up to 6 relative to C+C reactions, whereas the corresponding pion ratio is reduced. The ratio of the K+ meson excitation functions for Au+Au and C+C collisions increases with decreasing beam energy. This behavior is expected for a soft nuclear equation-of-state.

Journal Article↗
PubMed2001

The push-and-pull mechanism to scavenge redox-active transition metals: a novel concept in myocardial protection.

OBJECTIVE: Traces of redox-active transition metals such as iron and copper play an important role in free radical formation during postischemic reperfusion of the heart. Two studies were conducted to assess the efficacy of the complexes of desferrioxamine with zinc or gallium to prevent this aspect of reperfusion injury. METHODS: In study I, isolated working rat hearts (n = 96) were subjected to 2 hours of hypothermic arrest at 10 degrees C induced by use of St Thomas' Hospital cardioplegic solution II supplemented with desferrioxamine, zinc-histidinate, zinc-desferrioxamine, gallium-nitrate, or gallium-desferrioxamine. In study II, isolated nonworking rat hearts (n = 23) were subjected to normothermic regional (10 minutes) or global (35 minutes) unprotected ischemia. In this study, the perfusate was supplemented with gallium-desferrioxamine during preischemic and postischemic periods. RESULTS: In study I, the addition of desferrioxamine, zinc-histidinate, or gallium-nitrate to St Thomas' Hospital solution II improved postischemic aortic flow recovery. When the binary complexes zinc-desferrioxamine or gallium-desferrioxamine were added, however, functional recovery was further enhanced significantly. In study II, high-performance liquid chromatography analyses of tissue from postischemic hearts exposed to unsupplemented perfusate revealed a marked increase of malondialdehydes. In hearts perfused with perfusate supplemented with gallium-desferrioxamine, however, tissue malondialdehyde concentrations were significantly smaller, indicating reduced free radical formation. CONCLUSIONS: The data suggest synergistic protection by the complexes of the iron chelator desferrioxamine with zinc or gallium. The single components neutralize transition metals by 2 different but complementary push-and-pull mechanisms, thereby leading to an inhibition of metal-mediated site-specific free radical formation and improvement of postischemic cardiac function.

Analysis of Variance↗
PubMed2001

Acridizinium salts as a novel class of DNA-binding and site-selective DNA-photodamaging chromophores.

It was demonstrated that the interaction of the aminoacridizinium salts 2a-2d with DNA depends on the substitution pattern of the chromophore. Spectrophotometric and fluorometric titrations of the acridizinium salts 2a-2d with natural and synthetic polynucleotides reveal that the degree of interaction of the acridizinium salts 2a-2d with the nucleic acid differs significantly. The binding mode of the dyes with DNA was evaluated by circular dichroism and linear dichroism spectroscopy and compared with the parent system 2c. Whereas the 9-aminoacridizinium (2a) mainly intercalates into DNA, the salts 2b-c show a higher degree of association to the DNA backbone. The intercalated aminoacridizinium 2a caused few strand breaks upon UVA exposure, whereas the salts 2b-2d exhibit relatively efficient DNA-damaging properties. All acridizinium salts showed a sequence-selective strand cleavage for guanine-rich DNA regions.

Acridines↗
PubMed2001

Structurally related immunological effects of triterpenoid saponins.

The influence of the triterpenoid saponins 1-10 has been investigated on murine spleenocytes in the lymphocyte transformation test and on murine macrophages in an phagocytosis assay. The lymphocyte transformation test and the phagocytosis assay showed that the tested compounds have no stimulating effect. However, a significant inhibition of lymphocyte proliferation by the triterpenoid saponins 2, 6 and 10 was demonstrated.

Animals↗
PubMed2000

Emission pattern of high-energy pions: A new probe for the early phase of heavy-Ion collisions

The emission pattern of charged pions has been measured in Au+Au collisions at 1 GeV/nucleon incident energy. In peripheral collisions and at target rapidities, high-energy pions are emitted preferentially towards the target spectator matter. In contrast, low-energy pions are emitted predominantly in the opposite direction. The corresponding azimuthal anisotropy is explained by the interaction of pions with projectile and target spectator matter. This interaction with the spectator matter causes an effective shadowing which varies with time during the reaction. Our observations show that high-energy pions stem from the early stage of the collision whereas low-energy pions freeze out later.

Journal Article↗
PubMed2000

Involvement of inferior turbinate mucosa in chronic sinusitis--localization of T-cell subset.

BACKGROUND: In chronic sinusitis (CS), different subsets of leukocytes are involved in development of persistent inflammation of the nasal mucosa. The localization and differentiation of these infiltrating lymphocytes may help us to understand the inflammatory interactions in the epithelium, lamina propria, and seromucous glands of the nasal mucosa in CS. METHODS: We examined frozen sections of inferior turbinates from 14 patients with nonallergic CS and 10 normal nonallergic controls. We used the avidin-biotin-peroxidase (ABC) technique with monoclonal antibodies against CD3 (total T cells), CD4 (T-helper/inducer cells), CD8 (T-suppressor/cytotoxic cells), CD22 (B cells), CD56 (natural killer cells), elastase (neutrophil granulocytes), eosinophil cationic protein (eosinophil granulocytes), and CD68 (macrophages). RESULTS: We found significant increases (P < 0.05) of CD3, CD4, and CD8 T cells and B cells in the nasal mucosa of patients with CS. The number of CD68 cells and eosinophils showed no significant rise. CONCLUSIONS: The different types of leukocytes play a key role in the defense of the respiratory tract. The analysis of the distribution of cells in the epithelium, mucosa, and glands of the inferior turbinate confirmed that nonallergic CS is, in fact, chronic, bacterial rhinosinusitis involving the inferior turbinates, and that the pathomechanism is therefore different from that of nasal polyposis.

Adolescent↗
PubMed1999

[Polyposis nasi--effective treatment without operation? Broad etiological spectrum, individual therapy].

Various factors are thought to be involved in the etiology and pathogenesis of nasal polyps. The clinical symptoms include nasal obstruction, hyposmia or anosmia and recurrent sinusitis. At the cellular level eosinophilic granulocytes appear to have an important role to play, the growth, differentiation and degranulation of which is apparently controlled by interleukin 5. In the present study, practically relevant aspects of the pathophysiology, diagnosis, treatment and diagnostic differentiation of the various types of polyps are discussed, with the latter point also being examined for its importance with regard to therapeutic consequences.

Diagnosis, Differential↗
PubMed1999

[The diagnosis of stages T1 and T2 in laryngeal carcinoma with multislice spiral CT].

The purpose of the study was to preoperatively investigate small laryngeal carcinomas using multi-slice spiral CT (MSCT) and subsequent multiplanar reconstructions (MPR) and to compare the results to the detailed spread found at surgery and histology. Nine patients with small (T1, T2) laryngeal cancer were investigated on a MSCT scanner (Siemens plus 4 Volume Zoom, Siemens). A 4 x 1 mm collimation, 120 kV, 200 mAs and a 0.5 seconds rotation time were used, allowing a coverage of the entire larynx in approximately 10 seconds within a single breathhold. Multiplanar reconstruction's (MPR) in sagittal and coronal plane were reconstructed in all patients and rated in consensus reading. In 8 of nine patients, the glottic spread was detected by MSCT, in one cause of a supraglottic tumor a glottic invasion was excluded. The infiltration of the anterior commissure, the infiltration into the subglottic space and the extension into the hypopharynx was correctly assessed in all patients. MSCT was not able to predict infiltration of the arythnoids in two patients. The use of multi-slice spiral CT for the preoperative assessment of small laryngeal tumors shows great promise. The detection or exclusion of subtle spread of these tumors into the supra- or subglottic space and along the glottic level was possible with high accuracy. As the examination time is short, artifacts are rare and multiplanar reconstructions gain in clinical importance.

Carcinoma↗
PubMed1997

Particulate ANP-sensitive guanylyl cyclase in blood and bone marrow cells of patients with acute leukemia.

Increases in plasma cyclic GMP levels have been shown to correlate with increased plasma levels of atrial natriuretic peptide (ANP) in patients with fluid overload due to increased secretion of ANP. There is evidence that plasma cyclic GMP levels are also elevated in some patients with acute leukemia, but increased ANP secretion has not been demonstrated. To elucidate the possibility that a newly expressed guanylyl cyclase may be responsible for the increase of plasma cyclic GMP levels patients with acute and chronic leukemia as well as patients with lymphoma and healthy volunteers were studied. Plasma levels of cyclic GMP were measured and isolated peripheral blood mononuclear or bone marrow cells were incubated with increasing concentrations of ANP. The stimulation of cells was measured as cGMP accumulation in the supernatant. Furthermore guanylyl cyclase activity was measured in membrane preparations of peripheral blood mononuclear cells. While leukocytes of healthy subjects were devoid of detectable ANP-stimulated particulate guanylyl cyclase activity, ANP-sensitivity was observed in seven patients with acute lymphoblastic and in three patients with acute myelogenous leukemia. Cyclic GMP in the supernatant of cells was elevated between 2- and 132-fold of basal when cells were incubated with 1 microM ANP for 60 minutes. Like in healthy volunteers, no effect of ANP on freshly isolated mononuclear cells was observed in cases with chronic leukemia or in patients with lymphoma. Expression of ANP-sensitive particulate gunaylyl cyclase may be connected with malignant transformation of lymphocytes in patients with acute leukemia and might be useful for their diagnosis and classification.

Acute Disease↗
PubMed1997

[Significance of vascular endothelium for specific functional behavior of nasal mucosa].

BACKGROUND: During the last decade the morphological structure of nasal blood vessels was understood as a functional basis for different physiological and immunological reactions. RESULTS: Under normal conditions the vascular endothelium is involved in many activities including hemostasis, defense reactions, and angiogenesis during repair and pathological events. Most of the required components are synthesized by the endothelium itself, including extracellular matrix components, coagulation reactants, and growth factors. The complex vasculature of the human nasal mucosa plays an important role in the protection of the respiratory tract by generation of nasal fluid under normal and pathologic conditions. Increased plasma exudation in inflammatory processes including increased plasma protein concentrations binds cytokines, mediators, and cell release products and transports them to the respiratory lumen. During inflammation, endothelial cells stimulated by cytokines like TNF (tumor necrosis factor) regulate the recruitment of leukocytes by expression of certain surface proteins, called adhesion molecules. They also secrete chemokines like IL-8 (interleukin-8) and MCP (monocyte chemotactic protein) to increase the affinity of adhesion molecules, spread the leukocyte form to a flat, migrating one, and stimulate cell locomotion. Last but not least, endothelial cells may also act as antigen presenting cells (APC), although antigen presentation by endothelium is not responsible for the generalized homing of T-cells once the response is working. CONCLUSION: The new scientific results on the functional behaviour of vascular endothelium have opened new perspectives for our understanding of nasal blood vessels; it might also stimulate and enable us to search for new therapeutical concepts based on these findings.

Capillary Permeability↗
PubMed1996

Particulate ANP-sensitive guanylyl cyclase: induction in cultured human peripheral CD3+ mononuclear blood cells.

There have been conflicting reports about the occurrence and/or activity of atrial natriuretic peptide (ANP) sensitive guanylyl cyclase in the immune system. This study reports on ANP-sensitive guanylyl cyclase mRNA expression and guanylyl cyclase activity in human peripheral blood mononuclear cells (PBMC). Reverse transcription polymerase chain reaction (RT-PCR) shows that activated human PBMC of healthy blood donors express functional active ANP-sensitive guanylyl cyclase after vitro culture, whereas freshly isolated PBMC show neither specific mRNA for particulate guanylyl cyclase nor ANP-sensitive activity of this enzyme. To define the subpopulation of PBMC expressing this enzyme, cultivated PBMC were subfractioned and analyzed by RT-PCR and in situ PCR. Only CD3+ PBMC showed mRNA for ANP-sensitive guanylyl cyclase. Induction of the guanylyl cyclase required coincubation with other cells, indicating that a factor or factors secreted from cells other than CD3+ cells induces this expression. In summary, ANP-sensitive guanylyl cyclase is an inducible enzyme in human CD3+ PBMC in contrast to other cells where it is considered to be constitutive.

Animals↗
PubMed1996

[Transoral CO2 laser resection of extensive nasal and oropharyngeal teratoma].

BACKGROUND: Teratomas are quite rare congenital tumours, especially originating from the skull base in the region of the nasopharynx (1:40,000). PATIENTS: We report on a premature 36-week old girl with an extensive nasopharyngeal and oral teratoma. METHOD: With CO2 laser and micro-endoscopic techniques the tumour was successfully resected directly via the transoral route without needing external incisions. RESULTS AND CONCLUSIONS: These techniques, and particularly the use of CO2 laser, allow gentle resection of nasopharyngeal teratomas with only moderate bleeding. General pathological aspects, clinical symptoms and update management or teratomas in the head and neck area are discussed, based on this case. CO2 laser in conjunction with microscope and videoendoscope seems to offer an advantage compared to resection with conventional instruments alone.

Adult↗