Improving biliary stent patency by the use of stent coating - a prospective randomized porcine study.

BACKGROUND: Endoscopic stenting of the bile duct is a standard procedure for almost 35 years. In the case of long-term stenting occlusion of the stent is a major concern. Therefore optimizing biliary stents with respect to their patency is of great importance. We tested in an in animal study if coating of self-expanding metal stents with hydrophobin alone or hydrophobin with heparin reduces stent clogging as there were promising results in an in vitro study with this approach. MATERIAL AND METHODS: In a randomized prospective animal study we implanted self-expanding metal stents either native or coated with hydrophobin alone or coated with hydrophobin and heparin into the bile duct of 15 pigs. After a survival period of 6 weeks we measured which part of the stent surface (%) was covered with clogging material using a commercially available image editing program on scanning electron microscopic images. RESULTS: We found no differences between the native self-expanding metals stents and those coated with hydrophobin alone or hydrophobin and heparin. CONCLUSION: There are important differences in the clogging process between in vitro and in vivo models. Coating with hydrophobin with or without heparin is not able to inhibit the clogging process in an animal model.

Static Magnetic Proximity Effect in Pt/NiFe2O4 and Pt/Fe Bilayers Investigated by X-Ray Resonant Magnetic Reflectivity.

The spin polarization of Pt in Pt/NiFe2O4 and Pt/Fe bilayers is studied by interface-sensitive x-ray resonant magnetic reflectivity to investigate static magnetic proximity effects. The asymmetry ratio of the reflectivity is measured at the Pt L3 absorption edge using circular polarized x-rays for opposite directions of the magnetization at room temperature. The results of the 2% asymmetry ratio for Pt/Fe bilayers are independent of the Pt thickness between 1.8 and 20 nm. By comparison with ab initio calculations, the maximum magnetic moment per spin polarized Pt atom at the interface is determined to be (0.6±0.1) µB for Pt/Fe. For Pt/NiFe2O4 the asymmetry ratio drops below the sensitivity limit of 0.02 µB per Pt atom. Therefore, we conclude, that the longitudinal spin Seebeck effect recently observed in Pt/NiFe2O4 is not influenced by a proximity induced anomalous Nernst effect.

Transverse spin Seebeck effect versus anomalous and planar Nernst effects in Permalloy thin films.

Transverse magnetothermoelectric effects are studied in Permalloy thin films grown on MgO and GaAs substrates and compared to those grown on suspended SiN(x) membranes. The transverse voltage along platinum strips patterned on top of the Permalloy films is measured versus the external magnetic field as a function of the angle and temperature gradients. After the identification of the contribution of the planar and anomalous Nernst effects, we find an upper limit for the transverse spin Seebeck effect, which is several orders of magnitude smaller than previously reported.

Magnetic vortex core reversal by excitation with short bursts of an alternating field.

The vortex state, characterized by a curling magnetization, is one of the equilibrium configurations of soft magnetic materials and occurs in thin ferromagnetic square and disk-shaped elements of micrometre size and below. The interplay between the magnetostatic and the exchange energy favours an in-plane, closed flux domain structure. This curling magnetization turns out of the plane at the centre of the vortex structure, in an area with a radius of about 10 nanometres--the vortex core. The vortex state has a specific excitation mode: the in-plane gyration of the vortex structure about its equilibrium position. The sense of gyration is determined by the vortex core polarization. Here we report on the controlled manipulation of the vortex core polarization by excitation with small bursts of an alternating magnetic field. The vortex motion was imaged by time-resolved scanning transmission X-ray microscopy. We demonstrate that the sense of gyration of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT. This reversal unambiguously indicates a switching of the out-of-plane core polarization. The observed switching mechanism, which can be understood in the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application in data storage.

Tunneling magnetothermopower in magnetic tunnel junction nanopillars.

We study tunneling magnetothermopower (TMTP) in CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars. Thermal gradients across the junctions are generated by an electric heater line. Thermopower voltages up to a few tens of µV between the top and bottom contact of the nanopillars are measured which scale linearly with the applied heating power and hence the thermal gradient. The thermopower signal varies by up to 10 µV upon reversal of the relative magnetic configuration of the two CoFeB layers from parallel to antiparallel. This signal change corresponds to a large spin-dependent Seebeck coefficient of the order of 100 µV/K and a large TMTP change of the tunnel junction of up to 90%.

Scaling behavior of the spin pumping effect in ferromagnet-platinum bilayers.

We systematically measured the dc voltage V(ISH) induced by spin pumping together with the inverse spin Hall effect in ferromagnet-platinum bilayer films. In all our samples, comprising ferromagnetic 3d transition metals, Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V(ISH) invariably has the same polarity, and scales with the magnetization precession cone angle. These findings, together with the spin mixing conductance derived from the experimental data, quantitatively corroborate the present theoretical understanding of spin pumping in combination with the inverse spin Hall effect.

Ab initio prediction of ferrimagnetism, exchange interactions and Curie temperatures in Mn2TiZ Heusler compounds.

The Heusler compounds Mn(2)TiZ (Z = Al, Ga, In, Si, Ge, Sn, P, As, Sb) are of great interest due to their potential ferrimagnetic properties and high spin polarization. Here, we present calculations of the structural and magnetic properties of these materials. Their magnetic moment follows the Slater-Pauling rule m = N(V) - 24. None of them is actually a perfect half-metallic ferrimagnet, but some exhibit more than 90% spin polarization and Curie temperatures well above room temperature. The exchange interactions are complex; direct and indirect exchange contributions are identified. The Curie temperature scales with the total magnetic moment, and it has a positive pressure dependence. The role of the Z element is investigated: it influences the properties of the compounds mainly via its valence electron number and its atomic radius, which determines the lattice parameter. Based on these results, Mn(2)TiSi, Mn(2)TiGe, and Mn(2)TiSn are proposed as candidates for spintronic applications.

[Development of an emergency room algorithm for treatment of multiple trauma. Wolfsburg model]. / Entwicklung eines Schockraumalgorithmus für die Polytraumaversorgung. "Wolfsburger Modell."

Within the framework of restructuring for the certification to a regional trauma centre of the DGU (German Society for Casualty Surgery), a uniform algorithm for multiple trauma was developed in the medical centre of Wolfsburg. The Wolfsburg multiple trauma algorithm is based on ATLS (advanced trauma life support) with integration of FAST (focused assessment with sonography for trauma), as well as the white paper of the DGU and regional-specific features. Thus structural, instrumental, organizational and personnel conditions were created to improve the care of multiply traumatized patients even further. The conditions for transition to a regional trauma centre of the DGU were confirmed by a successful audit.

Peritonsillar abscess: is there any evidence of lateralized distribution? An analysis of 294 patients.

OBJECTIVE: Generally, peritonsillar abscess (PTA) occurs only on one side. Diseases of paired organs show a distinct asymmetry of occurrence: for instance gynaecomastia, varicocele, trigeminal neuralgia, carcinoma of the breast and carcinoma of the ethmoid sinus. Therefore, the goal of the present study was to investigate a possible dominance of one side in PTA. MATERIAL AND METHOD: Lateralization of a PTA was studied in 294 patients treated at Radebeul Hospital between January 2004 and December 2009. RESULT: We found only a slight predominance of the left side in male as well as female patients. CONCLUSION: The cause of the slight asymmetry is unclear. It is also possible that the non significant dominance is coincidental.

Nonlinear hybridization of the fundamental eigenmodes of microscopic ferromagnetic ellipses.

We have studied experimentally with high spatial resolution the nonlinear eigenmodes of microscopic Permalloy elliptical elements. We show that the nonlinearity affects the frequencies of the edge and the center modes in an essentially different way. This leads to repulsion of corresponding resonances and to nonlinear mode hybridization resulting in qualitative modifications of the spatial characteristics of the modes. We find that the nonlinear counterparts of the edge and the center modes simultaneously exhibit features specific for both their linear analogues.

Association of hemoglobin C with erythrocyte ghosts.

The interaction of hemoglobin C (Hb C) with erythrocyte membranes was studied using changes in fluorescence intensity in a membrane-embedded probe. The affinity of Hb C for the membranes at pH 6.0 and pH 6.8 was compared to that of normal hemoglobin (Hb A). Steady-state and kinetic data were delivered. The affinity of Hb C for the erythrocyte membrane at pH 6.8 appeared to be about five times greater than that of Hb A. The associations of Hb C and Hb A with the membrane were reversible to about the same extent. The cytoplasmic portions of band 3 membrane proteins were suggested to be the binding sites for both hemoglobins. The membrane binding of Hb C at pH values of 6.8 to 7.0 indicates that this reaction may occur under physiological circumstances.

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method.

The determination of the longitudinal spin Seebeck effect (LSSE) coefficient is currently plagued by a large uncertainty due to the poor reproducibility of the experimental conditions used in its measurement. In this work we present a detailed analysis of two different methods used for the determination of the LSSE coefficient. We have performed LSSE experiments in different laboratories, by using different setups and employing both the temperature difference method and the heat flux method. We found that the lack of reproducibility can be mainly attributed to the thermal contact resistance between the sample and the thermal baths which generate the temperature gradient. Due to the variation of the thermal resistance, we found that the scaling of the LSSE voltage to the heat flux through the sample rather than to the temperature difference across the sample greatly reduces the uncertainty. The characteristics of a single YIG/Pt LSSE device obtained with two different setups was (1.143 ± 0.007) 10-7 Vm/W and (1.101 ± 0.015) 10-7 Vm/W with the heat flux method and (2.313 ± 0.017) 10-7 V/K and (4.956 ± 0.005) 10-7 V/K with the temperature difference method. This shows that systematic errors can be considerably reduced with the heat flux method.

Rational design and diversity-oriented synthesis of peptoid-based selective HDAC6 inhibitors.

A mini library of HDAC inhibitors with peptoid-based cap groups was synthesized using an efficient multicomponent approach. Four compounds were identified as potent HDAC6 inhibitors with a selectivity over other HDAC isoforms. The most potent HDAC6 inhibitor revealed remarkable chemosensitizing properties and completely reverted the cisplatin resistance in Cal27 CisR cells.

Loss of heterozygosity accumulation in primary breast carcinomas and additionally in corresponding distant metastases is associated with poor outcome.

The occurrence of distant metastases is the most feared manifestation of breast cancer, often occurring years after the primary surgery and associated with poor survival. The dominant metastatic clone is characterized by an accumulation of genetic alterations, but it is not actually known at what stage of the metastatic cascade these alterations have occurred. We investigated allelic losses during breast cancer progression in a series of 17 primary breast carcinomas and 22 corresponding brain, liver, lung, and bone metastases (mean metastasis-free interval, 31 months) by analyzing 19 microsatellite markers on seven breast cancer- or metastasis-related chromosomal regions and correlated the incidence of combined loss of heterozygosity (LOH) with metastasis-free and postmetastatic survival. We found that, in comparison with the corresponding primary tumor, additional LOH events are frequently found in metastases and that the incidence of combined LOH in the primary tumor, plus the occurrence of additional LOH events in the distant metastases, correlated significantly with decreased postmetastatic survival. Combined LOH of the three breast cancer-related chromosomal regions alone or in combination with allelic loss at the p53 gene region seems to have a specific influence on the aggressive behavior of metastases. We hypothesize that the occurrence of additional LOH events is either involved in termination of dormancy of micrometastatic tumor cells at distant organ sites or acquired during further progression of metastases.

Pi trapping in glycogenolytic pathway can explain transient Pi disappearance during recovery from muscular exercise. A 31P NMR study in the human.

31P NMR spectroscopy at 4.7 T has been used to follow changes in phosphorylated metabolites and pHi in the flexor digitorum superficialis muscle of 15 healthy volunteers subjected to a rest-exercise-recovery protocol. Phosphomonoesters (Pme) increased during exercise and exhibited a delayed recovery to resting level. During early recovery, Pi fell below resting concentration without correlated PCr oversynthesis while Pme level stayed above its resting value. The sum Pi + Pme remained constant. These observations suggest that Pi could be trapped into the glycogenolytic pathway during exercise leading to Pme production. This trapping and the slow Pme recovery could account for transient Pi disappearance observed during recovery.

Heterogeneity of metabolic response to muscular exercise in humans. New criteria of invariance defined by in vivo phosphorus-31 NMR spectroscopy.

31P NMR spectroscopy at 4.7 T has been used in vivo to follow metabolic changes associated with exercise and subsequent recovery in the forearm flexor digitorum superficialis muscle of 14 healthy volunteers. The muscle content in phosphomonoesters at rest provides an index of glycogenolytic activity. Quantitative linear correlations have been shown to link end-of-exercise acidosis to recovery kinetics of phosphocreatine and phosphocreatine/organic phosphate ratio. These linear relationships constitute new metabolic invariants to be used in the study of myopathies and muscle adaptation to exercise.

Synthesis of 7-benzylamino-6-chloro-2-piperazino-4-pyrrolidinopteridine and novel derivatives free of positional isomers. Potent inhibitors of cAMP-specific phosphodiesterase and of malignant tumor cell growth.

7-Benzylamino-6-chloro-2-piperazino-4-pyrrolidinopteridine (7a) is a potent inhibitor of the cAMP-specific phosphodiesterase isoenzyme family PDE4 and induces growth inhibition in a panel of tumor cell lines. In this study, we describe a synthesis that yields 7a and novel derivatives free of positional isomers. The synthesis of alkylamino substituted pteridines is based on the successive nucleophilic aromatic substitution of the chlorine atoms of 2,4,6, 7-tetrachloropteridine. For the reaction with secondary amines, the positional order of reactivity was found to be C4 > C7 > C2 > C6. Final structural proof is given by X-ray crystallography. To unravel structural elements of 7a crucial for the interaction with the target enzyme, the compound was modified systematically. The impact of the modifications on activity was tested by evaluating the ability of the compounds to inhibit cAMP hydrolysis by cAMP-specific phosphodiesterase (PDE4) purified from the solid human large cell lung tumor xenograft LXFL529. Growth inhibitory properties were determined by in vitro treatment of the respective cell line LXFL529L using the sulforhodamine B assay (SRB). The results show that for high activity, the heterocyclic substituent in position 2 of the pteridine ring system requires the presence of a basic nitrogen in 4'-position, as represented by piperazine.

Is the high concentration of ascorbic acid in the eye an adaptation to intense solar irradiation?

Ascorbic acid is known to exist in high concentration in the aqueous humor of the eye in many species. It has been observed that diurnal mammals have a very high concentration in aqueous humor whereas nocturnal mammals do not. It has been hypothesized that ascorbic acid protects the eye from the harmful effects of sunlight. We have discovered that of two closely related species of spiny mice, the diurnal species (Acomys russatus) has a concentration in aqueous humor that is 35 times higher than that of the nocturnal species (Acomys cahirinus). Studies of these two species may be fruitful to extend what is known about adaptation of the eye to protect itself from intense solar radiation.

Aqueous humor flow during sleep.

The rate of aqueous humor flow of 19 normal subjects was measured by a fluorescein clearance technique during the day, during sleep (at night) and during sleep deprivation (at night). Subjects engaged in routine activities during the daytime measurements and slept in comfortable quarters during the nighttime measurement. They remained awake and active during the sleep deprivation study. The nomographic method of Coakes and Brubaker , a method in which the subject is not disturbed at all during the critical 5-hr period, was used to calculate flow. Flow was lower during sleep in all but one subject. The range of nighttime flow suppression was 8% to 68% in all of the other subjects with a mean suppression of 45% +/- 20%. Aqueous flow was lower at night even when the subjects were awake but was lowest during sleep at night. The reduction of aqueous flow during sleep is comparable with the suppression that can be achieved with carbonic anhydrase inhibitors or beta adrenergic blockers.

Review article: hepatitis vaccination in patients with chronic liver disease.

Evidence regarding the outcomes of viral super-infection in patients with chronic liver disease and practical strategies for hepatitis A and B vaccination of these individuals are reviewed. Patients with acute hepatitis A and chronic hepatitis B have a more severe clinical course and a higher death rate compared with otherwise healthy individuals with hepatitis A, and these differences are most pronounced in older patients and those with histological evidence of chronic hepatitis or cirrhosis, rather than in asymptomatic hepatitis B carriers. Patients with acute hepatitis A super-infection and chronic hepatitis C have an increased risk of fulminant hepatitis and death. In addition, patients with other chronic liver diseases also appear to be at increased risk for more severe disease with superimposed hepatitis A. Patients with chronic hepatitis B and hepatitis C virus co-infection have more severe laboratory abnormalities, more severe histological disease, a greater frequency of cirrhosis and complications of cirrhosis, and a higher incidence of hepatocellular carcinoma. Vaccines for both hepatitis A and B are safe and effective if used early in the course of chronic liver disease. Hepatitis A and B vaccination should be part of the routine management of patients with chronic liver disease, preferably as early as possible in the natural course of their disease.